Department of Physics & Astronomy
Annual Report: NSF Award #EPS-1003897
I. Executive Summary 2
II. Detailed Report 3
A. RII participants and participating institutions 3
B. Program/Project Description 4
B. 1. RESEARCH ACCOMPLISHMENTS AND PLANS: 4
B.1.1. Science Driver 1: Electronic and Magnetic Materials 4
B.1.2. Science Driver 2: Energy Materials 8
B.1.3. Science Driver 3: Biomolecular Materials 8
B.2. DIVERSITY AND BROADENING PARTICIPATION, INCLUDING INSTITUTIONAL COLLABORATIONS 8
B.3. WORKFORCE DEVELOPMENT: 8
B.4. CYBERINFRASTRUCTURE: 8
B.5. EXTERNAL ENGAGEMENT: 8
B.6. EVALUATION AND ASSESSMENT: 8
B.7. SUSTAINABILITY AND PROJECT OUTPUTS: 8
C. Management Structure: 8
D. Jurisdictional and Other Support: 8
E. Planning Updates: 8
F. Unobligated Funds: 8
G. Progress with Respect to the RII Strategic Plan: 8
H. Jurisdiction Specific Terms and Conditions: 9
I. Reverse Site Visit (RSV) Recommendations: 9
J. Experimental Facilities: 9
K. Publications and Patents: 9
L. Honors and Awards: 9
References 9
I. Executive Summary (to be revised by PET)
Introduction. This NSF award has led to the establishment of the Louisiana Alliance for Simulation-Guided Materials Applications (LA-SiGMA), which brings together Louisiana academic institutions to focus on simulation-assisted materials by design in research and in the education of a new generation of Louisiana material scientists. Three “Science Driver” areas have been identified for specific focus: (1) correlated electronic materials, which show promise as new materials for the design of molecular computers, microelectronics, and high-density recording media; (2) energy materials, which show promise as catalysts, advanced materials for the storage and release of hydrogen, and electrochemical cells and capacitors that store and deliver electrical energy; and (3) biomolecular materials, which can provide encapsulation, delivery, and release of therapeutics to specified targets. LA-SiGMA takes advantage of the Louisiana Optical Network Initiative (LONI), the most advanced high performance computing, network, and communication infrastructure among EPSCoR states. Since the principal barrier to simulation-guided design of materials—multiple length and time scales—challenges conventional scientific disciplines, LA-SiGMA combines researchers with specialized expertise at each scale into teams. Teams include applied mathematicians and computer scientists to ensure efficient utilization of forthcoming high performance computers and include experimentalists to test, validate and guide the computational simulations. These collaborations will position Louisiana to compete effectively for a national center of excellence in multiscale materials modeling and simulation.
Vision: Transformative advances in materials science research and education through a sustained multidisciplinary and multi-institutional alliance of researchers.
Mission: to establish a sustained national center of excellence in computational material science by the end of the project period.
Goals:
Science Driver 1: Electronic and Magnetic Materials: Transform the field by extending many-body formalisms and first principles methods to much larger length scales than currently possible.
Science Driver 2: Materials for Energy Storage and Conversion: Develop and apply multi-scale computational tools to study materials for energy generation, storage, and conversion.
Science Driver 3: Biomolecular Materials: Develop, apply, and validate experimentally multi-scale computational tools for the design of novel vehicles for drug delivery and other applications.
Computational Teams: Develop multi-scale formalisms, algorithms, and codes for materials simulations and modeling; leverage existing tools and make optimum use of the next generation computing environments.
Research Efforts. LA-SiGMA consists of three Science Drivers (SD) and a cyberinfrastructure and cybertools team (CTCI) which incorporates three computational teams with membership rich in Science Driver participants. The structure of the CTCI team enables the development of common computational research tools.
Science Driver 1: Electronic and Magnetic Materials. The goals of the Science Driver 1 (SD1) team are to develop and validate methods that enable the study of complex phenomena in correlated electronic and magnetic materials ranging from transition metal oxides to organic magnets. Complex emergent phenomena include properties such as superconductivity, magnetic, charge or orbital ordering, or other phases that one cannot predict even with an exact and complete understanding of the constituent atoms. These phases often compete, making these materials very sensitive to applied fields and perturbations that can lead to new functionalities. As a consequence of their exotic and diverse physical properties, transition metal oxides are considered to be the frontier of research on “emergent research device materials.” To study these systems, the SD1 team is developing mulitscale methods able to treat physics on the different length scales which characterize these orders, non-local density functional theory methods able to treat the strong correlation effects, and methods which combine these two techniques. The SD1 team includes researchers at LATech, LSU, Southern, Tulane, Xavier and UNO, with a high degree of overlap with the CTCI team. Over 30 students and postdocs have been recruited into SD1.
Science Driver 2: Materials for Energy Storage and Generation. The goal of Science Driver 2 (SD2) is to build a molecular level understanding of materials of importance for energy storage and generation. This understanding is important for improving these materials to meet global energy challenges. The work targets electrode materials for supercapacitors and hydrogen storage materials, and is developing molecular models to investigate catalytic process for the formation of biofuels and toxic biproducts from combustion. The team’s computational goals are to bring insight into the described systems by utilizing accurate ab initio methods, while developing the computational methodology to link these insights—which are often on the scale of a few to dozens of atoms—to the macroscopic process being investigated. This requires the development of new force fields that allow for the simulation of 10,000s of atoms that are parameterized by accurate ab initio results. Furthermore, there is a need to link with longer timescales that are outside the purview of atomistic simulations. Hence, the SD2 team is developing a mathematical model that can link the molecular level properties with long scale dynamical variables.
Science Driver 3: Biomolecular Materials. The goals of Science Driver 3 (SD3) team are to develop, apply, and validate experimentally multi-scale computational tools that will enable the design of novel drug delivery vehicles. The barriers to achieving these goals are the complexity associated with modeling systems with atomistic details over length scales on the order of 10-9 to 10-7 m and the lack of sufficiently efficient force fields to enable simulations to reach time scales of 10-6 to 10-3 s is required for meaningful predictions. SD3 is composed of multi-disciplinary teams of scientists at four institutions (Tulane, LSU, UNO, and LA Tech) that combine theoretical/computational scientists with experimentalists to investigate aspects necessary for building predictive models of uni-molecular and multi-molecular vehicles for targeted drug delivery.
Cyberinfrastructure, Cybertools and Computational Teams (CTCI). CTCI is focused on the development of the formalisms, algorithms and codes used in this project needed to efficiently utilize the next generation of supercomputers. A major research goal of CTCI is to collaborate with the computational teams: (1) Next Generation Monte Carlo Codes, (2) Massively Parallel DFT and Force Field Methods, and (3) Large-scale Molecular Dynamics. In addition, CTCI is also working on execution management, data management, visualization and heterogeneous (GPU) computing. CTCI includes members of all of computational and SD teams. CTCI is the glue that holds the three SDs together.
Diversity. The Diversity Advisory Council is coordinating existing and planned efforts to meet the project’s diversity goals. One major accomplishment, for instance, is the establishment of the Supervised Undergraduate Research Experience program, which is restricted to women and underrepresented minorities. Thirty (30) Louisiana students were competitively selected out of 127 applicants to work with faculty mentors at universities around the State, and future competitions are planned.
Workforce Development. The project contributes to workforce development in the State through the creation of a multi-tiered set of educational programs for graduate and postgraduate students who will enter the workforce as well-trained computational materials scientists. Four graduate level courses have been offered using HD synchronous video. Additional programs encourage high school, community college, and undergraduate students to explore computational materials science as a career, including Research Experiences for Teachers summer programs in New Orleans, Baton Rouge, and Ruston, as well as Research Experiences for Undergraduates (REU) programs at six LA-SiGMA universities.
External Engagement. LA-SiGMA maintains a web portal, a Facebook page, and an SVN (a collaborative software and revision system that maintains current and historical versions of files such as source code, web pages, and documentation). Synchronous collaboration tools such as EVO enable inter-institutional collaboration. The LA EPSCoR monthly newsletter continues to highlight the role played by LA EPSCoR in promoting the development of the State’s S&T resources through partnerships involving its universities, industry, and government. The newsletter is distributed to approximately 1,000 individuals, including faculty members, State legislators, and other stakeholders. The Speaking of Science (SoS) speaker’s bureau introduces thousands of K-12 students to the exciting science being undertaken by Louisiana’s best researchers. During this reporting period, 60 presentations were given to over 2,200 students, an audience comprised of 49% females and 38% underrepresented minorities. Two industry/academia collaborative workshops were held, with the goal of fostering interactions between Louisiana’s leading researchers and representatives of Louisiana’s industrial Research & Development community. One focused on the theme of energy and materials science (100 attendees) and the other (60 attendees) centered on Digital Media and Software Development, a rapidly growing industry in Louisiana.
Evaluation and Assessment. Multiple layers of evaluation and assessment is available to LA-SiGMA: An internal Evaluation and Assessment team, an external evaluator, and the External Review Board (ERB). The Office of Educational Innovation and Evaluation (OEIE) of Kansas State University continues to act as the external evaluator for Louisiana's EPSCoR programs. The logic models and strategic plan developed during Year 1 and accepted by the NSF were used to design and implement an on-line data collection portal called the "Online Advancing Science Information System (OASIS)." Launched towards the end of Year 1, OASIS was used extensively for the data collection needed for the Year 2 report. The data collection templates in OASIS were designed specifically to provide the data requested in the NSF templates and also to help the evaluators assess LA-SiGMA's progress in meeting the strategic plan milestones and outcomes.
Sustainability. A host of initiatives for improving the State’s research infrastructure and enhancing sustainability are administered by the LA EPSCoR office. These programs include: Pilot Funding for New Research ; Links with Industry, Research Centers and National Labs ; Opportunities for Partnerships with Industry ; Preliminary Planning Grants for Major Initiatives ; Travel Grants for Emerging Faculty ; Grantwriting Workshops ; the LA Genius Faculty Expertise Database ; and the SBIR/STTR Phase Zero program. All of these programs have a significant impact on propelling Louisiana’s S&T enterprise to become more competitive and sustainable. LA-SiGMA is actively focused on development of structures that will sustain it well beyond the end of the funding. LA-SiGMA members have led the effort to obtain a DOE Predictive Theory and Modelling Center which would bring the development of NWChem to the state and establish a significant collaboration with Pacific Northwest National Lab. We hosted an NWChem training workshop attended by ??? students. We have taught and are developing graduate level courses to train the current and future generation of computational materials scientists. LA-SiGMA is leveraging its funding and equipment purchases to obtain additional funding and equipment based on our successes. LA-SiGMA is developing new national and international collaborations.
Management Structure. Dr. Michael Khonsari is the Project Director (PD), and Mr. Jim Gershey is Project Administrator (PA). The PD ensures that the various stakeholders operate as a cohesive research enterprise progressing towards realization of project goals and objectives. A 21-member EPSCoR Committee meets at least twice a year. Assisting Dr. Khonsari and the EPSCoR Committee is a professional staff of five full-time individuals whose responsibilities include program management, fiscal and contract management, database administration, coordination of statewide outreach, and communications. The Project Execution Team (PET) oversees the day-to-day activities of the LA-SiGMA project and provides direction and guidance to project participants in each of the science driver and computational teams. The management structure features several interconnected teams designed to effectively implement and assess the project goals, promote project-wide participation in leadership, and ensure effective communications. These teams include the following: Science & Cyberinfrastructure Team; External Engagement & Workforce Development Team; Evaluation & Assessment Team; Industrial Liaison Team (ILT); and Diversity Advisory Council (DAC). An External Review Board (ERB), consisting of a diverse group of eminent scholars, conducts comprehensive programmatic reviews and forwards objective guidance, feedback, and recommendations to the PD and PET, to ensure that program goals and objectives are being met. Biannual “all-hands” face-to-face meetings are used for coordination and identification of new collaborations. The DAC and ILT participate in the biannual all-hands meetings. The ERB attends at least one of these biannual meetings to evaluate all aspects of the project.
Key Accomplishments. Intellectual Merit: New technologies often depend on designing new materials for specific tasks. Examples include materials for computer memories, batteries, and controlled drug delivery. When developing new materials, scientists and engineers search through a vast range of possibilities including complicated mixtures of ingredients, or architectural organizations of materials that present themselves in structures of different sizes and shapes. For example, a material for controlled drug delivery may have to be porous enough to absorb a drug but have a coating that protects the contents until the release environment is encountered. Design of useful, cost effective, and environmentally friendly new materials is a grand challenge for materials scientists. This challenge requires understanding, modeling, and exploiting the complexity of materials on numerous levels, from the small scale of minute constituents to the grand scale of technological applications. The interplay of behavior on multiple time and length scales (i.e., multiscale behavior) can lead to unexpected complex emergent phenomena. Such problems are generally unsolved in materials science.
Modern methods of experimental science and engineering heighten the design challenge by offering the ability to produce designed materials and to test detailed design features, though testing all possibilities is usually not economically feasible. Paralleling this expansion of experimental methods has been an explosion in the power of modern computers, and the evolution of the sophisticated computational science algorithms for simulation of materials, particularly specialized algorithms that take advantage of the hardware advances. The combined progress suggests the goal of simulation-assisted materials by design. This goal has been widely appreciated, and steady progress continues, but transformative progress will require a confluence of experimental and computational facilities together with directed intellectual collaboration. This RII research project builds upon existing state and federal investments in experimental and computational facilities in Louisiana.
Broader Impact : LA-SiGMA is effecting a transformative and sustainable change in computational materials research, education, and applications throughout the State of Louisiana and making the State competitive for a federally funded research center. LA-SiGMA is pushing the scientific frontiers in computational materials science, and enabling Louisiana researchers to use the next generation of heterogeneous, multicore and hyperparallel cyberinfrastructure effectively. LA-SiGMA is building statewide interdisciplinary research collaborations involving computational scientists, computer scientists and engineers, applied mathematicians, theorists and experimentalists. Most significantly, the project will build an inter-institutional computational materials science graduate program that will be unique in its statewide reach and impact, and may be the only one of its kind in the nation.
SD1: Research highlights include a partnership with CTCI to develop massively parallel GPU enhanced codes. These codes employ the state's GPU supercomputers to enable new discovery, and are also ready for use on BlueWaters. John Perdew and his collaborators are developing greatly improved semilocal and nonlocal density functionals that will be employed in electronic structure calculations for molecular magnets and other complex materials of interest to the SD1 science driver team. Experiments are used to both validate our methods and to suggest new materials for study. They are being performed on a wide spectrum of materials, ranging from iron-based high temperature superconductors to organic magnets. SD1 researchers have led the way in teaching four semester-long distance learning courses open to all LA-SiGMA participants, as well as numerous researchers in Europe and North America, teaching methods directly relevant to the research being done in SD1 and CTCI. Our efforts are coordinated through bi-weekly meetings of SD1 and of the GPU team in which SD1 is heavily involved.
SD2: One of the stated milestones is to develop algorithms that combine chemistry and physics of energy storage. During the second year, the SD2 team has carried out calculations to understand how charge is carried and distributed in the electrochemical double-layer capacitors, which are potential components for supercapacitors. Simulations have also been performed to understand how the addition of impurities to a sodium magnesium hydride can increase its ability to store hydrogen, and investigated how adding impurities to C60 influence its thermoelectric properties. The team has carried out DFT calculations to extract appropriate force field parameters to study catalysis. Furthermore, the team has moved into an exciting new area of Lithium-ion battery research, which combines experimental real time imaging combined with DFT calculations. The team’s efforts are coordinated via monthly synchronous meetings using the EVO collaboration tool and strong collaborations with the force field methods and Monte Carlo computational teams with CTCI.
SD3: The goals of the Science Driver 3 (SD3) team are to develop, apply, and experimentally validate multi-scale computational tools to enable the design of novel unimolecular and self-assembled drug delivery vehicles. The barriers to achieving these goals are the complexity associated with modeling systems with molecular detail from nm to μm in size and up to μs or ms in time required to make meaningful predictions. SD3 is composed of multi-disciplinary teams of scientists at five institutions (Tulane, LSU, LSU-Ag, UNO, and LA Tech), combining theoretical/computational scientists with experimentalists to build predictive targeted drug delivery models. Over the first year, a solid foundation was laid recruiting graduate and post-doctoral scholars who developed models and performed preliminary studies to map out interesting systems to explore. In year two, studies have advanced to examine delivery vehicle shapes, conformations, and free energies in depth, as well as to synthesize new vehicles to determine delivery efficacy. SD3 efforts are coordinated locally through weekly meetings and across campuses monthly via synchronous video.
CTCI: In collaboration with SD1, SD2 and SD3, CTCI is developing new techniques (compilation and runtime) for the effective execution of codes on GPUs (Graphics Processing Units), which have become an integral part of next-generation heterogeneous architectures. In collaboration with SD1, CTCI has developed the world's second fastest simulation of spin-glass models. Unlike our main competitor, our codes run on GPU supercomputers like those now being constructed by the NSF. In collaboration with SD1, we have attracted resources to purchase a 400TFLOP GPU supercomputer. In collaboration with all the SDs, CTCI is focused on new force-field development and analysis of data from simulations. In order to foster close collaboration between the SDs and CTCI, six graduate students have been placed on shared appointments with the SDs and have PhD advisory committees consisting of members from CTCI as well as the SDs. Our efforts are coordinated through weekly joint meetings with the SDs. Five CTCI researchers have led the way in teaching semester-long courses in high-performance computing, computational science and compiler optimizations, and are organizing a ‘bootcamp’ for Louisiana high school students and teachers.
Actions Taken in Response to Recommendations
II. Detailed Report
A. RII participants and participating institutions
See FastLane and Template A.
B. Program/Project Description
B. 1. RESEARCH ACCOMPLISHMENTS AND PLANS:
B.1.1. Science Driver 1: Electronic and Magnetic Materials
[M. Jarrell (LSU) and J. Perdew (Tulane)]
Program/Project Description
Methods Developed/Employed
|[pic] |
|[pic] |
|Figure 1: Current vs. Voltage for Polythiophenes |
|containing an in-chain cobaltabisdicarbollide . a) |
|DFT/Green functions simualtions. b) experiment [3]. |
|1T, 2T, 3T=one, two, and three thiophenes. |
1. Polythiophenes Containing In-Chain Cobalt Carborane centers: Experimental and computational explorations of cobalt-carborane complexes that are covalently linked to polythiophenes were performed to investigate their physical properties [1]. Polythiophenes are polymerized thiophenes, a sulfur heterocycle that can become conducting with doping of their conjugated π-orbitals. The goal of the work here was to assess the expected improvements to the electrical conductivity of these metallopolymers with the inclusion of the boron containing clusters that are known to contain delocalized electrons. J. Garno (LSU) performed atomic force microscopy (AFM) surface studies and conducting probe measurements of charge transport of these novel systems. Her conducting probe AFM characterizations indicate that polymers with bithienyl and terthienyl behave like heavily doped semiconductors rather than pure semiconductors, while the current-voltage (I-V) profile for poly-thienyl exhibits no measurable current consistent with the insulating character of the film (submitted). Related simulations of these structures by P. Derosa, and N. Ranjitkar (LaTech) employing Gaussian09 [2] determined the spin state of these systems. By using a variety of density functionals in their simulations, they concluded that the ground state system is in a spin singlet. In addition, they calculated the conductivity of these structures using Green’s functions on a density functional theory (DFT) Hamiltonian [3] which compared well to the conducting probe AFM measurements as shown in Fig. 1.
2. Magnetic and Multiferroic Materials
LaSigma supports several projects investigating multiferroic materials, materials that exhibit both ferromagnetic and ferroelectric properties, where there has been intense recent interest. S. Whittenburg (UNO) has expanded his micromagnetics code to include ferroelectric materials through the use of a Landau-Devonshire potential and correctly predicted the ferroelectric phase transition temperatures of BaTiO3. In addition, he has extended the code so that it can model the elastic properties of materials so that stress-induced changes to the morphology can be simulated. Thus, the electric or magnetic field induced stress, and the resulting shape changes, can be calculated and directly compared to the experimental results of several multiferroic systems being investigated with support provided by LaSigma. G. Caruntu (UNO), for example, has developed a novel experimental methodology for the local measurement of the strain-mediated magneto-elastic coupling in nanocomposite films. Here he employs an AFM tip to monitor the piezoresponse of a perovskite layer caused by the magnetostriction of a ferrite layer [pic][4-8]. LaSigma support to L. Malkinski (UNO) has also assisted the development of new technologies to form multiwall microtubes of magnetic or magnetic and piezoelectric materials where the magnetic properties have been found to depend on the curvature of the films. He is also involved in the investigation of thin Fe1-xNix alloy films whose composition varies across its thickness and displaying unusual hysteresis curves. In addition, he has explored liquid crystal/ferromagnetic nanoparticles composites where switching characteristics of the liquid crystal devices were found to depend on the applied magnetic field.
|[pic] |
|Figure 2: Optimized structure of an iron |
|cluster of the spinel-type moiety |
|[pic] |
|Figure 3: Fe1-xCoxSi nanowire device. |
|Successive magnifica-tions of a device |
|designed to measure the electrical |
|conducti-vity of a single crystalline |
|nano-wire. |
The understanding and control of the magnetic properties of nano- and microscopic materials is important for a large range of applications from pharmaceuticals to improvements in magnetic storage densities. A. Burin (Tulane) has used ORCA quantum chemistry software [9] (BPW91/LanL2DZ level) to model nanoscopic iron oxide clusters finding a high spin (S=12) ground state (Fig. 2) [pic][10, 11]. He plans on extending these calculations to include relativistic corrections [12] to rule out other, nearly degenerate, high spin states of this molecular magnet. Other calculations include the study of DNA base pair radical cations [13, 14] and the modeling of electronic glasses exposed to electric fields [15]. Related experimental work comes from the team of Kucheryavy, Goloverda, and Kolesnichenko (Xavier U.) which has produced ultrasmall superparamagnetic iron oxide nanoparticles in a surfactant-free colloidal form with sizes ranging from 4 to 8 nm. This was accomplished by varying the nucleation and growth conditions, and using a sequential growth technique. Since the T1 relaxivity for magnetite and its oxidized form, estimated by NMR, was found to be similar, they concluded that oxidized magnetite would be preferred as a more stable and potentially less toxic MRI contrast agent.
Several experimental investigations supported by LaSigma have both fundamental exploratory goals and offer a forum for direct comparison to computations. R. Kurtz and P. Sprunger (LSU) investigated the magnetic properties of FeAl where DFT calculations [pic][16-23] predict a ferromagnetic ground state at odds with experiment [pic][24, 25]. However, DFT+U methods find a paramagnetic state when U, the correlation energy, is sufficiently strong [26]. More interestingly, DFT indicates that the bulk terminated and incommensurate FeAl(110) surfaces may exhibit ferromagnetic ordering of the Fe atoms, with moments enhanced compared to the bulk [23]. In addition to magnetometry showing that the bulk is paramagnetic, their synchrotron X-ray magnetic circular dichroism (XMCD) measurements carried out at CAMD indicates no ferromagnetism at either the commensurate FeAl(110) or the surface reconstructed incommensurate FeAl2 surface [pic][27-29].
Other examples include the investigation of the magnetism of transition metal silicides, germanides and gallium compounds to explore their interesting magnetic and electrical transport properties by J. DiTusa (LSU). These materials are interesting and important because they are relatively simply grown, have crystal structures that lack inversion symmetry, and range from good metals, to magnetic semiconductors and small band gap insulators. They have explored bulk crystals and crystalline nanowires demonstrating the accurate control of Co dopants in FeSi at the 0.5% substitution level, the ability to measure the conductance of 20 nm wide nanowires to temperatures below 300 mK (Fig. 3), and the discovery of interesting behavior in the Hall effect of, Fe3Ga4. These results were presented by students at the 2012 March meeting of the APS and at a poster session at a Gordon Research conference on Strongly Correlated Electron Systems.
3. Iron-based superconductors and related materials. Since their discovery in 2008, iron-based superconductors have generated intense scientific interest because they seem to have an unusual underlying mechanism and because they may provide a next generation of high-temperature superconductors. The complex interplay between magnetism and superconductivity in these materials suggests that the attraction needed to form bound electron pairs could be provided by spin fluctuations [pic][30-34]. The typical crystal structure is layered tetragonal, with layers of positive iron ions separated by layers of negative ions. Most of the iron-based superconductors are pnictides, such as BaFe[pic]As[pic]. An exception is the binary iron chalcogenide material Fe1+y(Te1–xSex), with the excess Fe occupying interstitial sites of the chalcogen layers.
A systematic investigation of transport, magnetic, and superconducting properties of the phase diagram of the chalcogenide material using resistivity, Hall coefficient, magnetic susceptibility, specific heat, and neutron scattering was reported in 2010 [pic][35]. Leonard Spinu is completing this picture by measuring the London penetration depth in single crystals at ultra-low temperatures as a function of temperature and Se concentration (25% to 45%). The penetration depth of a magnetic field is one of the most important characteristic parameters in a type II superconductor, because it can give information about the pairing mechanism. Its zero-temperature value is directly related to the density of superconductive electrons in the crystal, and its low-temperature behavior can give insight into the pairing symmetry and pairing energy gaps. The measurements employ a tunnel diode oscillator set up in a dilution refrigerator that can reach temperatures as low as 40mK. Results were presented at several conferences [36, 37].
The Zhiqiang Mao group has synthesized a new layered iron pnictide CuFeSb [38]. In contrast with the metallic antiferromagnetic or superconducting states of other iron pnictides and chalcogenides, this material exhibits a metallic ferromagnetic state with a Curie temperature of 375 K. This finding suggests that a competition between antiferromagnetic and ferromagnetic coupling may exist in iron-based superconductors. It also supports theoretical predictions [39, 40] that the nature of the magnetic coupling within the iron plane depends on the height of the anion plane above the iron plane (~1.8 Å for the Sb plane in CuFeSb vs. ~1.4 in FeAs compounds).
In strongly-correlated materials such as those discussed above, there is typically a close coupling between structure, charge, and spin, leading to a competition among several phases at low temperature. Structural changes in the topmost layers that occur at surfaces or crystal-vacuum interfaces are interesting in themselves and can also drive changes in material functionality. Ward Plummer and Von Braun Nascimento are measuring surface structure in complex materials via low energy electron diffraction (LEED) [41], since the electron beam penetrates only into the surface region. But the analysis of LEED data is an inverse problem: one must search for the surface structure that yields a given diffraction pattern. The Plummer group has developed novel LEED codes that use global search algorithms [42] and can also tackle the structural determination of multiple terminated crystallographic surfaces. A LA-SiGMA supported graduate student, Diogo D. dos Reis, is participating in this work. The codes have been tested successfully for BaTiO3 ultra-thin films [42], and will next be applied to multi-phase (001) surfaces of the BaFe2As2 and Ba(Fe1–x Cox)2As2 iron pnictide superconducting materials.
4. Broad-impact computational methodologies. The computation and theoretical prediction of materials properties must confront the electron-electron interaction, which ties the electrons together into a correlated whole. Correlated wavefunction methods, including Quantum Monte Carlo (QMC) [43], are computationally inefficient for systems of many electrons. One way to deal with this problem is to perform the wavefunction calculations for small systems, to introduce multiscale corrections, and to then extrapolate calculated properties to larger or infinite systems. The remaining problems are then to do the wavefunction calculations efficiently for small systems and to find effective multiscale corrections. The other and more common way is to use Kohn-Sham density functional theory (DFT) [44], an orbital-based approach in which the electron exchange-correlation energy is provided by a functional of the electron density that must be approximated in practical calculations. The remaining problems are then to improve the accuracy of the available approximations, to understand long-range correlations including van der Waals interactions, and to deal with the fact that even the exact Kohn-Sham band structure can underestimate the fundamental energy gap of a solid [45].
Mark Jarrell and Juana Moreno, with C.E. Ekuma, Z. Meng, S. Feng, and C. Moore, are developing multiscale methods for disordered and interacting systems. They have found that graphics processing units (GPU’s) greatly accelerate materials simulations, including simulations of Ising-model glasses [46, 47] and QMC calculations. They are developing QMC codes tuned [pic][48, 49] for the next generation of Kepler GPU’s. To incorporate nonlocal correlations systematically, they have proposed a Cluster Typical Medium Theory (CTMT) that opens a new avenue to the study of Anderson localization in both model and real materials, unlike the coherent phase approximation [50] and its cluster extensions, including the DCA [51]. The idea is to extend the Typical Medium Theory [52], which replaces average quantities with typical values, to its cluster version. They have also shown that size extrapolations of calculated properties over multiple scales can converge much better if three length scales are invoked: the shortest one for explicit correlation, an intermediate one treated perturbatively, and a longest one treated for the first time via mean field correlations [53]. Finally, they have used density functional theory to generate a band structure for (Ga,Mn)As and (Ga,Mn)N, then applied a Wannier-based downfolding method [54] to get effective interacting Hamiltonians.
The van der Waals interaction is a weak long-range attraction between two objects due to correlations among their fluctuating multipole moments. It is most important when the objects are not otherwise strongly bonded, as for two biological molecules or nanostructures. The accurate calculation of this interaction via many-electron wavefunctions or DFT is feasible only for a pair of atoms or small molecules. Thus standard intermolecular interactions are often based on an atom pair potential picture. Jianmin Tao, John P. Perdew, and Adrienn Ruzsinszky have shown [pic][55-57] how to evaluate this interaction between two quasispherical objects accurately and efficiently, using just the electron densities and static dipole polarizabilities. They have found that the atom pair potential picture is correct at best for the interaction between two solid spheres, but not when one or both objects are spherical shells (e.g., fullerenes). Other work from the Perdew group [pic][58-62] concerns improvements to semilocal and nonlocal DFT approximations. The fundamental gaps in the Kohn-Sham band structure are maybe 20-100% too small compared to experiment. Diola Bagayoko and C.E. Ekuma have shown how to find accurate gaps and other properties by using a basis set of atom-centered orbitals which is extended only so far as it must be to predict accurate occupied orbitals [pic][63-69]. This method has been applied to ZnO [65] [65], ScN [66], YN[66], SrTiO[pic][67], Ge [68], and InP [69].
B.1.2. Science Driver 2: Materials for Energetic Storage and Generation
[C. D. Wick (Louisiana Tech) and L. Pratt (Tulane)]
Program/Project Description
Efficient and clean generation and storage of energy is a major challenge facing our nation and the world. The major focus of the SD2 research area is to develop a molecular level understanding of different energy storage and generation processes, and the how catalysis works to create fuels and harmful bioproducts from energy generation. We have three major thrusts that have been outlined in the proposed work that include investigations into supercapacitors, hydrogen storage materials, and catalysis. We have supplemented this with a new thrust related to lithium ion batteries, which shows greater potential for future funding opportunities related to battery technology. To address these challenges, we are implementing a multidisciplinary strategy that utilizes a variety of computational methods, mathematical models, and experimental measurements. They are designed to bridge length and time scales that can link electron behavior with macroscopic kinetic and thermodynamic properties.
Methods Developed/Employed
The work makes use of a variety of methodologies, ranging from ab initio electronic structure calculations to force field based molecular simulations to mathematical models. This work is also complemented by experimental measurements to verify any computational predictions made, but also the computational methods complement the experimental measurements to bring molecular level insight into the experiments. There is also a significant portion of this research in method and model development including new mathematical analyses of experimental data, mathematical models to predict macroscopic kinetics, and the paramerization of new molecular models or force fields to scale up the investigation of computational materials. It is important to develop these methodologies/models to bring our computational investigations closer to real world applications by either predicting macroscopic properties or investigating systems that more closely resemble realistic systems in size and timescales. The interdisciplinary manner of this research is focused on bring together a variety of experts to enhance the impact of the proposed research in both scope and viability.
Goals and Milestones
• Recruit, engage, and mentor a gender and ethnically diverse group of students and postdocs. Our success is described in the following section.
• Develop algorithms that combine chemistry and physics of energy storage. Our success is described under Foci 1 and 2.
• Develop new force fields for catalytic processes based on DFT functionals. Our success is described under Focus 3.
Hiring and Recruiting
Dr. Ayorinde Hassan was recruited as a post-doctoral fellow at Louisiana Tech to work on catalytic materials and the new direction to be described below. Dr. Hassan is black, of African origin.
Focus 1: Electrochemical Capacitors and Fuel Cell Electrodes
Electrochemical double-layer capacitors based on carbon nanotube forest (W. Zhang, G.G. Hoffman, L.R. Pratt, and N. Pesika, K.M. Aritakula and S.W. Rick)
Carbon nanotubes aligned on metal surfaces (nanotube forests) can have very high capacitance making them attractive materials for supercapacitors [70]. These materials consist of the carbon nanotubes, a solvent, propylene carbonate (PC), and an ion pair. By combining experiment, ab initio, and classical molecular dynamics (MD), we are developing the computational tools necessary to improve the design of capacitor materials, by improving energy densities while retaining good power densities [71]. First we need to verify that our molecular model used for classical MD simulations describes interactions between PC and graphite surfaces. To assess this, we carried out measurements of the contact angle between PC and graphite, which assesses the relative interaction strength between PC and graphite (see figure 1). We used this comparison to adjust our PC molecular model and its interactions with graphite to bring agreement between simulation and experiment.
Another aspect of importance is to understand how charge is carried and distributed in the electrochemical double-layer capacitors. Using ab initio MD with an 80-carbon atom nanotube and one tetra-methylammonium cation (TMA+), the total electron density, electrostatic potential and electron partial charges were extracted. The charges on the ion (see figure 2) for nine different configurations varied substantially with the distance from the carbon nanotube, indicating significant charge transfer between the ion and the nanotube. These ab initio results can be used to develop molecular models for classical simulations which include charge transfer, enabling accurate simulations for longer time and larger length scales than can be done at the ab initio level [72].
Focus 2: Thermodynamics and Kinetics in Hydrogen Storage Systems.(D.S. Mainardi and W. Dai)
The impact of dopants on the stability, dynamics, electronic structure and dehydrogenation properties of NaMgH3 have been studied using first-principle calculations. This investigation is based on methodology proposed by Dathar et al. [73] and findings by Wang et al. [74]. In this respect, the theoretical investigations shows that higher cohesive energies correlate with higher energies in the doped bulk model as illustrated in Figure 3. The partial doping of NaMgH3 results in stronger covalent bonds between transition elements such as Ti and Mg-H atoms, and a weaker interaction between Mg and H with respect to pristine NaMgH3. Based on our electronic structure analyses, NaMgH3 alloyed with co-dopants such as Ti, V, and Zn provides a viable pathway for destabilizing the bonding nature between Mg and H atoms of the material. Therefore, Gibbs Free-Energy Barrier values for desorption of H2 from transition metal doped NaMgH3 surface models show that hydrogen desorption energies can be reduced. This is in agreement with past experimental studies [75]. This finding prompt the research on the synergistic effect of co-dopants on a core/shell doped nanocluster (figure 4) to facilitate hydrogen desorption. Preliminary results of theoretical investigations conducted on nanoclusters show a positive correlation between cohesive energy and dehydrogenation energy. Furthermore, in nanocluster models, the dehydrogenation energy is lower than in bulk models, in agreement with previous computational studies [76].
To scale up some of this understanding to macroscopic reactors. We investigated metal-H2 reaction systems, which may become a practical means of storing hydrogen [77, 78]. However, the critical issues for storage materials, such as Mg, La, Li etc, are the amount of hydrogen absorbed/desorbed, thermal stability of the hydride, hydrating/dehydrating kinetics, thermodynamics and thermo-physical properties, crystal structures, surface processes like segregation, carbonization [79]. Efficient conditions to form metal alloys become the main targets. LaNi5 (Lanthanum and Nickel) is the most promising alloy because of its low working temperature and pressure, great number of hydrating/dehydrating cycle capacity and physical chemical characteristics, such as unchanged practical size, phase composition and processing at low temperature. We have developed 2D mathematical models governing the hydrogen absorption/desorption in LaNi5 – H2 cylindrical reactors and numerical schemes. The mathematical model includes the continuity equations for hydrogen and metal, momentum equations for hydrogen, and energy equation for hydrogen and metal, as well as the Neumann and Robin’s boundary conditions. Numerical results including temperature, gas and solid densities, and gas velocity, as well as pressure were obtained (see figure 5 for an example).
Focus 3: Investigation of Catalysis
Metal Oxide Clusters and Force Field Development (R. Hall, B. Dellinger, C. Wick, B. Ramachandran)
Polychlorinated dibenzo-p-dioxins/furans (PCCD/Fs) are toxic materials that can form on the surface of nanoscale metal oxides present in the environment in hazardous waste incinerators, auto exhaust and cigarette smoke [80]. The factors that facilitate the formation are being studied using a combination of computational methods and experimental measurements. Specifically, the studies demonstrate the reduction of metal particles by the dioxin and furan precursors is a stabilizing factor that leads to enhanced reactivity [81]. We are carrying out ab initio calculations (DFT with hybrid functionals) to determine how the structure of small copper oxides (CunOn) n=1-8 reactions with phenol, ortho-chlorophenol and para-chlorophenol. This study aims to identify the mechanism of their formation with the goal of developing procedures to prevent or hinder the formation reactions. Adsorption of, for example, phenol or a chlorinated phenol to a metal oxide cluster is the first step of the formation of PCDD/Fs [82]. The clusters are “hydroxylated” due to the presence of water in the environment. The reaction product of hydroxylated Cu5O5 with 2-chlorophenol is shown in Fig. 6.
While ab initio computational methods are well designed to investigate catalytic behavior of small clusters, most catalytic activity occurs at the surface of nanoparticles or in nanopores, which are larger than can be investigated with traditional ab initio methods. To facilitate the investigation of catalytically active nanoparticles and nanopores, a force field is being developed based on ab initio calculations of small clusters that can be used to investigate material properties for these larger materials. Our recent progress has developed a force field to describe copper oxides and aluminum oxide. Despite making all parameterizations to small clusters (fewer than 100 atoms in all situations), we have developed a model that does a good job of reproducing their bulk crystal structure (see Table 1). We are currently expanding the models to investigate reactive catalysis at the surface of the metal oxides, to allow a truly multi-scale approach to be used to investigate catalysis.
Advances in Ab Initio Predictive Calculations for Properties of Materials (D. Bagayoko, G.L. Zhao, M. Jarrell, J. Moreno)
The critical importance of our work in this reporting period stems from the very many current and potential applications of the materials we studied (SrTiO3, Ge, ScN, YN, InP, and ZnO) and from the excellent agreement of calculated properties with corresponding, experimental ones, as this agreement paves the way for accurate, descriptive and predictive calculations of properties of materials [pic][65-67]. This statement holds for electronic, catalytic, photonic, magnetic, structural, optical, and related properties of existing or novel materials.
Identification of Catalytic Sites on Nitrogen Doped Carbon Nanotubes as New Catalyst for Hydrogen Fuel Cells (G.L. Zhao and S. Yang)
Understanding and identifying the elementary steps of catalytic reaction mechanisms and dynamics of catalyzed transformations have been identified as a grand challenge for catalysis research. We carried out an ab initio investigation of how doping carbon nanotubes (CNTs) with nitrogen affects its ability to catalyze oxygen and hydrogen for fuel cells without the need for expensive precious metals [pic][83-85]. Our results show that nitrogen prefers to be at the open-edge of the CNT, and oxygen can adsorb and partially reduce on the carbon-nitrogen complex site [86]. We investigated this further and found that the Pauling site is a catalytic for the reduction of oxygen, and investigated potential pathways for its catalyzed rection with hydrogen to form water. This work is building towards our goal of designing new catalysts through computer-aided simulation for reducing Pt loading in energy technology applications.
Changes in Research Direction, Future Work Investigating Lithium Ion Batteries (L. Butler, C. Wick, B. Ramachandran, L. Meda)
We are developing new in situ experiments to make real-time observations of the performance of lithium-ion polymer batteries. These are important to investigate the mechanism for electrode degradation, allowing the ability to maximize their lifetimes. Currently, Phase Contrast X-ray Imaging (APS/LSU): Researchers at APS have temporarily built an X-ray interferometer at APS 32-ID to collect data, but its analysis a great challenge. Consultation with an LSU gravity wave physicist led to a new algorithm that reduced computation time from an estimated one-half year to an hour. A second problem has been X-ray optics instability in the test system at APS; more consultation has yielded another new algorithm for unwrapping phase drift errors.
Nanostructured thin films of transition metal oxides such as (RuO2)n have been found to be extremely promising as electrode materials for increasing the energy density of solid-state lithium ion batteries [87]. We are investigating the structure and energetics of (RuO2)n clusters ab initio (DFT) calculations [88], and determining the voltage and structure for the addition and reduction of up to two lithium ions. We have determined how lithium ions affect the structure of the clusters, and are working towards determining the most probable pathways for lithium oxidation and reduction. This work is being complimented by experimental measurements to compare our structural and energetic results with.
B.1.3. Science Driver 3: Biomolecular Materials
[H. Ashbaugh (Tulane) and D. Moldovan (LSU)]
Program/Project Description
SD3 encompasses multi-disciplinary teams of scientists, post-docs, and graduate students from five institutions (Tulane, LSU, LSU-Ag, UNO, and LATech) that combine theoretical/computational scientists with experimentalists working together to develop methodologies for building new predictive models of unimolecular and self-assembled vehicles for targeted drug delivery. The SD3 research projects are conducted under two focus areas: focus 1: Unimolecular delivery vehicles, and focus 2: Self-assembled delivery vehicles.
Methods Employed/Developed
New computational methods are being developed on several fronts within SD3. Specifically, Ashbaugh and Rick are working to port/validate the previously developed Replica Exchange with Dynamical Sampling (REDS) [89] for sampling equilibrium biomolecule conformations in solvent onto LONI. Moldovan and Nikitopoulos are continuing to work with LAMMPS developers at Sandia to link explicit molecular dynamics simulations with commercial CFD solving packages. Mobley has developed a new automated tool for performing high throughput free energy analyses on thousands of systems. Applications of these methods are described below under Research Accomplishments.
Goals and Milestones
The goals of the SD3 team are to develop, apply, and experimentally validate multi-scale computational tools to enable the design of novel unimolecular and self-assembled drug delivery vehicles. To achieve these goals the following milestones were set for the second year: i) Synthesize modular library of core molecules and amphiphilic side chains to explore encapsulation based on architecture and chemistry, ii) Develop new inter-atomic interaction potentials and new coarse-grained force fields for systems containing both biological and non-biological molecules; iii) Develop new hybrid MD/continuum and coarse-grained and accelerated simulation strategies to link length and time scales in biological systems; iv) Synthesize, characterize, and assess new trans-membrane drug delivery systems.
Recruiting, Hiring, and Project Coordination
In the first year of this project SD3 successfully filled the majority of the graduate student and post-doctoral positions allocated to this driver. In year two, we filled vacant positions, including a new post-doctoral scholar, S. Paraeswaran, and a new graduate student, Janene Baker, both working under S. Rick and D. Mobley at UNO and in collaboration with H. Ashbaugh at Tulane. Additionally in year two, Anne Robinson, was recruited as department chair of Chemical and Biomolecular Engineering at Tulane and joined LA-SiGMA as a faculty member of SD3.
Research Accomplishments
Utilizing the resources made available through LA-SiGMA over year two we continue to make significant progress in achieving the research goals and milestones of both SD3 focus areas. Below we detail progress in each research project undertaken over the second funding year.
Focus 1: Unimolecular delivery vehicles
Simulation of polymeric drug delivery carriers: [H. Ashbaugh (Tulane), L. Liu (Tulane), S. Grayson (Tulane), S. Rick (UNO), and S. Parameswaran (UNO)]. In the Ashbaugh lab a study of the temperature induced collapse transition of poly(n-isopropylacrylamide) in aqueous solution was performed as a potential trigger for drug release from gels. Large-scale simulations were carried out at LONI using replica exchange molecular dynamics, allowing an unprecedented characterization of conformational populations over a broad temperature range. As a result, the thermodynamics of the collapse transition were characterized for the first time via a two-state model, demonstrating the hydrophobic origin of this unusual behavior. This project advances milestones ii and iii.
The Rick and Ashbaugh groups are presently developing models and strategies for simulating the linear and cyclic amphiphilic polymer delivery vehicles synthesized by Grayson [90]. DFT calculations have been carried out to assign partial charges and preliminary simulations have been performed to examine vehicle conformations in water (Figure A). Over the next year, simulations will be carried out using the REDS [89] algorithm developed by Rick to more comprehensively sample polymer conformations in polar and non-polar environments. This project advances milestone iii.
|[pic] |
|Figure 8. Initial and final molecular dynamics simulation snapshots of linear amphiphilic delivery vehicles in water. Similar conformations |
|are observed for cyclic amphiphilic delivery vehicles. |
Synthesis of new unimolecular drug delivery vehicles: [S. Grayson (Tulane) and Y. Yang (Tulane)]. Research in the Grayson laboratory has shifted towards efficient means of assembling novel amphiphilic polymeric components via efficient “click” couplings [91]. The two conjugation reactions that exhibit the most utility are the copper-catalyzed azide-alkyne coupling, and the thiol-ene reaction. The versatility of this modular approach – the synthesis of individual amphiphilic components and the assembly of multifunctional amphiphilic polymers – requires substantial input from modeling in order to direct synthetic efforts. The modeling efforts of Ashbaugh and Rick (above) provide insight into the most effective means for preparing amphiphilic systems which are likely to assemble into discreet nanometer sized carriers that are of most use as biological delivery vehicles. This project advances milestones i and iv.
Nanoparticle delivery to cancer tissues: [P. DeRosa (LATech)]. Diffusion of nanoparticles in blood vessels and tumors was simulated using a combination of fluid dynamics and Monte Carlo. The model accurately predicts particle delivery to tumors as a function of relevant parameters such us blood pressure, particle size, pore size, interstitial pressure and nanoparticle concentration. This year activities were aligned with Patrick O’Neal’s (LATech) experimental group, and common ground for validating our simulation predictions have been established. This project advances milestones iii and iv.
Focus 2: Self-Assembled delivery vehicles
Simulation studies of span-80 assembly [D. Moldovan (LSU), C. Sabliov (LSU-Ag), D. Nikitopoulos (LSU), H. Ashbaugh (Tulane), B. Thakur (LSU), B. Novak (LSU), R. Kumuditha (LSU), J. Lin (LSU), and K. Xia (LSU)]: Span-80 is nonionic surfactant whose assembled structures might be used for drug delivery. Improved potential energy parameters for span-80 were previously developed, leading to simulated densities in agreement with experiment. The self-assembly behavior of span-80 in water was also different with the improved parameters. With the improved parameters, span-80 was found to form curved bicelles (bilayer with closed edges) in water (Figure B), in difference to the original parameterization that only predicts spherical micelles. This structure is a precursor to vesicles, which have been observed for span-80 [92]. The simulation was terminated after 200 ns, and it was determined that the time and length scales for the self-assembly of span-80 are beyond the capability of atomistic simulations. A periodic span-80 bilayer will therefore be used to study drug molecule interactions as a model for a vesicle patch. This project advances milestones ii and iii.
Hybrid MD-continuum simulation methodology for biomolecular systems: [D. Nikitopoulos (LSU), D. Moldovan (LSU), K. Hesary (LSU), B. Novak (LSU)]. Work has been conducted towards further development of formalisms and computational tools for coupling continuum CFD and MD simulation codes for study of non-equilibrium flow phenomena in mixed-scale domains involving biological materials. Kasra Hesary, working with the group, has successfully used these tools to couple LAMMPS to a commercial continuum code (ANSYS/ Fluent) and verified the results for simple test problems. The hybrid simulation implementation was tested using sudden-start Couette flow in single and two-phase systems, demonstrating the capability of these hybrid tools to yield quantitative predictions in agreement with analytical solutions. Currently we are working with CTCI colleagues to leverage use of CPU/GPU computing to further accelerate these simulations. This project advances milestone iii.
|[pic] |
|Figure 9. Simulation snapshots of a single span-80 monomer and a self-assembled span-80 bicelle. |
Polymeric nanoparticle-cell interactions [C. Sabliov (LSU-Ag), S. Grayson (Tulane), D. Moldovan (LSU), and R. Devireddy (LSU)]: The entrapment of bioactive compounds in polymeric nanoparticles enhances cellular uptake, drug efficacy, and drug stability. Particle size (1nm - 1μm), surface charge, and hydrophobicity play a vital role in the ability of nanoparticles to be endocytosed by the cell. Poly (lactic-co-glycolic) acid (PLGA) and chitosan-coated PLGA particles (PLGA/Chi) were developed to utilize the mucoadhesive property of chitosan and PLGA’s ability to efficiently entrap hydrophobic and hydrophilic drugs. PLGA and PLGA/Chi NPs loaded with antioxidants were synthesized and characterized. Particles measured 120 nm on average, with 100% entrapment efficiency. TEM clearly indicates PLGA particles aggregate under acidic conditions, while Chi/PLGA particles aggregate near neutral conditions. Loss of the positive charge of Chi/PLGA NPs near the pKa of chitosan (~6.5) adversely affects their mucoadhesive capacity and uptake. To ensure a positive charge of the nanoparticles under neutral physiological conditions, a chemically modified chitosan soluble at basic pH was synthesized and particles was made. The effect of size and charge on NP uptake will be assessed in Caco-2 cells over the next year. This project advances milestone iv.
Strategies for free energy evaluation in biomolecular systems: [D. Mobley (UNO), S. Rick (UNO), J. Baker (UNO), and H. Ashbaugh (Tulane)]. Over the past year an automated method for planning relative free energy calculations has been developed, enabling high throughput free energy estimates for as many as tens of thousands of systems. This work has been presented at national and international meetings, and this tool will be publicly distributed. We also have an ongoing collaboration within SD3 on improving sampling of biomolecular interactions, and are applying a new weighted ensemble technique from collaborators at the University of Pittsburgh to these problems. We continue to work on improving free energy techniques for molecular design in the context of biomolecular interactions, testing these techniques with applications to DNA gyrase and trypsin. This project advances milestone iii.
Changes in research direction, future work
Anne Robinson’s addition has initiated new research on tau-protein fibrogenesis [93]. In collaboration with Ashbaugh, an REU student has been recruited in the summer of 2012 to explore this direction. This new project is an addition to SD3’s ongoing efforts in drug delivery vehicles.
B.2. DIVERSITY AND BROADENING PARTICIPATION, INCLUDING INSTITUTIONAL COLLABORATIONS
Strategy One:
The Diversity Advisory Council (DAC) has been established. There are 5 out-of-state members and 2 in-state members (Dr. Warner resigned), 86% are women, and 57% are African American.
They met on August 6, 2011 to provide feedback to the EEWD Committee. The DAC suggested that the Industrial Liaison Team needed to add a member from an HBCU. LA-SIGMA followed that suggestion and Rachel Cruthirds (from Xavier) has joined.
The DAC also suggested that LA-SIGMA faculty advertise to GEM scholars, which are highly sought after URM undergraduate students that are considering graduate school in a STEM field. The EEWD committee drafted a recruitment letter and sent it to the 2012 GEM list.
They will also meet on July 23, 2012 at the second annual RII Symposium.
*The LA-SiGMA External Engagement and Workforce Development Committee has created a document with existing and planned diversity strategies at each school that will serve as a starting point with our discussion with the DAC. * Are we updating the document?
Strategy Two:
LA-SiGMA has announced supplemental research assistantships for women and URM graduate students to all faculty LA-SiGMA members. These supplements offer \$3750 to \$7500 to women and URM graduate students on a competitive basis.
LA Tech-Dwayne Teamer, an African-American, was recruited into the PhD program by
Daniela, he was given a fellowship worth $30K + tuition, but he has changed
advisors and is no longer associated with LA-SiGMA.
We have one LSU student gathering the application materials for the supplement.
Strategy Three:
LA-SiGMA has announced the availability for funds to supplement department start-up packages to LA-SiGMA institutions to recruit new URM and female faculty members with research interests in Materials Science.
Tulane used the funds to recruit Anne Robinson. LA Tech used the funds to recruit Erica Murray. Erica Murray, an African-American female and Research Assistant Professor at IfM, has been included in the LA-Tech team as a collaborator. LA-SiGMA is providing support for one student and lab supplies for Erica.
Strategy Four:
The LA-SiGMA outreach coordinator has collected contact information for existing 3+2 and 4+1 programs in the state with the goal of creating pipelines for students to LA-SiGMA institutions and contacted the program leaders in 2011.
The SUBR program is not currently active.
The GSU/LA Tech program is working-LA Tech has agreed to allowing GSU undergraduate students to enroll in LA Tech graduate courses.
Xavier has an active 3+2 program with Tulane. We have one LaSiGMA student who transferred to Tulane last year and she is majoring in Biomedical Engineering and will graduate next year.
Ongoing Milestones for Strategic Plan for Year 2:
Hold Annual DAC Meetings-Second Annual Meeting planned for July 23, 2012
Reach 30% women and 15% URM graduate students within the Alliance by Y3-ACTUAL:
Year 2: 24% female graduate students, 15% URM graduate students
Recruit at least 5 students through pipelines described in proposal by end of Year 2.
B.3. WORKFORCE DEVELOPMENT:
Strategy One-Outreach to High Schools:
One graduating student from the Louisiana School for Math, Science, and the Arts has been selected to participate in the LA Tech REU program. Open House events have been held at LA Tech/Grambling University and LSU. Tulane plans to hold an Open House in Fall 2012.
Dr. Grayson (Tulane) has undergraduate students working with a local high school to develop Chemistry AP program. They provide demonstrations and tutor students who have little access to other resources.
Strategy Two-RET:
Research Experiences for Teachers programs are offered annually in New Orleans, Baton Rouge, and Ruston. For the summer of 2012, four teachers have been selected for LSU's program, three for Southern University’s program, three for Tulane’s program, and five for LA Tech/GSU's program. Of the fourteen teachers, nine are male, they teach at a mix of public and private schools, and two of the teachers are faculty members at the Louisiana School for the Math Science and the Arts. The teachers will conduct research in LA-SiGMA faculty members' labs, attend weekly professional development seminars, and present their research findings at the end of each program. A follow up survey from Year One RET participants was conducted in April 2012.
Strategy Three-Community Colleges:
LA Tech offered a short course in the Fall of 2011 in Advanced Microscopy Techniques. The 2012 Beowulf Boot Camp for high school students and teachers plans to add one Baton Rouge Community College instructor and one Baton Rouge Community College student to study how to best reach out to community college students. LA-SiGMA is also sponsoring the workshop with funding. Two community college students are participating in the REU program-one at LSU and one at SUBR. Two community college faculty members are participating in the RET program as well.
Strategy Four-REU:
The REU is a nine week program where students work collaboratively on a wide variety of computational science projects. LA-SiGMA provides six different sites and numerous projects for the REU student to become familiar with interdisciplinary research. The participants work on cutting edge research in material sciences and computational tools.
The students will learn how to use the most current cyberinfrastructure tools with individually designed training sessions targeted to their specific degree of preparation. In addition, since most LA-SiGMA research groups collaborate with international researchers, REU students are exposed to how international collaborations work. This program is in its second year, and for the summer of 2012, 26 students have been selected (5 at LSU, 5 at LA Tech, 4 at Tulane, 5 at SUBR, 5 at Tulane, 2 at Xavier). A follow up survey from Year One REU participants was conducted in April 2012.
Strategy Five:
Workshops and graduate level courses are being presented to give LA-SiGMA graduate students a transformative educational experience in materials science.
Two Courses were offered during Fall 2011:
Randy (LSU) taught Statistical Mechanics.
Adrienne (Tulane) taught Solid State Physics.
Three Courses were offered during Spring 2012:
Juana (LSU) taught Computational Physics.
Mark (LSU) taught Many Body Theory.
Les (LSU) taught 3D+ Visualization: Avizo, VisIt, and Mathematica.
*I don’t know of any workshops offered specifically for LA-SiGMA students in Year Two.*
Supada Laosooksathit attended Supercomputing '11 in Oregon along with Tom Bishop. They had been selected by the LittleFe project () to receive a mini-supercomputer. The computer
has been transported back to LA Tech and is being used in various outreach events and in teaching. Travel funds were used to take 5 students (1PhD, 2MS, and 2 undergrads) to the Louisiana Academy of Science meeting.
Strategy Six-Postdocs Professional Development:
Internships & Travel:
Pavel Kucheryavy (a post-doctoral research associate at Xavier) traveled to New York University in June 2011 to learn about NMR relaxivity measurements. He is using this knowledge in our current project. He will also attend the 9th International Conference on the Scientific and Clinical Applications of Magnetic Carriers in May, 2012, then the National ACS meeting in August 2012.
LA-SIGMA has contracted with Dr. Cynthia Sisson and Dr. Stephanie Aamodt at LSU-Shreveport to develop a LA-SIGMA workshop for Postdocs and senior level graduate students based on Michigan State’s FIRST program (Faculty Institute for Reforming Science Teaching). The FIRST program in Michigan is based on Life Sciences, so Drs. Sisson and Aamodt are customizing a program for LA-SiGMA; the first workshop will be held in July 2012. Participants will attend remotely, and the workload will be about 10 hours per week. Drs. Sisson and Aamodt will hold online video chats once a week to check in with students and monitor their progress.
Ongoing Milestones from Strategic Plan:
Increased Attendees at Open House Events-
20 RET Participants each year-
Expansion of Short Courses in Year 2-
Five two-year college participants in Beowulf Bootcamp-behind schedule
Expansion of 2+2 and other programs by Year 3-
30 REU participants each year-50% will pursue higher education
Incorporation into graduate curricula on two campuses by Y2-
Participation in Effective Teaching Workshops-will occur in July 2012
Five internships and extended visits each year-
B.4. CYBERINFRASTRUCTURE:
[J. Ramanujam (LSU) and S. Dua (LA Tech)]
Program/Project Description
The ‘glue’ that holds the three SDs together are the formalisms, algorithms and codes being developed in this project. Therefore, to achieve the goals of this RII project, a cybertools and cyberinfrastructure (CTCI) group of participants, led by Ramanujam at LSU and Dua at LaTech, are working to enable Alliance members to more efficiently utilize the next generation of high-performance computers. CTCI includes members of all of computational and science driver teams, drawn from LA Tech, LSU and Southern. There has been significant interaction between the science drivers and CTCI, including regular meetings with researchers from the science drivers and sharing of students. The coming generation of heterogeneous and multicore machines will present challenges that can only be overcome with the shared experiences of the CTCI teams and applied mathematicians [Lipton and Bourdin (LSU), Dai (LA Tech)], and Li (SU) and experts in high-performance computing [Jha, Koppelman, Ramanujam (LSU) and Bishop and Leangsuksun (LA Tech)] and data analytics [Dua (LaTech)].
Methods Employed/Developed
During the second year so far, the CTCI group has focused on the following issues: (a) Development of novel compilation techniques [Ramanujam (LSU)]; (b) Development of high-quality codes for parallel tempering and quantum monte carlo techniques; (c) Parallel programming tools [Leangsuksun (LA Tech)]; (d) Execution management tools and environment [Jha (LSU), Bishop (LaTech)]; (e) integration of CFD and MD simulation techniques; and (f) Analysis of MD simulation data [Dua (LA Tech)].
Progress towards Goals and Milestones
A major research goal of CTCI is to collaborate with the computational teams in the development of: (1) Next Generation Monte Carlo Codes, (2) Massively Parallel Density Functional Theory and Force Field Methods, and (3) Large-scale Molecular Dynamics. In order to achieve the proposed goals, the following milestones were set for year 2: (i) development of techniques to achieve good performance on GPUs for Monte Carlo and Parallel Tempering codes; (ii) development of programming models and compilation support for the developed codes; (iii) develop software support for execution management; and, (iv) work on analysis techniques for MD simulation data.
Recruiting, Hiring and Project Coordination
In the second year of the project, CTCI has recruited a new postdoc and a new graduate student to complement the postdoc and the shared graduate students continuing from Year 1. The students are shared between faculty in CTCI and the three SDs. CTCI participants have been engaged in weekly meetings with the science drivers on several aspects including code development and compiler optimizations for GPUs and support for execution management.
Research Accomplishments
Focus 1: Next Generation Monte Carlo Codes:
Monte Carlo (MC) simulations can bypass long time scales by directly calculating free energies associated with activated (long time) processes and by allowing dynamical properties to be studied without following the dynamics serially. Efforts in this area have focused on programming tool and compiler solutions for this problem, in addition to closely working with the Monte Carlo computational team and SD1.
Compilers and Tools [Ramanujam (LSU), Leungsuksun (LaTech)]: The emergence of GPUs as cost-effective and powerful processors for general-purpose computing has raised interest in their use for many scientific and engineering applications (e.g., due the availability of the CUDA programming model on NVIDIA GPUs) but further exacerbates the software development challenges. Hence, the automatic transformation of sequential input programs into efficient parallel CUDA programs is of considerable interest. Recently, Ramanujam (LSU) and others have started work on developing an end-to-end automatic C-to-CUDA code generator using a polyhedral compiler transformation framework. We have used and adapted PLUTO [BH+2008] (our state-of-the-art tool for polyhedral compilation) and other publicly available tools that have made polyhedral compiler optimization practically effective. The result is a C-to-CUDA transformation system that generates two-level parallel CUDA code that is optimized for efficient data access. Experimental results demonstrated the performance improvements achieved using the framework. Leangsuksun (LaTech) has collaborated with Alex Safarenko and Sven-Bodo Scholz (Univ. of Hertfordshire, UK) in parallel programming tool development. The project is based on a SAC (Single Assignment C) toolset that enables parallel application developers to express their problems in a high-level language and the toolset is able to generate codes for various target HPC architectures including multicore and GPGPU. The collaborative work will introduce fault tolerance to SAC and its parallel applications.
Development of High-Performance Codes:
Hirch-Fye QMC [Abuasal, Moore, Tam, Thakur, Yun, Ramanujam, Moreno, Jarrell]: One of the first successful applications of QMC was to study the problem of a correlated impurity in an uncorrelated host. The Hirsch-Fye QMC (HFQMC) algorithm was developed for this problem. More recently, together with similar methods such as continuous time QMC (CTQMC), it has gained broader acceptance as the impurity or cluster solver for dynamical mean field theory and its cluster extensions such as the dynamical cluster approximation (DCA). We are developing GPU-accelerated HFQMC code. The GPUs’ sheer number of concurrent parallel computations and large bandwidth to many shared memories take advantage of the inherent parallelism in the Green function update and measurement routines, and can substantially improve the efficiency of the Hirsch-Fye code.
Parallel Tempering [Feng, Fang, Tam, Thakur, Yun, Ramanujam, Moreno, Jarrell]: We develop high-performance GPU versions of the parallel tempering method (also called replica exchange). Parallel tempering is now widely used to improve the efficiency of Monte Carlo calculations. We use parallel tempering [46] together with multi-spin coding [94] to perform GPU simulations of Ising glasses, in addition to a number of code optimizations. We have explored a number of choices such as data layouts, GPU kernel granularities, parallel tempering swap frequency, loop optimizations, etc. The performance of the latest version of the code is around 49ps/spin flip.
Focus 2: Massively Parallel Density Functional Theory and Force Field Methods [Wick (LaTech), Rick (UNO)]
The development of new force fields relevant for catalysis and biological simulations has been carried out. It is important to elucidate the role of charge transfer on interfacial properties of liquids and materials. The interfacial region has symmetry breaking, which results in changes in interaction behavior, such as asymmetric hydrogen bonding, and differences in dielectric mediums. Wick (LaTech) and Rick (UNO) added intermolecular charge transfer to a recently developed flexible and polarizable water model [95]. This model was compared with ones recently developed by Lee and Rick [72], which included one with intramolecular charge transfer and one without. The effect of including intermolecular charge transfer is modest on interfacial properties, but it was found that a negative charge at the air-water interface was calculated, but below that of capillary electrophoresis experiments [96]. The work shows that part, but not all, of the observed negative charge at the air-water interface may be explained by intermolecular charge transfer between water molecules.
Focus 3: Large-scale Molecular Dynamics
Workflow management for MD [Bishop (LaTech), Jha (LSU)]: While MC simulations can study the statistical properties of long time scale processes, simulating the dynamics at the molecular level requires Molecular Dynamics (MD) methods. A significant aspect of running Monte Carlo simulations is workflow management, which also has implications in other areas. Using software tools developed as part of LA-SiGMA (by Bishop at LaTech and Jha at LSU), we are able to successfully distribute thousands of high-performance simulations across Louisiana Optical Network Initiative (LONI) and XSEDE resources. We completed nearly 4,000 simulations (820,000 SU) in support of the Ascona B-DNA Consortium's efforts to conduct approximately 40 separate 1 microsecond long molecular dynamics simulations of DNA. In total the simulations provide a comprehensive case study of the material properties of DNA as a function of sequence. ManyJobs (which implements the notion of pilot jobs) and its SAGA based cousin BigJob demonstrate how many high performance computing tasks can be efficiently scaled across widely distributed computational resources such as LONI or XSEDE.
Hybrid MD/Continuum Methodologies [Kasra Fattah-Hesary, Moldovan, Nikitopoulos, Pacheco (LSU)]: Kasra Fattah-Hesary, a shared student between CTCI at LSU and the group led by Moldovan and Nikitopoulos, with significant help from Alexander Pacheco (HPC, LSU), has worked on developing new algorithms and codes based on a variational approach and hybrid MD/continuum methodologies, which have been added as modules to the LAMMPS package.
Other Areas
Data Mining: Data Adaptive Classification and Clustering [Dua (LaTech)]: Multi-dimensional data, such as that from MD simulations, is challenging to analyze due to its large volume, complexity and sparseness of the points within the data, which affect both the accuracy and efficiency of supervised learning methods. Data mining techniques such as feature selection and feature extraction are employed to reduce the dimensionality of the data but in these methods, each feature is considered separately and ignores feature dependencies, which can adversely affect the accuracy and efficiency of classification techniques. Our research here is focused on partitioning based rule-based supervised classification, where rules are generated by discovering feature dependencies among discovered partitions of each dimension of the dataset we have developed a data-adaptive rule-based classification system that generates relevant rules by finding adaptive partitions using two unique methods: slope based partitioning and non-slope based partitioning of the data. The adaptive partitions are generated from histogram by analyzing tuple tests such as peak-valley-peak triplet, valley-peak-valley triplet, peak-valley-peak-valley-peak set and valley-peak-valley-peak-valley set. These partitions allow discovering efficient and relevant rules that classify new data correctly. In addition, we have developed a data mining algorithm for data shrinking and clustering multidimensional datasets.
Changes in Research Directions, Future Work
Given the relatively early stage of the project, no major change in research direction was undertaken, in spite of the fact that some of the CTCI faculty originally engaged in parallel software at LSU (Sterling) have moved on from LSU. We have added David Koppelman (ECE, LSU) for GPU software development. We are in the process of finding additional faculty participants for CTCI starting from fall 2012.
B.5. EXTERNAL ENGAGEMENT:
External Engagement:
Strategy One-Public Lectures and Events:
LA-SiGMA faculty and graduate students from Louisiana State University participated in two Baton Rouge area's NanoDays events. NanoDays is a nationwide festival celebrating the science of the ultra small. LA-SiGMA faculty members gave two public lectures and graduate students led demonstrations to 125 visitors on March 24, 2012 at BREC's Highland Road Observatory and 400 guests on March 31, 2012, at the Louisiana Arts and Science Museum.
Dr. Bagayoko (SUBR) presented a talk at the AAPT Summer Meeting in Philadelphia, and also at the New Physics Faculty Workshop, APS Headquarters, College Park, MD.
Strategy Two:
LA-SiGMA created a web portal for distribution of project () deliverables, which is currently in use.
Strategy Three:
LA-SiGMA has also created a repository and version control system for code development and distribution, which is currently in use.
Strategy Four:
LA-SiGMA is currently in negotiation with vendors to order required HD hardware so that all LA-SiGMA institutions can distribute high quality video to all LA-SiGMA institutions.
Strategy Five:
LA-SiGMA has created a professional brochure, as well as several brochures for specific events, like the REU and RET programs. LA-SiGMA has also created a facebook page to post pictures and update members about events. Highlights have been prepared for distribution to NSF. LA-SiGMA has been mentioned once in the LA EPSCoR newsletter.
Strategies Six and Eight:
An all-hands meeting was held April 2, 2012. A second all-hands meeting has been scheduled on July 23, 2012. The NSF program officer, the External Review Board, the Diversity Advisory Council, and the Industrial Liaison Team will attend the second meeting.
Strategy Seven:
International and national collaborations
Milestones for Y2 in External Engagement:
-At least one LPB appearance per year by a LA-SiGMA member
-At least one public lecture delivered each quarter
-At least one lecture delivered to industrial audiences each quarter.
-Web traffic increases 20% annually
- SVN maintained and upgraded in Y2-5; 100 code downloads per year starting Y3
- At least two LASiGMA highlights featured in LA EPSCoR newsletter each year
-At least one story picked up by regional/national press
- At least one LA-SiGMA faculty and at least one student will visit and work in an international lab for one or more weeks each year
B.6. EVALUATION AND ASSESSMENT:
B.7. SUSTAINABILITY AND PROJECT OUTPUTS:
C. Management Structure:
D. Jurisdictional and Other Support:
E. Planning Updates:
F. Unobligated Funds:
G. Progress with Respect to the RII Strategic Plan:
H. Jurisdiction Specific Terms and Conditions:
I. Reverse Site Visit (RSV) Recommendations:
J. Experimental Facilities:
K. Publications and Patents:
L. Honors and Awards:
References
1. Fabre, B., et al., Polythiophenes containing in-Chain cobaltabisdicarbollide centers. ACS Applied Materials and Interfaces, 2010. 2(3): p. 691-702.
2. Frisch, M.J.T., G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb, M. A.; Cheeseman, J. R.; Scalmani, G.; Barone, V.; Mennucci, B.; Petersson, G. A.; Nakatsuji, H.; Caricato, M.; Li, X.; Hratchian, H. P.; Izmaylov, A. F.; Bloino, J.; Zheng, G.; Sonnenberg, J. L.; Hada, M.; Ehara, M.; Toyota, K.; Fukuda, R.; Hasegawa, J.; Ishida, M.; Nakajima, T.; Honda, Y.; Kitao, O.; Nakai, H.; Vreven, T.; Montgomery, Jr., J. A.; Peralta, J. E.; Ogliaro, F.; Bearpark, M.; Heyd, J. J.; Brothers, E.; Kudin, K. N.; Staroverov, V. N.; Kobayashi, R.; Normand, J.; Raghavachari, K.; Rendell, A.; Burant, J. C.; Iyengar, S. S.; Tomasi, J.; Cossi, M.; Rega, N.; Millam, N. J.; Klene, M.; Knox, J. E.; Cross, J. B.; Bakken, V.; Adamo, C.; Jaramillo, J.; Gomperts, R.; Stratmann, R. E.; Yazyev, O.; Austin, A. J.; Cammi, R.; Pomelli, C.; Ochterski, J. W.; Martin, R. L.; Morokuma, K.; Zakrzewski, V. G.;Voth, G. A.; Salvador, P.; Dannenberg, J. J.; Dapprich, S.; Daniels, A. D.; Farkas, Ö.; Foresman, J. B.; Ortiz, J. V.; Cioslowski, J.; Fox, D. J., Gaussian 09, Rev. A.1, 2009, Gaussian Inc.: Wallingford, CT. p. Gaussian 09.
3. Derosa, P.A. and J.M. Seminario, Electron transport through single molecules: Scattering treatment using density functional and green function theories. Journal of Physical Chemistry B, 2001. 105(2): p. 471-481.
4. Caruntu, G., et al., Probing the local strain-mediated magnetoelectric coupling in multiferroic nanocomposites by magnetic field-assisted piezoresponse force microscopy. Nanoscale, 2012. 4(10): p. 3218-3227.
5. Yourdkhani, A., et al., Magnetoelectric perovskite-spinel bilayered nanocomposites synthesized by liquid-phase deposition. Chemistry of Materials, 2010. 22(22): p. 6075-6084.
6. Damjanovic, D., Ferroelectric, dielectric and piezoelectric properties of ferroelectric thin films and ceramics. Reports on Progress in Physics, 1998. 61(11): p. 1267-1324.
7. Kalinin, S.V. and D.A. Bonnell, Contrast mechanism maps for piezoresponse force microscopy. Journal of Materials Research, 2002. 17(5): p. 936-939.
8. Harnagea, C., et al., Possibilities and limitations of voltage-modulated scanning force microscopy: Resonances in contact mode. Integrated Ferroelectrics, 2004. 60: p. 101-110.
9. Neese, F., ORCA – an ab initio, Density Functional and Semiempirical program package, 2004, Max-Planck-Insitut für Bioanorganische Chemie: Mülheim and der Ruhr.
10. Castro, M. and D.R. Salahub, Density-functional calculations for small iron clusters: Fen, Fen+, and Fen- for n5. Physical Review B, 1994. 49(17): p. 11842-11852.
11. Gutsev, G.L. and C.W. Bauschlicher Jr, Electron Affinities, Ionization Energies, and Fragmentation Energies of Fen Clusters (n = 2-6): A Density Functional Theory Study. Journal of Physical Chemistry A, 2003. 107(36): p. 7013-7023.
12. Milios, C.J., et al., A record anisotropy barrier for a single-molecule magnet. Journal of the American Chemical Society, 2007. 129(10): p. 2754-2755.
13. Burin, A. and A. Kurnosov, Fluctuator Model of Memory Dip in Hopping Insulators. Journal of Low Temperature Physics, 2012. 167(3): p. 318-328.
14. Burin, A.L. and A.K. Kurnosov Fluctuator model of memory dip in hopping insulators. IEEE/CSC &ESAS European Superconductivity News Forum, 2011. 18, .
15. Tesar, S.L., et al., Temperature dependence for the rate of hole transfer in DNA: Nonadiabatic regime. Chemical Physics, 2012. 393(1): p. 13-18.
16. Moruzzi, V.L. and P.M. Marcus, Magnetic structure of ordered FeAl and FeV. Physical Review B, 1993. 47(13): p. 7878-7884.
17. Sundararajan, V., et al., Cohesive, electronic and magnetic properties of the transition metal aluminides FeAl CoAl and NiAl. Journal of Physics: Condensed Matter, 1995. 7(30): p. 6019-6034.
18. Zou, J. and C.L. Fu, Structural, electronic, and magnetic properties of 3d transition-metal aluminides with equiatomic composition. Physical Review B, 1995. 51(4): p. 2115-2121.
19. Papaconstantopoulos, D.A. and K.B. Hathaway, Predictions of magnetism in transition metal aluminides. Journal of Applied Physics, 2000. 87(9 II): p. 5872-5874.
20. Das, G.P., et al., Electronic structure of substoichiometric Fe-Al intermetallics. Physical Review B - Condensed Matter and Materials Physics, 2002. 66(18): p. 1842031-18420313.
21. Gonzales-Ormeño, P.G., H.M. Petrilli, and C.G. Schön, Ab-initio calculations of the formation energies of BCC-based superlattices in the Fe-Al system. Calphad: Computer Coupling of Phase Diagrams and Thermochemistry, 2002. 26(4): p. 573-582.
22. Yang, S.H., et al., Application of a tight-binding total-energy method for FeAl. Journal of Physics Condensed Matter, 2002. 14(8): p. 1895-1902.
23. Pan, J.L., J. Ni, and B. Yang, Stability of FeAl(110) alloy surface structures: A first-principles study. European Physical Journal B, 2010. 73(3): p. 367-373.
24. Shukla, P. and M. Wortis, Spin-glass behavior in iron-aluminum alloys: A microscopic model. Physical Review B, 1980. 21(1): p. 159-164.
25. Bogner, J., et al., Magnetic order and defect structure of FexAl1-x alloys around x = 0.5: An experimental and theoretical study. Physical Review B - Condensed Matter and Materials Physics, 1998. 58(22): p. 14922-14933.
26. Mohn, P., et al., Correlation induced paramagnetic ground state in FeAl. Physical Review Letters, 2001. 87(19): p. 196401/1-196401/4.
27. Baddorf, A.P. and S.S. Chandavarkar, Identification of an incommensurate FeAl2 overlayer on FeAl(1 1 0) using x-ray diffraction and reflectivity. Physica B: Condensed Matter, 1996. 221(1-4): p. 141-144.
28. Kizilkaya, O., et al., Surface reconstruction of FeAl(110) studied by scanning tunnelling microscopy and angle-resolved photoemission spectroscopy. Journal of Physics Condensed Matter, 2004. 16(30): p. 5395-5406.
29. Hammer, L., et al., Segregation phenomena on surfaces of the ordered bimetallic alloy FeAl. Surface Science, 1998. 412-413: p. 69-81.
30. Ahilan, K., et al., F 19 NMR investigation of the iron pnictide superconductor LaFeAsO0.89 F0.11. Physical Review B - Condensed Matter and Materials Physics, 2008. 78(10).
31. Nakai, Y., et al., Evolution from itinerant antiferromagnet to unconventional superconductor with fluorine doping in LaFeAs(O 1-xF x) revealed by 75As and 139La nuclear magnetic resonance. Journal of the Physical Society of Japan, 2008. 77(7).
32. Christianson, A.D., et al., Unconventional superconductivity in Ba0.6K0.4Fe 2As2 from inelastic neutron scattering. Nature, 2008. 456(7224): p. 930-932.
33. Lumsden, M.D., et al., Two-dimensional resonant magnetic excitation in BaFe1.84Co0.16As2. Physical Review Letters, 2009. 102(10).
34. Chi, S., et al., Inelastic neutron-scattering measurements of a three-dimensional spin resonance in the FeAs-based BaFe1.9Ni0.1As2 superconductor. Physical Review Letters, 2009. 102(10).
35. Liu, T.J., et al., From (π,0) magnetic order to superconductivity with (π,π) magnetic resonance in Fe1.02 Te1-x Sex. Nature Materials, 2010. 9(9): p. 716-720.
36. Spinu, L. London penetration depth measurements in FeSeTe single crystals at ultra-low temperatures. in APS March Meeting. 2012. Boston.
37. Spinu, L. London penetration depth measurements in FeSeTe single crystals at ultra-low temperatures. in 56th MMM Conference. 2012. Scottsdale, AZ.
38. Qian, B., et al., Ferromagnetism in CuFeSb: Evidence of competing magnetic interactions in iron-based superconductors. Physical Review B - Condensed Matter and Materials Physics, 2012. 85(14).
39. Moon, C.Y. and H.J. Choi, Chalcogen-height dependent magnetic interactions and magnetic order switching in FeSexTe1-x. Physical Review Letters, 2010. 104(5).
40. Yin, W.G., C.C. Lee, and W. Ku, Unified picture for magnetic correlations in iron-based superconductors. Physical Review Letters, 2010. 105(10).
41. van Hove, M.A., W.H. Weinberg, and C.M. Chan, Low-Energy Electron Diffraction: Experiment, Theory and Surface Structure Determination. 1986, Berlin: Springer-Verlag.
42. Nascimento, V.B. and E.W. Plummer, Differential evolution: Global search problem in LEED-IV surface structural analysis, Submitted. Surface Science, 2012 (submitted).
43. Foulkes, W.M.C., et al., Quantum Monte Carlo simulations of solids. Reviews of Modern Physics, 2001. 73(1): p. 33-83.
44. Kohn, W. and L.J. Sham, Self-consistent equations including exchange and correlation effects. Physical Review, 1963. 140: p. A1133-A1138.
45. Perdew, J.P. and M. Levy, Physical content of the exact kohn-sham orbital energies: Band gaps and derivative discontinuities. Physical Review Letters, 1983. 51(20): p. 1884-1887.
46. Yan, Q. and J.J. de Pablo, Hyperparallel tempering Monte Carlo simulation of polymeric systems. Journal of Chemical Physics, 2000. 113(3): p. 1276-1282.
47. de Oliveira, P.M.C., Computing Boolean Statistical Models. 1991, Singapore: World Scientific Pub Co Inc.
48. Hirsch, J.E. and R.M. Fye, Monte Carlo Method for Magnetic Impurities in Metals. Physical Review Letters, 1986. 56(23): p. 2521-2524.
49. Rubtsov, A.N., V.V. Savkin, and A.I. Lichtenstein, Continuous-time quantum Monte Carlo method for fermions. Physical Review B - Condensed Matter and Materials Physics, 2005. 72(3).
50. Elliott, R.J., J.A. Krumhansl, and P.L. Leath, The theory and properties of randomly disordered crystals and related physical systems. Reviews of Modern Physics, 1974. 46(3): p. 465-543.
51. Jarrell, M. and H.R. Krishnamurthy, Systematic and causal corrections to the coherent potential approximation. Physical Review B - Condensed Matter and Materials Physics, 2001. 63(12): p. 1251021-12510210.
52. Dobrosavljević, V., A.A. Pastor, and B.K. Nikolić, Typical medium theory of Anderson localization: A local order parameter approach to strong-disorder effects. Europhysics Letters, 2003. 62(1): p. 76-82.
53. Yang, S.X., et al., Dual fermion dynamical cluster approach for strongly correlated systems. Physical Review B - Condensed Matter and Materials Physics, 2011. 84(15).
54. Ku, W., et al., Insulating ferromagnetism in La4Ba2Cu2O10: An ab initio wannier function analysis. Physical Review Letters, 2002. 89(16): p. 167204/1-167204/4.
55. Tao, J., J.P. Perdew, and A. Ruzsinszky, Accurate van der Waals coefficients from density functional theory. Proceedings of the National Academy of Sciences, 2012. 109(1): p. 18-21.
56. Perdew, J.P., et al., Spherical-shell model for the van der Waals coefficients between fullerenes and/or nearly-spherical nanoclusters. Journal of Physics Condensed Matter, 2012 (accepted).
57. Tao, J. and J.P. Perdew, Understanding long-range van der Waals interactions: Huge coefficients between nanoclusters. 2012 (submitted).
58. Haunschild, R., et al., Hyper-generalized-gradient functionals constructed from the Lieb-Oxford bound: Implementation via local hybrids and thermochemical assessment. Journal of Chemical Physics, 2012. 136(18): p. 184102-184102.
59. Pederson, M.R. and J.P. Perdew, Self-Interaction Correction in Density
Functional Theory: The Road Less Traveled. Psi-k Newsletter, 2012. 109 (February): p. 77-100.
60. Hao, P., et al., Lattice constants from semilocal density functionals with zero-point phonon correction. Physical Review B, 2012. 85(1): p. 014111-014111.
61. Ruzsinszky, A., et al., A meta-GGA made free of the order-of-limits problem. Journal of Chemical Theory and Computation, 2012 (to be published).
62. Sun, J., B. Xiao, and A. Ruzsinszky, Effect of the orbital-overlap dependence of the meta-generalized gradient approximation. 2012 (submitted).
63. Bagayoko, D., et al., Ab initio calculations of the electronic structure and optical properties of ferroelectric tetragonal BaTiO 3. Journal of Physics Condensed Matter, 1998. 10(25): p. 5645-5655.
64. Zhao, G.L., D. Bagayoko, and T.D. Williams, Local-density-approximation prediction of electronic properties of GaN, Si, C, and RuO2. Physical Review B - Condensed Matter and Materials Physics, 1999. 60(3): p. 1563-1572.
65. Franklin, L., et al., Density functional description of electronic properties of wurtzite zinc oxide. Canadian Journal of Physics, 2012 (submitted).
66. Ekuma, C.E., et al., Electronic, structural, and elastic properties of metal nitrides XN (X=Sc,Y): a first principle study. Journal of Applied Physics, 2012 (submitted).
67. Ekuma, C.E., et al., First principle electronic, structural, elastic, and optical properties of strontium titanate. AIP Advances, 2012. 2(1): p. 012189-012189-14-012189-012189-14.
68. Ekuma, C.E., et al., Re-examining the electronic structure of germanium: a first principle study. Physical Review Letters, 2012 (submitted).
69. Malozovsky, Y., et al., Electronic and transport properties of InP: An ab-initio study, 2012: in preparation.
70. Hata, K., et al., Water-assisted highly efficient synthesis of impurity-free single-walled carbon nanotubes. Science, 2004. 306(5700): p. 1362-1364.
71. Yang, L., et al., Molecular simulation of electric double-layer capacitors based on carbon nanotube forests. Journal of the American Chemical Society, 2009. 131(34): p. 12373-12376.
72. Lee, A.J. and S.W. Rick, The effects of charge transfer on the properties of liquid water. The Journal of Chemical Physics, 2011. 134: p. 184507.
73. Dathara, G.K.P. and D.S. Mainardi, Structure and dynamics of Ti-Al-H compounds in Ti-doped NaAlH4. Molecular Simulation, 2008. 34(2): p. 201-210.
74. Wang, Y.L., et al., A first principles study of the thermal stability of Am(MH 4)n light complex hydrides. Journal of Physics Condensed Matter, 2010. 22(17).
75. Wang, J., et al., Effect of graphite as a co-dopant on the dehydrogenation and hydrogenation kinetics of Ti-doped sodium aluminum hydride. Journal of Alloys and Compounds, 2005. 395(1-2): p. 252-262.
76. Wagemans, R.W.P., et al., Hydrogen storage in magnesium clusters: Quantum chemical study. Journal of the American Chemical Society, 2005. 127(47): p. 16675-16680.
77. Freni, A. and F. Cipitì. 3D Dynamic Simulation of a Metal Hydride-Based Hydrogen Storage Tank. in COMSOL Conference. 2008. Hannover.
78. Freni, A., F. Cipitì, and G. Cacciola, Finite element-based simulation of a metal hydride-based hydrogen storage tank. International Journal of Hydrogen Energy, 2009. 34(20): p. 8574-8582.
79. Demircan, A., et al., Experimental and theoretical analysis of hydrogen absorption in LaNi 5-H2 reactors. International Journal of Hydrogen Energy, 2005. 30(13-14): p. 1437-1446.
80. Lomnicki, S. and B. Dellinger, A detailed mechanism of the surface-mediated formation of PCDD/F from the oxidation of 2-chlorophenol on a CuO/Silica surface. Journal of Physical Chemistry A, 2003. 107(22): p. 4387-4395.
81. Lomnicki, S., et al., Copper oxide-based model of persistent free radical formation on combustion-derived particulate matter. Environmental Science and Technology, 2008. 42(13): p. 4982-4988.
82. Bae, G.T., B. Dellinger, and R.W. Hall, Density functional calculation of the structure and electronic properties of CunOn (n = 1-8) clusters. Journal of Physical Chemistry A, 2011. 115(11): p. 2087-2095.
83. Matter, P.H. and U.S. Ozkan, Non-metal catalysts for dioxygen reduction in an acidic electrolyte. Catalysis Letters, 2006. 109(3-4): p. 115-123.
84. Matter, P.H., L. Zhang, and U.S. Ozkan, The role of nanostructure in nitrogen-containing carbon catalysts for the oxygen reduction reaction. Journal of Catalysis, 2006. 239(1): p. 83-96.
85. Gong, K., et al., Nitrogen-doped carbon nanotube arrays with high electrocatalytic activity for oxygen reduction. Science, 2009. 323(5915): p. 760-764.
86. Yang, S., G.L. Zhao, and E. Khosravi, First principles studies of nitrogen doped carbon nanotubes for dioxygen reduction. Journal of Physical Chemistry C, 2010. 114(8): p. 3371-3375.
87. Li, N., C.R. Martin, and B. Scrosati, High-rate, high-capacity, nanostructured tin oxide electrode. Electrochemical and Solid-State Letters, 2000. 3(7): p. 316-318.
88. Zhao, Y. and D.G. Truhlar, The M06 suite of density functionals for main group thermochemistry, thermochemical kinetics, noncovalent interactions, excited states, and transition elements: Two new functionals and systematic testing of four M06-class functionals and 12 other functionals. Theoretical Chemistry Accounts, 2008. 120(1-3): p. 215-241.
89. Rick, S.W., Replica exchange with dynamical scaling. Journal of Chemical Physics, 2007. 126(5).
90. Laurent, B.A. and S.M. Grayson, Synthesis of cyclic amphiphilic homopolymers and their potential application as polymeric micelles. Polymer Chemistry, 2012(in press).
91. Li, Y., et al., A versatile and modular approach to functionalisation of deep-cavity cavitands via "click" chemistry. Chemical Communications, 2011. 47(32): p. 9036-9038.
92. Kato, K., et al., Temperature-sensitive nonionic vesicles prepared from Span 80 (sorbitan monooleate). Langmuir, 2008. 24(19): p. 10762-10770.
93. Ballatore, C., V.M.Y. Lee, and J.Q. Trojanowski, Tau-mediated neurodegeneration in Alzheimer's disease and related disorders. Nature Reviews Neuroscience, 2007. 8(9): p. 663-672.
94. Wansleben, S., J.G. Zabolitzky, and C. Kalle, Monte Carlo simulation of Ising models by multispin coding on a vector computer. Journal of Statistical Physics, 1984. 37(3-4): p. 271-282.
95. Wick, C.D., Hydronium behavior at the air-water interface with a polarizable multistate empirical valence bond model. Journal of Physical Chemistry C, 2012. 116(6): p. 4026-4038.
96. Takahashi, M., ζ Potential of microbubbles in aqueous solutions: Electrical properties of the gas - Water interface. Journal of Physical Chemistry B, 2005. 109(46): p. 21858-21864.
-----------------------
[pic]
[pic]
Figure 1. Experimental picture (top) an湳灡桳瑯映潲楳畭慬楴湯⠠潢瑴浯
景琠敨挠湯慴瑣愠杮敬漠䍐渠硥⁴潴朠慲桰瑩䘁杩牵⸲†䵔⭁挠慨杲潦楤晦牥湥⁴牯敩瑮瑡潩獮渠硥⁴潴愠挠牡潢慮潮畴敢മč楆畧敲㐠慎潮汣獵整潭敤ⱬ眠敨敲堠椠牴湡楳楴湯洠瑥污搠灯湡ā䘍杩牵⸵䌠潲獳猠捥楴湯漠祣楬摮楲慣慌楎ⴵ㉈爠慥瑣牯⠠敬瑦
湡景愠挠畯瑮畯景栠摹潲敧敤獮瑩⁹楤瑳楲畢楴湯愠潬杮琠敨爠慥瑣牯愠瑦牥㘠‰業畮整䘁杩牵⸳删汥瑡癩潣敨楳敶攠敮杲⁹慶畬d snapshot from simulation (bottom) of the contact angle of PC next to graphite.
[pic]Figure 2. TMA+ charge for different orientations next to a carbon nanotube.
[pic]Figure 4. Nanocluster model, where X is transition metal dopant.
[pic][pic]
Figure 5. Cross section of a cylindrical LaNi5-H2 reactor (left) and of a countour of hydrogen density distribution along the reactor after 60 minutes.
[pic]Figure 3. Relative cohesive energy values in doped bulk model
[pic]Figure 6. Copper oxide nanoparticle bound with dioxin/furan precursor
Table 1. Experimental and Forcefield Predictions for CuO
|Property |Exp. |Predicted |
|α |90° |90.3° |
| β |99.6° |96.9° |
| γ |90° |91.0° |
|a(Å) |4.68 |4.56 |
|b(Å) |3.42 |3.55 |
|c(Å) |5.13 |5.03 |
[pic]
Figure 7. Snapshot of possible early catalytic pathway for H2+O2
................
................
In order to avoid copyright disputes, this page is only a partial summary.
To fulfill the demand for quickly locating and searching documents.
It is intelligent file search solution for home and business.
Related download
- osnova správy o činnosti vedeckého pracoviska sav
- anna university chennai 600 025
- department of physics astronomy
- ap chemistry lab manual
- check in safety avoiding contmination issues pipetting
- registration of subject for dissertation
- formulation optimization and evaulation of
- schrödinger schrödinger is the scientific leader in
Related searches
- journal of physics communications
- journal of physics conference series impact factor
- journal of physics a mathematical theoretical
- institute of physics iop
- journal of physics and astronomy
- american journal of physics online
- journal of physics and chemistry
- institute of physics uk
- new journal of physics latex
- journal of physics education
- journal of physics and chemistry solids
- journal of physics c