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2002 IEEE/ACM Conference on Supercomputing, SC 2002

作者： Kikuchi, Hideaki Kalia, Rajiv K. Nakano, Aiichiro Vashishta, Priya Iyetomi, Hiroshi Ogata, Shuji Kouno, Takahisa Shimojo, Fuyuki Tsuruta, Kenji Saini, Subhash Computer Science Department Department of Materials Science Department of Physics and Astronomy Department of Biomedical Engineering University of Southern California United States Concurrent Computing Laboratory for Materials Simulations Department of Computer Science Department of Physics and Astronomy Louisiana State University United States Department of Physics Niigata University Japan Department of Applied Sciences Yamaguchi University Japan Faculty of Integrated Arts and Sciences Hiroshima University Japan Department of Electrical and Electronic Engineering Okayama University Japan IT Modeling and Simulation NASA Ames Research Center United States

ISBN: (纸本)076951524X

A multidisciplinary, collaborative simulation has been performed on a Grid of geographically distributed PC clusters. The multiscale simulation approach seamlessly combines i) atomistic simulation based on the molecular dynamics (MD) method and ii) quantum mechanical (QM) calculation based on the density functional theory (DFT), so that accurate but less scalable computations are performed only where they are needed. The multiscale MD/QM simulation code has been Grid-enabled using i) a modular, additive hybridization scheme, ii) multiple QM clustering, and iii) computation/communication overlapping. The Gridified MD/QM simulation code has been used to study environmental effects of water molecules on fracture in silicon. A preliminary run of the code has achieved a parallel efficiency of 94% on 25 PCs distributed over 3 PC clusters in the US and Japan, and a larger test involving 154 processors on 5 distributed PC clusters is in progress. © 2002 IEEE.

关键词： Density functional theory

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Pressure-induced structural transformation in GaAs: A molecular-dynamics study

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Physical Review B 2002年第19期65卷 195206-195206页

作者： José Pedro Rino Alok Chatterjee Ingvar Ebbsjö Rajiv K. Kalia Aiichiro Nakano Fuyuki Shimojo Priya Vashishta Concurrent Computing Laboratory for Materials Simulations Department of Physics and Astronomy and Department of Computer Science Louisiana State University Baton Rouge Louisiana 70803 Department of Physics Universidade Federal de São Carlos São Carlos São Paulo Brazil Studsvik Neutron Research Laboratory University of Uppsala Nyköping Sweden Faculty of Integrated Arts and Sciences Hiroshima University Higashi-Hiroshima Japan

Structural phase transformation in crystalline gallium arsenide is studied with the isothermal-isobaric molecular-dynamics method. The pair-distribution functions and bond-angle distributions indicate that the fourfold-coordinated zinc-blende structure transforms into a sixfold-coordinated orthorhombic structure under a pressure of 22 GPa. The reverse transformation, from an orthorhombic to a zinc-blende structure, shows hysteresis, and is observed at a pressure of ≅10 GPa. Molecular-dynamics results are in good agreement with experiments. The energy barrier associated with this structural transformation is estimated to be ∼0.06 eV.

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Immersive and interactive exploration of billion atom systems

Immersive and interactive exploration of billion atom system...

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IEEE Annual International Symposium Virtual Reality

作者： A. Sharma Xinlian Liu P. Miller A. Nakano R.K. Kalia P. Vashishta Wei Zhao T.J. Campbell A. Haas Concurrent Computing Laboratory for Materials Simulations Biological Computation and Visualization Center Department of Computer Science Department of Physics & Astronomy Louisiana State University LA USA Naval Oceanographic Office Major Shared Resource Center Stennis Space Center Logicon Inc. MS USA

ISBN: (纸本)0769514928

Recent advances in parallel computing have made it possible for scientists to perform atomistic simulations of materials involving billions of atoms. An immersive and interactive virtual environment such as ImmersaDesk is an ideal platform for exploring complex material processes in these simulations. However rendering such large datasets at an interactive speed is a major challenge. To solve this problem we have developed a visualization system by incorporating parallel and distributed computing paradigms. The system uses a parallelized fast visibility-culling algorithm based on the octree data structure to reduce the number of atoms sent to the graphics pipeline. An adaptive multiresolution algorithm based on atomic density is employed to further reduce the load on the graphics pipeline. The resulting system renders a billion-atom system at nearly interactive frame rates on a dual processor SGI Onyx2 with an InfiniteReality2 graphics pipeline connected to a 4-node PC cluster.

关键词： Graphics Pipelines Computational modeling Parallel processing Virtual environment Data visualization Distributed computing Data structures Clustering algorithms Rendering (computer graphics)

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Grain Boundaries in Gallium Arsenide Nanocrystals Under Pressure: A Parallel Molecular-Dynamics Study

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Physical Review Letters 2001年第1期86卷 55-55页

作者： Sanjay Kodiyalam Rajiv K. Kalia Hideaki Kikuchi Aiichiro Nakano Fuyuki Shimojo Priya Vashishta Concurrent Computing Laboratory for Materials Simulations Department of Physics & Astronomy and Department of Computer Science Louisiana State University Baton Rouge Louisiana 70803-4001

Structural transformation in gallium arsenide nanocrystals under pressure is studied using molecular-dynamics simulations on parallel computers. It is found that the transformation from fourfold to sixfold coordination is nucleated on the nanocrystal surface and proceeds inwards with increasing pressure. Inequivalent nucleation of the high-pressure phase at different sites leads to inhomogeneous deformation of the nanocrystal. This results in the transformed nanocrystal having grains of different orientations separated by grain boundaries. A new method based on microscopic transition paths is introduced to uniquely characterize grains and deformations.

关键词： Nanostructured materials

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Scalable Atomistic simulation Algorithms for materials Research 01

Scalable Atomistic Simulation Algorithms for Materials Resea...

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2001 ACM/IEEE Conference on Supercomputing, SC 2001

作者： Nakano, Aiichiro Kalia, Rajiv K. Vashishta, Priya Campbell, Timothy J. Ogata, Shuji Shimojo, Fuyuki Saini, Subhash Concurrent Computing Laboratory Materials Simulations Biological Computation and Visualization Center Department of Computer Science Department of Physics and Astronomy Louisiana State University United States Logicon Inc. Naval Oceanographic Office Major Shared Resource Center Department of Applied Sciences Yamaguchi University Japan Faculty of Integrated Arts and Sciences Hiroshima University Japan It Modeling and Simulation Nasa Ames Research Center

ISBN: (纸本)158113293X

A suite of scalable atomistic simulation programs has been developed for materials research based on space-time multiresolution algorithms. Design and analysis of parallel algorithms are presented for molecular dynamics (MD) simulations and quantum-mechanical (QM) calculations based on the density functional theory. Performance tests have been carried out on 1,088-processor Cray T3E and 1,280-processor IBM SP3 computers. The linear-scaling algorithms have enabled 6.44-billion-atom MD and 111,000-atom QM calculations on 1,024 SP3 processors with parallel efficiency well over 90%. The production-quality programs also feature wavelet-based computational-space decomposition for adaptive load balancing, spacefilling-curve-based adaptive data compression with user-defined error bound for scalable I/O, and octree-based fast visibility culling for immersive and interactive visualization of massive simulation data. © 2001 ACM.

关键词： Density functional theory

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Large-scale molecular dynamics simulations of materials on parallel computers

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AIP Conference Proceedings 2001年第1期583卷 57-62页

作者： Aiichiro Nakano Timothy J. Campbell Rajiv K. Kalia Sanjay Kodiyalam Shuji Ogata Fuyuki Shimojo Priya Vashishta Phillip Walsh 1Concurrent Computing Laboratory for Materials Simulations Department of Computer Science Department of Physics & Astronomy Louisiana State University Baton Rouge Louisiana 70803 2Logicon Inc. Naval Oceanographic Office Major Shared Resource Center Stennis Space Center Mississippi 39529 3Department of Applied Sciences Yamaguchi University Ube 755-8611 Japan 4Faculty of Integrated Arts and Sciences Hiroshima University Higashi-Hiroshima 739-8521 Japan

Scalable space-time multiresolution algorithms implemented on massively parallel computers enable large-scale molecular dynamics simulations involving up to a billion atoms, which are applied to the study of nanosystems of great technological importance. These include sintering, structure, and mechanical properties of nanostructured ceramics and nanocomposites, structural transformation in semiconductor nanocrystals, nanoindentation, and oxidation of metallic nanoparticles.

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Multi-Million Atom Molecular-Dynamics simulations of Stresses in Si(111)/Si 3 N 4 Nanopixels

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MRS Online Proceedings Library 2000年第1期592卷 24-29页

作者： Martina E. Bachlechner Andrey Omeltchenko Phillip Walsh Aiichiro Nakano Rajiv K. Kalia Priya Vashishta Ingvar Ebbsjö Anupam Madhukar Concurrent Computing Laboratory for Materials Simulation Department of Physics & Astronomy Department of Computer Science Louisiana State University Baton Rouge USA University of Uppsala Sweden University of Southern California Los Angeles USA

The stress distribution in Si(l1l)/Si3N4(0001) and Si(111)/a-Si3N4 nanopixels are studied using molecular dynamics simulations on parallel computers. Bulk Si is described by the Stillinger-Weber potential and Si3N4 is represented by a combination of two- and three-body interactions that include steric, charge transfer, polarizability and covalent forces. The charge transfer at the interface is extracted from self-consistent electronic structure calculations. The molecular dynamics simulations for Si(l11)/a-Si3N4 nanopixels involve two pixel sizes: 25nm and 54 nm (the systems consist of 3.7 million and 10 million atoms, respectively). In both systems we find stress domains at the interface, which extend into the silicon substrate. The nature of the stress domains is discussed.

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Molecular Dynamics simulation of Structural Transformation in Silicon Carbide under Pressure

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Physical Review Letters 2000年第15期84卷 3338-3338页

作者： Fuyuki Shimojo Ingvar Ebbsjö Rajiv K. Kalia Aiichiro Nakano Jose P. Rino Priya Vashishta Concurrent Computing Laboratory for Materials Simulations Department of Physics and Astronomy and Department of Computer Science Louisiana State University Baton Rouge Louisiana 70803 Faculty of Integrated Arts and Sciences Hiroshima University Higashi-Hiroshima 739-8521 Japan Studsvik Neutron Research Laboratory University of Uppsala Nyköping Sweden Department of Physics Universidade Federal de São Carlos São Carlos São Paulo Brazil

Pressure-induced structural transformation in cubic silicon carbide is studied with the isothermal-isobaric molecular-dynamics method using a new interatomic potential scheme. The reversible transformation between the fourfold coordinated zinc-blende structure and the sixfold coordinated rocksalt structure is successfully reproduced by the interatomic potentials. The calculated volume change at the transition and hysteresis are in good agreement with experimental data. The atomistic mechanisms of the structural transformation involve a cubic-to-monoclinic unit-cell transformation and a relative shift of Si and C sublattices in the {100} direction.

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Molecular dynamics simulations of nanoindentation of silicon nitride

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materials Research Society Symposium - Proceedings 1999年 539卷 119-124页

作者： Walsh, Phillip Omeltchenko, Andrey Kikuchi, Hideaki Kalia, Rajiv K. Nakano, Aiichiro Vashishta, Priya Concurrent Computing Laboratory for Materials Simulation Department of Physics and Astronomy Louisiana State University Baton Rouge LA 70803-4001 United States

This is a report of work in progress on 10 million atom Molecular Dynamics (MD) simulations of nanoindentation of crystalline and amorphous silicon nitride (Si3N4). Nanoindentation is used to determine mechanical properties of extremely thin films such as hardness and elastic moduli. We report load-displacement curves for several Si3N4 configurations using an idealized non-deformable indenter and analyze the local stress distributions in the vicinity of the indenter tip. Preliminary results for surface adhesion using Si3N4 for both tip and substrate are also reported.

关键词： Silicon nitride

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Multimillion atom molecular dynamics simulations of glasses and ceramic materials

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AIP Conference Proceedings 1999年第1期489卷

作者： Priya Vashishta Rajiv K. Kalia Aiichiro Nakano Concurrent Computing Laboratory for Materials Simulations Department of Physics & Astronomy and Department of Computer Science Louisiana State University Baton Rouge Louisiana 70803-4001

Molecular dynamics simulations are a powerful tool for studying physical and chemical phenomena in materials. In these lectures we shall review the molecular dynamics method and its implementation on parallel computer architectures. Using the molecular dynamics method we will study a number of materials in different ranges of density, temperature, and uniaxial strain. These include structural correlations in silica glass under pressure, crack propagation in silicon nitride films, sintering of silicon nitride nanoclusters, consolidation of nanophase materials, and dynamic fracture. Multimillion atom simulations of oxidation of aluminum nanoclusters and nanoindentation in silicon nitride will also be discussed.

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