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Hierarchical Atomistic Simulation Methods

Hierarchical Atomistic Simulation Methods. Molecular Dynamics (MD). Electron wave function. Atom. ReaxFF. Train. Adaptive E MD. First principles-based reactive force-field (in collaboration with Goddard at Caltech). Quantum Mechanics (QM).

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Hierarchical Atomistic Simulation Methods

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  1. Hierarchical Atomistic Simulation Methods Molecular Dynamics (MD) Electron wave function Atom ReaxFF Train Adaptive EMD First principles-based reactive force-field (in collaboration with Goddard at Caltech) Quantum Mechanics (QM) Embedded divide-&-conquer (EDC) algorithm on adaptive multigrids for linear-scaling density functional theory (DFT) P. Vashishta, R. Kalia, A. Nakano DMR-0427188 W. Goddard, T. Cagin, P. Meulbroek, M. Ortiz, A. van Duin DMR-0427177 and A. Grama DMR-0427540

  2. Scalable Parallel Molecular Dynamics Algorithms Design-space diagram on 1,920 Itanium2 (1.5GHz) procs. of NASA Columbia • 19 billion-atom multiresolution molecular dynamics (MRMD) of SiO2 • 0.56 billion-atom fast reactive force-field (F-ReaxFF) MD of RDX • 1.4 million-atom (0.12 trillion grid points) embedded divide-&-conquer density functional theory (EDC-DFT) MD of Al2O3

  3. Nanoindentation on Nanophase SiC 19 million-atom MD simulation Load-displacement curve Hardness MD: 39 GPa (grain size, d = 8 nm) Expt.: 30-50 GPa (d = 5-20 nm) [Liao et al., APL, ‘05] “A crossover in the mechanical response of nanocrystalline ceramics” Science309, 911 (2005)

  4. Crossover in Mechanical Responses Crossover from intergrain continuous response to intragranular discrete response White: ordered atoms (12 6-membered rings) Yellow: disordered atoms Blue: disorder-to-order change Red: order-to-disorder change Mixture of crystalline grains & amrphous grain boundary phases “A crossover in the mechanical response of nanocrystalline ceramics” Science309, 911 (2005)

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