Bulletin of the American Physical Society
16th APS Topical Conference on Shock Compression of Condensed Matter
Volume 54, Number 8
Sunday–Friday, June 28–July 3 2009; Nashville, Tennessee
Session K2: MD-3: Molecular Dynamics III |
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Chair: Marc Cawkwell, Los Alamos National Laboratory Room: Hermitage AB |
Tuesday, June 30, 2009 1:30PM - 1:45PM |
K2.00001: Analysis of $\alpha $-phase RDX vibrational lattice modes under hydrostatic pressure William Slough, Warren Perger Calculations employing density functional theory are performed on $\alpha $-phase RDX using the all-electron CRYSTAL06 program. The lowest frequency infrared active lattice modes are investigated as a function of hydrostatic pressure from ambient conditions up to 3 GPa. The strength of coupling between lattice and molecular modes as a function of pressure is examined. The anharmonic deviation of each mode from simple harmonic behavior as a function of pressure is also illustrated. [Preview Abstract] |
Tuesday, June 30, 2009 1:45PM - 2:00PM |
K2.00002: A Theoretical Study of Vibrational Spectroscopy in Hydrostatically Compressed Nitromethane Crystal Using an Empirical Form Molecular Dynamics Force Field Ali Siavosh-Haghighi, Richard Dawes, Thomas D. Sewell, Donald L. Thompson Molecular dynamics simulations have been used with an unreactive but vibrationally accurate force field [Sorescu et al., J. Phys. Chem. B \textbf{104}, 8406 (2000)] to investigate the effects of isothermal hydrostatic stress on the vibrational spectrum of crystalline nitromethane. Power spectra corresponding to the classical vibrational density of states were obtained as Fourier transforms of the mass-weighted velocity-velocity autocorrelation functions at 298 K for seven hydrostatic pressures between 0.0 and 13.5 GPa. The goal is to provide an explanation for the pressure-induced shifts, splittings, and appearance/disappearance of bands in the infrared and Raman spectra observed in recent experimental [Ouillon et al., J. Raman Spectrosc. \textbf{39}, 354 (2008); Citroni et al., J. Phys. Chem. B \textbf{112}, 1095 (2008)] and electronic structure-based [Liu et al., J. Chem. Phys. \textbf{124}, 124501 (2006)] studies. [Preview Abstract] |
Tuesday, June 30, 2009 2:00PM - 2:15PM |
K2.00003: Molecular Dynamics Simulations of Shock-Induced Defect Healing in Silicon Xiang Gu, You Lin, Ivan Oleynik, Carter White Molecular dynamics (MD) simulations of the interaction of planar shock waves with point defects (interstitials and vacancies, or Frenkel pairs) have been performed to investigate the possibility defect reduction in Si resulting from substantial mechanical stress behind the shock wave front. The MD shock experiments were run in Si samples containing Frenkel pairs of varying concentration and composition. The defect dynamics behind the shock wave front were studied as a function of the shock wave intensity and the crystallographic orientation of its propagation. We also simulated shock unloading that returns the compressed samples to their uncompressed state. The overall effectiveness of shock-induced defect healing was studied as well. Such an unusual application of the shock compression of solids might be useful in the microelectronics industry where such defects produced by ion implantation are considered a serious obstacle towards the further size reduction of Si CMOS devices. [Preview Abstract] |
Tuesday, June 30, 2009 2:15PM - 2:30PM |
K2.00004: Density Functional Theory (DFT) Simulations of Shocked Liquid Xenon Thomas R. Mattsson, Rudolph J. Magyar Xenon is not only a technologically important element used in laser technologies and jet propulsion, but it is also one of the most accessible materials in which to study the metal-insulator transition with increasing pressure. Because of its closed shell electronic configuration, Xenon is often assumed to be chemically inert, interacting almost entirely through the van der Waals interaction, and at liquid density, is typically modeled well using Leonard-Jones potentials. However, such modeling has a limited range of validity as Xenon is known to form compounds at normal conditions and likely exhibits considerably more chemistry at higher densities when hybridization of occupied orbitals becomes significant. In this talk, we present DFT-MD simulations of shocked liquid Xenon with the goal of developing an improved equation of state. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000. [Preview Abstract] |
Tuesday, June 30, 2009 2:30PM - 2:45PM |
K2.00005: Microscopic theory and kinetic model of fracture of liquids Vasiliy Pisarev, Alexey Kuksin, Genri Norman, Vladimir Stegailov, Alexey Yanilkin Fracture kinetic model of liquids based on molecular dynamics simulations is presented. Stretched liquid appears as a result of large energy deposition to condensed matter, for example, under laser processing or shock-wave loading of materials. The kinetic model of fracture includes two processes: nucleation and growth of voids (NAG approach). The rates of nucleation and growth of voids are evaluated separately from molecular dynamics simulations on the example of Lennard-Jones liquid. Pressure and temperature dependences of nucleation rate can be approximated in the form of classical nucleation theory. The kinetics of void growth is shown to satisfy the hydrodynamic Rayleigh-Plesset equation. The fracture kinetics and spall strength are determined by means of the proposed model. The results of calculations show good agreement with the experimental data. This work was supported by the RAS programs {\#} 11, 12, and SNL under the US DOE/NNSA ASC program. [Preview Abstract] |
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