Bulletin of the American Physical Society
APS March Meeting 2016
Volume 61, Number 2
Monday–Friday, March 14–18, 2016; Baltimore, Maryland
Session C53: Massively Parallel Simulations of Chemical, Materials and Biological SystemsInvited

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Sponsoring Units: DCOMP Chair: Priya Vashisthta, University of Southern California Room: Hilton Baltimore Holiday Ballroom 4 
Monday, March 14, 2016 2:30PM  3:06PM 
C53.00001: Firstprinciples temperaturedependent phonons and elastic constants Invited Speaker: Lin Yang Calculations of thermodynamic properties of materials from firstprinciples are critical for equation of state and materials strength modeling. ~Here we present the thermodynamic properties of a select set of metals based on density functional theory. In particular, we present elastic constants and lattice dynamics for bodycentered cubic metals obtained from firstprinciples molecular dynamics and a selfconsistent phonon approach. In order to calculate the thermodynamic properties, we make use of fluctuation formulas associated with the canonical ensemble form of \textit{ab initio} molecular dynamics (AIMD). This procedure is efficient and takes into account the anharmonic contributions to the equilibrium thermodynamic properties. In the selfconsistent lattice dynamics approach, the phonon dispersions at finite temperature are determined from small displacements along normal modes associated with the chosen temperature.~ This method provides an efficient and accurate technique for phonon spectrum and finitetemperature acoustic sound speeds and elastic constants. We found that both methods provide consistent results for the temperature and pressuredependent elastic moduli. The AIMD include full anharmonicity but suffers from statistical errors of the order of 5{\%}. The selfconsistent phonon method, on the other hand, has less statistical uncertainty but does not explicitly account for electronphonon coupling. At ambient pressure, our calculations (both methods) agree quite well with experimental data.\\ \\This work performed under the auspices of the U.S. DOE by LLNL under Contract DEAC5207NA27344. [Preview Abstract] 
Monday, March 14, 2016 3:06PM  3:42PM 
C53.00002: The ReaxFF method  new applications and developments Invited Speaker: Adri van Duin The ReaxFF method provides a highly transferable simulation method for atomistic scale simulations on chemical reactions at the nanosecond and nanometer scale. It combines concepts of bondorder based potentials with a polarizable charge distribution. Since it initial development for hydrocarbons in 2001, we have found that this concept is transferable to applications to elements all across the periodic table, including all first row elements, metals, ceramics and ionic materials. For all these elements and associated materials we have demonstrated that ReaxFF can reproduce quantum mechanicsbased structures, reaction energies and reaction barriers with reasonable accuracy, enabling the method to predict reaction kinetics in complicated, multimaterial environments at a relatively modest computational expense. This presentation will describe the current concepts of the ReaxFF method, the current status of the various ReaxFF codes, including parallel implementations and recently developed hybrid Grand Canonical Monte Carlo options  which significantly increase its application areas. Also, we will present and overview of recent applications to a range of materials of increasing complexity, with a focus on applications to combustion, biomaterials, batteries, tribology and catalysis. [Preview Abstract] 
Monday, March 14, 2016 3:42PM  4:18PM 
C53.00003: Discovering chemistry with an ab initio nanoreactor Invited Speaker: Todd Martinez Traditional approaches for modeling chemical reaction networks such as those involved in combustion have focused on identifying individual reactions and using theoretical approaches to explore the underlying mechanisms. Recent advances involving graphical processing units (GPUs), commodity products developed for the videogaming industry, have made it possible to consider a distinct approach wherein one attempts to discover chemical reactions and mechanisms. We provide a brief summary of these developments and then discuss the concept behind the ``ab initio nanoreactor'' which explores the space of possible chemical reactions and molecular species for a given stoichiometry. The nanoreactor concept is exemplified with an example to the UreyMiller reaction network which has been previously advanced as a potential model for prebiotic chemistry. We briefly discuss some of the future directions envisioned for the development of this nanoreactor concept. [Preview Abstract] 
Monday, March 14, 2016 4:18PM  4:54PM 
C53.00004: Multipetaflop/s quantum and reactive molecular dynamics simulations Invited Speaker: Aiichiro Nakano We have developed a divideconquerrecombine algorithmic framework for large quantum molecular dynamics (QMD) and reactive molecular dynamics (RMD) simulations. The algorithms have achieved parallel efficiency over 0.98 on 786,432 IBM Blue Gene/Q processors for 39.8 trillion electronic degreesoffreedom QMD in the framework of density functional theory and 67.6 billionatom RMD. We will discuss several applications including (1) 16,616atom QMD simulation of rapid hydrogen production from water using metallic alloy nanoparticles, (2) 6,400atom nonadiabatic QMD simulation of exciton dynamics for efficient solar cells, and (3) 112 millionatom RMD simulation of nanocarbon synthesis by high temperature oxidation of SiC nanoparticles. [Preview Abstract] 
Monday, March 14, 2016 4:54PM  5:30PM 
C53.00005: Massively parallel models of human hemodynamics Invited Speaker: Amanda Randles 
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