Adaptive Strain-Boost Hyperdynamics Simulations of Stress-Driven Atomic Processes

Abstract

The deformation and failure phenomena of materials are the results of stress-driven, thermally activated processes at the atomic scale. Molecular-dynamics (MD) simulations can only span a very limited time range which hinders one from gaining full view of the deformation physics. Inspired by the Eshelby transformation formalism, we present here a transformation “strain-boost” method for accelerating atomistic simulations, which is often more efficient and robust than the bond-boost hyperdynamics method [R. A. Miron and K. A. Fichthorn, J. Chem. Phys. 119, 6210 (2003)] for exploring collective stress-driven processes such as dislocation nucleation, that have characteristic activation volumes larger than one atomic volume. By introducing an adaptive algorithm that safely maximizes the boost factor, we directly access the finitetemperature dynamical process of dislocation nucleation in compressed Cu nanopillar over time scale comparable to laboratory experiments. Our method provides stressand temperature-dependent activation enthalpy, activation entropy and activation volume for surface-dislocation nucleation with no human guidance about crystallography or deformation physics. Remarkably, the accelerated MD results indicate that harmonic transition-state theory and the empirical Meyer-Neldel compensation rule give reasonable approximations of the dislocation nucleation rate. Disciplines Engineering | Materials Science and Engineering Comments Suggested Citation: Hara, S. and J. Li. (2010). "Adaptive strain-boost hyperdynamics simulations of stress-driven atomic processes." Physical Review B. 82, 184114. © 2010 The American Physical Society http://dx.doi.org/10.1103/PhysRevB.82.184114 This journal article is available at ScholarlyCommons: http://repository.upenn.edu/mse_papers/187 Adaptive strain-boost hyperdynamics simulations of stress-driven atomic processes Shotaro Hara1,2 and Ju Li2,* 1Department of Mechanical Engineering, The University of Tokyo, Tokyo 113-8656, Japan 2Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6272, USA Received 2 November 2010; published 19 November 2010 The deformation and failure phenomena of materials are the results of stress-driven, thermally activated processes at the atomic scale. Molecular-dynamics MD simulations can only span a very limited time range which hinders one from gaining full view of the deformation physics. Inspired by the Eshelby transformation formalism, we present here a transformation “strain-boost” method for accelerating atomistic simulations, which is often more efficient and robust than the bond-boost hyperdynamics method R. A. Miron and K. A. Fichthorn, J. Chem. Phys. 119, 621

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@inproceedings{Hara2010AdaptiveSH, title={Adaptive Strain-Boost Hyperdynamics Simulations of Stress-Driven Atomic Processes}, author={Shotaro Hara and Ju Li}, year={2010} }