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Publication 75

An Accelerated Finite-Temperature Quasicontinuum Method using Hyperdynamics

Authors:

MinnesotaWoo Kyun Kim
Department of Aerospace Engineering and Mechanics
University of Minnesota
Minneapolis, Minnesota


MinnesotaMitchell Luskin
School of Mathematics, University of Minnesota 206 Church Street SE, Minneapolis, MN 55455, U.S.A.


Danny Perez
Los Alamos National Laboratory, Theoretical Division T-1, Los Alamos, NM, USA


MinnesotaE. B. Tadmor
Department of Aerospace Engineering and Mechanics
University of Minnesota
Minneapolis, Minnesota


Art Voter
Los Alamos National Laboratory, Theoretical Division T-1, Los Alamos, NM, USA


Abstract:
The quasicontinuum (QC) method is a spatial multiscale method that extends the length scales accessible to fully atomistic simulations (like molecular dynamics (MD)) by several orders of magnitude. While the recent development of the so-called "hot-QC method" enables dynamic simulations at finite temperature, the times accessible to these simulations remain limited to the sub-microsecond time scale due to the small time step required for stability of the numerical integration. To address this limitation, we develop a novel finite-temperature QC method that can treat much longer time scales by coupling the hot-QC method with hyperdynamics - a method for accelerating time in MD simulations. We refer to the new approach as "hyper-QC". As in the original hyperdynamics method, hyper-QC is targeted at dynamical systems that exhibit a separation of time scales between short atomic vibration periods and long waiting times in metastable states. Acceleration is achieved by modifying the hot-QC potential energy to reduce the energy barriers between metastable states in a manner that ensures that the characteristic dynamics of the system are preserved. First, the high accuracy of hot-QC in reproducing rare event kinetics is demonstrated. Then, the hyper-QC methodology is validated by comparing hyper-QC results with those of hot-QC and full MD for a one-dimensional chain of atoms interacting via a Lennard-Jones potential.
Get the paper in its entirety
KimLuskinPerez.pdf

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