The quasicontinuum (QC) technique,in which the atomic lattice of a solid is coarse-grained by overlaying it with a finite-element mesh,has been employed previously to treat the quasistatic evolution of defects in materials at zero temperature.It is extended here to nonzero temperature.A coarse-grained Hamiltonian is derived for the nodes of the mesh,which behave as quasiparticles whose in teractions are mediated by the underlying (non-nodal)atoms constrained to move in unison iwth the nodes.Coarse-grained thermophysical properties are computed by means of the Monte Carlo (MC) method.This dynamiclly constrined QC MC procedure is applied to a simple model:A pure single crystal of two-dimensional lennard-Jonesium.The coarse-grained isotropic stress (tau_c) is compared with the "exact" tau computed by the usual atomistic MC procedure for several thermodynamic states.The observed linear dependence of the error in tau_c on the degree of coarse-graining is rationalized by an analyticla treatment of the mode within the local harmonic approximation.
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