Coarse-graining description of solid systems at nonzero temperature Z. B. Wu, D. J. Diestler, R. Feng and X. C. Zeng Journal of Chemical Physics, 119, 8013-8023 (2003). ABSTRACT 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 interactions are mediated by the underlying (non-nodal) atoms constrained to move in unison with the nodes. Coarse-grained thermophysical properties are computed by means of the Monte Carlo (MC) method. This dynamically constrained 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 analytical treatment of the model within the local harmonic approximation.