I will discuss a coarse-grained model of molecular dynamics in
crystalline solids. Such system usually has an underlying lattice
structure, and the empirical potentials are of quite simple forms.
Thus it provides a nice setting in which coarse-graining (CG) methods
can be considered. The goal of the CG method is to reduce the
atomic degrees of freedom, and arrive at an effective model in
which only a small number of atoms are explicitly involved.