Monte Carlo Simulations of the Metastability in Molecular Crystals

A measure of the non-ergodicity has been introduced for plastic phases of molecular crystals. Monte Carlo simulations of the cubic, disordered phase of cyanoadamantane have been examined from the point of view of quasi-ergotic behavior. It has been shown that the conventional way of sampling based on the Metropolis algorithm is not efficient when temperature is lowered and the crystal is put into a quenched metastable situation. New methods are required to allow the system to overcome energy barriers which separate equally important volumes in the configuration space.