A MOLECULAR-DYNAMICS SIMULATION STUDY OF THE EFFECTS OF DEFECTS ON THE TRANSFORMATION PRESSURE OF POLYMORPHIC PHASE-TRANSFORMATIONS

The effect of defects (in the form of vacancies) on the transformation pressure of the Fm3m-Pm3m phase transition of KCl has been examined u sing molecular dynamics simulations. The simulated transformation has been found to be reversible, exhibiting a large hysteresis. Vacancy de fects were systematically introduced into the crystal structure of the parent phase, and then a series of simulations using the Parrinello-R ahman method were performed to elucidate the transformation pressure. With an increase in the density of the defects, the hysteresis decreas es. These results are entirely consistent with the observed behavior. (C) 1996 American Institute of Physics.