Simulation of polytype formation in zinc sulphide

A simple model for the formation of polytypes in ZnS is presented. It is based on theoretically calculated stacking fault energies for this material. Polytypes are explained as metastable structures occurring during the wurtzite-zincblende phase transition. A Monte Carlo simulation of the process results in structures very similar to those observed in experiment. The same mechanism also explains the main features of X-ray data obtained from disordered highly twin-faulted cubic crystals of ZnS.