A MOLECULAR-DYNAMICS SIMULATION OF THE ORIENTATIONAL MELTING OF POTASSIUM PERCHLORATE

A constant-pressure molecular-dynamics simulation of the first-order p hase transition of potassium perchlorate is presented. The simulation yields the correct structures in both the low-temperature ordered phas e and the high-temperature orientationally disordered phase. While exp eriments show a rather ill-behaved reconstructive transition, the simu lation, despite its excellent agreement with known crystallographic da ta, follows a very straightforward transition process. This suggests t hat the behaviour of the real sample, which is presumably connected wi th the large volume increase at the transition, is driven by effects o n a non-microscopic scale.