A MOLECULAR-DYNAMICS SIMULATION OF THE ORIENTATIONALLY DISORDERED PHASE OF POTASSIUM PERCHLORATE

The orientationaly disordered phase of a relatively large system of po tassium perchlorate is simulated on a massively parallel computer with strict SIMD architecture. Crystallographic results are compared with known diffraction data. Correlation densities of orientational and tra nslational variables are computed showing orientation-translation coup ling of the perchlorate ions, and coupling between a perchlorate orien tation and the translation of neighbouring potassium and perchlorate i ons. The orientation-orientation correlation between neighbouring perc hlorate ions shows antiferromagnetic pseudo-spin type coupling corresp onding to ions in opposite T-d orientations. This correlation has a li fetime which is longer than the single molecule orientational lifetime , evidence of correlated orientational motion.