Order-disorder structural phase transitions in alkali perchlorates

Order-disorder structural phase transitions in alkali perchlorates MClO4 (M = Na, K, Rb, Cs) are investigated using molecular dynamics simulation. The potentials in the simulations are based on the Gordon-Kim modified electron gas formalism extended to molecular ions. The simulations yield first-order phase transitions in perchlorates from low temperature orthorhombic structures to high temperature cubic NaCl structures. The perchlorate ions are found to be orientational disordered in the high temperature phases. (C) 2002 Elsevier Science.