Molecular dynamics simulation of structural phase transitions in RbNO3 andCsNO3

,Structural phase transitions in RbNO3 and CsNO3 are studied by molecular d ynamics. The simulations are based on the parameter-free potentials calcula ted from the Gordon-Kim modified electron gas formalism, extended to ionic molecular crystals. The microscopic mechanism of the structural phase trans itions in RbNO3 and CsNO3 is revealed. It is found that the phase IV-III tr ansition in RbNO3 and the phase U-I transition in CsNO3 are initiated by th e in-plane and out-of-plane rotations of the NO3 ions, and the phase III-II -I transitions in RbNO3 are due to dilation along a trigonal axis of phase III, giving phase II a rhombohedral structure. (C) 2001 Academic Press.