Pressure-induced cubic to tetragonal transition in CsI.

Abstract

First-principles self-consistent total-energy calculations within the local-density approximation show, in agreement with experiments, that CsI undergoes a transition from the cubic (CsCl) structure to a tetragonal structure at a pressure ${P}_{t}\ensuremath{\simeq}40$ GPa. The calculated volume at the transition is \ensuremath{\sim} 53% of the zero-pressure volume. We find that the phase transition is driven by an "intercellular" electrostatic interaction. A structural bistability is found around the transition.