On the Structural Transition from NaCl to CsCl Type in Alkali Hydrides

Abstract

The solid sphere ion model is used to compare specific volumes of NaCl and CsCl phases of alkali hydrides. The transition of the NaCl to CsCl type is shown to be thermodynamically possible in K, Rb, and Cs hydrides. A phase transition is detected in KH at pressures about 40 kbar, and the T—P diagram of KH is studied. On the basis of the analysis performed, the NaCl to CsCl transition in LiH is unlikely, unless the electron configurations of the ions are changed.