A note on the equation of state for systems that underqo valence changes.

Abstract

In this paper we want to discuss in a simple way the equation of state of a system that undergoes valence changes. This requires consideration of the cohesive energy of the compounds which is, in general, a major problem. For this reason we shall consider only those compounds which are mainly ionic in character, so that their cohesive energy can be reasonably described by the Madelung and repulsive core contributions. In fact, the collapsed phases form rather poor metals and there should still be a high degree of ionicity left, as is indicated by the stability of the NaCl structure.