Vacancies and a generalised melting curve of alkali halides
Katarzyna Ksiazek, Tadeusz Górecki
The vacancy model of the melting process is used as a starting point for deriving an expression for the pressure dependence of the melting temperature of alkali halides. The results obtained for the initial slope of the melting curve are compared with experimental data for 15 alkali halides and in most cases the agreement is very good. The curvature of the melting curve and the appearance of the maximum on the melting curve at a pressure approximately equal to the bulk modulus are also predicted. A relationship between the vacancy formation energy, molar volume, and bulk modulus of alkali halides is established. On the basis of this relationship and the proposed vacancy model, a generalised equation for the pressure dependence of the melting temperature of alkali halides is derived.