Analysis of melting for alkali halides based on the potential energy curve

Abstract

We present an analysis of melting of alkali halides on the basis of lattice potential energy ( Φ) versus interionic separation ( r) curve. The point of inflection in the potential energy curve is identified corresponding to d 2 Φ/d r 2=0. Values of interionic separations of melting points for 16 alkali halides have been calculated using the Born–Mie inverse power form and the Born–Mayer exponential forms for the potential energy functions. The parameters in the potential energy functions used are those derived from the ultrasonic data for thermoelastic properties. Values of interionic separations ( r m) at melting temperature ( T m) calculated in the present study are found to compare well with the corresponding values of interionic separations obtained using the Anderson formula for thermal expansivity. The expression for T m, in terms of r m and the derivative of potential energy, has been found to be satisfied with the data for alkali halides at melting.