Structural studies of charged hard-sphere mixtures through Blum's generalized "Γ" parameter. Application to molten RbCl and RbBr

Abstract

The most general solution for the direct correlation function of unequal diameters for charged hard-sphere mixtures is given by Blum and Tibavisco in the mean spherical model approximation. Hiroike has given expressions for C_ij(r), the direct correlation function (DCF), in a form convenient for numerical caluculations. These equations are used in the evaluation of partial structure factors of RbCl and RbBr. The DCF expressions contain a parameter Γ which is analogous to the Debye inverse length parameter. This parameter is calculated numerically. From the partial structure factors, the partial radial distribution functions, the co-ordination numbers, charge-charge and number-number correlation functions are obtained. Also computed are the compressibilities from the partial structure factors in the long wave limit, which are in satisfactory agreement with literature values. For the case of RbCl no literature values are available. The present method is different from the previous ones in the sense that it requires a minimum number of parameters, namely the ionic diameters. It is found that this model reproduces all the characteristics of fused salts, and the results compare satisfactorily with experiment.