A new approach to repulsion in ionic crystals II. further refinement on the alkali halides

Abstract

The repulsion paralileters in the formulation by the authors (J. Phys. Chettt. Solids, 1976,37,395; Ctirr. Sci., 1976, 45, 357) for the alkali and the halogen ions have bee11 refined using more experitilental data. These parameters could be used to calculate the repulsion potential in any cryztalof any structure in which these ions may occur. The r.m.s. error in the alkali halides between the measurea and calculated values of the nearest neighbour distance is 0.712% and that in d'W Idr'is 7.40%. The corresponding values in the theory of Tosi and Fumi (J. Phys. Clterrt. Solids, i961,25,45) are 1.381"/, and 6.06%. Our earlier claim that our values were much better than Tosi ar.a Funli arose out of a coniputational error and is her'ce retracted here. Our present repulsion par;i-~iletcrsin dicate that the alkalt ions are (as is to be expected) much less coniprcssiblc conlp;t~eut o t l ~ c halogen ions.