Structural Analysis of Some Molten Materials by X-ray Diffraction: Part 2.—Li2SO4, Na2SO4 and the Mixed System

Abstract

The structures of molten Li2SO4, Na2SO4 and their mixtures have been examined by co nsideration of the radial distribution function and the molar volume. The existence of tetrahedral su phate ions in these molten salts has been demonstrated. S—O and O—O distances for the sulphate ion in the molten state arc 1.50o and 2.450 A, respectively. A close packed arrangement of sulphate ions appears to be the configuration realized in molten Li2SO4 ; the calculated correlation function based on this structural model is qualitatively in good agreement with the observed one. In molten Na2SO4, sodium ions probably occupy a position intermediate between the edge and face sites of the sulphate ion; the nearest-neighbour distances of Na—S and Na—O pairs are 2.8 and 2.33 A, respectively.