Structural analysis of molten Cs2So4

Abstract

The structure of molten Cs₂SO₄ has been investigated using the radial distribution function based on X-ray scattered intensity data collected at ca. 1100 °C and has been analysed by the correlation method. The SO₄ tetrahedron which exists in the crystalline state of Cs₂SO₄ has been shown to be preserved in the molten state. The most likely model for the short-range arrangement is that ca. 7/8 of the Cs atoms occupy the corner-sharing sites with an average Cs—O distance of 3.07 Å and the others occupy the face-sharing sites with an average Cs—O distance of 3.48 Å. The most likely model for the long-range arrangement within 10 Å is simulated by CaF₂-type packing where the Ca and F atoms are replaced by the SO₄ tetrahedron and the Cs atom, respectively. One Cs₂SO₄ unit is surrounded by ca. 18 Cs₂SO₄ units with an average inter-unit distance of 7.56 Å. The structure of molten Cs₂SO₄ has been discussed in relation to those of molten M₂SO₄(M = Li, Na, K and Ag).