The Densities and Structures of Silicate Melts

Abstract

As the density of a silicate melt is determined by the masses of the individual particles and by the manner in which the particles are arranged with respect to one another, the results of studies of the variations of melt density with composition and temperature are amenable to structural interpretation. Furthermore, as melt density, via its relationship with molar volume, is also a thermodynamic property, the interpretation of melt density in terms of the geometrical arrangements and configurations of ionic entities can be augmented by the interpretation of thermodynamic activities in terms of the extents and magnitudes of the interactions occurring among the various structural entities. This is particularly so in the consideration of ternary silicate melts. Recent X-ray diffraction studies of liquid alkali silicates (Waseda and Suito, 1977; Waseda and Toguri, 1977a) and alkaline earth silicates (Waseda and Toguri, 1977b) have confirmed that the tetrahedral coordination of silicon by oxygen, long detected in silicate glasses, persists in the melt, and hence the structures of melts can be approached by considering the ways in which silicate tetrahedra can be arranged with respect to one another.