Abstract
A fairly extensive review of the literature on the nature of liquid-liquid phase separation in silicate melts and glasses has already been given in the preceding paper by Galakhov and Varshal. The views of various writers on the nature of phase separation are in the main either purely qualitative or involve attempts to find formal relationships between ionic radii, cationic field strengths, hypothetical local structures, and experimental characteristics of phase separation. All this can be regarded merely as preliminary steps toward derivation of a theory of phase separation, which must be a statistical physical theory based on more or less detailed analysis of interatomic interactions. An advance in this direction is, for example, the work of Kozheurov [1], who made an attempt to write an expression for the free energy of a silicate melt undergoing phase separation. Owing to the complexity of his polymeric model, he did not fully succeed in substantiating theoretically the addition of free energy postulated by him, so that the final formulas are of semiempirical character. In the present paper we derive a model, based on simplified concepts of structure and atomic-ionic interactions, making it possible to make approximate calculations of the free energy of a silicate melt or glass as a function of its composition and temperature. In our opinion, this model combines to a certain degree the views put forward earlier by Warren and Pincus [2], Dietzel [3], and Markhasev and Sedletskii [4] on the nature of phase separation.
Published Version
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