Analysis of disproportionation of Qn structons in the simulation of the structure of melts in the Na2O-SiO2 system

A new version of the STRUCTON-1.2 computer program (2009) has been presented. The program combines the algorithm for calculating real distributions of Q ⁿ structons in binary silicate melts (with allowance made for their disproportionation) and the statistical simulation of molecular-mass distributions of polymerized ions at different temperatures. This model has been used to perform test calculations for two melts in the Na₂O-SiO₂ system (Na₆Si₂O₇, Na₆Si₃O₉). The results of the calculations have made it possible to trace variations in the set and concentrations of chain and ring silicon-oxygen complexes with a decrease in the temperature in the order: stochastic molecular-mass → distribution molecular-mass distribution at T = 2000 K → molecular-mass distribution at the liquidus temperature. The main result of these calculations is that the dominant species of silicon-oxygen anions at the liquidus temperatures (in contrast to the stochastic distributions) exactly correspond to the stoichiometry of the initial melts: the Si₂O₇⁶⁻ chain anions and (Si _n O_3n )³ⁿ⁻ ring complexes are dominant in the Na₆Si₂O₇ and Na₆Si₃O₉ melts, respectively. It has been established that, with a decrease in the temperature, the average size of polymer complexes varies weakly in the Na₆Si₂O₇ melt but increases by a factor of approximately 1.5 in the metasilicate system.