Molecular dynamics simulation of thermodynamic and structural properties of silicate glass: Effect of the alkali oxide modifiers

Molecular dynamics simulation was applied to elucidate the effect of adding alkali oxides (M2O)(x)(SiO2)(SiO2)((1-x)) with M = (Na, Li or K) into silicate glass matrix. We are interested in the study of this effect particularly on structural and thermodynamic properties of the material. Some interesting results were obtained given a new insight on the bridging process and its reliability to the observed depolymerization phenomena affecting the existing Si-O network and depending on both the kind of the alkali modifier and its molar fraction. We observed that the thermodynamic properties are influenced by these structural modifications. Indeed, the glass transition temperature T-g has been found to decrease as the molar fraction of modifier increases depending strongly on the alkali modifier kind. On the other hand, we extracted the fictive temperature from the calculated total energy of the system and determined the glass transition by studying the variation of the fictive temperature as a function of the conventional one using different cooling and heating rates. (C) 2016 Elsevier B.V. All rights reserved.