Influence of Magnesium on the Structure of Complex Multicomponent Silicates: Insights from Molecular Simulations and Neutron Scattering Experiments.

Abstract

A series of multicomponent glasses containing up to five oxides are studied using classical molecular dynamics simulations and neutron scattering experiments. The focus is on the role of magnesium in determining the structural properties of these glasses and the possible mixed effect during a sodium/magnesium substitution. Calculated structure functions (pair correlation function and structure factor) rather accurately reproduce their experimental counterpart, and we show that more fine structural features are qualitatively reproduced well, despite some discrepancies in the preferential spatial distribution between sodium and magnesium to aluminum and boron, as well as the nonbridging oxygen, distribution. The simulated systems offer a solid basis to support previous experimental findings on the composition-structure relationship, allowing for further analysis and property calculation. It is confirmed that the substitution of sodium by magnesium leads to the decrease of four-fold boron and a modification of the alkali coordinations with a significant change of the network structure. Specifically, magnesium coordination extracted from numerical simulations highlights a potential dissociation from penta- to tetra- and hexahedral units with increasing MgO contents along the glass series, which could not be resolved experimentally.