Structural, vibrational and thermal properties of densified silicates : insights from Molecular Dynamics

TL;DR

This study uses molecular dynamics simulations to explore how densification affects the structure, vibrations, and thermal properties of sodium silicate glass and liquid, revealing network reorganization and thermal behavior changes.

Contribution

It provides new insights into the structural and vibrational changes in densified sodium silicate, including network repolymerization and vibrational shifts, using comprehensive molecular dynamics simulations.

Findings

Repolymerization from tetrahedral to octahedral silicon environments.

Shift of the Boson peak to higher frequencies with densification.

Thermal behavior modeled successfully with Birch-Murnaghan equation.

Abstract

Structural, vibrational and thermal properties of densified sodium silicate (NS2) are investigated with classical molecular dynamics simulations of the glass and the liquid state. A systematic investigation of the glass structure with respect to density was performed. We observe a repolymerization of the network manifested by a transition from a tetrahedral to an octahedral silicon environment, the decrease of the amount of non-bridging oxygen atoms and the appearance of three-fold coordinated oxygen atoms (triclusters). Anomalous changes in the medium range order are observed, the first sharp diffraction peak showing a minimum of its full-width at half maximum according to density. The previously reported vibrational trends in densified glasses are observed, such as the shift of the Boson peak intensity to higher frequencies and the decrease of its intensity. Finally, we show that the thermal behavior of the liquid can be reproduced by the Birch-Murnaghan equation of states, thus allowing us to compute the isothermal compressibility.