The importance of intermediate range order in silicates: molecular dynamics simulation studies

TL;DR

This study uses large-scale molecular dynamics simulations to explore the intermediate range order and unique dynamic behaviors in sodium and aluminum silicate melts, revealing structural features beyond silica and unexpected sodium ion dynamics.

Contribution

It demonstrates the presence of intermediate range order in silicate melts and links structural features to sodium ion dynamics using advanced parallel supercomputing simulations.

Findings

Intermediate range order exists in silicate melts beyond silica.

Sodium ions exhibit rapid one-particle motion compared to ion correlation times.

Structural features are connected to unique ion dynamics.

Abstract

We present the results of large scale computer simulations in which we investigate the structural and dynamic properties of silicate melts with the compositions (Na_2O)2(SiO_2) and (Al_2O_3)2(SiO_2). In order to treat such systems on a time scale of several nanoseconds and for system sizes of several thousand atoms it is necessary to use parallel supercomputers like the CRAY T3E. We show that the silicates under consideration exhibit additional intermediate range order as compared to silica (SiO_2) where the characteristic intermediate length scales stem from the tetrahedral network structure. For the sodium silicate system it is demonstrated that the latter structural features are intimately connected with a surprising dynamics in which the one--particle motion of the sodium ions appears on a much smaller time scale than the correlations between different sodium ions.