Structural and dynamic properties of soda-lime-silica in the liquid phase

TL;DR

This study uses molecular dynamics simulations to analyze the structure and diffusion of soda-lime-silica glass in its liquid state, revealing ion-specific organization and mobility differences at high temperatures.

Contribution

It introduces an advanced aspherical ion model with polarization effects to accurately characterize liquid soda-lime-silica properties.

Findings

Na+ ions diffuse faster than Ca2+ ions.

Ca2+ ions have a greater affinity for non-bridging oxygens.

Diffusion is limited by escape from the first oxygen coordination shell.

Abstract

Soda-lime-silica is a glassy system of strong industrial interest. In order to characterize its liquid state properties, we performed molecular dynamics simulations employing an aspherical ion model that includes atomic polarization and deformation effects. They allowed to study the structure and diffusion properties of the system at temperatures ranging from 1400 to 3000 K. We show that Na$^+$ and Ca$^{2+}$ ions adopt a different structural organization within the silica network, with Ca$^{2+}$ ions having a greater affinity for non-bridging oxygens than Na$^+$. We further link this structural behavior to their different diffusivities, suggesting that escaping from the first oxygen coordination shell is the limiting step for the diffusion. Na$^+$ diffuses faster than Ca$^{2+}$ because it is bonded to a smaller number of non-bridging oxygens. The formed ionic bonds are also less strong in the case of Na$^+$.