Slow dynamics in a primitive tetrahedral network model

TL;DR

This study uses simulations to explore the slow dynamics and glass transition behavior in a primitive tetrahedral network model for silica, highlighting the role of bonding patterns and geometric constraints.

Contribution

It provides detailed simulation analysis of silica's primitive model, comparing it with other network models to understand bonding and structural effects on glass formation.

Findings

Arrest is driven by tetrahedral bonding at moderate densities.

Dynamics are classified as strong in Angell's scheme.

Structural and dynamic similarities with water and colloidal gel models.

Abstract

We report extensive Monte Carlo and event-driven molecular dynamics simulations of the fluid and liquid phase of a primitive model for silica recently introduced by Ford, Auerbach and Monson [J. Chem. Phys. 17, 8415 (2004)]. We evaluate the iso-diffusivity lines in the temperature-density plane to provide an indication of the shape of the glass transition line. Except for large densities, arrest is driven by the onset of the tetrahedral bonding pattern and the resulting dynamics is strong in the Angell's classification scheme. We compare structural and dynamic properties with corresponding results of two recently studied primitive models of network forming liquids -- a primitive model for water and a angular-constraint free model of four-coordinated particles -- to pin down the role of the geometric constraints associated to the bonding. Eventually we discuss the similarities between "glass" formation in network forming liquids and "gel" formation in colloidal dispersions of patchy particles.