Microscopic theory of network glasses

TL;DR

This paper develops a microscopic theory combining phonon and liquid state approaches to explain the glass transition in network forming liquids, predicting how bonding affects transition temperatures and fragility.

Contribution

It introduces a novel molecular theory that links bonding degree and density to glass transition behavior using a combined theoretical framework.

Findings

The ratio of dynamical transition to laboratory transition temperature increases with bonding.

The Kauzmann temperature decreases relative to the laboratory transition as bonding increases.

Highly coordinated liquids tend to be 'strong', while van der Waals liquids are 'fragile'.

Abstract

A molecular theory of the glass transition of network forming liquids is developed using a combination of self-consistent phonon and liquid state approaches. Both the dynamical transition and the entropy crisis characteristic of random first order transitions are mapped out as a function of the degree of bonding and the density. Using a scaling relation for a soft-core model to crudely translate the densities into temperatures, the theory predicts that the ratio of the dynamical transition temperature to the laboratory transition temperature rises as the degree of bonding increases, while the Kauzmann temperature falls relative to the laboratory transition. These results indicate why highly coordinated liquids should be "strong" while van der Waals liquids without coordination are "fragile".