How glass breaks -- Damage explains the difference between surface and fracture energies in amorphous silica

TL;DR

This study uses multi-scale simulations to distinguish between surface energy and fracture energy in amorphous silica, clarifying the brittle fracture mechanisms by separating energy contributions at the atomic and continuum levels.

Contribution

It introduces a combined molecular dynamics and phase-field approach to quantify and differentiate energy contributions during fracture in amorphous silica.

Findings

Surface energy is localized as potential energy on the surface.

Damage diffusion occurs over a 16-23 Å range around the crack.

Plastic contributions are negligible in the fracture process.

Abstract

The difference between free surface energy and fracture toughness in amorphous silica is studied via multi-scale simulations. We combine the homogenization of a molecular dynamics fracture model with a phase-field approach to track and quantify the various energy contributions. We clearly separate free surface energy localized as potential energy on the surface and damage diffusion over a 16-23 A range around the crack path. The plastic contribution is negligible. These findings, which clarify brittle fracture mechanisms in amorphous materials, align with toughness measurements in silica.