Exploring structural inhomogeneities in glasses during cavitation

TL;DR

This study uses large-scale molecular dynamics simulations to investigate how dense glasses develop cavities and inhomogeneities during expansion, revealing instability thresholds, long-lived voids, and hysteresis effects in the glassy state.

Contribution

It provides new insights into the formation of cavities and inhomogeneities in glasses under expansion, including the stability limits and hysteretic behavior, using extensive simulations.

Findings

Identification of instability points leading to cavity formation.

Discovery of long-lived inhomogeneous configurations with negative pressure.

Observation of hysteresis effects upon compression of cavitated glasses.

Abstract

Using large-scale molecular dynamics simulations for a system of $10^6$ particles, the response of a dense amorphous solid to the continuous expansion of its volume is investigated. We find that the spatially uniform glassy state becomes unstable via the formation of cavities, which eventually leads to failure. By scanning through a wide range of densities and temperatures, we determine the state points at which the instability occurs and thereby provide estimates of the co-existence density of the resultant glass phase. Evidence for long-lived, inhomogeneous configurations with a negative pressure is found, where the frozen-in glass structure contains spherical cavities or a network of void space. Furthermore, we demonstrate the occurrence of hysteretic effects when the cavitated solid is compressed to regain the dense glassy state. As a result, a new glass state is obtained, the pressure of which is different from the initial one due to small density inhomogeneities that are generated by the dilation-compression cycle.