Numerical simulation of alpha-quartz under non-hydrostatic compression. Memory glass and five-coordinated crystalline phases

TL;DR

This study uses molecular dynamics simulations to explore how non-hydrostatic stresses influence the amorphization and phase transitions of alpha-quartz under high pressure, revealing that stress direction affects crystalline and amorphous phase formation.

Contribution

It demonstrates that non-hydrostatic stress conditions can alter amorphization thresholds and induce a new five-coordinated crystalline phase in alpha-quartz.

Findings

Amorphization threshold remains unchanged under certain non-hydrostatic stresses.

Positive uniaxial stress along c-axis induces five-coordinated silicon crystalline phase.

Mean amorphization pressure can be lowered with non-hydrostatic conditions.

Abstract

The behavior of $\alpha$-quartz under hydrostatic and non-hydrostatic high-pressure conditions has been investigated in Molecular Dynamics simulations of silica in order to clarify the role of non-hydrostatic stresses in the amorphization process. It is shown that the amorphization threshold is not modified if the stress along the {\bf c} direction is lowered, so that the mean amorphization pressure can effectively be lowered under non-hydrostatic conditions. On the other hand, the application of a positive uniaxial stress along the {\bf c} axis, results in the appearance of a new crystalline phase, where all silicon atoms are in five-fold coordination.