The $\epsilon$-$\zeta$ Transition in Solid Oxygen

TL;DR

This study investigates the structural phases of solid oxygen under high pressure using advanced computational methods, identifying the most stable structure at 300K and comparing with experimental data.

Contribution

It introduces a comprehensive computational analysis of solid oxygen's phases at high pressures, identifying the most stable structure at 300K using hybrid density functional theory.

Findings

Pm structure is most stable above 111 GPa at 300K.

Multiple candidate structures identified at 0 K.

Comparison with experimental data supports the theoretical predictions.

Abstract

The structure of solid oxygen has been studied at pressures from 50 to 140~GPa using static structure search methods and molecular dynamics simulations with density functional theory and a hybrid exchange functional. Several crystalline structures with space group symmetries {\it Pnma}, {\it P}\,2$_{1}${\it /m}, {\it Pm} and {\it P}\,6$_3$/{\it mmc} have been identified as candidates for the $\zeta$ phase of oxygen at 0~K. Within the hybrid exchange functional framework and at 300~K temperature, {\it Pm} is shown to be energetically most favorable above 111~GPa. A comparison with experimental X-ray diffraction, spectroscopic and superconductivity measurements is provided for all competing structures.