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}\,21{\it /m}, {\it Pm} and {\it P}\,63/{\it mmc} have been identified as candidates for the ζ 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.
@article{arxiv.2309.13936,
title = {The $\epsilon$-$\zeta$ Transition in Solid Oxygen},
author = {Sabri F. Elatresh and V. Askarpour and S. A. Bonev},
journal= {arXiv preprint arXiv:2309.13936},
year = {2023}
}