Stability and metallization of solid oxygen under high pressure

2018/12/07 by Elatresh, S. F., Bonev, S. A.
#Computational Physics (physics.comp-ph) #FOS: Physical sciences #Materials Science (cond-mat.mtrl-sci)

paper · doi:10.48550/arxiv.1812.03112

Abstract

The phase diagram of oxygen is investigated for pressures from 50 to 130~GPa and temperatures up 1200 K using first principles theory. A metallic molecular structure with the P6₃/mmc symmetry (η^' phase) is determined to be thermodynamically stable in this pressure range at elevated temperatures above the ε(O₈) phase. Long-standing disagreements between theory and experiment for the stability of ε(O₈), its metallic character, and the transition pressure to the ζ oxygen phase are resolved. Crucial for obtaining these results are the inclusion of anharmonic lattice dynamics effects and accurate calculations of exchange interactions in the presence of thermal disorder.

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