First-principles study on superconductivity of solid oxygen

Abstract

The superconductivity of solid oxygen in ζ phase was investigated by first-principles calculations based on the density functional theory. Using a monoclinic C2/m structure, we calculated the superconducting transition temperature by the Allen–Dynes formula and obtained 2.4 K at 100 GPa for the effective screened Coulomb repulsion constant μ* of 0.13. The transition temperature slowly decreases with increasing pressure and becomes 1.3 K at 200 GPa. The phonon analysis shows that the electron–phonon coupling is dominantly enhanced by the intermolecular vibrations of O₂ rather than the intramolecular ones. The phonon modes showing the strong electron–phonon coupling were found to be concentrated in the phonon frequency range of 100–150 cm⁻¹ at around the M-point in the Brillouin zone.

Keywords:

• first-principles calculation
• oxygen
• superconductivity
• phonon

Acknowledgements

This research is supported by the Japan Society for the Promotion of Science through its ‘Funding Program for Next Generation World-Leading Researchers (NEXT Program)’ No. GR068.

Notes

^†This paper was presented at the L^th European High Pressure Research Group (EHPRG 50) Meeeting at Thessaloniki (Greece), 16–21 September 2012.