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.
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 Lth European High Pressure Research Group (EHPRG 50) Meeeting at Thessaloniki (Greece), 16–21 September 2012.