High-pressure hydrogen sulfide from first principles: a strongly anharmonic phonon-mediated superconductor.
We use first-principles calculations to study structural, vibrational, and superconducting properties of H_{2}S at pressures P≥200  GPa. The inclusion of zero-point energy leads to two different possible dissociations of H2S, namely 3H2S→2H3S+S and 5H2S→3H3S+HS2, where both H3S and HS2 are metallic. For H3S, we perform nonperturbative calculations of anharmonic effects within the self-consistent harmonic approximation and show that the harmonic approximation strongly overestimates the electron-phonon interaction (λ≈2.64 at 200 GPa) and Tc. Anharmonicity hardens H─S bond-stretching modes and softens H─S bond-bending modes. As a result, the electron-phonon coupling is suppressed by 30% (λ≈1.84 at 200 GPa). Moreover, while at the harmonic level Tc decreases with increasing pressure, the inclusion of anharmonicity leads to a Tc that is almost independent of pressure. High-pressure hydrogen sulfide is a strongly anharmonic superconductor.
Donostia International Physics Center (DIPC), Manuel de Lardizabal Pasealekua 4, 20018 Donostia-San Sebastián, Basque Country, Spain.|IKERBASQUE, Basque Foundation for Science, Bilbao, Spain.
Ion
I
Errea
IMPMC, UMR CNRS 7590, Sorbonne Universités-UPMC University Paris 06, MNHN, IRD, 4 Place Jussieu, F-75005 Paris, France.
Matteo
M
Calandra
Department of Physics & Astronomy, University College London, Gower Street, London WC1E 6BT, United Kingdom.
Chris J
CJ
Pickard
Theory of Condensed Matter Group, Cavendish Laboratory, J.J. Thomson Avenue, Cambridge CB3 0HE, United Kingdom.
Joseph
J
Nelson
Theory of Condensed Matter Group, Cavendish Laboratory, J.J. Thomson Avenue, Cambridge CB3 0HE, United Kingdom.
Richard J
RJ
Needs
School of Physics and Electronic Engineering, Jiangsu Normal University, Xuzhou 221116, People's Republic of China.
Yinwei
Y
Li
Department of Physics and Engineering Physics, University of Saskatchewan, Saskatchewan S7N 5E2, Canada.
Hanyu
H
Liu
State Key Laboratory of Superhard Materials, Jilin University, Changchun 130012, People's Republic of China.
Yunwei
Y
Zhang
State Key Laboratory of Superhard Materials, Jilin University, Changchun 130012, People's Republic of China.
Yanming
Y
Ma
IMPMC, UMR CNRS 7590, Sorbonne Universités-UPMC University Paris 06, MNHN, IRD, 4 Place Jussieu, F-75005 Paris, France.
Francesco
F
Mauri