Errea, I; Calandra, M; Pickard, CJ; Nelson, J; Needs, RJ; Li, Y; Liu, H; ... Mauri, F; + view all Errea, I; Calandra, M; Pickard, CJ; Nelson, J; Needs, RJ; Li, Y; Liu, H; Zhang, Y; Ma, Y; Mauri, F; - view fewer (2015) High-pressure hydrogen sulfide from first principles: a strongly anharmonic phonon-mediated superconductor. Physical Review Letters , 114 (15) , Article 157004. 10.1103/PhysRevLett.114.157004.

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Abstract

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.

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