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A unique metallic phase of H3S at high-pressure: sulfur in three different local environments

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Abstract

We propose a new metallic phase (R[3 with combining macron]m, Z = 24) for H3S in a large pressure interval (∼108–166 GPa) using an evolutionary crystal structure search algorithm combined with first-principles calculations. This structure consists of SH6, SH3 and S units which are connected through strong S⋯H hydrogen-bonds. It supports four-types of S⋯H hydrogen-bonds that symmetrize at ∼166 GPa. This is the only phase in the H–S family where sulfur exists in three different local environments. Sulfur in SH6 behaves as a cation, like in the SF6 molecule, whereas other sulfurs behave as anions. Hydrogens in SH6 behave like halogens (anions) whereas other hydrogens behave like alkalis (cations). The new structure has a substantially smaller DOS at the Fermi-level in comparison to earlier structures R3m and Im[3 with combining macron]m. This implies a lower superconducting temperature (TC) for the new phase and thus questions the validity of earlier high-TC explanations. We also find that S–H covalent bonds are different from the B–B bonds of MgB2.

Graphical abstract: A unique metallic phase of H3S at high-pressure: sulfur in three different local environments

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Publication details

The article was received on 12 Jul 2018, accepted on 01 Oct 2018 and first published on 02 Oct 2018


Article type: Paper
DOI: 10.1039/C8CP04410D
Citation: Phys. Chem. Chem. Phys., 2018, Advance Article
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    A unique metallic phase of H3S at high-pressure: sulfur in three different local environments

    A. K. Verma and P. Modak, Phys. Chem. Chem. Phys., 2018, Advance Article , DOI: 10.1039/C8CP04410D

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