Repository logo
 

Zero-point energies prevent a trigonal to simple cubic transition in high-pressure sulfur

Published version
Peer-reviewed

Change log

Authors

Whaley-Baldwin, Jack  ORCID logo  https://orcid.org/0000-0001-9350-7115

Abstract

jats:titleAbstract</jats:title> jats:pRecently published density functional theory results using the PBE functional (Whaley-Baldwin and Needs 2020 jats:italicNew J. Phys.</jats:italic> 22 023020) suggest that elemental sulfur does not adopt the simple-cubic (SC) jats:inline-formula jats:tex-math</jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> mml:miP</mml:mi> mml:mim</mml:mi> mml:mrow <mml:mover accent="true"> mml:mrow mml:mn3</mml:mn> </mml:mrow> mml:mō</mml:mo> </mml:mover> </mml:mrow> mml:mim</mml:mi> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="estabd487ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> phase at high pressures, in disagreement with previous works (Rudin and Liu 1999 jats:italicPhys. Rev. Lett.</jats:italic> jats:bold83</jats:bold> 3049--52; Gavryushkin jats:italicet al</jats:italic> 2017 jats:italicPhys. Status Solidi</jats:italic> B jats:bold254</jats:bold> 1600857). We carry out an extensive set of calculations using a variety of different exchange–correlation functionals (both local and non-local), and show that even though under LDA and PW91 a high-pressure SC phase does indeed become favourable at the static lattice level, when zero-point energies (ZPEs) are included, the transition to the SC phase is suppressed in every case, owing to the larger ZPE of the SC phase; thus confirming the transition sequence as jats:inline-formula jats:tex-math</jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> mml:miR</mml:mi> mml:mrow <mml:mover accent="true"> mml:mrow mml:mn3</mml:mn> </mml:mrow> mml:mō</mml:mo> </mml:mover> </mml:mrow> mml:mim</mml:mi> mml:mo→</mml:mo> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="estabd487ieqn2.gif" xlink:type="simple" /> </jats:inline-formula> BCC, with no intervening SC phase. We reproduce these findings with pseudopotentials that explicitly include core electronic states, and show that even at these high pressures, only the jats:italicn</jats:italic> = 3 valence shell contributes to bonding in sulfur. We then compare our findings against the all-electron code jats:monospaceELK</jats:monospace>, which is in excellent agreement with our pseudopotential results, and examine the roles of the exchange and correlation contributions to the total energy. We further calculate anharmonic vibrational corrections to the ZPEs of the two phases, and find that such corrections are several orders of magnitude smaller than the ZPEs and are thus negligible. The effect of finite temperatures is also considered, and we show that the jats:inline-formula jats:tex-math</jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> mml:miP</mml:mi> mml:mim</mml:mi> mml:mrow <mml:mover accent="true"> mml:mrow mml:mn3</mml:mn> </mml:mrow> mml:mō</mml:mo> </mml:mover> </mml:mrow> mml:mim</mml:mi> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="estabd487ieqn3.gif" xlink:type="simple" /> </jats:inline-formula> phase becomes even more unfavourable with an increase in temperature. Finally, the experimental consequences of our results on the equation of state of sulfur and its superconducting critical temperature are explicitly calculated.</jats:p>

Description

Funder: Engineering and Physical Sciences Research Council; doi: https://doi.org/10.13039/501100000266

Keywords

51 Physical Sciences, 34 Chemical Sciences, 5102 Atomic, Molecular and Optical Physics, 3406 Physical Chemistry

Journal Title

Electronic Structure

Conference Name

Journal ISSN

2516-1075
2516-1075

Volume Title

2

Publisher

IOP Publishing
Sponsorship
EPSRC (2126316)