Show simple item record

dc.contributor.authorWhaley-Baldwin, Jack
dc.contributor.authorNeeds, Richard
dc.date.accessioned2020-03-02T13:23:03Z
dc.date.available2020-03-02T13:23:03Z
dc.date.issued2020-03-02
dc.date.submitted2019-10-01
dc.identifier.othernjpab6068
dc.identifier.otherab6068
dc.identifier.othernjp-111145
dc.identifier.urihttps://www.repository.cam.ac.uk/handle/1810/302903
dc.description.abstractAbstract: We use first-principles density functional theory to conduct an extensive structure search using the AIRSS package for elemental sulfur in the range 50–550 GPa. We then obtain the low-temperature phase diagram of sulfur in the same pressure range, including vibrational effects through the harmonic approximation. We do not find any structures lower in energy than those already reported in experiment, although the phase diagram below 100 GPa is found to be crowded with structures separated by only a few meV. We report the transition sequence I 4 1 / acd → P 1 ¯ → ICM → C 2 / m → R 3 ¯ m → I m 3 ¯ m and obtain accurate pressures for each transition, although we find the second-order C 2 / m → R 3 ¯ m transition particularly difficult to define. Contrary to previous first-principles works (Pavel et al; Rudin and Liu 1999 Phys. Rev. Lett. 83 3049–52), we do not reproduce a trigonal → simple cubic transition at either the static lattice or harmonic level. We also undertake a detailed analysis of the incommensurately modulated (ICM) phase of sulfur phase using a commensurate approximant found in the structure search. We find that the modulation amplitude is zero above 96 GPa; some 40 GPa below the experimentally reported transition to the unmodulated phase. We find that the body-centred atoms in the relaxed ICM approximant are, in addition to the dominant transverse modulation (which is a frozen-in optical phonon mode), slightly displaced longitudinally in the b-direction. We subsequently discover that this (small) longitudinal modulation is coupled to the transverse mode, and hence report previously unnoticed weak-mode coupling between transverse and longitudinal optical phonons in the ICM phase.
dc.languageen
dc.publisherIOP Publishing
dc.rightsAttribution 3.0 Unported (CC BY 3.0)en
dc.rights.urihttps://creativecommons.org/licenses/by/3.0/en
dc.subjectPaper
dc.subjectcharge density wave
dc.subjectincommensurate structure
dc.subjectstructure searching
dc.subjecthigh pressure
dc.subjectphase diagram
dc.subjectphonon dispersion
dc.subjectsoft mode
dc.titleFirst-principles high pressure structure searching, longitudinal-transverse mode coupling and absence of simple cubic phase in sulfur
dc.typeArticle
dc.date.updated2020-03-02T13:23:02Z
prism.issueIdentifier2
prism.publicationNameNew Journal of Physics
prism.volume22
dc.identifier.doi10.17863/CAM.49978
dcterms.dateAccepted2019-12-10
rioxxterms.versionofrecord10.1088/1367-2630/ab6068
rioxxterms.versionVoR
rioxxterms.licenseref.urihttp://creativecommons.org/licenses/by/3.0/
dc.contributor.orcidWhaley-Baldwin, Jack [0000-0001-9350-7115]
dc.identifier.eissn1367-2630


Files in this item

Thumbnail
Thumbnail

This item appears in the following Collection(s)

Show simple item record

Attribution 3.0 Unported (CC BY 3.0)
Except where otherwise noted, this item's licence is described as Attribution 3.0 Unported (CC BY 3.0)