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Anharmonicity in the High-Temperature Cmcm Phase of SnSe: Soft Modes and Three-Phonon Interactions

Skelton, JM; Burton, LA; Parker, SC; Walsh, A; Kim, C-E; Soon, A; Buckeridge, J; ... Tanaka, I; + view all (2016) Anharmonicity in the High-Temperature Cmcm Phase of SnSe: Soft Modes and Three-Phonon Interactions. Physical Review Letters , 117 (7) , Article 075502. 10.1103/PhysRevLett.117.075502. Green open access

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Abstract

The layered semiconductor SnSe is one of the highest-performing thermoelectric materials known. We demonstrate, through a first-principles lattice-dynamics study, that the high-temperature Cmcm phase is a dynamic average over lower-symmetry minima separated by very small energetic barriers. Compared to the low-temperature Pnma phase, the Cmcm phase displays a phonon softening and enhanced three-phonon scattering, leading to an anharmonic damping of the low-frequency modes and hence the thermal transport. We develop a renormalization scheme to quantify the effect of the soft modes on the calculated properties, and confirm that the anharmonicity is an inherent feature of the Cmcm phase. These results suggest a design concept for thermal insulators and thermoelectric materials, based on displacive instabilities, and highlight the power of lattice dynamics calculations for materials characterization.

Type: Article
Title: Anharmonicity in the High-Temperature Cmcm Phase of SnSe: Soft Modes and Three-Phonon Interactions
Open access status: An open access version is available from UCL Discovery
DOI: 10.1103/PhysRevLett.117.075502
Publisher version: http://dx.doi.org/10.1103/PhysRevLett.117.075502
Language: English
Additional information: Published by the American Physical Society. This article is available under the terms of the Creative Commons Attribution 3.0 License.
Keywords: Science & Technology, Physical Sciences, Physics, Multidisciplinary, Physics, Performance Bulk Thermoelectrics, Augmented-wave Method, Lead Chalcogenides, Pbte
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Chemistry
URI: https://discovery.ucl.ac.uk/id/eprint/1513272
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