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

Jonathan M. Skelton; Lee A. Burton; Stephen C. Parker; Aron Walsh; Chang Eun Kim; Aloysius Soon; John Buckeridge; Alexey A. Sokol; C. Richard A. Catlow; Atsushi Togo; Isao Tanaka

doi:10.1103/PhysRevLett.117.075502

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

Jonathan M. Skelton, Lee A. Burton, Stephen C. Parker, Aron Walsh, Chang Eun Kim, Aloysius Soon, John Buckeridge, Alexey A. Sokol, C. Richard A. Catlow, Atsushi Togo, Isao Tanaka

Department of Materials Science and Engineering

Research output: Contribution to journal › Article › peer-review

124 Citations (Scopus)

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.

Original language	English
Article number	075502
Journal	Physical review letters
Volume	117
Issue number	7
DOIs	https://doi.org/10.1103/PhysRevLett.117.075502
Publication status	Published - 2016 Aug 10

Bibliographical note

Funding Information:
We gratefully acknowledge helpful discussions with Dr J.M. Frost. J.M.S. is supported by an EPSRC programme grant (Grant No.EP/K004956/1). L.A.B. is currently supported by the JSPS (Grant No.26.04792). J.B. acknowledges support from the EPSRC (Grant No.EP/K016288/1). Calculations were carried out on the ARCHER supercomputer, accessed through membership of the UK HPC Materials Chemistry Consortium, which is funded by the EPSRC (Grant No.EP/L000202). We also made use of the Bath University HPC cluster, which is maintained by the Bath University Computing Services, and the SiSu supercomputer at the IT Center for Science (CSC), Finland, via the Partnership for Advanced Computing in Europe (PRACE) Project No.13DECI0317/IsoSwitch.

Publisher Copyright:
© 2016 authors. Published by the American Physical Society.

All Science Journal Classification (ASJC) codes

Physics and Astronomy(all)

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10.1103/PhysRevLett.117.075502

Cite this

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

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.",

author = "Skelton, {Jonathan M.} and Burton, {Lee A.} and Parker, {Stephen C.} and Aron Walsh and Kim, {Chang Eun} and Aloysius Soon and John Buckeridge and Sokol, {Alexey A.} and Catlow, {C. Richard A.} and Atsushi Togo and Isao Tanaka",

note = "Funding Information: We gratefully acknowledge helpful discussions with Dr J.M. Frost. J.M.S. is supported by an EPSRC programme grant (Grant No.EP/K004956/1). L.A.B. is currently supported by the JSPS (Grant No.26.04792). J.B. acknowledges support from the EPSRC (Grant No.EP/K016288/1). Calculations were carried out on the ARCHER supercomputer, accessed through membership of the UK HPC Materials Chemistry Consortium, which is funded by the EPSRC (Grant No.EP/L000202). We also made use of the Bath University HPC cluster, which is maintained by the Bath University Computing Services, and the SiSu supercomputer at the IT Center for Science (CSC), Finland, via the Partnership for Advanced Computing in Europe (PRACE) Project No.13DECI0317/IsoSwitch. Publisher Copyright: {\textcopyright} 2016 authors. Published by the American Physical Society.",

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AU - Walsh, Aron

AU - Kim, Chang Eun

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AU - Buckeridge, John

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AU - Catlow, C. Richard A.

AU - Togo, Atsushi

AU - Tanaka, Isao

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PY - 2016/8/10

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N2 - 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.

AB - 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.

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

Abstract

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