TY - JOUR
T1 - Anharmonicity in the High-Temperature Cmcm Phase of SnSe
T2 - Soft Modes and Three-Phonon Interactions
AU - Skelton, Jonathan M.
AU - Burton, Lee A.
AU - Parker, Stephen C.
AU - Walsh, Aron
AU - Kim, Chang Eun
AU - Soon, Aloysius
AU - Buckeridge, John
AU - Sokol, Alexey A.
AU - Catlow, C. Richard A.
AU - Togo, Atsushi
AU - Tanaka, Isao
N1 - Publisher Copyright:
© 2016 authors. Published by the American Physical Society.
PY - 2016/8/10
Y1 - 2016/8/10
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.
UR - https://www.scopus.com/pages/publications/84982106722
U2 - 10.1103/PhysRevLett.117.075502
DO - 10.1103/PhysRevLett.117.075502
M3 - Article
AN - SCOPUS:84982106722
SN - 0031-9007
VL - 117
JO - Physical Review Letters
JF - Physical Review Letters
IS - 7
M1 - 075502
ER -