Stronger three-phonon interactions revealed by molecular dynamics in materials with restricted phase space

CZ Zhang and ZZ Zeng and Q Sun and Y Chen, JOURNAL OF APPLIED PHYSICS, 130, 205101 (2021).

DOI: 10.1063/5.0065889

Utilizing molecular dynamics (MD) simulations based on the highly precise force-fields, we find that phonon scattering strengths induced by the cubic anharmonicity can be significantly underestimated by the perturbation theory (PT) approach in materials with sizable frequency gaps or branch bunching. We trace this result to the additional three- phonon scatterings in MD enabled by the fluctuating phonon energy and the continuous energy exchange between modes. These channels are essential to accurately evaluate the zone-center phonon linewidth in boron arsenide as compared to the experiment and could noticeably lower the lattice thermal conductivity of beryllium telluride and tungsten carbide. Accordingly, due to the stronger three-phonon scatterings, four-phonon scatterings would become less important than previously believed in this type of material. Moreover, our work emphasizes the different phonon scattering processes in MD and PT simulations, offering new insights for an improved description of anharmonic properties.

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