Anomalous pressure dependence of thermal conductivities of large mass ratio compounds

The lattice thermal conductivities (kappa) of binary compound materials are examined as a function of hydrostatic pressure P using a first-principles approach. Compounds with relatively small mass ratios, such as MgO, show an increase in kappa with P, consistent with measurements. Conversely, compounds with large mass ratios that create significant frequency gaps between acoustic and optic phonons (e.g., BSb, BAs, BeTe, BeSe) exhibit decreasing. with increasing P, a behavior that cannot be understood using simple theories of kappa. This anomalous P dependence of kappa arises from the fundamentally different nature of the intrinsic scattering processes for heat-carrying acoustic phonons in large mass ratio compounds compared to those with small mass ratios. This work demonstrates the power of first-principles methods for thermal properties and advances a broad paradigm for understanding thermal transport in nonmetals.