Thermal transport properties of anisotropic materials RbCaX (X = As, Sb) with strong anharmonicity

Abstract

We study the thermal transport properties of the anisotropic materials RbCaX (X = As, Sb) using first-principles calculations combined with self-consistent phonon (SCP) theory and Boltzmann transport equations (BTE). The weak bonding of Rb atoms results in strong anharmonicity of the material, and the lattice thermal conductivity κL along the c-axis is much smaller than that along the a(b)-axis. We fully deal with the quartic anharmonicity, which consists of four-phonon scattering and temperature-dependent phonon frequency-shift, and find that its influence on κL is not negligible. The results show that the κL of the c-axis of RbCaAs and RbCaSb is only 0.80 Wm−1K−1 and 0.85 Wm−1K−1 at 300K, which is lower than the 0.9 Wm−1K−1 of the classical thermoelectric material quartz glass, indicating that they have great application potential in thermoelectricity and thermal management fields. Our findings point the way to studying the thermal transport properties of anisotropic materials with strong anharmonicity.