Lattice Thermal Transport in the Homogeneous Cage-Like Compounds Cu3 VSe4 and Cu3 NbSe4 : Interplay between Phonon-Phase Space, Anharmonicity, and Atomic Mass

Abstract

Understanding the correlation between crystal structure and thermal conductivity in semiconductors is very important for designing heat-transport-related devices, such as high-performance thermoelectric materials and heat dissipation in micro-nano-scale devices. In this work, the lattice thermal conductivity ( ${\kappa }_L$ ) of the cage-like compounds Cu₃ VSe₄ and Cu₃ NbSe₄ was investigated by experimental measurements and first-principles calculations. The experimental ${\kappa }_L$ of Cu₃ NbSe₄ is approximately 25 % lower than that of Cu₃ VSe₄ at 300 K. The relevant important physical parameters, including the sound velocity, heat capacity, weighted phonon phase space (W), and third-order force constants along with atomic mass were theoretically analyzed. It is found that W is the dominant parameter in determining the ${\kappa }_L$ , and the other factors only play a minor role. The physical origin is the relatively "soft" lattice of Cu₃ NbSe₄ with heavier atomic mass. This research provides deep insight into the correlation between the thermal conductivity and crystal structure and paves the way for discovering high-performance thermal management device and thermoelectric materials with intrinsically low ${\kappa }_L$ .

Keywords: Grüneisen parameters; cage-like compounds; lattice thermal conductivity; phonon-phase space; third-order force constant.