Lattice Thermal Transport in the Homogeneous Cage-Like Compounds Cu 3 VSe 4 and Cu 3 NbSe 4 : Interplay between Phonon-Phase Space, Anharmonicity, and Atomic Mass

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 ( ) of the cage-like compounds Cu VSe and Cu NbSe was investigated by experimental measurements and first-principles calculations. The experimental of Cu NbSe is approximately 25 % lower than that of Cu VSe 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 , and the other factors only play a minor role. The physical origin is the relatively "soft" lattice of Cu NbSe 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 .