Thermal Transport of Part-crystalline Part-liquid Materials

Multi-component materials usually manifest crystal structure with chemical bond hierarchy, exhibiting the part-crystalline part-liquid (PCPL) or part-crystalline part-amorphous state as the emerging candidates of thermoelectric materials. These materials contain at least two different types of sublattices, one crystalline and another one strongly disordered or liquid-like, leading to extremely low lattice thermal conductivity. This talk presents a survey on the general characteristics of the thermal transport in the part-crystalline materials. We also develop an approach to simulate the complex thermal transport process. We also compare the results in Green-Kubo method and Boltzmann transport theory to elucidate the thermal conductivity of PCPL materials by using empirical interatomic potentials fitting to the liquid-like thermoelectrics like Cu₂Se. The contribution to thermal transport from each structural component, i.e. the rigid-crystalline, strongly disordered, and/or liquid-like parts, are respectively analyzed, and the underlying mechanism is elucitated. Based on the observation, a general trend about the thermal transport in a large group of materials is analyzed. Relationship to minimum thermal conductivity is also discussed.