Effect of hydrostatic pressure on thermal transport properties of Tl3XSe4 (X = V, Ta, Nb): A First-Principles study

Recently, Tl3XSe4 (Abbreviated as TlXSe; X = V, Ta, Nb) crystals have been found to exhibit ultra low lattice thermal conductivities rcl (-0.15 W/mK at 300 K), ultra high figure of merit ZT (3 - 4 at 300 K) and thus show great potentials in the fields of thermoelectric and engineering thermal management. Generally, thermal insulation devices and thermoelectric devices are used in harsh working environment, such high/low temperature, high pressure and so on. In order to further evaluate the industrial application values of TlXSe crystals, in this work, we explored their thermal transport behaviors under high pressures based on first-principles calculations method. The results show that TlXSe materials can maintain structural stability under high pressure up to 8 GPa, and their rcl values increase about 2 - 4 times under the high pressure of 0 - 8 GPa. The increases of rcl values are mainly due to the co-coupling effects of the increased phonon harmonicity and decreased phonon anharmonicity caused by high pressures. For all that, the rcl values of TlXSe compounds are still below 0.5 W/mK at 300 K under the high pressure of 0 - 8 GPa, which are also lower than those of most thermal insulation and thermoelectric materials. This work highlights the future potential applications of TlXSe crystals in thermal management, thermoelectric and many other fields, and thus provides useful information for further experimental and theoretical studies.