Simulation research on thermal conductivity of thermoelectric material β-Cu_2-<i>x</i>Se

Abstract

Phonon-liquid thermoelectric material β-Cu2-xSe can achieve an excellent thermoelectric performance. Molecular dynamic simulations were performed to study the thermal conductivity of β-Cu2-xSe. The correlation between diffusivity of "liquid-like" ions and the thermal conductivity was analyzed. The effect of doping and vacancies on the material's thermal conductivity was also investigated. The results show that "liquid-like" ion's diffusivity and the thermal conductivity are strongly connected. Enhancement of Cu ions mobility in β-Cu2-x Se increases the non-harmonic vibration of the crystal lattice, which strengthens the phonon scattering and reduces the thermal conductivity. Doping and vacancies have different influences on "phonon-liquid" materials' thermal conductivity. Vacancies are conducive to the movement of "liquid-like" ions, leading to the decrease in the phonon acoustic branch frequency, which effectively reduce the thermal conductivity. Vacancies may significantly improve "phonon-liquid" materials' thermoelectric conversion efficiency, while the effect of doping on thermal conductivity is not significant.

Keywords

• thermoelectric material
• "phonon-liquid"
• thermal conductivity
• molecular dynamics