First-principles study on lattice thermal conductivity of thermoelectrics HgTe in different phases

Abstract

Accurate description of thermal conductivity of high pressure phase of materials is a key for predicting the thermoelectric performance. In this paper, by combining first-principle calculation and phonon Boltzmann transport equation, we investigate the lattice thermal conductivity of HgTe in low pressure zinc blende and high pressure cinnabar phases. The results show that the phononic thermal conductivity of high pressure cinnabar phase HgTe is more than an order of magnitude lower than that for the low pressure zinc blende phase. This is mainly originated from the suppressed group velocity and reduced phonon relaxation time due to the nature of mixed phonon branches in the cinnabar phase of HgTe. Based on the new and precise value of the lattice thermal conductivity calculated in this work, the figure of merit of HgTe is re-calculated and the maximum figure of merit is found to approach 1.4 at room temperature. Our first principles study highlights the high pressure HgTe phase as a very promising candidate for thermoelectric applications and provides the insight for exploring other similar materials at high pressure phases in the future.