Temperature and isotope effects on the thermoelectric properties in SnTe

The temperature and Sn isotope effects on SnTe are investigated using the hybrid scheme that combines ab initio molecular dynamics and lattice dynamics (AIMD  +  LD). The unstable softening of TA phonon mode at 0 K in cubic phase SnTe disappears and the TO mode is stiffened by considering the temperature effect, in agreement with the inelastic neutron scattering (INS) observations. A linear dependence on isotope mass of phonon frequency, lifetime, and mean free path for isolate phonon mode is observed with the possibility of positive, negative, and nearly zero shifts. The lattice thermal conductivity ([Formula: see text]) shows saturation characteristic as Sn isotope mass increases to ¹²⁰SnTe, with an increase rate of  ∼2.1% from ¹¹²SnTe to ¹²⁴SnTe. Considering the effects of partial isotope doping, we obtain a reduced [Formula: see text] with respect to the undoped case. The [Formula: see text] is reduced by  ∼14.6% at 600 K when considering the volumetric expansion.