Lattice thermal conductivity origin of Mg3Sb2: A study via self-consistent phonon theory with bubble correction

Abstract

Zintl-phase Mg3Sb2-based thermoelectric materials exhibit remarkable performance; however, pronounced inconsistencies remain in the reported lattice thermal conductivity (κl) and its temperature dependence. In this work, we conduct a systematic first-principles investigation of the intrinsic κl of Mg3Sb2 within the harmonic approximation, self-consistent phonon (SCP) theory, and bubble-corrected SCP framework. Our results demonstrate that κl of Mg3Sb2 is nearly isotropic. The inclusion of different higher-order corrections markedly modifies the value of κl and reshapes its temperature dependence. Most notably, bubble corrections substantially enhance the off diagonal contributions to κl, leading to pronounced deviations from conventional SCP predictions. These findings reconcile the long-standing discrepancies among different computational schemes and provide deeper microscopic insight into the lattice thermal transport behavior of Mg3Sb2.