Point-defect effects on thermal conductivity in BAs and MgO: a first-principles study

Point defects and impurities critically limit thermal conductivity () in crystalline solids, with implications for thermal management and fundamental heat transport physics. In this work, we use first-principles methods to study phonon scattering by point defects in two materials: the ultrahigh-thermal-conductivity semiconductor BAs and the refractory oxide MgO. In BAs, we consider intrinsic vacancies and anti-sites (Vac_B, Vac_As, B_As, As_B, and B_As-As_B). In MgO, we study substitutional impurities on Mg (e.g., Al, Ca, Fe, Nb, Ti, V, B, Si) and cation/anion vacancies (Vac_Mg and Vac_O) are considered. Phonon–impurity scattering is treated with the T-matrix formalism, where the T matrix is defined via the retarded Green’s function, which is evaluated using the tetrahedron method. Both mass and bond perturbations are included explicitly. Results show while all defects strongly reduce BAs , Nb_Mg, B_Mg, and Vac_Mg most strongly suppress MgO . Resonance scattering occurs when Boron is involved. This work provides a microscopic understanding of phonon–defect interactions, guiding thermal transport control in semiconductors and refractory oxides.