First-principles predictions of thermal conductivity of bulk diamond under isotropic and uniaxial (100) strains

The miniaturization of high-frequency electronic devices is associated with significant heat accumulation by individual components. Diamond exhibits ultrahigh thermal conductivity and is thus an ideal material for heat dissipation. Considering the sensitive stress-thermal responses of diamond, this study uses first-principles calculations and the phonon Boltzmann transport equation to compare and analyze the effects of uniaxial strain along the <100> crystal direction, as well as isotropic strain, on the thermal conductivity of bulk diamond. Under isotropic strain, the thermal conductivity is principally influenced by bond length; the relationship between thermal conductivity and the bond length deformation index follows a power law. During uniaxial strain, the bond angle and bond length change simultaneously, superimposing their effects on thermal conductivity. This study provides essential insights into the mechanisms of diamond thermal conductivity under different strains; the findings can guide prediction of the strain-thermal conductivity relationships of other crystalline materials.