Shear-strain-dependent thermal conductivity of diamond explored via a machine learning potential

Diamond is regarded as a critical material for the thermal management of high-power electronics. However, the impact of shear strain, which is a prevalent deformation mode in complex stress fields, remains unclear. In this work, the lattice thermal conductivity of diamond under shear strain has been systematically investigated using high-accuracy neuroevolution potential and homogeneous non-equilibrium molecular dynamics. Distinct from isotropic or uniaxial strain cases, shear strain induces pronounced threshold effects and strong anisotropy. Beyond a critical shear strain of 0.01, the thermal conductivity exhibits a sharp decay, with the reduction along the [001] direction (perpendicular to the (001) shear plane) being markedly greater than that along the [100] and [010] directions (parallel to the (001) shear plane). This anisotropy is attributed to a distinct phonon frequency shift compensation mechanism. Along the [100] and [010] directions (parallel to the shear plane), a phonon redshift drives high-frequency modes into the 10–30 THz range critical for thermal transport, thereby partially compensating for scattering-induced losses. Consequently, it can be concluded that the microscopic origins of strain-dependent thermal transport provide further theoretical insights into the thermal management of electronic devices employing diamond heat spreaders under complex stress fields.