Phonon mechanism of compressive strain enhanced thermal transport in defective high entropy alloy heterojunctions.

High-entropy alloy (HEA)/graphene (Gr) heterojunctions hold significant promise for thermal management in micro/nanoelectronic devices, yet the interfacial defect and thermal transport regulation mechanisms remain to be further elucidated. Using non-equilibrium molecular dynamics simulations, this study systematically investigates the through-plane thermal conductivity and interfacial thermal conductance (ITC) of HEA/Gr/HEA heterojunctions containing nanoscale void defects, and explores the regulatory effect of compressive strain on interfacial thermal transport and its microscopic phonon mechanisms. The results show that void defects significantly suppress thermal transport: the ITC is approximately 212.3 MW/m2K in the defect-free case and decreases to about 139.6 MW/m2K (a reduction of 34.2%) when the number of nanopores increases to nine. Within the elastic strain range of 0-4%, compressive strain effectively enhances ITC; as the strain increases from 0 to 4%, ITC rises from 185.2 MW/m2K to 353.4 MW/m2K (an increase of 90.8%). Applying only 2% strain completely compensates for the thermal conductivity degradation induced by void defects. Phonon density of states analysis reveals that compressive strain increases the PDOS of the Gr layer in the low-frequency region (0-15 THz) while decreasing that of the HEA layer, thereby improving their phonon spectral overlap. The phonon energy coupling coefficient increases from 0.44 to 0.53 (a 20.45% enhancement), mainly originating from strengthened coupling in the 5-20 THz frequency range. This study elucidates the phonon physics mechanism underlying the enhancement of interfacial thermal transport performance, providing a theoretical foundation for thermal management of HEA/Gr heterojunctions and strain-modulated interfacial thermal resistance.