Molecular dynamics study on the effects of cuboid nanostructure on the distribution of local thermal resistance at a solid-liquid interface

This study focuses on thermal transport at the interface between solid and liquid with various cuboid nanostructure systems. We calculated the solid-liquid interfacial thermal resistance (ITR) and the distribution of local ITRs with a 0.2 nm spatial resolution. The results were obtained using non-equilibrium molecular dynamics. Applying a thermal circuit model, we computed the thermal resistance by combining the local ITRs. Also, we introduced spectral analysis to explain the distribution of local ITR magnitudes. As a result, we found that the local ITRs decreased at the top corner of the nanostructure and increased at its base. The thermal transport at the top corner contributed significantly to the total thermal transport at the solid-liquid interface. It was revealed that the ratio of the overall ITR to the combined local ITRs agreed with the ratio of the area of a flat surface to the area along the lower wall and the nanostructure, including the Cassie-Baxter state, only when the local temperature jumps around the interface are closely similar i.e. the interaction strength between solid and liquid is not extremely high. Moreover, from spectral analysis of solid atoms, we found that the vibrational density of states (VDOS) and the spectral heat flux of the solid atoms at the top corner of the nanostructure peaked in a low-frequency range and the VDOS overlap became higher at the top corner in all cases. This strong vibrational coupling is another factor contributing to the lowest local ITR at the top corner of the nanostructure.