The effects of contact atom distribution at the interface on the phonon transport

At the nanometer scale, heat (phonon) transport is sensitive to the contact details at the interface due to the phonon wave property. However, the effects of contact atom distribution are ignored. In this work, the atomic Green's function (AGF) method and molecular dynamics (MD) simulation are applied to explore those effects. A parameter named as the average distance d[combining macron] is raised here to measure the distribution of contacted atoms at the interface. Based on the AGF method, phonon transmission profiles at different d[combining macron] (distribution) with the same number of contacted atoms have a coincident point, the reverse frequency fr. If the phonon frequency f is smaller (larger) than fr, smaller d[combining macron] has smaller (larger) phonon transmission. The overlap of the vibrational density of states from the MD simulation and the local density of states from the AGF method indicate that the reverse frequency is caused by the match degree of vibration modes across the interface. The existence of reverse frequency leads to the reverse temperature Tr. Increasing the contact area or the interfacial coupling strength can cause the blue shift of fr and the increase of Tr. The MD simulations observe a larger temperature jump at the interface for larger d[combining macron], similar to that from the AGF method at temperatures higher than Tr due to the high-temperature limit property in MD. The results are independent of the choice of cutoff distance in potential and interfacial coupling strength, indicating that the conclusion here is applicable for the general interface.