Spectral mapping of thermal transport across SiC-water interfaces

In this investigation, the thermal transport across 3C-type silicon carbide (SiC) and water interfaces was analyzed by means of nonequilibrium molecular dynamics (NEMD) simulations. To understand the details of the mechanisms involved in the transport of energy across hard-soft interfaces, spectral mapping methods were implemented. It was observed that the phonon density of states (DOS) at the interface is affected by the atomic surface termination, crystallographic plane, and the wetting conditions for both phases, indicating that different vibrational modes contribute to the interfacial heat transfer process based on the interface configuration. Low-frequency modes were found to contribute the most for the C- and Si-terminated SiC(1 0 0) planes and the C-terminated SiC(1 1 1) plane, while a noticeable contribution from high-frequency modes was observed for the Si-terminated SiC(1 1 1) plane. Out-of-plane modes significantly contributed to the heat transfer in all the analyzed surfaces, while the heat flux composition by in-plane modes was notably smaller, particularly for the SiC(1 1 1) plane. The in-plane modes lower contribution to the interfacial heat flux was related to the interfacial bonding strength and liquid structuring formed at the interface. An agreement was found between the thermal boundary conductance dependence on the DOS overlap and the interfacial liquid structure, while the interfacial bonding strength did not conclusively inform on the thermal transport behavior across these interfaces.