What is the effect of liquid coarse-graining on the Kapitza conductance at the interface between water and non-polar surfaces?

Quantities like heat capacity and thermal conductivity are largely reduced when one performs coarse-graining of the molecular systems by removing certain of degrees of freedom. However, it is not clearly known what influence coarse-graining has on energy transport through the interfaces. To address this issue, we compute Kapitza conductance ( or thermal boundary conductance) of water-graphite interfaces, using two model resolutions (fully atomistic and coarse-grained) of water at a wide range of wetting strengths. Rather surprisingly, we observe that, the removal of liquid degrees of freedom only has a marginal influence on the Kapitza conductance. We notice that the first adsorbed water layer plays the most crucial role in determining the interfacial conductance. Similarities in adsorbed water layer structure and vibrations explain the similarity in conductance. Through spectrally resolved heat flux, we also identified that, most of the heat transport is made possible by the coupling of low frequency vibrations. These insights are a first step in the direction of understanding the influence of coarse-graining on interfacial energy transport and could pave ways to develop multiscale models to study large scale systems with high density of interfaces.