Simulating Interfacial Thermal Conductance at Metal-Solvent Interfaces: The Role of Chemical Capping Agents
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Abstract
With the non-isotropic velocity scaling (NIVS) approach to reverse non-equilibrium molecular dynamics (RNEMD), it is possible to impose an unphysical thermal flux between different regions of inhomogeneous systems such as solid/liquid interfaces. We have applied NIVS to compute the interfacial thermal conductance at a metal/organic solvent interface that has been chemically capped by butanethiol molecules. Our calculations suggest that coupling between the metal and liquid phases is enhanced by the capping agents, leading to a greatly enhanced conductivity at the interface. Specifically, the chemical bond between the metal and the capping agent introduces a vibrational overlap that is not present without the capping agent, and the overlap between the vibrational spectra (metal to cap, cap to solvent) provides a mechanism for rapid thermal transport across the interface. Our calculations also suggest that this is a nonmonotonic function of the fractional coverage of the surface, as moderate coverages allow diffusive heat transport of solvent molecules that have been in close contact with the capping agent.