Heterogeneous thermal conductance of nanoparticle-fluid interfaces: An atomistic nodal approach

The Interfacial Thermal Conductance (ITC) is a fundamental property of materials and has particular relevance at the nanoscale. The ITC quantifies the thermal resistance between materials of different compositions or between fluids in contact with materials. Furthermore, the ITC determines the rate of cooling/heating of the materials and the temperature drop across the interface. Here, we propose a method to compute local ITCs and temperature drops of nanoparticle-fluid interfaces. Our approach resolves the ITC at the atomic level using the atomic coordinates of the nanomaterial as nodes to compute local thermal transport properties. We obtain high-resolution descriptions of the interfacial thermal transport by combining the atomistic nodal approach, computational geometry techniques, and "computational farming" using non-equilibrium molecular dynamics simulations. We use our method to investigate the ITC of nanoparticle-fluid interfaces as a function of the nanoparticle size and geometry, targeting experimentally relevant structures of gold nanoparticles: capped octagonal rods, cuboctahedrons, decahedrons, rhombic dodecahedrons, cubes, icosahedrons, truncated octahedrons, octahedrons, and spheres. We show that the ITC of these very different geometries varies significantly in different regions of the nanoparticle, increasing generally in the order face < edge < vertex. We show that the ITC of these complex geometries can be accurately described in terms of the local coordination number of the atoms in the nanoparticle surface. Nanoparticle geometries with lower surface coordination numbers feature higher ITCs, and the ITC generally increases with the decreasing particle size.