Thermal Transport is Influenced by Nanoparticle Morphology: A Molecular Dynamics Study

Molecular dynamics simulations were performed to model the interfacial thermal conductance (<i>G</i>) from bare gold nanoparticles (icosahedral, cuboctahedral, and spherical) to a hexane solvent. The computed conductance was found to depend not only on particle shape, but also on the size of the nanoparticles, particularly for nanospheres. These results are compared with conductance out of the planar facets: (111), (100), and (110); all commonly exhibited in small patches on the spherical particles. Undercoordination of the surface atoms and the vibrational density of states in the icosahedra explain some of these observations. The exposed surfaces of icosahedral particles are dominated by (111) facets with 9-coordinated gold atoms. Cuboctahedral particles are dominated by the (100) and (111) facets with 8- and 9-coordinated surface atoms, respectively. The nanospheres approach a constant surface density of 6–9 coordinated sites at large particle sizes, and these surface atoms play a large role in the conductance to the solvent. The surface-normal vibrational densities of states were used to explain a simple surface undercoordination model, which recovers most of the contributions to the size-dependent conductance