  A new formalism for extracting the modal contributions to thermal interface
conductance with full inclusion of anharmonicity is presented. The results
indicate that when two materials are joined a new set of vibrational modes are
required to correctly describe the transport across the interface. Among these
new modes, certain classifications emerge, as most modes extend at least
partially into the other material. Localized interfacial modes are also present
and exhibit the highest conductance contributions on a per mode basis. The
results also show that anharmonicity enables inelastic scattering at
temperatures as low as 10K and inelastic processes contribute 20% of the
conductance for the system studied.
