  We present the results of classical molecular dynamics simulations to assess
the relative contributions to interfacial thermal conductance from inelastic
phonon processes at the interface and in the adjacent bulk materials. The
simulated system is the prototypical interface between argon and "heavy argon"
crystals, which enables comparison with many past computational studies. We run
simulations interchanging the Lennard-Jones potential with its harmonic
approximation to test the effect of anharmonicity on conductance. The results
confirm that the presence of anharmonicity is correlated with increasing
thermal conductance with temperature, which supports conclusions from prior
experimental and theoretical work. However, in the model Ar/heavy-Ar system,
anharmonic effects at the interface itself contribute a surprisingly small part
of the total thermal conductance. The larger fraction of the thermal
conductance at high temperatures arises from anharmonic effects away from the
interface. These observations are supported by comparisons of the spectral
energy density, which suggest that bulk anharmonic processes increase
interfacial conductance by thermalizing energy from modes with low transmission
to modes with high transmission.
