  Phonon transmission across an interface between dissimilar crystalline solids
is calculated using molecular dynamics simulations with interatomic force
constants obtained from first principles. The results reveal that although
inelastic phonon-transmission right at the geometrical interface can become far
greater than the elastic one, its contribution to thermal boundary conductance
(TBC) is severely limited by the transition regions, where local phonon states
at the interface recover the bulk state over a finite thickness. This suggests
TBC can be increased by enhancing phonon equilibration in the transition region
for instance by phonon scattering, which is demonstrated by increasing the
lattice anharmonicity.
