  At the nanoscale, thermal transport across the interface between two lattice
insulators can be described by the transmission of bulk phonons and depends on
the crystallographic structure of the interface and the bulk crystal lattice.
In this tutorial, we give an account of how an extension of the Atomistic
Green's Function (AGF) method based on the concept of the Bloch matrix can be
used to model the transmission of individual phonon modes and allow us to
determine the wavelength and polarization dependence of the phonon
transmission. Within this framework, we can explicitly establish the
relationship between the phonon transmission coefficient and dispersion.
Details of the numerical methods used in the extended AGF method are provided.
To illustrate how the extended AGF method can be applied to yield insights into
individual phonon transmission, we study the (16,0)/(8,0) carbon nanotube
intramolecular junction. The method presented here sheds light on the modal
contribution to interfacial thermal transport between solids.
