Role of nonpairwise interactions on phonon thermal transport

In this paper, the phonon system for a perfect silicon lattice is obtained by means of a model considering a phenomenological potential that includes both two- and three-body contributions. Phonon dispersions are discussed, and anharmonic contributions to the phonon Hamiltonian are evaluated. The model is compared with a model involving a pairwise potential, previously used by the author in the calculation of silicon thermal conductivity. The equation of motion is solved for both models, obtaining phonon dispersions practically indistinguishable and in good agreement with the experimental data. The role of nonpairwise interactions in phonon-phonon–scattering processes, relevant for the calculation of thermal conductivity, is then discussed. The thermal conductivity obtained with the present model including two- and three-body interactions has a good agreement with the experimental data, better than the one previously achieved with the model involving a central potential.