  We introduce a novel approach to model heat transport in solids, based on the
Green-Kubo theory of linear response. It naturally bridges the Boltzmann
kinetic approach in crystals and the Allen-Feldman model in glasses, leveraging
interatomic force constants and normal-mode linewidths computed at mechanical
equilibrium. At variance with molecular dynamics, our approach naturally and
easily accounts for quantum mechanical effects in energy transport. Our
methodology is carefully validated against results for crystalline and
amorphous silicon from equilibrium molecular dynamics and, in the former case,
from the Boltzmann transport equation.
