  We present a generalized model to describe the lattice thermal conductivity
of low-dimensional (low-D) and disordered systems. The model is a
straightforward generalization of the Debye-Peierls and Allen-Feldman schemes
to arbitrary dimensions, accounting for low-D effects such as differences in
dispersion, density of states, and scattering. Similar in spirit to the
Allen-Feldman approach, heat carriers are categorized according to their
transporting capacity as propagons, diffusons, and locons. The results of the
generalized model are compared to experimental results when available, and
equilibrium molecular dynamics simulations otherwise. The results are in very
good agreement with our analysis of phonon localization in disordered low-D
systems, such as amorphous graphene and glassy diamond nanothreads. Several
unique aspects of thermal transport in low-D and disordered systems, such as
milder suppression of thermal conductivity and negligble diffuson
contributions, are captured by the approach.
