  Despite being the archetypal thermoelectric material, still today some of the
most exciting advances in the efficiency of these materials are being achieved
by tuning the properties of PbTe. Its inherently low lattice thermal
conductivity can be lowered to its fundamental limit by designing a structure
capable of scattering phonons over a wide range of length scales. Intrinsic
defects, such as vacancies or grain boundaries, can and do play the role of
these scattering sites. Here we assess the effect of these defects by means of
molecular dynamics simulations. For this we purposely parametrize a Buckingham
potential that provides an excellent description of the thermal conductivity of
this material over a wide temperature range. Our results show that intrinsic
point defects and grain boundaries can reduce the lattice conductivity of PbTe
down to a quarter of its bulk value. By studying the size dependence we also
show that typical defect concentrations and grain sizes realized in experiments
normally correspond to the bulk lattice conductivity of pristine PbTe.
