  We study the effect of nanoscale precipitates on lattice thermal conduction
in thermoelectric PbTe using a combination of ab-initio phonon calculations and
molecular dynamics. We take into account the effects of mass difference and
change in force constants, and find an enhanced influence of the latter with
increased precipitate concentration. As a consequence, our inclusion of the
change in force constants in the calculation affords a smaller predicted
optimal nano-precipitate size that minimizes the thermal conductivity. These
results suggest that the phonon scattering by nanoprecipitates in
thermoelectric composites could be stronger than previously thought.
