  Point defects exist widely in engineering materials and are known to scatter
vibrational modes to reduce thermal conductivity. The Klemens description of
point defect scattering is the most prolific analytical model for this effect.
This work reviews the essential physics of the model and compares its
predictions to first principles results for isotope and alloy scattering,
demonstrating the model as a useful materials design metric. A treatment of the
scattering parameter ($\Gamma$) for a multiatomic lattice is recommended and
compared to other treatments presented in literature, which have been at times
misused to yield incomplete conclusions about the system's scattering
mechanisms. Additionally, we demonstrate a reduced sensitivity of the model to
the full phonon dispersion and discuss its origin. Finally, a simplified
treatment of scattering in alloy systems with vacancies and interstitial
defects is demonstrated to suitably describe the potent scattering strength of
these off-stoichiometric defects.
