  In this study we present an alternative approach to separating contributions
to the NMR shift originating from the Knight shift and chemical shielding by a
combination of experimental solid-state NMR results and ab initio calculations.
The chemical and Knight shifts are normally distinguished through detailed
studies of the resonance frequency as function of temperature and carrier
concentration, followed by extrapolation of the shift to zero carrier
concentration. This approach is time-consuming and requires studies of multiple
samples. Here, we analyzed $^{207}$Pb and $^{125}$Te NMR spin-lattice
relaxation rates and NMR shifts for bulk and nanoscale PbTe. The shifts are
compared with calculations of the $^{207}$Pb and $^{125}$Te chemical shift
resonances to determine the chemical shift at zero charge carrier
concentration. The results are in good agreement with literature values from
carrier concentration-dependent studies. The measurements are also compared to
literature reports of the $^{207}$Pb and $^{125}$Te Knight shifts of $n$- and
$p$-type PbTe semiconductors. The literature data have been converted to the
currently accepted shift scale. We also provide possible evidence for the
"self-cleaning effect" property of PbTe nanocrystals whereby defects are
removed from the core of the particles, while preserving the crystal structure.
