Accurate calculations of the full NMR chemical shielding tensor in perovskites: B3LYP embedded cluster results for $^{17}$O and $^{47, 49}$Ti

B3LYP calculations of $^{17}$O and $^{47, 49}$Ti NMR in BaTiO$_3$ and SrTiO$_3$ will be presented. These systems were modeled with finite size quantum clusters embedded in classical fields generated from arrays of point charges and pseudopotentials. For polar clusters, an external E-field was applied to eliminate spurious depolarization fields. The full $^{17}$O chemical shielding tensors, $\hat{\sigma}$(O), in BaTiO$_3$ and SrTiO$_3$ are in very good agreement with recent precise single crystal measurements.\footnote{ R. Blinc, et al., J. Phys: Cond. Matt. {\bf 20}, 085204 (2008).} The calculated Ti isotropic chemical shielding values are within the range of all reported measurements of BaTiO$_3$. Results will also be presented for the solid solution PZT series.