Microscopic Sources of Solid-State NMR Shielding in Titanate of Alkaline Earth Perovskite Metals

Abstract

Nuclear magnetic resonance (NMR) parameters are calculated and analyzed in a series of titanate of alkaline earth perovskites to explore microscopic sources of their magnetic shieldings using a full-potential-based NMR scheme. In this method, there is no approximation to calculate the induced current density. The slope of the correlation between various approaches and available experimental data is successfully reproduced very close to the required ideal value (−1). Our NMR results are consistent with the experimental data and the available theoretical results calculated by the gauge-including projector augmented-wave (GIPAW) method. Moreover, we have predicted the chemical shifts of the compounds in which their experimental values have not been measured yet. Isotropic and anisotropic chemical shift parameters as well as associated asymmetries are analyzed. The analysis explores the relation between atomic and orbital characters of the valence and conduction bands wave functions as well as the 17O NMR shielding. Our results show that the NMR shielding varies by around 180 ppm through the materials under question. We, in agreement with the results reported on alkali fluorides, show that the variation of the NMR shielding in our investigated alkaline earth titanate perovskites is mostly related to the oxygen p-states. Furthermore, we show that the NMR chemical shifts strongly depend on the shape of the unoccupied titanium-d density of states (DOS) and alkaline-earth metals-d DOSs as well as their locations in the conduction region with respect to the Fermi level. It is also shown that the shielding calculated for the ordinary ice is less by 71.2 ppm than that derived for the water using TB-mBJ.