Understanding of S NMR Shielding in Inorganic Sulfides and Sulfates

Density functional theory (DFT) calculations of the magnetic shielding in solid state nuclear magnetic resonance (NMR) experiments provide an important contribution for the understanding of the experimentally observed chemical shifts. In this work we focus on the relation between atomic and orbital character of the valence and conduction band wave functions and the S NMR shielding in sulfides and sulfates. This allows us to understand the origin of the observed large (over 1000 ppm) variation of the chemical shifts measured at the sulfur nucleus. We show that the variation of the NMR chemical shifts in sulfides is mostly related to the presence of metal d states and their variation in the energy position within the conduction bands.