Characteristic features of the structure of Ca2+ hydration shells were considered. The results of quantum chemical calculations were compared with experimental data obtained from the study of nuclear magnetic relaxation of deuterons in aqueous solutions of calcium salts. The influence of the basis set and computational procedure on the calculated 2D quadrupole coupling constants (QCC) in isolated water molecule was investigated. The 2D QCC in molecular clusters (D₂O)₅ and Ca2+(D₂O)_n (n =6, 8, 10, 18) were calculated using the B3LYP/6-31 ++G** density functional method.