For every compound we optimized the atomic positions and lattice parameters using DFT self consistent calculation based on the generalized gradient approximation (GGA), using the Perdew-Burke-Ernzerhow (PBE) functional and Grimme D2 dispersion corrections . Projected augmented wave scalar relativistic pseudopotentials were used from PSlibrary version 1.0.0 were used . Semicore s and p electrons were included for calcium, Ca NMR chemical shifts (δ iso ) and DFT calculated chemical shieldings of references structures which were used to define the scaling factor (δ DFT ). Reference DFT calculations were taken from Moudrakovski et al . Experimental Ca NMR shifts are from Laurencin et al. . and nonlinear core correction was applied for heavy atoms. Wave function and charge density energy cutoffs were set to 80 and 320 Ry. A Monkhorst-Pack grid of k-points corresponding to a maximum spacing of 0.05 Å -1 was used . Following the geometry optimization, a single-point computation was carried out with the same parameters, and chemical shieldings were computed using the GIPAW method .