Theoretical analysis of NMR shieldings in XSe and XTe (X = Si, Ge, Sn and Pb): The spin-rotation constant saga

The nuclear spin-rotation (NSR) and absolute nuclear magnetic resonance (NMR) shielding tensors of the nuclei in the series of XSe and XTe (X = Si, Ge, Sn and Pb) are calculated using four-component relativistic density functional theory (DFT) and coupled-cluster singles-doubles with a perturbative triples correction (CCSD(T)). The results for the NSR constants are compared to available experimental data. The best theoretical estimates are obtained when relativistic corrections from DFT are added to the accurate non-relativistic CCSD(T) results. All the calculated NSR constants are in excellent agreement with the corresponding experimental values. Even though there are previously estimated absolute shielding constants and spans from experimental NSR tensors, new accurate values are reported following the same approach used to calculate the NSR constants in this study. The main reasons for the discrepancy between the previously reported NMR properties and the accurate results obtained in this study are also discussed.