Spin–orbit effects on the ¹¹⁹Sn magnetic-shielding tensor in solids: a ZORA/DFT investigation

Abstract

Periodic-boundary and cluster calculations of the magnetic-shielding tensors of (119)Sn sites in various co-ordination and stereochemical environments are reported. The results indicate a significant difference between the predicted NMR chemical shifts for tin(ii) sites that exhibit stereochemically-active lone pairs and tin(iv) sites that do not have stereochemically-active lone pairs. The predicted magnetic shieldings determined either with the cluster model treated with the ZORA/Scalar Hamiltonian or with the GIPAW formalism are dependent on the oxidation state and the co-ordination geometry of the tin atom. The inclusion of relativistic effects at the spin-orbit level removes systematic differences in computed magnetic-shielding parameters between tin sites of differing stereochemistries, and brings computed NMR shielding parameters into significant agreement with experimentally-determined chemical-shift principal values. Slight improvement in agreement with experiment is noted in calculations using hybrid exchange-correlation functionals.

Calculations of solid‐state 43Ca NMR parameters: A comparison of periodic and cluster approaches and an evaluation of DFT functionals

“…Three clusters of CaCl 2 Á2H 2 O of increasing size are shown in Figure 2. Based on these observations, and those of earlier work, [26,[29][30][31] we used thirdco-ordination-shell clusters in all subsequent calculations because clusters of this size appear to conserve sufficiently the local point-group symmetry of the calcium sites. For both the 43 Ca magnetic-shielding and quadrupolarcoupling tensors, there are large differences between computed results for the first-and third-co-ordination-shell clusters, whereas the third-and fifth-co-ordination-shell clusters yield similar values.…”

“…GIPAW calculations used the following functionals: CA-PZ, [47,48] PW91, [49] PBE, [50] rPBE, [51] PBEsol, [52] and WC. [23,[25][26][27][28][29][30][31][32][33][54][55][56][57][58] In this work, clusters were constructed by expanding to the third co-ordination shell of atoms around the central 43 Ca site. [23,[25][26][27][28][29][30][31][32][33][54][55][56][57][58] In this work, clusters were constructed by expanding to the third co-ordination shell of atoms around the central 43 Ca site.…”

“…[53] Cluster-based approaches to model lattice effects for the prediction of NMR parameters have been discussed previously. [23,[25][26][27][28][29][30][31][32][33][54][55][56][57][58] In this work, clusters were constructed by expanding to the third co-ordination shell of atoms around the central 43 Ca site. For the calcium carboxylates, ligands were not truncated, so that atoms beyond the third coordination shell were included in the clusters for calcium tartrate tetrahydrate and calcium dibenzoate trihydrate.…”

“…For example, the calculations presented in Ref. [23,[25][26][27][28][29][30][31][32][33] As Hartree-Fock exchange is difficult to implement in periodic calculations, we also illustrate the use of cluster models for calculating 43 Ca NMR parameters. [24] To the authors' knowledge, no systematic study has been undertaken to investigate model-chemistry effects on computed 43 Ca NMR parameters.…”

“…Cluster-based techniques for modeling magnetic-shielding tensors in crystalline solids, which account for extended lattice effects without using periodic-boundary conditions, have expanded the range of computational methods that can be applied to structural problems. [23,[25][26][27][28][29][30][31][32][33] As Hartree-Fock exchange is difficult to implement in periodic calculations, we also illustrate the use of cluster models for calculating 43 Ca NMR parameters.…”