Perovskites and perovskite-like materials with the general formule ABX\(_3\) or A\(_2\)BX\(_6\), where A is an inorganic (e.g. Cs\(^+\)) or organic (e.g. methylammonium=CH\(_3\)NH\(_3^+\)) cation, B a dication (e.g. Pb\(^{2+}\),Ge\(^{2+}\) or Sn\(^{2+}\)) and X a halide (Cl\(^-\), Br\(^-\), I\(^-\)) or mixture of halides, have received a great deal of attention due to their applicability in photovoltaic and optoelectronic devices. Due to their potential use, these materials have been characterized using a variety of different experimental and computational methods. Solid-state NMR has been shown to be an ideal experimental tool providing information about the local structure and even dynamic effects of halide nuclei. Experiments show that, depending on the perovskite, the chemical shift of the B centre can exhibit either a normal (NHD) or inverse halide dependency (IHD). Computational studies, using density functional theory (DFT), of chemical shifts on molecular models of perovskites, i.e., BX\(_6^{4-}\) octahedra, or perovskite-like materials, i.e., BX\(_6^{2-}\) octahedra, show good agreement with experimental measurements and even more, are able to capture the NHD and IHD behaviour, e.g., [1-4] Motivated by these findings, the chemical shifts in a series of metal halides in group 14, i.e., MX\(_n\) for M(II, IV)\(=\)Ge, Pb, Sn and X\(=\)Cl, Br, I, have been investigated computationally. Two key (computational) aspects are considered for these systems containing heavy elements: relativistic effects (with scalar ZORA) and spin-orbit coupling (SOC). Based on DFT results (PBE0/TZ2P), a natural bond order (NBO) partition of the chemical shielding tensor into its diamagnetic, paramagnetic, and SOC components is performed. The partitioning shows the key role SOC plays in reproducing the observed NHD and IHD trend for M(II, IV) nuclei. For completeness, the electric field gradients (EFG) of all quadrupolar nuclei (\(^{35}\)Cl, \(^{73}\)Ge, \(^{79}\)Br, \(^{119}\)Sn, \(^{127}\)I, \(^{207}\)Pb) are computed to permit comparison with future experimental measurements.

References (1) Hooper, R. W. et al. Exploring Structural Nuances in Germanium Halide Perovskites Using Solid-State \(^{73}\)Ge and \(^{133}\)Cs NMR Spectroscopy. The Journal of Physical Chemistry Letters 2022, 13, 1687–1696, DOI: 10.1021/acs.jpclett.1c04033. (2) Karmakar, A. et al. Uncovering Halogen Mixing and Octahedral Dynamics in Cs\(_2\)SnX\(_6\) by Multinuclear Magnetic Resonance Spectroscopy. Chemistry of Materials 2021, 33, 6078–6090, DOI: 10.1021/acs.chemmater.1c01561. (3) Ha, M. et al. Phase Evolution in Methylammonium Tin Halide Perovskites with Variable Temperature Solid-State \(^{119}\)Sn NMR Spectroscopy. The Journal of Physical Chemistry C 2020, 124, 15015–15027, DOI: 10.1021/acs.jpcc.0c03589. (4) Karmakar, A. et al. Mechanochemical Synthesis of Methylammonium Lead Mixed–Halide Perovskites: Unraveling the Solid-Solution Behavior Using Solid-State NMR. Chemistry of Materials 2018, 30, 2309–2321, DOI: 10.1021/acs.chemmater.7b05209.