Symmetry Effects at the Local Level in Solids

Abstract

Owing to their short-range nature, NMR interactions predominantly probe local structure and symmetry. The structural characterization of crystalline solid materials in terms of point and space-group symmetries, for instance by diffraction techniques, emphasizes long-range order based on the basic building blocks, the asymmetric unit and the unit cell, and it includes translational symmetry. The manifestation of the symmetry properties of the asymmetric unit/unit cell in the shape and orientation of the various NMR interaction tensors is examined, alongside the concommittant effects in the corresponding NMR spectra. Oriented single crystals as well as polycrystalline powders (in stationary samples and under magic-angle spinning conditions) are considered. Keywords: NMR interaction tensors; local symmetry; tensor shape; tensor orientation; crystalline materials