NMR selection of space groups in structural analysis of Ag7PSe6

Ag7PSe6 is an archetype of the argyrodite family. It, undergoes one phase t ransition at 453 K, and both phase structures have been recently determined by X-ray diffraction on single crystals. Argyrodites twin frequently when undergoing their phase transitions and solving the structures by diffractio n may become difficult or even impossible. It is shown in this paper that s olid-state NMR provides enough structural information to restrict the numbe r of possible space groups to a small subset. In the case of Ag7PSe6 at roo m temperature, a restriction to three space groups is thus obtained, one of them being the space group of the structure determined by diffraction, The method to obtain the necessary NMR information to perform restriction of t he subset of compatible space groups is explained and evaluated on this com pound.