NMR selection of space groups in structural analysis of Ag7PSe6

Ag7PSe6 is an archetype of the argyrodite family. It, undergoes one phase transition 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 diffraction may become difficult or even impossible. It is shown in this paper that solid-state NMR provides enough structural information to restrict the number of possible space groups to a small subset. In the case of Ag7PSe6 at room 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 the subset of compatible space groups is explained and evaluated on this compound.