Crystal structure analysis of van der Waals layered phosphorus chalcogenide CuVP2S6.

The crystal structure of CuVP2S6 is investigated by transmission electron microscopy (TEM) and single-crystal X-ray diffraction. Cu, V and dimerized P2 are each octahedrally coordinated by S atoms. Each metal ion species forms a triangular lattice, which is interdigitated to form a two-dimensional sheet. Each sheet forms a layered structure with van der Waals gaps between them. The crystal has a rotational twin structure, which is manifested in the form of stacking disorder. Refined structure analysis reveals characteristic rotational distortion of the octahedra. The existence of Cu sites protruding into the van der Waals gap is directly shown by high-resolution scanning TEM.