Electron diffraction evidence for domain structures in the low-temperature incommensurate phase in CuV₂S₄

A low-temperature electron diffraction study of the sulfo spinel CuV₂S₄ is presented. From the diffraction geometry analysis a deformation modulated structure of the room temperature spinel phase below 90 K is proposed. Taking the low-temperature reflection intensities into account qualitatively, evidence is presented for a domain structure consisting of six orientation variants, corresponding with a symmetry lowering from cubic (order 48) to orthorhombic (order 8). The observation of pairs of low-temperature reflections located at incommensurate positions leads to a structure model consisting of quasi-periodically stacked antiphase boundaries characterized by a displacement vectorR =12[101]. The deformation modulation is interpreted in terms of dimerized 〈110〉 types of copper-atom zig-zag chains, possibly associated with a charge density wave-type distortion.