A combined temperature-dependent electron and single-crystal X-ray diffraction study of the fresnoite compound Rb2V4+V25+O8

作者：Withers RL^*; Hoche T; Liu Y; Esmaeilzadeh S; Keding R; Sales B

来源：Journal of Solid State Chemistry, 2004, 177(10): 3316-3323.

DOI：10.1016/j.jssc.2004.05.056

• Rb2V3O8 fresnoite
• low-temperature incommensurate phase transition
• frozen RUM mode
• temperature-dependent electron diffraction study
• low-temperature average structure refinement

High-purity Rb2V3O8 has been grown and temperature-dependent electron and single-crystal X-ray diffraction used to carefully investigate its fresnoite-type reciprocal lattice. In contrast to other recently investigated representatives of the fresnoite family of compounds, Rb2V3O8 is not incommensurately modulated with an incommensurate basal plane primary modulation wave vector given by q similar to 0.3 <110>*. A careful low-temperature electron diffraction study has, however, revealed the existence of weak incommensurate satellite reflections characterized by the primitive primary modulation wave vector q(1) similar to 0.16c*. The reciprocal space positioning of these incommensurate satellite reflections, the overall (3 + 1)-d superspace group symmetry, as well as the shapes of the refined displacement ellipsoids determined from single-crystal XRD refinement, are all consistent with their arising from a distinct type of condensed rigid unit modes (RUMs) of distortion of the Rb2V3O8 parent structure.

• 出版日期2004-10