The P4₃ enanti­omorph of Sr₂As₂O₇

The crystal structure of strontium diarsenate has been reinvestigated from single-crystal X-ray diffraction data. In contrast to the previous determinations of this structure [Weil et al. (2009). Solid State Sci. 11, 2111-2117; Edhokkar et al. (2012). Mater. Sci. Eng., 28, 012017] and to all isotypic A₂B₂O₇ compounds that crystallize in the space group P4₁, the current redetermination revealed the P4₃ enanti­omorph of Sr₂As₂O₇ with a purity of 96.3 (8)%. The crystal structure is made up from two eclipsed As₂O₇ diarsenate groups (symmetry 1) with characteristically longer As-O bridging bonds [1.756 (4)-1.781 (4) Å] than the terminal As-O bonds [1.636 (4)-1.679 (4) Å] and four Sr²⁺ sites with coordination numbers ranging from seven to nine. The building units are arranged in sheets parallel to (001).