Crystal structure of CsCrAs2O7, a new member of the diarsenate family.

Caesium chromium(III) diarsenate(V), CsCrAs2O7, was prepared by solid-state reactions. The title structure consists of isolated CrO6 octa-hedra and As2O7 diarsenate groups, sharing corners to build up a three-dimensional [CrAs2O7](-) anionic framework. In this framework, channels extending parallel to [001] are present in which the ten-coordinate Cs(+) ions reside. CsCrAs2O7 is isotypic with the monoclinic A (I) M (III) X 2O7 (A (I) = alkali metal; M (III) = Al, Cr, Fe; X = As, P) type I family of compounds crystallizing in the space group P21/c.