Cover illustration: Displacement ellipsoid plot of one of the three independent molecules in the asymmetric unit of the polymorph of tris(2,4-pentanedionato-2O,O')aluminium(III). Ellipsoids are drawn at the 50% probability level. See von Chrzanowski, Lutz & Spek [Acta Cryst. (2007), C63, m129-m134]
The new structure type of CsAl(H2AsO4)2(HAsO4) is characterized by decorated kröhnkite-like chains of corner-sharing octahedra and tetrahedra. Cs atoms lie between these polyhedra and hydrogen bonds provide re-enforcement. The compound is closely related to CsGa(H1.5AsO4)2(H2AsO4), but crystallizes with lower space-group symmetry.