Données crystallographiques sur les formes α et β du dichromate de baryum BaCr₂O₇

Crystal data are given for both α and β forms of barium dichromate, BaCr₂O₇. The α form is monoclinic (C2/c) with a = 16.29 (5), b = 16.63 (5), c = 9.456 (1) Å; β = 92.52 (5)° and Z = 16. The β form, isotypic with SrCr₂O₇ and PbCr₂O₇, is tetragonal (P4₂/nmc) with a = 11.72 (5), c = 9.440 (3) Å and Z = 8.