Bi5O7Br and its structural relation to alpha-Bi5O7I.
Pentabismuth heptoxide bromide, Bi5O7Br, crystallizes in the space group Cmca. Its structure is compared with the closely related Ibca structure of alpha-Bi5O7I. The change in the space group is assumedly the result of a compromise between the different spatial needs of Br and I and the rigidity of the {(3)(infinity)}[Bi, O] frameworks into which they are embedded. A detailed procedure for the synthesis of Bi5O7Br is given.
Kristallographisches Institut, Albert-Ludwigs-Universität Freiburg, Hermann-Herder-Strasse 5, D-79104 Freiburg, Germany. egbert.keller@krist.uni-freiburg.de
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