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Low Temperature Crystal Growth and Structure of Ordered Ba7

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Low Temperature Crystal Growth and Structure of Ordered Ba

7

F

12

Cl

2

F. Kubel

a

, H. Bill

b

, H. Hagemann

b

a Institut für Mineralogie, Kristallographie und Strukturchemie, Technische Universität Wien, Getreidemarkt 9, Wien

b De´pt. de Chimie Physique, Univ. de Gene`ve, 30, quai Ernest-Ansermet, CH 1211 Geneva 4, Switzerland

Z. Naturforsch.54 b,515Ð518 (1999); received November 30, 1998

Bariumfluorochloride, Hexagonal Crystal Structure, Crystal Growth, Low Temperature Gel Method

Crystals of composition Ba7F12Cl2were obtained by a reaction at room temperature be- tween Ba2+/ClÐ/FÐin a gel of agar-agar/water. The hexagonal crystals have space group P6, a=1064.69(8),c=417.89(5)pm, V=410.24(8) 106 pm3and Z=1. The anions form a propeller type network located in tunnels parallel to thechexaxis; the chloride ions are located at the center on the propeller axes. The Ba2+ions are coordinated by a (distorted) tricapped trigo- nal environment of fluoride and chloride anions. Disorder is present for one particular Ba2+

site. The average structure is isotypic with the structure of Pb7F12Cl2.

* Reprint requests to Prof. H. Bill.

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