1. Univeristy of Bremen, Institute of Inorganic Chemistry and Crystallography, Leobener Straße 7, D-28359 Bremen, Germany
2. Univeristy of Bremen, MAPEX Center for Materials and Processes, Bibliothekstraße 1, D-28359 Bremen, Germany
3. University of Bremen, Crystallography, Faculty of Geosciences, Klagenfurter Straße 2-4, D-28359 Bremen, Germany
4. Institut Laue Langevin, 38042 GRENOBLE Cedex 9, France