1. Department of ChemistryUniversity of Munich (LMU) Butenandtstr. 5-13 81377 München Germany
2. Max Planck Institute for Solid State Research Heisenbergstr. 1 70569 Stuttgart Germany
3. Institute for Mineralogy, Crystallography and Materials Science, Faculty of Chemistry and MineralogyLeipzig University Scharnhorststr. 20 04275 Leipzig Germany