1. Institute of Inorganic Chemistry, University of Stuttgart, Pfaffenwaldring 55, 70569 Stuttgart, Germany, http://www.iac.uni‐stuttgart.de/arbeitskreise/akniewa/index.en.html
2. Chair in Inorganic Solid‐State Chemistry, Ludwig Maximilians University of Munich, Butenandtstrasse 5–13, 81377 München, Germany