1. Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin,
Germany
2. nanotech@surfaces
Laboratory, EMPA, Swiss Federal Laboratories for Materials Science and Technology, Ueberlandstrasse 129, 8600 Duebendorf,
Switzerland
3. Crystallography
Section, Department
of Earth and Environmental Sciences, Ludwig-Maximilians-Universität, Theresienstrasse 41, 80333 Munich, Germany
4. Max-Planck-Institut für Chemische Physik fester Stoffe, Nöthnitzer
Strasse 40, 01187 Dresden, Germany