1. Institute of Solid State Physics, University of Latvia, Riga LV-1063, Latvia
2. Faculty of Chemistry, Theoretical Inorganic Chemistry, University Duisburg-Essen, 45141 Essen, Germany
3. Cluster of Excellence RESOLV, 44801 Bochum, Germany
4. Center for Nanointegration (CENIDE) Duisburg-Essen, 47057 Duisburg, Germany