1. Centre for Materials Science and Nanotechnology, Department of Chemistry, Oslo University, 0371 Oslo, Norway
2. Department of Physics, Chalmers University of Technology, 412 96 Gothenburg, Sweden
3. Department of Chemistry and Chemical Engineering, Chalmers University of Technology, 412 96 Gothenburg, Sweden
4. Materials Theory Division, Department of Physics and Astronomy, Ångström Laboratory, Uppsala University, 751 20 Uppsala, Sweden