1. Institute for Computational Physics, University of Stuttgart, D-70569 Stuttgart, Germany
2. Institute of Physical Chemistry, Polish Academy of Sciences, 01-224 Warsaw, Poland
3. Max-Planck-Institut für Intelligente Systeme, Heisenbergstraße 3, 70569 Stuttgart, Germany
4. IV. Institut für Theoretische Physik, Universität Stuttgart, Pfaffenwaldring 57, 70569 Stuttgart, Germany