1. Bremen Center for Computational
Materials Science, Universität Bremen, Am Fallturm 1, 28359 Bremen, Germany
2. Institut de Ciència de Materials de Barcelona (ICMAB−CSIC), Campus
de Bellterra, 08193 Bellaterra, Barcelona, Spain
3. Institute for Solid State Physics
and Optics, Wigner Research Center for Physics, Hungarian Academy of Sciences, P.O. Box 49, 1525 Budapest, Hungary
4. Department of Atomic Physics, Budapest University of Technology and Economics, Budafoki
út 8., 1111 Budapest, Hungary