1. Faculty of Physics, Babeş-Bolyai University, 1 Kogǎlniceanu, RO-400084 Cluj-Napoca, Romania
2. Theoretical Materials Physics, Q-MAT, CESAM, Université de Liège (B5), B-4000 Liège, Belgium
3. Nanomat, Q-Mat, CESAM, and European Theoretical Spectroscopy Facility, Université de Liège (B5), B-4000 Liège, Belgium