1. Department of Chemical and Geological Sciences, University of Cagliari, Cittadella Universitaria S.S. 554 Bivio per Sestu, 09042 Monserrato, Italy
2. Consorzio Interuniversitario Nazionale per la Scienza e Tecnologia dei Materiali (INSTM), Via Giuseppe Giusti 9, 50121 Florence, Italy
3. Department of Inorganic Chemistry, Charles University, Hlavova 2030, 128 40 Prague 2, Czech Republic
4. Department of Physics and Astronomy, University of California, Irvine, CA 92617, USA