1. Contribution from Université de Rennes 1: Sciences Chimiques de Rennes, UMR-6226 Inorganic Materials: Soft Chemistry and Reactivity of Solids, F-35042 Rennes, France, Laboratoire Léon Brillouin, CEA-CNRS, F-91191 Gif sur Yvette, France, and Department of Inorganic, Physical and Materials Chemistry, NIS Center of Excellence, and INSTM “Centro di Riferimento”, University of Turin, 10125 Turin, Italy