[1] Ecole Polytech, CNRS, UMR 7643, Phys Mat Condensee Lab,Grp Chim Solide, F-91128 Palaiseau, France
[2] Lab CNRS St Gobain, UMR CNRS 125, F-93303 Aubervilliers, France
[3] Univ Paris 06, UMR CNRS 7590, Lab Mineral Cristallog, F-75252 Paris, France
[4] Univ Paris 07, UMR CNRS 7590, Lab Mineral Cristallog, F-75252 Paris 05, France