1. CEMES, 29 rue Jeanne Marvig, BP 94347, 31055 Toulouse Cedex 4, France
2. Laboratoire de Minéralogie-Cristallographie de Paris, Université Pierre et Marie Curie, 4, place Jussieu, 75252 Paris Cedex, France
3. TCM Group, Cavendish Laboratory, Madingley Road, Cambridge, CB3 OHE, United Kingdom
4. Department of Chemistry and Courant Institute of Mathematical Sciences, 100 Washington Square East, New York University, New York, New York 10003