1. Departamento de Química Inorgánica, Facultad de Químicas, Universidad Complutense de Madrid, E-28040-Madrid, Spain
2. Department of Material Science and Engineering, University of Sheffield, Mappin Street, Sheffield S1 3JD, U.K.
3. SpLine, Spanish CRG beamline at the ESRF 6 rue Jules Horowitz - B.P.220, F-38043 Grenoble CEDEX, France and Instituto de Ciencia de Materiales de Madrid- CSIC, Cantoblanco 28049, Spain