Affiliation: | a Department of Materials Science/CENIMAT-CEMOP, Faculty of Science and Technology, New University of Lisbon, 2829-516 Caparica, Portugal b Laboratoire de Physique des Solides et de Cristallogenèse, C.N.R.S., 1 Place Aristide Briand, 92195 MEUDON CEDEX, France c Centro de Química-Física Molecular, Complexo Interdisciplinar, IST 1049-001 Lisboa, Portugal |