I think that I've just found the answer: the SC is heavily doped! P.
-- Dr. pascal Boulet, computational chemist University of Aix-Marseille I Laboratoire Chimie Provence, UMR 6264 Group of Theoretical Chemistry Avenue Normandie-Niemen 13397 Marseille Cedex 20 France ********** Tel. (+33) (0)413.55.18.10 Fax. (+33) (0)491.55.18.50 ********** http://www.lc-provence.fr https://sites.google.com/a/univ-provence.fr/pb-comput-chem %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%