“…Quantitative surface crystallographic methods (especially dynamic LEED) have confirmed the LEIS results. The cases where the atomic structure of the topmost layer corresponds to that of a "mixed" bulk crystallographic plane For the L11 phase (fcc, Cu¢ Au type) has been reported, among other cases, for instance for Cu¢ Au(100) ( [56,57,54,58,59,55,60] and Ni¢ Al(100) [52,53] systems which have the same structure and termination as the Pt¢ Sn(100) [17,27]. In all these cases, obviously, the presence of different degrees of outward relaxation ("buckling") for the different chemical species present has been reported.…”