ATOMIC-STRUCTURE OF FEAL(001)

The atomic structure of a clean {001} surface of the ordered binary al loy FeAl with 46 at% Al (lattice parameter 2.904 angstrom) has been de termined by low-energy electron diffraction analysis. The bulk structu re is of the CsCl-type. The top surface plane is shown to be an Al lay er, with an Fe plane for the second layer. The first interlayer spacin g (between Al and Fe) is found to be contracted by 14.6%, while the se cond interlayer spacing (between Fe and Al) is found to be expanded by 4%. A sputter-cleaned but not annealed surface of this alloy is found to have ordered regions of predominantly bcc Fe{001}.