The local structure of p(2×2)-Na/Al(111) has been investigated using angle-scanned full hemispherical x-ray photoelectron diffraction. The resulting diffraction patterns allow a direct and unequivocal determination of the surface atomic structure. Even though Na and Al are completely immiscible in the bulk, the p(2×2)-Na/Al(111) phase consists of a composite double-layer surface alloy where Na atoms take substitutional and fcc hollow sites and Al atoms removed from the surface occupy hcp hollow sites.

• Received 3 April 1995

DOI:https://doi.org/10.1103/PhysRevB.52.R2313