Direct structure determination of a composite double-layer surface alloy by x-ray photoelectron diffraction: p(2 x 2)-Na/Al(111).

Abstract

The local structure of p(2\ifmmode\times\else\texttimes\fi{}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\ifmmode\times\else\texttimes\fi{}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.