The Ni3Al(111) surface structure:: experiment and theory

The structure of the Ni3Al(111) terminal layers has been studied by means of x-ray photoelectron diffraction and density functional theory. The analysis of the diffraction patterns, combined with multiple-scattering simulations, yields structural parameters which are in good agreement with the ab initio theoretical results. We find that the first-layer Al atoms move outwards with respect to the Ni atom plane, as previously found by low energy electron diffraction experiments and ab initio calculations. The experimentally (theoretically) determined distance between the outermost three layers is reduced by 0.07 +/- 0.07 angstrom (0.06 +/- 0.01 angstrom) and by 0.04 +/- 0.08 angstrom (0.01 +/- 0.01 angstrom) for the first-to-second-layer and second-to-third-layer distances with respect to the bulk value, respectively.