Atomic structure of alloy surfaces. III. Ni3Al{110}

Abstract

A low-energy-electron-diffraction intensity analysis of a clean and annealed {110} surface of ${\mathrm{Ni}}_{3}$Al reveals that the first layer is 50% Ni--50% Al and that the second layer is 100% Ni. In the first layer, the Ni and Al subplanes are slightly separated from one another by 0.02\ifmmode\pm\else\textpm\fi{}0.03 A\r{}, the Al atoms being outwards from the bulk. The first interlayer distance, as measured from the Ni subplane, is contracted by 0.15\ifmmode\pm\else\textpm\fi{}0.03 A\r{} (11.9% of the bulk value, 1.26 A\r{}). The second interlayer distance is expanded by 0.04\ifmmode\pm\else\textpm\fi{}0.03 A\r{} (3% of the bulk value). The r-factor values for normal (0.14) and oblique (0.13) incidence indicate a very good fit of theory to experiment.