Electronic band structure of orderedCu3Au:An angle-resolved photoemission study along the [001] direction

High-resolution angle-resolved ultraviolet photoemission spectra (ARUPS) have been recorded for ${\mathrm{Cu}}_3\mathrm{Au}\mathrm{}\left(001\right)\mathrm{}$ with the use of polarized synchrotron and rare-gas resonance radiation in the photon energy range 9–26 eV. A fully relativistic layer–Korringa-Kohn-Rostoker formalism was employed to calculate the initial- and final-state bulk band structure as well as one-step model photoemission spectra. Hole and photoelectron lifetime effects are taken into account. The calculated empty bulk bands along the [001] direction $(\Delta$ line in $\overrightarrow{k}$ space), which carry most of the electron flux into the normal direction along [001], were—after a real self-energy correction of $+2.5\mathrm{}$ eV—used to perform an experimental band mapping. The thus determined occupied Cu-like d bands and the $\mathrm{sp}$ band are in good agreement with the calculated “Kohn-Sham bands,” if the latter are shifted downward in energy by 0.3 eV. For the Au-like d bands, some deviations persist. Measured ARUPS spectra agree well with their calculated counterparts, which corroborates our identification of direct bulk transition features and our band mapping. In addition, numerous features are found to arise from surface states or resonances. Normal-incidence inverse photoemission data taken for $\mathrm{h}\nu =9.7\mathrm{}$ eV further support our findings.