Ab initio simulation of photoemission spectroscopy in solids:: Plane-wave pseudopotential approach with applications to normal-emission spectra of Cu(001) and Cu(111)

We develop a method for simulating photoemission spectra from bulk crystals in the ultraviolet energy range within a three-step model. Our method explicitly accounts for transmission and matrix-element effects, as calculated from state-of-the-art plane-wave pseudopotential techniques within the density-functional theory., Transmission effects, in particular, are included by extending to the present problem a technique previously employed with success to deal with ballistic conductance in metal nanowires. The spectra calculated for normal emission in Cu(001) and Cu(111) are in fair agreement with previous theoretical results and with experiments, including a recently determined experimental spectrum. The residual discrepancies between our results and the latter are mainly due to the well-known deficiencies of the density-functional theory in accounting for correlation effects in quasiparticle spectra. A significant improvement is obtained by the LDA + U method. Further improvements are obtained by including surface-optics corrections, as described by Snell's law and Fresnel's equations.