Imaging of a surface state from clean Cu(001)

First-principles electronic structure calculations and multiple-angle valence-band photoelectron spectroscopy were combined to image a clean surface-related electronic state of the Cu(001) surface. The surface band cresting at 4.30 eV below the Fermi level was computed to have a density of states at the lower end of the bulk Cu d bands. Based on the results of first-principles calculations for the clean and Cl-covered surfaces, we were able to successfully measure the surface state by taking a ratio of clean versus Cl-covered isoenergetic valence electron angular distributions. We have also carried out first-principles total-energy calculations for the multilayer atomic relaxation of the clean Cu(001) surface, and found that the topmost interlayer separation contracts by 2.9% relative to the bulk value, while the second interlayer is essentially unchanged and the third interlayer contracts by only 0.1%. © 1996 The American Physical Society.