Auger spectra and band structure of ${\mathrm{La}}_{1.85}$${\mathrm{Sr}}_{0.15}$${\mathrm{CuO}}_4$ and ${\mathrm{La}}_{1.85}$${\mathrm{Ba}}_{0.15}$${\mathrm{CuO}}_4$

High-resolution Auger electron spectra of ${\mathrm{La}}_{1.85}$${\mathrm{Sr}}_{0.15}$${\mathrm{CuO}}_4$ and ${\mathrm{La}}_{1.85}$${\mathrm{Ba}}_{0.15}$${\mathrm{CuO}}_4$ have been measured. The experimental Auger line shapes of the oxygen KLL and copper ${\mathit{L}}_{2,3}$VV transitions are compared with those generated from local-density-approximation linear-muffin-tin-orbital band-structure calculations. An analysis based on this comparison is used to determine the Coulomb parameters ${\mathit{U}}_{\mathit{p}}$ and ${\mathit{U}}_{\mathit{d}}$ of the oxygen and copper atoms, respectively. For this purpose, an extended version of Cini and Sawatzky’s expression for the theoretical Auger line shape is used, taking into account the multiplet structure of the Auger final states and the point symmetry of the oxygen sites. We find ${\mathit{U}}_{\mathit{p}}$ of approximately 5 and 7 eV for the planar and apical oxygen sites, respectively, and ${\mathit{U}}_{\mathit{d}}$ of 7–8 eV for copper. An estimate of the effect of electron correlations on the band structure suggests a decrease of the anisotropy found in ${\mathit{U}}_{\mathit{p}}$.