Nid-band self-energy beyond the low-density limit

Previous calculations of the Ni d-band self-energy within the low-density approximation are improved by considering correlations due to both hole-hole and electron-hole interactions. It is shown that these additional processes tend to reduce the satellite binding energy and enhance the narrowing of the d band. The exchange splitting is decreased only by a small amount from the value obtained in the low-density limit. The new results are in good agreement with experimental photoemission spectra.