ELECTRONIC-STRUCTURE AND X-RAY PHOTOELECTRON-SPECTROSCOPY OF THE ALPHA-PHASE, BETA-PHASE, AND GAMMA-PHASE OF NP

The electronic structure, density of states, and x-ray photoelectron s pectroscopy (XPS) intensities of the alpha, beta, and gamma phases of Np have been theoretically determined from self-consistent, fully rela tivistic, linear muffin-tin-orbital band-structure calculations. The c alculated XPS intensities show a large f peak that narrows (due to the larger volumes per atom) and moves closer to the Fermi energy as one progresses through the alpha, beta, and gamma phases. Experimental XPS intensities of the alpha and beta phases are also presented and compa red to the theoretical calculations. Experimentally, the alpha and bet a intensities are found to be almost identical, and do not show any ev idence for the theoretically predicted f-band narrowing. In addition, there is a large additional experimental intensity at higher binding e nergy that is not present in the calculations. This extra intensity ma y be evidence for quasilocalized behavior of the 5f electronic states that is induced by the XPS process. For example, the low-energy tail m ay be related to either multiplet or satellite structure due to final- state localized atomiclike correlation effects.