Surface electronic behavior of actinide metals

Abstract

The self-consistent film linearized muffin-tin orbital method has been used to calculate the surface electronic structure of plutonium. This has been done using a (111)-oriented five-layer slab geometry. We believe this is the first self-consistent all-electron surface electronic structure calculation for an actinide system. We use the full potential in the interstitial and vacuum, while the non-muffin-tin (NMT) potential in the spheres is approximated by the extended interstitial NMT potential. The interest and difficulty of dealing with actinide electronic structure is associated with the large number of electrons in the atom, the importance of relativistic effects, and especially the behavior of the 5f electrons which typically are intermediate between itinerant and localized. The calculated work function of plutonium is strongly affected by the treatment of the 6p electrons, and with spin–orbit coupling effects included is 4.3 eV with 6p electrons treated as core, in good agreement with experimental values of 3.4 to 4.3 eV for uranium. A much higher calculated value of 8.4 eV, if the 6p electrons are treated as valence electrons, shows that the 6p electrons are largely localized. The narrow bandwidth of the 5f electrons and the position relative to s and d bands relate to the intermediate delocalization of the 5f electrons and the existence of hybridization with the s and d electrons.