Hybridization strength in Ce compounds: A local-density study

Abstract

A systematic ab initio electronic-structure study of the late transition-metal--cerium compounds forming in the cubic Laves-phase structure, and of those cerium compounds (${\mathrm{CeRh}}_{3}$, ${\mathrm{CePd}}_{3}$, and ${\mathrm{CePt}}_{3}$) forming in the ${\mathrm{AuCu}}_{3}$ structure, is performed using the local-density approximation. Magnetic and cohesive properties are shown to be crucially dependent on the treatment of the cerium 4f electron. In all cases investigated (except for the palladium and platinum compounds) our calculations favor a picture with delocalized 4f electrons. Photoemission data for the strongly 4f-4d hybridized ${\mathrm{CeRh}}_{3}$ system is discussed and shown to have a substantial itinerant 4f character. Calculations for some fictitious ${\mathrm{AuCu}}_{3}$ compounds Ce${\mathit{A}}_{3}$, where A is a 4d element preceding Rh or a 5d element preceding Pt, are also presented. This is done in order to elucidate how the position of the cerium 4f band, relative to the Fermi level, changes when such a series of compounds is traversed. The hybridization between the cerium 4f states and the transition-metal d states is shown to vary in a systematic way, which, together with the filling of the transition-metal d band, can explain the position of the 4f band. The calculated 4f position is compared with data from inverse photoemission spectroscopy. Especially the anomalous position of the 4${\mathit{f}}^{1}$ peak, previously found in bremsstrahlung isochromat spectroscopy experiments for ${\mathrm{CeRh}}_{3}$, is found to fit into the calculated trend in a consistent manner.