ELECTRONIC-STRUCTURE OF NOBLE-METAL MONOXIDES - PDO, PTO, AND AGO

The electronic structure and properties of the noble-metal monoxides, PdO, PtO, and AgO have been determined by the full-potential linearize d augmented-plane-wave (FLAPW) and full-potential linear-muffin-tin-or bital (FLMTO) methods. The calculated band structures show PdO and PtO to be poor metals with very low densities of states at the Fermi leve l. Thus, as in the 3d oxides, both methods used within the scope of th e local-density approximation fail to produce the band gaps observed e xperimentally for PdO and PtO; they do, however, show that these band gaps are of the type that occur from crystal-field effects rather than being of the Mott-Hubbard or charge-transfer type. For AgO, the monoc linic crystal-field splitting of the d states is strong enough to indu ce a small direct band gap, which partially separates the electronic s tates of two nonequivalent silver atoms and results in Ag1+ and Ag2+ c onfigurations rather than Ag1+ and Ag3+. Thus, correlation effects app ear to be important for the detailed description of electronic states near E(F) not only for 3d metal monoxides, but for noble-metal oxides with much-less-localized metallic d states. Finally, the excellent agr eement between the FLAPW and FLMTO results shows the possible advantag e of using the much-less time-consuming FLMTO method in quantitative b and-structure calculations of complex crystals.