X-RAY-SPECTRA AND ELECTRONIC-STRUCTURE OF LIXNBO2 SUPERCONDUCTOR AND OTHER NIOBIUM OXIDE COMPOUNDS

X-ray emission Nb L(beta2,15) and O K(alpha) spectra and O1s total pho toelectron yield spectra for superconductor Li0.71NbO2 and other niobi um oxide compounds NbO, BaNb4O6, Ba2Nb5O9, BaNb5O8, LiNbO2, NbO2, LiNb O3 were investigated. It was found that in stoichiometric LiNbO2, niob ium oxidation degree is 3 +. Under the lithium deintercalation down to Li0.71NbO2 CoMPoSition, the niobium ions oxidation degree increases u p to 3.3 +. As more electrons are supplied by Nb to fill the O2p band, the degree of O2p-Nb4d hybridization is increased. Using the full-pot ential linear muffin-tin orbital method, the self-consistent band stru cture calculations of LixNbO2 (x = 1.0; 0.7; 0.5) compounds were carri ed out. Agreement between partial Nb4d and O2p densities of states and corresponding X-ray spectra was observed. For the x = 0.7; 0.5 the Fe rmi level is placed on the slope of sharp density of states peak forme d mostly by the Nb4d states. With the decrease of x the p - d hybridiz ation becomes stronger, although remains well below the values typical for the high-temperature superconductors.