A study of transition metal K-edge x-ray absorption spectra ofLaBO3 (B = Mn, Fe,Co, Ni), La2CuO4, and SrMnO3 using partial density of states

Abstract

Transition metal K-edge x-ray absorption near edge structure (XANES) studies have been carried outon LaBO3 (B = Mn, Fe,Co, Ni), La2CuO4, and SrMnO3 compounds. The theoretical spectra have been calculated using the transition metal (TM)4p density of states (DOS) obtained from full-potential LMTO density functional theory.The exchange–correlation functional used in this calculation is taken under the localdensity approximation (LDA). The comparison of experimental spectra with the calculatedones indicates that single-particle transitions under the LDA are sufficient to generateall the observed XANES, including that which has earlier been attributed tomany-body shake-up transitions and core–hole potentials. The present studyreveals that all the experimentally observed features are mainly due to distributionin TM 4p DOS influenced by hybridization with other orbitals. Specifically, forLaMnO3, the feature earlier attributed to the shake-up process is seen toarise from hybridization of Mn 4p with La 6p and O 2p orbitals; inLa2CuO4 the features attributed to the core hole potential correspond to hybridization ofCu 4p with La 6p, La 5d, and O 2p orbitals. To see the effect of inhomogeneouselectronic charge distribution and on-site Coulomb and exchange interaction(U′) on the XANES of these compounds the generalized-gradient approximation andU′ corrections are incorporated in the calculations. These corrections do not generate any newfeatures in the spectra but affect the detailed intensity and positions of some of thefeatures.