Valence states of copper ions and electronic structure of LiCu2O2

Abstract

The electronic structure of LiCu2O2 was studied using x-ray emission (Cu L-alpha, O K-alpha) and photoelectron spectroscopy (valence band and core levels) as well as band-structure calculations in terms of local spin-density approximation (LSDA) and LSDA U approaches. According to the x-ray-emission and photoelectron spectra the valence states of the Cu atoms are found to be mixed, i.e., 2+ and 1+. The LSDA calculations are contradictory to the experimental data and cannot reproduce the band gap and magnetic properties of LiCu2O2. The LSDA U calculations describe the insulator and antiferromagnetic properties much better but the overestimation of the screened Coulomb parameter U leads to a binding-energy shift of the Cu-II 3d states and this distorts the proper modeling of the valence-band structure. The magnetic structure of LiCu2O2 is discussed, taking our LSDA U band-structure calculations into account. [S0163-1829(98)04108-3].