1 4 Ja n 20 00 On the electronic structure of CaCuO 2 and SrCuO

Recent electronic structure calculations for the title compounds performed by Wu et. al. [1] are critically reconsidered, applying high precision full-potential bandstructure methods. It is shown that the bandstructure calculations presented by the authors contain several important inconsistencies, which make their main conclusions highly questionable. In a recent paper Wu et. al. [1] presented bandstructure calculations for the quasi one-dimensional CuO-chain compound SrCuO 2 and the quasi two-dimensional material CaCuO 2 , both being of prototypical character and therefore of general interest. Wu et. al. used a full-potential linear combination of atomic orbitals method [2] in the framework of the local spin density approximation (LSDA) and included on-site Coulomb interaction corrections (LSDA+U). The authors of Ref. [1] claim that on the basis of their full-potential band structure experimental findings can be well fit with an U of 5 eV, significantly smaller than U values reported in previous calculations [3]. However, there are obvious inconsistencies and important differences between the calculations of Ref. [1] and previous studies [3, 4, 5, 6], concerning (i) the proper symmetry in k-space, (ii) the widths and the orbital character of the shown bands, (iii) the total (DOS) as well as the partial densities of states (PDOS). Therefore, we reinvestigated the electronic structures of CaCuO 2 and SrCuO 2 using two independent, well basis converged full-potential bandstructure methods to find out whether or not the differences mentioned above could be understood as a consequence of the differences between a full-potential [1] and the earlier non-full-potential calculations [3, 5, 6]. We carried out LSDA bandstructure calculations for CaCuO 2 within a full-potential minimum-basis local-orbital scheme (FPLO) [7] and within a full-potential linearized augmented plane wave (FLAPW) scheme [8], both in scalar relativistic versions. (We note that relativistic effects are in the order of 0.1 eV only.) In the FPLO-scheme, modified Ca 3d, 4s, 4p, (Sr 5s, 5p ,4d), Cu 3d, 4s, 4p, and O 2s, 2p, 3d states were used as valence states for CaCuO 2 (SrCuO 2), the lower lying states were treated as core states. The WIEN97-code [8] employs local orbitals (LO) to relax linearisation errors and to treat the O-2s and semicore Cu-3p and Ca-3s, 3p states. Well converged basis sets of over 500 APW functions plus LOs were used. The radii of the atomic spheres in the latter case were 1.8 a.u. for all atoms. The basic calculations were performed with 125 and …