Eur. Phys. J. B 84, 203-217 (2011)
https://doi.org/10.1140/epjb/e2011-10994-3

Regular Article

Electron correlation in Sr(Ca)RuO₃ by GWA and LSDA+U

Magnet Research Laboratory (MRL), Department of Physics, Sharif University of Technology, P.O. Box 11365 - 9161, Tehran, Iran

^a e-mail: akhavan@sharif.edu

Received: 19 December 2010
Received in final form: 24 July 2011
Published online: 10 November 2011

Abstract

We have investigated the role of electron-electron correlation in SrRuO₃ and CaRuO₃ bulk structures. At first, the DOS of SrRuO₃ and CaRuO₃ is obtained using the full potential linearized augmented plane wave method by LSDA. We have then calculated the electronic structure, dielectric function, self-energy, and spectral function for the bulk SrRuO₃ and CaRuO₃ by GWA. The shifting of the Ru t_2g orbitals, broadening in Ru valance bands, and also the enhancement in exchange splitting shows better agreement between the GWA many-body correction with the bulk experimental results. But, in spite of the many-body correction, the GWA results is not completely consistent with the PES experimental results due to small shifting of the Ru t_2g bands and small broadening of the valance states specially in the Ca-based system. Inclusion of Coulomb correlation by LSDA+U for both Sr- and Ca-based compounds shows significant difference in the results as compared with the LSDA and GWA calculations, and is consistent with the PES results. So, the discrepancy between the bulk ab-initio calculation and experiment is attributed to the surface effects which is not considered in the both LSDA and GWA bulk calculations. Due to the more distorted structure of CaRuO₃, electron correlation at surface in the Ca-based system is more important than that in the Sr-based system. Hence, the bulk character of both SrRuO₃ and CaRuO₃ experimental results can be well described by GWA.