Journal of Magnetism and Magnetic Materials 272–276 (2004) 122–123 LSD-SIC studies of localization in the 4d-transition metal oxides Sr 2 RuO 4 and Ca 2 RuO 4 G. Malcolm Stocks a, * ,1 , W.M. Temmerman a , Z. Szotek b , A. Svane c , D. K . odderitzsch d , H. Winter e a Metals and Ceramics Division, Oak Ridge National Laboratory, P.O. Box 2008-6114, Oak Ridge, TN 37830, USA b Daresbury Laboratory, Daresbury, Warrington WA4 4AD, UK c Institute of Physics and Astronomy, University of Aarhus, DK-8000 Aarhus C, Denmark d Fachbereich Physik, Martin-Luther-Universit . at Halle-Wittenberg, Friedemann-Bach-Platz 6 Halle, 06099 Wittenberg, Germany e INFP, Forschungszentrum Karlsruhe GmbH, Postfach 3640, D-76021 Karlsruhe, Germany Abstract Self-interaction corrected local spin density approximation has been used to study the possibility of localization in Sr 2 RuO 4 and Ca 2 RuO 4 : Although the energy difference between specific localized and delocalized solutions can be small ðB30 mRy=RuÞ; we do not find evidence for strong static correlations. r 2003 Published by Elsevier B.V. PACS: 75.50.Gg; 75.47.Pq Keywords: LSD-SIC; Localization Although many of the structural properties of the isoelectronic alloy series ½Sr x Ca 1x  2 RuO 4 between the endpoint compounds Sr 2 RuO 4 and Ca 2 RuO 4 appear to be well described by standard local density approxima- tion (LDA) density functional theory methods [1], the fact that this series undergoes a complex series of structural, magnetic, and metal/insulator transitions as a function of Sr concentration, x [2], still leaves open the question as to the extent that these materials should be regarded as strongly correlated. Particularly when it is recalled that, for small Sr concentration ðxB0:2Þ; the system undergoes a metal/insulator transi- tion into an antiferromagnetic insulating Ca 2 RuO 4 - based phase [2]. Here we use self-interaction corrected (SIC) local spin density (LSD) [3] calculations to study how close these 4d-transition metal oxides are to a localization/deloca- lization transition. The specifics of our approach are: to base all calculations on the experimentally determined crystal structures; to calculate the LSD energy in the appropriate magnetic states; and to sequentially apply the SIC to single t 2g and e g orbitals as well as various combinations of them. The Sr 2 RuO 4 calculations were performed in the K 2 NiF 4 (I4/mmm)crystal structure. The Ca 2 RuO 4 calculations were performed for the low- temperature (Pbca) structure determined by Braden et al. [4], in particular the A-centered antiferromagnetic structure. The most salient results are displayed in Table 1, where the LSD-SIC energies (DE; mRy) relative to the LSD energy are shown. Also shown are the Ru-site magnetic moments ðM Ru ; m B ) and Fermi energy density of states (nðe F Þ; states/formula unit/Ry). For the equilibrium structures we do not find localization in either compound. However, the energy difference between some of the localized (LSD-SIC) and ARTICLE IN PRESS *Corresponding author. Tel.: +1-865-574-5163; fax: +1- 865-574-7659. E-mail address: gms@ornl.gov (G.M. Stocks). 1 Work supported by DOE-OS, BES-DMSE and OASCR- MICS under Contract No. DE-AC05-00OR22725 with UT– Battelle LLC. Calculations were performed at ORNL-CCS and NERSC. 0304-8853/$ - see front matter r 2003 Published by Elsevier B.V. doi:10.1016/j.jmmm.2003.11.060