https://doi.org/10.1140/epjb/e2008-00080-6
Electric field gradients in PrBa2Cu3O7: LSDA+U results and comparison with experiment
1
Superconductivity Research Laboratory (SRL), Department of Physics, University of Tehran, P.O. Box 14395, North Karegar Ave., Tehran, Iran
2
Department of Nano-Science, Institute for Studies in Theoretical Physics and Mathematics (IPM), P.O. Box 19395, Tehran, Iran
Corresponding author: a zadeh@ut.ac.ir
Received:
11
November
2006
Revised:
1
August
2007
Published online:
29
February
2008
Electric-field gradient (EFG) and asymmetry parameter (η) at all oxygen and copper sites of nonsuperconducting PrBa2Cu3O7 (Pr123) compound were calculated using the full-potential (linearized)-augmented-plane-wave plus local orbitals method. Exchange and correlation effects were treated by LSDA+U for Cu(3d) and Pr(4f) electrons. The effects of changing screened Coulomb parameters UPr, UCu1, and UCu2 on the results were individually studied. The calculated EFG of O2 site is close to the EFG of O3 site at variance with the experimental result. It was shown that by increasing superconducting holes in O2 and O3 sites the EFG at these sites increase and vice versa. The most famous theories which have been proposed to explain the suppression of superconductivity in perfect (without any mis-substitution or other defects) Pr123 compound are not consistent with the experimental EFG at O2 and O3 sites. By replacing one Pr atom at the Ba site on unit cell of Pr123 (PrBa), it was shown that PrBa mis-substitution reduces the superconducting holes in both O2 and O3 sites and could be responsible for the suppuration of superconductivity in Pr123 samples. It is very probable that the unusual behaviors of experimental EFG at O2 and O3 sites of Pr123 are related to oxygen defects which are produced with PrBa mis-substitution.
PACS: 74.25.Jb – Electronic structure / 74.72.Bk – Y-based cuprates / 71.15.Mb – Density functional theory, local density approximation, gradient and other corrections / 76.60.-k – Nuclear magnetic resonance and relaxation
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2008