Strain effects on point defects and chain-oxygen order-disorder transition in 123 cuprate compounds
Welch, David O.
Date of Issue2004
School of Materials Science and Engineering
The energetics of Schottky defects in 123 cuprate superconductor series RBa2Cu3O7 (where R =lanthandies) and YA2Cu3O7 (A=alkali earths), were found to have unusual relations if one considers only the volumetric strain. Our calculations reveal the effect of nonuniform changes of interatomic distances within the R-123 structures, introduced by doping homovalent elements, on the Schottky defect formation energy. The energy of formation of Frenkel pair defects, which is an elementary disordering event, in 123 compounds can be substantially altered under both stress and chemical doping. Scaling the oxygen-oxygen short-range repulsive parameter using the calculated formation energy of Frenkel pair defects, the transition temperature between orthorhombic and tetragonal phases is computed by quasichemical approximations (QCA’s). The theoretical results illustrate the same trend as the experimental measurements in that the larger the ionic radius of R, the lower the orthorhombic/tetragonal phase transition temperature. This study provides strong evidence of the strain effects on order-disorder transition due to oxygens in the CuO chain sites.
Physical review B
© 2004 American Physical Society. This paper was published in Physical Review B and is made available as an electronic reprint (preprint) with permission of American Physical Society. The paper can be found at: [DOI: http://dx.doi.org/10.1103/PhysRevB.70.054517]. One print or electronic copy may be made for personal use only. Systematic or multiple reproduction, distribution to multiple locations via electronic or other means, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper is prohibited and is subject to penalties under law.