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Point Defects of La 2 CuO 4 ‐Based Ceramics, Part I: Oxygen Interstitials
Author(s) -
Wu Yue,
Ellis Donald E.,
Shen Li,
Mason Thomas O.
Publication year - 1996
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.1996.tb08770.x
Subject(s) - crystallographic defect , seebeck coefficient , interstitial defect , oxygen , chemistry , dimer , molecular physics , materials science , condensed matter physics , atomic physics , crystallography , thermodynamics , thermoelectric effect , physics , organic chemistry , doping
Theoretical and experimental studies are reported on oxygen excess defect structure of lanthanum cuprate, La 2 CuO 4+δ . The local density functional formalism is applied to theoretical analysis. The self‐consistent discrete variational method has been used to find energy levels, densities of states, charge transfer, wavefunctions, and potentials for a fragment consisting of N (30–44) atoms embedded in the infinite crystal. Calculations have been performed on three interstitial oxygen models, with and without local relaxations. These models include sites proposed on the basis of neutron diffraction and interstitial dimers [O 2 ] q . The dimer charge q is found to be consistent with that of normal oxygens, and not ‐1 as proposed in “superoxide” models. Electrostatic energies are used to estimate the relative stabilities of the proposed interstitial structures. The experimental Seebeck coefficient also shows that the charge of interstitial oxygen is ‐2. Effective atomic configurations for the ideal lattice are compared with those in the vicinity of the defects, and defect‐related spectro‐scopic consequences are examined.