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Internet Electronic Journal of Molecular Design - IEJMD, ISSN 1538-6414, CODEN IEJMAT
| ABSTRACT - Internet Electron. J. Mol. Des. April 2004, Volume 3, Number 4, 189-199 |
Generalized Solutions of the Quantum Chemistry Equations for Symmetric
Systems. Some Applications
Evgeny Z. Liverts
Internet Electron. J. Mol. Des. 2004, 3, 189-199
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Abstract:
The conventional technique for solving the equations of quantum
chemistry (of solid state) is extended unconventionally to the
structures possessing certain symmetries. This proposal concerns
changing the way for selection of the occupied orbitals, and
allows revealing the unoccupied electronic states located lower
than the ground-state Fermi level of a specific system. Such
states can be treated as "spectral holes". Application of this
technique, in particular, when calculating the electronic structure
of the HTSC-compound YBa2Cu3O7-δ
(0 ≤ δ ≤ 1) results in the
following. The spectral holes of high spatial localization are
found. These "spatial spectral holes" are located mainly at the
py-orbitals of the apex oxygens. These orbitals overlap and form
linear chains which are parallel to the known Cu(1)-O chains,
disappearing when δ is close to 1. One can suppose that the
linear chains of the overlapping hole states form a
"superconducting channel". Some other parameters closely
related to the critical characteristics of HTSC-materials are also
calculated. The calculations show that "the superconducting
channel" is broken when the oxygen chain atoms O(1) are
removed (δ > 0). One could easily connect the obtained results to
the high-temperature superconductivity of Little's linear chains
as well as Ginzburg's two-dimensional layers and even to
BCS-model. It should be emphasized that the new approach in
question has a general nature and therefore it could be applied to
any symmetric quantum chemistry object.
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