Solving the Quantum Chemistry Equations and High-Temperature-Superconductivity Problem

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 occupied orbitals, allowing, in turn, to release the unoccupied electronic states located lower than the ground state Fermi level of a specific system. Such states can be treated as &#39;spectral holes&#39;. Application of this technique, in particular, when calculating the electronic structure of the HTSC-compound $YBa_2Cu_3O_{7-x}$ (0<x<1) results in the following. The spectral holes of high spatial localization are found. These &#39;spatial spectral holes&#39; are located, mainly at the $P_y$-orbitals of the apex oxygens. These orbitals overlap and form linear chains which are parallel to the known Cu(1)-O chains, disappearing when x is closed to 1. One can suppose that the linear chains of the overlapping hole states form a &#39;superconducting channel&#39;. Some other parameters closely related to the critical characteristics of HTSC-materials are also calculated. The calculations show that &#39;the superconducting channel&#39; is broken when the oxygen chain atoms O(1) are removed (x>0). One could easily connect the obtained results to the high-temperature superconductivity of Little&#39;s linear chains, as well as Ginzburg&#39;s two-dimensional layers and even to BCS-model.