THE INVESTIGATION OF THE EFFECT OF ELECTRONIC CHARGE-TRANSFER FOR THEYBA2CU3O7 PHASE

It is proposed the systematization for the HTSC compounds. The electro nic structure of [CuO2](q) plane depending on the value of q charge (q =0; -1; -1.5; -2; -2.5) have been investigated using the RLMTO method. For this aim, the band structure calculations for the A(BCuO2)(2) (A= Y, Ca, square) model compounds and YBa2Cu3O7 (YBCO) compound have bee n carried out. It was shown, that the energy spectrum of valence elect rons in the CuO2 plane changes strongly depending on the q charge. The changes take place through all width of valence band. It is shown tha t when q= -1.5 (corresponds to YBCO compound), specially situated (nea r the Fermi level) Cu d -O 2p energy bands are formed in the CuO2 plan e.