ساختار الکترونی123- Yدر فشار متعارف و فشارهای بالا

  The electronic properties of YBa2Cu3O7-δ have been investigated by the energy-pseudopotential method within the local density approximation (LDA) with and without including generalized gradient corrections (GGC). The band structure, density of states and charge density of YBa2Cu3O7- have been calculated. The results are compared with other approaches such as LAPW, LCAO and LMTO for this system. The overall shape of the band structure, density of states and charge density are in agreement with other works. However, in details, like other approaches, there are some differences. Considering our accuracy, the differences in results for LDA and GGC approaches are small. Also, the electronic and structural properties for this system have been investigated by applying pressure within LDA. We have calculated band structure, density of states, charge density, and length of bonds for high pressures, and the changes in hole concentration in this system with respect to pressure. Our results show the increase of hole in both CuO2 planes and Cu-O chains under high pressures. Although this result is in agreement with the pressure-induced charge transfer (PICT) model, it is in contrast with the definition of this model which believes that hole increases in the CuO2 planes come from the Cu-O chains. Bulk modules and equilibrium volume have been also calculated to be equal 184 Gpa and 174.89A03, respectively. The results of these calculations have been compared with the experimental and theoretical reports on this system.