Effect of oxygen deficiencies and the substitution of fluorine on the electronic states In Yba_2Cu_3O_(7-delta) superconductors

摘要

We present a systematic theoretical study of fluorine-substituted Yba_2Cu_3O7 crystal based on accurate first-principles all-electron total-energy calculations, using the full-potential linearized augmented plane wave (FP-LAPW) approach in the framework of density functional theory (DFT), and the generalized gradient approximation (GGA) for the exchange-correlation term. The electronic structure, energy levels and the density of states (DOS) at equilibrium volume with different oxygen deficiencies distribution or F substitution are studied. The existence of oxygen vacancies and the substitution of oxygen by one, two and up to three fluorine atoms on several selective sites change the electronic band structure in CuO_2 plane between two Ba planes. Thus, doping with charge carriers in the above materials is simulated and the resulting changes in the electronic distribution are compared to experimental and/or ab initio results.