Ab-initio study of potassium doping effects on electronic and crystallographic structure of superconductor YBa2-xKXCu3O7

DFT ab-initio calculation (using plane waves and pseudo-potential approach) has been employed for a systematic study of potassium substitution in YBa2-xKxCu3O7 samples. The electronic structure، energy levels and the density of states (DOS) with different potassium doping amounts (x=0. 16، 0. 25، 0. 5، 0. 75) were calculated under the generalized gradient approximation (GGA). The substitution of potassium changes the electronic band structure and DOS. These modifications are responsible for empirical reports of decreasing the TC with increasing of the potassium. In addition، our results about the variation of lattice parameters (a، b and c) of the system are in good agreement with experimental reports according to the Rietveld refinement of XRD data.