Atomic substitutions in ${\mathrm{YBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_7$: Modification of the electronic structure

We have performed semiempirical tight-binding calculations of the electronic structure of ${\mathrm{YBa}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_7$, with d and s orbitals included for all the metal atoms and p and s orbitals for the oxygen. Here we report studies of the following atomic substitutions: Al, Fe, Co, Ni, and Zn replacing Cu; Sr and La replacing Ba; Tl, Pb, and Bi replacing Y; and F and N replacing O. In each case, the modification of the local densities of states, the atomic valences, and the Fermi energy were calculated.