Starting from the correlation corrected ͑quasiparticle͒ band structures of the CuO 2 plane and the CuO chain ͑always including the apical oxygen atom͒ of YBa 2 Cu 3 O 7 we have calculated the exciton spectra of both systems. For this the intermediate exciton theory was applied in its first-principles form. This leads to a Green's-matrix equation for the determination of the E q exciton energies. We have applied in the denominator of the Green's-matrix quasiparticle one-electron energies instead of the Hartree-Fock ones. In this way we have found very good agreement with experiment for the calculated exciton energies of the CuO 2 plane ͑theoretical values 4.4-5.7 eV, experimental values 4.5-5.5 eV͒. Further there is a reflexion spectrum peak of YBa 2 Cu 3 O 6.9 at 8.0 eV which agrees well with our results obtained for the exciton energies of the chain.
Applying the wave functions and exciton energies determined and . described in two previous articles for YBa Cu O , we calculated the effective potential 2 3 7
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.