S. B. Sulaiman, N. Sahoo, S. Markert, J. Stein, T. P. Das, K. Nagamine: Theory of electron distributions and Cu-63 and O-17 nuclear quadrupole interactions in YBa2Cu3O7 and YBa2Cu3O6, Bull. Mater. Sci. 14 (1991) 149
Ab initio unrestricted Hartree-Fock cluster investigations have been carried out on the electronic structures of the YBa2Cu3O7 and YBa2Cu3O6 systems. The results of these investigations provide satisfactory explanations of available Cu-63 and O-17 nuclear quadrupole interaction data. The electron distributions obtained rule out the presence of Cu+3 ions and are supportive of the presence of Cu+2, Cu+1, O-1 ions in the O7 system and Cu+2, Cu+1, O-2 in the O6 system with actual charges departing significantly from the formal charges, especially in the O7 system, indicating the possible sources that can bridge the remaining gap between theoretical and experimental results for the nuclear quadrupole interaction parameters.