LENGTHS AND CONFIGURATIONS OF O-CU-O CHAINS IN YBA2CU3O6- COMPARISON WITH NMR, NQR, AND EPR EXPERIMENTS(X )

The lengths of the O-Cu-O chains in the basal CuO(x) plane are calcula ted by the cluster variation method for the orthorhombic phases O(I) a nd O(II) of YBa2Cu3O6+x. A variation of the interaction constants i pe rformed in order to obtain the best fit to experiments. The dependence on x of other quantities is performed in Cu NMR/NQR and Gd EPR experi ments, such as the monovalent copper count or the EPR line intensities for different oxygen chain configurations, is obtained. Also, the dep endence of the amount of the transferred O 2p holes on x is calculated . The plateau at x > 0.5 is found to be strongly related to the format ion of chains in the O(II) phase.