The influence of internal strain on the charge distribution and superconducting transition temperature in Ba2YCu3Ox

The bond lengths in Ba2YCu3Ox expected from chemical considerations alone are not compatible with the constraints imposed by the crystal structure. The resulting strain in the bond lengths can be relaxed inter alia by charge transfer between the two Cu atoms. The effect of the strain and its relaxation is examined using bond valences to model the structure at various compositions. At x = 7.0 the structure adapts by transferring charge between …