Correlation between T-c and the structural parameters of the cation sublattice in the perovskite layer of HgBa2CuO4+delta and Tl2Ba2CuO4+delta

The superconducting transition temperature, T-c, of HgBa2CuO4+delta and Tl2 Ba2CuO4+delta was correlated with the interatomic distances in their struct ures. T-c was found to vary parabolically with the ratio of the Cu-Cu dista nce along the diagonal direction in the CuO2 plane to the Ba-Ba distance be tween the Ba layers. The factors determining these interatomic distances ar e discussed. The structure of the cation sublattice (Ba-Cu) of the perovski te layer is shown to play an important role in the development of supercond uctivity in these phases.