Band-structure trend in hole-doped cuprates and correlation with Tcmax
  By calculation and analysis of the bare conduction bands in a large number of hole-doped high-temperature superconductors, we have identified the energy of the so-called axial-orbital as the essential, material-dependent parameter. It is uniquely related to the range of the intra-layer hopping. It controls the Cu 4s-character, influences the perpendicular hopping, and correlates with the observed Tc at optimal doping. We explain its dependence on chemical composition and structure, and present a generic tight-binding model. 
E. Pavarini, I. Dasgupta, T. Saha-Dasgupta, O. Jepsen, and O.K.   Andersen