Correlation between the Superconducting Transition Temperature and Madelung Site Potential Difference in YBa2Cu3Ox

[[abstract]]The Madelung site potentials have been calculated in YBa2Cu3OX system in order to find the role of the difference in the Madelung site potentials ΔVT and ΔVM within the ionic model. The bond valence sum of each of the ions in the YBa2Cu3OX compound is assigned as charge of the corresponding ion in the calculation of the Madelung site potential. Correlations between ΔV = 0.75 ΔVM +0.25ΔVT obtained and superconducting transition temperature Tc are examined and found qualitatively very good agreement with the well-know experimental result for the various oxygen content x. This also supports that the usual believing ΔVM is of primary important parameter to control Tc. The reason will be argued in this paper