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 DELTAV(T) and DELTAV(M) 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 DELTAV = 0.75 DELTAV(M) +0.25 DELTAV(T) obtained and superconducting transition temperature T(c) 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 DELTAV(M) is of primary important parameter to control T(c). The reason will be argrued in this paper.