Electron-phonon interaction was considered with regard to the positions of atoms in the unit cell. It was found that the strength of the interaction depended upon the number of Cu-O layers per unit cell only when defects were present. The transition temperature therefore depended upon the variable number, n, of Cu-O layers per unit cell. The larger the number of layers, the larger was the transition temperature. It was found that the lattice waves could be treated by using spherical Bessel functions, and that the electron-phonon interaction oscillated as a function of the number of Cu-O planar layers. The transition temperature of the superconductor then oscillated as a function of n. It had a high value at n = 3 and lower value at n = 4. It was predicted that the next maximum value would occur at n = 7. The predicted variation, in transition temperature as a function of n, was in reasonable agreement with experimental data.

N.M.Krishna, K.N.Shrivastava: Superconductor Science and Technology, 1997, 10[5], 278-83