Electron - phonon interaction in Ba sub 2 YCu sub 3 O sub 7.

A realistic tight-binding theory, based on the energy-band results of Mattheiss and Hamann, is applied to study the electron- phonon interaction in Ba sub 2 YCu sub 3 O sub 7. In contrast to previous results for the 40 K superconductor La sub 2-x (Ba,Sr) sub x CuO sub 4, the theoretical values for the electron- phonon coupling are much too small to yield superconducting transition temperatures in the 90 K range.