No abstract

We have calculated the ratio of the energy gap Ao to the critical temperature T, for a large number of known electron-phonon spectral densities with the use of the imaginary-axis formulation of Eliashberg theory with an analytic-continuation technique to the real axis. Agreement with experiment is within a few percent. It is found that the general trend obtained for 2AO/kqT, against T, /coh, where co&" is the popular Allen-Dynes expression for the average phonon energy, can be reproduced by a two-parameter functional form of the general type first given by Geilikman andKresin. The details, however, can only be understood with complete calculations.

No abstract

No abstract