The total electron-phonon coupling constant \lambda can be obtained by \lambda=\sum_{q\nu}\lambda_{q\nu}=2\int_0^{\omega}\frac{\alpha^2F(\omega)}{\omega}d\omega \lambda_{q\nu}=\frac{\gamma_{q\nu}}{\pi{h}N(E_f)\omega^2_{q\nu}} where Eliashberg spectral function is \alpha^{2}F(\omega)=\frac{1}{2\pi{N}(E_F)}\sum_{q\nu}\delta(\omega-\omega_{q\nu})\frac{\gamma_{q\nu}}{\hbar\omega_{q\nu}}
The cirtical temperatures T_c were estimated by Allan−Dynes-modified McMillan’s approximation of the Eliashberg equation[1,2],
T_c =\frac{\omega_{log}}{1.2}\exp[-\frac{1.04(1+\lambda)}{\lambda-\mu_c^*(1+0.62\lambda)}]
where \mu_c^* is effective screened Coulomb repulsion constant (typically \sim 0.1), \lambda is the overall electron−phonon coupling strength computed from the frequency-dependent Eliashberg spectral function and \omega_{log} is the properly defined logarithmic average frequency.