Functional derivative of T/sub c/ with α2(ω)F(ω) for weak coupling anisotropic superconductors

Approximate analytic calculations of the functional derivative of T/sub c/ with respect to α2(ω)F(ω) for anisotropic superconductors are presented, with the primary purpose of identifying the determining material parameters. The ''square-well model'' for the phonon-mediated electron-electron interaction, the weak coupling limit (ω/sub c//2πT/sub c/>>1), an separable anisotropy are used. The general behavior of deltaT/sub c//deltaα2(ω)F(ω) is the same as that found in numerical calculations for the case of small anisotropy, /(lambda-μ*)<<1; the regime of μ*approx. =lambda is also discussed