  Recent experiments introducing controlled disorder into optimally doped
cuprate superconductors by both electron irradiation and chemical substitution
have found unusual behavior in the rate of suppression of the critical
temperature Tc vs. increase in residual resistivity. We show here that the
unexpected discovery that the rate of Tc suppression vs. resistivity is
stronger for out-of-plane than for in-plane impurities may be explained by
consistent calculation of both Tc and resistivity if the potential scattering
is assumed to be nearly forward in nature. For realistic models of impurity
potentials, we further show that significant deviations from the universal
Abrikosov-Gor'kov Tc suppression behavior may be expected for out of plane
impurities.
