EFFECT OF SPATIAL VARIATIONS OF THE SUPERCONDUCTING GAP ON SUPPRESSION OF THE TRANSITION-TEMPERATURE BY IMPURITIES

We calculate correction to the critical temperature of a dirty superco nductor, which results from the local variations of the gap function n ear impurity sites. This correction is of the order of T-c/E-F and bec omes important for short-coherence length superconductors. It generall y reduces a pair-breaking effect. In s-wave superconductors small amou nts of nonmagnetic impurities can increase the transition temperature.