The electronic and structural properties of an isolated vacancy and self-in
terstitial defects in germanium are studied through 'parameter free' calcul
ations. We analyze the lattice relaxations and Jahn-Teller distortions for
several charge states. Our results for ionization levels of the Ge-vacancy
are in fair agreement with experimental results. In contrast to the silicon
vacancy we obtain that the germanium vacancy does not present an Anderson
negative-U. For the self-interstitial defect we obtain, similarly to silico
n, that the lowest-energy configuration is the split dumbbell configuration
. (C) 1999 Elsevier Science B.V. All rights reserved.