  Parity and time invariance violating (P,T-odd) nuclear forces produce P,T-odd
nuclear moments. In turn, these moments can induce electric dipole moments
(EDMs) in atoms through the mixing of electron wavefunctions of opposite
parity. The nuclear EDM is screened by atomic electrons. The EDM of an atom
with closed electron subshells is induced by the nuclear Schiff moment.
Previously the interaction with the Schiff moment has been defined for a
point-like nucleus. No problems arise with the calculation of the electron
matrix element of this interaction as long as the electrons are considered to
be non-relativistic. However, a more realistic model obviously involves a
nucleus of finite-size and relativistic electrons. In this work we have
calculated the finite nuclear-size and relativistic corrections to the Schiff
moment. The relativistic corrections originate from the electron wavefunctions
and are incorporated into a ``nuclear'' moment, which we term the local dipole
moment. For mercury these corrections amount to about 25%. We have found that
the natural generalization of the electrostatic potential of the Schiff moment
for a finite-size nucleus corresponds to an electric field distribution which,
inside the nucleus, is well approximated as constant and directed along the
nuclear spin, and outside the nucleus is zero. Also in this work the plutonium
atomic EDM is estimated.
