  We study the two-impurity Anderson model on finite chains using numerical
techniques. We discuss the departure of magnetic correlations as a function of
the interimpurity distance from a pure 2k_F oscillation due to open boundary
conditions. We observe qualitatively different behaviors in the interimpurity
spin correlations and in transport properties at different values of the
impurity couplings. We relate these different behaviors to a change in the
relative dominance between the Kondo effect and the
Ruderman-Kittel-Kasuya-Yoshida (RKKY) interaction. We also observe that when
RKKY dominates there is a definite relation between interimpurity magnetic
correlations and transport properties. In this case, there is a recovery of
2k_F periodicity when the on-site Coulomb repulsion on the chain is increased
at quarter-filling. The present results could be relevant for electronic
nanodevices implementing a non-local control between two quantum dots that
could be located at variable distance along a wire.
