  The problem of three interacting Kondo impurities is solved within a
numerically exact continuous time quantum Monte Carlo scheme. A suppression of
the Kondo resonance by interatomic exchange interactions for different cluster
geometries is investigated. It is shown that a drastic difference between the
Heisenberg and Ising cases appears for antiferromagnetically coupled adatoms.
The effects of magnetic frustrations in the adatom trimer are investigated, and
possible connections with available experimental data are discussed.
