  The electronic structure of a prototype Kondo system, a cobalt impurity in a
copper host is calculated with accurate taking into account of correlation
effects on the Co atom. Using the recently developed continuous-time QMC
technique, it is possible to describe the Kondo resonance with a complete
four-index Coulomb interaction matrix. This opens a way for completely
first-principle calculations of the Kondo temperature. We have demonstrated
that a standard practice of using a truncated Hubbard Hamiltonian to consider
the Kondo physics can be quantitatively inadequate.
