  We have applied the Numerical Renormalization Group method to study a
mesoscopic system consisting of two samples of metal separated by an insulating
barrier, with nanometer dimensions, which allows the tunnelling of a single
electron from one to the other side of the junction. The junction is
represented by a generalized orthodox model, taking into account the electronic
scattering interaction due the hole and the tunnelling electrons, localized in
the source and in the drain electrode, respectively. We have calculated the
static properties (charge transference, charge average, quadractic charge
average and specific heat) and the electric conductivity of the junction, for
the model parameters given by the tunneling matrices element, the barrier
energy and by the electronic scattering potentials acting on the electrons of
the left(right) electrode.
