For a numerical solution of the transport equations one has to discretize the
GREEN's functions in the energy domain. However, due to the presence of narrow
resonances at some energies one has to be careful about the selection of the
energy grid. An approximation for the electron concentration
due to a confined state is derived. This analytical function is used as a
reference for comparing the results of the non-adaptive and adaptive methods
of selecting the energy grid.
Subsections