The present work analyzes the importance of the different components of the
environment effects on the local spectroscopy of extended strongly correlated
systems. It has been found that the usual formal charge definition of the
charge transfer and Madelung potential are far too crude for an accurate
determination of the local excitation energies in embedded fragment
calculations. A criterion for the validation of the embedding against the
infinite system density of states has been proposed.Comment: 8 pages, 9 figure