2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/28922A model for description of materials with narrow energy bands is proposed. It is shown that in narrow-band materials electron-hole symmetry is absent in contrast to the Hubbard model. In this paper metal-insulator transition is studied. The obtained results are compared with experimental data for narrow-band materials. Some specific narrow-band effects are discussed.17 pages, 4 eps figures, Latex 2.09Strongly Correlated Electronstext