Essential ideas of metal-insulator transitions in 3d-metal compounds

The main mechanisms of a metal-insulator transition are considered. The present state of the theory of the Mott-Hubbard transition caused by strong interatomic correlations is discussed. The metal-insulator transition is considered in the Shubin-Vonsovski model. The allowance for the screening of a Coulomb long-range interaction leads to the first-kind transition. The concept of the metal order parameter proportional to the density of states on the Fermi level at the transition point is described. The theory allows a qualitative explanation of many experimental data, mainly thermodynamic, for vanadium and titanium oxides and 3d-metal sulphides with a metal-insulator transition