Phase transition of oxides of the Magneli series: O, V$_2$O$_3$, VO$_2$, V$_2$O$_5$

It is shown that the crystals of vanadium oxides inherit the correlation properties of the oxidized chemical element – vanadium, namely: the energy position of the electronic zones of the crystals essentially depends on the degree of filling these zones with electrons. The complex Mott-Peierls character of the phase transitions in all the listed strongly correlated compounds has been established. As the oxidation state of vanadium in VO$_x$ compounds increases (the $x$ index increases from 1 to 2.5), the metallic properties of the oxides weaken, accompanied by an increase in the temperature of the semiconductor-metal phase transition and an increase in the band gap.