97-26U

The transition from an insulating to a metallic state is studied in a model of narrow-band material with non-equivalent Hubbard subbands at half filling and zero temperature. Single-particle Green function is obtained by the variant of method of an approximate second quantization in a generalize Hartree-Fock approximation. The conditions for a metallic and an insulating states are determined. The concentration of polar states $c$, chemical potential of the electrons is found. We obtain an energy-gap as the function of $c$, on-site interaction $U$, half-width of "hole" band $w$ and half-width of "twice" band $\mathaccent "707E\relax {w}$.