Valery A. IVANOV, Kyuya YAKUSHI and Elena UGOLKOVA* (*N.S. Kurnakov Inst. of General and Inorg. Chem. of RAS)
[Physica C 275, 26 (1977)]
The electronic structure of (kappa)-ET2X salt is studied on the basis of the tight-binding approach for correlated electrons. The uncorrelated energy band constitutes of 4 branches. The analytical formula of the partial and total density of states are derived. The upper two branches which is partially filled is split into two by the introduction of the electron-electron correlation. These correlated energy dispersion and energy gap was calculated to be
where (epsilon)=U/2 is the half of the on-site Coulomb energy ant t is the interdimer transfer integral. Variations of ET donor arrangements at a fixed hole concentration lead to a variation of an energy scale and to a variety of properties. When the correlated bands widen, the insulator-metal transition occurs due to an electron scattering on spin and charge fluctuations. For this triangular lattice, this phase transition occurs at the following critical point
