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A derivation of the t-J model of a highly-correlated solid is given startingfrom the general many-electron Hamiltonian with account of thenon-orthogonality of atomic wave functions. Asymmetry of the Hubbard subbands(i.e. of ``electron'' and ``hole''cases) for a nearly half-filled bare band isdemonstrated. The non-orthogonality corrections are shown to lead to occurrenceof indirect antiferromagnetic exchange interaction even in the limit of theinfinite on-site Coulomb repulsion. Consequences of this treatment for themagnetism formation in narrow energy bands are discussed. Peculiarities of thecase of ``frustrated'' lattices, which contain triangles of nearest neighbors,are considered.Comment: 4 pages, RevTe

physical review. b, condensed matter

Derivation of the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>t</mml:mi><mml:mo>−</mml:mo><mml:mi>J</mml:mi></mml:math>model: Electron spectrum and exchange interactions in narrow energy bands

Derivation of thet−Jmodel: Electron spectrum and exchange interactions in narrow energy bands