Croatica Chemica Acta, Vol. 57 No. 6, 1984.
Original scientific paper
The Splitting Theorem and Properties of Alternant Systems
Tomislav P. Zivkovic
; »Ruder Boskovic« Institute, University of Zagreb, P. 0 . Box 1016, 41001 Zagreb, Yugoslavia
Abstract
The notion of alternant systems, as defined in various semiempirical
theories of alternant hydrocabrons, is generalised to
arbitrary symmetric Hamiltonians. Alternant operators are shown
to be linear combinations of the so called reduced alterpant operators,
and a simple construction of an arbitrary (symmetric) .
alternant Hamiltonian is presented. A simple test to decide whether
a given symmetric Hamiltonian is alternant or not is given as
well. A configuration interaction space X,, generated by n electrons
moving over 2n orthonormalised orbitals is considered. Eigenstates
'I' € X,, of alternant Hamiltonians are shown to be contained in
complementary spaces x n+ and x "-, subspaces of the space X,,.
Each state 'I'± E X n ± has characteristic properties of eigenstates
associated with neutral alternant hydrocarbon systems, a uniform
charge density distribution and vanishing bond orders between
vertices of the same parity. In addition to these properties of one-
particle density matrices, some general properties of two-particle
density matrices associated with states 'I' ± E X11 ± are also derived.
Keywords
Hrčak ID:
194043
URI
Publication date:
21.5.1985.
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