Circulant orbitals for atoms and molecules.
Circulant orbitals varphi(n) for a closed-shell system are the orbitals obtained when the N canonical orthonormal Hartree-Fock orbitals lambda([unk]) are subjected to a unitary transformation which is the discrete Fourier transformation: varphi(n) = 1/ radicalN Sigma([unk])lambda([unk])omega((n-1)([unk]-1)), where omega = exp(2pii/N). Electron densities associated with the orbitals varphi(n) are each close to the average total electron density. The Fock matrix, diagonal for canonical orbitals, for circulant orbitals is a Hermitian circulant matrix, epsilon(m, m+q) = 1/N Sigma([unk])epsilon([unk])omega(q([unk]-1)), where the epsilon([unk]) are the canonical orbital energies. The states ;Fvarphi(n) are uniformly distributed on the surface of a sphere in Hilbert space.
Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27514.
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