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Development of New Open-Shell Perturbation and Coupled-Cluster Theories Based on Symmetric Spin OrbitalsA new spin orbital basis is employed in the development of efficient open-shell coupled-cluster and perturbation theories that are based on a restricted Hartree-Fock (RHF) reference function. The spin orbital basis differs from the standard one in the spin functions that are associated with the singly occupied spatial orbital. The occupied orbital (in the spin orbital basis) is assigned the delta(+) = 1/square root of 2(alpha+Beta) spin function while the unoccupied orbital is assigned the delta(-) = 1/square root of 2(alpha-Beta) spin function. The doubly occupied and unoccupied orbitals (in the reference function) are assigned the standard alpha and Beta spin functions. The coupled-cluster and perturbation theory wave functions based on this set of "symmetric spin orbitals" exhibit much more symmetry than those based on the standard spin orbital basis. This, together with interacting space arguments, leads to a dramatic reduction in the computational cost for both coupled-cluster and perturbation theory. Additionally, perturbation theory based on "symmetric spin orbitals" obeys Brillouin's theorem provided that spin and spatial excitations are both considered. Other properties of the coupled-cluster and perturbation theory wave functions and models will be discussed.
Document ID
Document Type
Conference Paper
Lee, Timothy J. (NASA Ames Research Center Moffett Field, CA United States)
Arnold, James O.
Date Acquired
August 20, 2013
Publication Date
January 1, 1994
Subject Category
Atomic and Molecular Physics
Meeting Information
Electron Correlation in Atoms and Molecules: New Methods and Applications(Bratislava)
Funding Number(s)
PROJECT: RTOP 232-01-04
Distribution Limits
Work of the US Gov. Public Use Permitted.