Application of the unitary group approach to evaluate spin density for configuration interaction calculations in a basis of S2 eigenfunctions 2 eigenfunctions

Polyak, Iakov ORCID: https://orcid.org/0000-0002-2894-0657, Bearpark, Michael J. and Robb, Michael A. 2017. Application of the unitary group approach to evaluate spin density for configuration interaction calculations in a basis of S2 eigenfunctions 2 eigenfunctions. International Journal of Quantum Chemistry 2017 , e25559. 10.1002/qua.25559

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Abstract

We present an implementation of the spin‐dependent unitary group approach to calculate spin densities for configuration interaction calculations in a basis of spin symmetry‐adapted functions. Using S2 eigenfunctions helps to reduce the size of configuration space and is beneficial in studies of the systems where selection of states of specific spin symmetry is crucial. To achieve this, we combine the method to calculate U(n) generator matrix elements developed by Downward and Robb (Theor. Chim. Acta 1977, 46, 129) with the approach of Battle and Gould to calculate U(2n) generator matrix elements (Chem. Phys. Lett. 1993, 201, 284). We also compare and contrast the spin density formulated in terms of the spin‐independent unitary generators arising from the group theory formalism and equivalent formulation of the spin density representation in terms of the one‐ and two‐electron charge densities.

Item Type:	Article
Date Type:	Published Online
Status:	Published
Schools:	Chemistry
Publisher:	Wiley
ISSN:	0020-7608
Funders:	EPSRC
Date of First Compliant Deposit:	3 April 2018
Date of Acceptance:	17 November 2017
Last Modified:	02 May 2023 14:32
URI:	https://orca.cardiff.ac.uk/id/eprint/110444

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