Application of the unitary group approach (UGA) to evaluate spin density for Configuration Interaction (CI) calculations in a basis of S$^{2}$ eigenfunctions

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Title: Application of the unitary group approach (UGA) to evaluate spin density for Configuration Interaction (CI) calculations in a basis of S$^{2}$ eigenfunctions
Authors: Polyak, I
Bearpark, MJ
Robb, MA
Item Type: Journal Article
Abstract: We present an implementation of the spin-dependent unitary group approach to calculate spin densities for CI calculations in a basis of spin symmetry-adapted functions. Using S$^{2}$ 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. In order to achieve this, we combine the method to calculate $U(n)$ generator matrix elements developed by Robb and Downward~[\onlinecite{downward_1977}] with the approach of Gould and Battle to calculate $U(2n)$ generator matrix elements~[\onlinecite{battle_1993}]. 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.
Issue Date: 15-Jun-2018
Date of Acceptance: 17-Nov-2017
URI: http://hdl.handle.net/10044/1/54352
DOI: 10.1002/qua.25559
ISSN: 0020-7608
Publisher: Wiley
Journal / Book Title: International Journal of Quantum Chemistry
Volume: 118
Issue: 12
Copyright Statement: © 2017 The Authors International Journal of Quantum Chemistry Published by Wiley Periodicals, Inc. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Sponsor/Funder: Engineering & Physical Science Research Council (EPSRC)
Funder's Grant Number: EP/I032517/1
Keywords: Science & Technology
Physical Sciences
Chemistry, Physical
Mathematics, Interdisciplinary Applications
Physics, Atomic, Molecular & Chemical
Chemistry
Mathematics
Physics
configuration interaction
configuration state function
quantum chemistry
spin density
unitary group approach
MANY-ELECTRON PROBLEM
PERTURBATION-THEORY CALCULATIONS
GROUP THEORETICAL APPROACH
ADJOINT TENSOR-OPERATORS
MATRIX-ELEMENTS
DEPENDENT OPERATORS
EXPLICIT FORMULAS
GENERAL FORMALISM
MOLECULAR-SYSTEMS
U(2N) GENERATORS
0306 Physical Chemistry (Incl. Structural)
0307 Theoretical And Computational Chemistry
Chemical Physics
Publication Status: Published
Article Number: e25559
Online Publication Date: 2017-12-07
Appears in Collections:Chemistry
Faculty of Natural Sciences



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