Spin-Symmetry Projected constrained Unrestricted Hartree-Fock

• URL: http://arxiv.org/abs/2412.16458v1
• Date: Sat, 21 Dec 2024 03:17:13 GMT
• Title: Spin-Symmetry Projected constrained Unrestricted Hartree-Fock
• Authors: Amir Ayati, Hugh G. A. Burton, Stijn De Baerdemacker,
• Abstract summary: We introduce an electronic structure approach for spin symmetry breaking and restoration from the mean-field level.<n>The spin-projected constrained-unrestricted Hartree-Fock (SPcUHF) method restores the broken spin symmetry inherent in spin-constrained-UHF determinants.
• Score: 0.0
• License: http://creativecommons.org/licenses/by/4.0/
• Abstract: We introduce an electronic structure approach for spin symmetry breaking and restoration from the mean-field level. The spin-projected constrained-unrestricted Hartree-Fock (SPcUHF) method restores the broken spin symmetry inherent in spin-constrained-UHF determinants by employing a non-orthogonal Configuration Interaction (NOCI) projection method. This method includes all possible configurations in spin space compatible with a Clebsch-Gordon recoupling scheme in a NOCI calculation. The tunable one-pair-at-a-time characteristics of the symmetry-breaking process in c-UHF allow us to reduce the computational costs of full projection. SPcUHF is tested on 4-, 6-, and 8-electron systems that exhibit dominant static and/or dynamic correlations.

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