Unitary Coupled-Cluster theory for the treatment of molecules in strong magnetic fields

Fuente: arXiv
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Main Authors: Grazioli, Laura, Kitsaras, Marios-Petros, Stopkowicz, Stella
Format: Preprint
Published: 2025
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author Grazioli, Laura
Kitsaras, Marios-Petros
Stopkowicz, Stella
author_facet Grazioli, Laura
Kitsaras, Marios-Petros
Stopkowicz, Stella
contents In Coupled-Cluster (CC) theory, unphysical complex energies may arise in the presence of strong magnetic fields, near conical intersections, or in systems exhibiting complex Abelian point group symmetries. This issue originates from the non-Hermitian nature of the CC energy expression. A promising solution is provided by unitary Coupled-Cluster (UCC) theory, which retains the advantages of an exponential parameterization while ensuring real-valued energy eigenvalues. In this work, we present an implementation of finite-field second-order (ff-UCC2) and third-order (ff-UCC3) UCC theory. We assess the performance of these truncation levels in comparison to conventional finite-field CC methods, using the methylidyne ion, water, and boric acid.
format Preprint
id arxiv_https___arxiv_org_abs_2507_19270
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Unitary Coupled-Cluster theory for the treatment of molecules in strong magnetic fields
Grazioli, Laura
Kitsaras, Marios-Petros
Stopkowicz, Stella
Chemical Physics
In Coupled-Cluster (CC) theory, unphysical complex energies may arise in the presence of strong magnetic fields, near conical intersections, or in systems exhibiting complex Abelian point group symmetries. This issue originates from the non-Hermitian nature of the CC energy expression. A promising solution is provided by unitary Coupled-Cluster (UCC) theory, which retains the advantages of an exponential parameterization while ensuring real-valued energy eigenvalues. In this work, we present an implementation of finite-field second-order (ff-UCC2) and third-order (ff-UCC3) UCC theory. We assess the performance of these truncation levels in comparison to conventional finite-field CC methods, using the methylidyne ion, water, and boric acid.
title Unitary Coupled-Cluster theory for the treatment of molecules in strong magnetic fields
topic Chemical Physics
url https://arxiv.org/abs/2507.19270