Similarity Constrained CC2 for Efficient Coupled Cluster Nonadiabatic Dynamics

Fuente: arXiv
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Autores principales: Stoll, Leo, Angelico, Sara, Kjønstad, Eirik F., Koch, Henrik
Formato: Preprint
Publicado: 2025
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author Stoll, Leo
Angelico, Sara
Kjønstad, Eirik F.
Koch, Henrik
author_facet Stoll, Leo
Angelico, Sara
Kjønstad, Eirik F.
Koch, Henrik
contents Despite their high accuracy, standard coupled cluster models cannot be used for nonadiabatic molecular dynamics simulations because they yield unphysical complex excitation energies at conical intersections between same-symmetry excited states. On the other hand, similarity constrained coupled cluster theory has enabled the application of coupled cluster theory in such dynamics simulations. Here, we present a similarity constrained perturbative doubles (SCC2) model with same-symmetry excited-state conical intersections that exhibit correct topography, topology, and real excitation energies. This is achieved while retaining the favorable computational scaling of the standard CC2 model. We illustrate the model for conical intersections in hypofluorous acid and thymine, and compare its performance with other methods. The results demonstrate that conical intersections between excited states can be described correctly and efficiently at the SCC2 level. We therefore expect that the SCC2 model will enable coupled cluster nonadiabatic dynamics simulations for large molecular systems.
format Preprint
id arxiv_https___arxiv_org_abs_2504_11157
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Similarity Constrained CC2 for Efficient Coupled Cluster Nonadiabatic Dynamics
Stoll, Leo
Angelico, Sara
Kjønstad, Eirik F.
Koch, Henrik
Chemical Physics
Despite their high accuracy, standard coupled cluster models cannot be used for nonadiabatic molecular dynamics simulations because they yield unphysical complex excitation energies at conical intersections between same-symmetry excited states. On the other hand, similarity constrained coupled cluster theory has enabled the application of coupled cluster theory in such dynamics simulations. Here, we present a similarity constrained perturbative doubles (SCC2) model with same-symmetry excited-state conical intersections that exhibit correct topography, topology, and real excitation energies. This is achieved while retaining the favorable computational scaling of the standard CC2 model. We illustrate the model for conical intersections in hypofluorous acid and thymine, and compare its performance with other methods. The results demonstrate that conical intersections between excited states can be described correctly and efficiently at the SCC2 level. We therefore expect that the SCC2 model will enable coupled cluster nonadiabatic dynamics simulations for large molecular systems.
title Similarity Constrained CC2 for Efficient Coupled Cluster Nonadiabatic Dynamics
topic Chemical Physics
url https://arxiv.org/abs/2504.11157