Second order N-Electron Valence state Perturbation Theory for polaritonic systems
Abstract
Molecules strongly coupled to optical cavities often show multi-configurational character, which the cavity can enhance by mixing electronic states. Describing them accurately requires a complete treatment of correlation between all the involved quantum particles. The available QED ab-initio methods do not treat it in its completeness except for QED-FCI. We extend second-order N-electron valence state perturbation theory (NEVPT2) to polaritonic chemistry, in its state-specific (QED-NEVPT2) and quasi degenerate (QED-QD-NEVPT2) forms. Here, the correlation due to the interaction of more degenerate configurations comes from a QED-CASSCF reference, while that associated with instantaneous interactions between the particles is added by second-order perturbation theory. Application of the methods to ammonia, ethylene and formaldimine revealed that this approach represents the perfect alternative to the well established QED-Coupled Cluster approach when the molecular system is described by more degenerate configurations. The approaches developed in this work have the potential to become state-of-the-art methodologies for the description of reactivity and photochemistry in polaritonic systems.
Related
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BibTeX
@misc{ascani2026second,
title = {{Second order N-Electron Valence state Perturbation Theory for polaritonic systems}},
author = {Edoardo Ascani and Riccardo Alessandro and Celestino Angeli and Enrico Ronca},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.34416},
eprint = {2610.34416},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.34416},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Second order N-Electron Valence state Perturbation Theory for polaritonic systems
AU - Edoardo Ascani
AU - Riccardo Alessandro
AU - Celestino Angeli
AU - Enrico Ronca
PY - 2026
DA - 2026/10/25
PB - arXiv
DO - 10.48550/arxiv.2610.34416
UR - https://arxiv.org/abs/2610.34416
AB - Molecules strongly coupled to optical cavities often show multi-configurational character, which the cavity can enhance by mixing electronic states. Describing them accurately requires a complete treatment of correlation between all the involved quantum particles. The available QED ab-initio methods do not treat it in its completeness except for QED-FCI. We extend second-order N-electron valence state perturbation theory (NEVPT2) to polaritonic chemistry, in its state-specific (QED-NEVPT2) and quasi degenerate (QED-QD-NEVPT2) forms. Here, the correlation due to the interaction of more degenerate configurations comes from a QED-CASSCF reference, while that associated with instantaneous interactions between the particles is added by second-order perturbation theory. Application of the methods to ammonia, ethylene and formaldimine revealed that this approach represents the perfect alternative to the well established QED-Coupled Cluster approach when the molecular system is described by more degenerate configurations. The approaches developed in this work have the potential to become state-of-the-art methodologies for the description of reactivity and photochemistry in polaritonic systems.
ER -