When optimized geometries are not optimal: Implications for inverted singlet-triplet gap predictions
Abstract
Pseudo-Jahn-Teller distortions can substantially alter singlet-triplet gaps, potentially reversing the predicted excited-state ordering in molecules proposed to exhibit inverted singlet-triplet (INVEST) gaps. In this study, we benchmark geometry optimization methods for 13 azaphenalenes against CCSD(T)-quality reference geometries, assessing their ability to reproduce symmetry lowering and its consequences for singlet-triplet gaps. Among the methods examined, ωB97M-D4 reliably describes the distorted geometries and corresponding gaps, whereas the commonly used methods B3LYP and MP2 retain high-symmetry structures, potentially leading to false-positive INVEST assignments. We further assess ωB97M-D4 geometries across 337 molecules comprising azaphenalenes, boron/nitrogen-substituted polycyclic aromatic hydrocarbons, and non-alternant hydrocarbons. Subsequent L-CC2/aug-cc-pVDZ calculations predict negative singlet-triplet gaps for 85 molecules and identify discrepancies with previously reported INVEST assignments. These findings demonstrate that the choice of geometry optimization method is crucial for reliable INVEST screening, particularly in systems susceptible to symmetry-breaking distortions.
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BibTeX
@misc{majumdar2026when,
title = {{When optimized geometries are not optimal: Implications for inverted singlet-triplet gap predictions}},
author = {Atreyee Majumdar and Elamathi Selvan Samynathan and Raghunathan Ramakrishnan},
howpublished = {arXiv},
year = {2026},
month = nov,
doi = {10.48550/arxiv.2611.06871},
eprint = {2611.06871},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2611.06871},
}
RIS
TY - UNPB
TI - When optimized geometries are not optimal: Implications for inverted singlet-triplet gap predictions
AU - Atreyee Majumdar
AU - Elamathi Selvan Samynathan
AU - Raghunathan Ramakrishnan
PY - 2026
DA - 2026/11/04
PB - arXiv
DO - 10.48550/arxiv.2611.06871
UR - https://arxiv.org/abs/2611.06871
AB - Pseudo-Jahn-Teller distortions can substantially alter singlet-triplet gaps, potentially reversing the predicted excited-state ordering in molecules proposed to exhibit inverted singlet-triplet (INVEST) gaps. In this study, we benchmark geometry optimization methods for 13 azaphenalenes against CCSD(T)-quality reference geometries, assessing their ability to reproduce symmetry lowering and its consequences for singlet-triplet gaps. Among the methods examined, ωB97M-D4 reliably describes the distorted geometries and corresponding gaps, whereas the commonly used methods B3LYP and MP2 retain high-symmetry structures, potentially leading to false-positive INVEST assignments. We further assess ωB97M-D4 geometries across 337 molecules comprising azaphenalenes, boron/nitrogen-substituted polycyclic aromatic hydrocarbons, and non-alternant hydrocarbons. Subsequent L-CC2/aug-cc-pVDZ calculations predict negative singlet-triplet gaps for 85 molecules and identify discrepancies with previously reported INVEST assignments. These findings demonstrate that the choice of geometry optimization method is crucial for reliable INVEST screening, particularly in systems susceptible to symmetry-breaking distortions.
ER -