Limitations of MRSF-TDDFT for Applications in Photochemistry

Fuente: arXiv
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Auteurs principaux: Janoš, Jiří, Orr-Ewing, Andrew J., Curchod, Basile F. E., Slavíček, Petr
Format: Preprint
Publié: 2026
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author Janoš, Jiří
Orr-Ewing, Andrew J.
Curchod, Basile F. E.
Slavíček, Petr
author_facet Janoš, Jiří
Orr-Ewing, Andrew J.
Curchod, Basile F. E.
Slavíček, Petr
contents Mixed-reference spin-flip time-dependent density functional theory (MRSF-TDDFT) has recently emerged as an attractive electronic-structure method for studying photochemical processes, given that it bridges the computational efficiency of single-reference approaches with the versatility of multireference methods. In the following, we critically assess the general applicability of MRSF-TDDFT to photochemistry and identify two important limitations. First, the doubly-excited configurations included in MRSF-TDDFT come at the cost of missing some singly-excited configurations. Second, MRSF-TDDFT provides unreliable excited-state energies when its triplet reference - a cornerstone of the method - abruptly changes its nature, e.g., when the T$_1$ and T$_2$ triplet states become nearly degenerate and exchange electronic character. This change of character of the triplet reference can induce discontinuities or sharp distortions in electronic potential energy curves of the response states in unsuspected regions of the nuclear configuration space. We propose strategies and diagnostics to detect these limitations in the exploration of potential energy surfaces and nonadiabatic molecular dynamics using MRSF-TDDFT.
format Preprint
id arxiv_https___arxiv_org_abs_2604_09230
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Limitations of MRSF-TDDFT for Applications in Photochemistry
Janoš, Jiří
Orr-Ewing, Andrew J.
Curchod, Basile F. E.
Slavíček, Petr
Chemical Physics
Mixed-reference spin-flip time-dependent density functional theory (MRSF-TDDFT) has recently emerged as an attractive electronic-structure method for studying photochemical processes, given that it bridges the computational efficiency of single-reference approaches with the versatility of multireference methods. In the following, we critically assess the general applicability of MRSF-TDDFT to photochemistry and identify two important limitations. First, the doubly-excited configurations included in MRSF-TDDFT come at the cost of missing some singly-excited configurations. Second, MRSF-TDDFT provides unreliable excited-state energies when its triplet reference - a cornerstone of the method - abruptly changes its nature, e.g., when the T$_1$ and T$_2$ triplet states become nearly degenerate and exchange electronic character. This change of character of the triplet reference can induce discontinuities or sharp distortions in electronic potential energy curves of the response states in unsuspected regions of the nuclear configuration space. We propose strategies and diagnostics to detect these limitations in the exploration of potential energy surfaces and nonadiabatic molecular dynamics using MRSF-TDDFT.
title Limitations of MRSF-TDDFT for Applications in Photochemistry
topic Chemical Physics
url https://arxiv.org/abs/2604.09230