Analytic Derivative Couplings for MRSF-TDDFT: Applications to Nonadiabatic Molecular Dynamics and Conical Intersections
Abstract
We present an analytic formulation of derivative couplings for mixed-reference spin-flip time-dependent density functional theory (MRSF-TDDFT). Cross terms between the two states' excitation amplitudes and the orbital-rotation derivative of their wave-function overlap enter the interstate Lagrangian. Together they define the source of a state-pair Z-vector equation with the reference orbital Hessian, yielding the analytic derivative coupling vector. The analytic vectors enable conical-intersection searches using both branching directions. At twelve reference conical-intersection geometries, the median branching-plane projector overlap between MRSF-TDDFT and multireference configuration interaction with singles and doubles (MRCISD) is 0.991. As a further application, nonadiabatic molecular dynamics (NAMD) simulations of uracil photorelaxation reproduce the previously predicted rapid formation of a twisted intermediate while using the analytic derivative-coupling direction for nuclear-momentum adjustment at surface hops. We also identify four major numerical causes of premature trajectory termination and develop corresponding treatments to improve trajectory stability and reduce trajectory loss in NAMD ensembles.
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BibTeX
@misc{choi2026analytic,
title = {{Analytic Derivative Couplings for MRSF-TDDFT: Applications to Nonadiabatic Molecular Dynamics and Conical Intersections}},
author = {Cheol Ho Choi},
howpublished = {ChemRxiv},
year = {2026},
month = oct,
doi = {10.26434/chemrxiv.15010812/v1},
url = {https://chemrxiv.org/doi/full/10.26434/chemrxiv.15010812/v1},
note = {CC BY},
}
RIS
TY - UNPB
TI - Analytic Derivative Couplings for MRSF-TDDFT: Applications to Nonadiabatic Molecular Dynamics and Conical Intersections
AU - Cheol Ho Choi
PY - 2026
DA - 2026/10/21
PB - ChemRxiv
DO - 10.26434/chemrxiv.15010812/v1
UR - https://chemrxiv.org/doi/full/10.26434/chemrxiv.15010812/v1
AB - We present an analytic formulation of derivative couplings for mixed-reference spin-flip time-dependent density functional theory (MRSF-TDDFT). Cross terms between the two states' excitation amplitudes and the orbital-rotation derivative of their wave-function overlap enter the interstate Lagrangian. Together they define the source of a state-pair Z-vector equation with the reference orbital Hessian, yielding the analytic derivative coupling vector. The analytic vectors enable conical-intersection searches using both branching directions. At twelve reference conical-intersection geometries, the median branching-plane projector overlap between MRSF-TDDFT and multireference configuration interaction with singles and doubles (MRCISD) is 0.991. As a further application, nonadiabatic molecular dynamics (NAMD) simulations of uracil photorelaxation reproduce the previously predicted rapid formation of a twisted intermediate while using the analytic derivative-coupling direction for nuclear-momentum adjustment at surface hops. We also identify four major numerical causes of premature trajectory termination and develop corresponding treatments to improve trajectory stability and reduce trajectory loss in NAMD ensembles.
ER -