Analytic Gradients and Nonadiabatic Couplings for Device-Resident DMRG-QD-NEVPT2 Through Conical Intersections on a Consumer GPU
Abstract
Nonadiabatic dynamics through a conical intersection requires both static and dynamic correlation and, at every geometry, an excited-state gradient and interstate nonadiabatic coupling (NACME). Analytic multireference derivatives at this level have been confined to datacenter-scale hardware. We report device-resident \mbox{DMRG-QD-NEVPT2} with analytic gradients and NACMEs within the $8$\,GB of a consumer GPU: a density-matrix-renormalization-group (DMRG) active-space reference supplies the static correlation, and quasi-degenerate SC-NEVPT2 dresses it through a multi-state effective Hamiltonian that remains valid \emph{through} a conical intersection, where single-state perturbation theory develops a vanishing denominator and fails. Every gradient and NACME is one reverse-mode transpose of a single contraction graph: the DMRG sweep enters as a gauge-free differentiable node, and all two-electron work is AO-direct through Cholesky factors. The DMRG reference is exact within the active space (∼ 10−15\,Ha). The corrected adiabats close smoothly to a real S0/S1 conical intersection with a non-vanishing, 1/ΔE-divergent NACME---where linear-response TDDFT returns zero identically---and the dressing restores the differential dynamic correlation that ionic ππ* states require. DMRG-NEVPT2 and quasi-degenerate NEVPT2 are each established; what is new is the combined stack---multi-state and through a conical intersection, with analytic gradients and couplings---realized device-resident on commodity hardware.
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BibTeX
@misc{guerrero2026analytic,
title = {{Analytic Gradients and Nonadiabatic Couplings for Device-Resident DMRG-QD-NEVPT2 Through Conical Intersections on a Consumer GPU}},
author = {Rubén Darío Guerrero},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.09990},
eprint = {2609.09990},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.09990},
}
RIS
TY - UNPB
TI - Analytic Gradients and Nonadiabatic Couplings for Device-Resident DMRG-QD-NEVPT2 Through Conical Intersections on a Consumer GPU
AU - Rubén Darío Guerrero
PY - 2026
DA - 2026/09/16
PB - arXiv
DO - 10.48550/arxiv.2609.09990
UR - https://arxiv.org/abs/2609.09990
AB - Nonadiabatic dynamics through a conical intersection requires both static and dynamic correlation and, at every geometry, an excited-state gradient and interstate nonadiabatic coupling (NACME). Analytic multireference derivatives at this level have been confined to datacenter-scale hardware. We report device-resident \mbox{DMRG-QD-NEVPT2} with analytic gradients and NACMEs within the $8$\,GB of a consumer GPU: a density-matrix-renormalization-group (DMRG) active-space reference supplies the static correlation, and quasi-degenerate SC-NEVPT2 dresses it through a multi-state effective Hamiltonian that remains valid \emph{through} a conical intersection, where single-state perturbation theory develops a vanishing denominator and fails. Every gradient and NACME is one reverse-mode transpose of a single contraction graph: the DMRG sweep enters as a gauge-free differentiable node, and all two-electron work is AO-direct through Cholesky factors. The DMRG reference is exact within the active space (∼ 10^−15\,Ha). The corrected adiabats close smoothly to a real S_0/S_1 conical intersection with a non-vanishing, 1/ΔE-divergent NACME---where linear-response TDDFT returns zero identically---and the dressing restores the differential dynamic correlation that ionic ππ^* states require. DMRG-NEVPT2 and quasi-degenerate NEVPT2 are each established; what is new is the combined stack---multi-state and through a conical intersection, with analytic gradients and couplings---realized device-resident on commodity hardware.
ER -