{"ID":6024133,"CreatedAt":"2026-07-08T01:00:23.257252134Z","UpdatedAt":"2026-07-09T20:17:26.950452338Z","DeletedAt":null,"paper_url":"https://arxiv.org/abs/2607.05622","arxiv_id":"2607.05622","title":"EOM-CC Excited-State Gradients and Nonadiabatic Couplings on a Consumer GPU from a Contraction-DAG with Laplace-Transform J/K Kernels","abstract":"We present a unified, memory-bounded GPU realization of equation-of-motion coupled-cluster (EOM-CC) excited-state gradients and interstate nonadiabatic couplings (NACMEs) on a single 8\\,GB consumer GPU. Both are built from one contraction directed acyclic graph: the EOM-CC relaxation is the reverse-mode transpose of the forward density build rather than a per-state re-derivation, and an atomic-orbital-direct Laplace-transform $J/K$ kernel, made non-symmetric ($J^x(A,B)\\neq J^x(B,A)$) by the transition densities, resolves every energy denominator with no four-index molecular-orbital tensor; a two-sided Davidson returns both eigenvectors from one device-resident, spin-pure solve. The pipeline is \\emph{validated end to end at small scale}: gradients and NACMEs match finite differences across four spin multiplicities and full configuration interaction to $\u003c\\!10^{-12}$ for two electrons, and the excited-state gradient matches the independent \\textsc{Psi4} code to $\\le\\!4.6\\times10^{-7}~E_h/a_0$ from \\ce{H2O} to aromatic benzene. The kernels and the ground-state solve reach chromophores ($\\le\\!730$ AO) in 8\\,GB, and a frozen-natural-virtual compression lets the eigensolver \\emph{execute} a complete excited-state gradient and $Q$--$B$ NACME of the chlorophyll-core chromophore \\ce{Mg}-porphine (def2-SVP, $439$ AO) on the card. We present that run as a \\emph{capability demonstration} -- executed and translationally invariant to machine zero, but anchored only piece-wise and bounded by a direct convergence study at ${\\sim}10^{-2}~E_h/a_0$ -- not a converged spectroscopic result. The validated small-scale capability and the memory-bounded implementation are the contribution.","short_abstract":"We present a unified, memory-bounded GPU realization of equation-of-motion coupled-cluster (EOM-CC) excited-state gradients and interstate nonadiabatic couplings (NACMEs) on a single 8\\,GB consumer GPU. Both are built from one contraction directed acyclic graph: the EOM-CC relaxation is the reverse-mode transpose of th...","url_abs":"https://arxiv.org/abs/2607.05622","url_pdf":"https://arxiv.org/pdf/2607.05622v1","authors":"[\"Rubén Darío Guerrero\"]","published":"2026-07-06T20:31:33Z","proceeding":"physics.chem-ph","tasks":"[\"physics.chem-ph\",\"cs.DC\",\"physics.comp-ph\"]","methods":"[]","has_code":false}