EOM-CC Excited-State Gradients and Nonadiabatic Couplings on a Consumer GPU from a Contraction-DAG with Laplace-Transform J/K Kernels

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 (Jx(A,B)neq Jx(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 validated end to end at small scale: gradients and NACMEs match finite differences across four spin multiplicities and full configuration interaction to <!10-12 for two electrons, and the excited-state gradient matches the independent textscPsi4 code to ≤!4.6×10-7~Eh/a0 from ceH2O to aromatic benzene. The kernels and the ground-state solve reach chromophores (≤!730 AO) in 8,GB, and a frozen-natural-virtual compression lets the eigensolver execute a complete excited-state gradient and Q--B NACME of the chlorophyll-core chromophore ceMg-porphine (def2-SVP, 439 AO) on the card. We present that run as a capability demonstration -- executed and translationally invariant to machine zero, but anchored only piece-wise and bounded by a direct convergence study at ~10-2~Eh/a0 -- not a converged spectroscopic result. The validated small-scale capability and the memory-bounded implementation are the contribution.