NEVPT2 multiple spawning molecular dynamics simulations for uracil

The quasidegenerate n-electron valence state second-order perturbation theory (QD-NEVPT2) for complete active space reference wavefunctions has been implemented in the OpenMolcas package. The implementation utilizes the efficient formulation of Kollmar et al. for the electronic energy, which is extended here to the calculation of analytic derivatives. To demonstrate its utility, the method is applied to classical and non-adiabatic molecular dynamics (MD) simulations of uracil. The non-adiabatic MD simulations describe the ultrafast deactivation of the initially excited bright ππ* state through the S2/S1 conical intersection, demonstrating the applicability of the method to photochemical processes. Furthermore, a machine learning-based analysis of the trajectory data extracts key geometrical parameters that are associated with the magnitude of the time-derivative coupling. These results highlight the effectiveness of this QD-NEVPT2 implementation for studying excited-state dynamics.