Quantum nonadiabatic dynamics at intersystem crossings is fundamental to many processes in chemistry, biology and material sciences. We have previously extended the Ab Initio Multiple Spawning (AIMS) nonadiabatic molecular dynamics method, originally developed to study internal conversions, to describe intersystem crossings where nonadiabatic transitions between the electronic states of different spin multiplicities are mediated by relativistic spin-orbit coupling. In the direct AIMS molecular dynamics, nuclei are described by the basis set of frozen multidimensional Gaussians propagating on electronic potential energy surfaces calculated on-the-fly. In our earlier implementation, the CASSCF electronic structure calculations are carried out with the GAMESS suite of programs interfaced with the AIMS molecular dynamics code. Here we report the implementation of the AIMS-DFT method to study nonadiabatic intersystem crossing dynamics. This new development is expected to extend the applicability of the AIMS molecular dynamics to larger systems for which the CASSCF electronic structure calculations are computationally prohibitive, and where dynamic electron correlation neglected in CASSCF plays an important role. To test the AIMS-DFT method, we performed simulations on the GeH<sub>2</sub> molecule using the UB3LYP/6-31G(d) potential energy surfaces and gradients. The excited triplet state lifetime and intersystem crossing rate constants were estimated using the first-order kinetics equation for a reversible unimolecular reaction. The rate constants and lifetime were compared with the previous results obtained with the AIMS-CASSCF molecular dynamics and nonadiabatic transition state theory.

Ab Initio multiple spawning molecular dynamics with DFT for intersystem crossings

253rd National Meeting (2017)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.