Electronic structure theory for excited state dynamics
I will present two approaches to describing excited state dynamics with an emphasis on underlying electronic structure methods. First, I will describe the so-called active-space decomposition (ASD) method, which provides model Hamiltonians for dynamics simulations based on quantum master equations-like approaches. ASD is not only an efficient active space method but can also be seen as chemical generalization of tensor network states. Second, I will present our recent development of multistate CASPT2 nuclear energy gradients and derivative couplings for trajectory-based on-the-fly non-adiabatic dynamics. Our work has been the first realization of internally contracted CASPT2 nuclear gradients since CASPT2 was developed in 1992. Using our code, such dynamics simulations are now routine on parallel computers for large chromophores in the gas phase and condensed phases. Numerical examples will be presented.