A mixed density functional theory and semi-empirical framework for trajectory surface hopping on extended systems

Non-adiabatic molecular dynamics simulations enable theoretical understanding of various excited-state processes in photochemistry, giving access to band widths, radiative or nonradiative relaxation and corresponding lifetimes, excited-state energy and charge transfer. The range of method developments within the framework of time-dependent density functional theory is exceedingly large for molecular quantum chemistry, but shrinks significantly when aiming for the treatment of periodic boundary conditions. To address this gap and complement existing software packages for solid-state non-adiabatic molecular dynamics, we present an interface between the CP2K electronic structure and the NEWTON-X surface hopping codes. The interface features the generation of initial conditions, adiabatic molecular dynamics and non-adiabatic molecular dynamics based on phenomenological or numerical time-derivative couplings. Setups are validated on gas-phase pyrazine, with electronic absorption spectra and excited-state populations for transitions between the lowest singlet states being in agreement with established molecular quantum chemistry methods. Extending the system size to crystalline pyrazine, limitations of approximate couplings are discussed and the efficiency and applicability of the interface is demonstrated by computing broad spectra over several eV and 100 fs trajectories considering couplings between all 80th lowest excited states at low computational cost with a mixed semi-empirical density functional theory setup.