Enhanced Surface Hopping Method for Sampling Rare Nonadiabatic Events

We present a new nonadiabatic event sampling method that combines the fewest switches surface hopping (FSSH) method with enhanced sampling technology. In this new method, a biasing function is introduced to drive dynamic trajectories to cross high-energy barriers and toward product regions on potential energy surfaces, enabling this method to effectively sample rare nonadiabatic transition events and different decay channels between reactants and products. The biasing function also provides additional kinetic energy to the system, thereby accelerating the simulations and reducing the required computational cost. Two types of biasing functions, based on bond length differences and root-mean-square deviation, are designed to accommodate different reaction systems. The test results indicate that the new method can effectively sample rare nonadiabatic transition events and decay channels that are difficult to capture using the standard FSSH method.