State Tracking\nin Nonadiabatic Molecular Dynamics\nUsing Only Forces and Energies

A new algorithm for the identification of unavoided (trivial)\ncrossings\nin nonadiabatic molecular dynamics calculations is reported. The approach\ndoes not require knowledge of wave functions or wave function time\noverlaps and uses only information on state energies and gradients.\nIn addition, a simple phase consistency correction algorithm for time-derivative\nnonadiabatic couplings is proposed for situations in which wave function\ntime overlaps are not available. The performance of the two algorithms\nis demonstrated using several state crossing models. The approaches\nwork best for systems with localized nonadiabatic coupling regions\nbut may have difficulties for those with extended regions of nonadiabatic\ncoupling. It is found that state tracking alone is not sufficient\nfor producing correct population dynamics and that nonadiabatic coupling\nphase correction is required.