Nonadiabatic molecular dynamics simulations require a large number of independent trajectories and simulation relies on different parameters that should be tested and compared. The chosen parameters can sometimes lead to unanticipated changes in the accuracy of the simulated dynamics. We seek to investigate the impact of the number of trajectories and the various parameters on the simulation of photoinduced dynamics of distyrylbenzene within our previously developed NA-ESMD framework employing Tully's fewest switches surface hopping algorithm. Various parameters are analyzed: classical and quantum integration time steps, the friction coefficient for Langevin dynamics, and the initial seed for stochastic thermostat and hopping algorithms. Common approximations such as reduced number of nonadiabatic coupling terms and the classical path approximation are also investigated. Our analysis shows that for this system a minimum of ~400 independent trajectories should be calculated in order to achieve statistical averaging necessary for convergence of the calculated relaxation timescales.

Nonadiabatic excited-state molecular dynamics (NA-ESMD): Numerical tests of convergence and parameters

243rd National Meeting (2012)

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