Application of symplectic algorithm in the quasi-classical trajectory calculation of N + O₂ reaction

Quasi-classical trajectories of N + O₂ reaction system have been performed by the fourth-order explicit symplectic algorithm (S4), based on a new ground potential energy surface constructed by Sayos et al, and the results are compared with those of the fourth-order Runge-Kutta scheme (RK4). Conclusion has been drawn that RK4 cannot conserve the total energy of N + O₂ reaction system, and the computed trajectories do not actually describe the motion of N + O₂ reaction system. However, S4 can maintain both the symplectic structure of the Hamilton system and total energy of N + O₂ reaction system during integration. It is revealed that that S4 exhibits more excellence than RK4 in the quasi-classical trajectory calculation of N + O₂ reaction system.