Abstract: Classical trajectories of model molecule A₂B are calculated by means of both Symplectic and Runge-Kutta algorithms. The comparisons beween the results of the two are illustrated by figures. Further analyses indicate : Within the whole domain of time that should be considered by micro chemical reaction dynamics, the trajectories calculated from symplectic algorithm are always identical with physical analysis, but those from Runge-Kut-ta's are irregular and unpredicatable. Moreover, computation of classical trajectory by symplectic algorithm instead of traditional numerical approaches may critically improve classical trajectory method in chemical reaction dynamics.

Key words: Chemical reaction dynamics, Classical trajectory approach, Symplectic algorithm