| In recent years, the remarkable development of quantum scattering theory and the increasing abilities in relevant calculations have drawn more and more attention to the study of quantum dynamics of polyatomic reactions. The study of state-to-state chemical reaction dynamics from first principles is to be a major goal in quantum scattering calculations. During the last two decades, the quantum scattering theory has been substantially developed, and rigorous quantum reactive scattering calculations have already been done to reactions involving four atoms. The chemical or biological reactions, however, involve more than four atoms; therefore, considering the present calculation ability, it is necessary to develop some practical computational methods in order to carry out quantitatively accurate calculations in studying the quantum dynamics of polyatomic molecule reactions. To this end, some reduced dimensionality methods have been proposed for the study of polyatomic reaction systems such as adiabatic approach, fixed geometry approximations and mixed quantum-classical dynamics methods.In this thesis, a new reduced dimensionality method, semirigid vibrating rotor target (SVRT) model, is introduced. The SVRT model is a reduced model that is applicable to dealing with reaction dynamics of polyatomic systems and it can accurately describe spatial rotation of the reacting atoms. So the SVRT model preserves the correct stereodynamics of the reaction systems which is very important in polyatomic reactions.In this thesis, the dynamics of the D+CD4 →CD3+D2 reaction is studied for the first time by using atom-polyatom SVRT model. There are two main reasons for selecting this reaction system: at first, D+CD4 reaction is a typical atom-polyatom reaction; secondly, this system is measurable in experiments. The results of the study will be of much reference value forexperiment researches and for further study of more complicated systems. At present, there is no full-dimensional accurate quantum dynamics solution available to this reaction system.According to this theory, the reactive polyatomic molecule CD4 is regarded as a diatomic molecule D-CD3, therefore the reaction system can be regarded as an atom-diatom reaction system, thus reducing the system to a four-dimensional scattering system. In the process of calculation, the time-dependent wave packet method is used to obtain the Hamiltonian of reaction system; the split-operator method is employed to propagate the wave packet. To avoid boundary reflection of wave function, an optical absorbing potential is used in the calculation process. And considering the C3v symmetry of the molecule CD4, thesemiempirical potential energy surface developed by Jordan and Gilbert is employed for the calculation. In this thesis, reaction probability, scattering cross section and thermal rate constant are calculated. Three conclusions can be drawn from our calculations of the reaction probability: first, the graph of the calculated reaction probability changing with the energy dependence shows characteristic oscillatory structures, which are similar to those observed in many abstraction reactions such as H+H2 and H+CH4; second, the excitation of the stretching vibration of molecule D-CD3 enhances the reaction probability significantly, while the reaction threshold decreases with the vibrating excitation, which implies the substantial contribution made by the vibrating energy of the reacting molecules to the collision reaction of the molecules; third, detailed study of the effect of initial rotational states on reaction probability shows that the steric effect is strong. As demonstrated by the integral cross sections varying with the translational energy when CD4 is at v=0 or v=l, the vibrational excitation improves the reaction cross section significantly, and the reaction threshold decreases by about 0.3eV when the vibrating quantum number changes from 0 to 1 , which is consistent with the result obtained by reaction probability. Besides, the rate constants of the rea...
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