The State-to-state Dynamics Calculations And Reaction Mechanism Research Of The A+BC Reaction System

The theoretical calculations and numerical simulation of the state-to-state quantum dynamics studies can provide the most detailed accurate physical picture and model the elementary molecular reaction process. Because of the effect of reactant vibrational excitation on the quantum dynamics of the triatomic molecules elementary reactions, it has received considerable attention in the field of molecular reaction dynamics. In the present thesis, using the time dependent quantum wave packet?TDQWP? method, we investigated the effects of reagent vibrational excitation and the isotopic effect of the O?³P?+HD and N+H₂?HD, D₂? reactions, and discussed the reaction mechanism.Due to the importance in combustion processes and atmospheric reaction, the reaction O?³P?+HD has been widely studied, including the potential energy surfaces construction and quantum dynamical investigation. Time-dependent quantum wave packet dynamics calculations on GPUs have been performed in order to study the vibrational excitation and the reaction mechanism of O?³P? + HD?v = 0-1, j = 0?? OH+D and OD+H reactive collisions using the adiabatic potential energy surface. Special attention has been paid to the calculations and discussion of the state-to-state integral and differential cross sections and the product state distributions. In addition, the intramolecular isotopic branching ratio has been determined. The results revealed that the OD + H is the favored product channel and the product OH has the same quantum number v as the reactant HD. For low collision energy, the product angular distributions concentrate in the backward region being consistent with a rebounding mechanism. In the case of higher collision energy, the stripping collisions with larger impact parameters tend to produce sideways and forward scatterings, especially for the HD vibrationally excited state. The integral cross section and intramolecular isotopic branching ratio are in agreement with the previous theoretical results.The ground state abstraction reaction N?⁴S?+H₂?HD, D₂? plays an important role in thermal decomposition of cyclotrimethylenetrinitramine?C₃H₆N₆O₆? and cyclotetram-ethy-lenetetranitramine?C₄H₈N₈O₈?, which are nonnegligible ingredients in solid propellants used for rockets. Based on the accurate novel potential energy surface constructed by neural network and the AP function fitting methods and using the GPUs-time-dependent wave packet method, we studied the state-to-state dynamics and reaction mechanism of the reaction N?⁴S?+H₂?X¹?+??NH?X³?-?+H?²S?. The influences of the collision energy on the product state-to-state integral cross sections and total differential cross sections are calculated and discussed. The calculation results show that the products NH are predominated by the backward scattering due to the small impact parameter collisions, with only minor components being forward and sideways scattered, and have an inverted rotational distribution and no inversion in vibrational distributions; both rebound and stripping mechanisms exist in the case of high collision energies. In addition, using the CPU-time dependent quantum wave packet method, we have calculated the total state dynamics of the reactions N?⁴S?+H₂?HD, D₂?. The results reveal that the intramolecular isotopic effect is greater than the intermolecular one, and that the vibrational excitation of the diatomic molecules can promote the progress of this reaction. In addition, a limited number of rigorous Coriolis coupling calculations of the integral cross sections of the N?⁴S?+H₂ reaction have been carried out. Also shown is that since the Coriolis coupling plays a small part in this accurate quantum calculation, the cheaper centrifugal sudden calculations here reported are effective for this reactive system.