Dynamic Study Of The Several Important Elementary Chemical Reactions

Molecule reaction dynamics is a science of studying microcopic feature and mechanism of chemical reaction in molecular and atomic level. It can provide basic knowledge for interpreting general phenomena in the chemical reactions, and become the base of the macroscopic reaction dynamics.Quantum approach could describe the motion of atomic nuclear on the potential energy surface vividly and completely based on the first principle. Much effort has been devoted to the development of accurate quantum dynamics methods to perform reaction scattering calculation for elementary chemical reactions. At present, time-dependent (TD) quantum wave packet approach has emerged as a powerful computational tool for studying quantum reaction dynamics of triatomic and tetraatomic systems. The main attraction of solving the time-dependent, as opposed to the time-independent, Schrodinger equation stems from its favorable computational scaling with the number of basis functions. This makes the TD wavepacket approach an attractive choice for studying reaction dynamics of large molecular systems. In addition, the TD wavepacket approach is conceptually simple and provides a classical-like interpretation of the numerical results through time propagation of the wavepacket.The gas-phase reaction of H+HC1 and the corresponding to isotopic reactions system have played a major role in the development of chemical kinetics and to the environment in atmospheric chemistry. The reaction of fluorine atom with methane F+CH4HF+CH3 reaction and the corresponding isotopic reactions have been played an important role in atmospheric and combustion chemistry which deserves us to have more study. The reaction systems represent an especially important prototype for highly exothermic hydrogen abstraction reactions of F with hydrocarbons.A theoretical study of the dynamics is given in the thesis of the H+HC1, H+DC1, D+HC1, D+DC1 systems on the potential energy surface (PES) pubilshed by Bian and Werner. In the present work, the four reaction probabilities have been calculated by employing TDWP method for several values of the total angular momentum quantum number J> 0. Reaction probabilities are calculated from various initial rotational states of the reagent. The effects of the zero-point energy and the tunneling effect of the reactions are considered for depicting the behavior of the reactions. Those have then been used to estimate cross sections for exchanged and abstraction channels. The abstraction reaction for the H+HC1 reaction has a collinear transition state, and for the H+HC1 exchange reaction, which also has a collinear transition state. The thermal rate constants of HC1 are calculated by employing the uniform J -shifting method, and a comparison with experimental measurement is provided.In this work, the reaction of fluorine with methane and the isotopic reactions system are calculated through the time-dependent quantum scattering, which has been carried out using the SVRT model, based on the analytic the modified Jl (MJ1) PES which reported by Corchado, J. C. etc. The barrier height about 1.8Kcal/mol, which among the experimental estimate of 0.96-2.39 kcal/mol. The reagent molecule CH4 that is consisted of an H atom and a CH3 fragment which is treated as a semirigid vibrating rotor. The fragment CH3 is fixed in the geometry in the basic SVRT model. For example, since during the reactant to thetransition state the C-H bond in the CH3 group essentially remains constant, which can be treated as a spectator bond, therefore we fixed it at its transition state value-1.090A.In the current study, reaction probability, cross section, and rate constant are calculated for the title reaction from the ground state of the reagent on the MJl PES. Numerical calculation shows that the oscillatory structures in the energy dependence of the calculated reaction probability. Those structures are generally associated with broad dynamical resonances.The calculated results can compared with the results of previous calculations in the references and reaction dynam...