Quantum Dynamics Study Of The OD/H+CH₃ And F^–+CH₃I Reaction Systems

In this thesis,we use the method of reduced quantum and molecular reaction dynamics to study the OD/H+CH₃ isotope reactions and F^–+CH₃I reaction system of nucleophilic substitution.The reaction probability,integral scattering cross section,energy efficiency and reaction rate constant of the two reactions were calculated,and the calculated results were discussed with quasi-classical QCT and experimental data.And a lot of important progress has been made in our research.On the one hand,we calculated the integral scattering cross sections of the isotopic reaction systems with different vibration dynamics to explore the isotopic effect of the kinetics.And the cumulative reaction probability of the whole dimension is calculated by the above method.The reaction rate constant of the isotope system is calculated and the zero point energy is modified by the experimental data,which fits well with the experimental data,and the conclusion is drawn that the lighter the mass,the more obvious the quantum effect.And the isotope effect of OD/H+CH₃ isotope reactions were tested by the six degree-of-freedom time-dependent quantum reaction kinetics method to investigate the accuracy of reduced degree of freedom quantum program wave packet.The energy and J-K shift method is utilized to measure the cumulative reaction probability and the twelve degree of freedom reaction rate constant.By comparing the reaction probability of the two isotope reactions and the integral cross sections,we found that the OD+CH₃ system had a larger energy threshold than that of OH+CH₃ system.At the same time,we found that both of these two isotope reactions had the obvious tunneling effect.And the tunneling effect of OD+CH₃ system was significantly smaller than that of OH+CH₃ system.The full dimensional reaction rate constants were calculated by the zero point energy correction of the experimental value.Due to the isotope effect,the value of the rate constants in OD+CH₃system was less than that of OH+CH₃ system.At the same time,these two isotope reactions should have twelve dimensional of freedom which three N minus six is equal to.And the reduced dimensional quantum dynamics method is feasible and reliable.On the other hand,based on the full-dimensional potential energy surface published by Professor Gábor group in Chemical Science in 2017,and we have carried out the quantum four-dimensional dynamic calculation of F^–+CH₃I→FCH₃+I^–nucleophilic substitution reaction.First,we have calculated the integral scattering cross section of the ground state of the system,and compared the results with the quasi-classical（QCT）results.The data fit well.And the two potential wells in the reactant channel on the potential energy surface have important effects on the energy efficiency of the traction.Therefore,we calculated the first excited state of the stretching vibration of the reactant I-CH₃ and the first excited state of the umbrella vibration of C-H₃ respectively.In general,the stretching vibration of the reactant I-CH₃ and the umbrella vibration of C-H₃ both promote the reaction more effectively than translational energy.In addition,based on the four-degree-of-freedom quantum dynamics method,we used the energy and J-K shift method to calculate the full dimensional system of12 DOF reaction rate constants.We selected the two points with temperatures of 300K and302K from the theoretically calculated rate constant values,and compared them with the experimental values below 300K and 302K.It was found that the theoretical calculated values were basically the same as the experimental value.And based on the two reduced quantum dynamics studies,we further verify that the calculated results of reduced degree of freedom quantum are quite accurate.