The Investigation For Potential Energy Surface And Dynamics Of The Reaction System C⁺+H₂ And S^-+H₂

Based on the Born-Oppenheimer approximation,potential energy surface presents the form of a potential energy function in which potential energy changes with the spacing of nucleus distance.The motion of the nucleus and the electron outside the nucleus can be treated separately.The Born-Oppenheimer approximation,sometimes called the adiabatic approximation,can be employed to investigate the motion of the electron relative to the nucleus when the electron moves much faster than the nucleus and the nucleus can be regarded as static.For polyatomic molecule systems,a series of lattice energies can be obtained by solving the Schr（?）dinger equations satisfied by electron motion in different configurations.Employing fitting and interpolating methods,these obtained energy lattices will be used to construct potential energy surface of the system.With the development of computer technology and the demand for high precision potential energy surface,the method of multiple reference configuration interaction（MRCI）or coupling cluster（CC）is widely used to obtain high precision ab initio energy points,which provides theoretical support for constructing new analytical potential energy functions.To check the correctness of the potential energy function,the dynamics characteristics of molecular reaction can be deeply studied on the basis of the precise potential surface.Then,the dynamics of molecular reaction are calculated to obtain some information such as integral scattering cross sections,differential reaction cross sections and chemical reaction rate constants.In recent years,due to the increasingly serious environmental problems such as air pollution,acid rain and global climate change,a large number of scholars have devoted themselves to the study the systems containing C,S,N and H elements.Macromolecules composed of elements C,S and H play a key role in the combustion of C and S and the reactions of various small molecular.The SH^-ion has been observed in the universe,and similar to the CH⁺ion,both are interstellar molecules.Therefore,this paper focuses on the study of the structures of interstellar ion molecules SH₂^-and CH₂⁺has been studied.The main research content of this paper includes the following three parts.（1）For the first excited state CH₂⁺ionic molecule system,the full valence complete active space is taken as the reference wave function,and the ab initio energy point under the aug-CC-p V6Z base group are calculated by using the multi reference configuration interaction method.The two body term CH⁺,H₂and the three body term CH₂⁺are fitted by analytic potential energy function and three-body distribution polynomial,and a new analytical expression is obtained.Then,the contours of different geometries are shown,and several stable points on the potential energy surface are discussed,which are in agreement with the experimental and theoretical values.Finally,in order to verify the accuracy of the potential energy surface.Based on the first excited state CH₂⁺（1²A′′）global potential energy surface,the molecular reaction dynamics of the reaction C⁺+H₂were measured,and the dynamic parameters and integral scattering cross section of the reaction were determined.（2）For the ground state SH₂^-ionic molecule potential energy surface reaction system,the dynamics of S^-（²P）+H₂（¹Σ_g⁺）→SH^-（¹Σ）+H（²S）reactions are further studied using time-dependent wave packet method based on the previously published ground state potential energy surface.The reaction probability and integral scattering cross section with impact energy are calculated.The results show that there are significant oscillating structures in the probability range of all the impact energy.Increasing the vibration and rotation of the diatomic H₂significantly increase the activity of the reaction.Moreover,the calculated results of quantum dynamics are in good agreement with the experimental values.（3）For the ground state SH₂^-ionic molecule reaction system,the potential energy surface of ground state ions is calculated by using the aug-CC-p VQZ basis set at the multi-reference configuration interaction level.The semi-empirical correction of dynamic correlation is carried out by using the multi-body expanded external correlation method,and the potential energy surface of SH₂^-ground state is obtained.To verify the accuracy of the potential surface.Using the wave-packet method,we have carried out the kinetic calculation of the reaction,and then study the influence of coriolis coupling on the reaction,calculate the thermal rate constant and integral scattering cross section.and further improve the kinetic study of SH₂^-system,providing effective theoretical support for the experiment.