The Establishment Of The Accurate Potential Energy Surface Of SH₂^- System And Its Molecular Reaction Kinetics

Elemental sulfur,nitrogen and hydrogen are widely used in nature.NO,as an environmental pollutant,is the main material of air pollution and has a great impact on human health.Sulfur is one of the most abundant elements in the earth's crust.The chemical reaction between sulfur atoms and sulfur-bearing molecules has attracted much attention.As we all know,hydrogen atom transfer reaction is very important in biological chemistry,atmospheric and combustion chemistry.The atomic ions with hydrogen reactions play important role in many cases,for example,interstellar processes,electric discharges and planetary ionospheres.This paper mainly used the method of extrapolating to the complete basis set?CBS?to fit the accurate potential energy curve?PEC?and the full dimensional global potential energy surface?PES?,and completed the molecular reaction dynamics research on the basis of the accurate PES obtained.Part one:PECs of NO,using full valence complete active space self-consistent field?CASSCF?and multireference configuration interaction?MRCI?method,the molpro calculated hundreds ab initio energy points with a basis set of aug-cc-pVXZ?X=T,Q,5 and 6?to calculate the potential energy,by extrapolation to CBS?4,5?limit method,get more precise energy.The extended hartree-fock approximate correlation energy model was used to study the electronic structure spectrum,and the accurate analytical potential function was obtained.The spectral parameters of NO molecule were calculated,which were in good agreement with the experimental and theoretical results.Finally,the radial schr?dinger equation of nuclear motion is solved,and the complete dynamical set of vibration is obtained.For each vibration state,vibrational levels,classical turning points,inertial rotation constant and six centrifugal distortion constants are obtained,and the vibration energy spectrum is successfully predicted.Part two:PES of SH₂^-.In this paper,the ab initio energies point of aug-cc-pVXZ?X=T and Q?is extrapolated to CBS limit by MRCI method,using FVCAS as reference wave function and USTE?T,Q?method.The analytical functions and the three-body distribution polynomials are used to fit the two-body terms and the three-body terms respectively,and a new analytical potential energy expression is obtained.On the basis of the new PES,using quasi-classical trajectory?QCT?method calculated the reaction S^??²P?+H₂?¹?_g⁺??SH^??¹??+H?²S?.The rate constants,integral cross section?ICS?and differential scattering cross section?DCS?of the reaction were investigated.Finally,the reaction kinetics of S^-+H₂ ion molecule on the PES was studied by quantum wave packet method.The effects of the rotation and vibration of the reactants on the reaction probability were discussed.The ICSs is calculated and the results are in good agreement with experiment value.Compared with the experimental data in other literatures,our PES can be widely used in the study of dynamics.