Construction Of Potential Energy Surface Of ArH₂⁺ System And Study On Its Dynamics

From the perspective of molecular reaction dynamics,the occurrence process of chemical reactions can be simulated as the movement of representative points on a specific potential energy surface.Therefore,in the process of simulating the collision of atomic molecules,the potential energy surface is one of the most important theoretical foundations.The reaction of Ar H₂ and its isotopic reaction are very important triatomic ion molecular reactions.So that many researchers have a great interest in the construction of the potential energy surface of the system.Our team used UCCSD?T?/aug-cc-pV5Z to construct the ground state potential energy surface?2011-PES?of the system in 2011.The potential energy surface constructed by this method converges well in the region near the equilibrium bond length.However,it was later found that when the distance between ArH⁺diatoms became larger,that is,more than 6 bohr,the potential energy curve was no longer smooth.Later,in 2013,our team rebuilt the ground state potential energy surface?2013-PES?of the system by using?MRCI-Q?/aug-cc-pVQZ method to solve the above problems.Although the problem of the non-convergence of the potential energy curve when the spacing of the ArH⁺double nuclei is large is successfully solved.But we once again found that the potential energy surface of the potential energy surface has no longer converged when the remote zone-to-core spacing of the 2013-PES is changed from 30 bohr to 60 bohr.In view of the above problems,our group has been optimized and modified many times,and finally,the method?UCCSD?T?-F12?of non-limiting single-double-three-excitation coupling cluster plus F12 perturbation correction is selected.At the same time,considering the problem of time resources,the aug-cc-pV5Z basis set is selected to construct a more accurate full three-dimensional potential energy surface,and on the basis of this potential energy surface,the theoretical study of molecular reaction dynamics is carried out.This paper is divided into five chapters.In the first chapter,the concept of molecular reaction dynamics is briefly described.The second chapter focuses on the basic concept of potential energy surface and the application of quasi-classical trajectory method.Next,the third and fourth chapters are the most critical parts of this paper.In the third chapter,how to construct the full three-dimensional ground state potential energy surface of the system is introduced in detail.We use unrestricted single double and three excited coupling clusters and F12 to modify?UCCSD?T?-F12?.The energy points of 4170 configurations are calculated at the aug-cc-pV5Z?augmented correlation consistent polarized valence quadruple zeta?level of the correlated consistent basis set.The latest full three-dimensional ground state potential energy surface is obtained by multi-body expansion fitting of Aguado-Paniagua function.It is found that the potential energy curve of the newly constructed potential energy surface is very smooth in both the reaction region,the interaction region and the product region,and still converges well when the HH core spacing is expanded to 30-60bohr,which completely solves the problems of 2013-PES.In chapter 4,in order to further detect the accuracy of potential energy surface,the stereoscopic dynamics of potential energy surface is studied based on the newly constructed potential energy surface.In this part,we adopt the quasi-classical orbital theory method,and observe the influence of the integral reaction cross section and the reaction probability with the change of collision energy.The conclusion is that the collision energy can not promote the reaction,which is in good agreement with the experimental value.Next,we fix that collision energy is 0.48 EV,and the vibration energy levels are 0,1 and 2,respectively.the change of integral reaction cross section and reaction probability is observed.It is found that the integral reaction cross section of 2013-PES decreases gradually with the increase of vibration energy level,which is contrary to the experimental results,while the integral reaction cross section data obtained by us increase with the increase of vibration energy level.It is in good agreement with the experimental values,which indicates that the newly constructed potential energy surface has higher reliability.In addition,the orientation and orientation distribution of the products under different collision energy and different vibration energy levels are also studied.The fifth chapter is a summary and prospect,focusing on the innovation and shortcomings.