Construction Of LiHX(X=O~+,N)Potential Energy Surface And Study On Molecular Reaction Dynamics

LiH molecule is an important component of lithium battery and other electrical storage materials.It is important to study its chemical reaction activity for exploring the stability of related electrical storage materials.Because Li H molecules are easy to react with N,O and other elements,these elements are often contacted in the manufacturing and transportation of electrical storage materials.Therefore,it is of great significance to study the reaction kinetics of LiH and N,O elements for the preparation and transportation of electrical materials.In this paper,a large number of single point energies of LiHO+and Li NH systems are calculated by high-precision ab initio method,and the analytic potential energy surfaces of LiHO~+and LiNH systems are constructed by the fitting method based on artificial neural network.Because the LiHO+system contains neutral molecules and ions,the interaction potential between reactants is very long,and the O+LiH~+reaction is an exothermic reaction without threshold,so the study of the reaction kinetic properties of the system can provide a reference for the experimental study of the ultracold reaction system.In this paper,we choose to study the O+LiH~+reaction kinetics on the LiHO~+potential energy surface.D is the most abundant isotope of H in the universe.We know that the isotopic effect can change the zero point energy of reactants and products,thus affecting the exothermic or endothermic reaction.In addition,when the atoms react with each other,the energy distribution mode of the collision energy into vibration and kinetic energy will be affected due to the role of isotope substitution.For most of the elements,the effect of isotopic effect is almost negligible,but since the mass of D element is twice that of H element,its isotopic effect is also obvious,so we also studied the kinetic properties of O+LiD+reaction.The work in this paper can be divided into three parts as follows:(1)The potential energy surface of LiHO+is constructed.Using molpro2012software package to calculate a large number of ground state single point energy of LiHO~+system from scratch,after obtaining high-precision single point energy,the potential energy surface is fitted by using the fitting method based on artificial neural network,and an accurate ground state potential energy surface of LiHO+system is constructed.The root mean square error of the fitted ground state LiHO~+potential energy surface is 1.82mev.We calculated the spectral constants and equilibrium bond lengths of the two body terms LiH~+,OH and LiO~+on the potential energy surface of the ground state LiHO~+,and compared them with the experimental values.It is found that the values of LiH~+,OH and Li O~+are consistent with the previous experimental values,indicating that the potential energy of the constructed LiHO~+system is accurate for the description of the long-range region.(2)The quasi-classical trajectories of O+LiH~+?Li~++OH and O+LiD~+?Li~++OD reactions were studied on the constructed LiHO~+potential energy surface.The integral cross sections(ICS)and differential cross sections(DCS)of the two reactions O+LiH~+?Li~++OH and O+LiD~+?Li~++OD are calculated.We found that the ICSS of the two reactions will gradually decrease with the increase of collision energy.In the range of collision energy studied,the ICSS of O+LiH~+?Li~++OH reaction is higher than that of O+Li D~+?Li~++OD reaction,and the gap will become larger with the increase of collision energy.In addition,we also studied the DCSs of two reactions.The results of DCSs show that the effect of isotope on forward scattering is obvious.In a relatively low collision energy range,the isotope effect enhances the isotropy of the scattering direction of the product,and the isotope effect has a significant impact on the scattering direction of the product molecules.However,in the higher collision energy range,the collision energy weakens the influence of isotope effect on the scattering direction of molecular products,and the collision energy plays a dominant role in the scattering direction.We conclude that under different collision energies,there are two reaction mechanisms of O+LiH~+?Li~++OH and O+LiD~+?Li~++OD:indirect reaction and direct reaction,and two different reaction mechanisms occupy different positions in different collision energies.At the same time,we calculated the vibrational state distribution of the product molecules,and analyzed the influence of isotope effect on energy distribution in detail.In order to better understand the reaction mechanism,we draw a picture of the change of nuclear distance with time,and find that the reaction mechanism changes with the increase of collision energy.The reaction mechanism will change from indirect reaction mechanism to direct reaction mechanism.In addition,we also calculated the integral cross section,differential cross section,nuclear spacing with time and vibration dynamic distribution of H/D isotope effect.(3)The potential energy surface of LiNH is constructed.The single point energy of 22299 LiNH system ground states is calculated by MRCI method,and the potential energy surface of LiNH system is constructed by artificial neural network fitting method.In order to verify the reliability of the fitted potential energy surface,we calculated the root mean square error,which was 2.65mev.We calculated the two body terms on the constructed potential energy surface,and compared the calculated equilibrium bond length and dissociation energy of the two body terms with the experimental values,and found that the spectral constants of LiH,Lin and NH are consistent.