Accurate Fitting Of Diatomic Molecular Potential Energy Curve And Molecular Dynamics Study Of N₂O System

Diatomic radicals play an important role in atmospheric chemistry,interstellar matter and other fields.Although the potential energy function of diatomic molecules has been widely studied,at present,people put forward higher requirements for the accuracy of the potential energy function of diatomic molecules.Generally,when constructing the potential energy function,the main errors are:the error generated in calculation,the error generated in basis set and the error generated in fitting.In the process of calculation,we use the correlation consistent basis set developed by Dunning group to reduce the error,but the correlation consistent basis set is not complete,and there will be errors.Our solution is to use the basis set extrapolation program proposed by Professor Varandas to extrapolate the incomplete basis set to the complete basis set to reduce the error.Finally,using a novel fitting program(CHIPR program),the fitting error is reduced to the minimum,and the accurate diatomic potential energy function is obtained,which will be used as the basis of constructing the three atoms and multi atoms potential energy surface in the future.After obtaining the diatomic potential energy function,we also introduce the root mean square deviation(RMSD)to evaluate the accuracy of CHIPR function.For all the diatomic potential energy functions introduced in this paper,RMSD is less than 10 cm-1.At the same time,the spectral constants of all diatomic molecules in this paper are further calculated based on CHIPR function,and compared with the theoretical values of other authors.The comparison results show that the spectral constants obtained by CHIPR function are very close to other theoretical values,and the results of chip function are also in good agreement with the experimental values.At the same time,we also calculated the Stereodynamics of the reaction O+N2?N+NO by using the quasiclassical traj ectory.First of all,for the rate constant of the reaction,from the potential energy surface,the reaction is endothermic and needs a high temperature to occur.However,for the reaction rate equation fitted by previous experiments,it is at low temperature.And in our calculation process,it is found that the reaction of O+N2?n+no only occurs at least above 10 000 K.Therefore,we refitted the rate equation of the reaction,and the expression is:K(T)=1.95×10-11exp(-37372/T)cm3 s-1 molecule-1.Secondly,forO+N2?N+NO reaction,the polarization-dependent differential cross-sections(PDDCS),reaction cross section and reaction probability,the variation of nuclear distances and P(?r)distribution,P(?r)distribution,P(?r,?r)distribution were calculated.P(?r)distribution,P(?r)distribution,P(?r,?r)distribution show that the angular momentum j of the product is not only perpendicular to the direction of the incident velocity vector,but also oriented along the negative direction of the Y-axis.PDDCS shows that the NO products change from forward scattering to backward scattering with increasing of the collision energy.The results of reaction cross section and reaction probability show that with the increase of collision energy,the reaction cross section and reaction probability increase first and then decrease.The variation of nuclear distances indicate that the reaction undergoes both the direct and indirect reaction mechanisms.