The Studies Of Molecular Structure And Potential Energy Function For LiO₂,Li₂O

In this paper, studies of molecular structure and potential energy function for tri-and diatomic molecules have been presented.By using ab initio calculations, the molecular structures for CH,LiO,Li₂,O₂,LiO₂(C_2V, X²A₂)and Li₂O(C_S, X¹A') have been optimized, and the possible electronic states and the reasonable dissociation limits for these moleculars have been derived based on the general principle of Atomic and Molecular Reaction Statics(1.The principles of resolution, derect product and reduction of grooup representations.2.The principle of microscopic reversibility.3.The principle of microscopic transitivity.4.The optimum energy process rule.) and the group theoretical derivation of molecular electronic states.The Murrell-Sorbie potential energy functions have been derived for the ground states of CH, LiO,Li₂,O₂,and the quadratic, cubic and quartic force constants have been calculated according to the experimental spectroscopic data,the analytic potential functions have to be fitted to ab initio data.The spectroscopic dataω_e,ω_eχ_e, B_e andα_e have been derived.In the present paper, the structure of LiO₂(C_2V, X²A₂)and Li₂O(C_S, X¹A')have been optimized by using the B3LYP method with basis 6-311++G(3df,3pd). The results shows the ground state of LiO₂(C_2V, X²A₂)and Li₂O(C_S, X¹A') belongs to C_2V and C_S group, the geometric structures of LiO₂ is R(LiO)=1.764A, R(LiO)=1.764A,∠OLiO=44.44°, and the harmonic frequencyν₁=491.54 cm^-1,ν₂=741.13 cm^-1,ν₃=1072.94 cm^-1 respectively.The dissociation energy D_e=8.7584eV according to the dissociation limit. The geometric structures of Li₂O(C_S, X¹A') is R(LiLi)=3.230A, R(LiO)=1.615A,∠LiOLi=179.92°, and the harmonic frequencyν₁=151.53 cm^-1,ν₂=810.73 cm^-1,γ₃=1065.55 cm^-1 respectively。The dissociation energy D_e=10.238eV according to the dissociation limit.The analytic potential:function for the ground state of LiO₂(C_2V, X²A₂)and Li₂O(C_S, X¹A') are derived by many-body expansion method based on equilibrium geometry, dissociation energy and harmonic force constants. The potential surface of LiO₂ (C_2V, X²A₂) and Li₂O (C_S, X¹A') successfully reproduces the equilibrium structures of ground states. Besides, they also describe the geometric structures and energy of the stable structures for triatomic molecules.