GaI2(X^2A1)分子的结构与势能函数

Structure and Potential Energy Function Investigation on GaI_2 Molecule

应用密度泛函理论B3P86和B3LYP,利用多种基组对GaI2分子的基态平衡结构进行优化,并用优选出的密度泛函B3P86/3-21G方法对该分子的离解能、谐振频率和力常数进行了计算.结果发现GaI2(X2A1)分子的基态稳定构型为C2V,其平衡核间距Re=0.26225 nm、∠IGaI=122.8135°,离解能为1.5303 eV,谐振频率为ω1(a1)=54.7691 cm-1、ω2(a1)=179.4269 cm-1、ω3(b2)=248.9129 cm-1,力常数为fR1R1=0.08995 a.u.,fR1R2=0.01238 a.u.,fR1α=-0.01335 a.u.,fαα=0.01362 a.u..在推断出GaI2的离解极限基础上,应用多体展式理论方法,推导出基态GaI2分子的分析势能函数,该势能表面准确地再现了分子GaI2(X2A1)的结构特征和能量变化.分析讨论势能面的静态特征时得到:GaI+I→GaI2反应中存在鞍点,活化能为144.728 kJ/mol.

The density-functional theory （B3P86,B3LYP） are used to optimize the ground-state structure of GaI2, and then B3P86 method is employed to calculate further. The results show that the ground state of GaI2 is of C2v symmetry and of X^2A1 state, the equilibrium bond length RGa-I equals 0. 262 25 nm, the bond angle ∠IGaI equals 122. 813 5° and dissociation energy is 1. 530 3 eV, and its harmonic frequencies are ω1 （a1） = 54. 769 1cm^-1 ,ω2 （a1） = 179. 426 9 cm^-1 ,ω3 （b2） = 248. 912 9 cm^-1 ,and force constants are fR1R1 = 0. 089 95a. u. ,fR1R2 = 0. 012 38 a. u. ,fR1a = -0. 013 35 a. u. ,faa = 0. 013 62 a. u. respectively. The present paper correctly determines the dissociation limits, based on group theory and atomic and molecular reactive statics （AMRS）. Analytical potential energy function for the ground state X^2 A1 of GaI2 has been derived using many- body expansion method. The structure and energy of GaI2 can correctly reappear on the potential surface. Molecular reaction kinetics of GaI＋ I based on the potential energy functions is discussed briefly.