Si_2S(X^1A_1)分子的结构与势能函数

Investigation of Structure and Potential Energy Function of Si_2S Molecule

应用多种方法多种基组对Si2S分子的基态结构进行优化,并用优选出的密度泛函B3P86/6-311++G(3d2f)方法对该分子进行了进一步的频率计算.结果发现:Si2S(X1A1)分子的基态稳定构型为C2v,其平衡核间距Rsis=0.213 3 nm、∠SiSSi=67.982 6°,离解能为9.233 2 eV,同时计算出了谐振频率及力常数.在推断出Si2S的离解极限基础上,应用多体展式理论方法,导出了基态Si2S分子的分析势能函数,该势能表面准确地再现了分子Si2S(X1A1)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SiS+Si→Si2S反应中不存在势垒,为无阈能反应.

Many methods are used to optimize the ground-state structure of Si2S, and then B3P86 method is employed in further calculation. The results show that the ground state of Si2S is of C2v symmetry and of X^1A1 state, the equilibrium bond length R sis =0. 2133 nm, the bond angle ∠SiSSi= 67. 982 6° and dissociation energy is 9. 2332 eV respectively, and its harmonic frequencies, force constants have been calculated. 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^1A1 of Si2 S has been derived with many-body expansion method. The structure and energy of Si2 S can correctly reappear on the potential surface. Molecular reaction kinetics of SiS＋Si based on the potential energy functions is discussed briefly.