SiH自由基分子基态解析势能函数的准确拟合

Accurate Fitting of Analytic Potential Energy Function for SiH Radical

使用原子分子反应静力学的有关理论,导出了SiH分子自由基X2Π态的合理离解极限.利用耦合簇方法QCISD(T)和一个较大的基组cc-PVQZ,对X2Π态进行了几何优化和频率计算,并在0.10～1.71nm的核间距范围内计算了这一自由基X2Π态的势能曲线.其中,几何优化得到的平衡核间距和谐振频率分别为0.15237nm和2047.5224cm-1,单点能扫描得到的离解能为3.1612eV,都与实验值相符得很好.利用4到7参数的Murrell-Sorbie函数对单点能扫描获得的势能曲线进行了拟合,并对拟合得到的解析势能函数进行了详尽的分析,结果表明只有6参数的Murrell-Sorbie函数才能给出较准确的拟合结果.

The reasonable dissociation limit of the ground state （X2H） of Sill radical is attained by employing the molecular reaction dynamics theory. The accurate equilibrium geometry and harmonic frequency of this state are calculated using the coupled-cluster theory [ QCISD（T） ] and a very large basis set （cc-PVQZ）. The potential energy curve is also calculated over the internuclear separation from 0.10 to 1.71 am. The equilibrium separation, harmonic frequency and dissociation energy of the vertical excitation energies from the ground state to the A^1Σ^＋ , B^1П and b^3П states are calculated to be 0. 152 37 nm, 2 047. 522 4 cm^-1, respectively. The ab initio calculated points are fitted in- to analytic form using 4-, 5-, 6- and 7-parameter Murrell-Sorbie functions. It has been pointed out that only 6-parame- ter Murrell-Sorbie function can give the best results.