中文摘要：

采用从头算的单双取代的二次组态相互作用方法及耦合簇理论对Si F2自由基的基态进行结构优化,发现用单双取代的二次组态相互作用方法配有基组6-311G（2df）计算得到的结构参数、谐振频率、离解能及力常数与实验值最接近并优于文献值.借助多体项展式理论导出Si F2自由基的势能函数并绘制了等值势能图.Si F2自由基对称伸缩振动和旋转势能图显示：在Si F＋F→Si F2反应通道上有鞍点出现,F原子需要越过4.38 e V的能垒才能生成稳定的Si F2自由基;只能通过Si F＋F→Si F2两个等价的通道才能生成稳定的Si F2自由基,并且该反应是有阈能的吸热反应.

英文摘要：

The ab initio configuration interaction method and coupled-cluster theory have been used to optimize the possible ground-state structures of Si F2. The method QCISD/6-311G（2df） is most suitable for the calculation of Si F2 by comparing the experimental value and the calculated value; and the calculated equilibrium structure, harmonic frequency,dissociation energy, force-constant are in good agreement with the experimental data. The potential energy functions of Si F2 have been derived from the many-body expansion theory. In the symmetry of stretching vibration and rotation potential energy diagram of Si F2, there is a saddle point in the reaction kinetics Si F＋F → Si F2. A stable Si F2 molecule could be formed when F atom with an energy surpassing 4.38 e V. These are completely reported so far as we know for the first time. In addition, it is found that a stable Si F2 molecule could be formed through two equivalent channels of Si F＋F → Si F2. And the reaction is endothermic with a threshold energy.