中文摘要：

利用Gaussian03程序包，在B3P86／cc-PV5Z水平土对自由基siH2分子基态X^1A1几何结构进行优化计算，得到其平衡几何结构、谐振频率和转动常数等性质参数；采用乘积近似法计算了自由基SiH2分子基态X^1A1从低温20K到高温6000K温度范围内的总配分函数．其中，转动配分函数采用WATSON的刚性转子模型，振动配分函数采用谐振子近似．然后我们把20～6000K的温度范围划分为五个区间段，计算的总配分函数在这五个温度区间分别被拟合到一个温度T的四阶多项式，从而在每个区间均得到五个拟合系数．由这些拟舍系数就可以快速、准确的获得该分子在所研究温度范围内任意温度的总的配分函数．

英文摘要：

The geometrical structure of free radical SiH2 molecule has been optimized at B3P86/cc-PV5Z level using Gaussian03 program, we gained its equilibrium geometry, vibrational frequencies and rotational constants et al. The total internal partition functions are calculated for temperatures from 20-6000 K for SiH2 with the product approximation. For rotational partition sums Qrot, the centrifugal distortion corrections are taken into account. The calculation method for the vibrational partition sums Qvib used is the harmonic oscillator approximation. The temperature range is divided into five regions and the calculated total internal partition functions are fit to a four-order polynomial expression in T, and the coefficients are evaluated in five temperature regions. This allows a rapid and accurate calculation of the total internal partition functions at the temperature from 20-6000 K.