中文摘要：

采用密度泛函B3P86方法，结合Dunning的相关一致五重基CC—PVSZ，设置不同的外电场参量进行优化计算，获得了不同外电场下BeH分子的键长、偶极矩、振动频率和红外光谱等物理性质参数．通过分析参数随外电场的变化关系，判断离解电场所处的范围，设置合适的外电场参数，采用单双取代耦合团簇CCSD（T）方法，扫描计算该范围的单点能获得其势能曲线．结果分析表明物理性质参数和势能随外电场的变化而变化。且外加反向电场时变化幅度更大．采用偶极近似构建外电场下的势能函数模型，编制程序拟合对应的势能函数，得出拟合参数，进而计算临界离解电场参量，结果与数值计算和理论分析较为一致，说明构建的模型是合理和可靠的．这为分析外场下分子光谱、动力学特性和分子Stark效应冷却囚禁提供重要的理论和实验参考．

英文摘要：

Adopting density functional B3P86/cc -PVSZ method and setting different electric fields, the geometric structures of Bell molecule are optimized, and the bond lengths, dipole moments, vibration frequencies and other physical properties parameters are obtained. On the basis of setting appropriate parameters and adop- ting the energy of high precision coupled cluster CCSD （T） method to scan single point energies, the potential energy curves under different external fields are given. The results show that the physical properties parameters and potential energy values will change with the external electric field change , especially at reverse direction e- lectric fields. In order to get the critical dissociation electric parameter, the dipole approximation is adopted to construct potential model, then the model is put to fit the corresponding potential energy curve of external electric field. It is found that the fitted critical dissociation electric parameter is consistent with numerical calculation, and so the constructed model is reliable and accurate. These will provide important theoretical and experimental reference for studying the molecular spectroscopy, dynamics and molecular cooling with Stark effect.