LaCl基态X^{1} σ ^+的解析Potential Energy函数
Analytical Potential Energy Function for the Ground State X^{1} Sigma^+ of LaCl
摘要：
在B3 LYP、MP2、QCISD（T）水平下，采用能量一致的相对论有效实势，计算了一氯化镧的平衡几何构型、谐振频率和离解能.根据原子分子反应静力学，确定了可能的电子态和基态的合理离解极限。由于B3 LYP和QCISD（T）方法在键能计算方面的优越性，我们对基态X^{1} Sigma^+进行了势能曲线扫描.当双原子间距为0.8nm时，用QCISD（T）方法计算的势能比离解能大0.5eV。分析了单参考从头算方法在计算镧系重金属元素时不能满足离解极限的问题。我们提出了计算方案，以获得解析的Murrell-Sorbie势能函数和Dunham展开在平衡位置。用标准Dunham处理方法得到的光谱常数与光谱实验转动分析结果符合得很好。该解析函数可用于精细过渡结构的预测和反应动力学过程的研究，具有重要的现实意义。
英文摘要：
The equilibrium geometry, harmonic frequency and dissociation energy of lanthanum monochloride have been calculated at B3LYP, MP2, QCISD(T) levels with energy-consistent relativistic effective core potentials. The possible electronic state and reasonable dissociation limit for the ground state are determined based on atomic and molecular reaction statics. Potential energy curve scans for the ground state X^{1} Sigma^+ have been carried out with B3LYP and QCISD(T) methods due to their better performance in bond energy calculations. We find the potential energy calculated with QCISD(T) method is about 0.5 eV larger than dissociation energy when the diatomic distance is as large as 0.8 nm. The problem that single-reference ab initio methods don't meet dissociation limit during calculations of lanthanide heavy-metal elements is analyzed. We propose the calculation scheme to derive analytical Murrell-Sorbie potential energy function and Dunham expansion at equilibrium position. Spectroscopic constants got by standard Dunham treatment are in good agreement with results of rotational analyses on spectroscopic experiments. The analytical function is of much realistic importance since it is possible to be applied to predict fine transitional structure and study reaction dynamic process.
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