MgH分子X^2∑^+,A^2∏电子态的势能函数

Analytical potential energy function for the electronic states X^2∑^+,A^2∏ of MgH molecule

利用QCISD(T)、SAC-CI方法,使用cc-PVQZ,aug-cc-PVTZ,6-311++g及6-311++G(3df,2pd)基组,对MgH分子的基态X2∑+、第一简并激发态A2∏平衡结构进行优化计算.通过对四个基组计算结果进行比较,得出6-311++G(3df,2pd)基组为最优基组.使用6-311++G(3df,2pd)基组和QCISD(T)方法对基态X2∑+,SAC-CI的GSUM(group sumof operators)方法对激发态A2∏进行单点能扫描计算,然后采用Murrell-Sorbie函数及修正的Murrell-Sorbie+c6函数进行拟合,得到了相应电子态的势能函数和对应的光谱常数.计算结果表明,用修正的Murrell-Sorbie+c6函数计算所得的MgH基态和第一简并激发态光谱常数(eω,ωeχe,Be,eα)与实验数据吻合很好.表明修正后的Murrell-Sorbie+c6函数能更为精确地描述MgH分子基态和第一激发态的势能函数.

The equilibrium geometries of two electronic states （the ground state X^2∑^＋ , the first degenerate state A^2 П） of MgH molecule have been calculated using the method of Symmetry Adapted Cluster-Configuration Interaction （SAC-CI） and the Quadratic CI method including Single and Double substitutions （QCISD （T）） with the basis sets cc-PVQZ, aug-cc-PVTZ, 6-311 ＋ ＋ g and 6-311 ＋ ＋ g （3df,2pd）. Comparing among the above mentioned four basis sets, the conclusion is gained that the basis set 6-311 ＋ ＋ g （3d f, 2pd） is the most suitable for the energy calculation of MgH molecule. The whole potential curves for these electronic states are further scanned using QCISD （T）/6-311 ＋ ＋ g（3df,2pd） method for the ground state and SAC- CI/6-311 ＋ ＋ g （3dr, 2pd） method for the excited states. The potential energy functions and relevant spectrum constants （ ωe, ωeχe, Be, αe） of these states are obtained by fitting to the Murrell-Sorbie function and the modified Murrell-Sorbie ＋ c6 function, respectively. The results show that the spectrum constants derived from the modified Murrell-Sorbie ＋ c6 function are in very good agreement with the experimental data, which indicate that the modified Murrell-Sorbie ＋ c6 function can correctly present the potential energy function of the ground state and the first degenerate state of MgH molecule.