摘要:
采用Davidson修正的内收缩多参考组态相互作用方法(MRCI+Q)结合Dunning等的相关一致基aug-cc-pVnZ (n=D,T,Q,5,6)计算了AlC分子X4Σ?和B4Σ?态的势能曲线,并利用总能量外推公式将这两个态的总能量分别外推至完全基组极限.对势能曲线进行核价相关修正及相对论修正,并详细讨论了基组、核价相关和相对论修正等对X4Σ?和B4Σ?电子态的能量和光谱常数的影响.拟合核价相关及相对论效应修正的外推势能曲线,得到了AlC分子X4Σ?和B4Σ?电子态的主要光谱常数Te, Re,ωe,ωexe,ωeye, Be和αe.它们与实验结果符合较好.求解双原子分子核运动的径向Schr¨odinger方程,找到了无转动的AlC分子两个电子态的全部振动态.针对每一振动态,还分别计算了其相应的振动能级和惯性转动常数等分子常数.它们与已有的实验结果一致.
Abstract:
The potential energy curves (PECs) of X4Σ? and B4Σ? states of the AlC molecule have been studied using highly accurate internally-contracted multireference configuration interaction approach with the Davidson modification. The Dunning’s correlation-consistent basis sets, aug-cc-pVnZ (n=D,T,Q,5,6) are used for the present study. To improve the quality of PECs, core-valence correlation and scalar relativistic corrections are considered. Core-valence correlation corrections are calculated with an aug-cc-pCVTZ basis set. Scalar relativistic correction calcualtions are made using the third-order Douglas-Kroll Hamiltonian approximation at the level of a cc-pV5Z basis set. Obvious effect on the PECs by the core-valence correlation and relativistic corrections has been observed. All the PECs are extrapolated to the complete basis set limit. The convergence observations of present calculations are made and the convergent behavior is discussed with respect to the basis set. Using these PECs, the spectroscopic parameters (Te, Re,ωe,ωe, xe,ωe, ye, Be andαe) of the X4Σ?and B4Σ?states are determined and compared with those reported in the literature. The vibration manifolds are evaluated for each state of non-rotation AlC molecule by numerically solving the radial Schr¨odinger equation of nuclear motion. For each vibrational state, the vibrational level and inertial rotation constants are obtained, which are in excellent accordance with the experimental findings.
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