ClF-分子离子的结构与势能函数

采用单、双取代包括三重激发的二次组态相互作用[QCISD(T)]方法和单、双取代包括非迭代三重激发的耦合簇理论[CCSD(T)]方法, 结合相关一致基组aug-cc-pVXZ (X=D, T, Q, 5)对基态³⁵ClF^-和³⁷ClF^- (X²Σ⁺)分子离子进行了结构优化计算. 对CCSD(T)方法的计算结果用四种方法分别外推至基组极限, 得到了体系在基组极限的平衡结构常数. 在CCSD(T)/aug-cc-pVXZ (X=D, T, Q, 5)理论水平进行了单点能扫描. 对扫描计算结果进行基组外推并用Murrell-Sorbie 势能函数拟合得到了体系的解析势能函数表达式, 并进一步得到了³⁵ClF^-和³⁷ClF^-的光谱常数. 拟合所得势能曲线准确地再现了其离解能和平衡结构特征. 对ClF 中性自由基采用完全相同的理论方法进行了计算. 所得结果与有关文献中的实验结果符合得很好, 而且在一定程度上证明了将该理论方法应用于ClF^-分子离子的计算是合适而可靠的. ClF 自由基的优化计算结果还被用于计算其电子亲和能.ClF^-的垂直解离能也同时计算得出. 基于ClF^-的结构优化和单点能扫描计算结果, 通过求解核运动的径向薛定谔方程, 得到了无转动³⁵ClF^-和³⁷ClF^-(X²Σ⁺)的全部振动态及相应的分子常数.

Structure and Potential Energy Function of ClF- Molecular Ion

The molecular structure of the ground electronic state (X²Σ⁺) of ³⁵ClF^- and ³⁷ClF^- molecular ions have been calculated using single and double substitution quadratic configuration interaction calculations with the triple contribution [QCISD(T)] method and the simple and double excitation coupled-cluster theory with noniterative treatment with the triple excitations [CCSD(T)] method in combination with the correlation consistent basis sets aug-cc-pVXZ (X=D, T, Q, 5). Basis set extrapolation procedures were employed to estimate the complete basis set limit using results obtained with the CCSD(T) method. The analytical potential energy curves for the ground state of the systems were determined by fitting the data of single point energy scans that were calculated at the CCSD(T)/aug-cc-pVXZ (X=D, T, Q, 5) level of theory. The obtained potential energy curves correctly described the configuration and dissociation energy of the molecular ion and was well reproduced by the Murrell-Sorbie function. The corresponding spectroscopic parameters for the ground states of ³⁵ClF^- and ³⁷ClF^- molecular ions were also deduced. Parallel computations were carried out for the neutral ClF radical on the same level of theory. The results were in good agreement with available experimental data. The consistency between our results and previously reported experimentally determined values demonstrated the feasibility of the theoretical approach performed in this work. The optimized equilibrium geometric parameters were further used to derive the electron affinities of the neutral ClF radical. The vertical detachment energy of ClF^- was also determined. Based on computation results for ClF^-, the vibrational levels and corresponding molecular constants for the X²Σ⁺ states of ³⁵ClF^- and ³⁷ClF^- molecular ions were obtained by solving the radical Schr?dinger equation of the nuclear motion.