迭代的多组态相互作用方法

本文提出了迭代的组态相互作用方法(IMRCI). IMRCI被用来计算H₂O和CH₂(单重态和三重态)在平衡态和远离平衡时的电子能量. IMRCI、MP2、MP3、MP4、CCSD和CCSD(T)还用来计算H₂O、CH₂(单重态和双重态)和N₂的势能曲线. 这些计算结果表明IMRCI的结果不依赖初始的多参考态组态函数，并能较快地收敛到完全组态相互作用的计算结果. 相比完全组态相互作用的结果，仅需2至4次迭代，IMRCI的误差就能达到10^-5 hartree数量级. 另外，IMRCI还提供了寻找势能面上主要电子组态的一个有效途径. 这将有助于单参考态和多参考态理论模型得到准确的计算结果.

Iterative Multireference Con guration Interaction

Iterative multireference configuration interaction (IMRCI) is proposed. It is exploited to compute the electronic energies of H₂O and CH₂ (singlet and triplet states) at equilibrium and non-equilibrium geometries. The potential energy curves of H₂O, CH₂ (singlet and triplet states) and N₂ have also been calculated with IMRCI as well as the M?ller Plesset perturbation theory (MP2, MP3, and MP4), the coupled cluster method with single and double substitutions (CCSD), and CCSD with perturbative triples correction (CCSD(T)). These calculations demonstrate that IMRCI results are independent of the initial guess of configuration functions in the reference space and converge quickly to the results of the full configuration interaction. The IMRCI errors relative to the full configuration interaction results are at the order of magnitude of 10^-5 hartree within just 2-4 iterations. Further, IMRCI provides an efficient way to find on the potential energy surface the leading electron configurations which, as correct reference states, will be very helpful for the single-reference and multireference theoretical models to obtain accurate results.