Vogiatzis Konstantinos D, Li Manni Giovanni, Stoneburner Samuel J, Ma Dongxia, Gagliardi Laura
Department of Chemistry, Chemical Theory Center, and Supercomputing Institute, University of Minnesota , Minneapolis, Minnesota 55455-0431, United States.
Max Planck Institut für Festkörperforschung , Heisenbergstraße 1, 70569 Stuttgart, Germany.
J Chem Theory Comput. 2015 Jul 14;11(7):3010-21. doi: 10.1021/acs.jctc.5b00191. Epub 2015 Jun 5.
The applicability and accuracy of the generalized active space self-consistent field, (GASSCF), and (SplitGAS) methods are presented. The GASSCF method enables the exploration of larger active spaces than with the conventional complete active space SCF, (CASSCF), by fragmentation of a large space into subspaces and by controlling the interspace excitations. In the SplitGAS method, the GAS configuration interaction, CI, expansion is further partitioned in two parts: the principal, which includes the most important configuration state functions, and an extended, containing less relevant but not negligible ones. An effective Hamiltonian is then generated, with the extended part acting as a perturbation to the principal space. Excitation energies of ozone, furan, pyrrole, nickel dioxide, and copper tetrachloride dianion are reported. Various partitioning schemes of the GASSCF and SplitGAS CI expansions are considered and compared with the complete active space followed by second-order perturbation theory, (CASPT2), and multireference CI method, (MRCI), or available experimental data. General guidelines for the optimum applicability of these methods are discussed together with their current limitations.
本文介绍了广义活性空间自洽场（GASSCF）方法和分裂广义活性空间（SplitGAS）方法的适用性和准确性。与传统的完全活性空间自洽场（CASSCF）方法相比，GASSCF方法通过将大空间分割成子空间并控制空间间的激发，能够探索更大的活性空间。在SplitGAS方法中，广义活性空间组态相互作用（CI）展开进一步分为两部分：主体部分，包括最重要的组态态函数；扩展部分，包含相关性较小但不可忽略的函数。然后生成一个有效哈密顿量，扩展部分作为主体空间的微扰。文中报道了臭氧、呋喃、吡咯、二氧化镍和四氯合铜二价阴离子的激发能。考虑了GASSCF和SplitGAS CI展开的各种划分方案，并与完全活性空间二阶微扰理论（CASPT2）、多参考CI方法（MRCI）或现有实验数据进行了比较。讨论了这些方法最佳适用性的一般指导原则及其当前的局限性。
