杂化耦合簇方法：将活性空间耦合簇方法与耦合簇单双激发和微扰三激发相结合。

Hybrid coupled cluster methods: combining active space coupled cluster methods with coupled cluster singles, doubles, and perturbative triples.

机构信息

School of Chemistry and Chemical Engineering, Key Laboratory of Mesoscopic Chemistry of Ministry of Education, Institute of Theoretical and Computational Chemistry, Nanjing University, Nanjing 210093, People's Republic of China.

出版信息

J Chem Phys. 2012 May 21;136(19):194105. doi: 10.1063/1.4716185.

DOI:10.1063/1.4716185

PMID:22612078

Abstract

Based on the coupled-cluster singles, doubles, and a hybrid treatment of triples (CCSD(T)-h) method developed by us [J. Shen, E. Xu, Z. Kou, and S. Li, J. Chem. Phys. 132, 114115 (2010); and ibid. 133, 234106 (2010); and ibid. 134, 044134 (2011)], we developed and implemented a new hybrid coupled cluster (CC) method, named CCSD(T)q-h, by combining CC singles and doubles, and active triples and quadruples (CCSDtq) with CCSD(T) to deal with the electronic structures of molecules with significant multireference character. These two hybrid CC methods can be solved with non-canonical and canonical MOs. With canonical MOs, the CCSD(T)-like equations in these two methods can be solved directly without iteration so that the storage of all triple excitation amplitudes can be avoided. A practical procedure to divide canonical MOs into active and inactive subsets is proposed. Numerical calculations demonstrated that CCSD(T)-h with canonical MOs can well reproduce the corresponding results obtained with non-canonical MOs. For three atom exchange reactions, we found that CCSD(T)-h can offer a significant improvement over the popular CCSD(T) method in describing the reaction barriers. For the bond-breaking processes in F(2) and H(2)O, our calculations demonstrated that CCSD(T)q-h is a good approximation to CCSDTQ over the entire bond dissociation processes.

摘要

基于我们开发的耦合簇单双加杂交三级（CCSD(T)-h）方法[J. Shen, E. Xu, Z. Kou, and S. Li, J. Chem. Phys. 132, 114115 (2010); and ibid. 133, 234106 (2010); and ibid. 134, 044134 (2011)]，我们开发并实现了一种新的混合耦合簇（CC）方法，称为 CCSD(T)q-h，通过将 CC 单双和活性三重和四重（CCSDtq）与 CCSD(T)相结合，处理具有显著多参考特性的分子的电子结构。这两种混合 CC 方法可以使用非规范和规范 MO 来解决。使用规范 MO，这两种方法中的 CCSD(T)类方程可以直接求解而无需迭代，从而避免了存储所有三重激发振幅。提出了一种将规范 MO 划分为活性和非活性子集的实用程序。数值计算表明，使用规范 MO 的 CCSD(T)-h 可以很好地再现使用非规范 MO 获得的相应结果。对于三个原子交换反应，我们发现 CCSD(T)-h 可以在描述反应势垒方面对流行的 CCSD(T)方法进行显著改进。对于 F(2)和 H(2)O 中的键断裂过程，我们的计算表明，对于整个键离解过程，CCSD(T)q-h 是 CCSDTQ 的良好近似。