期刊
JOURNAL OF CHEMICAL PHYSICS
卷 134, 期 20, 页码 -出版社
AMER INST PHYSICS
DOI: 10.1063/1.3592786
关键词
-
资金
- Verband der Chemischen Industrie
- Deutsche Forschungsgemeinschaft
The internally contracted multireference coupled cluster (icMRCC) method allows a highly accurate description of both static and dynamic correlation with a computational scaling similar to single reference coupled cluster theory. The authors show that the method can lose its orbital invariance and size consistency when no special care is taken in the elimination of redundant excitations. Using the BeH2 model system, four schemes are compared which differ in their treatment of linear dependencies between excitations of different rank (such as between singles and doubles). While the energy curves agree within tens of mu E-h when truncating the cluster operator at double excitations (icMRCCSD), inclusion of triple excitations (icMRCCSDT) leads to significant differences of more than 1 mE(h). One scheme clearly yields the best results, while the others even turn out to be not size consistent. The former procedure uses genuine single and double excitations and discards those linear combinations of (spectator) double and triple excitations which have the same effect on the reference function. With this approach, the equilibrium structure and harmonic vibrational frequencies of ozone obtained with icMRCCSDT are in excellent agreement with CCSDTQ. The authors further apply icMRCC methods to potential energy surfaces of HF, LiF, N-2, and to the singlet-triplet splitting of benzynes. In particular, the latter calculations have been made possible by implementing the method with the proper formal scaling using automated techniques. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3592786]
作者
我是这篇论文的作者
点击您的名字以认领此论文并将其添加到您的个人资料中。
推荐
暂无数据