TREATMENT OF QUASI-DEGENERACY IN SINGLE-REFERENCE COUPLED-CLUSTER THEORY - SEPARATION OF DYNAMICAL AND NONDYNAMIC CORRELATION-EFFECTS

被引：15

作者：

DATTA, B ^{[1
]}

MUKHERJEE, D ^{[1
]}

机构：

[1] INDIAN ASSOC CULTIVAT SCI, DEPT PHYS CHEM, THEORY GRP, CALCUTTA 700032, W BENGAL, INDIA

来源：

CHEMICAL PHYSICS LETTERS | 1995年 / 235卷 / 1-2期

关键词：

D O I：

10.1016/0009-2614(95)00055-9

中图分类号：

O64 [物理化学（理论化学）、化学物理学];

学科分类号：

070304 ; 081704 ;

摘要：

We show that the most important nondynamical correlation effects of quasidegeneracy arising, for example, out of bond-breaking, can be effectively handled using low-body cluster operators (usually up to rank two) via a modification of single-reference coupled-cluster (CC) theory. This is done by separating the effects of cluster operators leading to dynamical and nondynamical correlations. The former leads to direct excitations to the virtual functions chi(i) from the reference function phi, and the latter excites to chi(i) via intermediates phi(u) quasi-degenerate with phi. By utilizing a separability condition for the dynamical and nondynamical correlation energies, a rigorously size-extensive and size-consistent CC theory is developed which should be well-behaved and accurate at bond-breaking geometries.

引用

页码：31 / 36

页数：6

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