Second- and third-order triples and quadruples corrections to coupled-cluster singles and doubles in the ground and excited states

被引:53
|
作者
Shiozaki, Toru
Hirao, Kimihiko
Hirata, So [1 ]
机构
[1] Univ Florida, Dept Chem, Quantum Theory Project, Gainesville, FL 32611 USA
[2] Univ Tokyo, Grad Sch Engn, Dept Appl Chem, Tokyo 1138656, Japan
[3] Japan Sci & Technol Agcy, CREST, Saitama 3320012, Japan
来源
JOURNAL OF CHEMICAL PHYSICS | 2007年 / 126卷 / 24期
基金
日本科学技术振兴机构;
关键词
D O I
10.1063/1.2741262
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
Second- and third-order perturbation corrections to equation-of-motion coupled-cluster singles and doubles (EOM-CCSD) incorporating excited configurations in the space of triples [EOM-CCSD(2)(T) and (3)(T)] or in the space of triples and quadruples [EOM-CCSD(2)(TQ)] have been implemented. Their ground-state counterparts-third-order corrections to coupled-cluster singles and doubles (CCSD) in the space of triples [CCSD(3)(T)] or in the space of triples and quadruples [CCSD(3)(TQ)]-have also been implemented and assessed. It has been shown that a straightforward application of the Rayleigh-Schrodinger perturbation theory leads to perturbation corrections to total energies of excited states that lack the correct size dependence. Approximations have been introduced to the perturbation corrections to arrive at EOM-CCSD(2)(T), (3)(T), and (2)(TQ) that provide size-intensive excitation energies at a noniterative O(n(7)), O(n(8)), and O(n(9)) cost (n is the number of orbitals) and CCSD(3)(T) and (3)(TQ) size-extensive total energies at a noniterative O(n(8)) and O(n(10)) cost. All the implementations are parallel executable, applicable to open and closed shells, and take into account spin and real Abelian point-group symmetries. For excited states, they form a systematically more accurate series, CCSD < CCSD(2)(T)< CCSD(2)(TQ)< CCSD(3)(T)< CCSDT, with the second- and third-order corrections capturing typically similar to 80% and 100% of such effects, when those effects are large (> 1 eV) and the ground-state wave function has single-determinant character. In other cases, however, the corrections tend to overestimate the triples and quadruples effects, the origin of which is discussed. For ground states, the third-order corrections lead to a rather small improvement over the highly effective second-order corrections [CCSD(2)(T) and (2)(TQ)], which is a manifestation of the staircase convergence of perturbation series. (c) 2007 American Institute of Physics.
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