On the Size Consistency of Multireference CEPA Methods

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Title:On the Size Consistency of Multireference CEPA Methods
Creators:
Ruttink, Paul J. A.
Journal or Publication Title:
Collection of Czechoslovak Chemical Communications, 70, 5, pp. 638-656
Uncontrolled Keywords:<i>Ab initio</i> calculations, Size consistency, Coupled cluster, Diagonal shift, Multireference methods, Electron correlation, MRCEPA, Quantum chemistry, MRDCEPA

Abstract

The size consistency of various multireference coupled electron pair approaches (MRCEPA) is analysed. These methods include the MRCEPA0, MR averaged coupled pair functional (MR-ACPF), MR averaged quadratic coupled cluster (MR-AQCC), MR (singles and doubles) CEPA (MRDCEPA) and the recently proposed MR averaged CEPA (MR-ACEPA) methods. Test calculations on the O<sub>2</sub> dimer show that a correct treatment of the variationally included (VI) terms such as in the MRDCEPA and MR-ACEPA methods is necessary for obtaining nearly size-consistent results. On the other hand, the results strongly suggest that it is impossible to obtain exact size consistency with any method employing the diagonal shift formalism. The analysis also shows that the size consistency error is not significantly affected by the exclusion principle violating (EPV) terms. <p>

Title:On the Size Consistency of Multireference CEPA Methods
Creators:
Ruttink, Paul J. A.
Uncontrolled Keywords:<i>Ab initio</i> calculations, Size consistency, Coupled cluster, Diagonal shift, Multireference methods, Electron correlation, MRCEPA, Quantum chemistry, MRDCEPA
Divisions:Life and Chemical Sciences > Institute of Organic Chemistry and Biochemistry > Collection of Czechoslovak Chemical Communications
Journal or Publication Title:Collection of Czechoslovak Chemical Communications
Volume:70
Number:5
Page Range:pp. 638-656
ISSN:0010-0765
E-ISSN:1212-6950
Publisher:Institute of Organic Chemistry and Biochemistry
Related URLs:
URLURL Type
http://dx.doi.org/10.1135/cccc20050638UNSPECIFIED
ID Code:2383
Item Type:Article
Deposited On:06 Feb 2009 17:18
Last Modified:06 Feb 2009 16:18

Citation

Ruttink, Paul J. A. (2005) On the Size Consistency of Multireference CEPA Methods. Collection of Czechoslovak Chemical Communications, 70 (5). pp. 638-656. ISSN 0010-0765

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