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Persistent URL http://purl.org/net/epubs/work/29802
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Record Id 29802
Title Computational complexity of CCSD(T) algorithms in electron correlation studies for atoms and molecules
Abstract The CCSD(T) method, a coupled cluster approach including all single and double excitations together with an a posteriori perturbative correction for connected triple excitations, is believed to provide an optimum balance between accuracy and efficiency in electron correlation studies. In this report, we analyze the computational complexity of CCSD(T) algorithms. After considering a prototypical fourth order triple excitation energy diagram in the many-body perturbation theory (MBPT) expansion for a closed-shell system, we consider the tensor contraction which arises in the evaluation of the corresponding energy component and also the use of spin-adaptation and the efficiencies which follow in the computational algorithm from its effective exploitation. The CCSD(T) approximation is presented in a compact form and the algebraic complexity of algorithms for this approximation considered in detail. Reduced-complexity algorithms for CCSD(T) calculations are considered. In particular, we consider low-order scaling techniques for extended molecular systems, Laplace transform techniques, and Cholesky decomposition techniques.
Organisation CCLRC
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Language English (EN)
Type Details URI(s) Local file(s) Year
Report RAL Technical Reports RAL-TR-2004-001. 2004. raltr-2004001.pdf 2004
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