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On the validity and applicability of the connected moments expansion

✍ Scribed by Peter J. Knowles

Publisher: Elsevier Science
Year: 1987
Tongue: English
Weight: 533 KB
Volume: 134
Category: Article
ISSN: 0009-2614
DOI: 10.1016/0009-2614(87)87184-1

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✦ Synopsis

The theoretical justification, and typical convergence properties, of Cioslowski's connected moments expansion for the ground-state energy of a quantum-mechanical system are considered. This size extensive expansion is an alternative to Rayleigh-Schrodinger perturbation theory, and is expected to be useful in electronic structure calculations based on manydeterminant reference functions, where perturbation theory is not applicable. It is found from example molecular electronic structure calculations that, in some cases, the expansion does not converge correctly to the true energy. An improved expansion derived from a Pad& approximant, and an analysis of its validity, is presented here.

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