Effects of partial triple excitations in atomic coupled cluster calculations

dc.contributor.author	Sur, C
dc.contributor.author	Chaudhuri, R. K
dc.date.accessioned	2008-02-28T10:06:56Z
dc.date.available	2008-02-28T10:06:56Z
dc.date.issued	2007-07
dc.identifier.citation	Chemical Physics Letters, Vol. 442, No. 1 - 3, pp. 150 - 156	en
dc.identifier.uri	http://hdl.handle.net/2248/2087
dc.description.abstract	In this Letter, we study the effects of higher body excitations in the relativistic CC calculations for atoms and ions with one valence electron using Fock-space CCSD, CCSD(T) and its unitary variants. The present study demonstrates that CCSD(T) estimates the ionization potentials (IPs) and the valence electron removal energies quite accurately for alkali atoms and singly ionized alkaline earth ions, but yields unphysical energy levels for atoms and/or ions with partially filled sub-shell like C II. We further demonstrate that the higher body excitation effects can be incorporated more effectively through the unitary coupled cluster theory (UCC) compared to the CCSD(T) method.	en
dc.format.extent	250992 bytes
dc.format.mimetype	application/pdf
dc.language.iso	en	en
dc.publisher	Elsevier B.V.	en
dc.relation.uri	http://arxiv.org/abs/0707.3585	en
dc.relation.uri	http://linkinghub.elsevier.com/retrieve/pii/S0009261407006392	en
dc.subject	coupled cluster calculations	en
dc.title	Effects of partial triple excitations in atomic coupled cluster calculations	en
dc.type	Article	en