Generalization of coupled-cluster response theory to multireference expansion spaces: application of the coupled-cluster singles and doubles effective Hamiltonian

Ten-no, Seiichiro ; Iwata, Suehiro ; Pal, Sourav ; Mukherjee, Debashis (1999) Generalization of coupled-cluster response theory to multireference expansion spaces: application of the coupled-cluster singles and doubles effective Hamiltonian Theoretical Chemistry Accounts: Theory, Computation, and Modeling (Theoretica Chimica Acta), 102 (1-6). pp. 252-261. ISSN 1432-881X

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Official URL: http://www.springerlink.com/index/CAUV1GADR665Q5H3...

Related URL: http://dx.doi.org/10.1007/s002140050496

Abstract

Employing separate cluster ansatz in time-independent and time-dependent wave-operators, coupled-cluster (CC) response theory is generalized to multireference (MR) expansion spaces. For state energies, this corresponds to the MR secular problem with an arbitrary similarity-transformed effective Hamiltonian, H¯=Ω-1 HΩ. The effective Hamiltonian can be generated via size-extensive CC methods. Thus the states in MR linear response theory (MRLRT) maintain the usual CC core-extensive properties. We have used the Gelfand unitary group basis of the spin-adapted configurations to construct the matrix of H¯ in the MR excitation space. As a preliminary application, the CC singles and doubles effective Hamiltonian is applied to excitation and photoionization energies of the CH+ and N2 molecules, and is compared with experimental results and results from other numerical procedures including conventional CC linear response theory (CC-LRT), MR and full configuration interaction (MRCI and FCI) methods. The numerical results indicate that MRLRT reproduces valence and external excited states quantitatively, combining the best features of CC-LRT and MRCI.

Item Type:Article
Source:Copyright of this article belongs to Springer-Verlag.
Keywords:Coupled-cluster Theory; Response Theory; Effective Hamiltonian; Multireference Configuration Space; Excited States; Core-extensive
ID Code:21823
Deposited On:22 Nov 2010 10:55
Last Modified:05 Mar 2011 11:38

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