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Article Dans Une Revue Journal of Chemical Physics Année : 2011

Two- and four-component relativistic generalized-active-space coupled cluster method: Implementation and application to BiH

Résumé

A string-based coupled-cluster method of general excitation rank and with optimal scaling which accounts for special relativity within the four-component framework is presented. The method opens the way for the treatment of multi-reference problems through an active-space inspired single-reference based state-selective expansion of the model space. The evaluation of the coupled-clustervector function is implemented by considering contractions of elementary second-quantized operators without setting up the amplitude equations explicitly. The capabilities of the new method are demonstrated in application to the electronic ground state of the bismuth monohydride molecule. In these calculations simulated multi-reference expansions with both doubles and triples excitations into the external space as well as the regular coupled-cluster hierarchy up to full quadruples excitations are compared. The importance of atomic outer core-correlation for obtaining accurate results is shown. Comparison to the non-relativistic framework is performed throughout to illustrate the additional work of the transition to the four-component relativistic framework both in implementation and application. Furthermore, an evaluation of the highest order scaling for general-order expansions is presented.

Dates et versions

hal-00904923 , version 1 (15-11-2013)

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Lasse K. Sorensen, Jeppe Olsen, Timo Fleig. Two- and four-component relativistic generalized-active-space coupled cluster method: Implementation and application to BiH. Journal of Chemical Physics, 2011, 134, pp.214102. ⟨10.1063/1.3592148⟩. ⟨hal-00904923⟩
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