Size-consistent multireference configuration interaction method through the dressing of the norm of determinants |
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Authors: | JAROSLAW MELLER JEAN-PAUL MALRIEU JEAN-LOUIS HEULLY |
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Affiliation: | 1. Department of Informatics , Nicholas Copernicus University , ul.Grudziadzka 5, 87-100, Toruń, Poland;2. Laboratoire de Physique Quantique , IRSAMC, Université Paul Sabatier , 118 Rte de Narbonne, 31062, Toulouse Cedex, France |
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Abstract: | A new determinant-specific, effective change (‘dressing’) of the norm of the multireference configuration interaction (MRCI) wavefunction is proposed in order to achieve the size-consistency of the MRCI method. The new approach provides a unifying framework for analysis of size-consistent extensions of the MRCI method that are based on the coupled pair functional (CPF) strategy and lead to simplified computations of the analytical gradients. Using the new framework, a generalized multireference full coupled pair functional (MR-FCPF) method is introduced. The MR-FCPF method may be viewed as a functional counterpart of the recently proposed generalized (‘full’) coupled electron pair approximation (CEPA), referred to as the size-consistent self-consistent CI ((SC)2CI) method. A straightforward extension of the MR-FCPF method leads to a pseudo-functional form of the coupled cluster (CC) type formalisms. Therefore, the new approach may be used to introduce a simple alternative to existing CC-type gradient techniques. The new procedure is formally derived and compared with similar methods from the literature. Model systems calculations (H2O, LiF, CH+ 2) are further used to demonstrate the effect of various approximations and to elucidate the hierarchy of functional MR-CEPA schemes. |
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Keywords: | Well-tempered meta-dynamics potential of mean force mean-field polarisable water hydration shell radial distribution function coordination number density functional theory |
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