A benchmark set of relevant geometries of a model protein, the N-acetylphenylalanylamide, is presented to assess the validity of the approximate second-order coupled cluster (CC2) method in studying low-lying excited states of such bio-relevant systems. The studies comprise investigations of basis-set dependence as well as comparison with two multireference methods, the multistate complete active space 2nd order perturbation theory (MS-CASPT2) and the multireference difference dedicated configuration interaction (DDCI) methods. First of all, the applicability and the accuracy of the quasi-linear multireference difference dedicated configuration interaction method have been demonstrated on bio-relevant systems by comparison with the results obtained by the standard MS-CASPT2. Second, both the nature and excitation energy of the first low-lying excited state obtained at the CC2 level are very close to the Davidson corrected CAS+DDCI ones, the mean absolute deviation on the excitation energy being equal to 0.1 eV with a maximum of less than 0.2 eV. Finally, for the following low-lying excited states, if the nature is always well reproduced at the CC2 level, the differences on excitation energies become more important and can depend on the geometry.
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14 May 2018
Research Article|
May 09 2018
Low-lying excited states of model proteins: Performances of the CC2 method versus multireference methods
Nadia Ben Amor
;
Nadia Ben Amor
a)
1
CNRS, UPS, LCPQ (Laboratoire de Chimie et Physique Quantiques), IRSAMC
, 118, Rte de Narbonne, F-31062 Toulouse Cedex, France
2
UPS, LCPQ (Laboratoire de Chimie et Physique Quantiques), IRSAMC, Université de Toulouse
, 118, Rte de Narbonne, F-31062 Toulouse Cedex, France
a)Author to whom correspondence should be addressed: benamor@irsamc.ups-tlse.fr
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Sophie Hoyau;
Sophie Hoyau
2
UPS, LCPQ (Laboratoire de Chimie et Physique Quantiques), IRSAMC, Université de Toulouse
, 118, Rte de Narbonne, F-31062 Toulouse Cedex, France
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Daniel Maynau;
Daniel Maynau
1
CNRS, UPS, LCPQ (Laboratoire de Chimie et Physique Quantiques), IRSAMC
, 118, Rte de Narbonne, F-31062 Toulouse Cedex, France
2
UPS, LCPQ (Laboratoire de Chimie et Physique Quantiques), IRSAMC, Université de Toulouse
, 118, Rte de Narbonne, F-31062 Toulouse Cedex, France
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Valérie Brenner
Valérie Brenner
3
Laboratoire Interactions, Dynamiques et Lasers, LIDYL, CEA, CNRS, Université Paris-Saclay
, 91191 Gif-sur-Yvette Cedex, France
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a)Author to whom correspondence should be addressed: benamor@irsamc.ups-tlse.fr
J. Chem. Phys. 148, 184105 (2018)
Article history
Received:
February 14 2018
Accepted:
April 10 2018
Citation
Nadia Ben Amor, Sophie Hoyau, Daniel Maynau, Valérie Brenner; Low-lying excited states of model proteins: Performances of the CC2 method versus multireference methods. J. Chem. Phys. 14 May 2018; 148 (18): 184105. https://doi.org/10.1063/1.5025942
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