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Comparative study of multireference perturbative theories for ground and excited states
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10.1063/1.3265769
/content/aip/journal/jcp/131/20/10.1063/1.3265769
http://aip.metastore.ingenta.com/content/aip/journal/jcp/131/20/10.1063/1.3265769

Figures

Image of FIG. 1.
FIG. 1.

Energy difference curve (with respect to FCI) of the LiH bond dissociation process computed by second-order MR PT methods, in DZP basis set (Ref. 41). Reference function underlying all PT approximations is a CAS(2,5) function. Orbitals are optimized for the average of the ground and first excited singlet state.

Image of FIG. 2.
FIG. 2.

Energy difference curve (with respect to FCI) of the first excited singlet state of LiH as a function of the internuclear distance. Basis set and methods applied agree with those in Fig. 1.

Image of FIG. 3.
FIG. 3.

Energy difference curve (with respect to FCI) of the ground state of the system in valence double zeta basis set, obtained by a CAS(4,4) model and second-order MR PT approximations based on it. Molecular orbitals are optimized at the CAS level, for the average of the ground and first excited singlet state. See text for geometries.

Image of FIG. 4.
FIG. 4.

Energy difference curve (with respect to FCI) of the second lowest singlet state of the system. Basis set, methods, and geometries applied agree with those in Fig. 3.

Image of FIG. 5.
FIG. 5.

Total energy of the ethylene molecule as a function of the torsional angle of the two moieties, computed by second-order MR PT methods, in DZP basis set (Ref. 41). Reference function underlying all PT approximations is a CAS(2,2) function. State specific multiconfigurational CC method including up to triple excitations with 2 particle and two hole active indices is shown as benchmark.

Image of FIG. 6.
FIG. 6.

Energy difference curve (with respect to planar arrangement) of the ethylene torsion process, shown at around the top of the barrier. See caption of Fig. 5 for more details.

Image of FIG. 7.
FIG. 7.

Total energy of the ethylene molecule as a function of the torsional angle of the two moieties. Core orbitals are kept frozen. Apart from MRCISDTQ, methods and basis set agree with those in Fig. 5 Multireference CI up to quadruple excitations (MRCISDTQ) is shown as another, highly accurate curve in addition to to .

Image of FIG. 8.
FIG. 8.

Energy difference curve (with respect to planar arrangement) of the ethylene torsion process, shown at around the top of the barrier. See caption of Fig. 7 for more details.

Tables

Generic image for table
Table I.

Nonparallelity error (difference of largest and smallest deviation from full-CI) of various perturbation theories in milliHartree.

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/content/aip/journal/jcp/131/20/10.1063/1.3265769
2009-11-25
2014-04-21
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Comparative study of multireference perturbative theories for ground and excited states
http://aip.metastore.ingenta.com/content/aip/journal/jcp/131/20/10.1063/1.3265769
10.1063/1.3265769
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