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Assessment of Density Functional Methods for Obtaining Geometries at Conical Intersections in Organic Molecules.

Filatov M - J Chem Theory Comput (2013)

Bottom Line: The minimum energy conical intersections have been optimized for several molecular systems, which are widely used as paradigmatic models of photochemical rearrangements and models of biological chromophores.The results of the calculations are analyzed using the sign-change theorem of Longuet-Higgins and a method of elementary reaction coordinates of Haas et al.Overall, the BH&HLYP density functional yields the best results for the conical intersection geometries and energetics.

View Article: PubMed Central - PubMed

Affiliation: Institut für Physikalische und Theoretische Chemie, Universität Bonn , Beringstr. 4, D-53115 Bonn, Germany.

ABSTRACT
A number of commonly available density functionals have been tested for their ability to describe the energetics and the geometry at conical intersections in connection with the spin-restricted ensemble referenced Kohn-Sham (REKS) method. The minimum energy conical intersections have been optimized for several molecular systems, which are widely used as paradigmatic models of photochemical rearrangements and models of biological chromophores. The results of the calculations are analyzed using the sign-change theorem of Longuet-Higgins and a method of elementary reaction coordinates of Haas et al. The latter approach helps to elucidate the differences between the geometries at conical intersections as predicted by the multireference wave function ab initio methods and by the density functional methods. Overall, the BH&HLYP density functional yields the best results for the conical intersection geometries and energetics.

No MeSH data available.


Key geometric parameters of ethylidene MECIpoints optimized forC2H4 with the use of different density functionals.
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fig7: Key geometric parameters of ethylidene MECIpoints optimized forC2H4 with the use of different density functionals.

Mentions: This observation also holds truefor the ethylidene MECI in ethylene.Geometries of the ethylidene MECI structures obtained with the useof density functionals are shown in Figure 7. The M06-2X density functional yields a geometry for this CI thatdeviates strongly from the reference geometry. The distortion is mostlikely caused by a much too strong attraction between the C–Hbonds on the opposite ends of the molecule. M06-2X was parametrizedto include some medium range dispersion interaction in the groundstates of noncovalently bound systems.51 It is therefore desirable to develop density functionals which wouldbe capable of describing the dispersion interactions in the excitedstates of molecules as well.


Assessment of Density Functional Methods for Obtaining Geometries at Conical Intersections in Organic Molecules.

Filatov M - J Chem Theory Comput (2013)

Key geometric parameters of ethylidene MECIpoints optimized forC2H4 with the use of different density functionals.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3794441&req=5

fig7: Key geometric parameters of ethylidene MECIpoints optimized forC2H4 with the use of different density functionals.
Mentions: This observation also holds truefor the ethylidene MECI in ethylene.Geometries of the ethylidene MECI structures obtained with the useof density functionals are shown in Figure 7. The M06-2X density functional yields a geometry for this CI thatdeviates strongly from the reference geometry. The distortion is mostlikely caused by a much too strong attraction between the C–Hbonds on the opposite ends of the molecule. M06-2X was parametrizedto include some medium range dispersion interaction in the groundstates of noncovalently bound systems.51 It is therefore desirable to develop density functionals which wouldbe capable of describing the dispersion interactions in the excitedstates of molecules as well.

Bottom Line: The minimum energy conical intersections have been optimized for several molecular systems, which are widely used as paradigmatic models of photochemical rearrangements and models of biological chromophores.The results of the calculations are analyzed using the sign-change theorem of Longuet-Higgins and a method of elementary reaction coordinates of Haas et al.Overall, the BH&HLYP density functional yields the best results for the conical intersection geometries and energetics.

View Article: PubMed Central - PubMed

Affiliation: Institut für Physikalische und Theoretische Chemie, Universität Bonn , Beringstr. 4, D-53115 Bonn, Germany.

ABSTRACT
A number of commonly available density functionals have been tested for their ability to describe the energetics and the geometry at conical intersections in connection with the spin-restricted ensemble referenced Kohn-Sham (REKS) method. The minimum energy conical intersections have been optimized for several molecular systems, which are widely used as paradigmatic models of photochemical rearrangements and models of biological chromophores. The results of the calculations are analyzed using the sign-change theorem of Longuet-Higgins and a method of elementary reaction coordinates of Haas et al. The latter approach helps to elucidate the differences between the geometries at conical intersections as predicted by the multireference wave function ab initio methods and by the density functional methods. Overall, the BH&HLYP density functional yields the best results for the conical intersection geometries and energetics.

No MeSH data available.