Success of the PCILO method and failure of the CNDO/2 method for predicting conformations in some conjugated systems

doi:10.1016/0009-2614(73)87065-4

Chemical Physics Letters

Volume 19, Issue 1, 1973, Pages 73-75

https://doi.org/10.1016/0009-2614(73)87065-4 Get rights and content

Abstract

Contrary to the CNDO/2 method, the PCILO method accounts correctly for the preferred conformation of glyoxal, butadiene, benzaldehyde, benzoic acid, biphenyl and 2,2′-difluorobiphenyl.

References (20)

O. Gropen et al.
Chem. Phys. Letters
(1971)
F.A. Miller et al.
Spectrochim. Acta
(1967)
K. Kuchitsu et al.
J. Mol. Struct.
(196768)
J. Paldus et al.
Can. J. Phys.
(1967)
G.N. Currie et al.
Can. J. Phys.
(1971)
J.R. Durig et al.
J. Phys. Chem.
(1972)
J.G. Aston et al.
J. Chem. Phys.
(1946)
R.K. Kakar et al.
J. Chem. Phys.
(1970)
Y.G. Smeyers, private...
G.A. Sim et al.
Acta Cryst.
(1955)

There are more references available in the full text version of this article.

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Furthermore, static polarizability, polarizability anisotropy, first static hyperpolarizability and HOMO–LUMO molecular orbital energy difference were calculated at the stationary point on the energy surface.
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Success of the PCILO method and failure of the CNDO/2 method for predicting conformations in some conjugated systems

Abstract

Chem. Phys. Letters

Spectrochim. Acta

J. Mol. Struct.

Can. J. Phys.

Can. J. Phys.

J. Phys. Chem.

J. Chem. Phys.

J. Chem. Phys.

Acta Cryst.