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Extended model space, perturbation

Perturbation expansion from an extended model space... [Pg.274]

Because the n-networks of benzenoid hydrocarbons are the classical prototypical example of delocalized bonding, they provide a crucial test for chemical-bonding theories. Here there is revealed a systematic organization for valence-bond views to describe such n-bonding. With an initiation near the ab initio realm a sequence of semiempirical valence-bond models is identified and characterized. The refinement from one model to the next proceeds via either a (perturbative) restriction to a smaller model space or orthogonalization of a suitable natural basis for the model space. The known properties of the models are indicated, and possible methods of solution are mentioned. A great diversity of work is outlined, related, systematized and extended. New research is suggested. [Pg.58]

Neese F, Petrenko T, Ganyushin D, Olbrich G, Coord.Chem.Rev. 251 (2007) 288-327, CAS(6,5) reference space, addopted treshold values for the natural orbital populations (T at), multireference perturbation dieory (Tgei) and reference space (Tpje) selections are 10 , 10 and 10 , respectively. SAOP model functional used extended model cluster with geometry speciefied in Figure 19-2. [Pg.427]

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Extended model

Perturbation model

Perturbative model

Space model

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