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Theoretica chimica acta

, Volume 5, Issue 4, pp 346–368 | Cite as

Comparisons of the Hückel and Pariser-Parr-Pople-type MO methods: Closed forms for SCF charge distributions and bond orders

  • S. Ehrenson
Commentationes

Abstract

Analysis of the similarities and differences among the Hückel and Pariser-Parr-Pople-type methods is extended mainly through development for special molecular cases of closed form expressions for the self-consistent wavefunctions. By means of these expressions the various contributions of terms in the Hamiltonian to charge densities, bond orders and other related quantities may be compared term-by-term among the methods. Results on several direct observables, e.g. ionization potentials, electron affinities, bond lengths are similarly dissected. Simplified procedures for generation of the self-consistent charge densities and bond orders from their zeroth-order counterparts in the PPP method are detailed.

Keywords

Physical Chemistry Inorganic Chemistry Organic Chemistry Bond Length Charge Density 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Zusammenfassung

Für Moleküle spezieller Symmetrie werden geschlossene Ausdrücke für ‘self-consistent’Wellenfunktionen entwickelt. Aus ihnen lassen sich einfache explizite Reihenentwicklungen für Größen wie Ladungsdichte, Bindungsordnung, Ionisierungsenergie usw. erhalten. Die Verwandtschaft verschiedener MO-Methoden (HMO, ω-HMO, PPP) kann so eingehend analysiert werden.

Résumé

L'analyse des similitudes et des différences entre les méthodes de Hückel et celles du type Pariser-Parr-Pople est élargie essentiellement par l'établissement d'expressions implicites pour les fonctions d'onde self-consistantes dans des cas moléculaires particuliers. A l'aide de ces expressions les contributions des différents termes de l'Hamiltonien aux densités de charges, indices de liaison et autres quantités qui leurs sont liées, peuvent être comparées terme à terme entre les méthodes. Les résultats concernant différentes observables directes comme les potentiels d'ionisation, les affinités électroniques et les longueurs de liaison sont analysés de la même manière. Des procédés simplifiés, qui permettent d'engendrer dans la méthode PariserParr-Pople les densités de charge et les indices de liaison self-consistants à partir des quantités correspondantes à l'ordre zéro, sont exposés.

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Copyright information

© Springer-Verlag 1966

Authors and Affiliations

  • S. Ehrenson
    • 1
  1. 1.Chemistry DepartmentBrookhaven National LaboratoryUpton

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