ISSN:
0020-7608
Keywords:
Computational Chemistry and Molecular Modeling
;
Atomic, Molecular and Optical Physics
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
An important role of model Hamiltonians for quantum mechanical description of the molecular electronic structure is discussed, and the effectiveness of the Pariser-Parr-Pople (PPP) model in calculations of molecular properties, in building of other models, and in various theoretical exploits is emphasized. The striking simplicity and transparence, yet remarkable reality and credibility, of this model is illustrated by applying the basic coupled cluster approach (CCD), as well as its extension approximating triexcited clusters (CCSDT-1), to the PPP model of benzene. The explicit final equations are obtained using the symbolic computation language MAPLE for both the orthogonal and nonorthogonal versions of the CC formalism. These equations are presented using the interface between MAPLE and the typesetting language TROFF. In this way, the explicit CC equations are obtained in terms of basic parameters of the model, starting from the CI description and showing their equivalence with those obtained via diagrammatic techniques. A new insight into the structure of CC equations at various levels of approximation is thus achieved and a useful model for electron correlation is provided.
Additional Material:
9 Tab.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/qua.560380606
Permalink
