Extended Hiickel theory 438 Subject

This process and the related questions of the electronic structure of substituted methylenes (12), (13) were the subject of careful analysis by Extended Hiickel Theory (hence-... 

Abstract A historical view demystifies the subject. The focus is strongly on chemistry. The application of quantum mechanics (QM) to computational chemistry is shown by explaining the Schrodinger equation and showing how this equation led to the simple Hiickel method, from which the extended Hiickel method followed. This sets the stage well for ab initio theory, in Chapter 5. 

In concluding this section, we note that the physical arguments here are involved for a subject (the Debye-Hiickel theory) that is at once so basic, so firmly established, and so limited in physical scope to molecular science. The traditional presentation (e.g. Hill, 1986 Lewis etal., 1961, see Section 23) is fine as far as it goes but gives little support for extensions of the theory, and little perspective on the basic issues of the theory of solutions. The physical discussion here is different from the most conventional presentations, does give further perspective on the role of the PDT, but is too extended without other pieces of the theory of solutions in place. All these points surely mean that this is one area where the beautiful but more esoteric theoretical tools (Lebowitz et al, 1965) of professional theory of liquids are relevant to a simple view of the problem. This topic is taken up again after the developments of Section 6.1 see Eq. (6.28), p. 132. 

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