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Variational localized‐site cluster expansions. VI. General theory revisited
Author(s) -
Klein D. J.
Publication year - 1977
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.560120204
Subject(s) - simple (philosophy) , cluster expansion , cluster (spacecraft) , wave function , variety (cybernetics) , coupled cluster , extension (predicate logic) , function (biology) , general theory , statistical physics , matrix (chemical analysis) , mathematics , expression (computer science) , physics , computer science , theoretical physics , quantum mechanics , chemistry , statistics , philosophy , chromatography , evolutionary biology , molecule , biology , programming language , epistemology
A general and systematic localized‐site cluster expansion is described. It provides simple physically appealing and computationally feasible wave function ansätze , as well as, via extension of the cluster expansion, a unique expression for general, possibly exact, wave functions. We show that a variety of matrix element evaluation techniques are available and that they are sometimes exact though relatively simple. These techniques often proceed in terms of computational time proportional to the number of different types of sites, rather than their total number. Thus it seems we have a new and viable many‐body theory, which is expected to be most accurate and most readily implementable when a physical picture with slightly perturbed localized sites is relevant.