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Exact ground state for a Herndon–Simpson model via resonance–theoretic cluster expansion
Author(s) -
Klein D. J.,
Schmalz T. G.
Publication year - 1989
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.560350303
Subject(s) - ansatz , hamiltonian (control theory) , orthonormal basis , cluster expansion , ground state , wave function , range (aeronautics) , function (biology) , mathematical physics , physics , mathematics , statistical physics , quantum mechanics , mathematical optimization , materials science , composite material , evolutionary biology , biology
The Herndon–Simpson model for a particular catacondensed polyphene chain is considered as a nontrivial many‐body Hamiltonian, defined on a space with a basis of orthonormal Kekulé structures. An Explicitly correlated cluster expanded resonance–theoretic wave function is described for this model, and its quality is judged by calculation of the standard deviation for the energy expectation. The quality is found to be high. Indeed, for a particular parameter ratio within the range of experimental interest, the wave function ansatz is found to be exact. This very accurate solution is then used to gauge the quality of the common ansatz with equally weighted Kekulé structures, and it is found to be reasonably good.