Premium
The Hubbard connection
Author(s) -
Matsen F. A.
Publication year - 1990
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.560370410
Subject(s) - hubbard model , hamiltonian (control theory) , physics , electron , quantum mechanics , valence bond theory , electronic correlation , connection (principal bundle) , condensed matter physics , superconductivity , mathematics , atomic orbital , geometry , mathematical optimization
Hubbard theory is an approximation to the Pariser‐Parr‐Pople theory which presents many of its important features in a relatively simple form. Our Hubbard Hamiltonian employs a single electron ‐ correlation parameter : 0 ⩽ x ≡ U /( t + U ) ⩽ 1, where t is the one‐electron hopping integral (the negative of the Hueckel β), and U is the Hubbard one‐center, two‐electron repulsion parameter. This parameter provides the Hubbard connection between the following: (1) Molecular orbital and valence bond theory (2) The exchange approximation and full CI(3) Conductors and insulators (4) Fermi‐Dirac and Boltzmann statistics (5) Normal and superconductorsWe present Hubbard theory in the freeon (spin‐free) formulation where each N ‐electron state is pictorially represented by a Gel'fand diagram which specifies both the orbital configuration and the multiplicity. The simplicity of the freeon formulation makes the Hubbard connection quite transparent.