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Variational localized-site cluster expansions. II. Trees and near trees Klein, D.J. García Bach, Ma. de los Ángeles Termodinàmica estadística Teoria de grafs Arbres Statistical thermodynamics Graph theory Trees Cluster expanded wavefunctions involving localized‐site states and only pair excitations between nearest neighbor sites are considered. In the case that the bonds connecting these nearest neighbor sites form a tree graph (without rings), exact matrix element formulas are obtained in terms of the inverse of a modified type of topological matrix associated with this tree graph. The treatment of some near‐tree cases, without any touching rings, is also discussed. 2023-06-23T16:45:59Z 2023-06-23T16:45:59Z 1976 2023-06-23T16:45:59Z info:eu-repo/semantics/article info:eu-repo/semantics/publishedVersion 0021-9606 https://hdl.handle.net/2445/199749 003446 eng Reproducció del document publicat a: https://doi.org/10.1063/1.432144 Journal of Chemical Physics, 1976, vol. 64, p. 4873-4877 https://doi.org/10.1063/1.432144 (c) American Institute of Physics (AIP), 1976 info:eu-repo/semantics/openAccess 5 p. application/pdf American Institute of Physics (AIP) Articles publicats en revistes (Física de la Matèria Condensada)