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Spin‐free approach for evaluation of electronic matrix elements using character operators of ℒ N
Author(s) -
FriisJensen Britt,
Rettrup Sten
Publication year - 1996
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/(sici)1097-461x(1996)60:5<983::aid-qua4>3.0.co;2-t
Subject(s) - orthonormal basis , eigenfunction , character (mathematics) , hamiltonian (control theory) , basis (linear algebra) , spin (aerodynamics) , matrix (chemical analysis) , quantum mechanics , hamiltonian matrix , valence bond theory , valence (chemistry) , basis function , electron configuration , physics , computational chemistry , theoretical physics , chemistry , mathematics , electron , atomic orbital , eigenvalues and eigenvectors , symmetric matrix , thermodynamics , geometry , chromatography , mathematical optimization
A spin‐free method is presented for evaluating electronic matrix elements over a spin‐independent many‐electron Hamiltonian. The spin‐adapted basis of configuration state functions is obtained using a nonorthogonal spin basis consisting of projected spin eigenfunctions. The general expressions for the matrix elements are given explicitly, and it is demonstrated how the matrix elements may be obtained simply from the knowledge of the irreducible characters of the permutation group ℒ N . The presented formulas are very general and may be applied in connection with both spin‐coupled valence bond studies and in conventional configuration interaction (CI) methods based on an orthonormal orbital basis. © 1996 John Wiley & Sons, Inc.