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Some developments in the spin‐extended Hartree‐Fock method
Author(s) -
Mestechkin M. M.
Publication year - 1973
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.560070303
Subject(s) - spin (aerodynamics) , eigenvalues and eigenvectors , atomic orbital , basis (linear algebra) , hartree–fock method , density matrix , slater determinant , matrix (chemical analysis) , projection (relational algebra) , physics , quantum mechanics , chemistry , electron , mathematics , thermodynamics , geometry , chromatography , algorithm , quantum
All the second‐order density matrix spin components for the spin‐extended Hartree‐Fock method are obtained. The coefficients in the final formulae are only ω sM , ω sM ±1 , ω sM ±2 , where ω sM are the weights of pure states of spin s in the initial unprojected determinant with spin projection M . The eigenvalue problem for the best electron density natural orbitals in the spin‐extended method is formulated. All the second‐order transition density matrix spin components between pure spin basis functions built of orthogonal orbitals and distinguished by different core choice are also found. This basis may be used on CI calculations.