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Exponential transformation of molecular orbitals. II. General formulation for UHF calculations and application to diatomics and molecular fragments
Author(s) -
Bruceñta A.,
Vermeulin P.,
Archirel P.,
Berthier G.
Publication year - 1981
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.560200612
Subject(s) - molecular orbital , chemistry , atomic orbital , exponential function , molecular orbital theory , valence bond theory , spins , wave function , ultra high frequency , valence (chemistry) , linear combination of atomic orbitals , slater type orbital , quadratic equation , computational chemistry , transformation (genetics) , open shell , atomic physics , physics , quantum mechanics , molecule , mathematical analysis , mathematics , geometry , telecommunications , computer science , gene , condensed matter physics , electron , biochemistry
The exponential transformation of the molecular orbitals, that has been previously used to achieve a process with a convergence of quadratic quality in SCF closed‐shell calculations [J. Chem. Phys. 72 , 1452 (1980)] has been extended to UHF determinantal wave functions built from different orbitals for different spins. Explicit formulas are given for the first and second derivatives of the energy to be varied. The method is illustrated by UHF calculations for systems described as standard singlets (Li 2 and F 2 ) or triplets (NH) at the RHF approximation level, as well as for CH, CH 2 , CH 3 molecular fragments in their valence states.