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On the performance and parameter problems of approximate molecular orbital theory, with comparative calculations on the carbon monoxide molecule
Author(s) -
Roby Keith R.,
Ǧlu Oktay Sinano
Publication year - 2009
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.560030725
Subject(s) - molecular orbital , molecular orbital theory , slater type orbital , linear combination of atomic orbitals , atomic orbital , chemistry , basis set , atomic physics , electronic correlation , molecular orbital diagram , molecular physics , computational chemistry , electron , molecule , quantum mechanics , density functional theory , physics , organic chemistry
A theoretically correct breakdown of the molecular wave function into Hartree‐Fock and electron correlation components leads to the identification of four parameter problems important in approximate molecular orbital theory. The effects of the intramolecular environment on isolated atom optimized atomic orbitals, the deviation of simple basis atomic orbitals from true Hartree‐Fock atomic orbitals, differences made in transforming to a basis of orthogonal atomic orbitals, and the estimation of the molecular electron correlation energy are considered. Order‐of‐magnitude corrections are suggested for each of these problems. Comparative NDDO all electron calculations on the carbon monoxide molecule illustrate the improved results obtained. Additional information on the performance of methods more approximate than the NDDO all electron one indicates that quantitatively they leave much to be desired.