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  Home > JCE Print > Journal of Chemical Education > Issues > 2006  > August  >
Research: Science and Education
A Novel Exploration of the Hartree–Fock Homolytic Bond Dissociation Problem in the Hydrogen Molecule by Means of Electron Localization Measures
Eduard Matito, Miquel Duran, and Miquel Solà
Institut de Química, Computacional and Departament de Química, Universitat de Girona, 17071 Girona, Catalonia, Spain
Cover
August 2006
Vol. 83 No. 8
p. 1243
Abstract
Most introductory quantum chemistry textbooks discuss the well-known problem of the inappropriate description given by the restricted Hartree–Fock (HF) method of the homolytic bond dissociation. This weakness of the restricted HF method is generally addressed by analyzing the difference between the energies at long internuclear distances obtained with the configuration interaction (CI) and HF methods, which requires an exhaustive understanding of the methodology. In this article we provide a new insight into this subject using localization and delocalization indices defined in the framework of the atoms-in-molecules theory to analyze the homolytic bond dissociation in the hydrogen molecule. It is shown that the restricted HF requirement of molecular orbitals to be occupied simultaneously by a couple of electrons with different spin is responsible for localization to hold on the same value while dissociation is happening, thus reflecting the well-known deficiency of the HF method to deal with bond dissociation. On the other hand, when the CI method is used, the localizability of the electrons in the system turns into the intuitive scheme expected for homolytic bond dissociation.
Supplement
The derivations for the LI and DI approximations given in eqs. 16 and 17 are available.
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*  Citation
 Matito, Eduard; Duran, Miquel; Solà, Miquel. J. Chem. Educ. 2006 83 1243.
*  Keywords
 Computational Chemistry; Computer-Based Learning; Graduate Education / Research; Learning Theories; Lewis Structures; Molecular Properties / Structure; Physical Chemistry; Quantum Chemistry; Textbooks / Reference Books; Theoretical Chemistry; Upper-Division Undergraduate
*  History
 Created:
Last Updated:		 6/21/2006
6/30/2006
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