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HF–HL method: Combination of Hartree–Fock and Heitler–London approximations



Comparison of Hartree–Fock (HF) and Heitler–London (HL) ground-state computations for H2, LiH, Li2, BH, HF, and F2 leads to an approach that is a variational combination of the two approximations. This new HF–HL ab initio method is implemented at three levels. The first level variationally optimizes the linear combination of traditional HF and HL functions. It correctly predicts both molecular formation and dissociation for the above molecules, features not consistently found in either the HF or the HL approximations. The second level introduces valence correlation and the third level inner shells correlation, adapting standard multi-configuration techniques to the HF–HL function. The procedure for both levels has been preliminarily applied to LiH and Li2 and found to yield very encouraging results when compared to experimental data. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005

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