Enhancement factors in semi-empirical exchange-correlation functionals
Titel:
Enhancement factors in semi-empirical exchange-correlation functionals
Auteur:
Menconi, Giuseppina Tozer, David J.
Verschenen in:
Molecular physics
Paginering:
Jaargang 103 (2005) nr. 17 pagina's 2397-2405
Jaar:
2005-09-10
Inhoud:
It is demonstrated that the shape of the exchange enhancement factor and whether or not a functional satisfies the uniform density scaling condition can both be controlled, to some extent, in semi-empirical functional development. Specifically, this is achieved by varying the spatial weighting in a fit to high-quality exchange-correlation potentials. The observation is used to highlight the correlation between the exchange enhancement factor and the topography of the helium dimer potential energy curve. It is also used to determine a series of functionals that explicitly satisfy the uniform density scaling condition for the considered rs values. A modified version of the well-established Hamprecht-Cohen-Tozer-Handy (HCTH-93) functional is also determined, which satisfies this condition. For the systems considered, enforcing the condition has a relatively small effect on covalent bond lengths, thermochemistry, polarizabilities and shielding constants; it improves the potential energy curve of the helium dimer, due to the associated modification of the exchange enhancement factor.
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