Distributed Gaussian orbitals for molecular calculations:application to simple systems
Stefano Battaglia, David Bouet, Alexis Lecoq, Stefano Evangelisti, NoeliaFaginas Lago, Thierry Leininger, Andrea Lombardi
ABSTRACT
In this article, the possible use of sets of basis functions alternative with respectto the usual atom-centred orbitals sets is considered. The orbitals describing theinner part of the wavefunction (i.e. the region close to each nucleus) are still atomicGaussian functions: tight Gaussian orbitals having different angular momenta andlarge exponential coefficients, centred on each nucleus. On the other hand, the outerpart of the wavefunction is described through a set ofs-type distributed Gaussianorbitals:s-type Gaussians having aunique fixed exponent, and whosefixedcentresare placed on auniform mesh of pointsevenly distributed in the region surroundingall the atoms of the molecule. The resulting basis sets are applied to various one-electron systems in order to assess the capability to describe different types of one-electron wavefunctions. Moreover, the hydrogen atom and the dihydrogen cation,for which accurate solutions exist, are also considered for comparison, to assess theeffectiveness of the proposed approach. Preliminary results concerning the treatmentof electron correlation, necessary for a quantitatively correct description of many-electron atoms and molecules, are also presented.
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