Collect. Czech. Chem. Commun. 2003, 68, 2344-2354

Hardness and HOMO-LUMO Gap Probed by the Helium Atom Pushing the Molecular Surface of the First-Row Hydride Molecules

Edyta Małolepsza* and Lucjan Piela

Department of Chemistry, University of Warsaw, 02-093 Warsaw, Pasteura 1, Poland


A molecular surface defined as an isosurface of the valence repulsion energy may be hard or soft with respect to probe penetration. As a probe, the helium atom has been chosen. In addition, the Pauli exclusion principle makes the electronic structure change when the probe pushes the molecule (at a fixed positions of its nuclei). This results in a HOMO-LUMO gap dependence on the probe site on the isosurface. A smaller gap at a given probe position reflects a larger reactivity of the site with respect to the ionic dissociation.

Keywords: Hardness; HOMO-LUMO gap; Molecular surface; Valence repulsion; Ab initio calculations; Hydrides.

References: 17 live references.