Relationships between atomic chemical potentials, electrostatic potentials, and covalent radii

摘要

The chemical potential mgr; of a manyhyphen;electron system equals its total electrostatic potentialV(r) at any pointrat which dgr;T/dgr;rgr; =minus;dgr;(egr;X+egr;C)/dgr;rgr;, where rgr; is the electronic density andT, egr;X, and egr;Care, respectively, the kinetic, exchange, and correlation energy functionals. The Thomasndash;Fermindash;Dirac theory predicts that this relationship is satisfied at all points at which rgr;=0.008thinsp;72. This prediction has been tested for 25 groundhyphen;state atoms and has been found to give unsatisfactory results; the values ofV(r) at the points in question are not in good agreement with mgr;, as approximated by minus;0.5(I+A),IandAbeing the atomic ionization potentials and electron affinities. However, an investigation of the radial distancesrmgr;at whichV(r) does equal mgr; shows that these are very close to the standard covalent radii of the atoms. (This supports an early electronegativity formulation by Gordy.) It is also shown that there is a very good correlation between mgr; andVQ, the electrostatic potential created atrmgr;by the nuclear and electronic charge within this radial distance from the nucleus.VQis therefore a direct measure of the electronic rearranging power of the atom in the formation of chemical bonds. This further demonstrates the special significance ofrmgr;with regard to the bonding properties of the atom.