Average local ionization energy: A review

The average local ionization energy [`I] ( r ) overline {hbox{I}} left( {mathbf{r}} right) is the energy necessary to remove an electron from the point r in the space of a system. Its lowest values reveal the locations of the least tightly-held electrons, and thus the favored sites for reaction with electrophiles or radicals. In this paper, we review the definition of [`I] ( r ) overline {hbox{I}} left( {mathbf{r}} right) and some of its key properties. Apart from its relevance to reactive behavior, [`I] ( r ) overline {hbox{I}} left( {mathbf{r}} right) has an important role in several fundamental areas, including atomic shell structure, electronegativity and local polarizability and hardness. All of these aspects of [`I] ( r ) overline {hbox{I}} left( {mathbf{r}} right) are discussed.