Fukui function

In computational chemistry, the Fukui function or frontier function is a function that describes the electron density in a frontier orbital, as a result of a small change in the total number of electrons. The condensed Fukui function or condensed reactivity indicator is the same idea, but applied to an atom within a molecule, rather than a point in three-dimensional space.

The Fukui function allows one to predict, using density functional theory, where the most electrophilic and nucleophilic sites of a molecule are.