Chemical reactivity in density functional theory: the N-differentiability problem

Abstract

Making use of the definitions given by Berkowitz and Parr for hardness and softness quantities, and the properties of the static linear response function, it is shown that it is not necessary to invoke N-differentiability in order to calculate electronegativities, hardnesses and Fukui functions. This approach provides strong support for the description of chemical reactivity based on density functional theory.