Journal Article Fukui function atoms in molecules chemical reactivity conceptual density functional theory general‐purpose reactivity indicator radical addition reactions AIM Heisenberg Equation of motion Kullback-Leibler QTAIM Quantum Theory of Atoms in Molecules Research Support, U.S. Gov't, Non-P.H.S. atomic properties conceptual DFT density functional theory ehrenfest force electron density hirshfeld partitioning information-theoretic fitting least squares linear response function probabilty density fitting quantum theory of atoms in molecules radical CH functionalization radical chemistry relativity scalar relativistic zeroth-order regular approximation softness kernel stockholder population analysis