LAUSR

AbstractA novel approach to the response theory for the Kohn–Sham formalism is presented, and it shows that the linear responses of the electron density to changes in the number of electrons and in the external potential connected and they can be computed simultaneously. This procedure also applies to other quantities related to the density response kernel, such as the Hessian matrix, the dipole polarizability, and the perturbed density. Expressions for the directional Fukui functions go beyond the frontier orbital approximation, showing differential relaxation effects for electron-releasing and electron-withdrawing processes. Even for the simplest approximation, when only the frontier orbitals are included in the sum-over-states, the relaxation effects are different in each direction.