The linear response kernel of conceptual DFT as a measure of electron delocalisation

This letter is concerned with the calculation and interpretation of the atom-condensed linear response kernel as defined within conceptual density functional theory. An easily applicable and accurate methodology following from second order perturbation theory is used to analyse a series of cyclohexane and benzene derivatives. We show that the variation of the condensed linear response matrix elements with internuclear distance provides a means to differentiate between inductive, resonance and hyperconjugation effects and conclude that this quantity measures the extent of electron delocalisation.