On the use of Bader’s atomic charges for the evaluation of charge transfers between ground and excited states

[Display omitted] ► Transition dipole moments evaluated using QTAIM. ► Necessity to include both atomic charges and atomic dipoles. ► Separation of inter-atomic charge transfers and intra-atomic ones (polarization). In this letter, we assess to what extent Bader’s atomic charges are appropriate to quantify charge transfers in photon absorption processes. We actually underline the fundamental role of the atomic dipole moment, which is indeed involved in the change of the electron density polarization upon excitation. This contribution cannot be neglected and enables to reproduce the total transition dipole moments with full accuracy if an enough tight integration quadrature is used. As this scheme allows separating intra-atomic density reorganization and interatomic charge transfer, it is well suited to describe through-space charge-transfer excitations.