Charge-flow profiles along curvilinear paths: A flexible scheme for the analysis of charge displacement upon intermolecular interactions

The Charge-Displacement (CD) analysis has proven to be a powerful tool for a quantitative characterization of the electron-density flow occurring upon chemical bonding along a suitably chosen interaction axis. In several classes of interesting intermolecular interactions, however, an interaction axis cannot be straightforwardly defined, and the CD analysis loses consistency and usefulness. In this article, we propose a general, flexible reformulation of the CD analysis capable of providing a quantitative view of the charge displacement along custom curvilinear paths. The new scheme naturally reduces to ordinary CD analysis if the path is chosen to be a straight line. An implementation based on a discrete sampling of the electron densities and a Voronoi space partitioning is described and shown in action on two test cases of a metal-carbonyl and a pyridine-ammonia complex.