Atomic partitioning of molecular electrostatic potentials

The theory of atoms in molecules (AIM) defines bounded atomic fragments in real space that generate transferable atomic properties. As part of a progr am that investigates the topological partitioning of electromagnetic proper ties based on the electron density, we have calculated the exact atomic ele ctrostatic potential (AEP) of an AIM atom in a molecule. Second we expand t his atomic electrostatic potential in terms of AIM electrostatic multipole moments based on spherical tensors. We prove that the convergence of this e xpansion is faster than previously assumed, even for complicated atomic sha pes.