A model of atoms in molecules based on potential acting on one electron in a molecule: I. Partition and atomic charges obtained from ab initio calculations

Chemists have long searched for descriptions of atoms in molecules. A new model of atoms in molecules (AIM) is advanced, which shows that the atomic realm in a molecule is a subspace governed by its nucleus as a 3D attractor of the electron force lines defined by the negative gradient of the potential acting on one electron in molecule (PAEM), which is represented and calculated via ab initio methods. In this article, we demonstrate how the molecular space is partitioned into atomic realms and how the atomic charges in this PAEMAIM method are worked out. Atomic charges for more than 210 molecules and clusters were determined by integrating the electron density over individual atomic realms with our program. Notably, such atomic charges are nearly independent of the basis set used. The atomic charges obtained by PAEMAIM have good correlations with the Allen and Pauling electronegativity differences. Furthermore, charge transfer in prototype hydrogen bonding clusters, (H2O)2, H2O‐HF, and (HF)2, was investigated with this method. In brief, the atomic charges calculated by PAEMAIM are reasonable and significant for further exploration and practical applications. A new model of atoms in molecules based on potential acting on one electron in a molecule provides a new tool for partitioning molecules into nonfuzzy atomic realms. These are formed by the electronic force lines controlled by 3D nuclear attractors and separated by 2D surfaces of electronic force lines terminating at respective bond critical points. Computed atomic charges show the least dependence on the choice of basis sets used.