Transferable pseudoclassical electrons for aufbau of atomic ions

Abstract

Generalizing the LEWIS reactive force field from electron pairs to single electrons, we present LEWIS• in which explicit valence electrons interact with each other and with nuclear cores via pairwise interactions. The valence electrons are independently mobile particles, following classical equations of motion according to potentials modified from Coulombic as required to capture quantum characteristics. As proof of principle, the aufbau of atomic ions is described for diverse main group elements from the first three rows of the periodic table, using a single potential for interactions between electrons of like spin and another for electrons of unlike spin. The electrons of each spin are found to distribute themselves in a fashion akin to the major lobes of the hybrid atomic orbitals, suggesting a pointillist description of the electron density. The broader validity of the LEWIS• force field is illustrated by predicting the vibrational frequencies of diatomic and triatomic hydrogen species. © 2014 Wiley Periodicals, Inc. The development of force fields with explicit electrons is motivated by the computational difficulty of quantum simulations of chemical reactions. This study demonstrates that context-independent, pairwise interactions can describe the aufbau of diverse elements, including Hund's rule, the energies of electron transfers between atoms, and the spatial disposition of electrons according to orbital hybridization. In effect, LEWIS• constitutes a pointillist approach to density functional theory, providing an efficient route to reactive simulations. Copyright © 2014 Wiley Periodicals, Inc.