Gradient Bundle Analysis of Electric Field Induced Changes in Electron Charge Density

Abstract

Applying an electric field (EF) to a molecule is known to induce rearrangement of its electron charge density, ρ(r). Previous experimental and computational studies have investigated effects on reactivity by using homogeneous EFs with specific magnitudes and directions to control reaction rates and product selectivity. To best incorporate EFs into experimental design, a more fundamental understanding of how EFs rearrange ρ(r) is necessary. To gain this understanding, we first applied EFs to a set of 10 diatomic and linear triatomic molecules with various constraints on the molecules to determine the importance of rotation and altering bond lengths on bond energies. In order to capture the subtle changes in ρ(r) known to occur from EFs, an extension of the quantum theory of atoms in molecules called gradient bundle (GB) analysis was employed, allowing for quantification of the redistribution of ρ(r) within atomic basins. This allowed us to calculate GB-condensed EF-induced densities using conceptual density functional theory. Results were interpreted considering relationships between the GB-condensed EF-induced densities and properties including bond strength, bond length, polarity, polarizability, and frontier molecular orbitals (FMOs).