Bond Length and Local Energy Density Property Connections for Non-Transition-Metal Oxide-Bonded Interactions

• Published in: The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory Molecules, spectroscopy, kinetics, environment, & general theory, 2006-11, Vol.110 (44), p.12259-12266
• Main Authors: Gibbs, G. V, Spackman, M. A, Jayatilaka, D, Rosso, K. M, Cox, D. F
• Format: Article
• Language: English
• Subjects: Kinetics; Metals - chemistry; Oxides - chemistry; Static Electricity; Thermodynamics
• ISSN: 1089-5639; 1520-5215
• DOI: 10.1021/jp062992m

For a variety of molecules and earth materials, the theoretical local kinetic energy density, G(r c), increases and the local potential energy density, V(r c), decreases as the M−O bond lengths (M = first- and second-row metal atoms bonded to O) decrease and the electron density, ρ(r c), accumulates at the bond critical points, r c. Despite the claim that the local kinetic energy density per electronic charge, G(r c)/ρ(r c), classifies bonded interactions as shared interactions when less than unity and closed-shell when greater, the ratio was found to increase from 0.5 to 2.5 au as the local electronic energy density, H(r c) = G(r c) + V(r c), decreases and becomes progressively more negative. The ratio appears to be a measure of the character of a given M−O bonded interaction, the greater the ratio, the larger the value of ρ(r c), the smaller the coordination number of the M atom and the more shared the bonded interaction. H(r c)/ρ(r c) versus G(r c)/ρ(r c) scatter diagrams categorize the M−O bonded interactions into domains with the local electronic energy density per electron charge, H(r c)/ρ(r c), tending to decrease as the electronegativity differences for the bonded pairs of atoms decrease. The values of G(r c) and V(r c), estimated with a gradient-corrected electron gas theory expression and the local virial theorem, are in good agreement with theoretical values, particularly for the bonded interactions involving second-row M atoms. The agreement is poorer for shared C−O and N−O bonded interactions.