Si-O Bonded Interactions in Silicate Crystals and Molecules:  A Comparison

Journal Article · Wed Nov 01 00:00:00 EST 2006 · Journal of Physical Chemistry. A, Molecules, Spectroscopy, Kinetics, Environment, and General Theory

DOI:https://doi.org/10.1021/jp063881q· OSTI ID:1152424

Gibbs, G. V.; Jayatilaka, D.; Spackman, M. A.; Cox, D. F.; Rosso, K. M.

Bond critical point, local kinetic energy density, G(r_c), and local potential energy density, V(r_c), properties of the electron density distributions, ρ(r), calculated for silicates such as quartz and gas-phase molecules such as disiloxane are similar, indicating that the forces that govern the Si-O bonded interactions in silica are short-ranged and molecular-like. Using the G(r_c)/ρ(r_c) ratio as a measure of bond character, the ratio increases as the Si-O bond length, the local electronic energy density, H(r_c) = G(r_c) + V(r_c), and the coordination number of the Si atom decrease and as the accumulation of the electron density at the bond critical point, ρ(r_c), and the Laplacian, ∇²ρ(r_c), increase. The G(r_c)/ρ(r_c) and H(r_c)/ρ(r_c) ratios categorize the bonded interaction as observed for other second row atom M-O bonds into discrete categories with the covalent character of each of the M-O bonds increasing with the H(r_c)/ρ(r_c) ratio. The character of the bond is examined in terms of the large net atomic charges conferred on the Si atoms comprising disiloxane, stishovite, quartz, and forsterite and the domains of localized electron density along the Si-O bond vectors and on the reflex side of the Si-O-Si angle together with the close similarity of the Si-O bonded interactions observed for a variety of hydroxyacid silicate molecules and a large number of silicate crystals. Finally, the bond critical point and local energy density properties of the electron density distribution indicate that the bond is an intermediate interaction between Al-O and P-O bonded interactions rather than being a closed-shell or a shared interaction.

• Research Organization: Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Environmental Molecular Sciences Lab. (EMSL)
• Sponsoring Organization: USDOE Office of Science (SC), Biological and Environmental Research (BER)
• OSTI ID: 1152424
• Journal Information: Journal of Physical Chemistry. A, Molecules, Spectroscopy, Kinetics, Environment, and General Theory, Vol. 110, Issue 46; ISSN 1089-5639
• Publisher: American Chemical Society
• Country of Publication: United States
• Language: English