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

Abstract

Bond critical point, local kinetic energy density, G(rc), and local potential energy density, V(rc), properties of the electron density distributions, rho(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(rc)/rho(rc) ratio as a measure of bond character, the ratio increases as the Si-O bond length, the local electronic energy density, H(rc)= G(rc) + V(rc), and the coordination number of the Si atom decrease and as the accumulation of the electron density at the bond critical point, rho(rc), and the Laplacian, inverted Delta2 rho(rc), increase. The G(rc)/rho(rc) and H(rc)/rho(rc) 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(rc)/rho(rc) 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. 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.

Ab initio based polarizable force field generation and application to liquid silica and magnesia

“…In Table II, we compare the lattice parameters, Si-O bond length, and the Si-O-Si angle to analytical values. 40,41 The force field overestimates the equilibrium volume; the lattice parameters are too large by on average 2.8%. In an MD simulation at 300 K over 10 ns, our force field stabilized the alpha-quartz structure.…”

Surface functionalization of magnetic nanoparticles via palladium‐catalyzed Diels‐Alder approach

“…Three of them have nitrogen and oxygen heteroatoms in their structures. So, most probably the interaction between silicon atoms, present in the SiO 2 network as shell, and available heteroatoms exist in the structure of furfural, melamine and phenylallylidene aminophenol, lead them to prefer endo adduct . In contrast, it does not matter for anthracene and cyclohexadiene to prefer exo or endo orientation due to the lack of silicon‐heteroatom interaction (Figure ).…”

Molecular orbital model of the influence of interaction between O2 and aluminosilicate sites on the triplet–singlet energy gap and reactivity

“…We selected relatively small cluster models in order to include electron correlation and performing geometry optimization at reasonable computer times. They appear to be appropriate for the calculation of association properties in previous [30] and even very recent works [48][49][50]. Obviously, the cavity can affect the diffusion and accommodation of adsorbed molecules and this could be a shortcoming of this model.…”