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Si-O bonded interactions in silicate crystals and molecules: a comparison
G V Gibbs1, D Jayatilaka, M A Spackman
1Department of Geosciences, Materials Science and Engineering and Mathematics, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061, USA. gvgibbs@vt.edu
The Journal of Physical Chemistry. A
|November 17, 2006
Summary
The study reveals that silicon-oxygen bonds in silicates are short-ranged and molecular-like. Bond character, measured by energy density ratios, correlates with bond length, electron density, and atomic charge, classifying interactions between Al-O and P-O types.
Area of Science:
- Materials Science
- Quantum Chemistry
- Solid-State Chemistry
Background:
- Silicon-oxygen (Si-O) bonds are fundamental in silicates, influencing their diverse properties.
- Understanding the nature of these bonds is crucial for materials design and earth sciences.
- Previous studies have explored Si-O bond characteristics using various theoretical methods.
Purpose of the Study:
- To investigate the nature of Si-O bonded interactions in silicates and related molecules.
- To characterize the bond using electron density properties at the bond critical point.
- To compare Si-O bond character with other chemical interactions, such as Al-O and P-O bonds.
Main Methods:
- Calculation of electron density distributions, rho(r), for silicates (e.g., quartz) and molecules (e.g., disiloxane).
- Analysis of bond critical point properties, including local kinetic energy density, G(rc), and local potential energy density, V(rc).
- Utilizing the G(rc)/rho(rc) and H(rc)/rho(rc) ratios to quantify bond character and covalent contributions.
Main Results:
- Si-O bonded interactions in silicates exhibit short-ranged, molecular-like characteristics.
- The G(rc)/rho(rc) ratio effectively measures bond character, correlating with Si-O bond length, electron density accumulation, and atomic coordination.
- Si-O bonds were categorized as intermediate interactions, distinct from closed-shell or shared interactions, and comparable to Al-O and P-O bonds.
Conclusions:
- The electron density at the bond critical point provides a robust measure of Si-O bond character.
- Si-O bonds in silicates display characteristics intermediate between ionic and covalent, similar to Al-O and P-O bonds.
- These findings enhance our understanding of bonding in technologically important silicate materials.
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