Physics and Chemistry of Minerals

, Volume 25, Issue 8, pp 574–584

SiO and GeO bonded interactions as inferred from the bond critical point properties of electron density distributions

  • G. V. Gibbs
  • M. B. Boisen
  • F. C. Hill
  • O. Tamada
  • R. T. Downs
ORIGINAL PAPER

DOI: 10.1007/s002690050150

Cite this article as:
Gibbs, G., Boisen, M., Hill, F. et al. Phys Chem Min (1998) 25: 574. doi:10.1007/s002690050150

Abstract 

The topological properties of the electron density distributions for more than 20 hydroxyacid, geometry optimized molecules with SiO and GeO bonds with 3-, 4-, 6- and 8-coordinate Si and Ge cations were calculated. Electronegativities calculated with the bond critical point (bcp) properties of the distributions indicate, for a given coordination number, that the electronegativity of Ge (∼1.85) is slightly larger than that of Si (∼1.80) with the electronegativities of both atoms increasing with decreasing bond length. With an increase in the electron density, the curvatures and the Laplacian of the electron density at the critical point of each bond increase with decreasing bond length. The covalent character of the bonds are assessed, using bond critical point properties and electronegativity values calculated from the electron density distributions. A mapping of the (3, −3) critical points of the valence shell concentrations of the oxide anions for bridging SiOSi and GeOGe dimers reveals a location and disposition of localized nonbonding electron pairs that is consistent with the bridging angles observed for silicates and germanates. The bcp properties of electron density distributions of the SiO bonds calculated for representative molecular models of the coesite structure agree with average values obtained in X-ray diffraction studies of coesite and danburite to within ∼5%.

Copyright information

© Springer-Verlag Berlin Heidelberg 1998

Authors and Affiliations

  • G. V. Gibbs
    • 1
  • M. B. Boisen
    • 1
  • F. C. Hill
    • 1
  • O. Tamada
    • 2
  • R. T. Downs
    • 3
  1. 1.Departments of Geological Sciences, Mathematics and Material Science and Engineering, Virginia Tech, Blacksburg, VA 24061, USAUS
  2. 2.Graduate School of Human and Environmental Studies, Kyoto University, Kyoto 606, JapanJP
  3. 3.Department of Geological Sciences, University of Arizona, Tucson, AZ, USAUS