Gas-phase molecular structure and energetics of anionic silicates

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Gomes, Jose R. B. and Cordeiro, M. Natalia D. S. and Jorge, Miguel (2008) Gas-phase molecular structure and energetics of anionic silicates. Geochimica et Cosmochimica Acta, 72 (17). pp. 4421-4439. ISSN 0016-7037 (https://doi.org/10.1016/j.gca.2008.06.012)

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Abstract

The gas-phase stabilities of linear, branched and cyclic silicates made of up to five silicon atoms were studied with density functional theory (DFT). The starting geometries for the DFT calculations at the B3LYP/6-311+G(2d,2p) level of theory were obtained from classical molecular dynamics simulations. We have observed that geometric parameters and charges are mainly affected by the degree of deprotonation. Charges on Si atoms are also influenced by their degree of substitution. The enthalpy of deprotonation of the neutral species was found to decrease with the size of the molecule, while the average deprotonation enthalpy of highly charged compounds increased with molecular size. Furthermore, the formation of rings in highly charged silicates is enthalpically preferred to chain growth. These observations result from two competing effects: the easier distribution of negative charge in silicates with low charge density and the strong intramolecular repulsions present in silicates with high charge density. As a consequence, highly charged silicates in the gas phase tend to be as small and as highly condensed as possible, which is in line with experimental observations from solution NMR.

ORCID iDs

Gomes, Jose R. B., Cordeiro, M. Natalia D. S. and Jorge, Miguel ORCID logoORCID: https://orcid.org/0000-0003-3009-4725;
  • Item type:Article
    ID code:42568
    Dates:
    Date
    Event
    1 September 2008
    Published
    Notes:Notice: This is the author’s version of a work that was accepted for publication in Geochimica et Cosmochimica Acta. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Geochimica et Cosmochimica Acta, [72, 17, (2008)] DOI: 10.1016/j.gca.2008.06.012.
    Subjects:Technology > Chemical engineering
    Department:Faculty of Engineering > Chemical and Process Engineering
    Depositing user: Pure Administrator
    Date deposited:15 Jan 2013 15:33
    Last modified:02 Dec 2024 01:14
    Related URLs:
    URI:https://strathprints.strath.ac.uk/id/eprint/42568
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