Gas-phase molecular structure and energetics of anionic silicates

• Type: Article in International Scientific Journal
• Date: 2008

Authors

Jose R B Gomes (Author) Other; Natalia N D S Cordeiro (Author) FCUP; Miguel Jorge (Author) Other

Journal

Title: Geochimica et Cosmochimica Acta

Vol. 72 No. 17

Pages: 4421-4439

ISSN: 0016-7037

Publisher: Elsevier

Indexing

ISI Web of Knowledge - 36 Citations

ISI Web of Science

Scopus - 37 Citations

INSPEC

Scientific classification

CORDIS: Physical sciences > Chemistry > Computational chemistry

FOS: Natural sciences > Earth and related Environmental sciences

Other information

Authenticus ID: P-003-WGM

DOI: 10.1016/j.gca.2008.06.012

Abstract (EN): 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.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 19