Bond lengths and angles in sulfate molecules, with implications for sulfate crystals
Molecular orbital (MO) calculations, using a 6-31G* basis set, have been completed for various sulfate molecules, including isolated tetrahedra and tetrahedral dimers, to determine their optimized geometries. Theoretical bond-length and bond-angle relationships were generated and compared to similar experimental relationships. Because the bonding forces in these systems appear to be governed by short-range forces, these relationships are applicable to sulfate crystals containing fundamental units similar to these molecules. For isolated tetrahedra, calculated SO bond lengths are linearly related to the average of the three angles common to the bond, as observed experimentally. This has been found by other workers using semi-empirical methods. Previous work on silicates and phosphates indicates that the range of bridging bond angles in a corner-sharing dimer is relatively large where the total energy shows little variation with bond angle. The relatively narrow range of observed sulfate bond angles suggests a large variation in energy with bridging bond angle, and this was confirmed in the MO calculations, with the barrier to bending being three times larger for the sulfate group. The charge distributions near the bridging bonds show a greater tendency for electrons to migrate to localized regions in forming the SO bond than in forming SiO or PO bonds.
- Research Organization:
- Virginia Polytechnic Institute and State Univ., Blacksburg (USA)
- OSTI ID:
- 6458903
- Report Number(s):
- CONF-8510489-
- Journal Information:
- Geol. Soc. Am., Abstr. Programs; (United States), Journal Name: Geol. Soc. Am., Abstr. Programs; (United States) Vol. 17; ISSN GAAPB
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
400201 -- Chemical & Physicochemical Properties
58 GEOSCIENCES
580400* -- Geochemistry-- (-1989)
BINDING ENERGY
BOND ANGLE
BOND LENGTHS
CHEMISTRY
CRYSTAL STRUCTURE
DIMENSIONS
ENERGY
GEOCHEMISTRY
LENGTH
MATHEMATICAL MODELS
MOLECULAR MODELS
MOLECULAR STRUCTURE
OXYGEN COMPOUNDS
STRUCTURAL CHEMICAL ANALYSIS
SULFATES
SULFUR COMPOUNDS