Correlation corrected periodic Hartree--Fock study of the interactions between water and the (001) magnesium oxide surface
- Molecular Sciences Research Center, Pacific Northwest Laboratory, Richland, Washington 99352 (United States)
A theoretical study of water adsorption on the surface of a three-layer (001) magnesium oxide film has been performed using periodic Hartree--Fock (PHF) theory with density-functional-based correlation corrections. The calculations treated two water molecules per MgO unit cell (one on each side of the film), and for most of the calculations, the size of the unit cell was chosen such that the ratio of water molecules to surface magnesium ions was 1:4. In these configurations the water dipoles were aligned parallel and the water--water spacing was 5.95 A between molecules in neighboring cells. Nine geometries were examined, three of which were found to be strongly bound to the surface. The binding energies for the three bound configurations range from 4.1 to 8.9 kcal/mol at the PHF level of theory and 6.3 to 12.5 kcal/mol when correlation effects were included. For the two cases where the geometry of the bound water molecule was allowed to relax at the equilibrium water--film distance, the H--O--H angle increased 1--3[degree] from the 6-31G* free molecule value of 105.6[degree] and the O--H bond distance did not change. The six remaining geometries did not show significant binding to the surface. Additional calculations were performed in which the dipoles of the water molecules were aligned antiparallel. These calculations indicate that as the coverage increases the water molecules will tend to form islands on the magnesium oxide surface rather than wet the surface. The formation of a fully hydroxylated surface (one hydroxyl group added to every surface magnesium ion and one hydrogen atom to every surface oxygen ion) was also examined, but was found to be energetically unfavorable.
- DOE Contract Number:
- AC06-76RL01830; FG06-89ER75522
- OSTI ID:
- 6351692
- Journal Information:
- Journal of Chemical Physics; (United States), Vol. 99:4; ISSN 0021-9606
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
58 GEOSCIENCES
MAGNESIUM OXIDES
COUPLING
WATER
ADSORPTION
BINDING ENERGY
CORRECTIONS
EARTH CRUST
ELECTRON CORRELATION
FILMS
HARTREE-FOCK METHOD
LAYERS
SURFACES
ALKALINE EARTH METAL COMPOUNDS
CALCULATION METHODS
CHALCOGENIDES
CORRELATIONS
ENERGY
HYDROGEN COMPOUNDS
MAGNESIUM COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
SORPTION
360202* - Ceramics
Cermets
& Refractories- Structure & Phase Studies
360606 - Other Materials- Physical Properties- (1992-)
580000 - Geosciences