The energetics and structure of the hydrogarnet defect in grossular: A computer simulation study

Wright, Kate; Freer, Robert; Catlow, C. Richard A.

doi:10.1007/bf00203220

Cited by 47 publications

(37 citation statements)

References 21 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Using data compiled previously in a study of the energetics of hydrolysis of CaF2 (Catlow, 1977a) we may estimate this quantity as -9.74 eV. The full derivation of this term can be found in Appendix 1 or Wright et al (1993). Finally we have the formation of the defect complex at the vacant Mg site given by:…”

Section: Resultsmentioning

confidence: 98%

A computer simulation study of (OH) defects in olivine

Wright

Catlow

1994

Phys Chem Minerals

Self Cite

View full text Add to dashboard Cite

Abstract. Recent experiments (Miller et al. 1987; Bell and Rossman 1992;Bai and Kohlstedt 1992) have shown that olivine, the dominant mineral in the Earth's upper mantle, can contain substantial amounts of water in the form of OH. There is uncertainty, however, as to the mechanisms by which water dissolves into the mineral structure and as to the site it occupies in the host lattice. We have therefore used atomistic computer simulation techniques based on the Born model of solids, to investigate the structures and energies of OH defects in olivine. Our calculations suggest that the most favourable route for incorporation of OH into olivine involves reactions with water accompanied by the reduction of ferric iron for which we obtain a solution energy of 0.46 eV. We propose therefore that the OH content will be largely controlled by the concentration of Fe 3 +.

show abstract

Section: Resultsmentioning

confidence: 98%

A computer simulation study of (OH) defects in olivine

Wright

Catlow

1994

Phys Chem Minerals

Self Cite

View full text Add to dashboard Cite

show abstract

“…Over the past several decades, studies using atomistic methods have demonstrated that reliable values can be calculated for defect formation and migration energies. It is worth noting that Wright et al (1994) first used computer simulation methods to model the structure and energetics of the hydrogarnet defect in grossular. Recently, similar studies have been reported by Pigott et al (2015) for MgSiO 3 majorite up to 25 GPa employing both classical atomistic simulations and complementary first-principles calculations.…”

Section: Experimental Techniquesmentioning

confidence: 99%

Diffusion in garnet: a review

Zhang

2017

Acta Geochim

View full text Add to dashboard Cite

With improvements on high-pressure experimental techniques in multi-anvil apparatus and the development of new analytical tools, major progress has been made on diffusion in garnets in the past several decades. The data obtained in the experimental determination of diffusion coefficients in garnets are of fundamental importance for diffusion modeling and timescales of geological and planetary processes. In this review, we have compiled experimental data on self-diffusion (Si, O, cations), trace element diffusion (Li, Y, Ga, Cr, Sr, REEs), and interdiffusion (CaFe/Mg, Si-Al) in garnet in the light of new advances and recent applications. In addition, some empirical relationships among diffusion parameters (pre-exponential factor D 0 , activation energy E, ionic radius) are also discussed. We hope that this review can provide a useful data digest and guide to future study of diffusion in garnet.

show abstract

“…As a consequence, it is easier for hydroxyl ions to approach the surface and form chemical bonds with the exposed metal ions. In addition, the tilting of the proton end of the hydrogen atoms of bonded hydroxyl ions, together with the protons adsorbed to the tetrahedron oxygen atoms, can balance the negative surface charge produced by metal ion depletion, as observed before where the tilting of hydrogen atoms balanced the charge introduced by silicon vacancy (Wright et al, 1994). However, because (0 1 0)-water interface inferred from the electron density profile derived from the best fit result, which is plotted in (B).…”

Section: Hydration At the Olivine (0 1 0)-water Interfacementioning

confidence: 84%

Termination and hydration of forsteritic olivine (0 1 0) surface

Yan

Park

Ahn

et al. 2014

Geochimica et Cosmochimica Acta

View full text Add to dashboard Cite

Termination and hydration of the forsteritic (Fo90Fa10) olivine (0 1 0) surface have been investigated with high-resolution specular X-ray reflectivity and Atomic Force Microscopy. The surface was prepared by polishing a naturally grown {0 1 0} face, from which we found the polished surface in acidic (pH 3.5) alumina suspension exhibits regular steps while the basic (pH 9.5) silica polished surface is irregularly roughened, indicating there are two distinguishable mechanochemical processes for the surface dissolution. The quantitative interpretation of the regular steps from the alumina-polished surface suggests that the observed step heights correspond to multiples of crystallographic unit cell. Only this atomically terraced surface is investigated with the high-resolution X-ray reflectivity (HRXR) to determine the surface termination and hydration. The basic silica paste polished surface turned out too rough to measure with X-ray reflectivity. HRXR reveals that the alumina polished olivine (0 1 0) surface in pure water is terminated at a plane including half-occupied metal ion sites (M1), an oxygen vacancy site, and a silicate tetrahedral unit with one of its apices pointing outward with respect to the surface. An ideal termination with the oxygen vacancy would fulfill the stoichiometry of the formula unit; however, in the observation, the vacancy site is filled by an adsorbed water species and about a quarter of the remaining metal ions are further depleted. The terminating plane generates two distinct atomic layers in the laterally averaged electron density profile, on which two highly ordered adsorbed water layers are formed. The first layer formation is likely through the direct interaction with the M1 plane and the second layer is likely through the hydrogen bonding interaction with the first water layer. With this multilayered adsorbed water structure, the surface metal ion is partially hydrated by the vacancy-filling water species and adsorbed water molecules. The bulk water links to these distinct adsorbed water layers, with weak density oscillations that almost completely damp out after the first bulk water layer. The total thickness of the layered water structure including the two distinct adsorbed layers and the first layer of bulk water is slightly less than 1 nm, which corresponds to roughly three molecular layers of water. These results describe the steric constraints of the surface metal ion hydration and the iron redox environment during water-olivine interactions in this particular crystallographic orientation.

show abstract

The energetics and structure of the hydrogarnet defect in grossular: A computer simulation study

Cited by 47 publications

References 21 publications

A computer simulation study of (OH) defects in olivine

A computer simulation study of (OH) defects in olivine

Diffusion in garnet: a review

Termination and hydration of forsteritic olivine (0 1 0) surface

Contact Info

Product

Resources

About