Silicates crystal chemistry

In the silicate crystal chemistry, compounds such as Mg3Al2Si30i2 are classified within the orthosilicates owing to the isolated Si044+ tetrahedra existing in their structure, and better described by a chemical formula such as Mg3Al2(Si04)3. 

The properties of zeolites, most notably their stability, adsorptive capacity and catalytic activity, are strongly dependent on the precise location of Si and A1 in the emionic framework. This is one of the most challenging and debated problems in silicate crystal chemistry. 

Griffen, D.T. (1992) Silicate Crystal Chemistry, Oxford University Press,... 

A second feature of silicate crystal chemistry is peculiar to silicates alone, and arises accidentally from the particular value of the radius of the aluminium ion. The A1 0 radius ratio of 0 36 is so close to the critical value of 0 3 for transition from 6- to 4-co-ordination that this ion can occur in both conditions, sometimes in the same structure. When 4-co-ordinated the aluminium ion replaces silicon, and such replacement is purely random and may be of indefinite extent. For every aluminium ion so introduced a corresponding substitution of Ca2+ for Na+, Al3+ for Mg2+ or Fe3+ for Fe2+ must simultaneously occur else-... 

Be3Al2Si6018, a structure which we may describe in somewhat more detail as a particularly beautiful illustration of many of the principles of silicate crystal chemistry. 

Together with the structural principles established by the Bragg school concerning the many types of silicates, Goldschmidt s ideas were taken further by Linus Pauling in California to establish the modern science of crystal chemistry. A good early overview of the whole field can be found in a book by Evans (1939, 1964). 

Felsche J (1973) The Crystal Chemistry of the Rare-Earth Silicates. 13 99-197 Ferreira R (1976) Paradoxial Violations of Koopmans Theorem, with Special Reference to the 3d Transition Elements and the Lanthanides. 31 1-21 Fichtinger-Schepman AMJ, see Reedijk J (1987) 67 53-89... 

Felsche, J. The Crystal Chemistry of the Rare-Earth Silicates. Vol. 13, pp. 99-197. 

Fitting 71 Djh values (27 from their study and 44 from the literature) and subsequently excluding 5 outliers, Landwehr et al. (2001) derived the following expression for Th partitioning between clinopyroxene and silicate melt as a function of temperature, pressure, crystal chemistry and the molar MgMi partition coefficient ... 

It is well known that, as previously mentioned, close structural relationships exist between phosphates and silicates, as the crystal chemistry of both families is based upon similar X04 tetrahedral networks. The introduction of nitrogen within the P04 tetrahedra further increases the similarities when the cross-substitution is considered ... 

Chapman, D.M., and Roe, A.L. (1990) Synthesis, characterization and crystal chemistry of microporous titanium-silicate materials. Zeolites, 10, 730. 

Armbruster T. and Geiger C. A. (1993). Andradite crystal chemistry Dynamic X-site disorder and structural strain in silicate garnets. Eur. J. Min., 5 59-71. 

Cameron M. and Papike 1 1 (1982). Crystal chemistry of silicate pyroxenes. In Reviews in Mineralogy, vol. 7, 2d ed., P. H. Ribbe (series ed.), Mineralogical Society of America. 

Kostov I. (1975). Crystal chemistry and classification of silicate minerals. Geochem. Mineral Petrol, 1 5-14. 

Novak G. A. and Gibbs G. V. (1971). The crystal chemistry of silicate garnets. Amer. Mineral, 56 791-825. 

When three of the oxygens in the tetrahedra are shared (Si O ratio = 2 5), the complex ions that form take on a sheetlike configuration. The sheets can be stacked, and the associated cations are found between the sheets. Micas and clays are sheet-structure minerals with distinctive habits and physical properties, that reflect the planar silicate sheet structure (Fig. 2.1G). These normally platey minerals may also occur with fibrous-growth habits. The special crystal chemistry that produces such a distinctive habit is discussed later. 

Since silicates and aluminosilicates are by far the predominant rock-forming minerals, the crystal structures of most species have been determined. Liebau (1980) presents an overview of the structures of silicate and aluminosilicate minerals, and one can consult Berry, Mason, and Dietrich (1983, especially pp. 382-389) or other mineralogy texts for an introduction to the subject. The multivolume work of Eitel (1965) provides a general treatment of the crystal chemistry of all types of silicate materials. 

Bates, T. F. (1959). Morphology and crystal chemistry of 1 1 layer lattice silicates. Amer. Min. 44 78-92. 

Papike, J., and M. E. Cameron (1976). Crystal chemistry of silicate minerals of geophysical interest. Rev. Geophys. Space Phys. 14 37-80. 

Koretsky, E. M., Sverjensky, D. A., and Sahai, N. (1998). A model of surface site types on oxide and silicate minerals based on crystal chemistry— implications for site types and densities, multisite adsorption, surface infrared-spectroscopy, and dissolution kinetics. Amer. J. Sci. 298, 349-438. 

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