Silicate structures, higher order

Construction of Higher Order Silicate Structures from the SigO20 Silicate Species... 

Other than accelerating the formation of spherical nanoparticles of silica from metastable silicic acid solutions, the silaffins appear to have no structure-directing activity. If they are responsible for silica formation in the living diatom, as seems quite likely, control of the higher order architecture of the resulting silica apparently must be determined by the pre-formed shape of the silica deposition vesicle (the envelope within which the silica grows) serving as a complex three-dimensional mold. 

With regard to the chemical constitutions or structures of the intermediate addition compounds, not much can be said. The element which appears to be specifically responsible for the formation of these compounds is aluminium. Aluminium salts readily form onium or molecular compounds or compounds of the second and higher orders. The occurrence of complex aluminium salts in nature, such as the aluminium silicates, bauxite, etc., shows that complex inorganic aluminium compounds are capable of existing and are apparently extremely stable. The complex organic compounds of aluminium, some of which have been proven... 

All of the previous calculations have been concerned with static clusters, or structures, but recently work has been carried out to simulate silicate and zeolite structures by dynamic methods. A simple potential model was used which considered two-body interactions, with the inclusion of higher order terms to allow for... 

In addition to the use of H, C, and N NMR chemical shifts, it has been shown that observation of solid-state chemical shifts and quadrupolar couplings adds important information on the higher-ordered and hydrogen-bonded structures of polypeptides and peptides in the solid state [62-65], Solid-state NMR has been shown to be useful, moreover, for determining the local structures of alkali silicates [66-70]. Therefore, it is expected that solid-state NMR may reveal further dimensions of the structural and dynamic behavior of PDES in the crystalline, biphasic, and isotropic phases, in addition to the H, C, and Si NMR results reported previously. Due to the low natural abundance of nuclei (0.037%), the NMR analysis requires labeling. The structure and dynamics of 0-enriched... 

Synthetics and mineral fibers have other parallels. A few synthesized fibers show a higher level or secondary ordering of the crystalline structure, such as that described for chrysotile. Composed entirely of carbon, graphite fibers are synthetic fibers with such a secondary structure (see the following section). Tubular fibers of other compositions, such as aluminum silicate polymers, have also been synthesized (Farmer et al., 1977). 

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