Crystal Structures and Lattice Parameters

The distribution of aluminum within the framework sites was also theoretically analyzed. Two general rales concerning A1 distribution were considered to apply (1) the Lowenstein s rale, which states that no Al-O-Al 

The acidic natural chnoptilolite, AZH-1, was prepared by acid treatmerrt of Na-exchanged (AZ) natural clinoptilolite (NZ) [11R2]. The nitrogen adsorption indicated that the acid sarrtple has a homogeneoirs porous distribution and a considerable increase in the rrricropore voltrme with respect to NZ and AZ zeolites. 

The dominant chaimel cations in natural heulandites are and Na as well as minor content. The extraframework content can be modified by ion exchange with other cations. Before analyzing the extra-framework sites occupied by exchanged ions, the mechanisms involved in exchange processes in HEU-type framework will be presented. 

The relationship between cation radius and hydrated cation radius, at 298 K, is depicted in Fig. 2 [59N1, OlPl]. The radius of a fully hydrated ion is proportional to the ionic charge, but not proportional to the ionic radius without H2O shell. Cs rm- 1-69 A, rhyd= 3.29 A) is exchanged more easily thanUE (rion= 0.60 A, rhyd= 3.82 A) or Be = 0.31 A, rhyd = 4.59 A) [59N1, 88M2]. The elevated temperatures normally enhance the ion-exchange reactions, while the pH is also critical, particularly in the case of acidic solutions, because small H cations are very mobile and reactive over many other cations. Other factors concern the solid/liquid ratio, the zeolite particle sizes, and the treatment time. As mentioned above, this discussion is valid in case of alkali or alkaline-earth element cations which are practically stable in aqueous solutions. 

The distribution coefficients of cesium on natural and cation-enriched Na -, K -, NH -, and Ca -forms of clinoptilolites were measured by batch radioactive tracer technique [02A1]. 

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Epitaxy. There is often a sharp orientation relationship between a singlecrystal substrate and a thin-film deposit, depending on the crystal structures and lattice parameters of the two substances. When such a relationship exists, the deposit is said to be in epitaxy with the substrate. The simplest relationship is parallel orientation, and this is common in semiconductor heterostructures, but more complex relationships are often encountered. 

Crystal Structure and Lattice Parameters (nm) Orthorhombic, a = 0.283, b = 0.554, c = 1.1470 Cr3C2 is an intermediate carbide having carbon chains with C-C distance approximately 0.165 nm running through distorted metal lattice where the Cr atoms are at the corners of trigonal prisms and the carbon atoms in the center of the prisms.i li" ... 

Crystal growth 6.7.4,3 Crystal structure and lattice parameters 6.7.2.4.1 Electrical and magnetic properties 6.7.2.4.1... 

Crystal structure and lattice parameters 6.7.2.4 B4CrDy B4CrDy... 

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