Crystalline bonds

Fired-on. Decoration fused into the surface of glazed pottery or glass-ware. Firing. The process of heat treatment of ceramic ware in a kiln to develop a vitreous or crystalline bond, thus giving the ware properties associated with a ceramic material. 

Due to the corresponding crystalline bond lengths [1] and the negative scattering of Ti, it is reasonable to assume that the first peak in the total correlation... 

Fig. 4.19 Free energy curves with various crystalline bonds at the fixed temperature T = l.llAEflk in the single chain systems with different chain lengths as labeled (Hu et al. 2003b)...

Finally, certain elements are hard but ductile and malleable, conduct electricity, are shiny, and have variable but usually high melting points. These elements are metals, and their collective characteristics are explained by an idea called metallic bonding. In this type of bonding, the electrons of the individual metal atoms pool together to become electrons not of the individual atoms but of the whole solid. This explains the electrical and thermal conductivity of metals, and deeper analysis of this idea explains their other characteristics, too. This is beyond our scope, but understand that the interactions between atoms of metals is a different sort of crystalline bonding that does in fact account for the unique properties of metals. 

There is a fair amount of work reported with films at the mercury-air interface. Rice and co-workers [107] used grazing incidence x-ray diffraction to determine that a crystalline stearic acid monolayer induces order in the Hg substrate. Quinone derivatives spread at the mercury-n-hexane interface form crystalline structures governed primarily by hydrogen bonding interactions [108]. 

A related advantage of studying crystalline matter is that one can have synnnetry-related operations that greatly expedite the discussion of a chemical bond. For example, in an elemental crystal of diamond, all the chemical bonds are equivalent. There are no tenninating bonds and the characterization of one bond is sufficient to understand die entire system. If one were to know the binding energy or polarizability associated with one bond, then properties of the diamond crystal associated with all the bonds could be extracted. In contrast, molecular systems often contain different bonds and always have atoms at the boundary between the molecule and the vacuum. 

Wiliams D E 1965 Non-bonded potential parameters derived from crystalline aromatic hydrocarbons J. Chem. Phys. 45 3770... 

There are two classes of solids that are not crystalline, that is, p(r) is not periodic. The more familiar one is a glass, for which there are again two models, which may be called the random network and tlie random packing of hard spheres. An example of the first is silica glass or fiised quartz. It consists of tetrahedral SiO groups that are linked at their vertices by Si-O-Si bonds, but, unlike the various crystalline phases of Si02, there is no systematic relation between... 

The parameter /r tunes the stiffness of the potential. It is chosen such that the repulsive part of the Leimard-Jones potential makes a crossing of bonds highly improbable (e.g., k= 30). This off-lattice model has a rather realistic equation of state and reproduces many experimental features of polymer solutions. Due to the attractive interactions the model exhibits a liquid-vapour coexistence, and an isolated chain undergoes a transition from a self-avoiding walk at high temperatures to a collapsed globule at low temperatures. Since all interactions are continuous, the model is tractable by Monte Carlo simulations as well as by molecular dynamics. Generalizations of the Leimard-Jones potential to anisotropic pair interactions are available e.g., the Gay-Beme potential [29]. This latter potential has been employed to study non-spherical particles that possibly fomi liquid crystalline phases. 

Other authors have attributed the improved corrosion resistance with increasing Cr content with the increasing tendency of the oxide to become more disordered [69]. This would then suggest that an amoriDhous oxide film is more protective than a crystalline one, due to a bond and stmctural flexibility in amoriDhous films. 

Crystalline silicon has the tetrahedral diamond arrangement, but since the mean thermochemical bond strength between the silicon atoms is less than that found between carbon atoms (Si—Si, 226 kJmol , C—C, 356kJmol ), silicon does not possess the great hardness found in diamond. Amorphous silicon (silicon powder) is microcrystalline silicon. 

This substance is familiar as the blue crystalline pentahydrate CUSO4.5H2O. In this crystal, each Cu ion is surrounded by four water molecules at the corners of a square, while the fifth water molecule is held by hydrogen bonds (see Figure 13.8). 

The very low solubility of oxamide is almost undoubtedly the result of the extensively hydrogen-bonded nature of the crystalline compound (cf. E. M. Ayerst and J. R. C. Duke, Acta. Cryst. (1954), 7, 588). 

No polymer is ever 100% crystalline at best, patches of crystallinity are present in an otherwise amorphous matrix. In some ways, the presence of these domains of crystallinity is equivalent to cross-links, since different chains loop in and out of the same crystal. Although there are similarities in the mechanical behavior of chemically cross-linked and partially crystalline polymers, a significant difference is that the former are irreversibly bonded while the latter are reversible through changes of temperature. Materials in which chemical cross-linking is responsible for the mechanical properties are called thermosetting those in which this kind of physical cross-linking operates, thermoplastic. 

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