Bonding in crystals

A classification of crystals based on bonding is useful in understanding structure-property relations in solids. Five types of solids are readily defined on bonding considerations ionic, covalent, metallic and molecular (van der Waals) and hydrogen-bonded. In Table 1.2, the important characteristics of the five types of solids are presented. In real situations, however, solids may exhibit features of more than one type of bonding. 

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The Determination of the Type of Bond in Crystals. Resonance of Molecules and Crystals Among Several Electronic Structures. 

Buerger, M. J. (1937) Interatomic distances in marcasite and notes on the bonding in crystals of Iollingite, arsenopyrite, and marcasite types. Z. Kristallogr. A97, 504-513. 

The third bond, and perhaps the weakest of the three, is that due to van der Waals forces. These forces pull together particles of all material regardless of composition or electric charge. They vary with the size of the particle and would be greater for a hydrocolloid than for a smaller particle. They are the predominating bonds in crystals of fats and waxes. 

Metrangolo P, Resnati G, Pilati T, Biella S (2007) Halogen Bonding in Crystal Engineering. 126 105-136... 

R. D. Shannon, Bond distances in sulfides and a preliminary table of sulfide crystal radii. In Structure and Bonding in Crystals, Vol. II (M. O Keeffe, A. Navrotsky, eds.). Academic Press, 1981. 

For interpreting indentation behavior, a useful parameter is the ratio of the hardness number, H to the shear modulus. For cubic crystals the latter is the elastic constant, C44. This ratio was used by Gilman (1973) and was used more generally by Chin (1975) who showed that it varies systematically with the type of chemical bonding in crystals. It has become known as the Chin-Gilman parameter (H/C44). Some average values for the three main classes of cubic crystals are given in Table 2.1. 

Many papers concerning the structural determination of hydrogen bonds in crystals were recently reviewed26. Hydrogen bonds are responsible for the self-assembling of... 

Theory and practise of determining the electrostatic potential and chemical bonding in crystals... 

The values of the ESP at the nuclear positions, as obtained from the electron and Hartree-Fock structure amplitudes for the mentioned crystals (using a K-model and corrected on self-potential) are given in table 2. An analysis shows that the experimental values of the ESP are near to the ab initio calculated values. However, both set of values in crystals differ from their analogs for the free atoms [5]. It was shown earlier (Schwarz M.E. Chem. Phys. Lett. 1970, 6, 631) that this difference in the electrostatic potentials in the nuclear positions correlates well with the binding energy of Is-electrons. So an ED-data in principle contains an information on the bonding in crystals, which is usually obtaining by photoelectron spectroscopy. 

Now use Coulomb s law to compare the strengths of the ionic bonds in crystals of magnesium oxide and lithium fluoride. The sizes of the four ions are taken from the tabulation of radii of cations and anions in Table 5-4. 

The largest number of hydrogen bonds in crystal structures of alkyl hydroperoxides refer to intermolecular bonds between the hydroperoxide proton and functionalities of the type 0=X, where X denotes a sulfur (e.g. 27), carbon (e.g. 30) or a phosphorous atom (e.g. 32, Figure 14, Table 7)93,108,115 geometry of [l,2-bis(diphenylphosphinoyl)ethane] bis(2,2-dihydroperoxypropane) (32) in the solid state is a rare example of a bifurcated hydrogen bond between an OOH donor and an 0=X proton acceptor. 

The second largest number of hydrogen bonds in crystal structures of alkyl hydroperoxides refers to interactions of the type OO—H OR R, where R is an alkyl group and R denotes H, alkyl or R O. The OO OR R distances vary between 2.67-2.91 A and the associated O—H O angles range from 152 to 177°. In some compounds, formation of intramolecular hydrogen bonds of the type OO—H 0=X would in principle have been feasible. The number of examples documented in the literature so far is clearly in favor of the intermolecular type of H bonding. 

Cohen, M. L. (1981) in Structure and Bonding in Crystals (eds O Keeffe, M. Navrotsky, A.) Academic Press, New York. 

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