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The observed crystal structures of many metals can be described as a nearly mathematical close-packing of equal spheres. A simple model for both of these is to assume that the metal atoms are spherical and are packed together as closely as possible.
In the resonating valence bond theory, the factors that determine the choice of one from among alternative crystal structures of a metal or intermetallic compound revolve around the energy of resonance of bonds among interatomic positions. It is clear that some modes of resonance would make larger contributions (be more mechanically stable than ...
Metals crystallize rapidly and are almost always polycrystalline, though there are exceptions like amorphous metal and single-crystal metals. The latter are grown synthetically, for example, fighter-jet turbines are typically made by first growing a single crystal of titanium alloy, increasing its strength and melting point over polycrystalline ...
Crystal structures are typically categorized as minerals, metals-alloys, [4] inorganics, [5] organics, [6] nucleic acids, [7] and biological macromolecules. [8] [9] Individual crystal structure databases cater for users in specific chemical, molecular-biological, or related disciplines
The fcc structure is a close-packed structure unlike the bcc structure; thus the volume of the iron decreases when this transformation occurs. Crystallography is useful in phase identification. When manufacturing or using a material, it is generally desirable to know what compounds and what phases are present in the material, as their ...
The structure of graphite was determined from single-crystal diffraction in 1924 by two groups independently. [43] [44] Hull also used the powder method to determine the structures of various metals, such as iron [45] and magnesium. [46]
A crystal may have zero, one, or multiple axes of symmetry but, by the crystallographic restriction theorem, the order of rotation may only be 2-fold, 3-fold, 4-fold, or 6-fold for each axis. An exception is made for quasicrystals which may have other orders of rotation, for example 5-fold.
Crystal chemistry is the study of the principles of chemistry behind crystals and their use in describing structure-property relations in solids, as well as the chemical properties of periodic structures. [1]