Crystal space lattice

The changes in reorientation of surface atoms were explained using the dynamic model of the crystal space lattice. It was assumed that during anodic polarization, when the oxidation of adsorbed water is taking place, atoms oscillate mainly in a direction perpendicular to the electrode surface. This process leads to periodic separation of atoms in the first surface layer. Thus, the location of atoms in different orientations is possible. It was stated that various techniques of electrode pretreatment used for... 

ATOMIC PLANE. A plane passed through the atoms of a crystal space lattice, in accordance with certain rules relating its position to the crystallographic axes. See also Mineralogy. 

The color variations of a nonmetallic mineral are often the result of ionic trace impurities in the crystal space lattice structure. Since the impurities vary from sample to sample, the color may vary. Some nonmetallic minerals have no color and are referred to as colorless. This variability in color, which can sometimes be extreme, means that color is one of the least useful properties for identifying nonmetallic minerals even though it is probably the most obvious. The origin of a mineral s color can be explained by three types of electronic transitions in the crystalline solids. 

A lattice point, M, which describes the position of a microscopic entity (e.g., electrons, ions, atoms, molecules or clusters), is located in the crystal space lattice by giving the number of unit translations, along each of the three distinct translation directions, by which it is displaced from the point 0 as fixed origin. Therefore, each lattice point is entirely described by a set of three coordinates (m, v, w) or by the single position vector V ... 

Important note The rigorous deduction of entities (e.g., ions, atoms, molecules) contained inside the unit cell only depends on their particular locations in the crystal space lattice so that,... 

Therefore, a space group is a possible combination of all the symmetry elements, macroscopic and microscopic, in space of the Bravais lattice and can be derived. It is found that when all such symmetry elements are combined and applied in the Bravais lattices, 230 different types of crystal space lattices are possible. It is appropriate to mention here that any crystal either naturally free grown or crystallized artificially from the solutions of the synthesized compounds must belong to any of these possible 230 types of space groups [1,2]. 

It is often difficult to represent inorganic compounds with the usual structure models because these structures are based on complex crystals space groups), aggregates, or metal lattices. Therefore, these compounds are represented by individual polyhedral coordination of the ligands such as the octahedron or tetrahedron Figure 2-124d). 

Morphology. A crystal is highly organized, and constituent units, which can be atoms, molecules, or ions, are positioned in a three-dimensional periodic pattern called a space lattice. A characteristic crystal shape results from the regular internal stmcture of the soHd with crystal surfaces forming parallel to planes formed by the constituent units. The surfaces (faces) of a crystal may exhibit varying degrees of development, with a concomitant variation in macroscopic appearance. 

Crystal growth is a diffusion and integration process, modified by the effect of the solid surfaces on which it occurs (Figure 5.3). Solute molecules/ions reach the growing faces of a crystal by diffusion through the liquid phase. At the surface, they must become organized into the space lattice through an... 

Madelimg s proof of the hypothesis of space lattices was an indirect one. The direct proof was made in 1912 by Max von Lane, who used two conjectrrres as a starting point for his experiment. The first conjectrrre concerned the newly discovered x-rays, whose wave length was estimated in the range between 12 rrm and 5 pm. The other conjecture concerned the distance between the lattice planes. Based on these two conjectures he birilt the hypothesis that the interaction x-rays with crystal lattices should lead to interference, what he coitld show in experimerrts. 

The prindple of a LEED experiment is shown schematically in Fig. 4.26. The primary electron beam impinges on a crystal with a unit cell described by vectors ai and Uj. The (00) beam is reflected direcdy back into the electron gun and can not be observed unless the crystal is tilted. The LEED image is congruent with the reciprocal lattice described by two vectors, and 02". The kinematic theory of scattering relates the redprocal lattice vectors to the real-space lattice through the following relations... 

One of the concepts in use to specify crystal structures the space lattice or Bravais lattice. There are in all fourteen possible space (or Bravais) lattices. 

Space lattices and crystal systems provide only a partial description of the crystal structure of a crystalline material. If the structure is to be fully specified, it is also necessary to take into account the symmetry elements and ultimately determine the pertinent space group. There are in all two hundred and thirty space groups. When the space group as well as the interatomic distances are known, the crystal structure is completely determined. 

The term crystal structure in essence covers all of the descriptive information, such as the crystal system, the space lattice, the symmetry class, the space group and the lattice parameters pertaining to the crystal under reference. Most metals are found to have relatively simple crystal structures body centered cubic (bcc), face centered cubic (fee) and hexagonal close packed (eph) structures. The majority of the metals exhibit one of these three crystal structures at room temperature. However, some metals do exhibit more complex crystal structures. 

Like paraldehyde, metaldehyde can be preserved, and, when freshly prepared, is odourless. It also has no aldehydic properties. On keeping, however, a distinct odour of acetaldehyde becomes evident —a sign that here also an equilibrium is slowly being established. Metaldehyde can be completely depolymerised by heating. Molecular weight determinations (in phenol) show that metaldehyde is tetra-molecular (Hantzsch) the examination of the space lattice of crystals by the method of Laue and Bragg points to the same conclusion (Mark). 

The space lattice of a crystal is a representation of its translation repetition. 

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