Atomic crystal lattice

Any substance in nature, as is known, consists of smaller particles. They, in turn, are connected and form a specific structure that determines the properties of a particular substance.

The atomic crystal lattice is intrinsic to solids and occurs at low temperatures and high pressures. Actually, it is thanks to this structure that diamond, metals and a number of other materials acquire a characteristic strength.

The structure of such substances at the molecular level looks like a crystal lattice, each atom in which is connected with its neighbor by the strongest compound existing in nature - a covalent bond. All the smallest elements that form structures are arranged in an orderly and with a certain periodicity. Representing a grid, in the corners of which there are atoms surrounded by the same number of satellites, the atomic crystal lattice practically does not change its structure. It is well known that the structure of a pure metal or alloy can be changed only by heating it. At the same time, the temperature is higher the stronger the bonds in the lattice.

In other words, the atomic crystal lattice is the key to strength and hardness of materials. However, it should be borne in mind that the arrangement of atoms in different substances can also differ, which, in turn, affects the degree of strength. So, for example, diamond and graphite, which contain the same carbon atom, are highly different in terms of strength: diamond is the hardest substance on earth, graphite can also break down and break. The fact is that in the crystalline lattice of graphite, the atoms are arranged in layers. Each layer resembles a honeycomb cell, in which the carbon atoms are articulated rather weakly. This structure causes the lamellar crumbling of the pencil leads: if a part of the graphite breaks down, they simply exfoliate. Another thing is a diamond whose crystal lattice consists of excited carbon atoms, that is, those capable of forming four strong bonds. It is simply impossible to destroy such an articulation.

The crystal lattices of metals, in addition, have certain characteristics:

1. The lattice period is a quantity that determines the distance between the centers of two neighboring atoms, measured along the edge of the lattice. The conventional designation does not differ from that in mathematics: a, b, c - length, width, height of the lattice, respectively. Obviously, the dimensions of the figure are so small that the distance is measured in the smallest units-a tenth of a nanometer or an angstrom .

2. K is the coordination number . The exponent that determines the packing density of atoms within a single lattice. Accordingly, its density is the greater, the higher the number K. In fact, this figure is the number of atoms that are as close as possible and at an equal distance from the atom being studied.

3. The basis of the lattice . Also a quantity characterizing the lattice density. It is the total number of atoms that belong to a particular cell under study.

4. The coefficient of compactness is measured by counting the total volume of the lattice divided by the volume that all the atoms in it occupy. Like the previous two, this value reflects the density of the lattice under study.

We have considered only a few substances that are inherent in the atomic crystal lattice. Meanwhile, there are a lot of them. Despite the great variety, the crystalline atomic lattice includes units that are always connected by a covalent bond (polar or nonpolar). In addition, such substances practically do not dissolve in water and are characterized by low thermal conductivity.

In nature, there are three types of crystal lattices: cubic volume-centered, cubic face-centered, close-packed hexagonal.