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 intrinsicsolids 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 levellooks 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 definite 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. In this case, the temperature is higher the stronger the bonds in the lattice.

In other words, the atomic crystal latticeis the key to strength and hardness of materials. However, it should be taken into account 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 have the same carbon atom in the composition, are highly different in terms of strength indicators: diamond is the hardest substance on the 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 - a value that determines the distance betweencenters of two adjacent 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 angstroms.

2. K is the coordination number. The index that determines the packing densityatoms within the same 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. 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 examined only a few substances thatthe atomic crystal lattice is inherent. Meanwhile, there are a lot of them. Despite the great diversity, the crystalline atomic lattice includes units that are always connected by a covalent bond (polar or nonpolar). In addition, these substances are practically insoluble 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.