Any substance in nature, as you know, consists of smaller particles. They, in turn, are connected and form a certain structure, which determines the properties of a particular substance.
The atomic crystal lattice is inherent in solids and occurs at low temperatures and high pressures. Actually, precisely because of this structure, diamonds , metals, and a number of other materials acquire characteristic strength.
The structure of such substances at the molecular level looks like a crystal lattice, each atom in which is bound to its neighbor by the strongest compound existing in nature - a covalent bond. All the smallest elements that make up the structures are arranged orderly and with a certain frequency. Representing a grid, in the corners of which there are atoms surrounded always by the same number of satellites, the atomic crystal lattice practically does not change its structure. It is well known that you can only change the structure of a pure metal or alloy by heating it. The temperature is higher, the stronger bonds in the lattice.
In other words, the atomic crystal lattice is the key to the strength and hardness of materials. In this case, 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, having the same carbon atom in their composition, are highly different from each other in terms of strength: diamond is the hardest substance on Earth, graphite can stratify and break. The fact is that in the crystal lattice of graphite atoms are arranged in layers. Each layer resembles a bee honeycomb, in which carbon atoms are weakly articulated. A similar structure causes layered crumbling of pencil leads: when broken, parts of graphite simply peel off. Another thing is a diamond, the crystal lattice of which consists of excited carbon atoms, that is, those that are able to form 4 strong bonds. It is simply impossible to destroy such an articulation.
Crystal lattices of metals, in addition, have certain characteristics:
1. The lattice period - a value that determines the distance between the centers of two adjacent atoms, measured along the edge of the lattice. The generally accepted designation does not differ from that in mathematics: a, b, c - length, width, lattice height, respectively. Obviously, the size of the figure is so small that the distance is measured in the smallest units of measure - a tenth of a nanometer or angstroms .
2. K is the coordination number . An indicator that determines the packing density of atoms in a single lattice. Accordingly, its density is greater, the higher the number K. In fact, this figure represents the number of atoms located as close as possible and at an equal distance from the studied atom.
3. The basis of the lattice . Also a value characterizing the density of the lattice. Represents the total number of atoms that belong to a particular cell under study.
4. The compactness coefficient is measured by calculating the total volume of the lattice divided by the volume that all atoms in it occupy. Like the previous two, this value reflects the density of the studied lattice.
We examined only a few substances that are characterized by an atomic crystal lattice. Meanwhile, there are a great many of them. Despite the great variety, the crystalline atomic lattice includes units always connected by means of 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.