Importance of crystal structures Every physical body in this world is made up of a basic entity called atoms. When these atoms arranged in a regular pattern, unique arrangement, they form a lattice structure for a crystalline solid/liquid body. The lattice structure finally determines one's physical properties.
Types of lattice structure or crystal structure Basic of the crystal structure consists of a space lattice pattern and basis
Crystal structure = space lattice + basis
The Basis may contain one atom per lattice pattern
1) FCC (Space lattice) + 1 Aluminium atom at each lattice point (basis) = FCC Crsystal of Aluminium (Crystal structure)
2) BCC + 1 Iron atom at each lattice point (basis) = BCC Crystal of Iron
e.g. Copper, Aluminium, Nickel, Pb, Ag
e.g. W, Mo, Cr
Mg, Zn, Ti, Cd, Zr
Unit Cell: The basic difference between all these patterns lies in the difference between the unit cell which is nothing but the repeatability of each pattern in lattice space.
B.C.C (Body Centred Cubic)
F.C.C (Face Centred Cubic)
H.C.P.(Hexagonal Close Pack)
Because of allotropes of iron, it got two different lattice structures at different temperatures.
More articles: Engineering
When we see an item with our naked eyes, we see its macroscopic shape and structure. We recognise it from that as well as it's colour and texture. We are able to do all this analysis only in the presence of some light that falls on this item and reflects, refracts or disperses through it. With naked eyes, we can visualise all these external things about it.
But when we want to know more about the internal structure of these materials at the microscopic level, then we have to use high-efficiency microscopes like electron microscopes to find out the structure at atomic or molecular levels. The arrangement of atoms at that elementary level tells us the crystal structure of that material. The basic crystal structure of the material which is a characteristic property decides its apparent shape, appearance and overall impact by which we say that it is such and such material. So, understanding the crystal structure and arrangement of atoms in its lattice gives us a lot of information about the interatomic distances, packing and other physical parameters related to the physical properties of that material.
For example if we take a piece of natural limestone rock we will find that it has some crystal structure. Now we break this piece in smaller parts and then it seems to have lost that binding because of the breaking force that we applied on it. But if we take a small part then it would again look like the original material and inside it the same lattice structure would be preserved as we had visualised in the main original piece. So by dividing a material in smaller parts it is possible to reach the basic structure and photograph that for our understanding of the physics behind that. Of course thin film techniques and electron microscopy would be required to undertake such projects. In essence, learning of crystal structures gives us valuable information about the various engineering materials.