solid defects

What are crystal defects and how are they classfied?

How do impurities affect the structure and properties of a solid?

What are color centers and how do they affect electric conductivity of solids?

Solid defects

Few, if any, crystals are perfect in that all unit cells consist of the ideal arrangement of atoms or molecules and all cells line up in a three dimensional space with no distortion. Some cells may have one or more atoms less whereas others may have one or more atoms than the ideal unit cell. The imperfection of crystals are called crystal defects.

Crystal defects are results of thermaldynamic equilibrium contributed also by the increase in entropy T S term of the Gibb's free energy:

DG = DH - TDS.

Only at the unatainable absolute zero K will a crystal be perfect, in other words, no crystals are absolutely perfect. However, the degree of imperfection vary from compound to compound.

On the other hand, some solid-like structure called flickering clusters also exist in a liquid. For example, the density of water is the highest at 277 K. The flickering clusters increase as temperature drops below 277 K, and the water density decreases as a result.

Solids are important for many technologies, and this link gives a well organized presentation.

What are crystal defects and how are they classfied?

As mentioned earlier, the missing and lacking of atoms or ions in an ideal or imaginary crystal structure or lattice and the misalignment of unit cells in real crystals are called crystal defects or solid defects. The two terms are interchangeable.

Crystal defects occur as points, along lines, or in the form of a surface, and they are called point, line, or plane defects respectively.

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