Uploaded by pavan on Jul 01, 2014
CRYSTAL – ITS PROPERTIES
Matter exists in three forms solid , liquids, gases and finally plasma state. In the case of solids atoms or molecules will be in a fixed position i.e they do not move from one place to other because they are firmly fixed by the nuclear forces of attraction. In the case of liquids and gases atoms or molecules move from one place to other in random motion because they are weakly bounded by the forces of attraction. That is the reason why liquids and do not have definite shape, but solids have definite shape and volume, hence they are rigid in shape and structure. Since crystal belongs to the class of solids where atoms or molecules are arranged in regular, repeated and periodic fashion. They are arranged in regular fashion due to the presence of vectors called crystal translation vectors along x, y, z axes respectively. Crystal being made of transparent material glass it shows optical properties like reflection and refraction and mechanical properties like stress and strain, youngs modulus, bulk modulus, compressability and also used in the detection of methods of ultrasonics like piezoelectricity, magnetostriction method. Depending on whether atoms or molecules are arranged regularly or irregularly crystalline solids can be picturised into two types.
1. Single crystalline solids:- If the periodical arrangement of atoms is extended through a larger distance without any breakage in its structure such type are classified as single crystalline solids (or) if the regular arrangement of atoms or molecules is extended throughout the crystal without any breakage it can be termed as single crystalline solid.
2. Polycrystalline solids:- If the periodical arrangement of atoms is limited through a small regions called crystallites , i.e small pieces of crystal is called as crystallites. These crystallites are in different shape and size, separated by crystallite wall. Even though they are of different symmetries and shapes when considering the entering volume of the crystal the arrangement of atoms will be regular in fashion. Glass and plastic are best examples for polycrystalline solids.
Amorphous solids :- The behaviour and arrangement of atoms in...