Crystallography

Many of the properties of solid materials depend mainly on their structures. These solids can be broadly classified as either crystalline or non crystalline. In a crystal the atoms are arranged in a periodic manner in all three directions whereas in a noncrystalline solid the arrangement is random. A crystalline solid can either be a single crystal, or an aggregate of many crystals called polycrystalline. Noncrystalline substances are called amorphous and they have no directional properties and therefore they are called isotropic substances. They do not possess any regular shape and they have a wide range of melting points. A crystal has regular shape and when it is broken, all broken pieces have the same regular shape.