we know that crystalline compounds show the property of anisotropy due to different arrangement in different directions. is it true for all types of crystalline solids or only for ionic solids?? why is it so? and in case of covalentt solid(like diamond) and metallic solid (like aluminium), how does anisotropy occur? please explain both molecular and metallic individually.
Anisotropy is due to different behavior in different directions.
Crystalline compound are anisotropic in nature because it depends on melting point and boiling point, refractive index, cutting angle.
The molecular dynamics show that polished diamond undergoes an sp(3)-sp(2) order-disorder transition with a growth rate that strongly depends on surface orientation and sliding direction, in excellent correlation with experimental wear rates. This anisotropy originates in mechanically steered dissociation of individual crystal bonds. The anisotropy factor of diamond increases to 40% at high pressures and becomes temperature independent.
Metallic solids are like aluminium show anisotropy.The properties of aluminium , as with most metals, are never completely uniform in all directions - some degree of anisotropy is always present. Anisotropic properties can have a major effect on subsequent process stages, especially sheet metal forming processes such as deep drawing and stretch forming, and on in-service performance.