Crystal Structure-Types
Crystal Structure-Types
Crystal Structure-Types
MATERIAL
CRYSTALLINE
Ionic and Metallic
Bonds
AMORPHOUS
Covalent Bonds
In a crystalline solid, particles which may be (atoms, molecules or ions) are surrounded by
like neighbors according to a definite geometrical repetitive pattern.
When describing crystalline structures, atoms or ions are thought of as being solid spheres
having well-defined diameters.
How atoms
are
arranged ???
Fig.(a)
Fig.(b)
Dept. of Mechanical Engineering 02-Dec-21 5:07 PM 4
Crystalline Structure
Bravais Lattice
The unit vectors a, b and c are called lattice parameters.
Based on their length equality or inequality and their orientation (the
angles between them, α, β and γ) a total of 7 crystal systems can be
defined.
Hexagonal closed
Rhombohedral Hexagonal Triclinic
packing
a=b=c a=b≠c a≠b≠c
α = β = γ ≠ 90° a=b≠c
α = β = 90°, γ=120° α≠β≠γ≠90°
α = β = 90°, γ=120°