1. King Abdulaziz University Chemical and Materials Engineering Department Chapter 3 The Structure of Crystalline Solids Session III

2. King Abdulaziz University Chemical and Materials Engineering Department Crystal Systems 7 crystal systems 14 crystal lattices Unit cell: smallest repetitive volume which contains the complete lattice pattern of a crystal. a, b, and c are the lattice constants

3. King Abdulaziz University Chemical and Materials Engineering Department Axial AngleAxesSystem  =  =  = 90 O a = b = c Cubic  =  =  = 90 O a = b  ≠ c Tetragonal  =  = 90 O ≠  a ≠ b ≠ c Monoclinic  ≠  ≠  ≠ 90 O a ≠ b ≠ c Triclinic  =  =  = 90 O a ≠ b ≠ c orthorhombic  =  = 90 O ;  =120 O a = a ≠ c Hexagonal  =  =  ≠ 90 O a = b = c rhombohedral 7 Crystal Systems

4. King Abdulaziz University Chemical and Materials Engineering Department Noncubic unit cell a=b≠c, angles =90 o Tetragonal system a ≠ b≠c, angles =90 o orthorhombic system a = a ≠ c, angles =90 o, 120 o hexagonal system a b c a

5. King Abdulaziz University Chemical and Materials Engineering Department Lattices 7 systems can be divided into 14 patterns of points, called Bravais lattices. e.g. Cubic systems: Body centered cubic (BCC),Face centered cubic (FCC) Simple cubic (SC)