MAT E 201
Materials Science I
Assignment No.2 (15 marks)
1. What is a polycrystalline material? (0.2 marks)
2. What is a liquid crystal material? (0.4 marks)
3. What is an amorphous material? (0.4 marks)
4. Determine the crystal structure for the following: a) a metal with ao = 4.04159489 Ǻ, r
= 1.75 Ǻ and one atom per lattice point and b) a metal with ao = 0.42906 nm, r = 0.1517
nm and one atom per lattice point. (3 marks)
5. The density of iron, which has the BCC structure, is 7.87 g/cm3
. The atomic mass of
iron is 55.847 g/mol. Calculate: a) the lattice parameter of Fe and b) the atomic radius
of Fe. (3 marks)
6. A metal having a cubic structure has a density of 19.302 g/cm3
, an atomic mass of
196.97 g/mol and a lattice parameter 4.0786 Ǻ. One atom is associated with each lattice
point. Determine the crystal structure of the metal. (2 marks)
7. Yttrium has a hexagonal crystal structure, with ao=0.3648 nm and co=0.5732 nm. The
atomic radius is 0.1824 nm, the density is 4.469 g/cm3
and atomic mass is 88.91 g/mol.
Calculate a) the number of atoms in each unit cell and b) the packing factor in the unit
cell (3 marks)
8. Determine the indices for the directions A, B, C and D in the cubic unit cell shown in
the following Figure 1. (3 marks)
