(a) Calculate the Atomic Packing Factor (APF) of the materials shown below: (i) Po (Polonium) /3 (ii) Cs (Cesium) /3 (iii) Al (Aluminum) /3 (iv) Hf (Hafnium) /3 (v) -Fe (gamma-iron; austenite) /3 (b) Can you increase the number of atoms per unit cell, coordination number, and APF of the above crystal structure by changing the atomic radius? Why or why not? /3 (c) A group of atoms associated with each lattice point is called basis or motif, i.e. the repeating pattern. Give the number of atoms per unit cell of the BCC and FCC, and represent the atomic positions of the basis comprising the unit cell. Use simple cubic lattice to determine basis positions of the BCC and FCC. /4