11. Aluminium unit cell An Aluminium unit cell is shown here. All atoms in this unit cell are of equal size and have a radius 'r'. With reference to the cubic unit cell shown here. a) Identify the type of structure of this unit cell b) How many atoms are in the above unit cell c) Calculate the packing factor and show how it was derived. d) How many different types of crystal structure are there? e) How many different Bravais lattices are there? f) Name another type of close packed crystal structures that has the same packing factor