#1    (a): Kittel 1.3   (hcp structure)
        (b): Solid Na undergoes a bcc-to-hcp phase transition at 23K. Assuming constant density and ideal c/a ratio with a=0.423nm for bcc, determine a for the hcp phase.

#2:   Calculate the atomic packing fractions for diamond and for graphite.

#3:   Kittel 2.5  (structure factor of diamond)*
     *hint: the basis of the diamond structure referred to the fcc lattice has identical atoms at 000; 1/4 1/4 1/4.

#4:   Kittel 2.6  (form factor of atomic hydrogen)

#5    (a): Kittel 3.1  (quantum solid: helium)
        (b): Kittel 3.3  (solid molecular hydrogen)

#6    (a): Kittel 4.3  (basis of two unlike atoms)
         (b): Kittel 4.5  (diatomic chain)

#7    Extra Credit:  Calculate the Madelung constant for a ionic solid with cubic symmetry.* 
    *hint: evaluate in terms of electrically-neutral lattice units.