6.1 Qualitatively the melting point of a crystalline solid can be defined as the temperature Tm at which the amplitude of simple harmonic vibrations of the individual atoms about their lattice sites is about ten per cent of the interatomic spacing

a. Show that on this picture the frequency v of the vibrations of a monatomic crystal

(atomic weight M) satisfies the proportionality relation The Einstein temperatures of aluminium and of lead are 240 Κ

and 67 Κ respectively. Guess orders of magnitude or look up data to decide whether these temperatures and the above formula are in reasonable agreement.