Aste T., Weaire D. Pursuit of perfect packing (IOP 2000)(147s).pdf

22 Hard problems with hard spheres
(a)
(b)
Figure 3.2. Bernal packing of spheres.
variety. He also recognized the difficulty of doing so, other than by direct observation
of a model system. Why not ball bearings He called this unsophisticated
approach ‘a new way of looking’ at liquids.
Hence the shaking and kneading of ball bearings in a bag, the pouring in of
wax, the meticulous measurement of the positions of balls as the random cluster
was disassembled. The packing fraction of the Bernal packing was found to be
roughly 0.64; or slightly less if the balls are not kneaded to encourage them to
come together closely. Although particular local arrangements recur within it,
they are variable in shape and random in distribution 2 .
Subsequently, the chief scientific interest of the Bernal structure has been
in its application to describe the structures of amorphous (i.e. non-crystalline)
metals.
Si l’ordre satisfait la raison,
le désordre fait les délices de l’imagination.
Paul Claudel (1868–1955)
3.3 A new way of looking
Desmond Bernal, born in 1901 on an Irish farm, was one of the prime movers of
modern crystallography and biophysics. He is thought to have narrowly missed
a Nobel Prize for his work on sex hormones. This would have been singularly
appropriate for a man whose sexual appetite was rumoured to be prodigious. This
¾ Bernal J D and Mason J 1960 Co-ordination of randomly packed spheres Nature 385 910–11.