However, I want to celebrate the structure of materials which are not crystals: the study of which extends back almost as far and uses many of the same empirical and computational tools.
It is of the essence of a crystal – whether that be of common table salt, NaCl, or of a fiendishly complex biological molecule – that its constituent atoms are arranged in a very specific order. If we know the positions of a suitable sub-set of them then we can predict the positions of all the others: we use the concepts of unit cells, lattices and symmetry if order to extrapolate from the microscopic to the macroscopic. For much of the past century, X-ray diffraction was the initial experimental step in this process. Whilst laboratory-based X-ray sources continue to be used to great effect, it’s arguably the case that the advent of the synchrotron source, such as the UK’s Diamond facility, allowed much of modern crystallography to expand. Exploiting the wave-like properties of the neutron, using research facilities such as ISIS and the ILL, adds a new dimension. Why? Because neutrons interact with nuclei whereas X-rays scatter from an atom’s cloud of electrons – thus, we have access to the lighter elements (i.e. those which scatter X-rays relatively little) and we can use the fact that one of a given element’s isotopes may scatter neutrons very differently to another. Add to this the fact that a neutron has mass, unlike an X-ray photon, and one might now even look at the movement of atoms in a material.
One of these days I must write something longer on the science, art and technology of glass– not today though … . In the meantime, take a look at some of the videos on the subject available via YouTube: one recent favourite of mine, on why window glass is transparent, was put together by Prof. Mark Miodownik, who is a well known and highly accomplished science communicator in the materials arena. I have also uploaded a recording of one of my own talks to YouTube which was delivered a few years back at Canterbury’s Heritage Museum; progressively modified/updated versions of this talk have been delivered several times since then – with more bookings already agreed.
Most, if not all my published output on the structures of amorphous materials (including a lot on glasses and glassy materials) are available via ResearcherID or Google Scholar (search using "Robert Newport"); you can also find me on ResearchGate. New papers are touted via Twitter as well: @Bob_MatPhys.