What is Crystallography?

How would a material look if you could see through it and see the atoms it is made from? How does stuff actually stay together? Many of the answers to these questions are provided by the science of crystallography, which is what we are celebrating at this exhibition. This year has been declared the International Year of Crystallography by the United Nations. So what’s all the fuss about? 

Crystallography is a unique technique that allows us to peer inside a material and discover how the atoms that make it up are arranged . 

The first crystal structure was discovered 100 years ago, but crystallography is still used today by physicists, chemists, geologists, engineers and biologists to study how atoms are arranged in space. 

In a “nicely” arranged crystalline material we can identify a finite volume, or box, that is repeated in three dimensions. This box contains a selection of atoms in a particular arrangement. And the collection and arrangement of atoms are also repeated in three dimensions. 

This means that, using a combination of information about the box and the arrangement of atoms inside the box, we can define one gram of a material, or even one thousand tonnes, in the same way. 

The atomic arrangement is important because it directly influences the properties of the material. The most stunning example is carbon, which comes in a few forms (also known as allotropes or polymorphs) which are determined by how the carbon atoms are arranged in the boxes. An allotrope of carbon - graphite, which is found in the humble pencil - is flaky and fairly brittle, while another allotrope of carbon - diamond, like the one found in your precious ring - is one of the hardest materials known on Earth. 

Why should we, Australia, be one of the proudest crystallographic nations? Well, an Australian developed the entire field of crystallography. 

OK, this might be a slight exaggeration. But the Nobel Prize-winning father and son duo, William Henry Bragg and William Lawrence Bragg,  developed the fundamental equation, nl = 2dsinq, that is the cornerstone of crystallography. 

William Henry, the elder Bragg, moved from Britain to South Australia in 1885 to become Professor of Mathematics and Physics at the University of Adelaide. He met and married an Australian woman and then moved back to the UK with their Australian-born son, William Lawrence, who attended Cambridge University. 

The Braggs worked on projects together and experimented with X-rays and ideas about the interactions of waves and particles, building on the work of other scientists in this field, including Wilhelm Roentgen, Marie and Pierre Curie and Max Von Laue

The Braggs used their equation to solve the crystal structures of materials such as diamond and copper. They were awarded the Nobel Prize in Physics in 1915, making William Lawrence Bragg, who was only 25 at the time, the youngest person to ever receive this honour. 

The Bragg Institute at ANSTO’s Lucas Height’s Sydney campus is named in tribute to Nobel Prize winners William Henry and William Lawrence Bragg. It leads Australia in the use of neutron scattering used in crystallography. At the centre of the research institute is the OPAL research reactor, along with state-of-the-art neutron beam instruments used for diffractrion, affectionately named after Australian fauna.

Crystallography evolved from a predominantly physics-oriented challenge to one of a chemical nature, allowing chemists’ unparalleled insights into atomic distributions in their building blocks. 

It did not stop there, with geologists and mineralogists using this technique to assess ores and differentiate minerals. When highly-penetrating and non-destructive neutron scattering became available, engineers also started to look at welds and their failure mechanisms using this technique. 

Finally, biologists came on-board. The crystal structures of proteins, enzymes and DNA were all solved using crystallography.