National Physical Laboratory

2014 - The Year of Crystallography and X-Ray Diffraction

The Functional Materials Group at NPL is developing new measurement capabilities, in collaboration with world-leading facilities around the world, to study piezoelectric and magnetoelectric materials with X-rays and neutron diffraction techniques.

Ling Hao leads NPL's work on nanoSQUIDs
DNA polymerase I: An enzyme that participates
in the DNA replication, shown with a fragment
of DNA (image courtesy of iStockphoto)

The science of crystallography has played a key role in understanding why and how atoms form crystals both in pre-existing natural structures and manmade materials. Crystals are everywhere, in teeth, bones, medicines, optics, electronic chips, jewels, cultural artefacts, cosmetics and food. Crystallography has transformed both engineering and the physical sciences, even paving the way to modern biology, having played a crucial part in the discovery of the structure of DNA.

International Year of Crystallography

To celebrate its important role in the modern world, the United Nations has declared 2014 to be the International Year of Crystallography, commemorating not only the centenary of X-ray diffraction as a tool for the study of crystalline materials, but also the 400th anniversary of the observation of symmetry of ice crystals by Johannes Kepler, a historical landmark that began the study of the role of symmetry in matter. The UNESCO Year was launched on 20 January 2014 in Paris, France. In addition, the United Nations recognised that the understanding of the structure of matter is of fundamental importance for technological advances and highlighted that the teaching of crystallography and its application are essential to address key challenges for societal development.

Scientists have been developing methods to look into materials, pushing the limits beyond the resolution of optical microscopes. Crystallography is the science that describes crystals from using geometry and symmetry and describes how atoms are arranged in structures to form crystals. It is an underpinning technology used routinely for the development of practically all new materials. Using energetic beams of electrons, X-rays and neutrons to irradiate materials, scientists can detect the interference (diffraction) of those beams with the material and reconstruct the arrangement of the atomic crystal.

Have you ever wondered how we can make batteries lighter and smaller or how we can store more songs on an MP3 player? Or what about the difference between cheap and expensive pharmaceuticals, like paracetamol? Find the answers to these questions and more on the website of the British Crystallographic Association (BCA)

The Functional Materials team at NPL uses X-ray diffraction techniques to understand the aspects of crystal structure that directly control the properties of materials used in a wide range of applications, from medical imaging to automotive fuel injection and naval sonar.

Beyond X-Ray

Ling Hao leads NPL's work on nanoSQUIDs
Structural and magnetic model of a
magnetoelectric multiferroic compound determined
by neutron diffraction

While crystallography is the science of how matter is arranged, diffraction is the interference phenomenon which occurs when a wave encounters an obstacle. Diffraction occurs in all waves, including water or sound waves but also electromagnetic waves such as visible light or X-rays, because of the wave-particle duality of matter, electrons or neutrons. By observing the properties of the scattered (diffracted) radiation, it is possible through mathematical derivation to create models of how atoms are arranged in matter, how they vibrate (e.g. due to thermal motion) or how they displace (e.g. due to an applied strain or electric field in piezoelectric or ferroelectrics or when a magnetic ordering develops in magnetoelectrics/magnetostrictives).

As an example, piezoelectrics are interesting materials that change shape when an electric field is applied, or vice versa, developing a voltage when compressed. These materials are very useful for actuator applications or sensing devices and, recently, new ideas have been put forward to use them in very different fields to drive innovation in state of the art computer technology (Nanostrain Project). Understanding the crystallography of these materials, and therefore how the lattice changes or how atoms displace under the effect of external stimuli, is a crucial step in the development of new, more efficient and higher performance electronic devices.

NPL's Functional Materials Group is developing new metrology capabilities, in collaboration with world leading large scale facilities around the world, to study piezoelectric and magnetoelectric materials with X-rays or neutron diffraction techniques and to simultaneously apply an electric field and use interferometry to measure the induced electric polarisation, the macroscopic (nanometre size) strain together with valuable atomic scale information.

This work will help industry and academic researchers make advances in many areas such as in the development of new microelectronic devices, medical applications, telecommunications, aerospace, automotive and new storage methods.

History

Crystallography was invented by William Henry and William Lawrence Bragg, at the University of Leeds and University of Cambridge. The father-and-son team were awarded the Nobel Prize in Physics in 1915 for their discovery. X-rays had been discovered by Wilhelm Rontgen a few years earlier in 1895. The 'X' in 'X-ray' was used to signify an unknown type of radiation.

Gender balance

Crystallography, a technique that has done so much to unravel the structure of matter at the atomic level, is a branch of science that still seems to be closer to gender balance than many other branches of physics and chemistry. A large number of female scientists have been active in the field, including:

  • Dorothy Hodgking
  • Rosalind Franklin
  • Helen Megaw
  • Dorothy Wrinch
  • Olga Kennard
  • Clara Shoemaker
  • Rita Cornforth
  • Cecily Darwin Littleton
  • Jenny Pickworth Gluster
  • Eleanor Dodson
  • Judith Howard

Another notable scientist was Margaret Roberts, who went on to be better known as Margaret Thatcher, Britain's first female Prime Minister. Baroness Thatcher specialised in X-ray crystallography in the final year of her Chemistry degree at the University of Oxford, under the supervision of Dorothy Hodgkin. This also made her the first British Prime Minister to hold a science degree.

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Last Updated: 4 Nov 2015
Created: 27 Jan 2014

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