Atoms in materials can be arranged in a variety of different ways: a periodic arrangement of atoms in crystals, short-range correlations between the positions of atoms in glasses, or a hierarchy of arrangements of the components of proteins. Neutrons are one of the most powerful tools for determining the structure of materials on different length scales and provide information that is vital to understanding new materials.
ISIS neutrons enable the determination of the crystal structure for a wide range of novel materials, ranging from recently discovered iron-based superconductors to the metal alloys used inside nuclear reactors and aero-engine turbine blades.
An area attracting considerable interest in the last few years has been materials that shrink as they are heated, a phenomenon known as negative thermal expansion. Most materials expand as they are heated so materials that can counteract this could be very useful. Neutron measurements have investigated both how the atoms within the materials move around as a function of temperature, and also how their vibrations drive the negative thermal expansion.
Even very familiar materials can show new properties when pressure is applied to them, or their temperature is changed out of the region we know well. An example of this is the discovery of new structural phases of ice where the hydrogen atoms in the water molecules form different ordered structures. Water can also display different local structures in its liquid form, if a heavier isotope of hydrogen is present.