Project 9:

Short Range Order in Crystals Studied by Diffuse X-ray Scattering

Diffraction of x-rays, neutrons and electrons by crystals is one of the key ways we find out about how atoms are arranged in materials, from superconductors to proteins.  Most diffraction experiments look at the Bragg peaks, the diffraction maxima that obey Bragg’s law, nl = 2dsinq, and which are very intense.  However, a lot of information can be gained by looking at the short range order in crystalline materials.  This is studied using the scattering that occurs between the Bragg reflections.  This scattering is weak and often quite broad, so is known as diffuse scattering (for example, figure 1).

Figure 1: A plane of diffuse scattering from 33’-dimethoxybenzil.  The small white spots are the Bragg peaks; everything else is diffuse scattering.

In this project the student will gain experimental experience by preparing a sample for a diffuse scattering experiment, collecting the data and taking steps to analyse the scattering.  Possible materials to study include metal alloys, molecular crystals and pharmaceuticals.  The emphasis of the project can be more heavily computational or experimental, subject to discussions.

Supervisor:       Darren Goossens

                        Research School of Chemistry

                        Ph: X53536

                        email: goossens@rsc.anu.edu.au