Total scattering
The Disordered Materials group operates three neutron time-of-flight diffractometers for the fundamental and applied study of disordered and complex materials using total scattering. These instruments are SANDALS and GEM (co-operated with the Crystallography group) on Target Station 1, and NIMROD on Target Station 2. The group also runs two PANalytical X-ray diffractometers with Ag and Mo sources, and which are optimised for PDF measurements.
The group specialises in the analysis of total scattering data covering multiple length scales ranging from the atomic up to the nanoscopic regimes, and provides structural insights in to problems in chemistry, physics, materials science, and biology. To this end we support an extensive suite of data reduction and analysis tools, covering the processing of raw neutron data, analysis of target systems through Monte Carlo refinement of the data, and the subsequent extraction of structural properties.
Isotopic substitution plays a major role in most experiments on the NIMROD and SANDALS instruments since the majority of samples contain hydrogen, and which can usually be substituted for its heavy analogue, deuterium. Isotopic Substitution in Disordered Materials Experiments (pdf) – This is a short guide on the power of isotopic substitution in the context of total scattering experiments on the Disordered Materials instruments, as well as how to choose which isotopic systems to run to get the best out of your experiment.
Total scattering software
Gudrun is a the main data reduction program used for the processing and correction of total scattering data and is written and maintained by Alan Soper. It comes in two flavours:
- GudrunN is used for correcting neutron diffraction data taken (primarily) on SANDALS, NIMROD and GEM, taking the raw data and generating the experimental structure factor.
- GudrunX is used for correcting x-ray diffraction data, for example that taken on the group’s XRD instruments.
GudPy is a replacement user interface for Gudrun_GUI written by Jared Swift and offers a modern user interface with integrated plotting and enhanced workflows for data processing.
Installers for GudPy can be found on GitHub, along with the source code.
Data modelling
Empirical Potential Structure Refinement (EPSR)
EPSR is a Monte Carlo based modelling program that allows the reconstruction of a 3D model of the system under study, inputting information from the diffraction data in an iterative way. Once a suitable fit to the experimental data has been obtained, the underlying atomic model can then be probed for the structural properties of interest, either within EPSR itself or via external programs such as those in dlputils.
Dissolve builds on the success of EPSR and employs similar techniques, but utilises a full classical forcefield and is extensible to multi-configuration, million-atom simulations.
The source code for the project is hosted on GitHub.
The Multiscale Simulation Scattering Intensity Calculator (MuSSIC) is a tool to calculate neutron-weighted structure factors from coarse-grained simulation trajectories. The source code, user guide and documentation for the project is hosted on GitHub.
