STFC-ISIS-11 Neutron spectroscopy and molecular simulations – force-field optimisation
04 Feb 2019







This project aims to establish an innovative new method for analysing neutron spectroscopy.  The focus is in developing MDMC, an open source software package written in Python which allows force-field parameters of molecular simulations to be optimised against neutron spectroscopy data.  This project addresses real scientific questions and during testing is applied to experimental data from ISIS and our international collaborators.

As experimental techniques are used to probe increasingly complex systems, subtle emergent behaviour can lead to significant difficulties when interpreting the data. This is particularly evident for spectroscopic techniques such as quasi-elastic neutron scattering (QENS), which is a method for probing nanoscale motions such as atomic diffusion or molecular rotation.  Analysis of QENS data is typically limited to fitting simple analytical models, which may be unrepresentative of the underlying dynamics.  By augmenting QENS with molecular dynamics (MD) or other simulation techniques, it is possible to observe this complex behaviour.  However achieving agreement between scattering and simulation is frequently challenging; a significant source of the disparity is because intermolecular potentials are commonly established using structural rather than dynamical data, and often only at ambient conditions.  In order to address this problem, our method utilises derivative-free optimisation algorithms (initially Metropolis Monte Carlo) to refine the intermolecular potential parameters; the resulting improved agreement will provide the greatest confidence that the MD is representative of the experimental system.

The successful applicant will work on developing MDMC and applying it to QENS data.  This initial demonstration of the approach will provide vital information on the effectiveness of the analysis technique, while also addressing outstanding scientific problems.

The student will gain experience in all aspects of scientific software development, including design, implementation and testing.  Due to the strong research focus of the project, they will gain an understanding of two diverse areas of science: molecular dynamics simulations and neutron spectroscopy. In addition, they will get the opportunity to interact with ISIS instrument scientists. As MDMC is in the alpha phase of development, they will be able to make a significant contribution to a new scientific software package.​ 

Supervisor: Tom Farmer,