Validating crystal structures using NMR

General Background

The Solid-State NMR research group develops methods, theory and applications of Nuclear Magnetic Resonance to solid samples. In particular, the group is at the fore-front of the developing field of “NMR crystallography” applied to organic molecular solids. Solid-sate NMR is directly comparable with conventional solution-state NMR, but with the difference that samples are usually packed into rotors which are spun at speeds of 5–60 kHz. Durham is a centre of expertise in the area, having three high-field NMR spectrometers dedicated to solid-state NMR.

Project Description

Developments in DFT codes mean that it is now relatively straightforward to calculate NMR parameters, such as chemical shifts, for a given crystal structure. In recent work examining repeat structure determinations in the Cambridge Structural Database, we have found many cases where experimental evidence, e.g. from NMR, is needed to distinguish between alternative solutions derived from diffraction studies (1). Given the variety of NMR nuclei, the variety of NMR observables (e.g. isotropic chemical shifts, quadrupolar couplings etc.), and the variety of 1D and 2D NMR experiments available it is not always obvious, however, which NMR experiments distinguish most effectively between correct and incorrect structures.

Various approaches to validating crystal structures will be evaluated, ranging from simple measures of deviations between experimental and calculated shifts to more sophisticated methods e.g. Bayesian inference to determine quantitatively the information provided by different data sets. We will also exploit expertise in machine learning within the department to identify patterns in results, since it is likely that different situations will require different experimental inputs.

Studentship Profile

Like most of the projects in the NMR group, these involve a mix of experimental work, analysis and computation. It would suit anybody with interests in the solid state and pharmaceutical applications in particular. Past members of the NMR group have readily found employment in R&D positions (often within the pharmaceutical industry) or academic postdocs thanks to their knowledge of a range of characterisation techniques and skills (NMR, XRD, computation). While the project described leans towards the computational end, other, the project can be developed in more experimental directions. In general, applicants should be comfortable with computing and be enthusiastic problem solvers. Applicants should have (or expect to obtain) at least the equivalent of a UK 2.i honours masters level degree in Chemistry / Chemical Physics. The position is available from October 2019, and is funded for 39 months. For more information, including recent papers, visit our web site www.dur.ac.uk/solids.nmr.

Interested applicants should contact Dr Paul Hodgkinson ([Email Address Removed]) with a covering letter and CV, including the names of two suitable referees (academic or placement/project supervisors). Informal enquiries in advance of a formal application are very welcome.

Early applications before the 18th January at the latest are strongly encouraged. The position is likely to be filled if a suitable candidate is identified, and funding may not be available after this date.