Details of Grant 

EPSRC Reference:	EP/L012243/1
Title:	Realising the combined potential of solid-state NMR and structural databases
Principal Investigator:	Hodgkinson, Professor P
Other Investigators:	Yates, Dr JR Howard, Professor JAK
Researcher Co-Investigators:
Project Partners:	Cambridge Crystallographic Data Centre
Department:	Chemistry
Organisation:	Durham, University of
Scheme:	Standard Research
Starts:	01 October 2014	Ends:	31 July 2018	Value (£):	356,797
EPSRC Research Topic Classifications:	Chemical Structure
EPSRC Industrial Sector Classifications:	No relevance to Underpinning Sectors
Related Grants:
Panel History:	Panel Date Panel Name Outcome 05 Feb 2014 EPSRC Physical Sciences Chemistry - February 2014 Announced 17 Oct 2013 EPSRC Physical Sciences Chemistry - October 2013 Deferred
Summary on Grant Application Form
Databases of crystal structures are essential tools for researchers working in the solid state. Initially established as repositories of experimentally determined structures, the large data sets contained within databases, such as the Cambridge Structural Database (CSD), have become the subject of research in their own right through the development of "data mining". The usefulness of such databases is, however, highly dependent on the quality of the data they contain. In the vast majority of cases the structures were obtained via X-ray diffraction (XRD). While XRD is the pre-eminent tool for establishing the three-dimensional structure of crystalline materials, there are areas where XRD studies struggle and some art is required on the part of the crystallographer to establish a correct structure. For instance, hydrogen atoms scatter X-rays very weakly, and fragments with the same (OH vs F) or very similar (Si vs Al) numbers of electrons are very hard to distinguish. In addition, any disruption of the regular ordering of a crystal creates major challenges for structure solution; diffraction is not the natural tool for understanding such "disorder". Historically XRD experts have used measures such as "R factors" to assess how well a proposed structure fits to the experimental data, but ideally independent experimental evidence would be used to verify crystal structures. We and other research groups have shown in recent years that solid-state nuclear magnetic resonance (SS-NMR) can now be used very effectively to distinguish between different possible crystalline structures. Developments in quantum chemistry (mostly notably through Density Functional Theory) allow NMR spectra to be calculated with excellent precision. Since the NMR spectrum is sensitive to very small changes in the local structure - deviations of the order of a picometre (10^-12 m) will change the spectrum measurably - even small imperfections in a crystal structure solution can be identified. Moreover different types of "disorder" e.g. due to the motion of atoms or irregular atomic positioning, have clear and distinct effects on the NMR spectrum. This proposal seeks to develop systematic approaches to the validation of crystal structures via solid-state NMR and computational chemistry. We will establish which NMR experiments are required in order to distinguish crystal structure solutions and also to "validate" a structural solution. This will involve the creation of "NMR confidence parameters" which will measure the extent to which a structure is compatible with the NMR data available, and the effectiveness of these parameters will be verified against more traditional diffraction-based tools. By taking a systematic approach, we will be able to show how NMR can be used to resolve the different types of structural ambiguity and show the value of NMR as a complement to conventional diffraction-based studies.
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