MS18-P04 High-pressure neutron measurements of the highly-polymorphic 'ROY' Nicholas Funnell (UKRI - ISIS Neutron and Muon Facility, Didcot, United Kingdom) Craig Bull (UKRI - ISIS Neutron and Muon Facility, Didcot, United Kingdom) Christopher Ridley (UKRI - ISIS Neutron and Muon Facility, Didcot, United Kingdom) Silvia Capelli (UKRI - ISIS Neutron and Muon Facility, Didcot, United Kingdom)email: neutron-powder measurements are needed to discriminate between similar-Z elements, identify magnetic behaviour, or simply locate hydrogen atoms, large sample volumes are generally required for a successful measurement. This might appear problematic for high-pressure experiments where small sample volumes are necessary to access higher pressures. However, the large-volume Paris-Edinburgh press on the high-pressure PEARL beamline at ISIS, UK, allows us to make such measurements—striking a balance between sample quantity and accessible pressure.[1]

5-methyl-2-[(2-nitrophenyl)amino]-3-thiophenecarbonitrile is one of the most polymorphic organic materials known in the Cambridge Structural Database. It is more colloquially known as 'ROY', owing to the red, orange, and yellow polymorphs that it forms, all occurring under ambient conditions.[2] In this presentation, a recent compression study on ROY and its behaviour up to 9.3 GPa will be reported.[3] We show that the quality of PEARL data obtained, and careful DFT-assisted guidance of the refinement procedure, produce usable structural models from a weakly-scattering, hydrogenated sample. We discuss its structural response in the context of lattice- and intermolecular-energy calculations.

[1] Bull, C. L. et al. (2016), High Pressure Res., 36(4), 493-511.

[2] Yu, L., (2010), Acc. Chem. Res., 43, 1257-1266.

[3] Funnell, N. P. et al. In preparation.
Keywords: pressure, neutron, polymorphism