Speaker
Description
The majority of neutron total scattering experiments have been performed under ambient or variable-temperature conditions whereas comparatively little work has been carried out under high pressure. This is partly a consequence of the difficulties involved in accurately removing non-sample scattering contributions when using devices such as the Paris-Edinburgh press, which are required to deliver multi-GPa pressures.
The PEARL instrument at the ISIS Neutron and Muon Facility has a demonstrable track record in performing these measurements with non-crystalline samples where strain broadening is not an issue [1-3]. However there has been little work performed on crystalline materials as these usually require hydrostatic compression, achieved by the inclusion of a pressure-transmitting medium (PTM). The PTM can further complicate the analysis of pair distribution functions.
This talk will focus on the use of the unique gas-loading capability [4] at ISIS where argon is used as an 'invisible' PTM. Science examples will include the pressure-induced order-disorder transition in ammonium bromide [5] and the nature of correlated displacements in barium titanate under hydrostatic pressure [6].
[1] H Playford, M Tucker and C Bull, J. Appl. Crystallogr., 2017, 50, 87-95
[2] S Klotz et al, J. Phys.: Condens. Matter, 2005, 17, S967-S974
[3] P Salmon et al, J. Phys.: Condens. Matter, 2012, 24, 415102
[4] S Klotz et al, High Pressure Res., 2013, 33(1), 214-220
[5] N Funnell , C Bull, S Hull and C Ridley, J. Phys.: Condens. Matter, 2022, 34, 325401
[6] A Herlihy et al, Phys. Rev. B, 2022, 105, 094114