Future directions in high-pressure neutron diffraction

Abstract

The ability to manipulate structure and properties using pressure has been well known for many centuries. Diffraction provides the unique ability to observe these structural changes in fine detail on lengthscales spanning atomic to nanometre dimensions. Amongst the broad suite of diffraction tools available today, neutrons provide unique capabilities of fundamental importance. However, to date, the growth of neutron diffraction under extremes of pressure has been limited by the weakness of available sources. In recent years, substantial government investments have led to the construction of a new generation of neutron sources while existing facilities have been revitalized by upgrades. The timely convergence of these bright facilities with new pressure-cell technologies suggests that the field of high-pressure (HP) neutron science is on the cusp of substantial growth. Here, the history of HP neutron research is examined with the hope of gleaning an accurate prediction of where some of these revolutionary capabilities will lead in the near future. In particular, a dramatic expansion of current pressure-temperature range is likely, with corresponding increased scope for extreme-conditions science with neutron diffraction. This increase in coverage will be matched with improvements in data quality. Furthermore, we can also expect broad new capabilities beyond diffraction, including in neutron imaging, small angle scattering and inelastic spectroscopy.

Reversible structural transition in nanoconfined ice

“…There are approximately 16 different ice structures that have been confirmed using various techniques that include Neutron Scattering, infrared spectroscopy and Raman spectroscopy 33 . At a temperature of 300 K and with pressures of >1 GPa there are three potential bulk water structures, VI, VII and X.…”

Quantum Nuclear Dynamics of Protons within Layered Hydroxides at High Pressure

“…The proton transport is also responsible for the reactivity of hydroxides, being involved in the diffusion paths and conduction mechanisms of protons. The results of recent experiments and calculations have informed our efforts, which are herein focused on calcium hydroxides because the proton disorder should be observable at lower experimental pressures in these hydroxides 1, 6 . Although previous calculations tended to treat the nuclei in a classical way, an increasing number of studies point to the importance of nuclear quantum effects (NQEs) in protonated systems 13 , either for pure water 14–16 or for extrinsic defects for low concentrations of protons immersed in perovskites 17, 18 .…”

“…The hydroxide group of compounds continues to stimulate wide interest in view of the prospect of their use in broadening the scope of neutron diffraction techniques at high pressure 1 . For mineral hydroxides, it is also possible to see a more immediate interest in geosciences 2 and chemistry, for instance in the industrial applications of cements and glasses 1, 3 and materials for energy.…”

“…For mineral hydroxides, it is also possible to see a more immediate interest in geosciences 2 and chemistry, for instance in the industrial applications of cements and glasses 1, 3 and materials for energy. The pivotal feature of hydroxide crystals is that protons take an important role in the structure – hydrogen bonds form the link between sheets in the layered structure of many hydroxides.…”

Nuclear Magnetic Resonance Spectroscopy as a Dynamical Structural Probe of Hydrogen under High Pressure

“…Protons and deuterons have significant neutron scattering cross-sections, which might suggest that neutron diffraction would be an ideal probe for structural studies of high pressure hydrogen. However, the weakness of available neutron sources combined with the small samples in diamond anvil cells place practical limits to the applicability of this technique [6], and the highest pressure experiments reported in the hydrogen-deuterium system only reach 38 GPa [7].…”