Loveday, John

Guthrie, Malcolm

Massani, Bernhard

2022-09-22T15:21:30Z

2022-09-22T15:21:30Z

2022-09-22

A proton and an electron form the lightest element of the periodic table: Hydrogen. Despite the simplicity of this element and an ongoing research interest, surprisingly little is known about its solid phases and structures of hydrogen-rich compounds such as water, ammonia or methane. In the particular, high pressure phases of these compounds are poorly understood. The reason for this is of a two-fold nature; first and foremost, small, hydrogen-rich molecules have very complex phase diagrams - partially due to the quantum nature of hydrogen - and form a vast variety of crystal structures. And secondly, the only direct way of measuring the hydrogen positions in these crystal structures is neutron-diffraction. While very powerful in structure determination, this technique requires large sample volumes and, hence, the pressure range has been limited to below 40 GPa; until recently, neutron diffraction had to rely on large-volume pressure cell such as the Paris-Edinburgh-Press. The overall aim of this body of work was to overcome current pressure-limitations and the concomitant limitations in data quality using single-crystals in diamond anvil cells for neutron diffraction. This attempt has been successful and the data-reduction and correction procedure reported in this work are now being used at the Snap beamline at Sns (Oak Ridge National Laboratory). The original aim for the second half of this thesis was to use single-crystal neutron-diffraction to measure single-crystals of hydrogen (deuterium) and water. Due to the ongoing pandemic caused by Covid-19 and the restrictions to travel to Sns, this was not possible. Hence, the second half of this works tries to fill gaps in the knowledge of the high-pressure behaviour of water-gas compounds using existing techniques. In particular, studies on the water-nitrogen, water-ammonia and the water-ammonia-methane systems will be presented here.

https://hdl.handle.net/1842/39375

http://dx.doi.org/10.7488/era/2625

en

The University of Edinburgh

B. Massani, L. J. Conway, A. Hermann, and J. Loveday. On a new nitrogen sX hydrate from ice XVII. Journal of Chemical Physics, 151:104305, 2019.

B. Massani, J. S. Loveday, J. J. Molaison, A. M. dos Santos, X. P. Wang, L. L. Daemen, B. Haberl, R. Boehler, and M. Guthrie. On single-crystal neutron-diffraction in DACs: quantitative structure refinement of light elements on SNAP and TOPAZ. High Pressure Research, pages 1–19, 05 2020

B. Massani, C. G. Pruteanu, L. J. Conway, V. N. Robinson, A. Hermann, and J. S. Loveday. Ammonia mono hydrate iv: An attempted structure solution. Crystals, 12(2), 2022.

B. Massani, C. Mitterdorfer, and T. Loerting. Formation and decomposition of CO2-filled ice. Journal of Chemical Physics, 147(13):134503, 2017.

A Possible Crystal Structure of Ammonia Monohydrate IV B. Massani, C. Pruteanu, L. Conoway, A. Herrmann, and J. S. Loveday Crystals, 12(2), 135

On single-crystal neutron-diffraction in DACs: Quantitative structure refinement of light elements on SNAP and TOPAZ B. Massani, J. S. Loveday , J. J. Molaison , A. M. dos Santos , X. P. Wang , L. L. Daemen , B. Haberl , R. Boehler, and M. Guthrie HPR, 40(3), 339-357

Amorphous and Crystalline Ices Studied by Dielectric Spectroscopy L. J. Plaga, A. Raidt, V. Fuentes Landete, K. Amann-Winkel, B. Massani, T. Gasser, C. Gainaru, T. Loerting, and R. B¨ohmer J. Chem. Phys., 150, 244501

Structural Features and Pore Formation in Decomposing CO2 Clathrate Hydrate S. Arzbacher, N. Rahmatian, A. Ostermann, B. Massani, T. Loerting, J. Petrasch PCCP, 147, 134503

Diffusive dynamics during the high-to-low density transition in amorphous ice F.Perakis, K. Amann-Winkel, F. Lehmkuehler, M. Sprung, D. Pettersson, J. Sellberg, H. Pathak, A. Spaeh, F. Cavalca, D. Schlesinger, A. Ricci, A. Jain, B. Massani, F. Aubree, C. J. Benmore, T. Loerting, G. Gruebel, L. Pettersson, A. Nilsson Proc. Natl. Acad. Sci., 114, 8193-8198

high-pressure crystal structures

H-H bond-length

high-pressure structures

deuterated potassium dihydrogen phosphate

gas hydrates under pressure

Neutron-diffraction of hydrogen-rich molecules under high pressure

Thesis or Dissertation

Doctoral

PhD Doctor of Philosophy