Award Date

May 2023

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry and Biochemistry

First Committee Member

Paul Forster

Second Committee Member

Ashkan Salamat

Third Committee Member

Clemens Heske

Fourth Committee Member

Keith V. Lawler

Fifth Committee Member

Jason Steffen

Number of Pages

180

Abstract

Hydrogen was predicted to be a high-temperature superconductor at near-megabar conditions in 1968,[1] but only recently was been experimentally observed.[2] This is due to the extraneous metrological constraint of requiring 5 megabars of pressure to stabilize. A more practical approach for synthesis of high-temperature superconductors has been pro-posed through the use of hydride compounds. Recently, a surge of rare earth hydrides have achieved critical superconducting transition temperatures (T_C ) close to room temperature.[3, 4, 5, 6] However, due to limitations of the necessary instrumentation to achieve megabar pressures, many techniques traditionally used to measure stoichiometry are unavailable.Three works presented in this dissertation help elucidate the difficulties in measuring hydride composition in situ using the diamond anvil cell and approaches to guide future studies. The first study observes small displacements from a light crystallographic oxygen sublattice of GeO2 in a pre-transition disordered state using complementary X-ray techniques to observe both long and short-range order.[7] More broadly, this works displays how small changes to a light sublattice result in changes in the electrical properties. In the second study, a carbonaceous sulfur hydride is investigated using single-crystal X-ray diffraction at high pressures.[8] This work shows that even with high solid angle single crystal diffraction, it is still not possible to resolve hydrogen positions at high-pressure conditions. In the final study, measurements of both X-ray absorption and X-ray emission spectroscopy of the rare earth hydride yttrium hydride are also presented. This study shows that the sensitivity of X-ray spectroscopy to local coordination allows for whole integer resolution of stoichiometric hydride compounds.

Keywords

Condensed Matter; High-Pressure Physics; High-Temperature Superconductivity; Hydrides; Superconductivity; X-Ray Spectroscopy

Disciplines

Condensed Matter Physics | Other Physics | Physical Chemistry | Physics

Degree Grantor

University of Nevada, Las Vegas

Language

English

Rights

IN COPYRIGHT. For more information about this rights statement, please visit http://rightsstatements.org/vocab/InC/1.0/

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