Thesis (Ph. D.)--University of Missouri-Columbia, 2008. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed June 17, 2009). Vita. Includes bibliographical references.

Thesis (Ph. D.)--Duke University, 2008.

Thesis (Ph. D.)--Delft University, 2004. / Includes bibliographical references.

Thesis (Ph. D.)--Delft University, 2004. / Includes bibliographical references.

Carboxylic acids have played an important role in the field of actinide (An) and lanthanide (Ln) separations and the reprocessing of irradiated nuclear fuel. Recent bench-scale experiments have demonstrated that 3-carboxy-3-hydroxypentanedioic acid (citric acid) is a promising aqueous complexant that can effectively aid in the separation of transition metals from f-element mixtures. Furthermore, citric acid was found to be a suitable buffer for the nitrogen donating ligand diethylenetriamine-N,N,N',N'',N''-pentaacetic acid (DTPA) which has a higher complexation affinity for An over Ln. The complexation of Ln and An with anions of citric acid and DTPA have been previously studied with conflicting results regarding the coordination of metal ions between carboxylic groups, the feasibility of protonated metal complexes, and the formation constants themselves. Using potentiometry, spectrophotometry,microcalorimetry, and specific ion interaction modeling, we investigated metal complexes of citric acid and DTPA with selected trivalent and tetravalent Ln and An ions. The complexes were investigated with respects to stability constants, thermodynamics of complexation, oxidation states, the concentration of electrolyte, ligand size, thermodynamics of complexation, oxidation states, the concentration of electrolyte, ligand size, and metal ionic radius. / Graduation date: 2013 / Access restricted to the OSU Community at author's request from Jan. 3, 2013 - July 3, 2013

Thesis (Ph. D.)--University of Missouri-Columbia, 1997. / Typescript. Vita. Includes bibliographical references (leaves 180-182). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 1997. / Typescript. Vita. Includes bibliographical references (leaves 180-182). Also available on the Internet.

Thesis (Ph. D.)--Auburn University, 2005. / Abstract. Vita. Includes bibliographical references.

Thesis (Ph. D.)--Ohio State University, 2005. / Title from second page of PDF file. Document formatted into pages; contains xxiii, 151 p.; also includes graphics (some col.). Includes bibliographical references (p. 140-151). Available online via OhioLINK's ETD Center

First-principles calculations such as density functional theory (DFT) employ numerical approaches to solve the Schrodinger equation of a system. Standard functionals employed to determine the cohesive system energy, specifically the local density and generalized gradient approximations (LDA and GGA), underestimate the correlation of 5f electrons to their ions in AO₂ systems (A=U/Pu/Np). The standard correction, the "Hubbard +U," causes the multidimensional energy surface to develop a large number of local minima which do not correspond to the ground state (global minimum). Because all useful energy values derived from DFT calculations depend on small differences between relatively large cohesive energies, comparing systems wherein one or more of the samples are not in the ground state has the potential to introduce large errors. This work presents an analysis of the fundamental issues of metastable states in both pure and binary AO₂ systems, investigates novel methods of handling them, and describes why current literature approaches which appear to work well for the pure compounds are not well-suited for systems containing multiple actinide species.