SUBJECT: Ph.D. Proposal Presentation
BY: Benjamin Beeler
TIME: Tuesday, May 1, 2012, 2:00 p.m.
PLACE: Boggs Building, 3-47
TITLE: Atomistic investigations of uranium
COMMITTEE: Dr. Chaitanya Deo, Chair (ME/NRE)
Dr. Ting Zhu (ME)
Dr. Bojan Petrovic (ME/NRE)
Dr. Hamid Garmestani (MSE)
Dr. Mo Li (MSE)


Uranium (U) exhibits a high temperature body-centered cubic (b.c.c.) allotrope that is often stabilized by alloying with transition metals such as Zr, Mo, and Nb for technological applications. One such application involves U–Zr as nuclear fuel, where radiation damage and diffusion (processes heavily dependent on point defects) are of vital importance. Metallic nuclear fuels swell under fission conditions, creating fission product gases such as helium, xenon and krypton. Several systems of U are examined within a density functional theory (DFT) framework utilizing projector augmented wave pseudopotentials. Two separate generalized gradient approximations of the exchange-correlation are used to calculate defect properties and are compared. The bulk modulus, the lattice constant, and the Birch–Murnaghan equation of state for the defect free b.c.c. uranium allotrope are calculated. Defect parameters calculated include energies of formation of vacancies in the α and γ allotropes, as well as self-interstitials, Zr, He, Xe and Kr interstitial and substitutional defects. Results from the DFT investigation are utilized, in addition to experimental work in the literature, for the construction of a modified Embedded-Atom Method (MEAM) interatomic potential to describe b.c.c. uranium. Pure systems and defected systems are investigated at 0 K as well as at high temperatures. Finally, this MEAM interatomic potential is taken as the basis for the development of a binary U-Zr MEAM interatomic potential, and ternary potentials of U-Zr and the fission gases He, Xe and Kr. These systems are examined over a wide range of compositions and temperatures.