(gc2392)Immobilization of Radionuclides in Oxides
EMSL Project ID
2392
Abstract
We will carry out a series of theoretical calculations related to the immobilization of radionuclides in oxides, both crystalline and amorphous. The principal questions that will be addressed are: 1) How can long-lived excitons lead to degradation or annealing of the oxide network? 2) How do defects and / or long-lived excitons enable or hinder long-range migration of radioactive ions in the oxide, possibly causing extended structural transitions such as phase transformations, precipitation or amorphization? 3) What factors affect the rate of dissolution of the oxide in water? The oxides that will be studied include amorphous silica (with inclusion of Al, Na and B), zirconia and zircon, with likely applications to pyrochlore and zirconolite structured ceramics. An essential component of this work is development of methodology and implementation to enable accurate computational studies of long-lived excited states, in particular self-trapped excitons and holes. These methods include density functional theory with self-interaction correction, Optimized Effective Potentials for DFT, time-dependent DFT and FW extension of DFT. The methods will be tested on systems where wavefunction based NWCHEM density functional code an applied to extended systems subject to periodic boundary conditions. This is a grand challenge computational project in several ways: a) Atomic scale simulations will be carried out over long time scale using a recently developed algorithm, reaching time scales that are many orders of magnitude longer than direct classical dynamics simulations can cover. b) The dynamics in an excited electronic state will be simulated, a more challenging task than ground state dynamics. c) We will study the dynamics in amorphous solids, which are more complex that crystalline solids. The proposed work builds on the collaborative work of the J\nsson and Corrales groups on self-trapped excitons in quartz and silica glasses in a previous allocation period.
Project Details
Project type
Capability Research
Start Date
2002-01-25
End Date
2005-01-28
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members
Related Publications
Bylaska EJ, KL Tsemekhman, SB Baden, JH Weare, and H Jonsson. 2011. "Parallel Implementation of Gamma-Point Pseudopotential Plane-Wave DFT with Exact Exchange." Journal of Computational Chemistry 32(1):54-69.
Van Ginhoven RM, H Jonsson, B Park, and LR Corrales. 2005. "Cleavage and recovery of molecular water in silica." Journal of Physical Chemistry B 109(21):10936-10945
Van Ginhoven RM, H Jonsson, M Dupuis, LR Corrales, and KA Peterson. 2003. "An Ab Initio Study of Self-Trapped Excitons in Alpha-Quartz." Journal of Chemical Physics 118(14):6582-6593.