HR: 14:25h
AN: MR33A-04 INVITED    [Abstracts]
TI: Defect Interaction and Diffusion in Periclase (MgO)
AU: * Van Orman, J A
EM: james.vanorman@case.edu
AF: Case Western Reserve University, 10900 Euclid Avenue, Cleveland, 44106, United States
AU: Li, C
EM: cxl114@email.arizona.edu
AF: Case Western Reserve University, 10900 Euclid Avenue, Cleveland, 44106, United States
AU: Li, C
EM: cxl114@email.arizona.edu
AF: University of Arizona, 1040 E 4th St., Tucson, 85721,
AU: Crispin, K
EM: katherine.crispin@case.edu
AF: Case Western Reserve University, 10900 Euclid Avenue, Cleveland, 44106, United States
AB: Diffusion in minerals is the rate-limiting step in many mass transport processes that are fundamental to geochemistry and geophysics. Thus, there has been a long-standing interest in finding theoretical or empirical relationships that relate the diffusion coefficient in a mineral to well-known ionic properties such as radius and charge. In many silicate minerals the diffusion coefficient is negatively correlated with ionic charge. In periclase, and some other minerals with a strong component of ionic bonding, highly charged cations diffuse rapidly due to their association with cation vacancies. Experiments on Al³⁺ diffusion in MgO have been performed over a wide range of pressure (1 atm to 25 GPa) and temperature (1573 to 2273 K), and the association energy and Al- vacancy pair diffusivity inferred from each by applying a simple defect interaction model to the diffusion profiles. The binding energy for all but one experiment is in the range 0.45-0.62 eV, and shows no clear dependence on temperature or pressure. The activation energy for Al-vacancy pair diffusion is 2.1 eV, and the activation volume is 2.9 cm³/mol.
DE: 3630 Experimental mineralogy and petrology
DE: 3904 Defects
DE: 5139 Transport properties
SC: Mineral and Rock Physics [MR]
MN: 2007 Fall Meeting