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Title: Diffusion Mechanisms of Radiolytic Species in Irradiated Al (Oxy-)Hydroxides

Abstract

Rare-event simulations (climbing image nudge elastic band and metadynamics) were performed using density functional theory (DFT) and a hybrid exchange-correlation functional to elucidate and quantify the diffusion mechanisms of radiation-induced species (O -, H 0, and H 2) in boehmite (γ-AlOOH) and gibbsite (γ-Al(OH) 3). The two Al (oxy-)hydroxide phases are known to have much different radiolytic activities, but the underlying mechanisms remain unknown. The DFT calculations revealed that O - diffusion occurred via proton-coupled hole transfer with high energy barriers in both phases. In contrast, energy barriers for H 0 transfers were generally lower in boehmite than in gibbsite, suggesting a more facile diffusion in boehmite of H radicals to the surface, where H 2 formation can take place. Another key difference was the ability of H 0 and H 2 to diffuse across the structural layers in gibbsite but not in boehmite. Therefore, while the formation of O and H radicals was energetically favored in gibbsite compared to boehmite, the DFT calculations indicated that the mechanisms of diffusion are responsible for the higher H 2 yields measured for boehmite compared to gibbsite

Authors:
ORCiD logo [1]; ORCiD logo [1];  [1]; ORCiD logo [1]; ORCiD logo [1]
  1. Physical Sciences Division, Pacific Northwest National Laboratory, Richland, Washington 99352, United States
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1492310
Report Number(s):
PNNL-SA-136174
Journal ID: ISSN 1932-7447
DOE Contract Number:  
AC05-76RL01830
Resource Type:
Journal Article
Journal Name:
Journal of Physical Chemistry. C
Additional Journal Information:
Journal Volume: 122; Journal Issue: 50; Journal ID: ISSN 1932-7447
Publisher:
American Chemical Society
Country of Publication:
United States
Language:
English

Citation Formats

Shen, Zhizhang, Ilton, Eugene S., Prange, Micah P., Mundy, Christopher J., and Kerisit, Sebastien N. Diffusion Mechanisms of Radiolytic Species in Irradiated Al (Oxy-)Hydroxides. United States: N. p., 2018. Web. doi:10.1021/acs.jpcc.8b07809.
Shen, Zhizhang, Ilton, Eugene S., Prange, Micah P., Mundy, Christopher J., & Kerisit, Sebastien N. Diffusion Mechanisms of Radiolytic Species in Irradiated Al (Oxy-)Hydroxides. United States. doi:10.1021/acs.jpcc.8b07809.
Shen, Zhizhang, Ilton, Eugene S., Prange, Micah P., Mundy, Christopher J., and Kerisit, Sebastien N. Tue . "Diffusion Mechanisms of Radiolytic Species in Irradiated Al (Oxy-)Hydroxides". United States. doi:10.1021/acs.jpcc.8b07809.
@article{osti_1492310,
title = {Diffusion Mechanisms of Radiolytic Species in Irradiated Al (Oxy-)Hydroxides},
author = {Shen, Zhizhang and Ilton, Eugene S. and Prange, Micah P. and Mundy, Christopher J. and Kerisit, Sebastien N.},
abstractNote = {Rare-event simulations (climbing image nudge elastic band and metadynamics) were performed using density functional theory (DFT) and a hybrid exchange-correlation functional to elucidate and quantify the diffusion mechanisms of radiation-induced species (O-, H0, and H2) in boehmite (γ-AlOOH) and gibbsite (γ-Al(OH)3). The two Al (oxy-)hydroxide phases are known to have much different radiolytic activities, but the underlying mechanisms remain unknown. The DFT calculations revealed that O- diffusion occurred via proton-coupled hole transfer with high energy barriers in both phases. In contrast, energy barriers for H0 transfers were generally lower in boehmite than in gibbsite, suggesting a more facile diffusion in boehmite of H radicals to the surface, where H2 formation can take place. Another key difference was the ability of H0 and H2 to diffuse across the structural layers in gibbsite but not in boehmite. Therefore, while the formation of O and H radicals was energetically favored in gibbsite compared to boehmite, the DFT calculations indicated that the mechanisms of diffusion are responsible for the higher H2 yields measured for boehmite compared to gibbsite},
doi = {10.1021/acs.jpcc.8b07809},
journal = {Journal of Physical Chemistry. C},
issn = {1932-7447},
number = 50,
volume = 122,
place = {United States},
year = {2018},
month = {11}
}