Near Surface Stoichiometry in UO2: A Density Functional Theory Study
The mechanisms of oxygen stoichiometry variation in UO2 at different temperature and oxygen partial pressure are important for understanding the dynamics of microstructure in these crystals. However, very limited experimental studies have been performed to understand the atomic structure of UO2 near...
Saved in:
| Main Authors: | , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Wiley
2015-01-01
|
| Series: | Journal of Chemistry |
| Online Access: | http://dx.doi.org/10.1155/2015/142510 |
| Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
| _version_ | 1832562271192088576 |
|---|---|
| author | Jianguo Yu Billy Valderrama Hunter B. Henderson Michele V. Manuel Todd Allen |
| author_facet | Jianguo Yu Billy Valderrama Hunter B. Henderson Michele V. Manuel Todd Allen |
| author_sort | Jianguo Yu |
| collection | DOAJ |
| description | The mechanisms of oxygen stoichiometry variation in UO2 at different temperature and oxygen partial pressure are important for understanding the dynamics of microstructure in these crystals. However, very limited experimental studies have been performed to understand the atomic structure of UO2 near surface and defect effects of near surface on stoichiometry in which the system can exchange atoms with the external reservoir. In this study, the near (110) surface relaxation and stoichiometry in UO2 have been studied with density functional theory (DFT) calculations. On the basis of the point-defect model (PDM), a general expression for the near surface stoichiometric variation is derived by using DFT total-energy calculations and atomistic thermodynamics, in an attempt to pin down the mechanisms of oxygen exchange between the gas environment and defected UO2. By using the derived expression, it is observed that, under poor oxygen conditions, the stoichiometry of near surface is switched from hyperstoichiometric at 300 K with a depth around 3 nm to near-stoichiometric at 1000 K and hypostoichiometric at 2000 K. Furthermore, at very poor oxygen concentrations and high temperatures, our results also suggest that the bulk of the UO2 prefers to be hypostoichiometric, although the surface is near-stoichiometric. |
| format | Article |
| id | doaj-art-6e3f80220d38479ab330075d6e57a6fd |
| institution | Kabale University |
| issn | 2090-9063 2090-9071 |
| language | English |
| publishDate | 2015-01-01 |
| publisher | Wiley |
| record_format | Article |
| series | Journal of Chemistry |
| spelling | doaj-art-6e3f80220d38479ab330075d6e57a6fd2025-02-03T01:23:07ZengWileyJournal of Chemistry2090-90632090-90712015-01-01201510.1155/2015/142510142510Near Surface Stoichiometry in UO2: A Density Functional Theory StudyJianguo Yu0Billy Valderrama1Hunter B. Henderson2Michele V. Manuel3Todd Allen4Idaho National Laboratory, Idaho Falls, ID 83415, USAUniversity of Florida, Gainesville, FL 32611, USAUniversity of Florida, Gainesville, FL 32611, USAUniversity of Florida, Gainesville, FL 32611, USAIdaho National Laboratory, Idaho Falls, ID 83415, USAThe mechanisms of oxygen stoichiometry variation in UO2 at different temperature and oxygen partial pressure are important for understanding the dynamics of microstructure in these crystals. However, very limited experimental studies have been performed to understand the atomic structure of UO2 near surface and defect effects of near surface on stoichiometry in which the system can exchange atoms with the external reservoir. In this study, the near (110) surface relaxation and stoichiometry in UO2 have been studied with density functional theory (DFT) calculations. On the basis of the point-defect model (PDM), a general expression for the near surface stoichiometric variation is derived by using DFT total-energy calculations and atomistic thermodynamics, in an attempt to pin down the mechanisms of oxygen exchange between the gas environment and defected UO2. By using the derived expression, it is observed that, under poor oxygen conditions, the stoichiometry of near surface is switched from hyperstoichiometric at 300 K with a depth around 3 nm to near-stoichiometric at 1000 K and hypostoichiometric at 2000 K. Furthermore, at very poor oxygen concentrations and high temperatures, our results also suggest that the bulk of the UO2 prefers to be hypostoichiometric, although the surface is near-stoichiometric.http://dx.doi.org/10.1155/2015/142510 |
| spellingShingle | Jianguo Yu Billy Valderrama Hunter B. Henderson Michele V. Manuel Todd Allen Near Surface Stoichiometry in UO2: A Density Functional Theory Study Journal of Chemistry |
| title | Near Surface Stoichiometry in UO2: A Density Functional Theory Study |
| title_full | Near Surface Stoichiometry in UO2: A Density Functional Theory Study |
| title_fullStr | Near Surface Stoichiometry in UO2: A Density Functional Theory Study |
| title_full_unstemmed | Near Surface Stoichiometry in UO2: A Density Functional Theory Study |
| title_short | Near Surface Stoichiometry in UO2: A Density Functional Theory Study |
| title_sort | near surface stoichiometry in uo2 a density functional theory study |
| url | http://dx.doi.org/10.1155/2015/142510 |
| work_keys_str_mv | AT jianguoyu nearsurfacestoichiometryinuo2adensityfunctionaltheorystudy AT billyvalderrama nearsurfacestoichiometryinuo2adensityfunctionaltheorystudy AT hunterbhenderson nearsurfacestoichiometryinuo2adensityfunctionaltheorystudy AT michelevmanuel nearsurfacestoichiometryinuo2adensityfunctionaltheorystudy AT toddallen nearsurfacestoichiometryinuo2adensityfunctionaltheorystudy |