Atomistic Investigation of Plastic Deformation and Dislocation Motion in Uranium Mononitride
Uranium mononitride (UN) is a promising advanced nuclear fuel due to its high thermal conductivity and high fissile density. However, many aspects of its mechanical behavior, particularly at reactor-relevant conditions, remain unclear. In this study, molecular dynamics (MD) simulations were employed...
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2025-03-01
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| author | Mohamed AbdulHameed Benjamin Beeler Antoine Claisse |
| author_facet | Mohamed AbdulHameed Benjamin Beeler Antoine Claisse |
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| description | Uranium mononitride (UN) is a promising advanced nuclear fuel due to its high thermal conductivity and high fissile density. However, many aspects of its mechanical behavior, particularly at reactor-relevant conditions, remain unclear. In this study, molecular dynamics (MD) simulations were employed to investigate the deformation behavior and dislocation motion in UN. We found that the Kocevski potential predicts the principal slip system as <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mstyle scriptlevel="0" displaystyle="true"><mfrac><mn>1</mn><mn>2</mn></mfrac></mstyle><mrow><mo>⟨</mo><mn>110</mn><mo>⟩</mo></mrow><mrow><mo>{</mo><mn>110</mn><mo>}</mo></mrow></mrow></semantics></math></inline-formula>, aligning with experimental data. On the other hand, the Tseplyaev potential predicts slip to primarily occur on <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mstyle scriptlevel="0" displaystyle="true"><mfrac><mn>1</mn><mn>2</mn></mfrac></mstyle><mrow><mo>⟨</mo><mn>110</mn><mo>⟩</mo></mrow><mrow><mo>{</mo><mn>111</mn><mo>}</mo></mrow></mrow></semantics></math></inline-formula>. MD simulations of stress–strain behavior were used to estimate the nanoindentation hardness, revealing that the Kocevski potential accurately predicts hardness even though it fails to model dynamic plasticity. Complete dislocation mobility functions have been fitted for the edge and screw dislocations in both the thermally activated and phonon-drag regimes. The 300 K linear mobility of the edge dislocation using the Tseplyaev potential was found to be 817 <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msup><mi>Pa</mi><mrow><mo>−</mo><mn>1</mn></mrow></msup><mspace width="-0.166667em"></mspace><mo>·</mo><mspace width="-0.166667em"></mspace><msup><mi mathvariant="normal">s</mi><mrow><mo>−</mo><mn>1</mn></mrow></msup></mrow></semantics></math></inline-formula>, whereas that of the screw dislocation using the Kocevski potential was found to be 4546 <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msup><mi>Pa</mi><mrow><mo>−</mo><mn>1</mn></mrow></msup><mspace width="-0.166667em"></mspace><mo>·</mo><mspace width="-0.166667em"></mspace><msup><mi mathvariant="normal">s</mi><mrow><mo>−</mo><mn>1</mn></mrow></msup></mrow></semantics></math></inline-formula>. At intermediate stresses, we observed that the subsonic steady-state motion of the edge dislocation in UN is intermittently interrupted by velocity jumps, reaching the average sound velocity. Finally, the threshold Schmid stress is calculated as 179–197 MPa, which gives an upper-limit estimate of the uniaxial yield stress of polycrystalline UN of 548–603 MPa. These findings, including the fitted dislocation mobility function, provide essential input for future plasticity and dislocation dynamics models of nuclear fuels. |
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| spelling | doaj-art-aea00a522ff84922b789d7dac3463dc32025-08-20T02:04:35ZengMDPI AGApplied Sciences2076-34172025-03-01155266610.3390/app15052666Atomistic Investigation of Plastic Deformation and Dislocation Motion in Uranium MononitrideMohamed AbdulHameed0Benjamin Beeler1Antoine Claisse2Department of Nuclear Engineering, North Carolina State University, Raleigh, NC 27695, USADepartment of Nuclear Engineering, North Carolina State University, Raleigh, NC 27695, USAWestinghouse Electric Sweden, SE 72163 Vasteras, SwedenUranium mononitride (UN) is a promising advanced nuclear fuel due to its high thermal conductivity and high fissile density. However, many aspects of its mechanical behavior, particularly at reactor-relevant conditions, remain unclear. In this study, molecular dynamics (MD) simulations were employed to investigate the deformation behavior and dislocation motion in UN. We found that the Kocevski potential predicts the principal slip system as <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mstyle scriptlevel="0" displaystyle="true"><mfrac><mn>1</mn><mn>2</mn></mfrac></mstyle><mrow><mo>⟨</mo><mn>110</mn><mo>⟩</mo></mrow><mrow><mo>{</mo><mn>110</mn><mo>}</mo></mrow></mrow></semantics></math></inline-formula>, aligning with experimental data. On the other hand, the Tseplyaev potential predicts slip to primarily occur on <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mstyle scriptlevel="0" displaystyle="true"><mfrac><mn>1</mn><mn>2</mn></mfrac></mstyle><mrow><mo>⟨</mo><mn>110</mn><mo>⟩</mo></mrow><mrow><mo>{</mo><mn>111</mn><mo>}</mo></mrow></mrow></semantics></math></inline-formula>. MD simulations of stress–strain behavior were used to estimate the nanoindentation hardness, revealing that the Kocevski potential accurately predicts hardness even though it fails to model dynamic plasticity. Complete dislocation mobility functions have been fitted for the edge and screw dislocations in both the thermally activated and phonon-drag regimes. The 300 K linear mobility of the edge dislocation using the Tseplyaev potential was found to be 817 <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msup><mi>Pa</mi><mrow><mo>−</mo><mn>1</mn></mrow></msup><mspace width="-0.166667em"></mspace><mo>·</mo><mspace width="-0.166667em"></mspace><msup><mi mathvariant="normal">s</mi><mrow><mo>−</mo><mn>1</mn></mrow></msup></mrow></semantics></math></inline-formula>, whereas that of the screw dislocation using the Kocevski potential was found to be 4546 <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msup><mi>Pa</mi><mrow><mo>−</mo><mn>1</mn></mrow></msup><mspace width="-0.166667em"></mspace><mo>·</mo><mspace width="-0.166667em"></mspace><msup><mi mathvariant="normal">s</mi><mrow><mo>−</mo><mn>1</mn></mrow></msup></mrow></semantics></math></inline-formula>. At intermediate stresses, we observed that the subsonic steady-state motion of the edge dislocation in UN is intermittently interrupted by velocity jumps, reaching the average sound velocity. Finally, the threshold Schmid stress is calculated as 179–197 MPa, which gives an upper-limit estimate of the uniaxial yield stress of polycrystalline UN of 548–603 MPa. These findings, including the fitted dislocation mobility function, provide essential input for future plasticity and dislocation dynamics models of nuclear fuels.https://www.mdpi.com/2076-3417/15/5/2666uranium nitridemolecular dynamicsplastic deformationPeierls stressdislocation mobility |
| spellingShingle | Mohamed AbdulHameed Benjamin Beeler Antoine Claisse Atomistic Investigation of Plastic Deformation and Dislocation Motion in Uranium Mononitride Applied Sciences uranium nitride molecular dynamics plastic deformation Peierls stress dislocation mobility |
| title | Atomistic Investigation of Plastic Deformation and Dislocation Motion in Uranium Mononitride |
| title_full | Atomistic Investigation of Plastic Deformation and Dislocation Motion in Uranium Mononitride |
| title_fullStr | Atomistic Investigation of Plastic Deformation and Dislocation Motion in Uranium Mononitride |
| title_full_unstemmed | Atomistic Investigation of Plastic Deformation and Dislocation Motion in Uranium Mononitride |
| title_short | Atomistic Investigation of Plastic Deformation and Dislocation Motion in Uranium Mononitride |
| title_sort | atomistic investigation of plastic deformation and dislocation motion in uranium mononitride |
| topic | uranium nitride molecular dynamics plastic deformation Peierls stress dislocation mobility |
| url | https://www.mdpi.com/2076-3417/15/5/2666 |
| work_keys_str_mv | AT mohamedabdulhameed atomisticinvestigationofplasticdeformationanddislocationmotioninuraniummononitride AT benjaminbeeler atomisticinvestigationofplasticdeformationanddislocationmotioninuraniummononitride AT antoineclaisse atomisticinvestigationofplasticdeformationanddislocationmotioninuraniummononitride |