Estimates of Quantum Tunneling Effects for Hydrogen Diffusion in PuO<sub>2</sub>
We detail the estimation of activation energies and quantum nuclear vibrational tunneling effects for hydrogen diffusion in PuO<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mrow></mrow><m...
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2022-10-01
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author | Nir Goldman Luis Zepeda-Ruiz Ryan G. Mullen Rebecca K. Lindsey C. Huy Pham Laurence E. Fried Jonathan L. Belof |
author_facet | Nir Goldman Luis Zepeda-Ruiz Ryan G. Mullen Rebecca K. Lindsey C. Huy Pham Laurence E. Fried Jonathan L. Belof |
author_sort | Nir Goldman |
collection | DOAJ |
description | We detail the estimation of activation energies and quantum nuclear vibrational tunneling effects for hydrogen diffusion in PuO<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mrow></mrow><mn>2</mn></msub></semantics></math></inline-formula> based on Density Functional Theory calculations and a quantum double well approximation. We find that results are relatively insensitive to choice of exchange correlation functional. In addition, the representation of spin in the system and use of an extended Hubbard U correction has only a small effect on hydrogen point defect formation energies when the PuO<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mrow></mrow><mn>2</mn></msub></semantics></math></inline-formula> lattice is held fixed at the experimental density. We then compute approximate activation energies for transitions between hydrogen interstitial sites seeded by a semi-empirical quantum model and determine the quantum tunneling enhancement relative to classical kinetic rates. Our model indicates that diffusion rates in H/PuO<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mrow></mrow><mn>2</mn></msub></semantics></math></inline-formula> systems could be enhanced by more than one order of magnitude at ambient conditions and that these effects persist at high temperature. The method we propose here can be used as a fast screening tool for assessing possible quantum nuclear vibrational effects in any number of condensed phase materials and surfaces, where hydrogen hopping tends to follow well defined minimum energy pathways. |
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spelling | doaj.art-360f091790d344c8a3fbb8c1407cee972023-11-24T03:36:26ZengMDPI AGApplied Sciences2076-34172022-10-0112211100510.3390/app122111005Estimates of Quantum Tunneling Effects for Hydrogen Diffusion in PuO<sub>2</sub>Nir Goldman0Luis Zepeda-Ruiz1Ryan G. Mullen2Rebecca K. Lindsey3C. Huy Pham4Laurence E. Fried5Jonathan L. Belof6Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, CA 94550, USAPhysical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, CA 94550, USAPhysical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, CA 94550, USADepartment of Chemical Engineering, University of Michigan, Ann Arbor, MI 48109, USAPhysical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, CA 94550, USAPhysical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, CA 94550, USAPhysical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, CA 94550, USAWe detail the estimation of activation energies and quantum nuclear vibrational tunneling effects for hydrogen diffusion in PuO<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mrow></mrow><mn>2</mn></msub></semantics></math></inline-formula> based on Density Functional Theory calculations and a quantum double well approximation. We find that results are relatively insensitive to choice of exchange correlation functional. In addition, the representation of spin in the system and use of an extended Hubbard U correction has only a small effect on hydrogen point defect formation energies when the PuO<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mrow></mrow><mn>2</mn></msub></semantics></math></inline-formula> lattice is held fixed at the experimental density. We then compute approximate activation energies for transitions between hydrogen interstitial sites seeded by a semi-empirical quantum model and determine the quantum tunneling enhancement relative to classical kinetic rates. Our model indicates that diffusion rates in H/PuO<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mrow></mrow><mn>2</mn></msub></semantics></math></inline-formula> systems could be enhanced by more than one order of magnitude at ambient conditions and that these effects persist at high temperature. The method we propose here can be used as a fast screening tool for assessing possible quantum nuclear vibrational effects in any number of condensed phase materials and surfaces, where hydrogen hopping tends to follow well defined minimum energy pathways.https://www.mdpi.com/2076-3417/12/21/11005plutonium oxideDensity Functional Theoryhydrogen diffusionquantum tunneling effects |
spellingShingle | Nir Goldman Luis Zepeda-Ruiz Ryan G. Mullen Rebecca K. Lindsey C. Huy Pham Laurence E. Fried Jonathan L. Belof Estimates of Quantum Tunneling Effects for Hydrogen Diffusion in PuO<sub>2</sub> Applied Sciences plutonium oxide Density Functional Theory hydrogen diffusion quantum tunneling effects |
title | Estimates of Quantum Tunneling Effects for Hydrogen Diffusion in PuO<sub>2</sub> |
title_full | Estimates of Quantum Tunneling Effects for Hydrogen Diffusion in PuO<sub>2</sub> |
title_fullStr | Estimates of Quantum Tunneling Effects for Hydrogen Diffusion in PuO<sub>2</sub> |
title_full_unstemmed | Estimates of Quantum Tunneling Effects for Hydrogen Diffusion in PuO<sub>2</sub> |
title_short | Estimates of Quantum Tunneling Effects for Hydrogen Diffusion in PuO<sub>2</sub> |
title_sort | estimates of quantum tunneling effects for hydrogen diffusion in puo sub 2 sub |
topic | plutonium oxide Density Functional Theory hydrogen diffusion quantum tunneling effects |
url | https://www.mdpi.com/2076-3417/12/21/11005 |
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