About this Abstract |
| Meeting |
Materials in Nuclear Energy Systems (MiNES) 2025
|
| Symposium
|
Materials in Nuclear Energy Systems (MiNES) 2025
|
| Presentation Title |
Pressure-Enhanced Bonding Covalency Anisotropy and Mechanical Anisotropy in Coffinite (USiO₄): A DFT+U Study |
| Author(s) |
Xiaodong Zhao, Andrew Strzelecki, Jiayuan Liang, Shinhyo Bang, Liang Qi, Xiaofeng Guo |
| On-Site Speaker (Planned) |
Xiaodong Zhao |
| Abstract Scope |
Coffinite (USiO₄), a uranium orthosilicate with the zircon structure, is a critical alter-phase for immobilizing nuclear waste in deep geological repositories. This study employs DFT+U calculations to unravel its pressure-dependent mechanical anisotropy and phase stability. Results reveal that anisotropic covalency—enhanced U–O bonding within the a-b plane—drives divergent elastic responses under compression. While the bulk modulus increases, which indicates overall structural stiffening, but shear and Young’s moduli decline, which reduces resistance to non-uniform deformation. Elastic anisotropy, quantified by a universal index rising from 2.59 to 7.60, highlights directional weaknesses under pressure. On the other hand, the phonon dispersion and enthalpy analyses discovered that the zircon-to-scheelite transition at ~15 GPa is driven by B₂ᵤ phonon mode softening, instead of enthalpy stability or mechanical failure. Overall, this covalency-driven anisotropic mechanics are pivotal for predicting coffinite’s long-term persistence in deep geological sites, ensuring safer nuclear waste containment strategies. |
| Proceedings Inclusion? |
Undecided |