Christian Matthew S, Johnson Erin R, Besmann Theodore M
Nuclear Engineering Program, University of South Carolina, Columbia, South Carolina 29208, United States.
Center for Hierarchical Waste Form Materials (CHWM), University of South Carolina, Columbia, South Carolina 29208, United States.
J Phys Chem A. 2021 Apr 8;125(13):2791-2799. doi: 10.1021/acs.jpca.0c10533. Epub 2021 Mar 25.
High-throughput computational studies of lanthanide and actinide chemistry with density-functional theory are complicated by the need for Hubbard corrections, which ensure localization of the f-electrons, but can lead to metastable states. This work presents a systematic investigation of the effects of both Hubbard value and metastable states on the predicted structural and thermodynamic properties of four uranium compounds central to the field of nuclear fuels: UC, UN, UO, and UCl. We also assess the impact of the exchange-hole dipole moment (XDM) dispersion correction on the computed properties. Overall, the choice of Hubbard value and inclusion of a dispersion correction cause larger variations in the computed geometric properties than result from metastable states. The weak dependence of structure optimization on metastable states should simplify future high-throughput calculations on actinides. Conversely, addition of the dispersion correction is found to offset the repulsion introduced by the Hubbard term and provides greatly improved agreement with experiment for both cell volumes and heats of formation. The XDM dispersion correction is largely invariant to the chosen value, making it a robust dispersion correction for actinide systems.
利用密度泛函理论对镧系和锕系化学进行高通量计算研究，因需要哈伯德修正而变得复杂，哈伯德修正可确保f电子的局域化，但可能导致亚稳态。这项工作对哈伯德值和亚稳态对四种核燃料领域核心铀化合物（UC、UN、UO和UCl）预测的结构和热力学性质的影响进行了系统研究。我们还评估了交换空穴偶极矩（XDM）色散校正对计算性质的影响。总体而言，哈伯德值的选择和色散校正的纳入在计算几何性质方面引起的变化比亚稳态导致的变化更大。结构优化对亚稳态的弱依赖性应会简化未来对锕系元素的高通量计算。相反，发现添加色散校正可抵消哈伯德项引入的排斥作用，并在晶胞体积和生成热方面与实验结果达成大大改善的一致性。XDM色散校正对所选值基本不变，使其成为锕系元素体系的一种稳健色散校正。
