利用密度泛函理论预测含133Cs化合物的NMR参数与几何结构
Prediction of NMR Parameters and geometry in 133Cs-containing compounds using Density Functional Theory
AI总结：
针对含铯核废料固化基体中铯结合位点不明确、133Cs的DFT适用泛函未确立的问题，本工作基准测试多种泛函对含Cs化合物的结构与NMR参数的预测性能，筛选出rev-vdW-DF2和PBEsol+D3两种优选泛函。
摘要：
固定低放射性核废料（尤其是含137Cs的废料）的需求，使得除了针对该特定应用优化水泥基体组成的尝试外，人们对地聚物基废料基体的兴趣日益浓厚。尽管这些基体的整体相组成与结构已得到充分表征，但Cs在这些材料中的结合位点尚未被明确识别。近期研究表明，将固态核磁共振（SSNMR）对局部原子结构的敏感性与其他结构技术相结合，可揭示Cs的结合与释放模式。密度泛函理论（DFT）能够建立光谱参数与几何性质之间的关联。然而，DFT结果的可靠性很大程度上取决于合适的交换关联泛函的选择，而对于此类研究中用作NMR替代物的133Cs，其适用的泛函尚未得到充分确立。在本工作中，我们针对多种泛函在预测各类简单Cs化合物的几何结构、NMR四极耦合常数及化学位移值方面的性能进行了基准测试，同时优先考虑泛函纳入色散相互作用的能力并维持较低的计算成本。我们研究了Cs盐、Cs氧化物、钙钛矿、笼形材料、一种硼酸盐玻璃以及一种氟钪酸铯。虽然没有任何一种泛函能在所有参数上都表现得同样出色，但结果显示rev-vdW-DF2和PBEsol+D3是适用于这些体系的首选候选泛函，尤其是在几何结构和化学位移的预测方面，而这两项性质对Cs固化基体具有重要意义。
英文摘要：
The need to immobilize low-level nuclear waste, in particular 137Cs-bearing waste, has led to a growing interest in geopolymer-based waste matrices, in addition to optimization attempts of cement matrix compositions for this specific application. Although the overall phase composition and structure of these matrices are well characterized, the binding sites of Cs in these materials have not been clearly identified. Recent studies have suggested that combining the sensitivity of solid-state Nuclear Magnetic Resonance (SSNMR) to the local atomic structure with other structural techniques provides insights into the mode of Cs binding and release. Density Functional Theory (DFT) can provide the connection between spectroscopic parameters and geometric properties. However, the reliability of DFT results strongly relies on the choice of a suitable exchange-correlation functional, which for 133Cs, the NMR surrogate for such studies, is not well-established. In this work we benchmark various functionals against their performance in predicting the geometry of various simple Cs compounds, their NMR quadrupolar coupling constants, and their chemical shift values, while prioritizing the ability to incorporate dispersion interactions and maintaining low computational cost. We examined Cs salts, Cs oxides, perovskites, caged materials, a borate glass and a cesium fluoroscandate. While no single functional performs equally well for all parameters, the results show rev-vdW-DF2 and PBEsol+D3 to be leading candidates for these systems, in particular with respect to geometry and chemical shifts, which are of high importance for Cs-immobilization matrices.
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