Quantifying Actinide-Ligand Covalency with Resonant Inelastic X-ray Scattering

用共振非弹性 X 射线散射量化锕系配体共价

• 批准号: EP/V029347/1
• 负责人: Michael Lloyd Baker
• 金额: $ 51.31万
• 依托单位: University of Manchester
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2021
• 资助国家: 英国
• 起止时间: 2021 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=EP%2FV029347%2F1
• 关键词: Quantifying; Actinide; Ligand; Covalency; Resonant

The UK has invested in world-leading synchrotron X-ray facilities. This includes state-of-the-art resonant inelastic X-ray scattering (RIXS) techniques that measure electronic structure with unprecedented energy resolution. RIXS is, however, infrequently applied to its full potential due to a lack of analytical expertise that limits quantitative insights. The least developed area of all is the analysis of actinide RIXS. Actinides are amongst the largest elements within the periodic table, and their chemistry is notoriously challenging to predict. The development of RIXS at energies suitable for accessing actinides has opened up an unexplored avenue to experimentally measure actinide physical and chemical properties. RIXS is an element-specific technique that targets the outer actinide orbitals. The method is therefore selectively sensitive to how actinide orbitals engage in bonding at the molecular level. This project aims to develop RIXS into a quantitative tool to advance understanding of how actinides engage in chemical bonding. The extent and nature of bond-covalency is of particular importance since this profoundly influences physical properties, reactivity and the selectivity of actinide bond formation. There is much debate concerning the covalency of actinide bonding. On one hand, covalency can be considered as the mixing of electron density between atoms, and on the other covalency can be understood as occurring when the energy of the actinide and bonding atom orbitals match up. There are few experimental techniques with sensitivity to actinide covalency, and those that exist are limited to specific cases, i.e. only certain oxidation states, or types of bonded atom. RIXS has the potential to bridge the gap between the synthetic isolation of actinide compounds and first principle theory. Preliminary research by the PI has confirmed the sensitivity of RIXS to uranium bond covalency, identifying opportunities to advance understanding of actinide bonding.The complex chemical bonding properties of actinides represent a major challenge to the nuclear energy sector. This project will develop methodologies and new knowledge that could lead to improved processes for the separation of actinides from other elements in nuclear waste processing and to better understand how actinides interact within the environment. The proposed research requires an equal combination of RIXS measurement and theoretical simulations. Multiple levels of theory will be applied to identify the most accurate means to simulate spectra. Advances in synthetic chemistry have provided systematic families of compounds, that will be used to identify spectral trends, aiding the development of RIXS analysis. The focus will be on uranium and thorium, but the methods developed will be equally relevant to the study of transuranic compounds. The RIXS measurement methodologies, analysis and simulation methods developed will be distributed in an easy to use software package, to put the full potential of RIXS into the hands of the X-ray community.Initial studies will explore donor covalency in single and double bonds to elucidate how RIXS spectral shape correlates with electronic structure. Less explored situations will be investigated, including compounds predicted as being highly covalent.The developed RIXS analysis methods will then be applied to novel molecules prepared by collaborators and project partners. This will include a series of molecules that can adopt a variety of metal ions down a full column of the periodic table, such that our newfound understanding of U and Th bonding can be placed within the larger context of the periodic table. Finally, the complementary use of L and M-edge RIXS will be applied to pin down one of the most controversial and elusive problems in actinide electronic structure: the varying extent of 5f versus 6d orbital contributions to covalency.

英国已经投资了世界领先的同步X射线设施。这包括最新的共振非弹性X射线散射（RIX）技术，这些技术以前所未有的能量分辨率测量电子结构。但是，由于缺乏限制定量见解的分析专业知识，RIX很少会适用其全部潜力。所有最不发达的领域是对actacinide rix的分析。 actinides是周期表中最大的元素之一，众所周知，它们的化学作用是具有挑战性的。适合进入actinides的能量的RIX开发为实验测量actacinide物理和化学性质开辟了一条未开发的大道。 RIX是一种针对外部actacinide轨道的元素特异性技术。因此，该方法对肌动剂轨道如何在分子水平上进行键合敏感。该项目旨在将RIX开发为一种定量工具，以促进对actinides如何参与化学键合的理解。债券共价的程度和性质特别重要，因为这深刻影响了肌动剂键形成的物理特性，反应性和选择性。关于actinide键合的共价存在很多争论。一方面，可以将共价视为原子之间电子密度的混合，而在另一方面可以将其理解为当肌动剂和粘结原子轨道匹配时发生。对actinide共价敏感的实验技术很少，而存在的技术仅限于特定情况，即仅某些氧化态或键合原子的类型。 RIX有可能弥合actacinide化合物的合成分离与第一个原理理论之间的差距。 PI的初步研究证实了RIX对铀键的共价的敏感性，确定了提高对actinide键合的机会。actinides的复杂化学键合特性代表了对核能部门的主要挑战。该项目将开发方法和新知识，这可能会导致改进的过程，从而将actinides与核废料处理中其他元素分离，并更好地了解actinides在环境中的相互作用。拟议的研究需要将RIX测量和理论模拟相等的组合。将应用多个理论级别来确定模拟光谱的最准确手段。合成化学的进步提供了化合物的系统家族，这些家族将用于识别光谱趋势，并有助于RIXS分析的发展。重点将放在铀和th上，但是所开发的方法将与胸膜化合物的研究同样相关。 RIXS测量方法，开发的分析和仿真方法将以易于使用的软件包分发，以将RIX的全部潜力放在X射线社区的手中。Initial研究将探索单个和双键的捐助者的共和力，以探索单个和双重键的捐助者的共同点阐明RIXS光谱形状与电子结构的相关性。将研究较少的情况，包括预测为高价值的化合物。然后，开发的RIXS分析方法将应用于合作者和项目合作伙伴制备的新分子。这将包括一系列分子，这些分子可以在周期表的完整列下采用各种金属离子，以便我们对U和TH键的新发现可以放置在周期表的较大环境中。最后，将使用L和M边缘的互补使用来固定actinide电子结构中最具争议，最难以捉摸的问题之一：5F的变化程度与6D轨道贡献对共价贡献。

项目成果

Sulfidation and Reoxidation of U(VI)-Incorporated Goethite: Implications for U Retention during Sub-Surface Redox Cycling.

• DOI: 10.1021/acs.est.2c05314
• 发表时间: 2022-12-20
• 期刊: ENVIRONMENTAL SCIENCE & TECHNOLOGY
• 影响因子: 11.4
• 作者: Stagg, Olwen;Morris, Katherine;Townsend, Luke Thomas;Kvashnina, Kristina O.;Baker, Michael L.;Dempsey, Ryan L.;Abrahamsen-Mills, Liam;Shaw, Samuel
• 通讯作者: Shaw, Samuel