Obtaining definitive proof for 6d valence-delocalised antiferromagnetism in an actinide trimer

In 2021, we reported the first instance of thorium–thorium bonding in a crystalline cluster. This compound has sparked significant interest due to its hotly debated electronic structure, which is predicted by density functional theory to exhibit valence-delocalisation of two 6d electrons over three Th metal centres, leading to an antiferromagnetic 6d2 ground state. Ab initio RIXS calculations predict low energy transfer (<5 eV) 6d-6d and spin excitations, which will serve as direct experimental evidence of the electronic structure. We propose high energy resolution 2p6d RIXS at ID20 to test density functional theory predictions and settle the ongoing contention concerning the electronic structure of this molecule. By examining molecular Th analogues, we aim to demonstrate 2p6d RIXS as a reliable probe of valence d electron count in lanthanides and actinides.

2021年，我们首次报道了晶体团簇中钍-钍成键的首例案例。该化合物因其极具争议的电子结构引发广泛关注：密度泛函理论（Density Functional Theory）预测，其两个6d电子会在三个钍金属中心上发生价域离域，进而形成反铁磁性6d²基态。从头算共振非弹性X射线散射（Resonant Inelastic X-ray Scattering, RIXS）计算表明，体系存在低于5电子伏特的低能转移6d-6d与自旋激发，这将成为该电子结构的直接实验证据。我们提议在ID20束线开展高能量分辨率2p6d RIXS实验，以验证密度泛函理论的预测，解决该分子电子结构相关的持续争议。通过研究分子态钍的类似物，我们旨在证明2p6d RIXS可作为镧系元素与锕系元素价层d电子数的可靠探测手段。