Ab Initio X-ray Absorption Spectroscopy Study of the Solvation Structure of Th(IV), U(IV), and Np(IV) in Aqueous Solution

Abstract

The coordination structures of U(IV), Np(IV), and Th(IV) in aqueous solution have been determined by studying the X-ray absorption near edge structure (XANES) of the actinide (An) L(3)-edge absorption spectra. The high sensitivity of XANES to the bonding geometry provides an unambiguous determination of the coordination polyhedron. On the basis of the comparison of ab initio computations with the experimental data we conclude that the hydration sphere of the three An(IV) aqua-ions studied is best modeled by 9 water molecules forming a tricapped trigonal prism.

Periodic trends and complexation chemistry of tetravalent actinide ions with a potential actinide decorporation agent 5‐LIO(Me‐3,2‐HOPO): A relativistic density functional theory exploration

“…Although some ambiguity remains on the most‐probable hydration number of U 4+ and Np 4+ , ab initio molecular dynamics simulation studies on U 4+ hydration by Atta‐Fynn et al suggested that nine water molecules can be accommodated in the first coordination sphere . X‐ray near edge structure (XANES) investigations also inferred a stable hydration number of nine for U 4+ as well as for Np 4+ . Considering these reports, a nonahydrated model was used for U 4+ and Np 4+ .…”

XANES and EXAFS study of the local order in nanocrystalline yttria-stabilized zirconia

“…40 In this respect the study of XANES can provide useful complementary information as XANES is extremely sensitive to the stereochemical details of the absorbing site, i.e., overall symmetry, interatomic distances, and bond angles, offering better capabilities than a direct EXAFS analysis for the determination of the coordination polyhedron around the absorbing atom. [41][42][43] …”

Enhancing the analysis of disorder in X-ray absorption spectra: application of deep neural networks to T-jump-X-ray probe experiments

“…7,8 In T-jump pump/X-ray probe experiments, T-jump spectroscopy and XS are coupled together to deliver direct structural insight into thermally-activated chemical reactions; such experiments have, for example, been used to study the response of the structure of water following the transfer of heat via NIR excitation. 9,10 The use of X-ray absorption near-edge structure (XANES) [11][12][13][14][15][16][17] and/or extended X-ray absorption fine structure (EXAFS) [18][19][20][21][22][23] measurements to characterise solvent and/or solvation structures is well established. Consequently, T-jump pump/X-ray probe experiments have the potential to deliver information on the fundamental structural dynamics of thermally-activated processes occurring in solution, such as ligand exchange, which are common in chemical and biological systems.…”