An Atomic-Scale Understanding of the Solution Chemistry of Antimony(V): Insights from First-Principles Molecular Dynamics Simulation

Zhang, Chi; Liu, Libin; Jia, Hanzhong

doi:10.1021/acs.inorgchem.0c02162

Cited by 9 publications

(1 citation statement)

References 52 publications

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“…Recently, quantum chemistry methods have been successfully applied to investigate the thermodynamic properties of metal ions and their complexes, including those of U. − For example, classical molecular dynamics (CMD) techniques have been used to calculate the structural information of uranyl ions and uranyl carbonate species. ,,− Static density functional theory (DFT) calculations together with experiments have revealed the adsorption mechanism of uranyl ions and the possible structures of the uranium arsenate complex . Combining electronic structure calculation with molecular dynamics sampling, first-principles molecular dynamics (FPMD) have served as a more effective approach to probe the thermodynamic properties of uranium-related species in aqueous solution. ,, For instance, the structural information and nuclear magnetic resonance (NMR) properties of UO 2 2+ , UO 2 (CO 3 ) 3 4– , and (UO 2 ) 3 (CO 3 ) 6 6– in water were explored by using the FPMD method .…”

Section: Introductionmentioning

confidence: 99%

Structure, Stability, and Acidity of the Uranyl Arsenate Dimer in Aqueous Solution

Liu

et al. 2023

Inorg. Chem.

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The migration of uranium (U) in the surficial environment has received considerable attention. Due to their high natural abundance and low solubility, autunite-group minerals play a key role in controlling the mobility of U. However, the formation mechanism for these minerals has yet to be understood. In this work, we took the uranyl arsenate dimer ([UO2(HAsO4)(H2AsO4)(H2O)]2 2–) as a model molecule and carried out a series of first-principles molecular dynamics (FPMD) simulations to explore the early stage of the formation of trögerite (UO2HAsO4·4H2O), a representative autunite-group mineral. By using the potential-of-mean-force (PMF) method and vertical energy gap method, the dissociation free energies and the acidity constants (pK a’s) of the dimer were calculated. Our results show that the U in the dimer holds a 4-coordinate structure, which is consistent with the coordination environment observed in trögerite mineralogy, in contrast to the 5-coordinate U in the monomer. Furthermore, the dimerization is thermodynamically favorable in solution. The FPMD results also suggest that tetramerization and even polyreactions would occur at pH > 2, as observed experimentally. Additionally, it is found that trögerite and the dimer have very similar local structural parameters. These findings imply that the dimer could serve as an important link between the U–As complexes in solution and the autunite-type sheet of trögerite. Given the nearly identical physicochemical properties of arsenate and phosphate, our findings suggest that uranyl phosphate minerals with the autunite-type sheet may form in a similar manner. This study therefore fills a critical gap in atomic-scale knowledge of the formation of autunite-group minerals and provides a theoretical basis for regulating uranium mobilization in P/As-bearing tailing water.

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