Extended X-ray absorption fine structure spectroscopy measurements and ab initio molecular dynamics simulations reveal the hydration structure of the radium(II) ion

Yamaguchi, A.; Nagata, Koji; Kobayashi, Keita; Tanaka, Kohei; Kobayashi, Toshio; Tanida, Hajime; Shimojo, Kojiro; Sekiguchi, Takuya; Kaneta, Yui; Matsuda, Shohei; Yokoyama, Keiichi; Yaita, Tsuyoshi; Yoshimura, Takashi; Okumura, Masahiko; Takahashi, Yoshio

doi:10.1016/j.isci.2022.104763

Cited by 17 publications

(9 citation statements)

References 63 publications

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“…According to the study of Chen et al, SCAN can accurately describe the balance among covalent bonds, hydrogen bonds (HBs), and van der Waals interactions that can well capture the structural, electronic, and dynamic properties of liquid water . Meanwhile, only a few theoretical works studied hydrated ions using SCAN. ,,− It is urged to study the versatility of SCAN for hydrated ions.…”

Section: Introductionmentioning

confidence: 99%

Quantifying the Structure of Water and Hydrated Monovalent Ions by Density Functional Theory-Based Molecular Dynamics

2022

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The accurate description of the structures of water and hydrated ions is important in electrochemical desalination, ion separation, and supercapacitors. In this work, we present an ab initio atomistic simulation-based study to explore the structure of water and hydrated monovalent ions (Li+, Na+, K+, Rb+, F–, and Cl–) at ambient conditions using generalized gradient approximation (GGA)-based methods with and without van der Waals correction (PBE, PBE + D3, and revPBE + D3) and recently developed strongly constrained and appropriately normed (SCAN) meta-GGA. We find that both revPBE + D3 and SCAN can well capture the structure of bulk water with +30 K artificial high temperature in contrast to overstructuring water using PBE and PBE + D3. However, being the same as PBE + D3, revPBE + D3 overestimates the structure of the hydration shell, especially for monovalent cations. Surprisingly, SCAN can well match the experimental results of hydrated monovalent ions. Detailed structure analyzes of entropy reveal that the hydration shell under the level of PBE + D3 and revPBE + D3 is more disordered and looser than SCAN. The successful prediction of the flexible SCAN functional could facilitate the exploration of complex ionic processes in the aqueous phase, the interactions of hydrated ions with surfaces, and solvation states in nanopores at an accurate, efficient, predictive, and ab initio level.

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Section: Introductionmentioning

confidence: 99%

Quantifying the Structure of Water and Hydrated Monovalent Ions by Density Functional Theory-Based Molecular Dynamics

2022

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“…As shown in Table , the mean metal–oxygen distances in strontianite, witherite, cerussite, and Ra(Ba)CO 3 are in excellent agreement with the ionic radii for the corresponding metal ions in 9-fold coordination proposed by Shannon, as well as with the atomic radius of the carbonate oxygen (1.34 Å)proposed by Beattie and co-workers . Moreover, the ionic radius of Ra 2+ with the coordination number of 9(2) measured in 0.001 mol·L –1 of HNO 3 via EXAFS is also in good agreement with the ionic radius of Ra 2+ in 9-fold coordination measured in this work (1.53 and 1.545 Å, respectively).…”

Section: Resultsmentioning

confidence: 99%

Disordered Crystal Structure and Anomalously High Solubility of Radium Carbonate

et al. 2023

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Radium-226 carbonate was synthesized from radium−barium sulfate ( 226 Ra 0.76 Ba 0.24 SO 4 ) at room temperature and characterized by X-ray powder diffraction (XRPD) and extended X-ray absorption fine structure (EXAFS) techniques. XRPD revealed that fractional crystallization occurred and that two phases were formed�the major Ra-rich phase, Ra(Ba)CO 3 , and a minor Ba-rich phase, Ba(Ra)CO 3 , crystallizing in the orthorhombic space group Pnma (no. 62) that is isostructural with witherite (BaCO 3 ) but with slightly larger unit cell dimensions. Direct-space ab initio modeling shows that the carbonate oxygens in the major Ra(Ba)CO 3 phase are highly disordered. The solubility of the synthesized major Ra(Ba)CO 3 phase was studied from under-and oversaturation at 25.1 °C as a function of ionic strength using NaCl as the supporting electrolyte. It was found that the decimal logarithm of the solubility product of Ra(Ba)CO 3 at zero ionic strength (log 10 K sp 0 ) is −7.5(1) (2σ) (s = 0.05 g•L −1 ). This is significantly higher than the log 10 K sp 0 of witherite of −8.56 (s = 0.01 g•L −1 ), supporting the disordered nature of the major Ra(Ba)CO 3 phase. The limited co-precipitation of Ra 2+ within witherite, the significantly higher solubility of pure RaCO 3 compared to witherite, and thermodynamic modeling show that the results obtained in this work for the major Ra(Ba)CO 3 phase are also applicable to pure RaCO 3 . The refinement of the EXAFS data reveals that radium is coordinated by nine oxygens in a broad bond distance distribution with a mean Ra−O bond distance of 2.885(3) Å (1σ). The Ra−O bond distance gives an ionic radius of Ra 2+ in a 9-fold coordination of 1.545(6) Å (1σ).

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“…[9][10][11] In addition, in the light of the fact that Ra 2+ exists in the form of hydrated ions in both environmental and medical scenarios, the hydration and dynamics of Ra 2+ have been probed to reveal Ra 2+ is more labile than Ba 2+ . 12 Further applications of modern characterization techniques are needed to provide a more precise understanding radium and will likely demonstrate that its larger atomic/ionic radius can yield chemistry that is not accessible with barium. This is aptly illustrated by computational studies of radium fluoride compounds that predict higher oxidation states than 2+ should be accessible at high pressures, although experimental validation of this is needed.…”

Section: Main Bodymentioning

confidence: 99%

Radium Revisited: Revitalization of the Coordination Chemistry of Nature’s Largest 2+ Cation

Bai

Brannon

Celis-Barros

et al. 2023

Preprint

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The crystallization, single-crystal structure, and Raman spectroscopy of Ra(NO3)2 have been investigated by experiment and theory, which represent the first, pure radium compound characterized by single crystal X-ray diffraction. The Ra2+ centers are bound by six chelating nitrate anions to form an anticuboctahedral geometry. The Raman spectrum acquired from a single crystal of Ra(NO3)2 generally occurs at a lower frequency than found in Ba(NO3)2 as expected. Computational studies on Ra(NO3)2 provide an estimation of the bond orders via Wiberg bond indices and indicate that Ra–O interactions are weak with values of 0.025 and 0.026 for Ra–O bonds. Inspection of natural bond orbitals and natural localized molecular orbitals suggest negligible orbital mixing. However, second-order perturbation interactions show that donation from the lone pairs of the nitrate oxygen atoms to the 7s orbitals of Ra2+ stabilize each Ra–O interaction by ca. 5 kcal mol−1.

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Extended X-ray absorption fine structure spectroscopy measurements and ab initio molecular dynamics simulations reveal the hydration structure of the radium(II) ion

Cited by 17 publications

References 63 publications

Quantifying the Structure of Water and Hydrated Monovalent Ions by Density Functional Theory-Based Molecular Dynamics

Quantifying the Structure of Water and Hydrated Monovalent Ions by Density Functional Theory-Based Molecular Dynamics

Disordered Crystal Structure and Anomalously High Solubility of Radium Carbonate

Radium Revisited: Revitalization of the Coordination Chemistry of Nature’s Largest 2+ Cation

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