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DOE OSTI2019

Probing activated radioprotection of simple hydrophilic phosphonic acids in aqueous solution

Prior exploration into the radiation chemistry of the ligand octylphenyl-N,N-diisobutylcarbamoylmethyl phosphine oxide (CMPO) and its analogues demonstrated their ability to undergo activated radioprotection in an organic solvent – a feature most advantageous for spent nuclear fuel reprocessing scenarios. This phenomenon was dependent on these organophosphorus compounds forming a sacrificial complex involving extracted nitric acid and the presence of an adjacent phenylphosphine oxide motif in the molecule. However, the hydrophobic nature of these compounds prevented elucidation of which components were essential for activated radioprotection; for example, does the phenylphosphine oxide motif only require protonation, or simply the presence of complexed nitrate anion(s), or both? To begin to address these questions, we report on the effect of dissolved nitrate on the radiation chemistry of a series of simple hydrophilic phosphonic acids (methyl, ethyl, phenyl, and benzyl) in aqueous solution. An extensive suite of gamma irradiations supported by high performance liquid chromatography and nuclear magnetic resonance techniques was used to demonstrate that all four compounds were unable to undergo activated radioprotection. While some nitrate protection was observed, this was attributed to changes in the available suite of radiolysis products, and not to the formation of nitrate-phosphonic acid sacrificial complexes. The absence of activated radioprotection and evidence for the formation of a [PhPA•NO 3 -] complex further supports the necessity of complex formation to activate the radioprotection mechanism.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗

DOE OSTI2014

Excited States and Luminescent Properties of UO 2 F 2 and Its Solvated Complexes in Aqueous Solution

The electronic absorption and emission spectra of free UO 2 F 2 and its water solvated complexes below 32 000 cm –1 are investigated at the levels of ab initio CASPT2 and CCSD(T) with inclusion of scalar relativistic and spin–orbit coupling effects. The influence of the water coordination on the electronic spectra of UO 2 F 2 is explored by investigating the excited states of solvated complexes (H 2 O) n UO 2 F 2 (n = 1–3). In these uranyl complexes, water coordination is found to have appreciable influence on the 3 Δ (Ω = 1 g ) character of the luminescent state and on the electronic spectral shape. The simulated luminescence spectral curves based on the calculated spectral parameters of (H 2 O) n UO 2 F 2 from CCSD(T) approach agree well with experimental spectra in aqueous solution at both near-liquid-helium temperature and room temperature. The possible luminescence spectra of free UO 2 F 2 in gas phase are predicted on the basis of CASPT2 and CCSD(T) results, respectively, by considering three symmetric vibration modes. Finally, the effect of competition between spin–orbit coupling and ligand field repulsion on the luminescent state properties is discussed.

Environmental Molecular Sciences Laboratory↗

DOE OSTI2020

An isolated water droplet in the aqueous solution of a supramolecular tetrahedral cage

Water under nanoconfinement at ambient conditions has exhibited low-dimensional ice formation and liquid–solid phase transitions, but with structural and dynamical signatures that map onto known regions of water’s phase diagram. Using terahertz (THz) absorption spectroscopy and ab initio molecular dynamics, we have investigated the ambient water confined in a supramolecular tetrahedral assembly, and determined that a dynamically distinct network of 9 ± 1 water molecules is present within the nanocavity of the host. The low-frequency absorption spectrum and theoretical analysis of the water in the Ga 4 L 6 12– host demonstrate that the structure and dynamics of the encapsulated droplet is distinct from any known phase of water. A further inference is that the release of the highly unusual encapsulated water droplet creates a strong thermodynamic driver for the high-affinity binding of guests in aqueous solution for the Ga 4 L 6 12– supramolecular construct.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2024

Impacts of Neodymium Complexation on Radiolysis of Tetramethyl Diglycolamide (TMDGA) in Aqueous Solutions

Hydrophilic diglycolamides (DGA) ligands have been explored for use as stripping agents in various lanthanide and actinide partitioning processes.1 The separation of lanthanide fission products and transplutonic actinides can serve multifaceted advantages, in that the separation of neutron poisoning rare earth element (REE) fission products from the minor actinides in used nuclear fuel (UNF) can be mutually beneficial to the fundamental research behind REE separations and UNF separations. Considerable efforts have been devoted to understanding the radiation chemistry of hydrophilic DGAs. However, recent studies with lipophilic DGAs have shown that metal ion complexation can promote significant changes in their radiolytic susceptibility.2,3 These effects have been attributed to various parameters, including delocalization of electron density, the presence of radiolytically more susceptible counter ions, and steric hindrance. As such, it is pivotal for these complexation effects to be more thoroughly probed to establish mechanistic knowledge for their effects on hydrophilic DGA molecules. Here we present a time-resolved electron pulse and accumulated gamma dose irradiation study on neodymium ion complexes of tetramethyl diglycolamide (TMDGA) under aqueous solution conditions. References (1) Rostaing, C.; Poinssot, C.; Warin, D.; Baron, P.; Lorrain, B. Development and Validation of the EXAm Separation Process for Single Am Recycling. Procedia Chem. 2012, 7, 367–373. https://doi.org/doi: 10.1016/j.proche.2012.10.057. (2) Horne, G. P.; Conrad, J. K.; McLachlan, J. R.; Rotermund, B. M.; Cook, A. R.; Celis-Barros, C.; Mezyk, S. P. Impact of Lanthanide Complexation and Temperature on the Chemical Reactivity of N,N,N’,N’-Tetraoctyl Diglycolamide (TODGA) with the Dodecane Radical Cation. Phys. Chem. Chem. Phys. 2023, Under Review. (3) Kimberlin, A.; Saint-Louis, G.; Guillaumont, D.; Camès, B.; Guilbaud, P.; Berthon, L. Effect of Metal Complexation on Diglycolamide Radiolysis: A Comparison between Ex Situ Gamma and in Situ Alpha Irradiation. Phys. Chem. Chem. Phys. PCCP 2022, 24 (16), 9213–9228. https://doi.org/10.1039/d1cp05731f.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗

DOE OSTI2025

Removal of Selenium Oxyanions from Aqueous Solutions by Ion Exchange: Equilibrium, Kinetics, and Mechanistic Modeling

Selenium (Se) is an essential micronutrient but toxic at high concentrations, posing challenges for water treatment. This study investigated the removal of selenate (SeO 4 2– ) and selenite (SeO 3 2– ) using the strong-base anion-exchange resin IRA-900, particularly in the presence of competing sulfate (SO 4 2– ). The performance of the commercially available resin IRA-900 was systematically investigated. The batch equilibrium behavior was studied in both single- and binary-component systems, and the kinetic behavior was investigated in single-component systems. Results confirmed a selectivity order of SeO 4 2– > SO 4 2– > SeO 3 2– , indicating preferential SeO 4 2– removal over competing SO 4 2– but lower affinity for SeO 3 2– . The maximum total exchange capacity was determined to be 2.04 mequiv/g. Furthermore, SeO 3 2– uptake was found to be pH-dependent, whereas SeO 4 2– uptake remained stable across a broad pH range. From a modeling perspective, the Law of Mass Action model effectively described equilibrium data, and a transport–reaction modeling framework captured removal kinetics of oxyanions including film and intraparticle diffusion. Finally, X-ray photoelectron spectroscopy confirmed ion exchange between chloride and Se oxyanions as the primary removal mechanism. These findings provide fundamental insights into the removal of Se oxyanions from aqueous solutions by ion exchange.

IRA-900↗

DOE OSTI2017

Effect of laser radiation on aqueous solutions of beta-active nuclides

Experimental data are presented on the effect of pulsed laser irradiation of aqueous {sup 234}Th, {sup 231}Th and {sup 137}Cs solutions on the concentrations of the beta-active nuclides in the solutions. Central to the investigation technique used is that the solutions contain nanoparticles resulting from the interaction of laser radiation with a target placed in the cuvette. The concentration of the radionuclides was evaluated before, during and after laser irradiation from the area under gamma-ray lines corresponding to spontaneous gamma decay. The gamma photon energies of {sup 234}Th, {sup 231}Th and {sup 137}Cs are 92, 186 and 661 keV, respectively. It has been shown that laser irradiation reduces the concentration of the three beta-active nuclides without excess gamma-ray emission in the energy range of their spontaneous decay. This is possible if decay follows another mechanism, activated by interaction of laser radiation with the aqueous solutions of the nuclides in the presence of nanoparticles.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗

NASA NTRS1998

An Experimental Study of the Effects of A Rotating Magnetic Field on Electrically Conducting Aqueous Solutions

The use of a rotating magnetic field for stirring metallic melts has been a commonly adopted practice for a fairly long period. The elegance of the technique stems from its non-intrusive nature and the intense stirring it can produce in an electrically conducting medium. A further application of the method in recent times has been in the area of crystal growth from melts (e.g. germanium). The latter experiments have been mainly research oriented in order to understand the basic physics of the process and to establish norms for optimizing such a technique for the commercial production of crystals. When adapted for crystal growth applications, the rotating magnetic field is used to induce a slow flow or rotation in the melt which in effect significantly curtails temperature field oscillations in the melt. These oscillations are known to cause dopant striations and thereby inhomogeneities in the grown crystal that essentially degrades the crystal quality. The applied field strength is typically of the order of milli-Teslas with a frequency range between 50-400 Hz. In this investigation, we report findings from experiments that explore the feasibility of applying a rotating magnetic field to aqueous salt solutions, that are characterized by conductivities that are several orders of magnitude smaller than semi-conductor melts. The aim is to study the induced magnetic field and consequently the induced flow in such in application. Detailed flow field description obtained through non-intrusive particle displacement tracking will be reported along with an analytical assessment of the results. It is anticipated that the obtained results will facilitate in establishing a parameter range over which the technique can be applied to obtain a desired flow field distribution. This method can find applicability in the growth of crystals from aqueous solutions and give an experimenter another controllable parameter towards improving the quality of the grown crystal.

Ramachandran Narayanan↗

NASA NTRS2011

Aqueous solution dispersement of carbon nanotubes

Carbon nanotubes (CNTs) are dispersed in an aqueous buffer solution consisting of at least 50 weight percent water and a remainder weight percent that includes a buffer material. The buffer material has a molecular structure defined by a first end, a second end, and a middle disposed between the first and second ends. The first end is a cyclic ring with nitrogen and oxygen heteroatomes, the middle is a hydrophobic alkyl chain, and the second end is a charged group.

Kim, Jae-Woo↗

DOE OSTI2012

Ion Association in AlCl3 Aqueous Solutions from Constrained First-Principles Molecular Dynamics

Ab initio molecular dynamics was used to investigate the ion pairing behavior between Cl- and the Al3+ ion in an aqueous AlCl3 solution containing 63 water molecules. A series of constrained simulations was carried out at 300 K for up to 16 ps each, by fixing the inter-nuclear separation (rAl-Cl) between the Al3+ ion and one of the Cl- ions. The calculated potential of mean force of the Al3+-Cl- ion pair shows a pronounced minimum at rAl-Cl = 2.3 Å corresponding to a contact ion pair (CIP). Two local minima assigned to solvent separated ion pairs (SSIP) are identified at rAl-Cl= 4.4 and 6.0 Å. The positions of the free energy minima coincide with the hydration shell intervals of the Al3+ cation suggesting that the Cl- ion is inclined to reside in regions of low concentration of waters, i.e. between the 1st and 2nd shells of Al3+ and between the 2nd shell and bulk. A detailed analysis of solvent structure around the Al3+ and Cl- ions as a function of rAl-Cl is presented. The results are compared to structure data from X-ray measurements and unconstrained AIMD simulations of single ions Al3+ and Cl- and AlCl3 solutions. The dipole moment of the water molecules inside the 1st and 2nd hydration shells of Al3+ and in the bulk region and those of the Clion were calculated as a function of rAl-Cl. Major changes in the electronic structure of the system result from the removal of Cl- from the 1st hydration shell of the Al3+ cation. Finally, two unconstrained AIMD simulations of aqueous AlCl3 solutions corresponding to CIP and SSIP configurations were performed (17 ps, 300 K). Only minor structural changes are observed in these systems, confirming their stability.

ab initio↗

DOE OSTI2026

Custom-trained Machine-learning Interatomic Potentials: ZnCl2 Aqueous Solution

This dataset was generated using an iterative active-learning strategy implemented in the ArcaNN software package (https://github.com/arcann-chem/arcann_training) to train machine-learning interatomic potentials for aqueous ZnCl2 solutions. Each active-learning cycle consisted of three stages: training, exploration, and labeling. The initial training set combined configurations generated in this work from enhanced-sampling ab initio molecular dynamics simulations with configurations from a previously reported neural-network-potential study of aqueous ZnCl2. The enhanced-sampling ab initio molecular dynamics simulations involved Zn–Cl separation and the chloride coordination number around Zn²? as collective variables. These configurations served as the seed dataset. Subsequent active-learning cycles expanded the training set by identifying and labeling configurations that were poorly represented by the current models, thereby improving coverage of ion-association states and changes in local coordination and charge-state environments relevant to the solution free-energy landscape. For all selected configurations, single-point calculations of the total energies and atomic forces were performed within density functional theory using the CP2K Quickstep module. Reference calculations employed the revPBE-D3 and r2SCAN exchange-correlation functionals. Motivated by recent work on aqueous Zn²?, the main revPBE calculations omitted D3 dispersion contributions involving Zn²?, while retaining the D3 correction for water and chloride. For comparison, fully dispersion-corrected revPBE-D3 reference calculations were also performed, with D3 applied to all species, including Zn²?. Valence electrons were treated explicitly, while core electrons were represented using norm-conserving Goedecker–Teter–Hutter pseudopotentials. The wave functions were expanded using the mixed Gaussian-and-plane-wave scheme with TZV2P-MOLOPT basis sets for all elements and a 600 Ry auxiliary plane-wave cutoff for the electron density. Self-consistent-field convergence was accelerated using the orbital-transformation and Direct Inversion in the Iterative Subspace algorithms, with a convergence threshold of 10?6. All single-point calculations were performed in periodic orthorhombic cells. The CELL_REF keyword in CP2K was used to define a fixed reference cell with a box length of 25 Å. This treatment ensured a consistent reference for configurations extracted from NpT trajectories with fluctuating cell dimensions. The resulting DFT energies and atomic forces constitute the ground-truth labels used to train the MLIPs. The resulting MLIP was trained for aqueous ZnCl2 solutions spanning concentrations from 0 to 30 molal and a broad pH range, from strongly acidic to strongly basic conditions. Representative examples of configurations included in the MLIP training dataset are provided below. These include 1) Representative configurations from the dataset labeled at the revPBE-D3 level, with D3 dispersion interactions involving Zn2+ excluded (revPBE-wo-D3). 2) Representative configurations from the dataset labeled at the fully dispersion-corrected revPBE-D3 level, with D3 interactions applied to all species, including Zn2+ (revPBE-D3). 3) Representative configurations from the dataset labeled at the r2SCAN level of theory (r2SCAN).

Dinpajooh, Mohammadhasan [Pacific Northwest Nation↗

DOE OSTI2025

In situ Raman investigation of Dy complexation in Cl-bearing aqueous solutions at 20–300 °C

Raman spectroscopy provides a versatile tool for in situ characterization of aqueous rare earth elements (REE) speciation at the molecular level. Complexation of REE with ligands such as Cl – and OH – is of particular interest for understanding the mobility of REE in NaCl-bearing hydrothermal fluids responsible for enriching REE to economic levels in nature. Raman spectroscopic studies of REE speciation in Cl-bearing aqueous fluids are primarily conducted at ambient temperature, whereas natural systems indicate temperatures of >100–600 °C. In this study, the speciation of Dy in acidic chloride-bearing hydrothermal solutions was investigated using confocal Raman spectroscopy with a new capillary Raman heating stage at 20–300 °C. Background solutions (pure water, NaCl-solutions) and solutions with 0.14–1.8 mol kg –1 dissolved DyCl 3 were sealed in quartz capillary cells. Comparison of the spectra for Dy chloride solutions with those for background solutions and the spectra for reference Dy-bearing solids was used to identify Raman bands specific to Dy–O and Dy–Cl bonds. The Raman band for the Dy–O stretching mode of hydrated Dy 3+ aqua ions was measured at 365–384 cm –1 and a Raman band for the Dy–Cl stretching modes of Dy chloride complexes was measured near 240 cm –1 . The Dy–O band decreases systematically with temperature, whereas the Dy–Cl band systematically increases, indicating a systematic increase in the stability of Dy chloride complexes with temperature. Here, this study provides the framework for expanding the use of in situ Raman spectroscopy to investigate the speciation of REE in aqueous solutions to hydrothermal conditions.

58 GEOSCIENCES↗

NASA NTRS2007

Direct Assembly of Modified Proteins on Carbon Nanotubes in an Aqueous Solution

Carbon nanotubes (CNTs) have superior mechanical and electrical properties that have opened up many potential applications. However, poor dispersibility and solubility, due to the substantial van der Waals attraction between tubes, have prevented the use of CNTs in practical applications, especially biotechnology applications. Effective dispersion of CNTs into small bundles or individual tubes in solvents is crucial to ensure homogeneous properties and enable practical applications. In addition to dispersion of CNTs into a solvent, the selection of appropriate solvent, which is compatible with a desired matrix, is an important factor to improve the mechanical, thermal, optical, and electrical properties of CNT-based fibers and composites. In particular, dispersion of CNTs into an aqueous system has been a challenge due to the hydrophobic nature of CNTs. Here we show an effective method for dispersion of both single wall CNTs (SWCNTs) and few wall CNTs (FWCNTs) in an aqueous buffer solution. We also show an assembly of cationized Pt-cored ferritins on the well dispersed CNTs in an aqueous buffer solution.

Kim, Jae-Woo↗

DOE OSTI2017

Recovering Rare Earth Elements from Aqueous Solution with Porous Amine–Epoxy Networks

Recovering aqueous rare earth elements (REEs) from domestic water sources is one key strategy to diminish the U.S.’s foreign reliance of these precious commodities. Herein, we synthesized an array of porous, amine–epoxy monolith and particle REE recovery sorbents from different polyamine, namely tetraethylenepentamine, and diepoxide (E2), triepoxide (E3), and tetra-epoxide (E4) monomer combinations via a polymer-induced phase separation (PIPS) method. The polyamines provided -NH 2 (primary amine) plus -NH (secondary amine) REE adsorption sites, which were partially reacted with C–O–C (epoxide) groups at different amine/epoxide ratios to precipitate porous materials that exhibited a wide range of apparent porosities and REE recoveries/affinities. Specifically, polymer particles (ground monoliths) were tested for their recovery of La 3+ , Nd 3+ , Eu 3+ , Dy 3+ , and Yb 3+ (Ln 3+ ) species from ppm-level, model REE solutions (pH ≈ 2.4, 5.5, and 6.4) and a ppb-level, simulated acid mine drainage (AMD) solution (pH ≈ 2.6). Screening the sorbents revealed that E3/TEPA-88 (88% theoretical reaction of -NH 2 plus -NH) recovered, overall, the highest percentage of Ln 3+ species of all particles from model 100 ppm- and 500 ppm-concentrated REE solutions. Water swelling (monoliths) and ex situ, diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) (ground monoliths/particles) data revealed the high REE uptake by the optimized particles was facilitated by effective distribution of amine and hydroxyl groups within a porous, phase-separated polymer network. In situ DRIFTS results clarified that phase separation, in part, resulted from polymerization of the TEPA-E3 (N-N-diglycidyl-4-glycidyloxyaniline) species in the porogen via C–N bond formation, especially at higher temperatures. Most importantly, the E3/TEPA-88 material cyclically recovered >93% of ppb-level Ln 3+ species from AMD solution in a recovery–strip–recovery scheme, highlighting the efficacy of these materials for practical applications.

36 MATERIALS SCIENCE↗

DOE OSTI2026

Hydration and transport properties of cesium hydroxide and mixed cesium hydroxide–sodium nitrite aqueous solutions

Here, this study explores the hydration and transport properties of aqueous cesium hydroxide (CsOH) solution, with or without 1 molar (M) sodium nitrite (NaNO 2 ). Historic studies of electrolyte solutions indicate that Cs + ions decrease viscosity and increase diffusion rates, whereas OH − ions have the opposite effect. Here, the influence of OH − was dominant in CsOH solutions, leading to increased viscosity and reduced diffusion rates. There was a linear relationship between diffusion coefficients and water activity, emphasizing the significant role of ion–water interactions in determining transport properties. This may be because the interaction between Cs + and the anions is weak even when they are in direct contact with each other. The weakness of the ion-pairing was established through thermodynamic analysis. The findings suggest that ion-pairing is not the only important interaction controlling transport properties when ion-pairing is weak. Nonetheless, ion-pairing or obstructions did result in more sluggish transport properties as electrolyte concentrations increased. Overall, the research enhances the understanding of the complexities underlying ion interactions in multicomponent solutions.

Reynolds, Jacob G. [Hanford Site (HNF), Richland, ↗

DOE OSTI2014

Photoelectron spectroscopy of aqueous solutions: Streaming potentials of NaX (X = Cl, Br, and I) solutions and electron binding energies of liquid water and X{sup −}

The streaming potentials of liquid beams of aqueous NaCl, NaBr, and NaI solutions are measured using soft X-ray, He(I), and laser multiphoton ionization photoelectron spectroscopy. Gaseous molecules are ionized in the vicinity of liquid beams and the photoelectron energy shifts are measured as a function of the distance between the ionization point and the liquid beam. The streaming potentials change their polarity with concentration of electrolytes, from which the singular points of concentration eliminating the streaming potentials are determined. The streaming currents measured in air also vanish at these concentrations. The electron binding energies of liquid water and I{sup −}, Br{sup −}, and Cl{sup −} anions are revisited and determined more accurately than in previous studies.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2017

Heteronuclear complexation in the system 1-hydroxyethylidenediphosphonic acid—manganese(II)—gadolinium(III) in aqueous solution

pH-Potentiometric method in combination with mathematical modeling was used to study the system manganese(II)—gadolinium(III)—1-hydroxyethylidenediphosphonic acid (HEDP, H{sub 4}L). When both cations simultaneously are present in the solution, the accumulation of heteronuclear forms with the ratio of Gd: Mn: HEDP equal to 1: 1: 1, 1: 1: 2, and 1: 1: 3 was observed already in the strongly acidic pH region, while from homonuclear forms only five complexes were detected in the solution, namely, MnL{sub 2}{sup 6–}, GdH{sub 4}L{sub 2}{sup –}, GdH{sub 2}L{sup +}, KGd{sub 2}HL{sub 2}↓, and K{sub 3}Gd{sub 2}L{sub 2}(OH)↓. It was concluded that heteronuclear complexes are much stronger and replace homonuclear forms in solution.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2014

Theoretical analysis of aqueous solutions of mixed strong electrolytes by a smaller-ion shell electrostatic model

In spite of the great importance of mixed electrolytes in science and technology, no compelling theoretical explanation has been offered yet for the thermodynamic behavior of such systems, such as their deviation from ideality and the variation of their excess functions with ionic composition and concentration. Using the newly introduced Smaller-ion Shell treatment – an extension of the Debye–Hückel theory to ions of dissimilar size (hence DH–SiS) – simple analytic mathematical expressions can be derived for the mean and single-ion activity coefficients of binary electrolyte components of ternary ionic systems. Such expressions are based on modifying the parallel DH–SiS equations for pure binary ionic systems, by adding to the three ion-size parameters – a (of counterions), b{sub +} (of positive coions), and b{sub −} (of negative coions) – a fourth parameter. For the (+ + −) system, this is “b{sub ++},” the contact distance between non-coion cations. b{sub ++} is derived from fits with experiment and, like the other b’s, is constant at varying ion concentration and combination. Four case studies are presented: (1) HCl–NaCl–H{sub 2}O, (2) HCl–NH{sub 4}Cl–H{sub 2}O, (3) (0.01 M HX)–MX–H{sub 2}O with X = Cl, Br, and with M = Li, Na, K, Cs, and (4) HCl–MCl{sub n}–H{sub 2}O with n = 2, M = Sr, Ba; and n = 3, M = Al, Ce. In all cases, theory is fully consistent with experiment when using a of the measured binary electrolyte as the sole fitting parameter. DH–SiS is thus shown to explain known “mysteries” in the behavior of ternary electrolytes, including Harned rule, and to adequately predict the pH of acid solutions in which ionized salts are present at different concentrations.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2019

Identifying Water–Anion Correlated Motion in Aqueous Solutions through Van Hove Functions

Electrolyte solutions are ubiquitous in materials in daily use and in biological systems. However, the understanding of their molecular and ionic dynamics, particularly those of their correlated motions, are elusive despite extensive experimental, theoretical, and numerical studies. Here we report the real-space observations of the molecular/ionic-correlated dynamics of aqueous salt (NaCl, NaBr, and NaI) solutions using the Van Hove functions obtained by high-resolution inelastic X-ray scattering measurement and molecular dynamics simulation. Our results directly depict the distance-dependent dynamics of aqueous salt solutions on the picosecond time scale and identify the changes in the anion–water correlations. This study demonstrates the capability of the real-space Van Hove function analysis to describe the local correlated dynamics in aqueous salt solutions.

Shinohara, Yuya↗