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At least 991 records · Page 55
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Characterization of the primary hydration shell of the hydroxide ion with H 2 tagging vibrational spectroscopy of the OH - ∙ (H 2 O) n=2,3 and OD - ∙ (D 2 O) n=2,3 clusters

In this paper, we report the isotope-dependent vibrational predissociation spectra of the H 2 -tagged OH - ∙ (H 2 O) n=2,3 clusters, from which we determine the strongly coordination-dependent energies of the fundamentals due to the OH groups bound to the ion and the intramolecular bending modes of the water molecules. The HOH bending fundamental is completely missing in the delocalized OH - ∙ (H 2 O) binary complex but is recovered upon adding the second water molecule, thereby establishing that the dihydrate behaves as a hydroxide ion solvated by two essentially intact water molecules. The energies of the observed OH stretches are in good agreement with the values predicted by Takahashi and co-workers [Phys. Chem. Chem. Phys. 17, 25505 (2015); 15, 114 (2013)] with a theoretical model that treats the strong anharmonicities at play in this system with explicit coupling between the bound OH groups and the O–O stretching modes on an extended potential energy surface. We highlight a surprising similarity between the spectral signatures of OH - ∙ (H 2 O) 3 and the excess proton analogue, H 3 O + ∙ (H 2 O) 3 , both of which correspond to completed hydration shells around the proton defect. Finally, we discuss the origin of the extreme solvatochromicity displayed by both OH - and H + in the context of the anomalously large “proton polarizabilities” of the H 5 O 2 + and H 3 O 2 - binary complexes.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Molecular modeling and assignment of IR spectra of the hydrated excess proton in isotopically dilute water

Infrared (IR) spectroscopy of the water O–H stretch has been widely used to probe both the local hydrogen-bonding structure and dynamics of aqueous systems. Although of significant interest, the IR spectroscopy of excess protons in water remains difficult to assign as a result of extensive and strong intermolecular interactions in hydrated proton complexes. As an alternate approach, we develop a mixed quantum-classical model for the vibrational spectroscopy of the excess proton in isotopically dilute water that draws on frozen proton-water clusters taken from reactive molecular dynamics trajectories of the latest generation multi-state empirical valence bond proton model (MS-EVB 3.2). A semi-empirical single oscillator spectroscopic map for the instantaneous transition frequency and transition dipole moment is constructed using potential energy surfaces for the O–H stretch coordinate of the excess proton using electronic structure calculations. Calculated spectra are compared with experimental spectra of dilute H + in D 2 O obtained from double-difference FTIR to demonstrate the validity of the map. The model is also used to decompose IR spectra into contributions from different aqueous proton configurations. We find that the O–H transition frequency continuously decreases as the oxygen-oxygen length for a special pair proton decreases, shifting from Eigen- to Zundel-like configurations. In conclusion, the same shift is accompanied by a shift of the flanking water stretches of the Zundel complex to higher frequency than the hydronium O–H vibrations.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Revisiting the hydration structure of aqueous Na +

In this paper, a combination of theory, X-ray diffraction (XRD) and extended x-ray absorption fine structure (EXAFS) are used to probe the hydration structure of aqueous Na + . The high spatial resolution of the XRD measurements corresponds to Qmax = 24 Å –1 while the first-reported Na K-edge EXAFS measurements have a spatial resolution corresponding to 2k = Qmax = 16 Å –1 . Both provide an accurate measure of the shape and position of the first peak in the Na–O pair distribution function, g NaO (r). The measured Na–O distances of 2.384 ± 0.003 Å (XRD) and 2.37 ± 0.024 Å (EXAFS) are in excellent agreement. These measurements show a much shorter Na–O distance than generally reported in the experimental literature (Na–O avg ~ 2.44 Å) although the current measurements are in agreement with recent neutron diffraction measurements. The measured Na–O coordination number from XRD is 5.5 ± 0.3. The measured structure is compared with both classical and first-principles density functional theory (DFT) simulations. Both of the DFT-based methods, revPBE and BLYP, predict a Na–O distance that is too long by about 0.05 Å with respect to the experimental data (EXAFS and XRD). The inclusion of dispersion interactions (–D3 and –D2) significantly worsens the agreement with experiment by further increasing the Na–O distance by 0.07 Å. In contrast, the use of a classical Na–O Lennard-Jones potential with SPC/E water accurately predicts the Na–O distance as 2.39 Å although the Na–O peak is over-structured with respect to experiment.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Swelling of individual nanodomains in hydrated block copolymer electrolyte membranes

Here, we examine the swelling of nanostructured block copolymer electrolytes immersed in liquid water. A series of sulfonated polystyrene-b-polyethylene-b-polystyrene (S-SES) membranes having the same nominal chemical composition but two different morphologies are prepared by systematic changes in processing. We start with a membrane comprising a mixture of homopolymer polystyrene (hPS) and a polystyrene-b-polyethylene-b-polystyrene (SES) copolymer. hPS is subsequently selectively removed from the membrane and the polystyrene domains are sulfonated to give S-SES membranes. The morphology of the membranes is controlled by controlling Φ v , the volume fraction of hPS in the blended membrane. The morphology of the membranes was studied by small angle X-ray scattering (SAXS), cryogenic scanning transmission electron microscopy (cryo-STEM), and cryogenic electron tomography. The overall domain swelling measured by SAXS decreases slightly at Φ v = 0.29; a crossover from lamellar to bicontinuous morphology is obtained at the same value of Φ v . The bicontinuous morphologies absorb more water than the lamellar morphologies. By contrast, the nanodomain swelling of the bicontinuous membrane (120%) is slightly less than that of the lamellar membrane (150%). Quantitative analysis of the STEM images and electron tomography was used to determine the swelling on the hydrophilic and hydrophobic domains due to exposure to water. The hydrophilic sulfonated polystyrene-rich domain spacing increases while the hydrophobic polyethylene domain spacing decreases when the membranes are hydrated. The extent of increase and decrease is not a strong function of Φ v .

36 MATERIALS SCIENCE↗
DOE OSTI2020

Precipitation of calcium–alumino–silicate–hydrate gels: The role of the internal stress

Concrete gains its strength from the precipitation of a calcium–alumino–silicate–hydrate (C–A–S–H) colloidal gel, which acts as its binding phase. However, despite concrete’s ubiquity in the building environment, the atomic-scale mechanism of C–A–S–H precipitation is still unclear. Here, we use reactive molecular dynamics simulations to model the early-age precipitation of a C–A–S–H gel. We find that, upon gelation, silicate and aluminate precursors condensate and polymerize to form an aluminosilicate gel network. Notably, we demonstrate that the gelation reaction is driven by the existence of a mismatch of atomic-level internal stress between Si and Al polytopes, which are initially experiencing some local tension and compression, respectively. The polymerization of Si and Al polytopes enables the release of these competitive stresses.

Zhao, Cheng↗
DOE OSTI2022

Hydrogen bond arrangements in (H 2 O) 20, 24, 28 clathrate hydrate cages: Optimization and many-body analysis

Here we provide a detailed study of hydrogen bonding arrangements, relative stability, residual entropy, and an analysis of the many-body effects in the (H 2 O) 20 (D-cage), (H 2 O) 24 (T-cage), and (H 2 O) 28 (H-cage) hollow cages making up structures I (sI) and II (sII) of clathrate hydrate lattices. Based on the enumeration of the possible hydrogen bonding networks for a fixed oxygen atom scaffold, the residual entropy (S 0 ) of these three gas phase cages was estimated at 0.754 82, 0.754 44, and 0.754 17 · Nk b , where N is the number of molecules and k b is Boltzmann’s constant. A previously identified descriptor of enhanced stability based on the relative arrangement and connectivity of nearest-neighbor fragments on the polyhedral water cluster [strong-weak-effective-bond model] also applies to the larger hollow cages. The three cages contain a maximum of 7, 9, and 11 such preferable arrangements of trans nearest dimer pairs with one “free” OH bond on the donor molecule (t1d dimers). The Many-Body Expansion (MBE) up to the 4-body suggests that the many-body terms vary nearly linearly with the cluster binding energy. Using a hierarchical approach of screening the relative stability of networks starting from optimizations with the TIP4P, TTM2.1-F, and MB-pol classical potentials, subsequently refining at more accurate levels of electronic structure theory (DFT and MP2), and finally correcting for zero-point energy, we were able to identify a group of four low-lying isomers of the (H 2 O) 24 T-cage, two of which are antisymmetric and the other two form a pair of antipode configurations.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
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 OSTI2021

Stripping away ion hydration shells in electrical double-layer formation: Water networks matter

Significance For centuries the double layer at the solid/electrolyte interface has been a central concept in electrochemistry. Today, it is still crucial for virtually all renewable energy storage and conversion technologies. Here, the double-layer formation is probed by THz spectroscopy with ultrabright synchrotron light as a source. Our results capture the molecular details of double-layer formation at positively/negatively charged Au electrodes for an NaCl electrolyte. We reveal a contrasting response applying positive versus negative bias, which is dictated by the interfacial water network and rationalized by accompanying molecular dynamics simulations and electronic-structure calculations. While Na + is directly attracted toward the negatively charged electrode, stripping of the Cl − hydration shell is observed only at larger potential values.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Importance of nuclear quantum effects on the hydration of chloride ion

Path-integral ab initio molecular dynamics (PI-AIMD) calculations have been employed to probe the nature of chloride ion solvation in aqueous solution. Nuclear quantum effects (NQEs) are shown to weaken hydrogen bonding between the chloride anion and the solvation shell of water molecules. As a consequence, the disruptive effect of the anion on the solvent water structure is significantly reduced compared to what is found in the absence of NQEs. Additionally, the chloride hydration structure obtained from PI-AIMD agrees well with information extracted from neutron scattering data. In particular, the observed satellite peak in the hydrogen-chloride-hydrogen triple angular distribution serves as a clear signature of NQEs. The present results suggest that NQEs are likely to play a crucial role in determining the structure of saline solutions.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Examination of gamma-irradiated calcium silicate hydrates. Part I: Chemical-structural properties

The chemical-structural properties of synthetic calcium silicate hydrate (C-S-H) with C/S (Ca/Si) ratios of 0.75, 1 and 1.33 were studied after gamma irradiation-absorbed doses ranging from 0.145 to 0.784 MGy and compared with those of control specimens. The results showed that the total water content given by thermogravimetric analysis and the dimension of the basal spacing given by x-ray diffraction were comparable for control and irradiated samples, which indicate that the interlayer water content did not change. The morphology, C/S ratios, and silicate mean chain length were also found to be unaltered by the absorbed gamma doses.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Hydration and reaction mechanisms on sodium silicate glass surfaces from molecular dynamics simulations with reactive force fields

Recent development of reactive force fields have enabled molecular dynamics simulations of interactions between silicate glasses and water at the atomistic scale. While multicomponent silicate glasses encompass a wide variety of compositions and properties, one common structural feature in these glasses is the combination of the network structure that is made up of silica tetrahedra linked through corner sharing interspersed with network modifiers like alkali and alkaline-earth ions that break up the Si–O–Si linkages by forming nonbridging oxygen. In reactions with water, ion exchange between alkali ions in the glass and proton or hydronium in the solution, as well as hydrolysis reaction of the Si–O–Si linkages and subsequent silanol formation, is observed and well documented. Furthermore, we have used a set of recently developed reactive force field to investigate the reactions between water and the surfaces of silica and sodium silicate glasses of different compositions for reactions up to 8 nanoseconds. Our results indicate sodium leaching into water and diffusion of water molecules up to 25 Å into the glass surface. We examined the structural and compositional changes inside the glass and around the diffused ions and use these to explain the rates of silanol formation at the surface. We also observed proton transport in the glass which has an indirect influence on the silanol formation rates. While the surface of the glass was rough to start with, it undergoes further modification into a hydrated gel-like structure in the glass for up to 5 Å in the higher alkali containing glasses. It was found that the leached sodium ions remain close to the interface and that fragments of silicate network from the surface is capable of dislodging from the bulk glass and enter the aqueous solution. These simulations thus provide insights into the formation and structure of an alteration layers commonly observed in multicomponent silicate glasses corroded in aqueous solutions.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Dynamic sparse x-ray nanotomography reveals ionomer hydration mechanism in polymer electrolyte fuel-cell catalyst

Tomographic imaging of time-evolving samples is a challenging yet important task for various research fields. At the nanoscale, current approaches face limitations of measurement speed or resolution due to lengthy acquisitions. We developed a dynamic nanotomography technique based on sparse dynamic imaging and 4D tomography modeling. We demonstrated the technique, using ptychographic x-ray computed tomography as its imaging modality, on resolving the in situ hydration process of polymer electrolyte fuel cell (PEFC) catalyst. The technique provides a 40-time increase in temporal resolution compared to conventional approaches, yielding 28 nm half-period spatial and 12 min temporal resolution. The results allow a quantitative characterization of the water intake process inside PEFC catalysts with nanoscale resolution, which is crucial for understanding their electrochemical mechanisms and optimizing their performance. Our technique enables high-speed operando nanotomography studies and paves the way for wider application of dynamic tomography at the nanoscale.

Science & Technology - Other Topics↗
DOE OSTI2016

Aqua(pentahydrogennitrilotris(methylenephosphonato))lithium hydrate [Li(H{sub 2}O)(N(CH{sub 2}PO{sub 3}){sub 3}H{sub 5})] • H{sub 2}O: Synthesis and structure

Aqua(pentahydrogennitrilotris(methylenephosphonato))lithium hydrate is a linear coordination polymer. Its crystal structure is described in space group P{sup –}1, Z = 2; a = 5.5732(2), b = 7.0106(2), and c = 16.9010(5) Å; α = 97.515(2)°, β = 94.551(2)°, and γ = 95.123(2)°. The tetrahedral coordination of the Li atom includes two oxygen atoms of a phosphonate ligand, one oxygen atom of another phosphonate ligand, and a water molecule. Complex formation is accompanied by closing of the eight-membered Li–O–P–C–N–C–P–O chelate ring. Polymeric chains run along the [100] direction. The chains are connected by hydrogen bonds.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2017

Modular structure of highly ordered eudialyte and its place among hydrated minerals of rastsvetaevite family

The crystal structure of a representative of eudialyte group, which was found by A.P. Khomyakov at the Rasvumchorr mountain of the Khibiny alkaline massif (Kola Peninsula), has been studied by X-ray diffraction. The trigonal unit-cell parameters are found to be a = 14.2328(5) Å, c = 60.217(2) Å, V = 10564.08(3) Å3, sp. gr. R3m. The structure has been refined with the isotropic and anisotropic approximation displacement parameters to the total reliability factor R = 5.6%, based on 2989 reflections with |F| > 4σ(F). The idealized formula (Z = 3) is determined as [(H{sub 3}O){sub 11}Na{sub 10}K5]Cа{sub 12}(Na{sub 3}Fe{sub 2}Mn)Si{sub 4}Zr{sub 6}(Si{sub 48}O{sub 144})(OH,Cl){sub 5}(H{sub 2}O){sub 5}. The unit cell of the mineral is doubled due to the presence of two modules of different composition and structure in it (alluaivite-and kentbrooksite-like ones) and the formation of a polyhedral cluster in the kentbrooksite module. A comparison with two hydrated minerals having a modular structure shows that these minerals, being similar in their chemical composition, differ in the cation ordering over the sites of the two modules. The sample under study contains potassium in only one module, while oxonium groups are distributed in both modules but over different sites.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Design and construction of 3D printed devices to investigate active and passive bacterial dispersal on hydrated surfaces

Background: To disperse in water-unsaturated environments, such as the soil, bacteria rely on the availability and structure of water films forming on biotic and abiotic surfaces, and, especially, along fungal mycelia. Dispersal along such “fungal highways” may be driven both by mycelial physical properties and by interactions between bacteria and fungi. However, we still do not have a way to disentangle the biotic and abiotic elements. Results: We designed and 3D printed two devices establishing stable liquid films that support bacteria dispersal in the absence of biotic interactions. The thickness of the liquid film determined the presence of hydraulic flow capable of transporting non-motile cells. In the absence of flow, only motile cells can disperse in the presence of an energy source. Non-motile cells could not disperse autonomously without flow but dispersed as “hitchhikers” when co-inoculated with motile cells. Conclusions: The 3D printed devices can be used as an abiotic control to study bacterial dispersal on hydrated surfaces, such as plant roots and fungal hyphae networks in the soil. By teasing apart the abiotic and biotic dimensions, these 3D printed devices will stimulate further research on microbial dispersal in soil and other water-unsaturated environments.

3D printing↗
DOE OSTI2015

Role of hydration forces in the properties of electrolyte solutions in the bulk and at interfaces

We present a theoretical approach for modeling electrolyte solutions at interfaces that reaches into the mesoscale while retaining molecular detail. The total Hamiltonian of the system includes interactions arising from density and charge density (ion correlation) fluctuations, direct Coulomb interactions between ions, and at interfaces the image interactions, ion-solid and ion-water dispersion interactions. The model was validated against its ability to reproduce ion activity in 1:1 and 2:1 electrolyte solutions in the 0-2 M concentration range, its ability to capture the ion-specific effect in 1:1 electrolytes at the air-water interface, and solvent structure in a confined environment between hydrophobic surfaces, revealing the central role of ion hydration interactions in specific ion thermodynamic properties in the bulk solutions and at interfaces. The model is readily extensible to treat electrolyte interactions and forces across charged solid-water interfaces.

Sushko, Maria L.↗
DOE OSTI2020

The new K, Pb-bearing uranyl-oxide mineral kroupaite: Crystal-chemical implications for the structures of uranyl-oxide hydroxy-hydrates

Abstract Kroupaite (IMA 2017-031), ideally KPb0.5[(UO2)8O4(OH)10]·10H2O, is a new uranyl-oxide hydroxylhydrate mineral found underground in the Svornost mine, Jáchymov, Czechia. Electron-probe micro-analysis (WDS) provided the empirical formula (K1.28Na0.07)Σ1.35(Pb0.23Cu0.14Ca0.05Bi0.03Co0.02Al0.01)Σ0.48 [(UO2)7.90(SO4)0.04O4.04(OH)10.00]·10H2O, on the basis of 40 O atoms apfu. Sheets in the crystal structure of kroupaite adopt the fourmarierite anion topology, and therefore kroupaite belongs to the schoepite-family of minerals with related structures differing in the interlayer composition and arrangement, and charge of the sheets. Uptake of dangerous radionuclides (90Sr or 135Cs) into the structure of kroupaite and other uranyl-oxide hydroxy-hydrate is evaluated based on crystal-chemical considerations and Voronoi-Dirichlet polyhedra measures. These calculations show the importance of these phases for the safe disposal of nuclear waste.

Geochemistry & Geophysics↗
DOE OSTI2013

ConocoPhillips Gas Hydrate Production Test

Work began on the ConocoPhillips Gas Hydrates Production Test (DOE award number DE-NT0006553) on October 1, 2008. This final report summarizes the entire project from January 1, 2011 to June 30, 2013.

03 NATURAL GAS↗