Ice-like Structure Research Articles

Probing hydrogen bonding in benzene–(water)nclusters using resonant ion–dip IR spectroscopy

Resonant ion–dip infrared spectroscopy (RIDIRS) is used to record clustersize-specific spectra of C6H6–(H2O)n(BWn) clusters with n= 1–7 in the C—H and O—H stretch regions (2900–4000 cm–1). The Fermi triad characteristic of benzene in the C—H stretch region is virtually unchanged by addition of as many as seven water molecules. By contrast, the O—H stretch spectra show a dramatic dependence on cluster size. In C6H6–H2O, the O—H stretch transitions are complicated by additional structure due to internal rotation of H2O in the complex. In C6H6–(H2O)2, the O—H stretch spectrum closely mimics that of the free water dimer. For the n= 3–5 clusters, the spectra can be divided roughly into three categories, due to free O—H (3715 cm–1), π H-bonded O—H (3650 cm–1), and single donor O—H stretches, consistent with a BWn structure composed of a cyclic Wn cluster in which one of the free O—H groups is used in π hydrogen bonding with benzene. At n= 6, the spectra show distinct new transitions in the 3500–3600 cm–1 region. By comparing with the predictions of ab initio calculations of Wn, these new transitions are assigned to double donor O—H stretches associated with the formation of a more compact, ice-like structure in W6. The transformation to double-donating waters continues to develop in BW7, where additional transitions in the double-donor O—H stretch region appear at the expense of free O—H transition intensity.

イメージングプレート迅速Ｘ線回折法による高温高圧水の構造解析

A novel X-ray diffraction method for liquids using an imaging plate area detector has been successfully applied to constant-density measurements of water at high temperatures and high pressures covering the supercrital state. The radial distribution functions have shown that the local tetrahedral ice-like structure of water is ruptured above 416K and that the short-range O-O interactions at -2.9A still exist by -40% to the coordination number of 3.9, however, with large fluctuation and distorted hydrogen bonding in dense supercritical water at 649K.

Vibrational spectroscopy of water at the vapor/water interface.

Using infrared-visible sum-frequency generation we have obtained the OH stretch vibrational spectra of water at the vapor/water interface. From the spectra, we deduce that more than 20% of the surface water molecules have one free OH projecting into the vapor. The spectrum is weakly temperature dependent from 10 to 80 \ifmmode^\circ\else\textdegree\fi{}C. A monolayer of fatty alcohol on water surface terminates the free OH groups and induces an icelike structure in the spectrum.

Ordering of fractional monolayers of H 2O on Ni(110)

The ordering of water adsorbed on Ni(110) at monolayer and lower coverages was studied using molecular dynamics simulations. No long-range order could be found for the complete monolayer. At fractional coverage of θ ∼ 0.9, oriented zones of quasi-hexagonal ice-like structure are stabilized by the formation of empty gaps aligned along the 〈001〉 direction. At half coverage we observed the aggregation of hydrogen bonded patches. The growth process is dependent on the highly anistropic surface diffusion with the faster rate in the less dense 〈110〉 direction. These results have been obtained using a novel model for the water-substrate interaction, treating the site specific chemisorption and electrostatic induction in atomic detail.

Ordering of fractional monolayers of H2O on Ni(110)

The ordering of water adsorbed on Ni(110) at monolayer and lower coverages was studied using molecular dynamics simulations. No long-range order could be found for the complete monolayer. At fractional coverage of θ∼0.9, oriented zones of quasi-hexagonal ice-like structure are stabilized by the formation of empty gaps aligned along the 〈001〉 direction. At half coverage we observed the aggregation of hydrogen bonded patches. The growth process is dependent on the highly anistropic surface diffusion with the faster rate in the less dense 〈110〉 direction. These results have been obtained using a novel model for the water-substrate interaction, treating the site specific chemisorption and electrostatic induction in atomic detail.

On the stability of type I gas hydrates in the presence of methanol

Using computer simulations we have studied the stability of type I gas hydrates for different mixtures of methane/methanol at 270 K and atmospheric pressure. In the nanosecond time regime the empty and the methane-filled hydrate are stable with only small perturbations to the water cavity structure. Inclusion of methane stabilizes the lattice structure over the empty hydrate. A hydrate filled with methanol melts in roughly 1 ns with a concomitant destruction of the cavity structure. The resulting mixture is liquidlike in contrast to the icelike hydrate structure. Small amounts of methanol can be incorporated into the hydrate structure; thus a 4 wt % methanol solution is stable, whereas a 7 wt % solution melts. In the stable methanol hydrate cavity structure is maintained, but the perturbations relative to the empty hydrate emphasize the inherent flexibility of these structures. More alcohol can be incorporated into the hydrate if methane is allowed to stabilize the hydrate.

Adsorption of water vapor by iron oxides. 3. Inelastic incoherent neutron scattering from water adsorbed on magnetite: evidence for an icelike structure

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTAdsorption of water vapor by iron oxides. 3. Inelastic incoherent neutron scattering from water adsorbed on magnetite: evidence for an icelike structureN. S. Clarke and P. G. HallCite this: Langmuir 1992, 8, 2, 645–649Publication Date (Print):February 1, 1992Publication History Published online1 May 2002Published inissue 1 February 1992https://doi.org/10.1021/la00038a057RIGHTS & PERMISSIONSArticle Views70Altmetric-Citations2LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (346 KB) Get e-Alerts Get e-Alerts

Comparison of the structure and dynamics of water at the Pt(111) and Pt(100) interfaces: molecular dynamics study

The structural and dynamical properties of water next to the Pt(111) and Pt(100) surfaces were investigated using molecular dynamics simulations. At 300 K, the water layer adjacent to the surface displays solid-like properties. The adsorption sites for the water molecules are determined by the location of Pt atoms and the geometry of the surface. It is found that the Pt(111) surface induces a hexagonal pattern in the structure of adsorbed water layer. Patches of ice-like structure were also noticed in this layer. On both surfaces, the next two layers of water were found to display an orientational bias towards the ordering observed in ice-I.

Structure and dynamics of water at the Pt(111) interface: Molecular dynamics study

We prescribe an analytical form of the interaction potential between rigid water and a rigid platinum metal surface, which takes into account the surface symmetry and corrugation. Using this potential we perform a molecular dynamics computer simulation on water lamina restricted by two Pt(111) surfaces and investigate the structure and dynamics of water at the Pt interface. At 300 K the water layer adjacent to the metal surface displays solid-like properties. Patches of ice-like structure embedded in this layer are observed in the simulation. The next two layers of water display ordering similar to ice-I. Beyond these three layers the structure and dynamics of water are bulk-like.

Bacteriorhodopsin in ice: Accelerated proton transfer from the purple membrane surface

The photocycle and the proton pumping kinetics of bacteriorhodopsin, as well as the transfer rate of protons from the membrane surface into the aqueous bulk phase were examined for purple membranes in water and in ice. In water, the optical pH indicator pyranine residing in the aqueous bulk phase monitors the H +-release later than the pH indicator fluorescein covalently linked to the extracellular surface of BR. In the frozen state, however, pyranine responds to the ejected H + as fast as fluorescein attached to BR, demonstrating that the surface/bulk transfer is in ice no longer rate limiting. The pumped H + appears at the extracellular surface during the transition of the photocycle intermediate L 550 to the intermediate M 412. The Arrhenius plot of the M formation rate suggests that the proton is translocated through the protein via an ice-like structure.

Exact soliton solution in ice-like structures

In this letter, we present a kind of exact soliton solution for the nonlinear equations which describe proton motion in a system with ice-like structure.

On theory of ionic volumes in dilute aqueous solutions of electrolytes

For purposes of calculation of densities of aqueous solutions of strong electrolytes and of their mixtures, theoretical substantiation of the formerly outlined empirical model of apparent molar ionic volumes φ in solution is presented. According to the model, the hydration sheaths of ions consisting of radially close-packed H2O molecules having effective molar volume V’w the same for all ions, are on their contact with the adjacent structure of liquid water surrounded by a layer of excess voids. This layer can bee substituted in the model by continuous gap of which d0, which again is common to all the ions and is temperature-independent. Using experimental φ values of twenty-seven strong electrolytes together with the data on electrolytic transport of water on ions, V’w = 12 cm3 mol-1 and d0 = (40 ± 2) pm were found for mono- and divalent ions in 1 mol dm-3 solutions, independently of ionic charges and crystallographic radii. The exception are small ions Li+ and Na+, the volumes of which – if interpreted on the basis of the model – correspond to hydration sheaths formed by a cluster of voluminous ice-like structure. An anomaly in this respect has been encountered also in the case of NH+4 ion.

Effects of temperature and pressure on the near-infrared spectra of HOD in D2O

The near-infrared absorption spectra (9500 to 11000 cm−1) of HOD, 20 mol% in D2O were measured at temperatures between 4 and 55°C and pressures up to 500 MPa. From the analysis of the spectra, the following conclusions are drawn. (1) At temperatures below about 38°C, the ice I-like bulky structure is destroyed to form the dense structure which reflects the high-pressure ice-like structure as the pressure is increased. (2) At temperatures above about 38°C, the bulky structure hardly remains at atmospheric pressure and the formation of dense structure proceeds monotonically with increasing pressure. The results and conclusion obtained in the present paper agrees with those obtained for pure H2O water in the previous investigation.

Structure of bacteriophage T4 lysozyme refined at 1.7 Å resolution

The structure of the lysozyme from bacteriophage T4 has been refined at 1.7 Å resolution to a crystallographic residual of 19.3%. The final model has bond lengths and bond angles that differ from “ideal” values by 0.019 Å and 2.7 °, respectively. The crystals are grown from electron-dense phosphate solutions and the use of an appropriate solvent continuum substantially improved the agreement between the observed and calculated structure factors at low resolution. Apart from changes in the conformations of some side-chains, the refinement confirms the structure of the molecule as initially derived from a 2.4 Å resolution electron density map. There are 118 well-ordered solvent molecules that are associated with the T4 lysozyme molecule in the crystal. Four of these are more-or-less buried. There is a clustering of water molecules within the active site cleft but, other than this, the solvent molecules are dispersed around the surface of the molecule and do not aggregate into ice-like structures or pentagonal or hexagonal clusters. The apparent motion of T4 lysozyme in the crystal can be interpreted in terms of significant interdomain motion corresponding to an opening and closing of the active site cleft. For the amino-terminal domain the motion can be described equally well (correlation coefficients approx. 0.87) as quasi-rigid-body motion either about a point or about an axis of rotation. The motion in the crystals of the carboxy-terminal domain is best described as rotation about an axis (correlation coefficient 0.80) although in this case the apparent motion seems to be influenced in part by crystal contacts and may be of questionable relevance to dynamics in solution.

On chemical form of H+ ion in aqueous solutions

Using the method of the addition of another salt worked out and verified in the previous work, it has been concluded from experimental densities of aqueous NaCl + HCl solutions that even in highly diluted solutions, H+ ion exists as integral H3O+ species which is bonded to the ice-like structure of surrounding water only by relatively weak hydrogen bonds. This bonding does not prevent the outer hydration sheath from fully participating in hydration equilibria of other ions present in solution. The hypothesis about the stable H9O4+ complex could not be maintained.

Static and Dynamic Structure of Water in Hydrated Kaolinites. I. The Static Structure

AbstractFour hydrates with d(001) = 8.4, 8.6, and 10 Å (two types) were synthesized by intercalating kaolinite with dimethylsulfoxide and treating the intercalated clay with fluoride ions. X-ray powder diffraction, infrared spectroscopy, differential scanning calorimetry, thermal gravimetric analysis, and kinetics of dehydration experiments have led to the identification of two types of interlayer water. One type of water (hole water) is situated in the ditrigonal holes of the silica tetrahedral surface; the second type (associated water) forms a discontinuous layer of mobile water. The 8.4-Å and 8.6-Å hydrates have only hole water, whereas the two synthetic 10-Å hydrates and halloysite(10Å) contain both hole and associated water. The hole water is probably hydrogen bonded to the basal oxygens of the silica tetrahedra or, in the 8-Å hydrates when fluorine exchanges for inner-surface hydroxyls, the water molecules may reorient and form stronger hydrogen bonds to the fluorine. Associated water forms water-water hydrogen bonds approximately equal in strength to liquid water but is less strongly bonded to the clay surfaces than hole water. At room temperature the hole and associated water in the 10-Å hydrates do not form an ice-like structure.

Nucleation of water by hydrophobic silicas

In process of nucleation structure of water may play a fundamental role. According to model proposed by Frank and Evans (1) and by N6methy and Scheraga (2) liquid water has a considerable number of water molecules with an ice-like structure which increases as temperature is decreased. These same authors have also suggested existence of solutes which destroy ice-like structure and others which promote it. Hydrocarbons are among these latter solutes. On other hand, Zettlemoyer et al. (3) in their study on adsorption of water onto silver iodide have also suggested that a nucleating agent must possess the common attribute of having hydrophilic adsorption sites each located in a matrix of hydrophobic sites. In a further work (4) same author has concluded that water clusters are more easily formed on surfaces that appear mildly hydrophobic. The above picture suggested to us that transition from liquid water to ice under supercooled conditions could be favored by presence of hydrocarbon on nucleating surface. In this paper we show that silicas containing methyl residues act as nucleation agents for transition from liquid water to ice and

O–H stretching vibrations in ice clathrate

In H-bonded materials, the frequency of intramolecular vibrations is considered to depend only on the strength of the H-bond, or equivalently, the distance between the H-bonded molecular pairs. Therefore, in vibrational spectroscopic studies of the molecular structure of condensed phases with O–H⋯O bonds, the frequency of O–H stretching vibrations, ν, is generally taken as being directly proportional to the average distance, Ro–o, between the nearest oxygen atoms. Thus (∂ν/∂Ro–o) obtained from a study of various polymorphs of ice (Ro–o range, 2.75–2.83 A) has been used as a scaling factor to suggest: (1) a continuous random network structure of amorphous solid and liquid water1,2, and (2) the possibility of transformation of ice VII to a structure with centrosymmetric hydrogen bonds3. While such scaling of Ro–o from changes in ν may seem a good approximation, studies of hexagonal ice and ice clathrate suggest that factors other than the intermolecular distances affect the frequency of O–H stretching vibrations. A study of the Raman spectrum of ice clathrate, reported here, shows that in condensed phases where the O–H⋯O bonds are nonlinear and/or the intermolecular distances are distributed over a range (as in water, various amorphous and crystalline forms of ice, ice-like structures, alcohols, carboxylic acids and aqueous solutions), a treatment based on such scaling is an oversimplification; the geometry of the H-bond affects the frequency more than the strength of the H-bond.

Thermodynamics of autoionization of aqueous tetrahydrofuran and 1,2-dimethoxyethane and the structuredness of solvents

Autoionization constants (Ks) of aqueous mixtures of tetrahydrofuran (THF) and 1,2-dimethoxyethane (DME) containing 10, 30, and 50 wt.% cosolvent in each case have been determined from emf measurements of the cell: Pt, H2 (g, 1 atm)|KOH (m1), KBr (m2), solvent|AgBr, Ag at seven equidistant temperatures ranging from 5 to 35 °C. The standard free energies (ΔG0), entropies (ΔS0), and enthalpies (ΔH0) of autoionization of the solvents were also evaluated from these data. Relative free energy data, δΔG0(≡sΔG0 − wΔG0), for these solvents as well as those for dioxane (D) – water mixtures taken from the literature, when coupled with the previously determined transfer free energies of H+, ΔGt0(H+), yielded ΔGt0(OH−)app (≡ΔGt0(OH−) − ΔGt0(H2O)) values in the mixed solvents. Relative magnitudes of ΔGt0(H+) and ΔGt0(OH−)app and their non-Born parts, ΔGt,ch0(H+) and ΔGt,ch0(OH−)app in particular, suggest that the "basicity" of these aqueous cosolvents decreases in the order DME > THF > D and their "acidity" in the reverse order, as expected from structural and electronic consideration of these cosolvent molecules. Analysis of the relative entropie contributions, Tδ (ΔS0) (≡T (sΔS0 − wΔS0), for the autoionization of these aqueous cosolvents and in particular ΔSt0(H2O) values derived there from, suggests that while THF promotes three dimenstional (3D) ice-like water structures at initial compositions and D induces breakdown of the 3D structures right from the beginning, DME breaks down water structures at initial compositions, but induces some order around 4–14 mol% DME by forming the possible H-bonded bidentate DME–water complexes. And beyond certain compositions, depending upon the relative size and shape, all the cosolvents break down water structure due to packing imbalance.

Occurrence and acoustical significance of natural gas hydrates in marine sediments

The current knowledge of natural gas hydrates in marine sediments is reviewed. The Chemical structure, occurrence in nature, conditions of formation and acoustic properties of natural gas hydrates are discussed. Conditions suitable for the formation of this icelike crystalline structure, which traps the gas molecule within it, are found over 90% of the ocean floor. The hydrate structure can greatly increase compressional sound velocity and alter shear velocity and absorption processes from those expected for typical marine sediment types. The potential impact of hydrates on underwater acoustics is demonstrated through computations of bottom reflection loss for hypothetical subbottom structures containing hydrate zones. [Work sponsored by Naval Oceanographic Research and Development Activity.]