Dynamical Structure Of Water Research Articles

Quantum chemical investigation of the effect of alkali metal ions on the dynamic structure of water in aqueous solutions.

We report quantum chemical molecular dynamics (MD) simulations based on the density-functional tight-binding (DFTB) method to investigate the effect of K+, Na+, and Mg2+ ions in aqueous solutions on the static and dynamic structure of bulk water at room temperature and with various concentrations. The DFTB/MD simulations were validated for the description of ion solvation in aqueous ionic solutions by comparing static pair distribution functions (PDFs) as well as the cation solvation shell between experimental and available ab initio DFT data. The effect of the cations on the water structure, as well as relative differences between K+, Na+, and Mg2+ cations, were analyzed in terms of atomically resolved PDFs as well as time-dependent Van Hove correlation functions (VHFs). The investigation of the VHFs reveals that salt ions generally slow down the dynamic decay of the pair correlations in the water solvation sphere, irrespective of the cation size or charge. The analysis of partial metal–oxygen VHFs indicates that there are long-lived correlations between water and Na+ over long distances, in contrast to K+ and Mg2+.

Dynamic stability and management of supramolecular structures of water

The cluster structure of water is a recognized basis for studying the special properties of this liquid and, in particular, when interacting with biological systems.  An attempt has been made to identify patterns for the appearance of short-lived cluster supramolecular structures in the composition of water. They determine its effectiveness in relation to such biological systems. Their appearance is based on the patterns of bifurcation transition with a doubling of the number of bound molecules H2O. This is possible in a border area with chaos in intermolecular of bonds water. The use of I. Prigogine's principle of high-intensity fluctuations is proposed. They appear independently of changes in cluster structures in triatomic molecular associations based on the accumulation of internal energy to minimize dissipative processes. This is the basis for the organization of such stable structures with minimal change in the entropy of the entire system. Prigozhin's algorithm was applied to calculate the thermodynamic instability and behavior of triatomics as a control method. The index of the operator Liouville and the comparable criterion of stability of Lyapunov are involved. The processes of instantaneous reversibility and stability of short-lived clusters based on molecules were investigated, in full accordance with the existing provisions on the dynamic structure of water. The features of the action of high-frequency random oscillations are shown, which determine the periodicity of the creation of short-lived associations in the composition of water. It also shows the stability of such periodic processes in a limited period of time, as a basis for identifying repetitive states of the system. Energy interrelation in such systems is proposed to be considered as the basis to maintain their optimal state in the structure of water. This is also an indicator of its relationship to the perceiving biological systems

Polarized Water Wires under Confinement in Chiral Channels.

The alignment of water molecules along chiral pores may activate proton/ion conduction along dipolar hydrophilic pathways. Here we show that a simple synthetic "T-channel" forms a directional pore with its carbonyl moieties solvated by chiral helical water wires. Atom-scale simulations and experimental crystallographic assays reveal a dynamical structure of water and electrolyte solutions (alkali metal chlorides) confined in these organic T-channels. Oscillations in the dipole orientation, which correspond to alternative ordering (dipole up-dipole down) of the water molecules with a period of about 4.2 Å (imposed by the distance between two successive carbonyl groups) are observed. When ions are added to the system, despite the strong Coulombic water/ion interaction, confined water remains significantly ordered in the T-channel and still exhibits surface-induced polarization. Cation permeation can be achieved through alternated hydration-dehydration occurring along strongly oriented water wires. The T-channel, which exhibits chirality with strong water orientation, provides an opportunity to unravel novel water-channel systems that share many interesting properties of biomolecular systems.

Thermal stability of water up to super-critical states: Application of the singular value decomposition and grund functions

In the present work a systematic investigation of temperature on the dynamic structure of water and noble gases is given and a simple formula for the temperature dependent distribution functions with two terms is gained. The singular value decomposition tool is applied to temperature dependent radial and spatial distribution functions to decompose them into linear combinations of distant dependent grund radial/spatial distribution functions gi(r) and temperature dependent coefficients ci(T). The method condenses information from a large amount of data into a much smaller and manageable amount without loss of information. For the test systems (TIP3P water and noble gases with different force fields), the main temperature changes are condensed into the second grund function g2 and its coefficient c2. c2 obeys the Boltzmann distribution law and altogether we find thatgrT≈gcr+e−DR⋅T⋅gtrin a temperature range of more than 700K. We introduce the new property of the thermal stability and the thermal stability energy D. This single energy and the grund functions characterize the structural changes (e.g., hydrogen bonds) in liquids from ambient temperatures up to supercritical states.

Dielectric relaxation measurement and analysis of restricted water structure in rice kernels

Dielectric relaxation measurements were performed for rice kernels by time domain reflectometry (TDR) with flat-end coaxial electrodes. Difficulties in good contact between the surfaces of the electrodes and the kernels are eliminated by a TDR set-up with a sample holder for a kernel, and the water content could be evaluated from relaxation curves. Dielectric measurements were performed for rice kernels, rice flour and boiled rice with various water contents, and the water amount and dynamic behaviour of water molecules were explained from restricted dynamics of water molecules and also from the τ–β (relaxation time versus the relaxation-time distribution parameter of the Cole–Cole equation) diagram. In comparison with other aqueous systems, the dynamic structure of water in moist rice is more similar to aqueous dispersion systems than to aqueous solutions.

Dynamical structure of water around biopolymers investigated by microwave dielectric measurements using time domain reflectometry method

The dynamical structure of free water around biopolymers, such as gelatin, collagen, and globular proteins, has been characterized based on relaxation time, τ, and Cole–Cole parameter, β, obtained from microwave dielectric measurements using a time domain reflectometry method. As reported previously, the plots of β against τ for free water in seven types of synthetic polymers in aqueous solutions against τ are classified into two groups based on polymer hydrophilicity. It is indicated that the dynamical structure of water around low-hydrophilic polymers is more uniform than those around high-hydrophilic polymers. In the present work, the plots for the aqueous gels of gelatin and globular protein in aqueous solutions indicate the same feature as those for high-hydrophilic polymers. It can be expected that the dynamical structure of free water around biopolymers is uneven. However, the water structure around collagen appears to be uniform, although collagen consists almost of the same peptide chains as those of gelatin. These results suggested that the water structure around highly ordered polymers, e.g., collagen, is also uniform.

Dynamical structure of water in alkali halide aqueous solutions

The low-frequency Raman spectra of alkali halide AX (A=Na, K, Rb; X=Cl, Br) aqueous solutions with various temperatures and concentrations are investigated. We have found that at the supercooled temperature region the relaxation time of the KX and RbX aqueous solutions becomes shorter than that of pure water. Since in these solutions the viscosity decreases with increasing concentration, this result suggests that the relaxation time of the electrolytic solutions in the Raman region is strongly correlated with the viscosity. Moreover, through comparing the spectral profiles of the relaxation mode among AX aqueous solutions we demonstrate that the pattern of the concentration dependence of the relaxation mode parameters such as the activation energy changes between NaX and (KX, RbX) aqueous solutions.

Dynamical structure of water in aqueous solutions of LiCl, NaCl, and KCl by low-frequency Raman scattering: Comparison between the multiple random telegraph model and Cole-Cole relaxation

Depolarized low-frequency Raman spectra of aqueous solutions of LiCl, NaCl, and KCl have been investigated over a wide concentration range. The spectra were analyzed with one relaxation mode and two damped harmonic oscillators. We applied two types of relaxation model: the multiple random telegraph (MRT) model and the Cole-Cole-type relaxation. Each relaxation time becomes longer than that of liquid water in both relaxation models. Structure making (Li, Na) and structure breaking (K) effects were concluded from a fitting parameter corresponding to the modulation speed in the MRT model.

Dynamical structure of water in NaCl aqueous solution

We report on the dynamical structure of water in NaCl aqueous solutions as functions of temperature and concentration by a low-frequency Raman spectroscopy. The spectral profiles in the frequency range from −50 to 250 cm−1 have been analyzed with a superposition of one Cole–Cole type relaxation mode and two damped harmonic oscillator modes. The distributions of the characteristic frequencies of the intermolecular vibrational modes observed around 50 and 180 cm−1 in NaCl aqueous solutions are always wider than those in pure water. In NaCl aqueous solutions with various concentrations, the spectral line width g1=1/(2πcτ) of a central component, which corresponds to the reciprocal relaxation time, linearly changes with temperature from about 255 K to 300 K, while the relaxation time above 300 K holds an Arrhenius-type behavior. The slope of the spectral linewidth against temperature below 300 K decreases with increasing concentration. The distribution parameter of the relaxation time in the Cole–Cole type relaxation formula decreases with decreasing temperature and it becomes smaller with increasing concentration.

Dynamical structure of water by Raman spectroscopy

Raman spectra of liquid water have a broad background extended to 4000 cm −1 as well as molecular vibrational modes. Depolarized Raman spectra below 250 cm −1 in liquid water are well interpreted with a superposition of two damped harmonic oscillators and one Cole–Cole type relaxation mode. Two damped harmonic oscillators are interpreted as stretching and bending vibration modes of a temporal tetrahedral-like structure of five water molecules. High-frequency Raman spectra between 1600 cm −1 and 4000 cm −1 in liquid water are well explained by molecular vibration modes of a temporal C 2v tetrahedral-like structure around oxygen atom. This interpretation of high frequency spectra is consistent with the interpretation of low-frequency vibrational modes below 250 cm −1. Moreover, the high frequency tail of the above Cole–Cole type relaxation mode could explain the broad background spectra in liquid water.

Dynamical structure of water in dioxane aqueous solution by low-frequency Raman scattering

The low-frequency Raman spectra of dioxane aqueous solutions have been analyzed from a dynamical aspect of water structure. The reduced Raman spectra χ″(ν̄) of the dioxane aqueous solutions are well explained by a superposition of three characteristic modes of water and one Gaussian mode (∼60 cm−1) of dioxane. The concentration dependence of χ″(ν̄) spectra shows that the 190 cm−1 mode of water disappears below about 0.8 molar fraction of water. This molar fraction corresponds to the ratio of four water molecules to one dioxane molecule. This means that the tetrahedral-like structure of water which is formed by five water molecules is almost destroyed below about 0.8 molar fraction. Thus the basic idea of the five water molecules model of liquid water has been confirmed from Raman spectroscopic point of view.

Dynamic structure of water in ultra pure water producing system observed by dielecric and 17o-NMR relaxations.

In order to observe the influences on microscopic behavior of water molecules caused by water treatment processes, the changes of dynamic structure of water in an ultra pure water (UPW) producing system have been studied by dielectric and 17O-NMR relaxations. The UPW system used in this study consists of typical unit processes employed in current commercial systems for semiconductor manufacturing plants, and produces UPW of the highest quality with specific resistivity of 18.2 MΩ·cm. Throughout the whole system from city water till UPW dielectric relaxation time, τd, is kept constant at about 8.7 ps, while β, a parameter describing the distribution of τd, increases with each treatment step, reaching a constant value of about 1.00 after the removal of major impurities by a reverse osmosis membrane. The spin-lattice relaxation time, T1, obtained from 17O-NMR is unchanged at about 7.3 ms through all processes in the system. Spin-spin relaxation time, T2, shows drastic changes with each treatment step. The changes of T2 are well explained by proton-exchange reactions in water and should not be related directly with rotational motions of water molecules. These results indicate that the averaged rotational motion of water molecules is unchanged from city water to UPW. The distribution around the average, however, becomes narrower during purification, and the rotational motions of water molecules are highly homogenized in UPW.

Low-frequency Raman scattering of aqueous solutions of L-xyloascorbic acid and D-araboascorbic acid

Depolarized low-frequency Raman spectra of aqueous solutions of L-xyloascorbic acid and its epimer D-araboascorbic acid have been investigated as a function of concentration at 30 °C. The influence of fluorescence in the low-frequency Raman spectral intensity of D-araboascorbic acid aqueous solution was removed by the background correction. The reduced χ″(ν̄) spectrum, which corresponds to the imaginary part of the dynamical susceptibility due to the dynamical structure of water in aqueous solutions, was analyzed with the superposition of one Cole–Cole type relaxation mode and two damped harmonic oscillator modes. The effect of L-xyloascorbic acid on the dynamical structure of water is less than that of D-araboascorbic acid.

Dynamical aspects of water by low-frequency Raman scattering

Depolarized Raman spectra below 250 cm −1 in liquid water (H 2O, D 2O and H 2 18O), aqueous electrolyte solutions (LiCl, NaCl, KCl, RbCl, MgCl 2 and CaCl 2), d-glucose solution and ascorbic acid isomerism solutions ( l-xylo and d-arabo) were investigated. The Raman spectra below 250 cm −1 in these liquids are interpreted with a superposition of two damped harmonic oscillators and one Debye type relaxation mode (liquid water) or one Cole-Cole type relaxation mode (aqueus solutions). (1) With increasing temperature the half width of half maximum of the central component g 1 in H 2O has a small bend at about 20°C. (2) For aqueous electrolyte solutions, with increasing salt concentration the ratio of relaxation time τ/τ water shows just the same behavior as the ratio of viscosity η/η water. (3) In glucose solution the characteristic frequencies of two oscillator modes do not show any change. This means that the glucose can just embed in the dynamical structure of water. (4) The effect of L-xylo ascorbic acid (Vitamin C) on the dynamical structure of water is different from the effect of D-arabo ascorbic acid.

Dynamical structure of water in aqueous electrolyte solutions by low-frequency Raman scattering

Depolarized low-frequency Raman spectra of aqueous electrolyte solutions (ACl and BCl2; A=Li, Na, K, Rb and B=Mg, Ca) in the frequency region from −250 to 250 cm−1 have been investigated over a wide concentration range. The spectra were analyzed with one Cole–Cole type relaxation mode and two damped harmonic oscillators. A broad relaxation mode was found below 20 cm−1. For the present aqueous electrolyte solutions, with increasing salt concentration each relaxation time τ becomes longer than that of liquid water τwater. The relaxation time is considered to correspond to the duration time of the tetrahedral structure of bulk water. We have found that the concentration dependence of the ratio τ/τwater is equivalent to the ratio η/ηwater, where η is the viscosity of aqueous solutions.

Dynamical structure of water in aqueous solutions of D-glucose and D-galactose by low-frequency Raman scattering

Low-frequency depolarized Raman spectra of aqueous solutions of D-glucose and D-galactose have been investigated in the frequency region from −250 cm−1 to 250 cm−1 at 30.0 °C as a function of concentration up to 0.04 molar ratio. The dynamical structure of water in aqueous solution is analyzed by using the reduced Raman spectrum χ″(ν̄), which corresponds to the imaginary part of the dynamical susceptibility. The reduced spectrum is fitted with the superposition of one Cole–Cole type relaxation mode and two damped harmonic oscillator modes by a nonlinear least-squares fitting. The effects of D-glucose and D-galactose on the dynamical structure of water in aqueous solution are similar. The relaxation time of hydrogen bond among water molecules becomes slower with increasing sugar concentration. The characteristic frequencies of stretching-like and bending-like vibrations among water molecules do not change in both D-glucose and D-galactose aqueous solutions.

Dynamical Structure of Water in Aqueous Solutions of Ascorbic Acid by Low-Frequency Raman Scattering

Depolarized low-frequency Raman spectra of aqueous solutions of L-ascorbic acid and its isomer D-araboascorbic acid as a function of concentration have been investigated in the frequency region from -250 cm -1 to 250 cm -1 at 30°C. The reduced χ ′′ (\barν) spectrum, which corresponds to the imaginary part of the dynamical susceptibility, due to the dynamical structure of water in aqueous solutions, was analyzed with the superposition of one Cole-Cole-type relaxation mode and two damped harmonic oscillator modes. The effect of L-ascorbic acid on the dynamical structure of water is different from the effect of D-araboascorbic acid.

Dynamical structure of water: Low-frequency Raman scattering from a disordered network and aggregates

Low-frequency inelastic light scattering of water is observed from a temperature equal to 80 down to −20 °C in the supercooled regime. For energies higher than 3 cm−1 it is shown that the major part of the light scattering is Raman scattering. A broadband with a maximum at 50 cm−1 is interpreted as scattering from transverse acoustic modes of a disordered network. A weaker scattering which shifts towards the Rayleigh line when the temperature decreases is well explained by Raman scattering from the oscillations of water molecule aggregates which grow when the temperature decreases.

Static and dynamic structure of water in hydrated kaolinites. II. The dynamic structure

Nuclear magnetic resonance (NMR) measurements of water intercalated into kaolinite identify two types of interlayer water, one of which is more mobile than the other. This is consistent with previous work by P. M. Constanzo, R. F. Giese, and M. Lipsicas [ Clays Clay Miner. 32, 419 (1984)], and suggests that the less mobile water is attached to the tetrahedral surface (hole water) and that the more mobile water (associated water) is less strongly bonded to the clay surface. Both types of water are found in a 10-Å hydrate while only hole water is present in 8.4- and 8.6-Å hydrates. Motions of both types of water are slower than bulk water. Above 260 K, an anomaly in the specific heat of the water in the 10-Å hydrate is observed. The NMR measurements suggest that this is associated with a transition involving two-dimensional melting.

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.