Single particle slow dynamics of confined water

Gallo, Paola

doi:10.1039/a909268d

Cited by 40 publications

(30 citation statements)

References 31 publications

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“…This particular form of the MSD functions is appropriate to the case of the molecular dynamics in confined space, where the motion in some directions is restricted by the pore walls and the maximum value of the MSD function -which is reached in this case -defined by a pore size. The calculated values of the self-diffusion coefficient are close to that predicted in [14,15] for water adsorbed in Vycor-like glass at the similar conditions.…”

Section: Resultssupporting

confidence: 80%

Molecular dynamics study of aqueous uranyl in hydrophilic mesoporous confinement: the case of slit-like pore in amorphous silica

Patsahan¹,

Holovko²

2007

Condens. Matter Phys.

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Molecular dynamics simulations are used to study structural and dynamic properties of water and aqueous uranyl ion adsorbed in a slit-like pore of amorphous silica. Calculations are performed for the flexible SPC/E water model in the atomistically detailed pores with sizes in the range of 2.0-5.0 nm. The hydroxyl groups on the pore surfaces lead to a strong adsorption and strongly affect the mobility of water molecules. The uranyl ion and its aqueous environment adsorbed in the pores are studied at the room temperature for different amounts of water. The effect of hydroxylated silica pores on the formation of uranyl hydrate complexes is discussed within the present study.

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Section: Resultssupporting

confidence: 80%

Molecular dynamics study of aqueous uranyl in hydrophilic mesoporous confinement: the case of slit-like pore in amorphous silica

Patsahan¹,

Holovko²

2007

Condens. Matter Phys.

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“…39 Once confined in Vycor nanopores, 40 for example, water molecules exhibit at least two distinct regimes: a slow diffusion near the surface and a fast dynamics far away from the surface. 14,31,33,[41][42][43][44][45] This paper reports a study of the short-time proton dynamics in water confined in silica nanopores ͑xerogel powder͒, via deep inelastic neutron scattering ͑DINS͒ measurements, using the VESUVIO spectrometer at the ISIS spallation neutron source. 46 DINS measurements are performed in the attosecond time scale ͑i.e., 10 −15 -10 −16 s͒.…”

Section: Introductionmentioning

confidence: 99%

Proton quantum coherence observed in water confined in silica nanopores

Garbuio

Imberti

Pietropaolo

et al. 2007

The Journal of Chemical Physics

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Deep inelastic neutron scattering measurements of water confined in nanoporous xerogel powders, with average pore diameters of 24 and 82 Å, have been carried out for pore fillings ranging from 76% to nearly full coverage. DINS measurements provide direct information on the momentum distribution n͑p͒ of protons, probing the local structure of the molecular system. The observed scattering is interpreted within the framework of the impulse approximation and the longitudinal momentum distribution determined using a model independent approach. The results show that the proton momentum distribution is highly non-Gaussian. A bimodal distribution appears in the 24 Å pore, indicating coherent motion of the proton over distances d of approximately 0.3 Å. The proton mean kinetic energy ͗E K ͘ W of the confined water molecule is determined from the second moment of n͑p͒. The ͗E K ͘ W values, higher than in bulk water, are ascribed to changes of the proton dynamics induced by the interaction between interfacial water and the confining surface.

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“…For example, the coordinates of the hypothesized LL critical point lie in the experimentally-inaccessible NoMan's land of the bulk water phase digram, but appear to lie in an accessible region of the phase diagrams of both two-dimensionally and one-dimensionally confined water [89,90]. Simulations have been carried out to understand the effect of purely geometrical confinement [91,92,93,94,95,96] and of the interaction with hydrophflic [97,98,99,100,101] or hydrophobic [102,103,104,105] surfaces. It is interesting also to study the effects that confinement may have on the phase transition properties of supercooled water [96], in order to clarify the possible presence of a LL phase transition in the water Recent work on the phase behavior of confined water suggests a sensitive dependence on the interaction with the surfaces [104], as a LL phase transition appears to be consistent with simulations of water confined between two parallel flat hydrophobic walls [94].…”

Section: Selected Results From Simulationsmentioning

confidence: 99%

Liquid Polyamorphism: Some Unsolved Puzzles of Water in Bulk, Nanoconfined, and Biological Environments

Stanley¹,

Kumar²,

Franzese³

et al. 2008

AIP Conference Proceedings

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Abstract. We investigate the relation between changes in dynamic and thermodynamic anomalies arising from the presence of the liquid-liquid critical point in (i) Two models of water, TIP5P and ST2, which display a first order liquid-liquid phase transition at low temperatures; (ii) the Jagla model, a spherically symmetric two-scale potential known to possess a liquid-liquid critical point, in which the competition between two liquid structures is generated by repulsive and attractive ramp interactions; and (iii) A Hamiltonian model of water where the idea of two length/energy scales is built in; this model also displays a first order liquid-liquid phase transition at low temperatures besides the first order liquid-gas phase transition at high temperatures. We find a correlation between the dynamic fragility crossover and the locus of specific heat maxima Cp'^'^ ("Widom line") emanating from the critical point. Our findings are consistent with a possible relation between the previously hypothesized liquid-liquid phase transition and the transition in the dynamics recently observed in neutron scattering experiments on confined water. More generally, we argue that this connection between Cp'^'^ and the dynamic crossover is not limited to the case of water, a hydrogen bonded network liquid, but is a more general feature of crossing the Widom line, an extension of the first-order coexistence line in the supercritical region. We present evidence from experiments and computer simulations supporting the hypothesis that water displays polyamorphism, i.e., water separates into two distinct liquid phases. This concept of a new liquid-liquid phase transition is finding application to other liquids as well as water, such as silicon and silica. We also discuss related puzzles, such as the mysterious behavior of confined water and the "skin" of hydration water near a biomolecule. Specifically, using molecular dynamics simulations, we also investigate the relation between the dynamic transitions of biomolecules (lysozyme and DNA) and the dynamic and thermodynamic properties of hydration water. We find that the dynamic transition of the macromolecules, sometimes called a "protein glass transition", occurs at the temperature of dynamic crossover in the diffusivity of hydration water, and also coincides with the maxima of the isobaric specific heat Cp and the temperature derivative of the orientational order parameter. We relate these findings to the hypothesis of a liquid-liquid critical point in water. Our simulations are consistent with the possibility that the protein glass transition results from a change in the behavior of hydration water, specifically from crossing the Widom line.

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Single particle slow dynamics of confined water

Cited by 40 publications

References 31 publications

Molecular dynamics study of aqueous uranyl in hydrophilic mesoporous confinement: the case of slit-like pore in amorphous silica

Molecular dynamics study of aqueous uranyl in hydrophilic mesoporous confinement: the case of slit-like pore in amorphous silica

Proton quantum coherence observed in water confined in silica nanopores

Liquid Polyamorphism: Some Unsolved Puzzles of Water in Bulk, Nanoconfined, and Biological Environments

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