Resolving the hydrogen bond dynamics conundrum

Luzar, Alenka

doi:10.1063/1.1320826

Cited by 658 publications

(714 citation statements)

References 56 publications

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“…In a preceding study 54 , we presented a comparison between field effects on average numbers of hydrogen bonds determined by both the geometric 35 and energetic 55 criteria. Identical effects were found using either method, hence only the geometric definition is applied here.…”

Section: Interactions Among Water Molecules Aligned By Applied Electrmentioning

confidence: 99%

Field-exposed water in a nanopore: liquid or vapour?

Bratko

Daub

Luzar

2008

Phys. Chem. Chem. Phys.

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Field-exposed water behaviour in hydrophobic confinement confirms classical electrostriction in nanoscale channels and nanoporous materials. 2 AbstractWe study the behavior of ambient temperature water under the combined effects of nanoscale confinement and applied electric field. Using molecular simulations we analyze the thermodynamic causes of field-induced expansion at some, and contraction at other conditions. Repulsion among parallel water dipoles and mild weakening of interactions between partially aligned water molecules prove sufficient to destabilize the aqueous liquid phase in isobaric systems in which all water molecules are permanently exposed to a uniform electric field. At the same time, simulations reveal comparatively weak field-induced perturbations of water structure upheld by flexible hydrogen bonding.In open systems with fixed chemical potential, these perturbations do not suffice to offset attraction of water into the field; additional water is typically driven from unperturbed bulk phase to the field-exposed region. In contrast to recent theoretical predictions in the literature, our analysis and simulations confirm that classical electrostriction characterizes usual electrowetting behavior in nanoscale channels and nanoporous materials.

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Section: Interactions Among Water Molecules Aligned By Applied Electrmentioning

confidence: 99%

Field-exposed water in a nanopore: liquid or vapour?

Bratko

Daub

Luzar

2008

Phys. Chem. Chem. Phys.

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“…[1][2][3] Water is a very "dynamical" fluid in the sense that the rearrangements of the local structure surrounding a water molecule occur on the subpicosecond time scale. [4][5][6][7][8][9][10][11] Vibrational relaxation dynamics in water is also very fast. For instance, the population relaxation lifetime of the OH-stretching mode of HDO molecules in liquid D 2 O is about 740 fs.…”

Section: Introductionmentioning

confidence: 99%

“…Most probably, the reason for this lies in the fact that the survival time of a hydrogen bond in liquid water does not exceed 1 ps. [4][5][6][7][8][9][10] Therefore, the hydrogen bond is broken at a time scale that is much shorter than the rotational constant, after which the molecule can rotate more or less freely. Slightly slower orientational dynamics in pure water is apparently due to stronger hydrogen bonds as well as the presence of more than one hydrogen bond per water molecule.…”

Section: Orientational Dynamics Of Water Molecules In Acetonitrilementioning

confidence: 99%

Hydrogen Bonding and Vibrational Energy Relaxation in Water−Acetonitrile Mixtures

et al. 2004

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We present a study of the effect of hydrogen bonding on vibrational energy relaxation of the OH-stretching mode in pure water and in water-acetonitrile mixtures. The extent of hydrogen bonding is controlled by dissolving water at various concentrations in acetonitrile. Infrared frequency-resolved pump-probe measurements were used to determine the relative abundance of hydrogen-bonded versus non-hydrogen-bonded OH bonds in water-acetonitrile mixtures. Our data show that the main pathway for vibrational relaxation of the OH-stretching mode in pure water involves the overtone of the bending mode. Hydrogen bonding is found to accelerate the population relaxation from 3 ps in dilute solutions to 700 fs in neat water, as a result of increasing overlap between donor and acceptor modes. Hydroxyl groups that initially are not hydrogen bonded have two relaxation pathways: by direct nonresonant relaxation to the bending mode with a time constant of 12 ps or by making a hydrogen bond to a neighboring water molecule first (∼2 ps) and then relaxing as a hydrogen-bonded OH oscillator.

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“…[81][82][83][84][85][86] For comparison, in Table 2 with the same carboxyl carbon at time t, and meanwhile, it did not leave the coordination for times longer than t * ; otherwise H(t; t * ) = 0. The parameter t * is usually taken to be 2 ps -a typical lifetime of a hydrogen bond in liquid water at ambient conditions, 88 which also reflects the rate of exchange of water molecules in the first hydration shell of metal ions. 48 For a metal ion to form a CIP with the carboxylic group, at least one water molecule must leave the first hydration shell to allow its place can be taken by one of the carboxyl oxygens.…”

Section: Metal -Carboxylate Structure and Dynamics From Free MD Simulmentioning

confidence: 99%

Metal Cation Complexation with Natural Organic Matter in Aqueous Solutions: Molecular Dynamics Simulations and Potentials of Mean Force

Iskrenova-Tchoukova¹,

Kalinichev²,

2010

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Natural organic matter (NOM, or humic substance) has a known tendency to form colloidal aggregates in aqueous environments, with the composition and concentration of cationic species in solution, pH, temperature, and the composition of the NOM itself playing important roles. Strong interaction of carboxylic groups of NOM with dissolved metal cations is thought to be the leading chemical interaction in NOM supramolecular aggregation.Computational molecular dynamics (MD) study of the interactions of Na + , Mg 2+ , and Ca 2+ with the carboxylic groups of a model NOM fragment and acetate anions in aqueous solutions provides new quantitative insight into the structure, energetics, and dynamics of the interactions of carboxylic groups with metal cations, their association and the effects of cations on the colloidal aggregation of NOM molecules. Potentials of mean force and the equilibrium constants describing overall ion association and the distribution of metal cations between contact ion pairs and solvent separated ions pairs were computed from free MD simulations and restrained umbrella sampling calculations. The results provide insight into the local structural environments of metal-carboxylate association and the dynamics of exchange among these sites. All three cations prefer contact ion pair to solvent separated ion pair coordination, and Na + and Ca 2+ show a strong preference for bidentate contact ion pair formation. The average residence time of a Ca 2+ ion in a contact ion pair with the carboxylic groups is of the order of 0.5 ns, whereas the corresponding residence time of a Na + ion is only between 0.02 and 0.05 ns. The average residence times of a Ca 2+ ion in a bidentate coordinated contact ion pair vs. a monodentate coordinated contact ion pair are about 0.5 ns and about 0.08 ns, respectively. On the 10-ns time scale of our simulations, aggregation of the NOM molecules occurs in the presence of Ca 2+ but not Na + or Mg 2+ . These results agree with previous experimental observations and are explained 3 by both Ca 2+ ion-bridging between NOM molecules and decreased repulsion between the NOM molecules due to the reduced net charge of the NOM-metal complexes. Simulations on a larger scale are needed to further explore the relative importance of the different aggregation mechanisms and the stability of NOM aggregates.4

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Resolving the hydrogen bond dynamics conundrum

Cited by 658 publications

References 56 publications

Field-exposed water in a nanopore: liquid or vapour?

Field-exposed water in a nanopore: liquid or vapour?

Hydrogen Bonding and Vibrational Energy Relaxation in Water−Acetonitrile Mixtures

Metal Cation Complexation with Natural Organic Matter in Aqueous Solutions: Molecular Dynamics Simulations and Potentials of Mean Force

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