Solvent Structure, Dynamics, and Ion Mobility in Aqueous Solutions at 25 °C

Koneshan, S.; Rasaiah, Jayendran C.; Lynden‐Bell, R. M.; Lee, S. H.

doi:10.1021/jp980642x

Cited by 900 publications

(980 citation statements)

References 67 publications

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“…2 displays the result obtained for a flexible solvent. Its behavior is in good agreement with results reported in the past by many groups 17,46,55,57,[61][62][63] . The rationalization of general aspects of this function has been discussed numerous times as well (see the most recent review 9 for access to the extensive literature here): relaxation is basically bimodal with an initial fast decay (sometimes termed "inertial") 74 followed by a regime with much slower relaxation (often termed "diffusive").…”

Section: A Energy Gap Relaxation Functionsupporting

confidence: 91%

“…Refs. 55,57). There is a relatively tight structure for the anion, in which one hydrogen from each water molecule is closest to the central negative charge.…”

Section: Rotational Componentsmentioning

confidence: 99%

“…Indeed, a large part of the present insight on solvation relaxation comes from the study of simple ions [15][16][17]46,48,[54][55][56][57] or dipoles 50,58,59 . We note that in this case, for which the solute is initially neutral, the frequency shift can be directly identified with the Coulomb energy of the solute-solvent interaction 50 (see below).…”

Section: Introductionmentioning

confidence: 99%

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Solvation Dynamics in Liquid Water. 1. Ultrafast Energy Fluxes

Rey

Hynes

2015

J. Phys. Chem. B

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Solvation dynamics in liquid water is addressed via nonequilibrium energy transfer pathways activated after a neutral atomic solute acquires a unit charge, either positive or negative. It is shown that the well-known nonequilibrium frequency shift relaxation function can be expressed in a novel fashion in terms of energy fluxes, providing a clearcut and quantitative account of the processes involved. Roughly half of the initial excess energy is transferred into hindered rotations of first hydration shell water molecules, i.e. librational motions, specifically those rotations around the lowest moment of inertia principal axis. After integration over all water solvent molecules, rotations account for roughly 80 % of the energy transferred, while translations have a secondary role; transfer to intramolecular water stretch and bend vibrations is negligible. This picture is similar to that for relaxation of a single vibrationally or rotationally excited water molecule in neat liquid water, although solvation relaxation is more non-local. In addition, we find a remarkable independence of the main relaxation channels on the newly created charges sign. Although the methodology is applied here to the simplest solute case, the approach is rather general, and it should be at least equally useful in more realistic and complex scenarios.

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Section: A Energy Gap Relaxation Functionsupporting

confidence: 91%

“…Refs. 55,57). There is a relatively tight structure for the anion, in which one hydrogen from each water molecule is closest to the central negative charge.…”

Section: Rotational Componentsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Solvation Dynamics in Liquid Water. 1. Ultrafast Energy Fluxes

Rey

Hynes

2015

J. Phys. Chem. B

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“…8,9,28,29 Using a simple point charge model for water and charged spherical Lennard-Jones solutes, along with an extended Lagrangian or Hamiltonian in which the charge and the size of the ions are considered as dynamical variables, Lynden-Bell, Rasaiah and co-workers calculated entropies of solvation of halogen atoms as a function of the charge, introducing the terms hydrophobic and hydrophilic solvation. 8,9 They showed that the entropy of solvation of a solute passes through a minimum near zero charge, signaling cavity formation (hydrophobic hydration) with the water molecules held together by H-bonds. The solvation entropy increases gradually as the solute is charged positively or negatively, reflecting break-up of the cavity.…”

Section: Introductionmentioning

confidence: 99%

“…42 Our data show the formation of an expanded cage around I 0 which we attribute to hydrophobic solvation based on MD simulations and quantum chemical (QC) calculations of I 0 (H 2 O) n=1À4 clusters. Furthermore, QM/MM MD simulations of an I 0 (H 2 O) 9 cluster in bulk classical water point to the formation of a weakly bound I 0 (OH 2 ) complex, which is short-lived, typically a few picoseconds, before the water molecule of the complex merges back into the bulk. The lifetime of the complex is determined by the time it takes to complete the formation of a cavity of hydrogen bonded molecules around the solute (hydrophobic solvation) following electron abstraction from iodide.…”

Section: Introductionmentioning

confidence: 99%

Probing the Transition from Hydrophilic to Hydrophobic Solvation with Atomic Scale Resolution

et al. 2011

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Picosecond and femtosecond X-ray absorption spectroscopy is used to probe the changes of the solvent shell structure upon electron abstraction of aqueous iodide using an ultrashort laser pulse. The transient L1,3 edge EXAFS at 50 ps time delay points to the formation of an expanded water cavity around the iodine atom, in good agreement with classical and quantum mechanical/molecular mechanics (QM/MM) molecular dynamics (MD) simulations. These also show that while the hydrogen atoms pointed toward iodide, they predominantly point toward the bulk solvent in the case of iodine, suggesting a hydrophobic behavior. This is further confirmed by quantum chemical (QC) calculations of I–/I0(H2O) n=1–4 clusters. The L1 edge sub-picosecond spectra point to the existence of a transient species that is not present at 50 ps. The QC calculations and the QM/MM MD simulations identify this transient species as an I0(OH2) complex inside the cavity. The simulations show that upon electron abstraction most of the water molecules move away from iodine, while one comes closer to form the complex that lives for 3–4 ps. This time is governed by the reorganization of the main solvation shell, basically the time it takes for the water molecules to reform an H-bond network. Only then is the interaction with the solvation shell strong enough to pull the water molecule of the complex toward the bulk solvent. Overall, much of the behavior at early times is determined by the reorientational dynamics of water molecules and the formation of a complete network of hydrogen bonded molecules in the first solvation shell.

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Archie's Saturation Exponent for Natural Gas Hydrate in Coarse‐Grained Reservoirs

2018

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Accurately quantifying the amount of naturally occurring gas hydrate in marine and permafrost environments is important for assessing its resource potential and understanding the role of gas hydrate in the global carbon cycle. Electrical resistivity well logs are often used to calculate gas hydrate saturations, Sh, using Archie's equation. Archie's equation, in turn, relies on an empirical saturation parameter, n. Though n = 1.9 has been measured for ice‐bearing sands and is widely used within the hydrate community, it is highly questionable if this n value is appropriate for hydrate‐bearing sands. In this work, we calibrate n for hydrate‐bearing sands from the Canadian permafrost gas hydrate research well, Mallik 5L‐38, by establishing an independent downhole Sh profile based on compressional‐wave velocity log data. Using the independently determined Sh profile and colocated electrical resistivity and bulk density logs, Archie's saturation equation is solved for n, and uncertainty is tracked throughout the iterative process. In addition to the Mallik 5L‐38 well, we also apply this method to two marine, coarse‐grained reservoirs from the northern Gulf of Mexico Gas Hydrate Joint Industry Project: Walker Ridge 313‐H and Green Canyon 955‐H. All locations yield similar results, each suggesting n ≈ 2.5 ± 0.5. Thus, for the coarse‐grained hydrate bearing (Sh > 0.4) of greatest interest as potential energy resources, we suggest that n = 2.5 ± 0.5 should be applied in Archie's equation for either marine or permafrost gas hydrate settings if independent estimates of n are not available.

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Solvent Structure, Dynamics, and Ion Mobility in Aqueous Solutions at 25 °C

Cited by 900 publications

References 67 publications

Solvation Dynamics in Liquid Water. 1. Ultrafast Energy Fluxes

Solvation Dynamics in Liquid Water. 1. Ultrafast Energy Fluxes

Probing the Transition from Hydrophilic to Hydrophobic Solvation with Atomic Scale Resolution

Archie's Saturation Exponent for Natural Gas Hydrate in Coarse‐Grained Reservoirs

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