Effects of Polarizability on the Hydration of the Chloride Ion

Stuart, Steven J.; Berne, B. J.

doi:10.1021/jp961076d

Cited by 269 publications

(326 citation statements)

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“…Accurate simulations of ion solvation require polarizable force fields (12,16,(33)(34)(35). Here we applied the polarizable models of Lamoureux et al for water (SWM4-DP) (20) and for ions (21); these ion models were parameterized in conjunction with the SWM4-DP water model.…”

Section: Methodsmentioning

confidence: 99%

Atomistic simulation of ion solvation in water explains surface preference of halides

Caleman

Hub

Maaren

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

209

316

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Water is a demanding partner. It strongly attracts ions, yet some halide anions-chloride, bromide, and iodide-are expelled to the air/water interface. This has important implications for chemistry in the atmosphere, including the ozone cycle. We present a quantitative analysis of the energetics of ion solvation based on molecular simulations of all stable alkali and halide ions in water droplets. The potentials of mean force for Cl − , Br − , and I − have shallow minima near the surface. We demonstrate that these minima derive from more favorable water-water interaction energy when the ions are partially desolvated. Alkali cations are on the inside because of the favorable ion-water energy, whereas F − is driven inside by entropy. Models attempting to explain the surface preference based on one or more ion properties such as polarizability or size are shown to lead to qualitative and quantitative errors, prompting a paradigm shift in chemistry away from such simplifications.ozone layer | GROMACS | aerosol | thermodynamics S ea water becomes airborne in the form of droplets formed at the sea surface by the action of waves (1). These droplets can be carried by the wind, and they interact with other constituents of the atmosphere (Fig. 1A). On the surface of the small water droplets, halide anions can be converted into halogen atoms by absorption of light (2, 3), and the air-water interface serves to increase certain reaction probabilities (4, 5). One example is the oxidation of Cl − and Br − by OH radicals or O 3 that can occur at the air-water interface, with mechanisms different from those in the bulk phase (6), leading to natural ozone depletion in the stratosphere.Both theoretical and experimental studies have shown that Cl − , Br − and I − prefer to be at the surface of water droplets (Fig. 1A), whereas F − and alkali cations strive to become fully solvated in the bulk of water droplets (7-12). The Br − concentration is enhanced more at the surface than the Cl − concentration (13), an effect that may be enhanced in mixtures containing both Br − and Cl − , such as seawater (14). Because Br − is more reactive than Cl − , the surface preference has an impact on the chemistry in the atmosphere, despite the fact that the content of Cl − in bulk sea water is about three orders of magnitude higher than that of Br − (15). The energetic and structural mechanisms underlying the surface preference of large halide anions have been studied in quite some detail (16-18), but the phenomenon is still not understood quantitatively (10). Only very recently has the surface absorption free energy of one halide anion, Br − , been determined experimentally (19). Recent progress in development of force fields for water (20) and ions (21) finally allows establishment of the surface preferences for all halide and alkali ions quantitatively.Here we present the energetics of ion solvation in a water droplet with a radius of approximately 1.1 nm for all stable halide anions (F − , Cl − , Br − , I − ) and alkali cations (Li þ , Na þ , K þ...

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Section: Methodsmentioning

confidence: 99%

Atomistic simulation of ion solvation in water explains surface preference of halides

Caleman

Hub

Maaren

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

209

316

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“…1 However, a combination of computational [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] and experimental studies [16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33] has shown that ions can reside and even be enhanced at the interface.…”

Section: Introductionmentioning

confidence: 99%

The effect of cations on NO₂ production from the photolysis of aqueous thin water films of nitrate salts

Richards-Henderson

Anderson

Anastasio

et al. 2015

Phys. Chem. Chem. Phys.

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The photochemistry of nitrate ions in bulk aqueous solution is well known, yet recent evidence suggests that the photolysis of nitrate may be more efficient at the air-water interface. Whether and how this surface enhancement is altered by the presence of different cations is not known. In the present studies, thin aqueous films of nitrate salts with different cations were deposited on the walls of a Teflon chamber and irradiated with 311 nm light at 298 K. The films were generated by nebulizing aqueous 0.5 M solutions of the nitrate salts and the generation of gas-phase NO 2 was monitored with time. The nitrate salts fall into three groups based on their observed rate of NO 2 formation (R NO 2 ): (1) RbNO 3 and KNO 3 , which readily produce NO 2 (R NO 2 4 3 ppb min À1 ), (2) Ca(NO 3 ) 2 , which produces NO 2 more slowly (R NO 2 o 1 ppb min À1 ), and (3) Mg(NO 3 ) 2 and NaNO 3 , which lie between the other two groups. Neither differences in the UV-visible spectra of the nitrate salt solutions nor the results of bulk-phase photolysis studies could explain the differences in the rates of NO 2 production between these three groups. These experimental results, combined with some insights from previous molecular dynamic simulations and vibrational sum frequency generation studies, show that cations may impact the concentration of nitrate ions in the interface region, thereby directly impacting the effective quantum yields for nitrate ions.

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“…To keep the study of different methods ͑and ion-molecule systems͒ within a manageable limit, we will restrict to cases where all polarizable species ͑ion and molecule͒ are modeled with the same method. Indeed one could treat each polarizable site with different methods 55 but it is to be expected that, given the essentially similar nature of the various methods available, such approach would not change the essence of our conclusions. Therefore, in this study we compare the accuracy of PD and SH methods, applying them to the whole ion-molecule system.…”

Section: Introductionmentioning

confidence: 99%

On the performance of molecular polarization methods. II. Water and carbon tetrachloride close to a cation

Masia

Probst

Rey

2005

The Journal of Chemical Physics

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Our initial study on the performance of molecular polarization methods close to a positive point charge ͓M. Masia, M. Probst, and R. Rey, J. Chem. Phys. 121, 7362 ͑2004͔͒ is extended to the case in which a molecule interacts with a real cation. Two different methods ͑point dipoles and shell model͒ are applied to both the ion and the molecule. The results are tested against high-level ab initio calculations for a molecule ͑water or carbon tetrachloride͒ close to Li + , Na + , Mg 2+ , and Ca 2+ . The monitored observable is in all cases the dimer electric dipole as a function of the ion-molecule distance for selected molecular orientations. The moderate disagreement previously obtained for point charges at intermediate distances, and attributed to the linearity of current polarization methods ͑as opposed to the nonlinear effects evident in ab initio calculations͒, is confirmed for real cations as well. More importantly, it is found that at short separations the phenomenological polarization methods studied here substantially overestimate the dipole moment induced if the ion is described quantum chemically as well, in contrast to the dipole moment induced by a point-charge ion, for which they show a better degree of accord with ab initio results. Such behavior can be understood in terms of a decrease of atomic polarizabilities due to the repulsion between electronic charge distributions at contact separations. It is shown that a reparametrization of the Thole method for damping of the electric field, used in conjunction with any polarization scheme, allows to satisfactorily reproduce the dimer dipole at short distances. In contrast with the original approach ͑developed for intramolecular interactions͒, the present reparametrization is ion and method dependent, and corresponding parameters are given for each case.

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Effects of Polarizability on the Hydration of the Chloride Ion

Cited by 269 publications

References 54 publications

Atomistic simulation of ion solvation in water explains surface preference of halides

Atomistic simulation of ion solvation in water explains surface preference of halides

The effect of cations on NO₂ production from the photolysis of aqueous thin water films of nitrate salts

On the performance of molecular polarization methods. II. Water and carbon tetrachloride close to a cation

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Effects of Polarizability on the Hydration of the Chloride Ion

Cited by 269 publications

References 54 publications

Atomistic simulation of ion solvation in water explains surface preference of halides

Atomistic simulation of ion solvation in water explains surface preference of halides

The effect of cations on NO2 production from the photolysis of aqueous thin water films of nitrate salts

On the performance of molecular polarization methods. II. Water and carbon tetrachloride close to a cation

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Product

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The effect of cations on NO₂ production from the photolysis of aqueous thin water films of nitrate salts