Erratum: Many-body effects in molecular dynamics simulations of Na+(H2O)n and Cl−(H2O)n clusters [J. Chem. Phys. 95, 1954 (1991)]

Perera, Lalith; Berkowitz, Max L.

doi:10.1063/1.466234

Cited by 119 publications

(148 citation statements)

References 5 publications

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“…102 Accordingly, it has been shown through MD simulations of aqueous Na + and Cl -clusters, that Na + is solvated symmetrically in the center of the clusters, and Cl -resides on the surface of a water cluster. 104 This was confirmed experimentally for the larger halide ions in water dimer clusters by Johnson and co-workers. 105 The present ab initio optimized structures of formamide-solvated ions, however, show no evidence for hydrogen bonding with both the formamide-solvated Na + and I -ions located close to the centers of the corresponding clusters.…”

Section: Discussionsupporting

confidence: 61%

Nanojets, Electrospray, and Ion Field Evaporation: Molecular Dynamics Simulations and Laboratory Experiments

et al. 2008

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The energetics, interfacial properties, instabilities, and fragmentation patterns of electrosprays made from formamide salt solutions are investigated in a mass spectrometric vacuum electrospray experiment and using molecular dynamics (MD) simulations. The electrospray source is operated in a Taylor cone-jet mode, with the nanojet that forms being characterized by high surface-normal electric field strengths in the vicinity of 1 V/nm. Mass-to-charge ratios were determined for both positive and negative currents sprayed from NaI−formamide solutions with solute−solvent mole ratios of 1:8.4 and 1:36.9, and from KI−formamide solutions with mole ratios of 1:41 and 1:83. The molecular dynamics simulations were conducted on isolated 10 nm NaI−formamide droplets at mole ratios of 1:8 and 1:16. The droplet was subjected to a uniform electric field with strengths ranging between 0.5 and 1.5 V/nm. Both the experiments and simulations demonstrate a mixed charge emission regime where field-induced desorption of solvated ions and charged droplets occurs. The macroscopic parameters, such as average mass-to-charge ratio and maximum surface-normal field strengths deduced from the simulations are found to be in good agreement with the experimental work and consistent with electrohydrodynamic theory of cone-jets. The observed mass spectrometric Na+ and I− solvated ion distributions are consistent with a thermal evaporation process, and are correctly reproduced by the simulation after incorporation of the different flight times and unimolecular ion dissociation rates in the analysis. Alignment of formamide dipoles and field-induced reorganization of the positive and negative ionic charges in the interfacial region are both found to contribute to the surface-normal field near the points of charge emission. In the simulations the majority of cluster ions are found to be emitted from the tip of the jet rather than from the neck region next to the Taylor cone. This finding is consistent with the experimental energy distributions of the solvated ions which demonstrate that indeed most ions are emitted closer to the jet region, that is, beyond the cone-neck region where ohmic losses occur. This observation is also consistent with continuum electrohydrodynamic predictions of cluster-ion evaporation at surface regions of high curvature and therefore maximum surface electric field strengths, which may be the cone-neck region, the breakup region of the jet (usually near the tip of the jet), or the emitted charged droplets. In the nanoscale jets observed in this study, the regions of highest spatial curvature are at the ends of the jets where nascent drops either are forming or have just detached. The energetics, interfacial properties, instabilities, and fragmentation patterns of electrosprays made from formamide salt solutions are investigated in a mass spectrometric vacuum electrospray experiment and using molecular dynamics (MD) simulations. The electrospray source is operated in a Taylor cone-jet mode, with the nanojet that form...

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Section: Discussionsupporting

confidence: 61%

Nanojets, Electrospray, and Ion Field Evaporation: Molecular Dynamics Simulations and Laboratory Experiments

et al. 2008

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“…[14][15][16][17][18][19][20][21][22][23][24] The contribution of anion polarizability to interfacial enhancement is evident in the MD simulations where in the absence of the polarizability factor anion enhancement was not observed. [40][41][42] The results presented here for the multi component We see a significant surface enhancement (and subsurface depletion) of bromide, compared to which the surface peak of chloride is strongly suppressed. Sodium cations do not penetrate all the way to the surface but, being attracted by surface-bound anions, exhibit a subsurface peak.…”

Section: Resultsmentioning

confidence: 99%

Ion Partitioning at the Liquid/Vapor Interface of a Multicomponent Alkali Halide Solution: A Model for Aqueous Sea Salt Aerosols

et al. 2008

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The chemistry of Br species associated with sea salt ice and aerosols has been implicated in the episodes of ozone depletion reported at Arctic sunrise. However, Br -is only a minor component in sea salt, which has a Br -/Cl -molar ratio of ~0.0015. Sea salt is a complex mixture of many different species, with NaCl as the primary component. In recent years experimental and theoretical studies have reported enhancement of the large, more polarizable halide ion at the liquid/vapor interface of corresponding aqueous alkali halide solutions. The proposed enhancement is likely to influence the availability of sea salt Br -for heterogeneous reactions such as those involved in the ozone depletion episodes. We report here ambient pressure x-ray photoelectron spectroscopy studies and molecular dynamics simulations showing direct evidence of Br -enhancement at the interface of an aqueous NaCl solution doped with bromide. The experiments were carried out on samples with Br -/Cl -ratios in the range 0.1% to 10%, the latter being also the ratio for which simulations were carried out. This is the first direct measurement of interfacial enhancement of Br -in a multi-component solution with particular relevance to sea salt chemistry.

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“…In anion/water cluster calculations, surface solvation states have been observed in addition to a large number of near-lying isomers. 90,91 The solvation environment in the condensed phase can be expected to differ from that in clusters. 92,93,94 The approach developed in this paper provides a direct route to the IS part of the solvation free energy.…”

Section: Conclusion and Discussionmentioning

confidence: 99%

Modeling molecular and ionic absolute solvation free energies with quasichemical theory bounds

Rogers

Beck

2008

The Journal of Chemical Physics

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A recently developed statistical mechanical Quasi-Chemical Theory (QCT) has led to significant insights into solvation phenomena for both hydrophilic and hydrophobic solutes. The QCT exactly partitions solvation free energies into three components: 1) inner-shell chemical, 2) outer-shell packing, and 3) outer-shell long-ranged contributions. In this paper, we discuss efficient methods for computing each of the three parts of the free energy. A Bayesian estimation approach is developed to compute the inner-shell chemical and outer-shell packing contributions. We derive upper and lower bounds on the outer-shell long-ranged portion of the free energy by expressing this component in two equivalent ways. Local, high energy contacts between solute and solvent are eliminated by spatial conditioning in this free energy piece, leading to near-Gaussian distributions of solute-solvent interactions energies. Thus, the average of the two mean-field bounds yields an accurate and efficient free energy estimate. Aqueous solvation free energy results are presented for several solutes, including methane, perfluoromethane, water, and the sodium and chloride ions.The results demonstrate the accuracy and efficiency of the methods. The approach should prove useful in computing solvation free energies in inhomogeneous, restricted environments.

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Erratum: Many-body effects in molecular dynamics simulations of Na+(H2O)n and Cl−(H2O)n clusters [J. Chem. Phys. 95, 1954 (1991)]

Cited by 119 publications

References 5 publications

Nanojets, Electrospray, and Ion Field Evaporation: Molecular Dynamics Simulations and Laboratory Experiments

Nanojets, Electrospray, and Ion Field Evaporation: Molecular Dynamics Simulations and Laboratory Experiments

Ion Partitioning at the Liquid/Vapor Interface of a Multicomponent Alkali Halide Solution: A Model for Aqueous Sea Salt Aerosols

Modeling molecular and ionic absolute solvation free energies with quasichemical theory bounds

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