Temperature dependence and energetics of single ions at the aqueous liquid-vapor interface

Shuching Ou, Sandeep Patel

Research output: Contribution to journalArticle

17 Citations (Scopus)

Abstract

We investigate temperature-dependence of free energetics with two single halide anions, I- and Cl-, crossing the aqueous liquid-vapor interface through molecular dynamics simulations. The result shows that I- has a modest surface stability of 0.5 kcal/mol at 300 K and the stability decreases as the temperature increases, indicating the surface adsorption process for the anion is entropically disfavored. In contrast, Cl- shows no such surface state at all temperatures. Decomposition of free energetics reveals that water-water interactions provide a favorable enthalpic contribution, while the desolvation of ion induces an increase in free energy. Calculations of surface fluctuations demonstrate that I- generates significantly greater interfacial fluctuations compared to Cl -. The fluctuation is attributed to the malleability of the solvation shells, which allows for more long-ranged perturbations and solvent density redistribution induced by I- as the anion approaches the liquid-vapor interface. The increase in temperature of the solvent enhances the inherent thermally excited fluctuations and consequently reduces the relative contribution from anion to surface fluctuations, which is consistent with the decrease in surface stability of I-. Our results indicate a strong correlation with induced interfacial fluctuations and anion surface stability; moreover, resulting temperature dependent behavior of induced fluctuations suggests the possibility of a critical level of induced fluctuations associated with surface stability.

Original languageEnglish (US)
Pages (from-to)6512-6523
Number of pages12
JournalJournal of Physical Chemistry B
Volume117
Issue number21
DOIs
StatePublished - May 30 2013
Externally publishedYes

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liquid-vapor interfaces
Vapors
Ions
surface stability
Anions
temperature dependence
Negative ions
Liquids
anions
ions
Temperature
malleability
Water
Solvation
Surface states
temperature
Free energy
Molecular dynamics
water
halides

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Materials Chemistry
  • Surfaces, Coatings and Films

Cite this

Temperature dependence and energetics of single ions at the aqueous liquid-vapor interface. / Ou, Shuching; Patel, Sandeep.

In: Journal of Physical Chemistry B, Vol. 117, No. 21, 30.05.2013, p. 6512-6523.

Research output: Contribution to journalArticle

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