Density depletion and enhanced fluctuations in water near hydrophobic solutes: identifying the underlying physics

Mary K Coe, Robert Evans, Nigel B Wilding*

*Corresponding author for this work

Research output: Contribution to journalLetter (Academic Journal)peer-review

14 Citations (Scopus)
21 Downloads (Pure)

Abstract

We investigate the origin of the density depletion and enhanced density fluctuations that occur in water in the vicinity of an extended hydrophobic solute. We argue that both phenomena are remnants of the critical drying surface phase transition that occurs at liquid-vapor coexistence in the macroscopic planar limit, ie.~as the solute radius $R_s\to\infty$. Focusing on the density profile $\rho(r)$ and a sensitive spatial measure of fluctuations, the local compressibility profile $\chi(r)$, we develop a scaling theory which expresses the extent of the density depletion and enhancement in compressibility in terms of $R_s$, the strength of solute-water attraction $\varepsilon_s$, and the deviation from liquid-vapor coexistence $\delta\mu$. Testing the predictions against results of classical density functional theory for a simple solvent and Grand Canonical Monte Carlo simulations of a popular water model, we find that the theory provides a firm physical basis for understanding how water behaves at a hydrophobe.
Original languageEnglish
Article number045501
JournalPhysical Review Letters
Volume128
Issue number4
DOIs
Publication statusPublished - 25 Jan 2022

Bibliographical note

Funding Information:
This work used the facilities of the Advanced Computing Research Centre, University of Bristol. We thank F. Turci for valuable discussions. R. E. acknowledges Leverhulme Trust Grant No. EM-2020-029\4.

Funding Information:
This work used the facilities of the Advanced Computing Research Centre, University of Bristol. We thank F. Turci for valuable discussions. R. E. acknowledges Leverhulme Trust Grant No. EM-2020-029\4.

Publisher Copyright:
© 2022 American Physical Society

Keywords

  • Hydrophobic interactions
  • Classical fluids
  • Water
  • Density functional calculations
  • Metropolis algorithm
  • Monte Carlo methods
  • Condensed Matter, Materials & Applied Physics
  • Statistical Physics

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