Understanding the physics of hydrophobic solvation

Abstract

Simulations of water near extended hydrophobic spherical solutes have revealed the presence of a region of depleted density and accompanying enhanced density fluctuations.The physical origin of both phenomena has remained somewhat obscure. We investigate these effects employing a mesoscopic binding potential analysis, classical density functional theory (DFT) calculations for a simple Lennard-Jones (LJ) solvent and Grand Canonical Monte Carlo (GCMC) simulations of a monatomic water (mw) model. We argue that the density depletion and enhanced fluctuations are near-critical phenomena. Specifically, we show that they can be viewed as remnants of the critical drying surface phase transition that occurs at bulk liquid-vapor coexistence in the macroscopic planar limit, i.e.~as the solute radius $R_s\to \infty$. Focusing on the radial density profile $\rho (r)$ and a sensitive spatial measure of fluctuations, the local compressibility profile $\chi (r)$, our binding potential analysis provides explicit predictions for the manner in which the key features of $\rho (r)$ and $\chi (r)$ scale with $R_s$, the strength of solute-water attraction ${\epsilon }_{sf}$, and the deviation from liquid-vapor coexistence of the chemical potential, $\delta \mu$. These scaling predictions are confirmed by our DFT calculations and GCMC simulations. As such our theory provides a firm basis for understanding the physics of hydrophobic solvation.

18 pages

References in corpus (9)

• The molecular structure of the interface between water and a hydrophobic substrate is liquid-vapor like
• How water meets a very hydrophobic surface
• A unified description of hydrophilic and superhydrophobic surfaces in terms of the wetting and drying transitions of liquids
• The Local Compressibility of Liquids near Non-Adsorbing Substrates: A Useful Measure of Solvophobicity and Hydrophobicity?
• Critical Drying of Liquids
• Quantifying density fluctuations in water at a hydrophobic surface: evidence for critical drying
• Drying and Wetting Transitions of a Lennard-Jones Fluid: Simulations and Density Functional Theory
• Density depletion and enhanced fluctuations in water near hydrophobic solutes: identifying the underlying physics
• Measures of Fluctuations for a Liquid Near Critical Drying

Cited by in corpus (13)

• Neural functional theory for inhomogeneous fluids: Fundamentals and applications
• Perspective: How to overcome dynamical density functional theory
• Noether-Constrained Correlations in Equilibrium Liquids
• Hyper-density functional theory of soft matter
• Neural density functional theory of liquid-gas phase coexistence
• Neural density functionals: Local learning and pair-correlation matching
• A classical density functional theory for solvation across length scales
• Why hyperdensity functionals describe any equilibrium observable
• Local measures of fluctuations in inhomogeneous liquids: Statistical mechanics and illustrative applications
• Chemical Physics of Controlled Wettability and Super Surfaces
• Stability of nanoparticle laden aerosol liquid droplets
• Metadensity functional learning for classical fluids: Regularizing with pair correlations
• Wall slip and bulk flow heterogeneity in a sludge under shear