Molecular density functional theory for water with liquid-gas coexistence and correct pressure

Journal Article · Tue Apr 21 04:00:00 EDT 2015 · Journal of Chemical Physics

DOI:https://doi.org/10.1063/1.4917485· OSTI ID:22415663

Jeanmairet, Guillaume; Levesque, Maximilien ^[1]; Sergiievskyi, Volodymyr ^[2]; Borgis, Daniel ^[1]

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1. École Normale Supérieure - PSL Research University, Département de Chimie, Sorbonne Universités - UPMC Univ. Paris 06, CNRS UMR 8640 PASTEUR, 24 rue Lhomond, 75005 Paris (France)
2. SIS2M, LIONS, CEA, Saclay (France)

The solvation of hydrophobic solutes in water is special because liquid and gas are almost at coexistence. In the common hypernetted chain approximation to integral equations, or equivalently in the homogenous reference fluid of molecular density functional theory, coexistence is not taken into account. Hydration structures and energies of nanometer-scale hydrophobic solutes are thus incorrect. In this article, we propose a bridge functional that corrects this thermodynamic inconsistency by introducing a metastable gas phase for the homogeneous solvent. We show how this can be done by a third order expansion of the functional around the bulk liquid density that imposes the right pressure and the correct second order derivatives. Although this theory is not limited to water, we apply it to study hydrophobic solvation in water at room temperature and pressure and compare the results to all-atom simulations. The solvation free energy of small molecular solutes like n-alkanes and hard sphere solutes whose radii range from angstroms to nanometers is now in quantitative agreement with reference all atom simulations. The macroscopic liquid-gas surface tension predicted by the theory is comparable to experiments. This theory gives an alternative to the empirical hard sphere bridge correction used so far by several authors.

• OSTI ID: 22415663
• Journal Information: Journal of Chemical Physics, Journal Name: Journal of Chemical Physics Journal Issue: 15 Vol. 142; ISSN JCPSA6; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ALKANES
APPROXIMATIONS
ATOMS
COMPARATIVE EVALUATIONS
COMPUTERIZED SIMULATION
DENSITY
DENSITY FUNCTIONAL METHOD
FREE ENERGY
HYDRATION
INTEGRAL EQUATIONS
LIQUIDS
SOLUTES
SOLVENTS
TEMPERATURE RANGE 0273-0400 K
WATER