Multiscale Simulation Method for Quantitative Prediction of Surface Wettability at the Atomistic Level

Abstract

The solid-liquid interface is of great interest because of its highly heterogeneous character and its ubiquity in various applications. The most fundamental physical variable determining the strength of the solid-liquid interface is the solid-liquid interfacial tension, which is usually measured according to the contact angle. However, an accurate experimental measurement and a reliable theoretical prediction of the contact angle remain lacking because of many practical issues. Here, we propose a first-principles-based simulation approach to quantitatively predict the contact angle of an ideally clean surface using our recently developed multiscale simulation method of density functional theory in classical explicit solvents (DFT-CES). Using this approach, we simulate the surface wettability of a graphene and graphite surface, resulting in a reliable contact angle value that is comparable to the experimental data. From our simulation results, we find that the surface wettability is dominantly affected by the strength of the solid-liquid van der Waal's interaction. However, we further elucidate that there exists a secondary contribution from the change of water-water interaction, which is manifested by the change of liquid structure and dynamics of interfacial water layer. We expect that our proposed method can be used to quantitatively predict and understand the intriguing wetting phenomena at an atomistic level and can eventually be utilized to design a surface with a controlled hydrophobic(philic)ity.

Structure, Dynamics, and Wettability of Water at Metal Interfaces

“…The DFT-CES method is implemented by combining open-source density functional theory (DFT) and classical molecular dynamics (MD) programs; Quantum ESPRESSO 28 (a planewave DFT code) and Large-scale Atomic/Molecular Massively Parallel Simulator 30 (LAMMPS; a classical MD code). Detailed simulation procedure of DFT-CES can be found from our previous publications 5,6 .…”

“…The DFT-CES iteration was performed until the internal energy change of the DFT part became less than 0.1 kcal/mol. Optimized vdW parameters for interfacial interaction can be found from; the reference 6 for C of graphene/graphite systems; Fig. S9 for F of fluorographene (F-graphene); and Table S2 for metals.…”

“…In addition to the seamless treatment of the electrostatics, DFT-CES employs the parameterized pairwise interaction terms to account for the exchange repulsion and long-range nonlocal correlation (namely, dispersion) energies that are missing during the classical treatment of water. When these van der Waals (vdW) parameters are carefully prepared to reproduce the single water binding curve from the first-principles, our recent study has demonstrated that the DFT-CES can accurately describe the macroscopic wettability of the solid surface without having experimental input or empirical treatment 6 .

Figure 1Schematic diagram of the first-principles-based multiscale simulation of a solid (metal)-liquid (water) interfacial system. The classical treatment of water molecules and the quantum description of the metal surface enable an accurate description of both the single water-metal surface interaction and the liquid water-metal interfacial interaction using a single set of transferrable vdW parameters.

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Hydration Thermodynamics of Non-Polar Aromatic Hydrocarbons: Comparison of Implicit and Explicit Solvation Models

“…The 2PT model has been widely tested and proven successful for the quantitative prediction of the thermodynamics and phase behavior of Lennard-Jones particles at various densities [ 43 ], absolute entropy of water molecules [ 44 ] and organic solvents [ 45 ], and the interfacial thermodynamics of various liquids, e.g., surface tensions [ 46 ]. It is further emphasized that the combination of DFT-CES and 2PT has demonstrated a satisfactory description of the of the 17 polar solutes [ 37 ], which were adopted as the official SAMPL0 challenge test set [ 25 ], and of the solid-liquid interfacial tension of water-graphene/graphite system [ 49 ].…”

Characterizing the bifurcating configuration of hydrogen bonding network in interfacial liquid water and its adhesion on solid surfaces

“…First and foremost, a depletion region of liquid water is formed near a solid surface and such density decit becomes more prominent for hydrophobic surfaces. 15,16 Above the depletion region, wave-like spatial undulations of liquid density have been reported, [17][18][19] implying a new mechanism of energy dissipation in the form of layer-by-layer friction during the process of dynamic wetting. [20][21][22] It was also reported that such spatial undulations can break the ideal tetrahedron geometry of hydrogen bonds, 23 which is usually formed in bulk water, and may give rise to the polarity of interfacial water.…”