Water Force Field Research Articles

Diffusivity of α-, β-, γ-cyclodextrin and the inclusion complex of β-cyclodextrin: Ibuprofen in aqueous solutions; A molecular dynamics simulation study

Cyclodextrins (CDs) are widely used in drug delivery, catalysis, food and separation processes. In this work, a comprehensive simulation study on the diffusion of the native α-, β- and γ-CDs in aqueous solutions is carried out using Molecular Dynamics simulations. The effect of the system size on the computed self-diffusivity is investigated and it is found that the required correction can be as much as 75% of the final value. The effect of the water force field is examined and it is shown that the q4md-CD/TIP4P/2005 force field combination predicts the experimentally measured self-diffusion coefficients of CDs very accurately. The self-diffusion coefficients of the three native CDs were also computed in aqueous-NaCl solutions using the Joung and Cheatham (JC) and the Madrid-2019 force fields. It is found that Na+ ions have higher affinity towards the CDs when the JC force field is used and for this reason the predicted diffusivity of CDs is lower compared to simulations using the Madrid-2019 force field. As a model system for drug delivery and waste-water treatment applications, the diffusion of the β-CD:Ibuprofen inclusion complex in water is studied. In agreement with experiments for similar components, it is shown that the inclusion complex and the free β-CD have almost equal self-diffusion coefficients. Our analysis revealed that this is most likely caused by the almost full inclusion of the ibuprofen in the cavity of the β-CD. Our findings show that Molecular Dynamics simulation can be used to provide reasonable diffusivity predictions, and to obtain molecular-level understanding useful for industrial applications of CDs.

Ten Facets, One Force Field: The GAL19 Force Field for Water-Noble Metal Interfaces.

Understanding the structure of the water/metal interfaces plays an important role in many areas ranging from surface chemistry to environmental processes. The size, required phase-space sampling, and the slow diffusion of molecules at the water/metal interfaces motivate the development of accurate force fields. We develop and parametrize GAL19, a novel force field, to describe the interaction of water with two facets (111 and 100) of five metals (Pt, Pd, Au, Ag, Cu). To increase transferability compared to its predecessor GAL17, the water-metal interaction is described as a sum of pairwise terms. The interaction energy has three contributions: (i) physisorption is described via a Tang and Toennies potential, (ii) chemisorption and surface corrugation rely on an attractive Gaussian term, and (iii) the angular dependence is explicitly included as a truncated Fourier series. Thirteen parameters are used for each metal surface and were fitted on 250 water adsorption energies computed at the PBE+dDsC level. The performance of GAL19 was evaluated on a set of more than 600 DFT adsorption energies for each surface, leading to an average root-mean-square deviation of only 1 kcal/mol, correctly reproducing the adsorption trends: strong on Pt and Pd but weaker on Ag, Au, and Cu. This force field was then used to simulate the water/metal interface for all ten surfaces for 1 ns. Structural analyses reveal similar tendencies for all surfaces: a first, dense water layer that is mostly adsorbed on the metal top sites and a second layer up to around 6 Å, which is less structured. On Pt and Pd, the first layer is strongly organized with water lying flat on the surface. The pairwise additive functional form allows one to simulate the water adsorption on alloys, which is demonstrated at the example of Ag/Cu and Au/Pt alloys. The water/Ag-Cu interface is predicted to be disordered with water mostly adsorbed on Cu which should exacerbate the Ag reactivity. On the contrary, incorporating Pt into Au materials leads to a structuring of the water interface. Our promising results make GAL19 an ideal candidate to get representative sampling of complex metal/water interfaces as a first step toward accurate estimation of free energies of reactions in solution at the metal interface.

Scaled charges at work: Salting out and interfacial tension of methane with electrolyte solutions from computer simulations

The solubility of methane in water decreases when a small amount of salt is present. This is usually denoted as the salting out effect (i.e., the methane is expelled from the solution when it contains small amounts of salt). The effect is important, for instance the solubility is reduced by a factor of three in a 4 m (mol/kg) NaCl solution. Some years ago we showed that the salting out effect of methane in water can be described qualitatively by molecular models using computer simulations. However the salting out effect was overestimated. In fact, it was found that the solubility of methane was reduced by a factor of eight. This points to limitations in the force field used. In this work we have carried out direct coexistence simulations to describe the salting out effect of methane in water using a recently proposed force field (denoted as Madrid-2019) based on the use of scaled charges for the ions and the TIP4P/2005 force field for water. For NaCl the results of the Madrid-2019 force field significantly improve the description of salting out of methane. For other salts the results are quite reasonable. Thus the reduction of the charge of the ions also seems to be able to improve the description of salting out effect of methane in water. Besides this we shall show that the brine-methane interface exhibits an increased interfacial tension as compared to that of the water-methane system. It is well known that electrolytes tend to increase the surface tension of liquid water, and this seems also to be the case for the interface between water and methane.

On the transferability of ion parameters to the TIP4P/2005 water model using molecular dynamics simulations.

Countless molecular dynamics studies have relied on available ion and water force field parameters to model aqueous electrolyte solutions. The TIP4P/2005 model has proven itself to be among the best rigid water force fields, whereas many of the most successful ion parameters were optimized in combination with SPC/E, TIP3P, or TIP4P/Ew water. Many researchers have combined these ions with TIP4P/2005, hoping to leverage the strengths of both parameter sets. To assess if this widely used approach is justified and to provide a guide in selecting ion parameters, we investigated the transferability of various commonly used monovalent and multivalent ion parameters to the TIP4P/2005 water model. The transferability is evaluated in terms of ion hydration free energy, hydration radius, coordination number, and self-diffusion coefficient at infinite dilution. For selected ion parameters, we also investigated density, ion pairing, chemical potential, and mean ionic activity coefficients at finite concentrations. We found that not all ions are equally transferable to TIP4P/2005 without compromising their performance. In particular, ions optimized for TIP3P water were found to be poorly transferable to TIP4P/2005, whereas ions optimized for TIP4P/Ew water provided nearly perfect transferability. The latter ions also showed good overall agreement with experimental values. The one exception is that no combination of ion parameters and water model considered here was found to accurately reproduce experimental self-diffusion coefficients. Additionally, we found that cations optimized for SPC/E and TIP3P water displayed consistent underpredictions in the hydration free energy, whereas anions consistently overpredicted the hydration free energy.

On the validity of the Stokes–Einstein relation for various water force fields

The translational self-diffusion coefficient and the shear viscosity of water are related by the fractional Stokes–Einstein relation. We report extensive novel molecular dynamics simulations for the self-diffusion coefficient and the shear viscosity of water. The SPC/E and TIP4P/2005 water models are used in the temperature range 220–560 K and at 1 or 1,000 bar. We compute the fractional exponents t, and s that correspond to the two forms of the fractional Stokes–Einstein relation and respectively. We analyse other available experimental and numerical simulation data. In the current analysis two temperature ranges are considered (above or below 274 K) and in both cases deviations from the Stokes–Einstein relation are observed with different values for the fractional exponents obtained for each temperature range. For temperatures above 274 K, both water models perform comparably, while for temperatures below 274 K TIP4P/2005 outperforms SPC/E. This is a direct result of the ability of TIP4P/2005 to predict water densities more accurately and thus predict more accurately the water self-diffusion coefficient and the shear viscosity.

An effective force field to reproduce the solubility of MTBE in water

In this work, a force field has been developed for methyl tert-butyl ether (MTBE) in the pure liquid by adjusting the intermolecular parameters to reproduce three target thermodynamic properties: the dielectric constant, the surface tension and the density of the liquid. In addition to these three properties, the new force field was able to reproduce the experimental values for the heat of vaporization, the vapor pressure, the self-diffusion and the viscosity, with relative errors smaller than 5%. Moreover, the target properties were also calculated as a function of temperature, in the 288.15 to 313.15 K range. A remarkable agreement with experimental data was found. Finally, by combining the NEWFFP force field for MTBE with the TIP4P/ε force field for water, the solubility of MTBE in water as a function of temperature was obtained. The results follow the experimental line with a deviation which is less than 7%. The decrease in the solubility with temperature is explained by the formation, at low temperature, of stable, short-lived MTBE-water clusters that are clearly identified. These clusters contain one, two and three MTBE molecules that form hydrogen bonds with water molecules. At temperatures above 298.15 K no clusters are found, in agreement with the experimentally observed negative slope of the solubility versus temperature behavior.

A comprehensive molecular dynamics simulation study of hydrous magmatic liquids

Despite its low abundance, water has a great influence on the geodynamics of the Earth’s upper mantle. Indeed, water has the ability to modify the phase relations and to affect in a significant way the rheological properties of minerals and melts. However the mechanisms of water incorporation in silicate melts and the impact on the melt properties is still not fully understood. To improve our understanding of hydrous silicate melts, we have performed a series of molecular dynamics simulations to evaluate the H2O solubility, the liquid-vapour coexistence, the surface tension, the water speciation, the equation of state, the viscosity, the electrical conductivity, the diffusion of silicate elements and protonated species, as well as the melt structure of various magmatic liquids representative of the Earth’s upper mantle (rhyolite, andesite, MORB, peridotite, and kimberlite). For that, we introduce a new force field for water, which is compatible with an accurate force field for silicates recently developed (Dufils et al., 2018). A comparison between MD calculations and experimental data (when they exist) shows that the MD simulations are reliable. Among all the results obtained in this study, the following points may be emphasized. (1) The solubility of water changes very little when the melt composition evolves from rhyolitic to andesitic and basaltic, but it is strongly enhanced in ultramafic melts. (2) When hydrous melt and aqueous fluid are coexisting with each other, the oxide content of the aqueous fluid increases rapidly with the pressure. (3) A consequence of point (2) is that water has a large influence on the surface tension, as the latter one drops by a factor of 2 ∼ 4 when the water pressure increases from 1bar to a few kbar. (4) Concerning the water speciation, an important point is that the MD simulation probes the liquid phase, when most of the experimental studies are dealing with glasses. Thus at magmatic temperatures the concentration in hydroxyl groups and the one in molecular water are crossing for a water content of about 15wt%, a value much higher than the one observed in glasses (∼ 3–4wt%). (5) MD calculations show that the molar volume of the melt is a linear function of the water content, and so for all the chemical compositions investigated. Therefore the water partial molar volume (VH2O) is virtually independent of total water content and of water speciation. A by-product of this result is that an ideal mixing rule between water and the silicate component leads to an accurate estimate of the melt molar volume. (6) At fixed T and P, the melt viscosity decreases with water content, more depolymerized the melt the smaller the influence of water on the viscosity. However, at the high temperatures investigated in this study (T ≥ 1673K), the decrease in viscosity induced by water does not exceed one or two orders of magnitude, as compared with many orders of magnitude near the glass transition temperature. (7) The diffusivity of ions increases exponentially with water content. As for the protonated species, it is found that, DO2-<DOH- <DH2O≤DH3O+, the lower the NBO/T ratio the smaller the ratio DOH-/ DH2O. (8) A structural analysis shows that hydroxyl groups are more preferentially linked to metal cations than to structure makers. In contrast, H2O molecules (and H3O+ as well) are almost exclusively linked to metal cations. As for the melt polymerization, it decreases gradually with the water content in andesitic and basaltic melts, whereas it remains almost invariant in peridotitic melt. (9) O-H…O bonds (hydrogen bonding) taking place between the hydroxyl groups, the water molecules, and the oxygens of the silicate are characterized by O⋯O distances in the range 2.5 ∼ 3.2 A, and by O…H-O distances in the range 1.5 ∼ 2.2 A. But, because of the high temperature of investigation, these H-bonds are generally weak (weaker than in liquid water at ambient).

The Role of Post-translational Modifications on the Energy Landscape of Huntingtin N-Terminus.

Huntington disease is a neurodegenerative disease characterized by a polymorphic tract of polyglutamine repeats in exon 1 of the huntingtin protein, which is thought to be responsible for protein aggregation and neuronal death. The polyglutamine tract is preceded by a 17-residue sequence that is intrinsically disordered. This region is subject to phosphorylation, acetylation and other post-translational modifications in vivo, which modulate its secondary structure, aggregation and, subcellular localization. We used Molecular Dynamics simulations with a novel Hamiltonian-replica-exchange-based enhanced sampling method, SWISH, and an optimal combination of water and protein force fields to study the effects of phosphorylation and acetylation as well as cross-talk between these modifications on the huntingtin N-terminus. The simulations, validated by circular dichroism, were used to formulate a mechanism by which the modifications influence helical conformations. Our findings have implications for understanding the structural basis underlying the effect of PTMs in the aggregation and cellular properties of huntingtin.

Development of an Advanced Force Field for Water Using Variational Energy Decomposition Analysis.

Given the piecewise approach to modeling intermolecular interactions for force fields, they can be difficult to parametrize since they are fit to data like total energies that only indirectly connect to their separable functional forms. Furthermore, by neglecting certain types of molecular interactions such as charge penetration and charge transfer, most classical force fields must rely on, but do not always demonstrate, how cancellation of errors occurs among the remaining molecular interactions accounted for such as exchange repulsion, electrostatics, and polarization. In this work we present the first generation of the (many-body) MB-UCB force field that explicitly accounts for the decomposed molecular interactions commensurate with a variational energy decomposition analysis, including charge transfer, with force field design choices that reduce the computational expense of the MB-UCB potential while remaining accurate. We optimize parameters using only a single water molecule and water cluster data up through pentamers, with no fitting to condensed phase data, and we demonstrate that high accuracy is maintained when the force field is subsequently validated against conformational energies of larger water cluster data sets, radial distribution functions of the liquid phase, and the temperature dependence of thermodynamic and transport water properties. We conclude that MB-UCB is comparable in performance to MB-Pol but is less expensive and more transferable by eliminating the need to represent short-ranged interactions through large parameter fits to high order polynomials.

Feynman diagram description of 2D-Raman-THz spectroscopy applied to water.

2D-Raman-THz spectroscopy of liquid water, which has been presented recently [J. Savolainen et al., Proc. Natl. Acad. Sci. U. S. A. 110, 20402 (2013)], directly probes the intermolecular degrees of freedom of the hydrogen-bond network. However, being a relatively new technique, its information content is not fully explored to date. While the spectroscopic signal can be simulated based on molecular dynamics simulation in connection with a water force field, it is difficult to relate spectroscopic signatures to the underlying microscopic features of the force field. Here, a completely different approach is taken that starts from an as simple as possible model, i.e., a single vibrational mode with electrical and mechanical anharmonicity augmented with homogeneous and inhomogeneous broadening. An intuitive Feynman diagram picture is developed for all possible pulse sequences of hybrid 2D-Raman-THz spectroscopy. It is shown that the model can explain the experimental data essentially quantitatively with a very small set of parameters, and it is tentatively concluded that the experimental signal originates from the hydrogen-bond stretching vibration around 170 cm-1. Furthermore, the echo observed in the experimental data can be quantified by fitting the model. A dominant fraction of its linewidth is attributed to quasi-inhomogeneous broadening in the slow-modulation limit with a correlation time of 370 fs, reflecting the lifetime of the hydrogen-bond networks giving rise to the absorption band.

Liquid water is a dynamic polydisperse branched polymer

We developed the RexPoN force field for water based entirely on quantum mechanics. It predicts the properties of water extremely accurately, with Tmelt = 273.3 K (273.15 K) and properties at 298 K: ΔHvap = 10.36 kcal/mol (10.52), density = 0.9965 g/cm3 (0.9965), entropy = 68.4 J/mol/K (69.9), and dielectric constant = 76.1 (78.4), where experimental values are in parentheses. Upon heating from 0.0 K (ice) to 273.0 K (still ice), the average number of strong hydrogen bonds (SHBs, rOO ≤ 2.93 Å) decreases from 4.0 to 3.3, but upon melting at 273.5 K, the number of SHBs drops suddenly to 2.3, decreasing slowly to 2.1 at 298 K and 1.6 at 400 K. The lifetime of the SHBs is 90.3 fs at 298 K, increasing monotonically for lower temperature. These SHBs connect to form multibranched polymer chains (151 H2O per chain at 298 K), where branch points have 3 SHBs and termination points have 1 SHB. This dynamic fluctuating branched polymer view of water provides a dramatically modified paradigm for understanding the properties of water. It may explain the 20-nm angular correlation lengths at 298 K and the critical point at 227 K in supercooled water. Indeed, the 15% jump in the SHB lifetime at 227 K suggests that the supercooled critical point may correspond to a phase transition temperature of the dynamic polymer structure. This paradigm for water could have a significant impact on the properties for protein, DNA, and other materials in aqueous media.

The quantum mechanics-based polarizable force field for water simulations.

We report here a new force field for water based solely on quantum mechanics (QM) calculations with no empirical data. The QM was at a high level, coupled cluster single double triple, for all orientations and distances for water dimer plus X3LYP density functional theory (DFT) on 19 larger water clusters. In addition, we included charge and polarization based on the polarizable charge equilibration method and nonbond interactions from DFT-D3 calculations on the H2 and O2 crystal. This model, denoted as RexPoN, provides quite excellent agreement with experimental (expr) data for the solid and liquid phase of water: T melt = 273.3 K (expr = 273.15 K) and properties at 298 K: ΔH vap = 10.36 kcal/mol (expr = 10.52), density = 0.9965 gr/cm3 (expr = 0.9965), entropy = 68.4 (J/mol)/K (expr = 69.9), dielectric constant = 76.1 (expr = 78.4), and ln D s (self-diffusion coef) = -10.08 (expr = -11.24). Such an accurate force field for water will, we believe, be useful for full solvent calculations of electrocatalysis, where we can restrict QM water to just the first one or two layers involving reactions, using RexPoN to provide the polarization for a more distant solvent. Also, RexPoN may provide a better description of the solvent for proteins, DNA, polymers, and inorganic systems for applications to biomolecular, pharma, electrocatalysis (fuel cells and water splitting), and batteries where interaction with explicit water molecules plays a significant role.

A molecular dynamics study of water-soluble polymers: analysis of force fields from atomistic simulations

ABSTRACTA force field (FF) analysis was performed on three water-soluble polymers (PAM, PNIPAAm, and PEO), that are of significant interest for biomedical applications, by measuring the polymer radius of gyration (Rg), solvent accessible surface area (SASA), radial distribution functions (g(r)), and relative shape anisotropy (κ2) in dilute conditions. Three generalised FFs were utilised to model PAM and PNIPAAm (DREIDING, GAFF, and GAFF2) in conjunction with five water models: SPC, SPC/E, TIP3P, TIP4P, and TIP4P/2005. It was found that the DREIDING FF showed better agreement with PAM experimental data reported for Rg, irrespective of the water model. For PNIPAAm, the DREIDING FF was also the best performing among the FFs studied; however, the choice of water model played an important role in the predicted properties. The trends in SASA and κ2 are consistent with Rg. For PEO modelled with the CHARMM C35r FF, all water models except TIP3P resulted in good agreement with experimental and previous simulation data. These results highlight the considerable impact that polymer and water FFs can have on sampling appropriate polymer conformations in solvated systems.

Isotope Effects in Water: Differences of Structure, Dynamics, Spectrum, and Proton Transport between Heavy and Light Water from ReaxFF Reactive Force Field Simulations.

Investigating properties of both heavy and light water at the atomistic level is essential to understanding chemical and biological processes in aqueous solution. However, appropriately describing their difference on the nanoscale is still challenging. Employing ReaxFF reactive molecular dynamics simulations, we systematically study the structure, dynamics, and spectra of heavy and light water. With the water force field potential we developed, the different features between heavy and light water can be simulated appropriately by the classical treatment on large size and time scale. Here, we also report the structural difference between D3O+ and H3O+ in bulk heavy/light water. In addition, the diffusion constants of heavy and light water are successfully reproduced, and the Grotthuss hopping mechanism of proton transport in liquid water is properly described as well. It allows us to study a complex system in heavy/light aqueous environments, such as proton transport, chemical reaction, and tracing the reaction mechanism with an isotope substitute.

An efficient water force field calibrated against intermolecular THz and Raman spectra.

A polarizable water model is presented which has been calibrated against experimental THz and Raman spectra of bulk water. These low-frequency spectra directly probe the dynamics, and thereby intermolecular interactions, on time scales relevant to molecular motions. The model is based on the TL4P force field developed recently by Tavan and co-workers [J. Phys. Chem. B 117, 9486 (2013)], which has been designed to be transferable between different environments; in particular, to correctly describe the electrostatic properties of both the isolated water molecule in the gas-phase and the liquid water at ambient conditions. Following this design philosophy, TL4P was amended with charge transfer across hydrogen-bonded dimers as well as an anisotropic polarizability in order to correctly reproduce the THz and Raman spectra. The thermodynamic and structural properties of the new model are of equal quality as those of TL4P, and at the same time, an almost quantitative agreement with the spectroscopic data could be achieved. Since TL4P is a rigid model with a single polarizable site, it is computationally very efficient, while the numerical overhead for the addition of charge transfer and the anisotropic polarizability is minor. Overall, the model is expected to be well suited for, e.g., large scale simulations of 2D-Raman-THz spectra or biomolecular simulations.

Benchmark of ReaxFF force field for subcritical and supercritical water.

Water in the subcritical and supercritical states has remarkable properties that make it an excellent solvent for oxidation of hazardous chemicals, waste separation, and green synthesis. Molecular simulations are a valuable complement to experiments in order to understand and improve the relevant sub- and super-critical reaction mechanisms. Since water molecules under these conditions can act not only as a solvent but also as a reactant, dissociative force fields are especially interesting to investigate these processes. In this work, we evaluate the capacity of the ReaxFF force field to reproduce the microstructure, hydrogen bonding, dielectric constant, diffusion, and proton transfer of sub- and super-critical water. Our results indicate that ReaxFF is able to simulate water properties in these states in very good quantitative agreement with the existing experimental data, with the exception of the static dielectric constant that is reproduced only qualitatively.

Unexpected finite size effects in interfacial systems: Why bigger is not always better-Increase in uncertainty of surface tension with bulk phase width.

We present an unexpected finite size effect affecting interfacial molecular simulations that is proportional to the width-to-surface-area ratio of the bulk phase Ll/A. This finite size effect has a significant impact on the variance of surface tension values calculated using the virial summation method. A theoretical derivation of the origin of the effect is proposed, giving a new insight into the importance of optimising system dimensions in interfacial simulations. We demonstrate the consequences of this finite size effect via a new way to estimate the surface energetic and entropic properties of simulated air-liquid interfaces. Our method is based on macroscopic thermodynamic theory and involves comparing the internal energies of systems with varying dimensions. We present the testing of these methods using simulations of the TIP4P/2005 water forcefield and a Lennard-Jones fluid model of argon. Finally, we provide suggestions of additional situations, in which this finite size effect is expected to be significant, as well as possible ways to avoid its impact.

Force Field for Water Based on Neural Network.

We developed a novel neural network-based force field for water based on training with high-level ab initio theory. The force field was built based on an electrostatically embedded many-body expansion method truncated at binary interactions. The many-body expansion method is a common strategy to partition the total Hamiltonian of large systems into a hierarchy of few-body terms. Neural networks were trained to represent electrostatically embedded one-body and two-body interactions, which require as input only one and two water molecule calculations at the level of ab initio electronic structure method CCSD/aug-cc-pVDZ embedded in the molecular mechanics water environment, making it efficient as a general force field construction approach. Structural and dynamic properties of liquid water calculated with our force field show good agreement with experimental results. We constructed two sets of neural network based force fields: nonpolarizable and polarizable force fields. Simulation results show that the nonpolarizable force field using fixed TIP3P charges has already behaved well, since polarization effects and many-body effects are implicitly included due to the electrostatic embedding scheme. Our results demonstrate that the electrostatically embedded many-body expansion combined with neural network provides a promising and systematic way to build next-generation force fields at high accuracy and low computational costs, especially for large systems.

Bulk viscosity of molecular fluids.

The bulk viscosity of molecular models of gases and liquids is determined by molecular simulations as a combination of a dilute gas contribution, arising due to the relaxation of internal degrees of freedom, and a configurational contribution, due to the presence of intermolecular interactions. The dilute gas contribution is evaluated using experimental data for the relaxation times of vibrational and rotational degrees of freedom. The configurational part is calculated using Green-Kubo relations for the fluctuations of the pressure tensor obtained from equilibrium microcanonical molecular dynamics simulations. As a benchmark, the Lennard-Jones fluid is studied. Both atomistic and coarse-grained force fields for water, CO2, and n-decane are considered and tested for their accuracy, and where possible, compared to experimental data. The dilute gas contribution to the bulk viscosity is seen to be significant only in the cases when intramolecular relaxation times are in the μs range, and for low vibrational wave numbers (<1000 cm-1); This explains the abnormally high values of bulk viscosity reported for CO2. In all other cases studied, the dilute gas contribution is negligible and the configurational contribution dominates the overall behavior. In particular, the configurational term is responsible for the enhancement of the bulk viscosity near the critical point.

Force Field for Water over Pt(111): Development, Assessment, and Comparison.

Metal/water interfaces are key in many natural and industrial processes, such as corrosion, atmospheric, or environmental chemistry. Even today, the only practical approach to simulate large interfaces between a metal and water is to perform force-field simulations. In this work, we propose a novel force field, GAL17, to describe the interaction of water and a Pt(111) surface. GAL17 builds on three terms: (i) a standard Lennard-Jones potential for the bonding interaction between the surface and water, (ii) a Gaussian term to improve the surface corrugation, and (iii) two terms describing the angular dependence of the interaction energy. The 12 parameters of this force field are fitted against a set of 210 adsorption geometries of water on Pt(111). The performance of GAL17 is compared to several other approaches that have not been validated against extensive first-principles computations yet. Their respective accuracy is evaluated on an extended set of 802 adsorption geometries of H2O on Pt(111), 52 geometries derived from icelike layers, and an MD simulation of an interface between a c(4 × 6) Pt(111) surface and a water layer of 14 Å thickness. The newly developed GAL17 force field provides a significant improvement over previously existing force fields for Pt(111)/H2O interactions. Its well-balanced performance suggests that it is an ideal candidate to generate relevant geometries for the metal/water interface, paving the way to a representative sampling of the equilibrium distribution at the interface and to predict solvation free energies at the solid/liquid interface.