How does the electronic continuum model perform in the prediction of the surface tension of salt solutions?

International audienceThe electronic continuum (EC) model uses a scaling of the charges of the ions in order to model implicitly the polarization into nonpolarizable models. This scaling procedure is applied here to two standard nonpolarizable force fields to investigate the salt concentration dependence of the surface tension and density of NaCl aqueous solutions. The composition of the interface and the orientation of the water molecules at the water surface are reported for different combinations of force fields

Etude de l'adsorption d'alcanes dans des zéolithes de type faujasite par simulation moléculaire de Monte Carlo

Résumé françaisRésumé anglaisORSAY-PARIS 11-BU Sciences (914712101) / SudocSudocFranceF

Modeling the Pressure Dependence of Acid Gas plus n-Alkane Interfacial Tensions Using Atomistic Monte Carlo Simulations

International audienceThe dependence of the interfacial tension of binary mixtures composed of acid gases and n-alkanes has been investigated by molecular simulations. Two-phase Monte Carlo (MC) calculations have been performed to predict the interfacial tension of CO2+n-butane, CO2+n-decane, and H2S+n-pentane mixtures at different pressures. The phase densities and phase compositions of these different mixtures have been calculated from both of the two-phase Monte Carlo and Gibbs Ensemble Monte Carlo (GEMC) simulation methods. The comparison among the simulation data, the experimental measurements, and the parachor theory demonstrates the efficiency of molecular simulations for the prediction of the pressure dependence of the interfacial tension for binary mixtures. Such results demonstrate the capability of molecular simulation techniques to complete sets of available experimental data by generating some so-called pseudo-experimental data. Additionally, the molecular description of the interface has shown specific local arrangements of the CO2 at the decane surface

Quantitative prediction of the interface tension of liquid-liquid interfaces through atomistic and coarse-grained models.

International audienceWe report molecular simulations of oil–water liquid–liquid interfaces by using atomistic and coarse grained (CG) MARTINI force fields. We also apply the electronic continuum (EC) model to the MARTINI force field for the calculation of the interfacial tension of oil/water-salt systems. In a first step, we propose to calculate the interfacial tensions using thermodynamic and mechanical definitions of hydrocarbon–water interfacial systems modified by the addition of salts and alcohol. We also establish here the order of magnitude of the long-range corrections to the interfacial tension in fluid–fluid interfaces. Whereas the atomistic models are able to reproduce quantitatively the interfacial tension and the coexisting densities of oil–water systems, the coarse-description shows some deviations in the prediction of the interfacial tensions. Nevertheless, the physical features of these liquid–liquid interfaces are well-captured by this CG description. The CG force field offers then a very challenging alternative that will require however a more developed calibration of the parameters on the basis of liquid–liquid properties

Prediction of the concentration dependence of the surface tension and density of salt solutions : atomistic simulations with polarizable and nonpolarizable models.

International audienceMolecular simulations using polarizable and nonpolarizable models for water and ions are carried out to predict the dependence of the surface tension on salt concentration. The polarizable water and ion models are based on the classical Drude oscillators. The temperature dependence of the surface tension of water is examined for the different water models. The dependence of salt densities on salt concentration is investigated through the nonpolarizable and polarizable models. Lastly, the reproduction of the surface tension of salt solution over a large range of concentration is analyzed through a number of combinations between ions and water force fields. The structure of the interface is then discussed as a function of the polarization effects. We establish here the inability of the polarizable force fields based on the classical Drude oscillators to reproduce the salt concentration dependence of surface tension of NaCl aqueous solutions

Rapport expérimental final des mesures thermodynamiques du projet ANR CAPCO2

Nombres de pages : 145Rapport ANR du SP2 "Absorption par solvants chimiques" / ST21 "Méthodologie pour la recherche de nouveaux solvants

Mesures expérimentales pour définir un solvant permettant la capture du CO2

Communication oral

Adsorption of n-Alkanes in Faujasite Zeolites: Molecular Simulation Study and Experimental Measurements

An application of a previously developed force field for the adsorption of hydrocarbons onto silicalite (Pascual et al. 2003) to linear alkane/sodium faujasite systems is reported. In order to extend this force field from siliceous to cationic zeolites, it is proposed that account be taken of the polarization component of the zeolite-molecule interaction energy. A first-order polarization term is explicitly considered for this purpose, using standard molecular polarizabilities. Polarization appears to amount to 30–40% of the zeolite-alkane interaction energy as a consequence of the strong electric field created by the sodium cation distribution and the negatively charged framework. This approach is compared with the experimental adsorption isotherms of ethane, propane, n-octane and n-decane in NaY taken from the literature and with original measurements of n-butane isotherms in NaY obtained by thermogravimetric methods. Henry constants and heats of adsorption at zero coverage of n-alkanes (n = 6–10) have also been compared with experimental measurements. Although no specific parameter was invoked for extending the force field, general agreement between the simulation results and experiment was satisfactory. Cation redistribution upon alkane adsorption was not observed in these simulations