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

A non-additive repulsive contribution in an equation of state: The development for homonuclear square well chains equation of state validated against Monte Carlo simulation

International audienceThis work consists of the adaptation of a non-additive hard sphere theory inspired by Malakhov and Volkov, Polym. Sci. Ser. A. 2007;49(6):745-756 to a square-well chain. Using the thermodynamic perturbation theory, an additional term is proposed that describes the effect of perturbing the chain of square well spheres by a non-additive parameter. In order to validate this development, NPT Monte Carlo simulations of thermodynamic and structural properties of the non-additive square well (NASW) for a pure chain and a binary mixture of chains are performed. Good agreements are observed between the compressibility factor originating from the theory and those from molecular simulations

Role of Impurities on CO2 Injection: Experimental and Numerical Simulations of Thermodynamic Properties of Water-salt-gas Mixtures (CO2 + Co-injected Gases) Under Geological Storage Conditions

International audienceRole of impurities on CO 2 injection: experimental and numerical simulations of thermodynamic properties of water-salt-gas mixtures (CO 2 + co-injected gases) under geological storage conditions Abstract Regarding the hydrocarbon source and CO 2 capture processes, fuel gas from boilers may be accompanied by so-called "annex gases" which could be co-injected in a geological storage. These gases, such as SOx, NOx, or oxygen for instance, are likely to interact with reservoir fluids and rocks and well materials (casing and cement) and could potentially affect the safety of the storage. However, there are currently only few data on the behaviour of such gas mixtures, as well as on their chemical reactivity, especially in the presence of water. One reason for this lack comes from the difficulty in handling because of their dangerousness and their chemical reactivity. Therefore, the purpose of the Gaz Annexes was to develop new experimental and analytical protocols in order to acquire new thermodynamic data on these annex gases, in fine for predicting the behaviour of a geological storage of CO 2 + co-injected gases in the short, medium and long terms. This paper presents Gaz Annexes concerning acquisition of PVT experimental and pseudo-experimental data to adjust and validate thermodynamic models for water / gas / salts mixtures as well as the possible influence of SO 2 and NO on the geological storage of CO 2. The Gaz Annexes s new insights for the establishment of recommendations concerning acceptable content of annex gases

Gas Permeation in Semicrystalline Polyethylene as Studied by Molecular Simulation and Elastic Model

International audience— Perméation de gaz dans le polyéthylène semi-cristallin par simulation moléculaire et modèle élastique — Dans ce travail, nous utilisons la simulation moléculaire pour étudier la perméa-tion de deux gaz (CH 4 et CO 2) dans le polyéthylène. Ces simulations sont conduites à des températures inférieures à la température de fusion du polymère. Bien que dans de telles conditions, le polyéthylène soit à l'état semi-cristallin, des boîtes de simulation contenant exclusivement du polymère amorphe sont utilisées. Dans de précédents travaux [Memari P., Lachet V., Rousseau B. (2010) Polymer 51, 4978], nous avons montré que les effets de la morphologie complexe des matériaux semi-cristallins pouvaient être pris en compte de manière implicite par une contrainte ad-hoc exercée sur la phase amorphe. Dans le présent travail, nous montrons que cette approche peut être mise en oeuvre non seulement pour le calcul de propriétés d'équilibre mais également pour le calcul de propriétés de transport comme les coefficients de diffusion. De plus, en utilisant le modèle élastique de Michaels et Hausslein [Michaels A.S., Hausslein R.W. (1965) J. Polymer Sci. : Part C 10, 61], cette contrainte ad-hoc peut être reliée à la fraction de chaînes qui contribuent au terme d'énergie élastique dans le matériau. Nous constatons que les propriétés de transport dans les régions amorphes sont fortement influencées par cette fraction de chaînes. Abstract — Gas Permeation in Semicrystalline Polyethylene as Studied by Molecular Simulation and Elastic Model — We have employed molecular simulation to study the permeation of two different gases (CH 4 and CO 2) in polyethylene. The simulations have been performed at temperatures below the polymer melting point. Although under such conditions, polyethylene is in a semicrystalline state, we have used simulation boxes containing only a purely amorphous material. We showed in previous works [Memari P., Lachet V., Rousseau B. (2010) Polymer 51, 4978] that the effects of the complex morphology of semicrystalline materials on solubility can be implicitly taken into account by an ad-hoc constraint exerted on the amorphous phase. Here, it has been shown that our method can be applied not only for the calculation of equilibrium properties but also for transport properties like diffusion coefficients. In addition, the ad-hoc constraint has been theoretically related to the fraction of elastically effective chains in the material by making use of Michaels and Hausslein elastic model [Michaels A.S., Hausslein R.W. (1965) J. Polymer Sci.: Part C 10, 61]. We observe that the transport properties in amorphous regions are strongly governed by this fraction of elastically effective chains

Study of thermodynamic properties of U1−y_{1-y}Puy_yO2_2 MOX fuel using classical molecular Monte Carlo simulations

International audienceThe molecular Monte Carlo method, combined with the CRG interatomic potential, is used for the first time to investigate stoichiometric mixed oxides U$_{1-y}$Pu$_y$O$_2$ (with y in the range 0–1). The implementation of this Monte Carlo method for mixed oxides simulation was carried out involving two algorithms, with and without cation exchange. The use of these two Monte Carlo algorithms allowed us to test the effect of the substitutional disorder implied by the coexistence of two types of cations. Structural, thermodynamic, and mechanical properties of the stoichiometric mixed oxides fuel U$_{1-y}$Pu$_y$O$_2$ have been investigated over a wide temperature range (from 300 K to the melting temperature) and plutonium content (from 0 to 100 atom %). Our study shows that the exploration of cationic configurations through the cation exchange algorithm is required for a complete description of the mixed oxides fuel properties, especially for the atomic structural properties. Concerning thermodynamic properties, the evolution of the computed specific heat as a function of temperature exhibits one peak for all plutonium contents around 2300 K, i.e. at $\sim$0.8 T$_m$ (T$_m$ is the melting temperature). The same behavior is observed for the linear thermal expansion coefficient. These peaks, also observed in previous studies, are related to the Bredig transition known to occur around 0.8 T$_m$. A good agreement between our results, experiments, and previous calculations is found for temperatures up to about 2100 K. Above this temperature, our calculations show a behavior different from experimental recommendations

Calculation of the surface tension of cyclic and aromatic hydrocarbons from Monte Carlo simulaitons using the Anisotropic United Atom model

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Calculation of the surface tension of binary mixtures at high pressures from Monte Carlo simulations

Poste

Calculation of the surface tension and its long range corrections

Oral

Monte Carlo simulations of the pressure dependence of the water-acid gas interfacial tensions.

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