262 results found
Brumby PE, Wensink HH, Haslam AJ, et al., 2017, Structure and Interfacial Tension of a Hard-Rod Fluid in Planar Confinement., Langmuir
The structural properties and interfacial tension of a fluid of rodlike hard-spherocylinder particles in contact with hard structureless flat walls are studied by means of Monte Carlo simulation. The calculated surface tension between the rod fluid and the substrate is characterized by a nonmonotonic trend as a function of the bulk concentration (density) over the range of isotropic bulk concentrations. As suggested by earlier theoretical studies, a surface-ordering scenario is confirmed by our simulations: the local orientational order close to the wall changes from uniaxial to biaxial nematic when the bulk concentration reaches about 85% of the value at the onset of the isotropic-nematic phase transition. The surface ordering coincides with a wetting transition whereby the hard wall is wetted by a nematic film. Accurate values of the fluid-solid surface tension, the adsorption, and the average particle-wall contact distance are reported (over a broad range of densities into the dense nematic region for the first time), which can serve as a useful benchmark for future theoretical and experimental studies on confined rod fluids. The simulation data are supplemented with predictions from second-virial density functional theory, which are in good qualitative agreement with the simulation results.
Headen TF, Boek ES, Jackson G, et al., 2017, Simulation of Asphaltene Aggregation through Molecular Dynamics: Insights and Limitations, ENERGY & FUELS, Vol: 31, Pages: 1108-1125, ISSN: 0887-0624
Hutacharoen P, Dufal S, Papaioannou V, et al., 2017, Predicting the Solvation of Organic Compounds in Aqueous Environments: From Alkanes and Alcohols to Pharmaceuticals, Industrial & Engineering Chemistry Research, Vol: 56, Pages: 10856-10876, ISSN: 0888-5885
Jimenez-Serratos G, Herdes C, Haslam AJ, et al., 2017, Group Contribution Coarse-Grained Molecular Simulations of Polystyrene Melts and Polystyrene Solutions in Alkanes Using the SAFT-gamma Force Field, MACROMOLECULES, Vol: 50, Pages: 4840-4853, ISSN: 0024-9297
Schoen M, Haslam AJ, Jackson G, 2017, Perturbation Theory versus Thermodynamic Integration. Beyond a Mean-Field Treatment of Pair Correlations in a Nematic Model Liquid Crystal., Langmuir
The phase behavior and structure of a simple square-well bulk fluid with anisotropic interactions is described in detail. The orientation dependence of the intermolecular interactions allows for the formation of a nematic liquid-crystalline phase in addition to the more conventional isotropic gas and liquid phases. A version of classical density functional theory (DFT) is employed to determine the properties of the model, and comparisons are made with the corresponding data from Monte Carlo (MC) computer simulations in both the grand canonical and canonical ensembles, providing a benchmark to assess the adequacy of the DFT results. A novel element of the DFT approach is the assumption that the structure of the fluid is dominated by intermolecular interactions in the isotropic fluid. A so-called augmented modified mean-field (AMMF) approximation is employed accounting for the influence of anisotropic interactions. The AMMF approximation becomes exact in the limit of vanishing density. We discuss advantages and disadvantages of the AMMF approximation with respect to an accurate description of isotropic and nematic branches of the phase diagram, the degree of orientational order, and orientation-dependent pair correlations. The performance of the AMMF approximations is found to be good in comparison with the MC data; the AMMF approximation has clear advantages with respect to an accurate and more detailed description of the fluid structure. Possible strategies to improve the DFT are discussed.
Zhao B, Lindeboom T, Benner S, et al., 2017, Predicting the Fluid-Phase Behavior of Aqueous Solutions of ELP (VPGVG) Sequences Using SAFT-VR., Langmuir
The statistical associating fluid theory for potentials of variable range (SAFT-VR) is used to predict the fluid phase behavior of elastin-like polypeptide (ELP) sequences in aqueous solution with special focus on the loci of lower critical solution temperatures (LCSTs). A SAFT-VR model for these solutions is developed following a coarse-graining approach combining information from atomistic simulations and from previous SAFT models for previously reported relevant systems. Constant-pressure temperature-composition phase diagrams are determined for solutions of (VPGVG)n sequences + water with n = 1 to 300. The SAFT-VR equation of state lends itself to the straightforward calculation of phase boundaries so that complete fluid-phase equilibria can be calculated efficiently. A broad range of thermodynamic conditions of temperature and pressure are considered, and regions of vapor-liquid and liquid-liquid coexistence, including LCSTs, are found. The calculated phase boundaries at low concentrations match those measured experimentally. The temperature-composition phase diagrams of the aqueous ELP solutions at low pressure (0.1 MPa) are similar to those of types V and VI phase behavior in the classification of Scott and van Konynenburg. An analysis of the high-pressure phase behavior confirms, however, that a closed-loop liquid-liquid immiscibility region, separate from the gas-liquid envelope, is present for aqueous solutions of (VPGVG)30; such a phase diagram is typical of type VI phase behavior. ELPs with shorter lengths exhibit both liquid-liquid and gas-liquid regions, both of which become less extensive as the chain length of the ELP is decreased. The strength of the hydrogen-bonding interaction is also found to affect the phase diagram of the (VPGVG)30 system in that the liquid-liquid and gas-liquid regions expand as the hydrogen-bonding strength is decreased and shrink as it is increased. The LCSTs of the mixtures are seen to decrease as the ELP chain length is in
Avendano C, Jackson G, Muller EA, et al., 2016, Assembly of porous smectic structures formed from interlocking high-symmetry planar nanorings, PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, Vol: 113, Pages: 9699-9703, ISSN: 0027-8424
Braga C, Muscatello J, Lau G, et al., 2016, Nonequilibrium study of the intrinsic free-energy profile across a liquid-vapour interface, JOURNAL OF CHEMICAL PHYSICS, Vol: 144, ISSN: 0021-9606
Brand CV, Graham E, Rodriguez J, et al., 2016, On the use of molecular-based thermodynamic models to assess the performance of solvents for CO2 capture processes: monoethanolamine solutions, FARADAY DISCUSSIONS, Vol: 192, Pages: 337-390, ISSN: 1359-6640
Chow YTF, Eriksen DK, Galindo A, et al., 2016, Interfacial tensions of systems comprising water, carbon dioxide and diluent gases at high pressures: Experimental measurements and modelling with SAFT-VR Mie and square-gradient theory, FLUID PHASE EQUILIBRIA, Vol: 407, Pages: 159-176, ISSN: 0378-3812
Chremos A, Forte E, Papaioannou V, et al., 2016, Modelling the phase and chemical equilibria of aqueous solutions of alkanolamines and carbon dioxide using the SAFT-gamma SW group contribution approach, FLUID PHASE EQUILIBRIA, Vol: 407, Pages: 280-297, ISSN: 0378-3812
Eriksen DK, Lazarou G, Galindo A, et al., 2016, Development of intermolecular potential models for electrolyte solutions using an electrolyte SAFT-VR Mie equation of state, MOLECULAR PHYSICS, Vol: 114, Pages: 2724-2749, ISSN: 0026-8976
Gopinath S, Galindo A, Jackson G, et al., 2016, A feasibility-based algorithm for Computer Aided Molecular and Process Design of solvent-based separation systems, 26th European Symposium on Computer Aided Process Engineering (ESCAPE), Publisher: ELSEVIER SCIENCE BV, Pages: 73-78, ISSN: 1570-7946
Gopinath S, Jackson G, Galindo A, et al., 2016, Outer Approximation Algorithm with Physical Domain Reduction for Computer-Aided Molecular and Separation Process Design, AICHE JOURNAL, Vol: 62, Pages: 3484-3504, ISSN: 0001-1541
Herdes C, Forte E, Jackson G, et al., 2016, Predicting the adsorption of n-perfluorohexane in BAM-P109 standard activated carbon by molecular simulation using SAFT-gamma Mie coarse-grained force fields, ADSORPTION SCIENCE & TECHNOLOGY, Vol: 34, Pages: 64-78, ISSN: 0263-6174
Jackson G, 2016, Untitled, MOLECULAR PHYSICS, Vol: 114, Pages: 3420-3425, ISSN: 0026-8976
Lobanova O, Mejia A, Jackson G, et al., 2016, SAFT-gamma force field for the simulation of molecular fluids 6: Binary and ternary mixtures comprising water, carbon dioxide, and n-alkanes, JOURNAL OF CHEMICAL THERMODYNAMICS, Vol: 93, Pages: 320-336, ISSN: 0021-9614
Morgado P, Lobanova O, Muller EA, et al., 2016, SAFT-gamma force field for the simulation of molecular fluids: 8. Hetero-segmented coarse-grained models of perfluoroalkylalkanes assessed with new vapour-liquid interfacial tension data, MOLECULAR PHYSICS, Vol: 114, Pages: 2597-2614, ISSN: 0026-8976
Papadopoulos AI, Badr S, Chremos A, et al., 2016, Computer-aided molecular design and selection of CO2 capture solvents based on thermodynamics, reactivity and sustainability, MOLECULAR SYSTEMS DESIGN & ENGINEERING, Vol: 1, Pages: 313-334, ISSN: 2058-9689
Papaioannou V, Calado F, Lafitte T, et al., 2016, Application of the SAFT-gamma Mie group contribution equation of state to fluids of relevance to the oil and gas industry, FLUID PHASE EQUILIBRIA, Vol: 416, Pages: 104-119, ISSN: 0378-3812
Sadeqzadeh M, Papaioannou V, Dufal S, et al., 2016, The development of unlike induced association-site models to study the phase behaviour of aqueous mixtures comprising acetone, alkanes and alkyl carboxylic acids with the SAFT-gamma Mie group contribution methodology, FLUID PHASE EQUILIBRIA, Vol: 407, Pages: 39-57, ISSN: 0378-3812
Smit B, Styring P, Wilson G, et al., 2016, Modelling - from molecules to megascale: general discussion, FARADAY DISCUSSIONS, Vol: 192, Pages: 493-509, ISSN: 1359-6640
Burger J, Papaioannou V, Gopinath S, et al., 2015, A hierarchical method to integrated solvent and process design of physical CO2 absorption using the SAFT- Mie approach, AICHE JOURNAL, Vol: 61, Pages: 3249-3269, ISSN: 0001-1541
Dufal S, Lafitte T, Galindo A, et al., 2015, Developing intermolecular-potential models for use with the SAFT-VRMie equation of state, AIChE Journal, Vol: 61, Pages: 2891-2912, ISSN: 0001-1541
A major advance in the statistical associating fluid theory (SAFT) for potentials of variable range (SAFT-VR) has recently been made with the incorporation of the Mie (generalized Lennard–Jones [LJ]) interaction between the segments comprising the molecules in the fluid (Lafitte et al. J. Chem. Phys. 2013;139:154504). The Mie potential offers greater versatility in allowing one to describe the softness/hardness of the repulsive interactions and the range of the attractions, which govern fine details of the fluid-phase equilibria and thermodynamic derivative properties of the system. In our current work, the SAFT-VR Mie equation of state is employed to develop models for a number of prototypical fluids, including some of direct relevance to the oil and gas industry: methane, carbon dioxide and other light gases, alkanes, alkyl benzenes, and perfluorinated compounds. A complication with the use of more-generic force fields such as the Mie potential is the additional number of parameters that have to be considered to specify the interactions between the model molecules, leading to a degree of degeneracy in the parameter space. A formal methodology to isolate intermolecular-potential models and assess the adequacy of the description of the thermodynamic properties in terms of the complex parameter space is developed. Fluid-phase equilibrium properties (the vapor pressure and saturated-liquid density) are chosen as the target properties in the refinement of the force fields; the predictive capability for other properties such as the enthalpy of vaporization, single-phase density, speed of sound, isobaric heat capacity, and Joule–Thomson coefficient, is appraised. It is found that an overall improvement of the representations of the thermophysical properties of the fluids is obtained using the more-generic Mie form of interaction; in all but the simplest of fluids, one finds that the LJ interaction is not the most appropriate.
Dufal S, Lafitte T, Haslam AJ, et al., 2015, The A in SAFT: developing the contribution of association to the Helmholtz free energy within a Wertheim TPT1 treatment of generic Mie fluids, MOLECULAR PHYSICS, Vol: 113, Pages: 948-984, ISSN: 0026-8976
Gopinath S, Galindo A, Jackson G, et al., 2015, Computer aided molecular and process design using complex process and thermodynamic models: A screening based approach, Pages: 107-109
Copyright © American Institute of Chemical Engineers. All rights reserved. The design of optimal processing materials (molecules) and optimal process variables for a given process is referred to as Computer Aided Molecular and Process Design (CAMPD). Processing materials used to achieve process goals include mass separating agents (such as solvents for absorption, extraction, leaching and adsorbents), catalysts, heat transfer fluids and reaction medium solvents. Choosing processing molecules influences the optimal process variables and vice versa. Molecular and process decision variables are linked, interacting with each other in a complex manner. Hence, neither of these decisions can be made in isolation.
Jover J, Galindo A, Jackson G, et al., 2015, Fluid-fluid coexistence in an athermal colloid-polymer mixture: thermodynamic perturbation theory and continuum molecular-dynamics simulation, MOLECULAR PHYSICS, Vol: 113, Pages: 2608-2628, ISSN: 0026-8976
Jover JF, Mueller EA, Haslam AJ, et al., 2015, Aspects of Asphaltene Aggregation Obtained from Coarse-Grained Molecular Modeling, ENERGY & FUELS, Vol: 29, Pages: 556-566, ISSN: 0887-0624
Lau GV, Ford IJ, Hunt PA, et al., 2015, Surface thermodynamics of planar, cylindrical, and spherical vapour-liquid interfaces of water, JOURNAL OF CHEMICAL PHYSICS, Vol: 142, ISSN: 0021-9606
Lau GV, Hunt PA, Mueller EA, et al., 2015, Water droplet excess free energy determined by cluster mitosis using guided molecular dynamics, JOURNAL OF CHEMICAL PHYSICS, Vol: 143, ISSN: 0021-9606
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