Publications
216 results found
Herdes C, Santiso EE, James C, et al., 2015, Modelling the interfacial behaviour of dilute light-switching surfactant solutions, Journal of Colloid and Interface Science, Vol: 445, Pages: 16-23, ISSN: 1095-7103
The direct molecular modelling of an aqueous surfactant system at concentrations below the critical micelle concentration (pre-cmc) conditions is unviable in terms of the presently available computational power. Here, we present an alternative that combines experimental information with tractable simulations to interrogate the surface tension changes with composition and the structural behaviour of surfactants at the water–air interface. The methodology is based on the expression of the surface tension as a function of the surfactant surface excess, both in the experiments and in the simulations, allowing direct comparisons to be made. As a proof-of-concept a coarse-grained model of a light switching non-ionic surfactant bearing a photosensitive azobenzene group is considered at the air–water interface at 298 K. Coarse-grained molecular dynamic simulations are detailed based on the use of the SAFT force field with parameters tuned specifically for this purpose. An excellent agreement is obtained between the simulation predictions and experimental observations; furthermore, the molecular model allows the rationalization of the macroscopic behaviour in terms of the different conformations of the cis and trans surfactants at the surface.
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: 1089-7690
Frentrup H, Hart KE, Colina CM, et al., 2015, In Silico Determination of Gas Permeabilities by Non-Equilibrium Molecular Dynamics: CO2 and He through PIM-1., Membranes, Vol: 5, Pages: 99-119, ISSN: 2077-0375
We study the permeation dynamics of helium and carbon dioxide through an atomistically detailed model of a polymer of intrinsic microporosity, PIM-1, via non-equilibrium molecular dynamics (NEMD) simulations. This work presents the first explicit molecular modeling of gas permeation through a high free-volume polymer sample, and it demonstrates how permeability and solubility can be obtained coherently from a single simulation. Solubilities in particular can be obtained to a very high degree of confidence and within experimental inaccuracies. Furthermore, the simulations make it possible to obtain very specific information on the diffusion dynamics of penetrant molecules and yield detailed maps of gas occupancy, which are akin to a digital tomographic scan of the polymer network. In addition to determining permeability and solubility directly from NEMD simulations, the results shed light on the permeation mechanism of the penetrant gases, suggesting that the relative openness of the microporous topology promotes the anomalous diffusion of penetrant gases, which entails a deviation from the pore hopping mechanism usually observed in gas diffusion in polymers.
Theodorakis PE, Mueller EA, Craster RV, et al., 2015, Superspreading: Mechanisms and Molecular Design, Langmuir, Vol: 31, Pages: 2304-2309, ISSN: 1520-5827
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
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- Citations: 21
Yang J, Serratos MGJ, Fari-Arole DS, et al., 2015, Crude Oil Fouling: Fluid Dynamics, Reactions and Phase Change, IUTAM SYMPOSIUM ON MULTIPHASE FLOWS WITH PHASE CHANGE: CHALLENGES AND OPPORTUNITIES, Vol: 15, Pages: 186-193, ISSN: 2210-9838
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- Citations: 10
Coletti F, Crittenden BD, Haslam AJ, et al., 2015, Modeling of Fouling from Molecular to Plant Scale, CRUDE OIL FOULING: DEPOSIT CHARACTERIZATION, MEASUREMENTS, AND MODELING, Editors: Coletti, Hewitt, Publisher: GULF PROFESSIONAL PUBL, Pages: 179-320, ISBN: 978-0-12-801256-7
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- Citations: 7
Jimenez Serratos MG, Haslam AJ, Jackson G, et al., 2014, 5. Modeling of Fouling from Molecular to Plant Scale5.2 Thermodynamic and Molecular Modeling, Crude Oil Fouling Deposit Characterization, Measurements, and Modeling, Editors: Coletti, Hewitt, Publisher: Gulf Professional Publishing, ISBN: 9780128013595
With production from unconventional rigs continuing to escalate and refineries grappling with the challenges of shale and heavier oil feedstocks, petroleum engineers and refinery managers must ensure that equipment used with today’s crude ...
Jimenez Serratos MG, Haslam AJ, Jackson G, et al., 2014, 5. Modeling of Fouling from Molecular to Plant Scale5.2 Thermodynamic and Molecular Modeling, Crude Oil Fouling Deposit Characterization, Measurements, and Modeling, Editors: coletti, Hewitt, Publisher: Gulf Professional Publishing, ISBN: 9780128013595
With production from unconventional rigs continuing to escalate and refineries grappling with the challenges of shale and heavier oil feedstocks, petroleum engineers and refinery managers must ensure that equipment used with today’s crude ...
Cumicheo C, Cartes M, Segura H, et al., 2014, High-pressure densities and interfacial tensions of binary systems containing carbon dioxide plus <i>n</i>-alkanes: (<i>n</i>-Dodecane, <i>n</i>-tridecane, <i>n</i>-tettadecane), FLUID PHASE EQUILIBRIA, Vol: 380, Pages: 82-92, ISSN: 0378-3812
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- Citations: 59
Muller EA, Braga C, Galindo A, 2014, Nonequilibrium molecular dynamics simulation of diffusion at the liquid-liquid interface, Journal of Chemical Physics, Vol: 141, ISSN: 1089-7690
Molecular Dynamics simulations are performed to study the dynamical properties of molecules in the presence of a liquid-liquid (L/L) interface. In the vicinity of the interface the movement of the particles, coupled with the thermal fluctuations of the interface, can make the evaluation of properties such as the self-diffusion coefficient, particularly difficult. We explore the use of the Evans-Searles Fluctuation Theorem [D. Evans and D. Searles, Phys. Rev. E 50, 1645 (1994)] to obtain dynamical information of molecules in distinct regions of a model L/L system.We demonstrate that it is possible to analyse the effect of the interface on the mobility of molecules using a nonequilibrium approach. This information may provide a valuable insight into the understanding of dynamics of interphase mass transfer.
Mejia A, Cartes M, Segura H, et al., 2014, Use of Equations of State and Coarse Grained Simulations to Complement Experiments: Describing the Interfacial Properties of Carbon Dioxide plus Decane and Carbon Dioxide plus Eicosane Mixtures, JOURNAL OF CHEMICAL AND ENGINEERING DATA, Vol: 59, Pages: 2928-2941, ISSN: 0021-9568
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- Citations: 81
Mueller EA, Jackson G, 2014, Force-field parameters from the SAFT-gamma equation of state for use in coarse-grained molecular simulations, Annual Review of Chemical and Biomolecular Engineering, Vol: 5, Pages: 405-427, ISSN: 1947-5438
A description of fluid systems with molecular-based algebraic equations of state (EoSs) and by direct molecular simulation is common practice in chemical engineering and the physical sciences, but the two approaches are rarely closely coupled. The key for an integrated representation is through a well-defined force field and Hamiltonian at the molecular level. In developing coarse-grained intermolecular potential functions for the fluid state, one typically starts with a detailed, bottom-up quantum-mechanical or atomic-level description and then integrates out the unwanted degrees of freedom using a variety of techniques; an iterative heuristic simulation procedure is then used to refine the parameters of the model. By contrast, with a top-down technique, one can use an accurate EoS to link the macroscopic properties of the fluid and the force-field parameters. We discuss the latest developments in a top-down representation of fluids, with a particular focus on a group-contribution formulation of the statistical associating fluid theory (SAFT-γ). The accurate SAFT-γ EoS is used to estimate the parameters of the Mie force field, which can then be used with confidence in direct molecular simulations to obtain thermodynamic, structural, interfacial, and dynamical properties that are otherwise inaccessible from the EoS. This is exemplified for several prototypical fluids and mixtures, including carbon dioxide, hydrocarbons, perfluorohydrocarbons, and aqueous surfactants.
Mueller EA, Mejia A, 2014, Resolving Discrepancies in the Measurements of the Interfacial Tension for the CO<sub>2</sub> + H<sub>2</sub>O Mixture by Computer Simulation, JOURNAL OF PHYSICAL CHEMISTRY LETTERS, Vol: 5, Pages: 1267-1271, ISSN: 1948-7185
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- Citations: 43
Theodorakis PE, Müller EA, Craster RV, et al., 2014, Insights into surfactant-assisted superspreading, Current Opinion in Colloid & Interface Science, ISSN: 1359-0294
Mejia A, Herdes C, Mueller EA, 2014, Force Fields for Coarse-Grained Molecular Simulations from a Corresponding States Correlation, Industrial & Engineering Chemistry Research, Vol: 53, Pages: 4131-4141, ISSN: 0888-5885
We present a corresponding states correlation based on the description of fluid phase properties by means of an Mie intermolecular potential applied to tangentially bonded spheres. The macroscopic properties of this model fluid are very accurately represented by a recently proposed version of the Statistical Associating Fluid Theory (the SAFT-γ version). The Mie potential can be expressed in a conformal manner in terms of three parameters that relate to a length scale, σ, an energy scale, ε, and the range or functional form of the potential, λ, while the nonsphericity or elongation of a molecule can be appropriately described by the chain length, m. For a given chain length, correlations are given to scale the SAFT equation of state in terms of three experimental parameters: the acentric factor, the critical temperature, and the saturated liquid density at a reduced temperature of 0.7. The molecular nature of the equation of state is exploited to make a direct link between the macroscopic thermodynamic parameters used to characterize the equation of state and the parameters of the underlying Mie potential. This direct link between macroscopic properties and molecular parameters is the basis to propose a top-down method to parametrize force fields that can be used in the coarse grained molecular modeling (Monte Carlo or molecular dynamics) of fluids. The resulting correlation is of quantitative accuracy and examples of the prediction of simulations of vapor–liquid equilibria and interfacial tensions are given. In essence, we present a recipe that allows one to obtain intermolecular potentials for use in the molecular simulation of simple and chain fluids from macroscopic experimentally determined constants, namely the acentric factor, the critical temperature, and a value of the liquid density at a reduced temperature of 0.7.
Wu L, Mueller EA, Jackson G, 2014, Understanding and Describing the Liquid-Crystalline States of Polypeptide Solutions: A Coarse-Grained Model of PBLG in DMF, MACROMOLECULES, Vol: 47, Pages: 1482-1493, ISSN: 0024-9297
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- Citations: 14
Papaioannou V, Lafitte T, Avendano C, et al., 2014, Group contribution methodology based on the statistical associating fluid theory for heteronuclear molecules formed from Mie segments, Journal of Chemical Physics, Vol: 140, ISSN: 0021-9606
A generalization of the recent version of the statistical associating fluid theory for variable range Mie potentials [Lafitte et al., J. Chem. Phys. 139, 154504 (2013)] is formulated within the framework of a group contribution approach (SAFT-γ Mie). Molecules are represented as comprising distinct functional (chemical) groups based on a fused heteronuclear molecular model, where the interactions between segments are described with the Mie (generalized Lennard-Jonesium) potential of variable attractive and repulsive range. A key feature of the new theory is the accurate description of the monomeric group-group interactions by application of a high-temperature perturbation expansion up to third order. The capabilities of the SAFT-γ Mie approach are exemplified by studying the thermodynamic properties of two chemical families, the n-alkanes and the n-alkyl esters, by developing parameters for the methyl, methylene, and carboxylate functional groups (CH3, CH2, and COO). The approach is shown to describe accurately the fluid-phase behavior of the compounds considered with absolute average deviations of 1.20% and 0.42% for the vapor pressure and saturated liquid density, respectively, which represents a clear improvement over other existing SAFT-based group contribution approaches. The use of Mie potentials to describe the group-group interaction is shown to allow accurate simultaneous descriptions of the fluid-phase behavior and second-order thermodynamic derivative properties of the pure fluids based on a single set of group parameters. Furthermore, the application of the perturbation expansion to third order for the description of the reference monomeric fluid improves the predictions of the theory for the fluid-phase behavior of pure components in the near-critical region. The predictive capabilities of the approach stem from its formulation within a group-contribution formalism: predictions of the fluid-phase behavior and thermodynamic derivative propert
Müller E, 2014, Editorial, Adsorption Science and Technology, Vol: 32, ISSN: 0263-6174
Jackson G, Galindo A, Adjiman CS, et al., 2014, Employing a SAFT equation of state to obtain force fields for use in coarse-grained molecular simulations, Pages: 1231-1232
Forte E, Haslam AJ, Jackson G, et al., 2014, Effective coarse-grained solid-fluid potentials and their application to model adsorption of fluids on heterogeneous surfaces, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, Vol: 16, Pages: 19165-19180, ISSN: 1463-9076
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- Citations: 32
Mueller EA, 2014, Adsorption Science & Technology Interface Science for Advanced Materials & Technologies, ADSORPTION SCIENCE & TECHNOLOGY, Vol: 32, Pages: I-II, ISSN: 0263-6174
Lafitte T, Apostolakou A, Avendano C, et al., 2013, Accurate statistical associating fluid theory for chain molecules formed from Mie segments, JOURNAL OF CHEMICAL PHYSICS, Vol: 139, ISSN: 0021-9606
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- Citations: 347
Lu L, Wang S, Muller EA, et al., 2013, Adsorption and separation of CO2/CH4 mixtures using nanoporous adsorbents by molecular simulation, Fluid Phase Equilibria, Vol: 362, Pages: 227-234, ISSN: 0378-3812
A grand canonical Monte Carlo-simulation (GCMC) study is presented focussing on the adsorption of CO2/CH4 mixtures in different nanopore models, including pristine mesoporous carbons, carbon foams, carbon nanotubes (CNTs), and nanopore models modified with hydrophilic carboxylic groups. We also report and discuss the selectivity of the different adsorbent surfaces under a wide range of temperature and pressure. Our results show that foam structures have the highest adsorption capacity of all the pristine structures studied because of its special architecture. The selectivity markedly enhanced after modification, especially at low pressures, and modified CNTs are found to have the highest selectivity among all the models tested. The effect of temperature and pressure is evaluated and the change in the selectivity trends of modified nanopore models are in contrast to that of the pristine models. The results suggest that the separation performance in carbon nanopores is greatly affected by the nature of the architecture and the heterogeneity of the materials. These findings could be beneficial in conventional pressure swing adsorption processes and the nanoporous structures could be used as parts of mixed polymer membranes. The results of this work present some guidelines for the designing nanoporous structures in order to achieve optimal separation of CO2/CH4 mixtures.
Long Y, Palmer JC, Coasne B, et al., 2013, On the molecular origin of high-pressure effects in nanoconfinement: The role of surface chemistry and roughness, JOURNAL OF CHEMICAL PHYSICS, Vol: 139, ISSN: 0021-9606
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- Citations: 58
Santiso EE, Herdes C, Mueller EA, 2013, On the Calculation of Solid-Fluid Contact Angles from Molecular Dynamics, ENTROPY, Vol: 15, Pages: 3734-3745
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- Citations: 62
Dominguez H, Haslam AJ, Jackson G, et al., 2013, Modelling and understanding of the vapour-liquid and liquid-liquid interfacial properties for the binary mixture of <i>n</i>-heptane and perfluoro-<i>n</i>-hexane, JOURNAL OF MOLECULAR LIQUIDS, Vol: 185, Pages: 36-43, ISSN: 0167-7322
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- Citations: 9
Wu L, Jackson G, Mueller EA, 2013, Liquid Crystal Phase Behaviour of Attractive Disc-Like Particles, INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES, Vol: 14, Pages: 16414-16442, ISSN: 1661-6596
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- Citations: 10
Herdes C, Prosenjak C, Roman S, et al., 2013, Fundamental Studies of Methyl Iodide Adsorption in DABCO Impregnated Activated Carbons, LANGMUIR, Vol: 29, Pages: 6849-6855, ISSN: 0743-7463
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- Citations: 13
Mueller EA, 2013, Purification of water through nanoporous carbon membranes: a molecular simulation viewpoint, CURRENT OPINION IN CHEMICAL ENGINEERING, Vol: 2, Pages: 223-228, ISSN: 2211-3398
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- Citations: 26
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