Molecular dynamics investigation of a Newtonian black film

Gamba, Z.; Hautman, Joseph; Shelley, John C.; Klein, Michael L.

doi:10.1021/la00048a050

Cited by 50 publications

(44 citation statements)

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“…It should be pointed out, however, that alternative and more sophisticated models for simulations ͑which do take the molecular nature of the solvent into account͒ have also been used to investigate EDL properties since the early 1990s. [36][37][38][39][40] …”

Section: Model and Simulation Methodsmentioning

confidence: 99%

Effect of the surface charge discretization on electric double layers: A Monte Carlo simulation study

Madurga

Vilaseca

Mas

et al. 2007

The Journal of Chemical Physics

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The structure of the electric double layer in contact with discrete and continuously charged planar surfaces is studied within the framework of the primitive model through Monte Carlo simulations. Three different discretization models are considered together with the case of uniform distribution. The effect of discreteness is analyzed in terms of charge density profiles. For point surface groups, a complete equivalence with the situation of uniformly distributed charge is found if profiles are exclusively analyzed as a function of the distance to the charged surface. However, some differences are observed moving parallel to the surface. Significant discrepancies with approaches that do not account for discreteness are reported if charge sites of finite size placed on the surface are considered.

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Section: Model and Simulation Methodsmentioning

confidence: 99%

Effect of the surface charge discretization on electric double layers: A Monte Carlo simulation study

Madurga

Vilaseca

Mas

et al. 2007

The Journal of Chemical Physics

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“…Several works have reported classical computer simulation investigations of SDS black film foams 10,18,[21][22][23][24][25] . Simulation studies indicate that the equilibrium film contains between two and four water molecules per surfactant, and between two and three of these molecules are part of a solvation layer.…”

Section: Introductionmentioning

confidence: 99%

Electronic structure computations of Newton Black Films

Bresme

Artacho

2010

J. Mater. Chem.

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We investigate using quantum density functional theory (DFT) the electronic structure of sodium dodecyl sulfate Newton Black Films (NBF), consisting of water sandwiched between surfactants surrounded by vacuum. We generate a classical trajectory of the film using full-atom empirical potentials. DFT theory is employed to investigate the electron density and electrostatic properties of the film. The electrostatic potential derived directly from the electron and nuclear densities shows an important drop towards the vacuum side, similar to recent findings for the water-vacuum interface. We discuss the physical significance of this potential drop. We also consider as an alternative definition of the electrostatic potential, the deformation charge potential (DCP), to quantify the electrostatic properties of the interfaces. The analysis of the DCP potential indicates there is charge separation at the surfactant alkyl tails, showing that the surfactant-vacuum surface has an excess of positive charge. This result is consistent with molecular dynamics simulations employing classical force-fields, which incorporate partial charges to model the surfactant alkyl chain. The DCP potential also gives evidence for the existence of electronic polarization in the hydrophobic region of the NBF, whose origin is connected to charge transfer between the surfactant tails and the head group. We suggest that the deformation charge potential provides a route to compare the electrostatic potentials obtained from DFT and emprirical computations. This idea is illustrated by computing the electrostatic potential of the water-vapor interface. We discuss the relevance of these results in the context of DFT computations of soft interfaces.

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“…Although in this context we expect molecular modeling approaches such as molecular dynamics (MD) and Monte Carlo (MC) simulations to take an important role to provide atomistic or molecular details of NBF, just a few pioneering MD studies have been reported for foam (thin liquid film) systems: [17][18][19][20] Klein and co-workers 17 reported the first MD study on the SDSmediated NBF in which the simulated film structures are found in a good agreement with the X-ray reflectivity experiments; Weng et al 18 investigated a Lennard-Jones liquid thin film using MD simulation and discussed that the surface tension distribution is affected by the film thickness. The first disjoining pressure-thickness isotherm was reported by Radke and coworkers for the Lennard-Jones thin film 19 and water thin film, 20 discussing the Lifshitz theory in comparison with their simulations.…”

Section: Introductionmentioning

confidence: 99%

Structures and Properties of Newton Black Films Characterized Using Molecular Dynamics Simulations

2006

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We used molecular dynamics (MD) simulations to investigate the structures and properties of Newton black films (NBF) for several surfactants: sodium dodecyl sulfate (SDS), cetyltrimethylammonium bromide (C16TAB), and surfactin using film thicknesses up to 10 nm. By calculating the interface formation energy for various packing conditions on the surface pressure-area isotherm, we found that the most probable surface concentration is ∼42 Å 2 /molecule for SDS and C16TAB and ∼170 Å 2 /molecule for surfactin. We then used this most probable concentration of each surfactant to simulate NBF with various film thicknesses. From analyzing the disjoining pressure-film thickness isotherms with the density profiles and the solvation coordination number, we found that the increase of the disjoining pressure during the film thinning was coupled with the change in inner structure of the NBF (i.e., density profile and the solvation of ionic entities). In the range of film thicknesses less than ∼30 Å, the disjoining pressures for the SDS and C16TAB were found to be larger than that of the surfactin. We predicted the Gibbs elasticity (175 dyn/cm for surfactin; 109 dyn/cm for C16TAB; 38 dyn/cm for SDS) required to assess the stability of NBF against surface concentration fluctuations, and the shear modulus (6.5 GPa for the surfactin; 6.1 GPa for the C16TAB; 3.5 GPa for the SDS) and the yield stress (∼0.8 GPa for surfactin; ∼0.8 GPa for C16TAB; ∼0.4 GPa for the SDS) to assess the mechanical stability against the externally imposed mechanical perturbation.

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Molecular dynamics investigation of a Newtonian black film

Cited by 50 publications

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Effect of the surface charge discretization on electric double layers: A Monte Carlo simulation study

Effect of the surface charge discretization on electric double layers: A Monte Carlo simulation study

Electronic structure computations of Newton Black Films

Structures and Properties of Newton Black Films Characterized Using Molecular Dynamics Simulations

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