Molecular dynamics simulation of the effects of temperature on a dense monolayer of long-chain molecules

Hautman, Joseph; Klein, Michael L.

doi:10.1063/1.459423

Cited by 185 publications

(138 citation statements)

References 51 publications

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“…MD simulations suggest a sudden increase in rotational disorder at 200 K along with the onset of conformational disorder as temperature increases [127]. Direct experimental evidence for such a transition is still lacking; however, IR data show a two-sublattice low-temperature structure below 220 K. This simulation suggests a correlation between the rotator phase transition and the appearance of the conformations arising indirectly via the softening of torsional potential and enhanced flexibility of the chain backbone.…”

Section: Molecular Dynamics (Md)mentioning

confidence: 75%

Current understanding of the structure, phase transitions and dynamics of self-assembled monolayers on two- and three-dimensional surfaces

Sandhyarani

Pradeep

2003

International Reviews in Physical Chemistry

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Section: Molecular Dynamics (Md)mentioning

confidence: 75%

Current understanding of the structure, phase transitions and dynamics of self-assembled monolayers on two- and three-dimensional surfaces

Sandhyarani

Pradeep

2003

International Reviews in Physical Chemistry

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“…Molecular dynamics (MD) simulations suggest a sudden increase in rotational disorder at 200 K along with the onset of conformational disorder as temperature increases [47]. Direct experimental evidence for such a transition is still lacking, however, the IR data show a two sublattice low-temperature structure below 220 K. This simulation suggests a correlation between the rotator phase transition and the appearance of the conformations arising indirectly via the softening of torsional potential and enhanced flexibility of the chain backbone.…”

Section: Phase Transitionsmentioning

confidence: 79%

Structure and dynamics of monolayers on planar and cluster surfaces

Pradeep

Sandhyarani

2002

Pure and Applied Chemistry

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Organized molecular assemblies have been one of the intensely pursued areas of contemporary chemistry. Among the various methodologies used to make organized monolayer structures, self-assembled monolayers (SAMs) have been attractive to many materials chemists owing to the simplicity of the preparative method and high stability. Advances in various techniques and their application in the study of SAMs have significantly improved our understanding of these molecular systems. These studies have been further intensified since the successful preparation of stable metal clusters protected with monolayers. This article reviews the structure, temperature-induced phase transitions, and associated dynamics of monolayers, principally in the context of our own work in this area. Alkanethiols on Au (111) and Ag(111) are taken as archetypal systems to discuss the properties of 2D SAMs; studies from our laboratory have been on evaporated thin films. Alkanethiols on Au and Ag cluster surfaces are taken as examples of 3D SAMs. Although our principal focus will be on alkanethiols, we will touch upon a few other adsorbate systems as well.

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“…22 Of course, we are unable to completely distinguish whether this enhancement of the freezing is a kinetic or an equilibrium phenomenon because there is no computation of the freezing points of the alkanes modeled using these potentials.…”

Section: (B)mentioning

confidence: 99%

Thin films of n-octane confined between parallel solid surfaces: structure and adhesive forces vs film thickness from molecular dynamics simulations

Wang¹,

Hill²,

Harris³

1993

J. Phys. Chem.

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Molecular fluids in confined spaces exhibit behavior that cannot be properly described by continuum theories. We examine the structure of n-octane confined between crystalline surfaces and in equilibrium with the bulk liquid at 1 atm and 297 K using molecular dynamics simulations of a chemically realistic model of the molecules.We also compute the solvation forces acting upon the surfaces as a function of their separation. The films are studied between solid surfaces separated by gaps of 1 .O-2.4 nm. At 297 K, all films exhibit liquid-like dynamics and are strongly layered, although the sharpness of the layering oscillates with gap size. In addition, the solvation forces are oscillatory functions of the surface separations. An especially interesting anomaly appears at a gap size of 1.25 nm, barely enough to allow the molecules to extend lengthwise from one surface to the other. There is a strong tendency of the molecules to orient themselves normal to the solid surfaces, in contrast to molecules in other gap sizes and in similar systems studied by other researchers. Furthermore, the film readily freezes to a solid monolayer when cooled to 250 K in contrast to the 1 .S-nm-thick film which remains a liquid at that temperature. IntroductionIn problems ranging from adsorption to adhesion and lubrication, one often encounters situations in which molecular liquids are confined to regions with length scales of the order of only a few molecular diameters. In such situations, experimental evidence suggests that the normal continuum treatments of liquids break down, and a molecular level view is needed to understand the behavior of the fluids.One class of experiments which illustrates the importance of such situations to adhesion and forces between particles in a colloidal suspension is adhesive force measurements with the surface force apparatus.' In a typical surface force apparatus experiment, two cylindrical surfaces formed by bending perfectly cleaved mica sheets around the face of a cylinder are immersed in the liquid with their long axes perpendicular to each other. Sensitive equipment controls the forces acting upon the sheets while interferometry is used to measure the length of the narrowest section of the gap between the cylinders. Because the radii of curvature of the cylinders are much larger than the size of the gap, at a molecular level the walls of the gap appear as two flat surfaces-forming a geometry known to many as a "slit pore".The idealized "slit pore" is bounded by two flat surfaces of infinite area separated by a distance referred to as a pore width. Hence, simulations or theories of fluids in slit pores are often used to model these systems as well as adsorption phenomena. Many of the earlier simulations and theories of fluids in such pores are reviewed in a recent article by Evans.2For small spherical molecules, simulations indicate that when the pore width is less than about five atomic diameters, the molecules order in layers perpendicular to the sheets.2-5 Density functional and integral equati...

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Molecular dynamics simulation of the effects of temperature on a dense monolayer of long-chain molecules

Cited by 185 publications

References 51 publications

Current understanding of the structure, phase transitions and dynamics of self-assembled monolayers on two- and three-dimensional surfaces

Current understanding of the structure, phase transitions and dynamics of self-assembled monolayers on two- and three-dimensional surfaces

Structure and dynamics of monolayers on planar and cluster surfaces

Thin films of n-octane confined between parallel solid surfaces: structure and adhesive forces vs film thickness from molecular dynamics simulations

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