168 research outputs found
From dimers to the solid-state: Distributed intermolecular force-fields for pyridine
A.A. thanks A.W.E. financial support through the EngDoc studentship from M3S Centre for Doctoral Training (EPSRC Grant No. EP/G036675/1). General computational infrastructure used is developed under No. EPSRC EP/K039229/1
Quasi Harmonic Lattice Dynamics and Molecular Dynamics calculations for the Lennard-Jones solids
We present Molecular Dynamics (MD), Quasi Harmonic Lattice Dynamics (QHLD)
and Energy Minimization (EM) calculations for the crystal structure of Ne, Ar,
Kr and Xe as a function of pressure and temperature. New Lennard-Jones (LJ)
parameters are obtained for Ne, Kr and Xe to reproduce the experimental
pressure dependence of the density. We employ a simple method which combines
results of QHLD and MD calculations to achieve densities in good agreement with
experiment from 0 K to melting. Melting is discussed in connection with
intrinsic instability of the solid as given by the QHLD approximation. (See
http://www.fci.unibo.it/~valle for related papers)Comment: 7 pages, 5 figures, REVte
To wet or not to wet: that is the question
Wetting transitions have been predicted and observed to occur for various
combinations of fluids and surfaces. This paper describes the origin of such
transitions, for liquid films on solid surfaces, in terms of the gas-surface
interaction potentials V(r), which depend on the specific adsorption system.
The transitions of light inert gases and H2 molecules on alkali metal surfaces
have been explored extensively and are relatively well understood in terms of
the least attractive adsorption interactions in nature. Much less thoroughly
investigated are wetting transitions of Hg, water, heavy inert gases and other
molecular films. The basic idea is that nonwetting occurs, for energetic
reasons, if the adsorption potential's well-depth D is smaller than, or
comparable to, the well-depth of the adsorbate-adsorbate mutual interaction. At
the wetting temperature, Tw, the transition to wetting occurs, for entropic
reasons, when the liquid's surface tension is sufficiently small that the free
energy cost in forming a thick film is sufficiently compensated by the fluid-
surface interaction energy. Guidelines useful for exploring wetting transitions
of other systems are analyzed, in terms of generic criteria involving the
"simple model", which yields results in terms of gas-surface interaction
parameters and thermodynamic properties of the bulk adsorbate.Comment: Article accepted for publication in J. Low Temp. Phy
Formation and removal of alkylthiolate self-assembled monolayers on gold in aqueous solutions
Nanoscale Friction Switches: Friction Modulation of Monomolecular Assemblies Using External Electric Fields
Hybrid approaches to nanometer-scale patterning: Exploiting tailored intermolecular interactions
Water-graphite interaction and behavior of water near the graphite surface
Based on MP2 level electronic structure calculations of the binding energy and lowest energy conformation of waterâacene complexes [Feller, D.; Jordan, K. D. J. Phys. Chem. A 2000, 104 (44), 9971â9975], three waterâgraphite model potentials are suggested and tested in grand canonical Monte Carlo simulations of the behavior of water confined between two parallel graphite sheets. It is shown that the thermodynamics and structure of the waterâgraphite interfacial region are extremely sensitive to the range and orientation dependence of the model potential. This casts doubt on the results of previous molecular dynamics simulations using orientation-independent potentials and standard atomistic force fields. All of the three suggested potentials predict that the water monolayer compressed between two parallel graphite surfaces does not experience capillary evaporation and offers only slight resistance to shear. This explains why water can serve as a lubricant in the friction of graphitic carbons
Computer simulations of water-mediated force between phospholipid membranes
The knowledge of forces operating between phospholipid bilayer membranes in water and aqueous solutions is a prerequisite for understanding membrane-membrane coupling phenomena such as stacking, adhesion, and fusion. This explains the substantial efforts undertaken in the last two decades to measure and rationalize the intermembrane force as a function of separation, with an emphasis on short-range repulsion. Despite considerable progress in experimental measurements, the interpretation of the force-distance curves in terms of physically distinct force components involves serious difficulties because the experiment provides only the total magnitude of the force. All this imparts importance to computer simulations, that allow direct evaluation of the intermembrane force and its components through the respective ensemble averages. In this paper we briefly review these computer simulations, as well as some relevant studies. The simulation results are discussed in the context of the existing theories of the intermembrane forces
Erratum: âLong-ranged solvation forces in a fluid with short-ranged interactionsâ [J. Chem. Phys. 118, 8004 (2003)]
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