Michel Mareschal

Microscopic simulations of complex hydrodynamic phenomena

Introduction: From Fluid Particles to Physical Particles M. Mareschal, B.L. Holian. Non-Equilibrium Molecular Dynamics: Theoretical Foundation and Rheological Application of NonEquilibrium Molecular Dynamics G. Ciccotti, et al. Lattice Gases: Lattice Boltzmann Simulation of High Reynolds Number Fluid Flow in Two Dimensions G. McNamara, B.J. Alder. Other Simulation Methods: A Contemporary Implementation of the Direct Simulation Monte Carlo Method G.A. Bird. Chaos, Turbulence, and Irreversibility: Lyapunov Exponents and Bulk Transport Coefficients D. Evans, et al. Related Topics: Statistical Fracture Mechanics A. Chudnovsky, B. Kunin. Recollections: The Long Time Tail Story B.J. Adler. 22 additional articles. Index.

Bridging time scales : molecular simulations for the next decade

Protein Folding.- Sidechain Dynamics and Protein Folding.- Applications of Statistical Mechanics to Biological Systems.- A Coarse Grain Model for Lipid Monolayer and Bilayer Studies.- Polymer Structure and Dynamics.- Variable-Connectivity Monte Carlo Algorithms for the Atomistic Simulation of Long-Chain Polymer Systems.- Bridging the Time Scale Gap: How Does Foldable Polymer Navigate Its Conformation Space?.- Multiscale Computer Simulations for Polymeric Materials in Bulk and Near Surfaces.- Complex and Mesoscopic Fluids.- Effective Interactions for Large-Scale Simulations of Complex Fluids.- Slow Dynamics and Reactivity.- Simulation of Models for the Glass Transition: Is There Progress?.- Lattice Models.- Monte Carlo Methods for Bridging the Timescale Gap.- Go-with-the-Flow Lattice Boltzmann Methods for Tracer Dynamics.- Multiscale Modelling in Materials Science.- Atomistic Simulations of Solid Friction.- Methodological Developments in MD and MC.- Bridging the Time Scale Gap with Transition Path Sampling.- The Stochastic Difference Equation as a Tool to Compute Long Time Dynamics.- Numerical Simulations of Molecular Systems with Long Range Interactions.- Perpectives in ab initio MD.- New Developments in Plane-Wave Based ab initio Calculations.- Time and Length Scales in ab initio Molecular Dynamics.- Quantum Simulations.- A Statistical Mechanical Theory of Quantum Dynamics in Classical Environments.- The Coupled Electronic-Ionic Monte Carlo Simulation Method.

Computer modeling of a liquid–liquid interface

Molecular dynamics method and Lennard‐Jones potential functions are employed to model liquid–liquid interfaces. The simulations are carried out in a range of temperature and pressure near the triple point. The investigated systems are symmetric and composed of two identical liquids L1 and L2. The interactions between the atoms of L1 and L2 are obtained from modified Lennard‐Jones potential functions where extra parameters are introduced to reduce the miscibility between the two liquids. The interfacial tensions and the miscibilities are varied by using different parameters. The interfaces thus obtained are stable on the time scale of the simulation as shown by the density and pressure profiles. This is also confirmed by a geometrical analysis performed in order to characterize the fluctuations of the interfaces. The calculation of the diffusion coefficients shows clearly an anisotropy of the diffusion process in the interfacial region.

Computer simulation study of the local pressure in a spherical liquid–vapor interface

The pressure profiles across a liquid–vapor interface introduced previously [J. Chem. Phys. 106, 635 (1997)] have been evaluated with the aid of molecular dynamics simulations for a system of particles interacting via a (truncated and shifted) Lennard-Jones potential. This investigation extends earlier results [J. Chem. Phys. 106, 645 (1997)] to spherical interfaces. Further evidence is found that, for the range of curvatures investigated, the surface tension is curvature independent while the investigation of larger curvatures is prevented by the considerable noise found on the liquid side of the interface.

Thermal fluctuations in a lamellar phase of a binary amphiphile-solvent mixture: A molecular-dynamics study

We investigate thermal fluctuations in a smectic A phase of an amphiphile–solvent mixture with molecular-dynamics simulations. We use an idealized model system, where solvent particles are represented by simple beads, and amphiphiles by bead-and-spring tetramers. At a solvent bead fraction of 20% and sufficiently low temperature, the amphiphiles self-assemble into a highly oriented lamellar phase. Our study aims at comparing the structure of this phase with the predictions of the elastic theory of thermally fluctuating fluid membrane stacks [Lei et al., J. Phys. II 5, 1155 (1995)]. We suggest a method which permits to calculate the bending rigidity and compressibility modulus of the lamellar stack from the simulation data. The simulation results are in reasonable agreement with the theory.

Dissipative Irreversibility from Nosé's Reversible Mechanics

Abstract Noses Hamiltonian mechanics makes possible the efficient simulation of irreversible flows of mass, momentum and energy. Such flows illustrate the paradox that reversible microscopic equations of motion underlie the irreversible behavior described by the second law of thermodynamics. This generic behavior of molecular many-body systems is illustrated here for the simplest possible system, with only one degree of freedom: a one-body Frenkel-Kontorova model for isothermal electronic conduction. This model system, described by Nose-Hoover Hamiltonian dynamics, exhibits several interesting features: (1) deterministic and reversible equations of motion; (2) Lyapunov instability, with phase-space offsets increasing exponentially with time; (3) limit cycles; (4) dissipative conversion of work (potential energy) into heat (kinetic energy): and (5) phase-space contraction, a characteristic feature of steady irreversible flows. The model is particularly instructive in illustrating and explaining a paradox ...

Order and fluctuations in nonequilibrium molecular dynamics simulations of two-dimensional fluids

Finite systems of hard disks placed in a temperature gradient and in an external constant field have been studied, simulating a fluid heated from below. We used the methods of nonequilibrium molecular dynamics. The goal was to observe the onset of convection in the fluid. Systems of more than 5000 particles have been considered and the choice of parameters has been made in order to have a Rayleigh number larger than the critical one calculated from the hydrodynamic equations. The appearance of rolls and the large fluctuations in the velocity field are the main features of these simulations.

Pores in bilayer membranes of amphiphilic molecules: Coarse-grained molecular dynamics simulations compared with simple mesoscopic models

We investigate pores in fluid membranes by molecular dynamics simulations of an amphiphile-solvent mixture, using a molecular coarse-grained model. The amphiphilic membranes self-assemble into a lamellar stack of amphiphilic bilayers separated by solvent layers. We focus on the particular case of tensionless membranes, in which pores spontaneously appear because of thermal fluctuations. Their spatial distribution is similar to that of a random set of repulsive hard disks. The size and shape distribution of individual pores can be described satisfactorily by a simple mesoscopic model, which accounts only for a pore independent core energy and a line tension penalty at the pore edges. In particular, the pores are not circular: their shapes are fractal and have the same characteristics as those of two-dimensional ring polymers. Finally, we study the size-fluctuation dynamics of the pores, and compare the time evolution of their contour length to a random walk in a linear potential.

The local pressure in a cylindrical liquid–vapor interface: A simulation study

The equilibrium force distribution, or the local pressure in an interface as defined in a companion paper, has been determined from molecular dynamics simulations of a Lennard-Jones fluid. Both a cylindrical and a planar interface are considered. Limited evidence is found that the surface tension could be independent of the curvature of the interface.

Statistical mechanics of fluidized granular media: Short-range velocity correlations

A statistical mechanical study of fluidized granular media is presented. Using a special energy injection mechanism, homogeneous fluidized stationary states are obtained. Molecular dynamics simulations and theoretical analysis of the inelastic hard-disk model show that there is a large asymmetry in the two-particle distribution function between pairs that approach and separate. Large velocity correlations appear in the postcollisional states due to the dissipative character of the collision rule. These correlations can be well-characterized by a state dependent pair correlation function at contact. It is also found that velocity correlations are present for pairs that are about to collide. Particles arrive at collisions with a higher probability that their velocities are parallel rather than antiparallel. These dynamical correlations lead to a decrease of the pressure and of the collision frequency as compared to their Enskog values. A phenomenological modified equation of state is presented.