Landau / Lewis / Schüttler Computer Simulation Studies in Condensed-Matter Physics XVII

Proceedings of the Seventeenth Workshop, Athens, GA, USA, February 16-20, 2004
2006
ISBN: 978-3-540-26565-8
Verlag: Springer
Format: PDF
Kopierschutz: 1 - PDF Watermark

E-Book, Englisch, Band 103, 277 Seiten, eBook

Reihe: Springer Proceedings in Physics

Over ?fteen years ago, because of the tremendous increase in the power and utility of computer simulations, The University of Georgia formed the ?rst institutional unit devoted to the use of simulations in research and teaching: The Center for Simulational Physics. As the international simulations c- munityexpandedfurther,wesensedaneedforameetingplaceforbothex- riencedsimulatorsandneophytestodiscussnewtechniquesandrecentresults in an environment which promoted lively discussion. As a consequence, the Center for Simulational Physics established an annual workshop on Recent DevelopmentsinComputerSimulationStudiesinCondensedMatterPhysics. This year’s workshop was the seventeenth in this series, and the continued interest shown by the scienti?c community demonstrates quite clearly the useful purpose that these meetings have served. The latest workshop was held at The University of Georgia, February 16–20, 2004, and these proce- ings provide a “status report” on a number of important topics. This volume is published with the goal of timely dissemination of the material to a wider audience. We wish to o?er a special thanks to IBM and to SGI for partial support of this year’s workshop. This volume contains both invited papers and contributed presentations on problems in both classical and quantum condensed matter physics. We hope that each reader will bene?t from specialized results as well as pro?t from exposure to new algorithms, methods of analysis, and conceptual dev- opments.

Zielgruppe

Research

Autoren/Hrsg.

Landau, David P.

Lewis, Steven P.

Schüttler, Heinz-Bernd

Inhaltsverzeichnis

Systems out of Equilibrium.- Computer Simulation Studies in Condensed Matter Physics: An Introduction.- Shake, Rattle or Roll: Things to do with a Granular Mixture on a Computer.- A New Method of Investigating Equilibrium Properties from Nonequilibrium Work.- Numerical Simulations of Critical Dynamics far from Equilibrium.- Soft and Disordered Materials.- Entropy Driven Phase Separation.- Supercooled Liquids under Shear: Computational Approach.- Optimizing Glasses with Extremal Dynamics.- Stochastic Collision Molecular Dynamics Simulations for Ion Transfer Across Liquid-Liquid Interfaces.- Biological Systems.- Generalized-Ensemble Simulations of Small Proteins.- A Biological Coevolution Model with Correlated Individual-Based Dynamics.- An Image Recognition Algorithm for Automatic Counting of Brain Cells of Fruit Fly.- Preferred Binding Sites of Gene-Regulatory Proteins Based on the Deterministic Dead-End Elimination Algorithm.- Algorithms and Methods.- Geometric Cluster Algorithm for Interacting Fluids.- Polymer Simulations with a Flat Histogram Stochastic Growth Algorithm.- Convergence of the Wang-Landau Algorithm and Statistical Error.- Wang-Landau Sampling with Cluster Updates.- Multibaric-Multithermal Simulations for Lennard-Jones Fluids.- A Successive Umbrella Sampling Algorithm to Sample and Overcome Free Energy Barriers.- Computer Tools.- C++ and Generic Programming for Rapid Development of Monte Carlo Simulations.- Visualization of Vector Spin Configurations.- The BlueGene/L Project.- Molecules, Clusters and Nanoparticles.- All-Electron Path Integral Monte Carlo Simulations of Small Atoms and Molecules.- Projective Dynamics in Realistic Models of Nanomagnets.- Cumulants for an Ising Model for Folded 1-d Small-World Materials.- Embryonic Forms of Nickel and Palladium: A Molecular Dynamics Computer Simulation.- Surfaces and Alloys.- Usage of Pattern Recognition Scheme in Kinetic Monte Carlo Simulations: Application to Cluster Diffusion on Cu(111).- Including Long-Range Interactions in Atomistic Modelling of Diffusional Phase Changes.- Br Electrodeposition on Au(100): From DFT to Experiment.- Simulation of ZnSe, ZnS Coating on CdSe Substrate: The Electronic Structure and Absorption Spectra.- Simulation of Islands and Vacancy Structures for Si/Ge-covered Si(001) Using a Hybrid MC-MD Algorithm.- Spin-Polarons in the FM Kondo Model.

Leseproben

8 Stochastic Collision Molecular Dynamics Simulations for Ion Transfer Across Liquid–Liquid Interfaces (p. 80)

S. Frank, and W. Schmickler

1 Abteilung Elektrochemie, Universität Ulm, 89069 Ulm, Germany

2 Current address: Center for Materials Research and Technology and School of Computational Science and Information Technology, Florida State University, Tallahassee, FL 32306-4350, USA

[e-mail], [e-mail]

Abstract.

We compute the potential-energy surface for ion transfer across liquid– liquid interfaces from a lattice gas model and simulate the transfer as a random walk of the ion coupled to a heat bath. The kinetics obey Tafel behavior. The reaction rate is slowed down due to friction, and the friction effect is stronger than for a free particle.

8.1 Introduction

Ion transfer across liquid–liquid interfaces, though of considerable experimental interest, still lacks an established theoretical description. It is not clear whether this process should be viewed as a chemical reaction requiring an activation energy, or simply as a mass transport across a viscous boundary. Molecular dynamics simulations have shown a continuous increase of the chemical part of the free energy of ion transfer and no barrier (see, e.g., [1]).

However, the simulations were performed in the presence of a high field driving the ion across the interface, and in the absence of space charge regions. Thus, an essential part of the interaction energy of the transferring ion has been missing. In a model proposed by Schmickler [2], it is the combination of several interactions that constitutes a barrier at the interface. Here, we follow Schmickler’s ideas and treat ion transfer as a chemical reaction. The reaction coordinate – simply the distance from the average interface position – is singled out, and all the other degrees of freedom are represented as a heat bath, the same approach as in Kramers’ theory [3]. With this simplification, we can observe the reaction directly in a simulation.

8.2 Potential-energy Surface

We calculate the potential-energy surface of a transferring ion as the con.gurational energy of a positively charged test particle with fixed position in a simple cubic lattice gas, as a function of the distance z from the average interface position. Our model contains two solvents S1 and S2 and a different base electrolyte in each phase, and each lattice site is occupied by one particle.

The configurational energy is given by the sum over all nearestneighbor interactions, plus for ions the energy in the instantaneous electrostatic potential caused by all ions in the system. We calculate the equilibrium properties of this model using the Metropolis Monte Carlo algorithm. Details are given elsewhere [4]. The system is polarizable in a certain potential window, and the absolute value of the free energy of ion transfer, which is governed by a single interaction parameter ±r for the interaction with the two solvents, must be low enough for the ion to be transferable within this window.