Series in Soft Condensed Matter Vol. 3 Editors Wenbing Hu An-Chang Shi UNDERSTANDING SOFT CONDENSED MATTER VIA MODELING AND COMPUTATION World Scientific
UNDERSTANDING SOFT CONDENSED MATTER VIA MODELING AND COMPUTATION
Series in Soft Condensed Matter Vol. 3 UNDERSTANDING SOFT CONDENSED MATTER VIA MODELING AND COMPUTATION Editors Wenbing Hu Nanjing University, China An-Chang Shi McMaster University, Canada World Scientific NEW JERSEY LONDON SINGAPORE BEIJING SHANGHAI HONG KONG TAIPEI CHENNAI
SERIES IN SOFT CONDENSED MATTER ISSN: 1793-737X Founding Advisor: Pierre-Gilles de Gennes (1932 2007) Nobel Prize in Physics 1991 Collège de France Paris, France Series Editors: David Andelman Tel-Aviv University Tel-Aviv, Israel Günter Reiter Universität Freiburg Freiburg, Germany Published: Vol. 1 Polymer Thin Films edited by Ophelia K. C. Tsui and Thomas P. Russell Vol. 2 Vol. 3 Polymers, Liquids and Colloids in Electric Fields: Interfacial Instabilities, Orientation and Phase Transitions edited by Yoav Tsori and Ullrich Steiner Understanding Soft Condensed Matter via Modeling and Computation edited by Wenbing Hu and An-Chang Shi
Published by World Scientific Publishing Co. Pte. Ltd. 5 Toh Tuck Link, Singapore 596224 USA office: 27 Warren Street, Suite 401-402, Hackensack, NJ 07601 UK office: 57 Shelton Street, Covent Garden, London WC2H 9HE British Library Cataloguing-in-Publication Data A catalogue record for this book is available from the British Library. UNDERSTANDING SOFT CONDENSED MATTER VIA MODELING AND COMPUTATION Series in Soft Condensed Matter Vol. 3 Copyright 2011 by World Scientific Publishing Co. Pte. Ltd. All rights reserved. This book, or parts thereof, may not be reproduced in any form or by any means, electronic or mechanical, including photocopying, recording or any information storage and retrieval system now known or to be invented, without written permission from the Publisher. For photocopying of material in this volume, please pay a copying fee through the Copyright Clearance Center, Inc., 222 Rosewood Drive, Danvers, MA 01923, USA. In this case permission to photocopy is not required from the publisher. ISBN-13 978-981-4295-58-1 ISBN-10 981-4295-58-2 Printed in Singapore.
Foreword The study of Soft Condensed Matter has stimulated fruitful interactions between physicists, chemists, and engineers, and is now reaching out to biologists. A broad interdisciplinary community involving all these areas of science has emerged over the last 30 years, and with it our knowledge of Soft Condensed Matter has grown considerably with the active investigations of polymers, supramolecular assemblies of designed organic molecules, liquid crystals, colloids, lyotropic systems, emulsions, biopolymers and biomembranes, among others. Taking into account that research in Soft Condensed Matter involves ideas coming from physics, chemistry, materials science as well as biology, this series may form a bridge between all these disciplines with the aim to provide a comprehensive and substantial understanding of a broad spectrum of phenomena relevant to Soft Condensed Matter. The present Book Series, initiated by the late Pierre-Gilles de Gennes, comprises independent book volumes that touch on a wide and diverse range of topics of current interest and importance, covering a large number of diverse aspects, both theoretical and experimental, in all areas of Soft Condensed Matter. These volumes will be edited books on advanced topics with contributions by various authors and monographs in a lighter style, written by experts in the corresponding areas. The Book Series mainly addresses graduate students and junior researchers as an introduction to new fields, but it should also be useful to experienced people who want to obtain a general idea on a certain topic or may consider a change of their field of research. This Book Series aims to provide a comprehensive and instructive overview of all Soft Condensed Matter phenomena. The present volume of this Book Series, edited by Wenbing Hu and An-Chang Shi, provides a thorough set of examples for the power of modeling and computer simulations of Soft Condensed Matter. Each chapter addresses a different technique or system, but as an ensemble, all contributions provide evidence on how simulation approaches can complement v
vi Foreword theory and experiment, bridging the gap between atomistic models and coarse-grained ones. The diversity of the selected fields is representative to the large spectrum of Soft Condensed Matter. As special effort has been made to review important concepts and simulation techniques on an introductory level, we expect that this volume will serve as a useful guide to graduate students and young investigators who aim to get a broad overview on modeling approaches and simulation techniques used for Soft Condensed Matter. Within the next few years, our Series on Soft Condensed Matter will grow continuously and eventually cover the whole spectrum of phenomena in Soft Condensed Matter. We hope that many interested colleagues and scientists will participate and profit from these endeavours. David Andelman and Günter Reiter Series Editors
Preface Soft condensed matter physics is concerned with the study of soft materials. Examples of soft materials are polymers, bio-macromolecules, liquid crystals, surfactant solutions, colloidal suspensions, and lipids. The territory of these materials extends to plastics, rubber, textiles, pharmaceuticals, foodstuffs and biomaterials, which are important and useful materials for our daily life and high-tech industries. Furthermore, soft materials provide the ground for the birth of new physics based on the theme of softness, malleability and fragility. At the extreme, all living organisms can be regarded as soft matter. For these reasons, it is important to be able to understand and predict the structural and dynamical properties of soft materials. The present volume of the book series in soft condensed matter focuses on the modeling and simulation of soft matter, as an essential investigation often concerted with the efforts of experiment and theory. One of the advantages of computer simulations is that they allow us to vary controlling parameters of microscopic models and to visualize physical processes in detail. This makes the simulation approach particularly valuable in the study of complex physiochemical systems such as soft condensed matter. Although simulations of a given physiochemical system are ideally carried out on atomistic models, using this approach for macroscopic systems sets the demand for us to track a huge number of particles, of the order of 10 23 or so, which is a formidable task even for current computational abilities. In order to overcome this difficulty, a variety of coarse-grained models have been developed. The tasks of modeling and simulation are two-fold: to develop model parameters in the coarse-grained models arising from atomistic models, and to understand structure and dynamics of soft matter from simulations of the coarse-grained models. Both tasks require the development of sophisticated simulation methodologies and algorithms. This book collects a set of mini-reviews on a number of topics in soft condensed matter physics, emphasizing the advantages of simulation vii
viii Preface approaches. Each mini-review demonstrates how a carefully chosen algorithm leads to the understanding of some key properties of soft matter. Because the book is aimed at non-specialists, topics in each chapter are placed in a broader context combining experimental and theoretical approaches while technical issues are discussed at an introductory level. The content of this book can be roughly divided into five parts, covering colloids, polymers, bio-macromolecules, liquid crystals and fluid droplets. Using these various soft matter systems as a platform, a number of simulation techniques are introduced, including molecular dynamics simulations, Monte Carlo simulations, self-consistent field theory, density functional theory, quantum chemistry modeling, and finite element method of fluid mechanics. The first part begins with a brief overview by Daan Frenkel on the role of computer simulations in the study of soft matter, in particular, of colloids. The rationale of this approach is based on the fact that the weakness of cohesive energies of soft matter allows the entropic forces to drive phase transitions. This intrinsic feature of soft matter can be captured by an extension of the classical density functional theory, which is introduced by Hartmut Löwen in the second chapter. The non-equilibrium problems of soft matter, like colloids, liquid crystals and polymer solutions can be tackled by the dynamic density functional theory derived from the Smoluchowski equation. The second part focuses on phase separation and crystallization in polymeric systems. Marcus Müller first describes the modeling of liquid liquid demixing in polymer blends and solutions, as well as simulations of interfacial properties, phase boundaries in confined geometries, and wetting. Then, Feng Qiu et al. present an introduction to the self-consistent-field theory (SCFT) for the study of the phase behavior of block copolymers, focusing on a new generic reciprocal-space method for the discovery of ordered block copolymer phases. Furthermore, Toshihiro Kawakatsu introduces the recent development of dynamic SCFT in the study of nonequilibrium behaviors of diblock copolymers with various geometries of microdomains. Turning to polymer crystallization, Takashi Yamamoto combines molecular dynamics and Monte Carlo simulations to study crystallization of helical polymers, using isotactic polypropylene as the model system to demonstrate the relationship between the molecular chirality and the symmetry of the lattice. Finally, Wenbing Hu presents a study of the interplay of liquid liquid demixing and polymer crystallization in multi-component systems. Dynamic Monte Carlo simulations are performed