CONTENTS LIST OF SYMBOLS I INTRODUCTION 1 1.1 A short history of computer simulation 1 1.2 Computer simulation:motivation and applications 4 1.3 Model systems and interaction potentials 6 1.3.1 Introduction 6 1.3.2 Atomic systems 7 1.3.3 Molecular systems 12 1.3.4 Lattice systems 16 1.3.5 Calculating the potential 18 1.4 Constructing an intermolecular potential 1.4.1 Introduction 1.4.2 Building the model potential 1.4.3 Adjusting the model potential 1.5 Studying small systems 1.5.1 Introduction 1.5.2 Periodic boundary conditions 1.5.3 Potential truncation 20000023234792 1.5.4 Computer code for periodic boundaries 1.5.5 Spherical boundary conditions 2 STATISTICAL MECHANICS 33 2.1 Sampling from ensembles 2.2 Common statistical ensembles 3339 2.3 Transforming between ensembles 43 2.4 Simple thermodynamic averages 46 2.5 Fluctuations 51 2.6 Structural quantities 54 2.7 Time correlation functions and transport coefficients 58 2.8 Long-range corrections 64 2.9 Quantum corrections 65 2.10 Constraints 68 3 MOLECULAR DYNAMICS 71 3.1 Equations of motion for atomic systems 71 3.2 Finite difference methods 3 3.2.1 The Verlet algorithm 78 3.2.2 The Gear predictor-corrector 8 3.2.3 Other methods 84 3.3 Molecular dynamics of rigid non-spherical bodies 3.3.I Non-linear molecules 8 3.3.2 Linear molecules 90