Computational Approaches to Energy Materials

Professor Richard Catlow is the Dean of the Faculty of Mathematical and Physical Sciences at University College London and a Fellow of the Royal Society. He has worked in the field of computational and experimental studies of complex inorganic materials for over 30 years, pioneering a wide range of applications of computational techniques. His current research involves exploring the structures, properties and reactivities of complex materials including micro and mesoporous catalysts, electronic ceramics, minerals, fast ion conductors and molecular materials. Professor Catlow has published over 800 papers and authored or co-authored 12 books, including the widely used Computer Simulation of Solids and the influential Computer Modeling of Microporous Materials. Dr Alexey Sokol is a Senior Research Associate at University College London, where he has worked on the development and applications of computational methods for solid-state physics, chemistry and materials science for over 20 years. He has recently been involved with the development of multi-scale computational approaches to facilitate the accurate modelling of catalytic and defect processes in oxide and semiconducting materials. Dr Aron Walsh is a Marie Curie Fellow at University College London with a long standing interest in energy materials following postdoctoral work at the National Renewable Energy Laboratory (USA) where he still maintains close links. He has applied electronic structure techniques to the design of novel solar cell and solid-state lighting materials, and has pioneered a new field of theoretical research into semiconducting metal organic frameworks.

About the Editors xi List of Contributors xiii Preface xv Acknowledgments xvii 1 Computational Techniques 1 C. Richard A. Catlow, Alexey A. Sokol, and Aron Walsh 1.1 Introduction 1 1.2 Atomistic Simulations 1 1.2.1 Basic Concepts 1 1.2.2 Parameterization 3 1.2.3 Parameter Sets 3 1.2.4 Implementation 4 1.3 Electronic Structure Techniques 6 1.3.1 Wavefunction Methods 8 1.3.1.1 Hartree Fock Theory 9 1.3.1.2 Post-Hartree Fock Approaches 10 1.3.1.3 Semi-empirical Wavefunction Methods 11 1.3.2 Density Functional Theory 12 1.3.2.1 Exchange Correlation Functionals 12 1.3.2.2 Semi-empirical Density Functional Approaches 14 1.3.3 Excited States 15 1.4 Multiscale Approaches 15 1.4.1 Hybrid QM/MM Embedding Techniques 16 1.4.2 Beyond Atomistic Models 17 1.5 Boundary Conditions 19 1.6 Point-Defect Simulations 21 1.6.1 Mott Littleton Approach 21 1.6.2 Periodic Supercell Approach 24 1.7 Summary 25 References 25 2 Energy Generation: Solar Energy 29 Silvana Botti and Julien Vidal 2.1 Thin-Film Photovoltaics 29 2.2 First-Principles Methods for Electronic Excitations 32 2.2.1 Hedin s Equations and the GW Approximation 34 2.2.2 Hybrid Functionals 38 2.2.3 Bethe Salpeter Equation 40 2.2.4 Model Kernels for TDDFT 41 2.3 Examples of Applications 42 2.3.1 Cu-Based Thin-Film Absorbers 43 2.3.2 Delafossite Transparent Conductive Oxides 54 2.4 Conclusions 60 References 61 3 Energy Generation: Nuclear Energy 71 Dorothy Duffy 3.1 Introduction 71 3.2 Radiation Effects in Nuclear Materials 72 3.2.1 Fission 72 3.2.1.1 Structural Materials 73 3.2.1.2 Fuel 76 3.2.1.3 Cladding 79 3.2.2 Fusion 80 3.2.2.1 Structural Materials 81 3.2.2.2 Plasma-Facing Materials 82 3.2.3 Waste Disposal 83 3.3 Modeling Radiation Effects 85 3.3.1 BCA Modeling 86 3.3.2 Molecular Dynamics 87 3.3.2.1 Cascade Simulations 87 3.3.2.2 Sputtering Simulations 93 3.3.3 Monte Carlo Simulations 94 3.3.3.1 Kinetic Monte Carlo 95 3.3.3.2 Object Kinetic Monte Carlo 96 3.3.3.3 Transition Rates 97 3.3.3.4 Examples 98 3.3.4 Cluster Dynamics 99 3.3.4.1 Examples 99 3.3.4.2 Comparison with OKMC 100 3.3.5 Density Functional Theory 101 3.3.5.1 Interatomic Potentials 101 3.3.5.2 Transition Rates 102 3.4 Summary and Outlook 102 References 104 4 Energy Storage: Rechargeable Lithium Batteries 109 M. Saiful Islam and Craig A.J. Fisher 4.1 Introduction 109 4.2 Overview of Computational Approaches 110 4.3 Li Ion Batteries 112 4.4 Cell Voltages and Structural Phase Stability 113 4.5 Li Ion Diffusion and Defect Properties 116 4.6 Surfaces and Morphology 121 4.7 Current Trends and Future Directions 124 4.8 Concluding Remarks 125 References 125 5 Energy Storage: Hydrogen 131 Viet-Duc Le and Yong-Hyun Kim 5.1 Introduction 131 5.2 Computational Approach in Hydrogen Storage Research 133 5.3 Chemisorption Approach 133 5.4 Physisorption Approach 136 5.5 Spillover Approach 138 5.6 Kubas-Type Approach 138 5.7 Conclusion 145 References 146 6 Energy Conversion: Solid Oxide Fuel Cells 149 E.A. Kotomin, R. Merkle, Y.A. Mastrikov, M.M. Kuklja, and J. Maier 6.1 Introduction 149 6.2 Computational Details 152 6.3 Cathode Materials and Reactions 155 6.3.1 Surfaces: LaMnO3 and (La,Sr)MnO3 Perovskites 155 6.3.1.1 Surface Termination, Surface Point Defects 155 6.3.1.2 Oxygen Adsorption and Diffusion 158 6.3.1.3 Rate-Determining Step of the Surface Reaction 160 6.3.2 Bulk Properties of Multicomponent Perovskites 164 6.3.2.1 Oxygen Vacancy Formation in (Ba,Sr)(Co,Fe)O3 164 6.3.2.2 Oxygen Vacancy Migration in (Ba,Sr)(Co,Fe)O3 167 6.3.2.3 Disorder and Cation Rearrangement in (Ba,Sr)(Co,Fe)O3 170 6.3.3 Defects in (La,Sr)(Co,Fe)O3 173 6.4 Ion Transport in Electrolytes: Recent Studies 175 6.5 Reactions at SOFC Anodes 176 6.6 Conclusions 177 Acknowledgments 178 References 178 7 Energy Conversion: Heterogeneous Catalysis 187 Rutger A. van Santen, Evgeny A. Pidko, and Emiel J.M. Hensen 7.1 Introduction 187 7.1.1 Particle Size Dependence of Catalytic Reactivity 191 7.1.2 Activity and Selectivity as a Function of the Metal Type 192 7.1.3 Reactivity as a Function of State of the Surface 193 7.1.4 Mechanism of Acid Catalysis: Single Site versus Dual Site 193 7.2 Basic Concepts of Heterogeneous Catalysis 195 7.3 Surface Sensitivity in CH Activation 198 7.3.1 Homolytic Activation of CH Bonds 198 7.3.2 Heterolytic Activation of CH Bonds 203 7.3.2.1 Bronsted Acid Catalysis 204 7.3.2.2 Lewis Acid Catalysis 206 7.4 Surface Sensitivity for the C C Bond Formation 209 7.4.1 Transition Metal Catalyzed FT Reaction 209 7.4.2 C C Bond Formation Catalyzed by Zeolitic Bronsted Acids 213 7.5 Structure and Surface Composition Sensitivity: Oxygen Insertion versus CH Bond Cleavage 217 7.5.1 Silver-Catalyzed Ethylene Epoxidation 217 7.5.2 Benzene Oxidation by Iron-Modified Zeolite 221 7.6 Conclusion 223 References 224 8 Energy Conversion: Solid-State Lighting 231 E. Kioupakis, P. Rinke, A. Janotti, Q. Yan, and C.G. Van de Walle 8.1 Introduction to Solid-State Lighting 231 8.2 Structure and Electronic Properties of Nitride Materials 234 8.2.1 Density Functional Theory and Ground-State Properties 234 8.2.2 Electronic Excitations: GW and Exact Exchange 236 8.2.3 Electronic Excitations: Hybrid Functionals 240 8.2.4 Band-gap Bowing and Band Alignments 240 8.2.5 Strain and Deformation Potentials 241 8.3 Defects in Nitride Materials 243 8.3.1 Methodology 244 8.3.2 Example: C in GaN 246 8.4 Auger Recombination and Efficiency Droop Problem of Nitride LEDs 248 8.4.1 Efficiency Droop 248 8.4.2 Auger Recombination 249 8.4.3 Computational Methodology 251 8.4.4 Results 252 8.5 Summary 254 Acknowledgments 255 References 255 9 Toward the Nanoscale 261 Phuti E. Ngoepe, Rapela R. Maphanga, and Dean C. Sayle 9.1 Introduction 261 9.2 Review of Simulation Methods 263 9.2.1 Established Computational Methods 263 9.2.2 Evolutionary Methods 263 9.2.2.1 GM Methods 263 9.2.2.2 Amorphization and Recrystallization 264 9.3 Applications 266 9.3.1 Nanoclusters 266 9.3.1.1 ZnO 266 9.3.1.2 ZnS 268 9.3.1.3 MnO2 269 9.3.1.4 TiO2 271 9.3.2 Nanoarchitectures 272 9.3.2.1 MnO2 Nanoparticle (Nucleation and Crystallization) 272 9.3.2.2 MnO2 Bulk 275 9.3.2.3 MnO2 Nanoporous 278 9.3.2.4 TiO2 Nanoporous 284 9.3.2.5 ZnS and ZnO Nanoporous 286 9.4 Summary and Conclusion 289 Acknowledgments 290 References 290 Further Reading 295 Index 297