Preface ........................................................ xi
1 Mathematical Foundations ..................................... 1
1.1 Matrices and Systems of Linear Equations ................ 1
1.2 Properties of Eigenvalues and Eigenvectors .............. 6
1.3 Variational Approximations ............................. 10
1.4 Atomic Units ........................................... 15
1.5 The Electron Distribution in Molecules ................. 17
1.6 Exchange-overlap Densities and the Chemical Bond ....... 19
Part 1: Short-range Interactions ............................... 27
2 The Chemical Bond ........................................... 29
2.1 An Elementary Molecular Orbital Model .................. 30
2.2 Bond Energies and Pauli Repulsions in Homonuclear
Diatomics .............................................. 34
2.2.1 The Hydrogen Molecular Ion H2+ (N=1) ............ 35
2.2.2 The Hydrogen Molecule H2(N=2) ................... 35
2.2.3 The Helium Molecular Ion He2+ (N=3) ............. 35
2.2.4 The Helium Molecule He2 (N=4) ................... 36
2.3 Multiple Bonds ......................................... 37
2.3.1 σ2π2 Description of the Double Bond ............. 38
2.3.2 B12B22 Bent (or Banana) Description of the
Double Bond ..................................... 40
2.3.3 Hybridization Effects ........................... 42
2.3.4 Triple Bonds .................................... 46
2.4 The Three-centre Double Bond in Diborane ............... 47
2.5 The Heteropolar Bond ................................... 49
2.6 Stereochemistry of Polyatomic Molecules ................ 55
2.6.1 The Molecular Orbital Model of Directed
Valency ......................................... 55
2.6.2 Analysis of the MO Bond Energy .................. 58
2.7 sp-Hybridization Effects in First-row Hydrides ......... 60
2.7.1 The Methane Molecule ............................ 61
2.7.2 The Hydrogen Fluoride Molecule .................. 64
2.7.3 The Water Molecule .............................. 75
2.7.4 The Ammonia Molecule ............................ 87
2.8 Delocalized Bonds ...................................... 96
2.8.1 The Ethylene Molecule ........................... 98
2.8.2 The Allyl Radical ............................... 98
2.8.3 The Butadiene Molecule ......................... 100
2.8.4 The Cyclobutadiene Molecule .................... 102
2.8.5 The Benzene Molecule ........................... 104
2.9 Appendices ............................................ 108
2.9.1 The Second Derivative of the Hьckel Energy ..... 108
2.9.2 The Set of Three Coulson Orthogonal Hybrids .... 109
2.9.3 Calculation of Coefficients of Real MOs for
Benzene ........................................ 110
3 An Introduction to Bonding in Solids ....................... 119
3.1 The Linear Polyene Chain .............................. 120
3.1.1 Butadiene N=4 .................................. 122
3.2 The Closed Polyene Chain .............................. 123
3.2.1 Benzene N=6 .................................... 126
3.3 A Model for the One-dimensional Crystal ............... 131
3.4 Electronic Bands in Crystals .......................... 133
3.5 Insulators, Conductors, Semiconductors and
Superconductors ....................................... 138
3.6 Appendix: The Trigonometric Identity .................. 143
Part 2: Long-Range Interactions .............................. 145
4 The van der Waals Bond ..................................... 147
4.1 Introduction .......................................... 147
4.2 Elements of Rayleigh-Schrödinger (RS) Perturbation
Theory ................................................ 149
4.3 Molecular Interactions ................................ 151
4.3.1 Non-expanded Energy Corrections up to Second
Order .......................................... 152
4.3.2 Expanded Energy Corrections up to Second
Order .......................................... 153
4.4 The Two-state Model of Long-range Interactions ........ 157
4.5 The van der Waals Interactions ........................ 159
4.5.1 Atom-Atom Dispersion ........................... 161
4.5.2 Atom-Linear Molecule Dispersion ................ 162
4.5.3 Atom-Linear Dipolar Molecule10 Induction ....... 163
4.6 The С6 Dispersion Coefficient for the H-H
Interaction ........................................... 165
4.7 The van der Waals Bond ................................ 167
4.8 The Keesom Interaction ................................ 169
5 The Hydrogen Bond .......................................... 177
5.1 A Molecular Orbital Model of the Hydrogen Bond ........ 178
5.2 Electrostatic Interactions and the Hydrogen Bond ...... 179
5.2.1 The Hydrogen Fluoride Dimer (HF)2 .............. 182
5.2.2 The Water Dimer (H2O)2 ......................... 185
5.3 The Electrostatic Model of the Hydrogen Bond .......... 186
5.4 The Rg-HF Heterodimers ................................ 197
References ................................................. 201
Author Index .................................................. 209
Subject Index ................................................. 213
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