| Preface | p. xiii |
| List of abbreviations | p. xv |
| Theory and two-electron systems | |
| Introduction | p. 3 |
| History | p. 3 |
| Mathematical background | p. 4 |
| Schrodinger's equation | p. 5 |
| The variation theorem | p. 9 |
| General variation functions | p. 9 |
| Linear variation functions | p. 9 |
| A 2 x 2 generalized eigenvalue problem | p. 14 |
| Weights of nonorthogonal functions | p. 16 |
| Weights without orthogonalization | p. 18 |
| Weights requiring orthogonalization | p. 19 |
| H[subscript 2] and localized orbitals | p. 23 |
| The separation of spin and space variables | p. 23 |
| The spin functions | p. 23 |
| The spatial functions | p. 24 |
| The AO approximation | p. 24 |
| Accuracy of the Heitler-London function | p. 27 |
| Extensions to the simple Heitler-London treatment | p. 27 |
| Why is the H[subscript 2] molecule stable? | p. 31 |
| Electrostatic interactions | p. 32 |
| Kinetic energy effects | p. 36 |
| Electron correlation | p. 38 |
| Gaussian AO bases | p. 38 |
| A full MCVB calculation | p. 38 |
| Two different AO bases | p. 40 |
| Effect of eliminating various structures | p. 42 |
| Accuracy of full MCVB calculation with 10 AOs | p. 44 |
| Accuracy of full MCVB calculation with 28 AOs | p. 44 |
| EGSO weights for 10 and 28 AO orthogonalized bases | p. 45 |
| H[subscript 2] and delocalized orbitals | p. 47 |
| Orthogonalized AOs | p. 47 |
| Optimal delocalized orbitals | p. 49 |
| The method of Coulson and Fisher[15] | p. 49 |
| Complementary orbitals | p. 49 |
| Unsymmetric orbitals | p. 51 |
| Three electrons in doublet states | p. 53 |
| Spin eigenfunctions | p. 53 |
| Requirements of spatial functions | p. 55 |
| Orbital approximation | p. 58 |
| Advanced methods for larger molecules | p. 63 |
| Permutations | p. 64 |
| Group algebras | p. 66 |
| Some general results for finite groups | p. 68 |
| Irreducible matrix representations | p. 68 |
| Bases for group algebras | p. 69 |
| Algebras of symmetric groups | p. 70 |
| The unitarity of permutations | p. 70 |
| Partitions | p. 70 |
| Young tableaux and N and P operators | p. 71 |
| Standard tableaux | p. 72 |
| The linear independence of N[subscript i]P[subscript i] and P[subscript i]N[subscript i] | p. 75 |
| Von Neumann's theorem | p. 76 |
| Two Hermitian idempotents of the group algebra | p. 76 |
| A matrix basis for group algebras of symmetric groups | p. 77 |
| Sandwich representations | p. 79 |
| Group algebraic representation of the antisymmetrizer | p. 80 |
| Antisymmetric eigenfunctions of the spin | p. 81 |
| Two simple eigenfunctions of the spin | p. 81 |
| The [Xi] function | p. 84 |
| The independent functions from an orbital product | p. 85 |
| Two simple sorts of VB functions | p. 87 |
| Transformations between standard tableaux and HLSP functions | p. 88 |
| Representing [theta] NPN [Xi] as a functional determinant | p. 91 |
| Spatial symmetry | p. 97 |
| The AO basis | p. 98 |
| Bases for spatial group algebras | p. 98 |
| Constellations and configurations | p. 99 |
| Example 1. H[subscript 2]O | p. 100 |
| Example 2. NH[subscript 3] | p. 102 |
| Example 3. The [pi] system of benzene | p. 105 |
| Varieties of VB treatments | p. 107 |
| Local orbitals | p. 107 |
| Nonlocal orbitals | p. 108 |
| The physics of ionic structures | p. 111 |
| A silly two-electron example | p. 111 |
| Ionic structures and the electric moment of LiH | p. 113 |
| Covalent and ionic curve crossings in LiF | p. 115 |
| Examples and interpretations | |
| Selection of structures and arrangement of bases | p. 121 |
| The AO bases | p. 121 |
| Structure selection | p. 123 |
| N[subscript 2] and an STO3G basis | p. 123 |
| N[subscript 2] and a 6-31G basis | p. 123 |
| N[subscript 2] and a 6-31G* basis | p. 124 |
| Planar aromatic and [pi] systems | p. 124 |
| Four simple three-electron systems | p. 125 |
| The allyl radical | p. 125 |
| MCVB treatment | p. 126 |
| Example of transformation to HLSP functions | p. 129 |
| SCVB treatment with corresponding orbitals | p. 132 |
| The He[superscript + subscript 2] ion | p. 134 |
| MCVB calculation | p. 134 |
| SCVB with corresponding orbitals | p. 135 |
| The valence orbitals of the BeH molecule | p. 136 |
| Full MCVB treatment | p. 137 |
| An SCVB treatment | p. 139 |
| The Li atom | p. 141 |
| SCVB treatment | p. 142 |
| MCVB treatment | p. 144 |
| Second row homonuclear diatomics | p. 145 |
| Atomic properties | p. 145 |
| Arrangement of bases and quantitative results | p. 146 |
| Qualitative discussion | p. 148 |
| B[subscript 2] | p. 149 |
| C[subscript 2] | p. 152 |
| N[subscript 2] | p. 154 |
| O[subscript 2] | p. 157 |
| F[subscript 2] | p. 160 |
| General conclusions | p. 161 |
| Second row heteronuclear diatomics | p. 162 |
| An STO3G AO basis | p. 162 |
| N[subscript 2] | p. 164 |
| CO | p. 166 |
| BF | p. 168 |
| BeNe | p. 171 |
| Quantitative results from a 6-31G* basis | p. 173 |
| Dipole moments of CO, BF, and BeNe | p. 174 |
| Results for 6-31G* basis | p. 174 |
| Difficulties with the STO3G basis | p. 175 |
| Methane, ethane and hybridization | p. 177 |
| CH, CH[subscript 2], CH[subscript 3], and CH[subscript 4] | p. 177 |
| STO3G basis | p. 177 |
| 6-31G* basis | p. 186 |
| Ethane | p. 187 |
| Conclusions | p. 189 |
| Rings of hydrogen atoms | p. 191 |
| Basis set | p. 192 |
| Energy surfaces | p. 192 |
| Aromatic compounds | p. 197 |
| STO3G calculation | p. 198 |
| SCVB treatment of [pi] system | p. 200 |
| Comparison with linear 1,3,5-hexatriene | p. 203 |
| The 6-31G* basis | p. 205 |
| Comparison with cyclobutadiene | p. 208 |
| The resonance energy of benzene | p. 208 |
| Naphthalene with an STO3G basis | p. 211 |
| MCVB treatment | p. 211 |
| The MOCI treatment | p. 212 |
| Conclusions | p. 213 |
| Interaction of molecular fragments | p. 214 |
| Methylene, ethylene, and cyclopropane | p. 214 |
| The methylene biradical | p. 215 |
| Ethylene | p. 215 |
| Cyclopropane with a 6-31G* basis | p. 218 |
| Cyclopropane with an STO-3G basis | p. 224 |
| Formaldehyde, H[subscript 2]CO | p. 225 |
| The least motion path | p. 226 |
| The true saddle point | p. 227 |
| Wave functions during separation | p. 228 |
| References | p. 231 |
| Index | p. 235 |
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