Electronic States of Molecules and Atom Clusters: Foundations and Prospects of Semiempirical Methods: Lecture Notes in Chemistry, cartea 13

1. Models and concepts in molecular theory.- 1.1 Scope of the quantum theory of molecules.- 1.2 Born Oppenheimer states.- 1.3 Computational and interpretational problems.- 1.4 Rôle and limitations of simplified models.- 1.5 Simplified models and model Hamiltonians.- 1.6 Atoms in molecules and electronegativities.- 1.7 A conclusion: Models and the Plague of Non-observables.- 2. Mathematical foundations.- 2.1 Mathematical construction of many-electron models from an orbital basis.- 2.2 Model Hamiltonians.- 2.3 Matrix formalism. Inclusion of overlap.- 2.4 The spectral decomposition of the Hamiltonian and effective potentials.- 3. One-electron schemes.- 3.1 Hückel-type methods.- 3.2 A ‘naive’ method for ? electrons.- 3.3 The Hückel method for all valence-electrons: The tight binding (TB) approach of solid-state physics.- 3.4 All-valence-electron treatments: The extended Hückel theory (EHT).- 4. Simplified SCF one-electron schemes and beyond.- 4.1 The SCF Hamiltonian.- 4.2 Construction of non-SCF Hamiltonians.- 4.3 Many-electron models and their SCF version.- 4.4 Methods with iterative determination of atomic parameters.- 4.6 A general form of all valence SCF methods: The SCF extended-Hückel method.- 4.7 Beyond one-electron schemes. Correlation, PCILO method excited states.- 4.8 A case study in semiempirical computations: Molecular force fields.- 4.9 Limitations of semiempirical and limited-basis methods: The N2O4 molecule.- 5. The basis problem.- 5.1 MVAO basis.- 5.2 Non-orthogonality.- 5.3 General orbital bases.- 5.4 ?-Electron models and the ?-? separation.- 5.5 Basis problem in solid-state physics.- 5.6 Metal-metal bond and the X? method.- 5.7 Reliability of computations and choice of the orbital basis.- 5.8 A comment on the use of group theory incalculations on molecules and aggregates of atoms.