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Molecular orbital theory

About: Molecular orbital theory is a research topic. Over the lifetime, 4537 publications have been published within this topic receiving 251469 citations. The topic is also known as: molecular orbital method & MO theory.


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Journal ArticleDOI
TL;DR: In this article, the activation energy of the A1C02 reaction is 2.5 and 3.9 kcal/mol, respectively, while the experimentally estimated heat of reaction is about 5 kcal/molecular.
Abstract: calculated energy of the 2Z state of A10 is lower by 8.6 kcal/mol than that of the ZII state and in good agreement with the previously calculated valueZo (9.9 kcal/mol). The calculated energy of AIO(ZZ) + CO is 15.4 kcal/mol above that of the trans-type complex. From these values, the reaction A1 + C 0 2 AlO(’Z) + CO is 5.8 kcal/mol endothermic, and this value is consistent with the experimental estimation (4.5 kcal/mol: D(C-0) = 126 kcal/mol, D(A1-O) = 121.5 kcal/mol). The geometries of the transition states of the 22 and the 211 states are similar to each other except for the AlOC angle and the A10 distance. From the transition-state structures, both reactions (2Z and ZII) consequently becomes transition states, which is qualitatively consistant with the Hammond postulate.2’ The ,Z transition state correlates to the C,, complex, and the ZII transition state correlates to trans-type complex. The values of energy barriers of the products are 17.8 and 4.6 kcal/mol for the ZZ and Zll states, respectively. The ZII transition state is lower in energy by 4.6 kcai/mol than the transition state. This is explained by the fact that the 2Z state of A10 at the long A1-O distance from the equilibrium bond distance is higher in energy than the 211 state.19 Thus, both reaction surfaces possibly cross each other in the neighboring region of the transition states. Experimentally determined activation energies’*4 of the A1C02 reaction are 2.5 and 3.9 kcal/mol, while the experimentally estimated heat of reaction is about 5 kcal/mol endothermic. Therefore, the experimental activation energy is considered to be that of the reaction of the AlCO2 complex formation. The calculated activation energy of the complex formation is 2.3 kcal/mol

2,240 citations

Journal ArticleDOI
TL;DR: In this article, the selfconsistent field function for atoms with 2 to 36 electrons is computed with a minimal basis set of Slater-type orbitals, and the orbital exponent of the atomic orbitals are optimized as to ensure the energy minimum.
Abstract: The self‐consistent‐field function for atoms with 2 to 36 electrons are computed with a minimal basis set of Slater‐type orbitals. The orbital exponent of the atomic orbitals are optimized as to ensure the energy minimum. The analysis of the optimized orbital exponents allows us to obtain simple and accurate rules for the 1s, 2s, 3s, 4s, 2p, 3p, 4p, and 3d electronic screening constants. These rules are compared with those proposed by Slater and reveal the need of accounting for the screening due to the outside electrons. The analysis of the screening constants (and orbital exponents) is extended to the excited states of the groundstate configuration and to the positive ions.

2,135 citations

Journal ArticleDOI
TL;DR: In this paper, a simple level of ab initio molecular orbital theory with a split-valence shell basis with d-type polarization functions was used to predict equilibrium geometries for the ground and some low-lying excited states of AHn molecules and cations where A is carbon, nitrogen, oxygen or fluorine.
Abstract: A simple level of ab initio molecular orbital theory with a split-valence shell basis with d-type polarization functions (6–31G*) is used to predict equilibrium geometries for the ground and some low-lying excited states of AHn molecules and cations where A is carbon, nitrogen, oxygen or fluorine. The results are shown to be close to the limit for single determinant wave functions in cases where corresponding computations with more extensive bases are available. Comparison with experimental results also shows good agreement although a systematic underestimation of bond lengths up to 3 per cent is evident. For systems where no experimental data are available, the results provide predictions of equilibrium geometry.

1,964 citations

Book
01 Jan 1969
TL;DR: In this article, a survey of many-electron wavefunctions spin and permutation symmetry is presented, including the Electron Distribution Self-Consistent Field Theory Valence Bond Theory Multiconfiguration SCF Theory Perturbation Theory and Diagram Techniques Large-Scale CI and the Unitary-Group Approach Small Terms in the Hamiltonian Static Properties Dynamic Properties Dynamic properties and Response Theory Propagator and Equation-of-Motion Methods Intermolecular Forces Appendixes: Atomic Orbitals Angular Momentum Symmetry and Group Concepts Relativistic
Abstract: Introductory Survey Mathematical Methods Many-Electron Wavefunctions Spin and Permutation Symmetry Digression: The Electron Distribution Self-Consistent Field Theory Valence Bond Theory Multiconfiguration SCF Theory Perturbation Theory and Diagram Techniques Large-Scale CI and the Unitary-Group Approach Small Terms in the Hamiltonian Static Properties Dynamic Properties and Response Theory Propagator and Equation-of-Motion Methods Intermolecular Forces Appendixes: Atomic Orbitals Angular Momentum Symmetry and Group Concepts Relativistic Terms in the Hamiltonian References Index

1,802 citations

Journal ArticleDOI
TL;DR: In this paper, the electron density at each carbon atom, of the highest occupied π−orbital in the ground state of the molecule is calculated by means of the LCAO method.
Abstract: In the search for a quantitative correlation between reactivity and electronic configuration of aromatic hydrocarbons, the electron density, at each carbon atom, of the highest occupied π‐orbital in the ground state of the molecule is calculated by means of the LCAO method. Comparing the result of such a calculation on fifteen condensed aromatic hydrocarbons with their chemical reactivities, we find that the position at which the electron density is largest is most readily attacked by electrophilic or oxidizing reagents.It is, therefore, concluded that distinct from other π‐electrons the pair of π‐electrons occupying the highest orbital, which is referred to as frontier electrons, plays a decisive role in chemical activation of these hydrocarbon molecules. The theoretical significance of this discrimination of the frontier electrons in relation to the chemical activation is discussed.

1,791 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202315
202219
202128
202017
201913
201828