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Valence bond theory
About: Valence bond theory is a research topic. Over the lifetime, 3913 publications have been published within this topic receiving 139493 citations.
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TL;DR: In this paper, an ab initio gauge-invariant molecular orbital theory is developed for nuclear magnetic shielding, which is written as linear combinations of gauge invariant atomic orbitals, the wavefunctions in the presence of a uniform external magnetic field being determined by self-consistent field perturbation theory.
Abstract: An ab initio gauge-invariant molecular orbital theory is developed for nuclear magnetic shielding. The molecular orbitals are written as linear combinations of gauge-invariant atomic orbitals, the wavefunctions in the presence of a uniform external magnetic field being determined by self-consistent field perturbation theory. The final magnetic shielding result is broken up into contributions which can be related to various features of electronic structure. Calculated magnetic shielding constants are presented using three sets of atomic orbitals, all of which are taken as contracted gaussian-type functions. The first two sets are minimal and the third is slightly extended. All three levels of theory give good descriptions of shielding at first row and hydrogen atoms. Carbon and hydrogen chemical shifts calculated at the extended level are in excellent agreement with experimental values.
3,843 citations
TL;DR: In this article, a least square representation of Slater-type atomic orbitals as a sum of Gaussian-type orbitals is presented, where common Gaussian exponents are shared between Slater−type 2s and 2p functions.
Abstract: Least‐squares representations of Slater‐type atomic orbitals as a sum of Gaussian‐type orbitals are presented. These have the special feature that common Gaussian exponents are shared between Slater‐type 2s and 2p functions. Use of these atomic orbitals in self‐consistent molecular‐orbital calculations is shown to lead to values of atomization energies, atomic populations, and electric dipole moments which converge rapidly (with increasing size of Gaussian expansion) to the values appropriate for pure Slater‐type orbitals. The ζ exponents (or scale factors) for the atomic orbitals which are optimized for a number of molecules are also shown to be nearly independent of the number of Gaussian functions. A standard set of ζ values for use in molecular calculations is suggested on the basis of this study and is shown to be adequate for the calculation of total and atomization energies, but less appropriate for studies of charge distribution.
3,723 citations
TL;DR: In this paper, a single configuration model containing nonorthogonal magnetic orbitals is developed to represent the important features of the antiferromagnetic state of a transition metal dimer.
Abstract: A single configuration model containing nonorthogonal magnetic orbitals is developed to represent the important features of the antiferromagnetic state of a transition metal dimer. A state of mixed spin symmetry and lowered space symmetry is constructed which has both conceptual and practical computational value. Either unrestricted Hartree–Fock theory or spin polarized density functional theory, e.g., Xα theory, can be used to generate the mixed spin state wave function. The most important consequence of the theory is that the Heisenberg exchange coupling constant J can be calculated simply from the energies of the mixed spin state and the highest pure spin multiplet.
2,242 citations
TL;DR: In this article, the possibility of a new kind of electronic state corresponding roughly to Pauling's idea of resonance valence bonds in metals was pointed out, and an estimate of its energy was made in one case.
Abstract: The possibility of a new kind of electronic state is pointed out, corresponding roughly to Pauling's idea of “resonating valence bonds” in metals. As observed by Pauling, a pure state of this type would be insulating; it would represent an alternative state to the Neel antiferromagnetic state for S = 1/2. An estimate of its energy is made in one case.
2,022 citations
TL;DR: Theoretical Methodologies and Simulation Tools, and Poisson−Boltzmann Theory, and Phenomenology of Transport inProton-Conducting Materials for Fuel-CellApplications46664.2.1.
Abstract: 1. Introduction 46372. Theoretical Methodologies and Simulation Tools 46402.1. Ab Initio Quantum Chemistry 46412.2. Molecular Dynamics 46422.2.1. Classical Molecular Dynamics and MonteCarlo Simulations46432.2.2. Empirical Valence Bond Models 46442.2.3. Ab Initio Molecular Dynamics (AIMD) 46452.3. Poisson−Boltzmann Theory 46452.4. Nonequilibrium Statistical Mechanical IonTransport Modeling46462.5. Dielectric Saturation 46473. Transport Mechanisms 46483.1. Proton Conduction Mechanisms 46483.1.1. Homogeneous Media 46483.1.2. Heterogeneous Systems (ConfinementEffects)46553.2. Mechanisms of Parasitic Transport 46613.2.1. Solvated Acidic Polymers 46613.2.2. Oxides 46654. Phenomenology of Transport inProton-Conducting Materials for Fuel-CellApplications46664.1. Hydrated Acidic Polymers 46664.2. PBI−H
1,915 citations