Ab initio Computational Insight into the Interaction of Alkyl-substituted Ethene and Sulfenyl Halide

2011 ◽  
Vol 66 (8) ◽  
pp. 850-856 ◽  
Author(s):  
Ausra Vektariene ◽  
Gytis Vektaris
Keyword(s):  
Ab Initio ◽  
Ring Opening ◽  
Correlation Energy ◽  
Intrinsic Reaction Coordinate ◽  
Energy Profiles ◽  
Electron Correlation Energy ◽  
Reaction Proceeds ◽  
Mechanism Of Interaction ◽  
Moller Plesset ◽  
Insight Into

The ab initio calculations approach was used to determine the mechanism of interaction between propene and a sulfenyl halide. The second-order Møller-Plesset corrections for the electron correlation energy were applied to calculate the most probable Gibbs Free Energy profiles for the selected reaction. All optimized structures were confirmed by vibrational frequency analysis and intrinsic reaction coordinate calculations. Two possible reaction pathways were proposed and evaluated to conclusively characterize the reaction. The reaction proceeds via formation of a cyclic episulfonium intermediate, stereoselective ring opening of the episulfonium intermediate by the chloride anion, and isomerization of the adduct of the kinetically controlled reaction into the thermodynamically favorable product.

Relativistic AB Initio calculations of the properties of ionic solids

1986 ◽  
Vol 320 (1553) ◽  
pp. 107-158 ◽  
Keyword(s):  
Ab Initio ◽  
Short Range ◽  
Correlation Energy ◽  
Electron Gas ◽  
Empirical Method ◽  
Coulombic Interactions ◽  
Ionic Solids ◽  
Electron Correlation Energy ◽  
Crystal Properties ◽  
Semi Empirical

Relativistic ab initio calculations of inter-ionic potential energies are used to develop a reliable non-empirical method for predicting the properties of ionic solids containing the heaviest ions. A physically realistic method for describing the non-negligible differences between free and in-crystal ion wavefunctions is described. Functions are presented for describing the partial quenching, arising from ion wavefunction overlap, of the standard long-range form of the inter-ionic dispersive attractions. These attractions are shown to be distinct from the contributions to the inter-ionic potentials that arise from that portion of the electron correlation energy which is nonzero solely because of overlap of the ion wavefunctions. The results presented for NaCl, MgO and the fluorides of Li, Na, Ag and Pb show that these modifications overcome the deficiencies of previous calculations. Ab initio predictions of the closest cation-cation and anion-anion short-range interactions, which are not available from semi-empirical fits to experimental data, are presented. The non-point coulombic interactions between pairs of anions, derived by adding the dispersive attractions to the short-range interactions, are compared with previous semi-empirical and approximate ab initio results. The uncorrelated short-range inter-ionic potentials computed exactly are compared with those predicted from electron-gas theory. The use of the electron-gas approximation to describe any of these potentials degrades the quality of the predicted crystal properties.

An approximate ab initio method based on the DIM model

2000 ◽  
Vol 78 (12) ◽  
pp. 1575-1586 ◽  
Author(s):  
John M Cullen
Keyword(s):  
Ab Initio ◽  
Excited States ◽  
Electron Correlation ◽  
Correlation Energy ◽  
Basis Sets ◽  
Ab Initio Method ◽  
First Order ◽  
Hartree Fock ◽  
Modified Method ◽  
Electron Correlation Energy

Using a second quantized formulation, an approximate diatomics in molecules (DIM) theory is presented in which all three- and four-centered electronic integrals are neglected. To ameliorate the effects of this approximation, the DIM one electron operator is constructed so that the true ab initio first-order density matrix and total energy are reproduced at the Hartree–Fock level. The resulting model was extensively tested for a variety of basis sets for its capability of capturing both the dynamic and nondynamic components of the electron correlation energy as well as the energies of excited electronic states. A modified method in which the DIM one-electron operator is formed from the initial extended Hückel guess of the Hartree–Fock orbitals was also found to produce excellent results.Key words: DIM, electron correlation energy, excited states, semiempirical.

An ab initio study on the reaction of CH(X2π) with CH4

1993 ◽  
Vol 71 (4) ◽  
pp. 512-519 ◽  
Author(s):  
Zhonghua Yu ◽  
Congxiang Chen ◽  
Mingbao Huang
Keyword(s):  
Ab Initio ◽  
Correlation Energy ◽  
Reaction Path ◽  
Addition Reaction ◽  
High Energy ◽  
Insertion Reaction ◽  
Molecular Orbital Calculations ◽  
Configuration Interaction Method ◽  
State Abstraction ◽  
Moller Plesset

The mechanism of the reaction CH(X2π) + CH4 has been investigated by ab initio molecular orbital calculations. Addition, insertion, and abstraction–addition reaction paths have been examined by, in total, five methods of approach. The addition reaction path has a rather high energy barrier. Our calculations have implied that the assumed insertion reaction path does not seem to exist for the reaction CH + CH4, and a two-step mechanism (abstraction–addition reaction path) was then proposed. For the abstraction–addition reaction, the reactants, transition state, intermediates, and products were optimized at the HF/3-21G and HF/6-31G* levels, and vibrational frequencies were calculated at the HF/3-21G level. Electronic correlation energy was estimated by means of the Møller–Plesset perturbation theory and configuration interaction method. The excited-state abstraction reaction was also studied in some detail.

Atomic Partitioning of the MPn (N=2,3,4) Dynamic Electron Correlation Energy by the Interacting Quantum Atoms (IQA) Method: A Fast and Accurate Electrostatic Potential Integral Approach

2019 ◽  
Author(s):  
Mark A. Vincent ◽  
arnaldo silva ◽  
Paul Popelier
Keyword(s):  
Force Field ◽  
Electrostatic Potential ◽  
Electron Correlation ◽  
Correlation Energy ◽  
Integral Approach ◽  
Electron Correlation Energy ◽  
Order Of Magnitude ◽  
Interacting Quantum Atoms ◽  
Moller Plesset

The calculation of Moller-Plesset electron correlation energy of a topological atom interacting with its environment is now sped up by about an order of magnitude. Secondly, the proposed algorithm generates much more accurate energies for modest quadrature grids. Thus it becomes now possible to provide the training of the force field FFLUX with electron correlation energies.

Ab initio MO study of protonation of carbamic acid, methyl carbamate and methyl N-methylcarbamate

1988 ◽  
Vol 53 (6) ◽  
pp. 1141-1148 ◽  
Author(s):  
Milan Remko
Keyword(s):  
Ab Initio ◽  
Gas Phase ◽  
Correlation Energy ◽  
Geometry Optimization ◽  
Carbamic Acid ◽  
Proton Affinities ◽  
Acid Methyl ◽  
Methyl Derivatives ◽  
Moller Plesset ◽  
Complete Geometry Optimization

The ab initio SCF method was applied to the protonation of the carbonyl group in carbamic acid and its methyl derivatives, viz. methyl carbamate and methyl N-methylcarbamate. Complete geometry optimization was accomplished for these compounds and their protonated species using the MINI-1, 3-21 G, and 6-31 G* bases and the proton affinities were calculated at the MINI-1, 3-21 G, 6-31 G*, and 6-31 G** levels. 2nd and 3rd order Moller-Plesset perturbation calculations were also performed for examining the effect of the correlation energy on the calculated protonation energies. The carbonyl protonation energies were found to increase in order carbamic acid < methyl carbamate < methyl N-methylcarbamate. The absolute values of calculated gas phase proton affinities depend on the basis used and way of evaluating the correlation energy. The results are discussed with respect to the theoretical proton affinities of structurally related amides and to related available theoretical gas phase proton affinities.

Sign in / Sign up

Export Citation Format

Share Document