Topological Aspects of Chemical Reactivity. Electron Correlation in the Course of Chemical Reactions

1993 ◽  
Vol 58 (8) ◽  
pp. 1751-1760 ◽  
Author(s):  
Robert Ponec ◽  
Martin Strnad
Keyword(s):  
Chemical Reactions ◽  
Electron Correlation ◽  
Energy Barrier ◽  
Chemical Reactivity ◽  
Similarity Index ◽  
Pericyclic Reactions ◽  
Correlation Effects ◽  
Transient Species

The second order similarity index gRP, which has been proposed recently as a new means for a qualitative characterization of correlation effects in chemical reactivity, was generalized by incorporation into a topological model of the overlap determinant method. The resulting approach, which provides information about the variation of electron correlation during chemical reactions, was applied to the investigation of several selected pericyclic reactions. Consistent with what can be expected, the role of electron correlation was found to be the most critical for transition states of other transient species near the top of the energy barrier. The systematic differences in the extent of electron correlation between allowed and forbidden reactions are also discussed.

Topological aspects of chemical reactivity. On the possible use of similarity index in characterizing the transition state structure in concerted pericyclic reactions

1987 ◽  
Vol 52 (6) ◽  
pp. 1375-1385
Author(s):  
Robert Ponec
Keyword(s):  
Transition State ◽  
Chemical Reactivity ◽  
Transition States ◽  
Similarity Index ◽  
Pericyclic Reactions ◽  
State Structure ◽  
Transition State Structure ◽  
Topological Similarity

The use of the topological similarity index as a simple means for classification and characterization of the structure of the transition states in concerted pericyclic reactions is discussed. The suggested formulation makes it possible to bring a quantitative aspects into the empirical Dewar's classification of transition states in terms of aromaticity and/or antiaromaticity.

Geodesic Formulation of the Least Motion Principle in Chemical Reactivity

1992 ◽  
Vol 57 (2) ◽  
pp. 232-240 ◽  
Author(s):  
Martin Strnad ◽  
Robert Ponec
Keyword(s):  
Mathematical Model ◽  
Hilbert Space ◽  
Structural Changes ◽  
Chemical Reactivity ◽  
The State ◽  
Pericyclic Reactions ◽  
Electron States ◽  
Intuitive Criterion

In this study an attempt is presented at the quantitative formulation of the old intuitive criterion for the characterization of chemical reactivity known as the principle of the least motion. The proposed formulation originates from the abstract mathematical model, within the framework of which the criterion of minimal structural changes is realized by the requirement of minimal changes of the state vectors in the Hilbert space of electron states. The presented approach is demonstrated on the practical example of pericyclic reactions for which its results correctly reproduce the conclusions of Woodward-Hoffmann rules.

Topological aspects of chemical reactivity. Valency changes in the course of chemical reactions

1987 ◽  
Vol 52 (11) ◽  
pp. 2603-2612 ◽  
Author(s):  
Robert Ponec
Keyword(s):  
Electron Density ◽  
Chemical Reactions ◽  
Chemical Treatment ◽  
Quantum Chemical ◽  
Chemical Reactivity ◽  
Topological Analysis ◽  
Topological Description

The Jug and Gopinathan approach to the use of valency changes for the characterization of chemical reactions is generalized by incorporating it into the framework of the recently proposed topological description of chemical reactivity in terms of the overlap determinant method. The conclusions of the simple topological analysis agree with the results of the direct quantum chemical treatment, indicating thus that the overlap determinant method depicts correctly the principal features of the electron density reorganization occuring during the chemical reactions.

scholarly journals Electron correlation effects on exchange interactions and spin excitations in 2D van der Waals materials

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Liqin Ke ◽  
Mikhail I. Katsnelson
Keyword(s):  
Electron Correlation ◽  
Van Der Waals ◽  
Magnetic Interactions ◽  
High Symmetry ◽  
Electron Correlations ◽  
Correlation Effects ◽  
Spin Excitations ◽  
Electron Correlation Effects ◽  
Van Der Waals Materials

AbstractDespite serious effort, the nature of the magnetic interactions and the role of electron-correlation effects in magnetic two-dimensional (2D) van der Waals materials remains elusive. Using CrI3 as a model system, we show that the calculated electronic structure including nonlocal electron correlations yields spin excitations consistent with inelastic neutron-scattering measurements. Remarkably, this approach identifies an unreported correlation-enhanced interlayer super-superexchange, which rotates the magnon Dirac lines off, and introduces a gap along the high-symmetry Γ-K-M path. This discovery provides a different perspective on the gap-opening mechanism observed in CrI3, which was previously associated with spin–orbit coupling through the Dzyaloshinskii–Moriya interaction or Kitaev interaction. Our observation elucidates the critical role of electron correlations on the spin ordering and spin dynamics in magnetic van der Waals materials and demonstrates the necessity of explicit treatment of electron correlations in the broad family of 2D magnetic materials.

Perspectives on the Role of the Frontier Effective-for-Reaction Molecular Orbital (FERMO) in the Study of Chemical Reactivity: An Updated Review

2020 ◽  
Vol 24 (3) ◽  
pp. 314-331 ◽  
Author(s):  
Letícia S. Braga ◽  
Daniel H. S. Leal ◽  
Kamil Kuca ◽  
Teodorico C. Ramalho
Keyword(s):  
Molecular Orbital ◽  
Chemical Reactions ◽  
Chemical Reactivity ◽  
Molecular Orbitals ◽  
Frontier Molecular Orbital ◽  
Molecular Orbital Theory ◽  
Orbital Theory ◽  
Highest Occupied Molecular Orbital ◽  
Lowest Unoccupied Molecular Orbital

Molecular orbitals are critical in the rationalization of several chemical reactions. Thus, the frontier molecular orbital theory, proposed by Fukui's group, postulated the importance of the Highest Occupied Molecular Orbital (HOMO) and the Lowest Unoccupied Molecular Orbital (LUMO) for chemical reactions. It should be kept in mind, however, that there are limitations of this theory and new perspectives about the chemical reactivity have recently been arisen based on composition and location of other frontier molecular orbitals. In this review, we have reported the development and the most recent applications of the Frontier Effective-for-Reaction Molecular Orbital (FERMO) concept, which describes the breaking and formation of new chemical bonds and can in turn, provide important clues that modulate chemical reactivity of atoms and molecules.

Towards relativistic ECP / DFT description of chemical bonding in E112 compounds: spin-orbit and correlation effects in E112X versus HgX (X=H, Au)

Open Physics ◽  
2006 ◽  
Vol 4 (4) ◽  
Author(s):  
Andréi Zaitsevskii ◽  
Elena Rykova ◽  
Nikolai Mosyagin ◽  
Anatoly Titov
Keyword(s):  
Electron Correlation ◽  
Computational Procedure ◽  
Nuclear Model ◽  
Spin Orbit ◽  
Correlation Effects ◽  
Hartree Fock ◽  
Promising Tool ◽  
Magnetic Spin ◽  
High Level

AbstractThe relativistic effective core potential (RECP) approach combined with the spin-orbit DFT electron correlation treatment was applied to the study of the bonding of eka-mercury (E112) and mercury with hydrogen and gold atoms. Highly accurate small-core shape-consistent RECPs derived from Hartree-Fock-Dirac-Breit atomic calculations with Fermi nuclear model were employed. The accuracy of the DFT correlation treatment was checked by comparing the results in the scalar-relativistic (spin-orbit-free) limit with those of high level scalar-relativistic correlation calculations within the same RECP model. E112H was predicted to be slightly more stable than its lighter homologue (HgH). The E112-Au bond energy is expected to be ca. 25–30 % weaker than that of Hg-Au. The role of correlations and magnetic (spin-dependent) interactions in E112-X and Hg-X (X=H, Au) bonding is discussed. The present computational procedure can be readily applied to much larger systems and seems to be a promising tool for simulating E112 adsorption on metal surfaces.

Topological aspects of chemical reactivity. On the similarity of molecular structures

1987 ◽  
Vol 52 (3) ◽  
pp. 555-562 ◽  
Author(s):  
Robert Ponec
Keyword(s):  
Electron Density ◽  
Chemical Reactions ◽  
Chemical Reactivity ◽  
Similarity Index ◽  
Molecular Structures ◽  
Similarity Criteria ◽  
Topological Similarity

A topological similarity index is introduced, allowing to characterize quantitatively the extent of reorganization of electron density in the course of chemical reactions. The possible application of this new index for the description and the classification of chemical reactions is discussed on the basis of certain analogy of similarity criteria with the so-called least-motion principle.

scholarly journals The role of topology in organic molecules: origin and comparison of the radical character in linear and cyclic oligoacenes and related oligomers

2018 ◽  
Vol 20 (10) ◽  
pp. 7112-7124 ◽  
Author(s):  
A. Pérez-Guardiola ◽  
M. E. Sandoval-Salinas ◽  
D. Casanova ◽  
E. San-Fabián ◽  
A. J. Pérez-Jiménez ◽  
...  
Keyword(s):  
Electron Correlation ◽  
Organic Molecules ◽  
Correlation Effects ◽  
Combined Approach ◽  
Electron Correlation Effects ◽  
Carbon Nanorings ◽  
Radical Character

We discuss the nature of electron-correlation effects in carbon nanorings and nanobelts by a combined approach based on FT-DFT and RAS-SF methods.

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