scholarly journals Semiquantal Valence-Bond Wave Packet Description of Chemical Bonding

2009 ◽  
Vol 82 (8) ◽  
pp. 975-983 ◽  
Author(s):  
Koji Ando
Keyword(s):  
Wave Packet ◽  
Chemical Bonding ◽  
Valence Bond

scholarly journals An Investigation into the Approximations Used in Wave Packet Molecular Dynamics for the Study of Warm Dense Matter

Plasma ◽  
2021 ◽  
Vol 4 (2) ◽  
pp. 294-308
Author(s):  
William A. Angermeier ◽  
Thomas G. White
Keyword(s):  
Molecular Dynamics ◽  
Wave Packet ◽  
Hydrogen Plasma ◽  
Valence Bond ◽  
Dense Matter ◽  
Basis Set ◽  
Warm Dense Matter ◽  
Scaling Parameters ◽  
Oppenheimer Approximation ◽  
Semi Empirical

Wave packet molecular dynamics (WPMD) has recently received a lot of attention as a computationally fast tool with which to study dynamical processes in warm dense matter beyond the Born–Oppenheimer approximation. These techniques, typically, employ many approximations to achieve computational efficiency while implementing semi-empirical scaling parameters to retain accuracy. We investigated three of the main approximations ubiquitous to WPMD: a restricted basis set, approximations to exchange, and the lack of correlation. We examined each of these approximations in regard to atomic and molecular hydrogen in addition to a dense hydrogen plasma. We found that the biggest improvement to WPMD comes from combining a two-Gaussian basis with a semi-empirical correction based on the valence-bond wave function. A single parameter scales this correction to match experimental pressures of dense hydrogen. Ultimately, we found that semi-empirical scaling parameters are necessary to correct for the main approximations in WPMD. However, reducing the scaling parameters for more ab-initio terms gives more accurate results and displays the underlying physics more readily.

THE CHEMICAL BOND IN SEMICONDUCTORS: THE GROUP V B TO VII B ELEMENTS AND COMPOUNDS FORMED BETWEEN THEM

1956 ◽  
Vol 34 (12A) ◽  
pp. 1369-1376 ◽  
Author(s):  
E. Mooser ◽  
W. B. Pearson
Keyword(s):  
Optical Properties ◽  
Chemical Bond ◽  
Chemical Bonding ◽  
Valence Bond ◽  
Electrical And Optical Properties ◽  
Group V ◽  
New Model ◽  
Bond Model

A brief review is first given of the developments which led to an understanding of the important role played by chemical bonding in semiconductors. The properties of the Group V B to VII B elements and of some compounds formed between these elements are then considered according to the valence bond model of Pauling. This leads to the conclusion that the band scheme in these substances is somewhat different to that which has been generally accepted, and we discuss the new model in relation to their electrical and optical properties.

The nature of the chemical bonding and crystallography of π-cyclopentadienyl-hexakis(trifluoromethyl)benzene rhodium

1966 ◽  
Vol 292 (1428) ◽  
pp. 61-77 ◽  
Keyword(s):  
Crystal Structure ◽  
Electronic Structure ◽  
Chemical Bonding ◽  
Three Dimensional ◽  
Valence Bond ◽  
Transition Metal Ions ◽  
Arene Complexes ◽  
Ring Conformation ◽  
X Ray ◽  
Cyclopentadienyl Anion

A three-dimensional X-ray analysis of the crystal structure of π-cyclopentadienyl-hexakis- (trifluoromethyl)benzene rhodium, based on 2119 independent reflexions, is described. The crystals are monoclinic, a = 9·48 Å, b — 12·59 Å, c = 17·79 Å, β = 114·75°, Z = 4, space group P2 1/c . The final residual factor is 0·096, the Rh—C bond distances having standard deviations which range from 0·014 to 0·027 Å; bond lengths in the benzene ligand (σ = 0·020 Å), together with the ring conformation, illustrate a novel form of bonding for arene complexes of transition metal ions. The bonding of the π-cyclopentadienyl anion to the rhodium appears to be asymmetric and is related to that in similar molecules. Valence bond and molecular orbital descriptions of the electronic structure of the molecule are summarized together with those intra- and inter-molecular non-bonded interactions which stabilize the conformation of the —CF 3 groups.

Chemical Bonding 2: Modern Theories of Chemical Bonding

2021 ◽  
pp. 102-128
Author(s):  
Christopher O. Oriakhi
Keyword(s):  
Chemical Bonding ◽  
Valence Bond ◽  
Molecular Geometry ◽  
Electron Delocalization ◽  
Molecular Orbital Theory ◽  
Orbital Theory ◽  
Valence Bond Theory ◽  
Electron Group ◽  
Bond Theory ◽  
Lewis Structures

Chemical Bonding II: Modern Theories of Chemical Bonding explains four bonding theories related to molecular geometry and bonding. Lewis structures and the Valence-Shell Electron-Pair Repulsion (VSEPR) model are used to describe and predict the electron group geometry, molecular geometry and shapes of molecules. The VSEPR model is then used to predict molecular polarity as a function of shape. This leads to Valence Bond Theory, which uses the principles of orbital overlap and hybridization of atomic orbitals to describe chemical bonding. Finally the Molecular Orbital Theory (MOT) based on electron delocalization is discussed in terms of bonding and anti-bonding molecular orbitals.

scholarly journals A Critical Look at Linus Pauling’s Influence on the Understanding of Chemical Bonding

Molecules ◽  
2021 ◽  
Vol 26 (15) ◽  
pp. 4695
Author(s):  
Sudip Pan ◽  
Gernot Frenking
Keyword(s):  
Chemical Bonding ◽  
Close Association ◽  
Valence Bond ◽  
Theoretical Description ◽  
Binding Model ◽  
Linus Pauling ◽  
Bonding Theory ◽  
Pair Bonds ◽  
Wide Range ◽  
Further Development

The influence of Linus Pauling on the understanding of chemical bonding is critically examined. Pauling deserves credit for presenting a connection between the quantum theoretical description of chemical bonding and Gilbert Lewis’s classical bonding model of localized electron pair bonds for a wide range of chemistry. Using the concept of resonance that he introduced, he was able to present a consistent description of chemical bonding for molecules, metals, and ionic crystals which was used by many chemists and subsequently found its way into chemistry textbooks. However, his one-sided restriction to the valence bond method and his rejection of the molecular orbital approach hindered further development of chemical bonding theory for a while and his close association of the heuristic Lewis binding model with the quantum chemical VB approach led to misleading ideas until today.

Radiation-induced surface decomposition

1983 ◽  
Vol 41 ◽  
pp. 368-369
Author(s):  
M. L. Knotek
Keyword(s):  
Ionizing Radiation ◽  
Atomic Structure ◽  
Chemical Bonding ◽  
Neutral Species ◽  
Radiation Induced ◽  
Physical And Chemical ◽  
Surface Decomposition ◽  
The Relationship ◽  
Electron And Photon ◽  
Surface Bond

Modern surface analysis is based largely upon the use of ionizing radiation to probe the electronic and atomic structure of the surfaces physical and chemical makeup. In many of these studies the ionizing radiation used as the primary probe is found to induce changes in the structure and makeup of the surface, especially when electrons are employed. A number of techniques employ the phenomenon of radiation induced desorption as a means of probing the nature of the surface bond. These include Electron- and Photon-Stimulated Desorption (ESD and PSD) which measure desorbed ionic and neutral species as they leave the surface after the surface has been excited by some incident ionizing particle. There has recently been a great deal of activity in determining the relationship between the nature of chemical bonding and its susceptibility to radiation damage.

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