The Chemical bond: v.1: Fundamental aspects of chemical bonding

2015 ◽  
Vol 52 (09) ◽  
pp. 52-4773-52-4773
2019 ◽  
Vol 21 (18) ◽  
pp. 9590-9596 ◽  
Author(s):  
Nikolay V. Tkachenko ◽  
Alexander I. Boldyrev

A novel approach to chemical bond analysis for excited states has been developed.


2006 ◽  
Vol 61 (7) ◽  
pp. 799-807 ◽  
Author(s):  
Gérard Demazeau

Materials chemistry under high pressures is an important research area opening new routes for stabilizing novel materials or original structures with different compositions (oxides, oxoborates, nitrides, nitridophosphates, sulfides,. . .).Due to the varieties of chemical compositions and structures involved, high pressure technology is also an important tool for improving the investigations on chemical bonding and consequently the induced physico-chemical properties.Two different approaches can be described: (i) the chemical bond is pre-existing and in such a case, high pressures lead to structural transformations, (ii) the chemical bond does not exist and high pressures are able to help the synthesis of novel materials. In both cases the condensation effect (ΔV < 0 between precursors and the final product) is the general rule. In addition, through the improvement of the reactivity, high pressures can lead to materials that are not reachable through other chemical routes.


1956 ◽  
Vol 34 (12A) ◽  
pp. 1369-1376 ◽  
Author(s):  
E. Mooser ◽  
W. B. Pearson

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.


2020 ◽  
Vol 22 (1) ◽  
pp. 223
Author(s):  
Mihai V. Putz

The fashionable Parr–Pearson (PP) atoms-in-molecule/bonding (AIM/AIB) approach for determining the exchanged charge necessary for acquiring an equalized electronegativity within a chemical bond is refined and generalized here by introducing the concepts of chemical power within the chemical orthogonal space (COS) in terms of electronegativity and chemical hardness. Electronegativity and chemical hardness are conceptually orthogonal, since there are opposite tendencies in bonding, i.e., reactivity vs. stability or the HOMO-LUMO middy level vs. the HOMO-LUMO interval (gap). Thus, atoms-in-molecule/bond electronegativity and chemical hardness are provided for in orthogonal space (COS), along with a generalized analytical expression of the exchanged electrons in bonding. Moreover, the present formalism surpasses the earlier Parr–Pearson limitation to the context of hetero-bonding molecules so as to also include the important case of covalent homo-bonding. The connections of the present COS analysis with PP formalism is analytically revealed, while a numerical illustration regarding the patterning and fragmentation of chemical benchmarking bondings is also presented and fundamental open questions are critically discussed.


A symposium on the beginnings of solid state physics, organized by Sir Nevill Mott, F. R. S., was held by the Royal Society from 30 April to 2 May 1979, and 26 papers contributed to this symposium were published in Proc. R. Soc. Lond . A 371, 1-177 (1980). One aspect of solid state physics, that dealing with the nature of the chemical bond in solids, was presented to only a quite limited extent. The present paper, which emphasizes my own early work in this field, has been written to supplement the symposium papers.


2019 ◽  
Vol 20 (4) ◽  
pp. 667-684
Author(s):  
Asnat R. Zohar ◽  
Sharona T. Levy

This work seeks to solve one of the basic problems in chemistry learning: understanding the chemical bond as a dynamic equilibrium between attractive and repulsive forces. This force-based model is difficult to grasp, as there are no analogues from everyday life for both attractions and repulsions happening simultaneously. In addition, current teaching approaches often mislead by using mainly the ‘octet rule’ heuristic. As a result, students construct naïve models of the chemical bond, usually viewing atoms as solid balls that are attached to each other in order to “achieve an octet.” To represent the force-based dynamics of the bond, we designed the ELI-Chem learning environment. This environment enables interaction as an atom with another atom while observing the underlying forces and the potential energy curve. Our theoretical framework is based on Embodied Learning theory by relating conceptual learning to bodily experiences. The study uses qualitative and quantitative methods with 21 high school chemistry students in a pretest–intervention–posttest design. During a 40 minute activity with the ELI-Chem simulation, students were prompted to discover the underlying forces of bonding and relate them to energy changes. Findings show that learning with the ELI-Chem simulation supports students in gaining the knowledge elements that are required to build the dynamic force-based mental model of chemical bonding, and to conceptualize chemical energy as due to forces. Finally, the design principles of the ELI-Chem environment are discussed. Aligned with science standards, attending to students’ difficulties, and using the advantages of a computer simulation, the ELI-Chem environment provides an appropriate representation of chemical bonding, which is more valid scientifically yet makes the abstract concept accessible.


1996 ◽  
Vol 453 ◽  
Author(s):  
Alessandra Continenza ◽  
Teresa M. de Pascale ◽  
Franco Meloni ◽  
Marina Serra ◽  
Ali Shaukat ◽  
...  

AbstractAgGaS2 is a technologically important semiconductor for its large birefringence coefficient. In this work we compare the theoretical ab-initio all-electron FLAPW results with very refined experimental data obtained with accurate X-ray analysis. In particular we focus our attention to the electronic distribution along the significative bonding directions connecting the three different atoms. Furthermore, the charge density contours around Ag provide a clear evidence of the contribution of its d orbitals to the chemical bond.


The determination of surface chemical bonds has involved an interplay between theory and experiment. Two major techniques, I.e.e.d. and s.e.X.a.f.s., are discussed and some of their limitations analysed. Finally, I look forward to the development of other methods that will further extend our powers to unravel surface chemical bonding.


Author(s):  
M. L. Knotek

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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