ChemInform Abstract: The Electronic Structure of Cyclooctatetraene and the Modern Valence- Bond Understanding of Antiaromaticity.

ChemInform ◽  
2010 ◽  
Vol 26 (40) ◽  
pp. no-no
Author(s):  
P. B. KARADAKOV ◽  
J. GERRATT ◽  
D. L. COOPER ◽  
M. RAIMONDI
Keyword(s):  
Electronic Structure ◽  
Valence Bond

scholarly journals The electronic structure of carbones revealed: insights from valence bond theory

2021 ◽  
Vol 23 (5) ◽  
pp. 3327-3334
Author(s):  
Remco W. A. Havenith ◽  
Ana V. Cunha ◽  
Johannes E. M. N. Klein ◽  
Francesca Perolari ◽  
Xintao Feng
Keyword(s):  
Electronic Structure ◽  
Valence Bond ◽  
Carbon Suboxide ◽  
Valence Bond Theory ◽  
Bond Theory

Valence bond theory reveals the nature of the OC–C bond in carbon suboxide and related allene compounds.

Effect of Alloying Elements V, Cr and Ni on the Electronic Structure and Mechanical Properties of FeAl from First-Principles Calculation

2014 ◽  
Vol 887-888 ◽  
pp. 378-383 ◽  
Author(s):  
Yu Chen ◽  
Zheng Jun Yao ◽  
Ping Ze Zhang ◽  
Dong Bo Wei ◽  
Xi Xi Luo ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Electronic Structure ◽  
Elastic Constants ◽  
First Principles ◽  
Density Functional ◽  
Valence Bond ◽  
Ternary Alloys ◽  
First Principles Calculation ◽  
Structure Stability ◽  
Alloying Element

The structure stability, mechanical properties and electronic structures of B2 phase FeAl intermetallic compounds and FeAl ternary alloys containing V, Cr or Ni were investigated using first-principles density functional theory calculations. Several models are established. The total energies, cohesive energies, lattice constants, elastic constants, density of states, and the charge densities of Fe8Al8 and Fe8XAl7 ( X=V, Cr, Ni ) are calculated. The stable crystal structures of alloy systems are determined due to the cohesive energy results. The calculated lattice contants of Fe-Al-X ( X= V, Cr, Ni) were found to be related to the atomic radii of the alloy elements. The calculation and analysis of the elastic constants showed that ductility of FeAl alloys was improved by the addition of V, Cr or Ni, the improvement was the highest when Cr was used. The order of the ductility was as follows: Fe8CrAl7 > Fe8NiAl7 > Fe8VAl7 > Fe8Al8. The results of electronic structure analysis showed that FeAl were brittle, mainly due to the orbital hybridization of the s, p and d state electron of Fe and the s and p state electrons of Al, showing typical characteristics of a valence bond. Micro-mechanism for improving ductility of FeAl is that d orbital electron of alloying element is maily involved in hybridization of FeAl, alloying element V, Cr and Ni decrease the directional property in bonding of FeAl.

The spin-coupled valence bond theory of molecular electronic structure. I. Basic theory and application to the 2 Σ + states of BeH

1980 ◽  
Vol 371 (1747) ◽  
pp. 525-552 ◽  
Keyword(s):  
Electronic Structure ◽  
Ground State ◽  
Valence Bond ◽  
Present Theory ◽  
Hamiltonian Matrix ◽  
Molecular Electronic ◽  
Good Convergence ◽  
Valence Bond Theory ◽  
Bond Theory ◽  
Molecular Electronic Structure

The spin-coupled valence bond theory of molecular electronic structure is developed, according to which the single configuration spin-coupled theory is reformulated so as to yield both ground and excited orbitals. These orbitals are subsequently used to generate v.b. structures, the Hamiltonian matrix of which is diagonalized as in the conventional v.b. method. The fundamental feature of the excited spin-coupled orbitals is that, except those with the highest energy, they retain the characteristic distorted atomic form of the ground state orbitals, and correspondingly possess negative orbital energies. This leads to compact and rapidly convergent wavefunctions for the ground and lower-lying excited states, thus overcoming one of the basic drawbacks of the original v.b. theory. The theory is applied to the 2 ∑ + states of BeH by using 53, 71 and 80 structures of this kind. Very good convergence is found for the lowest six states, and the total energy of the ground state is below that given by a very large m.o.c.i. calculation. The present theory is thus a powerful and flexible alternative to m.o.c.i. calculations but using about an order of magnitude fewer functions.

Valence-bond studies of 4-electron 3-centre bonding units. I. The π-electrons of O3, NO2−, and CH2N2

1978 ◽  
Vol 56 (8) ◽  
pp. 1093-1101 ◽  
Author(s):  
Richard D. Harcourt ◽  
Walter Roso
Keyword(s):  
Electronic Structure ◽  
Ab Initio ◽  
Valence Bond ◽  
Ground States ◽  
Wave Functions ◽  
Dipolar Cycloaddition ◽  
Cycloaddition Reactions ◽  
Electronic Mechanism ◽  
Increased Valence

Some ab-initio valence-bond wave-functions are reported for the π-electrons of the ground-states of O3, NO2−, and CH2N2. Examination of these wave-functions provides further support for the hypothesis that, for the ground-states of many electron-excess molecules, important valence-bond structures are those that are compatible with the electroneutrality principle, i.e. they carry either small or zero formal charges on each of the atoms. For O3 and CH2N2, the important valence-bond structures with zero atomic formal charges are [Formula: see text]Each of these structures has a 'long-bond' between non-adjacent atoms. The significance of 'long-bond' (or spin-paired diradical) structures for the electronic mechanism of 1,3-dipolar cycloaddition reactions is discussed and 'increased-valence' descriptions of the electronic structure of each molecule are presented. Some comments on the utility of 'increased-valence' structures are provided.

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