Electron electrons, frontier

Keywords Chemical orbital theory. Electron delocalization. Frontier orbital. Orbital amplitude, Orbital energy, Orbital interaction. Orbital mixing rule, Orbital phase, Orbital phase continuity, Orbital phase environment. Orbital synunetry, Reactivity, Selectivity... 

CASSCF wave function includes only the static correlation only a small number of electrons spanning frontier orbitals are correlated between them, while... 

Electron occupation in the frontier bands of metal crystals varies with different metals as shown in Fig. 2-7. For metallic iron the frontier bands consist of hybridized 4s-3d-4p orbitals, in which 4s and 3d are partially occupied by electrons but 4p is vacant for electrons. Figure 2-8 shows the electron state density curve of metallic iron, where the 3d and 4s bands are partially filled with electrons. Electrons in metals occupy the energy states in a frontier band successively fix>m the lower band edge level to the Fermi level, leaving the higher levels vacant. 

PRIVACY SPEECH RIGHTS ORGs Electronic Frontier Foundation... 

Isolobal Relationship Two molecular fragments are isolobal if the number, symmetry properties, shapes and approximate energies of their frontier orbitals are the same. They may or may not also be isoelectronic. If the two fragments are isoelectronic, in the sense that the ratio of the number of electrons in frontier orbitals to the number of frontier orbitals is same, then the net charges on the two species will be the same. The orbitals whose similarity is critical in determining isolobality are called frontier orbitals. 

Diazoalkane addition to cyclopropenes having electron withdrawing substituents at 1- or 2-positions generally leads to the regioselectivity predicted on electronic or frontier orbital grounds ... 

Table 2. -Electron density, frontier density, and free valence at the exocyclic carbon of CTCX, HCX and TCX ...

V-Electron densities, CNDO/2. Total electron densities, CNDO/2. "Total electron densities, CNDO/2 for N(D—H. tr-Electron densities, frontier electron density calculation. "Frontier electron densities. 

As no reactivity studies of 38 were reported, facile and general routes to [Ln(BIPM ) (R)] complexes were required and this was addressed by the syntheses of [Y(BIPM ) (CH SiMejjCTHF)] (39), [Y(BlPMrws)(CHjPh)(THF)] (40) and [Y(BIPM s)(I)(THF)J (41) from yttrium alkyl precursors at room temperature (Scheme 27) [90], It was shown that 41 could alternatively be synthesized by deprotonation of [Y(BIPM H) (IfjfTHF)] with benzyl potassium [91]. These synthetic techniques have since been employed to synthesize a wide range of Ln methanediide complexes and this area has been reviewed thoroughly [85]. Computational studies on 39-41 revealed as expected localized electron density at the methanediide centers corresponding to approximately two lone pairs of electrons in frontier orbitals that do not interact appreciably with vacant Y orbitals (<5 % Y orbital contribution) [90]. The Y—C distances in... 

First, the number of valence functions (or frontier orbitals) and valence electrons (frontier orbital occupancy) determines the tendency toward cluster bonding. It is instructive to recall that the structural motif in elemental boron is the icosahedron with six-connected boron atoms see Borides Solid-state Chemistry)-, it is the tetrahedral carbon atom in the diamond form of elemental carbon with four-connected carbon atoms and it is three-connected phosphorus atoms in the sheets of elemental black phosphorus see Phosphides Solid-state Chemistrjlj. Boron has more valence orbitals than valence electrons, naturally leading to orbitally rich cluster formation for example, BH has three orbitals and two electrons and forms... 

Cans, D. and R.U. Sirius 1990. Civilizing the electronic frontier An interview with Mitch Kapor and John Barlow of the El-... 

Sterling, B. 1992, The Hacker Crackdown Law and Disorder on the Electronic Frontier. Bantam Books, New Ifork. 

When a solvent molecule becomes attached to a solute (which may be a reactant or a transition state), the electrons in frontier orbitals are affected to some extent. Therefore, when the solvated species undergoes an electron transition, absorption occurs at wavelengths that vary somewhat with the nature of the solvent. It is possible to make use of the spectral shifts (the so-called solvatochromic ect) to give some indication of the strength of solvent-solute interactions. 

Conversely, there was shown that the so-called macroscopic physicochemical structural features such as melting or boiling point or density are not the best indicators for rational ordering of the elemental periodicity this perhaps in all these cases all atomic electrons and levels are perturbed or regarded as equivalent when averaging for density, in contrast with the electronic frontier behavior quantified by electronegativity and related reactivity indices. 

To solve the electronic frontier (valence or bonding) problems on the basis of the many-electronic ground state stands for quantum chemists almost as to determine the weight of the captain of a large ship by weighing the ship when he is and when he is not on board (Coulson, 1960)... 

In 1998, the Electronic Frontier Foundation (FEE) actually built a DES-cracking computer, at the cost of 200,000, consisting of an ordinary personal computer with a large array of custom-designed chips. It cracks a DES key in an average of four and a half days. 

The figure shows a frontier orbital map of metal and ligands constructed for the [RuCl6-n(PhCN)n] family, by use of equations 1 and 2. Note that the vertical axis is related to electrode potential i.e. these data are electron-transfer couples, not orbital energies, and as such they are particularly appropriate for describing both redox and optical charge-transfer phenomena. For example, the metal-centered electron/electron... 

---