Electron pair interaction

Another interesting application of the total energy approach involves superconductivity. For conventional superconductors, the 1957 theory of Bardeen, Cooper and Schrieffer [26] has been subject to extensive tests and has emerged as one of the most successful theories in physics. However, because the superconducting transition temperature Tc depends exponentially on the electron-phonon coupling parameter X and the electron-electron Coulomb parameter p, it has been difficult to predict new superconductors. The sensitivity is further enhanced because the net attractive electron-electron pairing interaction is proportional to X-p, so when these parameters are comparable, they need to be determined with precision. 

Here, qj is the charge of electron j, r is the distance between electrons i and j. From the classical interaction energy we can extract the operator accounting for the electron-electron pair interaction g i,j) via the corresponding principle (c.p.) (21),... 

The heats of vaporization are measures of the work that must be done to overcome interatomic attractive forces. Since there are no ordinary electron-pair interactions between noble gas atoms, these weak forces (of the van der Waals or London type) are proportional to the polarizability and inversely proportional to the ionization enthalpies of the atoms they increase therefore as the size and diffuseness of the electron clouds increase. 

F 2p character than F 2s character and is also bonding with respect to the FI orbital. This set of orbitals (2cr, 3a) illustrates a central feature of the MO approach. Whereas a simple Lewis structure or valence picture would draw a localized electron pair interaction between two orbitals, the MO picture attributes some bonding character to two separate molecular orbitals. This simple MO diagram illustrates the difficulty of determining a meaningful definition for bond order in a polyatomic molecule. No single MO completely represents the bonding between two atoms. 

W.E. PALKE and B. KIRTMAN, Valence shell electron pair interactions in H2O and H2S a test of the valence shell electron pair repulsion theory. J. Am. Chem. Soc., 100, 5717 (1978). 

The coupled-cluster (CC) method (Cizek and Paldus, 1971 Harris, 1977a,b Bartlett and Purvis, 1978) is an attempt to introduce interactions among electrons within clusters (predominantly pairs) as well as coupling among these clusters of electrons and to permit the wavefunction to contain all possible disjoint clusters. For example, we know, from the early work of Sinanoglu (1962) and others, that electron pair interactions are of utmost importance and that contributions of quadruply excited configurations to... 

The GPRG estimate for the effective electron-pair interaction therefore is significantly shorter ranged ( r ) than the RPA estimate given by Eq. 

To this point, all reactions that have been used to effect cyclizations have involved steps that have been interpreted as depending on electron pair interactions. Much less common are syntheses in which free radicals are involved, but nevertheless such reactions are useful additions to the collection of methods available for ring formation. In most cases, radical reactions give rise to reduced or partially reduced heterocyclic systems. They proceed most readily when 5- or 6-membered rings are formed. We will consider only the most common t) es of radical cyclization, which are useful in illustrating some features of radical chemistry. 

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