Scf molecular orbital calculations

The SCF molecular orbital calculations were based on the structural model given in Figure 1. Detailed discussions of the calculations are given in references (1J.) and (24). We sum-... 

The SCF molecular orbital calculations are therefore unanimous that the direction of approach of the radical is perpendicular to the plane of the alkene and from above the attacked atom or on that side of it away from the double bond. Approach of the radical towards the centre of the double bond is... 

Table 4.11. Hartree-Fock-Roothaan SCF molecular-orbital calculations of Si-O-Si angles (in degrees) for (SiH l O and (OH)3SiOSi(OH)3...

Thiacyclobutadienes such as 244 were suggested to be 6-vr electron systems and, therefore, aromatic . Ab initio SCF molecular orbital calculations indicate the contrary the thiacyclobutadienes are predicted to have considerable ylide character. ... 

A number of SCF molecular orbital calculations for cyclopropane have been reported, among them those of Skancke, Kochanski and Lehn ", Kao and Radom, Hase and colleaguesBasch and colleagues Collins and Gallup and von Niessen and colleagues the most accurate appear to be those of Skancke (Table 1). 

The Barfield modification of INDO SCF molecular orbital calcul-... 

This result can be compared with the HMO DE,j, which is 5.38)8. Taking j8 to be 18 kcal/mol means that DE is 4.2 eV. By contrast, SCF molecular orbital calculations give a delocalization energy of 1.60 eV. Clearly, the structure-resonance method result is closer to the result from more advanced molecular... 

Results from self-consistent field (SCF) molecular orbital calculations, in combination with gas-phase photoelectron data and results from post-SCF calculations have provided a basis for descriptions of the valence electronic structure of gas-phase nucleotides and of nucleotides in water-counterion clusters. These descriptions contain values for 11 to 14 of the lowest energy ionization events in the DNA nucleotides 5 -dGMP , 5 -dAMP, 5 -dCMP and 5 -dTMP . When used with an evaluation of the difference between the Gibbs free energies of hydration for the initial and final states associated with ionization, this approach also describes the influence of hydration on the energetic ordering of ionization events in nucleotides. 

Molecular orbital calculations for the parent vinyl cation, Cj H3, were first reported by Hoffmann (161), who used the extended Hiickel method, and more recently by Yonezawa and co-workers (162), who used a semiempirical SCF procedure. Both treated the problem of classical, 172 (R = H), versus bridged structures, 173, but the methods suffered from their inability to account satisfactorily for bond-length changes, and neither discussed the question of linear, 172a, versus bent, 172b, structures. 

All three states were described by a single set of SCF molecular orbitals based on the occupied canonical orbitals of the X Z- state and a transformation of the canonical virtual space known as "K-orbitals" [10] which, among other properties, approximate the set of natural orbitals. Transition moments within orthogonal basis functions are easier to derive. For the X state the composition of the reference space was obtained by performing two Hartree-Fock single and double excitations (HFSD-CI) calculations at two typical intemuclear distances, i.e. R. (equilibrium geometry) and about 3Re,and adding to the HF... 

In contrast to the useful conceptual framework provided by the approximate approach just described, the results of more detailed molecular orbital calculations have on the whole been rather disappointing. Thus, although some semi-empirical SCF treatments were attempted, most of the earlier MO calculations for metallocene systems (18, 161, 162, 163, 164,165) suffered from such deficiencies as the neglect of the a-framework, or the use of various one-electron Hamiltonians, for example the various Wolfsberg-Helmholz techniques. Of late, Drago and his coworkers have carried out further Extended Htickel type computations for a wide range of both metallocene and bis-arene species (153, 154), and similar... 

Ab initio molecular orbital calculations have been carried out with the program GRAD-SCF. The results obtained for the >3d and 5V, structures are compared with experimental data. Calculated C—C and C—N bond distances are in good agreement, unlike the N—H lengths. The calculated geometry for NH2 groups is little different than that found experimentally. 

A method of molecular-orbital calculations, also referred to as the self-consistent field method (SCF), to characterize the bonding in unsaturated and aromatic molecules while neglecting electron-electron repulsion. The method has been extended to all valence electrons. 

The somewhat arbitrary use of the auxiliary inductive parameter in the Hiickel MO calculations has been questioned and the effect of the nonuniform distribution of a-electron densities, particularly in the CN bond,90 upon the 77-electron distribution has been discussed.65 Variable electronegativity self-consistent field (VESCF) molecular orbital calculations, which are an elaboration of the conventional SCF method and allow for the variation in electronegativity of an... 

For the benzenoid aromatic molecules considered here, we wish to include electron correlation for the N electrons of the 7t-eleetron system but not for the 2n a electrons. This is achieved most readily if we first carry out a standard Hartree-Fock MO theory calculation, yielding a set of orthogonal self-consistent field (SCF) molecular orbitals tp(. The spin-coupled wavefunction may then be written... 

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