Electronic structure of the first row hydrides BH, CH, NH, OH and FH. I. Ground states

1958 ◽  
Vol 248 (1252) ◽  
pp. 119-135 ◽  
Keyword(s):  
Molecular Orbital ◽  
Electron Correlation ◽  
Dipole Moments ◽  
Valence Bond ◽  
Orbital Method ◽  
Constant Amount ◽  
Consistent Field ◽  
Valence Electrons ◽  
Self Consistent Field ◽  
Experimental Values

Some recent calculations by the self-consistent field molecular orbital method are generalized to allow for electron correlation. Correlations between the motions of the valence electrons are introduced explicitly by means of configuration interaction, whilst the effects of intra-atomic electron correlation are estimated semi-empirically. Both forms of correlation, but especially the latter, are found to have a profound effect on the calculated properties of the hydrides. The total electronic energies obtained in the final calculations fall consistently above the experimental values by an almost constant amount (0.5 to 0.7 eV). The wave functions and dipole moments of the molecules are analyzed in the frameworks of both the valence-bond and molecular orbital theories.

The 'Variable Electronegativity ' Method. II. Pyrrole

1959 ◽  
Vol 12 (3) ◽  
pp. 319 ◽  
Author(s):  
RD Brown ◽  
ML Heffernan
Keyword(s):  
Dipole Moment ◽  
Molecular Orbital ◽  
Electron System ◽  
Orbital Method ◽  
Molecular Orbital Method ◽  
Consistent Field ◽  
Inductive Effects ◽  
Self Consistent Field ◽  
Negligible Contribution ◽  
Good Agreement

The properties of the π-electron system in pyrrole have been studied by a " variable electronegativity " self-consistent field molecular-orbital method and the results compared with those obtained by the conventional SCF procedure. The π-electron distribution calculated by the conventional SCF procedure cannot be satisfactorily reconciled with the observed dipole moment, but the distribution calculated by the VESCF method leads to a predicted dipole moment in good agreement with observation. Polarization of σ-bonds makes a negligible contribution to the dipole moment.Derivation of the coulomb parameters for the simple H�ckel molecular-orbital method from the VESCF results is considered and the factors responsible for auxiliary inductive effects are discussed. The π-electron ionization potential and the positions of the lowest excited states of pyrrole have been calculated by the VE method.

scholarly journals The Hydroalumination of Acetylene. A Self Consistent Field Molecular Orbital Study.

1981 ◽  
Vol 35a ◽  
pp. 305-309 ◽  
Author(s):  
Odd Gropen ◽  
Arne Haaland ◽  
Sten Ahrland ◽  
Ingmar Persson ◽  
Kastriot Spahiu
Keyword(s):  
Molecular Orbital ◽  
Molecular Orbital Study ◽  
Consistent Field ◽  
Orbital Study ◽  
Self Consistent ◽  
Self Consistent Field

scholarly journals Molecular-orbital and structural descriptors in theoretical investigation of electroreduction of nitrodiazoles

2005 ◽  
Vol 70 (7) ◽  
pp. 957-968 ◽  
Author(s):  
Branko Kolaric ◽  
Ivan Juranic ◽  
Dragica Dumanovic
Keyword(s):  
Molecular Orbital ◽  
Electrostatic Potential ◽  
Dipole Moments ◽  
Statistical Weight ◽  
Structural Parameter ◽  
Orbital Method ◽  
Structural Descriptors ◽  
Reduction Potentials ◽  
Lowest Unoccupied Molecular Orbital ◽  
Two Parameters

It is shown how a simple theoretical approach can be used for the investigation of electro-organic reactions.Mononitroimidazoles and mononitropyrazoles were studied by the semiempirical MNDO-PM3 molecular orbital method. The electrochemical reduction potentials of diazoles have been correlated with the energy of the lowest unoccupied molecular orbital (LUMO). It was found that an admirable correlation could be obtained by the introduction of simple structural descriptors as a correction to the energy of the LUMO. The interaction of a molecule with its surrounding depends on electrostatic potential and on steric hindrance. Most of these steric effects are taken into account using two parameters having a very limited set of integer values. The first (?) is the position of a ring substituent regarding ring nitrogens, which accounts for the different orientations of dipole moments and for the different shape of the electrostatic potential. The second (structural) parameter (?) is the type of the ring, which accounts mostly for different modes of electrode approach, and for different charge polarization patterns in two diazole rings. The extended correlation with ELUMO, ? and ?, is very good, having a regression coefficient r = 0.991. The intrinsic importance of ? and ? is exemplified by their high statistical weight.

scholarly journals Chemical insights into the electronic structure of Fe(II) porphyrin using FCIQMC, DMRG, and generalized active spaces

2020 ◽  
Author(s):  
Oskar Weser ◽  
Leon Freitag ◽  
Kai Guther ◽  
Ali Alavi ◽  
Giovanni Li Manni
Keyword(s):  
Electron Correlation ◽  
Quantitative Measure ◽  
Model System ◽  
Quintet State ◽  
Consistent Field ◽  
Self Consistent ◽  
Stabilizing Effect ◽  
Self Consistent Field ◽  
Preliminary Version

<div>Stochastic-CASSCF and DMRG procedures have been utilized to quantify the role of the electron correlation mechanisms that in a Fe-porphyrin model system are responsible for the differential stabilization of the triplet over the quintet state. Orbital entanglement diagrams and CI-coefficients of the wave function in a localised orbital basis allow for an effective interpretation of the role of charge-transfer configurations. A preliminary version of the <i>Stochastic Generalized Active Space Self-Consistent Field</i> method has been developed and is here introduced to further assess the pi-backdonation stabilizing effect.</div><div>By the new method excitations between metal and ligand orbitals can selectively be removed from the complete CI expansion. It is demonstrated that these excitations are key to the differential stabilization of the triplet, effectively leading to a quantitative measure of the correlation enhanced pi-backdonation.</div><div><br></div>

Sign in / Sign up

Export Citation Format

Share Document