Molecular Orbital Self-consistent Field Research Articles

Self-consistent field intermolecular orbital theory of the interaction between conjugated systems

Self-consistent field molecular orbitals are used to describe two interacting conjugated molecules with overlapping p orbitals. Perturbation theory is used to determine intermolecular orbitals which could serve as starting point for a self-consistent field calculation for the composite system. The total interaction energy is obtained as an expansion in powers of the overlap Srr between interacting atomic orbitals and of the net electronic charge Δ qr on the atoms. The energy expression contains an important term for net charge interactions. Expressions are also obtained when one of the interacting molecules is excited. Configuration interaction is examined in this case and the behaviour of singlets and triplets compared.

Theory of the Self-Trapped Hole in CaF2

Using a classical calculation of the lattice-distortion and polarization energies along with the self-consistent-field molecular-orbital (SCF-MO) results for the energies of ${\mathrm{F}}_{2}^{\ensuremath{-}}$, the configurational coordinate potential curves are obtained for the ground and excited states of the ${V}_{K}$ center in Ca${\mathrm{F}}_{2}$. From these curves, the optical-absorption frequencies and widths are determined, and the hyperfine constants, calculated with the SCF-MO wave functions, are given for the internuclear distance corresponding to the minimum of the ground-state potential curve. The results are compared with experiment, and the similarities between Ca${\mathrm{F}}_{2}$ and LiF are noted.

An attempted application of the extended h�ckel molecular orbital approach to reactions involving charged species

The semi-empirical extended Huckel molecular orbital (EHMO) and non-empirical self consistent field molecular orbital (SCF-MO) methods have been used to study protonation reactions of acids, amides and esters. The work has been extended to the charged intermediates and subsequent products in their “hydrolysis” reactions.

Semiempirical self-consistent field-molecular orbitals calculations, employing complete valence orbital basis sets, for methyl-substituted borazines and benzenes

Semiempirical self-consistent field-molecular orbitals calculations, employing complete valence orbital basis sets, for methyl-substituted borazines and benzenes

Interaction Energy of an Alkali Metal with a Rare Gas

A molecular orbital self-consistent field calculation is made for closed shell ions, LiHe+ and LiHe— as function of internuclear distance. The eigenfunctions obtained from these calculations were used to calculate the potential energy curves for the neutral Li–He. This system has some interesting properties. For example, these calculations suggest the probable quenching of certain excited states of an alkali metal when in close interaction with a rare-gas atom. All of the curves obtained are repulsive except for the LiHe+ curve which has a shallow minimum and follows an expected 1/r4 attractive potential. Fair values are obtained for the ionization energies of the Li and He atoms and the electron affinity of Li. These calculations indicate that open-shell systems with few electrons can be treated by making the simpler SCF calculation on a closely related closed-shell system and using the resulting eigenfunctions to calculate the energy of the closed shell system.

Electronic Structure and Hyperfine Structure Constants of NO Molecule

The coupling constants of the magnetic hyperfine, electric quadrupole, and spin-orbit interaction have been calculated from the self-consistent field molecular orbitals formed by linear combination of atomic orbitals. The calculated values of the electron spin-orbit, nuclear spin-orbit, and nuclear-electronic spin-spin interaction constants agree reasonably well with experiment. The results for the nuclear quadrupole coupling constant and the Fermi contact term are less satisfactory, although the latter can be improved by configuration mixing. The relations of these coupling parameters to the electronic structure of the molecule are discussed.

Electronic Structure of Some Diatomic Hydrides

The self-consistent field molecular orbital (SCF-MO) method is applied to the calculation of the ground states of the CH, CH+, NH, OH, and FH molecules. Results are reported for the ionization potentials, excitation energies, binding energies, and dipole moments. The relative behavior of the bonding in these molecules is exhibited by an electron distribution analysis and the importance of s-p promotion in a single configuration description of these molecules is emphasized.

Equivalent Orbital Bond Moments: Applications to Carbon Dioxide and Water

Self-consistent field molecular orbitals for CO2, H2O and the B2H4 skeleton of diborane have been transformed into equivalent orbital representations, and bond moments have been defined as the dipole moments of the corresponding equivalent orbitals. If a maximum localization criterion is imposed and if hybrid moments (atomic dipole terms) on central atoms are omitted, one obtains moments of 2.6D(C+O—) in CO2, 1.4D(O—H+) in water, and 2.03D(B2+H—) in a line perpendicular to the B–B bond in diborane. The treatment of water does not seem to allow a separation of well-localized bond and lone-pair moments with the proper directional properties. The bond moment of C–H in methane, according to these criteria, is 0.6D(C—H+). It is concluded that the method is a valid approach to the problem of nonempirical calculation of bond moments in polyatomic molecules.

Electronic States of Molecules. I. Electronic Structure of BH

The calculation of the wave function of the ground state (1 Σ+) of the BH molecule, by the self-consistent field (SCF) molecular orbital (MO) method, is reported together with its ionization potentials, dipole moment, total energy, and the binding energy. For these calculations, the interactions of all the electrons have been included explicitly, and all integrals have been computed exactly at the internuclear equilibrium distance, 1.2325 A, of BH. The electron distribution analysis is carried out to get intimate insight into the distribution of charges around and between the nuclei, and to determine the bonding and antibonding nature of MO's. This analysis supports the previous results of the SCF MO treatment of CO, where the most easily ionized electrons are in an MO which has a large gross atomic population, and the most bonding power resides in the lowest energy outer-shell MO. The comparison of the results of the present calculation with those of the previous calculations shows that the SCF MO treatment gives more accurate values of wave function and energy levels for a polar molecule than those for a homopolar molecule.