Showing papers on "Electronic structure published in 1968"

Self‐Consistent Perturbation Theory. I. Finite Perturbation Methods

Abstract: A general method is proposed for quantum‐mechanical study of physical properties of molecules involving polarization or distortion of the electronic structure. This consists of the calculation of self‐consistent molecular orbital wavefunctions (single determinants) in the presence of small but finite perturbations. The general theory of such methods is presented together with a preliminary discussion of numerical error.

Elementary quantum chemistry

Abstract: A composite approach to quantum chemistry, combining conceptual material with formal maths Topics discussed include the Schrodinger wave equation, the quantum theory of angular momentum, molecular structure and the electronic structure of linear and non-linear molecules

Approximate Hartree–Fock Wavefunctions, One‐Electron Properties, and Electronic Structure of the Water Molecule

Abstract: Several approximate Hartree–Fock SCF wavefunctions for the ground electronic state of the water molecule have been obtained using an increasing number of multicenter s, p, and d Slater‐type atomic orbitals as basis sets. The predicted charge distribution has been extensively tested at each stage by calculating the electric dipole moment, molecular quadrupole moment, diamagnetic shielding, Hellmann–Feynman forces, and electric field gradients at both the hydrogen and the oxygen nuclei. It was found that a carefully optimized minimal basis set suffices to describe the electronic charge distribution adequately except in the vicinity of the oxygen nucleus. Our calculations indicate, for example, that the correct prediction of the field gradient at this nucleus requires a more flexible linear combination of p orbitals centered on this nucleus than that in the minimal basis set. Theoretical values for the molecular octopole moment components are also reported.

High resolution molecular photoelectron spectroscopy II. Water and deuterium oxide

Abstract: Helium 584 $\overset{\circ}{\mathrm A}$ radiation produces photoelectron spectra from water and deuterium oxide, which show extensive vibrational fine structure. The results are discussed in terms of the electronic structure of the molecule, and the bonding characteristics of the various molecular orbitals. Water is inferred to have only three configurationally distinct ionization potentials smaller than 21.22 eV.

Mössbauer Study of Soluble Prussian Blue, Insoluble Prussian Blue, and Turnbull's Blue

Abstract: The electronic structures of soluble Prussian blue, insoluble Prussian blue, and Turnbull's blue were investigated by the Mossbauer effect of 57Fe. The results below their Curie temperatures of 5.5° ± 0.5°K show that all of them are ferric ferrocyanide: one kind of irons is Fe3 + with high spin and the other is Fe(II) with low spin. It is concluded that Prussian blue and Turnbull's blue have the same electronic structure. The results of a paramagnetic resonance absorption observed at room temperature also support the conclusions obtained by the Mossbauer study.

Atomic ordering in binary Al5‐type phases

Abstract: : The degree of long-range order has been determined for 20 binary A15-type phases containing various transition elements. A tendency toward a lower degree of order was noted as the component elements were chosen successively from columns in the periodic table approaching the Mn column. A comparison of the ordering in the A15-type phases with the ordering previously reported for various binary sigma phases suggests that the remarkable stability of these phases may result from an interdependence between the electronic structure and the ability of the atoms to undergo deformations in conforming to geometrical packing requirements. (Author)

All valence-electrons calculations of the biological purines and pyrimidines

Abstract: A calculation of the electronic structure of the bases of DNA has been performed by an SCF procedure including simultaneously all the valence electrons. The results are analyzed and compared to those of previous calculations made in the π electron approximation.

Variational Form of Van Vleck Degenerate Perturbation Theory with Particular Application to Electronic Structure Problems

Abstract: The variational equivalent of Van Vleck degenerate perturbation theory is derived. As an example we treat the Stark effect for the 2s and 2p states of a hydrogenic atom. Other applications involving angular momentum degeneracy as well as electronic and nuclear permutation degeneracy are discussed. The existence of interchange theorems is also noted.

Electronic Structure of Iron Nitrides Studied by Electron Diffraction. I. γ'-Fe4N

Abstract: Using the fact that low order reflection intensities in electron diffraction depend strongly on the electronic state of atoms in crystals, the electronic structure of γ'-Fe 4 N was determined by measuring superstructure reflection intensities, which are contributed almost by nitrogen atoms, from a polycrystalline film produced by nitriding evaporated iron film with ammonia-hydrogen gas. The observed superstructure reflection intensities were put on the absolute scale by comparing with higher order main reflection intensities free from the effect of atomic ionization. A detailed analysis lead to the conclusion that the electronic structure is Fe 0 (Fe +1/3 ) 3 N -1 . Although the present structure is different from the models proposed previously for the interpretation of the ferromagnetic properties of γ'-Fe 4 N, it is possible to interpret the magnetic moment distribution equally well. Some discussions are also given about the bonding nature in the nitride.

Electronic structure of the permanganate ion

Abstract: The electronic structure of the permanganate ion has been investigated, using a semiquantitative LCAO MO method without empirical parameters. The atomic orbital basis set for the central ion has been varied systematically, and the effect of symmetric changes of bond distances has also been examined. In addition, calculations have been performed in which the regions around the ligands have been made more attractive for electrons, to simulate the presence of cations in solution and in the crystalline state. The electronic absorption spectrum of MnO 4 − has been tentatively assigned, on the basis of predicted band shapes and transition energies.

Röntgenemissionsbanden und Struktur des Valenzbandes von elementarem Phosphor, III-V-Phosphiden und Phosphaten

Abstract: With a photon-counting concave grating spectrometer the PL2,3 emission bands of the semiconducting phosphides of the III-V-type, BP, AlP, GaP, and InP, of red and black phosphorus, and of the phosphates Na3PO4 and AlPO4 have been investigated. The intensity distributions of the PL2, 3 bands which show characteristic features for each of these three groups of substances are compared with recent measurements of the corresponding PK β bands. In all cases the width of theK bands is found to be markedly smaller than that of theL bands. The results are discussed with regard to the crystal structure and the electronic structure of the valence band.

Electronic Structure and Electronic Spectrum of Nitrogen Dioxide: Study by the Nonempirical Self‐Consistent Field Method

Abstract: The nonempirical self‐consistent field method, in its form devised by McWeeny, has been applied to the ground state and to a series of excited states of nitrogen dioxide, using as basis functions Gaussians centered on the various atoms of the molecule. Potential‐energy curves have been obtained by varying the bond angle; the resulting equilibrium bond angle for the ground state compares favorably well with the experimental value. It is found that five transitions fall into the range covered by the long‐wavelength spectrum, which explains the complexity of the latter. From the correlations between the electronic states of the bent molecule and those of the linear system, an attempt is made to obtain indications concerning the potential‐energy surfaces of the NO+O system. Finally, the significance of the potential‐energy diagram obtained is discussed in relation with two problems: the mechanism of the photolysis of the compound, and the anomalously long radiative lifetime of its first doublet excited state resulting from fluorescence decay.

A self consistent field molecular orbital treatment, including excited states of cyclopropane, ethylene oxide and ethylenimine

Abstract: The electronic structure of cyclopropane, ethylene oxide and ethylenimine, have been investigated using the Pople-Segal Complete Neglect of Differential Overlap self consistent field molecular orbital method, including all valence electrons. The theory gives a good account of the ground state charge distributions and dipole moments and a reasonable interpretation of the electronic spectra of the three molecules.

The Electronic Structure of CdO I. The Energy‐Band Structure (APW Method)

Abstract: The energy-band structure of CdO was calculated along the high symmetrical axes of the Brillouin zone by use of the APW method. This method seems to be more suitable for the rocksalt lattice than for the zincblende structure. The resulting energy bands are similar to the bands of silver halides.