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Showing papers on "Electronic structure published in 1974"


BookDOI
01 Jan 1974
TL;DR: In this article, the nature of the amorphous state and the electronic properties of the Amorphous Semi-conductors have been investigated in the context of liquid semiconductors.
Abstract: 1 The Nature of the Amorphous State.- 2 Structure of Amorphous Semi-conductors.- 3 Electronic Structure of Disordered Materials.- 4 Optical Properties of Amorphous Semiconductors.- 5 Electronic Properties of Amorphous Semiconductors.- 6 Switching and Memory in Amorphous Semiconductors.- 7 Structure and Electronic Properties of Liquid Semiconductors.

4,636 citations


Book
01 Jan 1974
TL;DR: In this article, a phenomenological theory of magnetic order impurities and alloys external fields electrons, phonons, and transport aspects of the electron-electron interaction is presented.
Abstract: Electronic structure lattice dynamics symmetry and its consequences phenomenological theories of magnetic order impurities and alloys external fields electrons, phonons, and transport aspects of the electron-electron interaction.

832 citations


Journal ArticleDOI
TL;DR: In this paper, a semi-empirical functional of the Hartree-Fock density is presented for estimates of the correlation energy correction, which is similar to the one proposed by Gombas and is parametrized with reference to few atomic systems.
Abstract: A semiempirical functional of the Hartree‐Fock density is presented for estimates of the correlation energy correction. The functional is similar to the one proposed by Gombas and is (a) parametrized with reference to few atomic systems, and (b) is modified as to reproduce the atomic correlation correction not only for closed but also for open shell systems. The functional is then applied to the ground state function of the hydrides LiH(1Σ+), BeH(2Σ+), BH(1Σ+), CH(2Π), NH(3Σ−), OH(2Π), and HF(1Σ+). Several internuclear distances have been considered for each hydride, scanning the potential energy curve from the repulsive region to the dissociation products (∼ 10 a.u.). For these points a simple multiconfigurational function (consisting of no more than three configurations) was computed to obtain Hartree‐Fock functions with proper dissociation behavior (H‐F‐P‐D functions). The semiempirical functional was applied both to the traditional H‐F functions and the H‐F‐P‐D functions in order to study how to selec...

378 citations


Journal ArticleDOI
TL;DR: In this paper, an Anderson formalism including overlap is used to treat the chemisorption of carbon monoxide on the transition metals Cu, Ni and Pd, where the wave functions of the metal surface are approximated by a linear combination of atomic d-orbitals, which are oriented in such a manner that maximum overlap with the 2π ∗ -orbital of CO is achieved.

244 citations


Journal ArticleDOI
TL;DR: In this paper, the electronic structure of the layer compound Pb${\mathrm{I}}_{2}$ is calculated within the framework of the empirical pseudopotential method.
Abstract: The electronic structure of the layer compound Pb${\mathrm{I}}_{2}$ is calculated within the framework of the empirical pseudopotential method. Spin-orbit interactions were necessarily included to explain experimental reflectivity measurements. Using the pseudo-wave-functions, electronic charge densities were computed. They are discussed in terms of the nature of the chemical bonding for Pb${\mathrm{I}}_{2}$.

185 citations


Journal ArticleDOI
TL;DR: Theoretical and experimental results for the band structure of polyethylene are presented in this paper, where an energy gap of 7.5 ± 0.5 eV and a C1s line at 284.6 eV are deduced.
Abstract: Theoretical and experimental results for the band structure of polyethylene are presented. Theoretical results are obtained from both semiempirical (CNDO/2 and extended Huckel) and nonempirical methods. The density of states is measured by the ESCA method. An energy gap of 7.5 ± 0.5 eV and a C1s line at 284.6 eV are deduced. Although CNDO/2 results appear to be unreliable, the correlation between theory and observed density of states is found to be very good for extended Huckel and ab initio results.

180 citations


Journal ArticleDOI
TL;DR: In this paper, the theoretical foundation of the selfconsistent statistical exchange (X α) multiple scattering method based on overlapping atomic spheres is presented, illustrated by a study of the electronic structure of the TCNQ molecule.
Abstract: The theoretical foundation of the self‐consistent statistical exchange (X α) multiple scattering method based on overlapping atomic spheres is presented. After discussing the principal assumptions and approximations, the theory is illustrated by a study of the electronic structure of the TCNQ molecule. Satisfactory results are obtained for the energy level structure and electronic charge distribution if the atomic sphere radii are chosen in accordance with the following guidelines: (a) the calculated first ionization energy should agree with experiment; and (b) the calculated virial coefficient should be equal to −2. The present work suggests that the overlapping sphere model can be used to obtain realistic electronic structures for large planar organic molecules as well as for arrays of such molecules.

138 citations



Journal ArticleDOI
TL;DR: In this paper, a non-empirical method is developed to determine atomic pseudopotentials; their parameters are calculated by means of a least-squares process, and the efficiency of such a method appears clearly in the calculation of the valence molecular orbitals of the silane molecule.

96 citations


Journal ArticleDOI
TL;DR: In this article, self consistent field molecular orbital calculations have been carried out for the ground electronic states for diatomic molecules XY, with X, Y=H, F, Cl, Br or I. Basis sets are critically discussed, and computed properties compared with experiment.
Abstract: Self consistent field molecular orbital calculations have been carried out for the ground electronic states for diatomic molecules XY, with X, Y=H, F, Cl, Br or I. Basis sets are critically discussed, and computed properties compared with experiment. The correlation between experimental ionization energies and those estimated through the use of Koopmans' theorem is given.

92 citations


Journal ArticleDOI
TL;DR: In this article, it was shown that any property P can be developed in the form ν=P′0+Σi=1NAi(νi+1/2)+ΣI≤ jNBij(nni+ 1/2) + NBij(NBij+1 2 ) + 1/ √ nn+1 /2 ).
Abstract: Perturbation theory is used in conjunction with ab initio electronic structure calculations to obtain information about the effects of pure vibration on properties of polyatomic molecules It is shown that any property P can be developed in the form ν=P′0+Σi=1NAi(νi+1/2)+Σi≤ jNBij(νi+1/2)(νj+1/2)+ ⋯, where P′0,{Aj}, and {Bij} are certain constants and (ν1, ν2, ⋯ νN) are the quantum numbers for N modes of vibration Several isotopic variants of the water molecule with Σiνi ≤ 3 are used to illustrate the utility of the method at the Hartree‐Fock level of approximation The properties examined include the energy, the dipole moment, and the nuclear quadrupole coupling constants


Journal ArticleDOI
F. Jellinek1, R.A. Pollak1, M.W. Shafer1
TL;DR: In this article, an unambiguous assignment of the chalcogen core levels was made by comparing the spectra with those of ZrS2 and ZrSe2 (where all chal cogen atoms are isolated), where the levels of the (Ch2) groups are found at higher binding energies than those of the isolated ch atoms, which is consistent with a larger negative charge on the isolated atoms.

Journal ArticleDOI
TL;DR: The reality of the electron pair as a fundamental unit in the electronic structure of molecular systems is evidenced by calculations which show that the most probable partitioning of a system is th... as discussed by the authors.
Abstract: The reality of the electron pair as a fundamental unit in the electronic structure of molecular systems is evidenced by calculations which show that the most probable partitioning of a system is th...

Journal ArticleDOI
TL;DR: In this article, an ab initio study of the electronic structure and properties of magnesium oxide was carried out and the self-consistent charge density in the crystal was obtained by solving the Adams-Gilbert local-orbitals equations.
Abstract: We have carried out an ab initio study of the electronic structure and properties of magnesium oxide. The self-consistent charge density in the crystal is obtained by solving the Adams-Gilbert local-orbitals equations. The Fock operator is then constructed with nonlocal exchange and the energy bands are computed. These bands are then corrected for correlation effects. Long-range contributions are calculated by means of the electronic-polaron model. Short-range contributions are found to be large as predicted recently by the authors for fluorides, oxides, and nitrides in general. The final energy bands are in agreement with optical and x-ray data for the gaps and other transition energies. We predict an indirect minimum gap in MgO. The structure in the uv optical spectra is reproduced by our joint density of states and ${\ensuremath{\epsilon}}_{2}(\ensuremath{\omega})$ calculation. We compare our results with previous theoretical studies in the empirical-pseudopotential scheme and the Hartree-Fock-Slater approximation. MgO is the first II-VI compound and the first oxide to be treated in the Hartree-Fock scheme.

Journal ArticleDOI
TL;DR: In this paper, a non-empirical quantum mechanical study of the electronic structure of C(CH/sub 2/)/sub 3/ has been carried out, where a double zeta basis set of contracted Gaussian functions was employed, and self-consistent field wave functions were obtained for the triplet ground state.
Abstract: A nonempirical quantum mechanical study of the electronic structure of C(CH/sub 2/)/sub 3/ has been carried out. A double zeta basis set of contracted Gaussian functions was employed, and self-consistent-field wave functions were obtained for the triplet ground state. The planar (D/sub 3h/) configuration is predicted to lie 17 kcal/mol below below the orthogonal (C/sub 2v/) form. The electronic structure is discussed in terms of Mulliken populations and orbital perspective plots. Some preliminary results for the lowest singlet states are reported. 2 tables.

Journal ArticleDOI
TL;DR: In this article, a comparison of the Mossbauer spectra of deoxy Hb•A and its isolated α and β subunits was carried out over the temperature range 77-200°K.
Abstract: A comparison study of the Mossbauer spectra of deoxy Hb‐A (low oxygen affinity) and its isolated α and β subunits (high oxygen affinity) was carried out over the temperature range 77–200°K. Within experimental error, no difference was detected between these three proteins, either in the isomeric shifts or in the quadrupole splittings. These results show that the characteristically different oxygen affinity of deoxy Hb‐A and its isolated subunits is not a consequence of different electronic states for the ferrous ions in Hb‐A and its isolated subunits. The electronic structure of the ferrous ion in hemoglobin was determined using a crystal field approximation. The adjustable parameters in the crystal field model were systematically searched for an electronic level configuration that would give good agreement with the experimental data of the temperature‐dependent quadrupole splitting and magnetic susceptibility of deoxy Hb‐A. The resulting low lying energy levels in order of increasing energy were 5B2, 1A1, 5E, and 3E. The spin and orbital degeneracy of these levels were removed by the spin‐orbit interaction and the rhombic perturbation of the crystalline field. The electronic ground state obtained produces an electric field gradient at the iron nucleus with a principal component of 0.11 e parallel to the heme plane and an asymmetry parameter η = 0.51.


Journal ArticleDOI
TL;DR: A survey on high-resolution experiments with atomic systems prepared by the beam-foil or beam-gas interaction is presented in this article, where RF-resonance, field-quenching, quantum-beat and level-crossing experiments are described in elementary terms.
Abstract: A survey on high resolution experiments with atomic systems prepared by the beam-foil or beam-gas interaction is presented. RF-resonance, field-quenching, quantum-beat and level-crossing experiments are described in elementary terms whereas more advanced theoretical techniques are sketched for quantum beats in an appendix.

Book ChapterDOI
TL;DR: In this article, a two-valence band model was proposed for lead-salt ionic semiconductors, based on the properties of PbS, PbSe, and PbTe.
Abstract: Publisher Summary Lead salts are ionic semiconductors with many properties in common. Their IV-VI electron configuration is relatively unusual, and appears to be reflected in the interesting phonon and dielectric properties they share. Among these are low values of the TO phonon frequency at Γ and high static dielectric constants. It is clear that the electronic structures of PbS, PbSe, and PbTe are much the same, with all three lead salts exhibiting a direct minimum energy gap E 0 at the L point. The surfaces of constant energy for both electrons and holes are ellipsoidal near the band edges, but approach a cylinder-like shape farther from the L point. The conduction and valence bands in all the lead salts are definitely nonparabolic, displaying a concomitant dependence of the effective mass on carrier concentration. Based primarily on studies of PbTe, a two-valence band model is well supported by experiment. The order of higher energy bands appears quite well established, and reliable values of the energies of several interband transitions have been obtained.

Journal ArticleDOI
TL;DR: In this article, a contract Gaussian basis set of essentially double zeta quality was employed for the ground state and 12 low-lying (< 10 eV) excited states of HCN.
Abstract: Ab initio quantum mechanical electronic structure calculations have been carried out for the ground state and 12 low‐lying (< 10 eV) excited states of HCN. A contracted Gaussian basis set of essentially double zeta quality was employed. A new theoretical approach, which should be widely applicable, was applied to the excited electronic states. First one selects a physically meaningful set of orbitals, which, hopefully, will be about equally suitable for all the electronic states of interest. After selecting a single configuration to describe each electronic state, configuration interaction is performed including all configurations differing by one orbital from any of the selected reference configurations. The method appears to be one of the simplest capable of treating several states of the same symmetry. The predicted geometries have been compared with the experimental results of Herzberg and Innes, as well as the appropriate Walsh diagram. The ab initio calculations and the Walsh diagram concur that Her...




Journal ArticleDOI
TL;DR: In this article, the down-and up-spin Green functions were obtained in the weak s − d interaction limit with the results of the molecular field approximation and in the strong interaction limit, respectively.
Abstract: Electronic structure in magnetic semiconductors is investigated on the basis of the s - d exchange model. The exchange scattering of an electron by localized spins is treated in the coherent potential approximation. Coupled equations for the down- and up- spin Green functions are obtained. These equations agree in the weak s - d interaction limit with the results of the molecular field approximation and in the strong interaction limit with those obtained previously by the present author. The density of states for down- and up- spins is calculated in the paramagnetic and completely ferromagnetic states for various values of interaction strength, by assuming a semi-elliptic form for unperturbed density of states.

Journal ArticleDOI
Frank Herman1, Inder P. Batra1
TL;DR: In this paper, the electronic structure of an isolated TCNQ mulecule has been calculated by the selfconsistent statistical exchange multiple-scattering method, using overlapping atomic spheres in place of nonoverlapping atomic spheres.
Abstract: The electronic structure of an isolated TCNQ mulecule has been calculated by the self-consistent statistical-exchange multiple-scattering method. By using overlapping atomic spheres in place of nonoverlapping atomic spheres, a significant increase in physical realism has been achieved. The theoretical model provides a satisfactory account of the photoemission spectra of TCNQ vapor and solid TCNQ. The singlet-triplet splitting for the lowest optical transition is found to be 0.84 eV.

Journal ArticleDOI
TL;DR: In this paper, the electronic structure of a model "surface complex" consisting of a Ni diatom and an ethylene molecule has been calculated using the self-consistent field, $X \ensuremath{\alpha}$, scattered-wave method.
Abstract: The electronic structure of a model "surface complex" consisting of a Ni diatom and an ethylene molecule has been calculated using the self-consistent-field, $X\ensuremath{\alpha}$, scattered-wave method. Comparison of calculated $\ensuremath{\pi}$-orbital bonding shifts with recent photoemission spectra for chemisorption of ethylene on nickel favors a $\ensuremath{\pi}$-bonded complex over a di-$\ensuremath{\sigma}$-adsorbed complex. Charge distributions of various molecular orbitals indicate that the C-C double bond is weakened more for the latter molecular arrangement, suggesting such a complex as a likely intermediate in heterogeneous reactions.


Journal ArticleDOI
TL;DR: In this paper, a model for the electronic structure of transition-metal monoxides is presented, which consists of a criterion based on 4s bandwidths and spectroscopic term values to decide on the metallic versus insulating character.
Abstract: A model for the electronic structure of the transition-metal monoxides is presented. It consists of: (a) A criterion based on 4s bandwidths and spectroscopic term values to decide on the metallic versus insulating character; (b) A quantitative description for the insulating oxides which includes itinerant metal 4s and oxygen 2p states and correlated localized ionic levels arising from the 3d electrons. Optical properties are studied in detail; comparison with experiment is reasonably good.

Journal ArticleDOI
TL;DR: In this article, the SCF-X α-SW method was used to carry out an approximate Hartree-Fock calculation on the electronic structure on UF6−, where the charge density within the atomic spheres was analyzed into its angular momentum components and the first two excited electronic states were computed.
Abstract: The SCF‐X α‐SW method is used to carry out an approximate Hartree‐Fock calculation on the electronic structure on UF6−. The charge density within the atomic spheres is analyzed into its angular momentum components and the first two excited electronic states are computed.