Self-consistent Energy Band Structure Research Articles

Electronic structure of CuCl

Self-consistent energy band structure obtained by two different ab initio methods (LCAO and LMTO) shows that CuCl is a direct gap semiconductor. No indirect gap is found at ambient or high pressures as required by Rusakov's model and Abrikosov's speculations invoking Herring's excitonium state as the origin of superdiamagnetism or high-temperature superconductivity in CuCl. Band gap predictions are compared with several existing experiments including new infrared absorption measurements we have performed and report here.

Dark currents of GaAs/AlGaAs quantum-well infrared photodetectors

We study the dark current of the GaAs/AlGaAs quantum-well infrared photodetector (QWIP) by assuming a drift-diffusion carrier transport in the barriers where the electric fields are obtained by the current continuity condition and the self-consistent energy band structure. It has been shown that due to the current continuity condition, the dark currents across the QWIP devices are determined by the thermionic emission from the emitter to the multiple quantum well (MQW) region. The self-consistent calculation of the Schrodinger and Poisson equations shows a weak electric field in the barrier region connecting to the emitter (much smaller than the average field across the QWIP at low bias) due to the accumulation of carriers in the triangle quantum well formed at the emitter-MQW interface, which results in a very small dark current at low bias. The numerical results explain well our experimental observation.

Ab initio calculation of the pleochroism of fayalite

Optical properties of fayalite, Fe 2SiO4, have been obtained from ab initio calculations on the basis of the self-consistent energy band structure. The semi-relativistic, extended linear-augmented plane wave method (ELAPW) was used. Comparison of the calculated polarized optical spectra with experimental absorbance spectra shows satisfactory agreement. This observation allows a semiquantitative interpretation of the origins of the observed d-d transitions. Energy level diagrams for Fe 21 ions in the M1 and M2 sites have been constructed using the Xa-scattered waves cluster method. These calculations quantitatively justify the use of the relationship DE ‘ 1/R 5 , which is often used for the derivation of crystal-field stabilization energies at high pressures.

Ab initio calculation of the Fermi surface of RuO 2

The Fermi surface (FS) of RuO 2 in the rutile structure is calculated on the base of the self-consistent energy band structure in the local density approximation (LDA). The results of two bandstructure methods are compared, the extended linear augmented plane wave method (ELAPW) in the muffin-tin approximation and the linear-muffin-tin-orbital method (LMTO) with combined correction (CC). The angular dependence of the extremal cross-sections of the Fermi surface is in a good agreement with magnetothermal oscillations measurements.

Theoretical study of optical and ultraviolet photoemission spectra of TiO 2 and VO 2 in rutile phase

The optical spectra for two light polarizations and the ultraviolet photoemission spectra (UPS) of TiO 2 and VO 2 in rutile phase have been calculated ab initio on the bbase of the self-consistent energy band structure. The semirelativistic extended linear augmented plane wave method (ELAPW) was employed. In the case of TiO 2 the structures in the theoretical reflectivity curves are shifted by 1–1.5 eV to lower energies with respect to their measured positions, which is attributed to strong quasiparticle effects in this material. The reflectivity spectra of the metallic VO 2 are in a good agreement with experiment. The photoelectron energy distribution curves (EDC's) agree well with experiment for both semiconducting TiO 2 and metallic VO 2 .

Solid state effects in the molecular crystals of Cl 2, Br 2 and I 2

The solid halogens CL 2, Br 2 and I 2 are a model system for studying the intermolecular interactions in a molecular crystal. Self-consistent energy band-structure calculations based on the local density approximation (LDA) are performed by the full potential linearised augmented plane wave method. A geometry optimisation in terms of bond length and rigid rotation of the molecules is done by total energy minimisation and yields results close to experiment. The electronic charge density is obtained from which the electric field gradient (EFG) is determined on a first principles basis. The EFG asymmetry parameter η turns out to be very sensitive to the intermolecular interactions, which are well described by the present method.

Energy band structure of silver azide (AgN3)

The self-consistent energy band structure of silver azide (AgN3) is calculated within the density-functional approximation with a mixed basis and a norm-conserving pseudopotential. The energy band diagram is displayed and the origin of the bands is analyzed by a comparison with the molecular states of N3−. The role of the d states of silver, which are partially responsible for the formation of a wide anionic-cationic top valence band, is pointed out. The obtained results agree with experimental data and exhibit similarities with the band structures of silver halides.

Ab initio Calculations of the Electric Field Gradients in Solids in Relation to the Charge Distribution

Abstract A first principles method for the computation of electric field gradients (EFGs) is illustrated for various solids. This scheme is based on self-consistent energy band-structure calculations by the full potential linearized augmented plan wave (FLAPW) method which provides the electronic charge density including all polarization effects. By numerically solving Poisson's equation we obtain the Coulomb potential in a form which allows to compute the EFG directly. Our method is demonstrated for insulators (Cu2O), metals (hcp-Zn), supercondutors (YBa2Cu3O7 ) and molecular crystals (Cl2, Br2 , I2).

Calculated spectral properties of LaS

The semi-relativistic self-consistent energy band structure of LaS is calculated, and the computed functions of joint and projected densities-of-states are used for direct calculation of optical, X-ray emission and absorption spectra for comparison with experiments.

Self‐consistent energy band structure of tetragonal lead oxide

physica status solidi (b)Volume 115, Issue 1 p. K15-K19 Short Note Self-consistent energy band structure of tetragonal lead oxide G. A. Bordovskii, G. A. Bordovskii State Pedagogical Institute, State University Leningrad Search for more papers by this authorN. L. Gordeev, N. L. Gordeev State Pedagogical Institute, State University Leningrad Search for more papers by this authorA. N. Ermoshkin, A. N. Ermoshkin State Pedagogical Institute, State University Leningrad Search for more papers by this authorV. A. Izvozchikov, V. A. Izvozchikov State Pedagogical Institute, State University Leningrad Search for more papers by this authorR. A. Evarestov, R. A. Evarestov State Pedagogical Institute, State University Leningrad Search for more papers by this author G. A. Bordovskii, G. A. Bordovskii State Pedagogical Institute, State University Leningrad Search for more papers by this authorN. L. Gordeev, N. L. Gordeev State Pedagogical Institute, State University Leningrad Search for more papers by this authorA. N. Ermoshkin, A. N. Ermoshkin State Pedagogical Institute, State University Leningrad Search for more papers by this authorV. A. Izvozchikov, V. A. Izvozchikov State Pedagogical Institute, State University Leningrad Search for more papers by this authorR. A. Evarestov, R. A. Evarestov State Pedagogical Institute, State University Leningrad Search for more papers by this author First published: 1 January 1983 https://doi.org/10.1002/pssb.2221150143Citations: 9 Moika 48, Leningrad, USSR. AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Citing Literature Volume115, Issue11 January 1983Pages K15-K19 RelatedInformation

The effect of vacancies on the electronic structure of Nbo

The crystal structure of NbO is considered as a NaCl structure with 25% ordered vacancies in each sublattice. Self-consistent energy band structure calculations using the augmented plane wave (APW) method have been carried out for a hypothetical NbO with the full NaCl structure and for the structure with the vacancies. We find that the introduction of the vacancies leads to (1) a lowering of the Nb- d like bands with respect to the O- p bands, (2) an almost completely filled “vacancy band”, and (3) a splitting and broadening of the O- p like band. These effects are shown to have a significant influence on both the theoretically calculated X-ray photoemission spectra (XPS) and the X-ray emission spectra (XES). All theoretical spectra obtained with the vacancy-structure are found to be in good agreement with experiments in contrast to those spectra calculated for hypothetical NbO in the NaCl structure.

Self-consistent energy band structure of magnesium fluoride using the LCAO method

A self-consistent energy band structure calculation for magnesium fluoride is presented. Comparison with experiment indicates that some of the peaks in the epsilon 2 spectra which were associated with interband transitions may be due to excitons associated with the onset of the interband transitions and that the band gap is direct Gamma point transition of 13.6 eV. Mulliken population analysis indicates that this a strongly ionic crystal even though its positive ion corresponds to a group-II element.

Electron irradiation effects in MOS systems

Flat-band shift measurements were made on p-type MOS devices irradiated with electrons at various gate-bias voltages. A structured reproducible curve of flat-band shift versus gate bias was obtained which could not be readily accounted for with existing models. Experimental data were taken over a wide range of negative and positive gate-bias voltages (consistent with electrical breakdown limits) in order to identify fundamental mechanisms as a basis for formulating a more general model of the entire device. A model is presented based on the known work functions and electron affinities for Al-SiO 2 -Si devices. It assumes that traps in the Oxide are occupied according to Fermi-Dirac statistics, subject to constraints determined by the interface parameters. A linearized quasi-Fermi level is assumed in the oxide, and the resulting distribution of charged traps is used with Poisson's equation to obtain a self-consistent energy-band structure throughout the entire device.

Measured radiation effects in MOS capacitors with a proposed new model

Flat-band shift measurements were made on p-type MOS devices irradiated with electrons at various gate bias voltages. A reproducible curve of flat-band shift versus gate bias was obtained that could not be readily accounted for with existing models. Data were taken over a wide range of negative and positive gate bias voltages. The model assumes that traps obey Fermi-Dirac statistics, subject to interface boundary constraints. A linearized quasi-Fermi level is assumed in the oxide. The resulting distribution of charged traps yields a self-consistent energy band structure throughout the entire device.