Showing papers on "Electronic band structure published in 1983"
TL;DR: In this paper, the Kohn-Sham density-functional theory was used to estimate the fundamental band gaps of semiconductors and insulators by about 40% due to derivative discontinuities of the exchange-correlation energy.
Abstract: The local-density approximation for the exchange-correlation potential understimates the fundamental band gaps of semiconductors and insulators by about 40%. It is argued here that underestimation of the gap width is also to be expected from the unknown exact potential of Kohn-Sham density-functional theory, because of derivative discontinuities of the exchange-correlation energy. The need for an energy-dependent potential in band theory is emphasized. The center of the gap, however, is predicted exactly by the Kohn-Sham band structure.
1,816 citations
TL;DR: In this paper, the energy-band gap of an insulator is obtained from the eigenvalues of the one-particle density-functional equation for the ground state and a finite correction due to the discontinuity of the functional derivative of the exchange and correlation energy.
Abstract: The energy-band gap of an insulator is obtained from the eigenvalues of the one-particle density-functional equation for the ground state and a finite correction due to the discontinuity of the functional derivative of the exchange and correlation energy. This correction is expressed in terms of the improper self-energy and the density-functional exchange-correlation potential. It is evaluated for a two-plane-wave model including exchange only.
1,365 citations
TL;DR: In this article, the electronic structure of six Cu-based ternary chalcopyrite semiconductors is calculated self-consistently for the first time within the density-functional formalism.
Abstract: The electronic structure of six Cu-based ternary chalcopyrite semiconductors is calculated self-consistently for the first time within the density-functional formalism. The chemical trends in the band structures, electronic charge densities, density of states, and chemical bonding are analyzed.
455 citations
TL;DR: In this article, single and many-particle effects contributing to the formation of energy-band gaps in semiconducting polymers are investigated using exact-exchange Hartree-Fock (HF) theory and Toyozawa's electronic-polaron model.
Abstract: Single- and many-particle effects contributing to the formation of energy-band gaps in semiconducting polymers are investigated using exact-exchange Hartree-Fock (HF) theory and Toyozawa's electronic-polaron model. The electron correlation is calculated by M\o{}ller-Plesset perturbation theory including explicitly all significant matrix elements in second order. Their efficient calculation is facilitated by the use of optimally localized Wannier functions. The importance of both short- and long-range contributions, of extended atomic basis sets, and of the use of the full virtual space is exhibited in the case of trans-polyacetylene (PA) as a model system. Correlation effects are shown to reduce the single-particle energy-band gap first by diminishing the bond alternation in PA. On the other hand, due to the self-energy corrections, the HF energy-band states are transformed to quasiparticle (electronic-polaron) states, the valence band is shifted upward, and the conduction band is shifted downward. The original HF energy-band gap of 5 eV is reduced to 3 eV at an estimated level of 70-75% of valence-shell correlation. Its extrapolated value for full correlation is found to be 2.5 eV. The remaining 0.5-eV difference between theory and experiment is assigned to phonon-polaron and relaxation effects.
274 citations
TL;DR: In this article, the electronic structure of CeO2 and PrO2 was determined by performing SCF band calculations, and it was shown that in both systems there are metal f-and d- electrons in the oxygen 2p bands.
243 citations
TL;DR: In this paper, the authors developed a method for calculating self-consistently the electronic structure around an impurity atom in a crystalline host using a matrix technique based on the linear muffin-tin orbital method in the atomic-spheres approximation.
Abstract: We have developed a method for calculating self-consistently the electronic structure around an impurity atom, or an impurity cluster, in a crystalline host. Our method is a Green-function matrix technique based on the linear muffin-tin orbital method in the atomic-spheres approximation. The calculation of the host Green function is extremely efficient and involves diagonalization of a small Hamiltonian matrix for the band structure and subsequent Hilbert transforms. The method is tested for the calculation of one-electron spectra and total energies on systems for which (essentially) exact solutions are known: the Hulth\'en potential, a free H atom, a H atom in jellium, and a Li atom in jellium. The accuracy is better and the computational speed significantly higher than that obtained with the standard Korringa-Kohn-Rostoker Green-function technique.
239 citations
TL;DR: In this article, a theoretical study of resonant tunneling in multilayered Ga1−xAlxAs/GaAs structures is presented, where the spectrum of the resonant energies and its dependence on the barrier structure are analyzed from calculated profiles of barrier transparency versus energy, and from currentvoltage characteristics computed at selected temperatures and Fermi levels.
Abstract: A theoretical study of resonant tunneling in multilayered Ga1−xAlxAs/GaAs structures is presented. The spectrum of resonant energies and its dependence on the barrier structure are analyzed from calculated profiles of barrier transparency versus energy, and from current–voltage characteristics computed at selected temperatures and Fermi levels. The present formalism is based on the effective mass approximation as done to date, but contains three significant improvements: a more realistic treatment of the spatial dependence of effective masses and band edges; the recognition of the special dynamical role played by the transverse energy as a consequence of the difference in itinerant two dimensional carrier motion from layer to layer; and the avoidance of plane‐wave or WKB approximations for calculating the wave function in favor of direct numerical evaluation. It is shown that these revisions lead to quantitative differences with results of previous work.
195 citations
TL;DR: In this article, the electronic properties of Me2O3 oxides (Me = Ti, V, Cr) were determined from XPS valence band and core level measurements.
Abstract: The electronic structure behaviour of Me2O3 oxides (Me = Ti, V, Cr) has been determined from XPS valence band and core level measurements. From Ti to Cr sesquioxide the relative intensity of the 3d band increases systematically which can be explained by the (atomic) photoelectric cross section and the number of 3d electrons. Simultaneously the 3d-2p band separation decreases indicating a more stronger band overlap equivalent an enhanced covalent bonding component. The different electrical properties among the corundum structure oxides are determined by the trigonal field splitted a1g and eg orbitals, their occupation and relative energy position at the Fermi level. The observations confirm the change from itinerant to more localized behaviour of d electrons caused by crystal structure parameter change (c/a ratio).
170 citations
TL;DR: In this paper, a general approach to calculate the quasiparticle excitation energies of semiconductors, including the energy dependence of the self-energy with a local density-functional approach, is presented.
Abstract: This Letter presents a general approach to calculation of the quasiparticle excitation energies of semiconductors which includes the energy dependence of the self-energy with a local density-functional approach. Both direct and indirect band gaps in Si are in much better agreement with experiment than are the bands from the ground-state theory. The relatively large corrections arise only after the dielectric screening of the electron gas is modified to account for a gap in the excitation spectrum.
166 citations
TL;DR: Semiempirical tight-binding electronic energy band structures of the following wurtzite materials are reported in this paper : AlN, CdS, CDSe, ZnS, and ZnO.
Abstract: Semiempirical tight-binding electronic energy band structures of the following wurtzite materials are reported: AlN, CdS, CdSe, ZnS, and ZnO.
156 citations
TL;DR: In this article, the effect of carrier degeneracy is shown to be weak, apart from where carrier concentrations are extremely high (n>or=1020 cm-3), and the uncertainties involved in the quantitative values of the Auger coefficients are discussed.
Abstract: Auger recombination in direct-gap semiconductors is reinvestigated taking into account a realistic band structure instead of using the usual parabolic approximation. It is found that the direct conduction band process is negligible in large-gap semiconductors (Eg>or=0.6 eV), contrary to what has been found using the parabolic approximation. The new values for the probabilities of the valence band process and of the phonon-assisted Auger processes are also found to be smaller, but not by so much. Altogether, smaller values for the total Auger recombination are obtained and these are in agreement with experimental results. In addition, the effect of carrier degeneracy is shown to be weak, apart from where carrier concentrations are extremely high (n>or=1020 cm-3). Finally, the uncertainties involved in the quantitative values of the Auger coefficients are discussed.
TL;DR: An overview of band structure calculations on the fourth and fifth group transition metal monocarbides, mononitrides, and monoxides, published since the review article by Calais as mentioned in this paper, is given here.
Abstract: An overview is given here of band structure calculations on the fourth and fifth group transition metal monocarbides, mononitrides, and monoxides, published since the review article by Calais [J.-L. Calais, Adv. Phys. 26, 847 (1977)]. Furthermore, the relations of three categories of experimental properties, which allow insight into the electronic structure of the above mentioned compounds, and the results of band structure calculations are discussed. Theoretical predictions are compared with experimental findings. The considered experimental properties are valence band photoemission spectra, valence band x-ray emission spectra, and optical properties.
TL;DR: In this article, a series of self-consistent band calculations have been performed for a ferromagnetic state of iron in both the bcc and fcc structures, and the dependence of the magnetic moment per atom on the lattice parameter was obtained.
Abstract: A series of self-consistent-band calculations have been performed for a ferromagnetic state of iron in both the bcc and fcc structures. The dependence of the magnetic moment per atom on the lattice parameter was obtained. The linear combination of Gaussian orbitals method was employed in conjunction with a local-density exchange-correlation potential. An explanation is given for the abrupt increase in the magnetic moment in the fcc case near ${r}_{s}=2.7$ in terms of behavior of the band structure.
TL;DR: In this paper, the authors measured the intervalence band absorption spectra of In 0.53 Ga 0.47 As, InP, and GaAs and showed that the measured spectra are broader, have less temperature dependence, and have 2× less peak intensity than theoretical curves predicted by an elementary k\cdotp band model.
Abstract: Measurements of intervalence band absorption spectra were made in p-type In 0.53 Ga 0.47 As, InP, and GaAs. The measured spectra are broader, have less temperature dependence, and have 2× less peak intensity than theoretical curves predicted by an elementary k\cdotp band model. For p = 10^{18} cm-3, all three crystals have absorption coefficients of about 13 cm-1at 1.3 μm and 25 cm-1at 1.6 μm. These values of absorption should also be applicable as estimates of intervalence band absorption in quaternary laser material. Because of the low strength and weak temperature dependence of the intervalence band absorption, it should have only a minor effect on the temperature dependence of laser threshold. For example, using our absorption data, we calculate that intervalence band absorption will reduce the experimental temperature parameter T 0 of 1.3 μm quaternary lasers from 194 to 179 K.
TL;DR: In this paper, a new type of infrared photodetector using free electron absorption in a heavily doped GaAs/GaAlAs quantum well structure has been demonstrated, and preliminary results indicate a strong response in the near infrared with a responsivity conservatively estimated at 200 A/W.
Abstract: A new type of infrared photodetector using free electron absorption in a heavily doped GaAs/GaAlAs quantum well structure has been demonstrated. Preliminary results indicate a strong response in the near infrared with a responsivity conservatively estimated at 200 A/W. The structure can potentially be tailored during fabrication for use in several infrared bands of interest, including the 3 to 5 micron band and the 8 to 10 micron band.
TL;DR: In this article, the occupied portion of the bands displays a dispersion in qualitative agreement with the nearly-free-electron model and self-consistent band calculations, and a new surface state was observed on the A1(100) surface.
Abstract: Angle-resolved photoemission utilizing synchrotron radiation as a source was used to measure the occupied and unoccupied band structure of aluminum. The occupied portion of the bands displays a dispersion in qualitative agreement with the nearly-free-electron model and self-consistent band calculations. The measured occupied bandwidth is 10.6 eV, which is 0.5 eV smaller than calculated, due to electron-electron interactions (self-energy). The measured gap at $X$ is 1.68\ifmmode\pm\else\textpm\fi{}0.08 eV wide and centered 1.99\ifmmode\pm\else\textpm\fi{}0.08 eV below the Fermi energy. The magnitude and position of this gap do not simultaneously agree with any calculation or fit to the Fermi surface. The band structures which are derived by fitting to the Fermi surface or to optical properties reproduce the gap magnitude correctly, but not its position. Band-structure calculations do not reproduce either the gap magnitude or position due to \ensuremath{\sim}0.5-eV discrepancy in the ${X}_{1}$ point. The experimental band structure above the vacuum level is in qualitative agreement with calculations, once inelastic scattering (short mean free path) and evanescent waves from the vacuum solid interface are included. The lifetime broadening of both initial and final states was measured. Finally, a new surface state was observed on the A1(100) surface.
IBM1
TL;DR: In this article, the authors investigated the electronic structure of aluminum and its defect states by using a semi-empirical method and found that the fundamental gap is indirect, and the charge transfer enhances the hybridization of aluminium and oxygen orbitals, which leads to the broad upper and lower valence bands.
Abstract: We have investigated the electronic structure of $\ensuremath{\alpha}$-alumina and its defect states by using a semiempirical method. Our results show that the fundamental gap is indirect, and the charge transfer enhances the hybridization of aluminum and oxygen orbitals, which in turn leads to the broad upper and lower valence bands. Using the calculated total and orbital density of states, we have provided a consistent interpretation of the existing spectra. For the ideal $\ensuremath{\alpha}$-${\mathrm{Al}}_{2}$${\mathrm{O}}_{3}$(0001) surface we have found that the Al---O bonds at the surface have a considerable covalent character and the Al---dangling bonds produce the major surface-state band. Energy positions of the oxygen-vacancy states, and of the surface states, strongly suggest that the oxygen deficiency is responsible for some of the lowenergy structures in the excitation spectra.
TL;DR: In this article, the authors corrected the incomplete cancellation of self-interaction in the density-functional formalism of energy-band theory of crystalline solids, and applied this SIC method to calculate the energy band structure of the argon and LiCl crystals.
Abstract: Although the self-interaction terms in the Coulomb and exchange potentials exactly cancel each other in the Hartree-Fock one-electron Hamiltonian, the cancellation is incomplete when the exchange interaction is treated by the density-functional approximation. The residual self-interaction pushes the orbital energy levels upward. This effect is especially serious for valence states of insulators with localized charge distribution and causes an underestimation of the energy band gap. We have corrected for this incomplete cancellation of self-interaction in the density-functional formalism of energy-band theory of crystalline solids. The self-interaction correction (SIC) to the total energy of the $N$-electron system is expressed in terms of the Wannier functions, and periodic SIC potentials for the Bloch-state wave functions are derived variationally from the energy functional. The resulting SIC one-electron Hamiltonians are state dependent, but a unified Hamiltonian has been devised so that energies of all levels of the same $\stackrel{\ensuremath{\rightarrow}}{\mathrm{k}}$ from different bands are obtained by diagonalizing the same matrix. We have applied this SIC method to calculate the energy band structure of the argon and LiCl crystals. Using the Kohn-Sham exchange along with the correlation potential of von Barth and Hedin, we obtain band gaps in excellent agreement with experiment, whereas without SIC the calculated band gaps are more than 35% below the experimental values.
TL;DR: In this article, angle-resolved inverse photoemission with tunable photon energies has been used to map out the unoccupied bands of graphite and lithium-intercalated graphite.
Abstract: Angle-resolved inverse photoemission with tunable photon energies has been used to map out the unoccupied bands of graphite and lithium-intercalated graphite. At the Brillouin zone center the bottom of the lowest band is found at 4.0\ifmmode\pm\else\textpm\fi{}0.5 eV above the Fermi level in graphite. This band shows strong dispersion normal to the basal plane in excellent agreement with recent self-consistent band-structure calculations. A similar three-dimensional band is found in lithium-intercalated graphite shifted 3 eV to lower energy.
TL;DR: In this article, the chemical bonding in the interesting class of refractory transition metal compounds is illustrated for TiC, TiN, and TiO. The electron densities corresponding to the occupied valence states are obtained from the LAPW calculations.
Abstract: The chemical bonding in the interesting class of refractory transition metal compounds is illustrated for TiC, TiN, and TiO. Self-consistent augmented plane wave (APW) calculations are already available for these compounds. Using the respective potentials we have repeated the band calculations on a finer k grid with the linearized APW method to obtain accurate densities of states (DOS). These DOS can be divided into local partial contributions to characterize the bonding. Further information can be obtained from a decomposition of the metal dDOS into t2g and eg symmetry components. These partial local DOS are compared with the LCAO counterpart and give a first picture of the chemical bonding in these compounds. The electron densities corresponding to the occupied valence states are obtained from the LAPW calculations. They provide further insight into characteristic trends in the series from TiC to TiO: around the nonmetal site the density shows increasing localization; around the metal site the deviation from spherical symmetry changes from eg to t2g. These effects can be traced back to the three types of valence bands. Electron density plots of characteristic band states (all energies of a selected k point in the Brillouin zone) will be shown. These plots can describe the different types of bonding occurring in these systems.
TL;DR: In this article, the effects of alloy disorder on the electronic structure of the HgTe band were examined with the use of the coherent-potential approximation, and an empirical tight-binding scheme including spin-orbit effects was employed.
Abstract: The effects of alloy disorder on the electronic structure of ${\mathrm{Hg}}_{1\ensuremath{-}x}{\mathrm{Cd}}_{x}\mathrm{Te}$ are examined with the use of the coherent-potential approximation. An empirical tight-binding scheme, including spin-orbit effects, is employed. The choice of parameters is given special emphasis. A new HgTe band structure is obtained. Alloying effects are illustrated by quasiparticle spectral densities, total and projected densities of states, and self-energy corrections to the virtual-crystal energy bands. Strong cation $s$ scattering results in significant damping far from the band edges and accounts for the split-band behavior seen in photoemission experiments. The unusual bowing effects of the fundamental band gap and that associated with the ${E}_{1}$ transition are well explained. The weak scattering regime is shown to apply near the band edges. The electron mobility due to alloy scattering is large and does not appear to limit the observed magnitude.
TL;DR: In this article, an orthorhombic CeNi compound was shown to behave as an enhanced Pauli paramagnet in which the magnetic susceptibility along the c axis passes through a maximum at around 140 K.
Abstract: Lattice parameter analysis and studies of thermal expansion show that the orthorhombic CeNi compound is, like CeSn 3 , an intermediate valence compound in which the cerium valence state varies from 3.5 to 3.3 between 4 and 300 K. This compound behaves as an enhanced Pauli paramagnet in which the magnetic susceptibility along the c axis passes through a maximum at around 140 K. Magnetic susceptibility, resistivity and heat capacity measurements are characteristic of an almost magnetic Fermi liquid in which spin fluctuations are present. Unlike the other cerium intermediate valence compounds which are generally cubic, large anisotropic effects due to the local surroundings are observed in CeNi because of its orthorhombic symmetry. All these properties can be understood in the light of the band structure of this type of alloy in which a large hybridization occurs between the Ni 3d electrons and the Ce 5d electrons.
TL;DR: In this paper, the absence of a linear Peierls effect is due to the symmetry of the degenerate pair of orbitals at the Fermi level: they do not interact directly in the distorted system.
TL;DR: In this paper, a theoretical calculation of the optical properties of GaAs•Ga1−xAlxAs superlattices is presented, which includes the detailed atomic nature of the super-lattice electronic states in a realistic tight binding model.
Abstract: A theoretical calculation of the optical properties of GaAs‐Ga1−xAlxAs superlattices is presented. The calculation includes the detailed atomic nature of the superlattice electronic states in a realistic tight‐binding model. It is found that the mixture of the bulk heavy hole and light hole states in the superlattice wave function substantially affects the optical properties.
TL;DR: In this article, an ab initio calculation of the structural and electronic properties of beryllium is presented, using a self-consistent pseudopotential approach within the local density functional scheme.
Abstract: An ab initio calculation of the structural and electronic properties of beryllium is presented. The calculational method used is the self-consistent pseudopotential approach within the local-density-functional scheme. The calculated lattice constants, cohesive energy, bulk modulus, Poisson's ratio, electronic band structure, density of states, and charge density are all in good agreement with the experimental measurements.
TL;DR: In this paper, the electronic structure of thin hydrogenated amorphous carbon films produced by dc glow discharges of hydrocarbons was studied using synchrotron-radiation facility at Brookhaven National Laboratory.
Abstract: Using the synchrotron-radiation facility at Brookhaven National Laboratory, we have studied the electronic structure of thin hydrogenated amorphous carbon films produced by dc glow discharges of hydrocarbons. Valence-band photoemission measurements on these films yielded information on the occupied valence-band density of states, while near-edge absorption at the carbon K edge elucidated features of the unoccupied conduction band. The as-deposited, unannealed films are essentially amorphous, showing no extended x-ray absorption fine-structure (EXAFS) features. Valence-band photoemission results show that these films are insulating, suggesting tetrahedral (diamondlike) coordination. The near-edge-absorption results, however, show some unsaturated carbon-carbon bonds as evidenced by a 1s..--> pi..( feature. Upon annealing, the films become more graphitic as evidenced by both the photoemission and near-edge-absorption measurements showing fine structure in agreement with that observed for crystalline or microcrystalline graphite. They also become conductive. Annealing is accompanied by evolution of hydrogen from the films, and this appears correlated with the development of certain features of the band structure as the film orders. The annealed films also show the beginnings of features in the EXAFS region.
TL;DR: In this article, it was shown that fully conjugated alternant nonclassical polymers are comparatively stable systems as a result of the considerable delocalisation energy, which is strongly determined by the electron spin distribution of the degenerate nonbonding molecular orbitals.
Abstract: It is shown that fully conjugated alternant nonclassical polymers are comparatively stable systems as a result of the considerable delocalisation energy. The energy characteristics of the polymers are strongly determined by the electron spin distribution of the degenerate nonbonding molecular orbitals; the full spin configuration,S>0, is favoured. The spin densities depend on the electron correlation and alternate; this corresponds to a ferrimagnetic state of the polymer at 0°K.
TL;DR: In this paper, the electronic structures and cohesive energies of hexagonal monolayers of the alkaline-earth metals Be to Ba were studied in terms of self-consistent all-electron local density functional calculations using the fullpotential linearised augmented plane-wave method for thin films.
Abstract: For ptI see ibid, vol13, p2313 (1983) The electronic structures and cohesive energies of hexagonal monolayers of the alkaline-earth metals Be to Ba are studied in terms of self-consistent all-electron local density functional calculations using the full-potential linearised augmented plane-wave method for thin films The energy band structures of the 'light' atoms Be and Mg show wide s bands overlapping with pz bands without any pronounced spectral features in their densities of states In contrast, the 'heavy' alkaline-earth metals Ca, Sr and Ba are characterized by much narrower s bands and by increasingly sharper features in their densities of states originating from d-like states Thus, the densities of states at the Fermi energy for the Be and Mg monolayers are low and increase dramatically for Ca, Sr and particularly Ba In contrast to recent Hartree-Fock results, the author's study shows that the Be monolayer is metallic The work functions of the monolayers are found to be about 02 eV higher than the experimental values for the clean metal surface The high cohesive energy of Be is explained by the absence of p-core electrons and the admixture of pi bonding Magnesium is found to form the most weakly bound alkaline-earth monolayer whereas those of Ca, Sr and Ba are stabilised by the contribution of d states
TL;DR: In this paper, the authors present a theory of steady-state impact ionization in GaAs including a realistic band structure and the electron-phonon interaction using a field-theoretic scheme that goes beyond first order processes.
Abstract: We present a theory of steady‐state impact ionization in GaAs including a realistic band structure and the electron‐phonon interaction using a field‐theoretic scheme that goes beyond first order processes. The theory explains most known experimental high‐field transport data for GaAs satisfactorily, except for the anisotropy of the impact ionization rate measured by Pearsall. It is concluded that this anisotropy is not connected to quantum effects influencing the scattering rate and is probably caused by transient phenomena at the metallurgical junction of the samples used for investigating the anisotropy of the ionization rate.