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Showing papers on "Electronic structure published in 2007"


Journal ArticleDOI
TL;DR: In this article, the authors focus on the origin of the D and G peaks and the second order of D peak and show that the G and 2 D Raman peaks change in shape, position and relative intensity with number of graphene layers.

6,496 citations


Journal ArticleDOI
14 Dec 2007-Science
TL;DR: The electronic properties of a prototypical correlated insulator vanadium dioxide in which the metallic state can be induced by increasing temperature is reported, setting the stage for investigations of charge dynamics on the nanoscale in other inhomogeneous correlated electron systems.
Abstract: Electrons in correlated insulators are prevented from conducting by Coulomb repulsion between them. When an insulator-to-metal transition is induced in a correlated insulator by doping or heating, the resulting conducting state can be radically different from that characterized by free electrons in conventional metals. We report on the electronic properties of a prototypical correlated insulator vanadium dioxide in which the metallic state can be induced by increasing temperature. Scanning near-field infrared microscopy allows us to directly image nanoscale metallic puddles that appear at the onset of the insulator-to-metal transition. In combination with far-field infrared spectroscopy, the data reveal the Mott transition with divergent quasi-particle mass in the metallic puddles. The experimental approach used sets the stage for investigations of charge dynamics on the nanoscale in other inhomogeneous correlated electron systems.

1,283 citations


Journal ArticleDOI
TL;DR: A graphene bilayer with a relative small angle rotation between the layers is considered and it is found that the low energy dispersion is linear, as in a single layer, but the Fermi velocity can be significantly smaller than the single-layer value.
Abstract: We consider a graphene bilayer with a relative small angle rotation between the layers--a stacking defect often seen in the surface of graphite--and calculate the electronic structure near zero energy in a continuum approximation. Contrary to what happens in an AB stacked bilayer and in accord with observations in epitaxial graphene, we find: (a) the low energy dispersion is linear, as in a single layer, but the Fermi velocity can be significantly smaller than the single-layer value; (b) an external electric field, perpendicular to the layers, does not open an electronic gap.

1,277 citations



Journal ArticleDOI
13 Jul 2007-Science
TL;DR: It is shown that, when its source is atomic-scale lattice defects, wave functions of different symmetries can mix and reflect both intravalley and intervalley scattering.
Abstract: A single sheet of carbon, graphene, exhibits unexpected electronic properties that arise from quantum state symmetries, which restrict the scattering of its charge carriers. Understanding the role of defects in the transport properties of graphene is central to realizing future electronics based on carbon. Scanning tunneling spectroscopy was used to measure quasiparticle interference patterns in epitaxial graphene grown on SiC(0001). Energy-resolved maps of the local density of states reveal modulations on two different length scales, reflecting both intravalley and intervalley scattering. Although such scattering in graphene can be suppressed because of the symmetries of the Dirac quasiparticles, we show that, when its source is atomic-scale lattice defects, wave functions of different symmetries can mix.

695 citations


Journal ArticleDOI
Abstract: The unusual transport properties of graphene are the direct consequence of a peculiar bandstructure near the Dirac point. We determine the shape of the {pi} bands and their characteristic splitting, and find the transition from two-dimensional to bulk character for 1 to 4 layers of graphene by angle-resolved photoemission. By detailed measurements of the {pi} bands we derive the stacking order, layer-dependent electron potential, screening length and strength of interlayer interaction by comparison with tight binding calculations, yielding a comprehensive description of multilayer graphene's electronic structure.

671 citations


Journal ArticleDOI
TL;DR: The long-range ordered surface alloy Bi/Ag(111) is found to exhibit a giant spin splitting of its surface electronic structure due to spin-orbit coupling, as is determined by angle-resolved photoelectron spectroscopy.
Abstract: The long-range ordered surface alloy Bi/Ag(111) is found to exhibit a giant spin splitting of its surface electronic structure due to spin-orbit coupling, as is determined by angle-resolved photoelectron spectroscopy. First-principles electronic structure calculations fully confirm the experimental findings. The effect is brought about by a strong in-plane gradient of the crystal potential in the surface layer, in interplay with the structural asymmetry due to the surface-potential barrier. As a result, the spin polarization of the surface states is considerably rotated out of the surface plane.

671 citations


Journal ArticleDOI
TL;DR: Methods to overcome the inability of almost all current density functionals to describe the ubiquitous attractive long-range van der Waals (dispersion) interactions are reviewed, and a very successful correction is described that is based on damped -C(6).R(-6) potentials (DFT-D).
Abstract: Kohn–Sham density functional theory (KS-DFT) is nowadays the most widely used quantum chemical method for electronic structure calculations in chemistry and physics. Its further application in e.g. supramolecular chemistry or biochemistry has mainly been hampered by the inability of almost all current density functionals to describe the ubiquitous attractive long-range van der Waals (dispersion) interactions. We review here methods to overcome this defect, and describe in detail a very successful correction that is based on damped –C6·R–6 potentials (DFT-D). As examples we consider the non-covalent inter- and intra-molecular interactions in unsaturated organic molecules (so-called π–π stacking in benzenes and dyes), in biologically relevant systems (nucleic acid bases/pairs, proteins, and ‘folding’ models), between fluorinated molecules, between curved aromatics (corannulene and carbon nanotubes) and small molecules, and for the encapsulation of methane in water clusters. In selected cases we partition the interaction energies into the most relevant contributions from exchange-repulsion, electrostatics, and dispersion in order to provide qualitative insight into the binding character.

663 citations


Journal ArticleDOI
TL;DR: In this paper, results of ab initio band structure calculations for A2BC Heusler compounds that have A and B sites occupied by transition metals and C by a main group element are presented.
Abstract: In this paper, results of ab initio band structure calculations for A2BC Heusler compounds that have A and B sites occupied by transition metals and C by a main group element are presented. This class of materials includes some interesting half-metallic and ferromagnetic properties. The calculations have been performed in order to understand the properties of the minority band gap, the peculiar transport properties and magnetic behaviour found in these materials. Among the interesting aspects of the electronic structure of the materials are the contributions from both A and B atoms to the total magnetic moment. The magnitude of the total magnetic moment shows a trend consistent with the Slater–Pauling type behaviour in several classes of these compounds. The total magnetic moment also depends on the kind of C atoms although they do not directly contribute to it. In Co2 compounds, a change of the C element changes the contribution of the t2g states to the moment at the Co sites. The localized moment in these magnetic compounds resides at the B site. Other than in the classical Cu2-based Heusler compounds, the A atoms in Co2, Fe2 and Mn2-based compounds may contribute significantly to the total magnetic moment. It is shown that the inclusion of electron–electron correlation in the form of LDA + U calculations helps to understand the magnetic properties of those compounds that already exhibit a minority gap in calculations where it is neglected. Besides the large group of Co2 compounds, half-metallic ferromagnetism was here found only in such compounds that contain Mn.

617 citations


Journal ArticleDOI
TL;DR: In this article, a first principle, theoretical study of MoS2 nanoparticles is presented, which provides a unified explanation of measured photoluminescence spectra and recent STM measurements as a function of size.
Abstract: We present a first principle, theoretical study of MoS2 nanoparticles that provides a unified explanation of measured photoluminescence spectra and recent STM measurements as a function of size. In addition, our calculations suggest ways to engineer the electronic properties of these systems so as to obtain direct band gap 3D layered nanoparticles or Mo doped metallic nanowires. In particular, we show that single sheet MoS2 nanoparticles up to ∼3.4 nm show no appreciable quantum confinement effects. Instead, their electronic structure is entirely dominated by surface states near the Fermi level. In 3D nanoparticles, we found a strong dependence of their electronic properties on layer stacking and distance, and we suggest that the observed photoluminescence variation as a function of size originates from the number of planes composing the system. The number of these planes and their distance can be tuned to engineer clusters with direct band gaps, at variance with the bulk. Our results also suggest ways to...

612 citations


Journal ArticleDOI
TL;DR: The Nextnano simulator as discussed by the authors is a simulation tool for semiconductor nanodevice simulation that has been developed for predicting and understanding a wide range of electronic and optical properties of semiconductor nano-structures.
Abstract: nextnano is a semiconductor nanodevice simulation tool that has been developed for predicting and understanding a wide range of electronic and optical properties of semiconductor nanostructures. The underlying idea is to provide a robust and generic framework for modeling device applications in the field of nanosized semiconductor heterostructures. The simulator deals with realistic geometries and almost any relevant combination of materials in one, two, and three spatial dimensions. It focuses on an accurate and reliable treatment of quantum mechanical effects and provides a self-consistent solution of the Schrodinger, Poisson, and current equations. Exchange-correlation effects are taken into account in terms of the local density scheme. The electronic structure is represented within the single-band or multiband kldrp envelope function approximation, including strain. The code is not intended to be a ldquoblack boxrdquo tool. It requires a good understanding of quantum mechanics. The input language provides a number of tools that simplify setting up device geometry or running repetitive tasks. In this paper, we present a brief overview of nextnano and present four examples that demonstrate the wide range of possible applications for this software in the fields of solid-state quantum computation, nanoelectronics, and optoelectronics, namely, 1) a realization of a qubit based on coupled quantum wires in a magnetic field, 2) and 3) carrier transport in two different nano-MOSFET devices, and 4) a quantum cascade laser.

Journal ArticleDOI
TL;DR: In this article, the magnetic interaction between edge states is found to be remarkably long ranged and intimately connected to the electronic structure of the ribbon, and various treatments of electronic exchange and correlation are used to examine the sensitivity of this result to details of electron-electron interactions.
Abstract: First-principles calculations are used to establish that the electronic structure of graphene ribbons with zigzag edges is unstable with respect to magnetic polarization of the edge states. The magnetic interaction between edge states is found to be remarkably long ranged and intimately connected to the electronic structure of the ribbon. Various treatments of electronic exchange and correlation are used to examine the sensitivity of this result to details of the electron-electron interactions, and the qualitative features are found to be independent of the details of the approximation. The possibility of other stablization mechanisms, such as charge ordering and a Peierls distortion, are explicitly considered and found to be unfavorable for ribbons of reasonable width. These results have direct implications for the control of the spin-dependent conductance in graphitic nanoribbons using suitably modulated magnetic fields.

Journal ArticleDOI
TL;DR: In this article, the electronic structure and geometry of the oxygen deficient TiO2 rutile (1 1 0) surface using both gradient-corrected density functional theory (GGA DFT) and DFT corrected for on-site Coulomb interactions was investigated.

Journal ArticleDOI
TL;DR: Werner et al. as discussed by the authors generalized the recently introduced impurity solver based on the diagrammatic expansion around the atomic limit and quantum Monte Carlo summation of the diagrams, which allowed a high-precision study of actinide and lanthanide based compounds with the combination of the dynamical mean-field theory and band-structure methods.
Abstract: We generalized the recently introduced impurity solver [P. Werner et al., Phys. Rev. Lett. 97, 076405 (2006)] based on the diagrammatic expansion around the atomic limit and quantum Monte Carlo summation of the diagrams. We present generalization to the cluster of impurities, which is at the heart of the cluster dynamical mean-field methods, and to realistic multiplet structure of a correlated atom, which will allow a high-precision study of actinide and lanthanide based compounds with the combination of the dynamical mean-field theory and band-structure methods. The approach is applied to both the two-dimensional Hubbard and $t\text{\ensuremath{-}}J$ models within cellular dynamical mean-field method. The efficient implementation of the algorithm, which we describe in detail, allows us to study coherence of the system at low temperature from the underdoped to overdoped regime. We show that the point of maximal superconducting transition temperature coincides with the point of maximum scattering rate, although this optimal doped point appears at different electron densities in the two models. The power of the method is further demonstrated in the example of the Kondo volume collapse transition in cerium. The valence histogram of the dynamical mean-field theory solution is presented, showing the importance of the multiplet splitting of the atomic states.

Journal ArticleDOI
TL;DR: In this article, the authors investigated the structure and mobility of single self-interstitial atom and vacancy defects in body-centered-cubic transition metals forming groups 5B (vanadium, niobium, and tantalum) and 6B (chromium, molybdenum, and tungsten) of the Periodic Table.
Abstract: We investigate the structure and mobility of single self-interstitial atom and vacancy defects in body-centered-cubic transition metals forming groups 5B (vanadium, niobium, and tantalum) and 6B (chromium, molybdenum, and tungsten) of the Periodic Table. Density-functional calculations show that in all these metals the axially symmetric self-interstitial atom configuration has the lowest formation energy. In chromium, the difference between the energies of the and the self-interstitial configurations is very small, making the two structures almost degenerate. Local densities of states for the atoms forming the core of crowdion configurations exhibit systematic widening of the "local" d band and an upward shift of the antibonding peak. Using the information provided by electronic structure calculations, we derive a family of Finnis-Sinclair-type interatomic potentials for vanadium, niobium, tantalum, molybdenum, and tungsten. Using these potentials, we investigate the thermally activated migration of self-interstitial atom defects in tungsten. We rationalize the results of simulations using analytical solutions of the multistring Frenkel-Kontorova model describing nonlinear elastic interactions between a defect and phonon excitations. We find that the discreteness of the crystal lattice plays a dominant part in the picture of mobility of defects. We are also able to explain the origin of the non-Arrhenius diffusion of crowdions and to show that at elevated temperatures the diffusion coefficient varies linearly as a function of absolute temperature.

Journal ArticleDOI
Karsten Held1
TL;DR: In this article, a combined density functional theory in its local density approximation (LDA) and dynamical mean field theory (DMFT) was proposed to deal with strongly correlated model Hamiltonians.
Abstract: The calculation of the electronic properties of materials is an important task of solid-state theory, albeit particularly difficult if electronic correlations are strong, e.g., in transition metals, their oxides and in f-electron systems. The standard approach to material calculations, the density functional theory in its local density approximation (LDA), incorporates electronic correlations only very rudimentarily and fails if the correlations are strong. Encouraged by the success of dynamical mean field theory (DMFT) in dealing with strongly correlated model Hamiltonians, physicists from the bandstructure and the many-body communities have joined forces and developed a combined LDA + DMFT method recently. Depending on the strength of electronic correlations, this new approach yields a weakly correlated metal as in the LDA, a strongly correlated metal or a Mott insulator. This approach is widely regarded as a breakthrough for electronic structure calculations of strongly correlated materials. We review ...

Journal ArticleDOI
TL;DR: In this paper, the electronic structure of bilayer graphene was investigated from a resonant Raman study of the band using different laser excitation energies, revealing the difference of the effective masses of electrons and holes.
Abstract: The electronic structure of bilayer graphene is investigated from a resonant Raman study of the ${G}^{\ensuremath{'}}$ band using different laser excitation energies. The values of the parameters of the Slonczewski-Weiss-McClure model for bilayer graphene are obtained from the analysis of the dispersive behavior of the Raman features, and reveal the difference of the effective masses of electrons and holes. The splitting of the two TO phonon branches in bilayer graphene is also obtained from the experimental data. Our results have implications for bilayer graphene electronic devices.

Journal ArticleDOI
TL;DR: Graphene is the first example of truly two-dimensional crystals - it's just one layer of carbon atoms as mentioned in this paper and it turns out that graphene is a gapless semiconductor with unique electronic properties resulting from the fact that charge carriers in graphene obey linear dispersion relation.
Abstract: Graphene is the first example of truly two-dimensional crystals - it's just one layer of carbon atoms. It turns out that graphene is a gapless semiconductor with unique electronic properties resulting from the fact that charge carriers in graphene obey linear dispersion relation, thus mimicking massless relativistic particles. This results in the observation of a number of very peculiar electronic properties - from an anomalous quantum Hall effect to the absence of localization. It also provides a bridge between condensed matter physics and quantum electrodynamics and opens new perspectives for carbon-based electronics. (c) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Journal ArticleDOI
TL;DR: In this article, the authors presented the analytical solution of the wave function and energy dispersion of armchair graphene nanoribbons (GNRs) based on the tight-binding approximation.
Abstract: We present the analytical solution of the wave function and energy dispersion of armchair graphene nanoribbons (GNRs) based on the tight-binding approximation. By imposing the hard-wall boundary condition, we find that the wave vector in the confined direction is discretized. This discrete wave vector serves as the index of different subbands. Our analytical solutions of wave function and associated energy dispersion reproduce the results of numerical tight-binding and the solutions based on the $\mathbf{k}∙\mathbf{p}$ approximation. In addition, we also find that all armchair GNRs with edge deformation have energy gaps, which agrees with recently reported first-principles calculations.

Journal ArticleDOI
TL;DR: This work establishes the diameter and chiral angle dependence of the poorly studied third and fourth optical transitions in semiconducting tubes and explains the result showing strongly bound excitons in the first and second transitions and a delocalized electron wave function in the third transition.
Abstract: We have studied the optical transition energies of single-wall carbon nanotubes over broad diameter (0.7–2.3 nm) and energy (1.26 –2.71 eV) ranges, using their radial breathing mode Raman spectra. We establish the diameter and chiral angle dependence of the poorly studied third and fourth optical transitions in semiconducting tubes. Comparative analysis between the higher lying transitions and the first and second transitions show two different diameter scalings. Quantum mechanical calculations explain the result showing strongly bound excitons in the first and second transitions and a delocalized electron wave function in the third transition. In carbon nanotubes [1], quantum confinement is responsible for 1D van Hove singularities in the electronic density of states and unusually strong many-body (electron-electron and electron-hole) interactions [2]. Current understanding of the photophysical properties of semiconducting carbon nanotubes [2 –7] are based mostly on experimental results for the first (E S ) and second (E S ) optical transitions (S superscript stands for semiconducting, while M will be used for metallic tubes), based on a set of fewer than 40 SWNTs (characterized by their (n, m) indices [1]) in the diameter range from 0.7 to 1.3 nm [8– 13]. Efforts have been made to extend these results to larger diameter tubes, and to establish the third (E S ) and fourth (E S ) transitions [14,15]. E S and E S are important for the optics of large diameter semiconducting single-wall carbon nanotubes (SWNTs), since for dt > 1: 3n m, E S is already in the infrared range [8–11]. Here we measure the optical properties of SWNTs over broad diameter (0.7–2.3 nm) and energy (1.26 –2.71 eV) ranges. We probe over 200 different SWNT species, about 378 different optical transition energies, going up to the fourth optical transition of semiconducting SWNTs, thus establishing the (n, m) dependence of the poorly studied E S and E S transitions. Surprisingly, we find that E S and E S follow a different (blue-shifted) diameter scaling when compared with E S and E S . These results are supported by electronic structure calculations showing that E S and E S are described by bound exciton states, whereas the E S transitions correspond to a delocalized exciton or to an unbound electron-hole pair. The sample consists of as-grown vertically aligned SWNTs, synthesized by the chemical vapor deposition method from alcohol, on top of a quartz substrate. Transmission Electron Microscopy shows a rather homogeneous sample formed by isolated SWNTs and very small

Journal ArticleDOI
TL;DR: In this article, the electronic structure of a spherical quantum dot with parabolic confinement that contains a hydrogenic impurity and is subjected to a DC electric field is studied, and the calculated electronic structure is further used for determining the nonlinear optical rectification coefficient of the quantum dot structure.
Abstract: The electronic structure of a spherical quantum dot with parabolic confinement that contains a hydrogenic impurity and is subjected to a DC electric field is studied. In our calculations we vary the position of the impurity and the electric field strength. The calculated electronic structure is further used for determining the nonlinear optical rectification coefficient of the quantum dot structure. We show that both the position of the impurity and the strength of the electric field influence the nonlinear optical rectification process.

Journal ArticleDOI
TL;DR: In this article, the structural and electronic properties of Li 4 Ti 5 O 12 spinel are studied from density functional theory based first principles calculations, and the optimized lattice constant of the spinel is 8.619 A, which is even a little larger (0.2%) than 8.604 A of the lithiated state Li 7 Ti 5O 12.

Journal ArticleDOI
TL;DR: In this article, a scanning tunneling spectroscopy (STS) study of the local electronic structure of single and bilayer graphene grown epitaxially on a SiC(0001) surface is presented.
Abstract: We present a scanning tunneling spectroscopy (STS) study of the local electronic structure of single and bilayer graphene grown epitaxially on a SiC(0001) surface. Low voltage topographic images reveal fine, atomic-scale carbon networks, whereas higher bias images are dominated by emergent spatially inhomogeneous large-scale structure similar to a carbon-rich reconstruction of SiC(0001). STS spectroscopy shows a ~100meV gap-like feature around zero bias for both monolayer and bilayer graphene/SiC, as well as significant spatial inhomogeneity in electronic structure above the gap edge. Nanoscale structure at the SiC/graphene interface is seen to correlate with observed electronic spatial inhomogeneity. These results are important for potential devices involving electronic transport or tunneling in graphene/SiC.

Journal ArticleDOI
TL;DR: An example of electronic structure-driven tuning of the excited-state properties is presented, thus opening the way to a combined theoretical and experimental strategy for the design of new iridium(III) phosphors with specific target characteristics.
Abstract: We report a combined experimental and theoretical study on cationic Ir(III) complexes for OLED applications and describe a strategy to tune the phosphorescence wavelength and to enhance the emission quantum yields for this class of compounds. This is achieved by modulating the electronic structure and the excited states of the complexes by selective ligand functionalization. In particular, we report the synthesis, electrochemical characterization, and photophysical properties of a new cationic Ir(III) complex, [Ir(2,4-difluorophenylpyridine)2(4,4'-dimethylamino-2,2'-bipyridine)](PF(6)) (N969), and compare the results with those reported for the analogous [Ir(2-phenylpyridine)2(4,4'-dimethylamino-2,2'-bipyridine)](PF(6)) (N926) and for the prototype [Ir(2-phenylpyridine)2(4,4'-tert-butyl-2,2'-bipyridine)](PF(6)) complex, hereafter labeled N925. The three complexes allow us to explore the (C/\N) and (N/\N) ligand functionalization: considering N925 as a reference, we investigate in N926 the effect of electron-releasing substituents on the bipyridine ligand, while in N969, we investigate the combined effect of electron-releasing substituents on the bipyridine ligand and the effect of electron-withdrawing substituents on the phenylpyridine ligands. For N969 we obtain blue-green emission at 463 nm with unprecedented high quantum yield of 85% in acetonitrile solution at room temperature. To gain insight into the factors responsible for the emission color change and the different quantum yields, we perform DFT and TDDFT calculations on the ground and excited states of the three complexes, characterizing the excited-state geometries and including solvation effects on the calculation of the excited states. This computational procedure allows us to provide a detailed assignment of the excited states involved in the absorption and emission processes and to rationalize the factors determining the efficiency of radiative and nonradiative deactivation pathways in the investigated complexes. This work represents an example of electronic structure-driven tuning of the excited-state properties, thus opening the way to a combined theoretical and experimental strategy for the design of new iridium(III) phosphors with specific target characteristics.

Journal ArticleDOI
TL;DR: In this paper, the electronic structure of the superconducting material LaOFeP is investigated by means of ab initio calculations using density functional theory, and the concept of two-dimensional building blocks as well as Bader analysis are used to obtain more insight about the charge transfer in this layered material.
Abstract: The electronic structure of the superconducting material LaOFeP is investigated by means of ab initio calculations using density functional theory. The concept of two-dimensional building blocks as well as Bader analysis are used to obtain more insight about the charge transfer in this layered material. The band structure and the Fermi surface are presented in order to be compared with future experiments. It is found that the intralayer chemical bonding present a significant part of covalency, whereas the interlayer bonding is almost completely ionic. Also, four sheets of the Fermi surface have a significant two-dimensional character.

Journal ArticleDOI
TL;DR: In this article, the authors present a scanning tunneling spectroscopy (STS) study of the local electronic structure of single and bilayer graphene grown epitaxially on a SiC(0001) surface.
Abstract: The authors present a scanning tunneling spectroscopy (STS) study of the local electronic structure of single and bilayer graphene grown epitaxially on a SiC(0001) surface Low voltage topographic images reveal fine, atomic-scale carbon networks, whereas higher bias images are dominated by emergent spatially inhomogeneous large-scale structure similar to a carbon-rich reconstruction of SiC(0001) STS spectroscopy shows an ∼100meV gaplike feature around zero bias for both monolayer and bilayer graphene/SiC, as well as significant spatial inhomogeneity in electronic structure above the gap edge Nanoscale structure at the SiC/graphene interface is seen to correlate with observed electronic spatial inhomogeneity These results are relevant for potential devices involving electronic transport or tunneling in graphene/SiC

Journal ArticleDOI
TL;DR: In this paper, the fullpotential linearized augmented plane wave method with the generalized gradient approximation for the exchange and correlation potential (LAPW-GGA) is used to understand the electronic and elastic properties of the first thorium-containing nitride perovskite TaThN3.
Abstract: The full-potential linearized augmented plane wave method with the generalized gradient approximation for the exchange and correlation potential (LAPW-GGA) is used to understand the electronic and elastic properties of the first thorium-containing nitride perovskite TaThN3. Total and partial density of states, charge distributions as well as the elastic constants, bulk modulus, compressibility, shear modulus, Young modulus and Poisson ratio are obtained for the first time and analyzed in comparison with cubic ThN. The chemical bonding in TaThN3 is a combination of ionic Th–N and of mixed covalent–ionic Ta–N bonds. The cubic TaThN3 is semiconducting with the direct gap at about 0.65 eV. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)


Book
17 Apr 2007
TL;DR: In this article, the authors describe the synthesis and manipulation of Semiconductor Quantum Dots and Quantum Dot Arrays, from fundamental photophysics to Quantum Dot Lasing, and apply them to photon conversion.
Abstract: SEMICONDUCTOR NANOCRYSTALS (NANOCRYSTAL QUANTUM DOTS) "Soft "Chemical Synthesis and Manipulation of Semiconductor Nanocrystals, J.A. Hollingsworth and V.I. Klimov Electronic Structure in Semiconductor Nanocrystals, D.J. Norris Fine Structure and Polarization Properties of Band-Edge Excitons in Semiconductor Nanocrystals, A.L. Efros Intraband Spectroscopy and Dynamics of Colloidal Semiconductor Quantum Dots, P. Guyot-Sionnest, M. Shim, and C. Wang Charge Carrier Dynamics and Optical Gain in Nanocrystal Quantum Dots:From Fundamental Photophysics to Quantum Dot Lasing, V.I. Klimov Optical Dynamics in Single Semiconductor Quantum Dots, K.T. Shimizu and M.G. Bawendi Electrical Properties of Semiconductor Nanocrystals, D.S. Ginger and N.C. Greenham Tunneling and Optical Spectroscopy of Semiconductor Nanocrystal Quantum Dots:Single-Particle and Ensemble Properties, U. Banin and O. Millo 9.III -V Quantum Dots and Quantum Dot Arrays: Synthesis, Optical Properties, Photogenerated Carrier Dynamics, and Applications to Photon Conversion, A.J. Nozik and O.I. Micic METAL NANOCRYSTALS Synthesis and Fabrication of Metal Nanocrystal Superlattices, R.C. Doty, M.B.Sigman, Jr., C.A. Stowell, P.S. Shah, A.E. Saunders, and B.A. Korgel Optical Spectroscopy of Surface Plasmons in Metal Nanoparticles, S. Link and M. A.El-Sayed Time-Resolved Spectroscopy of Metal Nanoparticles, G.V. Hartland References Index

Journal ArticleDOI
TL;DR: In this article, the optical properties of zinc monochalcogenides with zinc-blende-and wurtzite-type structures were studied using the ab initio density functional method within the local density approximation (LDA), generalized-gradient approximation, and $\mathrm{LDA}+U$ approaches.
Abstract: Electronic band structure and optical properties of zinc monochalcogenides with zinc-blende- and wurtzite-type structures were studied using the ab initio density functional method within the local-density approximation (LDA), generalized-gradient approximation, and $\mathrm{LDA}+U$ approaches. Calculations of the optical spectra have been performed for the energy range $0--20\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$, with and without including spin-orbit coupling. Reflectivity, absorption and extinction coefficients, and refractive index have been computed from the imaginary part of the dielectric function using the Kramers-Kronig transformations. A rigid shift of the calculated optical spectra is found to provide a good first approximation to reproduce experimental observations for almost all the zinc monochalcogenide phases considered. By inspection of the calculated and experimentally determined band-gap values for the zinc monochalcogenide series, the band gap of ZnO with zinc-blende structure has been estimated.