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Sample records for hueckel band calculations

  1. Relativistically parameterized extended Hueckel calculations. Part 8. Double-zeta parameters for the actinoids Th, Pa, U, Np, Pu, and Am and an application on uranyl

    International Nuclear Information System (INIS)

    Double-zeta Slater type fits to the radial, relativistic and nonrelativistic Hartree-Fock functions are given for the neutral atoms Th, Pa, U, Np, Pu, and Am. An application on uranyl indicates increased U(5f?)-O(2p?) bonding, compared to earlier relativistic single-zeta or nonrelativistic multiple-zeta calculations. The current understanding of bonding of uranyl is discussed. A possible CI mechanism for obtaining an eventual t/sub lg/ highest occupied molecular orbital (HOMO) for UF6, instead of a t/sub lu/ one, is pointed out

  2. Behavior of molecules on interstellar grains: Application of the Langevin equation and iterative extended Hueckel

    International Nuclear Information System (INIS)

    The Langevin equation was used to explore an adsorbate desorption mechanism. Calculations were performed using iterative extended Hueckel on a silica model site with various small adsorbates, e.g., H, CH, OH, NO, CO. It was found that barriers to free traversal from one site to another are substantial (approx.3-10 eV). A bootstrap desorption mechanism for some molecules in the process of forming at a site also became apparent from the calculations. The desorption mechanisms appear to be somewhat balanced by a counterforce--the attraction of sites for the newly desorbed molecule. The order of attraction to a silica grain site for the diatomic moleceules considered was OH>CH>CO>NO, when these entites were sufficiently distant. The nature of the silica grain and that of the ''cold'' desorption mechanism, when considered together, suggest that the abundance of very small grain might be less common than anticipated

  3. Energy Band Calculations for Maximally Even Superlattices

    Science.gov (United States)

    Krantz, Richard; Byrd, Jason

    2007-03-01

    Superlattices are multiple-well, semiconductor heterostructures that can be described by one-dimensional potential wells separated by potential barriers. We refer to a distribution of wells and barriers based on the theory of maximally even sets as a maximally even superlattice. The prototypical example of a maximally even set is the distribution of white and black keys on a piano keyboard. Black keys may represent wells and the white keys represent barriers. As the number of wells and barriers increase, efficient and stable methods of calculation are necessary to study these structures. We have implemented a finite-element method using the discrete variable representation (FE-DVR) to calculate E versus k for these superlattices. Use of the FE-DVR method greatly reduces the amount of calculation necessary for the eigenvalue problem.

  4. D band Raman intensity calculation in armchair edged graphene nanoribbons

    OpenAIRE

    Barros, E. B.; Sato, K; Samsonidze, Ge. G.; Souza Filho, A.G.; Dresselhaus, Mildred; SAITO, R.

    2011-01-01

    The D band Raman intensity is calculated for armchair edged graphene nanoribbons using an extended tight-binding method in which the effect of interactions up to the seventh nearest neighbor is taken into account. The possibility of a double resonance Raman process with multiple scattering events is considered by calculating a T matrix through a direct diagonalization of the nanoribbon Hamiltonian. We show that long-range interactions play an important role in the evaluation of both the D ban...

  5. First-principles electronic-band calculations on organic conductors

    OpenAIRE

    Shoji Ishibashi

    2009-01-01

    Predicting electronic-band structures is a key issue in understanding the properties of materials or in materials design. In this review article, application examples of first-principles calculations, which are not based on adjustable empirical parameters, to study electronic structures of organic conductors are described.

  6. Relativistic Band Calculation and the Optical Properties of Gold

    DEFF Research Database (Denmark)

    Christensen, N Egede; Seraphin, B. O.

    1971-01-01

    The energy band structure of gold is calculated by the relativistic augmented-plane-wave (RAPW) method. A nonrelativistic calculation is also presented, and a comparison between this and the RAPW results demonstrates that the shifts and splittings due to relativistic effects are of the same order of magnitude as the gaps (approximately 1 eV). Various integrated functions, density of states, joint density of states, and energy distributions of joint density of states are derived from the RAPW calculation. These functions are used in an interpretation of photoemission and static reflectance measurements. It is shown that the photoemission results are extremely well described in terms of a model assuming all transitions to be direct whereas a nondirect model fails. The ?2 profile calculated in a crude model assuming constant matrix elements matches well the corresponding experimental results. The calculated interband edge (??i=2.38 eV) agrees with experimental values, and the absorption tail below the interband edge which is found in experimental traces is also contained in the theoretical curve. By means of a calculation of the Fermi surface and the constant-energy-difference surfaces it has been possible to trace out the regions in k? space where the edge and tail transitions occur. It is demonstrated that structure in the static reflection curves are not related to critical points in the band structure. The arguments are supported by calculations of temperature shifts of the critical-point energies and comparison to the observed temperature shifts of the elements of structure in the experimental ?2 function. Such structure may originate in extended rather than localized regions of k? space. In contrast, critical-point transitions show up clearly in modulated reflectance spectra, and all elements of structure are fully accounted for by our band model. The temperature and strain responses in the band structure are determined by performing the RAPW calculation with two lattice constants and estimating the effects ofthe lattice vibrations by means of an OPW-LCAO (linear combination of atomic orbitals) scheme with pseudopotential Fourier constants reduced by the appropriate Debye-Waller factors. The phonon spectrum has been calculated for the latter purpose.

  7. Reduced Bloch mode expansion for periodic media band structure calculations

    CERN Document Server

    Hussein, Mahmoud I

    2008-01-01

    Reduced Bloch mode expansion is presented for fast periodic media band structure calculations. The expansion employs a natural basis composed of a selected reduced set of Bloch eigenfunctions. The reduced basis is selected within the irreducible Brillouin zone at high symmetry points determined by the medium's crystal structure and group theory (and possibly at additional related points). At each of the reciprocal lattice selection points, a number of Bloch eigenfunctions are selected up to the frequency range of interest for the band structure calculations. Since it is common to initially discretize the periodic unit cell and solution field using some choice of basis, reduced Bloch mode expansion is practically a secondary expansion that uses a selected set of Bloch eigenvectors. Such expansion therefore keeps, and builds on, any favorable attributes a primary expansion approach might exhibit. Being in line with the well known concept of modal analysis, the proposed approach maintains accuracy while reducing...

  8. One-Component Plasma: Going Beyond Debye-Hueckel

    OpenAIRE

    Moreira, Andre G; Netz, Roland R

    1999-01-01

    Using field-theoretic methods, we calculate the internal energy for the One-Component Plasma (OCP). We go beyond the recent calculation by Brilliantov [N. Brilliantov, Contrib. Plasma Phys. 38, pg. 489 (1998) / cond-mat/9805358] by including non-Gaussian terms. We show that, for the whole range of the plasma parameter Gamma, the effect of the higher-order terms is small and that the final result is not improved relative to the Gaussian theory when compared to simulations.

  9. Diffraction Calculations and Measurements in Millimeter Frequency Band

    Directory of Open Access Journals (Sweden)

    P. Pechac

    2004-09-01

    Full Text Available The paper deals with a study of diffraction on dielectric wedge(building corner in millimeter frequency band, both theoretically andexperimentally, to provide knowledge support for ray tracing/launchingcalculations of MWS interference issues in urban areas. The mainmotivation was to find balance between reasonably reliable results andnecessary demands on calculation complexity and input data accuracy.Verification of Uniform Theory of Diffraction (UTD was made both forperfectly conducting and dielectric wedge-shaped obstacle. Comparisonsof theoretical results and experimental measurement at millimeter wavesin anechoic chamber are presented.

  10. Emission bands of phosphorus and calculation of band structure of rare earth phosphides

    International Nuclear Information System (INIS)

    The method of x-ray emission spectroscopy has been used to investigate the electronic structure of monophosphides of rare-earth metals (REM). The fluorescence K bands of phosphorus have been obtained in LaP, PrP, SmP, GdP, TbP, DyP, HoP, ErP, TmP, YbP, and LuP and also the Lsub(2,3) bands of phosphorus in ErP, TmP, YbP, and LuP. Using the Green function technique involving the muffin-tin potential, the energy spectrum for ErP has been calculated in the single-electron approximation. The hystogram of electronic state distribution N(E) is compared with the experimental K and Lsub(2,3) bands of phosphorus in ErP. The agreement between the main details of N(E) and that of x-ray spectra allows to state that the model used provides a good description of the electron density distribution in crystals of REM monophosphides. In accordance with the character of the N(E) distribution the compounds under study are classified as semimetals or semiconductors with a very narrow forbidden band

  11. Energy bands in graphene: Comparison between the tight-binding model and ab initio calculations

    Science.gov (United States)

    Kogan, E.; Nazarov, V. U.; Silkin, V. M.; Kaveh, M.

    2014-04-01

    We compare the classification of the electron bands in graphene, obtained by group theory algebra in the framework of a tight-binding model (TBM), with that calculated in a density-functional-theory (DFT) framework. Identification in the DFT band structure of all eight energy bands (four valence and four conduction bands) corresponding to the TBM-derived energy bands is performed and the corresponding analysis is presented. The four occupied (three ?-like and one ?-like) and three unoccupied (two ?-like and one ?-like) bands given by the DFT closely correspond to those predicted by the TBM, both by their symmetry and their dispersion law. However, the two lowest lying at the ?-point unoccupied bands (one of them of a ?-like type and the other of a ?-like one), are not of the TBM type. According to both their symmetry and the electron density these bands are plane waves orthogonal to the TBM valence bands; dispersion of these states can be determined unambiguously up to the Brillouin zone borders. On the other hand, the fourth unoccupied band given by the TBM can be identified among those given by the DFT band calculations; it is situated rather high with respect to energy. The interaction of this band with the free-electron states is so strong that it exists only in part of the k space.

  12. Empiric k·p Hamiltonian calculation of the band-to-band photon absorption in semiconductors

    International Nuclear Information System (INIS)

    The Empiric k·p Hamiltonian method is usually applied to nanostructured semiconductors. In this paper, it is applied to a homogeneous semiconductor in order to check the adequacy of the method. In this case, the solutions of the diagonalized Hamiltonian, as well as the envelope functions, are plane waves. The procedure is applied to the GaAs and the interband absorption coefficients are calculated. They result in reasonable agreement with the measured values, further supporting the adequacy of the Empiric k·p Hamiltonian method

  13. Full Band Structure Calculation of Two-photon Indirect Absorption in Bulk Silicon

    OpenAIRE

    Cheng, J. L.; Rioux, J.; J. E. Sipe

    2010-01-01

    Degenerate two-photon indirect absorption in silicon is an important limiting effect on the use of silicon structures for all-optical information processing at telecommunication wavelengths. We perform a full band structure calculation to investigate two-photon indirect absorption in bulk silicon, using a pseudopotential description of the energy bands and an adiabatic bond charge model to describe phonon dispersion and polarization. Our results agree well with some recent e...

  14. Emergence of rotational bands in ab initio no-core configuration interaction calculations

    CERN Document Server

    Caprio, M A; Vary, J P; Smith, R

    2015-01-01

    Rotational bands have been observed to emerge in ab initio no-core configuration interaction (NCCI) calculations for p-shell nuclei, as evidenced by rotational patterns for excitation energies, electromagnetic moments, and electromagnetic transitions. We investigate the ab initio emergence of nuclear rotation in the Be isotopes, focusing on 9Be for illustration, and make use of basis extrapolation methods to obtain ab initio predictions of rotational band parameters for comparison with experiment. We find robust signatures for rotational motion, which reproduce both qualitative and quantitative features of the experimentally observed bands.

  15. Hybrid density functional calculations of the band gap of GaxIn1-xN

    Science.gov (United States)

    Wu, Xifan; Walter, Eric J.; Rappe, Andrew M.; Car, Roberto; Selloni, Annabella

    2009-09-01

    Recent theoretical work has provided evidence that hybrid functionals, which include a fraction of exact (Hartree-Fock) exchange in the density functional theory exchange and correlation terms, significantly improve the description of band gaps of semiconductors compared with local and semilocal approximations. Based on a recently developed order- N method for calculating the exact exchange in extended insulating systems, we have implemented an efficient scheme to determine the hybrid functional band gap. We use this scheme to study the band gap and other electronic properties of the ternary compound In1-xGaxN using a 64-atom supercell model.

  16. Dielectric band structure of crystals: General properties, and calculations for silicon

    International Nuclear Information System (INIS)

    We shift the dielectric band structure method, orginially proposed by Baldereschi and Tosatti for the description of microscopic electronic screening in crystals. Some general properties are examined first, including the requirements of causality and stability. The specific test case of silicon is then considered. Dielectric bands are calculated, according to several different prescriptions for the construction of the dielectric matrix. It is shown that the results allow a very direct appraisal of the screening properties of the system, as well as of the quality of the dielectric model adopted. The electronic charge displacement induced by ?sub(25') and X3 phonon-like displacements of the atoms is also calculated and compared with the results of existent full self-consistent calculations. Conclusions are drawn on the relative accuracies of the dielectric band structures. (author)

  17. Comparing photonic band structure calculation methods for diamond and pyrochlore crystals.

    Science.gov (United States)

    Vermolen, E C M; Thijssen, J H J; Moroz, A; Megens, M; van Blaaderen, A

    2009-04-27

    The photonic band diagrams of close-packed colloidal diamond and pyrochlore structures, have been studied using Korringa-Kohn-Rostoker (KKR) and plane-wave calculations. In addition, the occurrence of a band gap has been investigated for the binary Laves structures and their constituent large- and small-sphere substructures. It was recently shown that these Laves structures give the possibility to fabricate the diamond and pyrochlore structures by self-organization. The comparison of the two calculation methods opens the possibility to study the validity and the convergence of the results, which have been an issue for diamond-related structures in the past. The KKR calculations systematically give a lower value for the gap width than the plane-wave calculations. This difference can partly be ascribed to a convergence issue in the plane-wave code when a contact point of two spheres coincides with the grid. PMID:19399068

  18. Volume and surface photoemission from tungsten. I. Calculation of band structure and emission spectra

    DEFF Research Database (Denmark)

    Christensen, N. Egede; Feuerbacher, B.

    1974-01-01

    The electronic energy-band structure of tungsten has been calculated by means of the relativistic-augmented-plane-wave method. A series of mutually related potentials are constructed by varying the electronic configuration and the amount of Slater exchange included. The best band structure is obtained from an ad hoc potential based on a Dirac-Slater atomic calculation for the ground-state configuration and with full Slater exchange in the atomic as well as in the crystal potential. The selection of this best potential is justified by comparing the calculated band structure to Fermi-surface experiments and to optical-reflectance measurements up to 5-eV photon energy. The temperature and strain responses in the band structure are estimated from band calculations with four different lattice constants. The band structure was determined in the entire Brillouin zone and is applied to a calculation of photoemission spectra from W single crystals. The nondirect as well as the direct models for bulk photoemission processes are investigated. The emission from the three low-index surfaces (100), (110), and (111) exhibits strong dependence on direction and acceptance cone. According to the present band model there should essentially be no emission normal to the (110) face for photon energies between 9.4 and 10.6 eV. Experimental observation of emission in this gap, however, implies effects not included in the simple bulk models. In particular, effects arising from surface emission have been considered, i.e., emission of those electrons which are excited in a single-step process from initial states near the surface to final states outside the crystal. The electrons that are emitted from the surface in directions perpendicular to the crystal planes carry information on the one-dimensional surface density of states. The present work includes a crude estimate of this surface density of states, which is derived from the bulk band structure by narrowing the d bands according to an effective number of neighbors per surface atom. Estimates of surface relaxation effects are also included.

  19. Debye-Hueckel solution for steady electro-osmotic flow of a micropolar fluid in a cylindrical microcapillary

    CERN Document Server

    Siddiqui, Abuzar A

    2011-01-01

    Analytic expressions for the speed, flux, microrotation, stress, and couple stress in a micropolar fluid exhibiting steady, symmetric and one-dimensional electro-osmotic flow in a uniform cylindrical microcapillary were derived under the constraint of the Debye-Hueckel approximation, which is applicable when the cross-sectional radius of the microcapillary exceeds the Debye length, provided that the zeta potential is sufficiently small in magnitude. As the aciculate particles in a micropolar fluid can rotate without translation, micropolarity influences fluid speed, fluid flux, and one of the two non-zero components of the stress tensor. The axial speed in a micropolar fluid intensifies as the radius increases. The stress tensor is confined to the region near the wall of the microcapillary but the couple stress tensor is uniform across the cross-section.

  20. CdSe/CdTe interface band gaps and band offsets calculated using spin-orbit and self-energy corrections

    Energy Technology Data Exchange (ETDEWEB)

    Ribeiro, M. [Centro de Pesquisas Avancadas Wernher von Braun, Av. Alice de Castro P.N. Mattosinho 301, CEP 13098-392 Campinas, SP (Brazil); Ferreira, L.G. [Departamento de Fisica dos Materiais e Mecanica, Instituto de Fisica, Universidade de Sao Paulo, 05315-970 Sao Paulo, SP (Brazil); Fonseca, L.R.C. [Center for Semiconductor Components, State University of Campinas, R. Pandia Calogeras 90, 13083-870 Campinas, SP (Brazil); Ramprasad, R. [Department of Chemical, Materials and Biomolecular Engineering, Institute of Materials Science, University of Connecticut, 97 North Eagleville Road, Storrs, CT 06269 (United States)

    2012-09-20

    We performed ab initio calculations of the electronic structures of bulk CdSe and CdTe, and their interface band alignments on the CdSe in-plane lattice parameters. For this, we employed the LDA-1/2 self-energy correction scheme to obtain corrected band gaps and band offsets. Our calculations include the spin-orbit effects for the bulk cases, which have shown to be of importance for the equilibrium systems and are possibly degraded in these strained semiconductors. Therefore, the SO showed reduced importance for the band alignment of this particular system. Moreover, the electronic structure calculated along the transition region across the CdSe/CdTe interface shows an interesting non-monotonic variation of the band gap in the range 0.8-1.8 eV, which may enhance the absorption of light for corresponding frequencies at the interface between these two materials in photovoltaic applications.

  1. Precision photonic band structure calculation of Abrikosov periodic lattice in type-II superconductors

    International Nuclear Information System (INIS)

    We have performed a numerical solution for band structure of an Abrikosov vortex lattice in type-II superconductors forming a periodic array in two dimensions for applications of incorporating the photonic crystals concept into superconducting materials with possibilities for optical electronics. The implemented numerical method is based on the extensive numerical solution of the Ginzburg-Landau equation for calculating the parameters of the two-fluid model and obtaining the band structure from the permittivity, which depends on the above parameters and the frequency. This is while the characteristics of such crystals highly vary with an externally applied static normal magnetic field, leading to nonlinear behavior of the band structure, which also has nonlinear dependence on the temperature. The similar analysis for every arbitrary lattice structure is also possible to be developed by this approach as presented in this work. We also present some examples and discuss the results

  2. Tight binding electronic band structure calculation of achiral boron nitride single wall nanotubes

    International Nuclear Information System (INIS)

    In this paper we report the Tight-Binding method, for the electronic structure calculations of achiral single wall Boron Nitride nanotubes. We have used the contribution of ? electron only to define the electronic band structure for the solid. The Zone-folding method is used for the Brillouin Zone definition. Calculation of tight binding model parameters is done by fitting them to available experimental results of two-dimensional hexagonal monolayers of Boron Nitride. It has been found that all the boron nitride nanotubes (both zigzag and armchair) are constant gap semiconductors with a band gap of 5.27eV. All zigzag BNNTs are found to be direct gap semiconductors while all armchair nanotubes are indirect gap semiconductors. (author)

  3. Efficient calculation of inelastic vibration signals in electron transport: Beyond the wide-band approximation

    DEFF Research Database (Denmark)

    Lu, Jing Tao; Christensen, Rasmus Bjerregaard

    2014-01-01

    We extend the simple and efficient lowest order expansion (LOE) for inelastic electron tunneling spectroscopy (IETS) to include variations in the electronic structure on the scale of the vibration energies. This enables first-principles calculations of IETS line shapes for molecular junctions close to resonances and band edges. We demonstrate how this is relevant for the interpretation of experimental IETS using both a simple model and first-principles simulations.

  4. Vibronic contributions to the n ? ? ? absorption band of cyclopentanone. An ab initio SCF-RPA calculation

    Science.gov (United States)

    Flament, J. P.; Gervais, H. P.

    The SCF-RPA scheme is applied to the n ? ? ? absorption band of cyclopentanone in its ( C2) ground-state nuclear configuration. Using the Cederbaum-Domcke algorithm, the effects of the ( ?3) C=0 stretching, ( ?18) ring puckering and ( ?25) C=0 out-of-plane vibrations are investigated. The calculated spectrum shows both allowed and vibronic components, in agreement with the experimental observations of Howard-Lock and King.

  5. Zero band-gap polymers: Quantum-chemical study of electronic structures of degenerate {pi}-conjugated systems

    Energy Technology Data Exchange (ETDEWEB)

    Hong, S.Y.

    2000-02-01

    In search of very small band-gap polymers, the authors have quantum-chemically investigated the electronic structures of various polypentafulvalenes (PFVs) fused with six-membered rings. Geometrical parameters of the polymers were optimized through semiempirical Hartree-Fock band calculations at the Austin Model 1 (AM1) level. Electronic structures of the polymers were obtained through modified extended Hueckel band calculations by adopting AM1-optimized geometries. It is predicted that poly(di-vinylenedioxy-pentafulvalene) and poly(di-vinylenedithia-pentafulvalene) would possess nearly zero band gaps (corresponding to {lambda}{sub max}) despite their large bond-length alternation of {approximately}0.1 A. However, these polymers are expected to be very susceptible to oxidation. Poly(di-butylene-pentafulvalene) and poly(dipyrazinopentafulvalene) are estimated to possess band gaps comparable with that (1.13 eV) of PFV. The calculated band gap of poly(di-ethylenedioxy-pentafulvalene) is 0.77 eV, smaller than that of PFV by 0.36 eV. The authors explained the evolution of band gaps of the polymers through molecular orbital arguments.

  6. Model calculation of N2 Vegard-Kaplan band emissions in Martian dayglow

    CERN Document Server

    Jain, Sonal Kumar

    2011-01-01

    A model for N2 Vegard-Kaplan (VK) band (A^3Sigma_u^+ - X^1Sigma_g^+) emissions in Martian dayglow has been developed to explain the recent observations made by the Spectroscopy for Investigation of Characteristics of the Atmosphere of Mars (SPICAM) ultraviolet spectrograph aboard Mars Express. Steady state photoelectron fluxes and volume excitation rates have been calculated using the analytical yield spectra technique. Since interstate cascading is important for triplet states of N2, the population of any given level of N2 triplet states is calculated under statistical equilibrium considering direct excitation, cascading, and quenching effects. Relative population of all vibrational levels of each triplet state is calculated in the model. Line of sight intensities and height-integrated overhead intensities have been calculated for VK, first positive (B^3Pi_g - A^3Sigma_u^+), second positive (C^3Pi_u - B^3Pi_g), and Wu-Benesch (W^3Delta_u - B^3Pi_g) bands of N2. A reduction in the N2 density by a factor of 3 ...

  7. Accurate band gaps of semiconductors and insulators from Quantum Monte Carlo calculations

    Science.gov (United States)

    Nazarov, Roman; Hood, Randolph; Morales, Miguel

    2015-03-01

    Ab initio calculations are useful tools in developing materials with targeted band gaps for semiconductor industry. Unfortunately, the main workhorse of ab initio calculations - density functional theory (DFT) in local density approximation (LDA) or generalized gradient approximation (GGA) underestimates band gaps. Several approaches have been proposed starting from empirical corrections to more elaborate exchange-correlation functionals to deal with this problem. But none of these work well for the entire range of semiconductors and insulators. Deficiencies of DFT as a mean field method can be overcome using many-body techniques. Quantum Monte Carlo (QMC) methods can obtain a nearly exact numerical solutions of both total energies and spectral properties. Diffusion Monte Carlo (DMC), the most widely used QMC method, has been shown to provide gold standard results for different material properties, including spectroscopic constants of dimers and clusters, equation of state for solids, accurate descriptions of defects in metals and insulators. To test DMC's accuracy in a wider range of semiconductors and insulators we have computed band gaps of several semiconductors and insulators. We show that DMC can provide superior agreement with experiment compared with more traditional DFT approaches including high level exchange-correlation functionals (e.g. HSE).

  8. Calculation Method for Flight Limit Load of V-band Clamp Separation Shock

    Science.gov (United States)

    Iwasa, Takashi; Shi, Qinzhong

    A simplified calculation method for estimating a flight limit load of the V-band clamp separation shock was established. With this method, the flight limit load is estimated through addition of an appropriate envelope margin to the results acquired with the simplified analysis method proposed in our previous paper. The envelope margin used in the method was calculated based on the reviews on the differences observed between the results of a pyroshock test and the analysis. Using the derived envelope margin, a calculating formula of the flight limit load, which envelopes the actual pyroshock responses with a certain probability, was developed. Based on the formula, flight limit loads for several actual satellites were estimated and compared to the test results. The comparative results showed that the estimated flight limit loads appropriately envelope the test results, which confirmed the effectiveness of the proposed method.

  9. Band structure calculations for Ba$_{6}$Ge$_{25}$ and Ba$_{4}$Na$_{2}$Ge$_{25}$ clathrates

    CERN Document Server

    Zerec, I; Thalmeier, P; Grin, Y; Zerec, Ivica; Yaresko, Alexander; Thalmeier, Peter; Grin, Yuri

    2002-01-01

    Electronic band structures for Ba$_{6}$Ge$_{25}$ and Ba$_{4}$Na$_{2}$Ge$_{25}$ clathrates are calculated using linear muffin-tin orbital method within the local density approximation. It is found that barium states strongly contribute to the density of states at the Fermi level and thus can influence the transport properties of the compounds. A sharp peak of the density of states is found just at the Fermi level. It is also shown that the shifting of barium atoms toward experimentally deduced split positions in Ba$_{6}$Ge$_{25}$ produces a splitting of this peak which may therefore be interpreted as a band Jahn-Teller effect. If the locking of the barium atoms at the observed structural phase transition is assumed, this reduction of the density of states at the Fermi level can qualitatively account for the experimentally observed decrease of the magnetic susceptibility and electrical resistivity at the phase transition.

  10. First principles band structure calculations based on self-consistent screened Hartree-Fock exchange potential.

    Science.gov (United States)

    Shimazaki, Tomomi; Asai, Yoshihiro

    2009-04-28

    A screened Hartree-Fock (HF) exchange potential with the dielectric constant was previously reported by Shimazaki and Asai [Chem. Phys. Lett. 466, 91 (2008)], in which the inverse of the dielectric constant was used to represent a fraction of the HF exchange term. In that report, the experimentally obtained value for the dielectric constant was employed. Herein, we discuss a self-consistent technique, in which the value of the dielectric constant can be automatically determined. This technique enables the energy band structure to be determined without using the experimental value. The band energy structure of diamond is calculated, a self-consistent procedure is determined to give closer bandgaps compared with the local density approximation and the generalized gradient approximation. PMID:19405611

  11. Linear combination of bulk bands method for large-scale electronic structure calculations on strained nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Wang, L.; Zunger, A. [National Renewable Energy Laboratory, Golden, Colorado 80401 (United States)

    1999-06-01

    A {open_quotes}strained linear combination of bulk bands{close_quotes} method is introduced for calculating the single-particle electronic states of strained, million-atom nanostructure systems, within an empirical pseudopotential Hamiltonian. This method expands the wave functions of a nanostructure (superlattice, wire, and dot) as linear combinations of bulk Bloch states of the constituent materials, over band indices {ital n} and wave vectors {ital k}. This allows one to use physical intuition in selecting the {ital n} and {ital k} that are most relevant for a given problem. This constitutes a useful approximation over the {open_quotes}direct diagonalization{close_quotes} approach where the basis is complete (individual plane waves) but unintuitive. It also constitutes a dramatic improvement upon the {bold k}{center_dot}{bold p} approach, where the continuum model Hamiltonian is used, losing the atomistic details of the system. For a pyramidal InAs quantum dot embedded in GaAs, we find electronic eigenenergies that are within 20 meV of the exact direct diagonalization calculation, while the speed of the current method is 100{endash}1000 times faster. The sublinear scaling of the current method with the size of the system enables one to calculate the atomistic electronic states of a million-atom system on a personal computer in about 10 h. Sufficient detail is provided in the formalism, so that the method can be promptly implemented. {copyright} {ital 1999} {ital The American Physical Society}

  12. Comment on ''Laboratory measurements and theoretical calculations of O2 A-band electric quadrupole transitions''

    International Nuclear Information System (INIS)

    D. A. Long et al.[Phys. Rev. A 80, 042513 (2009)] recently reported accurate measurements on the ultraweak electric quadrupole (E2) transitions in the O2 A band. They also presented elegant theoretical calculation of the line intensities based on Hund's case (b) formulation. However, their theoretical elucidation fails to relate to a highly relevant previous work by Balasubramanian and Narayanan [Acta Phys. Hung 74, 341 (1994)] in which closed-form expressions for the E2 branch line strengths for the eight possible rotational branches of the b1?g+-X3?g- transition, in intermediate coupling, are derived. The complete equivalence of the two methods is proven through direct calculation. A second point of concern is that the magnetic dipole (M1) transition moment M1 = 0.0687 ?B deduced by Long et al. from the previously measured transition intensities is ?2.7 times the ab initio value of 0.0255 ?B computed by Minaev et al.[Chem. Phys. 208, 299 (1996)]. Since the latter reproduces closely the measured Einstein's spontaneous emission coefficient of the A band, this large discrepancy is intriguing.

  13. The use of bulk states to accelerate the band edge state calculation of a semiconductor quantum dot

    International Nuclear Information System (INIS)

    We present a new technique to accelerate the convergence of the folded spectrum method in empirical pseudopotential band edge state calculations for colloidal quantum dots. We use bulk band states of the materials constituent of the quantum dot to construct initial vectors and a preconditioner. We apply these to accelerate the convergence of the folded spectrum method for the interior states at the top of the valence and the bottom of the conduction band. For large CdSe quantum dots, the number of iteration steps until convergence decreases by about a factor of 4 compared to previous calculations

  14. Linear combination of bulk bands method for large-scale electronic structure calculations on strained nanostructures

    International Nuclear Information System (INIS)

    A open-quotes strained linear combination of bulk bandsclose quotes method is introduced for calculating the single-particle electronic states of strained, million-atom nanostructure systems, within an empirical pseudopotential Hamiltonian. This method expands the wave functions of a nanostructure (superlattice, wire, and dot) as linear combinations of bulk Bloch states of the constituent materials, over band indices n and wave vectors k. This allows one to use physical intuition in selecting the n and k that are most relevant for a given problem. This constitutes a useful approximation over the open-quotes direct diagonalizationclose quotes approach where the basis is complete (individual plane waves) but unintuitive. It also constitutes a dramatic improvement upon the k·p approach, where the continuum model Hamiltonian is used, losing the atomistic details of the system. For a pyramidal InAs quantum dot embedded in GaAs, we find electronic eigenenergies that are within 20 meV of the exact direct diagonalization calculation, while the speed of the current method is 100 endash 1000 times faster. The sublinear scaling of the current method with the size of the system enables one to calculate the atomistic electronic states of a million-atom system on a personal computer in about 10 h. Sufficient detail is provided in the formalism, so that the method can be promptly implemented. copyright 1999 The American Physical Society

  15. First calculation of phase and coherence of longitudinally separated L-band equatorial ionospheric scintillation

    Science.gov (United States)

    Shume, E. B.; Mannucci, A. J.

    2013-07-01

    We present the first calculation of phase and coherence of cross-wavelet transform applied to longitudinally separated L-band equatorial ionospheric scintillation observations received from Geostationary Earth Orbit (GEO) satellites. The phase and coherence analysis were employed on two pairs of observations: (1) São Luís and Rio Branco and (2) Alta Floresta and Huancayo. For these case studies, in statistically significant and high-coherence regions, scintillation observations over São Luís (Alta Floresta) lead that of Rio Branco (Huancayo) by ˜2 to 3 h with a 95%frequency. If L-band scintillation happens over São Luís (Alta Floresta), there is a 95%likelihood that scintillation would happen to the west over Rio Branco (Huancayo) after ˜2 to 3 h, suggesting that a forecast can be made ahead of scintillation occurrences. The phase and coherence relationships between the longitudinally separated scintillation-producing regions can be connected to the large-scale wave structures which are reported to be related to the generation of equatorial spread F and scintillation.

  16. Calculation and analysis of complex band structure in dispersive and dissipative two-dimensional photonic crystals

    CERN Document Server

    Brûlé, Yoann; Gralak, Boris

    2015-01-01

    Numerical calculation of modes in dispersive and absorptive systems is performed using the finite element method. The dispersion is tackled in the frame of an extension of Maxwell's equations where auxiliary fields are added to the electromagnetic field. This method is applied to multi-domain cavities and photonic crystals including Drude and Drude-Lorentz metals. Numerical results are compared to analytical solutions for simple cavities and to previous results of the literature for photonic crystals, showing excellent agreement. The advantages of the developed method lie on the versatility of the finite element method regarding geometries, and in sparing the use of tedious complex poles research algorithm. Hence the complex spectrum of resonances of non-hermitian operators and dissipative systems, like two-dimensional photonic crystal made of absorbing Drude metal, can be investigated in detail. The method is used to reveal unexpected features of their complex band structures.

  17. Ab-initio calculations of the Optical band-gap of TiO2 thin films

    CERN Document Server

    Wunderlich, W; Tanemura, M; Tanemura, S; Jin, P; Kaneko, K; Terai, A; Nabatova-Gabin, N; Belkada, R; Wunderlich, Wilfried; Miao, Lei; Tanemura, Masaki; Tanemura, Sakae; Jin, Ping; Kaneko, Kenji; Terai, Asuka; Nabatova-Gabin, Nataliya; Belkada, Rachid

    2004-01-01

    Titanium dioxide has been extensively studied in recent decades for its important photocatalytic application in environmental purification. The search for a method to narrow the optical band-gap of TiO2 plays a key role for enhancing its photocatalytic application. The optical band gap of epitaxial rutile and anatase TiO2 thin films deposited by helicon magnetron sputtering on sapphire and on SrTiO3 substrates was correlated to the lattice constants estimated from HRTEM images and SAED. The optical band-gap of 3.03 eV for bulk-rutile increased for the thin films to 3.37 on sapphire. The band gap of 3.20 eV for bulk-anatase increases to 3.51 on SrTiO3. In order to interpret the optical band gap expansion for both phases, ab-initio calculations were performed using the Vienna ab-initio software. The calculations for rutile as well anatase show an almost linear increase of the band gap width with decreasing volume or increasing lattice constant a. The calculated band gap fits well with the experimental values. T...

  18. GaAs quantum structures: Comparison between direct pseudopotential and single-band truncated-crystal calculations

    International Nuclear Information System (INIS)

    A single-band approach for semiconductor clusters which accounts for the nonparabolicity of the energy bands was recently used by Rama Krishna and Friesner [M.V. Rama Krishna and R.A. Friesner, Phys. Rev. Lett. 67, 629 (1991)]. We compare the results of this method (denoted here as single-band truncated-crystal, or SBTC, approximation) with a direct pseudopotential band-structure calculation for free-standing hydrogen-passivated GaAs quantum films, wires, and dots. The direct pseudopotential calculation, which includes coupling between all bands, shows that isolated GaAs quantum films, wires, and dots have an indirect band gap for thicknesses below 16, 28, and at least 30 A (8, 14, and at least 15 ML), respectively; beyond these critical dimensions the transition becomes direct. A comparison of the SBTC approximation with the direct pseudopotential calculation shows that (i) the confinement energy of the valence-band maximum is overestimated by the SBTC method, because the zero-confinement character of this state is neglected; (ii) the confinement energy of the ?-derived conduction state (direct band gap) is slightly overestimated by the SBTC approximation, mainly because of the assumption of infinite potential barriers at the boundaries; (iii) the confinement energy of the X-derived conduction state (indirect band gap) is severely underestimated by the SBTC method; (iv) while the SBTC approximation predicts open-quote open-quote quantum deconfinement close-quote close-quote (i.e., reduction of gap as size is reduced) for the direct gap of thin GaAs quantum wires, such effect is not present in the direct pseudopotential calculation. copyright 1996 American Institute of Physics

  19. Photonic band structure of one-dimensional metal/dielectric structures calculated by the plane-wave expansion method

    Science.gov (United States)

    Zong, YiXin; Xia, JianBai

    2015-07-01

    The plane-wave expansion (PWE) method is employed to calculate the photonic band structures of metal/dielectric (M/D) periodic systems. We consider a one-dimensional (1D)M/D superlattice with ametal layer characterized by a frequency-dependent dielectric function. To calculate the photonic band of such a system, we propose a new method and thus avoid solving the nonlinear eigenvalue equations. We obtained the frequency dispersions and the energy distributions of eigen-modes of 1D superlattices. This general method is applicable to calculate the photonic band of a broad class of physical systems, e.g. 2D and 3D M/D photonic crystals. For comparison, we present a simple introduction of the finite-difference (FD) method to calculate the same system, and the agreement turns out to be good. But the FD method cannot be applied to the TM modes of the M/D superlattice.

  20. Voltage effect in PTCR ceramics: Calculation by the method of tilted energy band

    International Nuclear Information System (INIS)

    A numerical model for the calculation of the electrical characteristics of donor-doped BaTiO3 semiconducting ceramics is suggested. This paper established a differential equation about electron level on the base of Poisson equation, and solved the equation with Runge-Kutta method. Under extra electric field, electrical characteristics have been calculated by the method of tilted energy band. We have quantitatively computed the positive temperature coefficient of resistivity (PTCR) behavior of donor-doped BaTiO3 semiconducting ceramics and its voltage effect, and further obtained non-linear current-voltage characteristics with different grain sizes at different temperature. The results pointed out that the resistance jumping is reduced with increasing electric field applied; current and voltage relation follows Ohm's law below Curie temperature, and exhibits strong non-linear above Curie temperature; the non-linear coefficient shows a maximum value at temperature the resistivity reaches maximum and with grain size closed to depletion region width. The results are compared with experimental data.

  1. Implementation of full ab initio band calculation of frequency-dependent third-order nonlinear optical susceptibilities: a sum-over-states calculation

    CERN Document Server

    Lan, You-Zhao

    2016-01-01

    We implement the full ab initio band calculation of the frequency-dependent third-order nonlinear optical susceptibility for the third harmonic generation process in the whole Brillouin zone on the basis of the sum-over-states formulation by Aversa and Sipe [Phys. Rev. B 52, 14636 (1995)]. The implementation was made to satisfy the intrinsic permutation symmetry and applied to calculate the frequency-dependent third harmonic generation of cubic silicon bulk. The accurate all-electron full potential linearized augmented plane wave method was used to calculate the energy band structure and momentum matrix elements. Both real and imaginary parts of susceptibility were directly calculated and checked by the Kramers-Kronig relation. Compared to theoretical results based on the two-band model and semi-empirical band calculations, our present results shows an improvement and agree well with recent theoretical results based on the ab initio real-time-based computational approach. The electronic origin of nonlinear op...

  2. Photon path length distributions for cloudy skies – oxygen A-Band measurements and model calculations

    Directory of Open Access Journals (Sweden)

    O. Funk

    Full Text Available This paper addresses the statistics underlying cloudy sky radiative transfer (RT by inspection of the distribution of the path lengths of solar photons. Recent studies indicate that this approach is promising, since it might reveal characteristics about the diffusion process underlying atmospheric radiative transfer (Pfeilsticker, 1999. Moreover, it uses an observable that is directly related to the atmospheric absorption and, therefore, of climatic relevance. However, these studies are based largely on the accuracy of the measurement of the photon path length distribution (PPD. This paper presents a refined analysis method based on high resolution spectroscopy of the oxygen A-band. The method is validated by Monte Carlo simulation atmospheric spectra. Additionally, a new method to measure the effective optical thickness of cloud layers, based on fitting the measured differential transmissions with a 1-dimensional (discrete ordinate RT model, is presented. These methods are applied to measurements conducted during the cloud radar inter-comparison campaign CLARE’98, which supplied detailed cloud structure information, required for the further analysis. For some exemplary cases, measured path length distributions and optical thicknesses are presented and backed by detailed RT model calculations. For all cases, reasonable PPDs can be retrieved and the effects of the vertical cloud structure are found. The inferred cloud optical thicknesses are in agreement with liquid water path measurements.

    Key words. Meteorology and atmospheric dynamics (radiative processes; instruments and techniques

  3. Comprehensive comparison and experimental validation of band-structure calculation methods in III-V semiconductor quantum wells

    Science.gov (United States)

    Zerveas, George; Caruso, Enrico; Baccarani, Giorgio; Czornomaz, Lukas; Daix, Nicolas; Esseni, David; Gnani, Elena; Gnudi, Antonio; Grassi, Roberto; Luisier, Mathieu; Markussen, Troels; Osgnach, Patrik; Palestri, Pierpaolo; Schenk, Andreas; Selmi, Luca; Sousa, Marilyne; Stokbro, Kurt; Visciarelli, Michele

    2016-01-01

    We present and thoroughly compare band-structures computed with density functional theory, tight-binding, k · p and non-parabolic effective mass models. Parameter sets for the non-parabolic ?, the L and X valleys and intervalley bandgaps are extracted for bulk InAs, GaAs and InGaAs. We then consider quantum-wells with thickness ranging from 3 nm to 10 nm and the bandgap dependence on film thickness is compared with experiments for In0.53Ga0.47 As quantum-wells. The impact of the band-structure on the drain current of nanoscale MOSFETs is simulated with ballistic transport models, the results provide a rigorous assessment of III-V semiconductor band structure calculation methods and calibrated band parameters for device simulations.

  4. Band gap engineering in amorphous AlxGa1-xN: Experiment and ab initio calculations

    Science.gov (United States)

    Chen, Hong; Chen, Kuiying; Drabold, D. A.; Kordesch, M. E.

    2000-08-01

    Amorphous alloys of aluminum nitride and gallium nitride deposited at 100 K at compositions ranging from pure AlN to pure GaN with optical band gaps which vary linearly with composition from 3.27 eV (a-GaN) to 5.95 eV (a-AlN) have been synthesized. Ab initio molecular dynamics calculations for these alloys reproduce the band gap versus composition data and give specific information on the electronic localization of the band tail states. There are no midgap states in amorphous AlxGa1-xN alloys. The calculated models have mixed four-fold and three-fold coordination and have no wrong (homopolar nuclear) bonds, demonstrating the strong ionicity in amorphous AlxGa1-xN alloys. It has been found that the valence band tail states are mostly localized on the three-fold coordinated N sites while the conduction band tail states are mostly localized on the three-fold coordinated Ga or Al sites.

  5. ZnxCd1?xSe nanomultipods with tunable band gaps: synthesis and first-principles calculations

    International Nuclear Information System (INIS)

    In this paper, we demonstrate that ZnxCd1?xSe nanomultipods can be synthesized via a facile and nontoxic solution-based method. Interesting aspects of composition, morphology and optical properties were deeply explored. The value of Zn/(Zn+Cd) could be altered across the entire range from 0.08 to 0.86 by varying the ratio of cation precursor contents. The band gap energy could be linearly tuned from 1.88 to 2.48 eV with respect to the value of Zn/(Zn+Cd). The experiment also showed that oleylamine played a dominant role in the formation of multipod structure. A possible growth mechanism was further suggested. First-principles calculations of band gap energy and density of states in the Vienna ab initio simulation package code were performed to verify the experimental variation tendency of the band gap. Computational results indicated that dissimilarities of electronic band structures and orbital constitutions determined the tunable band gap of the as-synthesized nanomultipod, which might be promising for versatile applications in relevant areas of solar cells, biomedicine, sensors, catalysts and so on. (paper)

  6. Variational band theory of vibronic polarons in crystals. III. Numerical calculations

    CERN Document Server

    Georgiev, M; Ivanovich, M D

    2006-01-01

    In the preceding Part II, we derived variational equations for the phonon Fourier amplitudes and for the Fourier amplitudes of the fractional contribution of the electronic bands to the trial variational state. These equations are now solved by means of iterations for each value of the total momentum in order to obtain the energy vs. momentum relation for the ground state. Another result is mapping out the phonon and band Fourier amplitudes in the parameter space of the mixing constant and the electron hopping energy.

  7. A new integral representation for quasiperiodic fields and its application to two-dimensional band structure calculations

    OpenAIRE

    Barnett, Alex H.; Greengard, Leslie

    2010-01-01

    In this paper, we consider band-structure calculations governed by the Helmholtz or Maxwell equations in piecewise homogeneous periodic materials. Methods based on boundary integral equations are natural in this context, since they discretize the interface alone and can achieve high order accuracy in complicated geometries. In order to handle the quasi-periodic conditions which are imposed on the unit cell, the free-space Green's function is typically replaced by its quasi-p...

  8. Hybrid density functional calculations of the band gap of Ga$_x$In$_{1-x}$N

    OpenAIRE

    Wu, Xifan; Walter, Eric J.; Rappe, Andrew M.; Car, Roberto; Selloni, Annabella

    2009-01-01

    Recent theoretical work has provided evidence that hybrid functionals, which include a fraction of exact (Hartree Fock) exchange in the density functional theory (DFT) exchange and correlation terms, significantly improve the description of band gaps of semiconductors compared with local and semilocal approximations. Based on a recently developed order-$N$ method for calculating the exact exchange in extended insulating systems, we have implemented an efficient scheme to det...

  9. Fermi surface of technetium from a constant-energy-search Korringa-Kohn-Rostoker band-theory calculation

    International Nuclear Information System (INIS)

    We generate two muffin-tin potentials for technetium using Slater exchange and calculate the Fermi energies and Fermi surfaces very accurately using the constant-energy-search Korringa-Kohn-Rostoker method. An explanation for experimental de Haas--van Alphen frequencies that were not previously understood is proposed. The bare-band theory contribution to the low-temperature specific heat is ?0 = 2.12 mJ/mol K2 for the better potential. We demonstrate the feasibility of using the methods outlined in this paper for carrying out highly detailed calculations on hcp metals

  10. A Formulation for the Static Permittivity of Water and Steam at Temperatures from 238 K to 873 K at Pressures up to 1200 MPa, Including Derivatives and Debye Hueckel Coefficients

    International Nuclear Information System (INIS)

    A new formulation is presented of the static relative permittivity or dielectric constant of water and steam, including supercooled and supercritical states. The range is from 238 K to 873 K, at pressures up to 1200 MPa. The formulation is based on the ITS-90 temperature scale. It correlates a selected set of data from a recently published collection of all experimental data. The set includes new data in the liquid water and the steam regions that have not been part of earlier correlations. The physical basis for the formulation is the so-called g-factor in the form proposed by Harris and Alder. An empirical 12-parameter form for the g-factor as a function of the independent variables temperature and density is used. For the conversion of experimental pressures to densities, the newest formulation of the equation of state of water on the ITS-90, prepared by Wagner and Pruss, has been used. All experimental data are compared with the formulation. The reliability of the new formulation is assessed in all subregions. Comparisons with previous formulations are presented. Auxiliary dielectric-constant formulations as functions of temperature are included for the saturated vapor and liquid states. The pressure and temperature derivatives of the dielectric constant and the Debye endash Hueckel limiting-law slopes are calculated, their reliability is estimated, and they are compared with experimentally derived values and with previous correlations. All equations are given in correlations. All equations are given in this paper, along with short tables. An implementation of this formulation for the dielectric constant is available on disk [A. H. Harvey, A. P. Peskin, and S. A. Klein, NIST/ASME Steam Properties, NIST Standard Reference Database 10, Version 2.1, Standard Reference Data Program, NIST, Gaithersburg, MD (1997)]. copyright 1997 American Institute of Physics and American Chemical SocietyA new formulation is presented of the static relative permittivity or dielectric constant of water and steam, including supercooled and supercritical states. The range is from 238 K to 873 K, at pressures up to 1200 MPa. The formulation is based on the ITS-90 temperature scale. It correlates a selected set of data from a recently published collection of all experimental data. The set includes new data in the liquid water and the steam regions that have not been part of earlier correlations. The physical basis for the formulation is the so-called g-factor in the form proposed by Harris and Alder. An empirical 12-parameter form for the g-factor as a function of the independent variables temperature and density is used. For the conversion of experimental pressures to densities, the newest formulation of the equation of state of water on the ITS-90, prepared by Wagner and Pruss, has been used. All experimental data are compared with the formulation. The reliability of the new formulation is assessed in all subregions. Comparisons with previous formulations are presented. Auxiliary dielectric-constant formulations as functions of temperature are included for the saturated vapor and liquid states. The pressure and temperature derivatives of the dielectric constant and the Debye endash Hueckel limiting-law slopes are calculated, their reliability is estimated, and they are compared with experimentally derived values and with previous correlations. All equations are given in

  11. Fermi surface of heavy fermion compounds CeTIn5 (T=Rh, Ir, and Co). Band-calculation and tight-binding approach

    International Nuclear Information System (INIS)

    Electronic properties of Ce-based heavy-fermion compounds are discussed by using the relativistic band-calculation method. To seek for a route from the band calculation to a many-body Hamiltonian, which is necessary to discuss the magnetic and superconducting properties, a minimal tight-binding model is proposed for f-electron systems. (author)

  12. Constrained Nudged Elastic Band calculation of the Peierls barrier with atomic relaxations.

    Czech Academy of Sciences Publication Activity Database

    Gröger, Roman; Vitek, V.

    2012-01-01

    Ro?. 20, ?. 3 (2012), 035019. ISSN 0965-0393 R&D Projects: GA ?R GAP204/10/0255; GA MŠk(CZ) ED1.1.00/02.0068 Institutional research plan: CEZ:AV0Z20410507 Keywords : dislocation * Peierls barrier * Nudged Elastic Band Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.932, year: 2012

  13. A new Green's function for the wake potential calculation of the SLAC S-band constant gradient accelerating section

    International Nuclear Information System (INIS)

    The behavior of the longitudinal wake fields excited by a very short bunch in the SLAC S-band constant gradient accelerating structures has been studied. Wake potential calculations were performed for a bunch length of 10?m using the author's code to obtain a numerical solution of Maxwell's equations in the time domain. We have calculated six accelerating sections in the series (60-ft) to find the stationary solution. While analyzing the computational results we have found a new formula for Green's function. Wake potentials, which are calculated using this Green's function are in amazingly good agreement with numerical results over a wide range of bunch lengths. Green's function simplifies the wake potential calculations and can be easily incorporated into the tracking codes. This is very useful for beam dynamics studies of the linear accelerators of LCLS and FACET .

  14. Cluster model and band structure calculations of V2O5 : Reduced V5+ symmetry and many-body effects

    Science.gov (United States)

    Mossanek, R. J. O.; Mocellin, A.; Abbate, M.; Searle, B. G.; Fonseca, P. T.; Morikawa, E.

    2008-02-01

    We studied the electronic structure of the V2O5 compound using cluster model calculations. The calculation included the reduced V5+ symmetry and the strong V3d-O2p covalence effects. The many-body effects are taken into account using the configuration interaction method. The ground state of V2O5 is highly covalent and dominated by the 3d1? (A11) configuration, where ? denotes a ligand hole. The V2O5 material is in the charge-transfer regime and the band gap is due to p-d transitions. The first removal state is given by the 3d0? (A12) configuration, and the first addition state is formed by the 3d1 (E2) configuration. The results of the cluster model are in good agreement with band structure calculations. The calculation results are also in good agreement with photoemission and x-ray absorption spectra. The V2p core-level spectra exhibit many-body effects despite the nominal 3d0 occupancy. These effects and the reduced V5+ symmetry are crucial to describe the electronic structure of V2O5 .

  15. Calculation of intraband electron and band-to-band hole luminescence spectra of some alkali halide crystals under pulse excitation by dense electron and laser beams of nano- and picosecond duration

    International Nuclear Information System (INIS)

    Theoretical calculation of spectra of two new types of fundamental radioluminescence of dielectrics - intraband electron and band-to-band hole ones - was conducted. These types of radioluminescence were revealed and studied experimentally due to the use of two high-power nano- and picosecond radiation sources for dielectric excitation - high-current electron accelerators and lasers with generators of ultraviolet harmonics. Satisfactory agreement of calculated spectra with ones, measured experimentally, was achieved. Correlation of calculation results with experimental data enabled to determine some important parameters of electron spectrum and specifically the upper boundary of passive region for conduction band ionization for CsI crystals. 27 refs., 8 figs

  16. Multi-band tight-binding calculation of electronic transport in Fe/trans-polyacetylene/Fe tunnel junctions

    Science.gov (United States)

    Abedi Ravan, B.

    2012-10-01

    In this paper, the electronic transport characteristics of Fe/trans-polyacetylene/Fe magnetic tunnel junctions (MTJs) are investigated using multi-band tight-binding calculations within the framework of nonequilibrium Green function theory. A CH2 radical is added to different positions on the polymer chain and its effects on the tunnelling magnetoresistance of the MTJ are studied. The ferromagnetic electrodes are assumed to be single-band and their tight-binding parameters are chosen in such a way as to simulate the ab initio density functional calculations of the band structure of bcc-Fe along its [001] crystallographic direction. In building the Hamiltonian of the trans-polyacetylene (t-PA) chain, we have assumed an s orbital on the H atoms and one s and three p(px,py,pz) orbitals on the C atoms, and the dimerization effects are taken into account. It is found that moving the radical out of the centre of the polymer chain enhances the tunnelling magnetoresistance of the MTJ.

  17. Band-gap corrected density functional theory calculations for InAs/GaSb type II superlattices

    Science.gov (United States)

    Wang, Jianwei; Zhang, Yong

    2014-12-01

    We performed pseudopotential based density functional theory (DFT) calculations for GaSb/InAs type II superlattices (T2SLs), with bandgap errors from the local density approximation mitigated by applying an empirical method to correct the bulk bandgaps. Specifically, this work (1) compared the calculated bandgaps with experimental data and non-self-consistent atomistic methods; (2) calculated the T2SL band structures with varying structural parameters; (3) investigated the interfacial effects associated with the no-common-atom heterostructure; and (4) studied the strain effect due to lattice mismatch between the two components. This work demonstrates the feasibility of applying the DFT method to more exotic heterostructures and defect problems related to this material system.

  18. Structural, vibrational, and quasiparticle band structure of 1,1-diamino-2,2-dinitroethelene from ab initio calculations

    Energy Technology Data Exchange (ETDEWEB)

    Appalakondaiah, S.; Vaitheeswaran, G., E-mail: gvaithee@gmail.com [Advanced Centre of Research in High Energy Materials (ACRHEM), University of Hyderabad, Prof. C. R. Rao Road, Gachibowli, Hyderabad 500 046, Andhra Pradesh (India); Lebègue, S. [Laboratoire de Cristallographie, Résonance Magnétique et Modélisations (CRM2, UMR CNRS 7036), Institut Jean Barriol, Université de Lorraine, BP 239, Boulevard des Aiguillettes, 54506 Vandoeuvre-lès-Nancy (France)

    2014-01-07

    The effects of pressure on the structural and vibrational properties of the layered molecular crystal 1,1-diamino-2,2-dinitroethelene (FOX-7) are explored by first principles calculations. We observe significant changes in the calculated structural properties with different corrections for treating van der Waals interactions to Density Functional Theory (DFT), as compared with standard DFT functionals. In particular, the calculated ground state lattice parameters, volume and bulk modulus obtained with Grimme's scheme, are found to agree well with experiments. The calculated vibrational frequencies demonstrate the dependence of the intra and inter-molecular interactions on FOX-7 under pressure. In addition, we also found a significant increment in the N–H...O hydrogen bond strength under compression. This is explained by the change in bond lengths between nitrogen, hydrogen, and oxygen atoms, as well as calculated IR spectra under pressure. Finally, the computed band gap is about 2.3 eV with generalized gradient approximation, and is enhanced to 5.1 eV with the GW approximation, which reveals the importance of performing quasiparticle calculations in high energy density materials.

  19. An improved treatment of overlapping absorption bands based on the correlated k distribution model for thermal infrared radiative transfer calculations

    International Nuclear Information System (INIS)

    This paper discusses several schemes for handling gaseous overlapping bands in the context of the correlated k distribution model (CKD). Commonly used methods are generally based on certain spectral correlation assumptions; thus they are either less accurate or less efficient and rarely apply to all overlapping bands. We propose a new treatment, which we developed from the traditional absorber amount weighted scheme and improved for application to various bands. This approach is quite efficient for treating the gaseous mixture as if it were a 'single gas.' Numerical experiments demonstrate that the new scheme achieves high accuracy with a fast operating speed. To validate the new scheme, we conducted spectrally integrated calculations and sensitivity experiments in the thermal infrared region. Compared to line-by-line integration results, errors in cooling rates were less than 0.2 K/day below 70 Km and rose to 1 K/day from above 70 Km up to 100 Km; flux differences did not exceed 0.8 W/m2 at any altitude. Changes in CO2 and H2O concentrations slightly influenced the accuracy of the results.

  20. The role of high-level calculations in the assignment of the Q-band spectra of chlorophyll

    Energy Technology Data Exchange (ETDEWEB)

    Reimers, Jeffrey R. [School of Physics and Materials Science, The University of Technology, Sydney NSW (Australia); Cai, Zheng-Li [School of Chemistry, Physics and Mechanical Engineering, Queensland University of Technology, Brisbane QLD4001 (Australia); Kobayashi, Rika [Australian National University Supercomputer Facility, Mills Rd, Canberra, ACT 0200 (Australia); Rätsep, Margus [Institute of Physics, University of Tartu, Riia 142, 51014 Tartu (Estonia); Freiberg, Arvi [Institute of Physics, University of Tartu, Riia 142, 51014 Tartu, Estonia and Institute of Molecular and Cell Biology, University of Tartu, Riia 23, 51010 Tartu (Estonia); Krausz, Elmars [Research School of Chemistry, The Australian National University, Canberra 2601 (Australia)

    2014-10-06

    We recently established a novel assignment of the visible absorption spectrum of chlorophyll-a that sees the two components Q{sub x} and Q{sub y} of the low-energy Q band as being intrinsically mixed by non-adiabatic coupling. This ended 50 years debate as to the nature of the Q bands, with prior discussion poised only in the language of the Born-Oppenheimer and Condon approximations. The new assignment presents significant ramifications for exciton transport and quantum coherence effects in photosystems. Results from state of the art electronic structure calculations have always been used to justify assignments, but quantitative inaccuracies and systematic failures have historically limited usefulness. We examine the role of CAM-B3LYP time-dependent density-functional theory (TD-DFT) and Symmetry Adapted Cluster-Configuration Interaction (SAC-CI) calculations in first showing that all previous assignments were untenable, in justifying the new assignment, in making some extraordinary predictions that were vindicated by the new assignment, and in then identifying small but significant anomalies in the extensive experimental data record.

  1. The role of high-level calculations in the assignment of the Q-band spectra of chlorophyll

    International Nuclear Information System (INIS)

    We recently established a novel assignment of the visible absorption spectrum of chlorophyll-a that sees the two components Qx and Qy of the low-energy Q band as being intrinsically mixed by non-adiabatic coupling. This ended 50 years debate as to the nature of the Q bands, with prior discussion poised only in the language of the Born-Oppenheimer and Condon approximations. The new assignment presents significant ramifications for exciton transport and quantum coherence effects in photosystems. Results from state of the art electronic structure calculations have always been used to justify assignments, but quantitative inaccuracies and systematic failures have historically limited usefulness. We examine the role of CAM-B3LYP time-dependent density-functional theory (TD-DFT) and Symmetry Adapted Cluster-Configuration Interaction (SAC-CI) calculations in first showing that all previous assignments were untenable, in justifying the new assignment, in making some extraordinary predictions that were vindicated by the new assignment, and in then identifying small but significant anomalies in the extensive experimental data record

  2. Determination of the Optimal Sampling Depth for Calculating Soil Effective Temperature at L-band: Maqu Case

    Science.gov (United States)

    Lv, Shaoning; Zeng, Yijian; Wen, Jun; Su, Zhongbo

    2015-04-01

    Soil effective temperature Teff is one of the basic parameter in passive microwave remote sensing for soil moisture. Meanwhile, the dedicated current and future satellite soil moisture monitoring missions use L-Band as the operating frequency. However, Teff at L-Band is strongly affected by the soil moisture and temperature profiles. A two-layer scheme and its corresponding multilayer form were developed to accommodate such influence. In this study, the soil moisture/temperature data collected at Maqu Network are used to verify the newly developed schemes. The key findings are:1) the new two-layer scheme is able to assess which site is relatively in higher accuracy for estimating Teff. It is found that on average nearly 20% of the signal cannot be captured by Maqu Network, with the currently-assumed common installation configuration. It is important to know this since the spatial averaged value is used to retrieve soil moisture with the brightness temperature sensed by the satellite sensors; 2) With the developed method, it is able to identify that the observation pair at 5cm and 20cm is the optimal sampling depth for calculating Teff for the core-site in Maqu Network. It is suggested that the newly developed method can provide an objective way in configuring an optimal soil moisture/temperature network and improve the representativeness of the existing networks, in terms of calculating Teff, by identifying the optimal sampling depth.

  3. Constrained nudged elastic band calculation of the Peierls barrier with atomic relaxations

    Science.gov (United States)

    Gröger, R.; Vitek, V.

    2012-04-01

    We demonstrate that the straightforward application of the nudged elastic band (NEB) method does not determine the correct Peierls barrier of 1/2 screw dislocations in bcc metals. Although this method guarantees that the states (images) of the system are distributed uniformly along the minimum energy path, it does not imply that the dislocation positions are distributed uniformly along this path. In fact, clustering of dislocation positions near potential minima occurs which leads to an overestimate of both the slope of the Peierls barrier and the Peierls stress. We propose a modification in which the NEB method is applied only to a small number of degrees of freedom that determine the position of the dislocation, while all other coordinates of atoms are relaxed by molecular statics as in any atomistic study. This modified NEB method with relaxations gives the Peierls barrier that increases smoothly with the dislocation position and the corresponding Peierls stress agrees well with that evaluated by the direct application of stress in the atomistic modeling of the dislocation glide.

  4. Constrained nudged elastic band calculation of the Peierls barrier with atomic relaxations

    International Nuclear Information System (INIS)

    We demonstrate that the straightforward application of the nudged elastic band (NEB) method does not determine the correct Peierls barrier of 1/2?1 1 1? screw dislocations in bcc metals. Although this method guarantees that the states (images) of the system are distributed uniformly along the minimum energy path, it does not imply that the dislocation positions are distributed uniformly along this path. In fact, clustering of dislocation positions near potential minima occurs which leads to an overestimate of both the slope of the Peierls barrier and the Peierls stress. We propose a modification in which the NEB method is applied only to a small number of degrees of freedom that determine the position of the dislocation, while all other coordinates of atoms are relaxed by molecular statics as in any atomistic study. This modified NEB method with relaxations gives the Peierls barrier that increases smoothly with the dislocation position and the corresponding Peierls stress agrees well with that evaluated by the direct application of stress in the atomistic modeling of the dislocation glide. (paper)

  5. Ab initio calculations of quasiparticle band structure in correlated systems LDA++ approach

    CERN Document Server

    Lichtenstein, A I

    1997-01-01

    We discuss a general approach to a realistic theory of the electronic structure in materials containing correlated d- or f- electrons. The main feature of this approach is the taking into account the energy dependence of the electron self-energy with the momentum dependence being neglected (local approximation). In the case of strong interactions (U/W>>1 - rare-earth system) the Hubbard-I approach is the most suitable. Starting from an exact atomic Green function with the constrained density matrix the band structure problem is formulated as the functional problem on Nmm' for f-electrons and the standard LDA-functional for delocalized electrons. In the case of moderate correlations (U/W=1 metal-insulator regime) we start from the dynamical mean field iterative perturbation scheme (IPS) of G. Kotliar et. al. and also make use of our multiband atomic Green function. Finally for the weak interactions (U/W<1 -transition metals) the self-consistent diagrammatic fluctuation- exchange (FLEX)-approach of N. Bicker...

  6. Exchange interaction in the heavy rare-earth metals calculated from energy bands

    International Nuclear Information System (INIS)

    The exchange interaction in the ordered phases was calculated and found to be significantly influenced by the magnetic perturbation of the conduction electron states. The exchange interaction is intrinsically temperature dependent and is anisotropic. The effect explains how it is possible to have a spiral phase of Tb, although spin wave measurements show no maximum in J/sub q/ for q not equal to 0. The energy difference between the ferromagnetic and spiral phases is of correct order of magnitude to be counterbalanced by the magnetoelastic energy. The wave vector dependent matrix element is found to be similar for Gd, Tb, Dy, and Er with a narrow central conduction electron contribution and a flat region. (U.S.)

  7. Calculations of intersection cross-slip activation energies in fcc metals using nudged elastic band method

    International Nuclear Information System (INIS)

    The nudged elastic band (NEB) method is used to evaluate activation energies for dislocation intersection cross-slip in face-centered cubic (fcc) nickel and copper, to extend our prior work which used an approximate method. In this work we also extend the study by including Hirth locks (HL) in addition to Lomer-Cottrell locks and glide locks (GL). Using atomistic (molecular statics) simulations with embedded atom potentials we evaluated the activation barrier for a dislocation to transform from fully residing on the glide plane to fully residing on the cross-slip plane when intersecting a 120o forest dislocation in both Ni and Cu. The initial separation between the screw and the intersecting dislocation on the (1 1 1) glide plane is varied to find a minimum in the activation energy. The NEB method gives energies that are ?10% lower than those reported in our prior work. It is estimated that the activation energies for cross-slip from the fully glide plane state to the partially cross-slipped state at the 120o intersection forming GL in Ni and Cu are ?0.47 and ?0.65 eV, respectively, and from the fully cross-slip plane state to the partially cross-slipped state forming LC are ?0.68 and ?0.67 eV. The activation energies for cross-slip from the fully glide plane state to the partially cross-slipped state at the 120o intersection forming HL in Ni and Cu are estimated to be ?0.09 and ?0.31 eV, respectively. These values are a factor of 3-20 lower than the activation energy for bulk cross-slip in Ni and, a factor of 2-6 lower than the activation energy for cross-slip in Cu estimated by Friedel-Escaig analysis. These results suggest that cross-slip should nucleate preferentially at selected screw dislocation intersections in fcc materials and the activation energies for such mechanisms are also a function of stacking fault energy.

  8. ALattice parameters and band structure of ternary mixed crystals AlxGa1-xAs from first-principle calculations

    Science.gov (United States)

    Mao, Y.; Liang, X. X.; Zhao, G. J.; Song, T. L.

    2014-03-01

    Lattice parameters and band structure of the ternary mixed crystal AlxGa1-xAs of zinc blende structure are calculated by first-principle calculations within the framework of the density functional theory. The results for the equilibrium lattice parameters and band gaps of AlxGa1-xAs for the Al-composition varying from 0.0 to 1.0 by step of 0.125 are presented and discussed. The results show that the lattice constants vary with the composition almost linearly following the Vegard's law. The electron band gap at Gamma; point exhibits non-linear behavior versus the composition. The Al-3s, 3p states shift to high energy region in the conduction band with increasing the Al concentration. It leads to an increase of the band gap and the blue shift phenomenon.

  9. ALattice parameters and band structure of ternary mixed crystals AlxGa1–xAs from first-principle calculations

    International Nuclear Information System (INIS)

    Lattice parameters and band structure of the ternary mixed crystal AlxGa1-xAs of zinc blende structure are calculated by first-principle calculations within the framework of the density functional theory. The results for the equilibrium lattice parameters and band gaps of AlxGa1-xAs for the Al-composition varying from 0.0 to 1.0 by step of 0.125 are presented and discussed. The results show that the lattice constants vary with the composition almost linearly following the Vegard's law. The electron band gap at Gamma; point exhibits non-linear behavior versus the composition. The Al-3s, 3p states shift to high energy region in the conduction band with increasing the Al concentration. It leads to an increase of the band gap and the blue shift phenomenon

  10. Electronic structures and valence band XPS spectra of BeO and SiC calculated by X? cluster method

    International Nuclear Information System (INIS)

    The DV-X? cluster method has been applied for calculations of the electronic structures and for analysis of valence band XPS spectra of BeO, ?-SiC (Wurutzite type) and ?-SiC (Zinc-blende type). Clusters studied are [Be4O4] for BeO, and [Si4C4] and [Si5C4]sup(0.75+) for ?-SiC and ?-SiC, respectively. The calculation for BeO has yielded the electronic level structure characteristic of an insulating material. For ?-SiC and ?-SiC the level structures can be related well with their semiconducting behavior. The calculated XPS spectrum of ?-SiC is very similler to that of ?-SiC and is in good agreement with the observed one. However, the effective charge on Si atom in ?-SiC obtained is about twice that in ?-SiC (?-SiC : +1.56, ?-SiC : +0.75). The marked difference indicates that ?-SiC is a material more ionic than ?-SiC. (author)

  11. Calculation of vibrational (J=0) excitation energies and band intensities of formaldehyde using the recursive residue generation method

    Science.gov (United States)

    Poulin, Nicolas M.; Bramley, Matthew J.; Carrington, Tucker, Jr.; Kjaergaard, Henrik G.; Henry, Bryan R.

    1996-05-01

    We use the recursive residue generation method (RRGM) with an exact kinetic energy operator to calculate vibrational excitation energies and band intensities for formaldehyde. The basis is a product of one-dimensional potential optimized discrete variable representation (PO-DVR) functions for each coordinate. We exploit the symmetry by using symmetry adapted basis functions obtained by taking linear combinations of PO-DVR functions. Our largest basis set consists of 798 600 functions (per symmetry block). The Lanczos tridiagonal representation of the Hamiltonian is generated iteratively (without constructing matrix elements explicitly) by sequential transformations. We determine a six-dimensional dipole moment function from the ab initio dipole moment values computed at the QCISD level with a 6-311++G(d,p) basis set. We converged all A1, B2 and B1 vibrational states up to the combination band with two quanta in the C-O stretch and one quantum in a C-H stretch at about 6 350 cm-1 above zero point energy. We present a simulated (J=0) infrared spectrum of CH2O for transitions from the ground state.

  12. LMTO band structure calculations of ThCr{sub 2}Si{sub 2}-type transition metal compounds

    Energy Technology Data Exchange (ETDEWEB)

    Johrendt, D. [Institut des Materiaux de Nantes (France)]|[Heinrich-Heine-Universitaet, Duesseldorf (Germany); Felser, C. [Institut des Materiaux de Nantes (France)]|[Max Planck Institut fuer Festkoerperforschung, Stuttgart (Germany); Jepsen, O. [Max Planck Institut fuer Festkoerperforschung, Stuttgart (Germany)] [and others

    1997-05-01

    The electronic structures of ThCr{sub 2}Si{sub 2}-type compounds were studied by means of self-consistent LMTO band structure calculations. Different bonding interactions in SrRh{sub 2}P{sub 2} are analyzed and their dependence on the electron count are discussed in terms of the formal substitution of elements. The overall bonding situation can be characterized as an interplay between covalent, metallic, and ionic interactions, although metal-metal bonding plays an important role. Particularly, the evolution of the inter-layer bonding between the nonmetal atoms by changing the transition metal is examined in more detail. It turns out that the shortening of the interlayer bonds by filling the d shell of the transition metal is due to an increasing occupation of nonmetal bonding states which are pushed up to the vicinity of the Fermi level by antibonding metal-nonmetal interactions. The band structures of superconducting LuNi{sub 2}B{sub 2}C and nonsuperconducting SrRh{sub 2}P{sub 2} are compared and their similarities are pointed out. A van Hove singularity, generated by metal-metal interaction, coincides with the Fermi level in LuNi{sub 2}B{sub 2}C and lies about 0.2 eV higher in SrRh{sub 2}P{sub 2}. By doping, it should be possible to induce superconductivity in SrRh{sub 2}P{sub 2} and related compounds.

  13. Band structure engineering of monolayer MoS2 on h-BN: first-principles calculations

    International Nuclear Information System (INIS)

    We have carried out first-principles calculations and theoretical analysis to explore the structural and electronic properties of MoS2/n-h-BN heterostructures consisting of monolayer MoS2 on top of h-BN substrates with one to five layers. We find that the MoS2/n-h-BN heterostructures show indirect bandgap features with both of CBM (in the K point) and VBM (in the ? point) localized on the monolayer MoS2. Difference charge density and surface bands indicate there is no obvious charge exchange in the heterostructure systems. We show that the changes from a direct bandgap in monolayer free-stranding MoS2 to an indirect bandgap in MoS2/n-h-BN heterostructure is induced by the strain. Moreover, we find that the bandgaps of MoS2/n-h-BN heterostructures decrease with increasing number of h-BN layers, which is proposed to result from the different strain distributions in MoS2 due to the varieties of lattice mismatch rates between MoS2 and h-BN layers. Our results suggest that the MoS2/n-h-BN heterostructure could serve as a prototypical example for band structure engineering of 2D crystals with atomic layer precision. (paper)

  14. Angular momentum projected multi-cranked configuration mixing for reliable calculation of high-spin rotational bands

    Science.gov (United States)

    Shimada, Mitsuhiro; Tagami, Shingo; Shimizu, Yoshifumi R.

    2015-06-01

    By employing the angular momentum projection technique, we propose a method to reliably calculate the quantum spectrum of nuclear collective rotation. The method utilizes several cranked mean-field states with different rotational frequencies, which are superposed in the sense of configuration mixing or the generator coordinate method after performing the projection; the idea was originally suggested by Peierls-Thouless in 1962 [Nucl. Phys. 38, 154 (1962)]. It is found that the spectrum as a result of the configuration mixing does not essentially depend on chosen sets of cranking frequencies if the number of mean-field states utilized in the mixing is larger than a certain small value. We apply this method to three examples employing the Gogny D1S effective interaction and show that it is useful to study high-spin rotational bands by means of the angular momentum projection method.

  15. Minimum-energy configurations of metallic clusters obtained by simulated annealing molecular dynamics using an Extended-Hueckel Hamiltonian

    Energy Technology Data Exchange (ETDEWEB)

    Rincon, Luis [Universidad de Los Andes, Merida (Venezuela)

    2001-03-01

    Semiempirical simulated annealing molecular dynamics method using a fictitious Lagrangian has been developed for the study of structural and electronic properties of micro- and nano-clusters. As an application of the present scheme, we study the structure of Na{sub n} clusters in the range of n=2-100, and compared the present calculation with some ab-initio model calculation. [Spanish] Se desarrollo un metodo de Dinamica Molecular-Recocido simulado usando un Lagrangiano ficticio para estudiar las propiedades electronicas y estructurales de micro- y nano-agregados. Como una aplicacion del presente esquema, se estudio la estructura de agregados de Na{sub n} en el rango entre n=2-100, y se compararon los resultados con algunos calculos ab-initio modelo.

  16. Electronic band structure and specific features of Sm{sub 2}NiMnO{sub 6} compound: DFT calculation

    Energy Technology Data Exchange (ETDEWEB)

    Reshak, A.H. [Institute of complex systems, FFPW, CENAKVA, University of South Bohemia in CB, Nove Hrady 37333 (Czech Republic); Center of Excellence Geopolymer and Green Technology, School of Material Engineering, University Malaysia Perlis, 01007 Kangar, Perlis (Malaysia); Azam, Sikander, E-mail: sikander.physicst@gmail.com [Institute of complex systems, FFPW, CENAKVA, University of South Bohemia in CB, Nove Hrady 37333 (Czech Republic)

    2013-09-15

    The band structure, density of states, electronic charge density, Fermi surface and optical properties of Sm{sub 2}NiMnO{sub 6} compound have been investigated with the support of density functional theory (DFT). The atomic positions of Sm{sub 2}NiMnO{sub 6} compound were optimized by minimizing the forces acting on the atoms, using the full potential linear augmented plane wave method. We employed the local density approximation (LDA), generalized gradient approximation (GGA) and Engel–Vosko GGA (EVGGA) to treat the exchange correlation potential by solving Kohn–Sham equations. The calculation shows that the compound is metallic with strong hybridization near the Fermi energy level (E{sub F}). The calculated density of states at the E{sub F} is about 21.60, 24.52 and 26.21 states/eV, and the bare linear low-temperature electronic specific heat coefficient (?) is found to be 3.74, 4.25 and 4.54 mJ/mol K{sup 2} for EVGGA, GGA and LDA, respectively. The Fermi surface is composed of two sheets. The bonding features of the compounds are analyzed using the electronic charge density in the (011) crystallographic plane. The dispersion of the optical constants was calculated and discussed. - Highlights: • The compound is metallic with strong hybridization near the Fermi energy. • The density of states at the Fermi energy is calculated. • The bare linear low-temperature electronic specific heat coefficient is obtained. • Fermi surface is composed of two sheets. • The bonding features are analyzed using the electronic charge density.

  17. Pseudopotential Calculations of Band Gaps and Band Edges of Short-Period (InAs)n/(GaSb)m Superlattices with Different Substrates, Layer Orientations and Interfacial Bonds

    Energy Technology Data Exchange (ETDEWEB)

    Piquini, P.; Zunger, A.; Magri, R.

    2008-01-01

    The band edges and band gaps of (InAs){sub n}/(GaSb){sub m} (n,m=1,20) superlattices have been theoretically studied through the plane-wave empirical pseudopotential method for different situations: (i) different substrates, GaSb and InAs; (ii) different point group symmetries, C{sub 2v} and D{sub 2d}; and (iii) different growth directions, (001) and (110). We find that (a) the band gaps for the (001) C{sub 2v} superlattices on a GaSb substrate exhibit a nonmonotonic behavior as a function of the GaSb barrier thickness when the number of (InAs){sub n} layers exceed n=5; (b) substrate effects: compared with the GaSb substrate, the different strain field generated by the InAs substrate leads to a larger variation of the band gaps for the (001) C{sub 2v} superlattices as a function of the InAs well thickness; (c) effect of the type of interfacial bonds: the In-Sb bonds at the interfaces of the (001) D{sub 2d} superlattices partially pin the band edge states, reducing the influence of the confinement effects on electrons and holes, and lowering the band gaps as compared to the (001) C{sub 2v} case. The valence band maximum of the (001) D{sub 2d} superlattices with Ga-As bonds at the interfaces are shifted down, increasing the band gaps as compared to the (001) C{sub 2v} case; (d) effect of layer orientation: the presence of In-Sb bonds at both interfaces of the (110) superlattices pin the band edge states and reduces the band gaps, as compared to the (001) C{sub 2v} case. An anticrossing between the electron and hole levels in the (110) superlattices, for thin GaSb and thick InAs layers, leads to an increase of the band gaps, as a function of the InAs thickness; (e) superlattices vs random alloys: the comparison between the band edges and band gaps of the superlattices on a GaSb substrate and those for random alloys, lattice matched to a GaSb substrate, as a function of the In composition, shows that the random alloys present almost always higher band gaps and give a clear indication of the effect of superlattice's ordering and period on the behavior of the band gaps and band edges. Inclusion of interfacial interdiffusion, using the approach of Magri and Zunger [Phys. Rev. B 65, 165302 (2002)], is shown to significantly increase the band gaps relative to the predictions for abrupt superlattices, bringing the results closer to experiment. It is noteworthy that k {center_dot} p model fit instead measured gaps corresponding to interdiffused interfaces using a chemically abrupt model.

  18. Calculation of tunable type-II band alignments in InAsxSbyP1?x?y/InAs heterojunctions

    Science.gov (United States)

    Shim, Kyurhee

    2016-01-01

    The energy band gaps of the alloy InAsxSbyP1?x?y are calculated using the correlated function expansion (CFE) technique over the entire composition space x and y, for which the CFE band gap composition contour for the mid-infrared (MIR) spectral region of 2 (0.62)–5 µm (0.25 eV) is presented. The composition dependence of the valence-band maximum (VBM) is obtained using the universal tight binding (UTB) method, and the corresponding conduction-band minimum (CBM) can be computed from the difference between the band gap and the VBM. By organizing the relative positions of the VBM and CBM between the quaternary alloy InAsSbP and the binary compound InAs, the band alignments and band types of InAsSbP/InAs heterojunctions (HJs) along the lattice-matching conditions x and y [i.e., y = 0.311(1 ? x)] are determined. It is found that the VBMs of the alloy InAsxSbyP1?x?y are located within the band gap of InAs, whereas the CBMs of the alloy lie outside the band gap of InAs over the entire composition range. This implies that the InAsxSbyP1?x?y/InAs HJs exhibit composition-tunable, type-II (staggered) band alignments. In addition, the conduction-band offset (CBO) and valence-band offset (VBO) of InAsSbP/InAs HJs both present the upward bowing trend, with the CBO curves appearing sharp and the VBO curves appearing smooth.

  19. First-principles band-structure calculations and X-ray photoelectron spectroscopy studies of the electronic structure of TlPb{sub 2}Cl{sub 5}

    Energy Technology Data Exchange (ETDEWEB)

    Khyzhun, O.Y., E-mail: khyzhun@ipms.kiev.ua [Institute for Problems of Materials Science, National Academy of Sciences of Ukraine, 3 Krzhyzhanivsky Street, Kyiv 03142 (Ukraine); Bekenev, V.L.; Denysyuk, N.M. [Institute for Problems of Materials Science, National Academy of Sciences of Ukraine, 3 Krzhyzhanivsky Street, Kyiv 03142 (Ukraine); Parasyuk, O.V. [Department of Inorganic and Physical Chemistry, Eastern European National University, 13 Voli Avenue, Lutsk 43025 (Ukraine); Fedorchuk, A.O. [Department of Inorganic and Organic Chemistry, Lviv National University of Veterinary Medicine and Biotechnologies, Pekarska St., 50, 79010 Lviv (Ukraine)

    2014-01-05

    Highlights: • Electronic structure of TlPb{sub 2}Cl{sub 5} is calculated by the FP-LAPW method. • The valence band is dominated by contributions of Cl 3p states. • Contributions of Pb 6p{sup *} states dominate at the bottom of the conduction band. • The FP-LAPW data allow concluding that TlPb{sub 2}Cl{sub 5} is an indirect-gap material. • XPS core-level and valence-band spectra of polycrystalline TlPb{sub 2}Cl{sub 5} are measured. -- Abstract: We report on first-principles calculations of total and partial densities of states of atoms constituting TlPb{sub 2}Cl{sub 5} using the full potential linearized augmented plane wave (FP-LAPW) method. The calculations reveal that the valence band of TlPb{sub 2}Cl{sub 5} is dominated by contributions of the Cl 3p-like states, which contribute mainly at the top of the valence band with also significant contributions throughout the whole valence-band region. In addition, the bottom of the conduction band of TlPb{sub 2}Cl{sub 5} is composed mainly of contributions of the unoccupied Pb 6p-like states. Our FP-LAPW data indicate that the TlPb{sub 2}Cl{sub 5} compound is an indirect-gap material with band gap of 3.42 eV. The X-ray photoelectron core-level and valence-band spectra for pristine and Ar{sup +} ion-irradiated surfaces of a TlPb{sub 2}Cl{sub 5} polycrystalline sample were measured. The measurements reveal high chemical stability and confirm experimentally the low hygroscopicity of TlPb{sub 2}Cl{sub 5} surface.

  20. Calculation of the band structure of GdCo2, GdRh2 e GdIr2 by the APW method

    International Nuclear Information System (INIS)

    The band structure of GdCo2, GdRh2, GdIr2 has been calculated by the APW method. A histogram of the density of states is presented for each compound. The bands are transition-metal-like, with s-d hybridization near the Fermi level. The 5d character near the Fermi level increases as one goes from Co to Ir

  1. A new integral representation for quasiperiodic fields and its application to two-dimensional band structure calculations

    CERN Document Server

    Barnett, Alex H

    2010-01-01

    In this paper, we consider band-structure calculations governed by the Helmholtz or Maxwell equations in piecewise homogeneous periodic materials. Methods based on boundary integral equations are natural in this context, since they discretize the interface alone and can achieve high order accuracy in complicated geometries. In order to handle the quasi-periodic conditions which are imposed on the unit cell, the free-space Green's function is typically replaced by its quasi-periodic cousin. Unfortunately, the quasi-periodic Green's function diverges for families of parameter values that correspond to resonances of the empty unit cell. Here, we bypass this problem by means of a new integral representation that relies on the free-space Green's function alone, adding auxiliary layer potentials on the boundary of the unit cell itself. An important aspect of our method is that by carefully including a few neighboring images, the densities may be kept smooth and convergence rapid. This framework results in an integr...

  2. Electronic properties of ZnWO{sub 4} based on ab initio FP-LAPW band-structure calculations and X-ray spectroscopy data

    Energy Technology Data Exchange (ETDEWEB)

    Khyzhun, O.Y., E-mail: khyzhun@ipms.kiev.ua [Frantsevych Institute for Problems of Materials Science, National Academy of Sciences of Ukraine, 3 Krzhyzhanivsky Street, Kyiv UA-03142 (Ukraine); Bekenev, V.L. [Frantsevych Institute for Problems of Materials Science, National Academy of Sciences of Ukraine, 3 Krzhyzhanivsky Street, Kyiv UA-03142 (Ukraine); Atuchin, V.V. [Laboratory of Optical Materials and Structures, Institute of Semiconductor Physics, SB RAS, Novosibirsk 630090 (Russian Federation); Galashov, E.N.; Shlegel, V.N. [Nikolaev Institute of Inorganic Chemistry, SB RAS, Novosibirsk 630090 (Russian Federation)

    2013-07-15

    Total and partial densities of states of the atoms constituting zinc tungstate, ZnWO{sub 4}, have been calculated using the ab initio full potential linearized augmented plane wave (FP-LAPW) method. The theoretical data reveal that main contributors in the valence band of ZnWO{sub 4} are the Zn 3d-, W 5d- and O 2p-like states: the Zn 3d- and W 5d-like states contribute mainly at the bottom, whilst the O 2p-like states at the top of the valence band, with also significant portions of contributions of the above states throughout the whole valence-band region of the tungstate under study. In addition, data of our band-structure FP-LAPW calculations indicate that the conduction band of ZnWO{sub 4} is dominated by contributions of the W 5d-like states. To verify the theoretical findings, high-quality inclusion-free ZnWO{sub 4} single crystals were specially grown along the [010] direction for the present experimental studies employing the low thermal gradient Czochralski technique. It has been established that, comparison on a common energy scale of the X-ray photoelectron valence-band spectrum and the X-ray emission bands representing the energy distribution of mainly the Zn 3d-, W 5d- and O 2p-like states of ZnWO{sub 4} confirm experimentally the present FP-LAPW theoretical data regarding the occupations of the valence band of zinc tungstate. - Graphical abstract: Display Omitted - Highlights: • Total and partial densities of states of the atoms constituting ZnWO{sub 4} are calculated. • Zn 3d and W 5d states are dominant contributors at the bottom of the valence band. • Contributions of O 2p states dominate at the top of the valence band. • Bottom of the conduction band is dominated by contributions of W 5d* states. • The theoretical results are confirmed experimentally by X-ray spectroscopy data.

  3. Spectroscopic and electrical calculation of band alignment between atomic layer deposited SiO2 and ?-Ga2O3 ( 2 ¯ 01 )

    Science.gov (United States)

    Jia, Ye; Zeng, Ke; Wallace, Joshua S.; Gardella, Joseph A.; Singisetti, Uttam

    2015-03-01

    The energy band alignment between atomic layer deposited (ALD) SiO2 and ?-Ga2O3 ( 2 ¯ 01 ) is calculated using x-ray photoelectron spectroscopy and electrical measurement of metal-oxide semiconductor capacitor structures. The valence band offset between SiO2 and Ga2O3 is found to be 0.43 eV. The bandgap of ALD SiO2 was determined to be 8.6 eV, which gives a large conduction band offset of 3.63 eV between SiO2 and Ga2O3. The large conduction band offset makes SiO2 an attractive gate dielectric for power devices.

  4. Spectroscopic and electrical calculation of band alignment between atomic layer deposited SiO{sub 2} and ?-Ga{sub 2}O{sub 3} (2{sup ¯}01)

    Energy Technology Data Exchange (ETDEWEB)

    Jia, Ye; Zeng, Ke; Singisetti, Uttam, E-mail: uttamsin@buffalo.edu [Electrical Engineering Department, University at Buffalo, Buffalo, New York 14260 (United States); Wallace, Joshua S.; Gardella, Joseph A [Chemistry Department, University at Buffalo, Buffalo, New York 14260 (United States)

    2015-03-09

    The energy band alignment between atomic layer deposited (ALD) SiO{sub 2} and ?-Ga{sub 2}O{sub 3} (2{sup ¯}01) is calculated using x-ray photoelectron spectroscopy and electrical measurement of metal-oxide semiconductor capacitor structures. The valence band offset between SiO{sub 2} and Ga{sub 2}O{sub 3} is found to be 0.43?eV. The bandgap of ALD SiO{sub 2} was determined to be 8.6?eV, which gives a large conduction band offset of 3.63?eV between SiO{sub 2} and Ga{sub 2}O{sub 3}. The large conduction band offset makes SiO{sub 2} an attractive gate dielectric for power devices.

  5. Band-structure calculations of noble-gas and alkali halide solids using accurate Kohn-Sham potentials with self-interaction correction

    International Nuclear Information System (INIS)

    The optimized-effective-potential (OEP) method and a method developed recently by Krieger, Li, and Iafrate (KLI) are applied to the band-structure calculations of noble-gas and alkali halide solids employing the self-interaction-corrected (SIC) local-spin-density (LSD) approximation for the exchange-correlation energy functional. The resulting band gaps from both calculations are found to be in fair agreement with the experimental values. The discrepancies are typically within a few percent with results that are nearly the same as those of previously published orbital-dependent multipotential SIC calculations, whereas the LSD results underestimate the band gaps by as much as 40%. As in the LSD---and it is believed to be the case even for the exact Kohn-Sham potential---both the OEP and KLI predict valence-band widths which are narrower than those of experiment. In all cases, the KLI method yields essentially the same results as the OEP

  6. First-principles calculation of the band gap of AlxGa1¡-xN and InxGa1¡-xN

    Directory of Open Access Journals (Sweden)

    Roberto Núñez-González

    2008-01-01

    Full Text Available Ab-initio calculations of the band gap variation of AlxGa1¡xN and InxGa1¡xN ternary compounds were carried out using the Full-Potential Linearized Augmented Plane Waves (FLAPW method, within the Density Functional Theory (DFT. These nitrides were modeled in their wurtzite structure using the supercell method, for concentrations x = 0, 0.25, 0.50, 0.75 and 1.0. To optimize the cell parameters of the binary compounds we used the PBE96 (Perdew et al., Phys. Rev. Lett. 77 (1996 3865 exchange correlation functional. For the band structure calculations, we used both PBE96 and EV93 (Engel et al., Phys. Rev. B 47 (1993 13164 exchange correlation functionals. We considered experimental and calculated (with PBE96 lattice parameters to work out the electronic properties. We found that the fundamental gap is direct in all compounds. The calculation with EV93 functional gives a better band gap estimation for binary nitrides. The bowing parameter was also estimated obtaining the values b = 0.74 eV for AlxGa1¡xN and b = 2.12 eV for InxGa1¡xN.

  7. Hopping and band mobilities of pentacene, rubrene, and 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT) from first principle calculations

    Science.gov (United States)

    Kobayashi, Hajime; Kobayashi, Norihito; Hosoi, Shizuka; Koshitani, Naoki; Murakami, Daisuke; Shirasawa, Raku; Kudo, Yoshihiro; Hobara, Daisuke; Tokita, Yuichi; Itabashi, Masao

    2013-07-01

    Hopping and band mobilities of holes in organic semiconductors at room temperature were estimated from first principle calculations. Relaxation times of charge carriers were evaluated using the acoustic deformation potential model. It is found that van der Waals interactions play an important role in determining accurate relaxation times. The hopping mobilities of pentacene, rubrene, and 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT) in bulk single crystalline structures were found to be smaller than 4 cm2/Vs, whereas the band mobilities were estimated between 36 and 58 cm2/Vs, which are close to the maximum reported experimental values. This strongly suggests that band conductivity is dominant in these materials even at room temperature.

  8. Quasiparticle self-consistent GW calculations for PbS, PbSe, and PbTe: Band structure and pressure coefficients

    DEFF Research Database (Denmark)

    Svane, Axel; Christensen, Niels Egede

    2010-01-01

    The electronic band structures of PbS, PbSe, and PbTe in the rocksalt structure are calculated with the quasiparticle self-consistent GW (QSGW) approach with spin-orbit coupling included. The semiconducting gaps and their deformation potentials as well as the effective masses are obtained. The GW approximation provides a correct description of the electronic structure around the gap, in contrast to the local-density approximation, which leads to inverted gaps in the lead chalcogenides. The QSGW calculations are in good quantitative agreement with experimental values of the gaps and masses. At moderate hole doping a complex filamental Fermi-surface structure develops with ensuing large density of states. The pressure-induced gap closure leads to linear (Dirac-type) band dispersions around the L point.

  9. Electronic band structure calculations on thin films of the L21 full Heusler alloys X2YSi (X, Y = Mn, Fe, and Co): Toward spintronic materials

    International Nuclear Information System (INIS)

    To design half-metallic materials in thin film form for spintronic devices, the electronic structures of full Heusler alloys (Mn2FeSi, Fe2MnSi, Fe2FeSi, Fe2CoSi, and Co2FeSi) with an L21 structure have been investigated using density functional theory calculations with Gaussian-type functions in a periodic boundary condition. Considering the metal composition, layer thickness, and orbital symmetries, a 5-layered Co2FeSi thin film, whose surface consists of a Si layer, was found to have stable half-metallic nature with a band gap of ca. 0.6 eV in the minority spin state. Using the group theory, the difference between electronic structures in bulk and thin film conditions was discussed. - Highlights: ? Electronic band structure calculations of L21 full Heusler alloy thin films. ? Spintronic materials. ? Electronic properties dependency on layer thickness.

  10. Dielectric-dependent screened Hartree-Fock exchange potential and Slater-formula with Coulomb-hole interaction for energy band structure calculations

    Science.gov (United States)

    Shimazaki, Tomomi; Nakajima, Takahito

    2014-09-01

    We previously reported a screened Hartree-Fock (HF) exchange potential for energy band structure calculations [T. Shimazaki and Y. Asai, J. Chem. Phys. 130, 164702 (2009); T. Shimazaki and Y. Asai, J. Chem. Phys. 132, 224105 (2010)]. In this paper, we discuss the Coulomb-hole (COH) interaction and screened Slater-formula and determine the energy band diagrams of several semiconductors, such as diamond, silicon, AlAs, AlP, GaAs, GaP, and InP, based on the screened HF exchange potential and Slater-formula with COH interaction, to demonstrate the adequacy of those theoretical concepts. The screened HF exchange potential and Slater-formula are derived from a simplified dielectric function and, therefore, include the dielectric constant in their expressions. We also present a self-consistent calculation technique to automatically determine the dielectric constant, which is incorporated into each self-consistent field step.

  11. Real-space finite-difference calculation method of generalized Bloch wave functions and complex band structures with reduced computational cost

    Science.gov (United States)

    Tsukamoto, Shigeru; Hirose, Kikuji; Blügel, Stefan

    2014-07-01

    Generalized Bloch wave functions of bulk structures, which are composed of not only propagating waves but also decaying and growing evanescent waves, are known to be essential for defining the open boundary conditions in the calculations of the electronic surface states and scattering wave functions of surface and junction structures. Electronic complex band structures being derived from the generalized Bloch wave functions are also essential for studying bound states of the surface and junction structures, which do not appear in conventional band structures. We present a novel calculation method to obtain the generalized Bloch wave functions of periodic bulk structures by solving a generalized eigenvalue problem, whose dimension is drastically reduced in comparison with the conventional generalized eigenvalue problem derived by Fujimoto and Hirose [Phys. Rev. B 67, 195315 (2003)], 10.1103/PhysRevB.67.195315. The generalized eigenvalue problem derived in this work is even mathematically equivalent to the conventional one, and, thus, we reduce computational cost for solving the eigenvalue problem considerably without any approximation and losing the strictness of the formulations. To exhibit the performance of the present method, we demonstrate practical calculations of electronic complex band structures and electron transport properties of Al and Cu nanoscale systems. Moreover, employing atom-structured electrodes and jellium-approximated ones for both of the Al and Si monatomic chains, we investigate how much the electron transport properties are unphysically affected by the jellium parts.

  12. On the importance of constrained atomic relaxations in the Nudged Elastic Band calculations of the Peierls barriers of dislocations

    OpenAIRE

    Gröger, R.; Vitek, V.

    2011-01-01

    We demonstrate that the straightforward application of the Nudged Elastic Band (NEB) method does not determine the correct Peierls barrier of 1/2 screw dislocations in BCC metals. Although this method guarantees that the states (images) of the system are distributed uniformly along the minimum energy path, it does not imply that the dislocation positions are distributed uniformly along this path. In fact, clustering of dislocation positions near potential minima occurs which...

  13. Rain Rate-Radar Reflectivity Relationship for Drop Size Distribution and Rain Attenuation Calculation of Ku Band Signals

    OpenAIRE

    Govardhani.Immadi; Sarat K Kotamraju; Habibulla Khan; M. Venkata Narayana

    2014-01-01

    With the increased demand for long distance Tele communication day by day, satellite communication system was developed. Satellite communications utilize L, C, Ku and Ka bands of frequency to fulfil all the requirements. Utilization of higher frequencies causes severe attenuation due to rain. Rain attenuation is noticeable for frequencies above 10ghz. Amount of attenuation depends on whether the operating wave length is comparable with rain drop diameter or not. In this paper the main focus i...

  14. Photolysis rate coefficients in the upper atmosphere: Effect of line by line calculations of the O2 absorption cross section in the Schumann-Runge bands

    International Nuclear Information System (INIS)

    A line by line (LBL) method to calculate highly resolved O2 absorption cross sections in the Schumann-Runge (SR) bands region was developed and integrated in the widely used Tropospheric Ultraviolet Visible (TUV) model to calculate accurate photolysis rate coefficients (J values) in the upper atmosphere at both small and large solar zenith angles (SZA). In order to obtain the O2 cross section between 49,000 and 57,000cm-1, an algorithm which considers the position, strength, and half width of each spectral line was used. Every transition was calculated by using the HIgh-resolution TRANsmission molecular absorption database (HITRAN) and a Voigt profile. The temperature dependence of both the strength and the half widths was considered within the range of temperatures characteristic of the US standard atmosphere, although the results show a very good agreement also at 79K. The cross section calculation was carried out on a 0.5cm-1 grid and the contributions from all the lines lying at +/-500cm-1 were considered for every wavelength. Both the SR and the Herzberg continuums were included. By coupling the LBL method to the TUV model, full radiative transfer calculations that compute J values including Rayleigh scattering at high altitudes and large SZA can now be done. Thus, the J values calculations were performed for altitudes from 0 to 120km and for SZA up to 89o. The results show, in the JO2 case, differences of more than +/-10% (e.g. at 96km and 30o) when compared against the last version of the TUV model (4.4), which uses the Koppers and Murtagh parameterization for the O2 cross section. Consequently, the J values of species with cross sections overlapping the SR band region show variable differences at lower altitudes. Although many species have been analyzed, the results for only four of them (O2, N2O, HNO3, CFC12) are presented. Due to the fact that the HNO3 absorption cross section extends up to 350nm this molecule was used to verify the consistency of the new TUV-LBL at lower altitudes. Thus, it shows differences up to 5.7% at 21km but 0% in the troposphere. Because of the more accurate consideration of the Rayleigh scattering the distribution of the actinic flux in its direct and diffuse components (in the SR bands wavelength interval) is also modified

  15. On the importance of constrained atomic relaxations in the Nudged Elastic Band calculations of the Peierls barriers of dislocations

    CERN Document Server

    Gröger, R

    2011-01-01

    We demonstrate that the straightforward application of the Nudged Elastic Band (NEB) method does not determine the correct Peierls barrier of 1/2 screw dislocations in BCC metals. Although this method guarantees that the states (images) of the system are distributed uniformly along the minimum energy path, it does not imply that the dislocation positions are distributed uniformly along this path. In fact, clustering of dislocation positions near potential minima occurs which leads to an overestimate of both the slope of the Peierls barrier and the Peierls stress. We propose a modification in which the NEB method is applied only to a small number of degrees of freedom that determine the position of the dislocation, while all other coordinates of atoms are relaxed by molecular statics as in any atomistic study. This modified NEB method with relaxations gives the Peierls barrier that increases smoothly with the dislocation position and the corresponding Peierls stress agrees well with that evaluated by the direc...

  16. Rain Rate-Radar Reflectivity Relationship for Drop Size Distribution and Rain Attenuation Calculation of Ku Band Signals

    Directory of Open Access Journals (Sweden)

    Govardhani.Immadi

    2014-05-01

    Full Text Available With the increased demand for long distance Tele communication day by day, satellite communication system was developed. Satellite communications utilize L, C, Ku and Ka bands of frequency to fulfil all the requirements. Utilization of higher frequencies causes severe attenuation due to rain. Rain attenuation is noticeable for frequencies above 10ghz. Amount of attenuation depends on whether the operating wave length is comparable with rain drop diameter or not. In this paper the main focus is on drop size distribution using empirical methods, especially Marshall and Palmer distributions. Empirical methods deal with power law relation between the rain rate(mm/h and radar reflectivity(dBz. Finally it is discussed about the rain rate variation, radar reflectivity, drop size distribution, that is made for two rain events at K L University, Vijayawada on 4th September 2013 and on 18 th August 2013.

  17. Electronic band structure calculations for GaxIn1?xASyP1?y alloys lattice matched to InP

    International Nuclear Information System (INIS)

    A pseudopotential formalism coupled with the virtual crystal approximation are applied to study the effect of compositional disorder upon electronic band structure of cubic GaxIn1?xAsyP1?y quarternary alloys lattice matched to InP. The effects of compositional variations are properly included in the calculations. Very good agreement is obtained between the calculated values and the available experimental data for the lattice–matched alloy to InP. The absorption at the fundamental optical gaps is found to be direct within a whole range of the y composition whatever the lattice-matching to the substrate of interest. The alloy system GaxIn1?xAsyP1?y lattice matched to InP is suggested to be suitable for an efficient light emitting device (ELED) material.

  18. Penetration of solar irradiance in the Schumann-Runge bands of O2 - A comparison of balloon-borne measurements and calculations

    Science.gov (United States)

    Frederick, J. E.; Hudson, R. D.; Mentall, J. E.

    1981-01-01

    Measurements of the attenuated solar irradiance made from the STRATCOM VIII balloon are compared with calculated values of the solar irradiance reaching the 40 km level for a solar zenith angle of 66.18 deg. The ability of theory to match intensity maxima which correspond to the cross section minima between the bands is investigated. The comparisons show that model results are too small by a factor of 1.8 between 199 and 22 nm, which is attributed to a systematic calibration offset between the balloon data and the irradiances of Bruckner et al. (1976). A large disagreement between the observed and calculated intensities at peaks H and I results from an error in the cross sections used in current aeronomic work.

  19. Band alignment and directional stability in abrupt and polar-compensated Si/ZnS interface calculations

    OpenAIRE

    Foster, David H.; Schneider, Guenter

    2014-01-01

    We perform a first principles investigation of Si/ZnS interface properties for the [111], [100], and [110] directions, including single-substitution polar-compensated interfaces. The asymmetry of general interface directions poses known challenges for standard methods of calculation: a multiplicity of interface distinctions, artificial electric fields, and indeterminacy of orientation stability. By placing each distinct interface in a variety of supercell environments, we de...

  20. Electronic band calculation of BaPd{sub 2}Sb{sub 2}: Which polymorph is stable?

    Energy Technology Data Exchange (ETDEWEB)

    Hase, I., E-mail: i.hase@aist.go.jp; Yanagisawa, T.

    2013-11-15

    Highlights: •Crystal structure of BaPd{sub 2}Sb{sub 2} is CaBe{sub 2}Ge{sub 2}-type. •Fermi surfaces are quasi-2D similar to iron pnictides. •In ThCr{sub 2}Si{sub 2}-type structure, Fermi surfaces are 3D. •Magnetic interaction via Pd is to be small. •Superconductivity in BaPd{sub 2}Sb{sub 2} is expected. -- Abstract: Iron-pnictide superconductor (Ba,K)Fe{sub 2}As{sub 2} and nickelate superconductor BaNi{sub 2}As{sub 2} both have the ThCr{sub 2}Si{sub 2}-type crystal structure. On the other hand, platinum superconductor SrPt{sub 2}As{sub 2} has the CaBe{sub 2}Ge{sub 2}-type crystal structure. We focused on BaPd{sub 2}Sb{sub 2}, which contains Pd located between Ni and Pt on the periodic table. We have calculated the electronic structure of BaPd{sub 2}Sb{sub 2} from first-principles, and found that the CaBe{sub 2}Ge{sub 2}-type structure is more stable. The Fermi surfaces of BaPd{sub 2}Sb{sub 2} are two-dimensional for the CaBe{sub 2}Ge{sub 2}-type structure, and are three-dimensional for the ThCr{sub 2}Si{sub 2}-type structure. The calculated D(E{sub F}) is 32.1 States/Ry, which is comparable with that in SrPt{sub 2}As{sub 2}. These results strongly suggest that superconductivity also occurs in BaPd{sub 2}Sb{sub 2}.

  1. Calibrating transition-metal energy levels and oxygen bands in first-principles calculations: Accurate prediction of redox potentials and charge transfer in lithium transition-metal oxides

    Science.gov (United States)

    Seo, Dong-Hwa; Urban, Alexander; Ceder, Gerbrand

    2015-09-01

    Transition-metal (TM) oxides play an increasingly important role in technology today, including applications such as catalysis, solar energy harvesting, and energy storage. In many of these applications, the details of their electronic structure near the Fermi level are critically important for their properties. We propose a first-principles-based computational methodology for the accurate prediction of oxygen charge transfer in TM oxides and lithium TM (Li-TM) oxides. To obtain accurate electronic structures, the Heyd-Scuseria-Ernzerhof (HSE06) hybrid functional is adopted, and the amount of exact Hartree-Fock exchange (mixing parameter) is adjusted to reproduce reference band gaps. We show that the HSE06 functional with optimal mixing parameter yields not only improved electronic densities of states, but also better energetics (Li-intercalation voltages) for LiCo O2 and LiNi O2 as compared to the generalized gradient approximation (GGA), Hubbard U corrected GGA (GGA +U ), and standard HSE06. We find that the optimal mixing parameters for TM oxides are system specific and correlate with the covalency (ionicity) of the TM species. The strong covalent (ionic) nature of TM-O bonding leads to lower (higher) optimal mixing parameters. We find that optimized HSE06 functionals predict stronger hybridization of the Co 3 d and O 2 p orbitals as compared to GGA, resulting in a greater contribution from oxygen states to charge compensation upon delithiation in LiCo O2 . We also find that the band gaps of Li-TM oxides increase linearly with the mixing parameter, enabling the straightforward determination of optimal mixing parameters based on GGA (? =0.0 ) and HSE06 (? =0.25 ) calculations. Our results also show that G0W0@GGA +U band gaps of TM oxides (M O ,M =Mn ,Co ,Ni ) and LiCo O2 agree well with experimental references, suggesting that G0W0 calculations can be used as a reference for the calibration of the mixing parameter in cases when no experimental band gap has been reported.

  2. Valence bands of the Cu-III-VI2 chalcopyrites studied by photoemission spectra, X-ray emission spectra, and electronic structure calculations

    International Nuclear Information System (INIS)

    Ultraviolet and X-ray excited photoemission spectra and Cu K?5 X-ray emission spectra are used to measure the valence band density of states in CuGaTe2 and CuInTe2. In both compounds the density of states exhibits five structures which are ascribed to Cu 3d-Te 5p hybridized states, Ga 4s/In 5s-Te 5p bonding states, and Te 5s states. The valence band density of states of all Ga- and In-containing Cu-III-VI2 is calculated in an atomic orbital basis with the noble metal d states explicitly included. The agreement between theory and experiment is good for CuGaTe2 and except the In 5s-VI p bonding states also for the Cu-In-VI2 chalcopyrites. Larger discrepancies between theory and experiment are found for CuGaS2 and CuGaSe2. (author)

  3. RPC Calculations for K-forbidden Transitions in 183W, Evidence for Large Inertial Parameter Connected with High-lying Rotational Bands

    International Nuclear Information System (INIS)

    Recent measurements have shown that the transitions deexciting the 453 keV 7/2- level in 183W to the K = 1/2- and 3/2- bands are strongly retarded. The data for B(M1) and B(E2) are analyzed in terms of the RPC model (rotation + particle motion + coupling). With the ?K = 1 (Coriolis) coupling, the K-forbidden M1-transitions proceed via admixtures of high-lying 5/2- bands. A reasonable and unambiguous fit to the data is obtained by varying the strength of the coupling. Allowing for various uncertainties and corrections, one finds that the inertial parameter (the inverse of the coupling constant, i. e. 2J(2?)2/(?)2 may have values between roughly 1 and 3 times the rigid rotator value of 2J(2?)2/(?)2, thus being unexpectedly large. Calculations with the ?K=2 coupling were also performed and turn out not to give better agreement with experiment

  4. Study of morphology effects on magnetic interactions and band gap variations for 3d late transition metal bi-doped ZnO nanostructures by hybrid DFT calculations

    Science.gov (United States)

    Datta, Soumendu; Kaphle, Gopi Chandra; Baral, Sayan; Mookerjee, Abhijit

    2015-08-01

    Using density functional theory (DFT) based electronic structure calculations, the effects of morphology of semiconducting nanostructures on the magnetic interaction between two magnetic dopant atoms as well as a possibility of tuning band gaps have been studied in the case of the bi-doped (ZnO)24 nanostructures with the impurity dopant atoms of the 3d late transition metals—Mn, Fe, Co, Ni, and Cu. To explore the morphology effect, three different structures of the host (ZnO)24 nano-system, having different degrees of spatial confinement, have been considered: a two dimensional nanosheet, a one dimensional nanotube, and a finite cage-shaped nanocluster. The present study employs hybrid density functional theory to accurately describe the electronic structure of all the systems. It is shown here that the magnetic coupling between the two dopant atoms remains mostly anti-ferromagnetic in the course of changing the morphology from the sheet geometry to the cage-shaped geometry of the host systems, except for the case of energetically most stable bi-Mn doping, which shows a transition from ferromagnetic to anti-ferromagnetic coupling with decreasing aspect ratio of the host system. The effect of the shape change, however, has a significant effect on the overall band gap variations of both the pristine as well as all the bi-doped systems, irrespective of the nature of the dopant atoms and provides a means for easy tunability of their optoelectronic properties.

  5. Energy band structure calculations based on screened Hartree-Fock exchange method: Si, AlP, AlAs, GaP, and GaAs.

    Science.gov (United States)

    Shimazaki, Tomomi; Asai, Yoshihiro

    2010-06-14

    The screening effect on the Hartree-Fock (HF) exchange term plays a key role in the investigation of solid-state materials by first-principles electronic structure calculations. We recently proposed a novel screened HF exchange potential, in which the inverse of the dielectric constant represents the fraction of the HF exchange term incorporated into the potential. We demonstrated that this approach can be used to reproduce the energy band structure of diamond well [T. Shimazaki and Y. Asai, J. Chem. Phys. 130, 164702 (2009)]. In the present paper, we report that the screened HF exchange method is applicable to other semiconductors such as silicon, AlP, AlAs, GaP, and GaAs. PMID:20550388

  6. Valence band electronic structure of Nd1?xYxMnO3 using X-ray absorption, photoemission and GGA + U calculations

    International Nuclear Information System (INIS)

    Highlights: •Decrease in the occupancy of Mn 3d orbitals with doping. •Greater splitting of the eg orbitals due to the increased Jahn–Teller distortion with doping. •Decrease in O 2p–Mn 3d charge transfer character with doping. •Increase in charge transfer energy and band gap with doping. •Calculations hint a subtle change from a charge transfer to Mott–Hubbard type insulator with doping. -- Abstract: The electronic structures of Nd1?xYxMnO3 (x = 0–0.5) were studied using X-ray absorption near-edge structure (XANES) at the Mn L3,2- and O K-edge along with valence-band photoemission spectroscopy (VB-PES). The systematic increase in white-line intensity of the Mn L3,2-edge with doping, suggests a decrease in the occupancy of Mn 3d orbitals. The O K-edge XANES shows a depletion of unoccupied states above the Fermi energy. The changes in the O K-edge spectra due to doping reflects an increase in the Jahn–Teller distortion. The VB-PES shows broadening of the features associated with Mn 3d and O 2p hybridized states and the shift of these features to a slightly higher binding energy in agreement with our GGA + U calculations. The system shows a net shift of the occupied and unoccupied states away from the Fermi energy with doping. The shift in theoretical site-projected density of states of x = 0.5 composition with respect to x = 0 suggest a subtle change from a charge transfer to Mott Hubbard type insulator

  7. Estimation of various scattering parameters and 2-DEG mobilities from electron mobility calculations in the three conduction bands , L and X of gallium arsenide

    Indian Academy of Sciences (India)

    Sonal Singhal; A. K. Saxena; S. Dasgupta

    2007-10-01

    The electron drift mobility in conduction band of GaAs has been calculated before, but for the first time, we have made attempts to estimate the electron mobilities in higher energy L and X minima. We have also calculated the value of mobility of two-dimensional electron gas needed to predict hetero-structure device characteristics using GaAs. Best scattering parameters have been derived by close comparison between experimental and theoretical mobilities. Room temperature electron mobilities in , L and X valleys are found to be nearly 9094, 945 and 247 cm2 /V-s respectively. For the above valleys, the electron masses, deformation potentials and polar phonon temperatures have been determined to be (0.067, 0.22, 0.39m 0 ), (8.5, 9.5, 6.5 eV), and (416, 382, 542 K) as best values, respectively. The 2-DEG electron mobility in minimum increases to $1.54 \\times 10^{6}$ from $1.59 \\times 10^{5}$ cm2 /V-s (for impurity concentration of 1014 cm-3) at 10 K. Similarly, the 2-DEG electron mobility values in L and X minima are estimated to be $2.28 \\times 10^{5}$ and $1.44 \\times 10^{5}$ cm2 /V-s at 10 K, which are about $\\sim 4.5$ and $\\sim 3.9$ times higher than normal value with impurity scattering present.

  8. Optimization of the Jastrow factor using the random-phase approximation and a similarity-transformed Hamiltonian: Application to band-structure calculation for some semiconductors and insulators

    Energy Technology Data Exchange (ETDEWEB)

    Ochi, Masayuki, E-mail: ochi@cms.phys.s.u-tokyo.ac.jp [Department of Physics, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033 (Japan); Sodeyama, Keitaro [Elements Strategy Initiative for Catalysis and Batteries, Kyoto University, Goryo-Ohara, Nishikyo-ku, Kyoto 615-8245 (Japan); WPI International Center for Materials Nanoarchitectonics, National Institute for Material Science, Tsukuba, Ibaraki 305-0044 (Japan); Tsuneyuki, Shinji [Department of Physics, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033 (Japan); Institute for Solid State Physics, Kashiwa, Chiba 277-8581 (Japan)

    2014-02-21

    Based on the random-phase approximation and the transcorrelated (TC) method, we optimize the Jastrow factor together with one-electron orbitals in the Slater determinant in the correlated wave function with a new scheme for periodic systems. The TC method is one of the promising wave function theories for first-principles electronic structure calculation, where the many-body wave function is approximated as a product of a Slater determinant and a Jastrow factor, and the Hamiltonian is similarity-transformed by the Jastrow factor. Using this similarity-transformed Hamiltonian, we can optimize the one-electron orbitals without evaluating 3N-dimensional integrations for the N-electron system. In contrast, optimization of the Jastrow factor within the framework of the TC method is computationally much more expensive and has not been performed for solid-state calculations before. In this study, we also benefit from the similarity-transformation in optimizing the Jastrow factor. Our optimization scheme is tested in applications to some solids from narrow-gap semiconductors to wide-gap insulators, and it is verified that the band gap of a wide-gap insulator and the lattice constants of some solids are improved by this optimization with reasonable computational cost.

  9. First-principles calculation of the band gap of Al xGa1-xN and In xGa1-x N

    Scientific Electronic Library Online (English)

    Roberto, Núñez-González; Armando, Reyes-Serrato; Alvaro, Posada-Amarillas; Donald H, Galván.

    2008-11-01

    Full Text Available En este trabajo se realizaron cálculos de primeros principios de la variación del ancho de banda prohibido en los compuestos ternarios Al xGa1-xN e In xGa1-x N, utilizando el Método Linealizado de Ondas Planas Aumentadas con Potencial Completo (FLAPW), dentro del marco de la Teoría del Funcional de [...] la Densidad (DFT). Los nitruros fueron modelados en una estructura tipo wurzita utilizando el método de supercelda, y considerando las concentraciones x = 0, 0.25, 0.50, 0.75 y 1.0. Para la optimización de los parámetros de red se utilizó el potencial de correlación-intercambio PBE96 (Perdew et al., Phys. Rev. Lett. 77 (1996) 3865). Para el cálculo de la estructura de bandas de energía se utilizaron los funcionales PBE96 y EV93 (Engel et al., Phys. Rev. B 47 (1993) 13164). Se consideraron parámetros de red experimentales y calculados (con PBE96) para los cálculos de las propiedades electrónicas. Nuestros cálculos indican que la banda prohibida fundamental es directa en estos compuestos. Los cálculos con el funcional EV93 dan como resultado una mejor estimación de los anchos de las bandas prohibidas de los compuestos binarios. Calculamos el parámetro de curvatura, obteniendo los valores b = 0.74 eV para Al xGa1-xN y b = 2.12 eV para In xGa1-x N. Abstract in english Ab-initio calculations of the band gap variation of Al xGa1-xN and In xGa1-x N ternary compounds were carried out using the Full-Potential Linearized Augmented Plane Waves (FLAPW) method, within the Density Functional Theory (DFT). These nitrides were modeled in their wurtzite structure using the su [...] percell method, for concentrations x = 0, 0.25, 0.50, 0.75 and 1.0. To optimize the cell parameters of the binary compounds we used the PBE96 (Perdew et al., Phys. Rev. Lett. 77 (1996) 3865) exchange-correlation functional. For the band structure calculations, we used both PBE96 and EV93 (Engel et al., Phys. Rev. B 47 (1993) 13164) exchange-correlation functionals. We considered experimental and calculated (with PBE96) lattice parameters to work out the electronic properties. We found that the fundamental gap is direct in all compounds. The calculation with EV93 functional gives a better band gap estimation for binary nitrides. The bowing parameter was also estimated obtaining the values b = 0.74 eV for Al xGa1-xN and b = 2.12 eV for In xGa1-x N.

  10. Band Calculations for Ce Compounds with AuCu3-type Crystal Structure on the basis of Dynamical Mean Field Theory: I. CePd3 and CeRh3

    Science.gov (United States)

    Sakai, Osamu

    2010-11-01

    Band calculations for Ce compounds with the AuCu3-type crystal structure were carried out on the basis of dynamical mean field theory (DMFT). The auxiliary impurity problem was solved by a method named NCA f2vc (noncrossing approximation including the f2 state as a vertex correction). The calculations take into account the crystal-field splitting, the spin-orbit interaction, and the correct exchange process of the f1 ? f0, f2 virtual excitation. These are necessary features in the quantitative band theory for Ce compounds and in the calculation of their excitation spectra. The results of applying the calculation to CePd3 and CeRh3 are presented as the first in a series of papers. The experimental results of the photoemission spectrum (PES), the inverse PES, the angle-resolved PES, and the magnetic excitation spectra were reasonably reproduced by the first-principles DMFT band calculation. At low temperatures, the Fermi surface (FS) structure of CePd3 is similar to that of the band obtained by the local density approximation. It gradually changes into a form that is similar to the FS of LaPd3 as the temperature increases, since the 4f band shifts to the high-energy side and the lifetime broadening becomes large.

  11. Band calculations for Ce compounds with AuCu3-type crystal structure on the basis of dynamical mean field theory. 1. CePd3 and CeRh3

    International Nuclear Information System (INIS)

    Band calculations for Ce compounds with the AuCu3-type crystal structure were carried out on the basis of dynamical mean field theory (DMFT). The auxiliary impurity problem was solved by a method named NCA f2vc (noncrossing approximation including the f2 state as a vertex correction). The calculations take into account the crystal-field splitting, the spin-orbit interaction, and the correct exchange process of the f1 ? f0, f2 virtual excitation. These are necessary features in the quantitative band theory for Ce compounds and in the calculation of their excitation spectra. The results of applying the calculation to CePd3 and CeRh3 are presented as the first in a series of papers. The experimental results of the photoemission spectrum (PES), the inverse PES, the angle-resolved PES, and the magnetic excitation spectra were reasonably reproduced by the first-principles DMFT band calculation. At low temperatures, the Fermi surface (FS) structure of CePd3 is similar to that of the band obtained by the local density approximation. It gradually changes into a form that is similar to the FS of LaPd3 as the temperature increases, since the 4f band shifts to the high-energy side and the lifetime broadening becomes large. (author)

  12. Photodissociation of water. II. Wave packet calculations for the photofragmentation of H2O and D2O in the B˜ band

    Science.gov (United States)

    van Harrevelt, Rob; van Hemert, Marc C.

    2000-04-01

    A complete three-dimensional quantum mechanical description of the photodissociation of water in the B˜ band, starting from its rotational ground state, is presented. In order to include B˜-X˜ vibronic coupling and the B˜-Ã Renner-Teller coupling, diabatic electronic states have been constructed from adiabatic electronic states and matrix elements of the electronic angular momentum operators, following the procedure developed by A. J. Dobbyn and P. J. Knowles [Mol. Phys. 91, 1107 (1997)], using the ab initio results discussed in the preceding paper. The dynamics is studied using wave packet methods, and the evolution of the time-dependent wave function is discussed in detail. Results for the H2O and D2O absorption spectra, OH(A)/OH(X) and OD(A)/OD(X) branching ratios, and rovibrational distributions of the OH and OD fragments are presented and compared with available experimental data. The present theoretical results agree at least qualitatively with the experiments. The calculations show that the absorption spectrum and the product state distributions are strongly influenced by long-lived resonances on the adiabatic B˜ state. It is also shown that molecular rotation plays an important role in the photofragmentation process, due to both the Renner-Teller B˜-X˜ mixing, and the strong effect of out-of-plane molecular rotations (K>0) on the dynamics at near linear HOH and HHO geometries.

  13. Semiclassical calculations of half-widths and line shifts for transitions in the 30012?00001 and 30013?00001 bands of CO2 II: Collisions with O2 and air

    International Nuclear Information System (INIS)

    The complex Robert-Bonamy (CRB) formalism was used to calculate the half-width, its temperature dependence, and the line shift for CO2 for transitions in the 30012?00001 and 30013?00001 bands with O2 as the perturbing gas. The calculations were done for rotational quantum numbers from J=0 to J=120 with no ad hoc scaling of the line shape equations. The intermolecular potential parameters are adjusted on accurate experimental measurements of the half-widths, its temperature dependence, and the pressure-induced line shifts so that a single intermolecular potential reproduces all three parameters. Using the results of this work and previous results for N2-broadening, air-broadening line shape parameters were also determined. The comparison of the CRB calculations with the experimental data available in the literature for the three line shape coefficients demonstrates the quality of the present calculations for the both bands under study.

  14. Band Calculations for Ce Compounds with AuCu$_{3}$-type Crystal Structure on the basis of Dynamical Mean Field Theory I. CePd$_{3}$ and CeRh$_{3}$

    OpenAIRE

    Sakai, Osamu

    2010-01-01

    Band calculations for Ce compounds with the AuCu$_{3}$-type crystal structure were carried out on the basis of dynamical mean field theory (DMFT). The auxiliary impurity problem was solved by a method named NCA$f^{2}$vc (noncrossing approximation including the $f^{2}$ state as a vertex correction). The calculations take into account the crystal-field splitting, the spin-orbit interaction, and the correct exchange process of the $f^{1} \\rightarrow f^{0},f^{2}$ virtual excitat...

  15. Use of EO-1 Hyperion data to calculate spectral band adjustment factors (SBAF) between the L7 ETM+ and Terra MODIS sensors

    Science.gov (United States)

    Chander, Gyanesh; Mishra, N.; Helder, Dennis L.; Aaron, D.; Choi, T.; Angal, A.; Xiong, X.

    2010-01-01

    Different applications and technology developments in Earth observations necessarily require different spectral coverage. Thus, even for the spectral bands designed to look at the same region of the electromagnetic spectrum, the relative spectral responses (RSR) of different sensors may be different. In this study, spectral band adjustment factors (SBAF) are derived using hyperspectral Earth Observing-1 (EO-1) Hyperion measurements to adjust for the spectral band differences between the Landsat 7 (L7) Enhanced Thematic Mapper Plus (ETM+) and the Terra Moderate Resolution Imaging Spectroradiometer (MODIS) top-of-atmosphere (TOA) reflectance measurements from 2000 to 2009 over the pseudo-invariant Libya 4 reference standard test site.

  16. Energy bands and optical properties of HgTe and CdTe calculated on the basis of the tight-binding model with spin-orbit interaction

    International Nuclear Information System (INIS)

    It is shown that inclusion of spin-orbit interaction and omission of the usual two-center approximation in the second neighbour Slater-Koster tight-binding method leads to an improved interpolation formula for the energy bands of II-VI semiconducting compounds such as CdTe. Due to the inclusion of spin-orbit interaction it is possible to obtain the inverted band structure of HgTe. Reflectivity spectra are computed in fairly good agreement with experiment, up to 5 eV. A detailed discussion of critical points contributed to E1, E1 + ?1 and E2 maxima is carried out. Moreover, the local properties near the GAMMA point (e.g. effective mass, g factor, Kane's matrix element P, nonparabolicity, warping) of the valence and conduction bands are found to be in excellent agreement with experimental data. (author)

  17. Ultrawide Band Electromagnetic Pulses

    International Science & Technology Center (ISTC)

    Development of New Calculation-Theoretical and Metrologic Approaches in Technology of Ultrawide Band Electromagnetic Pulses, Elaboration and Investigation of Standard Field-Forming Systems of Subnanosecond Pulse Field

  18. Band Calculations for Ce Compounds with AuCu$_{3}$-type Crystal Structure on the basis of Dynamical Mean Field Theory II. - CeIn$_{3}$ and CeSn$_{3}$

    OpenAIRE

    Sakai, Osamu; Harima, Hisatomo

    2012-01-01

    Band calculations for Ce compounds with the AuCu$_{3}$-type crystal structure were carried out on the basis of dynamical mean field theory (DMFT). The results of applying the calculation to CeIn$_{3}$ and CeSn$_{3}$ are presented as the second in a series of papers. The Kondo temperature and crystal-field splitting are obtained, respectively, as 190 and 390 K (CeSn$_{3}$), 8 and 160 K (CeIn$_{3}$ under ambient pressure), and 30 and 240 K (CeIn$_{3}$ at a pressure of 2.75 GPa...

  19. Band Calculations for Ce Compounds with AuCu3-Type Crystal Structure on the Basis of Dynamical Mean Field Theory: II. CeIn3 and CeSn3

    Science.gov (United States)

    Sakai, Osamu; Harima, Hisatomo

    2012-02-01

    Band calculations for Ce compounds with the AuCu3-type crystal structure were carried out on the basis of dynamical mean field theory (DMFT). The results of applying the calculation to CeIn3 and CeSn3 are presented as the second in a series of papers. The Kondo temperature and crystal-field splitting are obtained, respectively, as 190 and 390 K (CeSn3), 8 and 160 K (CeIn3 under ambient pressure), and 30 and 240 K (CeIn3 at a pressure of 2.75 GPa). Experimental results for the photoemission spectrum are reasonably well reproduced. In CeSn3, a Fermi surface (FS) structure similar to that obtained by a refined calculation based on the local density approximation (LDA) is obtained. In CeIn3, the topology of the FS structure is different from that obtained by the LDA calculation but seems to be consistent with the results of de Haas--van Alphen experiments. Cyclotron mass of the correct magnitude is obtained in both compounds. The experimental result for the angular correlation of the electron-positron annihilation radiation is reasonably well reproduced on the basis of the itinerant 4f picture. A band calculation for CeIn3 in the antiferromagnetic state was carried out, and it was shown that the occupied 4f state should have a very shallow level.

  20. Excited bands in fixed CNS configurations

    International Nuclear Information System (INIS)

    Exact and approximate quantum numbers of the cranked Nilsson-Strutinsky (CNS) formalism are exploited to calculate excited bands in fixed configurations with the energy of the individual bands minimized with respect to deformation for all spin values. The formalism is illustrated to calculate all bands which appear important in the decay out of the superdeformed band in 59Cu

  1. Real-structure effects: Band gaps of Mg_xZn_{1-x}O, Cd_xZn_{1-x}O, and n-type ZnO from ab-initio calculations

    Energy Technology Data Exchange (ETDEWEB)

    Schleife, A; Bechstedt, F

    2012-02-15

    Many-body perturbation theory is applied to compute the quasiparticle electronic structures and the optical-absorption spectra (including excitonic effects) for several transparent conducting oxides. We discuss HSE+G{sub 0}W{sub 0} results for band structures, fundamental band gaps, and effective electron masses of MgO, ZnO, CdO, SnO{sub 2}, SnO, In{sub 2}O{sub 3}, and SiO{sub 2}. The Bethe-Salpeter equation is solved to account for excitonic effects in the calculation of the frequency-dependent absorption coefficients. We show that the HSE+G{sub 0}W{sub 0} approach and the solution of the Bethe-Salpeter equation are very well-suited to describe the electronic structure and the optical properties of various transparent conducting oxides in good agreement with experiment.

  2. First-principles energy band calculation of Ruddlesden-Popper compound Sr3Sn2O7 using modified Becke-Johnson exchange potential

    Science.gov (United States)

    Kamimura, Sunao; Obukuro, Yuki; Matsushima, Shigenori; Nakamura, Hiroyuki; Arai, Masao; Xu, Chao-Nan

    2015-12-01

    The electronic structure of Sr3Sn2O7 is evaluated by the scalar-relativistic full potential linearized augmented plane wave (FLAPW+lo) method using the modified Becke-Johnson potential (Tran-Blaha potential) combined with the local density approximation correlation (MBJ-LDA). The fundamental gap between the valence band (VB) and conduction band (CB) is estimated to be 3.96 eV, which is close to the experimental value. Sn 5s states and Sr 4d states are predominant in the lower and upper CB, respectively. On the other hand, the lower VB is mainly composed of Sn 5s, 5p, and O 2p states, while the upper VB mainly consists of O 2p states. These features of the DOS are well reflected by the optical transition between the upper VB and lower CB, as seen in the energy dependence of the dielectric function. Furthermore, the absorption coefficient estimated from the MBJ-LDA is similar to the experimental result.

  3. Mental Calculation Methods Used by 11-Year-Olds in Different Attainment Bands: A Reanalysis of Data from the 1987 APU Survey in the UK.

    Science.gov (United States)

    Foxman, Derek; Beishuizen, Meindert

    2002-01-01

    Reanalyzes data obtained in 1987 on mental calculation strategies used by 11-year-olds in England, Wales, and Northern Ireland. Classifies mental strategies developed in the past decade in international research. Compares frequency and effectiveness of the strategies used by pupils of different levels of attainment. Discusses basic arithmetic…

  4. Chemical trends of the band gaps of idealized crystal of semiconducting silicon clathrates, M8Si38A8 (M = Na, K, Rb, Cs; A = Ga, Al, In), predicted by first-principle pseudopotential calculations

    International Nuclear Information System (INIS)

    Research highlights: ? This paper reports the results of electronic structural calculations of Si clathrate, M8Si38Ga8 (M: the encapsulated guest alkali atom; Na, K, Rb, and Cs). ? All of them are found to be indirect semiconductors with the calculated gaps (Eg) from 0.45 to 0.89 eV, which should be compared to the calculated gap of 0.65 eV of crystalline Si with the diamond structure. The gaps become wider with the promotion to the heavier guest alkali atoms and the reasons of gap widening are discussed using the calculated dependence of Eg on the cell-volume of guest-free silicon clathrate (Si46). Effect of the substitutional elements in the clathrate framework (Al and In in place of Ga) was also discussed. - Abstract: We have calculated the band structures of Si clathrate, M8Si38Ga8 (M = Na, K, Rb, and Cs), using the density-functional theory under the generalized gradient corrected local density approximation, where M is the encapsulated guest alkali atom. They are found to be indirect semiconductors with the calculated gaps (Eg) from 0.45 to 0.89 eV, which should be compared to the calculated gap of 0.65 eV of crystalline Si with the diamond structure. The gaps become wider with the promotion to the heavier guest alkali atoms and the reasons of gap widening are discussed using the calculated dependence of Eg on the cell-volume of guest-free silicon clathrate (Si46). Effect of the substitutional elements in the clathrate framework (Al and In in place of Ga) was also discussed.

  5. Comparison of trajectory models in calculations of N2-broadened half-widths and N2-induced line shifts for the rotational band of H216O and comparison with measurements

    International Nuclear Information System (INIS)

    In this work, Complex Robert-Bonamy calculations of half-widths and line shifts were done for N2-broadening of water for 1639 transitions in the rotational band using two models for the trajectories. The first is a model correct to second order in time, the Robert-Bonamy parabolic approximation. The second is the solution of Hamilton's equations. Both models use the isotropic part of the atom-atom potential to determine the trajectories. The present calculations used an intermolecular potential expanded to 20th order to assure the convergence of the half-widths and line shifts. The aim of the study is to assess if the difference in the half-widths and line shifts determined from the two trajectory models is greater than the accuracy requirements of the spectroscopic and remote sensing communities. The results of the calculations are compared with measurements of the half-widths and line shifts. It is shown that the effects of the trajectory model greatly exceed the needs of current remote sensing measurements and that line shape parameters calculated using trajectories determined by solving Hamilton's equations agree better with measurement.

  6. Comparison of Trajectory Models in Calculations of N2-broadened Half-widths and N2-induced Line Shifts for the Rotational Band of H2O-16 and Comparison with Measurements

    Science.gov (United States)

    Lamouroux, J.; Gamache, R. R.; Laraia, A. L.; Ma, Q.; Tipping, R. H.

    2012-01-01

    In this work, Complex Robert-Bonamy calculations of half-widths and line shifts were done for N2-broadening of water for 1639 transitions in the rotational band using two models for the trajectories. The first is a model correct to second order in time, the Robert-Bonamy parabolic approximation. The second is the solution of Hamilton's equations. Both models use the isotropic part of the atom-atom potential to determine the trajectories. The present calculations used an intermolecular potential expanded to 20th order to assure the convergence of the half-widths and line shifts. The aim of the study is to assess if the difference in the half-widths and line shifts determined from the two trajectory models is greater than the accuracy requirements of the spectroscopic and remote sensing communities. The results of the calculations are compared with measurements of the half-widths and line shifts. It is shown that the effects of the trajectory model greatly exceed the needs of current remote sensing measurements and that line shape parameters calculated using trajectories determined by solving Hamilton's equations agree better with measurement.

  7. Room-temperature Broadening and Pressure-shift Coefficients in the nu(exp 2) Band of CH3D-O2: Measurements and Semi-classical Calculations

    Science.gov (United States)

    Predoi-Cross, Adriana; Hambrook, Kyle; Brawley-Tremblay, Shannon; Bouanich, Jean-Pierre; Devi, V. Malathy; Smith, Mary Ann H.

    2006-01-01

    We report measured Lorentz O2-broadening and O2-induced pressure-shift coefficients of CH3D in the nu(exp 2) fundamental band. Using a multispectrum fitting technique we have analyzed 11 laboratory absorption spectra recorded at 0.011 cm(exp 1) resolution using the McMath-Pierce Fourier transform spectrometer, Kitt Peak, Arizona. Two absorption cells with path lengths of 10.2 and 25 cm were used to record the spectra. The total sample pressures ranged from 0.98 to 339.85 Torr with CH3D volume mixing ratios of 0.012 in oxygen. We report measurements for O2 pressure-broadening coefficients of 320 nu(exp 2) transitions with quantum numbers as high as J0(sup w) = 17 and K = 14, where K(sup w) = K' is equivalent to K (for a parallel band). The measured O2-broadening coefficients range from 0.0153 to 0.0645 cm(exp -1) atm(exp -1) at 296 K. All the measured pressure-shifts are negative. The reported O2-induced pressure-shift coefficients vary from about -0.0017 to -0.0068 cm(exp -1) atm(exp -1). We have examined the dependence of the measured broadening and shift parameters on the J(sup W), and K quantum numbers and also developed empirical expressions to describe the broadening coefficients in terms of m (m = -J(sup W), J(sup W), and J(sup w) + 1 in the QP-, QQ-, and QR-branch, respectively) and K. On average, the empirical expressions reproduce the measured broadening coefficients to within 4.4%. The O2-broadening and pressure shift coefficients were calculated on the basis of a semiclassical model of interacting linear molecules performed by considering in addition to the electrostatic contributions the atom-atom Lennard-Jones potential. The theoretical results of the broadening coefficients are generally larger than the experimental data. Using for the trajectory model an isotropic Lennard-Jones potential derived from molecular parameters instead of the spherical average of the atom-atom model, a better agreement is obtained with these data, especially for |m| shifts whose vibrational contribution are either derived from parameters fitted in the QQ-branch of selfinduced shifts of CH3D or those obtained from pressure shifts induced by Xe in the nu(sup 3) band of CH3D are in reasonable agreement with the scattered experimental data (17.0% for the first calculation and 18.7% for the second calculation).

  8. Electronic properties of cubic TaCxN1-x: A comparative study using self-consistent cluster and ab initio band-structure calculations and X-ray spectroscopy

    International Nuclear Information System (INIS)

    To investigate the influence of substitution of carbon atoms for nitrogen atoms in the cubic TaCxN1-x carbonitrides, total and partial densities of states were calculated for TaC, TaC0.5N0.5 and TaN compounds (NaCl structure) using the self-consistent cluster (with the FEFF8 code) and ab initio band-structure augmented plane wave + local orbitals (APW + LO) methods. In the present work a rather good agreement of the theoretical FEFF8 and APW + LO data for electronic properties of the TaCxN1-x system under consideration was obtained. The results indicate that a strong hybridization of the Ta 5d- and C(N) 2p-like states is characteristic for the valence band of the TaCxN1-x carbonitrides. When going from TaC to TaN through the TaC0.5N0.5 carbonitride, the main maxima of curves representing total and partial Ta 5d densities of states shift in the direction opposite to the position of the Fermi level. In the above sequence of compounds, an increase of occupation of the near-Fermi sub-band formed by contributions of Ta 5d(t2g) states has been detected. The theoretical FEFF8 and APW + LO results for the electronic structure of the TaCxN1-x carbonitrides were found to be in excellent agreement with the experimental data derived in the present work employing X-ray photoelectron, emission and absorption spectroscopy methods for cubic TaC0.98, TaC0.52N0.49 and TaN0.97 compounds

  9. Electronic properties of cubic TaC{sub x}N{sub 1-x}: A comparative study using self-consistent cluster and ab initio band-structure calculations and X-ray spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Lavrentyev, A.A.; Gabrelian, B.V.; Vorzhev, V.B.; Nikiforov, I.Ya. [Department of Physics, Don State Technical University, Gagarin Sq. 1, Rostov-on-Don (Russian Federation); Khyzhun, O.Yu. [Frantsevych Institute for Problems of Materials Science, National Academy of Sciences of Ukraine, 3 Krzhyzhanivsky Street, UA-03142 Kyiv (Ukraine)], E-mail: khyzhun@ipms.kiev.ua

    2009-03-20

    To investigate the influence of substitution of carbon atoms for nitrogen atoms in the cubic TaC{sub x}N{sub 1-x} carbonitrides, total and partial densities of states were calculated for TaC, TaC{sub 0.5}N{sub 0.5} and TaN compounds (NaCl structure) using the self-consistent cluster (with the FEFF8 code) and ab initio band-structure augmented plane wave + local orbitals (APW + LO) methods. In the present work a rather good agreement of the theoretical FEFF8 and APW + LO data for electronic properties of the TaC{sub x}N{sub 1-x} system under consideration was obtained. The results indicate that a strong hybridization of the Ta 5d- and C(N) 2p-like states is characteristic for the valence band of the TaC{sub x}N{sub 1-x} carbonitrides. When going from TaC to TaN through the TaC{sub 0.5}N{sub 0.5} carbonitride, the main maxima of curves representing total and partial Ta 5d densities of states shift in the direction opposite to the position of the Fermi level. In the above sequence of compounds, an increase of occupation of the near-Fermi sub-band formed by contributions of Ta 5d(t{sub 2g}) states has been detected. The theoretical FEFF8 and APW + LO results for the electronic structure of the TaC{sub x}N{sub 1-x} carbonitrides were found to be in excellent agreement with the experimental data derived in the present work employing X-ray photoelectron, emission and absorption spectroscopy methods for cubic TaC{sub 0.98}, TaC{sub 0.52}N{sub 0.49} and TaN{sub 0.97} compounds.

  10. Gastric Banding

    Science.gov (United States)

    ... gastric banding before deciding to have the procedure. Advertisements for a device or procedure may not include ... demonstrated benefits for people who have not been successful using non-surgical weight loss methods. This surgical ...

  11. Semiclassical calculations of half-widths and line shifts for transitions in the 30012?00001 and 30013?00001 bands of CO2, I: Collisions with N2

    International Nuclear Information System (INIS)

    Calculations of the half-width, its temperature dependence, and the line shift are made for the rotational states J=0-120 for two of the Fermi-tetrad bands (30012?00001 and 30013?00001) of CO2 perturbed by N2. The calculations employ the semi-classical complex Robert-Bonamy method with no ad hoc scaling, J-dependent or otherwise, and an intermolecular potential (IP) comprised of an electrostatic part, an atom-atom part, and an isotropic London dispersion part. The averaging over the impact parameter b and relative speed v are explicitly carried out. Many interesting features about CO2 as the radiating molecule are elucidated. Effects of the trajectory model, the order of the expansion of the atom-atom component of the potential, and the inclusion of the imaginary terms are studied. It is shown that the results are very sensitive to the intermolecular potential. The final IP parameters give results that demonstrate excellent agreement with measurement for the three line shape parameters studied in this work.

  12. Quasirelativistic band structure of bismuth telluride

    International Nuclear Information System (INIS)

    The band structure of bismuth telluride belonging to the group of the Asub(2)Ssup(5)BsUb(3)-type crystals with the Dsub(3d)sup(5) symmetry is under consideration. The Bi2Te3 band structure was calculated using the Pauli equation pseudopotential method. Calculation results are presented for the Brillouin zone symmetric points. The energy bands are classified according to their symmetry. The evailable basic parameters of the bismuth telluride band structure are compared with the result of other paper. Analysis of the calculated band structure shows that there is some difference of the band behaviour in the direction perpendicular to quintet (GITAL, KA, XU) layers that of bands lying in the quintet plane (other Brillouin zone directions). In the first case the energy band dispersion is well below than that in the second case. This fact conforms with a lower current carrier mobility in the direction perpendicular to the layers, as compared to other crystal directions

  13. Band Together!

    Science.gov (United States)

    Olson, Cathy Applefeld

    2011-01-01

    After nearly a decade as band director at St. James High School in St. James, Missouri, Derek Limback knows that the key to building a successful program is putting the program itself above everything else. Limback strives to augment not only his students' musical prowess, but also their leadership skills. Key to his philosophy is instilling a…

  14. Calculation of attenuation by rain using the DAH model and diameter of antennas for the Ka Band in Mexico; Calculo de atenuacion por lluvia usando el modelo DAH y diametro de antena para Banda Ka en Mexico

    Energy Technology Data Exchange (ETDEWEB)

    Landeros-Ayala, S.; Neri-Vela, R; Cruz-Sanchez, H.; Hernandez-Bautista, H. [Universidad Nacional Autonoma de Mexico, Mexico, D.F. (Mexico)

    2002-03-01

    In the last years, the peak in the demand of satellite communication service has caused the saturation in the use of the frequencies corresponding to the band, Cand Ku. Due to this, the engineers have looked for viable alternatives, in order to satisfy the current requisition, as well as the future demand, for which a considerable increment is expected. One of these alternatives is the use of the Ka Band (20Hz/30Hz), that is why the importance of studying the propagation effects that are experienced at these frequencies, especially the attenuation effect by rain, as in this case, where it is significant. The present article has the purpose to describe the use of the Modelo DAH (whose authors are Asoka Dissanayake, Jeremy Allnutt and Fatim Haidara), mixed with the global maps of distribution of rain by Crane, for the calculation of the attenuation by rain in satellite communication systems operated in the Ka Band. Besides, antenna diameters for the systems of communications in Ka Band in different locations of the Mexican Republic, using for it the attenuation margins for rain obtained through the Modelo DAH, and using as references the characteristics of the ANIK F2 satellite and a terrestrial station VSAT, are proposed. [Spanish] En los ultimos anos, el auge en la demanda de servicios de comunicacion por satelite ha provocado la saturacion en los uso de la frecuencia correspondientes a las bandas C y Ku. Debido a esta razon, se han buscado alternativas viables para poder satisfacer la demanda actual, asi como la demanda futura, para la cual se espera un incremento considerable. Una de estas alternativas es el uso de Banda Ka (20Hz/30Hz), de ahi la importancia del estudio sobre los efectos de programacion que se experimentan a esta frecuencia, en especial, el efecto de atencion por lluvias, ya que sen este caso resulta ser significativa. El presente articulo tiene como finalidad describir el uso del Modelo DAH (cuyos autores son Asoka Dissanayake, Jeremy Allnutt y Fatim Haidara), combinado con los mapas globales de distribucion de lluvia de Crane, para el calculo de la atencion por lluvia en sistema de comunicacion por satelite que operen en la Banda Ka. Ademas, se proponen diametros de antena para los sistemas de comunicaciones en Banda Ka en diferentes localidades de la Republica Mexicana, empleando para ello, los margenes de atencion por lluvia obtenidos a trav del Modelo DAH, y usando como referencia las caracteristicas del satelite de comunicaciones ANIK F2 y de una estacion terrena VSAT.Se muestra una fig. de la atenuacion por lluvia a 27.5 gHz y de los diametros de antena para banda Ka en Mexico. Se da una tabla de la atenuacion por lluvia a 29.5 GHz y a 20.2 GHz.

  15. Candidate chiral bands in 198Tl

    International Nuclear Information System (INIS)

    High-spin states in 198Tl were studied using the 197Au(?, 3n) reaction. The level scheme was considerably extended including two new bands and several non-yrast levels. One of the new bands is possibly a chiral partner to the yrast ?h9/2 x ?i13/2-1 band. Two-quasiparticle-plus-triaxial-rotor model calculations suggest an aplanar orientation of the total angular momenta for these bands, thus supporting possible chirality. (orig.)

  16. Silicon nanowire band gap modification.

    Science.gov (United States)

    Nolan, Michael; O'Callaghan, Sean; Fagas, Giorgos; Greer, James C; Frauenheim, Thomas

    2007-01-01

    Band gap modification for small-diameter (approximately 1 nm) silicon nanowires resulting from the use of different species for surface termination is investigated by density functional theory calculations. Because of quantum confinement, small-diameter wires exhibit a direct band gap that increases as the wire diameter narrows, irrespective of surface termination. This effect has been observed in previous experimental and theoretical studies for hydrogenated wires. For a fixed cross-section, the functional group used to saturate the silicon surface significantly modifies the band gap, resulting in relative energy shifts of up to an electronvolt. The band gap shifts are traced to details of the hybridization between the silicon valence band and the frontier orbitals of the terminating group, which is in competition with quantum confinement. PMID:17212436

  17. Nonzero Quadrupole Moments of Candidate Tetrahedral Bands

    International Nuclear Information System (INIS)

    Negative-parity bands in the vicinity of 156Gd and 160Yb have been suggested as candidates for the rotation of tetrahedral nuclei. We report the observation of the odd and even-spin members of the lowest energy negative-parity bands in 160Yb and 154Gd. The properties of these bands are similar to the proposed tetrahedral band of 156Gd and its even-spin partner. Band-mixing calculations are performed and absolute and relative quadrupole moments deduced for 160Yb and 154Gd. The values are inconsistent with zero, as required for tetrahedral shape, and the bands are interpreted as octupole vibrational bands. The failure to observe the in-band E2 transitions of the bands at low spins can be understood using the measured B(E1) and B(E2) values.

  18. Investigation of chiral bands in 106Ag

    International Nuclear Information System (INIS)

    Dipole bands in 106Ag have been studied with the ?-detector array AFRODITE at iThemba LABS, South Africa. A 96Zr(14N,4n)106Ag reaction at a beam energy of 71 MeV has been used. The three previously known negative-parity bands in 106Ag have been extended. Bands 1 and 2 were proposed to be chiral partner bands. However, in view of the present results, bands 2 and 3 seem to be better candidates for chiral partner bands since their staggering parameters, B(M1)/B(E2) ratios, kinematic moments of inertia and quasiparticle alignments agree much better than those of bands 1 and 2. Triaxial relativistic mean field (RMF) and particle-rotor model (PRM) calculations support this interpretation. In the potential energy surface of 106Ag, obtained in RMF calculations, two minima have been found in the ?2-? plane. Based on PRM calculations using the deformation parameters of the two minima and a ?h11/2 x ?g-19/2 particle-hole configuration, bands 2 and 3 may represent partners with chiral vibration at ??12degree. Band 1, located in the other minimum, may be a magnetic dipole band or the partner of a second pair of chiral bands.

  19. Band Magnetism

    International Nuclear Information System (INIS)

    Introduction. 1. Experimental properties of transitional metals. 1.1. Magnetic properties. 1.2. Other properties. 2. The band model. 3. Hartree-Fock Stoner theory. 3.1. Non-magnetic Hartree-Fock solution at T = 0. 3.2. Magnetic solutions. 3.3. Applications. 4. Spin waves in the random phase approximation. 5. Susceptibilities - equivalence between the RPA and the time-dependent Hartree-Fock approximation. 5.1. Definition and properties of the susceptibilities. 5.2. Susceptibilities in the RPA. Time-dependent Hartree-Fock approximation. 6. Spin density waves. 6.1. Appearance of spin density waves at Tc. 6.2. Spin density waves below Tc. 6.3. Application to-chiomium. 7. Influence of correlation. 7.1. The Landau theory of Fermi liquids. 7.2. Approximate treatment of correlation. 7.3. Applications. 8. Nearly ferromagnetic metals. 8.1. Mass enhancement due to phonons. 8.2. Mass enhancement due to paramagnons. 8.3. Applications. Conclusion. (author)

  20. System and method for progressive band selection for hyperspectral images

    Science.gov (United States)

    Fisher, Kevin (Inventor)

    2013-01-01

    Disclosed herein are systems, methods, and non-transitory computer-readable storage media for progressive band selection for hyperspectral images. A system having module configured to control a processor to practice the method calculates a virtual dimensionality of a hyperspectral image having multiple bands to determine a quantity Q of how many bands are needed for a threshold level of information, ranks each band based on a statistical measure, selects Q bands from the multiple bands to generate a subset of bands based on the virtual dimensionality, and generates a reduced image based on the subset of bands. This approach can create reduced datasets of full hyperspectral images tailored for individual applications. The system uses a metric specific to a target application to rank the image bands, and then selects the most useful bands. The number of bands selected can be specified manually or calculated from the hyperspectral image's virtual dimensionality.

  1. Band-limited power flow into enclosures

    Science.gov (United States)

    Pope, L. D.; Wilby, J. F.

    1977-01-01

    Equations for the band-limited power flow to a cavity in the low-frequency regime are derived. The total power to cavity is obtained by summing separate calculations of the power from structural modes resonant in the band and power from structural modes resonant below the band. High-frequency relations compatible with the usual statistical energy analysis and generalized to include other excitations in addition to diffuse fields are also provided.

  2. Come Join the Band

    Science.gov (United States)

    Olson, Cathy Applefeld

    2011-01-01

    A growing number of students in Blue Springs, Missouri, are joining the band, drawn by a band director who emphasizes caring and inclusiveness. In the four years since Melissia Goff arrived at Blue Springs High School, the school's extensive band program has swelled. The marching band alone has gone from 100 to 185 participants. Also under Goff's…

  3. Rotational band properties of 173W

    Science.gov (United States)

    Wang, H. X.; Zhang, Y. H.; Zhou, X. H.; Liu, M. L.; Ding, B.; Li, G. S.; Hua, W.; Zhou, H. B.; Guo, S.; Qiang, Y. H.; Oshima, M.; Koizumi, M.; Toh, Y.; Kimura, A.; Harada, H.; Furutaka, K.; Kitatani, F.; Nakamura, S.; Hatsukawa, Y.; Ohta, M.; Hara, K.; Kin, T.; Meng, J.

    2012-10-01

    High-spin states in 173W have been studied using the 150Nd(28Si,5n)173W reaction at beam energies of 135 and 140 MeV. The previously known bands associated with the 7/2+[633], 5/2-[512], and 1/2-[521] configurations are extended significantly, and the unfavored signature branch of the 1/2-[521] band is established for the first time. The band properties, such as level spacings, band-crossing frequencies, alignment gains, and signature splittings, are discussed with an emphasis on the low-spin signature inversion observed in the 5/2-[512] band. By comparing the experimental B(M1)/B(E2) ratios with the theoretical values, we conclude that the configuration of the 5/2-[512] band is quite pure at low spins without appreciable admixture of the 5/2-[523] orbit, in conflict with the particle rotor model calculated results.

  4. Systematic Study of Electronic Phases, Band Gaps and Band Overlaps of Bismuth Antimony Nanowires

    OpenAIRE

    Tang, Shuang; Dresselhaus, Mildred

    2013-01-01

    We have developed an iterative one dimensional model to study the narrow band-gap and the associated non-parabolic dispersion relations for bismuth antimony nanowires. An analytical approximation has also been developed. Based on the general model, we have developed, we have calculated and analyzed the electronic phase diagrams and the band-gap/band-overlap map for bismuth antimony nanowires, as a function of stoichiometry, growth orientation, and wire width.

  5. Band structure of semiconductors

    CERN Document Server

    Tsidilkovski, I M

    2013-01-01

    Band Structure of Semiconductors provides a review of the theoretical and experimental methods of investigating band structure and an analysis of the results of the developments in this field. The book presents the problems, methods, and applications in the study of band structure. Topics on the computational methods of band structure; band structures of important semiconducting materials; behavior of an electron in a perturbed periodic field; effective masses and g-factors for the most commonly encountered band structures; and the treatment of cyclotron resonance, Shubnikov-de Haas oscillatio

  6. Photonic band gap materials

    International Nuclear Information System (INIS)

    An overview of the theoretical and experimental efforts in obtaining a photonic band gap, a frequency band in three-dimensional dielectric structures in which electromagnetic waves are forbidden, is presented

  7. Band structure analysis of the conduction-band mass anisotropy in 6H and 4H SiC

    OpenAIRE

    Lambrecht, Walter R. L.; Segall, Benjamin

    1995-01-01

    The band structures of 6H and 4H SiC calculated by means of the FP-LMTO method are used to determine the effective mass tensors for their conduction-band minima. The results are shown to be consistent with recent optically detected cyclotron resonance measurements and predict an unusual band filling dependence for 6H-SiC.

  8. Ab initio calculations on potential energy curves and radiative lifetimes for the band systems A(2)?-X(2)?(+) of magnesium monohalides MgX (X=F, Cl, Br, I).

    Science.gov (United States)

    Wu, Dong-Lan; Tan, Bin; Qin, Jiu-Ying; Wan, Hui-Jun; Xie, An-Dong; Yan, Bing; Ding, Da-Jun

    2015-11-01

    Ab initio calculations on potential energy curves (PECs), spectroscopic constants, transition dipole moments, radiative transition probabilities and lifetimes for the ground state (X(2)?(+)) and the first excited state (A(2)?) of MgX (X=F, Cl, Br, I) molecules are determined by high-level internally contracted multi-reference configuration interaction (ic-MRCI) method. In order to improve the calculation, the Davidson modification (+Q) and scalar relativistic correction are included. The present results show that most of spectroscopic constants are in accordance with the measurements, the equilibrium internuclear distance Re increases while the other spectroscopic constants reduce along with the increasing of the atomic number of the halogen from F to I. Diagonal vibrational transitions are found to be dominant for the A(2)??X(2)?(+) system of MgX molecules. The corresponding radiative lifetimes of ?'=0 are computed to be 7.24, 9.98, 18.94 and 22.72ns for MgF, MgCl, MgBr, and MgI, respectively. The calculated result of MgF molecule is in good agreement with the recent theoretical result of 7.16ns, with a small relative error percent of 1.11%. PMID:26072381

  9. Spectral band selection for classification of soil organic matter content

    Science.gov (United States)

    Henderson, Tracey L.; Szilagyi, Andrea; Baumgardner, Marion F.; Chen, Chih-Chien Thomas; Landgrebe, David A.

    1989-01-01

    This paper describes the spectral-band-selection (SBS) algorithm of Chen and Landgrebe (1987, 1988, and 1989) and uses the algorithm to classify the organic matter content in the earth's surface soil. The effectiveness of the algorithm was evaluated comparing the results of classification of the soil organic matter using SBS bands with those obtained using Landsat MSS bands and TM bands, showing that the algorithm was successful in finding important spectral bands for classification of organic matter content. Using the calculated bands, the probabilities of correct classification for climate-stratified data were found to range from 0.910 to 0.980.

  10. Photonic band structure of highly deformable, self-assembling systems

    OpenAIRE

    Bermel, Peter A.; Warner, Mark

    2001-01-01

    We calculate the photonic band structure at normal incidence of highly deformable, self-assembling systems - cholesteric elastomers subjected to external stress. Cholesterics display brilliant reflection and lasing owing to gaps in their photonic band structure. The band structure of cholesteric elastomers varies sensitively with strain, showing new gaps opening up and shifting in frequency. A novel prediction of a total band gap is made, and is expected to occur in the vici...

  11. Band offsets in heterojunctions between cubic perovskite oxides

    OpenAIRE

    Lebedev, Alexander I.

    2014-01-01

    The band offsets for nine heterojunctions between titanates, zirconates, and niobates with the cubic perovskite structure were calculated from first principles. The effect of strain in contacting oxides on their energy structure, many-body corrections to the position of the band edges (calculated in the GW approximation), and the splitting of the conduction band resulting from spin-orbit interaction were consistently taken into account. It was shown that the neglect of the m...

  12. Yrast Band in 122I and Band Termination

    International Nuclear Information System (INIS)

    High spin states of the odd-odd nucleus 122I have been investigated via the fusion-evaporation reaction 116Cd(11B, 5n) at a beam energy of 68 MeV. The yrast band is extended up to I? = (29+). The band termination at I? = (22+) reported in previous studies is confirmed and interpreted as arising from a shape change from collective prolate to noncollective oblate according to Total-Routhian-Surface (TRS) calculations. In addition, the I?=(29+) state is assigned to the [?h11/2(?g7/2)2]23/2-[(?h11/2)3(?d5/2)2]35/2- configuration corresponding to the full alignment of all valance nucleons outside the semi-closed shell.

  13. Collective bands in neutron-rich 104Mo nucleus

    International Nuclear Information System (INIS)

    Levels in the neutron-rich 104Mo nucleus have been investigated by observing prompt ?-rays from the spontaneous fission of 252Cf with the Gamma sphere detector array. The ground-state band, the one-phonon and the two-phonon ?-vibrational bands as well as a quasiparticle band have been confirmed and expanded with spin up to 14?. Other two side bands probably built on new quasiparticle states are identified. The possible configurations for the quasiparticle bands are discussed. Two of the quasiparticle bands show larger moments of inertia and may have pair-free characteristics. The levels of the ground-state band, the one-phonon ?-band and the two-phonon ?-band calculated from a general collective model are in close agreement with the experimental data

  14. Superconductivity in W{sub 5}SiB{sub 2} with the T{sub 2}-phase structure studied by the specific heat measurement and band structure calculation

    Energy Technology Data Exchange (ETDEWEB)

    Fukuma, M., E-mail: fukuma.0816@phys.aoyama.ac.jp [Department of Physics and Mathematics, Aoyama Gakuin University, Fuchinobe 5-10-1, Chuo-ku, Sagamihara-shi, Kanagawa 229-8558 (Japan); Kawashima, K.; Maruyama, M.; Akimitsu, J. [Department of Physics and Mathematics, Aoyama Gakuin University, Fuchinobe 5-10-1, Chuo-ku, Sagamihara-shi, Kanagawa 229-8558 (Japan)

    2011-11-15

    The new superconductor W{sub 5}SiB{sub 2} with the T{sub 2}-phase. H{sub C2} (0) is estimated in greater detail. W{sub 5}SiB{sub 2} can be described within the conventional framework of BCS theory. W d-orbital plays an important role for the superconductivity. The superconducting state of W{sub 5}SiB{sub 2} with the T{sub 2}-phase structure has been investigated by a specific heat measurement and a density of state calculation. The estimated {Delta}C{sub p}/{gamma}T{sub c} and 2{Delta}(0)/k{sub B}T{sub c} values are 1.49 and 3.32, which are close to 1.43 and 3.53 within the weak coupling regime. The electronic specific heat data clearly indicates the absence of gap nodes in the superconducting order parameter, suggesting an isotropic s-wave superconductor. From the density of state calculations, we found that W d-orbital plays an important role for the superconductivity in W{sub 5}SiB{sub 2}.

  15. Calculation of Spectra of Solids:

    DEFF Research Database (Denmark)

    Lindgård, Per-Anker

    1975-01-01

    The Gilat-Raubenheimer method simplified to tetrahedron division is used to calculate the real and imaginary part of the dynamical response function for electrons. A frequency expansion for the real part is discussed. The Lindhard function is calculated as a test for numerical accuracy. The conduction electron susceptibility is calculated for Gd, Tb and Dy using the RAPW energy bands by Keeton and Louks.

  16. Influence of band interaction on superdeformed rotational bands

    International Nuclear Information System (INIS)

    With the first discovery of high spin superdeformed (SD) band in 152Dy, more than 250 SD bands have been observed in A ? 190, 150, 130, 80 mass regions. Except for a few SD bands, the spins of most of them have not been established experimentally. The influence of band interaction on SD bands is investigated in detail. The results based on an analysis of the band-mixing of two bands for such bands will be presented

  17. Band parameters of N2O and CO2 determined by whole band analysis

    Science.gov (United States)

    Hawkins, R. L.; Hoke, M. L.; Shaw, J. H.

    1981-01-01

    Whole band analysis, a method of obtaining band parameters from spectra by nonlinear least squares fitting of calculated to observed spectra, has been applied to bands of N2O and CO2. The retrieved N2 broadened widths of the 02(0)00 - 00(0) and 12(0)0 - 00(0)0 bands of N2O suggest that the air broadened widths on the AFGL listing are about 10% high. The intensities and (C-12)(O-16)2 broadened widths of the 20002-00001 and 21102-01101 bands of (C-12)(O-16)(O-18) and the 20002-00001 band of (C-12)(O-16)(O-17) have also been determined.

  18. Plasmon bands in metallic nanostructures

    CERN Document Server

    Inglesfield, J E; Kemp, R

    2004-01-01

    The photonic band structure of a three-dimensional lattice of metal spheres is calculated using an embedding technique, in the frequency range of the Mie plasmons. For a small filling factor of the spheres, Maxwell-Garnett theory gives an almost exact description of the dipole modes, and the multipole modes are fairly dispersionless. For a larger filling factor, crystal field effects modify the multipole frequencies, which show dispersion. These multipole bands are enclosed between the dipole modes. For touching spheres, there is a wide continuum of plasmon modes between zero frequency and the bulk metal plasmon frequency, which yield strong absorption of incident light. These plasmon modes are responsible for the blackness of colloidal silver.

  19. Bolus calculators.

    Science.gov (United States)

    Schmidt, Signe; Nørgaard, Kirsten

    2014-09-01

    Matching meal insulin to carbohydrate intake, blood glucose, and activity level is recommended in type 1 diabetes management. Calculating an appropriate insulin bolus size several times per day is, however, challenging and resource demanding. Accordingly, there is a need for bolus calculators to support patients in insulin treatment decisions. Currently, bolus calculators are available integrated in insulin pumps, as stand-alone devices and in the form of software applications that can be downloaded to, for example, smartphones. Functionality and complexity of bolus calculators vary greatly, and the few handfuls of published bolus calculator studies are heterogeneous with regard to study design, intervention, duration, and outcome measures. Furthermore, many factors unrelated to the specific device affect outcomes from bolus calculator use and therefore bolus calculator study comparisons should be conducted cautiously. Despite these reservations, there seems to be increasing evidence that bolus calculators may improve glycemic control and treatment satisfaction in patients who use the devices actively and as intended. PMID:24876436

  20. Highly deformed Bands in 175Hf

    International Nuclear Information System (INIS)

    Two high-spin regularly spaced rotational bands with large dynamical moments of inertia have been identified in 175Hf with the Gammasphere spectrometer. These new bands are very similar to the previously identified triaxial superdeformed bands in the hafnium nuclei. However, the new bands in 175Hf have been linked into the known level scheme and thereby provide the first firm spin assignments for these structures in this region. In order to understand the new bands, theoretical calculations have been performed based on the ULTIMATE CRANKER code. The new bands in 175Hf are deduced to be built upon highly deformed structures. No experimental evidence for triaxiality was established and this work suggests that the structure of the so-called 'triaxial' superdeformed bands in the Hf nuclei may be quite different from those identified in the lighter mass Lu nuclei. Since the two highly deformed bands in 175Hf are associated with different deformations, this work also identifies the role of the intruder orbits in polarizing the nuclear shape

  1. Fluctuations in a superconducting quantum critical point of multi-band metals

    OpenAIRE

    Ramires, Aline; Continentino, Mucio A.

    2010-01-01

    In multi-band metals quasi-particles arising from different atomic orbitals coexist at a common Fermi surface. Superconductivity in these materials may appear due to interactions within a band (intra-band) or among the distinct metallic bands (inter-band). Here we consider the suppression of superconductivity in the intra-band case due to hybridization. The fluctuations at the superconducting quantum critical point (SQCP) are obtained calculating the response of the system t...

  2. Chiral bands in 105Rh

    Scientific Electronic Library Online (English)

    J.A., Alcántara-Núñez; J.R.B., Oliveira; E.W., Cybulska; N.H., Medina; M.N., Rao; R.V., Ribas; M.A., Rizzutto; W.A., Seale; F., Falla-Sotelo; K.T., Wiedemann; V.I., Dimitrov; S., Frauendorf.

    2004-09-01

    Full Text Available The 105Rh nucleus has been studied by in-beam gamma spectroscopy with the heavy-ion fusion-evaporation reaction 100Mo(11B, 02ngamma) at 43 MeV. A rich variety of structures was observed at high and low spin, using gamma - gamma - t and gamma - gamma - particle coincidences a [...] nd directional correlation ratios. Four magnetic dipole bands have also been observed at high spin. Two of them are nearly degenerate in excitation energy and could be chiral partners, as predicted by Tilted Axis Cranking calculations.

  3. Chiral bands in 105Rh

    International Nuclear Information System (INIS)

    The 105Rh nucleus has been studied by in-beam ? spectroscopy with the heavy-ion fusion-evaporation reaction 100Mo(11B, ?2n?) at 43 MeV. A rich variety of structures was observed at high and low spin, using ?-?-t and ?-?-particle coincidences and directional correlation ratios. Four magnetic dipole bands have also been observed at high spin. Two of them are nearly degenerate in excitation energy and could be chiral partners, as predicted by Tilted Axis Cranking calculations. (author)

  4. Photonic band structure and omnidirectional band gap in anisotropic superlattice

    Energy Technology Data Exchange (ETDEWEB)

    Ouchani, N.; Bria, D.; Nougaoui, A. [Laboratoire de Dynamique et d' Optique des Materiaux, Departement de Physique, Faculte des Sciences, Universite Mohamed I, B.P. 524, 60000 Oujda (Morocco); Djafari-Rouhani, B. [Laboratoire de Dynamique et Structure des Materiaux Moleculaires, UMR CNRS 8024, UFR de Physique, Universite de Lille 1, 59655 Villeneuve d' Ascq (France)

    2006-06-15

    We investigate theoretically the photonic band structure of one-dimensional superlattices (SL) composed of alternating anisotropic layers with their principal axes oriented at arbitrary directions. The dispersion relation of second order is calculated analytically by using the 4 x 4 matrix method which is based on the boundary conditions of the electric and magnetic fields at each interface. It is shown that such structures can exhibit coupled electromagnetic modes between transverse magnetic TM and transverse electric TE modes, and dispersion curves that do not exist in superlattices composed only of isotropic layers. For a given value of the wave vector k {sub ?} (parallel to the layers), the dispersion curves (frequency ?) versus k {sub B} (where k {sub B} is the Bloch wave vector of the periodic system along the axis of the superlattice) are illustrated. Specific applications of these results are given for the case of the biaxial superlattice. We show that with an appropriate choice of the superlattice parameters an absolute (or omnidirectional) band gap for these coupled electromagnetic waves can be obtained. The band gap width depends on the anisotropic parameters of the media forming the SL. (author)

  5. Magnetism in disjoint/non-disjoint composite bands

    Energy Technology Data Exchange (ETDEWEB)

    Hatanaka, Masashi, E-mail: mhatanaka@xug.biglobe.ne.jp [Department of Green and Sustainable Chemistry, School of Engineering, Tokyo Denki University, 2-2 Kanda Nishiki-cho, Chiyoda-ku, Tokyo 101-8457 (Japan)

    2012-01-02

    Graphical abstract: Non-bonding degenerate systems with disjoint/non-disjoint composite bands are suggested. Regardless of the disjoint bands, these systems are predicted to be ferromagnetic due to non-trivial exchange interactions in the non-disjoint bands. Highlights: Black-Right-Pointing-Pointer Non-bonding systems with disjoint/non-disjoint composite bands are suggested. Black-Right-Pointing-Pointer Regardless of the disjoint bands, these systems are predicted to be ferromagnetic. Black-Right-Pointing-Pointer Organic ferromagnets based on the composite bands are suggested. Black-Right-Pointing-Pointer Wannier analysis and DFT calculations supported the ferromagnetic interactions. - Abstract: Non-bonding degenerate systems with disjoint/non-disjoint composite bands are suggested. In these systems, one of the non-bonding bands is disjoint, and another is non-disjoint type. Whereas the Wannier functions in the former bands span no common atoms, the Wannier functions in the latter bands span common atoms. Regardless of the disjoint bands, these systems are predicted to be ferromagnetic due to non-trivial exchange interactions in the non-disjoint bands. The ferromagnetic interactions are supported by DFT calculations.

  6. Singing with the Band

    Science.gov (United States)

    Altman, Timothy Meyer; Wright, Gary K.

    2012-01-01

    Usually band, orchestra, and choir directors work independently. However, the authors--one a choral director, the other a band director--have learned that making music together makes friends. Not only can ensemble directors get along, but joint concerts may be just the way to help students see how music can reach the heart. Combined instrumental…

  7. Stretch Band Exercise Program

    Science.gov (United States)

    Skirka, Nicholas; Hume, Donald

    2007-01-01

    This article discusses how to use stretch bands for improving total body fitness and quality of life. A stretch band exercise program offers a versatile and inexpensive option to motivate participants to exercise. The authors suggest practical exercises that can be used in physical education to improve or maintain muscular strength and endurance,…

  8. Particle-rotor-model calculations in 125I

    Indian Academy of Sciences (India)

    Hariprakash Sharma; B Sethi; P Banerjee; Ranjana Goswami; R K Bhandari; Jahan Singh

    2001-07-01

    Recent experimental data on 125I has revealed several interesting structural features. These include the observation of a three quasiparticle band, prolate and oblate deformed bands, signature inversion in the yrast positive-parity band and identi?cation of the unfavoured $\\pi h_{11/2}$ band showing very large signature splitting. In the present work, particle-rotor-model calculations have been performed for the $\\pi h_{11/2}$ band, using an axially symmetric deformed Nilsson potential. The calculations reproduce the experimental results well and predict a moderate prolate quadrupole deformation of about 0.2 for the band.

  9. Two-Photon Absorption in Size-Quantized Semiconductors with Degenerated Valence Band

    OpenAIRE

    ISMAILOV, T. G.

    2000-01-01

    Two photon absorption in size-quantized films of semiconductors with degenerated band structures are investigated. The carrier energy spectrum and wavefunctions in the bands are calculated using two-band Kane model with spin taken into accont. Two-photon absorption coefficients for different polarizations of incident radiations are calculated. The strong dependence of two-photon absorption on polarizations are stated.

  10. New results on the superdeformed {sup 196}Pb nucleus: The decay of the excited bands to the yrast band

    Energy Technology Data Exchange (ETDEWEB)

    Bouneau, S.; Azaiez, F.; Duprat, J. [IPN, Orsay (France)] [and others

    1996-12-31

    The study of the superdeformed (SD) {sup 196}Pb nucleus has been revisited using the EUROGAM phase 2 spectrometer. In addition to the known yrast and two lowest excited SD bands, a third excited SD band has been seen. All of the three excited bands were found to decay to the yrast SD band through, presumably, E1 transitions, allowing relative spin and excitation energy assignments. Comparisons with calculations using the random-phase approximation suggest that all three excited bands can be interpreted as octupole vibrational structures.

  11. Progressive band processing of pixel purity index for hyperspectral imagery

    Science.gov (United States)

    Li, Yao; Gao, Cheng; Li, Hsiao-Chi; Song, Meiping; Chang, Chein-I.

    2015-05-01

    Pixel Purity Index (PPI) is a very popular endmember finding algorithm due to its availability in ENVI software. According to the band sequential (BSQ) format of data acquisition this paper introduces a new concept of executing PPI band-by-band in a progressive manner. It is called progressive band processing of PPI (PBP-PPI) which allows users to process PPI band by band without waiting for full bands of data information acquired. To accomplish this goal PPI must be capable of calculating and updating PPI counts of data samples band by band. Furthermore, progressive-band-processing progressive PPI (PBP-P-PPI) and progressive-band-processing causal PPI (PBP-C-PPI) are proposed to address the issues that the number of skewers is undefined and only partial pixels are available correspondingly. Many benefits can be gained from PBP-PPI, for example, providing progressive profiles of PPI counts of data samples as more bands are included for data processing, finding crucial bands according to progressive changes in PPI counts.

  12. Evolution of the Impurity Band to Diamond-Like Valence Bands in Boron Doped Diamond

    Science.gov (United States)

    Inushima, Takashi; Ota, Yuichi; Shiomi, Hiromu

    2014-02-01

    We present the absorption coefficient and the refractive index of boron doped diamond having an impurity band at 0.07 eV above the valence band maximum and compare them with those obtained by first principles calculation using a C63B supercell model containing 1.57% boron. These optical constants are in good accordance with each other, indicating that the impurity band that forms at 2p excited states of impurity boron becomes top of the valence bands in metallic condition. Based on this result we present a model of the evolution of boron atoms from isolated impurity to constituent atoms in the boron doped diamond, where the valence electrons of boron become to have k dependence and form the top of the valence bands of the C63B supercell diamond.

  13. Multi bunch dynamics in detuned x-band structures

    International Nuclear Information System (INIS)

    The multi bunch dynamics of a 2 x 250 GeV version of the JLC is studied. The rf-properties of detuned x-band tubes are calculated with the Computer codes URMEL and MAFIA. The dispersion curve found with these codes is compared with an equivalent circuit model. The calculation of the dipole mode loss parameters is investigated in detail. Tracking calculations are used to investigate the misalignment tolerances for detuned x-band structures. Also tilted x-band tubes are considered. (author)

  14. Band parameters of phosphorene

    Science.gov (United States)

    Voon, L. C. Lew Yan; Wang, J.; Zhang, Y.; Willatzen, M.

    2015-09-01

    Phosphorene is a two-dimensional nanomaterial with a direct band-gap at the Brillouin zone center. In this paper, we present a recently derived effective-mass theory of the band structure in the presence of strain and electric field, based upon group theory. Band parameters for this theory are computed using a first-principles theory based upon the generalized-gradient approximation to the density-functional theory. These parameters and Hamiltonian will be useful for modeling physical properties of phosphorene.

  15. Band parameters of phosphorene

    DEFF Research Database (Denmark)

    Lew Yan Voon, L. C.; Wang, J.

    2015-01-01

    Phosphorene is a two-dimensional nanomaterial with a direct band-gap at the Brillouin zone center. In this paper, we present a recently derived effective-mass theory of the band structure in the presence of strain and electric field, based upon group theory. Band parameters for this theory are computed using a first-principles theory based upon the generalized-gradient approximation to the density-functional theory. These parameters and Hamiltonian will be useful for modeling physical properties of phosphorene.

  16. Distribution Free Prediction Bands

    OpenAIRE

    Lei, Jing; Wasserman, Larry

    2012-01-01

    We study distribution free, nonparametric prediction bands with a special focus on their finite sample behavior. First we investigate and develop different notions of finite sample coverage guarantees. Then we give a new prediction band estimator by combining the idea of "conformal prediction" (Vovk et al. 2009) with nonparametric conditional density estimation. The proposed estimator, called COPS (Conformal Optimized Prediction Set), always has finite sample guarantee in a ...

  17. Supersymmetry and Identical Bands

    OpenAIRE

    Von Brentano, P.

    2003-01-01

    Supersymmetry as applied to identical bands is discussed. A review of the work of the Koeln-Dubna group on this topic is given and examples in 171,172Yb, 173,174Hf, and 195,194Pt are discussed. The role of pseudo-spin in the supersymmetry is investigated. A recent precision lifetime measurement for identical bands in 171,172Yb is discussed.

  18. Band structures and shape coexistence in {sup 187}Pt

    Energy Technology Data Exchange (ETDEWEB)

    Hojman, D. [Comision Nacional de Energia Atomica, Departamento de Fisica, Buenos Aires (Argentina); CONICET, Buenos Aires (Argentina); Cardona, M.A. [Comision Nacional de Energia Atomica, Departamento de Fisica, Buenos Aires (Argentina); CONICET, Buenos Aires (Argentina); Universidad Nacional de San Martin, Buenos Aires (Argentina); Roussiere, B.; Sauvage, J. [IN2P3/CNRS/Universite Paris-Sud, Institut de Physique Nucleaire, Orsay (France); Riley, M.A.; Tabor, S.L.; Hoffman, C.R.; Aguilar, A.; Cluff, W.T.; Hinners, T.; Lagergren, K.; Lee, S.; Perry, M.; Pipidis, A.; Tripathi, V. [Florida State University, Department of Physics, Tallahassee, Florida (United States)

    2012-06-15

    High-spin states in {sup 187}Pt have been studied by means of {gamma}-ray spectroscopy techniques. Known bands have been significantly extended and new bands have been found. The band structures are discussed in the framework of the cranking model and negative-parity states are compared with calculations performed with a semi-microscopic axial-rotor plus one-quasiparticle coupling model. Shape coexistence is observed from low excitation energy. (orig.)

  19. The alpha-cluster bands in 94Mo

    Scientific Electronic Library Online (English)

    Marco Antonio de, Souza; H., Miyake.

    2005-09-01

    Full Text Available The 94Mo nucleus is treated as an alpha-cluster interacting with an inert core through a phenomenological local potential. The properties of the ground state band of the alpha+90Zr system, such as the energy levels, intercluster rms radii and B(E2) transition strengths were calculated. These results [...] are compared with previous references and available experimental data. Some predictions were made concerning the negative parity band and the excited positive parity band.

  20. Band structures and shape coexistence in 187Pt

    International Nuclear Information System (INIS)

    High-spin states in 187Pt have been studied by means of ?-ray spectroscopy techniques. Known bands have been significantly extended and new bands have been found. The band structures are discussed in the framework of the cranking model and negative-parity states are compared with calculations performed with a semi-microscopic axial-rotor plus one-quasiparticle coupling model. Shape coexistence is observed from low excitation energy. (orig.)

  1. Band structure of SnTe studied by Photoemission Spectroscopy

    OpenAIRE

    Littlewood, P B; Mihaila, B.; Schulze, R. K.; Safarik, D. J.; Gubernatis, J. E.; Bostwick, A; Rotenberg, E.; Opeil, C.P.; Durakiewicz, T.; Smith, J. L.; J. C. Lashley

    2010-01-01

    We present an angle-resolved photoemission spectroscopy study of the electronic structure of SnTe, and compare the experimental results to ab initio band structure calculations as well as a simplified tight-binding model of the p-bands. Our study reveals the conjectured complex Fermi surface structure near the L-points showing topological changes in the bands from disconnected pockets, to open tubes, and then to cuboids as the binding energy increases, resolving lingering is...

  2. Optical band-gap determination of nanostructured WO3 film

    OpenAIRE

    Gonzalez-Borrero, P. P.; Sato, F.; Medina, A. N.; Baesso, M.L.; Bento, A.C.; Baldissera, G.; Persson, C.; Gunnar A. Niklasson; Granqvist, Claes Göran; da Silva, A. Ferreira

    2010-01-01

    The optical band-gap energy of a nanostructured tungsten trioxide film is determined using the photoacoustic spectroscopy method under continuous light excitation. The mechanism of the photoacoustic signal generation is discussed. The band-gap energy is also computed by other methods. The absorption coefficient as well as the band-gap energy of three different crystal structures of tungsten trioxide is calculated by a first-principles Green's function approach using the projector augmented wa...

  3. Loss of solutions in shear banding fluids in shear banding fluids driven by second normal stress differences

    CERN Document Server

    Skorski, Stanislav

    2011-01-01

    Edge fracture occurs frequently in non-Newtonian fluids. A similar instability has often been reported at the free surface of fluids undergoing shear banding, and leads to expulsion of the sample. In this paper the distortion of the free surface of such a shear banding fluid is calculated by balancing the surface tension against the second normal stresses induced in the two shear bands, and simultaneously requiring a continuous and smooth meniscus. We show that wormlike micelles typically retain meniscus integrity when shear banding, but in some cases can lose integrity for a range of average applied shear rates during which one expects shear banding. This meniscus fracture would lead to ejection of the sample as the shear banding region is swept through. We further show that entangled polymer solutions are expected to display a propensity for fracture, because of their much larger second normal stresses. These calculations are consistent with available data in the literature. We also estimate the meniscus di...

  4. Band moment of inertia in signature partner and identical SD bands in A = 190 mass region

    International Nuclear Information System (INIS)

    Since the observation of the first high spin superdeformed (SD) band in 152Dy, they have been discovered and intensively studied in several mass regions A ? 190, 150, 130 and 80. However, it is still difficult to observe the links between the SD bands and normal deformed (ND) states with known spins. Therefore, the exact excitations energies, spins, and parities of SD bands remain uncertain. The discrete ?-rays connecting the states of the yrast SD band 194Hg(1) to ND states with known spins were observed and the spins and excitation energies of all members of 194Hg(1) band were established experimentally. Recently, a link between SD and ND bands has also been observed in 190Hg. Therefore, the measured spins of these SD bands provide a significant test of the validity of the approaches to fix the spins of the SD bands. It is noted that all the available approaches profit from the comparison of the calculated transition energies or dynamic moment of inertia with the experimental results and usually are referred to as the best fit method (BFM). This also implies that the kinematic moment of inertia is also not a well established quantity

  5. Structure of negative parity yrast bands in odd mass 125-131Ce nuclei

    Indian Academy of Sciences (India)

    Arun Bharti; Suram Singh; S K Khosa

    2010-04-01

    The negative parity yrast bands of neutron-deficient 125-131Ce nuclei are studied by using the projected shell model approach. Energy levels, transition energies and $B(M1)/B(E2)$ ratios are calculated and compared with the available experimental data. The calculations reproduce the band-head spins of negative parity yrast bands and indicate the multi-quasiparticle structure for these bands.

  6. Rotational analysis of CO2 bands near 4 microns

    Science.gov (United States)

    Hoke, M. L.; Shaw, J. H.

    1982-01-01

    The band constants of CO2 bands near 2600 per cm have been estimated by the nonlinear least squares method and spectral curve fitting. The synthetic spectra calculated from these constants predict experimental values accurately and give very similar values for the line positions (to within 0.003 per cm for all but the weakest lines).

  7. Study of positive parity bands in 137Pr

    International Nuclear Information System (INIS)

    In this paper the analysis and interpretation of the positive parity states in 137Pr have been reported. The detailed interpretation with configuration assignments and the calculations for the bands will be reported

  8. Quantitative analysis on electric dipole energy in Rashba band splitting

    Science.gov (United States)

    Hong, Jisook; Rhim, Jun-Won; Kim, Changyoung; Ryong Park, Seung; Hoon Shim, Ji

    2015-09-01

    We report on quantitative comparison between the electric dipole energy and the Rashba band splitting in model systems of Bi and Sb triangular monolayers under a perpendicular electric field. We used both first-principles and tight binding calculations on p-orbitals with spin-orbit coupling. First-principles calculation shows Rashba band splitting in both systems. It also shows asymmetric charge distributions in the Rashba split bands which are induced by the orbital angular momentum. We calculated the electric dipole energies from coupling of the asymmetric charge distribution and external electric field, and compared it to the Rashba splitting. Remarkably, the total split energy is found to come mostly from the difference in the electric dipole energy for both Bi and Sb systems. A perturbative approach for long wave length limit starting from tight binding calculation also supports that the Rashba band splitting originates mostly from the electric dipole energy difference in the strong atomic spin-orbit coupling regime.

  9. New materials for intermediate band photovoltaic cells. A theoretical and experimental approach

    OpenAIRE

    Wahnón Benarroch, Perla; Palacios Clemente, Pablo; Aguilera Bonet, Irene; Seminóvski Pérez, Yohanna; Conesa, Jose Carlos; Lucena, Raquel

    2010-01-01

    Density functional theory calculations of certain transition-metal doped semiconductors show a partially occupied relatively narrow band located between valence band and conduction band. These novel systems, containing the metallic band, are called intermediate-band materials. They have enhanced optoelectronic properties which allow an increase in solar energy conversion efficiency of conventional solar cells. We previously proposed III-V, chalcopyrite and sulfide derived compounds show...

  10. Photonic band structure and omnidirectional band gap in anisotropic superlattice

    International Nuclear Information System (INIS)

    We investigate theoretically the photonic band structure of one-dimensional superlattice (SL) composed of alternating anisotropic layers with their principal axis oriented at arbitrary directions. The dispersion relation of order two is calculated analytically by using the 4 x 4 matrix method which is based on boundary conditions of the electric and magnetic fields at each interface. It is shown that such structures can exhibit coupled electromagnetic modes between transverse magnetic TM and transverse electric TE modes, and dispersion curves that do not exist in superlattices composed only of isotropic layers. For a given value of the wave vector kparallel (parallel to the layers), the dispersion curves (frequency ?) versus kB (where kB is the Bloch wave vector of the periodic system along the axis of the superlattice) is illustrated. Specific applications of these results are given for the case of biaxial superlattice. With an appropriate choice of the superlattice parameters, we show that it is possible to realise, for these coupled electromagnetic waves, an absolute (or omnidirectional) band gap of width depending on the anisotropic parameters of the media forming the SL. (author)

  11. Band structures of 121,123I

    International Nuclear Information System (INIS)

    The band structures of 121,123I nuclei have been studied using a version of the particle-rotor-model in which the experimental excitation energies of the neighbouring (A-1) cores can be fed directly as input parameters. The calculations have been carried out with axially symmetric Nilsson potential with both prolate and oblate deformations. The parameters of the model have been chosen from earlier theoretical work and experimental odd-even mass differences. Only the Coriolis attenuation factor has been treated as adjustable parameter. The theoretical band structures are in very good agreement with the available experimental data. (orig.)

  12. Bulk band structure of Bi2Te3

    DEFF Research Database (Denmark)

    Michiardi, Matteo; Aguilera, Irene; Bianchi, Marco; Eustáquio de Carvalho, Vagner; Orlando Ladeira, Luiz; Gomes Teixeira, Nayara; Avellar Soares, Edmar; Friedrich, Christoph; Blügel, Stefan; Hofmann, Philip

    2014-01-01

    The bulk band structure of Bi2Te3 has been determined by angle-resolved photoemission spectroscopy and compared to first-principles calculations. We have performed calculations using the local density approximation (LDA) of density functional theory and the one-shot GW approximation within the all-electron full-potential linearized augmented-plane-wave (FLAPW) formalism, fully taking into account spin-orbit coupling. Quasiparticle effects produce significant changes in the band structure of Bi2T...

  13. Band Gaps and Single Scattering of Phononic Crystal

    OpenAIRE

    Xiaoyi Huang; Jingcui Peng; Huanyou Wang; Gui Jin

    2011-01-01

    A method is introduced to study the transmission and scattering properties of acoustic waves in two–dimen- sional phononic band gap (PBG) materials. First, it is used to calculate the transmission coefficients of PBG samples. Second, the transmitted power is calculated based on the far field approach. We have also calcu- lated the scattering cross section, the results indicate that phononic band gap appear in frequency regions between two well separated resonance states.

  14. Distribution Free Prediction Bands

    CERN Document Server

    Lei, Jing

    2012-01-01

    We study distribution free, nonparametric prediction bands with a special focus on their finite sample behavior. First we investigate and develop different notions of finite sample coverage guarantees. Then we give a new prediction band estimator by combining the idea of "conformal prediction" (Vovk et al. 2009) with nonparametric conditional density estimation. The proposed estimator, called COPS (Conformal Optimized Prediction Set), always has finite sample guarantee in a stronger sense than the original conformal prediction estimator. Under regularity conditions the estimator converges to an oracle band at a minimax optimal rate. A fast approximation algorithm and a data driven method for selecting the bandwidth are developed. The method is illustrated first in simulated data. Then, an application shows that the proposed method gives desirable prediction intervals in an automatic way, as compared to the classical linear regression modeling.

  15. Photoemission and Band Structure

    International Nuclear Information System (INIS)

    Principally through experimental work in the past twenty-five years, it has become apparent that in most solids photoemission is a process in which the photoelectron is excited a significant distance from the surface and the optical excitation process is closely related to the electronic or band structure of the solid. After excitation, the electron must pass through a certain distance of the solid before it can reach the surface and escape into vacuum. Both the excitation and escape processes depend on the electronic or band structure of the solid. By making three types of measurement: (1) the spectral distribution of the quantum yield, (2) the energy distribution of the electrons excited by monochromatic light, and (3) that of the optical constants of the solid, much can often be learned about the band structure of the solid. Conversely, the quantum structure (band structure, phonon spectra, etc. ) determines the manner in which electrons are optically excited in the solid and the probability of their moving to the surface. The probability of escape over the surface is determined by the potential barrier at the surface, (i. e. the work function of a metal or electron affinity of a semiconductor or insulator). In this paper a simple relationship will first be developed between parameters of the electronic structure such as the band structure and the height of the surface potential barrier on the one hand and the photoemission quantities such as the quantum yield and energy distributions on the other hand. This part of the paper will be illustrated by examples from specific solids. The last part of the paper will take the opposite approach. Here we will show how photoemission and optical measurements can be used to determine important apsects of the band structure. Illustrations will be given from semiconductors such as Si, GaAs and CdTe and from metals such as Cu and Ni. (author)

  16. Banded transformer cores

    Science.gov (United States)

    Mclyman, C. W. T. (inventor)

    1974-01-01

    A banded transformer core formed by positioning a pair of mated, similar core halves on a supporting pedestal. The core halves are encircled with a strap, selectively applying tension whereby a compressive force is applied to the core edge for reducing the innate air gap. A dc magnetic field is employed in supporting the core halves during initial phases of the banding operation, while an ac magnetic field subsequently is employed for detecting dimension changes occurring in the air gaps as tension is applied to the strap.

  17. Ultra wide band antennas

    CERN Document Server

    Begaud, Xavier

    2013-01-01

    Ultra Wide Band Technology (UWB) has reached a level of maturity that allows us to offer wireless links with either high or low data rates. These wireless links are frequently associated with a location capability for which ultimate accuracy varies with the inverse of the frequency bandwidth. Using time or frequency domain waveforms, they are currently the subject of international standards facilitating their commercial implementation. Drawing up a complete state of the art, Ultra Wide Band Antennas is aimed at students, engineers and researchers and presents a summary of internationally recog

  18. Scaling and paleodepth of compaction bands, Nevada and Utah

    Science.gov (United States)

    Schultz, Richard A.

    2009-03-01

    Measurements of the lengths and thicknesses of compaction bands in Navajo Sandstone from the Buckskin Gulch, Utah, field site demonstrate displacement-length scaling with a power law exponent of ˜0.5, consistent with previous values obtained independently for compaction bands from the Valley of Fire, southern Nevada, site. Compaction energies calculated in this paper for the Utah bands, Gc = 55-120 kJ/m2, and for the Nevada bands, Gc = 30-60 kJ/m2, are consistent with those estimated from laboratory experiments despite major differences in band length, thickness, degree of grain fracturing, and remote stress state. Using the field measurements of bands from both sites in the recently proposed inverse relation between the magnitude of remote band-normal compression and compaction band thickness predicts values of band-normal compression of 24-30 MPa for the Utah bands and 31-62 MPa for the Nevada bands. Given that compaction bands at both sites are steeply dipping, these values correspond to a regional tectonic compression oriented subhorizontally at the time of band growth. The results suggest that the compaction bands formed at relatively shallow paleodepths of 0.92-1.3 km at the Utah site and 0.54-1.1 km at the Nevada site, in accord with estimates of the thickness of overlying stratigraphic cover during Sevier-Laramide deformation at both sites. Growth of compaction bands at both field sites was likely facilitated by favorable host rock properties (well-sorted, coarse-grained, high-porosity sandstone sequences) deformed within a thrust faulting tectonic environment.

  19. Two dimensional rotational band searching technique

    International Nuclear Information System (INIS)

    A method for searching for rotational band structures in multidimensional data sets will be discussed. By ordering ?-ray transition energies E3 > E2 > E1, and plotting E3 - E2 vs. E2 - E1, one produces a characteristic spot pattern that depends upon the dynamic moment-of-inertia of the nucleus. We have developed a simple model to calculate such spot patterns using the rotational model equation: E(I) = AI(I+ 1)+BI2(I+ 1)2 +CI3(I+1)3+.... Calculated patterns for superdeformed bands using two parameters (A, B) and three parameters (A, B, C) will be shown and compared to experimental data for 193Pb and 194Pb. The calculated pattern is compared to the experimental pattern by generating a open-quotes figure-of-meritclose quotes, X2 = ?ij (ICij-Ixij)2/N, where Ic is the calculated intensity in channel ij, Ix is the experimental intensity in that channel, and N is the total number of channels (for normalization). Searches for new bands can be performed by generating gated E3 - E2 vs. E2 - E1 experimental spectra, calculating spot patterns for reasonable ranges of A, B and C parameters, and finally calculating X2 for all calculated patterns for all experimental spectra and investigating the promising X2 valuesA method for searching for rotational band structures in multidimensional data sets will be discussed. By ordering ?-ray transition energies E3 > E2 > E1, and plotting E3 - E2 vs. E2 - E1, one produces a characteristic spot pattern that depends upon the dynamic moment-of-inertia of the nucleus. We have developed a simple model to calculate such spot patterns using the rotational model equation: E(I) = AI(I+ 1)+BI2(I+ 1)2 +CI3(I+1)3+.... Calculated patterns for superdeformed bands using two parameters (A, B) and three parameters (A, B, C) will be shown and compared to experimental data for 193Pb and 194Pb. The calculated pattern is compared to the experimental pattern by generating a open-quotes figure-of-meritclose quotes, X2 = ?ij (ICij-Ixij)2/N, where Ic is the calculated intensity in channel ij, Ix is the experimental intensity in that channel, and N is the total number of channels (for normalization). Searches for new bands can be performed by generating gated E3 - E2 vs. E2 - E1 experimental spectra, calculating spot patterns for reasonable ranges of A, B and C parameters, and finally calculating X2 for all calculated patterns for all experimental spectra and investigating the promising X

  20. Polymer photonic band-gaps fabricated by nanoimprint lithography

    Science.gov (United States)

    Reboud, V.; Kehoe, T.; Romero Vivas, J.; Kehagias, N.; Zelsmann, M.; Alsina, F.; Sotomayor Torres, C. M.

    2012-10-01

    We report on the fabrication and characterization of photonic band-gaps structures by nanoimprint lithography in a dye-doped polymer. Photonic band calculations show that photonic crystal slabs composed of a triangular array of polymer pillars could exhibit photonic band-gaps for the magnetic-like modes. The resulting structures show that the nanoimprint lithography process is well-suited to fabricate in a single-step process, these challenging photonic structures opening perspectives to realize integrated photonic band-gap circuits.

  1. Multiple antimagnetic rotation bands in odd-A 107Cd

    Science.gov (United States)

    Choudhury, Deepika; Jain, A. K.; Kumar, G. Anil; Kumar, Suresh; Singh, Sukhjeet; Singh, P.; Sainath, M.; Trivedi, T.; Sethi, J.; Saha, S.; Jadav, S. K.; Naidu, B. S.; Palit, R.; Jain, H. C.; Chaturvedi, L.; Pancholi, S. C.

    2013-03-01

    Lifetimes of the excited states of a pair of positive-parity ?I=2 bands of 107Cd have been measured by using the Doppler-shift attenuation method. The obtained B(E2) transition rates significantly decrease with increasing spin, a behavior typical of antimagnetic rotation (AMR). The observed results, interpreted by the semiclassical model (SCM) calculations, confirm these bands to be AMR bands resulting from the coupling of a pair of high-? g9/2 proton holes to aligned g7/2(h11/2)2 neutron particles. This is the first evidence for two AMR bands in a single nucleus.

  2. Multiple superdeformed bands in Sr, Y, and Zr nuclei

    International Nuclear Information System (INIS)

    Multiple superdeformed bands in the nuclei 80-83Sr, 82-84Y, and 83,84Zr have been studied in a backed-target experiment using the Gammasphere and Microball detector arrays. For 15 bands in these nuclei, average transition quadrupole moments (Qt) have been measured accurately. Among those are two pairs of 'isospectral' bands and the Qt values obtained in each case are nearly identical. The measured Qt values and dynamical moments of inertia place stringent conditions on configuration assignments for the bands obtained from mean field calculations

  3. Photonic band structure of highly deformable, self-assembling systems

    CERN Document Server

    Bermel, P A; Bermel, Peter A.; Warner, Mark

    2001-01-01

    We calculate the photonic band structure at normal incidence of highly deformable, self-assembling systems - cholesteric elastomers subjected to external stress. Cholesterics display brilliant reflection and lasing owing to gaps in their photonic band structure. The band structure of cholesteric elastomers varies sensitively with strain, showing new gaps opening up and shifting in frequency. A novel prediction of a total band gap is made, and is expected to occur in the vicinity of the previously observed de Vries bandgap, which is only for one polarisation.

  4. Wobbling motion in the multi-bands crossing region

    OpenAIRE

    Oi, Makito; Ansari, Ahmad; Horibata, Takatoshi; Onishi, Naoki

    1998-01-01

    The backbending in the A=180 mass region is expected to be caused by multi-bands crossing between low-K (g- and s-bands) and high-K bands. % We analyze a mechanism of coupling of these bands in terms of a dynamical treatment for nuclear rotations, i.e., the wobbling motion. The wobbling states are produced through the generator coordinate method after angular momentum projection, in which the intrinsic states are constructed through the 2d-cranked HFB calculations.

  5. DUAL BAND MONOPOLE ANTENNA DESIGN

    Directory of Open Access Journals (Sweden)

    P. Jithu

    2013-06-01

    Full Text Available The WLAN and Bluetooth applications become popular in mobile devices, integrating GSM and ISM bands operation in one compact antenna, can reduce the size of mobile devices. Recently, lot many investigations are carried out in designing a dual band antennas with operating frequencies in GSM band and in ISM band for mobile devices. Printed monopoles are under this investigation. In this paper, dual-band printed monopoles are presented to operate at GSM band i.e. 900 MHz and ISM band i.e. 2.4 GHz. We intend to observe the antenna characteristics on the network analyzer and verify the theoretical results with the practical ones.

  6. Calculation Software

    Science.gov (United States)

    1994-01-01

    MathSoft Plus 5.0 is a calculation software package for electrical engineers and computer scientists who need advanced math functionality. It incorporates SmartMath, an expert system that determines a strategy for solving difficult mathematical problems. SmartMath was the result of the integration into Mathcad of CLIPS, a NASA-developed shell for creating expert systems. By using CLIPS, MathSoft, Inc. was able to save the time and money involved in writing the original program.

  7. Burnout calculation

    International Nuclear Information System (INIS)

    Reviewed is the effect of heat flux of different system parameters on critical density in order to give an initial view on the value of several parameters. A thorough analysis of different equations is carried out to calculate burnout is steam-water flows in uniformly heated tubes, annular, and rectangular channels and rod bundles. Effect of heat flux density distribution and flux twisting on burnout and storage determination according to burnout are commended

  8. Amniotic band syndrome.

    Science.gov (United States)

    Shetty, Prathvi; Menezes, Leo Theobald; Tauro, Leo Francis; Diddigi, Kumar Arun

    2013-10-01

    Amniotic band syndrome is an uncommon congenital disorder without any genetic or hereditary disposition. It involves fetal entrapment in strands of amniotic tissue and causes an array of deletions and deformations. Primary treatment is plastic and reconstructive surgery after birth with in utero fetal surgery also coming in vogue. PMID:24426485

  9. Amniotic Band Syndrome

    OpenAIRE

    Shetty, Prathvi; Menezes, Leo Theobald; Tauro, Leo Francis; Diddigi, Kumar Arun

    2012-01-01

    Amniotic band syndrome is an uncommon congenital disorder without any genetic or hereditary disposition. It involves fetal entrapment in strands of amniotic tissue and causes an array of deletions and deformations. Primary treatment is plastic and reconstructive surgery after birth with in utero fetal surgery also coming in vogue.

  10. Linear methods in band theory

    DEFF Research Database (Denmark)

    Andersen, O. Krogh

    1975-01-01

    Two approximate methods for solving the band-structure problem in an efficient and physically transparent way are presented and discussed in detail. The variational principle for the one-electron Hamiltonian is used in both schemes, and the trial functions are linear combinations of energy-independent augmented plane waves (APW) and muffin-tin orbitals (MTO), respectively. The secular equations are therefore eigenvalue equations, linear in energy. The trial functions are defined with respect to a muffin-tin (MT) potential and the energy bands depend on the potential in the spheres through potential parameters which describe the energy dependence of the logarithmic derivatives. Inside the spheres, the energy-independent APW is that linear combination of an exact solution, at the arbitrary but fixed energy E?, and its energy derivative which matches continuously and differentiably onto the plane-wave part in the interstitial region. The energies obtained with the linear-APW method for the MT potential have errors of order (E-Ev)4. Similarly, the energy-independent MTO is that linear combination which matches onto that solution of the Laplace equation in the interstitial region which is regular at infinity. The energies obtained with the linear-MTO method have additional errors of order (E-Vmtz)2, arising from the interstitial region where the potential is Vmtz. The linear-APW (LAPW) method combines desirable features of the APW and OPW methods; it can treat d bands, the energy dependence of its pseudopotential is linear and, owing to the smoothness of the energy-independent APW at the spheres, non-MT contributions to the potential are included principally through their Fourier components. The linear-MTO (LMTO) method is particularly suited for closely packed structures and it combines desirable features of Korringa-Kohn-Rostoker, linear-combination-of-atomic-orbitals, and cellular methods; the secular matrix is linear in energy, the overlap integrals factorize as potential parameters and structure constants, the latter are canonical in the sense that they neither depend on the energy nor the cell volume and they specify the boundary conditions on a single MT or atomic sphere in the most convenient way. This method is very well suited for self-consistent calculations. The empty-lattice test is applied to the linear-MTO method and the free-electron energy bands are accurately reproduced. Finally, it is shown how relativistic effects may be included in both the LAPW and LMTO methods.

  11. Symmetrical band-pass loudspeaker systems

    Science.gov (United States)

    Matusiak, Grzegorz Piotr

    2001-12-01

    Loudspeaker systems are analyzed in a doctoral dissertation. The dissertation concerns loudspeaker systems, which are known as subwoofers or band-pass loudspeaker systems. Their advantages include: high- quality sound reproduction in the low-frequency range, small dimensions, small nonlinear distortions and the fact that they can be placed anywhere in a room or car. Band-pass loudspeaker systems are used widely in the so- called Home Theatre as well as to provide sound in cinema, theatre, concert, discotheque, opera, operetta, philharmonic and amphitheater halls, at open-air concerts, and so on. Various designs are mass-produced by a large number of manufacturers. The study covers an analysis of band-pass loudspeaker systems to which the frequency transformation, i.e. the reactance transformation, has been applied. Since this is a symmetrical transformation, amplitude frequency responses of the studied band-pass systems are also symmetrical (logarithmic scale of a frequency). As a result, the high-pass loudspeaker system design method, known as the Thiele-Small, Benson analysis, can be employed. The investigations include the formulation of band-pass system equations (fourth, sixth and eighth-order polynomials) and the subsequent derivation of relations for the calculation of system parameters. The obtained results enable the calculation of optimum designs for prescribed alignments, e.g. (Chebyshev) equal-ripple, (Butterworth) maximally flat, or quasi-maximally flat (QB). The analysis covers fourth, sixth and eighth-order symmetrical systems. Eighth-order systems have been divided into three kinds according to three ways of physical realization. The doctoral dissertation includes band-pass loudspeaker systems, which can be designed with active or passive filters or without the filter. Designed systems consist of a loudspeaker whose front of a diaphragm is loaded with a Helmholtz resonator, i.e. an enclosure with a vent, which radiates sound outwards. The back is loaded with a closed-box or the Helmholtz resonator.

  12. Calculator calculus

    CERN Document Server

    McCarty, George

    1982-01-01

    How THIS BOOK DIFFERS This book is about the calculus. What distinguishes it, however, from other books is that it uses the pocket calculator to illustrate the theory. A computation that requires hours of labor when done by hand with tables is quite inappropriate as an example or exercise in a beginning calculus course. But that same computation can become a delicate illustration of the theory when the student does it in seconds on his calculator. t Furthermore, the student's own personal involvement and easy accomplishment give hi~ reassurance and en­ couragement. The machine is like a microscope, and its magnification is a hundred millionfold. We shall be interested in limits, and no stage of numerical approximation proves anything about the limit. However, the derivative of fex) = 67.SgX, for instance, acquires real meaning when a student first appreciates its values as numbers, as limits of 10 100 1000 t A quick example is 1.1 , 1.01 , 1.001 , •••• Another example is t = 0.1, 0.01, in the functio...

  13. Reliability calculations

    International Nuclear Information System (INIS)

    Risk and reliability analysis is increasingly being used in evaluations of plant safety and plant reliability. The analysis can be performed either during the design process or during the operation time, with the purpose to improve the safety or the reliability. Due to plant complexity and safety and availability requirements, sophisticated tools, which are flexible and efficient, are needed. Such tools have been developed in the last 20 years and they have to be continuously refined to meet the growing requirements. Two different areas of application were analysed. In structural reliability probabilistic approaches have been introduced in some cases for the calculation of the reliability of structures or components. A new computer program has been developed based upon numerical integration in several variables. In systems reliability Monte Carlo simulation programs are used especially in analysis of very complex systems. In order to increase the applicability of the programs variance reduction techniques can be applied to speed up the calculation process. Variance reduction techniques have been studied and procedures for implementation of importance sampling are suggested. (author)

  14. Magnetic and Cohesive Properties from Cononical Bands

    DEFF Research Database (Denmark)

    Poulsen, U. K.; Kollar, J.; Andersen, O. K.

    1976-01-01

    The atomic volumes, the bulk moduli, the magnetizations, the gain susceptibilities and the derivatives of these quantities with respect to pressure have been obtained from first principles for Fe, Ni, Rh, Pd, Ir and Pt at 0K using canonical band theory and the local spin-density approximation for exchange and correlation. The agreement with experiment is surprisingly good. For Fe the calculated ferromagnetic contribution to the pressure is nearly large enough to account for the relative softness...

  15. Rotational and vibrational bands in 108Pd

    Scientific Electronic Library Online (English)

    J.A., Alcántara-Núñez; J.R.B., Oliveira; E.W., Cybulska; N.H., Medina; M.N., Rao; R.V., Ribas; M.A., Rizzutto; W.A., Seale; F., Falla-Sotelo.

    2004-09-01

    Full Text Available The 108Pd nucleus has been studied with the 100Mo(11B, p2ngamma) reaction at 43 MeV incident energy. gamma -gamma - t, gamma -gamma - charged particle coincidences and directional correlation ratios were measured using the gamma spectrometer formed by four Compton suppressed HPGe detectors and a 4pi [...] charged-particle ancillary detector system. The struture of the bands was interpreted within the framework of the cranked shell model and total Routhian calculations.

  16. CMB Broad-Band Power Spectrum Estimation

    OpenAIRE

    Bond, J. Richard

    1994-01-01

    The natural outcome of theoretical calculations of microwave background anisotropy is the angular power spectrum ${\\cal C}_\\ell$ as a function of multipole number $\\ell$. Experimental ${\\cal C}_\\ell$'s are needed for direct comparison. Estimation procedures using statistics linear in the pixel amplitudes as well as the conventional but less useful quadratic combinations are described. For most current experiments, a single broad-band power amplitude is all that one can get w...

  17. Rotational and vibrational bands in 108Pd

    International Nuclear Information System (INIS)

    The 108Pd nucleus has been studied with the 100Mo(11B, p2n?) reaction at 43 MeV incident energy. ?-?-t, ?-?-charged particle coincidences and directional correlation ratios were measured using the ? spectrometer formed by four Compton suppressed HPGe detectors and a 4? charged-particle ancillary detector system. The structure of the bands was interpreted within the framework of the cranked shell model and total Routhian calculations. (author)

  18. The demodulated band transform

    CERN Document Server

    Kovach, Christopher K

    2015-01-01

    Background: Windowed Fourier decompositions (WFD) are widely used in measuring stationary and non-stationary spectral phenomena and in describing pairwise relationships among multiple signals. Although a variety of WFDs see frequent application in electrophysiological research, including the short-time Fourier transform, continuous wavelets, band-pass filtering and multitaper-based approaches, each carries certain drawbacks related to computational efficiency and spectral leakage. This work surveys the advantages of a WFD not previously applied in electrophysiological settings. New Methods: A computationally efficient form of complex demodulation, the demodulated band transform (DBT), is described. Results: DBT is shown to provide an efficient approach to spectral estimation with minimal susceptibility to spectral leakage. In addition, it lends itself well to adaptive filtering of non-stationary narrowband noise. Comparison with existing methods: A detailed comparison with alternative WFDs is offered, with an...

  19. Rotational band 111Sn

    International Nuclear Information System (INIS)

    Partial level scheme of the neutron deficient 111Sn isotope is established upto an excitation energy of about 9 MeV and I? = 43/2- from ?-rays following 103Rh(12C,p3n) reaction. Clear evidence for the existence of a negative parity rotational band above I? = 23/2-, most probably based on 3p-2h configuration, is obtained. (orig.)

  20. Ab Initio Calculations of Oxosulfatovanadates

    DEFF Research Database (Denmark)

    Frøberg, Torben; Johansen, Helge

    1996-01-01

    Restricted Hartree-Fock and multi-configurational self-consistent-field calculations together with secondorder perturbation theory have been used to study the geometry, the electron density, and the electronicspectrum of (VO2SO4)-. A bidentate sulphate attachment to vanadium was found to be stable with anO-V-O angle of 72.5 degrees . The calculated spectrum shows bands in reasonable agreement with anexperimental spectrum which has been attributed to (VO2SO4)-. The geometry and the electron densi...

  1. Bandcrossing of magnetic rotation bands in 137Pr

    International Nuclear Information System (INIS)

    The odd mass nucleus 137Pr has been studied to high spins in order to investigate the magnetic rotation phenomenon in mass 130 region using the 122Sn(19F,4n)137Pr reaction at a beam energy of 80 MeV. A known ?I=1 band has been extended to J?=47/2- with the addition of three new transitions. Directional Correlation of Oriented Nuclei (DCO) ratios and linear polarization measurements have been performed to assign the multipolarities of gamma transitions and the spins and parities of the energy levels in this band, now established as the M1 band. The combination of M1 transitions along with cross over E2 transitions have been observed in this band for the first time. The experimentally deduced B(M1)/B(E2) ratios show a decrease with increasing spin after band-crossing suggesting magnetic rotation. TAC calculations for the 3qp: ?h11/2 x ?(h11/2)-2 configuration reproduce the experimental observations in the lower spin part of the ?I=1 band and the 5qp: ?h11/2(g7/2)2 x ?(h11/2)-2 configuration reproduces the ?I=1 band at higher spins; the crossing of the bands based on the two configuration leads to a back-bending also. Theoretical calculations also support a magnetic rotation nature for both the configurations

  2. Comparison of broad-band and narrow-band red and near-infrared vegetation indices

    International Nuclear Information System (INIS)

    An experiment has been conducted in which narrow-band field reflectance spectra were acquired of a rooted pinyon pine canopy with five different gravel backgrounds. Leaf area was successively removed as the measurements were repeated. From these reflectance spectra, narrow-band and broad-band (AVHRR, TM, MSS) red and near-infrared (NIR) vegetation index values were calculated. The performance of the vegetation indices was evaluated based on their capability to accurately estimate leaf area index (LAI) and percent green cover. Background effects were found for each of the tested vegetation indices. However, the background effects are most pronounced in the normalized difference vegetation index (NDVI) and ratio vegetation index (RVI). Background effects can be reduced using either the perpendicular vegetation index (PVI) or soil adjusted vegetation index (SAVI) formulations. The narrow-band versions of these vegetation indices had only slightly better accuracy than their broad-band counterparts. The background effects were minimized using derivative based vegetation indices, which measure the amplitude of the chlorophyll red-edge using continuous narrow-band spectra from 626 nm to 795 nm. (author)

  3. Noise exposure in marching bands

    Science.gov (United States)

    Keefe, Joseph

    2005-09-01

    Previous studies involving orchestras have shown that music ensembles can produce hazardous noise levels. There are no similar data for marching bands and pep bands. In order to evaluate the noise levels produced by marching and pep bands, 1/3-octave-band sound-pressure levels were measured while these groups rehearsed and performed. Data were collected while marching with the bands to ensure a realistic environment. Comparing these data to OSHA and NIOSH criteria, marching and pep band exposures often exceed safe values. For typical exposures, OSHA doses range from 11% to 295%, while NIOSH doses range from 35% to 3055%. Exposures that would be considered hazardous in the workplace are common in marching and pep bands; students and band directors should take steps to recognize the risk posed by various instruments and various locations, and should implement hearing conservation efforts.

  4. Band structures of defective graphenes

    Energy Technology Data Exchange (ETDEWEB)

    Hatanaka, Masashi, E-mail: mhatanaka@xug.biglobe.ne.j [Department of Green and Sustainable Chemistry, School of Engineering, Tokyo Denki University, 2-2 Kanda Nishiki-cho, Chiyoda-ku, Tokyo 101-8457 (Japan)

    2011-03-15

    Band structures of defective graphenes are analyzed by crystal orbital method. In laterally slipped faults, there appear {sigma} bands consisting of weakly interacted dangling bonds. The peculiar {sigma} bands cross with frontier {pi} bands, and the resultant double occupation leads to the disappearance of ferromagnetic interactions. On the other hand, in longitudinally slipped faults, there are no crossings of the {sigma} bands within the frontier levels, and the ferromagnetic interactions result from polycarbene-type spin alignment. - Research Highlights: Band structures in defective graphenes are analyzed. Lateral slipping in graphenes quenches the ferromagnetic interactions. In the lateral slipping modes, {sigma} bands cross with {pi} frontier bands and reduce the magnetism. Longitudinal slipping in graphenes causes carbene-type ferromagnetic interactions.

  5. Possible existence of new K?=0+ low-lying excited bands in 168Er

    Science.gov (United States)

    Lin, Lu; Tsai, Shang-Fang

    1987-11-01

    Using the angular momentum projection approach with the l2-depressing parameter ?p in the Nilsson model reduced by 15%, the band heads of the 0+2, 0+3, and 0+4 bands in 168Er are calculated to lie at 1221, 1426, and 1823 keV, respectively, in good agreement with recent experimental data. An additional low-lying 0+ band with a band head at 1966 keV is also predicted. A general criterion for the existence of a low-lying 0+ excited band is described and invoked to substantiate the calculated results.

  6. Quadrupole collective correlations and termination of the superdeformed bands in mercury

    International Nuclear Information System (INIS)

    Fully self-consistent Generator Coordinate Method calculations have been performed on a basis of quadrupole constrained Hartree-Fock plus BCS wave functions for the five even mercury isotopes 190-198 Hg. The GCM results support conclusions drawn from previous HF+BCS calculations. The predicted evolution of superdeformed band head (shape isomer) properties as a function of the neutron number is consistent with the data. Using calculated transition matrix elements, we evaluate in-band versus out-of-band quadrupole decay and explain the sudden termination of the superdeformed band

  7. Relative spins and excitation energies of superdeformed bands in 190Hg: Further evidence for octupole vibration

    International Nuclear Information System (INIS)

    An experiment using the Eurogam phase II ?-ray spectrometer confirms the existence of an excited superdeformed (SD) band in 190Hg and its very unusual decay into the lowest SD band over 3--4 transitions. The energies of the transitions linking the two SD bands have been firmly established, and their angular distributions are consistent with a dipole character. Comparisons with calculations using random-phase approximation indicate that the excited SD band can be interpreted as an octupole-vibrational structure

  8. A Multi-band Wavelet Watermarking Scheme

    Directory of Open Access Journals (Sweden)

    Xiangui Kang

    2008-03-01

    Full Text Available This paper presents a new multi-band wavelet watermarking scheme. Compared with conventional watermarking schemes implemented in two-band wavelet domain, by incorporating the principal component analysis (PCA technique the proposed blind watermarking in the multi-band wavelet domain can achieve higher perceptual transparency and stronger robustness. Specifically, the developed watermarking scheme can successfully resist common signal processing such as JPEG compression with quality factor as low as 15, and some geometric distortions such as cropping (cropped by 50\\%. In addition, the proposed multi-band wavelet based watermarking scheme can be parameterized, thus resulting in more security. That is, an attacker may not be able to detect the embedded watermark if the attacker does not know the parameter. Different from many other watermarking schemes, in which the watermark detection threshold is chosen empirically, the false positive rate of the proposed watermarking scheme can be calculated analytically so that watermark detection threshold can be chosen based solely on the targeted false positive.

  9. Electron band theory 1952-1962

    International Nuclear Information System (INIS)

    Work undertaken by the Theoretical Physics Division between 1952 and 1965 to obtain an understanding of electrons in metals, with uranium and the actinides and the structurally-important transition metals as the main targets is examined. A main result of that period was a conviction that the majority of the physical properties of all metals, except the 4f rare-earth series and the actinides beyond uranium, were dominated by band effects which could be described well enough for most purposes by simple one-electron calculations with simple self-consistent fields. The period from 1960 on showed increasingly clearly the necessity of incorporating relativistic spin-orbit coupling terms in the heavy metals, and some 'local exchange field' correction to the fields close to nuclei. The problems of the non-local interaction of spins - highly important for alloy theory and for antiferromagnetic instability -required the evolution of computers large enough to produce wave-functions at all wave-vectors for all bands so that the susceptibility at arbitrary wave-vector could be computed. This work has not proved to be very illuminating so far, and much interest again focusses today on heuristic arguments that give qualitative descriptions of band structures, such as canonical d-bands to account for crystal structure. (UK)

  10. Superfluidity in topologically nontrivial flat bands.

    Science.gov (United States)

    Peotta, Sebastiano; Törmä, Päivi

    2015-01-01

    Topological invariants built from the periodic Bloch functions characterize new phases of matter, such as topological insulators and topological superconductors. The most important topological invariant is the Chern number that explains the quantized conductance of the quantum Hall effect. Here we provide a general result for the superfluid weight Ds of a multiband superconductor that is applicable to topologically nontrivial bands with nonzero Chern number C. We find that the integral over the Brillouin-zone of the quantum metric, an invariant calculated from the Bloch functions, gives the superfluid weight in a flat band, with the bound Ds?|C|. Thus, even a flat band can carry finite superfluid current, provided the Chern number is nonzero. As an example, we provide Ds for the time-reversal invariant attractive Harper-Hubbard model that can be experimentally tested in ultracold gases. In general, our results establish that a topologically nontrivial flat band is a promising concept for increasing the critical temperature of the superconducting transition. PMID:26586543

  11. Infrared spectroscopy of electronic bands in bilayer graphene

    OpenAIRE

    Kuzmenko, Alexey; van Heumen, Erik; Marel, Dirk van der,; Lerch, P.; Blake, P; Novoselov, K. S.; Geim, A. K.

    2008-01-01

    We present infrared spectra (0.1-1 eV) of electrostatically gated bilayer graphene as a function of doping and compare it with tight binding calculations. All major spectral features corresponding to the expected interband transitions are identified in the spectra: a strong peak due to transitions between parallel split-off bands and two onset-like features due to transitions between valence and conduction bands. A strong gate voltage dependence of these structures and a sig...

  12. Prompt Proton Decay and Deformed Bands in 56Ni

    International Nuclear Information System (INIS)

    High-spin states in the doubly magic N=Z nucleus 56Ni have been investigated with three fusion-evaporation reaction experiments. New ?-ray transitions are added, and a confirmation of a previously suggested prompt proton decay from a rotational band in 56Ni into the ground state of 55Co is presented. The rotational bands in 56Ni are discussed within the framework of cranked Nilsson-Strutinsky calculations

  13. Flat-band ferromagnetism in quantum dot superlattices

    OpenAIRE

    Tamura, Hiroyuki; Shiraishi, Kenji; Kimura, Takashi; Takayanagi, Hideaki

    2001-01-01

    Possibility of flat-band ferromagnetism in quantum dot arrays is theoretically discussed. By using a quantum dot as a building block, quantum dot superlattices are possible. We consider dot arrays on Lieb and kagome lattices known to exhibit flat band ferromagnetism. By performing an exact diagonalization of the Hubbard Hamiltonian, we calculate the energy difference between the ferromagnetic ground state and the paramagnetic excited state, and discuss the stability of the f...

  14. Systematic description of superdeformed bands in the mass-190 region

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Yang; Guidry, M. [Oak Ridge National Lab., TN (United States)]|[Univ. of Tennessee, Knoxville, TN (United States); Zhang, Jing-ye [Univ. of Tennessee, Knoxville, TN (United States)

    1996-12-31

    Superdeformed bands for the mass-190 region are described by the Projected Shell Model. Even-even, odd mass and odd-odd nuclei are equally well described. Good agreement with available data for all isotopes studied is obtained. The authors calculation of electromagnetic properties and pairing correlations provides an understanding of the observed gradual increase of dynamical moments of inertia with angular momentum observed in many bands in this mass region.

  15. Dissociation of molecular oxygen in the Schumann-Runge bands

    Science.gov (United States)

    Frederick, J. E.; Hudson, R. D.

    1980-01-01

    Oscillator strengths and predissociation linewidths deduced in recent studies predict a dissociation rate for O2 in the Schumann-Runge bands which is significantly larger in the upper stratosphere and lower mesosphere than previously believed. Error bars on molecular parameters required in the cross-section calculation translate into uncertainties in the dissociation rate which are less than plus or minus 10% at all altitudes where the Schumann-Runge bands are aeronomically significant.

  16. Stop bands for elastic waves in periodic composite materials

    Energy Technology Data Exchange (ETDEWEB)

    Economou, E.N. (Research Center of Crete-FORTH, Crete (Greece) Univ. of Crete (Greece)); Sigalas, M. (Research Center of Crete-FORTH, Crete (Greece))

    1994-04-01

    The frequency [omega] versus wave vector k of elastic waves propagating in periodic binary composites consisting of solid inclusions placed periodically in a host matrix was calculated. Attention was focused on the possibility of stop bands (spectral gaps) for all directions of propagation in such composites. It was found that gold or lead inclusions of about 10% volume fraction in a Si or Be matrix give rise to stop bands. 30 refs., 7 figs.

  17. Band transport model for discotic liquid crystals

    Science.gov (United States)

    Lever, L. J.; Kelsall, R. W.; Bushby, R. J.

    2005-07-01

    A theoretical model is presented for charge transport in discotic liquid crystals in which a charge is delocalized over more than one lattice site. As such, charge transport is via a banded conduction process in a narrow bandwidth system and takes place over coherent lengths of a few molecules. The coherent lengths are disrupted by the geometrical disorder of the system and are treated as being terminated by quantum tunnel barriers. The transmission probabilities at these barriers have been calculated as a function of the charge carrier energy. Phononic interactions are also considered and the charge carrier scattering rates are calculated for intermolecular and intramolecular vibrations. The results of the calculations have been used to develop a Monte Carlo simulation of the charge transport model. Simulated data are presented and used to discuss the nature of the tunnel barriers required to reproduce experimental data. We find that the model successfully reproduces experimental time of flight data including temperature dependence.

  18. Morphologies of three-dimensional shear bands in granular media

    CERN Document Server

    Fazekas, S; Kertész, J; Wolf, D E

    2005-01-01

    Using three-dimensional Distinct Element Method with spherical particles we simulated shear band formation of granular materials in axisymmetric triaxial shear test. The calculated three-dimensinoal shear band morphologies are in good agreement with those found experimentally. We observed spontaneous symmetry braking strain localization provided it was allowed by the boundaries. If the symmetry was enforced, we found strain hardening. We discuss the formation mechanism of shear bands in the light of our observations and compare our results with high resolution NMR experiments.

  19. Electronic band structure of pseudodirect chalcopyrite semiconductors. 1

    International Nuclear Information System (INIS)

    The band structure of the chalcopyrite semiconductor CdSiP2 is calculated using the empirical pseudopotential method applied successfully already in the case of ZnSiP2. The band structure is in good agreement with recent experimental data, especially with the inverse crystal field splitting found by Shileika et al. The influence of the three contributions to the deviation of the chalcopyrite structure from a cubic one (antisymmetric cation potential, tetragonal compression and distortion of the anion sublattice) on the band structure and the optical transition energies is investigated in detail for both ZnSiP2 and CdSiP2. (author)

  20. A new construction algorithm of narrow-band function for artificial history simulation method based on narrow-band superposition

    International Nuclear Information System (INIS)

    In this paper, a new type of narrow-band function is proposed for the artificial history simulation method based on narrow-band superposition, which aims to meet the needs of both fitting of the target response spectrum and envelop of the power spectral density. The new narrow-band function is based on the normal distribution function and trigonometric functions. Its band width can be controlled and it decays rapidly on both sides. While the target response spectrum is fitted by superimposing the new narrow-band time history, the power spectral density is enveloped by modifying the Fourier amplitude spectrum locally. The numerical example demonstrates that not only the artificial time history generated by this algorithm reaches high matching precision to the target response spectrum, but also the corresponding calculated power spectrum envelopes the target power spectrum. (authors)

  1. Band structures of ZnTe:O alloys with isolated oxygen and with clustered oxygen impurities

    Energy Technology Data Exchange (ETDEWEB)

    Ling, Chen, E-mail: chen.ling@tema.toyota.com; Zhou, Li Qin; Banerjee, Debasish; Jia, Hongfei

    2014-01-25

    Highlights: • Band structures of ZnTe:O alloy highly depends on the status of oxygen. • Clustered oxygen lowers the bandgap while isolated oxygen increases the bandgap. • The solar adsorption efficiency of ZnTe:O can be improved by oxygen clustering. -- Abstract: First-principles calculations reveal that band structures of ZnTe:O alloys highly depend on the configuration of oxygen in the alloy. For alloys with isolated oxygen, the calculated band structure shows the formation of intermediate states between valence and conduction band and the shift of conduction band to higher energy level. It expands the gap between valence and conduction band. For alloys with clustered oxygen, the formation of intermediate band is still observed, while the gap between valence and conduction band is decreased. For alloys with oxygen impurities adjacent to Zn vacancy, the band structure only shows the decrease of the gap between valence and conduction band without the formation of any intermediate band. These results suggest the critical role of Zn–O bonding in determining the energy level of the impurity states. On the basis of our results, a possible band engineering approach is suggested in order to improve the performance of ZnTe:O alloy as intermediate band solar adsorbent.

  2. Band structure and hole scattering in p-PbTe

    International Nuclear Information System (INIS)

    Mobility (u), thermoemf (?), and temperature dependences of the Hall constant (R) in p-PbTe were calculated. While calculating considered has been the effect of the free electron mass contribution to the density mass of states at the band bottom and to the effective width of the forbidden band in the framework of the Cane type model, which leads to the absence of a ''mirror property'' of conductivity and valency bands. It is shown that, while taking into account the temperature dependence of the Hall factor, the appearance of maximum on R(T) curves may be explained only with due account of the contribution from interband scattering. Taking account of acoustic and optical mechanisms of scattering, it becomes possible to explain satisfactorily the temperature and concentration dependences of u, the temperature dependences of R and concentration dependences of ? up to concentrations of about 1020 cm-3 at heavy band parameters of msub(h)=1msub(e), ?0.18 eV. Qualitative considerations of the shape of isoenergetic surfaces of a heavy band were undertaken to explain the concentration dependences of b=usub(h)/usub(l) and causes of deviation of experimental and calculated values of ?. It is shown that the above surfaces have a complicated structure, and the heavy band may be substantially nonparabolic

  3. Himmelsmechanik. Band III: Gravitationstheorie.

    Science.gov (United States)

    Schneider, M.

    This book is the third in a now four volume set (for the first volume see 55.003.023, the second see 58.003.013). Der dritte Band des Lehrbuchs über Himmelsmechanik behandelt deren Formulierung auf der Grundlage der Einsteinschen Gravitationstheorie. Dargestellt werden zunächst die Strukturen der Minkowskischen Raumzeit und ihre Folgen für die Orts- und Zeitmessung. Anschließend werden die Einsteinsche Raumzeit durch eine konstruktive Axiomatik begründet und die Einsteinschen Feldgleichungen aufgestellt. Ausführlich werden das Schwarzschild-Problem, lineare und nach-Newtonsche Näherungen der Feld- und Bewegungsgleichungen behandelt. Daran schließt sich an die Behandlung der Ausbreitung elektromagnetischer Wellen und eine Theorie der Bezugssysteme in der Einsteinschen Raumzeit. Breiten Raum nimmt die Darstellung des relativistischen Zwei- und N-Körper-Problems, die Spin-Bahn-Kopplung, die relativistische Theorie von Rotation und Figur von Körpern ein.

  4. Unfolding the band structure of non-crystalline photonic band gap materials

    Science.gov (United States)

    Tsitrin, Samuel; Williamson, Eric Paul; Amoah, Timothy; Nahal, Geev; Chan, Ho Leung; Florescu, Marian; Man, Weining

    2015-08-01

    Non-crystalline photonic band gap (PBG) materials have received increasing attention, and sizeable PBGs have been reported in quasi-crystalline structures and, more recently, in disordered structures. Band structure calculations for periodic structures produce accurate dispersion relations, which determine group velocities, dispersion, density of states and iso-frequency surfaces, and are used to predict a wide-range of optical phenomena including light propagation, excited-state decay rates, temporal broadening or compression of ultrashort pulses and complex refraction phenomena. However, band calculations for non-periodic structures employ large super-cells of hundreds to thousands building blocks, and provide little useful information other than the PBG central frequency and width. Using stereolithography, we construct cm-scale disordered PBG materials and perform microwave transmission measurements, as well as finite-difference time-domain (FDTD) simulations. The photonic dispersion relations are reconstructed from the measured and simulated phase data. Our results demonstrate the existence of sizeable PBGs in these disordered structures and provide detailed information of the effective band diagrams, dispersion relation, iso-frequency contours, and their angular dependence. Slow light phenomena are also observed in these structures near gap frequencies. This study introduces a powerful tool to investigate photonic properties of non-crystalline structures and provides important effective dispersion information, otherwise difficult to obtain.

  5. Bulk band structure of Bi2Te3

    DEFF Research Database (Denmark)

    Michiardi, Matteo; Aguilera, Irene

    2014-01-01

    The bulk band structure of Bi2Te3 has been determined by angle-resolved photoemission spectroscopy and compared to first-principles calculations. We have performed calculations using the local density approximation (LDA) of density functional theory and the one-shot GW approximation within the all-electron full-potential linearized augmented-plane-wave (FLAPW) formalism, fully taking into account spin-orbit coupling. Quasiparticle effects produce significant changes in the band structure of Bi2Te3 when compared to LDA. Experimental and calculated results are compared in the spectral regions where distinct differences between the LDA and GW results are present. Overall a superior agreement with GW is found, highlighting the importance of many-body effects in the band structure of this family of topological insulators.

  6. Diffusion Quantum Monte Carlo Calculations of Excited States of Silicon

    CERN Document Server

    Williamson, A J; Needs, R J; Rajagopal, G; Hood, Randolph Q.

    1998-01-01

    The band structure of silicon is calculated at the Gamma, X, and L wave vectors using diffusion quantum Monte Carlo methods. Excited states are formed by promoting an electron from the valence band into the conduction band. We obtain good agreement with experiment for states around the gap region and demonstrate that the method works equally well for direct and indirect excitations, and that one can calculate many excited states at each wave vector. This work establishes the fixed-node DMC approach as an accurate method for calculating the energies of low lying excitations in solids.

  7. Spectra of {gamma} rays feeding superdeformed bands

    Energy Technology Data Exchange (ETDEWEB)

    Lauritsen, T.; Khoo, T.L.; Henry, R.G. [and others

    1995-08-01

    The spectrum of {gamma}rays coincident with SD transitions contains the transitions which populate the SD band. This spectrum can provide information on the feeding mechanism and on the properties (moment of inertia, collectivity) of excited SD states. We used a model we developed to explain the feeding of SD bands, to calculate the spectrum of feeding {gamma}rays. The Monte Carlo simulations take into account the trigger conditions present in our Eurogam experiment. Both experimental and theoretical spectra contain a statistical component and a broad E2 peak (from transitions occurring between excited states in the SD well). There is good resemblance between the measured and calculated spectra although the calculated multiplicity of an E2 bump is low by {approximately}30%. Work is continuing to improve the quality of the fits, which will result in a better understanding of excited SD states. In addition, a model for the last steps, which cool the {gamma} cascade into the SD yrast line, needs to be developed. A strong M1/E2 low-energy component, which we believe is responsible for this cooling, was observed.

  8. M-Band Graphic Equalizer

    OpenAIRE

    Dr. P. Mallikarjuna Rao; Prof. Ch.Srinivasa Kumar

    2011-01-01

    This paper deals with the concept of filter banks. Filter banks are a group of band-pass filters connected in parallel. Each parallel connection forms a channel for different frequency-bands present in the input signal. The output of the filter bank is formed by merging these channels. The main theme behind the use of filter banksis to boost or attenuate different individual bands of frequencies present in a signal, without affecting other bands. There are several ways of realizing an filter ...

  9. Superdeformed bands in 189Tl

    International Nuclear Information System (INIS)

    Two superdeformed bands of 10 transitions each have been found in 189Tl extending the mass 190 region of superdeformation down to neutron number N=108. The new bands can be interpreted as signature partners and are proposed to be based on a proton i13/2 (?=5/2) configuration, in analogy with the yrast superdeformed band structures in the heavier odd-mass Tl isotopes. The dynamic moments of inertia of all these bands show no noticeable differences as function of N, consistent with an essentially constant quadrupole deformation from the center of the island to its edges. copyright 1998 The American Physical Society

  10. Sequential chromosome banding in fishes.

    Czech Academy of Sciences Publication Activity Database

    Rábová, Marie; Völker, M.; Pelikánová, Šárka; Ráb, Petr

    Enfield : CRC Press, 2015, s. 92-102. ISBN 9781482211986 Institutional support: RVO:67985904 Keywords : fish cytogentics * genetic analyses * chromosome banding Subject RIV: EB - Genetics ; Molecular Biology

  11. Energy band gaps in periodic bent graphene

    Science.gov (United States)

    Xie, Wenze; Li, Zhongyao

    2016-01-01

    Based on the first-principles calculations, we studied the energy bandgaps of the two kinds of periodic bent graphenes: smooth-bent graphene and stepped graphene. In the smooth-bent graphene, the sinusoidal type of graphene superlattice is a gapless semiconductor as the flattened graphene. The periodic smooth bending is unable to open the bandgap of graphene. Although the bandgap can be larger than 100 meV in stepped graphene, it is sensitively dependent on the details of structure. Band gap can only be opened in a certain range of tilt angle. The localized states greatly influence the bandgap opening in stepped graphene.

  12. Single Band Helical Antenna in Axial Mode

    Directory of Open Access Journals (Sweden)

    Parminder Singh

    2012-11-01

    Full Text Available Helical antennas have been widely used in a various useful applications, due to their low weight and low profile conformability, easy and cheap realization.Radiation properties of this antenna are examined both theoretically and experimentally. In this paper, an attempt has been made to investigate new helical antenna structure for Applications. CST MWS Software is used for the simulation and design calculations of the helical antennas. The axial ratio, return loss, VSWR, Directivity, gain, radiation pattern is evaluated. Using CST MWS simulation software proposed antenna is designed/simulated and optimized. The antenna exhibits a single band from 0 GHz to 3 GHz for GPS and several satellite applications

  13. Sculpting the band gap: a computational approach

    Science.gov (United States)

    Prasai, Kiran; Biswas, Parthapratim; Drabold, D. A.

    2015-10-01

    Materials with optimized band gap are needed in many specialized applications. In this work, we demonstrate that Hellmann-Feynman forces associated with the gap states can be used to find atomic coordinates that yield desired electronic density of states. Using tight-binding models, we show that this approach may be used to arrive at electronically designed models of amorphous silicon and carbon. We provide a simple recipe to include a priori electronic information in the formation of computer models of materials, and prove that this information may have profound structural consequences. The models are validated with plane-wave density functional calculations.

  14. Characterization of band structure for transverse acoustic phonons in Fibonacci superlattices by a bandedge formalism

    International Nuclear Information System (INIS)

    We present a divergence-free method to determine the characteristics of band structures and projected band structures of transverse acoustic phonons in Fibonacci superlattices. A set of bandedge equations is formulated to solve the band structures for the phonon instead of using the traditional dispersion relation. Numerical calculations show band structures calculated by the present method for the Fibonacci superlattice without numerical instability, which may occur in traditional methods. Based on the present formalism, the band structure for the acoustic phonons has been characterized by closure points and the projected bandgaps of the forbidden bands. The projected bandgaps are determined by the projected band structure, which is characterized by the cross points of the projected bandedges. We observed that the band structure and projected band structure and their characteristics were quite different for different generation orders and the basic layers for the Fibonacci superlattice. In this study, concise rules to determine these characteristics of the band structure and the projected band structure, including the number and the location of closure points of forbidden bands and those of projected bandgaps, in Fibonacci superlattices with arbitrary generation order and basic layers are proposed.

  15. Long Lake banding project, 1965

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This report summarizes the results of a banding project on Long Lake in 1965. The dates at the banding site were July 27th through August 8th. As in the past, the...

  16. Interplay between proton and neutron S-bands in the Xe-Ba-Ce-region

    International Nuclear Information System (INIS)

    Two-quasiparticle bands of positive parity (S-bands) in even-even nuclei in the Xe-Ba-Ce region are systematically examined. The equilibrium deformations for the ground-state band as well as for proton and neutron (h11/2)2 configurations are obtained from total routhian surface (TR-surfaces) calculations. By comparing systematic trends of calculated and experimental crossing frequencies, attempts are made to assign the various bands as having an (h11/2)2 neutron or proton character, respectively. (orig.)

  17. W-Band Sheet Beam Klystron Simulation

    Energy Technology Data Exchange (ETDEWEB)

    Colby, E.R.; Caryotakis, G.; Fowkes, W.R.; /SLAC; Smithe, D.N.; /Mission Res., Newington

    2005-09-12

    With the development of ever higher energy particle accelerators comes the need for compactness and high gradient, which in turn require very high frequency high power rf sources. Recent development work in W-band accelerating techniques has spurred the development of a high-power W-band source. Axisymmetric sources suffer from fundamental power output limitations (P{sub sat} {approx} {lambda}{sup 2}) brought on by the conflicting requirements of small beam sizes and high beam current. The sheet beam klystron allows for an increase in beam current without substantial increase in the beam current density, allowing for reduced cathode current densities and focusing field strengths. Initial simulations of a 20:1 aspect ratio sheet beam/cavity interaction using the 3 dimensional particle-in-cell code Magic3D have demonstrated a 35% beam-power to RF power extraction efficiency. Calculational work and numerical simulations leading to a prototype W-band sheet beam klystron will be presented, together with preliminary cold test structure studies of a proposed RF cavity geometry.

  18. Colloidal Nanoparticles for Intermediate Band Solar Cells

    Science.gov (United States)

    Voros, Marton; Galli, Giulia; Zimanyi, Gergely

    2015-03-01

    The Intermediate Band (IB) solar cell concept is a promising idea to transcend the Shockley-Queisser limit. Using the results of first principles calculations, we proposed that colloidal nanoparticles (CNPs) are a viable and efficient platform for the implementation of the IB solar cell concept. We focused on CdSe and we showed that intragap states present in the isolated dots with reconstructed surfaces combine to form an IB in arrays of NPs, which is well separated from the valence and conduction band edges. We also showed that in solution such IB may be electron doped using, e.g. decamethylcobaltocene, thus activating an IB-induced absorption process. Our results, together with the recent report of a nearly 9% efficient CNP solar cell indicate that colloidal nanoparticle intermediate band solar cells are a promising platform to overcome the Shockley-Queisser limit. Work supported by NSF Solar Collaborative under DMR-1035468 and the Center for Advanced Solar Photophysics, an Energy Frontier Research Center funded by the US Department of Energy, Office of Science, Office of Basic Energy Sciences.

  19. Information retrieval from wide-band meteorological data - An example

    Science.gov (United States)

    Adelfang, S. I.; Smith, O. E.

    1983-01-01

    The methods proposed by Smith and Adelfang (1981) and Smith et al. (1982) are used to calculate probabilities over rectangles and sectors of the gust magnitude-gust length plane; probabilities over the same regions are also calculated from the observed distributions and a comparison is also presented to demonstrate the accuracy of the statistical model. These and other statistical results are calculated from samples of Jimsphere wind profiles at Cape Canaveral. The results are presented for a variety of wavelength bands, altitudes, and seasons. It is shown that wind perturbations observed in Jimsphere wind profiles in various wavelength bands can be analyzed by using digital filters. The relationship between gust magnitude and gust length is modeled with the bivariate gamma distribution. It is pointed out that application of the model to calculate probabilities over specific areas of the gust magnitude-gust length plane can be useful in aerospace design.

  20. Band gap engineering strategy via polarization rotation in perovskite ferroelectrics

    International Nuclear Information System (INIS)

    We propose a strategy to engineer the band gaps of perovskite oxide ferroelectrics, supported by first principles calculations. We find that the band gaps of perovskites can be substantially reduced by as much as 1.2?eV through local rhombohedral-to-tetragonal structural transition. Furthermore, the strong polarization of the rhombohedral perovskite is largely preserved by its tetragonal counterpart. The B-cation off-center displacements and the resulting enhancement of the antibonding character in the conduction band give rise to the wider band gaps of the rhombohedral perovskites. The correlation between the structure, polarization orientation, and electronic structure lays a good foundation for understanding the physics of more complex perovskite solid solutions and provides a route for the design of photovoltaic perovskite ferroelectrics

  1. Analysis of Factors Affecting Log Band Saw Capacity

    Directory of Open Access Journals (Sweden)

    Rajka Karan

    2009-06-01

    Full Text Available The goal of this research was to measure the capacity of the log band saw by monitoring the sawing process per operation for each log and to determine what the influencing factors were and their effect on the technological capacity of the log band saw, based on recorded and processed data. The analysis of the recorded data shows that the processed log volume, whose increase also increases the saw capacity, has the most important effect on log band saw capacity. It is imperative to take into account the volume of logs being processed when calculating the capacity of the log band saw. When monitoring the work of the operator, the use of fixed norms is not recommended and it is imperative that norms are connected to the volume of logs being processed.

  2. Superdeformed rotational band in framework of three parameters rotational formula

    International Nuclear Information System (INIS)

    The discovery of superdeformation is one of the significant advances in nuclear structure physics. Superdeformed (SD) bands were first observed in fission isomers in the actinide region. The discrete line SD shapes were found in 152Dy nucleus. Since then vast experimental and theoretical studies have been undertaken. At present numerous SD bands have been observed in various mass region A = 30, 60, 80, 130, 150 and 190. In present work, we aim to describe the nuclear properties and SD bands of 192Hg (SD-1), 194Hg(SD-1) and 194Hg(SD-2) nuclei. We have employed the two-parameters ab formula and power law to calculate the transition energies of above mentioned bands

  3. Strain-driven band inversion and topological aspects in Antimonene

    Science.gov (United States)

    Zhao, Mingwen; Zhang, Xiaoming; Li, Linyang

    2015-11-01

    Searching for the two-dimensional (2D) topological insulators (TIs) with large bulk band gaps is the key to achieve room-temperature quantum spin Hall effect (QSHE). Using first-principles calculations, we demonstrated that the recently-proposed antimonene [Zhang et al., Angew. Chem. Int. Ed. 54, 3112–3115 (2015)] can be tuned to a 2D TI by reducing the buckling height of the lattice which can be realized under tensile strain. The strain-driven band inversion in the vicinity of the Fermi level is responsible for the quantum phase transition. The buckled configuration of antimonene enables it to endure large tensile strain up to 18% and the resulted bulk band gap can be as large as 270?meV. The tunable bulk band gap makes antimonene a promising candidate material for achieving quantum spin Hall effect (QSH) at high temperatures which meets the requirement of future electronic devices with low power consumption.

  4. The effect of the band edges on the Seebeck coefficient

    International Nuclear Information System (INIS)

    The classical thermopower formulae generally applied for the calculation of the Seebeck coefficient S are argued to be incomplete. S can be separated into two different contributions, a scattering term, S0, and a thermodynamic term, ?S, representing the additional change of the electrochemical potential ? with temperature T caused by 'non-scattering' effects, for instance, the band edge shift with T. On the basis of this separation into S0 and ?S, it is shown that shifts of the band edges with T lead to an additional contribution to the classical thermopower formulae. This separation provides the basis for an interpretation of positive thermopowers measured for many metals. Positive thermopower is expected if the energy of the conduction band edge increases with T and if this effect overcompensates for the influence of the energy dependent conductivity, ?(E). Using experimental thermopower data, the band edge shifts are determined for a series of liquid normal metals.

  5. Lasing at the band edges of plasmonic lattices

    CERN Document Server

    Schokker, A Hinke

    2014-01-01

    We report room temperature lasing in two-dimensional diffractive lattices of silver and gold plasmon particle arrays embedded in a dye-doped polymer that acts both as waveguide and gain medium. As compared to conventional dielectric distributed feedback lasers, a central question is how the underlying band structure from which lasing emerges is modified by both the much stronger scattering and the disadvantageous loss of metal. We use spectrally resolved back-focal plane imaging to measure the wavelength- and angle dependence of emission below and above threshold, thereby mapping the band structure. We find that for silver particles, the band structure is strongly modified compared to dielectric reference DFB lasers, since the strong scattering gives large stop gaps. In contrast, gold particles scatter weakly and absorb strongly, so that thresholds are higher, but the band structure is not strongly modified. The experimental findings are supported by finite element and fourier modal method calculations of the...

  6. Band Structure of SnTe Studied by Photoemission Spectroscopy

    Science.gov (United States)

    Littlewood, P. B.; Mihaila, B.; Schulze, R. K.; Safarik, D. J.; Gubernatis, J. E.; Bostwick, A.; Rotenberg, E.; Opeil, C. P.; Durakiewicz, T.; Smith, J. L.; Lashley, J. C.

    2010-08-01

    We present an angle-resolved photoemission spectroscopy study of the electronic structure of SnTe and compare the experimental results to ab initio band structure calculations as well as a simplified tight-binding model of the p bands. Our study reveals the conjectured complex Fermi surface structure near the L points showing topological changes in the bands from disconnected pockets, to open tubes, and then to cuboids as the binding energy increases, resolving lingering issues about the electronic structure. The chemical potential at the crystal surface is found to be 0.5 eV below the gap, corresponding to a carrier density of p=1.14×1021cm-3 or 7.2×10-2 holes per unit cell. At a temperature below the cubic-rhombohedral structural transition a small shift in spectral energy of the valance band is found, in agreement with model predictions.

  7. Massive band gap variation in layered oxides through cation ordering

    Science.gov (United States)

    Balachandran, Prasanna V.; Rondinelli, James M.

    2015-01-01

    The electronic band gap is a fundamental material parameter requiring control for light harvesting, conversion and transport technologies, including photovoltaics, lasers and sensors. Although traditional methods to tune band gaps rely on chemical alloying, quantum size effects, lattice mismatch or superlattice formation, the spectral variation is often limited to <1?eV, unless marked changes to composition or structure occur. Here we report large band gap changes of up to 200% or ~2?eV without modifying chemical composition or use of epitaxial strain in the LaSrAlO4 Ruddlesden-Popper oxide. First-principles calculations show that ordering electrically charged [LaO]1+ and neutral [SrO]0 monoxide planes imposes internal electric fields in the layered oxides. These fields drive local atomic displacements and bond distortions that control the energy levels at the valence and conduction band edges, providing a path towards electronic structure engineering in complex oxides.

  8. Band-edge diagrams for strained III-V semiconductor quantum wells, wires, and dots

    CERN Document Server

    Pryor, C E

    2005-01-01

    We have calculated band-edge energies for most combinations of zincblende AlN, GaN, InN, GaP, GaAs, InP, InAs, GaSb and InSb in which one material is strained to the other. Calculations were done for three different geometries, quantum wells, wires, and dots, and mean effective masses were computed in order to estimate confinement energies. For quantum wells, we have also calculated band-edges for ternary alloys. Energy gaps, including confinement, may be easily and accurately estimated using band energies and a simple effective mass approximation, yielding excellent agreement with experimental results. By calculating all material combinations we have identified novel and interesting material combinations, such as artificial donors, that have not been experimentally realized. The calculations were perfomed using strain-dependent k-dot-p theory and provide a comprehensive overview of band structures for strained heterostructures.

  9. Coupling effect of quantum wells on band structure

    Science.gov (United States)

    Jie, Chen; Weiyou, Zeng

    2015-10-01

    The coupling effects of quantum wells on band structure are numerically investigated by using the Matlab programming language. In a one dimensional finite quantum well with the potential barrier V0, the calculation is performed by increasing the number of inserted barriers with the same height Vb, and by, respectively, varying the thickness ratio of separated wells to inserted barriers and the height ratio of Vb to V0. Our calculations show that coupling is strongly influenced by the above parameters of the inserted barriers and wells. When these variables change, the width of the energy bands and gaps can be tuned. Our investigation shows that it is possible for quantum wells to achieve the desired width of the bands and gaps.

  10. Band Structure and Quantum Confined Stark Effect in InN/GaN superlattices

    DEFF Research Database (Denmark)

    Gorczyca, I.; Suski, T.

    2012-01-01

    InN/GaN superlattices offer an important way of band gap engineering in the blue-green range of the spectrum. This approach represents a more controlled method than the band gap tuning in quantum well systems by application of InGaN alloys. The electronic structures of short-period wurtzite InN/GaN(0001) superlattices are investigated, and the variation of the band gap with the thicknesses of the well and the barrier is discussed. Superlattices of the form mInN/nGaN with n ? m are simulated using band structure calculations in the Local Density Approximation with a semiempirical correction for the gap error. The calculated band gap shows a strong decrease with the thickness (m) of the InN well. In superlattices containing a single layer of InN (m = 1) the band gap increases weakly with the GaN barrier thickness n, reaching a saturation value around 2 eV. In superlattices with n = m and n > 5 the band gap closes and the systems become “metallic”. These effects are related to the existence of the built-in electric fields that strongly influence valence- and conduction-band profiles and thus determine effective band gap and emission energies of the superlattices. Varying the widths of the quantum wells and barriers one may tune band gaps over a wide spectral range, which provides flexibility in band gap engineering.

  11. Microstrip microwave band gap structures

    Indian Academy of Sciences (India)

    V Subramanian

    2008-04-01

    Microwave band gap structures exhibit certain stop band characteristics based on the periodicity, impedance contrast and effective refractive index contrast. These structures though formed in one-, two- and three-dimensional periodicity, are huge in size. In this paper, microstrip-based microwave band gap structures are formed by removing the substrate material in a periodic manner. This paper also demonstrates that these structures can serve as a non-destructive characterization tool for materials, a duplexor and frequency selective coupler. The paper presents both experimental results and theoretical simulation based on a commercially available finite element methodology for comparison.

  12. Electronic band structure and optical properties of the cubic, Sc, Y and La hydride systems

    International Nuclear Information System (INIS)

    Electronic band structure calculations are used to interpret the optical spectra of the cubic Sc, Y and La hydride systems. Self-consistent band calculations of ScH2 and YH2 were carried out. The respective joint densities of states are computed and compared to the dielectric functions determined from the optical measurements. Additional calculations were performed in which the Fermi level or band gap energies are rigidly shifted by a small energy increment. These calculations are then used to simulate the derivative structure in thermomodulation spectra and relate the origin of experimental interband features to the calculated energy bands. While good systematic agreement is obtained for several spectral features, the origin of low-energy interband transitions in YH2 cannot be explained by these calculated bands. A lattice-size-dependent premature occupation of octahedral sites by hydrogen atoms in the fcc metal lattice is suggested to account for this discrepancy. Various non-self-consistent calculations are used to examine the effect of such a premature occupation. Measurements of the optical absorptivity of LaH/sub x/ with 1.6 2 lattice. These experimental results also suggest that, in contrast to recent calculations, LaH3 is a small-band-gap semiconductor

  13. First-principles study of Cu2ZnSnS4 and the related band offsets for photovoltaic applications.

    Science.gov (United States)

    Nagoya, A; Asahi, R; Kresse, G

    2011-10-12

    First-principles calculations of the band offsets between Cu(2)ZnSnS(4) (CZTS) and XS (X = Cd, Zn) are performed. While the interface dipole contribution for the band offsets is calculated using the Perdew-Burke-Ernzerhof functional, the Heyd-Scuseria-Ernzerhof hybrid functional is employed to introduce the quasiparticle corrections to the band offsets. The calculated conduction band offset between CZTS and CdS is 0.2 eV, validating CdS for the buffer layer of the CZTS solar cell. The small conduction band offset stems from the band gap narrowing of CdS under the interface strain caused by the lattice misfit with CZTS. A large valence band offset over 0.9 eV between CZTS and ZnS indicates that precipitated ZnS is regarded as an inactive insulator phase in CZTS absorbers. PMID:21931185

  14. First-principles study of Cu2ZnSnS4 and the related band offsets for photovoltaic applications

    International Nuclear Information System (INIS)

    First-principles calculations of the band offsets between Cu2ZnSnS4 (CZTS) and XS (X = Cd, Zn) are performed. While the interface dipole contribution for the band offsets is calculated using the Perdew-Burke-Ernzerhof functional, the Heyd-Scuseria-Ernzerhof hybrid functional is employed to introduce the quasiparticle corrections to the band offsets. The calculated conduction band offset between CZTS and CdS is 0.2 eV, validating CdS for the buffer layer of the CZTS solar cell. The small conduction band offset stems from the band gap narrowing of CdS under the interface strain caused by the lattice misfit with CZTS. A large valence band offset over 0.9 eV between CZTS and ZnS indicates that precipitated ZnS is regarded as an inactive insulator phase in CZTS absorbers.

  15. Amchitka 1980 waterfowl banding report

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — Waterfowl banding on Amchitka Island, Alaska was conducted between 5 August and 6 October 1980. Five traps were constructed and set for a total of 195 trap days....

  16. Jena Band of Louisiana Choctaw

    Science.gov (United States)

    Gregory, Hiram F.

    1977-01-01

    Documenting the development and struggles of the Jena Band of American Indian Choctaws in Louisiana, this article describes the remarkable autonomy of these people in the face of governmental/racial discrimination. (JC)

  17. Ultraviolet bands of potassium dimer

    International Nuclear Information System (INIS)

    The ultraviolet band spectra of potassium dimer have been investigated. The studies were performed in absorption in the second order of a 3.4 m Ebert spectrograph with a reciprocal dispersion of 2.6 A/mm. A number of new bands in the electronic states G and H not previously reported have been observed. The vibrational analysis is performed and molecular constants are evaluated. (author)

  18. Narrow-Band Microwave Filters

    Directory of Open Access Journals (Sweden)

    A.V. Strizhachenko

    2010-01-01

    Full Text Available Original design of the narrow-band compact filters based on the high-quality waveguide-dielectric resonator with anisotropic materials has been presented in this work. Designed filters satisfy the contradictory requirements: they provide the narrow frequency band (0.05 ÷ 0.1 % of the main frequency f0 and the low initial losses ?0 ? 1 dB.

  19. 'Pudding mold'-type band as an origin of large thermopower in ?-type organic conductors

    International Nuclear Information System (INIS)

    We study the origin of the large thermopower in quasi-two-dimensional ?-type organic conductor, ?-(EDO-S,S-DMEDT-TTF)2(AuBr2)1+y (y?0.875), from the view point of a 'pudding mold'-type band structure. We calculate the electronic band structure using an ab initio band calculation package, and obtain a tight binding model fit to the ab initio band structure. Using the model and Boltzmann's equation approach, we calculate the temperature dependence of the Seebeck coefficient. We conclude that the peculiar band structure is the origin of the large Seebeck coefficient and the appearance of the maximum value at a certain temperature.

  20. The band structure of BeTe a combined experimental and theoretical study

    CERN Document Server

    Nagelstrasser, M; Fischer, F; Litz, T; Waag, A; Fleszar, A; Hanke, W; Steinrück, H P; Landwehr, Gottfried

    1998-01-01

    Using angle-resolved synchrotron-radiation photoemission spectroscopy we have determined the dispersion of the valence bands of BeTe(100) along $\\Gamma X$, i.e. the [100] direction. The measurements are analyzed with the aid of a first-principles calculation of the BeTe bulk band structure as well as of the photoemission peaks as given by the momentum conserving bulk transitions. Taking the calculated unoccupied bands as final states of the photoemission process, we obtain an excellent agreement between experimental and calculated spectra and a clear interpretation of almost all measured bands. In contrast, the free electron approximation for the final states fails to describe the BeTe bulk band structure along $\\Gamma X$ properly.

  1. Calculated thermoelectric properties of La-filled skutterudites

    CERN Document Server

    Singh, D J

    1997-01-01

    The thermoelectric properties of La-filled skutterudites are discussed from the point of view of their electronic structures. These are calculated from first principles within the local density approximation. The electronic structure is in turn used to determine transport related quantities. Virtual crystal calculations for La(Fe,Co)_4Sb_{12} show that the system obeys near rigid band behavior with varying Co concentration, and has a substantial band gap at a position corresponding to the composition LaFe_3% CoSb_{12}. The valence band maximum occurs at the $\\Gamma$ point and is due to a singly degenerate dispersive band, which by itself would not be favorable for high thermopower. However, very flat transition metal derived bands occur in close proximity and become active as the doping level is increased, giving a non-trivial dependence of the properties on carrier concentration and explaining the favorable thermoelectric properties.

  2. Formation of dispersive hybrid bands at an organic-metal interface

    OpenAIRE

    González-Lakunza, N.; Fernández-Torrente, I.; Franke, K. J.; Lorente, N.; Arnau, Andrés; Pascual, J. I.

    2008-01-01

    An electronic band with quasi-one dimensional dispersion is found at the interface between a monolayer of a charge-transfer complex (TTF-TCNQ) and a Au(111) surface. Combined local spectroscopy and numerical calculations show that the band results from a complex mixing of metal and molecular states. The molecular layer folds the underlying metal states and mixes with them selectively, through the TTF component, giving rise to anisotropic hybrid bands. Our results suggest tha...

  3. Enhancement of optical absorption in Ga-chalcopirite-based intermediate-band materials for high efficiency solar cells

    OpenAIRE

    Aguilera Bonet, Irene; Palacios Clemente, Pablo; Wahnón Benarroch, Perla

    2010-01-01

    We present absorption properties enhancement for two CuGaS2-based intermediate-band materials, as promising compounds for high efficiency, lower-cost photovoltaic devices. Previous band diagrams calculations predicted that these materials present a partially filled localized band within the band gap of the host semiconductor, which would increase the absorption of low-energy photons, creating additional electron–hole pairs respect to a conventional semiconductor. This could ideally result in ...

  4. Use of propagators in the Hueckel model, 4. Chemical reactivity in radiation field

    Energy Technology Data Exchange (ETDEWEB)

    Ohmae, T.; Nishikawa, K.; Deguchi, K.; Aono, S. (Kanazawa Univ. (Japan). Faculty of Science)

    1981-11-01

    The propagator approach is applied to chemical reactivity in the presence of radiation field. The Woodward-Hoffmann's rule in photochemical reactions is generally derived. As an illustrative example, the ring closure or ring opening reactions are discussed.

  5. Fluctuations in a superconducting quantum critical point of multi-band metals

    CERN Document Server

    Ramires, Aline

    2011-01-01

    In multi-band metals quasi-particles arising from different atomic orbitals coexist at a common Fermi surface. Superconductivity in these materials may appear due to interactions within a band (intra-band) or among the distinct metallic bands (inter-band). Here we consider the suppression of superconductivity in the intra-band case due to hybridization. The fluctuations at the superconducting quantum critical point (SQCP) are obtained calculating the response of the system to a fictitious space and time dependent field, which couples to the superconducting order parameter. The appearance of superconductivity is related to the divergence of a generalized susceptibility. For a single band superconductor this coincides with the \\textit{Thouless criterion}. For fixed chemical potential and large hybridization, the superconducting state has many features in common with breached pair superconductivity with unpaired electrons at the Fermi surface. The T=0 phase transition from the superconductor to the normal state ...

  6. Theoretical study of relative width of photonic band gap for the 3-D dielectric structure

    Indian Academy of Sciences (India)

    G K Johri; Akhilesh Tiwari; Saumya Saxena; Rajesh Sharma; Kuldeep Srivastava; Manoj Johri

    2002-03-01

    Calculations for the relative width $(\\Delta\\omega/\\omega_{0})$ as a function of refractive index and relative radius of the photonic band gap for the fcc closed packed 3-D dielectric microstructure are reported and comparison of experimental observations and theoretical predictions are given. This work is useful for the understanding of photonic crystals and occurrence of the photonic band gap.

  7. Band modes of hydrogen in the bcc metals Nb, V, and Ta

    International Nuclear Information System (INIS)

    A calculation of the frequency spectrum of the band modes of hydrogen located at a tetrahedral interstitial site shows a strong resonantlike peak with very little isotope effect. This mode was observed by neutron scattering in NbHatsub 0.05at at 3.8 THz. The band modes provide a mechanism for classical diffusion with low activation energies

  8. Search for superdeformed bands in {sup 154}Dy

    Energy Technology Data Exchange (ETDEWEB)

    Nisius, D.; Janssens, R.V.F.; Khoo, T.L. [and others

    1995-08-01

    The island of superdeformation in the vicinity of the doubly magic {sup 152}Dy yrast superdeformed (SD) band is thought to be well understood in the framework of cranked mean field calculations. In particular, the calculations suggested that in {sup 154}Dy there should be no yrast or near yrast SD minimum in the 40-60 h spin range, where SD bands in this mass region are thought to be {sup 153}Dy nucleus, it is populated. However, with the presence of five SD bands in the neighboring necessary to ascertain if the addition of one single neutron diminishes the importance of shell effects to the extent that superdeformation can no longer be sustained. In an experiment utilizing the increased resolving power of the early implementation phase of Gammasphere, the reaction {sup 122}Sn({sup 36}S,4n) at 165 MeV was employed to populate high spin states in {sup 154}Dy. In a four-day run with 36 detectors, over one billion triple and higher fold coincidence events were recorded. One new SD band was identified and was assigned to {sup 154}Dy. From comparisons with the Im{sup (2)} moments of inertia of the SD bands in {sup 152}Dy and {sup 153}Dy, a configuration based on (514)9/2{sup 2} neutrons coupled to the {sup 152}Dy SD core was proposed. One unexpected and as yet unexplained feature of this new SD band is that the transition energies are almost identical to those of an excited SD band in {sup 153}Dy. It is also worth noting that the feeding of the yrast states is similar to that achieved by the deexcitation from the ensemble of all entry states in the reaction. This observation emphasizes the statistical nature of the decay-out process. A paper reporting these results was accepted for publication.

  9. Spins of superdeformed band in {sup 192}Hg

    Energy Technology Data Exchange (ETDEWEB)

    Lauritsen, T.; Khoo, T.L.; Henry, R.G. [and others

    1995-08-01

    Determination of the spins of SD states is the most important challenge in the study of superdeformation. Knowledge of the spin will provide crucial information on SD bands, in particular on the fascinating phenomenon of bands with identical energies and moments of inertia. Angular distribution coefficients of the {gamma}rays decaying out of the {sup 192}Hg SD band were determined using Eurogam data. These coefficients, as well as the spectral shape and multiplicity of the spectrum, are compared with the results of calculations, thereby providing a check on these calculations. From the measured decay multiplicity and the calculated average spin removed per photon (0.3 h), we deduce the average spin {bar I}{sub decay} removed by the {gamma} rays connecting SD and normal states. The spin I{sub SD} of the SD band from which the decay occurs is given by I{sub SD} = {bar I} decay + {bar I} ND, where {bar I} ND is the average spin removed by the normal yrast states. The state from which the major decay out of the SD band occurs is found to have spin 9.5 {plus_minus} 0.8 h. Since angular momentum is (quantized), this leads to a spin assignment of 9 or 10 h. The latter value is favored since the yrast band in the SD well must have only even spin values. This constitutes the first deduction of spin from data in the mass 150 and 190 regions. The spin of 10 h agrees with the spin which is inferred from a model, using the observed moment of inertia (Im){sup (2)}{omega}.

  10. Band crossing and shape evolution in Ge73

    Science.gov (United States)

    Sun, J. J.; Xu, C.; Li, X. Q.; Hua, H.; Zhang, S. Q.; Xu, F. R.; Liang, W. Y.; Jiao, C. F.; Meng, J.; Wu, X. G.; Hu, S. P.; Zhang, H. Q.; Li, Z. H.; Ye, Y. L.; Jiang, D. X.; Cheng, Y. Y.; He, C.; Han, R.; Niu, C. Y.; Li, C. G.; Wang, C. G.; Li, Z. H.; Li, G. S.; He, C. Y.; Zheng, Y.; Li, C. B.; Li, H. W.; Wang, J. L.; Liu, J. J.; Wu, Y. H.; Luo, P. W.; Yao, S. H.; Yu, B. B.; Cao, X. P.; Sun, H. B.

    2015-11-01

    The spectroscopy of Ge73 has been investigated via the (Li7Zn70,3 n p )Ge73 fusion-evaporation reaction. A previously known band built on the ? (f5 /2) orbital is extended up to higher-spin states and a new rotational band built on the ? (g9 /2) orbital is established. The observed band crossing and shape evolution induced by the alignment in Ge73 are studied in comparison with the similar structures in the neighboring N =41 isotones and the cranked Woods-Saxon-Strutinsky calculations by means of total-Routhian-surface (TRS) methods. The inversion of the order of the g9 /2 neutron and the g9 /2 proton crossing frequency observed in the negative-parity ? (f5 /2) bands between Ge73 and Se75Kr77, can be ascribed to their different triaxial deformations. At higher spins, both the ? (f5 /2) and ? (g9 /2) bands in Ge73 undergo a shape evolution with sizable alignments occurring. The characters of large signature splitting in ? (g9 /2) band of Ge73 are discussed.

  11. Single-Band and Dual-Band Infrared Detectors

    Science.gov (United States)

    Ting, David Z. (Inventor); Gunapala, Sarath D. (Inventor); Soibel, Alexander (Inventor); Nguyen, Jean (Inventor); Khoshakhlagh, Arezou (Inventor)

    2015-01-01

    Bias-switchable dual-band infrared detectors and methods of manufacturing such detectors are provided. The infrared detectors are based on a back-to-back heterojunction diode design, where the detector structure consists of, sequentially, a top contact layer, a unipolar hole barrier layer, an absorber layer, a unipolar electron barrier, a second absorber, a second unipolar hole barrier, and a bottom contact layer. In addition, by substantially reducing the width of one of the absorber layers, a single-band infrared detector can also be formed.

  12. Calculation of Gilbert damping in ferromagnetic ?lms

    Directory of Open Access Journals (Sweden)

    Edwards D. M.

    2013-01-01

    Full Text Available The Gilbert damping constant in the phenomenological Landau-Lifshitz-Gilbert equation which describes the dynamics of magnetization, is calculated for Fe, Co and Ni bulk ferromagnets, Co ?lms and Co/Pd bilayers within a nine-band tight-binding model with spin-orbit coupling included. The calculational effciency is remarkably improved by introducing ?nite temperature into the electronic occupation factors and subsequent summation over the Matsubara frequencies. The calculated dependence of Gilbert damping constant on scattering rate for bulk Fe, Co and Ni is in good agreement with the results of previous ab initio calculations. Calculations are reported for ferromagnetic Co metallic ?lms and Co/Pd bilayers. The dependence of the Gilbert damping constant on Co ?lm thickness, for various scattering rates, is studied and compared with recent experiments.

  13. Correlations in a Band Insulator

    Science.gov (United States)

    Sentef, Michael; Kunes, Jan; Kampf, Arno P.; Werner, Philipp

    2010-03-01

    Using DMFT we find a discontinuous band-to-Mott insulator transition upon an increase in the local Coulomb repulsion in a covalent band insulator [1,2], defined as a band insulator with partially filled local orbitals. The corresponding band gap is a hybridization gap arising from a particular pattern of hopping integrals. Similar characteristics apply to materials such as FeSi, FeSb2 or CoTiSb [3], some of which exhibit temperature dependent magnetic and transport properties reminiscent of Kondo insulators. Both charge and spin gaps in the covalent band insulator shrink with increasing Coulomb repulsion. At moderate interaction strengths the gap renormalization is well described by a renormalization factor analogous to the quasiparticle weight in a Fermi liquid. [4pt] [1] M. Sentef, J. Kunes, P. Werner, and A.P. Kampf, Phys. Rev. B 80, 155116 (2009) [0pt] [2] A.P. Kampf, M. Kollar, J. Kunes, M. Sentef, and D. Vollhardt, arXiv:0910.5126

  14. Analysis of CO2 bands near 2600 per cm

    Science.gov (United States)

    Hoke, M. L.; Shaw, J. H.

    1982-01-01

    The parameters of three bands of CO2 near 2600 per cm have been determined by the nonlinear least squares method of whole-band analysis. Careful modeling of the effect of the Fourier transform spectrometer on the spectrum has made it possible to reduce the difference between the observed and calculated spectra to values close to the estimated noise in the experimental spectrum. In particular, it is found necessary to model the effects of phase error even though these are difficult to observe in the experimental spectra.

  15. Band renormalization effects in correlated f-electron systems

    Science.gov (United States)

    Durakiewicz, T.; Joyce, J. J.; Li, Y.; Riseborough, P. S.; Oppeneer, P. M.; Bauer, E. D.; Graham, K. S.

    2011-01-01

    Two band renormalization effects, novel in the context of f-electron systems, are presented here. First, the interband scattering mechanism leads to the point-like Fermi surface renormalization along kx/ky directions in the Brillouin zone. Second, in the normal direction the renormalization leads to reduction in the number of Fermi sheets and in creation of additional periodicity in band dispersion. It is shown that such renormalization effects can lead to significant differences between calculated and measured electronic structures, and need to be considered in f-electron systems.

  16. Band renormalization effects in correlated f-electron systems

    International Nuclear Information System (INIS)

    Two band renormalization effects, novel in the context of f-electron systems, are presented here. First, the interband scattering mechanism leads to the point-like Fermi surface renormalization along kx/ky directions in the Brillouin zone. Second, in the normal direction the renormalization leads to reduction in the number of Fermi sheets and in creation of additional periodicity in band dispersion. It is shown that such renormalization effects can lead to significant differences between calculated and measured electronic structures, and need to be considered in f-electron systems.

  17. Band renormalization effects in correlated f-electron systems

    Energy Technology Data Exchange (ETDEWEB)

    Durakiewicz, T; Joyce, J J; Li, Y; Bauer, E D; Graham, K S [Los Alamos National Laboratory, PO Box 1663, Los Alamos (United States); Riseborough, P S [Physics Department, Temple University, Philadelphia (United States); Oppeneer, P M, E-mail: tomasz@lanl.gov [Department of Physics and Astronomy, Uppsala University, SE-75120 Uppsala (Sweden)

    2011-01-01

    Two band renormalization effects, novel in the context of f-electron systems, are presented here. First, the interband scattering mechanism leads to the point-like Fermi surface renormalization along k{sub x}/k{sub y} directions in the Brillouin zone. Second, in the normal direction the renormalization leads to reduction in the number of Fermi sheets and in creation of additional periodicity in band dispersion. It is shown that such renormalization effects can lead to significant differences between calculated and measured electronic structures, and need to be considered in f-electron systems.

  18. Microscopic insight in the study of yrast bands in selenium isotopes

    Indian Academy of Sciences (India)

    Parvaiz Ahmad Dar; Sonia Verma; Rani Devi; S K Khosa

    2008-05-01

    The yrast bands of even-even selenium isotopes with $A = 68-78$ are studied in the framework of projected shell model, by employing quadrupole plus monopole and quadrupole pairing force in the Hamiltonian. The oblate and prolate structures of the bands have been investigated. The yrast energies, backbending plots and reduced $E2$ transition probabilities and -factors are calculated and compared with the experimental data. The calculated results are in reasonably good agreement with the experiments.

  19. Charge state of the O$_{2}$ molecule during silicon oxidation through hybrid functional calculations

    OpenAIRE

    Alkauskas, Audrius; Broqvist, Peter; Pasquarello, Alfredo

    2008-01-01

    We study the charge state of the diffusing O$_2$ molecule during silicon oxidation through hybrid functional calculations. We calculate charge transition levels of O$_2$ in bulk SiO$_2$ and use theoretical band offsets to align these levels with respect to the Si band edges. To overcome the band-gap problem of semilocal density fuctionals, we employ hybrid functionals with both predefined and empirically adjusted mixing coefficients. We find that the charge transition level ...

  20. Dual-Band Tunable Recursive Active Filter

    OpenAIRE

    Segovia Vargas, Daniel; García Pérez, Oscar Alberto; González Posadas, Vicente; Aznar Ballesta, Francisco

    2011-01-01

    This letter presents a novel recursive active filter topology that provides dual-band performance, with independent tuning capability in both bands. The dual-band operation is achieved by using two independent feedback lines. Additionally, linear phase shifters based on left-handed cells are included in these two branches in order to tune the center frequency of both pass bands.

  1. Crossing of shears bands in 196Pb

    International Nuclear Information System (INIS)

    High-spin states in 196Pb have been populated using the reaction 170Er(30Si, 4n). The previously observed shear bands in this nucleus have been extended and some of their transitions have been reordered. They now form regular bands with band crossings. One of the bands splits into two pathways at high spin. (orig.)

  2. Theoretical Isochrones with Extinction in the K Band. II. J - K versus K

    OpenAIRE

    Kim, Sungsoo S.; Donald F. Figer; Lee, Myung Gyoon

    2006-01-01

    We calculate theoretical isochrones in a consistent way for five filter pairs near the J and K band atmospheric windows (J-K, J-K', J-Ks, F110W-F205W, and F110W-F222M) using the Padova stellar evolutionary models of Girardi et al. We present magnitude transformations between various K-band filters as a function of color. Isochrones with extinction of up to 6 mag in the K band are also presented. As found for the filter pairs composed of H & K band filters, we find that the r...

  3. Features of the band structure for semiconducting iron, ruthenium, and osmium monosilicides

    International Nuclear Information System (INIS)

    The pseudopotential method has been used to optimize the crystal lattice and calculate the energy band spectra for iron, ruthenium and, osmium monosilicides. It is found that all these compounds are indirect-gap semiconductors with band gaps of 0.17, 0.22, and 0.50 eV (FeSi, RuSi, and OsSi, respectively). A distinctive feature of their band structure is the 'loop of extrema' both in the valence and conduction bands near the center of the cubic Brillouin zone.

  4. Band structures in odd-even bromine isotopes A=77-81

    International Nuclear Information System (INIS)

    The collective bands in odd-even bromine isotopes A=77, 79 and 81 are studied within our deformed configuration-mixing shell model based on self-consistently derived single-particle states. The calculated K=3/2- negative-parity ground band and the K=9/2+ positive-parity band agree reasonably well with experiment. An attempt is made to study the structure of the three quasi-particle band of high-spin states built on the J=13/2- level in these nuclei. (orig.)

  5. Curvature-induced D-band Raman scattering in folded graphene

    Energy Technology Data Exchange (ETDEWEB)

    Gupta, Awnish K; Lammert, Paul E; Crespi, Vincent H; Eklund, Peter C [Department of Physics, Pennsylvania State University, University Park, PA 16802 (United States); Nisoli, Cristiano, E-mail: crespi@phys.psu.ed [Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States)

    2010-08-25

    Micro-Raman scattering from folds in single-layer graphene sheets finds a D-band at the fold for both incommensurate and commensurate folding, while the parent single-layer graphene lacks a D-band. A coupled elastic-continuum/tight-binding calculation suggests that this D-band arises from the spatially inhomogeneous curvature around a fold in a graphene sheet. The polarization dependence of the fold-induced D-band further reveals that the inhomogeneous curvature acts as a very smooth, ideal one-dimensional defect along the folding direction.

  6. Curvature-induced D-band Raman scattering in folded graphene

    International Nuclear Information System (INIS)

    Micro-Raman scattering from folds in single-layer graphene sheets finds a D-band at the fold for both incommensurate and commensurate folding, while the parent single-layer graphene lacks a D-band. A coupled elastic-continuum/tight-binding calculation suggests that this D-band arises from the spatially inhomogeneous curvature around a fold in a graphene sheet. The polarization dependence of the fold-induced D-band further reveals that the inhomogeneous curvature acts as a very smooth, ideal one-dimensional defect along the folding direction.

  7. Grain size dependent optical band gap of CdI2 films

    Indian Academy of Sciences (India)

    Pankaj Tyagi; A G Vedeshwar

    2001-06-01

    The thermally evaporated stoichiometric CdI2 films show good -axis alignment normal to substrate plane for film thickness up to 200 nm. The optical absorption data indicate an allowed direct interband transition across a gap of 3.6 eV in confirmation with earlier band structure calculations. However, part of the absorption data near band edge can be fitted to an indirect band gap of 3 eV. The dependence of band gap on film thickness ($\\gt$ 200 nm) can be explained qualitatively in terms of decreasing grain boundary barrier height with grain size.

  8. Band gaps and radii of metallic zigzag single wall carbon nanotubes

    International Nuclear Information System (INIS)

    The band gaps of metallic zigzag single wall carbon nanotubes are difficult to determine both experimentally and theoretically: Experimentally, it is hard to synthesize pure single carbon nanotubes individually, and theoretically, the main approach, density functional theory is not good at the prediction of a band gap. Here we show a density hybrid functional theory calculation using 6–31 G† basis set to yield accurate band gaps. Consequently, an analytical expression was obtained, indicating that the band gap is related to the nearest-neighbor distance and the radius. These findings should shed light on the electron structure of the single wall carbon nanotubes

  9. Programmable calculator stress analysis

    International Nuclear Information System (INIS)

    Advanced programmable alphanumeric calculators are well suited for closed-form calculation of pressure-vessel stresses. They offer adequate computing power, portability, special programming features, and simple interactive execution procedures. Representative programs that demonstrate calculator capabilities are presented. Problems treated are stress and strength calculations in thick-walled pressure vessels and the computation of stresses near head/pressure-vessel junctures

  10. Search for excited superdeformed bands in {sup 151}Dy

    Energy Technology Data Exchange (ETDEWEB)

    Nisius, D.; Janssens, R.V.F.; Crowell, B. [and others

    1995-08-01

    Following the first report of superdeformed (SD) bands with identical transition energies in the pairs ({sup 151}Tb*,{sup 152}Dy), ({sup 150}Gd*, {sup 151}Tb) and ({sup 153}Dy*, {sup 152}Dy) (where * denotes an excited SD band), it was proposed by Nazarewicz et al. that the observations could be understood in a strong-coupling approach if pseudo SU(3) symmetry were invoked. In this model there are three limiting values of the decoupling parameter; i.e. a = 0, {plus_minus}1. In the first two cases mentioned above the pairs of bands have nearly identical transition energies and are interpreted as proton excitations involving the [200]1/2 pseudospin orbital coupled to the {sup 152}Dy core, for which the value of the decoupling parameter is calculated to be a =+1.

  11. Band structure analysis in SiGe nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Amato, Michele [' Centro S3' , CNR-Istituto Nanoscienze, via Campi 213/A, 41100 Modena (Italy); Dipartimento di Scienze e Metodi dell' Ingegneria, Universita di Modena e Reggio Emilia, via Amendola 2 Pad. Morselli, I-42100 Reggio Emilia (Italy); Palummo, Maurizia [European Theoretical Spectroscopy Facility (ETSF) (Italy); CNR-INFM-SMC, Dipartimento di Fisica, Universita di Roma, ' Tor Vergata' , via della Ricerca Scientifica 1, 00133 Roma (Italy); Ossicini, Stefano, E-mail: stefano.ossicini@unimore.it [' Centro S3' , CNR-Istituto Nanoscienze, via Campi 213/A, 41100 Modena (Italy) and Dipartimento di Scienze e Metodi dell' Ingegneria, Universita di Modena e Reggio Emilia, via Amendola 2 Pad. Morselli, I-42100 Reggio Emilia (Italy) and European Theoretical Spectroscopy Facility - ETSF (Italy) and Centro Interdipartimentale ' En and Tech' , Universita di Modena e Reggio Emilia, via Amendola 2 Pad. Morselli, I-42100 Reggio Emilia (Italy)

    2012-06-05

    One of the main challenges for Silicon-Germanium nanowires (SiGe NWs) electronics is the possibility to modulate and engine their electronic properties in an easy way, in order to obtain a material with the desired electronic features. Diameter and composition constitute two crucial ways for the modification of the band gap and of the band structure of SiGe NWs. Within the framework of density functional theory we present results of ab initio calculations regarding the band structure dependence of SiGe NWs on diameter and composition. We point out the main differences with respect to the case of pure Si and Ge wires and we discuss the particular features of SiGe NWs that are useful for future technological applications.

  12. Topological Magnon Bands in a Kagome Lattice Ferromagnet.

    Science.gov (United States)

    Chisnell, R; Helton, J S; Freedman, D E; Singh, D K; Bewley, R I; Nocera, D G; Lee, Y S

    2015-10-01

    There is great interest in finding materials possessing quasiparticles with topological properties. Such materials may have novel excitations that exist on their boundaries which are protected against disorder. We report experimental evidence that magnons in an insulating kagome ferromagnet can have a topological band structure. Our neutron scattering measurements further reveal that one of the bands is flat due to the unique geometry of the kagome lattice. Spin wave calculations show that the measured band structure follows from a simple Heisenberg Hamiltonian with a Dzyaloshinkii-Moriya interaction. This serves as the first realization of an effectively two-dimensional topological magnon insulator-a new class of magnetic material that should display both a magnon Hall effect and protected chiral edge modes. PMID:26551820

  13. Topological Magnon Bands in a Kagome Lattice Ferromagnet

    Science.gov (United States)

    Chisnell, R.; Helton, J. S.; Freedman, D. E.; Singh, D. K.; Bewley, R. I.; Nocera, D. G.; Lee, Y. S.

    2015-10-01

    There is great interest in finding materials possessing quasiparticles with topological properties. Such materials may have novel excitations that exist on their boundaries which are protected against disorder. We report experimental evidence that magnons in an insulating kagome ferromagnet can have a topological band structure. Our neutron scattering measurements further reveal that one of the bands is flat due to the unique geometry of the kagome lattice. Spin wave calculations show that the measured band structure follows from a simple Heisenberg Hamiltonian with a Dzyaloshinkii-Moriya interaction. This serves as the first realization of an effectively two-dimensional topological magnon insulator—a new class of magnetic material that should display both a magnon Hall effect and protected chiral edge modes.

  14. Microscopic study of superdeformed rotational bands in 151 Tb

    International Nuclear Information System (INIS)

    Structure of eight superdeformed bands in the nucleus 151Tb is analyzed using the results of the Hartree-Fock and Woods-Saxon cranking approaches. It is demonstrated that far going similarities between the two approaches exit and predictions related to the structure of rotational bands calculated within the two models are nearly parallel. An interpretation scenario for the structure of the superdeformed bands is presented and predictions related to the exit spins are made. Small but systematic discrepancies between experiment and theory, analyzed in terms of the dynamical moments, J(2), are shown to exist. The pairing correlations taken into account by using the particle-number-projection technique are shown to increase the disagreement. Sources of these systematic discrepancies are discussed - they are most likely related to the yet not optimal parametrization of the nuclear interactions used. (authors)

  15. Band-engineered SrTiO{sub 3} nanowires for visible light photocatalysis

    Energy Technology Data Exchange (ETDEWEB)

    Fu, Q.; He, T.; Li, J. L.; Yang, G. W. [State Key Laboratory of Optoelectronic Materials and Technologies, Institute of Optoelectronic and Functional Composite Materials, Nanotechnology Research Center, School of Physics and Engineering, Sun Yat-sen University, Guangzhou 510275, Guangdong (China)

    2012-11-15

    We have theoretically investigated the structural, electronic, and optical properties of perovskite SrTiO{sub 3} nanowires for use in visible light photocatalytic applications using pseudopotential density-functional theory calculations. The electronic structure calculations show that the band gap is modified in the SrTiO{sub 3} nanowires compared with that of the bulk. For TiO{sub 2}-terminated nanowires, the mid-band states induced by the combination of oxygen and strontium atoms on the surface lead to a shift in the valence band toward the conduction band without interference from the edge of the conduction band, which reduces the band gap. On the contrary, the electronic states induced by the combination of oxygen and strontium atoms on the surface of SrO-terminated nanowires lead to a shift in the conduction band toward the valence band. The calculated optical results indicate that the absorption edge of the nanowires shift towards the red-light region. These theoretical results suggest that perovskite SrTiO{sub 3} nanowires are promising candidates for use in visible light photocatalytic processes such as solar-assisted water splitting reactions.

  16. Curriculum Guide for Beginners Band.

    Science.gov (United States)

    Bazar, W. Gayre

    This curriculum guide for beginners band is the product of a team of teachers, administrators, and supervisory personnel. The prime objectives in the beginning instrument class is the development of correct playing habits, with emphasis on posture, holding position, embouchure, breathing, tonguing, good tone production and intonation. Subjects…

  17. Correlations in a band insulator.

    Czech Academy of Sciences Publication Activity Database

    Sentef, M.; Kuneš, Jan; Werner, P.; Kampf, A. P.

    2009-01-01

    Ro?. 80, ?. 15 (2009), 155116/1-155116/7. ISSN 1098-0121 Institutional research plan: CEZ:AV0Z10100521 Keywords : electronic correlations * dynamical mean-field theory * band insulator Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.475, year: 2009

  18. X-band preamplifier filter

    Science.gov (United States)

    Manshadi, F.

    1986-01-01

    A low-loss bandstop filter designed and developed for the Deep Space Network's 34-meter high-efficiency antennas is described. The filter is used for protection of the X-band traveling wave masers from the 20-kW transmitter signal. A combination of empirical and theoretical techniques was employed as well as computer simulation to verify the design before fabrication.

  19. What about a Military Band?

    Science.gov (United States)

    Snyder, Neal

    1996-01-01

    Provides an overview of the benefits and limitations of pursuing a musical career in the military. Military band members enjoy greater job security and benefits than most musicians. The military, however, remains a highly structured environment and most musicians have to go through basic training. (MJP)

  20. Intermediate-Frequency-to-Video-Band Converter

    Science.gov (United States)

    Ham, N. C.; Chavez, V. M.; Chen, V. S.; Sato, T.

    1986-01-01

    Analog and digital circuits combined to frequency-convert from intermediate frequencies directly to video-band frequencies to meet stringent requirements. IF-to-video-band converter operates on principle of signal-band cancellation in phase-quadrature circuits. Downconverts intermediate frequencies directly to video-band frequencies to near-zero frequency with good image-band rejection and low phase variation within passband.

  1. Lamb wave band gaps in a homogenous plate with periodic Gaussian surfaces

    Science.gov (United States)

    Ming, Chen; Chen, Jiujiu; Han, Xu; Zhang, Hongbo

    2013-09-01

    The Lamb wave band structure of a one-dimensional thin plate with periodic Gaussian surfaces is calculated based on the eigen-mode matching theory (EMMT) method. The finite element method is also employed to calculate the transmission power spectra and the band structure, which are both in good agreement with the results of the EMMT method. In contrast with the straight stubs, the low-frequency band gap of the system with the Gaussian surfaces is wider, when the Gaussian domain's height and area are equal to those of the stub, and the two systems' main plate size and materials are the same. This can be confirmed by the ‘spring-mass' model, which can be used to estimate the resonant frequency. We also investigate the effects of the geometrical parameters on band structure, including the height of the Gaussian domain, the plate thickness and the filling fraction. The results suggest that the band gaps have a close relevance to them.

  2. Shear horizontal guided wave band gaps in a homogenous plate with periodic tapered surface

    Science.gov (United States)

    Song, Guang-huang; Chen, Jiu-jiu; Han, Xu

    2014-09-01

    The shear horizontal (SH) guided wave band structures and transmission coefficients in a homogenous plate with periodic tapered surface, whose width is gradually decreases from the lower base to the upper base, are calculated based on the eigen-mode matching theory (EMMT) method. The finite element method (FEM) is also employed to calculate the band structures, which is in good agreement with the results by EMMT method. Numerical results show that the SH guided wave band structures in reduced frequency keep unchanged even if the whole homogenous plate with periodic tapered surface is filled with different materials. We also present the numerical investigations of the geometrical factors’ effect on the band structures, including the upper base width, the lower base width, the tapered surface thickness and the plate thickness. These properties of SH guided wave can potentially be utilized to design acoustic sensors, tune band gaps and generate filters.

  3. Optical properties of chalcopyrite-type intermediate transition metal band materials from first principles

    International Nuclear Information System (INIS)

    The optical properties of a novel potential high-efficiency photovoltaic material have been studied. This material is based on a chalcopyrite-type semiconductor (CuGaS2) with some Ga atom substituted by Ti and is characterized by the formation of an isolated transition-metal band between the valence band and the conduction band. We present a study in which ab-initio density functional theory calculations within the generalized gradient approximation are carried out to determine the optical reflectivity and absorption coefficient of the materials of interest. Calculations for the host semiconductor are in good agreement with experimental results within the limitations of the approach. We find, as desired, that because of the intermediate band, the new Ti-substituted material would be able to absorb photons of energy lower than the band-gap of the host chalcopyrite. We also analyze the partial contributions to the main peaks of its spectrum

  4. Wide band SAR sub-band splitting and inter-band coherence measurements

    OpenAIRE

    De Rauw, Dominique; Orban, Anne; Barbier, Christian

    2010-01-01

    Range resolution of SAR images is determined by transmitted radar signal bandwidth. Most recent SAR sensors use wide band signals in order to achieve metric range resolution, whereas metric azimuth resolution can be achieved in spotlight mode. As an example, ENVISAT ASAR sensor uses a 15-MHz bandwidth chirp whereas TerraSAR-X spotlight mode uses signals having a 150-MHz bandwidth leading to a potentially 10 times higher resolution. One can also take advantage of wide band to split the full ba...

  5. Residual stress dependant anisotropic band gap of various (hkl) oriented BaI2 films

    International Nuclear Information System (INIS)

    The thermally evaporated layer structured BaI2 grows in various completely preferred (hkl) film orientations with different growth parameters like film thickness, deposition rate, substrate temperature, etc. which were characterized by structural, morphological, and optical absorption measurements. Structural analysis reveals the strain in the films and the optical absorption shows a direct type band gap. The varying band gaps of these films were found to scale linearly with their strain. The elastic moduli and other constants were also calculated using Density Functional Theory (DFT) formalism implemented in WIEN2K code for converting the strain into residual stress. Films of different six (hkl) orientations show stress free anisotropic band gaps (2.48–3.43?eV) and both positive and negative pressure coefficients. The negative and positive pressure coefficients of band gap are attributed to the strain in I-I (or Ba-Ba or both) and Ba-I distances along [hkl], respectively. The calculated band gaps are also compared with those experimentally determined. The average pressure coefficient of band gap of all six orientations (?0.071?eV/GPa) found to be significantly higher than that calculated (?0.047?eV/GPa) by volumetric pressure dependence. Various these issues have been discussed with consistent arguments. The electron effective mass me*=0.66m0 and the hole effective mass mh*=0.53m0 have been determined from the calculated band structure

  6. Reinvestigation of the collective band structures in odd-odd {sup 138}Pm nucleus

    Energy Technology Data Exchange (ETDEWEB)

    Li, H.J. [Tsinghua University, Department of Physics, Beijing (China); Royal Institute of Technology, Department of Physics, Stockholm (Sweden); Xiao, Z.G. [Tsinghua University, Department of Physics, Beijing (China); Collaborative Innovation Center of Quantum Matter, Beijing (China); Zhu, S.J.; Yeoh, E.Y.; Zhang, Z.; Wang, R.S.; Yi, H.; Yan, W.H.; Xu, Q. [Tsinghua University, Department of Physics, Beijing (China); Qi, C. [Royal Institute of Technology, Department of Physics, Stockholm (Sweden); Wu, X.G.; He, C.Y.; Zheng, Y.; Li, G.S.; Li, C.B.; Li, H.W.; Liu, J.J.; Hu, S.P.; Wang, J.L.; Yao, S.H. [China Institute of Atomic Energy, Beijing (China)

    2015-05-15

    The high-spin states in the odd-odd {sup 138}Pm nucleus have been reinvestigated via the {sup 124}Te({sup 19}F, 5n) reaction at the beam energy of 103 MeV. Most of the known transitions and levels are confirmed. A number of bands are revised and one new band has been established. For the yrast ?h{sub 11/2} x ?h{sub 11/2} band based on 8{sup +} state, no evidence supporting the occurence of signature inversion is found. The experimental and theoretical B(M1)/B(E2) ratios have been calculated for band (2), which support the ?g{sub 7/2}[413]5/2{sup +} x ?h{sub 11/2}[514]9/2{sup -} Nilsson configuration assignment. Four bands with ?I = 2 transitions are tentatively assigned as doubly decoupled bands. The other three bands are proposed as oblate-triaxial bands. The possible configuration assignments for these bands are also discussed under the calculations of total Routhian surface and particle-rotor model. (orig.)

  7. Band structure of fcc-C60 solid state crystal study

    Directory of Open Access Journals (Sweden)

    S Javanbakht

    2009-09-01

    Full Text Available We studied the architecture of the C60 cluster to drive its atomic positions which can be seen at room temperature. We then used the obtained carbon positions as a basis set for the fcc structure to construct the fcc-C60 compound. Self consistent calculations were performed based on the density functional theory (DFT utilizing the accurate WIEN2K code to solve the single-particle Kohen-Sham equation within the augmented plane waves plus local orbital (APW+lo method. The cohesive energy has been found to be 1.537 eV for the fcc-C60 . The calculated small cohesive energy that results from the weak Van der Waals-London interactions among a C60 cluster with its nearest neighbors is in good agreement with experiment. The electron densities of states (DOSs were calculated for a C60 macromolecule as well as the fcc-C60 compound and the results were compared with each other. The band gap from DOS calculations has been found to be 0.7 eV. Band structures were also calculated within the generalized gradient approximation (GGA. The band structure calculation results in 1.04 eV for the direct band gap. Two kinds of ? and ? bonds were determined in the band structure. Our results are in good agreement with experiment and pseudopotential calculations.

  8. Systematics of band moment of inertia of yrast and excited SD bands of even-even nuclei in A~150 mass region

    Science.gov (United States)

    Sharma, Neha; Mittal, H. M.

    2015-07-01

    A four parameter formula has been applied to all the yrast and excited superdeformed (SD) bands of even-even nuclei in the A 150 mass region to obtain band moment of inertia J0. In even-even nuclei, totally three yrast SD bands and 16 excited SD bands have been fitted. The measured Qt values and hence the axes ratios have been used to calculate the rigid body J0 values and compared with the fitted values of J0. It is interesting to look at the yrast SD band 152Dy(1), the doubly magic SD nucleus and the first one to be discovered that the J0 values are quite larger than that extracted from Qt measurement. We found that all the excited SD bands in even-even nuclei are signature partner SD bands because the J0 value of each signature partner SD band is almost identical. Among all these excited SD bands, 150Gd(4) is found to be super-rigid in nature having J0 value larger than that observed from the measured Qt value.

  9. Evaluation bases for calculation methods in radioecology

    International Nuclear Information System (INIS)

    The seven contributions in this book deal with the state and problems of radioecology. In particular it analyses: The propagation of radioactive materials in the atmosphere, the transfer of radioactive substances from the soil into plants, respectively from animal feed into meat, the exposure pathways for, and high-risk groups of the population, the uncertainties and the band width of the ingestion factor, as well as the treatment of questions of radioecology in practice. The calculation model is assessed and the difficulty evaluated of laying down data in the general calculation basis. (DG)

  10. Electronic band structure of the ordered Zn0.5Cd0.5Se alloy calculated by the semi-empirical tight-binding method considering second-nearest neighbor / Estructura electrónica de bandas de la aleación ordenada de Zn0.5Cd0.5Se calculada por el método semi-empírico de enlace fuerte teniendo en cuenta interacción a segundos vecinos

    Scientific Electronic Library Online (English)

    Juan Carlos, Salcedo-Reyes.

    2008-07-01

    Full Text Available Aunque la descripción de las aleaciones ternarias semiconductoras se hace tradicionalmente asumiendo la aproximación de compuesto pseudo-binario. Para el caso de aleaciones artificiales de compuestos II-VI y III-V, en las cuales se ha reportado un ordenamiento inducido por el crecimiento, una aproxi [...] mación de este tipo no es aplicable, de modo que, con el fin de hacer una descripción adecuada de las propiedades ópticas y electrónicas de dichas aleaciones artificiales, se debe asumir una descripción atomística que tenga en cuenta la estructura local. En particular, para la aleación ordenada de Zn0.5Cd0.5Se, el cambio de simetría implica que se debe usar una estructura tetragonal simple, dando lugar, principalmente, a dos efectos: i) disminución de la brecha prohibida del material y ii) un desdoblamiento en el máximo de la banda de valencia. En este trabajo se calcula la estructura de bandas de la aleación ordenada de Zn0.5Cd0.5Se usando la aproximación semi-empírica de enlace fuerte teniendo en cuenta interacción a segundos vecinos y se compara con la estructura de bandas obtenida por el método FP-LAPW (full-potential linearized augmentedplane wave). Se obtiene una buena concordancia de las principales características entre las estructuras de bandas calculadas por el método semi-empírico y el método ab initio. Abstract in english Usually, semiconductor ternary alloys are studied via a pseudo-binary approach in which the semiconductor is described like a crystalline array were the cation/anion sub-lattice consist of a random distribution of the cationic/anionic atoms. However, in the case of reported III-V and II-VI artificia [...] l structures, in which an ordering of either the cations or the anions of the respective fcc sub-lattice is involved, a pseudo-binary approach can no longer be employed, an atomistic point of view, which takes into account the local structure, must be used to study the electronic and optical properties of these artificial semiconductor alloys. In particular, the ordered Zn0.5Cd0.5Se alloy has to be described as a crystal with the simple-tetragonal Bravais lattice with a composition equal to the zincblende random ternary alloy. The change of symmetry properties of the tetragonal alloy, in relation to the cubic alloy, results mainly in two effects: i) reduction of the banned gap, and ii) crystal field cleavage of the valence band maximum. In this work, the electronic band structure of the ordered Zn0.5Cd0.5Se alloy is calculated using a second nearest neighbor semi-empirical tight binding method. Also, it is compared with the electronic band structure obtained by FP-LAPW (fullpotential linearized augmented-plane wave) method.

  11. MOLECULAR ORBITAL CALCULATION ON THE INTERSTITIAL CARBON IN STEEL MARTENSITE

    OpenAIRE

    Fujita, F.; Nasu, S.; Adachi, H.

    1982-01-01

    Local electronic state around an intersititial carbon atom in bct iron lattice is calculated by using the discrete variational x-? cluster method in molecular orbital calculation. Hybridization between C-2s, 2p and Fe-3d,4s,4p orbitals produces bonding and antibonding levels, which control the local band structure. By taking account of the up and down spin configuration, magnetic moments of the first, second and farther neighbor iron atoms surrounding the carbon atom are calculated and compar...

  12. Broad-Band Spectral Indices Variability of BL Lacertae by Wavelet Method

    Indian Academy of Sciences (India)

    Hao-Jing Zhang; Jing-Ming Bai; Yu-Ying Bao; Xiong Zhang

    2014-09-01

    BL Lacertae is one of the famous AGN that shows convincing evidence to support periodic variability. We compile R-band data and radio 22 GHz database from the available literature to build the light curves and to calculate broad-band spectral indices. This paper employs the wavelet periodic estimation method. The analysis results indicate that the most possible period is 7.02–7.36 yr in the selected wave-bands. The broad-band spectral indices have a possible period of 4.11 yr as a half value in selected wave-bands. The results confirm that the variability period in the radio 22 GHz is in agreement with the optical R band of about 7.01 yr, as also mentioned in other literatures.

  13. Slave-boson theory of the Mott transition in the two-band Hubbard model

    CERN Document Server

    Rügg, A; Pilgram, S; Sigrist, M

    2005-01-01

    We apply the slave-boson approach of Kotliar and Ruckenstein to the two-band Hubbard model with an Ising like Hund's rule coupling and bands of different widths. On the mean-field level of this approach we investigate the Mott transition and observe both separate and joint transitions of the two bands depending on the choice of the inter- and intraorbital Coulomb interaction parameters. The mean-field calculations allow for a simple physical interpretation and can confirm several aspects of previous work. Beside the case of two individually half-filled bands we also examine what happens if the original metallic bands possess fractional filling either due to finite doping or due to a crystal field which relatively shifts the atomic energy levels of the two orbitals. For appropriate values of the interaction and of the crystal field we can observe a a band insulating state and a ferromagnetic metal.

  14. Theory of Band Warping and its Effects on Thermoelectronic Transport Properties

    CERN Document Server

    Mecholsky, Nicholas A; Pegg, Ian L; Fornari, Marco

    2014-01-01

    Optical and transport properties of materials depend heavily upon features of electronic band structures in proximity to energy extrema in the Brillouin zone (BZ). Such features are generally described in terms of multi-dimensional quadratic expansions and corresponding definitions of effective masses. Multi-dimensional expansions, however, are permissible only under strict conditions that are typically violated by degenerate bands and even some non-degenerate bands. Suggestive terms such as "band warping" or "corrugated energy surfaces" have been used to refer to such situations and ad hoc methods have been developed to treat them. While numerical calculations may reflect such features, a complete theory of band warping has not been developed. We develop a generally applicable theory, based on radial expansions, and a corresponding definition of angular effective mass. Our theory also accounts for effects of band non-parabolicity and anisotropy, which hitherto have not been precisely distinguished from, if n...

  15. Band structure of CdTe under high pressure

    International Nuclear Information System (INIS)

    The band structures and density of states of cadmium telluride (CdTe) under various pressures ranging from normal to 4.5 Mbar are obtained. The electronic band structure at normal pressure of CdTe (ZnS structure) is analyzed and the direct band gap value is found to be 1.654 eV. CdTe becomes metal and superconductor under high pressure but before that it undergoes structural phase transition from ZnS phase to NaCl phase. The equilibrium lattice constant, bulk modulus and the phase transition pressure at which the compounds undergo structural phase transition from ZnS to NaCl are predicted from the total energy calculations. The density of states at the Fermi level (N(EF)) gets enhanced after metallization, which leads to the superconductivity in CdTe. In our calculation, the metallization pressure (PM = 1.935 Mbar) and the corresponding reduced volume ((V/V0)M = 0.458) are estimated. Metallization occurs via direct closing of band gap at ? point. (author)

  16. Superdeformation in 146Gd: First observation of a band crossing

    International Nuclear Information System (INIS)

    High-spin states of the nucleus 146Gd were populated in a 110Pd(40Ar, 4n) reaction. The emitted ?-radiation was measured using the OSIRIS-spectrometer. A superformed band consisting of 13 discrete transitions was found in 146Gd. From the data obtained in a second experiment, using a backed target, the lifetimes of the states in the SDB have been measured using the DSA-method. An average quadrupolmoment of Q0 = 12 ± 2 eb could be deduced for the band. A band crossing occurs at rotational frequency of ?? = 0.65 MeV. It is for the first time that a crossing could be observed in a superdeformed band. From theoretical calculations a ?62 ?71 configuration with odd spin an odd parity is suggested. The behaviour of the dynamic moment of inertia can be reproduced by cranked Nilsson-model calculations assuming a crossing of the [651 1/2] and [642 5/2] single-neutron levels. (orig.)

  17. Superdeformed band in the $N = Z+4$ nucleus $^{40}$Ar: A projected shell model analysis

    CERN Document Server

    Yang, Ying-Chun; Sun, Yang; Guidry, Mike

    2015-01-01

    It has been debated whether the experimentally-identified superdeformed rotational band in $^{40}$Ar [E. Ideguchi, et al., Phys. Lett. B 686 (2010) 18] has an axially or triaxially deformed shape. Projected shell model calculations with angular-momentum-projection using an axially-deformed basis are performed up to high spins. Our calculated energy levels indicate a perfect collective-rotor behavior for the superdeformed yrast band. However, detailed analysis of the wave functions reveals that the high-spin structure is dominated by mixed 0-, 2-, and 4-quasiparticle configurations. The calculated electric quadrupole transition probabilities reproduce well the known experimental data and suggest a reduced, but still significant, collectivity in the high spin region. The deduced triaxial deformation parameters are small throughout the entire band, suggesting that triaxiality is not very important for this superdeformed band.

  18. Table of superdeformed nuclear bands and fission isomers

    International Nuclear Information System (INIS)

    A minimum in the second potential well of deformed nuclei was predicted and the associated shell gaps are illustrated in the harmonic oscillator potential shell energy surface calculations shown in this report. A strong superdeformed minimum in 152Dy was predicted for ?2-0.65. Subsequently, a discrete set of ?-ray transitions in 152DY was observed and, assigned to the predicted superdeformed band. Extensive research at several laboratories has since focused on searching for other mass regions of large deformation. A new generation of ?-ray detector arrays is already producing a wealth of information about the mechanisms for feeding and deexciting superdeformed bands. These bands have been found in three distinct regions near A=l30, 150, and 190. This research extends upon previous work in the actinide region near A=240 where fission isomers were identified and also associated with the second potential well. Quadrupole moment measurements for selected cases in each mass region are consistent with assigning the bands to excitations in the second local minimum. As part of our committment to maintain nuclear structure data as current as possible in the Evaluated Nuclear Structure Reference File (ENSDF) and the Table of Isotopes, we have updated the information on superdeformed nuclear bands. As of April 1994, we have complied data from 86 superdeformed bands and 46 fission isomers identified in 73 nuclides for this report. For each nuclide there is a complete level table listing both normal and superdeformed band assignments; level energy, spin, parity, half-life, magneto moments, decay branchings; and the energies, final levels, relative intensities, multipolarities, and mixing ratios for transitions deexciting each level. Mass excess, decay energies, and proton and neutron separation energies are also provided from the evaluation of Audi and Wapstra

  19. Table of superdeformed nuclear bands and fission isomers

    Energy Technology Data Exchange (ETDEWEB)

    Firestone, R.B. [Lawrence Berkeley Lab., CA (United States); Singh, B. [McMaster Univ., Hamilton, ON (Canada)

    1994-06-01

    A minimum in the second potential well of deformed nuclei was predicted and the associated shell gaps are illustrated in the harmonic oscillator potential shell energy surface calculations shown in this report. A strong superdeformed minimum in {sup 152}Dy was predicted for {beta}{sub 2}-0.65. Subsequently, a discrete set of {gamma}-ray transitions in {sup 152}DY was observed and, assigned to the predicted superdeformed band. Extensive research at several laboratories has since focused on searching for other mass regions of large deformation. A new generation of {gamma}-ray detector arrays is already producing a wealth of information about the mechanisms for feeding and deexciting superdeformed bands. These bands have been found in three distinct regions near A=l30, 150, and 190. This research extends upon previous work in the actinide region near A=240 where fission isomers were identified and also associated with the second potential well. Quadrupole moment measurements for selected cases in each mass region are consistent with assigning the bands to excitations in the second local minimum. As part of our committment to maintain nuclear structure data as current as possible in the Evaluated Nuclear Structure Reference File (ENSDF) and the Table of Isotopes, we have updated the information on superdeformed nuclear bands. As of April 1994, we have complied data from 86 superdeformed bands and 46 fission isomers identified in 73 nuclides for this report. For each nuclide there is a complete level table listing both normal and superdeformed band assignments; level energy, spin, parity, half-life, magneto moments, decay branchings; and the energies, final levels, relative intensities, multipolarities, and mixing ratios for transitions deexciting each level. Mass excess, decay energies, and proton and neutron separation energies are also provided from the evaluation of Audi and Wapstra.

  20. Electron impact excitation of the gamma bands of nitric oxide

    International Nuclear Information System (INIS)

    The excitation of several pronounced ? bands of NO by electron impact was studied from threshold to 1000 eV. A high optical efficiency was achieved by using an ellipsoidal collision chamber with mirrored interior surfaces. The interaction volume viewed was located at one of the foci of the ellipsoid. A 0.25 m double monochromator and single photon counting techniques were employed to monitor molecular band intensities. The optical sensitivity between 2000 and 4000 A was obtained with the molecular branching ratio method by monitoring 1NG CO+, 1NG N+2, 2PG N2 band intensities and suitable progressions in the ? system of NO. Second order effects were avoided by low NO densities (approx.10-1 torr) in the collision chamber. No ionization gauges were used during measurement, thus eliminating the possible dissociation of NO and subsequent formation of N2. Absolute cross sections for ? bands were obtained by normalizing to the 2PG (0,0) band of N2. For this purpose, a known mixture of NO and N2 was prepared in a gas handling manifold using a manometer. For the unambiguously identifiable (0,1), (0,2), (1,0), (1,5), and (2,7) ? bands of NO, the cross sections peaked near 18 eV and had values of 2.2, 1.8, 6.3, 1.3, and 0.57times10-19 cm2, respectively, with a possible error of 25%. The relative peak cross sections agree with calculated band intensities within 20%

  1. Strain sensitivity of band gaps of Sn-containing semiconductors

    DEFF Research Database (Denmark)

    Li, Hong; Castelli, Ivano Eligio

    2015-01-01

    Tuning of band gaps of semiconductors is a way to optimize materials for applications within photovoltaics or as photocatalysts. One way to achieve this is through applying strain to the materials. We investigate the effect of strain on a range of Sn-containing semiconductors using density functional theory and many-body perturbation theory calculations. We find that the band gaps of bulk Sn oxides with SnO6 octahedra are highly sensitive to volumetric strain. By applying a small isotropic strain of 2% (-2%), a decrease (increase) of band gaps as large as 0.8 to 1.0 eV are obtained. We attribute the ultrahigh strain sensitivity to the pure Sn s-state character of the conduction-band edges. Other Sn-containing compounds may show both increasing and decreasing gaps under tensile strain and we show that the behavior can be understood by analyzing the role of the Sn s states in both the valence and the conduction bands.

  2. Electronic structures of (Zn, TM)O (TM: V, Cr, Mn, Fe, Co, and Ni) in the self-interaction-corrected calculations

    International Nuclear Information System (INIS)

    We calculate the electronic structures of ZnO-based dilute magnetic semiconductors within the self-interaction-corrected local density approximation. The results are compared with those calculated within the standard local density approximation. We find the differences in the band gap energy, the energetic position of the Zn 3d bands, and the description of the transition-metal d bands

  3. Stability of the split-band solution and energy gap in the narrow-band region of the Hubbard model

    International Nuclear Information System (INIS)

    By inserting quasielectron energies ? calculated from the fully renormalized Green's function of the Hubbard model obtained in the preceding paper into the exact expression of Galitskii and Migdal, the ground-state energy, the chemical potential, and the dynamic- and thermodynamic-stability conditions are calculated in the narrow-band region. The results show that as long as the interaction energy I is finite, electrons in the narrow-band region do not obey the Landau theory of Fermi liquids, and a gap appears between the lowest quasielectron energy ? and the chemical potential ? for any occupation n, regardless of whether the lower band is exactly filled or not. This unusual behavior is possible because, when an electron is added to the system of N electrons, the whole system relaxes due to the strong interaction, introducing a relaxation energy difference between the two quantities. We also show that all previous solutions which exhibit the split-band structure, including Hubbard's work, yield the same conclusion that electrons do not behave like Landau quasiparticles. However, the energy gap is calculated to be negative at least for some occupations n, demonstrating the dynamic instability of those solutions. They also exhibit thermodynamic instability for certain occupations, while the fully renormalized solution, having sufficient electron correlations built in, satisfies the dynamic and thermodynamic stability conditions for all occupations. When the lower band is nearly filled, the nature of the solution is shown to change, making the coherent motion of electrons with fixed k values more difficult. In the pathological limit where I=infinity, however, the gap vanishes, yielding a metallic state

  4. Motion of dislocations during formation of crystallographic gliding band

    International Nuclear Information System (INIS)

    Mathematical model, describing dynamics of dislocation motion and change of its kinetic energy during formation of gliding band, was formulated. Calculations for Ni and Cu showed, that velocity of screw dislocation grew achieving some maximal value and then began to decrease. Velocity of edge dislocation can (other conditions being equal) exceed sufficiently the velocity of screw ones and grows monotonously with increase of its path, achieving asymptotically some stationary value. 10 refs.; 6 figs

  5. Pressure-induced s-band ferromagnetism in alkali metals

    OpenAIRE

    Pickard, Chris J.; Needs, R. J.

    2011-01-01

    First-principles density-functional-theory calculations show that compression of alkali metals stabilizes open structures with localized interstitial electrons which may exhibit a Stoner-type instability towards ferromagnetism. We find ferromagnetic phases of the lithium-IV-type, simple cubic, and simple hexagonal structures in the heavier alkali metals, which may be described as s-band ferromagnets. We predict that the most stable phases of potassium at low temperatures and...

  6. Mechanism of photonic band gap, optical properties, tuning and applications

    International Nuclear Information System (INIS)

    Mechanism of occurrence of Photonic Band Gap (PBG) is presented for 3-D structure using close packed face centered cubic lattice. Concepts and our work, specifically optical properties of 3-D photonic crystal, relative width, filling fraction, effective refractive index, alternative mechanism of photonic band gap scattering strength and dielectric contrast, effect of fluctuations and minimum refractive index contrast, are reported. The temperature tuning and anisotropy of nematic and ferroelectric liquid crystal infiltrated opal for different phase transitions are given. Effective dielectric constant with filling fraction using Maxwell Garnet theory (MG), multiple modified Maxwell Garnet (MMMG) and Effective Medium theory (EM) and results are compared with experiment to understand the occurrence of PBG. Our calculations of Lamb shifts including fluctuations are given and compared with those of literature values. We have also done band structure calculations including anisotropy and compared isotropic characteristic of liquid crystal. A possibility of lowest refractive index contrast useful for the fabrication of PBG is given. Our calculations for relative width as a function of refractive index contrast are reported and comparisons with existing theoretical and experimental optimal values are briefed. Applications of photonic crystals are summarized. The investigations conducted on PBG materials and reported here may pave the way for understanding the challenges in the field of PBG. (author)

  7. First-principles calculation of the energy of compressed calcium

    Science.gov (United States)

    Kasatkin, A. N.; Olesnitskii, T. A.; Sarry, M. F.

    2011-03-01

    The energy of a calcium crystal with a simple cubic lattice as a function of the ratio ( t/ U) between two internal parameters of the Hubbard model has been calculated using the Hubbard model for the s bands, equations of motion, and direct algebraic method. The electronic spectra have been calculated for the 4 s band of the crystal in two principal symmetry directions of the first Brillouin zone. The calculations have been performed at temperatures T 1 = 0 K and T 2 = 1000 K. All calculations have been carried out for different interaction energies U of s electrons, one angle, and their different concentrations n in the range 0 ? n ? 2. The calculations have demonstrated that the dependences of the energy and electronic spectra in this compressed state are very smooth. The occupation of the Ca 4 s band is in good agreement with the results of the pioneering calculations of compressed Ca (and a number of other metals), which were carried out by Gandel'man and his colleagues in the Wigner-Seitz spherical cell approximation. It has been shown that the performed analysis accurately reproduces the data obtained on the superconductivity in terms of the Bardeen-Cooper-Schrieffer theory if the 4 s band is half-occupied.

  8. Signature Splitting in 7/2 [633]v band of 175Hf

    Directory of Open Access Journals (Sweden)

    Singh Jagjit

    2014-03-01

    Full Text Available In this paper, we present an explanation of signature splitting observed in the one quasiparticle rotational band (7/2[633]? of 175Hf in terms of one particle plus rotor model (PRM calculations. The role of angular momentum dependence of the inertia parameter and rotational correction term appearing in Coriolis mixing calculations to explain signature effects is discussed.

  9. Crossing of large multi-quasiparticle magnetic rotation bands in $^{198}$Bi

    CERN Document Server

    Pai, H; Bhattacharya, S; Bhattacharya, C; Bhattacharyya, S; Bhattacharjee, T; Basu, S K; Kundu, S; Ghosh, T K; Banerjee, K; Rana, T K; Meena, J K; Bhowmik, R K; Singh, R P; Muralithar, S; Chanda, S; Garg, R; Maheshwari, B; Jain, A K

    2014-01-01

    High-spin states in the doubly-odd $^{198}$Bi nucleus have been studied by using the $^{185,187}$Re($^{16}$O, xn) reactions at the beam energy of 112.5 MeV. $\\gamma-\\gamma$ coincidence were measured by using the INGA array with 15 Compton suppressed clover HPGe detectors. The observed levels have been assigned definite spin-parity. The high spin structure is grouped into three bands (B1, B2 and B3), of which two (B1 and B2) exhibit the properties of magnetic rotation (MR). Tilted axis cranking calculations were carried out to explain the MR bands having large multi-quasiparticle configurations. The calculated results explain the bands B1 and B2 very nicely, confirming the shears mechanism and suggest a crossing of two MR bands in both the cases. The crossing is from 6-qp to 8-qp in band B1 and from 4-qp to 6-qp in band B2, a very rare finding. A semiclassical model has also been used to obtain the particle-hole interaction strengths for the bands B1 and B2, below the band crossing.

  10. Band gap of ?-PtO2 from first-principles

    Directory of Open Access Journals (Sweden)

    Yong Yang

    2012-06-01

    Full Text Available We studied the band gap of ?-PtO2 using first-principles calculations based on density functional theory (DFT. The results are obtained within the framework of the generalized gradient approximation (GGA, GGA+U, GW, and the hybrid functional methods. For the different types of calculations, the calculated band gap increases from ?0.46 eV to 1.80 eV. In particular, the band gap by GW (conventional and self-consistent calculation shows a tendency of converging to ?1.25 ± 0.05 eV. The effect of on-site Coulomb interaction on the bonding characteristics is also analyzed.

  11. Orchestrating the Band: A New Direction.

    Science.gov (United States)

    Mairs, David

    2000-01-01

    Contends that marching bands should explore the classical repertoire of the symphony orchestra. Discusses three reasons why the audience and students enjoy this type of music. Includes a list of classical music that has worked for bands. (CMK)

  12. Origin of wide-band IP type II bursts

    Science.gov (United States)

    Pohjolainen, S.; Allawi, H.; Valtonen, E.

    2013-10-01

    Context. Different types of interplanetary (IP) type II bursts have been observed, where the more usual ones show narrow-band and patchy emissions, sometimes with harmonics, and which at intervals may disappear completely from the dynamic spectrum. The more unusual bursts are wide-band and diffuse, show no patches or breaks or harmonic emission, and often have long durations. Type II bursts are thought to be plasma emission, caused by propagating shock waves, but a synchrotron-emitting source has also been proposed as the origin for the wide-band type IIs. Aims: Our aim is to find out where the wide-band IP type II bursts originate and what is their connection to particle acceleration. Methods: We analyzed in detail 25 solar events that produced well-separated, wide-band IP type II bursts in 2001-2011. Their associations to flares, coronal mass ejections (CMEs), and solar energetic particle events (SEPs) were investigated. Results: Of the 25 bursts, 18 were estimated to have heights corresponding to the CME leading fronts, suggesting that they were created by bow shocks ahead of the CMEs. However, seven events were found in which the burst heights were significantly lower and which showed a different type of height-time evolution. Almost all the analyzed wide-band type II bursts were associated with very high-speed CMEs, originating from different parts of the solar hemisphere. In terms of SEP associations, many of the SEP events were weak, had poor connectivity due to the eastern limb source location, or were masked by previous events. Some of the events had precursors in specific energy ranges. These properties and conditions affected the intensity-time profiles and made the injection-time-based associations with the type II bursts difficult to interpret. In several cases where the SEP injection times could be determined, the radio dynamic spectra showed other features (in addition to the wide-band type II bursts) that could be signatures of shock fronts. Conclusions: We conclude that in most cases (in 18 out of 25 events) the wide-band IP type II bursts can be plasma emission, formed at or just above the CME leading edge. The results for the remaining seven events might suggest the possibility of a synchrotron source. These events, however, occurred during periods of high solar activity, and coronal conditions affecting the results of the burst height calculations cannot be ruled out. The observed wide and diffuse emission bands may also indicate specific CME leading edge structures and special shock conditions. Figures 2-26 and Table 4 are available in electronic form at http://www.aanda.org

  13. First-principles study of Cu{sub 2}ZnSnS{sub 4} and the related band offsets for photovoltaic applications

    Energy Technology Data Exchange (ETDEWEB)

    Nagoya, A; Asahi, R [Toyota Central R and D Laboratories, Incorporated, Nagakute, Aichi 480-1192 (Japan); Kresse, G, E-mail: e1405@mosk.tytlabs.co.jp [Faculty of Physics, Universitaet Wien and Center for Computational Materials Science, Sensengasse 8/12, A-1090, Wien (Austria)

    2011-10-12

    First-principles calculations of the band offsets between Cu{sub 2}ZnSnS{sub 4} (CZTS) and XS (X = Cd, Zn) are performed. While the interface dipole contribution for the band offsets is calculated using the Perdew-Burke-Ernzerhof functional, the Heyd-Scuseria-Ernzerhof hybrid functional is employed to introduce the quasiparticle corrections to the band offsets. The calculated conduction band offset between CZTS and CdS is 0.2 eV, validating CdS for the buffer layer of the CZTS solar cell. The small conduction band offset stems from the band gap narrowing of CdS under the interface strain caused by the lattice misfit with CZTS. A large valence band offset over 0.9 eV between CZTS and ZnS indicates that precipitated ZnS is regarded as an inactive insulator phase in CZTS absorbers.

  14. The laparoscopic banded gastric bypass – operation technique

    OpenAIRE

    Simon Küsters; Goran Marjanovic; Tobias Baumann; Philipp Holzner; Wojciech K. Karcz

    2010-01-01

    The banded Roux-en-Y gastric bypass can be used as a primary or revisionary bariatric procedure. This article describesthe operation technique including materials, size and placement of the banding and gives an overview con cerningevolution and indications of the operation. A video of a primary banded Roux-en-Y gastric bypass is presented.

  15. The laparoscopic banded gastric bypass – operation technique

    Directory of Open Access Journals (Sweden)

    Simon Küsters

    2010-03-01

    Full Text Available The banded Roux-en-Y gastric bypass can be used as a primary or revisionary bariatric procedure. This article describesthe operation technique including materials, size and placement of the banding and gives an overview con cerningevolution and indications of the operation. A video of a primary banded Roux-en-Y gastric bypass is presented.

  16. Core calculations of JMTR

    Energy Technology Data Exchange (ETDEWEB)

    Nagao, Yoshiharu [Japan Atomic Energy Research Inst., Oarai, Ibaraki (Japan). Oarai Research Establishment

    1998-03-01

    In material testing reactors like the JMTR (Japan Material Testing Reactor) of 50 MW in Japan Atomic Energy Research Institute, the neutron flux and neutron energy spectra of irradiated samples show complex distributions. It is necessary to assess the neutron flux and neutron energy spectra of an irradiation field by carrying out the nuclear calculation of the core for every operation cycle. In order to advance core calculation, in the JMTR, the application of MCNP to the assessment of core reactivity and neutron flux and spectra has been investigated. In this study, in order to reduce the time for calculation and variance, the comparison of the results of the calculations by the use of K code and fixed source and the use of Weight Window were investigated. As to the calculation method, the modeling of the total JMTR core, the conditions for calculation and the adopted variance reduction technique are explained. The results of calculation are shown. Significant difference was not observed in the results of neutron flux calculations according to the difference of the modeling of fuel region in the calculations by K code and fixed source. The method of assessing the results of neutron flux calculation is described. (K.I.)

  17. Bonds and bands in semiconductors

    CERN Document Server

    Phillips, Jim

    2009-01-01

    This classic work on the basic chemistry and solid state physics of semiconducting materials is now updated and improved with new chapters on crystalline and amorphous semiconductors. Written by two of the world's pioneering materials scientists in the development of semiconductors, this work offers in a single-volume an authoritative treatment for the learning and understanding of what makes perhaps the world's most important engineered materials actually work. Readers will find: --' The essential principles of chemical bonding, electron energy bands and their relationship to conductive and s

  18. Identification of the UIR Bands

    Science.gov (United States)

    Johnson, Fred

    2015-08-01

    Starlight undergoing multiple scattering processes within fluffy grains results in extinction, UV 2175A bump, DIBs and the UIR bands. Spectroscopic lab and DIB data has identified the highly fluorescent molecule Dipyridyl Madnesium Tetrabenzoporphyrin (mgTBP). Reflection and Raman scattering experimental data will be presented which designates this molecule as the primary source for UIR signals. MgTBP sublimes at about 500°C. It is produced via high temperature plasma synthesis within and subsequently ejected from comets which in turn are by-products of solar system-planetary development. Interstellar dust is the left-over refuse which implies prodigious solar system evolution in each galaxy.

  19. Nonlinear thermodynamic magnetic field and specific heat of two-band superconductors in the Ginzburg-Landau theory

    International Nuclear Information System (INIS)

    Temperature dependence of thermodynamic magnetic field superconducting magnesium diboride MgB2 is studied in the vicinity of Tc using the two-band Ginzburg-Landau theory. The results are in good agreement with calculations from experimental data. In addition, the two-band Ginzburg-Landau theory gives a smaller specific heat jump than a single-band Ginzburg-Landau theory and nonlinear temperature dependence below Tc (Author)

  20. Band offset measurements in Zn1-x Sb x O/ZnO hetero-junctions

    Science.gov (United States)

    Devi, Vanita; Kumar, Manish; Kumar, Ravindra; Singh, Amanpal; Joshi, B. C.

    2015-08-01

    Accurate knowledge of the alignment of conduction and valence bands of layers at the heterojunction and warrant knowledge of the band offsets at the interface is essential for Zn1-x Sb x O/ZnO based quantum well device designing and modeling. Under this scenario, valence band offsets of Zn1-x Sb x O/ZnO heterostructures grown by the pulsed laser deposition technique was measured by photoelectron spectroscopy and consequently, the conduction band offset was calculated by UV-visible spectroscopy. The change in band alignment has been observed with the dopant (Sb) concentration. Ratios of conduction band offset to valence band offset were estimated to be 1.67 and 0.04 for x = 0.03 and 0.06, respectively, for Sb doped films. A Type-II band alignment was observed at the Zn0.97Sb0.03O/ZnO interface, whereas the Type-I band alignment took place at the Zn0.94Sb0.06O/ZnO interface.

  1. Wavelength influence in sub-pixel temperature retrieval using the dual-band technique

    Directory of Open Access Journals (Sweden)

    M. F. Buongiorno

    2006-06-01

    Full Text Available The thermal model proposed by Crisp and Baloga (1990 for active lava flows considers thermal flux as a function of the fractional area of two thermally distinct radiant surfaces. In this model, the larger surface area corresponds to the cooler crust of the flow and the other, much smaller to fractures in the crust. These cracks temperature is much higher than the crust one and approaches the temperature of the molten or plastic interior flow. The dual-band method needs two distinct SWIR (short wave infrared bands to formulate a two equations system from the simultaneous solution of the Planck equation in each band. The system solutions consist in the crust temperature and the fractional area of the hot component. The dual band technique originally builds on data acquired by sensors (such as Landsat TM with two SWIR bands only. The use of hyperspectral imaging spectrometers allows us to test the dual-band technique using different wavelengths in the SWIR range of the spectrum. DAIS 7915 is equipped with 40 bands into the range 1.54-2.49 nm which represent potential input in dual band calculation. This study aims to compare results derived by inserting assorted couples of wavelengths into the equation system. The analysis of these data provides useful information on dual-band technique accuracy.

  2. Calibration of VIIRS F1 Sensor Fire Detection Band Using lunar Observations

    Science.gov (United States)

    McIntire, Jeff; Efremova, Boryana; Xiong, Xiaoxiong

    2012-01-01

    Visible Infrared Imager Radiometer Suite (VIIRS) Fight 1 (Fl) sensor includes a fire detection band at roughly 4 microns. This spectral band has two gain states; fire detection occurs in the low gain state above approximately 345 K. The thermal bands normally utilize an on-board blackbody to provide on-orbit calibration. However, as the maximum temperature of this blackbody is 315 K, the low gain state of the 4 micron band cannot be calibrated in the same manner as the rest of the thermal bands. Regular observations of the moon provide an alternative calibration source. The lunar surface temperature has been recently mapped by the DIVINER sensor on the LRO platform. The periodic on-board high gain calibration along with the DIVINER surface temperatures was used to determine the emissivity and solar reflectance of the lunar surface at 4 microns; these factors and the lunar data are then used to fit the low gain calibration coefficients of the 4 micron band. Furthermore, the emissivity of the lunar surface is well known near 8.5 microns due to the Christiansen feature (an emissivity maximum associated with Si-O stretching vibrations) and the solar reflectance is negligible. Thus, the 8.5 micron band is used for relative calibration with the 4 micron band to de-trend any temporal variations. In addition, the remaining thermal bands are analyzed in a similar fashion, with both calculated emissivities and solar reflectances produced.

  3. Comparative studies on photonic band structures of diamond and hexagonal diamond using the multiple scattering method

    International Nuclear Information System (INIS)

    Photonic band structures are investigated for both diamond and hexagonal diamond crystals composed of dielectric spheres, and absolute photonic band gaps (PBGs) are found in both cases. In agreement with both Karathanos and Moroz's calculations, a large PBG occurs between the eighth and ninth bands in diamond crystal, but a PBG in hexagonal diamond crystal is found to occur between the sixteenth and seventeenth bands because of the doubling of dielectric spheres in the primitive cell. To explore the physical mechanism of how the photonic band gap might be broadened, we have compared the electric field distributions (|E|2) of the 'valence' and 'conduction' band edges. Results show that the field intensity for the 'conduction' band locates in the inner core of the sphere while that of the 'valence' band concentrates in the outer shell. With this motivation, double-layer spheres are designed to enhance the corresponding photonic band gaps; the PBG is increased by 35% for the diamond structure, and 14% for the hexagonal diamond structure

  4. ESC : energy saving calculations

    OpenAIRE

    Hrafn Jóhannesson

    2007-01-01

    The document describes the work on the development of an online Energy Calculation System. The system was developed from an idea from Bjarni P. Hjarðar and in cooperation with Orkusetur, the Energy Agency in Iceland. The system is an interface to a database and a calculation engine. It provides means for users to compare calculated energy usage of their house against their actual use of energy. This energy is used to warm up houses that do not have access to geothermal energy. If ...

  5. Dust bands in the asteroid belt

    Science.gov (United States)

    Sykes, Mark V.; Greenberg, Richard; Dermott, Stanley F.; Nicholson, Philip D.; Burns, Joseph A.

    1989-01-01

    This paper describes the original IRAS observations leading to the discovery of the three dust bands in the asteroid belt and the analysis of data. Special attention is given to an analytical model of the dust band torus and to theories concerning the origin of the dust bands, with special attention given to the collisional equilibrium (asteroid family), the nonequilibrium (random collision), and the comet hypotheses of dust-band origin. It is noted that neither the equilibrium nor nonequilibrium models, as currently formulated, present a complete picture of the IRAS dust-band observations.

  6. Dust bands in the asteroid belt

    International Nuclear Information System (INIS)

    This paper describes the original IRAS observations leading to the discovery of the three dust bands in the asteroid belt and the analysis of data. Special attention is given to an analytical model of the dust band torus and to theories concerning the origin of the dust bands, with special attention given to the collisional equilibrium (asteroid family), the nonequilibrium (random collision), and the comet hypotheses of dust-band origin. It is noted that neither the equilibrium nor nonequilibrium models, as currently formulated, present a complete picture of the IRAS dust-band observations. 32 refs

  7. Electrical installation calculations basic

    CERN Document Server

    Kitcher, Christopher

    2013-01-01

    All the essential calculations required for basic electrical installation workThe Electrical Installation Calculations series has proved an invaluable reference for over forty years, for both apprentices and professional electrical installation engineers alike. The book provides a step-by-step guide to the successful application of electrical installation calculations required in day-to-day electrical engineering practice. A step-by-step guide to everyday calculations used on the job An essential aid to the City & Guilds certificates at Levels 2 and 3Fo

  8. Electrical installation calculations advanced

    CERN Document Server

    Kitcher, Christopher

    2013-01-01

    All the essential calculations required for advanced electrical installation workThe Electrical Installation Calculations series has proved an invaluable reference for over forty years, for both apprentices and professional electrical installation engineers alike. The book provides a step-by-step guide to the successful application of electrical installation calculations required in day-to-day electrical engineering practiceA step-by-step guide to everyday calculations used on the job An essential aid to the City & Guilds certificates at Levels 2 and 3For apprentices and electrical installatio

  9. Electronics Environmental Benefits Calculator

    Data.gov (United States)

    U.S. Environmental Protection Agency — The Electronics Environmental Benefits Calculator (EEBC) was developed to assist organizations in estimating the environmental benefits of greening their purchase,...

  10. Multiphase flow calculation software

    Science.gov (United States)

    Fincke, James R. (Idaho Falls, ID)

    2003-04-15

    Multiphase flow calculation software and computer-readable media carrying computer executable instructions for calculating liquid and gas phase mass flow rates of high void fraction multiphase flows. The multiphase flow calculation software employs various given, or experimentally determined, parameters in conjunction with a plurality of pressure differentials of a multiphase flow, preferably supplied by a differential pressure flowmeter or the like, to determine liquid and gas phase mass flow rates of the high void fraction multiphase flows. Embodiments of the multiphase flow calculation software are suitable for use in a variety of applications, including real-time management and control of an object system.

  11. The Effects of Band Director Leadership Style and Student Leadership Ability on Band Festival Ratings

    Science.gov (United States)

    Davison, P. Dru

    2007-01-01

    This study examined the relationship between band director leadership styles and the strength of student leadership within the bands. This study also examined the differences between leadership styles, student leadership strength, and band festival ratings (marching and concert). Subjects (N = 42) were band directors from Texas and Arkansas who…

  12. Dipole bands in high spin states of {sub 57}{sup 135}La{sub 78}

    Energy Technology Data Exchange (ETDEWEB)

    Garg, Ritika; Kumar, S.; Saxena, Mansi; Goyal, Savi; Siwal, Davinder; Verma, S.; Mandal, S. [Department of Physics and Astrophysics, University of Delhi, Delhi - 110007 (India); Palit, R.; Saha, Sudipta; Sethi, J.; Sharma, Sushil K.; Trivedi, T.; Jadav, S. K.; Donthi, R.; Naidu, B. S. [Department of Nuclear and Atomic Physics, Tata Institute of Fundamental Research, Mumbai - 400005 (India)

    2014-08-14

    High spin states of {sup 135}La have been investigated using the reaction {sup 128}Te({sup 11}B,4n){sup 135}La at a beam energy of 50.5 MeV. Two negative parity dipole bands (?I = 1) have been established. Crossover E2 transitions have been observed for the first time in one of the dipole bands. For the Tilted Axis Cranking (TAC) calculations, a three-quasiparticle (3qp) configuration ?(h{sub 11/2}){sup 1}??(h{sub 11/2}){sup ?2} and a five-quasiparticle (5qp) configuration ?(h{sub 11/2}){sup 1}(g{sub 7/2}/d{sub 5/2}){sup 2}??(h{sub 11/2}){sup ?2} have been taken for the two negative parity dipole bands. The comparison of experimental observables with TAC calculations supports the configuration assignments for both the dipole bands.

  13. A Novel Ku-Band/Ka-Band and Ka-Band/E-Band Multimode Waveguide Couplers for Power Measurement of Traveling-Wave Tube Amplifier Harmonic Frequencies

    Science.gov (United States)

    Wintucky, Edwin G.; Simons, Rainee N.

    2015-01-01

    This paper presents the design, fabrication and test results for a novel waveguide multimode directional coupler (MDC). The coupler, fabricated from two dissimilar frequency band waveguides, is capable of isolating power at the second harmonic frequency from the fundamental power at the output port of a traveling-wave tube (TWT) amplifier. Test results from proof-of-concept demonstrations are presented for a Ku-band/Ka-band MDC and a Ka-band/E-band MDC. In addition to power measurements at harmonic frequencies, a potential application of the MDC is in the design of a satellite borne beacon source for atmospheric propagation studies at millimeter-wave (mm-wave) frequencies (Ka-band and E-band).

  14. Table of members of quasi-bands

    International Nuclear Information System (INIS)

    The probable members of the quasi-bands in even-even nuclei for Z between 6 and 100 are listed in this table. The terms quasi-bands have been introduced in the so-called spherical regions as the counter parts of the collective bands in the deformed regions. In the present compilation, the data for deformed nuclei are classified for convenience under the same titles, Quasi-Ground Band, Quasi-Beta Band and Quasi-Gamma Band, as are used for other nuclear regions. The present edition covers the literature through September, 1983. Fifteen newly discovered nuclides are included. The classification of energy level into quasi-bands is made on the basis of the systematic trend in the data over large groups of nuclei. (Kato, T.)

  15. First-principles calculations of yttrium tantalate and niobate crystals

    International Nuclear Information System (INIS)

    The structural and electronic properties of yttrium tantalate (YTaO4) and yttrium niobate (YNbO4) crystals are studied using experimental and first-principles GGA+U total energy calculations. The band gap of the host lattice from absorption and luminescence experiment is measured to be 5.1 eV for YTaO4 and 4.1eV for YNbO4. This is close to 5.14 eV and 4.28 eV, respectively, reproduced by means of GGA+U approach. In our calculation, we tune both Hubbard energy U and exchange parameter J to reproduce the energy gap measured experimentally. It is found that Hubbard energy U plays a major role in reproducing the experimentally measured energy gap, but exchange parameter J does not. We also calculate the density of states (DOS) using the optimized U to interpret the experimentally measured luminescence spectra. Both the experimental and DOS calculations show that the valence band of tantalate (Ta) and niobate (Nb) systems is mainly composed of oxygen (O) 2p states. The lower conduction band is mainly composed of Ta 5d states or Nb 4d states, respectively, while the upper conduction band involves the contribution mainly from yttrium (Y) 4d states, with the middle conduction band mainly a mixture of Ta or Nb and Y states. The calculated partial DOS of each atom in the tantalate and niobate system is then compared with the UV and VUV spectra from photoluminescence excitation (PLE) experiment to explain the nature of the bands observed. (authors)

  16. Multi-band pyrometer uncertainty analysis and improvement

    Science.gov (United States)

    Yang, Yongjun; Zhang, Xuecong; Cai, Jing; Wang, Zhongyu

    2011-05-01

    According to the energy ratio value of multi-band radiating from the measured surface, the 'true' temperature can be calculated by multi-band pyrometer. Multi-band pyrometer has many advantages: it can hardly be affected by the emission of measured surface and the environment radiation, and it has higher Signal-to-Noise Ratio and higher temperature measurement accuracy. This paper introduces the principle of a multi-band pyrometer and the uncertainty of measurement result is evaluated by using Monte-Carlo Method (MCM). The result shows that the accuracy of effective wavelength is the largest source of uncertainty and the other main source is reference temperature. When using ordinary blackbody furnace with continuous temperature, which can provide reference temperature and calibrate effective wavelength, the uncertainty component is 2.17K and 2.48K respectively. The combined standard uncertainty is 3.30K. A new calibration method is introduced. The effective wavelength is calibrated by monochromator, and the reference temperature is provided by fixed point black body furnace. The uncertainty component is decreased to 0.73K and 0.12K respectively. The measurement uncertainty is decreased to 0.74K. The temperature measurement accuracy is enhanced.

  17. Lasing at the band edges of plasmonic lattices

    Science.gov (United States)

    Schokker, A. Hinke; Koenderink, A. Femius

    2014-10-01

    We report room-temperature lasing in two-dimensional diffractive lattices of silver and gold plasmon particle arrays embedded in a dye-doped polymer that acts both as waveguide and gain medium. As compared to conventional dielectric distributed feedback (DFB) lasers, a central question is how the underlying band structure from which lasing emerges is modified by both the much stronger scattering and the disadvantageous loss of metal. We use spectrally resolved back-focal plane imaging to measure the wavelength and angle dependence of emission below and above threshold, thereby mapping the band structure. We find that, for silver particles, the band structure is strongly modified compared to dielectric reference DFB lasers since the strong scattering gives large stop gaps. In contrast, gold particles scatter weakly and absorb strongly, so that thresholds are higher, but the band structure is not strongly modified. The experimental findings are supported by finite element and Fourier modal method calculations of the single-particle scattering strength and lattice extinction.

  18. Collective band structures in doubly odd 136La nucleus

    International Nuclear Information System (INIS)

    Using heavy-ion nuclear reaction and in-beam ?-ray spectroscopy technique, high spin states of 136La have been studied. The nuclear reaction used is 130Te(11B, 5n) with a beam energy 60 MeV. The level scheme with three collective band structures has been updated with spin up to 20 ?. The collective backbending has been observed in ?h11/2 direct x ?h11/2 band. According to the TRS calculations, this backbending is due to the alignment of a pair of h11/2 neutrons. The signature splitting and inversion for the ?h11/2 direct x ?h11/2 band were also discussed. Other two bands based on 12- and 16+ levels were proposed as oblate deformation with ??-60 degree. They most probably originate from four- and six- quasiparticle configurations, that is, ?h11/2 direct x ?g7/2h11/22 and ?g7/2 direct x ?g7/22d5/2h11/22 respectively. (authors)

  19. Investigation of the Band Gap in Co3O4

    Science.gov (United States)

    Sholte, Mark; Lin, Chungwei; Kormondy, Kristy; Nunley, Timothy; Posadas, Agham; Zollner, Stefan; Demkov, Alexander

    2015-03-01

    Co3O4 is a strongly correlated oxide with a spinel structure and G-type antiferromagnetic order at temperatures below 40 K. It is a widely studied material owing to its applications in gas sensing, spintronics, batteries, and catalysis. The strong correlation and magnetism make it a difficult material to model from first principles. Density functional theory calculations require the use of a Hubbard U to correctly model its magnetic behavior. The band gap is sensitive to the choice of U allowing one to tailor the gap to a wide range of values. This often provides a phenomenological approach to determining U, but in the case of Co3O4 there is no experimental consensus on the actual value of the band gap. We utilize an alternate approach by matching the theoretical valence band structure to the actual valence band data obtained via x-ray photoemission spectroscopy. This generated set of U values is used to compute an absorption spectrum, which is in good agreement with ellipsometry results.

  20. An alternative tool to explain Hooke’s Law and the principle of Dynamometer: The rubber band

    Directory of Open Access Journals (Sweden)

    Gül Ünal Çoban

    2011-03-01

    Full Text Available In this experiment, behaviors of the elastic materials when exerted a force were interpreted through the graphs wherethe elasticity coefficient of the rubber band was calculated. At the same time, the reason for using an elastic materialinside the dynamometer and the limits of elasticity were discussed by two different demonstrations conducted withrubber band.

  1. Computing the band structure and energy gap of penta-graphene by using DFT and G0W0 approximations

    OpenAIRE

    Einollahzadeh, H.; R S Dariani; Fazeli, S. M.

    2015-01-01

    In this paper, we consider the optimum coordinate of the penta-graphene. Penta-graphene is a new stable carbon allotrope which is stronger than graphene. Here, we compare the band gap of penta-graphene with various density functional theory (DFT) methods. We plot the band structure of penta-graphene which calculated with the generalized gradient approximation functional, about Fermi energy.

  2. Recent developments in high-spin calculations in atomic nuclei

    International Nuclear Information System (INIS)

    A brief introduction to the recent achievements in the high-spin domain in nuclear physics is given. Results of the calculations in highly developed rotational bands in deformed nuclei, as well as the calculations in the structure of the yrast isomers are presented. The calculations fail in two aspects: local minima in the yrast line are not confirmed experimentally, the overall slope of the yrast line in 152Dy is considerably overestimated. The calculations of the yrast line with new Woods-Saxon parameters are now in progress. The parameters are chosen to reproduce the large gap in the levels at proton number Z=64. (M.H.)

  3. Straddling to staggered band gap transition and optics of double-walled carbon nanotubes

    Science.gov (United States)

    Kutana, Alex; Artyukhov, Vasilii I.; Yakobson, Boris I.

    2015-03-01

    Single-walled carbon nanotubes have outstanding optical properties that show pronounced dependence on their helicity. Techniques for helicity separation or selective growth enabled extensive studies of their optics. However, in double-walled nanotubes (DWNT) the inner wall helicity is hard to control. Only recently effective techniques for DWNT sorting and helicity assignment were developed, and experiments on helicity-controlled DWNT reveal remarkable new optical effects. Here we study the effect of breaking of ? band symmetry by wall curvature, creating a potential difference between the inside and outside of a nanotube. In DWNT, this intrinsic flexoelectric voltage, V ~ 1 / R , shifts the bands of the inner wall, and above a certain threshold the voltage exceeds the band offset (~ 1 /R2), marking the transition from conventional straddling to staggered band structure, where frontier electronic bands are localized on different walls. This has dramatic optical implications which we study using density functional theory and many-body GW +BSE calculations.

  4. UV and x-ray photoelectron spectra of valence band of LaB6

    International Nuclear Information System (INIS)

    The total density of occupied states in the electronic structure of lanthanum hexaboride has been measured by use of high-resolution photoelectron spectroscopy combining far UV (Ne and He resonance lines) and x-ray excitation (monochromatized Al K ? radiation). The investigation was performed with clean and stoichiometric surfaces from poly-crystalline bulk samples and thin films, both prepared in situ. The data give new insights into bonding, band structure and thermal stability of LaB6. The valence band (approximately 12eV wide) is characterized by three main bands located at about 2 eV, 5 eV and 10 eV with additional subsidiary structures. The data are compared with published results of soft x-ray studies and the energy, position and width of the experimental bands compared and interpreted with available band-structure calculations. (author)

  5. Study of the satellite bands of RbCs molecule in the near UV

    International Nuclear Information System (INIS)

    By comparing high-resolution absorption spectra of Rb and Cs vapor with Rb–Cs vapor mixture spectrum we were able to identify several satellite bands of RbCs molecule at 362.2 nm, 372.5 nm and 390.7 nm. These bands represent lower Rydberg states of the RbCs molecule which may be further studied at ultracold conditions. - Highlights: • Comparison of high-resolution absorption spectra of Rb, Cs and RbCs vapor mixture. • Satellite bands of RbCs molecule at 362.2 nm, 372.5 nm and 390.7 nm. • Avoided crossings of potential curves at long-range inter-atomic region. • The observed satellite bands may be observed in the mixed Rb–Cs MOT. • The satellite bands can be used for comparison with ab initio RbCs calculations

  6. Electron correlations in narrow energy bands: modified polar model approach

    Directory of Open Access Journals (Sweden)

    L. Didukh

    2008-09-01

    Full Text Available The electron correlations in narrow energy bands are examined within the framework of the modified form of polar model. This model permits to analyze the effect of strong Coulomb correlation, inter-atomic exchange and correlated hopping of electrons and explain some peculiarities of the properties of narrow-band materials, namely the metal-insulator transition with an increase of temperature, nonlinear concentration dependence of Curie temperature and peculiarities of transport properties of electronic subsystem. Using a variant of generalized Hartree-Fock approximation, the single-electron Green's function and quasi-particle energy spectrum of the model are calculated. Metal-insulator transition with the change of temperature is investigated in a system with correlated hopping. Processes of ferromagnetic ordering stabilization in the system with various forms of electronic DOS are studied. The static conductivity and effective spin-dependent masses of current carriers are calculated as a function of electron concentration at various DOS forms. The correlated hopping is shown to cause the electron-hole asymmetry of transport and ferromagnetic properties of narrow band materials.

  7. Band mixing in {sup 29}Si and {sup 29}P

    Energy Technology Data Exchange (ETDEWEB)

    Hossain, S [Department of Physics, University of Rajshahi, Rajshahi 6205 (Bangladesh); Abdullah, M N A [Department of Physics, University of Rajshahi, Rajshahi 6205 (Bangladesh); Das, S K [Department of Physics, Shahjalal University of Science and Technology, Sylhet (Bangladesh); Uddin, M A [Department of Physics, University of Rajshahi, Rajshahi 6205 (Bangladesh); Basak, A K [Department of Physics, University of Rajshahi, Rajshahi 6205 (Bangladesh); Gupta, H M Sen [Department of Physics, University of Dhaka, Dhaka (Bangladesh); Thompson, I J [Department of Physics, University of Surrey, Guildford GU2 7XH (United Kingdom); Malik, F B [Department of Physics, Southern Illinois University, Carbondale, IL 62901 (United States)

    2005-05-01

    The experimental data of the {sup 28}Si({alpha}, t){sup 29}P and {sup 28}Si({alpha}, {sup 3}He){sup 29}Si reactions at 45 MeV have been analysed in terms of full finite-range coupled-channels calculations. In the calculations, the reaction paths, direct and two step via the inelastic states of the initial and final nuclei have been treated in terms of the finite-range transfer theory. The spectroscopic amplitudes connecting the deformed initial and final nuclei in both the reactions are obtained from Nilsson's model. The data of both the reactions, populating the 1/2{sup +}, 3/2{sup +} and 5/2{sup +} states in the K{sup {pi}} = 1/2{sup +} band and the 3/2{sup +} and 5/2{sup +} states in the K{sup {pi}} = 3/2{sup +} band, are best described by about 20% mixing of between the two bands. The effects of normal Woods-Saxon (WS), squared WS and molecular type of {alpha}-nucleus potentials are also discussed.

  8. CO Cameron band and CO2+ UV doublet emissions in the dayglow of Venus: Role of CO in the Cameron band production

    CERN Document Server

    Bhardwaj, Anil

    2013-01-01

    Present study deals with the model calculations of CO Cameron band and CO2+ ultraviolet doublet emissions in the dayglow of Venus. The overhead and limb intensities of CO Cameron band and CO2+ UV doublet emissions are calculated for low, moderate, and high solar activity conditions. Using updated cross sections, the impact of dierent e-CO cross section for Cameron band production is estimated. The electron impact on CO is the major source mechanism of Cameron band, followed by electron and photon impact dissociation of CO2. The overhead intensities of CO Cameron band and CO2+ UV doublet emissions are about a factor of 2 higher in solar maximum than those in solar minimum condition. The effect of solar EUV flux models on the emission intensity is ~30-40% in solar minimum condition and ~2-10% in solar maximum condition. At the altitude of emission peak (135 km), the model predicted limb intensity of CO Cameron band and CO2+ UV doublet emissions in moderate (F10.7 = 130) solar activity condition is about 2400 an...

  9. MODIS/Terra 8-Day Clear Sky Radiance Bias Daily L3 Global 1Deg Zonal Bands V006

    Data.gov (United States)

    National Aeronautics and Space Administration — MODIS 8-day clear-sky radiance bias (observed - calculated) statistics are provided for 1Deg latitudinal zones and selected thermal bands. Separation by day and...

  10. MODIS/Aqua 8-Day Clear Sky Radiance Bias Daily L3 Global 1Deg Zonal Bands V006

    Data.gov (United States)

    National Aeronautics and Space Administration — MODIS 8-day clear-sky radiance bias (observed - calculated) statistics are provided for 1Deg latitudinal zones and selected thermal bands. Separation by day and...

  11. MODIS/Aqua 8-Day Clear Sky Radiance Bias Daily L3 Global 1Deg Zonal Bands V005

    Data.gov (United States)

    National Aeronautics and Space Administration — MODIS 8-day clear-sky radiance bias (observed - calculated) statistics are provided for 1Deg latitudinal zones and selected thermal bands. Separation by day and...

  12. MODIS/Terra 8-Day Clear Sky Radiance Bias Daily L3 Global 1Deg Zonal Bands V005

    Data.gov (United States)

    National Aeronautics and Space Administration — MODIS 8-day clear-sky radiance bias (observed - calculated) statistics are provided for 1Deg latitudinal zones and selected thermal bands. Separation by day and...

  13. The Soret absorption band of isolated chlorophyll a and b tagged with quaternary ammonium ions

    DEFF Research Database (Denmark)

    Stockett, Mark H; Musbat, Lihi; Kjær, Christina; Houmøller, Jørgen; Toker, Yoni; Rubio, Angel; Milne, Bruce F; Brøndsted Nielsen, Steen

    2015-01-01

    We have performed gas-phase absorption spectroscopy in the Soret-band region of chlorophyll (Chl) a and b tagged by quaternary ammonium ions together with time-dependent density functional theory (TD-DFT) calculations. This band is the strongest in the visible region of metalloporphyrins and an important reporter on the microenvironment. The cationic charge tags were tetramethylammonium, tetrabutylammonium, and acetylcholine, and the dominant dissociation channel in all cases was breakage of the...

  14. Theory of valence-band and core-level photoemission from plutonium dioxide

    OpenAIRE

    Kolorenc, Jindrich; Kozub, Agnieszka L.; Shick, Alexander B.

    2014-01-01

    The correlated-band theory implemented as a combination of the local-density approximation with the dynamical mean-field theory is applied to PuO2. An insulating electronic structure, consistent with the experimental valence-band photoemission spectra, is obtained. The calculations yield a nonmagnetic ground state that is characterized by a noninteger filling of the plutonium 5f shell. The noninteger filling as well as the satellites appearing in the 4f core-level photoemiss...

  15. Information on the band structure of ferromagnetic Ni from ?SR-Knight shift measurements

    International Nuclear Information System (INIS)

    The authors present results on the temperature dependence of the Knight shift of the hyperfine field at a positive muon in ferromagnetic Nickel and show that the results allow a determination of the Stoner gap, that is the gap between the top of the majority d-band and the Fermi energy. The consistency of the analysis supports the SWS-model but the obtained value for the Stoner gap is far below the predictions of most ferromagnetic band structure calculations. (Auth.)

  16. First observation of a rotational band in the odd-Z transfermium nucleus 101251Md

    International Nuclear Information System (INIS)

    A rotational band has been unambiguously observed in an odd-proton transfermium nucleus for the first time. An in-beam ?-ray spectroscopic study of 101251Md has been performed using the ?-ray array JUROGAM combined with the gas-filled separator RITU and the focal plane device GREAT. The experimental results, compared to Hartree-Fock-Bogolyubov calculations, lead to the interpretation that the rotational band is built on the [521]1/2- Nilsson state. (authors)

  17. Observing Abnormally Large Group Velocity at the Plasmonic Band Edge via a Universal Eigenvalue Analysis

    OpenAIRE

    Sha, Wei E. I.; Meng, Ling Ling; Choy, Wallace C. H.; Chew, Weng Cho

    2015-01-01

    We developed a novel universal eigenvalue analysis for 2D arbitrary nanostructures comprising dispersive and lossy materials. The complex dispersion relation (or complex Bloch band structure) of a metallic grating is rigorously calculated by the proposed algorithm with the finite-difference implementation. The abnormally large group velocity is observed at a plasmonic band edge with a large attenuation constant. Interestingly, we found the abnormal group velocity is caused b...

  18. Band bending at the surface of Bi$_2$Se$_3$ studied from first principles

    OpenAIRE

    Rakyta, P.; Ujfalussy, B.; Szunyogh, L.

    2015-01-01

    The band bending (BB) effect on the surface of the second-generation topological insulators implies a serious challenge to design transport devices. The BB is triggered by the effective electric field generated by charged impurities close to the surface and by the inhomogeneous charge distribution of the occupied surface states. Our self-consistent calculations in the Korringa-Kohn-Rostoker framework showed that in contrast to the bulk bands, the spectrum of the surface stat...

  19. Unified description of perturbation theory and band center anomaly in one-dimensional Anderson localization

    OpenAIRE

    Kang, Kai; Qin, Shaojing; Wang, Chuilin

    2010-01-01

    We calculated numerically the localization length of one-dimensional Anderson model with diagonal disorder. For weak disorder, we showed that the localization length changes continuously as the energy changes from the band center to the boundary of the anomalous region near the band edge. We found that all the localization lengths for different disorder strengths and different energies collapse onto a single curve, which can be fitted by a simple equation. Thus the descripti...

  20. 5f band dispersion in epitaxial films of UO2

    Energy Technology Data Exchange (ETDEWEB)

    Durakiewicz, Tomasz [Los Alamos National Laboratory; Jia, Quanxi [Los Alamos National Laboratory; Roy, Lindsay E [Los Alamos National Laboratory; Martin, Richard L [Los Alamos National Laboratory; Joyce, John J [Los Alamos National Laboratory

    2009-01-01

    Polymer-assisted deposition of epitaxial films utilizes lattice pinning to produce films of very high stability and properties identical with bulk crystal. Dispersion of the 5f band is shown for the first time in a actinide Mott insulator system, which suggestes hybridization as a leading process in establishing the electronic structure. Hybrid density functional is succesfully employed to calculate the electronic structure of UO{sub 2} in agreement with experiments. UO{sub 2} continues to be a mysterious and elusive compound in terms of understanding the physical properties of a material. Most actinide oxides, including UO{sub 2} are predicted to be metallic. However, UO{sub 2} is an antiferromagnetic insulator with a relatively large gap of about 2eV. The f orbital charater of the excitations across the gap places UO{sub 2} in a Mott insulator category, but no states at the gap center have ever been measured directly, in spite of intensive efforts. In this work we present the first results of the electronic structure investigation of a epitaxial film of UO{sub 2}, where we find even more unexpected properties, like the dispersive nature of 5f bands. We also demonstrate the unexpected, very high stability of the epitaxial film of UO{sub 2}. In the lattice-pinning scheme, the crystalline nature of the film is preserved all the way up to the topmost layers even after prolonged exposure to atmospheric conditions. Hybridized, dispersive bands are common in the itinerant uranium compounds. One usually finds hybridization of f-orbitals with conduction band to be quite common in f-electron systems at low temperatures. Such bands may reside in the vicinity of the Fermi level and participate in the construction of the Fermi surface. However, in the insulator like UO{sub 2}, one expects a more atomic band nature, where f-bands are relatively flat and shifted away from the Fermi level by the gap energy scale. Precise location of UO{sub 2} on the localization-delocalization axis could be pinned down by measurements of band dispersion.

  1. Band description of materials with localizing orbitals

    International Nuclear Information System (INIS)

    Density functional theory is a form of many-body theory which maps the problem onto an equivalent single particle-like system by limiting to the ground state (or some limited ensemble). So it should be surprising that this ground state theory could have any relevance whatsoever to the excitation properties of a material - and yet it does when used carefully. However, the most interesting materials involve active orbitals which are at least partially localized in space and this has profound effects both on the ground state and the excitation spectrum. My long term interest is in Ce and actinide compounds such that the popular concerns are mixed valence, heavy fermions, and the various forms of magnetic transitions. Band structure calculations can give a great deal of information concerning the mechanisms and degree of the localization as shown by examples using the Ce and U Ll2 structured materials and the Ce cubic Laves phase materials. There are some difficulties due to an incomplete knowledge of the functionals involved which causes an underestimate of the local character. This is illustrated and discussed

  2. Band inversion mechanism in topological insulators: A guideline for materials design

    KAUST Repository

    Zhu, Zhiyong

    2012-06-01

    Alteration of the topological order by band inversion is a key ingredient of a topologically nontrivial material. Using first-principles calculations for HgTe, PtScBi, and Bi2Se3, we argue that it is not accurate to ascribe the band inversion to the spin-orbit coupling. Instead, scalar relativistic effects and/or lattice distortions are found to be essential. Therefore, the search for topologically nontrivial materials should focus on band shifts due to these mechanisms rather than spin-orbit coupling. We propose an effective scheme to search for new topological insulators.

  3. Determination of conduction and valence band electronic structure of anatase and rutile TiO2

    Indian Academy of Sciences (India)

    Jakub Szlachetko; Katarzyna Michalow-Mauke; Maarten Nachtegaal; Jacinto Sá

    2014-03-01

    Electronic structures of rutile and anatase polymorph of TiO2 were determined by resonant inelastic X-ray scattering measurements and FEFF9.0 calculations. Difference between crystalline structures led to shifts in the rutile Ti -band to lower energy with respect to anatase, i.e., decrease in band gap. Anatase possesses localized states located in the band gap where electrons can be trapped, which are almost absent in the rutile structure. This could well explain the reported longer lifetimes in anatase. It was revealed that HR-XAS is insufficient to study in-depth unoccupied states of investigated materials because it overlooks the shallow traps.

  4. Prediction of Band Structure of $Bi_2Te_3$-related Binary and Ternary Thermoelectric Materials

    OpenAIRE

    Ryu, Byungki; Oh, Min-Wook; Kim, Bong-Seo; Lee, Ji Eun; Joo, Sung-Jae; Min, Bok-Ki; Lee, HeeWoong; Park, Sudong

    2015-01-01

    Density functional calculations have performed to study the band structures of $Bi_2Te_3$-related binary ($Bi_2Te_3$, $Sb_2Te_3$, $Bi_2Se_3$, and $Sb_2Se_3$) and $Sb$/$Se$ doped ternary compounds [$(Bi_{1-x}Sb_x)_2Te_3$ and $Bi_2(Te_{1-y}Se_y)_3$]. It is found that the band gap can be increased by $Sb$ doping and it is monotonically increased by $Se$ doping. In ternary compounds, the change of the conduction band structure is more significant, as compared to the change of va...

  5. Direct experimental visualization of waves and band structure in 2D photonic crystal slabs

    International Nuclear Information System (INIS)

    We demonstrate for the first time the ability to perform time resolved imaging of terahertz (THz) waves propagating within a photonic crystal (PhC) slab. For photonic lattices with different orientations and symmetries, we used the electro-optic effect to record the full spatiotemporal evolution of THz fields across a broad spectral range spanning the photonic band gap. In addition to revealing real-space behavior, the data let us directly map the band diagrams of the PhCs. The data, which are in good agreement with theoretical calculations, display a rich set of effects including photonic band gaps, eigenmodes and leaky modes

  6. Optical properties of chalcopyrite-type intermediate transition metal band materials from first principles

    OpenAIRE

    Aguilera Bonet, Irene; Palacios Clemente, Pablo; Wahnón Benarroch, Perla

    2008-01-01

    The optical properties of a novel potential high-efficiency photovoltaic material have been studied. This material is based on a chalcopyrite-type semiconductor (CuGaS2) with some Ga atom substituted by Ti and is characterized by the formation of an isolated transition-metal band between the valence band and the conduction band. We present a study in which ab-initio density functional theory calculations within the generalized gradient approximation are carried out to determine the optical re...

  7. Band dispersion of MgB sub 2 , graphite and diamond from resonant inelastic scattering

    CERN Document Server

    Sokolov, A V; Leitch, S; Moewes, A; Kortus, J; Finkelstein, L D; Skorikov, N A; Xiao, C; Hirose, A

    2003-01-01

    The quantitative band mapping for MgB sub 2 , graphite and diamond are realized using resonant inelastic x-ray scattering (RIXS) measurements. RIXS shows distinct dispersive features when the excitation energy is tuned near B 1s and C 1s thresholds, which are assigned to the calculated energy bands using k sup->-momentum conservation. The agreement between experiment and theory suggests that electron-electron interactions are not important for MgB sub 2 , which behaves like a conventional metal and is well described by band theory.

  8. Surface energy bands of p(1 x 1)Cr(1 0 0) and p(1 x 1)O/Cr(1 0 0)

    International Nuclear Information System (INIS)

    Angle resolved photoemission spectra have been measured on clean p(1 x 1)/Cr(1 0 0) and p(1 x 1)O/Cr(1 0 0) using a He discharge lamp as an excitation source. The dispersion curves of surface energy bands have been obtained. The results are compared with reported results of the energy band calculation. The measured energy band dispersion curves for the surface states of a clean sample agree well with the calculated bands for the surface state with aligned spins. Some parts of the dispersion curves of the surface bands agree with those of the bulk band. The energy bands observed here appear to be favourable to the surface ferromagnetic state. In case of the sample with adsorbed oxygen, the band dispersion obtained here for the deep band region coincides with the reported data. The bands with binding energies larger than 5 eV are attributed to the O 2p state forming the surface band. The bands within a binding energy of 4 eV from the Fermi level, are ascribed to the bands caused by Cr atoms in the first sub-layer forming the O-Cr bond

  9. Microstructural characterization and evolution mechanism of adiabatic shear band in a near beta-Ti alloy

    International Nuclear Information System (INIS)

    Research highlights: ? The thermo-mechanical history during the shear localization was calculated for the first time in this new beta-Ti alloy. ? The microstructures within the adiabatic shear band were observed by means of TEM. ? The ? ? ?(althermal) phase transformation was observed within adiabatic shear band in the near ?-phase Ti alloy for the first time. - Abstract: The adiabatic shear band (ASB) was obtained by split Hopkinson pressure bar (SHPB) technique in the hat-shaped specimen of a near beta-Ti alloy. The microstructure and the phase transformation within the ASB were investigated by means of TEM. The results show that the elongated subgrains with the width of 0.2-0.4 ?m have been observed in the shear band boundary, while the microstructure inside the ASB consists of fine equiaxed subgrains that are three orders of magnitude smaller than the grains in the matrix. The ? ? ?(althermal) phase transformation has been observed in the ASB, and further analysis indicates that the shear band offers thermodynamic and kinetic conditions for the ?(althermal) phase formation and the high alloying of this alloy is another essential factor for this transformation to take place. The thermo-mechanical history during the shear localization is calculated. The rotational dynamic recrystallization (RDR) mechanism is used to explain the microstructure evolution mechanism in the shear band. Kinetic calculations indicate that the recrystallized fine subgrains are formed during the deformation and do not undergo significant growth by grain boundary migration after deformation.

  10. The APOGEE Spectral Line List for H band Spectroscopy

    CERN Document Server

    Shetrone, Matthew; Lawler, James; Prieto, Carlos Allende; Johnson, Jennifer A; Smith, Verne; Cunha, Katia; Holtzman, Jon; Perez, Ana Garcia; Meszaros, Szabolcs; Sobeck, Jennifer; Zamora, Olga; Garcia-Hernandez, Anibal; Souto, Diogo; Chojnowski, Drew; Koesterke, Lars; Majewski, Steven

    2015-01-01

    We present the $H$ band spectral line lists adopted by the Apache Point Observatory Galactic Evolution Experiment (APOGEE). The APOGEE line lists comprise astrophysical, theoretical, and laboratory sources from the literature, as well as newly evaluated astrophysical oscillator strengths and damping parameters. We discuss the construction of the APOGEE line list, which is one of the critical inputs for the APOGEE Stellar Parameters and Chemical Abundances Pipeline (ASPCAP), and present three different versions that have been used at various stages of the project. The methodology for the newly calculated astrophysical line lists is reviewed. The largest of these three line lists contains 134457 molecular and atomic transitions. In addition to the format adopted to store the data, the line lists are available in MOOG, Synspec and Turbospectrum formats. We also present a list of $H$ band spectral features that are either poorly represented or completely missing in our line list. This list is based on the average...

  11. Band gap bowing in quaternary nitride semiconducting alloys

    DEFF Research Database (Denmark)

    Gorczyka, Isabela; Suski, T.

    2011-01-01

    Structural properties of InxGayAl1?x?yN alloys are derived from total-energy minimization within the local-density approximation (LDA). The electronic properties are studied by band structure calculations including a semiempirical correction for the “LDA gap error.” The effects of varying the composition and atomic arrangements are examined using a supercell geometry. An analytical expression for the band gap is derived for the entire range of compositions. The range of (x, y) values for which InxGayAl1?x?yN is lattice matched to GaN, and the ensuing energy gaps, are given. This range of available gaps becomes smaller when In atoms form clusters. Comparison to experimental data is made.

  12. Band structure in 104Ag

    International Nuclear Information System (INIS)

    The level structure of 104Ag has been studied through the 103Rh(?,3n?) reaction at E?=40 and 45 MeV. The principal features of the proposed level scheme are in agreement with those obtained earlier through heavy ion reaction. A two-quasiparticle-plus-rotor model calculation has been performed, and the results are compared with experimental data. (orig.)

  13. Calculation of statistical entropic measures in a model of solids

    Energy Technology Data Exchange (ETDEWEB)

    Sañudo, Jaime, E-mail: jsr@unex.es [Departamento de Física, Facultad de Ciencias, Universidad de Extremadura, E-06071 Badajoz (Spain); BIFI, Universidad de Zaragoza, E-50009 Zaragoza (Spain); López-Ruiz, Ricardo, E-mail: rilopez@unizar.es [DIIS and BIFI, Facultad de Ciencias, Universidad de Zaragoza, E-50009 Zaragoza (Spain)

    2012-07-09

    In this work, a one-dimensional model of crystalline solids based on the Dirac comb limit of the Krönig–Penney model is considered. From the wave functions of the valence electrons, we calculate a statistical measure of complexity and the Fisher–Shannon information for the lower energy electronic bands appearing in the system. All these magnitudes present an extremal value for the case of solids having half-filled bands, a configuration where in general a high conductivity is attained in real solids, such as it happens with the monovalent metals. -- Highlights: ? A simplified model of solids is considered. Its electronic band structure is calculated. ? The statistical complexity and the Fisher–Shannon information are computed on this model. ? The extremal value for this indicators are taken on the configurations showing the highest conductivity.

  14. Radioactive cloud dose calculations

    International Nuclear Information System (INIS)

    Radiological dosage principles, as well as methods for calculating external and internal dose rates, following dispersion and deposition of radioactive materials in the atmosphere are described. Emphasis has been placed on analytical solutions that are appropriate for hand calculations. In addition, the methods for calculating dose rates from ingestion are discussed. A brief description of several computer programs are included for information on radionuclides. There has been no attempt to be comprehensive, and only a sampling of programs has been selected to illustrate the variety available

  15. Benchmark on Superphenix calculations

    International Nuclear Information System (INIS)

    The Superphenix benchmark calculations have been performed to intercompare core characteristics (keff, burnup reactivity swing, sodium void reactivity, Doppler reactivity, burnup, linear heat rate, power and flux shapes, mass inventories, breeding gains, Pu and/or actinides burning rates etc.) and to investigate calculational accuracy of the core with high neutron leakage fraction. It was found that the calculational code systems of CEA and PNC have the very good general agreement of the predictions for the nuclear characteristics of the fast reactor core. (author)

  16. 47 CFR 15.713 - TV bands database.

    Science.gov (United States)

    2010-10-01

    ...2010-10-01 2010-10-01 false TV bands database. 15.713 Section 15.713 Telecommunication...Television Band Devices § 15.713 TV bands database. (a) Purpose. The TV bands database serves the following functions:...

  17. The Antiferromagnetic Band Structure of La2CuO4 Revisited

    CERN Document Server

    Perry, J K; Perry, Jason K.; Tahir-Kheli, Jamil; III, William A. Goddard

    2000-01-01

    Using the Becke-3-LYP functional, we have performed band structure calculations on the high temperature superconductor parent compound, La2CuO4. For the restricted spin paramagnetic case (rho(alpha) equal to rho(beta)), the B3LYP band structure agrees well with the standard LDA band structure. It has a metallic ground state with a single Cu x2-y2/O p(sigma) band crossing the Fermi level. For the unrestricted spin case (rho(alpha) not equal to rho(beta)), a spin polarized antiferromagnetic state is found with a band gap of 2.0 eV, agreeing well with experiment. This state is 1.0 eV (per formula unit) lower than the calculated paramagnetic state. This large energy difference is particularly startling given that the ferromagnetic state is also calculated to be 0.82 eV lower than the paramagnetic state. The apparent high energy of the spin restricted state is attributed to an overestimate of on-site Coulomb repulsion which is corrected in the unrestricted spin calculations. The stabilization of the total energy w...

  18. Proposed Chiral Doublet Bands in 98Tc

    International Nuclear Information System (INIS)

    High spin states in odd-odd98 Tc nuclei are studied by in-beam ?-ray spectroscopy with the 96Zr(6Li, 4n) fusion-evaporation reaction at a beam energy of 35 MeV. The previous level scheme is updated. A band based on 1090.7 keV is expanded, and another band based on 1920.6 keV is newly identified. The observed two negative parity bands in 98Tc are proposed to be a pair of chiral doublet bands with the configuration ?g9/2 ?h11/2. The evidence supporting the assignment of the chiral doublet bands is discussed. Signature splitting and signature inversion are observed in the ?g9/2 ?h11/2 band in 98Tc. (nuclear physics)

  19. Shut up and calculate

    OpenAIRE

    Tegmark, Max

    2007-01-01

    I advocate an extreme "shut-up-and-calculate" approach to physics, where our external physical reality is assumed to be purely mathematical. This brief essay motivates this "it's all just equations" assumption and discusses its implications.

  20. Thermal calculations in shale

    International Nuclear Information System (INIS)

    Thermal calculations were performed for underground nuclear waste disposal sites assuming shale as the site material. Average thermal properties were used for zero inclined layered shale with waste disposal at a depth of 2000 feet below the surface. No thermal property variations due to water content of the shale were considered. Long-term, steady-state calculations showed that site depth of 2000 feet has negligible effect on surface temperatures. Time-dependent calculations considering thermal source decay with time show that steady state calculations are very conservative. It is also shown that room air temperature can be reduced to reasonable levels with an approximately two day air conditioning cycle using 600F air supply. Maximum temperatures close to the canisters are reached approximately two years after the waste canisters are emplaced. Governing criterion for personnel and equipment will be room floor temperature which reaches about 3700F maximum for the unventilated condition

  1. Casio Graphical Calculator Project.

    Science.gov (United States)

    Stott, Nick

    2001-01-01

    Shares experiences of a project aimed at developing and refining programs written on a Casio FX9750G graphing calculator. Describes in detail some programs used to develop mental strategies and problem solving skills. (MM)

  2. Alcohol Calorie Calculator

    Science.gov (United States)

    Alcohol Calorie Calculator Find out the number of beer and hard alcohol calories you are consuming. Simply enter the number ... click ‘Compute’ and see the number of calories alcohol adds up for you in a month and ...

  3. Activities for Calculators.

    Science.gov (United States)

    Hiatt, Arthur A.

    1987-01-01

    Ten activities that give learners in grades 5-8 a chance to explore mathematics with calculators are provided. The activity cards involve such topics as odd addends, magic squares, strange projects, and conjecturing rules. (MNS)

  4. Target Heart Rate Calculator

    Science.gov (United States)

    ... My Saved Articles » My ACS » + - Text Size Target Heart Rate Calculator Compute your best workout Enter your age ... is your age? years. How to Check Your Heart Rate Right after you stop exercising, take your pulse: ...

  5. Ultrawide band signal analysis in urban environment

    Science.gov (United States)

    Schiavone, Guy A.; Palaniappan, Ravishankar; Tracy, Judd; Wahid, Parveen; Dere, Troy P.

    2002-06-01

    Ultra-wide band (UWB) is a relatively new term used to describe a technology that has been known since the 1960's as carrier free, baseband or impulse technology. The basic concept is to develop, transmit and receive an extremely short duration burst of radio frequency energy-typically a few tens of pico seconds to a few nanoseconds in duration. The resultant waveforms are extremely broadband, so much so that it is often difficult to determine an actual RF center frequency- thus the term carrier free. Since UWB waveforms are of such short time duration, they have some rather unique properties. In communications, for example, UWB pulses can be used to provide extremely high data rate performance in multi-user network applications [1]. For radar applications, these same pulses can provide very fine range resolution and precision distance and/or positioning measurement capabilities. These short duration waveforms are relatively immune to multi-path cancellation effects as observed in mobile and in-building environments. As a consequence, UWB systems are particularly well suited for high-speed, mobile wireless applications. As bandwidth is inversely related to pulse duration, the spectral extent of these waveforms can be made quite large. With proper engineering design, the resultant energy densities (i.e., transmitted watts of power per unit hertz of bandwidth) can be quite low. This low energy density translates into a low probability of detection (LPD) RF signature. An LPD signature is of particular interest for military applications (e.g., for covert communications and radar); however, an LPD signature also produces minimal interference to proximity systems and minimal RF health hazards, significant for both military and commercial applications. In this paper we consider the development of a simulation model to calculate ultra-wide band signal propagation characteristics in urban indoor and outdoor environments. The simulation is accomplished using a hybrid model that combines ray tracing and FDTD. The model takes into account the material characteristics of the surrounding walls and buildings, and other obstructions, and accounts for effects due to multiple reflections. The application operates on a 3D terrain database representation of an urban area. The ultimate goal of the simulation is to determine is to maximize coverage in and urban environment given a fixed number of base stations, or, conversely, to optimize the number and location of base stations given a predetermined coverage pattern.

  6. On the persistence of adiabatic shear bands

    OpenAIRE

    Bassim M.N.; Boakye-Yiadom S.; Al-Ameeri S.

    2012-01-01

    It is generally agreed that the initiation and development of adiabatic shear bands (ASBs) are manifestations of damage in metallic materials subjected to high strain rates and large strains as those due to impact in a Hopkinson Bar system. Models for evolution of these bands have been described in the literature. One question that has not received attention is how persistent these bands are and whether their presence and effect can be reversed or eliminated by using a process of thermal (hea...

  7. Low band gap polymers for organic photovoltaics

    DEFF Research Database (Denmark)

    Bundgaard, Eva; Krebs, Frederik C

    2007-01-01

    Low band gap polymer materials and their application in organic photovoltaics (OPV) are reviewed. We detail the synthetic approaches to low band gap polymer materials starting from the early methodologies employing quinoid homopolymer structures to the current state of the art that relies on alternating copolymers of donor and acceptor groups where strategies for band gap design are possible. Current challenges for OPV such as chemical stability and energy level alignment are discussed. We final...

  8. Efficient Spectrum Utilization of Uhf Broadcast Band

    OpenAIRE

    Shi, Lei

    2014-01-01

    The UHF band between 470-790 MHz, currently occupied by digital ter- restrial TV (DTT) distribution in Europe, is widely regarded as a premium spectrum band for providing mobile coverage. With the exponential increase in wireless data traffic in recent years, there has been growing interests in gaining access to this spectrum band for wireless broadband services. The secondary access in TV White Space is considered as one cost-effective way to reuse the spectrum unoccupied by the primary DTT ...

  9. A model for the direct-to-indirect band-gap transition in monolayer MoSe2 under strain

    Indian Academy of Sciences (India)

    Ruma Das; Priya Mahadevan

    2015-06-01

    A monolayer of MoSe2 is found to be a direct band-gap semiconductor. We show, within ab-initio electronic structure calculations, that a modest biaxial tensile strain of 3% can drive it into an indirect band-gap semiconductor with the valence band maximum (VBM) shifting from point to point. An analysis of the charge density reveals that while Mo–Mo interactions contribute to the VBM at 0% strain, Mo–Se interactions contribute to the highest occupied band at point. A scaling of the hopping interaction strengths within an appropriate tight binding model can capture the transition.

  10. Current interruption transients calculation

    CERN Document Server

    Peelo, David F

    2014-01-01

    Provides an original, detailed and practical description of current interruption transients, origins, and the circuits involved, and how they can be calculated Current Interruption Transients Calculationis a comprehensive resource for the understanding, calculation and analysis of the transient recovery voltages (TRVs) and related re-ignition or re-striking transients associated with fault current interruption and the switching of inductive and capacitive load currents in circuits. This book provides an original, detailed and practical description of current interruption transients, origins,

  11. Fast focus field calculations

    OpenAIRE

    Leutenegger, M.; Rao, R.; Leitgeb, R. A.; Lasser, T.

    2006-01-01

    We present a fast calculation of the electromagnetic field near the focus of an objective with a high numerical aperture (NA). Instead of direct integration, the vectorial Debye diffraction integral is evaluated with the fast Fourier transform for calculating the electromagnetic field in the entire focal region. We generalize this concept with the chirp z transform for obtaining a flexible sampling grid and an additional gain in computation speed. Under ...

  12. Reactor lattice transport calculations

    International Nuclear Information System (INIS)

    The present lecture is a continuation of the lecture on Introduction to the Neutron Transport Phenomena. It comprises three aspects of lattice calculations. First the idea of a reactor lattice is introduced. Then the main definitions used in reactor lattice analysis are given, and finally two basic methods applied for solution of the transport equations are defined. Several remarks on secondary results from lattice transport calculations are added. (author)

  13. Quantum Chemical Calculations

    Science.gov (United States)

    Bauschlicher, Charles W.; Arnold, James O. (Technical Monitor)

    1997-01-01

    The current methods of quantum chemical calculations will be reviewed. The accent will be on the accuracy that can be achieved with these methods. The basis set requirements and computer resources for the various methods will be discussed. The utility of the methods will be illustrated with some examples, which include the calculation of accurate bond energies for SiF$_n$ and SiF$_n^+$ and the modeling of chemical data storage.

  14. Calculation of Counterrotating Propellers

    Science.gov (United States)

    Ginzel, F.

    1949-01-01

    A method for calculation of a counterrotating propeller which is similar to Walchner's method for calculation of the single propeller in the free air stream is developed and compared with measurements. Several dimensions which are important for the design are given end simple formulas for the gain in efficiency derived. Finally a survey of the behavior of the propeller for various operating conditions is presented.

  15. Resonant photoemission spectroscopy for intermediate band materials

    Science.gov (United States)

    Mazzola, F.; Nematollahi, M.; Li, Z. S.; Cooil, S.; Yang, X.; Reenaas, T. W.; Wells, J. W.

    2015-11-01

    Resonant photoemission spectroscopy is used to study the intermediate-band material Cr doped ZnS. Using resonant photoemission, we show that the intermediate-band can be characterized, revealing the filling and specific orbital character of the states contributing to the resonant photoemission signal. We demonstrate that resonant photoemission spectroscopy is a powerful approach for understanding the origin of intermediate bands in doped ZnS. The methodology can be widely extended to a large variety of materials, providing useful information towards engineering of high efficiency intermediate band solar cells and of other optoelectronic devices.

  16. Flat-band engineering of mobility edges

    Science.gov (United States)

    Danieli, Carlo; Bodyfelt, Joshua D.; Flach, Sergej

    2015-06-01

    Properly modulated flat-band lattices have a divergent density of states at the flat-band energy. Quasiperiodic modulations are known to host a metal-insulator transition already in one space dimension. Their embedding into flat-band geometries consequently allows for a precise engineering and fine tuning of mobility edges. We obtain analytic expressions for singular mobility edges for two flat-band lattice examples. In particular, we engineer cases with arbitrarily small energy separations of mobility edge, zeroes, and divergencies.

  17. Possible chiral bands in 194Tl

    International Nuclear Information System (INIS)

    High spin states in 194Tl, excited through the 181Ta(18O,5n) fusion evaporation reaction, were studied using the AFRODITE array at iThemba LABS. Candidate chiral bands built on the ?h9/2 x ?i13/21 configuration were found. Furthermore these bands were observed through a band crossing caused by the excitation of a ?i13/2 pair. Above the band crossing the excitation energies remain close, suggesting that chirality may persist for the four quasiparticle configuration too.

  18. UWB Band Pass Filter with WLAN notch

    OpenAIRE

    Kumar, Harish; Bhardwaj, Vibhor Kumar; M.D, Upadhayay

    2012-01-01

    In this paper, UWB technology operating in broad frequency range of 3.1-10.6 GHz has shown great achievement for high- speed wireless communications. to satisfy the UWB system requirements, a band pass filter with a broad pass band width, low insertion loss, and high stop-band suppression. UWB band-pass filter (BPF) with wireless local area network (WLAN) notch at 5.8 GHz and 3-dB fractional bandwidth of 108% using a microstrip structure is presented. Initially a two transmission pole UWB ban...

  19. Mach bands explained by response normalization

    OpenAIRE

    Kingdom, Frederick A. A.

    2014-01-01

    Mach bands are the illusory dark and bright bars seen at the foot and knee of a luminance trapezoid. First demonstrated by Ernst Mach in the latter part of the 19th century, Mach bands are a test bed not only for models of brightness illusions but of spatial vision in general. Up until 50 years ago the dominant explanation of Mach Bands was that they were caused by lateral inhibition among retinal neurons. More recently, the dominant idea has been that Mach bands are a consequence of a visual...

  20. Extended mode in blocked impurity band detectors for terahertz radiation detection

    International Nuclear Information System (INIS)

    We demonstrate the existence of an interfacial barrier in blocked impurity band (BIB) detectors using temperature-dependent dark current and corresponding theoretical calculations. Considering the effects of the interfacial barrier, the calculated photoresponse is in good agreement with the experimental results. A dual-excitation model, including the direct excitation over the full barrier and excitation to the band minimum with subsequent tunneling into the blocking layer, is proposed to quantitatively explain the observed photoresponse extension. A concept of extended-mode detection is developed to suggest the option for some selective photoresponse in the terahertz region and open the possibility of extending BIB photoresponse to lower frequency.

  1. Band crossing in the O(6) symmetry region around A=130

    International Nuclear Information System (INIS)

    The band crossing in 128,132Ba has been studied by using the model in which two neutrons and two protons have been coupled to a proton-neutron boson model core. The properties of the isomeric 10+ state in 132Ba have been well described. The most striking features of 128Ba are the three-band mixing and the fact that both 10+ and 12+ states are mixed. Lifetimes in the yrast cascade and E2 branching ratios have been calculated. The calculation is in satisfactory agreement with the experimental data. (author)

  2. Anomalous composition dependence of the band gap pressure coefficients in In-containing nitride semiconductors

    DEFF Research Database (Denmark)

    Gorczyca, I.; Kami?ska, A.; Staszczak, G.; Czernecki, R.; ?epkowski, S. P.; Suski, T.; Schenk, H. P. D.; Glauser, M.; Butté, R.; Carlin, J.-F.; Feltin, E.; Grandjean, N.; Christensen, Niels Egede; Svane, Axel

    2010-01-01

    The pressure-induced changes in the electronic band structures of In-containing nitride alloys, InxGa1-xN and InxAl1-xN are examined experimentally as well as by ab initio calculations. It is found that the band gap pressure coefficients, dEg/dp, exhibit very large bowing with x, and calculations with simulation of clustered distributions of the In atoms over the cation sites show a strong enhancement of this effect. This relates well to the experimental data obtained from pressure dependent pho...

  3. Effect of conduction band nonparabolicity on the dark current in a quantum well infrared detector

    Science.gov (United States)

    Panda, Sudhira; Panda, B. K.; Fung, S.

    2007-02-01

    Taking into account electron scattering with confined plasmon-phonon coupled modes in a many-body formalism, the dark currents in a quantum well structure based on the Al0.27Ga0.73As/GaAs heterojunctions have been calculated The nonparabolicity of the conduction band, finite temperature, and applied bias has been included in the calculation of the scattering rates. Good agreement with the experiments has been obtained by the inclusion of the nonparabolicity of the conduction band in the theory.

  4. Linewidth of Cyclotron Absorption in Band-Gap Graphene: Relaxation Time Approximation vs. Monte Carlo Method

    Directory of Open Access Journals (Sweden)

    S.V. Kryuchkov

    2015-03-01

    Full Text Available The power of the elliptically polarized electromagnetic radiation absorbed by band-gap graphene in presence of constant magnetic field is calculated. The linewidth of cyclotron absorption is shown to be non-zero even if the scattering is absent. The calculations are performed analytically with the Boltzmann kinetic equation and confirmed numerically with the Monte Carlo method. The dependence of the linewidth of the cyclotron absorption on temperature applicable for a band-gap graphene in the absence of collisions is determined analytically.

  5. Influence of distortion on the electronic band structure of CuInSe2

    CERN Document Server

    Tototzintle-Huitle, H; Rodríguez, José Alberto; Baquero, R

    2005-01-01

    We present a tight-binding calculation of the influence of distorsion on the bulk electronic structure of the chalcopyrite CuInSe2. We calculate the ideal case and then the effect of the inclusion of the distortions. We analyze our results in detail and conclude from a comparison with other work that the distortions must be included in the Hamiltonian to get a proper account of the electronic band structure. We use our new Hamiltonian to study the effect that both the tetragonal and the anionic distortion have on the (112) surface electronic band structure. We find this effect non-negligible.

  6. A general purpose Fortran 90 electronic structure program for conjugated systems using Pariser-Parr-Pople model

    CERN Document Server

    Sony, Priya

    2009-01-01

    Pariser-Parr-Pople (P-P-P) model Hamiltonian has been used extensively over the years to perform calculations of electronic structure and optical properties of $\\pi$-conjugated systems successfully. In spite of tremendous successes of \\emph{ab initio} theory of electronic structure of large systems, the P-P-P model continues to be a popular one because of a recent resurgence in interest in the physics of $\\pi$-conjugated polymers, fullerenes and other carbon based materials. In this paper, we describe a Fortran 90 computer program developed by us, which uses P-P-P model Hamiltonian to not only solve Hartree-Fock (HF) equation for closed- and open-shell systems, but also for performing correlation calculations at the level of single configuration interactions (SCI) for molecular systems. Moreover, the code is capable of computing linear optical absorption spectrum at various levels, such as, tight binding (TB) Hueckel model, HF, SCI, and also of calculating the band structure using the Hueckel model. The code ...

  7. First-principle studies of the electronic band structure and the phonon dispersion properties of wurtzite BN

    Science.gov (United States)

    Lei, X.; Liang, X. X.; Zhao, G. J.; Song, T. L.

    2014-03-01

    The electronic band structure and phonon dispersion of wurtzite BN are studied by the first principle calculations. The local density approximation (LDA) and the generalized gradient approximation (GGA) exchange-correlation potentials are applied in the calculations and compared. The computational results for the band structure and density of states with indirect band gaps as well as the phonon dispersive curves and density of states are obtained. The corresponding dielectric and thermodynamic properties are discussed. The conclusions are consistent with other theoretical results and experimental data.

  8. Broad-band BVRI photometry of isolated spiral galaxies

    Science.gov (United States)

    Hernández-Toledo, H. M.; Ortega-Esbrí, S.

    2008-08-01

    Context: Uniform and high resolution observations in samples of isolated galaxies are required to estimate fundamental morphological and structural parameters for comparative studies of environmental effects and for confronting model predictions of galaxy evolution. A subsample of The Catalog of Isolated Galaxies (CIG), Karachentseva (1973), has been uniformly observed at San Pedro Mártir National Observatory in México and a photometric and morphological study of these galaxies has been carried out. Aims: We report multicolor broad band (BVRI) photometry for a subsample of 40 isolated spirals drawn from the CIG. Total magnitudes and colors at various circular apertures as well as a detailed morphological analysis that is extended into the NIR bands are presented. Some structural parameters are estimated from the global light distribution in the optical and NIR bands to complement our morphological analysis and several correlations between the photometric and structural parameters are explored. Emphasis was given to the detection of morphological distortions at high/low intensity levels. Methods: The observations, data reduction, and analysis are described. Morphology is reevaluated from a combination of optical logarithmically scaled R band images, filter-enhanced R band images, (B-I) color index maps, archived near IR {JHK} images from the TwoMicron Survey and optical-NIR ? and PA radial profiles after an isophotal analysis. {RGB} images from the SDSS database were retrieved when available to complement our analysis. The {CAS} structural parameters (Concentration, Asymmetry, and Clumpiness) were calculated from the images in each band. Results: The fraction of galaxies with well-identified optical/near-IR bars (SB) is 40%, while another 25% shows evidence of weak or suspected bars (SAB). The sample average value of the maximum bar ellipticity is ?_max? 0.35. 57.5% of the galaxies in the sample show rings. The {CAS} parameters change with the observed band, the morphological type and global color. We found 9 isolated galaxies with disturbed morphology. After reviewing their local number density and tidal strength parameters, we identified CIG 744 as a morphologically disturbed isolated galaxy having M_HI/LI > 1; a tentative candidate to interact with a dark gas-rich object. However, its loci in the ?0 ^I/log(M_HI/LI) diagram, suggests that CIG 744 is itself a gas-rich disturbed-isolated galaxy probably in a lengthy or ongoing process of formation, instead. Appendices A and B are only available in electronic form at http://www.aanda.org

  9. Multi-band optical radiometer

    International Nuclear Information System (INIS)

    JAXA (Japan Aerospace eXploration Agency) is now promoting GCOM (Global Change Observation Mission). GCOM consists of GCOM-W (Water) series, in which the satellites carry microwave radiometers to observe water circulation, and GCOM-C (Climate) series, in which the satellites carry optical radiometers to observe climate change and carbon circulation. The GCOM-C1, which is the first satellite for the observation of climate change and is loaded with a multi-band optical radiometer SGLI (Second Generation GLobal Imager), is scheduled to be launched in 2016. The test of the engineering model of SGLI has been completed showing high observation ability. At present the satellite GCOM-C1 and the proto-flight-model are under fabrication. It is expected that various physical parameters on the global environment will be produced by precise observation data from SGLI and will contribute to clarify the mechanism of climate change and to improve the estimation accuracy of long-term climate. (J.P.N.)

  10. Comparison of X-Band, L-Band and C-Band Radar Images in Monitoring Subsidence in Agricultural Regions

    Science.gov (United States)

    Motagh, Mahdi; Haghshenas Haghighi, Mahmud; Shamshiri, Roghaye; Esmaeili, Mustapha

    2015-05-01

    The ongoing pattern of groundwater induced land subsidence in major valleys and agricultural regions of Iran has been recently documented by several studies (e.g. [1-4]) using C-band Interferometric Synthetic Aperture Radar (InSAR) observations. In this article we present the results of our research in which we evaluated the performance of C-band, L-band and X-band SAR data, using time-series method of small baseline subset (SBAS), to retrieve long time series of ground subsidence in agricultural regions in the country. Two major groundwater basins have been selected for this purpose: (1) Rafsanjan Valley in the Kerman province of central Iran and (2) Tehran Plain (capital of Iran). We also report on our experience using dualpolarimetry (HH/VV) X-band SAR data for Persistent Scatterer (PS) deformation analysis in natural terrains subject to high rate of deformation.

  11. Theoretical Isochrones with Extinction in the K Band

    OpenAIRE

    Kim, Sungsoo S.; Donald F. Figer; Lee, Myung Gyoon; Oh, Seungkyung

    2005-01-01

    We calculate theoretical isochrones in a consistent way for five filters (K, K', Ks, F205W, and F222M) in the atmospheric window between 1.9 and 2.5 micron using the Padova stellar evolutionary models by Girardi et al. Even when displayed in the same Vega magnitude system, the near-infrared colors of the same isochrone can differ by up to 0.18 mag at its bright end, depending on the filter. We present magnitude transformations between K-band filters as a function of color fr...

  12. Surface stress in d-band metal surfaces

    International Nuclear Information System (INIS)

    Using calculations within the density functional approach, we make a survey of the surface stresses of relevant d-band metal surfaces. Unlike the case for surface energies, where volcano-shaped dependences have been found across the d period, the surface stress values show a non-trivial dependence on the metal species and surface termination, which cannot be anticipated from homogeneous electron gas models. A qualitative interpretation as regards the origin of this dependence can be given on the basis of the decomposition of the surface stress into repulsive and attractive electronic components.

  13. Structure of Dipole Bands in 112In: Through Lifetime Measurement

    Science.gov (United States)

    Trivedi, T.; Palit, R.; Sethi, J.; Saha, S.; Kumar, S.; Naik, Z.; Parkar, V. V.; Naidu, B. S.; Deo, A. Y.; Raghav, A.; Joshi, P. K.; Jain, H. C.; Sihotra, S.; Mehta, D.; Jain, A. K.; Choudhury, D.; Negi, D.; Roy, S.; Chattopadhyay, S.; Singh, A. K.; Singh, P.; Biswas, D. C.; Bhowmik, R. K.; Muralithar, S.; Singh, R. P.; Kumar, R.; Rani, K.

    2012-09-01

    High-spin states of the 112In nucleus have been populated via 100Mo(16O, p3n) reaction at 80 MeV beam energy. Lifetimes of excited states of dipole bands have been measured using Doppler-shift attenuation method. The B(M1) transition rates deduced from the measured lifetimes show a rapid decrease with increasing angular momentum. The decrease in B(M1) values are well accounted by the prediction of tilted axis cranking calculations. These measurements confirm the presence of shears mechanism in this nuclei.

  14. g-Factor of the superdeformed band in 133 Nd

    International Nuclear Information System (INIS)

    In this paper we report on a first g-factor measurement in a superdeformed band, performed by using the transient field method applied in coincidence mode. The 133 Nd nuclei have been populated in the reaction 104 Pd (32 S, 2 p n) at 135 MeV bombarding energy and the ?-rays have been registered by the multidetector array GASP at the Legnaro National Laboratory XTU Tandem accelerator. The experimental g-factor g = 0.31 (8) is consistent with the superdeformed neutron orbital [660]1/2+ as predicted by cranked Woods-Saxon calculations. (Author)

  15. Systematic study of ?-band and correlation with g- band using power law and soft rotor formula

    International Nuclear Information System (INIS)

    The nuclear structure of even Z even N medium mass transitional nuclei consist of ground state band, K?=01 ?-band, K?=21 ?- band and other higher bands. As we move away from closed shell, energy levels are low lying from spherical to deformed nuclei and energy deviated from ideal rotor behavior. The energy of these transitional nuclei in ground band can also be studied using Bohr Mottelson energy expression, Soft Rotor Formula (SRF), Power Law (PL) etc. Recently, Gupta et al. (2013) modified SRF for non zero band head K?=21 ?-band and reproduced the level energies. Here same formula applied for K?=01 ?-band and the level energies are reproduced and compared with experimental energies. The power law is also used for recalculation of level energies and for useful comparison

  16. Elastic band-to-band registration for airborne multispectral scanners with large field of view

    Science.gov (United States)

    Li, Feng; Li, ChuanRong; Tang, LingLi; Guo, Yi

    2012-11-01

    Multispectral line scanners with large field of view improve efficiency in Earth observation. Small volume of the instruments born with a short focal length, however, may bring a problem: there are different none-linear warping and local transformation between bands. Alignment accuracy of bands is a criteria factor impacting product quality in remote sensing. In this paper, a new elastic band-to-band image registration method is proposed for solving the problem. Rather than carry out registration between bands straightforwardly, corresponding featured images of each band are constructed and used to conduct an intensity based elastic image registration. In this method, the idea of the inverse compositional algorithm is borrowed and expended when dealing with local warping, and a smoothness constraint is also added in the procedure. Experimental results show that the proposed band-to-band registration method works well both visually and quantitatively.

  17. Solid State KA-Band, Solid State W-Band and TWT Amplifiers Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Phase I of the proposal describes plans to develop a state of the art transmitter for the W-Band and KA -Band Cloud Radar system. Our focus will be concentrated in...

  18. Band width and multiple-angle valence-state mapping of diamond

    Energy Technology Data Exchange (ETDEWEB)

    Jimenez, I.; Terminello, L.J.; Sutherland, D.G.J. [Lawrence Berkeley National Lab., CA (United States)] [and others

    1997-04-01

    The band width may be considered the single most important parameter characterizing the electronic structure of a solid. The ratio of band width and Coulomb repulsion determines how correlated or delocalized an electron system is. Some of the most interesting solids straddle the boundary between localized and delocalized, e.g. the high-temperature superconductors. The bulk of the band calculations available today is based on local density functional (DF) theory. Even though the Kohn-Sham eigenvalues from that theory do not represent the outcome of a band-mapping experiment, they are remarkably similar to the bands mapped via photoemission. Strictly speaking, one should use an excited state calculation that takes the solid`s many-body screening response to the hole created in photoemission into account. Diamond is a useful prototype semiconductor because of its low atomic number and large band width, which has made it a long-time favorite for testing band theory. Yet, the two experimental values of the band width of diamond have error bars of {+-}1 eV and differ by 3.2 eV. To obtain an accurate valence band width for diamond, the authors use a band-mapping method that collects momentum distributions instead of the usual energy distributions. This method has undergone extensive experimental and theoretical tests in determining the band width of lithium fluoride. An efficient, imaging photoelectron spectrometer is coupled with a state-of-the-art undulator beam line at the Advanced Light Source to allow collection of a large number of data sets. Since it takes only a few seconds to take a picture of the photoelectrons emitted into a 84{degrees} cone, the authors can use photon energies as high as 350 eV where the cross section for photoemission from the valence band is already quite low, but the emitted photoelectrons behave free-electron-like. This make its much easier to locate the origin of the inter-band transitions in momentum space.

  19. Direct Enumeration Studies of Band-Gap Properties of AlxGayIn1-x-yP Alloys

    Energy Technology Data Exchange (ETDEWEB)

    Jungthawan, S.; Limpijumnong, S.; Collins, R.; Kim, K.; Graf, P. A.; Turner, J. A.

    2009-01-01

    A band-gap database of a large number of configurations ({approx} 5000 configurations) is produced for AlGaInP semiconductor alloys using an empirical pseudopotential method. Our results show that the band gap of this alloy system depends strongly on the cation arrangement in addition to the alloy composition. This indicates that one can effectively control the band gap of alloys by controlling the cation arrangement. For each given alloy composition, the range of possible band gaps is calculated and the complete database of the results is made available online. Our results show that a majority of alloy configurations have band gaps smaller than those predicted by Vegard's law. Our results also show several systematic trends in the band gaps depending on the superlattice directions.

  20. RF performance measurement of the DSS-14 70-meter antenna at C-band/L-band

    Science.gov (United States)

    Gatti, M. S.; Freiley, A. J.; Girdner, D.

    1989-01-01

    The calibration of the 70-meter antenna at C-band (5.01 GHz) and L-band (1.668 GHz) is described. This calibration comes after a modification to an existing L-band feed to include the C-band frequencies. The test technique employs noise-adding radiometers and associated equipment running simultaneously at both frequencies. The test procedure is described including block diagrams, and results are presented for efficiency, system temperature, and pointing.

  1. Triple Band X Shape Microstrip Patch Antenna for Ku/K Band Applications

    OpenAIRE

    Md. Samsuzzaman Sobuz; M.T. Islam; J. S. Mandeep

    2013-01-01

    In this article, electrically small, triple band, triple frequency X shaped patch antenna is presented. The proposed X shape patch antenna consists of five rectangular slots which produces dual band operation for Ku band applications and another one for K band applications. In order to achieve multiband operation from conventional rectangular slot, it is introduced three equilateral triangle slots in left, right and upper edge respectively, and two small triangular slots are protruding both s...

  2. An Example of Suppression of Spurious Stop-Bands of EBG Band-Stop Filter

    OpenAIRE

    Dušan Neši?; Branko Kolundžija

    2011-01-01

    Based on the well known theory of infinite periodic structures, analytical theory of EBG (electromagnetic band gap) cells suppressing 6 higher (spurious) stop-bands is developed. Using such cells in a cascade the straight-forward procedure for design of the corresponding EBG band-stop filter is proposed, with possibility to control the width and the depth of the stop-band. The analytical theory is confirmed by the EM simulation of the filter realized in the microstrip technology.

  3. Calculating Quenching Weights

    CERN Document Server

    Salgado, C A; Salgado, Carlos A.; Wiedemann, Urs Achim

    2003-01-01

    We calculate the probability (``quenching weight'') that a hard parton radiates an additional energy fraction due to scattering in spatially extended QCD matter. This study is based on an exact treatment of finite in-medium path length, it includes the case of a dynamically expanding medium, and it extends to the angular dependence of the medium-induced gluon radiation pattern. All calculations are done in the multiple soft scattering approximation (Baier-Dokshitzer-Mueller-Peign\\'e-Schiff--Zakharov ``BDMPS-Z''-formalism) and in the single hard scattering approximation (N=1 opacity approximation). By comparison, we establish a simple relation between transport coefficient, Debye screening mass and opacity, for which both approximations lead to comparable results. Together with this paper, a CPU-inexpensive numerical subroutine for calculating quenching weights is provided electronically. To illustrate its applications, we discuss the suppression of hadronic transverse momentum spectra in nucleus-nucleus colli...

  4. Geogebra: Calculation of Centroid

    Directory of Open Access Journals (Sweden)

    Qamil Kllogjeri

    2012-09-01

    Full Text Available Our paper is result of the research done in a special direction for solving problems of physics by using GeoGebra programme: calculation of centroid. Lots of simulations of physical phenomena from the class of Mechanics can be performed and computational problems can be solved with GeoGebra. GeoGebra offers many commands and one of them is the command “centroid” to calculate the coordinates of the centroid of a polygon but, we have created a new tool to calculate the coordinates of the centroid of a plane region bounded by curves. Our work is part of the passionate work of many GeoGebra users which will result with a very rich fund of GeoGebra virtual tools, examples and experiences that will be worldwidely available for many teachers and practioners.

  5. Semiconductor resonator solitons above band gap

    OpenAIRE

    Taranenko, V. B.; Weiss, C. O.; Stolz, W

    2001-01-01

    We show experimentally the existence of bright and dark spatial solitons in semiconductor resonators for excitation above the band gap energy. These solitons can be switched on, both spontaneously and with address pulses, without the thermal delay found for solitons below the band gap which is unfavorable for applications. The differences between soliton properties above and below gap energy are discussed.

  6. Hazing in the College Marching Band

    Science.gov (United States)

    Silveira, Jason M.; Hudson, Michael W.

    2015-01-01

    The purpose of this study was to investigate hazing in collegiate marching bands. Specifically, the researchers were interested in marching band students' experiences with hazing behaviors, to whom they were reported, attitudes toward hazing, and level of awareness of institutional hazing policies. Using a multistage cluster sampling approach, we…

  7. Getting Elementary Students Involved in Band

    Science.gov (United States)

    Moore, Patience

    2009-01-01

    The author discusses getting elementary students involved in a band. The goals of an elementary band instructor should include introduction of good practice habits, working within an ensemble, and rehearsal procedures, along with the focusing on the essentials of music. Instructors should let students use the basic instruments: flute, clarinet,…

  8. Concert Band Instrumentation: Realities and Remedies.

    Science.gov (United States)

    Rogers, George L.

    1991-01-01

    Suggests ways to solve problems resulting from imbalanced instrumentation in school concert bands. Identifies sources of imbalance. Encourages band directors to plan for correct instrumentation, to match students' characteristics and abilities to instruments, and to recruit students to play needed instruments. Discusses the benefits of balanced…

  9. Electrical installation calculations advanced

    CERN Document Server

    Watkins, AJ

    2009-01-01

    Designed to provide a step-by-step guide to successful application of the electrical installation calculations required in day-to-day electrical engineering practice, the Electrical Installation Calculations series has proved an invaluable reference for over forty years, for both apprentices and professional electrical installation engineers alike.Now in its seventh edition, Volume 2 has been fully updated in line with the 17th Edition IEE Wiring Regulations (BS 7671:2008) and references the material covered to the Wiring Regs throughout. The content meets the requirements of the 2330 Level 3

  10. Sample Size Calculations

    OpenAIRE

    2011-01-01

    The sample size is the number of patients or other experimental units that need to be included in a study to answer the research question. Pre-study calculation of the sample size is important; if a sample size is too small, one will not be able to detect an effect, while a sample that is too large may be a waste of time and money. Methods to calculate the sample size are explained in statistical textbooks, but because there are many different formulas available, it can be difficult for inves...

  11. Electrical installation calculations

    CERN Document Server

    Watkins, AJ

    2006-01-01

    Designed to provide a step by step guide to successful application of the electrical installation calculations required in day to day electrical engineering practice, the Electrical Installation Calculations series has proved an invaluable reference for over forty years, for both Foundation and Modern Apprentices, and professional electrical installation engineers alike.Now in its sixth edition, Volume 2 has been fully updated to meet the requirements of the 2330 Level 3 Certificate in Electrotechnical Technology from City & Guilds, and will also prove a vital purchase for students of Level 3

  12. Variational DVR calculations

    International Nuclear Information System (INIS)

    In the discrete variable representation (DVR) method the potential energy matrix ? has a particular simple form. It is diagonal with values of the interaction potential at the discrete points. However, this simple form is obtained by making approximations in the calculation of the matrix elements of ?. As a consequence the results cannot be considered as variational estimates. We will show how to recover the variational character of the method using the discrete variable representation eigenvectors as trial functions and performing a variational calculation in a restricted Hilbert space. (author)

  13. Extraction of Optimal Spectral Bands Using Hierarchical Band Merging Out of Hyperspectral Data

    Science.gov (United States)

    Le Bris, A.; Chehata, N.; Briottet, X.; Paparoditis, N.

    2015-08-01

    Spectral optimization consists in identifying the most relevant band subset for a specific application. It is a way to reduce hyperspectral data huge dimensionality and can be applied to design specific superspectral sensors dedicated to specific land cover applications. Spectral optimization includes both band selection and band extraction. On the one hand, band selection aims at selecting an optimal band subset (according to a relevance criterion) among the bands of a hyperspectral data set, using automatic feature selection algorithms. On the other hand, band extraction defines the most relevant spectral bands optimizing both their position along the spectrum and their width. The approach presented in this paper first builds a hierarchy of groups of adjacent bands, according to a relevance criterion to decide which adjacent bands must be merged. Then, band selection is performed at the different levels of this hierarchy. Two approaches were proposed to achieve this task : a greedy one and a new adaptation of an incremental feature selection algorithm to this hierarchy of merged bands.

  14. Line broadening coefficient calculations for methane perturbed by nitrogen

    International Nuclear Information System (INIS)

    We report semiclassical line broadening calculations for methane perturbed by nitrogen at room temperature. For this, we have developed a symmetrized version of the Robert and Bonamy theory. The interaction potential was built from electrostatic (octopole and hexadecapole for methane, quadrupole for nitrogen) and atom-atom contributions. The relative (classical) trajectories of the molecules were computed in the frame of the usual parabolic model, through analytical formula. High orders of developments had to be used for the short range molecular interactions. As a consequence, a combination of symbolic computation and source code generation was employed to implement practical calculations. We have compared our calculations to the most recent experimental data available in the ?4 band, the ?3 band and the octad spectral region of methane.

  15. Quantum chemical calculations for polymers and organic compounds

    Science.gov (United States)

    Lopez, J.; Yang, C.

    1982-01-01

    The relativistic effects of the orbiting electrons on a model compound were calculated. The computational method used was based on 'Modified Neglect of Differential Overlap' (MNDO). The compound tetracyanoplatinate was used since empirical measurement and calculations along "classical" lines had yielded many known properties. The purpose was to show that for large molecules relativity effects could not be ignored and that these effects could be calculated and yield data in closer agreement to empirical measurements. Both the energy band structure and molecular orbitals are depicted.

  16. BCS theory on a flat band lattice

    International Nuclear Information System (INIS)

    It is important to study the many-body effects of the electrons on the flat band lattice, since the flatness of the dispersion may lead to instabilities in the presence of interactions. To clarify the effects of flat dispersion for superconductivity, we investigate a simple two-band BCS Hamiltonian, where one of the bands has a flat dispersion, in the mean field approximation. A superconducting gap ? and a critical temperature Tc strongly depend on the pairing coupling constant V. Especially, for small coupling constant, ? and Tc are proportional to V, which are quite different from the single band BCS cases. Higher Tc, compared to the normal BCS system, are realized due to the existence of the flat band

  17. Relaxation of femtosecond photoexcited electrons in a polar indirect band-gap semiconductor nanoparticle

    Indian Academy of Sciences (India)

    Navinder Singh

    2005-01-01

    A model calculation is given for the energy relaxation of a non-equilibrium distribution of hot electrons (holes) prepared in the conduction (valence) band of a polar indirect band-gap semiconductor, which has been subjected to homogeneous photoexcitation by a femtosecond laser pulse. The model assumes that the pulsed photoexcitation creates two distinct but spatially interpenetrating electron and hole non-equilibrium subsystems that initially relax non-radiatively through the electron (hole)–phonon processes towards the conduction (valence) band minimum (maximum), and finally radiatively through the phonon-assisted electron–hole recombination across the band-gap, which is a relatively slow process. This leads to an accumulation of electrons (holes) at the conduction (valence) band minimum (maximum). The resulting peaking of the carrier density and the entire evolution of the hot electron (hole) distribution has been calculated. The latter may be time resolved by a pump-probe study. The model is particularly applicable to a divided (nanometric) polar indirect band-gap semiconductor with a low carrier concentration and strong electron–phonon coupling, where the usual two-temperature model $[1–4]$ may not be appropriate.

  18. Band structures of 182Os studied by GCM based on 3D-CHFB

    Science.gov (United States)

    Horibata, Takatoshi; Oi, Makito; Onishi, Naoki; Ansari, Ahmad

    1999-02-01

    Band structure properties of 182Os are investigated through a particle number and angular momentum constrained generator coordinate (GCM) calculation based on self-consistent threedimensional cranking solutions. From the analysis of the wave function of the lowest GCM solution, we confirm that this nucleus shows a tilted rotational motion in its yrast states, at least with the present set of force parameters of the pairing-plus-quadrupole interaction Hamiltonian. A close examination of the behaviour of the other GCM solutions reveals a sign of a possible occurrence of multi-band crossing in the nucleus. We have also found a new potential curve along the prime meridian on the globe of the J = 18 h? sphere. Along this new solution the characters of proton and neutron gap parameters get interchanged. Namely, ? p almost vanishes while ? n grows to a finite value close to the one corresponding to the principal axis rotation (PAR). A state in the new solution curve at the PAR point turns out to have almost the same characteristic features of an yrare s-band state which is located just above the g-band in our calculation. This fact suggests a new type of seesaw vibrational mode of the proton and the neutron pairing, occurring through a wobbling motion. This mode is considered to bridge the g-band states and the s-band states in the backbending region.

  19. Band structures of 182Os studied by GCM based on 3D-CHFB

    International Nuclear Information System (INIS)

    Band structure properties of 182Os are investigated through a particle number and angular momentum constrained generator coordinate (GCM) calculation based on self-consistent three-dimensional cranking solutions. From the analysis of the wave function of the lowest GCM solution, we confirm that this nucleus shows a tilted rotational motion in its yrast states, at least with the present set of force parameters of the pairing-plus-quadrupole interaction Hamiltonian. A close examination of the behaviour of the other GCM solutions reveals a sign of a possible occurrence of multi-band crossing in the nucleus. We have also found a new potential curve along the prime meridian on the globe of the J = 18(?/2?) sphere. Along this new solution the characters of proton and neutron gap parameters get interchanged. Namely, ?p almost vanishes while ?n grows to a finite value close to the one corresponding to the principal axis rotation (PAR). A state in the new solution curve at the PAR point turns out to have almost the same characteristic features of an yrast s-band state which is located just above the g-band in our calculation. This fact suggests a new type of seesaw vibrational mode of the proton and the neutron pairing, occurring through a wobbling motion. This mode is considered to bridge the g-band states and the s-band states in the backbending region

  20. Angle-resolved photoemission study and first-principles calculation of the electronic structure of LaSb2

    International Nuclear Information System (INIS)

    In this work we present valence band studies of LaSb2 using angle-resolved photoelectron spectroscopy with synchrotron radiation and compare these data with band structure calculations. Valence band spectra reveal that Sb 5p states are dominant near the Fermi level and are hybridized with the La 5d states just below. The calculations show a fair agreement with the experimentally determined valence band spectra, allowing an identification of the observed features. We measured some dispersion for kbar, especially for Sb 5p states; no significant dispersion was found for k||. (letter to the editor)

  1. Atomistic simulation study of the shear-band deformation mechanism in Mg-Cu metallic glasses

    DEFF Research Database (Denmark)

    Bailey, Nicholas; SchiØtz, Jakob

    2006-01-01

    We have simulated plastic deformation of a model Mg-Cu metallic glass in order to study shear banding. In uniaxial tension, we find a necking instability occurs rather than shear banding. We can force the latter to occur by deforming in plane strain, forbidding the change of length in one of the transverse directions. Furthermore, in most of the simulations a notch is used to initiate shear bands, which lie at a 45 degrees angle to the tensile loading direction. The shear bands are characterized by the Falk and Langer local measure of plastic deformation D-min(2), averaged here over volumes containing many atoms. The D-min(2) profile has a peak whose width is around 10 nm; this width is largely independent of the strain rate. Most of the simulations were, at least nominally, at 100 K, about T-g/3 for this system. The development of the shear bands takes a few tens of ps, once plastic flow has started, more or less independent of strain rate. The shear bands can also be characterized using a correlation function defined in terms of D-min(2), which, moreover, can detect incipient shear bands in cases where they do not fully form. By averaging the kinetic energy over small regions, the local temperature can be calculated, and this is seen to be higher in the shear bands by about 50-100 K. Increases in temperature appear to initiate from interactions of the shear bands with the free surfaces and with each other, and are delayed somewhat with respect to the localization of plastic flow itself. We observe a slight decrease in density, up to 1%, within the shear band, which is consistent with notions of increased free volume or disorder within a plastically deforming amorphous material.

  2. Using Superlattice Ordering to Reduce the Band Gap of Random (In,Ga)As/InP Alloys to a Target Value Via the Inverse Band Structure Approach

    Energy Technology Data Exchange (ETDEWEB)

    Piquini, P.; Zunger, A.

    2008-10-01

    Thermophotovoltaic (TPV) devices are intended to absorb photons from hot blackbody radiating objects, often requiring semiconductor absorbers with band gap of {approx_equal} 0.6 eV. The random In{sub x}Ga{sub 1-x}As alloy lattice matched (x{sub In}=0.53) to a (001) InP substrate has a low-temperature band gap of 0.8 eV, about 0.2 eV too high for a TPV absorber. Bringing the band gap down by raising the In concentration induces strain with the substrate, leading to a two-dimensional (2D) {yields} three-dimensional (3D) morphological transition occurring before band gaps suitable for TPV applications are achieved. We use the inverse band structure approach, based on a genetic algorithm and empirical pseudopotential calculations, to search for lattice-matched InAs/GaAs multiple-repeat unit structures with individual layer thicknesses lower than the critical thickness for a 2D {yields} 3D transition. Despite the fact that quantum confinement usually increases band gaps, we find a quantum superlattice structure with the required reduced gap (and a significant optical transition) that matches all target requirements. This is explained by the predominance of (potential-energy) level anticrossing effects over (kinetic) quantum confinement effects.

  3. Using Superlattice Ordering to Reduce the Band Gap of Random (In,Ga)As/InP Alloys to a Target Value Via the Inverse Band Structure Approach

    International Nuclear Information System (INIS)

    Thermophotovoltaic (TPV) devices are intended to absorb photons from hot blackbody radiating objects, often requiring semiconductor absorbers with band gap of ? 0.6 eV. The random InxGa1-xAs alloy lattice matched (xIn=0.53) to a (001) InP substrate has a low-temperature band gap of 0.8 eV, about 0.2 eV too high for a TPV absorber. Bringing the band gap down by raising the In concentration induces strain with the substrate, leading to a two-dimensional (2D) ? three-dimensional (3D) morphological transition occurring before band gaps suitable for TPV applications are achieved. We use the inverse band structure approach, based on a genetic algorithm and empirical pseudopotential calculations, to search for lattice-matched InAs/GaAs multiple-repeat unit structures with individual layer thicknesses lower than the critical thickness for a 2D ? 3D transition. Despite the fact that quantum confinement usually increases band gaps, we find a quantum superlattice structure with the required reduced gap (and a significant optical transition) that matches all target requirements. This is explained by the predominance of (potential-energy) level anticrossing effects over (kinetic) quantum confinement effects

  4. Cooling tower calculations

    International Nuclear Information System (INIS)

    The problems are summed up of the dynamic calculation of cooling towers with forced and natural air draft. The quantities and relations are given characterizing the simultaneous exchange of momentum, heat and mass in evaporative water cooling by atmospheric air in the packings of cooling towers. The method of solution is clarified in the calculation of evaporation criteria and thermal characteristics of countercurrent and cross current cooling systems. The procedure is demonstrated of the calculation of cooling towers, and correction curves and the effect assessed of the operating mode at constant air number or constant outlet air volume flow on their course in ventilator cooling towers. In cooling towers with the natural air draft the flow unevenness is assessed of water and air relative to its effect on the resulting cooling efficiency of the towers. The calculation is demonstrated of thermal and resistance response curves and cooling curves of hydraulically unevenly loaded towers owing to the water flow rate parameter graded radially by 20% along the cross-section of the packing. Flow rate unevenness of air due to wind impact on the outlet air flow from the tower significantly affects the temperatures of cooled water in natural air draft cooling towers of a design with lower demands on aerodynamics, as early as at wind velocity of 2 m.s-1 as was demonstrated on a concrete example. (author). 11 figs., 10 refs

  5. Thermal load calculations Isar

    International Nuclear Information System (INIS)

    The thermal ratios of the Isar from the Loisach mouth to the Danube have been electronically calculated and presented with regard to the present and by 1980 planned thermal power plants and the various cooling methods. Further load conditions were investigated in order to determine the site possibilities for thermal power plants on the Isar. (orig./LH)

  6. Languages for structural calculations

    International Nuclear Information System (INIS)

    The differences between human and computing languages are recalled. It is argued that they are to some extent structured in antagonistic ways. Languages in structural calculation, in the past, present, and future, are considered. The contribution of artificial intelligence is stressed

  7. Plutonium 239 Equivalency Calculations

    International Nuclear Information System (INIS)

    This document provides the basis for converting actual weapons grade plutonium mass to a plutonium equivalency (PuE) mass of Plutonium 239. The conversion can be accomplished by performing calculations utilizing either: (1) Isotopic conversions factors (CFisotope), or (2) 30-year-old weapons grade conversion factor (CF30yr) Both of these methods are provided in this document. Material mass and isotopic data are needed to calculate PuE using the isotopic conversion factors, which will provide the actual PuE value at the time of calculation. PuE is the summation of the isotopic masses times their associated isotopic conversion factors for plutonium 239. Isotopic conversion factors are calculated by a normalized equation, relative to Plutonium 239, of specific activity (SA) and cumulated dose inhalation affects based on 50-yr committed effective dose equivalent (CEDE). The isotopic conversion factors for converting weapons grade plutonium to PuE are provided in Table-1. The unit for specific activity (SA) is curies per gram (Ci/g) and the isotopic SA values come from reference (1). The cumulated dose inhalation effect values in units of rem/Ci are based on 50-yr committed effective dose equivalent (CEDE). A person irradiated by gamma radiation outside the body will receive a dose only during the period of irradiation. However, following an intake by inhalation, some radionuclides persist in the body and irradiate the various tissues for many years. There are three groups CEDE data representing lengths of time of 0.5 (D), 50 (W) and 500 (Y) days, which are in reference (2). The CEDE values in the (W) group demonstrates the highest dose equivalent value; therefore they are used for the calculation.

  8. Normal mode calculations of trigonal selenium

    DEFF Research Database (Denmark)

    Hansen, Flemming Yssing; McMurry, H. L.

    1980-01-01

    The phonon dispersion relations for trigonal selenium have been calculated on the basis of a short range potential field model. Electrostatic long range forces have not been included. The force field is defined in terms of symmetrized coordinates which reflect partly the symmetry of the space group. With such coordinates a potential energy, calculated with only a diagonal force matrix, is equivalent to one calculated with both off diagonal and diagonal elements when conventional coordinates are used. Another advantage is that often some force constants may be determined directly from frequencies at points of high symmetry. The intrachain force field is projected from a valence type field including a bond stretch, angle bend, and dihedral torsion. With these coordinates we obtain the strong dispersion of the upper optic modes as observed by neutron scattering, where other models have failed and give flat bands. The interchain force field is projected from relative rotations and translations of groups of atoms in adjacent chains. This type of coordinate is very well adopted to describing interactions between groups of nonbonded atoms as found in molecular crystals, and they also seem to apply very well for this crystal. In this way we have eliminated the ambiguity in the choice of valence coordinates, which has been a problem in previous models which used valence type interactions. Calculated sound velocities and elastic moduli are also given. The Journal of Chemical Physics is copyrighted by The American Institute of Physics.

  9. Dynamic Beam Shaping Using a Dual-Band Metasurface-Inspired Electronically Tunable Reflectarray Antenna

    CERN Document Server

    Tayebi, Amin; Paladhi, Pavel Roy; Udpa, Lalita; Udpa, Satish; Rothwell, Edward

    2015-01-01

    An electronically reconfigurable dual-band-reflectarray antenna is presented in this paper. The tunable unit cell, a ring loaded square patch with a single varactor diode connected across the gap between the ring and the patch, is modeled using both a full-wave solver and an equivalent circuit. The parameters of the equivalent circuit are calculated independently of the simulation and experiment using analysis techniques employed in frequency selective surfaces. The reflection phase of the proposed unit cell is shown to provide an excellent phase range of 335$^{\\circ}$ in F band and 340$^{\\circ}$ in S band. Results from the analysis are used to design and build a 10x10 element reflectarray antenna. The high tuning phase range of each element allows the fabricated reflectarray to demonstrate a very broad steering range of up to $\\pm$60$^{\\circ}$ in both frequency bands.

  10. Determination of band alignment in the single-layer MoS2/WSe2 heterojunction

    KAUST Repository

    Chiu, Ming-Hui

    2015-07-16

    The emergence of two-dimensional electronic materials has stimulated proposals of novel electronic and photonic devices based on the heterostructures of transition metal dichalcogenides. Here we report the determination of band offsets in the heterostructures of transition metal dichalcogenides by using microbeam X-ray photoelectron spectroscopy and scanning tunnelling microscopy/spectroscopy. We determine a type-II alignment between MoS2 and WSe2 with a valence band offset value of 0.83?eV and a conduction band offset of 0.76?eV. First-principles calculations show that in this heterostructure with dissimilar chalcogen atoms, the electronic structures of WSe2 and MoS2 are well retained in their respective layers due to a weak interlayer coupling. Moreover, a valence band offset of 0.94?eV is obtained from density functional theory, consistent with the experimental determination.

  11. Curvature-induced D-band Raman scattering in folded graphene

    Science.gov (United States)

    Gupta, Awnish K.; Nisoli, Cristiano; Lammert, Paul E.; Crespi, Vincent H.; Eklund, Peter C.

    2010-08-01

    Micro-Raman scattering from folds in single-layer graphene sheets finds a D-band at the fold for both incommensurate and commensurate folding, while the parent single-layer graphene lacks a D-band. A coupled elastic-continuum/tight-binding calculation suggests that this D-band arises from the spatially inhomogeneous curvature around a fold in a graphene sheet. The polarization dependence of the fold-induced D-band further reveals that the inhomogeneous curvature acts as a very smooth, ideal one-dimensional defect along the folding direction. The work described herein constitutes one of the last research projects with Peter's active involvement. We are honored to be able to share authorship with him one last time.

  12. Tunable bandwidth of pass-band metamaterial filter based on coupling of localized surface plasmon resonance

    Science.gov (United States)

    Han, Bing; Dong, Beibei; Nan, Jingyu; Zhong, Min

    2015-12-01

    A broad pass-band compound structure metamaterial is designed which consists of periodic two metallic particles and hole arrays. The operating bandwidth of the designed structure reaches to ?f ? 33.8 THz. Physical mechanisms are analyzed and validated based on calculated electric field distribution that the interaction and coupled of LSP modes between two metallic particles leads to the bandwidth increased and resonance frequency blue-shifted, while the interaction and coupled between metallic particle and metallic arrays results in the reduced of the pass-band. The pass-band can be expanded through reducing the permittivity of dielectric layer or reducing the width of the metallic particle (a). The effect of the angles of incidence on the pass-band is also analyzed for normal, 15°, 30° and 45°.

  13. (100) ideal-surface band structure for the series of Cu-based chalcopyrites

    CERN Document Server

    Tototzintle-Huitle, H

    2005-01-01

    We use the Surface Green Function Matching (SGFM) method and a tight-binding hamiltonian to calculate the (100)-surface electronic band structure and local density of states of the series of Cu-based A^{I}B^{III}C2^{VI} chalcopyrites . We find four surface states in the optical gap energy region of s-p character and three surface states in the conduction band region of p-character. We show the trends of different characteristics within the series by means of figures and tables so that the quantitave behavior can be evaluated as well. We did not find Frontier Induced Semi-Infinite states of non-dispersive character in the studied range of energy within the valence band as we found in the case of the (112) surface electronic band structure for CuInSe2.

  14. Band Engineering of Dirac Surface States in Topological-Insulator-Based van der Waals Heterostructures

    Science.gov (United States)

    Chang, Cui-Zu; Tang, Peizhe; Feng, Xiao; Li, Kang; Ma, Xu-Cun; Duan, Wenhui; He, Ke; Xue, Qi-Kun

    2015-09-01

    The existence of a gapless Dirac surface band of a three dimensional (3D) topological insulator (TI) is guaranteed by the nontrivial topological character of the bulk band, yet the surface band dispersion is mainly determined by the environment near the surface. In this Letter, through in situ angle-resolved photoemission spectroscopy and first-principles calculation on 3D TI-based van der Waals heterostructures, we demonstrate that one can engineer the surface band structures of 3D TIs by surface modifications without destroying their topological nontrivial property. The result provides an accessible method to independently control the surface and bulk electronic structures of 3D TIs, and sheds light on designing artificial topological materials for electronic and spintronic purposes.

  15. Photon path length distributions for cloudy skies ? oxygen A-Band measurements and model calculations

    OpenAIRE

    Funk, O.; Pfeilsticker, K.

    2003-01-01

    This paper addresses the statistics underlying cloudy sky radiative transfer (RT) by inspection of the distribution of the path lengths of solar photons. Recent studies indicate that this approach is promising, since it might reveal characteristics about the diffusion process underlying atmospheric radiative transfer (Pfeilsticker, 1999). Moreover, it uses an observable that is directly related to the atmospheric absorption and, therefore, of climatic relevance. However, these studies ...

  16. Photon pathlengths distributions for cloudy skies : Oxygen A-band measurements and radiative transfer model calculations

    OpenAIRE

    Funk, Oliver

    2000-01-01

    Der kurzwellige Strahlungstransport in der Atmosphäre stellt eine der bedeutenden Unsicherheiten in den gegenwärtigen Klimamodellen dar. Diese Unsicherheiten werden zum Teil einer vereinfachten Beschreibung von Wolkeninhomogenitäten zugeschrieben. Thema dieser Arbeit ist die Untersuchung des Strahlungstransports durch Betrachtung der Weglängenverteilung solarer Photonen, einer Observablen die direkt mit der atmosphärischen Absorption verknüpft ist. Dazu wurde eine verbesserte Methode zur Best...

  17. The energy band memory server algorithm for parallel Monte Carlo transport calculations

    International Nuclear Information System (INIS)

    An algorithm is developed to significantly reduce the on-node footprint of cross section memory in Monte Carlo particle tracking algorithms. The classic method of per-node replication of cross section data is replaced by a memory server model, in which the read-only lookup tables reside on a remote set of disjoint processors. The main particle tracking algorithm is then modified in such a way as to enable efficient use of the remotely stored data in the particle tracking algorithm. Results of a prototype code on a Blue Gene/Q installation reveal that the penalty for remote storage is reasonable in the context of time scales for real-world applications, thus yielding a path forward for a broad range of applications that are memory bound using current techniques. (authors)

  18. Direct band gap measurement of Cu(In,Ga)(Se,S)2 thin films using high-resolution reflection electron energy loss spectroscopy

    Science.gov (United States)

    Heo, Sung; Lee, Hyung-Ik; Song, Taewon; Park, Jong-Bong; Ko, Dong-Su; Chung, JaeGwan; Kim, KiHong; Kim, Seong Heon; Yun, Dong-Jin; Ham, YongNam; Park, Gyeong Su; Lee, Dongho; Nam, Junggyu; Kang, Hee Jae; Choi, Pyung-Ho; Choi, Byoung-Deog

    2015-06-01

    To investigate the band gap profile of Cu(In1-x,Gax)(Se1-ySy)2 of various compositions, we measured the band gap profile directly as a function of in-depth using high-resolution reflection energy loss spectroscopy (HR-REELS), which was compared with the band gap profile calculated based on the auger depth profile. The band gap profile is a double-graded band gap as a function of in-depth. The calculated band gap obtained from the auger depth profile seems to be larger than that by HR-REELS. Calculated band gaps are to measure the average band gap of the spatially different varying compositions with respect to considering its void fraction. But, the results obtained using HR-REELS are to be affected by the low band gap (i.e., out of void) rather than large one (i.e., near void). Our findings suggest an analytical method to directly determine the band gap profile as function of in-depth.

  19. Applications of the quadratic Korringa-Kohn-Rostoker band-theory method

    International Nuclear Information System (INIS)

    Comparisons with other calculations in the literature are used to demonstrate that the quadratic Korringa-Kohn-Rostoker band-theory method gives excellent eigenvalues for full self-consistent potentials with no shape approximation. The equations for the Green function are reformulated, thus eliminating a problem that had hampered calculations of self-consistent potentials and total energies with the use of this method

  20. Simplification of QPLDA: A practical method to the correction for the LDA band gap problem

    OpenAIRE

    Kikuchi, Akihito

    2012-01-01

    It is necessary to employ quasi-particle calculations to correct band gap problems in LDA. As an expedient way for the reliable but massive GWA, Quasi-Particle-LDA (QPLDA) is proposed by several authors, where the total computational cost scales with N. Historically, Sham and Kohn introduced the idea of the local mass operator based on local wavenumber similar to WKB, but did not execute actual numerical calculations. They took into account exchange interaction only, from wh...