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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. 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...... 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...... 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 of the lattice vibrations by means of an OPW-LCAO (linear combination of atomic...

  5. 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...

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

    International Nuclear Information System (INIS)

    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. (topical review)

  7. 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.

  8. Four-band Hamiltonian for fast calculations in intermediate-band solar cells

    Science.gov (United States)

    Luque, Antonio; Panchak, Aleksandr; Vlasov, Alexey; Martí, Antonio; Andreev, Viacheslav

    2016-02-01

    The 8-dimensional Luttinger-Kohn-Pikus-Bir Hamiltonian matrix may be made up of four 4-dimensional blocks. A 4-band Hamiltonian is presented, obtained from making the non-diagonal blocks zero. The parameters of the new Hamiltonian are adjusted to fit the calculated effective masses and strained QD bandgap with the measured ones. The 4-dimensional Hamiltonian thus obtained agrees well with measured quantum efficiency of a quantum dot intermediate band solar cell and the full absorption spectrum can be calculated in about two hours using Mathematica© and a notebook. This is a hundred times faster than with the commonly-used 8-band Hamiltonian and is considered suitable for helping design engineers in the development of nanostructured solar cells.

  9. Band gap calculations with Becke-Johnson exchange potential

    International Nuclear Information System (INIS)

    Recently, a simple analytical form for the exchange potential was proposed by Becke and Johnson. This potential, which depends on the kinetic-energy density, was shown to reproduce very well the shape of the exact exchange potential (obtained with the optimized effective potential method) for atoms. Calculations on solids show that the Becke-Johnson potential leads to a better description of band gaps of semiconductors and insulators with respect to the standard local density and Perdew-Burke-Ernzerhof approximations for the exchange-correlation potential. Comparison is also made with the values obtained with the Engel-Vosko exchange potential which was also developed using the exact exchange potential

  10. 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.

  11. One approach to adiabatic population transfer by Hueckel molecular orbital theory

    International Nuclear Information System (INIS)

    To achieve the selective population transfer to the specific excited state of molecules, the delayed-pulse method developed in the three-level system is more attractive and effective than the ordinary ?-pulses method. However, two pulses in this adiabatic method are in a counterintuitive order and are significantly overlapped, so that it is very difficult to understand the physical meanings of the dynamical process. Here the authors develop the effective method to understand the adiabatic processes in a pictorial and easy way by using the concept of the Hueckel molecular orbital theory. Then the authors investigate the complete population transfer in the four-level system in detail

  12. 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

  13. Energy bands in graphene: Comparison between the tight-binding model and {\\it ab initio} calculations

    OpenAIRE

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

    2013-01-01

    We compare the classification of the electron bands in graphene, obtained by group theory algebra in the framework of tight-binding model (TBM), with that calculated in the 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 corresponding analysis is presented. The four occupied (three $\\sigma$- and one $\\pi$-like) and three unoccupi...

  14. 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.

  15. Self-Consistent Calculation of the correct Band-Gap and Low Energy Conduction Bands in Gallium-Nitride

    Science.gov (United States)

    Zhao, G. L.; Bagayoko, D.; Fan, J. D.

    1998-03-01

    The III-V nitrides are viewed as new semiconductors for optoelectronic applications in the blue and UV wavelengths and, more recently, as high-power, high-temperature electronic devices. However, a reliable prediction of the band gap and the low energy conduction bands had, until now, remained a problem in ab initio computations. A spurious effect of the variational procedure and of basis sets is shown to be a source of this problem. We present first principle computational steps that avoid this effect. We applied our new approach to calculate the electronic structure of III-V gallium-nitride using a local density approximation (LDA) for the exchange-correlation potential. Our calculated electronic structure and band gap, for an optimum basis set, agree qualitatively and quantitatively with experiment. *Work supported in part by funding from the Department of the Navy, Office of Naval Research (ONR), and from the Physics Graduate Program at Southern University and A & M College.

  16. Empiric kp Hamiltonian calculation of the band-to-band photon absorption in semiconductors

    International Nuclear Information System (INIS)

    The Empiric kp 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 kp Hamiltonian method

  17. Definition of two band parameters for use in photon transport calculations

    Energy Technology Data Exchange (ETDEWEB)

    Cullen, D.E.

    1978-04-01

    The multigroup photon diffusion equations are derived from the Boltzmann equation. Limitations and assumptions imposed by the diffusion equation are thus apparent. In addition, this approach serves to define all of the required diffusion parameters in terms of cross sections; the relationship to the multi-band parameters used in neutron transport calculations can thus be clearly established. All required two-band parameters are defined in terms of Planckian and Rosseland mean values. (RWR)

  18. 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...

  19. 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.

  20. 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.

  1. 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)

  2. 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

    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......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.......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...

  3. Density of states calculations of small diameter single graphene sheets

    Energy Technology Data Exchange (ETDEWEB)

    Gerouki, A.; Goldner, M.A.; Goldner, R.B.; Haas, T.E.; Liu, T.Y.; Slaven, S. [Tufts Univ., Medford, MA (United States). Electro-Optics Technology Center

    1996-11-01

    The densities of states for the {pi}-band of single graphene sheets with small diameters were calculated by employing a linear combination of atomic orbital approach using as the basis set the carbon p{sub z} atomic orbitals together with a modified Hueckel approximation wherein the overlap integrals out to the fourth nearest neighbors set were included. These densities of states were used to predict the voltage of lithiated carbon vs. lithium metal, an important characteristic for disordered carbon used as the negative electrode in rechargeable lithium-ion batteries. Calculations were made for isolated single graphene sheets, C{sub n}, with n = 24, 54, 96, 150, and 216. The results suggested that the lowest voltage should occur for lithiated carbon electrodes composed of single graphene sheets with the smallest diameter ({approx} 0.7 nm for C{sub 24}).

  4. 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.

  5. 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.

  6. XPS valence band spectra and theoretical calculations for investigations on thiogermanate and thiosilicate glasses

    International Nuclear Information System (INIS)

    This paper reports on investigations of thiogermanate and thiosilicate crystals and glasses by means of XPS valence band spectra and theoretical calculations (FLAPW method). The calculations were achieved on three crystallized phases GeS2, Na2GeS3 and SiS2 and valence band spectra (visualization of the occupied electronic density of states) were precisely interpreted through modulated density of states and charge density maps. This information was used to go further in the structural investigations of some thiogermanate and thiosilicate glasses. In sodium thiogermanates, an increase in Ge-Ge bonds was revealed as the modifier content (Na2S) increases. In thiosilicates, the evolution of the valence spectra according to the nature of the alkaline atoms (Li, Na) has been interpreted as changes in the local connectivity of units (edge or corner sharing tetrahedra). This study exhibits the potentialities of valence band spectra to provide information on glassy systems

  7. Tunneling through a semiconducting spacer: complex band predictions vs. thin film calculations

    International Nuclear Information System (INIS)

    Using a simple tight-binding model, we compare the limitations of the tunneling predictions coming out of the complex band structure of a semiconductor with the output of thin film calculations done for the same semiconducting spacer but considering it to be of finite width, and sandwiched by metallic electrodes. The comparison is made as a function of spacer width and interfacial roughness

  8. Calculation of isotopic profile during band displacement on ion exchange resins

    International Nuclear Information System (INIS)

    A method has been developed to calculate the isotopic profile during band displacement on ion exchange resins using computer simulation. Persoz had utilized this technique earlier for calculating the isotopic profile during band displacement as well as frontal analysis. The present report deals with a simplification of the method used by Persoz by reducing the number of variables and making certain approximations where the separation factor is not far from unity. Calculations were made for the typical case of boron isotope separation. The results obtained by the modified method were found to be in very good agreement with those obtained by using an exact equation, at the same time requiring conside--rably less computer time. (author)

  9. Full band structure calculation of two-photon indirect absorption in bulk silicon

    International Nuclear Information System (INIS)

    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 experimental results. The transverse acoustic/optical phonon-assisted processes dominate.

  10. BoltzTraP. A code for calculating band-structure dependent quantities

    Science.gov (United States)

    Madsen, Georg K. H.; Singh, David J.

    2006-07-01

    A program for calculating the semi-classic transport coefficients is described. It is based on a smoothed Fourier interpolation of the bands. From this analytical representation we calculate the derivatives necessary for the transport distributions. The method is compared to earlier calculations, which in principle should be exact within Boltzmann theory, and a very convincing agreement is found. Program summaryTitle of program:BoltzTraP Catalogue identifier:ADXU_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADXU_v1_0 Program obtainable from: CPC Program Library, Queen's University of Belfast, N. Ireland Licensing provisions:none Programming language used:Fortran 90 Computer:The program should work on any system with a F90 compiler. The code has been tested with the Intel Fortran compiler Operating system:Unix/Linux RAM:bytes up to 2 GB for low symmetry, small unit cell structures No. of lines in distributed program, including test data, etc.:1 534 213 No. of bytes in distributed program, including test data, etc.:27 473 227 Distribution format:tar.gz External routines:The LaPack and Blas libraries are needed Nature of problem:Analytic expansion of energy-bands. Calculation of semi-classic integrals. Solution method:Smoothed Fourier expansion of bands. Running time:Up to 3 hours for low symmetry, small unit cell structures.

  11. 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

  12. CdSe/CdTe interface band gaps and band offsets calculated using spinorbit and self-energy corrections

    International Nuclear Information System (INIS)

    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 spinorbit 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 0.81.8 eV, which may enhance the absorption of light for corresponding frequencies at the interface between these two materials in photovoltaic applications.

  13. 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.

  14. 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)

  15. 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.

  16. Comparison of angular resolved photoemission on Pt(110) with DFT bulk band calculations

    Energy Technology Data Exchange (ETDEWEB)

    Menzel, Alexander; Braun, Christian; Amann, Peter; Bertel, Erminald [Institute forPhysical Chemistry, University of Innsbruck (Austria)

    2009-07-01

    Angular resolved photoemission (ARPES) experiments of clean and halogenated Pt(110) are compared with the DFT-derived bulk band structure of platinum. Numerous dispersion features agree with the calculated one-dimensional density of states (kz-histogram) indicating emission from near surface transitions. In order to distinguish the effects of initial state (surface resonances), matrix element (surface photoemission) and final state (strong photoelectron damping), we varied incident polarization, photon energy, and surface phase symmetry.

  17. Calculation of the band structure of 2d conducting polymers using the network model

    International Nuclear Information System (INIS)

    the network model has been used to calculate the band structure the gap energy and Fermi level of conducting polymers in two dimensions. For this purpose, a geometrical classification of possible polymer chains configurations in two dimensions has been introduced leading to a classification of the unit cells based on the number of bonds in them. The model has been applied to graphite in 2D, represented by a three bonds unit cell, and, as a new case, the anti-parallel Polyacetylene chains (PA) in two dimensions, represented by a unit cell with four bons. The results are in good agreement with the first principles calculations. (author)

  18. 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 ...

  19. Band-structure calculations and structure-factor estimates of Cu - their complementarity

    International Nuclear Information System (INIS)

    Rather than an uncritical comparison of experimental and theoretical values, the various sets of structure-factor values of copper metal derived from experimental diffraction procedures are mutally compared as also are the various sets of theoretical values derived from band-structure calculations. This approach reveals the presence of outlier sets in each group and allows recognition of their condition before any attempt is made to intercompare the groups. Within the experimental group, the ?-ray values do not appear to sustain the absolute status originally claimed from them. Within the theoretical group, an inadequacy in defining the core contribution is indicated. The latter conclusion suggests that it is an inappropriate operation to make direct comparison between diffraction-sourced experimental values of structure factors and theoretical values from band-structure calculations. Instead, the latter should be used on a complementary basis with the full (sin ?)/? range of experimental values to establish the best core contribution. The minor valence-bond contribution to scattering, which is largely restricted to the low (sin ?)/? region, is most sensitively defined by reference to band-structure prediction of photoemission spectral distribution. Attention is drawn to the possible significance of the form-factor curve versus (sin ?)/? being dependent on the unit-cell dimension. (orig.)

  20. 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).

  1. 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.

  2. A Hartree-Fock ab initio band-structure calculation employing Wannier-type orbitals

    CERN Document Server

    Albrecht, M; Dolg, M; Fulde, P; Stoll, H; Albrecht, Martin; Shukla, Alok; Dolg, Michael; Fulde, Peter; Stoll, Hermann

    1998-01-01

    An ab initio Wannier-function-based approach to electronic ground-state calculations for crystalline solids is outlined. In the framework of the linear combination of atomic orbitals method the infinite character of the solid is rigorously taken into account. The Hartree-Fock ground-state energy, cohesive energy, lattice constant and bulk modulus are calculated in a fully ab initio manner as it is demonstrated for sodium chloride, NaCl, using basis sets close to the Hartree-Fock limit. It is demonstrated that the Hartree-Fock band-structure can easily be recovered with the current approach and agrees with the one obtained from a more conventional Bloch-orbital-based calculation. It is argued that the advantage of the present approach lies in its capability to include electron correlation effects for crystalline insulators by means of well-established quantum chemical procedures.

  3. 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

  4. 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}

  5. Crystal structure and band gap studies of sodalite: experimental and calculated results

    Science.gov (United States)

    Pan, Lijun; Liu, Wanchao; Chen, Weiguang; Yan, Kun; Yang, Huizhi; Yu, Jia

    2016-02-01

    In this paper, we investigated the crystal structural properties of sodalite sample by X-ray diffraction and the band gap studies by means of UV-Vis absorption spectroscopy, and compared with the calculated results using density functional theory. The results of X-ray diffraction suggests that the chemical formula should be Na8(AlSiO6)4(OH)22(H2O). The optimized lattice parameter is found to be larger 0.45% than experimental value and the calculations demonstrated the structural details of the hydrogen bond located in sodalite cage. The hydrogen bond formed by water molecule and hydroxyl is implied from charge distribution analysis. As the rotation angle of O-O lines in hydrogen bond is 51.8, the structure should be of the lowest energy. The optical band gap is measured to be 4.5-4.7eV experimentally, while, the calculated value is 4.16eV which is attributed to the localized state below Fermi level formed by the hydrogen bonds. Our results are favorable for the understanding the role of sodalite in silicate mud and contribute to further disposals and treatments.

  6. SGFM applied to the calculation of surface band structure of V

    International Nuclear Information System (INIS)

    The surface Green function matching (SGFM) method has been developed recently to deal with a great variety of problems in a unified way. The method was first developed for continuum systems. The recent advances for discrete structures can deal with surfaces, interfaces, quantum wells, superlattices, intercalated layered compounds, and other systems. Several applications of this formalism are being carried out. In the present note we will describe how the formalism applies to the calculation of the electronic surface band structure of vanadium which is a quite interesting transition metal with very active magnetic properties at the surface, in particular at the (100) surface. It is straightforward, on the basis of the calculation presented here, to obtain the magnetic moment on the surface, for example, through the method followed by G. Allan or the surface paramagnon density which should be particularly enhanced at this surface as compared to the bulk

  7. Accounting for many-body correlation effects in the calculation of the valence band photoelectron emission spectra of ferromagnets

    Energy Technology Data Exchange (ETDEWEB)

    Minar, J. [Department Chemie und Biochemie, Physikalische Chemie, Universitaet Muenchen, Butenandtstr. 5-13, D-81377 Munich (Germany)]. E-mail: jan.minar@cup.uni-muenchen.de; Chadov, S. [Department Chemie und Biochemie, Physikalische Chemie, Universitaet Muenchen, Butenandtstr. 5-13, D-81377 Munich (Germany); Ebert, H. [Department Chemie und Biochemie, Physikalische Chemie, Universitaet Muenchen, Butenandtstr. 5-13, D-81377 Munich (Germany); Chioncel, L. [Institut fuer Theoretische Physik - Computational Physics, Technische Universitaet Graz, A-8010 Graz (Austria); Lichtenstein, A. [Institut fuer theoretische Physik, Universitaet Hamburg, 20355 Hamburg (Germany); De Nadai, C. [European Synchrotron Radiation Facility, BoIte Postale 220, 38043 Grenoble Cedex (France); Brookes, N.B. [European Synchrotron Radiation Facility, BoIte Postale 220, 38043 Grenoble Cedex (France)

    2005-07-21

    The influence of dynamical correlation effects on the valence band photoelectron emission of ferromagnetic Fe, Co and Ni has been investigated. Angle-resolved as well as angle-integrated valence band photoelectron emission spectra were calculated on the basis of the one-particle Green's function, which was obtained by using the fully relativistic Korringa-Kohn-Rostoker method. The correlation effects have been included in terms of the electronic self-energy which was calculated self-consistently within Dynamical Mean-Field Theory (DMFT). In addition a theoretical approach to calculate high-energy angle-resolved valence band photoelectron emission spectra is presented.

  8. Accounting for many-body correlation effects in the calculation of the valence band photoelectron emission spectra of ferromagnets

    International Nuclear Information System (INIS)

    The influence of dynamical correlation effects on the valence band photoelectron emission of ferromagnetic Fe, Co and Ni has been investigated. Angle-resolved as well as angle-integrated valence band photoelectron emission spectra were calculated on the basis of the one-particle Green's function, which was obtained by using the fully relativistic Korringa-Kohn-Rostoker method. The correlation effects have been included in terms of the electronic self-energy which was calculated self-consistently within Dynamical Mean-Field Theory (DMFT). In addition a theoretical approach to calculate high-energy angle-resolved valence band photoelectron emission spectra is presented

  9. 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.

  10. 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 kp 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

  11. 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) So Lus and Rio Branco and (2) Alta Floresta and Huancayo. For these case studies, in statistically significant and high-coherence regions, scintillation observations over So Lus (Alta Floresta) lead that of Rio Branco (Huancayo) by 2 to 3 h with a 95%frequency. If L-band scintillation happens over So Lus (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.

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

    CERN Document Server

    Brl, 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.

  13. The electronic band structure and non-empirical calculations of cohesive properties of refractory compounds

    International Nuclear Information System (INIS)

    The first part of the review presents basic facts about computational methods, especially about linearized methods of muffin-tin orbitals (LMTO), augmented plane waves (LAPW), and augmented spherical waves (ASW) for a number of energy characteristics of interatomic coupling. The energy band structure and the energetics of the chemical bonding in stoichiometric binary refractory compounds such as monoxides, monocarbides, and mononitrides of transition metals and in dicarbides of yttrium, strontium, and barium are discussed including a study of the equations of state and internal pressures. The electronic structure, properties, and chemical bonding of ternary refractory compounds (Ti and Nb nitrocarbides, Sc oxicarbides) and of vacancy-containing phases of non-stoichiometric refractory compounds are calculated and discussed. The results demonstrate that the studies are fairly fruitful. 83 refs

  14. 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.

  15. 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...

  16. 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

  17. 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.

  18. 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...

  19. 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 CLARE98, 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

  20. Calculation of wakefields in a 17 GHz beam-driven photonic band-gap accelerator structure

    Science.gov (United States)

    Hu, Min; Munroe, Brian J.; Shapiro, Michael A.; Temkin, Richard J.

    2013-02-01

    We present the theoretical analysis and computer simulation of the wakefields in a 17 GHz photonic band-gap (PBG) structure for accelerator applications. Using the commercial code CST Particle Studio, the fundamental accelerating mode and dipole modes are excited by passing an 18 MeV electron beam through a seven-cell traveling-wave PBG structure. The characteristics of the longitudinal and transverse wakefields, wake potential spectrum, dipole mode distribution, and their quality factors are calculated and analyzed theoretically. Unlike in conventional disk-loaded waveguide (DLW) structures, three dipole modes (TM11-like, TM12-like, and TM13-like) are excited in the PBG structure with comparable initial amplitudes. These modes are separated by less than 4 GHz in frequency and are damped quickly due to low radiative Q factors. Simulations verify that a PBG structure provides wakefield damping relative to a DLW structure. Simulations were done with both single-bunch excitation to determine the frequency spectrum of the wakefields and multibunch excitation to compare to wakefield measurements taken at MIT using a 17 GHz bunch train. These simulation results will guide the design of next-generation high-gradient accelerator PBG structures.

  1. Calculation on frequency and temperature properties of birefringence of nematic liquid crystal 5CB in terahertz band

    Science.gov (United States)

    Chen, Zezhang; Jiang, Lijuan; Ma, Heng

    2016-02-01

    This letter provides a computational method for predicting birefringence of nematic liquid crystal (LC) in the terahertz band. Using Vuks' approximation and Haller's approach combination with density functional theory (DFT) and time-dependent density functional theory (TDDFT) method, we calculated the frequency and temperature dependence refractive indices and birefringence of LC 5CB in a frequency range 0.2-1.0 THz. The greater agreement between calculated results and experimental values indicates that this is an applicable method to predict optoelectronic properties of LC materials in THz band. The present work gives a useful guide to screen or design LC molecules for THz applications.

  2. Band gap calculations of the semiconductor BNxP1?x using modified BeckeJohnson approximation

    International Nuclear Information System (INIS)

    Highlights: ? The Modified BeckeJohnson scheme gives a very accurate band gap. ? We have shown the invalidity of Vegards linear rule for BNxP1?x. ? The band gap changes with alloy concentration are important in band gap engineering. - Abstract: In this work, the electronic properties of BN, BP and BNxP1?x compounds have been investigated by means of first-principles density-functional total-energy calculation using the all-electron full potential linear augmented plane-wave method (FP-LAPW). The (FP-LAPW) method was used within the density functional theory (DFT) along with the EngelVosko and BeckeJohnson exchange correlation potential. The energy bands along high symmetry directions, the density of states and bowing distributions are calculated. The results have been discussed in terms of previously existing experimental and theoretical data, and comparisons with similar compounds have been made. Analysis of band structure suggests direct and pseudo-direct band gaps for both compounds.

  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. Improved cache performance in Monte Carlo transport calculations using energy banding

    Science.gov (United States)

    Siegel, A.; Smith, K.; Felker, K.; Romano, P.; Forget, B.; Beckman, P.

    2014-04-01

    We present an energy banding algorithm for Monte Carlo (MC) neutral particle transport simulations which depend on large cross section lookup tables. In MC codes, read-only cross section data tables are accessed frequently, exhibit poor locality, and are typically too much large to fit in fast memory. Thus, performance is often limited by long latencies to RAM, or by off-node communication latencies when the data footprint is very large and must be decomposed on a distributed memory machine. The proposed energy banding algorithm allows maximal temporal reuse of data in band sizes that can flexibly accommodate different architectural features. The energy banding algorithm is general and has a number of benefits compared to the traditional approach. In the present analysis we explore its potential to achieve improvements in time-to-solution on modern cache-based architectures.

  5. 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

  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. Unified calculations of the optical band positions and EPR g factors for NaCrS2 crystal

    International Nuclear Information System (INIS)

    Six optical band positions and EPR g factors g||, g? for the trigonal Cr3+ octahedral clusters in NaCrS2 crystal are calculated together through the complete diagonalization (of energy matrix) method based on the two-spinorbit-parameter model, where besides the contribution due to the spinorbit parameter of central dn ion in the conventional crystal-field theory, the contribution due to the spinorbit parameter of ligand ion via the covalence effect is also considered. In the calculations, the crystal-field parameters Bkl are obtained from the superposition model with the structural data of Cr3+ octahedral clusters in NaCrS2 crystal measured exactly by the X-ray diffraction method. The calculated optical and EPR spectral data are in a reasonable agreement with the observed values. So, the reliability of the superposition model in the studies of crystal-field parameters for dn ions in crystals is confirmed, and the complete diagonalization (of energy matrix) method based on the two-spinorbit-model is effective in the unified calculations of optical and EPR spectral data for dn ions in crystals. - Highlights: Six optical band positions and g factors g||, g? of NaCrS2 are calculated together. Calculation is using the complete diagonalization (of energy matrix) method. The diagonalization method is based on the two-spinorbit-parameter model. Reliability of superposition model in the studies of CF parameters is confirmed

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

    Czech Academy of Sciences Publication Activity Database

    Grger, Roman; Vitek, V.

    2012-01-01

    Ro?. 20, ?. 3 (2012), 035019. ISSN 0965-0393 R&D Projects: GA ?R GAP204/10/0255; GA Mk(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

  9. First-principles energy band calculation and one step synthesis of N-doped BiPO4

    International Nuclear Information System (INIS)

    Highlights: Nitrogen doped BiPO4 was synthesized by one step hydrothermal method. The valence and conduction bands, density of states and the band gap energy of BiPO4 are calculated with first-principles. The photocatalytic activity of BiPO4 were enhanced after N-doping. The reason for the enhancement of photocatalytic activity were investigated. - Abstract: N-doped BiPO4 photocatalyst was synthesized by a simple one step hydrothermal method. The crystal structure, morphology, and photophysical properties of the samples were characterized by XRD, SEM, XPS, UVVis and Raman. The valence and conduction bands, density of states and the band gap energy of BiPO4 are calculated with first-principles. The results showed that both BiPO4 and N-doped BiPO4 have same monoclinic structure. The substitution of O2? by N3? ions in BiPO4 could not only cause the red-shift of the adsorption edge, but also change the morphology. The photocatalytic activity of BiPO4 was enhanced about 50% under UV light irradiation when the molar ratio of N/Bi is 0.2, this can be ascribed to the N3? introduced into BiPO4 crystal lattice restrain the recombination of photogenerated electronhole pairs. However, overdoping would decrease the photocatalytic activity of BiPO4

  10. Systematic Two-band Model Calculations of the GMR Effect with Metallic and Nonmetallic Spacers and with Impurities

    CERN Document Server

    Gebele, O; Krey, U; Krompiewski, S

    1999-01-01

    By an accurate Green's function method we calculate resistances and the corresponding Giant Magneto-Resistance effects (GMR) of two metallic ferromagnetic films separated by different spacers, metallic and non-metallic ones, in a simplified model on a sc lattice, in CPP and CIP geometries (i.e. current perpendicular or parallel to the planes), without impurities, or with interface- or bulk impurities. The electronic structure of the systems is approximated by two hybridized orbitals per atom, to mimic s-bands and d-bands and their hybridization. We show that such calculations usually give rough estimates only, but of the correct order of magnitude; in particular, the predictions on the impurity effects depend strongly on the model parameters. One of our main results is the prediction of huge CPP-GMR effects for {\\it non-metallic} spacers in the ballistic limit.

  11. Time Dependent Density Functional Theory Calculations of Large Compact PAH Cations: Implications for the Diffuse Interstellar Bands

    Science.gov (United States)

    Weisman, Jennifer L.; Lee, Timothy J.; Salama, Farid; Gordon-Head, Martin; Kwak, Dochan (Technical Monitor)

    2002-01-01

    We investigate the electronic absorption spectra of several maximally pericondensed polycyclic aromatic hydrocarbon radical cations with time dependent density functional theory calculations. We find interesting trends in the vertical excitation energies and oscillator strengths for this series containing pyrene through circumcoronene, the largest species containing more than 50 carbon atoms. We discuss the implications of these new results for the size and structure distribution of the diffuse interstellar band carriers.

  12. 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...

  13. 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...

  14. 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 .

  15. 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)

  16. Band-Filling Correction Method for Accurate Adsorption Energy Calculations: A Cu/ZnO Case Study.

    Science.gov (United States)

    Hellstrm, Matti; Spngberg, Daniel; Hermansson, Kersti; Broqvist, Peter

    2013-11-12

    We present a simple method, the "band-filling correction", to calculate accurate adsorption energies (Eads) in the low coverage limit from finite-size supercell slab calculations using DFT. We show that it is necessary to use such a correction if charge transfer takes place between the adsorbate and the substrate, resulting in the substrate bands either filling up or becoming depleted. With this correction scheme, we calculate Eads of an isolated Cu atom adsorbed on the ZnO(101?0) surface. Without the correction, the calculated Eads is highly coverage-dependent, even for surface supercells that would typically be considered very large (in the range from 1 nm 1 nm to 2.5 nm 2.5 nm). The correction scheme works very well for semilocal functionals, where the corrected Eads is converged within 0.01 eV for all coverages. The correction scheme also works well for hybrid functionals if a large supercell is used and the exact exchange interaction is screened. PMID:26583386

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

    International Nuclear Information System (INIS)

    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.

  18. 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.

  19. Calculation of the Hartree-Fock band structure in solid rare gases and ionic compounds - Application to the optical transitions

    International Nuclear Information System (INIS)

    The well-known 'augmented plane waves' method, for the calculation of electronic states in crystals, is first reviewed. A modification of this method in the case of insulators is then described, which treats exchange in the exact Hartree-Fock formulation, without use of the common free-electron approximation. The band structure of several rare gases (Ne, Ar) and ionic compounds (LiF, NaF, KF, LiCl, NaCl, KCl) has been calculated and discussed. The main point is the strong influence of correlation effects which must be taken into account before comparison between calculated and measured optical transitions. Such an improvement is obtained by including a local polarization potential in the one-electron Hamiltonian, leading to a good agreement of the theoretical transitions with the experimental ones. (author)

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

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Jianwei; Zhang, Yong [Department of Electrical and Computer Engineering, The University of North Carolina at Charlotte, 9201 University City Boulevard, Charlotte, North Carolina 28223 (United States)

    2014-12-07

    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.

  1. 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.

  2. Calculation of the pressure dependence of the EFG in BCT In, HCP Ti and Zn from energy band structures

    International Nuclear Information System (INIS)

    The energy band structures of bct In, hcp Ti and Zn have been calculated at various lattice parameters using the full potential linearized augmented plane wave method. It has been shown for several hcp metals that the EFG at the atomic sites can be obtained from the total self-consistent charge densities without further approximations. The calculated EFGs for the systems studied here are in good agreement with experiment and originate mainly from the anisotropy of the valence states, while contributions from the core states and the lattice are small. From calculations for different c/a ratios and volumes we can deduce the derivatives d(ln EFG)/dp, but also d(ln EFG)/d(ln V) and d(ln EFG)/d(ln c/a), quantities, which are not easily accessible by experiment. (orig.)

  3. 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

  4. 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); Lebgue, S. [Laboratoire de Cristallographie, Rsonance Magntique et Modlisations (CRM2, UMR CNRS 7036), Institut Jean Barriol, Universit de Lorraine, BP 239, Boulevard des Aiguillettes, 54506 Vandoeuvre-ls-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 NH...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.

  5. Interfacial Properties of Monolayer and Bilayer MoS2 Contacts with Metals: Beyond the Energy Band Calculations

    Science.gov (United States)

    Zhong, Hongxia; Quhe, Ruge; Wang, Yangyang; Ni, Zeyuan; Ye, Meng; Song, Zhigang; Pan, Yuanyuan; Yang, Jinbo; Yang, Li; Lei, Ming; Shi, Junjie; Lu, Jing

    2016-03-01

    Although many prototype devices based on two-dimensional (2D) MoS2 have been fabricated and wafer scale growth of 2D MoS2 has been realized, the fundamental nature of 2D MoS2-metal contacts has not been well understood yet. We provide a comprehensive ab initio study of the interfacial properties of a series of monolayer (ML) and bilayer (BL) MoS2-metal contacts (metal = Sc, Ti, Ag, Pt, Ni, and Au). A comparison between the calculated and observed Schottky barrier heights (SBHs) suggests that many-electron effects are strongly suppressed in channel 2D MoS2 due to a charge transfer. The extensively adopted energy band calculation scheme fails to reproduce the observed SBHs in 2D MoS2-Sc interface. By contrast, an ab initio quantum transport device simulation better reproduces the observed SBH in 2D MoS2-Sc interface and highlights the importance of a higher level theoretical approach beyond the energy band calculation in the interface study. BL MoS2-metal contacts generally have a reduced SBH than ML MoS2-metal contacts due to the interlayer coupling and thus have a higher electron injection efficiency.

  6. Refractive index, band gap energy, dielectric constant and polarizability calculations of ferroelectric Ethylenediaminium Tetrachlorozincate crystal

    Science.gov (United States)

    Kalyanaraman, S.; Shajinshinu, P. M.; . Vijayalakshmi, S.

    2015-11-01

    Single crystal of Ethylenediaminium Tetrachlorozincate has been grown by slow evaporation method. The single crystal XRD study confirms the orthorhombic structure of the crystal. The presence of functional group vibrations are ascertained through FTIR and Raman studies. In optical studies, the insulating behaviour of the material is established by Tauc plot. The refractive index and the real dielectric constant of the crystal are calculated. The electronic polarizability in the high frequency optical region is also calculated from the dielectric constant values by using the Clausius-Mossotti equation. The large value of dielectric constant is identified through dielectric studies and it points to the ferroelectric behaviour of the material. Further an experimental study confirms the ferroelectric behaviour of the material. The total polarizability of the crystal owing to the space charge, dipole, ionic and electronic polarizability contributions is obtained experimentally, and it matches well with the theoretically obtained value from Penn analysis. Further, Plasmon energy and Fermi energy of the material are also calculated using Penn analysis.

  7. 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)

  8. A modified band approach for the accurate calculation of online photolysis rates in stratospheric-tropospheric Chemical Transport Models

    Directory of Open Access Journals (Sweden)

    J. E. Williams

    2006-01-01

    Full Text Available Here we present an efficient and accurate method for the online calculation of photolysis rates relevant to both the stratosphere and troposphere for use in global Chemistry Transport Models and General Circulation Models. The method is a modified version of the band model introduced by Landgraf and Crutzen (1998 which has been updated to improve the performance of the approach for solar zenith angles >72 without the use of any implicit parameterisations. For this purpose, additional sets of band parameters have been defined for instances where the incident angle of the light beam is between 7293, in conjunction with a scaling component for the far UV region of the spectrum (?=178.6202.0 nm. For incident angles between 8593 we introduce a modification for pseudo-sphericity that improves the accuracy of the 2-stream approximation. We show that this modified version of the Practical Improved Flux Method (PIFM is accurate for angles <93 by comparing the resulting height resolved actinic fluxes with a recently developed full spherical reference model. We also show that the modified band method is more accurate than the original, with errors generally being less than 10% throughout the atmospheric column for a diverse range of chemical species. Moreover, we perform certain sensitivity studies that indicate it is robust and performs well over a wide range of conditions relevant to the atmosphere.

  9. 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.

  10. Electronic band structure pseudopotential calculation of wurtzite III-nitride materials

    International Nuclear Information System (INIS)

    The electronic properties of the wurtzite III-nitride compound semiconductors GaN, InN and AlN are studied within the empirical pseudopotential approach. An analytical function for both symmetric and antisymmetric parts of the pseudopotential with adjustable coefficients has been reported. Using this model the selected features of these materials such as energy gap, bandwidth, crystal-field splitting energy, Luttinger-like parameters, and effective masses are calculated and compared to experimental and recently published theoretical results and the comparisons show a good agreement

  11. 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.

  12. 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

  13. 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); Rtsep, 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.

  14. 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.)

  15. 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.

  16. 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.

  17. 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)

  18. Infinitesimal cranking for triaxial angular-momentum-projected configuration-mixing calculation and its application to the gamma vibrational band

    CERN Document Server

    Tagami, Shingo

    2016-01-01

    Inclusion of time-odd components into the wave function is important for reliable description of rotational motion by the angular-momentum-projection method; the cranking procedure with infinitesimal rotational frequency is an efficient way to realize it. In the present work we investigate the effect of this infinitesimal cranking for triaxially deformed nucleus, where there are three independent cranking axes. It is found that the effects of cranking about three axes on the triaxial energy spectrum are quite different and inclusion of all of them considerably modify the resultant spectrum from the one obtained without cranking. Employing the Gogny D1S force as an effective interaction, we apply the method to the calculation of the multiple gamma vibrational bands in $^{164}$Er as a typical example, where the angular-momentum-projected configuration-mixing with respect to the triaxial shape degree of freedom is performed. With this method, both the $K=0$ and $K=4$ two-phonon gamma vibrational bands are obtain...

  19. 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.

  20. 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.

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

    CERN Document Server

    Shimada, Mitsuhiro; Shimizu, Yoshifumi R

    2015-01-01

    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 and they are superposed in the sense of the configuration mixing or the generator coordinate method, after performing the projection; the idea was originally suggested by Peierls-Thouless in 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.

  2. 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.

  3. 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 EngelVosko GGA (EVGGA) to treat the exchange correlation potential by solving KohnSham 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.

  4. Model construction and superconductivity analysis of organic conductors ?-(BDA-TTP)2MF6 (M = P, As, Sb and Ta) based on first-principles band calculation

    International Nuclear Information System (INIS)

    We perform a first-principles band calculation for a group of quasi-two-dimensional organic conductors ?-(BDA-TTP)2MF6 (M = P, As, Sb and Ta). The ab-initio calculation shows that the density of states is correlated with the bandwidth of the singly occupied (highest) molecular orbital, while it is not necessarily correlated with the unit-cell volume. The direction of the major axis of the cross section of the Fermi surface lies in the ?B-direction, which differs from that obtained by the extended Hckel calculation. Then, we construct a tight-binding model which accurately reproduces the ab-initio band structure. The obtained transfer energies give a smaller dimerization than in the extended Hckel band. As to the difference in the anisotropy of the Fermi surface, the transfer energies along the inter-stacking direction are smaller than those obtained in the extended Hckel calculation. Assuming spin-fluctuation-mediated superconductivity, we apply random phase approximation to a two-band Hubbard model. This two-band Hubbard model is composed of the tight-binding model derived from the first-principles band structure and an on-site (intra-molecule) repulsive interaction taken as a variable parameter. The obtained superconducting gap changes sign four times along the Fermi surface like in a d-wave gap, and the nodal direction is different from that obtained in the extended Hckel model. Anion dependence of Tc is qualitatively consistent with the experimental observation. (paper)

  5. Model construction and superconductivity analysis of organic conductors ?-(BDA-TTP)2MF6 (M = P, As, Sb and Ta) based on first-principles band calculation

    Science.gov (United States)

    Aizawa, H.; Kuroki, K.; Yasuzuka, S.; Yamada, J.

    2012-11-01

    We perform a first-principles band calculation for a group of quasi-two-dimensional organic conductors ?-(BDA-TTP)2MF6 (M = P, As, Sb and Ta). The ab-initio calculation shows that the density of states is correlated with the bandwidth of the singly occupied (highest) molecular orbital, while it is not necessarily correlated with the unit-cell volume. The direction of the major axis of the cross section of the Fermi surface lies in the ?-B-direction, which differs from that obtained by the extended Hckel calculation. Then, we construct a tight-binding model which accurately reproduces the ab-initio band structure. The obtained transfer energies give a smaller dimerization than in the extended Hckel band. As to the difference in the anisotropy of the Fermi surface, the transfer energies along the inter-stacking direction are smaller than those obtained in the extended Hckel calculation. Assuming spin-fluctuation-mediated superconductivity, we apply random phase approximation to a two-band Hubbard model. This two-band Hubbard model is composed of the tight-binding model derived from the first-principles band structure and an on-site (intra-molecule) repulsive interaction taken as a variable parameter. The obtained superconducting gap changes sign four times along the Fermi surface like in a d-wave gap, and the nodal direction is different from that obtained in the extended Hckel model. Anion dependence of Tc is qualitatively consistent with the experimental observation.

  6. 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.

  7. 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.

  8. 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

  9. 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...

  10. Calculation and fitting of potential energy and dipole moment surfaces for the water molecule: Fully ab initio determination of vibrational transition energies and band intensities

    International Nuclear Information System (INIS)

    Potential energy and dipole moment surfaces for the water molecule have been generated by multireference singles-and-doubles configuration interaction calculations using a large basis set of the averaged-atomic-natural-orbital type and a six-orbital-six-electron complete-active-space reference space. The surfaces are suitable for modeling vibrational transitions up to about 11000cm-1 above the ground state. A truncated singular-value decomposition method has been used to fit the surfaces. This fitting method is numerically stable and is a useful tool for examining the effectiveness of various fitting function forms in reproducing the calculated surface points and in extrapolating beyond these points. The fitted surfaces have been used for variational calculations of the 30 lowest band origins and the corresponding band intensities for transitions from the ground vibrational state. With a few exceptions, the results compare well with other calculations and with experimental data. copyright 1997 American Institute of Physics

  11. 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.

  12. 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.

  13. 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.

  14. Self-consistent calculations of energy band structure and thermomechanical properties of some transition metals and their refractory carbides by LMTO-ASA method

    International Nuclear Information System (INIS)

    Self-consistent band structure calculations of V, Nb, VC, NbC, WC are carried out by the methods of LMTO and canonical Anderson zones with account for hybridization. The presence of an abnormally wide the 2pC-5dW-band and band of the 5d-states of tungsten below the Fermi level, predominantly, is found for WC. The crystal lattice constants, moduli of volume elasticity and sound velocities, Debye temperatures and melting temperatures are calculated. The results mainly correspond to the trends observed in the experiements. It is shown that a high VC elasticity is, basically, determined by hybridization of the metal s- and p-states with the carbon 2s- and 2p-states, while hybridization of the 5d-W- and 2pC-, 2sC-states makes the greatest contribution to the extreme elasticity

  15. LDA+DMFT calculations of X-ray absorption and x-ray circular dichroism spectra: Role of valence-band correlations

    Energy Technology Data Exchange (ETDEWEB)

    Sipr, Ondrej; Simunek, Antonin [Institute of Physics AS CR, Cukrovarnicka 10, Prague (Czech Republic); Minar, Jan; Ebert, Hubert [Universitaet Muenchen (Germany)

    2010-07-01

    L{sub 2,3}-edge XAS and XMCD spectra of 3d elements are calculated via a self-consistent LDA+DMFT method (including thus valence-band correlations). It is found that the asymmetry of the calculated XAS white lines increases upon inclusion of the correlations for Fe and Co but not for Ni. The change in the height of the L{sub 3} and L{sub 2} peaks in the XMCD spectra is in a good agreement with the change of the orbital magnetic moment caused by adding the valence-band correlations. As a whole, adding valence-band correlations improves the agreement between the theory and experiment but visible differences still remain. Therefore, a core hole is additionally accounted for via the final state approximation and the impact of such a procedure is assessed.

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

    DEFF Research Database (Denmark)

    Svane, Axel; Christensen, Niels Egede; Cardona,, M.; Chantis, A.N.; van Schilfgaarde,, M.; Kotani, T.

    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...

  17. Calculation of the Energy-Band Structure of the Kronig-Penney Model Using the Nearly-Free and Tightly-Bound-Electron Approximations

    Science.gov (United States)

    Wetsel, Grover C., Jr.

    1978-01-01

    Calculates the energy-band structure of noninteracting electrons in a one-dimensional crystal using exact and approximate methods for a rectangular-well atomic potential. A comparison of the two solutions as a function of potential-well depth and ratio of lattice spacing to well width is presented. (Author/GA)

  18. Prediction model of band gap for inorganic compounds by combination of density functional theory calculations and machine learning techniques

    Science.gov (United States)

    Lee, Joohwi; Seko, Atsuto; Shitara, Kazuki; Nakayama, Keita; Tanaka, Isao

    2016-03-01

    Machine learning techniques are applied to make prediction models of the G0W0 band gaps for 270 inorganic compounds using Kohn-Sham (KS) band gaps, cohesive energy, crystalline volume per atom, and other fundamental information of constituent elements as predictors. Ordinary least squares regression (OLSR), least absolute shrinkage and selection operator, and nonlinear support vector regression (SVR) methods are applied with two levels of predictor sets. When the KS band gap by generalized gradient approximation of Perdew-Burke-Ernzerhof (PBE) or modified Becke-Johnson (mBJ) is used as a single predictor, the OLSR model predicts the G0W0 band gap of randomly selected test data with the root-mean-square error (RMSE) of 0.59 eV. When KS band gap by PBE and mBJ methods are used together with a set of predictors representing constituent elements and compounds, the RMSE decreases significantly. The best model by SVR yields the RMSE of 0.24 eV. Band gaps estimated in this way should be useful as predictors for virtual screening of a large set of materials.

  19. Experimental study and calculations of nitric oxide absorption in the ?(0,0) and ?(1,0) bands for strong temperature conditions

    International Nuclear Information System (INIS)

    Absorption spectra of nitric oxide in the ?(0,0) and ?(1,0) bands have been measured for hard temperature conditions up to 1700 K in order to validate a model for the simulation of these two bands. The good agreement between experiments and calculations (relative errors of 2-5% for the ?(0,0) band and 10-15% for the ?(1,0) band) consolidates the two important assumptions concerning the intermediate Hund's case between (a) and (b) for the X2? state of the ?(0,0) and ?(1,0) absorption bands and the use of collisional broadening parameters of ?(0,0) to simulate the ?(1,0) band. Using this simulation, a study of the Beer-Lambert law behavior at high temperature has been carried out. With the instrument resolution used for these experiments, it was shown that a correction of the Beer-Lambert law is necessary. To apply this technique for the measurements of NO concentrations inside the combustion chamber of an optical SI engine, a new formulation of the Beer-Lambert law has been introduced, since the modified form proposed in the literature is no longer applicable in the total column range of interest

  20. 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

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

    Directory of Open Access Journals (Sweden)

    Roberto Nez-Gonzlez

    2008-01-01

    Full Text Available Ab-initio calculations of the band gap variation of AlxGa1xN and InxGa1xN 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 AlxGa1xN and b = 2.12 eV for InxGa1xN.

  2. 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.

  3. Precise band structure and Fermi-surface calculation for YBa2Cu3O7: Importance of three-dimensional dispersion

    International Nuclear Information System (INIS)

    With the appearance of angle-resolved photoemission data allowing the identification and measurement of the Fermi surface of the high-Tc cuprate superconductors, it is important to have precise local-density calculations with which to compare. We present well-converged local-density predictions of the band structure and Fermi surface of YBa2Cu3O7, giving special attention to the position of the flat Cu-O chain-derived bands and the effect of the buckling of the Cu-O chain that is predicted by total-energy calculations and that has been inferred by an x-ray-scattering study. We emphasize the c-axis dispersion that will lead to apparent broadening of the Fermi surface in experiments interpreted in terms of a two-dimensional electronic structure

  4. 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.

  5. 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.

  6. 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.

  7. The electronic band parameters calculated by the Kronig-Penney method for Cd1-xZnxS quantum dot superlattices

    International Nuclear Information System (INIS)

    This work reports on a theoretical study of superlattices based on Cd1-xZnxS quantum dots embedded in an insulating material. We show, in particular, how this system can be assumed to a series of flattened cylindrical quantum dots with a finite barrier height at the boundary. In this paper, are also reviewed the approximations needed to calculate the band edges of the Cd1-xZnxS superlattices with use of the Kronig-Penney model. The electronic states and the electron effective masses of both ?1- and ?2-minibands have been computed as a function of zinc composition for different inter-quantum dot separations. As is found, the CdS system is appropriate to give rise a superlattice behavior for conduction electrons in a relatively large range of inter-sheet separations. An attempt to explain the electron band parameters calculated will be presented.

  8. 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; Blgel, 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.

  9. CALCULATION OF ELECTRONIC BAND STRUCTURE OF FERROELECTRIC SEMICONDUCTOR BISMUTH NIOBIUM OXYFLUORIDE (Bi2NbO5F) CRYSTAL

    OpenAIRE

    Erdinç, Bahattin; McCabe, Emma; Duran, Duygu; Secuk, Nurullah; Gülebağlan, Sinem; Doğan, Emel; Aycibin, Murat; Akkuş, Harun

    2014-01-01

    In this study, the geometric structural optimization, electronic band structure and total density of states for electrons of ferroelectric Bi2NbO5F structure with space group Pca21 at room temperature have been investigated by Augmented Plane Wave method (APW) using the density functional theory (DFT) under the local density approximation (LDA). The ground state properties of ferroelectric Bi2NbO5F structure are studied. The computed ground state properties and experimental results are consis...

  10. 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...

  11. 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.

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

    CERN Document Server

    Grger, 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...

  13. Semiclassical calculations of half-widths and line shifts for transitions in the 30012?00001 and 30013?00001 bands of CO2. III: Self collisions

    International Nuclear Information System (INIS)

    This paper is the third in a series devoted to accurate semi-empirical calculations of pressure-broadened half-widths, pressure-induced line shifts, and the temperature dependence of the half-widths of carbon dioxide. In this work complex Robert-Bonamy (CRB) calculations were made for transitions in two of the Fermi-tetrad bands for self-collisions, i.e. the CO2-CO2 system. The intermolecular potential (IP) was adjusted to match measurements of the half-width, its temperature dependence, and the line shift. It is shown that small changes in the parameters describing the IP lead to noticeable changes in the line shape parameters and that it is possible to find a set of IP parameters, which, when used in the CRB formalism, yield half-widths, their temperature dependence, and line shifts in excellent agreement with measurement. This work demonstrates that this agreement can be obtained if the atom-atom potential is expanded to high order and rank (here 20 4 4), the real and imaginary (S1 and Im(S2)) components are retained, and the determination of the trajectories is made by solving Hamilton's equations. It was found that the temperature dependence of the half-width is sensitive to the range of temperatures used in the fit and that the vibrational dependence of the line shape parameters for these two bands is very small. Databases of the half-width, its temperature dependence, and the line shift for the atmospheres of Venus (296-700 K fit range for the temperature exponents of the half-widths) and Mars (125-296 K fit range for the temperature exponents of the half-widths) are provided. The calculations are compared with the measured data for the bands under study.

  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. 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...

  16. A modified band approach for the accurate calculation of on-line photolysis rates in stratospheric-tropospheric Chemical Transport Models

    Directory of Open Access Journals (Sweden)

    J. E. Williams

    2006-05-01

    Full Text Available Here we present an efficient and accurate method for the online calculation of photolysis rates relevant to both the stratosphere and troposphere for use in global Chemistry Transport Models. The method is a modified version of the band model introduced by Landgraf and Crutzen (1998 which has been updated to improve the performance of the approach for solar zenith angles >75 without the use of any implicit parameterisations. For this purpose, additional sets of band parameters have been defined for instances where the incident angle of the light beam is between 7593, in conjunction with a scaling component for the far UV region of the spectrum (?=176.6202.0 nm. For incident angles between 8593 we introduce a modification for pseudo-sphericity that improves the accuracy of the 2-stream approximation. We show that this modified version of PIFM is accurate for angles <93 by comparing the resulting height resolved actinic fluxes with a recently developed full spherical reference model. We also show that the modified band method is more accurate than the original, with errors generally being 10% throughout the atmospheric column for a diverse range of chemical species. Moreover, we perform certain sensitivity studies that indicate it is robust and performs well over a wide range of conditions relevant to the atmosphere.

  17. Stability and band gaps of InGaAs, BGaAs, and BInGaAs alloys: Density-functional supercell calculations

    International Nuclear Information System (INIS)

    The influence of arrangement and content of substituents (B, In) in BGaAs, InGaAs, and BInGaAs alloys on the stabilities and band gaps is investigated using density-functional supercell calculations. The stability of ternary alloys decreases from InGaAs over BGaAs to GaAsN. Typical substituent structures show the following stability order: isolated substituents - [110] chains - clusters - twisted [111] chains - (200/211) arrangements (most stable). This is valid for both the In- and B-poor as well as the In- and B-rich alloys. From the fact that grown InGaAs provides a different gap than the most stable arrangement one can conclude that other structures (isolated indium atoms or InmAs clusters) are formed during the growth. Simultaneous substitutions (BInGaAs) of larger (In) and smaller (B) atoms prefer arrangements in larger distances (220) for isovalent boron substitution and in In-B bonds for antisite boron substitution. The high degree boron antisite substitution induces partially occupied acceptor bands which lead to a strong reduction of the band gap in comparison to the isovalent substitution. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  18. 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 latticematched 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.

  19. 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.

  20. Interfacial Properties of Monolayer and Bilayer MoS2 Contacts with Metals: Beyond the Energy Band Calculations

    OpenAIRE

    Zhong, Hongxia; Ni, Zeyuan; Wang, Yangyang; Ye, Meng; Song, Zhigang; Pan, Yuanyuan; Quhe, Ruge; Yang, Jinbo; YANG, LI; Shi, Junjie; Lu, Jing

    2015-01-01

    Although many prototype devices based on two-dimensional (2D) MoS2 have been fabricated and wafer scale growth of 2D MoS2 has been realized, the fundamental nature of 2D MoS2-metal contacts has not been well understood yet. We provide a comprehensive ab initio study of the interfacial properties of a series of monolayer (ML) and bilayer (BL) MoS2-metal contacts (metal = Sc, Ti, Ag, Pt, Ni, and Au). A comparison between the calculated and observed Schottky barrier heights (SBHs) suggests that ...

  1. 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}.

  2. Effect of unoxidized residual Al at the boundary of Co/Al-oxide/Co junction on TMR estimated by LMTO band calculation

    International Nuclear Information System (INIS)

    The magneto-resistance effect of Co/Al-oxide/Co tunneling junction is evaluated by a first-principles band calculation. To clarify the effect of unoxidized Al in the Al-oxide layer on the Co layer, we calculated the electronic structures of the junction with a local density approximation using the LMTO-ASA method. Periodic superlattices which consist of layers separated by vacant layers were used for the conventional calculation method. The magneto-resistance ratio, ?R/R, was estimated by the equation ?R/R = 2P 1 P 2/(P 1 + P 2), where P 1 is the polarization of a boundary Co atom on one side of a layer and P 2 is the polarization of a Co or Al atom with a vacant layer on the other side. The polarization of Co atoms near the boundary between the Co and Al layers decreases greatly due to the paramagnetic Al, although the Al was polarized by the ferromagnetic Co. These changes of polarization affect the magneto-resistance ratio with calculations indicating that the ratio is reduced by half for two atomic layers of residual Al

  3. 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 (α =0.0 ) and HSE06 (α =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.

  4. 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

  5. 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 metalsMn, 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.

  6. 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

  7. Chemical state analysis of heat-treated 6, 13-bis(triisopropylsilylethynyl) pentacene investigated by XPS valence band spectra, XANES spectra and first-principles calculation

    International Nuclear Information System (INIS)

    X-ray photoelectron spectroscopy (XPS) valence band spectra reflect the chemical bonding states. To take this advantage, we tried to interpret experimental spectra by the occupied density of states (DOS) based on first principles calculation. In this work, we discussed XPS and X-ray Absorption Near Edge Structure (XANES) spectra of 6, 13-bis(triisopropylsilylethynyl) pentacene (TIPS-Pen), which is well known as an organic semiconductor. We studied chemical structure change of TIPS-Pen caused by heat-treatment at 300degC under nitrogen and under the air. It has been suggested that the structural change of pentacene skeleton by Diels-Alder type reaction occurs in both cases. In addition, the sample heat-treated under the air showed desorption of the isopropyl group and increase of oxygen concentration. (author)

  8. Different doping from apical and planar oxygen vacancies in Ba2CuO4-? and La2CuO4-?: First-principles band structure calculations

    Science.gov (United States)

    Jarlborg, T.; Barbiellini, B.; Markiewicz, R. S.; Bansil, A.

    2012-12-01

    First-principles band structure calculations for large supercells of Ba2CuO4-? and La2CuO4-? with different distributions and concentrations of oxygen vacancies show that the effective doping on copper sites strongly depends on where the vacancy is located. A vacancy within the Cu layer produces a weak doping effect while a vacancy located at an apical oxygen site acts as a stronger electron dopant on the copper layers and gradually brings the electronic structure close to that of La2-xSrxCuO4. These effects are robust and only depend marginally on lattice distortions. Our results show that deoxygenation can reduce the effect of traditional La/Sr or La/Nd substitutions. Our study clearly identifies location of the dopant in the crystal structure as an important factor in doping of the cuprate planes.

  9. 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.

  10. 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.

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

    Scientific Electronic Library Online (English)

    Roberto, Nez-Gonzlez; Armando, Reyes-Serrato; Alvaro, Posada-Amarillas; Donald H, Galvn.

    2008-11-01

    Full Text Available En este trabajo se realizaron clculos de primeros principios de la variacin del ancho de banda prohibido en los compuestos ternarios Al xGa1-xN e In xGa1-x N, utilizando el Mtodo Linealizado de Ondas Planas Aumentadas con Potencial Completo (FLAPW), dentro del marco de la Teora del Funcional de [...] la Densidad (DFT). Los nitruros fueron modelados en una estructura tipo wurzita utilizando el mtodo de supercelda, y considerando las concentraciones x = 0, 0.25, 0.50, 0.75 y 1.0. Para la optimizacin de los parmetros de red se utiliz el potencial de correlacin-intercambio PBE96 (Perdew et al., Phys. Rev. Lett. 77 (1996) 3865). Para el clculo de la estructura de bandas de energa se utilizaron los funcionales PBE96 y EV93 (Engel et al., Phys. Rev. B 47 (1993) 13164). Se consideraron parmetros de red experimentales y calculados (con PBE96) para los clculos de las propiedades electrnicas. Nuestros clculos indican que la banda prohibida fundamental es directa en estos compuestos. Los clculos con el funcional EV93 dan como resultado una mejor estimacin de los anchos de las bandas prohibidas de los compuestos binarios. Calculamos el parmetro 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.

  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- 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. Gastric Banding

    Science.gov (United States)

    ... Radiation-Emitting Products Vaccines, Blood & Biologics Animal & Veterinary Cosmetics Tobacco ... Banding Benefits of Gastric Banding Lifestyle Changes after Gastric Banding Surgery Gastric banding is a weight loss option for ...

  14. 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.

  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. Absorption intensity changes and frequency shifts of fundamental and first overtone bands for OH stretching vibration of methanol upon methanol-pyridine complex formation in CCl4: analysis by NIR/IR spectroscopy and DFT calculations.

    Science.gov (United States)

    Futami, Yoshisuke; Ozaki, Yasushi; Ozaki, Yukihiro

    2016-02-21

    Infrared (IR) and near infrared (NIR) spectra were measured for methanol and the methanol-pyridine complex in carbon tetrachloride. Upon the formation of the methanol-pyridine complex, the frequencies of both the fundamental and first overtone bands of the OH stretching vibration shifted to lower frequencies, and the absorption intensity of the fundamental increased significantly, while that of the first overtone decreased markedly. By using quantum chemical calculations, we estimated the absorption intensities and frequencies of the fundamental and first overtone bands for the OH stretching vibration based on the one-dimensional Schrdinger equation. The calculated results well reproduced the experimental results. The molecular vibration potentials and dipole moment functions of the OH stretching vibration modes were compared between methanol and the methanol-pyridine complex in terms of absorption intensity changes and frequency shifts. The large change in the dipole moment function was found to be the main cause for the variations in absorption intensity for the fundamental and first overtone bands. PMID:26862859

  19. Spectra calculations in central and wing regions of CO2 IR bands between 10 and 20 ?m. III: atmospheric emission spectra

    International Nuclear Information System (INIS)

    A theoretical model for the prediction of CO2 absorption in both central and wing regions of infrared absorption bands was presented in the companion paper I. It correctly accounts for line-mixing effects and was validated by comparisons with laboratory spectra in the 600-1000 cm-1 region. This quality was confirmed using atmospheric transmissions measured by solar occultation experiments in the second paper. The present work completes these studies by now considering atmospheric emission in the 10-20 ?m range. Comparisons are made between computed atmospheric radiances and measurements obtained using four different Fourier transform experiments collecting spectra for nadir, up-looking, as well as limb (from balloon and satellite) geometries. Our results confirm that using a Voigt model can lead to very large errors that affect the spectrum more than 300 cm-1 away from the center of the CO2 ?2 band. They also demonstrate the capability of our model to represent accurately the radiances in the entire region for a variety of atmospheric paths. This success opens interesting perspectives for the sounding of pressure and temperature profiles, particularly at low altitudes. Another benefit of the quality of the model should be an increased accuracy in the retrieval of atmospheric state parameters from broad features in the measured spectra (clouds, aerosols, heavy trace gases)

  20. 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.

  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. Revised vibrational band assignments for the experimental IR and Raman spectra of 2,3,4-trifluorobenzonitrile based on ab initio, DFT and normal coordinate calculations

    Science.gov (United States)

    Hiremath, C. S.; Kalkoti, G. B.; Aralakkanavar, M. K.

    2009-09-01

    In the present study, a systematic vibrational spectroscopic investigation for the experimental IR and Raman spectra of 2,3,4-trifluorobenzonitrile (TFB), aided by electronic structure calculations has been carried out. The electronic structure calculations - ab initio (RHF) and hybrid density functional methods (B3LYP) - have been performed with 6-31G* basis set. Molecular equilibrium geometries, electronic energies, IR intensities, harmonic vibrational frequencies, depolarization ratios and Raman activities have been computed. The results of the calculations have been used to simulate IR and Raman spectra for TFB that showed excellent agreement with the observed spectra. Potential energy distribution (PED) and normal mode analysis have also been performed. The assignments proposed based on the experimental IR and Raman spectra have been reviewed. A complete assignment of the observed spectra has been proposed.

  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. 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

  5. Electronic band structure calculations on thin films of the L2{sub 1} full Heusler alloys X{sub 2}YSi (X, Y = Mn, Fe, and Co): Toward spintronic materials

    Energy Technology Data Exchange (ETDEWEB)

    Mori, Hirotoshi, E-mail: mori.hirotoshi@ocha.ac.jp [Division of Advanced Sciences, Ocha-dai Academic Production, Ochanomizu University, 2-1-1 Ohtsuka, Bunkyo-ku, Tokyo 112-8610 (Japan); Odahara, Yosuke; Shigyo, Daisuke; Yoshitake, Tsuyoshi; Miyoshi, Eisaku [Graduate School of Engineering Sciences, Kyushu University, 6-1 Kasuga park, Kasuga, 816-8580 (Japan)

    2012-05-31

    To design half-metallic materials in thin film form for spintronic devices, the electronic structures of full Heusler alloys (Mn{sub 2}FeSi, Fe{sub 2}MnSi, Fe{sub 2}FeSi, Fe{sub 2}CoSi, and Co{sub 2}FeSi) with an L2{sub 1} 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 Co{sub 2}FeSi 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: Black-Right-Pointing-Pointer Electronic band structure calculations of L2{sub 1} full Heusler alloy thin films. Black-Right-Pointing-Pointer Spintronic materials. Black-Right-Pointing-Pointer Electronic properties dependency on layer thickness.

  6. Electronic band structure and optical properties of titanium oxyphosphates Li0.50Co0.25TiO(PO4) single crystals: An ab-initio calculations

    International Nuclear Information System (INIS)

    From the refined atomic positions obtained by Belmal et al. (2004) using X-ray diffraction for Li0.50Co0.25TiO(PO4), we have performed a structural optimization by minimizing the forces acting on the atoms keeping the lattice parameters fixed at the experimental values. With this relaxed (optimized) geometry we have performed a comprehensive theoretical study of electronic properties and dispersion of the linear optical susceptibilities using the full potential linear augmented plane wave (FP-LAPW) method. The generalized gradient approximation (GGA) exchange-correlation potential was applied. In addition, the Engel-Vosko generalized gradient approximation (EVGGA) was used for comparison with GGA because it is known that EVGGA approach yields better band splitting compared to the GGA. We have calculated the band structure, and the total and partial densities of states. The electron charge densities and the bonding properties were analyzed and discussed. The complex dielectric optical susceptibilities were discussed in detail. - Graphical abstract: It is shown that P is tetrahedrally coordinated by four O ions. Highlights: ? Comprehensive theoretical study of electronic and optical properties was performed. ? Using X-ray diffraction data we have performed a structural optimization. ? The electron charge densities and the bonding properties were analyzed and discussed. ? Fermi surface was analyzed since it is useful for predicting thermal, magnetic, and optical properties. ? The density of states at EF and the electronic specific heat coefficient were calculated.

  7. The structure of the valence band of Cs2PuO2Cl4 single crystal by the XPS data and relativistic calculation results

    International Nuclear Information System (INIS)

    In this work for the first time the XPS spectra of the valency and core electrons of Cs2PuO2Cl4 single crystal containing the PuO22+ group were measured and analyzed in order to establish a correlation of the fine spectral structure with the plutonium ion oxidation state, the structure of its close environment and the nature of the chemical bond. Also the relativistic SCF X? DV calculation of the PuO2Cl42- (D4d) cluster at RPu-O=0.171nm and RPu-Cl=0.262 nm was done. For comparison the spectra of Cs2UO2ClO4 were studied. (author)

  8. 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.

  9. Theoretical calculations of the optical band positions and zero-field splitting 2D for Cr3+ ions in fluoride garnet Na3Li3In2F12

    International Nuclear Information System (INIS)

    Five optical band positions and one EPR zero-field splitting 2D for Cr3+ ions at the trigonally-distorted octahedral In3+ site in fluoride garnet Na3Li3In2F12 are calculated together from the complete diagonalization (of energy matrix) method based on the two-spinorbit-parameter model, where the contributions from both the spinorbit parameters of central dn ion and ligand ion are contained. The calculated results are in reasonable agreement with the experimental values. The calculations show that similar to the bonding length (i. e., metal-ligand distance) R, the bonding angle ? (between the direction of R and C3 axis) is different from the corresponding one in the host crystal Na3Li3In2F12 because of the size mismatching substitution. It appears that the complete diagonalization (of energy matrix) method based on the two-spinorbit-parameter model is effective in the unified calculation of optical spectra and EPR zero-field splitting for d3 ions in crystals

  10. 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.

  11. 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

  12. 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.

  13. Electronic Structure of $Cu_{1-x}Ni_{x}Rh_{2}S_{4}$ and $CuRh_{2}Se_{4} Band Structure Calculations, X-ray Photoemission and Fluorescence Measurements

    CERN Document Server

    Hart, G L W; Kurmaev, E Z; Hartmann, D; Moewes, A; Neumann, M; Ederer, D L; Endoh, R; Taniguchi, K; Nagata, S

    2000-01-01

    The electronic structure of spinel-type Cu_(1-x)Ni_xRh_2S_4 (x = 0.0, 0.1, 0.3, 0.5, 1.0) and CuRh_2Se_4 compounds has been studied by means of X-ray photoelectron and fluorescent spectroscopy. Cu L_3, Ni L_3, S L_(2,3) and Se M_(2,3) X-ray emission spectra (XES) were measured near thresholds at Beamline 8.0 of the Lawrence Berkeley Laboratory's Advanced Light Source. XES measurements of the constituent atoms of these compounds, reduced to the same binding energy scale, are found to be in excellent agreement with XPS valence bands. The calculated XES spectra which include dipole matrix elements show that the partial density of states reproduce experimental spectra quite well. States near the Fermi level (E_F) have strong Rh d and S(Se) p character in all compounds. In NiRh_2S_4 the Ni 3d states contribute strongly at E_F, whereas in both Cu compounds the Cu 3d bands are only ~1 eV wide and centered ~2.5 eV below E_F, leaving very little 3d character at E_F. The density of states at the Fermi level is less in ...

  14. High-energy band structure of gold

    DEFF Research Database (Denmark)

    Christensen, N. Egede

    1976-01-01

    The band structure of gold for energies far above the Fermi level has been calculated using the relativistic augmented-plane-wave method. The calculated f-band edge (?6-) lies 15.6 eV above the Fermi level is agreement with recent photoemission work. The band model is applied to interpret...

  15. 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.

  16. Chemically induced compaction bands in geomaterials

    Science.gov (United States)

    Stefanou, Ioannis; Sulem, Jean

    2013-04-01

    Compaction bands play an important role in oil production and may provide useful information on various geological processes. Various mechanisms can be involved at different scales: the micro scale (e.g. the grain scale), the meso scale (e.g. the Representative Element Volume) and the macro scale (e.g. the structure). Moreover, hydro-chemo-mechanical couplings might play an important role in triggering instabilities in the form of compaction bands. Compaction bands can be seen as an instability of the underneath mathematical problem leading to localization of deformation [1,2,3]. Here we explore the conditions of compaction banding in quartz-based geomaterials by considering the effect of chemical dissolution and precipitation [4,5]. In due course of the loading process grain crushing affects the residual strength, the porosity and the permeability of the material. Moreover, at the micro-level, grain crushing results in an increase of the grain specific surface, which accelerates the dissolution [6]. Consequently, the silica is removed more rapidly from the grain skeleton and the overall mechanical properties are degraded due to chemical factors. The proposed model accounts for these phenomena. In particular, the diffusion of the diluted in the water silica is considered through the mass balance equation of the porous medium. The reduction of the mechanical strength of the material is described through a macroscopic failure criterion with chemical softening. The grain size reduction is related to the total energy input [7]. A grain size and porosity dependent permeability law is adopted. These degradation mechanisms are coupled with the dissolution/precipitation reaction kinetics. The obtained hydro-chemo-mechanical model is used to investigate the conditions, the material parameters and the chemical factors inducing compaction bands formation. References [1] J.W. Rudnicki, and J.R. Rice. "Conditions for the Localization of Deformation in Pressure-sensitive Dilatant Materials." Journal of the Mechanics and Physics of Solids 23.6 (1975): 371-394. [2] I. Vardoulakis and J. Sulem: Bifurcation analysis in geomechanics. Blackie. 1995. [3] J.W. Rudnicki, "Conditions for Compaction and Shear Bands in a Transversely Isotropic Material." International Journal of Solids and Structures 39.13-14 (2002): 3741-3756. [4] L.-B. Hu and T. Hueckel. "Coupled Chemo-mechanics of Intergranular Contact: Toward a Three-scale Model." Computers and Geotechnics 34.4 (2007): 306-327. [5] R. Nova, R. Castellanza, and C. Tamagnini. "A Constitutive Model for Bonded Geomaterials Subject to Mechanical And/or Chemical Degradation." International Journal for Numerical and Analytical Methods in Geomechanics 27.9 (2003): 705-732. [6] J.D. Rimstidt and H.L. Barnes. "The Kinetics of Silica-water Reactions." Geochimica et Cosmochimica Acta 44.11 (1980): 1683-1699. [7] P.V. Lade, J.A. Yamamuro and P.A. Bopp "Significance of Particle Crushing in Granular Materials." Journal of Geotechnical Engineering, 122.4 (1996): 309-316.

  17. 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

  18. 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.

  19. 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

  20. 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

  1. 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.)

  2. 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.

  3. 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.

  4. 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.

  5. Congenital Constriction Band Syndrome

    Directory of Open Access Journals (Sweden)

    Rajesh Gupta, Fareed Malik, Rishabh Gupta, M.A.Basit, Dara Singh

    2008-04-01

    Full Text Available Congenital constriction bands are anomalous bands that encircle a digit or an extremity. Congenitalconstriction band syndrome is rare condition and is mostly associated with other musculoskeletaldisorders.We report such a rare experience.

  6. 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.

  7. 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

  8. Band Structures of Plasmonic Polarons

    Science.gov (United States)

    Caruso, Fabio; Lambert, Henry; Giustino, Feliciano

    2015-03-01

    In angle-resolved photoemission spectroscopy (ARPES), the acceleration of a photo-electron upon photon absorption may trigger shake-up excitations in the sample, leading to the emission of phonons, electron-hole pairs, and plasmons, the latter being collective charge-density fluctuations. Using state-of-the-art many-body calculations based on the `GW plus cumulant' approach, we show that electron-plasmon interactions induce plasmonic polaron bands in group IV transition metal dichalcogenide monolayers (MoS2, MoSe2, WS2, WSe2). We find that the energy vs. momentum dispersion relations of these plasmonic structures closely follow the standard valence bands, although they appear broadened and blueshifted by the plasmon energy. Based on our results we identify general criteria for observing plasmonic polaron bands in the angle-resolved photoelectron spectra of solids.

  9. 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

  10. 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.

  11. 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

  12. Band parameters of phosphorene

    DEFF Research Database (Denmark)

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

    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...

  13. 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.

  14. Wide band systems

    Science.gov (United States)

    Baier, Paul Walter; Kleinhempel, Werner

    Most radio communication systems being presently introduced are digital systems. Depending on the transmission bandwidth relative to the information rate, such systems can be divided into the class of narrow band systems and wide band systems. The advantages that wide band systems offer under adverse propagation conditions are studied. After introducing digital information transmission, digital wide band systems are defined on the basis of the used transmission signal forms and are compared with narrow band systems. The need for the application of wide band systems is pointed out referring to information theory, with the resistance against noise and interference as well as the capabilities of multiple access and selective addressing being addressed. Different types of wide band systems including spread spectrum are presented. The quantitative treatment of propagation problems in narrow band and wide band systems due to time variant multipath propagation is tackled and the potential of wide band systems in combatting propagation effects is shown. It is explained that properly designed spread spectrum systems are less affected by multipath reception than narrow band systems.

  15. 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.

  16. 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.

  17. 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.

  18. Bolus calculators.

    Science.gov (United States)

    Schmidt, Signe; Nrgaard, 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

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

    OpenAIRE

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

    2015-01-01

    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 calc...

  20. 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...

  1. Multiple superdeformed bands in 153Dy

    International Nuclear Information System (INIS)

    Multiple superdeformed rotational bands have been identified in a nucleus for the first time. Cascades of 14, 13, and 11 transitions have been assigned to three bands in 153Dy. Despite the small intensities, it has been possible to follow the decay of these bands from an angular frequency of 0.7 down to 0.4 MeV/ℎ. In all three cases, the dynamic moment of inertia I(2) is nearly constant. Assignments to high-N intruder orbitals are suggested through comparison of these values of I(2) with theoretical calculations based on the cranked shell model

  2. Calculation of Spectra of Solids:

    DEFF Research Database (Denmark)

    Lindgrd, 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.

  3. 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

  4. 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,

  5. 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

  6. Investigation of chiral bands in {sup 106}Ag

    Energy Technology Data Exchange (ETDEWEB)

    Lieder, Evgenia [Themba LABS, Somerset West (South Africa); FhG, INT, Euskirchen (Germany); Lieder, Rainer; Bark, Rob; Lawrie, Elena; Lawrie, Kobus; Ntshangase, Sifiso; Mullins, Simon; Papka, Paul; Kheswa, Ntombi [Themba LABS, Somerset West (South Africa); Meng, Jie [PhS, PKU, Beijing (China); PhS, BUAA, Beijing (China); Qi, Bin [SDU, Weihai (China); Zhang, Shuangquan; Li, Zhipan [PhS, PKU, Beijing (China)

    2010-07-01

    Dipole bands in {sup 106}Ag have been studied with the {gamma}-detector array AFRODITE at iThemba LABS, South Africa. A {sup 96}Zr({sup 14}N,4n){sup 106}Ag reaction at a beam energy of 71 MeV has been used. The three previously known negative-parity bands in {sup 106}Ag 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 {sup 106}Ag, obtained in RMF calculations, two minima have been found in the {beta}{sub 2}-{gamma} plane. Based on PRM calculations using the deformation parameters of the two minima and a {nu}h{sub 11/2} x {pi}g{sup -1}{sub 9/2} particle-hole configuration, bands 2 and 3 may represent partners with chiral vibration at {gamma}{approx}12degree. Band 1, located in the other minimum, may be a magnetic dipole band or the partner of a second pair of chiral bands.

  7. 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...

  8. 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.

  9. 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.

  10. 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.

  11. Smooth band termination in the mass A=110 region

    International Nuclear Information System (INIS)

    The systematics of smoothly terminating rotational bands based on proton 2p-2h excitations in the A=110 mass region are presented. Terminating bands (or nearly so) based on this proton excitation have been found in nuclei ranging from 107In, up to 114Te, and possibly extending to 54Xe nuclei. The impressive agreement between experimental data and theoretical calculations is also presented. However, recently discovered structures based on proton 1p-1h excitations begin to show disagreement with theoretical calculations. These new bands are also discussed. The current and future directions of research into smooth band termination will be presented

  12. Smooth band termination in the mass A=110 region

    International Nuclear Information System (INIS)

    The systematics of smoothly terminating rotational bands based on proton 2p-2h excitations in the A=110 mass region are presented. Terminating bands (or nearly so) based on this proton excitation have been found in nuclei ranging from 107In, up to 114Te, and possibly extending to 54Xe nuclei. The impressive agreement between experimental data and theoretical calculations is also presented. However, recently discovered structures based on proton 1p-1h excitations begin to show disagreement with theoretical calculations. These new bands are also discussed. The current and future directions of research into smooth band termination will be presented. (c) 1999 American Institute of Physics

  13. 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 ...

  14. 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.

  15. Criticism of the OPW method for band structure calculations

    International Nuclear Information System (INIS)

    The OPW method is associated with a general eigenvalue problem of type (A - lambda B) x vector = 0, in which the matrix B and in particular its lowest eigenvalue decide upon the stability of the solutions lambda and, therefore, upon the applicability of the method which may become very questionable for heavier substances. Analytical proofs as well as explicit numerical estimates for several solids are given

  16. Strain analysis using quartz deformation bands

    Science.gov (United States)

    Wu, Schuman; Groshong, Richard H.

    1991-05-01

    Quartz deformation bands are kink bands in quartz crystals. A deformation band develops as a region of localized crystal-plastic deformation with boundaries perpendicular to the slip plane and slip direction, which usually is along an ?-axis in the basal plane. Under cross-polarized light, the difference in crystallographic orientation between a deformation band and its host is indicated by a difference in extinction positions. The displacement between the c axis in a deformation band and the c axis in the host represents the angular shear of the deformation band in the direction of the c axis in the host grain. Assuming the deformation is homogeneous at the grain scale, the angular shear of the grain (the gauge) is calculated by multiplying the angular shear of the deformation band by the ratio of the sheared part to the whole grain. Using the strain-gauge method for three-dimensional infinitesimal strain analysis, a minimum number of five grains measured on universal stage is needed to solve for the deviatoric strain components of the aggregate if the strain is homogeneous in the aggregate. Data from more than five grains are used to find the best-fit strain components by a least-squares method. The principal strains and their orientations are found from these strain components by calculating the eigenvalues and eigenvectors. A 3-D strain ellipsoid also is obtained from strain ellipses in three perpendicular planes determined from the two-dimensional flat-stage measurements by the Wellman method. Both the strain-gauge method and the Wellman method are tested by using synthetic data sets and applied to a naturally deformed sample. Both methods give similar results; the established Wellman method thus confirms the strain-gauge calculation.

  17. CONTAIN calculations

    International Nuclear Information System (INIS)

    In the first phase of a benchmark comparison, the CONTAIN code was used to calculate an assumed EPR accident 'medium-sized leak in the cold leg', especially for the first two days after initiation of the accident. The results for global characteristics compare well with those of FIPLOC, MELCOR and WAVCO calculations, if the same materials data are used as input. However, significant differences show up for local quantities such as flows through leakages. (orig.)

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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)

  5. 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

  6. 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.

  7. 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.)

  8. 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...

  9. 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.)

  10. 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.

  11. 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 Gran; 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...

  12. HELIOS calculations

    International Nuclear Information System (INIS)

    Comparison of HELIOS and KASSETA-TWEG spectral codes is presented. Benchmark for WWER-440 FA Burn-Up Comparison (P. Mikolas, Sixth Symposium of AER, Kirkonummi 1996) and typical Kasseta type burn-up calculation for macro code data preparation are used for comparison. Differences of reactivity effects are discussed. (Authors)

  13. 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...

  14. 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.)

  15. Electron currents associated with an auroral band

    International Nuclear Information System (INIS)

    Measurements of electron pitch angle distributions and energy spectra over a broad auroral band were used to calculate net electric current carried by auroral electrons in the vicinity of the band. The particle energy spectrometers were carried by a Nike-Tomahawk rocket launched from Poker Flat, Alaska, at 0722 UT on February 25, 1972. Data are presented which indicate the existence of upward field-aligned currents of electrons in the energy range 0.5-20 keV. The spatial relationship of these currents to visual structure of the auroral arc and the characteristics of the electrons carrying the currents are discussed

  16. 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

  17. 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.

  18. Reliability Calculations

    DEFF Research Database (Denmark)

    Petersen, Kurt Erling

    1986-01-01

    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...... 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...... 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....

  19. 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

  20. 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.

  1. 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.

  2. 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.

  3. Braille Calculator

    OpenAIRE

    Yoshit V. Gidh; Mahesh S. Latey; Arpita roy, Kunal Shah; Savita Ingle

    2013-01-01

    A thorough grounding in mathematics enhances educational and occupational opportunities for all people, whether sighted or visually impaired. In day-to-day routines, a practical understanding of mathematics allows a person to function more successfully and independently.? Access to, and doing mathematics, is one of the biggest obstacles for blind students in school and at the university. Our Braille Calculator will present new approaches to offering blind students better access to math, to pr...

  4. 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

  5. Calculator thermometer

    International Nuclear Information System (INIS)

    An inexpensive substitution for calibrated thermocouples, linearizing electronics, and the NBS thermocouple tables is obtained through the use of a hand-held calculator. Automatic offset corrections and interpolations to an output temperature are possible in a one button operation beginning with voltmeter EMF. The inverse operation is also given. Appropriate constants have been found for the Cu-constantan, iron-constantan, and chromel-alumel thermocouples

  6. 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.

  7. Bulk band structure of Bi2Te3

    DEFF Research Database (Denmark)

    Michiardi, Matteo; Aguilera, Irene; Bianchi, Marco; Eustquio de Carvalho, Vagner; Orlando Ladeira, Luiz; Gomes Teixeira, Nayara; Avellar Soares, Edmar; Friedrich, Christoph; Blgel, 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...

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

    OpenAIRE

    Wahnn Benarroch, Perla; Palacios Clemente, Pablo; Aguilera Bonet, Irene; Seminvski Prez, 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...

  9. A study on properties of uranium oxide using band theory

    International Nuclear Information System (INIS)

    This report describes the study done by author as a postdoctoral research associate at Japan Nuclear Cycle Development Institute. This report is divided into three parts: construction of a relativistic band calculation formalism based on the density functional theory, using this method, investigation of the electrical properties for ferromagnetic UGe2 and antiferromagnetic UO2. 1) A relativistic band calculation (RBC) method. Band calculations for the s, p, and d electric structure have been developed well in the practical application and theoretical study. But band calculation method threading magnetic 5f electrons as actinide compounds are complicated and needed relativistic approach, so it is behind with the study of the 5f system. In this study we construct the relativistic band calculation formalism valid for magnetic 5f electrons. 2) Electric properties of UGe2. The actinide compounds UGe2 is ferromagnetic, so the theoretical analysis is not well yet. The electric structure and Fermi surface of UGe2 are analyzed using the RBC. The theoretical results show that UGe2 is heavy electron with the 5f character and are agreement with experimental one. 3) Electric structure of nuclear fuel UO2. It is important to understand the mechanism of the thermal conductivity of nuclear fuel as antiferromagnetic UO2. The UO2 band calculation reflecting the thermal properties, into account of relativistic effect, have not done yes. So using the RBC the detailed electric structure of UO2 are obtained. (author)

  10. 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.

  11. Band theory of superlattices

    International Nuclear Information System (INIS)

    We present a first-principles theory of the band structure of lattice-matched superlattices. We formulate the one-electron problem of superlattices in the Bloch representation of one of the constituent materials. In this formulation, the symmetry breaking along the superlattice axis leads to partitioning and folding of the original homogeneous crystal Brillouin zone onto a thin region around the center of the zone. A single homogeneous crystal Bloch function becomes a multicomponent wave function. Each component represents a superlattice subband. We use Loewdin's theorem to derive series expressions for the subband energies and wave functions, and discuss the relation between these solutions and the eigenvalues and eigenfunctions corresponding to quantum-well models. We apply the general results to a superlattice composed of two different types of simple two-band model materials

  12. 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...

  13. 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.)

  14. Gutzwiller theory of band magnetism in LaOFeAs

    International Nuclear Information System (INIS)

    For the iron pnictide LaOFeAs we investigate multi-band Hubbard models which are assumed to capture the relevant physics. In our calculations, we employ the Gutzwiller variational theory which is a genuine many particle approach. We will present results both on the paramagnetic and antiferromagnetic phases of our model systems. These results show that a five band-model is not adequate to capture the relevant physics in LaOFeAs. However, our results for the eight band-model which includes the arsenic 4p bands reproduce the experimental data, especially the small magnetic moment, for a broad parameter regime.

  15. 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.

  16. 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

  17. 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.

  18. 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.

  19. 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...

  20. 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)

  1. 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.

  2. Small Quadrupole Deformation for the Dipole Bands in 112In

    CERN Document Server

    Trivedi, T; 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

    2012-01-01

    High spin states in $^{112}$In were investigated using $^{100}$Mo($^{16}$O, p3n) reaction at 80 MeV. The excited level have been observed up to 5.6 MeV excitation energy and spin $\\sim$ 20$\\hbar$ with the level scheme showing three dipole bands. The polarization and lifetime measurements were carried out for the dipole bands. Tilted axis cranking model calculations were performed for different quasi-particle configurations of this doubly odd nucleus. Comparison of the calculations of the model with the B(M1) transition strengths of the positive and negative parity bands firmly established their configurations.

  3. An innovative band-to-band tunneling analytical model and implications in compact modeling of tunneling-based devices

    Science.gov (United States)

    De Michielis, L.; Daǧtekin, N.; Biswas, A.; Lattanzio, L.; Selmi, L.; Luisier, M.; Riel, H.; Ionescu, A. M.

    2013-09-01

    In this paper, an analytical band-to-band tunneling model is proposed, validated by means of drift-diffusion simulation and comparison with experimental data, implemented in Verilog-A, and finally proven with SPICE simulator through simulation of circuits featuring tunneling diodes. The p-n junction current calculation starts from a non-local Band-to-Band tunneling theory including the electron-phonon interaction and therefore it is particularly suited for indirect semiconductor materials such as silicon- or germanium-based interband tunneling devices.

  4. Structures calculation

    International Nuclear Information System (INIS)

    Structures calculation is a research and applications field in permanent evolution thanks to the development of more and more performing computer tools for the modeling and the numerical simulation of complex structures taking into account the behaviour of more and more sophisticated materials. The aim of the Computational Structural Mechanics Association (CSMA) is to develop technical and scientific exchanges between industrial and research partners. This colloquium, organized every 2 years comprises 4 general conferences and 125 communications. Five papers were selected for INIS. Three of them deal with the dynamical modeling of the vibrational behaviour of reactor core components (fuel assemblies and control rod clusters), one concerns the load resistance of multi-perforated metal structures like steam generator tube plates or turbine blades, and the last paper concerns the humidity stability of composite materials used in particle detectors. (J.S.)

  5. Elucidating the stop bands of structurally colored systems through recursion

    CERN Document Server

    Amir, Ariel

    2012-01-01

    Interference phenomena are the source of some of the spectacular colors of animals and plants in nature. In some of these systems, the physical structure consists of an ordered array of layers with alternating high and low refractive indices. This periodicity leads to an optical band structure that is analogous to the electronic band structure encountered in semiconductor physics; namely, specific bands of wavelengths (the stop bands) are perfectly reflected. Here, we present a minimal model for optical band structure in a periodic multilayer and solve it using recursion relations. We present experimental data for various beetles, whose optical structure resembles the proposed model. The stop bands emerge in the limit of an infinite number of layers by finding the fixed point of the recursive relations. In order for these to converge, an infinitesimal amount of absorption needs to be present, reminiscent of the regularization procedures commonly used in physics calculations. Thus, using only the phenomenon of...

  6. Search for positive parity bands in 117Xe

    International Nuclear Information System (INIS)

    Excited states of 117Xe were populated via the reaction 28Si+92Mo at 100-120MeV. More than 40 new ?-transitions and three new positive parity bands have been observed by means of in-beam ?-ray spectroscopy. The previously known ?h11/2 bands were confirmed, and the ?g7/2 favored band was extended up to 47/2+ in which two bandcrossings have been observed at h?=0.33 and 0.44MeV, respectively. The band structures have been discussed by means of TRS and CSM calculations. A newly observed rotational band consisting of five ?-transitions has been considered as the ?h11/2 band of 117Cs. ((orig.))

  7. Multi-quasiparticle isomers and rotational bands in 181 Re

    International Nuclear Information System (INIS)

    High-spin states in 181 Re have been populated using the 176 Yb( 11 B, 6n) reaction and their decays studied using the CAESAR ? -ray spectrometer. Thirteen bands of rotational states have been observed based on 1-, 3- and 5-quasiparticle structures, including two new 5-quasiparticle isomers, with half-lives of 1.2 ?s and 22 ns. Angular correlation and distribution coefficients were obtained and ? -ray intensity ratios were used to extract |gK-gR|/Q0 ratios. Three K -forbidden decays were observed and their reduced hindrance factors were obtained and found to be consistent with known systematic behaviour. Band crossings were observed between 1- and 3-quasiparticle bands. These rotation-aligned 3-quasiparticle bands appear to have high K , and are identified as t -bands. Band mixing calculations support the assigned K -values. A unique degeneracy was observed for two I?=23/2- states at 1883 keV

  8. Rotational and vibrational bands in 108Pd

    Scientific Electronic Library Online (English)

    J.A., Alcntara-Nez; 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.

  9. 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...

  10. 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...

  11. Propagation Energies Inferred from Deformation Bands in Sandstone

    Science.gov (United States)

    Schultz, R. A.; Soliva, R.

    2011-12-01

    The J-integral is used to calculate the band propagation energies Jband for pure and shear-enhanced compaction bands from four sandstones from around the world. The value obtained previously for the Valley of Fire (Utah) site assumed compactional offsets only across the bands; shearing offsets along these and shear-enhanced compaction bands (SECBs) from the Buckskin Gulch (Utah) and the recently reported Boncava quarry near Mornas (France) are consistent with trigonometrically obtained estimates calculated from band thickness and angle to the maximum compressive principal stress. Compactional offsets were calculated from porosity reductions from host rock to band. Cataclastic deformation bands from the Quartier de l'Etang quarry near Orange (France) were also analyzed for comparison with bands having smaller ratios of shear/compaction. Normal and shear stresses resolved across the bands at the time of their formation were estimated from stratigraphic overburden and friction coefficients for porous sandstones measured in the laboratory. Assuming that the SECBs may be characterized by small-scale yielding, so that Jband is equivalent to the strain energy release rate G, the values of Jband can be compared to the previous values. SECBs having strike-slip offsets from Valley of Fire have Jband = 11.1 kJ/m2, consistent with the previously reported range of GIc = 10-60 kJ/m2 calculated by using the J-integral approach by Rudnicki and Sternlof [2005]. Pure compaction bands (PCBs) from the same site have Jband = 5.5 kJ/m2, implying that less work is required to propagate PCBs than SECBs. The value of Jband for the Buckskin Gulch site, 60.5 kJ/m2, is consistent with the lower range of values for strain energy release rate obtained previously, GIc = 55-120 kJ/m2. Band propagation energy for SECBs from the Boncava quarry site, Jband = 16.4 kJ/m2, is comparable to that for similar structures from the Valley of Fire site. Cataclastic deformation bands at the Orange quarry site accommodate much larger values of shear offsets than do SECBs, with ratios of shear to compactional offsets > 5. Jband for these bands, 83.2 kJ/m2, exceeds those for either pure or shear-enhanced compaction bands deformed at approximately the same depth of burial by at least a factor of 5-15. This suggests that approximately an order of magnitude more work is required to propagate cataclastic deformation bands through the finer-grained host rock at the Orange quarry site than to produce SECBs in more poorly consolidated sandstones at the same depth.

  12. 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.

  13. 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.

  14. New Kronig-Penney equation emphasizing the band edge conditions

    International Nuclear Information System (INIS)

    The Kronig-Penney problem is a textbook example for discussing band dispersions and band gap formation in periodic layered media. For example, in photonic crystals, the behaviour of bands next to the band edges is important for further discussions of such effects as inhibited light emission, slow light and negative index of refraction. However, the standard Kronig-Penney equation does not explicitly state the band edge conditions. This paper derives a new solution for the Kronig-Penney problem that explicitly displays the band edge conditions as well as contains all other essential physics of band formation. Therefore, the present exposition should show the student that the band edge conditions are not simply special cases of the familiar Kronig-Penney equation but, instead, are an integral part of the band theory. For the computationally minded student, the new equation is particularly convenient for calculating the positions of closely spaced band edges. The present results can be taught alongside the Kronig-Penney equation in advanced undergraduate or beginning graduate quantum mechanics, solid state theory and photonics courses dealing with wave propagation through periodic layered media

  15. 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)

  16. Ab Initio Calculations of Oxosulfatovanadates

    DEFF Research Database (Denmark)

    Frberg, 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...

  17. 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

  18. 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 ber Himmelsmechanik behandelt deren Formulierung auf der Grundlage der Einsteinschen Gravitationstheorie. Dargestellt werden zunchst die Strukturen der Minkowskischen Raumzeit und ihre Folgen fr die Orts- und Zeitmessung. Anschlieend werden die Einsteinsche Raumzeit durch eine konstruktive Axiomatik begrndet und die Einsteinschen Feldgleichungen aufgestellt. Ausfhrlich werden das Schwarzschild-Problem, lineare und nach-Newtonsche Nherungen der Feld- und Bewegungsgleichungen behandelt. Daran schliet 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-Krper-Problems, die Spin-Bahn-Kopplung, die relativistische Theorie von Rotation und Figur von Krpern ein.

  19. 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.

  20. Shadow bands in the cuprates

    CERN Document Server

    Haas, S W; Dagotto, E; Lab, F; Haas, Stephan; Moreo, Adriana; Dagotto, Elbio; Lab, Field

    1994-01-01

    A consequence of strong antiferromagnetic correlations in models of high-Tc cuprates is the appearance in photoemission (PES) calculations of considerable more weight above the Fermi momentum {\\rm {\\bf p}_F } than expected for non-interacting electrons. This effect, first discussed by Kampf and Schrieffer (Phys. Rev. {\\bf B 41}, 6399 (1990)) under the name of ``shadow bands'', is here analyzed in the two dimensional Hubbard and t-J models using Monte Carlo and exact diagonalization techniques. It is concluded that for underdoped compounds weight above {\\rm {\\bf p}_F } could be observable in experimental PES data, while in the overdoped regime it will be likely hidden in the experimental background. In the intermediate region the signal is weak. Our results are thus compatible with recent experimental data by Aebi et al. (Phys. Rev. Lett. {\\bf 72}, 2757 (1994)) for Bi2212 at optimal doping. However, to definitely prove the existence of this effect in the cuprates, experiments in the underdoped regime are neces...

  1. 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.

  2. 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)

  3. Superfluidity in topologically nontrivial flat bands.

    Science.gov (United States)

    Peotta, Sebastiano; Trm, Pivi

    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

  4. Franck-Condon simulation of the B-A bands of BO

    Science.gov (United States)

    Anti?-Jovanovi?, A.; Kuzmanovi?, M.; Khakoo, M. A.; Laher, R. R.

    2013-12-01

    Franck-Condon simulation of the emission B-A band system of boron monoxide are given. The computed band origin wavenumbers are found to be in good agreement with those derived from measured band head positions. In the absence of intensity measurements for the B-A bands, the simulated intensities were tested by calculation of the relative intensities of the well known A-X bands under the assumption that the electronic transition moment function is constant. The resulting good agreement between the simulated and experimentally obtained intensity patterns for A-X bands supports the reliability of our simulated B-A spectrum.

  5. 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.

  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. Effect of tool eccentricity on surface periodic banded structures in friction stir welding

    Science.gov (United States)

    Guo, N.; Wang, M. R.; Meng, Q.; Zhou, L.; Tang, D. Y.

    2015-12-01

    This paper describes the relationship between tool eccentricity and surface formation of periodic banded structures in friction stir welding. Motion characteristics of welding tool are calculated to explore the forming mechanism of banded structures. The results reveal that the welding tool motion differences on advancing side and retreating side caused by eccentricity are crucial for the formation of banded structures. The crests and troughs of banded structures form during tool motion on retreating side and advancing side, respectively.

  8. Relative spins and excitation energies of superdeformed bands in $^{190}$Hg further evidence for octupole vibration

    CERN Document Server

    Crowell, B; Janssens, R V F; Blumenthal, D J; Wilson, A N; Sharpey-Schafer, J F; Nakatsukasa, T; Ahmad, I; Astier, A; Azaiez, F; Du Croix, L; Gall, B J P; Hannachi, F; Khoo, T L; Korichi, A; Lauritsen, T; Lpez-Martens, A; Meyer, M R; Nisius, D; Paul, E S; Porquet, M G; Redon, N; Crowell, B; Carpenter, M P; Janssens, R V F; Blumenthal, D J; Wilson, A N; Sharpey-Schafer, J F; Nakatsukasa, T; du Croux, L; Gall, B J P; Hannachi, F; Khoo, T L; Korichi, A; Lauritsen, T; Lopez-Martens, A; Meyer, M; Nisius, D; Paul, E S; Porquet, M G; Redon, N

    1994-01-01

    An experiment using the Eurogam Phase II gamma-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 and dipole character of the transitions linking the two SD bands have been firmly established. Comparisons with RPA calculations indicate that the excited SD band can be interpreted as an octupole-vibrational structure.

  9. 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

  10. Flat Bands Under Correlated Perturbations

    OpenAIRE

    Bodyfelt, Joshua D.; Leykam, Daniel; Danieli, Carlo; Yu, Xiaoquan; Flach, Sergej

    2014-01-01

    Flat band networks are characterized by coexistence of dispersive and flat bands. Flat bands (FB) are generated by compact localized eigenstates (CLS) with local network symmetries, based on destructive interference. Correlated disorder and quasiperiodic potentials hybridize CLS without additional renormalization, yet with surprising consequencies: (i) states are expelled from the FB energy $E_{FB}$, (ii) the localization length of eigenstates vanishes as $\\xi \\sim 1 / \\ln (E- E_{FB})$, (iii)...

  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. 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...

  13. 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.

  14. 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.

  15. Nuclear field theory treatment of K not= 0 rotational bands

    International Nuclear Information System (INIS)

    The properties of the lowest members of K not= 0 rotational bands are described as anharmonic vibrational bands. The anharmonicity is calculated by the method called Nuclear Field Theory (particle-vibration coupling). It is shown to be important not to truncate the diagrammatic expansion at a fixed number of vertices. Instead, the way in which the diagrams depend on the number of degrees of freedom participating is used to guide the truncation. (orig.)

  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. 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 ...

  18. 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

  19. Sequential chromosome banding in fishes.

    Czech Academy of Sciences Publication Activity Database

    Rbov, Marie; Vlker, M.; Peliknov, rka; Rb, 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

  20. 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 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. PMID:25635516

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

    CERN Document Server

    Fazekas, S; Kertsz, 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.

  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. 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.

  4. 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.

  5. 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 ZnO 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.

  6. 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...

  7. Superdeformed band in 147Tb

    International Nuclear Information System (INIS)

    A superdeformed band has been observed in the 147Tb nucleus which was produced with the reaction 100Mo(51V,4n)147Tb at a bombarding energy of 230 MeV. The band configuration is assigned as π63ν71 with a total parity and signature of (π,α)=(-,+1/2). copyright 1996 The American Physical Society

  8. 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.

  9. 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.

  10. 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

  11. 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.

  12. 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.

  13. Compatibility of infrared band models with scattering

    Science.gov (United States)

    Reed, R. A.; Brown, D. G.; Hiers, R. S., III; Cromwell, B. K.; Zaccardi, V. A.

    1994-04-01

    Techniques for the computation of radiative heating from aluminized solid propellant rocket exhaust plumes must account for infrared emission and absorption by hot H2O and CO2 in the presence of strong three-dimensional aerosol scattering by micron-sized Al2O3 droplets and particles. Radiative heating computations are usually performed over wide spectral intervals using infrared band models. However, no rigorous extension to infrared band models has been proposed for situations with scattering. Indeed, band models and scattering are widely held to be incompatible. Practical engineering calculations of plume radiative heating have therefore proceeded, using various approximations to the transport equation. Although the errors in these approximations are believed to be reasonably small, they have never been quantified because of the lack of rigorous results. In order to help remedy this deficiency, this article develops two different rigorous solutions. Although they are currently restricted to homogeneous media, they nevertheless provide a previously unavailable means of calibrating code performance and assessing the accuracy of various approximation schemes. Some sample applications are provided for the Space Shuttle Solid Rocket Booster.

  14. Population of rotational bands in superheavy nuclei

    Directory of Open Access Journals (Sweden)

    Antonenko N.V.

    2012-02-01

    Full Text Available Using the statistical approach, we study the population of ground-state rotational bands of superheavy nuclei produced in the fusion-evaporation reactions 208Pb(48Ca, 2n254No, 206Pb(48Ca, 2n252No, and 204Hg(48Ca, 2n250Fm. We calculate relative intensities of E2-transitions between the rotational states and entry spin distributions of the residual nuclei, evaporation residue cross sections, and excitation functions for these reactions. Fermi-gas model is used for the calculation of level density, and damping of shell effects both with excitation energy and angular momentum is taking into account. The results are in a good agreement with the experiment data.

  15. 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.

  16. Integrated calculator programs for pharmacokinetic calculations.

    Science.gov (United States)

    Robb, R A; Bauer, L A; Koup, J R

    1982-05-01

    A package of integrated programs for calculating pharmacokinetic variables and drug-dosing regimens using a hand-held programmable calculator is described. Twelve pharmacokinetic programs, which were based on previously published pharmacokinetic equations, were developed for use in a HP-41C hand-held calculator (Hewlett-Packard). The programs perform, pharmacokinetic calculations for many drugs, including digoxin, theophylline, phenytoin, nd the aminoglycosides. Also programs for ideal body weight, body surface area, and creatinine clearance calculations are included. Eleven of the 12 programs can be stored in the calculator at any time. Values generated in one program are stored in memory registers and can be recalled directly for use in other programs. The calculator has a continuous memory; therefore, all stored data, programs, and functions are maintained when the calculator is turned off. The integrated calculator programs provide a quick and reliable means of applying pharmacokinetic principles to everyday hospital pharmacy practice. PMID:7081256

  17. 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.

  18. Nuclear dissipation and the feeding of superdeformed bands

    International Nuclear Information System (INIS)

    Statistical model calculations including nuclear dissipation were performed to calculate the high-energy ?-ray spectrum following the reaction 16O+159Tb. Including dissipation changes the spin population distribution leading to evaporation residues and fission. The calculations show that a larger fraction of the highest partial waves contributes to evaporation residues than standard statistical model calculations predict (an increase of 65% for spins >65?). This effect is shown to provide an explanation for enhanced feeding of superdeformed bands which are populated by the highest partial waves leading to evaporation residues

  19. Effect of hydrogenation on the band gap of graphene nano-flakes

    International Nuclear Information System (INIS)

    The effects of hydrogenation on the band gap of graphene have been investigated by means of density functional theory method. It is generally considered that the band gap increases with increasing coverage of hydrogen atom on the graphene. However, the present study shows that the band gap decreases first with increasing hydrogen coverage and reaches the lowest value at finite coverage (? = 0.3). Next, the band gap increases to that of insulator with coverage from 0.3 to 1.0. This specific feature of the band gap is reasonably explained by broken symmetry model and the decrease of pi-conjugation. The electronic states of hydrogenated graphene are discussed. - Highlights: Density functional theory calculations were carried out for hydrogen on graphene Effects of hydrogenation on the band gap of graphene were examined. The band gap showed a minimum at a finite coverage. Mechanism of specific band gap feature was discussed

  20. Spin susceptibility of Anderson impurities in arbitrary conduction bands

    Science.gov (United States)

    Fang, Tie-Feng; Tong, Ning-Hua; Cao, Zhan; Sun, Qing-Feng; Luo, Hong-Gang

    2015-10-01

    Spin susceptibility of Anderson impurities is a key quantity in understanding the physics of Kondo screening. Traditional numerical renormalization group (NRG) calculation of the impurity contribution ?imp to susceptibility, defined originally by Wilson in a flat wide band, has been generalized before to structured conduction bands. The results brought about non-Fermi-liquid and diamagnetic Kondo behaviors in ?imp, even when the bands are not gapped at the Fermi energy. Here, we use the full density-matrix (FDM) NRG to present high-quality data for the local susceptibility ?loc and to compare them with ?imp obtained by the traditional NRG. Our results indicate that those exotic behaviors observed in ?imp are unphysical. Instead, the low-energy excitations of the impurity in arbitrary bands only without gap at the Fermi energy are still a Fermi liquid and paramagnetic. We also demonstrate that unlike the traditional NRG yielding ?loc less accurate than ?imp, the FDM method allows a high-precision dynamical calculation of ?loc at much reduced computational cost, with an accuracy at least one order higher than ?imp. Moreover, artifacts in the FDM algorithm to ?imp and origins of the spurious non-Fermi-liquid and diamagnetic features are clarified. Our work provides an efficient high-precision algorithm to calculate the spin susceptibility of impurity for arbitrary structured bands, while negating the applicability of Wilson's definition to such cases.

  1. Band gap anomaly and topological properties in lead chalcogenides

    Science.gov (United States)

    Simin, Nie; Xiao, Yan Xu; Gang, Xu; Zhong, Fang

    2016-03-01

    Band gap anomaly is a well-known issue in lead chalcogenides PbX (X = S, Se, Te, Po). Combining ab initio calculations and tight-binding (TB) method, we have studied the band evolution in PbX, and found that the band gap anomaly in PbTe is mainly related to the high on-site energy of Te 5s orbital and the large s–p hopping originated from the irregular extended distribution of Te 5s electrons. Furthermore, our calculations show that PbPo is an indirect band gap (6.5 meV) semiconductor with band inversion at L point, which clearly indicates that PbPo is a topological crystalline insulator (TCI). The calculated mirror Chern number and surface states double confirm this conclusion. Project supported by the National Natural Science Foundation of China (Grant No. 11204359), the National Basic Research Program of China (Grant No. 2013CB921700), and the Strategic Priority Research Program (B) of the Chinese Academy of Sciences (Grant No. XDB07020100).

  2. Study of intruder band in 112Sn

    International Nuclear Information System (INIS)

    Excited states of the positive-parity intruder band in 112Sn, populated in the 100Mo(20Ne,?4n) reaction at a beam energy of 136 MeV, have been studied. The band has been observed up to 11570.0 keV with spin (24+). Mean lifetimes have been measured for six states up to the 22+, 10335.1 keV level and an upper limit of the lifetime has been estimated for the 11570.0 keV (24+) state. The B(E2) values, derived from the present lifetime results, correspond to a moderate quadrupole deformation of ?2?0.18 for states with spin J?>=12+, and the decrease in B(E2) for the 14+->12+ transition is consistent with a ?(h11/2)2 alignment at ??0.35 MeV, predicted by a cranked shell-model calculation. Total Routhian surface calculations predict a triaxial shape following the alignment

  3. 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.

  4. 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....

  5. 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)

  6. 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.)

  7. Superdeformed bands of odd nuclei in A=190 region in the quasiparticle picture

    International Nuclear Information System (INIS)

    Properties of the superdeformed (SD) bands of 195Pb and 193Hg have been studied by the cranked Hartree-Fock-Bogoliubov method. The calculations reproduce the flat behavior of the dynamical moment of inertia of two of the SD bands of 195Pb measured recently. Possible configuration assignments for the observed bands 3 and 4 of 195Pb are discussed. The two interacting SD bands of 193Hg have also been calculated. The analysis confirms the superiority of a density-dependent pairing force over a seniority pairing interaction. (author)

  8. 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.

  9. 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.

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

    Science.gov (United States)

    Wang, Fenggong; Grinberg, Ilya; Rappe, Andrew M.

    2014-04-01

    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.

  11. 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.

  12. Multiple triaxial bands and abnormal signature inversion in 7433As

    International Nuclear Information System (INIS)

    Excited states of the oddodd nucleus 74As have been investigated via heavy ion fusion evaporation reaction 70Zn(7Li,3n)74As at beam energy of 30 MeV. The properties of the positive- and the negative- parity bands can be interpreted in terms of the Cranked NilssonStrutinsky (CNS) model calculations which show that the observed bands are built on the triaxial deformed shape. The inversion of the favored and unfavored signature branches observed in the positive-parity bands presents at high spins rather than normal signature inversion occurs at low spins. This phenomenon may be explained as the origin of unpaired band crossing in a highly rotating triaxial nucleus.

  13. Band structure in the doubly magic nucleus 56Ni

    International Nuclear Information System (INIS)

    Band structures near yrast lines of the Z=N doubly magic nucleus 56Ni are investigated with the configuration-dependent cranked Nilsson-Strutinsky approach. The observed deformed bands are confirmed as highly deformed and their properties are explained theoretically. The calculated transition quadrupole moments Qt, ?1.7 eb at low spin as well as the kinematic and dynamic moments of inertia J(1) and J(2) for configurations of interest are found to be generally in good agreement with the observed results. Two terminating states at 20+ and 29- for the two observed bands and other terminations in 56Ni are also predicted. It is found that the configuration-dependent cranked Nilsson-Strutinsky approach is better in the description of nuclear properties and band structures at high spin than other models. (author)

  14. 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

  15. 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=1.141021cm-3 or 7.210-2 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.

  16. 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...

  17. 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, 31123115 (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.

  18. 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.

  19. Description of Properties of Triaxial Superdeformed Bands in Odd-A Lu Isotopes

    International Nuclear Information System (INIS)

    Properties of the triaxial superdeformed (TSD) bands of odd-A Lu isotopes are investigated systematically within the supersymmetry scheme including many-body interactions and a perturbation possessing the SO(5) (or SU(5)) symmetry on the rotational symmetry. Quantitatively good results of the ?-ray energies, the dynamical moments of inertia and the spin of the TSD bands in odd-A Lu isotopes are obtained. The calculation shows that the competition between the pairing and anti-pairing effects exists in these TSD bands. Meanwhile, the SU(3) symmetry in TSD bands are broken more seriously than in superdeformed (SD) bands. (nuclear physics)

  20. Description of the triaxial strongly deformed bands in 160,161Tm and 163Tm

    International Nuclear Information System (INIS)

    Properties of the triaxial strongly deformed (TSD) bands of 160,161Tm and 163Tm are investigated systematically within the supersymmetry scheme including many-body interactions and a perturbation possessing SO(5) (or SU(5)) symmetry on the rotational symmetry. Quantitatively good results of the ?-ray energies, the dynamical moments of inertia and the spin of the TSD bands in 160,161Tm and 163Tm are obtained. The calculation shows that competition between the pairing and anti-pairing effects exist in these TSD bands. Meanwhile, the SU(3) symmetry in TSD bands is broken more seriously than that in superdeformed bands. (authors)

  1. Interface termination and band alignment of epitaxially grown alumina films on Cu-Al alloy

    Science.gov (United States)

    Yoshitake, Michiko; Song, Weijie; Libra, Ji?; Maek, Karel; utara, Frantiek; Matoln, Vladimr; Prince, Kevin C.

    2008-02-01

    Epitaxial ultrathin alumina films were grown on a Cu-9 at. % Al(111) substrate by selective oxidation of Al in the alloy in ultrahigh vacuum. The photoelectron spectra of Al 2p and valence band were measured in situ during oxidation. By analyzing multiple peaks of Al 2p, the interface atomic structure was discussed. The energy difference between the Fermi level of the substrate and the valence band maximum of alumina (band offset) was obtained. The relation between the interface atomic structure and the band offset was compared with the reported first-principles calculations. A novel method for controlling the band offset was proposed.

  2. Valence band excitations in $V_{2}O_{5}$

    CERN Document Server

    Atzkern, S; Knupfer, M; Golden, M S; Fink, J; Yaresko, A N; Antonov, V N; Klemm, M; Horn, S

    1999-01-01

    We present a joint theoretical and experimental investigation of the electronic and optical properties of vanadium pentoxide. Electron energy-loss spectroscopy in transmission was employed to measure the momentum-dependent loss function. This in turn was used to derive the optical conductivity, which is compared to the results of band structure calculations. A good qualitative and quantitative agreement between the theoretical and the experimental optical conductivity was observed. The experimentally observed anisotropy of the optical properties of V_2O_5 could be understood in the light of an analysis of the theoretical data involving the decomposition of the calculated optical conductivity into contributions from transitions into selected energy regions of the conduction band. In addition, based upon a tight binding fit to the band structure, values are given for the effective V3d_xy-O2p hopping terms and are compared to the corresponding values for alpha'-NaV_2O_5.

  3. 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.

  4. Dosimetry of narrow band UVB treatments

    International Nuclear Information System (INIS)

    Full text: For many years psoriasis has been treated with broad band UVB lamps. These lamps have a bell shaped spectrum which peaks at 305 nm and extends from 280 nm to 350 nm. However research with monochromatic UV radiation has shown that wavelengths between 300 nm and 320 nm are the most efficacious for clearing psoriasis while wavelengths below 305 nm are most effective for producing the undesirable side effect of erythema (sunburn). In response to these findings Philips developed a narrow band UVB tube in which a large fraction of the output was confined to a narrow peak (bandwidth 2.5 nm) situated at 311 nm. Christchurch Hospital replaced broad band UVB with narrow band treatments in August 1995 and as this required UV exposures to be substantially increased new protocols had to be developed. Three aspects needed to be addressed. These were translating the dose from broad band to narrow band for current patients, determining the initial dose for new patients and developing a formula for increasing subsequent exposures to both types of patient. To translate doses the spectral irradiance (μW/cm2/nm) that would fall on the patient was measured in both the old broad band and the new narrow band treatment units and from this UV doses were calculated. All doses were expressed in mJ/cm2 of unweighted UV over the range 250 nm to 400 nm. The erythemal effectiveness of the two units were compared by using the CIE 1987 curve to express doses in terms of the equivalent exposure of monochromatic 297 nm radiation. It was found that an exposure of 3.96 mJ/cm2 from the broad band FS40 tubes and 12.79 mJ/cm2 from the narrow band TL/01 tubes were both equivalent to 1.00 mJ/cm2 of monochromatic 297 nm radiation so when transferring patients all broad band doses needed to be increased by a factor of 3.2. Before transferring any patients this factor was confirmed by conducting two minimal erythema dose (MED) tests on a normal subject, one in each unit. For new patients a narrow band treatment schedule has been developed which is based on the patient' s MED. Before commencing treatments the patient is given an MED test using untanned skin on the inner surface of the forearm. The initial dose is 70% of the MED and each subsequent exposure is increased by a constant increment, namely 21.4% of the initial dose. This progression continues until the dose reaches three times the MED at which time it is held constant. Treatments are given twice per week up to a maximum of 30 treatments or until the psoriasis clears. If mild erythema occurs the next treatment is held at the previous dose while for more severe erythema it is missed entirely. This schedule is similar to the one in use at The Royal Victoria Infirmary, Newcastle upon Tyne, but with two minor exceptions. In Newcastle the increments are larger (on average 45% of the initial dose) but they only occur once a week. The transfer from broad band to narrow band was accomplished successfully without any incidence of erythema. After four months experience the 31 patients who were currently following the MED based protocol were reviewed. The lowest MED measured was 500 mJ/cm2 while the highest (three in number) exceeded 1110 mJ/cm2. Eleven of the patients exhibited erythema at some point in their treatment but it was only necessary to reduce the dose increment in one case. Of the remaining 20 patients, 13 who showed poor clearing of their psoriasis were placed on a dose schedules in which the dose increments were increased by between 20 % to 33%. In view of the fact almost equal numbers of patients received too large or too small a dose the schedule can be considered to be a good compromise

  5. 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.

  6. 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.

  7. 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.

  8. 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

  9. New low-energy levels calculation for 155Eu

    Scientific Electronic Library Online (English)

    F. A., Genezini; C. B., Zamboni; J., Mesa; M. T. F. da, Cruz.

    2005-09-01

    Full Text Available We have revisited the low-energy calculation of odd Z 155Eu in the frame of a semi-microscopic formalism as a support for the interpretation of the experimental results for the multipole mixing ratios of some electromagnetic transitions. The deformation parameters were obtained through a macroscopic [...] -microscopic method, and the proton single particle levels, calculated with realistic Woods-Saxon potential were used as input in a quasi-particle calculation of the first few rotational band heads in the Lipkin-Nogami BCS aproximation. A better agreement is found between the experimental and calculated band heads if compared with previous evaluations and RIPL recommended values.

  10. 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

  11. 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

  12. 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.

  13. '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.

  14. Quasiparticle Band Gap Renormalization in Doped Two-Dimensional Materials

    Science.gov (United States)

    Liang, Yufeng; Yang, Li

    2015-03-01

    Recently, atomically thin two-dimensional (2D) materials have emerged as new prototypes for a variety of electronic and optoelectronic devices, for which charge carrier doping is an effective approach for modifying their intrinsic properties. In the process of producing monolayer metal dichalcogenides, doping can occur naturally and may lead to exotic many-body phenomena as evidenced in recent optical experiments. Despite the common occurrence of doping in 2D structures, little knowledge has been obtained for the evolution of the band gap with the carrier concentration, which is key to harnessing the electronic properties and understanding more complicated many-body effects. Here, we investigate how the band gap changes with doping density in various 2D structures. Based on the conventional GW method for semiconductors, we devised and implemented an efficient calculation scheme to capture the unique dielectric screening arising from intraband transitions in low-dimensional structures, specifically MoS2 and MoSe2. We reveal that an enhanced band gap renormalization of a few hundred meV can be achieved and the band gap evolution displays an unusual nonlinear behavior with doping density. Our calculated band gap is in excellent agreement with the recent ARPES experiments on MoSe2. This work is supported by NSF DMR-1207141 and was done at Washington University.

  15. X-Band PLL Synthesizer

    OpenAIRE

    P. Kutin; Vagner, P.

    2006-01-01

    This paper deals with design and realization of a PLL synthesizer for the microwave X−band. The synthesizer is intended for use as a local oscillator in a K−band downconverter. The design goal was to achieve very low phase noise and spurious free signal with a sufficient power level. For that purpose a low phase noise MMIC VCO was used in phase locked loop. The PLL works at half the output frequency, therefore there is a frequency doubler at the output of the PLL. The output signal ...

  16. Nonequilibrium Green's function formulation of intersubband absorption for nonparabolic single-band effective mass Hamiltonian

    Science.gov (United States)

    Kolek, Andrzej

    2015-05-01

    The formulas are derived that enable calculations of intersubband absorption coefficient within nonequilibrium Green's function method applied to a single-band effective-mass Hamiltonian with the energy dependent effective mass. The derivation provides also the formulas for the virtual valence band components of the two-band Green's functions which can be used for more exact estimation of the density of states and electrons and more reliable treatment of electronic transport in unipolar n-type heterostructure semiconductor devices.

  17. 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.

  18. 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.

  19. Comparing C- and L-band SAR images for sea ice motion estimation

    Science.gov (United States)

    Lehtiranta, J.; Siiri, S.; Karvonen, J.

    2015-02-01

    Pairs of consecutive C-band synthetic-aperture radar (SAR) images are routinely used for sea ice motion estimation. The L-band radar has a fundamentally different character, as its longer wavelength penetrates deeper into sea ice. L-band SAR provides information on the seasonal sea ice inner structure in addition to the surface roughness that dominates C-band images. This is especially useful in the Baltic Sea, which lacks multiyear ice and icebergs, known to be confusing targets for L-band sea ice classification. In this work, L-band SAR images are investigated for sea ice motion estimation using the well-established maximal cross-correlation (MCC) approach. This work provides the first comparison of L-band and C-band SAR images for the purpose of motion estimation. The cross-correlation calculations are hardware accelerated using new OpenCL-based source code, which is made available through the author's web site. It is found that L-band images are preferable for motion estimation over C-band images. It is also shown that motion estimation is possible between a C-band and an L-band image using the maximal cross-correlation technique.

  20. 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}.

  1. 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.

  2. Cold versus hot shear banding in bulk metallic glass

    Science.gov (United States)

    Cheng, Y. Q.; Han, Z.; Li, Y.; Ma, E.

    2009-10-01

    We present an analysis of the shear-banding dynamics in a bulk metallic glass (BMG), including the temperature rise in the band, the sliding speed of the band, and the time elapsed as well as the step size of the shear offset growth in a stop-and-go cycle. This model analysis quantitatively demonstrates that the major shear band can remain cold and slide in a stick-slip manner. We predict that the shear step (distance covered by a stop-and-go cycle) scales with the sample size and machine stiffness. We also illustrate the conditions when such serrated shear is unsustainable and a hot shear band directly develops in a runaway instability (catastrophe). These findings provide physical insight into the shear-instability processes and offer useful information for improving the plasticity of BMGs. The calculation results are used to explain several intriguing recent experimental observations, including the stick slip of the dominant shear-band and the sample-size effects on the plastic-flow behavior of BMGs.

  3. Configuration-dependent bands in {sup 169}Re

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, X.H.; Zhang, Y.H.; Zheng, Y.; Xu, Y.B. [Institute of Modern Physics, Chinese Academy of Sciences, 730000, Lanzhou (China); Oshima, M.; Toh, Y.; Koizumi, M.; Osa, A.; Hayakawa, T.; Hatsukawa, Y.; Shizuma, T. [Japan Atomic Energy Research Institute, 319-1195, Ibaraki, Tokai (Japan); Xu, F.R. [Department of Technical Physics and MOE Key Laboratory, Peking University, 100871, Beijing (China); Sugawara, M. [Chiba Institute of Technology, 275-0023, Chiba, Narashino (Japan)

    2004-01-01

    High-spin states in {sup 169}Re were studied and resulted in the identification of a strongly coupled band based on the 9/2{sup -}[514] Nilsson state and a decoupled band built on the h{sub 9/2} 1/2{sup -}[541] intruder proton orbit. The cranked-shell-model calculations present configuration-dependent deformations that can explain the different band crossing frequencies. The 9/2{sup -}[514] band in {sup 169}Re shows the largest signature splitting at low spin among the known odd-mass Re isotopes. After the alignment of a pair of i{sub 13/2} neutrons, the phase of the splitting is inverted with a significantly reduced amplitude. For the 9/2{sup -}[514] bands in light odd-A Re isotopes, the signature splitting of the Routhians and its relation with the signature dependence of M1 transition matrix elements are investigated in connection with the deviation of nuclear shape from axial symmetry, suggesting an appreciable negative {gamma} deformation for the very neutron-deficient odd-A Re isotopes. Additionally, a three-quasiparticle band was observed and assigned to be built likely on the {pi}9/2{sup -}[514] x AE configuration. (orig.)

  4. 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 ...

  5. Hypersonic crystal band gaps in Ni/Cu superlattice nanowire arrays

    Science.gov (United States)

    Hu, Jia-Guang; Shen, Tie

    2016-03-01

    The hexagonal and tetragonal ordered arrays were prepared by Ni/Cu superlattice nanowires on the porous anodic alumina membrane template, and their phonon band structures were calculated by using the plane wave expansion method. Numerical results show that the hypersonic band gaps can be acquired by adjusting the structural parameters. Along the different wave-vector directions, the width and position of band gap would vary. If the nanowires'filling fraction is increased continuously, the width of the first band gap firstly increases and then decreases within a certain range. The height of superlattice nanowire elementary unit can only affect the width of band gap within a quite narrow range. When the height of elementary unit remains unchanged, the decrease of the Cu-component ratio can contribute to the formation of a wider band gap. Additionally, the wide band gap is more easily formed in tetragonal structure than in hexagonal structure.

  6. X-ray aided permeability computations inside compaction bands in sandstones

    Science.gov (United States)

    Andrade, J.; Lenoir, N.; Sun, W.; Rudnicki, J. W.

    2009-12-01

    This work presents preliminary data on permeability calculations using 3D X-ray tomography images taken inside and outside compaction bands. Aztec sandstone samples are taken from the Valley of Fire in Nevada and are scanned using the synchrotron APS facility at Argonne National Laboratory. The 3D microstructures inside and outside the compaction bands, formed in situ, are then used to perform lattice Boltzmann computations to estimate the components of permeability in different principal directions. We show that i) the permeability component in the direction perpendicular to the compaction band is reduced by orders of magnitude in the presence of a compaction band, ii) inside the compaction band, there is a strong anisotropy manifested by the permeability tensor, and iii) the Kozeny-Carman relation does a pretty good job at estimating the permeability outside of the compaction band, but fails to estimate the reduction in permeability in the presence of compaction bands.

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

    OpenAIRE

    Aguilera Bonet, Irene; Palacios Clemente, Pablo; Wahnn 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 electronhole pairs respect to a conventional semiconductor. This could ideally result in ...

  8. Acoustic band pinning in the phononic crystal plates of anti-symmetric structure

    International Nuclear Information System (INIS)

    Acoustic bands are studied numerically for a Lamb wave propagating in an anti-symmetric structure of a one-dimensional periodic plate by using the method of supercell plane-wave expansion. The results show that all the bands are pinned in pairs at the Brillouin zone boundary as long as the anti-symmetry remains and acoustic band gaps (ABGs) only appear between certain bands. In order to reveal the relationship between the band pinning and the anti-symmetry, the method of eigenmode analysis is introduced to calculate the displacement fields of different plate structures. Further, the method of harmony response analysis is employed to calculate the reference spectra to verify the accuracy of numerical calculations of acoustic band map, and both the locations and widths of ABGs in the acoustic band map are in good agreement with those of the reference spectra. The investigations show that the pinning effect is very sensitive to the anti-symmetry of periodic plates, and by introducing different types of breakages, more ABGs or narrow pass bands will appear, which is meaningful in band gap engineering. (condensed matter: structural, mechanical, and thermal properties)

  9. Elucidating the Band Gap of Niobium Dioxide

    Science.gov (United States)

    O'Hara, Andrew; Vigil-Fowler, Derek; Louie, Steven G.; Demkov, Alexander A.

    2015-03-01

    Like VO2, niobium dioxide (NbO2) belongs to the family of transition metal oxides with a temperature-driven metal-to-insulator transition. However, NbO2 has received considerably less attention, and several open questions about the material remain. One such question, of both practical and fundamental importance, is the nature and size of the band gap in the low-temperature, distorted rutile phase with a range reported for the gap of 0.5 eV to 1.2 eV. In this work, we investigate the low-temperature phase, utilizing several methodologies - density functional theory within the standard local density approximation (LDA), LDA +U, hybrid functional, and the GW approximation, to better understand the physics of the band gap in NbO2. Comparisons of the calculations are made to recent experimental work on NbO2 utilizing photoemission spectroscopy and ellipsometry. This work is supported by DOE under the SciDAC program, the NSF, and SRC.

  10. 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.

  11. 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.

  12. 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.

  13. Multiple chiral doublet bands of identical configuration in 103Rh

    CERN Document Server

    Kuti, I; Timar, J; Sohler, D; Zhang, S Q; Zhang, Z H; Zhao, P W; Meng, J; Starosta, K; Koike, T; Paul, E S; Fossan, D B; Vaman, C

    2014-01-01

    Three sets of chiral doublet band structures have been identified in the 103Rh nucleus. The properties of the observed chiral doublet bands are in good agreement with theoretical results obtained using constrained covariant density functional theory and particle rotor model calculations. Two of them belong to an identical configuration, and provide the first experimental evidence for a novel type of multiple chiral doublets, where an "excited" chiral doublet of a configuration is seen together with the "yrast" one. This observation shows that the chiral geometry in nuclei can be robust against the increase of the intrinsic excitation energy.

  14. Correlation Effects in Auger CVV Spectra from Partially Filled Bands

    Science.gov (United States)

    Cini, Michele

    1992-01-01

    Auger Line Shape Analysis from solids with open bands has been made considerable progress in recent years. Calculations on Graphite and Pd were encouraging, and new developements in the formalism look promising. However, it must be recognized that the current theory remains much more phenomenological and less predictive and reliable than it is for closed bands. In some sense, the comparison with experiments is more succcesful than our real understanding deserves. This is hardly surprising, in view of the much more fundamental character of the problems involved. An attempt will be made to assess the present state of the theory and foreshadow the directions of future research.

  15. C-band wavelength conversion in silicon photonic wire waveguides

    Science.gov (United States)

    Espinola, Richard L.; Dadap, Jerry I.; Osgood, Richard M., Jr.; McNab, Sharee J.; Vlasov, Yurii A.

    2005-05-01

    We demonstrate C-band wavelength conversion in Si photonic-wire waveguides with submicron cross-section by means of nonresonant, nondegenerate four-wave mixing (FWM) using low-power, cw-laser sources. Our analysis shows that for these deeply scaled Si waveguides, FWM can be observed despite the large phase mismatch imposed by strong waveguide dispersion. The theoretical calculations agree well with proof-of-concept experiments. The nonresonant character of the FWM scheme employed allows to demonstrate frequency tuning of the idler from ~ 20 GHz to > 100 GHz thus covering several C-band DWDM channels.

  16. 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.

  17. Electronic Band Structure and Magnetism of Cu2Sb-TYPE Transition-Metal Compounds

    Science.gov (United States)

    Shirai, Masafumi; Motizuki, Kazuko

    1993-03-01

    The following sections are included: * Introduction * Procedure of Band Calculation * Non-magnetic Band * Ferrimagnetic Mn2Sb * Ferromagnetic MnAlGe and MnGaGe * Antiferromagnetic Cr2As, Mn2As, Fe2As * Comparison with Photoemission and Inverse Photoemission Spectra * Acknowledgments * References

  18. 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

  19. 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.

  20. Resistive band for turbomachine blade

    Energy Technology Data Exchange (ETDEWEB)

    Roberts, Herbert Chidsey; Taxacher, Glenn Curtis

    2015-08-25

    A turbomachine system includes a rotor that defines a longitudinal axis of the turbomachine system. A first blade is coupled to the rotor, and the first blade has first and second laminated plies. A first band is coupled to the first blade and is configured to resist separation of the first and second laminated plies.

  1. Correlations in a band insulator.

    Czech Academy of Sciences Publication Activity Database

    Sentef, M.; Kune, 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

  2. 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

  3. Metaphyseal bands in osteogenesis imperfecta

    Directory of Open Access Journals (Sweden)

    Suresh S

    2010-01-01

    Full Text Available An increasing number of patients with osteogenesis imperfecta are undergoing pamidronate therapy to prevent the incidence of fragility fractures. The authors herein report a child aged 3 years who received five cycles of pamidronate, resulting in metaphyseal bands, known as "zebra lines."

  4. Metaphyseal bands in osteogenesis imperfecta

    OpenAIRE

    Suresh S.; Thomas John

    2010-01-01

    An increasing number of patients with osteogenesis imperfecta are undergoing pamidronate therapy to prevent the incidence of fragility fractures. The authors herein report a child aged 3 years who received five cycles of pamidronate, resulting in metaphyseal bands, known as "zebra lines."

  5. Band structure and nuclear dynamics

    International Nuclear Information System (INIS)

    The relation between the Variable Moment of Inertia model and the Interacting Boson Model are discussed from a phenomenological viewpoint. New results on ground state mean-square radii in nuclei far from stability are reported, and a discussion of band structure extending to high angular momentum states and methods of extracting information on the underlying dynamics is given

  6. Study of low-lying band structure of transitional nuclei using Particle-rotor model - 109Sb

    International Nuclear Information System (INIS)

    Calculation of the low-lying band structure of 109Sb using PRM show that there is an onset of collectivity in comparison to the primarily spherical Sn nuclei. The band structure under investigation are based on pure configuration with no admixture. The calculation was pursued with complete attenuation of Coriolis interaction. The nuclei is observed to behave like a soft rotor

  7. Electronic band gaps of diamond nanowires

    Science.gov (United States)

    Barnard, A. S.; Russo, S. P.; Snook, I. K.

    2003-12-01

    Recent advances in the fabrication and characterization of semiconductor and metallic nanowires are proving very successful in meeting the high expectations of nanotechnologists. Although diamond has been found to possess remarkable electronic and chemical properties, development of diamond nanowires has been slow. Successes in this are expected to increase, making a description of the electronic properties of diamond nanowires of significant importance. In an attempt to predict the electronic properties of diamond nanowires, we have used ab initio techniques to calculate the electronic density of states of stable diamond nanowires, with cubic and dodecahedral surface facets. Our results indicate that the energy band gap of diamond nanowires is significantly reduced, due to the contributions from occupied and unoccupied surface states. This reduction is shown to be dependent on the nanowire diameter, surface morphology, and surface hydrogenation.

  8. Dual-Band Tunable Recursive Active Filter

    OpenAIRE

    Segovia Vargas, Daniel; Garca Prez, Oscar Alberto; Gonzlez 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.

  9. 47 CFR 90.531 - Band plan.

    Science.gov (United States)

    2010-10-01

    ... 47 Telecommunication 5 2010-10-01 2010-10-01 false Band plan. 90.531 Section 90.531...-805 MHz Bands 90.531 Band plan. This section sets forth the band plan for the 763-775 MHz and 793... and portables subject to Commission-approved regional planning committee regional plans....

  10. 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.)

  11. 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...

  12. Photonic band gaps of a two-dimensional square lattice composed by superconducting hollow rods

    Energy Technology Data Exchange (ETDEWEB)

    Diaz-Valencia, B.F., E-mail: brayanfdv@gmail.com; Calero, J.M.

    2014-10-15

    Highlights: The photonic band structures for hollow superconducting cylinders were calculated. New photonic band gaps were finded in comparison with solid superconducting rods. The quantity of photonic band gaps can be modulated by means of the width of shell. The photonic band gaps can be shifted by means of the system temperature. The ratio gapmidgap show the behavior of band gaps with the increasing of the inner radius. - Abstract: In this paper by means of the plane wave expansion method, we have calculated the photonic band structure of 2D photonic crystals consisting of high temperature superconducting hollow cylinders arranged in a square lattice. Band structures were obtained at low frequencies and assuming TM polarization of the incident wave, for different inner radii of the cylinders and for two different temperatures (5 K and 15 K), showing the tunability of photonic band gaps with respect to these parameters. Interesting features, such as the decreasing of cutoff frequency and separation of photonic modes were observed by increasing both the temperature and inner radius. Permittivity contrast and the difference between the inner and outer radius lead to the appearance of new band gaps when compared with the case of solid cylinders. These band gaps can be modulated by the width of the shell and temperature, which may be used for the development of novel optical devices.

  13. Photonic band gaps of a two-dimensional square lattice composed by superconducting hollow rods

    International Nuclear Information System (INIS)

    Highlights: • The photonic band structures for hollow superconducting cylinders were calculated. • New photonic band gaps were finded in comparison with solid superconducting rods. • The quantity of photonic band gaps can be modulated by means of the width of shell. • The photonic band gaps can be shifted by means of the system temperature. • The ratio gap–midgap show the behavior of band gaps with the increasing of the inner radius. - Abstract: In this paper by means of the plane wave expansion method, we have calculated the photonic band structure of 2D photonic crystals consisting of high temperature superconducting hollow cylinders arranged in a square lattice. Band structures were obtained at low frequencies and assuming TM polarization of the incident wave, for different inner radii of the cylinders and for two different temperatures (5 K and 15 K), showing the tunability of photonic band gaps with respect to these parameters. Interesting features, such as the decreasing of cutoff frequency and separation of photonic modes were observed by increasing both the temperature and inner radius. Permittivity contrast and the difference between the inner and outer radius lead to the appearance of new band gaps when compared with the case of solid cylinders. These band gaps can be modulated by the width of the shell and temperature, which may be used for the development of novel optical devices

  14. 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.

  15. Electronic band structures of binary skutterudites

    International Nuclear Information System (INIS)

    The electronic properties of complex binary skutterudites, MX3 (M = Co, Rh, Ir; X = P, As, Sb) are explored, using various density functional theory (DFT) based theoretical approaches including Green's Function (GW) as well as regular and non-regular Tran Blaha modified Becke Jhonson (TB-mBJ) methods. The wide range of calculated bandgap values for each compound of this skutterudites family confirm that they are theoretically as challenging as their experimental studies. The computationally expensive GW method, which is generally assume to be efficient in the reproduction of the experimental bandgaps, is also not very successful in the calculation of bandgaps. In this article, the issue of the theoretical bandgaps of these compounds is resolved by reproducing the accurate experimental bandgaps, using the recently developed non-regular TB-mBJ approach, based on DFT. The effectiveness of this technique is due to the fact that a large volume of the binary skutterudite crystal is empty and hence quite large proportion of electrons lie outside of the atomic spheres, where unlike LDA and GGA which are poor in the treatment of these electrons, this technique properly treats these electrons and hence reproduces the clear electronic picture of these compounds. - Highlights: • Theoretical and experimental electronic band structures of binary skutterudites are reviewed. • The literature reveals that none of the existing theoretical results are consistent with the experiments. • GW, regular and non-regular TB-mBJ methods are used to reproduce the correct results. • The GW and regular TB-mBJ results are better than the available results in literature. • However, non-regular TB-mBJ reproduces the correct experimental band structures

  16. 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

  17. Yrast bands in 117I and 116-118Xe: Anomalous quasiparticle alignment frequencies and band termination

    International Nuclear Information System (INIS)

    The yrast bands of neutron-deficient 117I and 116Xe have been extended to I?34?, and 117,118Xe to I?46?, using highfold ?-ray coincidence data collected with the Eurogam II spectrometer. Systematic quasiparticle alignment frequencies are discussed and compared to theoretical cranked Woods-Saxon calculations. The first pair alignment is attributed to h11/2 protons despite theoretical expectations for h11/2 neutron alignment; the neutron alignment appears significantly delayed. At higher spins, the 117I and 117Xe isobars exhibit contrasting forms of band termination

  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. 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.

  20. Microscopic study of superdeformed rotational bands in {sup 151} Tb

    Energy Technology Data Exchange (ETDEWEB)

    El Aouad, N.; Dudek, J.; Li, X.; Luo, W.D.; Molique, H.; Bouguettoucha, A.; Byrski, TH.; Beck, F.; Finck, C.; Kharraja, B. [Strasbourg-1 Univ., 67 (France). Centre de Recherches Nucleaires; Dobaczewski, J. [Warsaw Univ. (Poland); Kharraja, B. [Notre Dame Univ., IN (United States). Dept. of Physics

    1996-12-31

    Structure of eight superdeformed bands in the nucleus {sup 151}Tb 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{sup (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). 60 refs.

  1. Collective band properties in actinide nuclei well deformed

    International Nuclear Information System (INIS)

    In actinides, proton i13/2 orbitals and neutron j15/2 orbitals are both near Fermi surface. At a great rotation speed, driving and Coriolis forces change the surface forces, in particular, they lower pairing forces inside the nucleus. The use of Coulomb excitation with the help of heavy and very heavy projectiles such as 32S, 84Kr, 142Nd, 208Pb at 232Th together with the most recent techniques of spectroscopy allowed to populate yrast bands of 230Th, 232Th, 235U and 237Np nuclei up to high spin states and together the even-even nuclei states in different collective bands. Experimental results have been analyzed in the frame of the different current models. The low spin states of rotational bands have been reproduced in a previous calculation using the nucleon-nucleon effective interaction of Skyrme III

  2. 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

  3. 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 insulatora new class of magnetic material that should display both a magnon Hall effect and protected chiral edge modes.

  4. 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)

  5. Photo field emission spectroscopy of the tantalum band structure

    International Nuclear Information System (INIS)

    Photo field emission (PFE) currents of clean and barium covered tantalum tips have been measured with single lines of the mercury arc spectrum and phase-sensitive detection. Field strength and work function were determined from Fowler-Nordheim plots of the FE currents. Shoulders in the PFE current-voltage characteristics could be correlated to transitions in the band structure of tantalum according to a recently proposed two-step PFE model. A comparison with the relativistic calculations of Mattheiss and the nonrelativistic bands of Petroff and Viswanathan shows that Mattheiss' bands are more appropriate. Beside direct transitions several nondirect transitions from the different features composing the upper two density of states maxima below the Fermi edge of tantalum have been found. (Auth.)

  6. 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.

  7. 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...

  8. 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.

  9. 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.

  10. 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.

  11. 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 (> 200 nm) can be explained qualitatively in terms of decreasing grain boundary barrier height with grain size.

  12. A phase diagram for band inversion of topological materials as a function of interactions between two involved bands

    Science.gov (United States)

    Yu, Jie-Xiang; Che, J. G.

    2016-01-01

    Basing on first-principles calculations, we predicate that Bi on a graphene derivative, g-C14N3, which involves a 3 × 3 unit cell of graphene with four C atoms substituted by three N atoms, is a topological insulator with a gap of 50 meV. With the help of maximally localized Wannier functions, we find that its band inversion gap can be determined by examining a pair of interaction parameters between the two involved bands. Accordingly, a phase diagram for band inversion of topological materials as a function of the interactions is obtained. The conclusion also holds for Sb, Ir and Rh on g-C14N3. These materials are topological nontrivial either insulator or semimetal, indicating that g-C14N3 is a good platform for conceiving topological materials.

  13. Unexpected red shift of C-H vibrational band of Methyl benzoate

    CERN Document Server

    Maiti, Kiran Sankar; Scheurer, Christoph

    2016-01-01

    The C-H vibrational bands become more and more important in the structural determination of biological molecules with the development of CARS microscopy and 2DIR spectroscopy. Due to the congested pattern, near degeneracy, and strong anharmonicity of the C-H stretch vibrations, assignment of the C-H vibrational bands are often misleading. Anharmonic vibrational spectra calculation with multidimensional potential energy surface interprets the C-H vibrational spectra more accurately. In this article we have presented the importance of multidimensional potential energy surface in anharmonic vibrational spectra calculation and discuss the unexpected red shift of C-H vibrational band of Methyl benzoate.

  14. Electronic band structures and photovoltaic properties of MWO4 (M=Zn, Mg, Ca, Sr) compounds

    International Nuclear Information System (INIS)

    Divalent metal tungstates, MWO4, with wolframite (M=Zn and Mg) and scheelite (M=Ca and Sr) structures were prepared using a conventional solid state reaction method. Their electronic band structures were investigated by a combination of electronic band structure calculations and electrochemical measurements. From these investigations, it was found that the band structures (i.e. band positions and band gaps) of the divalent metal tungstates were significantly influenced by their crystal structural environments, such as the W-O bond length. Their photovoltaic properties were evaluated by applying to the working electrodes for dye-sensitized solar cells. The dye-sensitized solar cells employing the wolframite-structured metal tungstates (ZnWO4 and MgWO4) exhibited better performance than those using the scheelite-structured metal tungstates (CaWO4 and SrWO4), which was attributed to their enhanced electron transfer resulting from their appropriate band positions. - Graphical abstract: The electronic band structures of divalent metal tungstates are described from the combination of experimental results and theoretical calculations, and their electronic structure-dependent photovoltaic performances are also studied. Highlights: ? MWO4 compounds with wolframite (M=Zn and Mg) and scheelite structure (M=Ca and Sr) were prepared. ? Their electronic band structures were investigated by the calculations and the measurements. ? Their photovoltaic properties were determined by the crystal and electronic structures.

  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. 8-band and 14-band kp modeling of electronic band structure and material gain in Ga(In)AsBi quantum wells grown on GaAs and InP substrates

    Science.gov (United States)

    Gladysiewicz, M.; Kudrawiec, R.; Wartak, M. S.

    2015-08-01

    The electronic band structure and material gain have been calculated for GaAsBi/GaAs quantum wells (QWs) with various bismuth concentrations (Bi ? 15%) within the 8-band and 14-band kp models. The 14-band kp model was obtained by extending the standard 8-band kp Hamiltonian by the valence band anticrossing (VBAC) Hamiltonian, which is widely used to describe Bi-related changes in the electronic band structure of dilute bismides. It has been shown that in the range of low carrier concentrations n kp Hamiltonians are similar. It means that the 8-band kp model can be used to calculate material gain in dilute bismides QWs. Therefore, it can be applied to analyze QWs containing new dilute bismides for which the VBAC parameters are unknown. Thus, the energy gap and electron effective mass for Bi-containing materials are used instead of VBAC parameters. The electronic band structure and material gain have been calculated for 8 nm wide GaInAsBi QWs on GaAs and InP substrates with various compositions. In these QWs, Bi concentration was varied from 0% to 5% and indium concentration was tuned in order to keep the same compressive strain (? = 2%) in QW region. For GaInAsBi/GaAs QW with 5% Bi, gain peak was determined to be at about 1.5 ?m. It means that it can be possible to achieve emission at telecommunication windows (i.e., 1.3 ?m and 1.55 ?m) for GaAs-based lasers containing GaInAsBi/GaAs QWs. For GaInAsBi/Ga0.47In0.53As/InP QWs with 5% Bi, gain peak is predicted to be at about 4.0 ?m, i.e., at the wavelengths that are not available in current InP-based lasers.

  17. Macroscopic optical response and photonic bands

    International Nuclear Information System (INIS)

    We develop a formalism for the calculation of the macroscopic dielectric response of composite systems made of particles of one material embedded periodically within a matrix of another material, each of which is characterized by a well-defined dielectric function. The nature of these dielectric functions is arbitrary, and could correspond to dielectric or conducting, transparent or opaque, absorptive and dispersive materials. The geometry of the particles and the Bravais lattice of the composite are also arbitrary. Our formalism goes beyond the long-wavelength approximation as it fully incorporates retardation effects. We test our formalism through the study of the propagation of electromagnetic waves in two-dimensional photonic crystals made of periodic arrays of cylindrical holes in a dispersionless dielectric host. Our macroscopic theory yields a spatially dispersive macroscopic response which allows the calculation of the full photonic band structure of the system, as well as the characterization of its normal modes, upon substitution into the macroscopic field equations. We can also account approximately for the spatial dispersion through a local magnetic permeability and analyze the resulting dispersion relation, obtaining a region of left handedness. (paper)

  18. Determination of Band Energy Levels for Tungsten Nitrosyldithiolene

    International Nuclear Information System (INIS)

    The chemical and physical properties of tungsten nitrosyldithiolene complexes with a general formulae of [WTp(NO) (L)] where Tp = tris(3,5-dimethyl pyrazolyl)hydroborate and L = toluene-3,4-di thiolate (L1), 1,2-benzenediethanol (L2), 3,6-dichloro-1,2-benzenedithiolato (L3), have been studied for application as a photosensitizers in an anode for photoelectrochemical cell. These complexes were synthesized and characterised by infrared (IR), ultraviolet-visible (UV-Vis) spectroscopy and CHNS micro elemental analysis. Cyclic voltammetry (CV) was used to determine their redox potentials and their band energies were calculated from the potentials obtained. All three complexes showed energy band gaps in the range of 1.59 - 1.63 eV. The calculated band gaps from CV analyses were comparable with the estimated values obtained from the UV-Vis absorption data. Based on the postulated band diagram, these complexes may be a potential photosensitizers to be used in the photoeletrodes for photoelectrochemical cells. (author)

  19. 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.)

  20. 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)

  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. 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.)

  4. The metal-insulator transitions of VO2: A band theoretical approach

    Science.gov (United States)

    Eyert, V.

    2002-10-01

    The results of first principles electronic structure calculations for the metallic rutile and the insulating monoclinic phase of vanadium dioxide are presented. In addition, the insulating phase is investigated for the first time. The density functional calculations allow for a consistent understanding of all three phases. In the rutile phase metallic conductivity is carried by metal orbitals, which fall into the one-dimensional band, and the isotropically dispersing bands. Hybridization of both types of bands is weak. In the phase splitting of the band due to metal-metal dimerization and upshift of the bands due to increased p-d overlap lead to an effective separation of both types of bands. Despite incomplete opening of the optical band gap due to the shortcomings of the local density approximation, the metal-insulator transition can be understood as a Peierls-like instability of the band in an embedding background of electrons. In the phase, the metal-insulator transition arises as a combined embedded Peierls-like and antiferromagnetic instability. The results for VO2 fit into the general scenario of an instability of the rutile-type transition-metal dioxides at the beginning of the d series towards dimerization or antiferromagnetic ordering within the characteristic metal chains. This scenario was successfully applied before to MoO2 and NbO2. In the compounds, the and bands can be completely separated, which leads to the observed metal-insulator transitions.

  5. 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 β2-0.65. Subsequently, a discrete set of γ-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 γ-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

  6. 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.

  7. 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%

  8. 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.

  9. 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.

  10. 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

  11. 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.

  12. 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...

  13. Research on the elastic wave band gaps of curved beam of phononic crystals

    Energy Technology Data Exchange (ETDEWEB)

    Shaogang, Liu; Shidan, Li; Haisheng, Shu, E-mail: shuhaisheng@hrbeu.edu.cn; Weiyuan, Wang; Dongyan, Shi; Liqiang, Dong; Hang, Lin; Wei, Liu

    2015-01-15

    Based on wave equations of Timoshenko curved beam, the theoretical derivation and numerical calculation of the behavior of in-plane and out-of-plane wave propagating in curved beam of phononic crystals (CBPC) are carried out using transfer matrix method combined with the Bloch theorem. Finite CBPC is also simulated by FEM method. It is shown that both in-plane and out-of-plane elastic waves band gaps exist in CBPC. Compared with equivalent straight beam of phononic crystals (SBPC), CBPC has some unique characteristics, such as the first complete in-plane band gap, special in-plane coupling band gap, and out-of-plane coupling band gap. In those band gaps, CBPC has a better property of vibration reduction than the equivalent SBPC in some ways. Furthermore, effects of curvature of CBPC on the in-plane and out-of-plane band gaps are discussed.

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

    CERN Document Server

    Rgg, 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.

  15. Band termination and signature crossing observation in some rare-earth nuclei

    International Nuclear Information System (INIS)

    Predictions are very interesting features of moderately high angular momentum configurations as Band Termination, in nuclei with 10-12 valence particles outside the gadolinium 146Gd core. Which are made by core excitation or by promotion as the valence particles to the next shell. General properties of terminating bands are reviewed and exemplified on the observed high-angular momentum properties of 153Ho, 155Ho, 157Ho holmium nuclei. The very similar features are observed in the non-collective ones with N=88 isotones of dysprosium Dy, Erbium Er and tribium Yb nuclei.The spin contribution from different bands is calculated in terminating bands as well as more collective bands. The relation between the level energy minus rigid-rotor rotational energy versus spin for the yrast states is discussed and the plot serves to indicate that something interesting is happing above a certain value of (I). Above this value the nuclei seem to exhibit dominantly band termination behavior

  16. 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...

  17. Generalized pseudopotential theory of d-band metals

    International Nuclear Information System (INIS)

    The generalized pseudopotential theory (GPT) of metals is reviewed with emphasis on recent developments. This theory, which attempts to rigorously extend to d-band metals the spirit of conventional simple-metal pseudopotential perturbation theory, has now been optimized and fully integrated with the Kohn-Sham local-density-functional formalism, allowing for systematic first-principles calculations. Recent work on the problems of cohesion, lattice dynamics, structural phase stability, pressure- and temperature-induced phase transitions, and melting is discussed

  18. Properties of alpha decay to rotational bands of heavy nuclei

    International Nuclear Information System (INIS)

    In the framework of the generalized liquid drop model (GLDM) and improved Royer's formula, we investigate the branching ratios and half-lives of ?-decay to the members of the ground-state rotational bands of heavy eveneven Fm and No isotopes. The calculated results are in good agreement with the available experimental data and some useful predictions are provided for future experiments. (author)

  19. New results on the superdeformed band in 192Hg

    International Nuclear Information System (INIS)

    New results on the 192Hg superdeformed band have been obtained with EUROGAM. The experiment has been performed with the 160Gd(36S, 4n) reaction at 159 MeV. Above 800 keV the ?-ray energies differ from the previously published ones. Thus the rise of the dynamical moment of inertia F(2) above h? = 0.4 MeV is no longer observed. This is in better agreement with recent cranked Hartree-Fock-Bogoliubov calculations. (orig.)

  20. ''Shears bands'' in Pb nuclei - a new nuclear structure effect

    International Nuclear Information System (INIS)

    In nuclei in the mass region around A = 190-200 a large number of regular dipole sequences have recently been found. In these bands the gain in angular momentum may not be created by collective rotation as is usual for more deformed nuclei, but stems from aligning the proton and neutron spins in the direction of the total spin axis. Calculations within the framework of the tilted axis cranking model reproduce the available experimental data and support the alignment picture. (orig.)

  1. Deformation bands in porous sandstones their microstructure and petrophysical properties

    Energy Technology Data Exchange (ETDEWEB)

    Torabi, Anita

    2007-12-15

    Deformation bands are commonly thin tabular zones of crushed or reorganized grains that form in highly porous rocks and sediments. Unlike a fault, typically the slip is negligible in deformation bands. In this dissertation the microstructure and petrophysical properties of deformation bands have been investigated through microscopy and numerical analysis of experimental and natural examples. The experimental work consists of a series of ring-shear experiments performed on porous sand at 5 and 20 MPa normal stresses and followed by microscopic examination of thin sections from the sheared samples. The results of the ring-shear experiments and comparison of them to natural deformation bands reveals that burial depth (level of normal stress in the experiments) and the amount of shear displacement during deformation are the two significant factors influencing the mode in which grains break and the type of shear zone that forms. Two end-member types of experimental shear zones were identified: (a) Shear zones with diffuse boundaries, which formed at low levels of normal stress and/or shear displacement; and (b) Shear zones with sharp boundaries, which formed at higher levels of normal stress and/or shear displacement. Our interpretation is that with increasing burial depth (approximately more than one kilometer, simulated in the experiments by higher levels of normal stress), the predominant mode of grain fracturing changes from flaking to splitting; which facilitates the formation of sharp-boundary shear zones. This change to grain splitting increases the power law dimension of the grain size distribution (D is about 1.5 in sharp boundary shear zones). Based on our observations, initial grain size has no influence in the deformation behavior of the sand at 5 MPa normal stresses. A new type of cataclastic deformation band is described through outcrop and microscopic studies; here termed a 'slipped deformation band'. Whereas previously reported cataclastic deformation bands are characterized by strain hardening, these new bands feature a central slip surface, which indicates late strain softening. They lack the characteristic compaction envelop, and are typified by higher porosity and lower permeability than previously-described cataclastic deformation bands. Intense background fracturing of the host rock and significant initial porosity are considered to be important in creating these newly-discovered deformation bands. In a related study, we investigate, for millimeter- wide deformation bands, the scale limitation inherent in laboratory measurements of porosity and permeability. The scale limitations imposed by the deformation band relative to the physical sample size motivated us to develop a new method for determining porosity and permeability based on image processing. While plug measurements measure the effective permeability across a 25.4 mm (1 inch) long sample, which includes both host rock and deformation band, the method presented here provides a means to estimate porosity and permeability of deformation band on microscale. This method utilizes low-order (one- and two orders) spatial correlation functions to analyze high-resolution, high-magnification backscatter images, to estimate the porosity and specific surface area of the pore-grain interface in the deformed sandstones. Further, this work demonstrates the use of a modified version of the Kozeny-Carmen relation to calculate permeability by using porosity and specific surface area obtained through the image processing. The result shows that permeability difference between the band and the host rock is up to four orders of magnitude. Moreover, the porosities and permeabilities estimated from image processing are lower than those obtained from their plug measurements; hence the traditional laboratory measurements have been overestimating permeability because of the previously-unrecognized scale problem. In addition, the image processing results clearly show that, as a result of microstructural variation, both porosity and permeability vary along the leng

  2. Band Structure and Effective Mass in Monolayer MoS2.

    Science.gov (United States)

    Wu, Ming-Ting; Fan, Jun-Wei; Chen, Kuan-Ting; Chang, Shu-Tong; Lin, Chung-Yi

    2015-11-01

    Monolayer transition-metal dichalcogenide is a very promising two-dimensional material for future transistor technology. Monolayer molybdenum disulfide (MoS2), owing to the unique electronic properties of its atomically thin two-dimensional layered structure, can be made into a high-performance metal-oxide-semiconductor field-effect transistor, or MOSFET. In this work, we focus on band structure and carrier mobility calculations for MoS2. We use the tight-binding method to calculate the band structure, including a consideration of the linear combination of different atomic orbitals, the interaction of neighboring atoms, and spin-orbit coupling for different tight-binding matrices. With information about the band structure, we can obtain the density of states, the effective mass, and other physical quantities. Carrier mobility using the Kubo-Greenwood formula is calculated based on the tight-binding band structure. PMID:26726660

  3. 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.

  4. 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...

  5. Bosonic condensation in a flat energy band

    CERN Document Server

    Baboux, F; Jacqmin, T; Biondi, M; Lemaître, A; Gratiet, L Le; Sagnes, I; Schmidt, S; Türeci, H E; Amo, A; Bloch, J

    2015-01-01

    Flat bands are non-dispersive energy bands made of fully degenerate quantum states. Such bands are expected to support emergent phenomena with extraordinary spatial and temporal structures, as they strongly enhance the effect of any perturbation induced by disorder, dissipation or interactions. However, flat bands usually appear at energies above the ground state, preventing their study in systems in thermodynamic equilibrium. Here we use cavity polaritons to circumvent this issue. We engineer a flat band in a frustrated lattice of micro-pillar optical cavities. By taking advantage of the non-hermiticity of our system, we achieve for the first time bosonic condensation in a flat band. This allows revealing the peculiar effect of disorder in such band: The condensate fragments into highly localized modes, reflecting the elementary eigenstates produced by geometric frustration. This non-hermitian engineering of a bosonic flat band condensate offers a novel approach to studying coherent phases of light and matte...

  6. Relativistic Model for two-band Superconductivity

    OpenAIRE

    Ohsaku, Tadafumi

    2003-01-01

    To understand the superconductivity in MgB2, several two-band models of superconductivity were proposed. In this paper, by using the relativistic fermion model, we clearize the effect of the lower band in the superconductivity.

  7. Floquet engineering with quasienergy bands of periodically driven optical lattices

    Science.gov (United States)

    Holthaus, Martin

    2016-01-01

    A primer on the Floquet theory of periodically time-dependent quantum systems is provided, and it is shown how to apply this framework for computing the quasienergy band structure governing the dynamics of ultracold atoms in driven optical cosine lattices. Such systems are viewed here as spatially and temporally periodic structures living in an extended Hilbert space, giving rise to spatio-temporal Bloch waves whose dispersion relations can be manipulated at will by exploiting ac-Stark shifts and multiphoton resonances. The elements required for numerical calculations are introduced in a tutorial manner, and some example calculations are discussed in detail, thereby illustrating future prospects of Floquet engineering.

  8. 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)

  9. Predicting superdeformed rotational band-head spin in A ? 190 mass region using variable moment of inertia model

    Indian Academy of Sciences (India)

    V S Uma; Alpana Goel; Archana Yadav; A K Jain

    2016-01-01

    The band-head spin (0) of superdeformed (SD) rotational bands in ? 190 mass region is predicted using the variable moment of inertia (VMI) model for 66 SD rotational bands. The superdeformed rotational bands exhibited considerably good rotational property and rigid behaviour. The transition energies were dependent on the prescribed band-head spins. The ratio of transition energies over spin /2 (RTEOS) vs. angular momentum ( ) have confirmed the rigid behaviour, provided the band-head spin value is assigned correctly. There is a good agreement between the calculated and the observed transition energies. This method gives a very comprehensive interpretation for spin assignment of SD rotational bands which could help in designing future experiments for SD bands.

  10. 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

  11. Self energy corrections to the ''ab initio'' band structure: Chromium

    International Nuclear Information System (INIS)

    We describe the effect of many particle corrections to improve the electronic energy spectrum calculated in the framework of the Density Functional Formalism (DFF). We show that it is possible to consider an n particle diagram like a correction to the DFF results for electronic structure, if we take into account the electron-electron interaction with non-zero transmitted momentum q or energy ?. The model is proposed for calculating the leading term of the self-energy expansion as a power series in interactions, i.e. the second order term under the conditions q=O and ??O. This model is illustrated by calculating the electronic band structure and optical properties of anti ferromagnetic chromium. The self-energy correction leads to a better agreement between the theoretical calculations and experimental measurements of electronic properties. (author). 40 refs, 5 figs, 3 tabs

  12. The laparoscopic banded gastric bypass operation technique

    Directory of Open Access Journals (Sweden)

    Simon Ksters

    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.

  13. 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.)

  14. 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

  15. 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]ν 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.

  16. 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.

  17. Shear bands in aluminium-lithium alloys

    International Nuclear Information System (INIS)

    The formation of shear bands in Al-Li alloys in cold rolling and their influence on mechanical properties of rolled and heat treated sheets are under consideration. It is shown that shear bands as well as the network of recrystallized grains along previous bands are undesirable structural constituents in aluminum alloy sheets as they decrease processing and operational properties of alloys. In further metal forming the localization of strain is observed along shear bands or zones of recrystallized grains. To avoid failure due to shear band formation it is recommended to roll alloys in as-annealed state and properly regulate reduction degree

  18. Calcul interactif haute performance

    OpenAIRE

    Raffin, Bruno

    2009-01-01

    La puissance de calcul disponible poursuit sa progression exponentielle mais en offrant plus de paralllisme. Cette progression de la puissance disponible peut tre mise profit pour rendre interactifs certains calculs. La structure et les objectifs de l'application diffrent alors sensiblement de ceux du calcul intensif traditionnel. Le rle de l'utilisateur devient central. Il motive le recours des priphriques d'entre et sortie avancs, impose des contraintes de cohrence, de latence,...

  19. ESC : energy saving calculations

    OpenAIRE

    Hrafn Jhannesson

    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. Hjarar 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 ...

  20. SYSTEM MODELLING OF DTH BROADCASTING AT KA BAND MULTIBEAM SATELLITE SYSTEM OVER INDIA

    Directory of Open Access Journals (Sweden)

    Swastik Sahoo

    2015-12-01

    Full Text Available A major application of satellite is broadcasting and in India this is done at Ku band. But with the increase of demand of number of channels Ku band is getting saturated. So, to satisfy this requirement an approach is to go to higher frequency band, i.e. Ka band. As India is allocated with seven fixed GEO locations, so the purpose is to calculate what is the suitable satellite position for India at Ka band, what is the best EIRP available at that position and what will be the smallest ground antenna diameter and satellite antenna diameter at Ka band. Broadcasting is done at 20GHz Ka band downlink frequency. At this frequency, as the signal will face lots of impairments during propagation, so the attenuation caused by variety of factors are discussed here. To overcome the attenuation maximum EIRP is given. The link equation is taken as a reference to calculate quality of the signal, G/T ratio and EIRP of the satellite. The extreme west region of India is being taken as earth station and after some brief calculations all the results are discussed. Out of seven allocated GEO locations, 74?E gives best output in terms of minimum loss & small antenna diameters.

  1. 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

  2. Waste Package Lifting Calculation

    International Nuclear Information System (INIS)

    The objective of this calculation is to evaluate the structural response of the waste package during the horizontal and vertical lifting operations in order to support the waste package lifting feature design. The scope of this calculation includes the evaluation of the 21 PWR UCF (pressurized water reactor uncanistered fuel) waste package, naval waste package, 5 DHLW/DOE SNF (defense high-level waste/Department of Energy spent nuclear fuel)--short waste package, and 44 BWR (boiling water reactor) UCF waste package. Procedure AP-3.12Q, Revision 0, ICN 0, calculations, is used to develop and document this calculation

  3. 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

  4. 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

  5. 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,...

  6. 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.

  7. The metal-insulator transitions of VO2 A band theoretical approach

    CERN Document Server

    Eyert, V

    2002-01-01

    The results of first principles electronic structure calculations for the metallic rutile and the insulating monoclinic M1 phase of vanadium dioxide are presented. In addition, the insulating M2 phase is investigated for the first time. The density functional calculations allow for a consistent understanding of all three phases. In the rutile phase metallic conductivity is carried by metal t_2g orbitals, which fall into the one-dimensional d_parallel band, and the isotropically dispersing e_g^pi bands. Hybridization of both types of bands is weak. In the M1 phase splitting of the d_parallel band due to metal-metal dimerization and upshift of the e_g^pi bands due to increased p-d overlap lead to an effective separation of both types of bands. Despite incomplete opening of the optical band gap due to the shortcomings of the local density approximation, the metal-insulator transition can be understood as a Peierls-like instability of the d_parallel band in an embedding background of e_g^pi electrons. In the M2 p...

  8. Inter-Band Radiometric Comparison and Calibration of ASTER Visible and Near-Infrared Bands

    Directory of Open Access Journals (Sweden)

    Kenta Obata

    2015-11-01

    Full Text Available The present study evaluates inter-band radiometric consistency across the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER visible and near-infrared (VNIR bands and develops an inter-band calibration algorithm to improve radiometric consistency. Inter-band radiometric comparison of current ASTER data shows a root mean square error (RMSE of 3.8%5.7% among radiance outputs of spectral bands due primarily to differences between calibration strategies of the NIR band for nadir-looking (Band 3N and the other two bands (green and red bands, corresponding to Bands 1 and 2. An algorithm for radiometric calibration of Bands 2 and 3N with reference to Band 1 is developed based on the band translation technique and is used to obtain new radiometric calibration coefficients (RCCs for sensor sensitivity degradation. The systematic errors between radiance outputs are decreased by applying the derived RCCs, which result in reducing the RMSE from 3.8%5.7% to 2.2%2.9%. The remaining errors are approximately equal to or smaller than the intrinsic uncertainties of inter-band calibration derived by sensitivity analysis. Improvement of the radiometric consistency would increase the accuracy of band algebra (e.g., vegetation indices and its application. The algorithm can be used to evaluate inter-band radiometric consistency, as well as for the calibration of other sensors.

  9. 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

  10. 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.)

  11. 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).

  12. Endoscopic Treatment of an extruded gastric band

    International Nuclear Information System (INIS)

    We present the case of a patient in whom a gastric band was placed for the treatment of morbid obesity with good results of loss of weight. One year after the procedure the gastric band started to be extruded into the stomach and this was almost total at 26 months. At this time the band was held only by a small tissue bridge. We did two endoscopic procedures to extract the band. In the first one the tissue bridge was cut using the duodenoscope for a better vision and handling and a needle knife papilotome. The band could not be extracted at the time because it continued to be fixed by the connector to the subcutaneous reservoir. The reservoir had been previously removed. One week later in a second procedure the band was cut using a monofilament biliary wire guide and lithotriptor. Then the band could be extracted easily. We describe the procedures, the difficulties we had and how we resolved them

  13. 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.

  14. Investigation of group IVA elements combined with HAXPES and first-principles calculations

    Science.gov (United States)

    Cui, Y.-T.; Li, G.-L.; Oji, H.; Son, J.-Y.

    2014-04-01

    The core level and valence band spectra of group IVA elements were investigated with hard x-ray photoemission spectroscopy (HAXPES) photon energy of 7.939 keV by bulk sensitive manner. The survey and valance band spectra were presented, relative peaks intensity are discussed by thinking about inelastic mean free path (IMFP) and photoionization cross section of photoelectrons (PICS). In order to understand bulk band structures, valence bands are compared with the calculated ones by considering PICS, IMFP and total energy resolution. The calculated results by GGA, HSE06 and GW0 methods are simply discussed by comparing with experiment spectra.

  15. Investigation of group IVA elements combined with HAXPES and first-principles calculations

    International Nuclear Information System (INIS)

    The core level and valence band spectra of group IVA elements were investigated with hard x-ray photoemission spectroscopy (HAXPES) photon energy of 7.939 keV by bulk sensitive manner. The survey and valance band spectra were presented, relative peaks intensity are discussed by thinking about inelastic mean free path (IMFP) and photoionization cross section of photoelectrons (PICS). In order to understand bulk band structures, valence bands are compared with the calculated ones by considering PICS, IMFP and total energy resolution. The calculated results by GGA, HSE06 and GW0 methods are simply discussed by comparing with experiment spectra.

  16. Burmese eclipse calculations

    Science.gov (United States)

    Gisln, Lars

    2015-03-01

    Two Burmese eclipse calculations, one lunar and one solar, are analysed using examples from a Burmese manuscript. The fundamental parameters are with some important exceptions the same as in Suryasiddhanta, but the handling of, for instance, parallax in the solar eclipse is different and much simplified. Specific to Burma are also the shadow calculations.

  17. 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.)

  18. Deformation bands evolving from dilation to cementation bands in a hydrocarbon reservoir (Vienna Basin, Austria)

    OpenAIRE

    Exner, Ulrike; Kaiser, Jasmin; Gier, Susanne

    2013-01-01

    In this study we analyzed five core samples from a hydrocarbon reservoir, the Matzen Field in the Vienna Basin (Austria). Deformation bands occur as single bands or as strands of several bands. In contrast to most published examples of deformation bands in terrigeneous sandstones, the reduction of porosity is predominantly caused by the precipitation of Fe-rich dolomite cement within the bands, and only subordinately by cataclasis of detrital grains. The chemical composition of this dolomite ...

  19. Sample size calculations.

    Science.gov (United States)

    Noordzij, Marlies; Dekker, Friedo W; Zoccali, Carmine; Jager, Kitty J

    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 investigators to decide which method to use. Moreover, these calculations are prone to errors, because small changes in the selected parameters can lead to large differences in the sample size. This paper explains the basic principles of sample size calculations and demonstrates how to perform such a calculation for a simple study design. PMID:21293154

  20. 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

  1. Engineering Electronic Band Structure for New Elpasolite Scintillators

    Science.gov (United States)

    Du, Mao-Hua; Biswas, Koushik; Singh, David

    2012-02-01

    The utilization of scintillator materials is one of the primary methods for radiation detection. Elpasolites are a large family of quaternary halides that have recently attracted considerable interest for their potential applications as ?-ray and neutron scintillators. A large number (on the order of 10^3) of different chemical compositions exist in the elpasolite family of compounds. This wide range of compositions offers numerous opportunities for fine-tuning the material chemistry to target specific scintillation properties, but they also pose significant challenges in identifying the most promising ones. Many elpasolite scintillator materials currently under development suffer from low light output and long scintillation decay time. The low light output is partially due to a large band gap while the long scintillation decay time is a result of the slow carrier transport to Ce impurities, where carriers recombine to emit photons. We suggest that these problems may be mitigated by optimizing the band gap and carrier mobility by selecting constituent elements of proper electronegativity. For example, cations with lower electronegativity may lower the conduction band and increase the conduction band dispersion simultaneously, resulting in higher light output and faster scintillation. We demonstrate by first-principles calculations that the strategy of manipulating electronegativity can lead to a number of new elpasolite compounds that are potentially brighter and faster scintillators.

  2. 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.

  3. 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)

  4. 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.

  5. 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.

  6. 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

  7. 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.

  8. 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.

  9. 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.

  10. Optimal band separation of extracellular field potentials.

    Science.gov (United States)

    Magri, Cesare; Mazzoni, Alberto; Logothetis, Nikos K; Panzeri, Stefano

    2012-09-15

    Local Field Potentials (LFPs) exhibit a broadband spectral structure that is traditionally partitioned into distinct frequency bands which are thought to originate from different types of neural events triggered by different processing pathways. However, the exact frequency boundaries of these processes are not known and, as a result, the frequency bands are often selected based on intuition, previous literature or visual inspection of the data. Here, we address these problems by developing a rigorous method for defining LFP frequency bands and their boundaries. The criterion introduced for determining the boundaries delimiting the bands is to maximize the information about an external correlate carried jointly by all bands in the partition. The method first partitions the LFP frequency range into two bands and then successively increases the number of bands in the partition. We applied the partitioning method to LFPs recorded from primary visual cortex of anaesthetized macaques, and we determined the optimal band partitioning that describes the encoding of naturalistic visual stimuli. The first optimal boundary partitioned the LFP response at 60 Hz into low and high frequencies, which had been previously found to convey independent information about the natural movie correlate. The second optimal boundary divided the high-frequency range at approximately 100 Hz into gamma and high-gamma frequencies, consistent with recent reports that these two bands reflect partly distinct neural processes. A third important boundary was at 25 Hz and it split the LFP range below 50 Hz into a stimulus-informative and a stimulus-independent band. PMID:22101145

  11. Dust bands in the asteroid belt

    Energy Technology Data Exchange (ETDEWEB)

    Sykes, M.; Greenberg, R.; Dermott, S.; Nicholson, P.; Burns, J.

    1989-09-08

    The Infrared Astronomical Satellite (IRAS) discovered three bands of dust: one above, below, and approximately in the plane of the ecliptic. These bands are located in the asteroid belt and are believed to arise from collisional activity. Debris from an asteroid collision, over time, fills a torus having peaks in particle number density near its inner and outer corners, corresponding to the locus of perihelia and aphelia, respectively. As a consequence of this geometry, such a swarm should produce two pairs of bands that straddle the ecliptic - a perihelion band pair and an aphelion band pair (which generally overlap along the line of sight from earth). Indeed, processing of the IRAS data now resolves the band structure into at least three such band pairs, with indications of several more pairs distributed over a large range of ecliptic latitudes. Some of these bands appear to be associated with major Hirayama asteroid families, while others are not. Possible origins of the observed dust bands include: (1) the gradual comminution of the asteroid belts as a whole, in which the local dust population is maximum where the concentration of asteroids is greatest (e.g. families); (2) one or a few large random asteroid collisions enhancing the local population of small debris, which in turn is comminuted into dust; and (3) the disintegration of one or more large comets. Dust bands are not necessarily constant features of the solar system.

  12. 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.

  13. 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.

  14. 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)

  15. Band structure of metal diboride AlB2 under high pressure

    International Nuclear Information System (INIS)

    The band structure, density of states (DOS), electronic charge distribution and superconductivity of Aluminium diboride (AlB2) as a function of pressure are investigated. The normal pressure, band structure, DOS and superconducting transition temperature of AlB2 agree well with the previous calculations. The high pressure band structure exhibits significant deviations from the normal pressure band structure. It is found that, the charge transfer from s state to p and d states will cause superconductivity in AlB2. According to the present calculation, at normal pressure, the superconducting transition of AlB2 occurs at 13.57 K which is comparable with the previous theoretical observation of 9K. On further increase of pressure, Tc increases considerably and its maximum value may exceed 32K (at .683 Mbar). The high pressure Tc values are reported for the first time and this metal diboride (AlB2) is identified as pressure induced superconductors. (author)

  16. Theoretical determinations of semiconductor band structures and optical properties, and applications to TPV devices

    Energy Technology Data Exchange (ETDEWEB)

    Geller, G.B.; Blazeck, T.S. [Bettis Atomic Power Laboratory, West Miffin, Pennsylvania 15122-0079 (United States)] Wolf, W. [c/o Molecular Simulations Inc., San Diego, California 92121-3752 (United States)] Mannstadt, W. [Northwestern University, Evanston, Illinois 60208-3112 (United States)

    1999-03-01

    Electron band structures have been calculated from first principles using the Full Potential Linearized Augmented Plane Wave (FLAPW) computational code (1), including nonlocal screened exchange (sX-LDA) and spin-orbit effects (2, 3) for representative elemental, binary III-V and II-VI semiconductors, and configurationally optimized In{sub x}Ga{sub 1{minus}x}As. Predicted band gaps for narrow gap semiconductors (Ge, InAs, In{sub x}Ga{sub 1{minus}x}As and InSb) are all within 20{percent} of experimental values, compared with errors of over 100{percent} (negative band gaps) obtained with previous calculations based on the Local Density Approximation. Effects of In{sub x}Ga{sub 1{minus}x}As conduction band dispersion on TPV device quantum efficiency are illustrated. {copyright} {ital 1999 American Institute of Physics.}

  17. 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.

  18. Raman bands in Ag nanoparticles obtained in extract of Opuntia ficus-indica plant

    Science.gov (United States)

    Bocarando-Chacon, J.-G.; Cortez-Valadez, M.; Vargas-Vazquez, D.; Rodrguez Melgarejo, F.; Flores-Acosta, M.; Mani-Gonzalez, P. G.; Leon-Sarabia, E.; Navarro-Badilla, A.; Ramrez-Bon, R.

    2014-05-01

    Silver nanoparticles have been obtained in an extract of Opuntia ficus-indica plant. The size and distribution of nanoparticles were quantified by atomic force microscopy (AFM). The diameter was estimated to be about 15 nm. In addition, energy dispersive X-ray spectroscopy (EDX) peaks of silver were observed in these samples. Three Raman bands have been experimentally detected at 83, 110 and 160 cm-1. The bands at 83 and 110 cm-1 are assigned to the silver-silver Raman modes (skeletal modes) and the Raman mode located at 160 cm-1 has been assigned to breathing modes. Vibrational assignments of Raman modes have been carried out based on the Density Functional Theory (DFT) quantum mechanical calculation. Structural and vibrational properties for small Agn clusters with 2?n?9 were determined. Calculated Raman modes for small metal clusters have an approximation trend of Raman bands. These Raman bands were obtained experimentally for silver nanoparticles (AgNP).

  19. 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)

  20. 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