WorldWideScience

Sample records for crystal lattice parameters

  1. Coefficient of crystal lattice matching as a parameter of substrate - crystal structure compatibility in silumins

    Directory of Open Access Journals (Sweden)

    J. Piątkowski

    2009-07-01

    Full Text Available Adding high-melting point elements (Mo, Nb, Ni, Ti, W to complex silumins results in hardening of the latter ones, owing to the formation of new intermetallic phases of the AlxMey type, with refinement of dendrites in α solution and crystals in β phase. The hardening is also due to the effect of various inoculants. An addition of the inoculant is expected to form substrates, the crystal lattice of which, or some (privileged lattice planes and interatomic spaces should bear a strong resemblance to the crystal nucleus. To verify this statement, using binary phase equilibria systems, the coefficient of crystal lattice matching, being one of the measures of the crystallographic similarity, was calculated. A compatibility of this parameter (up to 20% may decide about the structure compatibility between the substrate and crystal which, in turn, is responsible for the effectiveness of alloy modification. Investigations have proved that, given the temperature range of their formation, the density, the lattice type, and the lattice parameter, some intermetallic phases of the AlxMey type can act as substrates for the crystallisation of aluminium and silicon, and some of the silumin hardening phases.

  2. Transmission Electron Microscope Measures Lattice Parameters

    Science.gov (United States)

    Pike, William T.

    1996-01-01

    Convergent-beam microdiffraction (CBM) in thermionic-emission transmission electron microscope (TEM) is technique for measuring lattice parameters of nanometer-sized specimens of crystalline materials. Lattice parameters determined by use of CBM accurate to within few parts in thousand. Technique developed especially for use in quantifying lattice parameters, and thus strains, in epitaxial mismatched-crystal-lattice multilayer structures in multiple-quantum-well and other advanced semiconductor electronic devices. Ability to determine strains in indivdual layers contributes to understanding of novel electronic behaviors of devices.

  3. Influence of Nd dopants on lattice parameters and thermal and elastic properties in YVO4 single crystals

    International Nuclear Information System (INIS)

    Kucytowski, J.; Wokulska, K.; Kazmierczak-Balata, A.; Bodzenta, J.; Lukasiewicz, T.; Hofman, B.; Pyka, M.

    2008-01-01

    The influence of neodymium doping on YVO 4 single crystals has been studied. The crystals were grown by the Czochralski method. One of them was pure YVO 4 and the others were doped with neodymium (YVO 4 :Nd) at various concentrations of Nd = 0.3-3.0 at.%. The changes of the lattice parameters were determined by the Bond's method [W.L. Bond, Acta Cryst. 13 (1960) 814]. The thermal diffusivity and the velocity of ultrasound using the photothermal method with mirage effect and the pulse echo method [J. Bodzenta, M. Pyka, J. Phys. IV France 137 (2006) 259] were measured. In the examined crystals, it was found that the lattice parameters increase while the thermal diffusivity decreases with increasing concentration of Nd atoms

  4. Lattice parameters guide superconductivity in iron-arsenides

    Science.gov (United States)

    Konzen, Lance M. N.; Sefat, Athena S.

    2017-03-01

    The discovery of superconducting materials has led to their use in technological marvels such as magnetic-field sensors in MRI machines, powerful research magnets, short transmission cables, and high-speed trains. Despite such applications, the uses of superconductors are not widespread because they function much below room-temperature, hence the costly cooling. Since the discovery of Cu- and Fe-based high-temperature superconductors (HTS), much intense effort has tried to explain and understand the superconducting phenomenon. While no exact explanations are given, several trends are reported in relation to the materials basis in magnetism and spin excitations. In fact, most HTS have antiferromagnetic undoped ‘parent’ materials that undergo a superconducting transition upon small chemical substitutions in them. As it is currently unclear which ‘dopants’ can favor superconductivity, this manuscript investigates crystal structure changes upon chemical substitutions, to find clues in lattice parameters for the superconducting occurrence. We review the chemical substitution effects on the crystal lattice of iron-arsenide-based crystals (2008 to present). We note that (a) HTS compounds have nearly tetragonal structures with a-lattice parameter close to 4 Å, and (b) superconductivity can depend strongly on the c-lattice parameter changes with chemical substitution. For example, a decrease in c-lattice parameter is required to induce ‘in-plane’ superconductivity. The review of lattice parameter trends in iron-arsenides presented here should guide synthesis of new materials and provoke theoretical input, giving clues for HTS.

  5. Optical spectra and lattice dynamics of molecular crystals

    CERN Document Server

    Zhizhin, GN

    1995-01-01

    The current volume is a single topic volume on the optical spectra and lattice dynamics of molecular crystals. The book is divided into two parts. Part I covers both the theoretical and experimental investigations of organic crystals. Part II deals with the investigation of the structure, phase transitions and reorientational motion of molecules in organic crystals. In addition appendices are given which provide the parameters for the calculation of the lattice dynamics of molecular crystals, procedures for the calculation of frequency eigenvectors of utilizing computers, and the frequencies and eigenvectors of lattice modes for several organic crystals. Quite a large amount of Russian literature is cited, some of which has previously not been available to scientists in the West.

  6. The influence of high hydrostatic pressure on lattice parameters of a single crystal of BaTiO3

    International Nuclear Information System (INIS)

    Malinowski, M.; Lukaszewicz, K.; Asbrink, S.

    1986-01-01

    The lattice parameters of a single crystal of BaTiO 3 have been measured under high hydrostatic pressure up to 5 GPa using a diamond-anvil high-pressure cell of a new design. The lattice becomes cubic at 2.08(8) GPa and stays cubic at higher pressures. The pressure dependence of the tetragonal-cubic transition temperature is estimated to be -46 K GPa -1 . (orig.)

  7. Effect of γ-irradiation on the lattice parameter and colour centre concentration in pure Ca2+, Sr2+ and Eu2+ doped KCl crystals

    International Nuclear Information System (INIS)

    Damm, J.Z.; Stepien-Damm, J.

    1980-01-01

    The changes of lattice parameter and colour centre concentration are examined in KCl crystals (both pure and Me 2+ -doped) irradiated by γ-rays at room temperature. For the pure crystals the relative volume change vs. F-centre concentration plot reveals the presence of two stages, one ascribed to the introduction of colour centre pairs (or F centres only) and other to the generation of new dislocations (or new dislocations with trapped-hole centres). In Me 2+ doped crystals the lattice expansion bears a complex character (in the initial irradiation stage a transient maximum appears). Additional anomaly appears in Eu 2+ KCl in the high-dose range where in spite of a distinct F-centre concentration drop a marked raise of the lattice parameter is observed. (author)

  8. Common misconceptions about the dynamical theory of crystal lattices: Cauchy relations, lattice potentials and infinite crystals

    International Nuclear Information System (INIS)

    Elcoro, Luis; Etxebarria, Jesus

    2011-01-01

    The requirement of rotational invariance for lattice potential energies is investigated. Starting from this condition, it is shown that the Cauchy relations for the elastic constants are fulfilled if the lattice potential is built from pair interactions or when the first-neighbour approximation is adopted. This is seldom recognized in widely used solid-state textbooks. Frequently, pair interaction is even considered to be the most general situation. In addition, it is shown that the demand of rotational invariance in an infinite crystal leads to inconsistencies in the symmetry of the elastic tensor. However, for finite crystals, no problems arise, and the Huang conditions are deduced using exclusively a microscopic approach for the elasticity theory, without making any reference to macroscopic parameters. This work may be useful in both undergraduate and graduate level courses to point out the crudeness of the pair-potential interaction and to explore the limits of the infinite-crystal approximation.

  9. Change of lattice parameters in highly disperse nickel powders

    International Nuclear Information System (INIS)

    Gamarnik, M.Ya.

    1991-01-01

    A monotonous increase of the lattice parameters with the decrease of particle size is established by an X-ray study for highly disperse nickel powders in the interval of sizes from 4.9 to 35 nm. The relative changes of lattice parameters are from 4.9x10 -3 ±5x10 -4 up to 3x10 -4 ±1x10 -4 . The effect is explained by the decrease of the intracrystalline pressure in small particles stipulated by electrostatic interaction of the elements of crystal charge lattice. A calculated dependence of the lattice parameters which agrees with experimental curve is obtained in the framework of the model suggested by the charge lattice represented by an ion-electron lattice of positive ions and collectivized electrons with regard of the lattice of atomic neutral cores (the contribution of the latter is proved very small as found from the calculations). (orig.)

  10. Lattice Parameter of Polycrystalline Diamond in the Low-Temperature Range

    International Nuclear Information System (INIS)

    Paszkowicz, W.; Piszora, P.; Lasocha, W.; Margiolaki, I.; Brunelli, M.; Fitch, A.

    2010-01-01

    The lattice parameter for polycrystalline diamond is determined as a function of temperature in the 4-300 K temperature range. In the range studied, the lattice parameter, expressed in angstrom units, of the studied sample increases according to the equation a = 3.566810(12) + 6.37(41) x 10 -14 T 4 (approximately, from 3.5668 to 3.5673 A). This increase is larger than that earlier reported for pure single crystals. The observed dependence and the resulting thermal expansion coefficient are discussed on the basis of literature data reported for diamond single crystals and polycrystals. (authors)

  11. Low temperature anomalies in the lattice parameters of rare earth compounds and UPd3

    International Nuclear Information System (INIS)

    Pluemacher, D.

    1980-01-01

    Using a low temperature diffractometer, intermediate valence effects and crystal defects can be identified from the temperature dependence of the lattice parameters and the Debye-Waller factor. For polycrystalline powder samples the measuring error are too large. For intermediate valence systems the relative change in the 4f-level population probability can be calculated together with the anisotropic effects on the lattice parameters and on the unit cell colume. Pronounced effects on the lattice parameters can be observed in the case of RE Cu 2 Si 2 compounds with crystal fields. (DG) [de

  12. Partial rotational lattice order–disorder in stefin B crystals

    International Nuclear Information System (INIS)

    Renko, Miha; Taler-Verčič, Ajda; Mihelič, Marko; Žerovnik, Eva; Turk, Dušan

    2014-01-01

    Crystal lattice disorders are a phenomenon which may hamper the determination of macromolecular crystal structures. Using the case of the crystal structure of stefin B, identification of rotational order–disorder and structure determination are described. At present, the determination of crystal structures from data that have been acquired from twinned crystals is routine; however, with the increasing number of crystal structures additional crystal lattice disorders are being discovered. Here, a previously undescribed partial rotational order–disorder that has been observed in crystals of stefin B is described. The diffraction images revealed normal diffraction patterns that result from a regular crystal lattice. The data could be processed in space groups I4 and I422, yet one crystal exhibited a notable rejection rate in the higher symmetry space group. An explanation for this behaviour was found once the crystal structures had been solved and refined and the electron-density maps had been inspected. The lattice of stefin B crystals is composed of five tetramer layers: four well ordered layers which are followed by an additional layer of alternatively placed tetramers. The presence of alternative positions was revealed by the inspection of electron-density score maps. The well ordered layers correspond to the crystal symmetry of space group I422. In addition, the positions of the molecules in the additional layer are related by twofold rotational axes which correspond to space group I422; however, these molecules lie on the twofold axis and can only be related in a statistical manner. When the occupancies of alternate positions and overlapping are equal, the crystal lattice indeed fulfills the criteria of space group I422; when these occupancies are not equal, the lattice only fulfills the criteria of space group I4

  13. Measurement of lattice parameters of single crystals and thin layers

    Czech Academy of Sciences Publication Activity Database

    Drahokoupil, Jan; Veřtát, P.; Richterová, Kristina; Laufek, František

    2014-01-01

    Roč. 21, č. 2 (2014), s. 97-97 ISSN 1211-5894. [Struktura 2014 : kolokvium Krystalografické společnosti. 09.06.2014-12.06.2014, Kutná Hora] Institutional support: RVO:68378271 Keywords : XRD * lattice parameters Subject RIV: BM - Solid Matter Physics ; Magnetism http://www. xray .cz/ms/bul2014-2/wednesday1.pdf

  14. Modeling of monolayer charge-stabilized colloidal crystals with static hexagonal crystal lattice

    Science.gov (United States)

    Nagatkin, A. N.; Dyshlovenko, P. E.

    2018-01-01

    The mathematical model of monolayer colloidal crystals of charged hard spheres in liquid electrolyte is proposed. The particles in the monolayer are arranged into the two-dimensional hexagonal crystal lattice. The model enables finding elastic constants of the crystals from the stress-strain dependencies. The model is based on the nonlinear Poisson-Boltzmann differential equation. The Poisson-Boltzmann equation is solved numerically by the finite element method for any spatial configuration. The model has five geometrical and electrical parameters. The model is used to study the crystal with particles comparable in size with the Debye length of the electrolyte. The first- and second-order elastic constants are found for a broad range of densities. The model crystal turns out to be stable relative to small uniform stretching and shearing. It is also demonstrated that the Cauchy relation is not fulfilled in the crystal. This means that the pair effective interaction of any kind is not sufficient to proper model the elasticity of colloids within the one-component approach.

  15. Quantum concept of the rearrangement of a crystal lattice

    International Nuclear Information System (INIS)

    Gureev, M.D.; Mednikov, S.I.

    1995-01-01

    Using quantum considerations based on the concept of lattice rearrangement waves, we carried out an analysis of processes of rearrangement of a crystal lattice occurring on a moving front (interface) of crystal rearrangement. For the introduction and quantization of these waves we use the method of acoustomechanical analogy and the Sommerfeld quantum conditions. We calculate the energies and the propagation velocities of the lattice rearrangement waves. Along with quanta having a certain momentum, quanta that have a certain angular momentum are introduced into consideration. On the basis of the concepts developed, we suggest a new expression for calculating the probability of thermofluctuational processes in a crystal. We perform a numerical analysis of the rate of growth of the γ-phase in iron in the process of α-γ-conversion. Satisfactory agreement with experiment is obtained. We discuss the limitations and prospects of further development of the concept suggested. For direct experimental verification of the concept we propose to investigate the diffraction of electrons and other particles on the lattice rearrangement waves, i.e., in the process of phase conversions or disintegration of crystals

  16. A novel lattice energy calculation technique for simple inorganic crystals

    Energy Technology Data Exchange (ETDEWEB)

    Kaya, Cemal [Department of Chemistry, Faculty of Science, Cumhuriyet University, 58140 Sivas (Turkey); Kaya, Savaş, E-mail: savaskaya@cumhuriyet.edu.tr [Department of Chemistry, Faculty of Science, Cumhuriyet University, 58140 Sivas (Turkey); Banerjee, Priyabrata [Surface Engineering and Tribology Group, CSIR-Central Mechanical Engineering Research Institute, Mahatma Gandhi Avenue, Durgapur 713209 (India)

    2017-01-01

    In this pure theoretical study, a hitherto unexplored equation based on Shannon radii of the ions forming that crystal and chemical hardness of any crystal to calculate the lattice energies of simple inorganic ionic crystals has been presented. To prove the credibility of this equation, the results of the equation have been compared with experimental outcome obtained from Born-Fajans-Haber- cycle which is fundamentally enthalpy-based thermochemical cycle and prevalent theoretical approaches proposed for the calculation of lattice energies of ionic compounds. The results obtained and the comparisons made have demonstrated that the new equation is more useful compared to other theoretical approaches and allows to exceptionally accurate calculation of lattice energies of inorganic ionic crystals without doing any complex calculations.

  17. Lattice dynamics of ionic crystals

    International Nuclear Information System (INIS)

    Mahan, G.D.

    1990-01-01

    The theory of lattice dynamics for ionic and rare-gas crystals is derived in the harmonic approximation. We start from a Hamiltonian and average over electron coordinates in order to obtain an effective interaction between ion displacements. We assume that electronic excitations are localized on a single ion, which limits the theory to ionic crystals. The deformation-dipole model and the indirect-ionic-interaction model are derived. These two contributions are closely linked, and together provide an accurate description of short-range forces

  18. Investigations of the EPR parameters and local lattice structure for the rhombic Cu{sup 2+} centre in TZSH crystal

    Energy Technology Data Exchange (ETDEWEB)

    Li, Chao-Ying; Liu, Shi-Fei; Fu, Jin-Xian [Shangrao Normal University, Jiangxi (China). School of Physics and Electronic Information

    2016-07-01

    The electron paramagnetic resonance (EPR) parameters [i.e. g factors g{sub i} (i=x, y, z) and hyperfine structure constants A{sub i}] and the local lattice structure for the Cu{sup 2+} centre in Tl{sub 2}Zn(SO{sub 4}){sub 2}.6H{sub 2}O (TZSH) crystal were theoretically investigated by utilising the perturbation formulae of these parameters for a 3d{sup 9} ion under rhombically elongated octahedra. In the calculations, the admixture of d orbitals in the ground state and the ligand orbital and spin-orbit coupling interactions are taken into account based on the cluster approach. The theoretical EPR parameters show good agreement with the observed values, and the Cu{sup 2+}-H{sub 2}O bond lengths are obtained as follows: R{sub x}∼1.98 Aa, R{sub y}∼2.09 Aa, R{sub z}∼2.32 Aa. The results are discussed.

  19. Determination of lattice parameters, strain state and composition in semipolar III-nitrides using high resolution X-ray diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Frentrup, Martin, E-mail: frentrup@physik.tu-berlin.de; Wernicke, Tim; Stellmach, Joachim; Kneissl, Michael [Institute of Solid State Physics, Technische Universität Berlin, Hardenbergstr. 36, 10623 Berlin (Germany); Hatui, Nirupam; Bhattacharya, Arnab [Department of Condensed Matter Physics and Materials Science, Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400005 (India)

    2013-12-07

    In group-III-nitride heterostructures with semipolar or nonpolar crystal orientation, anisotropic lattice and thermal mismatch with the buffer or substrate lead to a complex distortion of the unit cells, e.g., by shearing of the lattice. This makes an accurate determination of lattice parameters, composition, and strain state under assumption of the hexagonal symmetry impossible. In this work, we present a procedure to accurately determine the lattice constants, strain state, and composition of semipolar heterostructures using high resolution X-ray diffraction. An analysis of the unit cell distortion shows that four independent lattice parameters are sufficient to describe this distortion. Assuming only small deviations from an ideal hexagonal structure, a linear expression for the interplanar distances d{sub hkl} is derived. It is used to determine the lattice parameters from high resolution X-ray diffraction 2ϑ-ω-scans of multiple on- and off-axis reflections via a weighted least-square fit. The strain and composition of ternary alloys are then evaluated by transforming the elastic parameters (using Hooke's law) from the natural crystal-fixed coordinate system to a layer-based system, given by the in-plane directions and the growth direction. We illustrate our procedure taking an example of (112{sup ¯}2) Al{sub κ}Ga{sub 1−κ}N epilayers with Al-contents over the entire composition range. We separately identify the in-plane and out-of-plane strains and discuss origins for the observed anisotropy.

  20. Certain methods for improving the accuracy of lattice parameter determination in sloping scanning with the use of single-crystal spectrometer

    International Nuclear Information System (INIS)

    Pinegin, V.I.; Koz'ma, A.A.; Fuks, M.Ya.

    1985-01-01

    Errors are accounted for the sloping scanning that is a base of X-ray tenzometry and requires high accuracy of lattice parameter determination including a limp state parameter. A technique is suggested for elimination of systematic alignment errors due to deviation of the primary beam and eccentricity of an irradiated sample surface relative to the main axis of a goniometer. The technique allows to decrease a relative error in interplanar distance determination from 10 -4 to 10 -5 using the DRON-20 diffractometer. Analytical expressions are obtained for correction calculations. The technique can be used in sloping scanning of imperfect single- and polycrystals. Experimental test of the technique has been carried out with epitaxy single-crystal nickel films 500 to 2000 A thick with the use of copper radiation

  1. Unidirectional edge states in topological honeycomb-lattice membrane photonic crystals.

    Science.gov (United States)

    Anderson, P Duke; Subramania, Ganapathi

    2017-09-18

    Photonic analogs of electronic systems with topologically non-trivial behavior such as unidirectional scatter-free propagation has tremendous potential for transforming photonic systems. Like in electronics topological behavior can be observed in photonics for systems either preserving time-reversal (TR) symmetry or explicitly breaking it. TR symmetry breaking requires magneto-optic photonics crystals (PC) or generation of synthetic gauge fields. For on-chip photonics that operate at optical frequencies both are quite challenging because of poor magneto-optic response of materials or substantial nanofabrication challenges in generating synthetic gauge fields. A recent work by Ma, et al. [Phys. Rev. Lett.114, 223901 (2015)] based on preserving pseudo TR symmetry offers a promising design scheme for observing unidirectional edge states in a modified honeycomb photonic crystal (PC) lattice of circular rods that offers encouraging alternatives. Here we propose through bandstructure calculations the inverse system of modified honeycomb PC of circular holes in a dielectric membrane which is more attractive from fabrication standpoint for on-chip applications. We observe trivial and non-trivial bandgaps as well as unidirectional edge states of opposite helicity propagating in opposite directions at the interface of a trivial and non-trivial PC structures. Around 1550nm operating wavelength ~55nm of bandwidth is possible for practicable values of design parameters (lattice constant, hole radii, membrane thickness, scaling factor etc.) and robust to reasonable variations in those parameters.

  2. Lattice location of gold in natural pyrite crystals

    International Nuclear Information System (INIS)

    Besten, Jacinta den; Jamieson, David N.; Ryan, Chris G.

    1999-01-01

    The lattice location of gold atoms in naturally occurring Au-doped pyrite crystals has been investigated with a nuclear microprobe using ion channeling. The specimens consisted of 300-μm diameter pyrite crystals in veins embedded in a quartz matrix from the Emperor mine in Fiji. The specimens were prepared by standard geological specimen preparation techniques and the pyrite crystals were analysed in situ in the quartz matrix. Significant trace elements in the crystals, determined by Proton Induced X-ray Emission with a 3 MeV H + microprobe, were Cu, As, Mo, Zn, Te, Au and Pb. The Au concentration was about 0.2 wt%. By the use of 2 MeV He + ion channeling, the Miller indices of the lowest order crystal axes nearest to the normal were determined from backscattering yield maps from two-dimensional angular scanning and comparison of the resulting patterns with published gnomonic projections. Channeling angular yield curves were obtained from Fe, S, As and Au signals. The results indicate that at least 35% of the Au is substituted onto lattice sites

  3. Coherent-potential approximation for the lattice vibrations of mixed III-V crystals

    International Nuclear Information System (INIS)

    Kleinert, P.

    1984-01-01

    The coherent-potential approximation (CPA) is applied to the lattice dynamics of some III-V mixed crystals. The calculations are based on an eleven-parameter rigid-ion model (RIM 11). Explicit results are reported for the one-mode system In/sub 1-c/Ga/sub c/P and the two mixed-mode crystals In/sub 1-c/Ga/sub c/Sb and GaSb/sub 1-c/As/sub c/. Both, the reflectivity spectra and the composition dependence of vibrations at the GAMMA and X points are compared with existing experimental data. Force-constant changes are considered by the virtual-crystal approximation (VCA). The CPA theory is uniquely successful for III-V mixed-mode systems, which appear to switch from one-mode to two-mode behaviour. (author)

  4. Impact of Heterogeneity and Lattice Bond Strength on DNA Triangle Crystal Growth.

    Science.gov (United States)

    Stahl, Evi; Praetorius, Florian; de Oliveira Mann, Carina C; Hopfner, Karl-Peter; Dietz, Hendrik

    2016-09-07

    One key goal of DNA nanotechnology is the bottom-up construction of macroscopic crystalline materials. Beyond applications in fields such as photonics or plasmonics, DNA-based crystal matrices could possibly facilitate the diffraction-based structural analysis of guest molecules. Seeman and co-workers reported in 2009 the first designed crystal matrices based on a 38 kDa DNA triangle that was composed of seven chains. The crystal lattice was stabilized, unprecedentedly, by Watson-Crick base pairing. However, 3D crystallization of larger designed DNA objects that include more chains such as DNA origami remains an unsolved problem. Larger objects would offer more degrees of freedom and design options with respect to tailoring lattice geometry and for positioning other objects within a crystal lattice. The greater rigidity of multilayer DNA origami could also positively influence the diffractive properties of crystals composed of such particles. Here, we rationally explore the role of heterogeneity and Watson-Crick interaction strengths in crystal growth using 40 variants of the original DNA triangle as model multichain objects. Crystal growth of the triangle was remarkably robust despite massive chemical, geometrical, and thermodynamical sample heterogeneity that we introduced, but the crystal growth sensitively depended on the sequences of base pairs next to the Watson-Crick sticky ends of the triangle. Our results point to weak lattice interactions and high concentrations as decisive factors for achieving productive crystallization, while sample heterogeneity and impurities played a minor role.

  5. Enhancement of polymer dye lasers by multifunctional photonic crystal lattice

    DEFF Research Database (Denmark)

    Christiansen, Mads Brøkner; Xiao, Sanshui; Mortensen, Asger

    2009-01-01

    The light output of dye doped hybrid polymer band-edge lasers is increased more than 100 times by using a rectangular lattice photonic crystal, which provides both feedback and couples more pump light into the laser.......The light output of dye doped hybrid polymer band-edge lasers is increased more than 100 times by using a rectangular lattice photonic crystal, which provides both feedback and couples more pump light into the laser....

  6. Improved ferroelectric and pyroelectric parameters in iminodiacetic acid doped TGS crystal

    Science.gov (United States)

    Rai, Chitharanjan; Sreenivas, K.; Dharmaprakash, S. M.

    2010-01-01

    Single crystals of Iminodiacetic acid (HN(CH 2COOH) 2) doped Triglycine sulphate (IDATGS) has been grown from aqueous solution at constant temperature by slow evaporation technique. The concentration of the dopant in the TGS solution was 2 mol%. The X-ray diffraction analysis indicates that there is significant change in the lattice parameters compared to pure TGS crystal. The IDATGS crystal has larger transition temperature and observed higher and uniform figure of merit over most part of the ferroelectric phase. These crystals also exhibit higher internal bias field and micro-hardness number compared to pure TGS. Therefore IDATGS may be a potential material for IR detectors.

  7. Effect of plasma absorption on dust lattice waves in hexagonal dust crystals

    Science.gov (United States)

    Kerong, HE; Hui, CHEN; Sanqiu, LIU

    2018-04-01

    In the present paper, the effect of plasma absorption on lattice waves in 2D hexagonal dust crystals is investigated. The dispersion relations with the effect of plasma absorption are derived. It is found that the temperature effect (electron-to-ion temperature ratio τ) enhances the frequency of the dust lattice waves, while the spatial effect (dimensionless Debye shielding parameter \\tilde{κ }) weakens the frequency of the dust lattice waves. In addition, the system stabilities under the conditions of plasma absorption are studied. It is found that the temperature effect narrows the range of instability, while the spatial effect extends this range. And the range of instability is calculated, i.e. the system will always in the stable state regardless of the value of \\tilde{κ } when τ > 3.5. However, the system will be unstable when τ = 1 and \\tilde{κ }> 4.1.

  8. Grain size and lattice parameter's influence on band gap of SnS thin nano-crystalline films

    Energy Technology Data Exchange (ETDEWEB)

    Gupta, Yashika [Department of Electronics, S.G.T.B. Khalsa College, University of Delhi, Delhi 110007 (India); Department of Electronic Science, University of Delhi-South Campus, New Delhi 110021 (India); Arun, P., E-mail: arunp92@physics.du.ac.in [Department of Electronics, S.G.T.B. Khalsa College, University of Delhi, Delhi 110007 (India); Naudi, A.A.; Walz, M.V. [Facultad de Ingeniería, Universidad Nacional de Entre Ríos, 3101 Oro Verde (Argentina); Albanesi, E.A. [Facultad de Ingeniería, Universidad Nacional de Entre Ríos, 3101 Oro Verde (Argentina); Instituto de Física del Litoral (CONICET-UNL), Guemes 3450, 3000 Santa Fe (Argentina)

    2016-08-01

    Tin sulphide nano-crystalline thin films were fabricated on glass and Indium Tin Oxide (ITO) substrates by thermal evaporation method. The crystal structure orientation of the films was found to be dependent on the substrate. Residual stress existed in the films due to these orientations. This stress led to variation in lattice parameter. The nano-crystalline grain size was also found to vary with film thickness. A plot of band-gap with grain size or with lattice parameter showed the existence of a family of curves. This implied that band-gap of SnS films in the preview of the present study depends on two parameters, lattice parameter and grain size. The band-gap relation with grain size is well known in the nano regime. Experimental data fitted well with this relation for the given lattice constants. The manuscript uses theoretical structure calculations for different lattice constants and shows that the experimental data follows the trend. Thus, confirming that the band gap has a two variable dependency. - Highlights: • Tin sulphide films are grown on glass and ITO substrates. • Both substrates give differently oriented films. • The band-gap is found to depend on grain size and lattice parameter. • Using data from literature, E{sub g} is shown to be two parameter function. • Theoretical structure calculations are used to verify results.

  9. Phonon-enhanced crystal growth and lattice healing

    Science.gov (United States)

    Buonassisi, Anthony; Bertoni, Mariana; Newman, Bonna

    2013-05-28

    A system for modifying dislocation distributions in semiconductor materials is provided. The system includes one or more vibrational sources for producing at least one excitation of vibrational mode having phonon frequencies so as to enhance dislocation motion through a crystal lattice.

  10. Photonic Crystal Waveguides in Triangular Lattice of Nanopillars

    DEFF Research Database (Denmark)

    Chigrin, Dmitry N.; Lavrinenko, Andrei

    2004-01-01

    Photonic nanopillars waveguides have been analysed. Dielectric nanopillars are arranged in such way that they from a tringular lattice of 2D photonic crystal. Dispersion of the modes depends on the direction of the triangular lattice, Ã-J or Ã-X, in which nanopillars arrays are extended. Light fi....... Transmission spectra calculated by FDTD method completely reflect peculiarities of modes dispersion, showing up to 80% transmission for a realistic SOI nanopillar structure....

  11. Lattice effects in YVO3 single crystal

    NARCIS (Netherlands)

    Marquina, C; Sikora, M; Ibarra, MR; Nugroho, AA; Palstra, TTM

    In this paper we report on the lattice effects in the Mott insulator yttrium orthovanadate (YVO3). Linear thermal expansion and magnetostriction experiments have been performed on a single crystal, in the temperature range from 5 K to room temperature. The YVO3 orders antiferromagnetically at T-N =

  12. Lattice dynamics and thermal diffuse scattering for molecular crystals

    International Nuclear Information System (INIS)

    Kroon, P.A.

    1977-01-01

    Thermal diffuse scattering (TDS) corrections on the observed reflection intensities in the accurate determination of crystal structures by X-ray diffraction are emphasized. A lattice-dynamical model and procedure for lattice-dynamical calculations are set up. Expression for first- and second-order TDS intensity distributions are derived. A comparison with other models is made. First-order TDS corrections for naphtalene at 100 K are presented

  13. Interaction between crystal lattice and mobile ions in copper selenides studied by EXAFS spectroscopy

    International Nuclear Information System (INIS)

    Asylgushina, G.N.; Bikkulova, N.N.; Titova, S.G.; Kochubey, D.I.

    2005-01-01

    Interaction between crystal lattice and mobile Cu ions has been studied in Cu 2- x Se in superionic and in normal state using EXAFS-spectroscopy. It has been found that the transition from normal to superionic state and change of mobile Cu ion concentration practically do not have an influence on local state of Cu atoms, but change of both these parameters is accompanied by a change of Se-sublattice state

  14. Size and shape dependent lattice parameters of metallic nanoparticles

    International Nuclear Information System (INIS)

    Qi, W. H.; Wang, M. P.

    2005-01-01

    A model is developed to account for the size and shape dependent lattice parameters of metallic nanoparticles, where the particle shape difference is considered by introducing a shape factor. It is predicted that the lattice parameters of nanoparticles in several nanometers decrease with decreasing of the particle size, which is consistent with the corresponding experimental results. Furthermore, it is found that the particle shape can lead to 10% of the total lattice variation. The model is a continuous media model and can deal with the nanoparticles larger than 1 nm. Since the shape factor approaches to infinity for nanowires and nanofilms, therefore, the model cannot be generalized to the systems of nanowires and nanofilms. For the input parameters are physical constants of bulk materials, therefore, the present model may be used to predict the lattice variation of different metallic nanoparticles with different lattice structures

  15. Influence of processing parameters on lattice parameters in laser deposited tool alloy steel

    Energy Technology Data Exchange (ETDEWEB)

    Sun, G.F., E-mail: gfsun82@gmail.com [Center for Laser-Aided Intelligent Manufacturing, University of Michigan, Ann Arbor, MI, 48109 (United States); School of Mechanical Engineering, Jiangsu University, Zhenjiang, Jiangsu, 212013 (China); Bhattacharya, S. [Center for Laser-Aided Intelligent Manufacturing, University of Michigan, Ann Arbor, MI, 48109 (United States); Dinda, G.P.; Dasgupta, A. [Center for Advanced Technologies, Focus: Hope, Detroit, MI, 48238 (United States); Mazumder, J. [Center for Laser-Aided Intelligent Manufacturing, University of Michigan, Ann Arbor, MI, 48109 (United States)

    2011-06-15

    Highlights: {yields} Orientation relationships among phases in the DMD are given. {yields} Martensite lattice parameters increased with laser specific energy. {yields} Austenite lattice parameters decreased with laser specific energy. - Abstract: Laser aided direct metal deposition (DMD) has been used to form AISI 4340 steel coating on the AISI 4140 steel substrate. The microstructural property of the DMD coating was analyzed by means of scanning electron microscopy, transmission electron microscopy and X-ray diffractometry. Microhardness of the DMD was measured with a Vickers microhardness tester. Results indicate that DMD can be used to form dense AISI 4340 steel coatings on AISI 4140 steel substrate. The DMD coating is mainly composed of martensite and retained austenite. Consecutive thermal cycles have a remarkable effect on the microstructure of the plan view of the DMD coating and on the corresponding microhardness distribution. Orientation relationships among austenite, martensite and cementite in the DMD coating followed the ones in conventional heat treated steels. As the laser specific energy decreased, cooling rate increased, and martensite peaks broadened and shifted to a lower Bragg's angle. Also martensite lattice parameters increased and austenite lattice parameters decreased due to the above parameter change.

  16. Influence of processing parameters on lattice parameters in laser deposited tool alloy steel

    International Nuclear Information System (INIS)

    Sun, G.F.; Bhattacharya, S.; Dinda, G.P.; Dasgupta, A.; Mazumder, J.

    2011-01-01

    Highlights: → Orientation relationships among phases in the DMD are given. → Martensite lattice parameters increased with laser specific energy. → Austenite lattice parameters decreased with laser specific energy. - Abstract: Laser aided direct metal deposition (DMD) has been used to form AISI 4340 steel coating on the AISI 4140 steel substrate. The microstructural property of the DMD coating was analyzed by means of scanning electron microscopy, transmission electron microscopy and X-ray diffractometry. Microhardness of the DMD was measured with a Vickers microhardness tester. Results indicate that DMD can be used to form dense AISI 4340 steel coatings on AISI 4140 steel substrate. The DMD coating is mainly composed of martensite and retained austenite. Consecutive thermal cycles have a remarkable effect on the microstructure of the plan view of the DMD coating and on the corresponding microhardness distribution. Orientation relationships among austenite, martensite and cementite in the DMD coating followed the ones in conventional heat treated steels. As the laser specific energy decreased, cooling rate increased, and martensite peaks broadened and shifted to a lower Bragg's angle. Also martensite lattice parameters increased and austenite lattice parameters decreased due to the above parameter change.

  17. Atomic lattice excitons: from condensates to crystals

    International Nuclear Information System (INIS)

    Kantian, A; Daley, A J; Toermae, P; Zoller, P

    2007-01-01

    We discuss atomic lattice excitons (ALEs), bound particle-hole pairs formed by fermionic atoms in two bands of an optical lattice. Such a system provides a clean set-up, with tunable masses and interactions, to study fundamental properties of excitons including exciton condensation. We also find that for a large effective mass ratio between particles and holes, effective long-range interactions can mediate the formation of an exciton crystal, for which superfluidity is suppressed. Using a combination of mean-field treatments, bosonized theory based on a Born-Oppenheimer approximation, and one-dimensional (1D) numerical computation, we discuss the properties of ALEs under varying conditions, and discuss in particular their preparation and measurement

  18. Atomic lattice excitons: from condensates to crystals

    Energy Technology Data Exchange (ETDEWEB)

    Kantian, A [Institute for Quantum Optics and Quantum Information of the Austrian Academy of Sciences, A-6020 Innsbruck (Austria); Daley, A J [Institute for Quantum Optics and Quantum Information of the Austrian Academy of Sciences, A-6020 Innsbruck (Austria); Toermae, P [Nanoscience Center, Department of Physics, University of Jyvaeskylae, PO Box 35, FIN-40014 (Finland); Zoller, P [Institute for Quantum Optics and Quantum Information of the Austrian Academy of Sciences, A-6020 Innsbruck (Austria)

    2007-11-15

    We discuss atomic lattice excitons (ALEs), bound particle-hole pairs formed by fermionic atoms in two bands of an optical lattice. Such a system provides a clean set-up, with tunable masses and interactions, to study fundamental properties of excitons including exciton condensation. We also find that for a large effective mass ratio between particles and holes, effective long-range interactions can mediate the formation of an exciton crystal, for which superfluidity is suppressed. Using a combination of mean-field treatments, bosonized theory based on a Born-Oppenheimer approximation, and one-dimensional (1D) numerical computation, we discuss the properties of ALEs under varying conditions, and discuss in particular their preparation and measurement.

  19. Investigation the effect of lattice angle on the band gap width in 3D phononic crystals with rhombohedral(I) lattice

    Science.gov (United States)

    Salehi, H.; Aryadoust, M.; Shoushtari, M. Zargar

    2014-07-01

    In this paper, the propagation of acoustic waves in the phononic crystal of 3D with rhombohedral(I) lattice is studied theoretically. The crystal composite constituted of nickel spheres embedded in epoxy. The calculations of the band structure and density of states are performed with the plane wave expansion method in the irreducible part of Brillouin zone. In the present work, we have investigated the effect of lattice angle on the band structure and width of the band gap rhombohedral(I) lattice in the irreducible part of the first Brillouin zone and its planes separately. The results show that more than one complete band gape are formed in the four planes of the irreducible part. The most complete band gaps are formed in the (111) plane and the widest complete band gap in (443) with an angle greater than 80. So, if the sound passes through the (111) and (443) planes for the lattice angle close to 90, the crystal phononic displays the excellent insulation behavior. Moreover, in the other planes, the lattice angle does not affect on the width and the number of band gaps. Also, for the filling fraction 5 %, the widest complete band gap is formed. These results are consistent with the effect of symmetry on the band gap width, because the (111) plane has the most symmetry.

  20. Application of Powder Diffraction Methods to the Analysis of the Atomic Structure of Nanocrystals: The Concept of the Apparent Lattice Parameter (ALP)

    Science.gov (United States)

    Palosz, B.; Grzanka, E.; Gierlotka, S.; Stelmakh, S.; Pielaszek, R.; Bismayer, U.; Weber, H.-P.; Palosz, W.; Curreri, Peter A. (Technical Monitor)

    2002-01-01

    The applicability of standard methods of elaboration of powder diffraction data for determination of the structure of nano-size crystallites is analysed. Based on our theoretical calculations of powder diffraction data we show, that the assumption of the infinite crystal lattice for nanocrystals smaller than 20 nm in size is not justified. Application of conventional tools developed for elaboration of powder diffraction data, like the Rietveld method, may lead to erroneous interpretation of the experimental results. An alternate evaluation of diffraction data of nanoparticles, based on the so-called 'apparent lattice parameter' (alp) is introduced. We assume a model of nanocrystal having a grain core with well-defined crystal structure, surrounded by a surface shell with the atomic structure similar to that of the core but being under a strain (compressive or tensile). The two structural components, the core and the shell, form essentially a composite crystal with interfering, inseparable diffraction properties. Because the structure of such a nanocrystal is not uniform, it defies the basic definitions of an unambiguous crystallographic phase. Consequently, a set of lattice parameters used for characterization of simple crystal phases is insufficient for a proper description of the complex structure of nanocrystals. We developed a method of evaluation of powder diffraction data of nanocrystals, which refers to a core-shell model and is based on the 'apparent lattice parameter' methodology. For a given diffraction pattem, the alp values are calculated for every individual Bragg reflection. For nanocrystals the alp values depend on the diffraction vector Q. By modeling different a0tomic structures of nanocrystals and calculating theoretically corresponding diffraction patterns using the Debye functions we showed, that alp-Q plots show characteristic shapes which can be used for evaluation of the atomic structure of the core-shell system. We show, that using a simple

  1. Band structures of phononic crystal composed of lattices with different periodic constants

    International Nuclear Information System (INIS)

    Hu, Jia-Guang; Xu, Wen

    2014-01-01

    With a square lattice mercury and water system being as the model, the band structures of nesting and compound phononic crystals with two different lattice constants were investigated using the method of the supercell plane wave expansion. It was observed that large band gaps can be achieved in low frequency regions by adjusting one of the lattice constants. Meanwhile, effects similar to interstitial impurity defects can be achieved with the increase of lattice constant of the phononic crystal. The corresponding defect modes can be stimulated in band gaps. The larger the lattice constant, the stronger the localization effect of defect modes on the wave. In addition, the change of the filling fraction of impurity exerts great influence on the frequency and localization of defect modes. Furthermore, the change of the position of impurity has notable influence on the frequency of defect modes and their localization. However, the geometry structure and orientation of impurity have little effect on the frequency of defect modes and their localization in the band gap.

  2. Orientation-dependent forces between flux lines and crystal lattice in pure niobium

    International Nuclear Information System (INIS)

    Holzhauser, W.

    1976-01-01

    Torque measurements were performed with cylindrical niobium crystals, due to the very small pinning of the high-purity material. A torque that tries to align the flux lines along special directions of the crystal lattice was studied

  3. Self-organization processes and nanocluster formation in crystal lattices by low-energy ion irradiation

    International Nuclear Information System (INIS)

    Tereshko, I.; Abidzina, V.; Tereshko, A.; Glushchenko, V.; Elkin, I.

    2007-01-01

    The goal of this paper is to study self-organization processes that cause nanostructural evolution in nonlinear crystal media. The subjects of the investigation were nonlinear homogeneous and heterogeneous atom chains. The method of computer simulation was used to investigate the interaction between low-energy ions and crystal lattices. It was based on the conception of three-dimensional lattice as a nonlinear atom chain system. We showed that that in homogeneous atom chains critical energy needed for self-organization processes development is less than for nonlinear atom chain with already embedded clusters. The possibility of nanostructure formation was studied by a molecular dynamics method of nonlinear oscillations in atomic oscillator systems of crystal lattices after their low-energy ion irradiation. (authors)

  4. Lattice effects in HoVo(3) single crystal

    NARCIS (Netherlands)

    Sikora, M.; Marquina, C.; Ibarra, M. R.; Nugroho, A. A.; Palstra, T. T. M.

    We report the study of lattice effects in the Mott insulator HoVO3 performed by means of linear thermal expansion on a single crystal in the temperature range 10-290 K. The holmium orthovanadate HoVO3 reveals gradual orbital ordering (OO) below T-OO = 200K and orders antiferromagnetically at T-N =

  5. Lattice distortion under an electric field in BaTiO3 piezoelectric single crystal

    International Nuclear Information System (INIS)

    Tazaki, Ryoko; Fu Desheng; Daimon, Masahiro; Koshihara, Shin-ya; Itoh, Mitsuru

    2009-01-01

    Lattice distortions under an electric field in a mono-domain of BaTiO 3 ferroelectric crystal have been detected with synchrotron x-ray radiation. The variation of the lattice constant with an electric field observed with high angle diffraction shows a linear response nature of the piezoelectric effect. When an electric field is applied along the spontaneous polarization direction, the c-axis of the lattice elongates and the a-axis of the lattice shrinks at a rate of d 33 = 149 ± 54 pm V -1 and d 31 = -82 ± 61 pm V -1 ; these represent the longitudinal and transverse piezoelectric coefficients of BaTiO 3 crystal, respectively. These results give an insight into the intrinsic piezoelectric response on the lattice scale in BaTiO 3 that has been widely used to explore high performance lead-free piezoelectric alloys.

  6. Steady-state hydrodynamic instabilities of active liquid crystals: hybrid lattice Boltzmann simulations.

    Science.gov (United States)

    Marenduzzo, D; Orlandini, E; Cates, M E; Yeomans, J M

    2007-09-01

    We report hybrid lattice Boltzmann (HLB) simulations of the hydrodynamics of an active nematic liquid crystal sandwiched between confining walls with various anchoring conditions. We confirm the existence of a transition between a passive phase and an active phase, in which there is spontaneous flow in the steady state. This transition is attained for sufficiently "extensile" rods, in the case of flow-aligning liquid crystals, and for sufficiently "contractile" ones for flow-tumbling materials. In a quasi-one-dimensional geometry, deep in the active phase of flow-aligning materials, our simulations give evidence of hysteresis and history-dependent steady states, as well as of spontaneous banded flow. Flow-tumbling materials, in contrast, rearrange themselves so that only the two boundary layers flow in steady state. Two-dimensional simulations, with periodic boundary conditions, show additional instabilities, with the spontaneous flow appearing as patterns made up of "convection rolls." These results demonstrate a remarkable richness (including dependence on anchoring conditions) in the steady-state phase behavior of active materials, even in the absence of external forcing; they have no counterpart for passive nematics. Our HLB methodology, which combines lattice Boltzmann for momentum transport with a finite difference scheme for the order parameter dynamics, offers a robust and efficient method for probing the complex hydrodynamic behavior of active nematics.

  7. Resolution of the hydroxyapatite crystal lattice in bone and dental enamel by electron microscopy

    International Nuclear Information System (INIS)

    Selvig, K.A.

    1975-01-01

    The molecular and atomic structure of hydroxyapatite was studied by transmission electron microscopy. The form, size and packing of hydroxyapatite crystals in sections of bone and dental hard tissues could be determined. Lattice fringe patterns with repeat distances in the range 2.7-8.2 A occurred in images of individual crystals. On the basis of these fringes the true orientation of the crystals relative to the plane of sectioning was calculated. The observed crystal lattice spacings and interplanar angles were in close agreement with data derived from X-ray diffraction analysis. This study shows that the possibility exists of relating crystallographic analysis to the morphology and fine structure of calcified tissue in health and disease

  8. Systematic and random erros in lattice parameter determinations

    International Nuclear Information System (INIS)

    Nascimento, E.M.

    1980-01-01

    A new method is proposed for evaluation of diffraction data used in precise determination of lattice parameters. The method is based on separation and systematic erros on the diffraction angles level, where the randon part of erros is independent on the 0 angle. The separation is enable by assumption that the systematic part of erros depends on the 0 angle linearly. In that situation the high precision in lattice parameters determination is related more to reducing the randon errors content that to the presence of unremoved systematic errors. (Author) [pt

  9. Lattice parameters of the Hg1-xFexSe and Cd1-xFexTe semimagnetic semiconductors

    International Nuclear Information System (INIS)

    Sarem, A.; Soulayman, S.

    2004-01-01

    Full text.Hg 1-x Fe x Se and Cd 1-x Fe x Te are members of a family of semiconducting alloys referred to as diluted magnetic semiconductors (DMS), i.e., ternary alloys whose lattice is made up in part of substitutional magnetic ions (in the present case, fe 2+ ). These materials are of considerable interest because, apart from the opportunities provided by the ternary nature of these compounds (e.g., tunability of the energy gap or the lattice constant), they display interesting magnetic properties as well as exchange interaction between the localized Fe 2+ moments and band electrons, resulting in a host of novel effects. In this paper we investigate the behavior of the crystal lattice of Hg 1-x Fe x Se and Cd 1-x Fe x Te, grown using modified Bridgman method. The purpose of the study is providing precise quantitative data for the lattice parameter as a function of x, which can then be used as a means of determining composition. The results of lattice parameter measurements on the ternary semiconductor alloys Hg 1-x Fe x Se over the range (0≤x≤0.15) and Cd 1-x Fe x Te in the range (0≤x≤0.03) are reports. Each sample was subjected to chemical analysis for determining the real concentration of iron. Here it was found that the differences between the nominal compositions and the real ones for all investigated samples are negligible. The powdered samples of Hg 1-x Fe x Se and Cd 1-x Fe x Te with different nominal compositions were studied using a DRON diffractometer with filtered Cο radiation (λ kα1 =1.78892A; λ kα2 =1.79278A). The diffraction patterns with a scan rate of 1 degree 2θ/min were taken. Precise measurements of the line position diffracted and extrapolation method to determine a to value θ=90 degree were made by Least Square Method. This method allowed determining cell parameters foe each sample with accuracy ±0.0001A. The crystal structure of these compounds was determined as a cubic one of the zinc blede type. The structural homogeneity of

  10. Effect of composition and. gamma. -irradiation on crystal lattice spacing of lead sulphide

    Energy Technology Data Exchange (ETDEWEB)

    Indenbaum, G V; Novikova, S F; Vanyukov, A V; Dvorkin, Yu V [Moskovskij Inst. Stali i Splavov (USSR)

    1981-02-01

    Value of crystal lattice spacing of lead sulphide after annealing and quenching at temperatures of 600, 700 and 800 deg C are found for the both boundaries of homogeneity region with error of 5x10/sup -5/A. The effect of ..gamma.. irradiation with quanta energy of 1.25 MeV from /sup 60/Co source (10/sup 4/, 10/sup 5/ and 10/sup 6/ G/kg) on crystal lattice spacing of lead sulphide preliminary saturated with sulphur or lead at 600 deg C, is studied. It is established that lattice spacing of lead sulphide depends on material prehistory and decreases at room temperature after quenching and ..gamma..-irradiation. Effect of natural ageing of lead sulphide is explained by the decomposition of nonstechiometric solid solution, supersaturated with components, at room temperature.

  11. Temperature dependence of lattice parameters of alpha-zirconium

    International Nuclear Information System (INIS)

    Versaci, R.A.; Ipohorski, M.

    1991-01-01

    This work presents a brief review of X-ray and thermal expansion determination of lattice parameters for α-Zirconium. Data reported by different authors cover almost all the field of existence of the hexagonal phase of Zirconium, from temperatures as low as 4.2 K up to about 1130 K, near the α→β transformation temperature. Polynomial expressions based on a least squares fitting of experimental data are also presented. The expressions obtained by Goldak et al. are considered to be the most complete. The influence of impurities on the lattice parameters is also discussed. (Author) [es

  12. Crystal structure of human CRMP-4: correction of intensities for lattice-translocation disorder

    Energy Technology Data Exchange (ETDEWEB)

    Ponnusamy, Rajesh [Universidade Nova de Lisboa, Avenida da República, EAN, 2781-901 Oeiras (Portugal); Lebedev, Andrey A. [Research Complex at Harwell, STFC Rutherford Appleton Laboratory, Didcot OX11 0FA (United Kingdom); Pahlow, Steffen [University of Hamburg, Ohnhorststrasse 18, 22609 Hamburg (Germany); Lohkamp, Bernhard, E-mail: bernhard.lohkamp@ki.se [Karolinska Institutet, Tomtebodavägen 6, 4tr, 17177 Stockholm (Sweden); Universidade Nova de Lisboa, Avenida da República, EAN, 2781-901 Oeiras (Portugal)

    2014-06-01

    Crystals of human CRMP-4 showed severe lattice-translocation disorder. Intensities were demodulated using the so-called lattice-alignment method and a new more general method with simplified parameterization, and the structure is presented. Collapsin response mediator proteins (CRMPs) are cytosolic phosphoproteins that are mainly involved in neuronal cell development. In humans, the CRMP family comprises five members. Here, crystal structures of human CRMP-4 in a truncated and a full-length version are presented. The latter was determined from two types of crystals, which were either twinned or partially disordered. The crystal disorder was coupled with translational NCS in ordered domains and manifested itself with a rather sophisticated modulation of intensities. The data were demodulated using either the two-lattice treatment of lattice-translocation effects or a novel method in which demodulation was achieved by independent scaling of several groups of intensities. This iterative protocol does not rely on any particular parameterization of the modulation coefficients, but uses the current refined structure as a reference. The best results in terms of R factors and map correlation coefficients were obtained using this new method. The determined structures of CRMP-4 are similar to those of other CRMPs. Structural comparison allowed the confirmation of known residues, as well as the identification of new residues, that are important for the homo- and hetero-oligomerization of these proteins, which are critical to nerve-cell development. The structures provide further insight into the effects of medically relevant mutations of the DPYSL-3 gene encoding CRMP-4 and the putative enzymatic activities of CRMPs.

  13. Crystal structure of human CRMP-4: correction of intensities for lattice-translocation disorder

    International Nuclear Information System (INIS)

    Ponnusamy, Rajesh; Lebedev, Andrey A.; Pahlow, Steffen; Lohkamp, Bernhard

    2014-01-01

    Crystals of human CRMP-4 showed severe lattice-translocation disorder. Intensities were demodulated using the so-called lattice-alignment method and a new more general method with simplified parameterization, and the structure is presented. Collapsin response mediator proteins (CRMPs) are cytosolic phosphoproteins that are mainly involved in neuronal cell development. In humans, the CRMP family comprises five members. Here, crystal structures of human CRMP-4 in a truncated and a full-length version are presented. The latter was determined from two types of crystals, which were either twinned or partially disordered. The crystal disorder was coupled with translational NCS in ordered domains and manifested itself with a rather sophisticated modulation of intensities. The data were demodulated using either the two-lattice treatment of lattice-translocation effects or a novel method in which demodulation was achieved by independent scaling of several groups of intensities. This iterative protocol does not rely on any particular parameterization of the modulation coefficients, but uses the current refined structure as a reference. The best results in terms of R factors and map correlation coefficients were obtained using this new method. The determined structures of CRMP-4 are similar to those of other CRMPs. Structural comparison allowed the confirmation of known residues, as well as the identification of new residues, that are important for the homo- and hetero-oligomerization of these proteins, which are critical to nerve-cell development. The structures provide further insight into the effects of medically relevant mutations of the DPYSL-3 gene encoding CRMP-4 and the putative enzymatic activities of CRMPs

  14. Optical trapping via guided resonance modes in a Slot-Suzuki-phase photonic crystal lattice.

    Science.gov (United States)

    Ma, Jing; Martínez, Luis Javier; Povinelli, Michelle L

    2012-03-12

    A novel photonic crystal lattice is proposed for trapping a two-dimensional array of particles. The lattice is created by introducing a rectangular slot in each unit cell of the Suzuki-Phase lattice to enhance the light confinement of guided resonance modes. Large quality factors on the order of 10⁵ are predicted in the lattice. A significant decrease of the optical power required for optical trapping can be achieved compared to our previous design.

  15. Effect of lattice disorder on the thermal conductivity of ZnBeSe, ZnMgSe and ZnBeMgSe crystals

    International Nuclear Information System (INIS)

    Strzałkowski, K.

    2015-01-01

    Zn 1−x−y Be x Mg y Se mixed crystals investigated in this work were grown from the melt by the high pressure high temperature modified Bridgman method in the range of composition 0 < x,y < 0.33. Photopyroelectric (PPE) calorimetry in the back (BPPE) and front (FPPE) configuration was applied for thermal investigation of solid samples. The thermal diffusivity and effusivity of investigated crystals were derived from the experimental data. Since dynamic thermal parameters are connected with each other, thermal conductivity of the specimens was calculated from theoretical dependencies between them. The influence of the beryllium (x) and magnesium (y) content on thermal properties of these crystals have been presented and discussed. Order-disorder effects observed for these materials previously have been also taken into account. Finally, thermal diagrams, i.e. thermal conductivity versus composition were presented and discussed applying model given by Sadao Adachi. - Highlights: • Investigated II–VI crystals were obtained by a high pressure modified Bridgman method. • A complete thermal characterization of Zn 1−x−y Be x Mg y Se semiconductors was carried out. • The effect of lattice disorder on thermal properties was presented and discussed. • Obtained data were analyzed applying lattice thermal conductivity model. • Contribution to thermal resistivity arising from lattice disorder was calculated

  16. Machine learning action parameters in lattice quantum chromodynamics

    Science.gov (United States)

    Shanahan, Phiala E.; Trewartha, Daniel; Detmold, William

    2018-05-01

    Numerical lattice quantum chromodynamics studies of the strong interaction are important in many aspects of particle and nuclear physics. Such studies require significant computing resources to undertake. A number of proposed methods promise improved efficiency of lattice calculations, and access to regions of parameter space that are currently computationally intractable, via multi-scale action-matching approaches that necessitate parametric regression of generated lattice datasets. The applicability of machine learning to this regression task is investigated, with deep neural networks found to provide an efficient solution even in cases where approaches such as principal component analysis fail. The high information content and complex symmetries inherent in lattice QCD datasets require custom neural network layers to be introduced and present opportunities for further development.

  17. Lattice location of helium in uranium dioxide single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Garrido, F.; Nowicki, L. E-mail: lech.nowicki@fuw.edu.pl; Sattonnay, G.; Sauvage, T.; Thome, L

    2004-06-01

    Lattice location of {sup 3}He atoms implanted into UO{sub 2} single crystals was performed by means of the channeling technique combined with nuclear reaction analysis (NRA) and Rutherford backscattering spectrometry (RBS). The {sup 3}He(d,p){sup 4}He reaction was used. The experimental angular scans show that helium atoms occupy octahedral interstitial positions.

  18. Lattice strain accompanying the colossal magnetoresistance effect in EuB6.

    Science.gov (United States)

    Manna, Rudra Sekhar; Das, Pintu; de Souza, Mariano; Schnelle, Frank; Lang, Michael; Müller, Jens; von Molnár, Stephan; Fisk, Zachary

    2014-08-08

    The coupling of magnetic and electronic degrees of freedom to the crystal lattice in the ferromagnetic semimetal EuB(6), which exhibits a complex ferromagnetic order and a colossal magnetoresistance effect, is studied by high-resolution thermal expansion and magnetostriction experiments. EuB(6) may be viewed as a model system, where pure magnetism-tuned transport and the response of the crystal lattice can be studied in a comparatively simple environment, i.e., not influenced by strong crystal-electric field effects and Jahn-Teller distortions. We find a very large lattice response, quantified by (i) the magnetic Grüneisen parameter, (ii) the spontaneous strain when entering the ferromagnetic region, and (iii) the magnetostriction in the paramagnetic temperature regime. Our analysis reveals that a significant part of the lattice effects originates in the magnetically driven delocalization of charge carriers, consistent with the scenario of percolating magnetic polarons. A strong effect of the formation and dynamics of local magnetic clusters on the lattice parameters is suggested to be a general feature of colossal magnetoresistance materials.

  19. Extraordinary lateral beaming of sound from a square-lattice phononic crystal

    Energy Technology Data Exchange (ETDEWEB)

    Bai, Xiaoxue; Qiu, Chunyin; He, Hailong; Peng, Shasha; Ke, Manzhu [Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education and School of Physics and Technology, Wuhan University, Wuhan 430072 (China); Liu, Zhengyou, E-mail: zyliu@whu.edu.cn [Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education and School of Physics and Technology, Wuhan University, Wuhan 430072 (China); Institute for Advanced Studies, Wuhan University, Wuhan 430072 (China)

    2017-03-03

    Highlights: • An extraordinary lateral beaming phenomenon is observed in a finite phononic crystal made of square lattice. • The phenomenon can be explained by the equivalence of the states located around the four corners of the first Brillouin zone. • The lateral beaming behavior enables a simple design of acoustic beam splitters. • In some sense, the phenomenon can be described by a near zero refractive index. - Abstract: This work revisits the sound transmission through a finite phononic crystal of square lattice. In addition to a direct, ordinary transmission through the sample, an extraordinary lateral beaming effect is also observed. The phenomenon stems from the equivalence of the states located around the four corners of the first Brillouin zone. The experimental result agrees well with the theoretical prediction. The lateral beaming behavior enables a simple design for realizing acoustic beam splitters.

  20. Chemical composition, crystal size and lattice structural changes after incorporation of strontium into biomimetic apatite.

    Science.gov (United States)

    Li, Z Y; Lam, W M; Yang, C; Xu, B; Ni, G X; Abbah, S A; Cheung, K M C; Luk, K D K; Lu, W W

    2007-03-01

    Recently, strontium (Sr) as ranelate compound has become increasingly popular in the treatment of osteoporosis. However, the lattice structure of bone crystal after Sr incorporation is yet to be extensively reported. In this study, we synthesized strontium-substituted hydroxyapatite (Sr-HA) with different Sr content (0.3%, 1.5% and 15% Sr-HA in mole ratio) to simulate bone crystals incorporated with Sr. The changes in chemical composition and lattice structure of apetite after synthetic incorporation of Sr were evaluated to gain insight into bone crystal changes after incorporation of Sr. X-ray diffraction (XRD) patterns revealed that 0.3% and 1.5% Sr-HA exhibited single phase spectrum, which was similar to that of HA. However, 15% Sr-HA induced the incorporation of HPO4(2-) and more CO3(2-), the crystallinity reduced dramatically. Transmission electron microscopy (TEM) images showed that the crystal length and width of 0.3% and 1.5% Sr-HA increased slightly. Meanwhile, the length and width distribution were broadened and the aspect ratio decreased from 10.68+/-4.00 to 7.28+/-2.80. The crystal size and crystallinity of 15% Sr-HA dropped rapidly, which may suggest that the fundamental crystal structure is changed. The findings from this work indicate that current clinical dosage which usually results in Sr incorporation of below 1.5% may not change chemical composition and lattice structure of bone, while it will broaden the bone crystal size distribution and strengthen the bone.

  1. Gate-tunable gigantic lattice deformation in VO2

    International Nuclear Information System (INIS)

    Okuyama, D.; Hatano, T.; Nakano, M.; Takeshita, S.; Ohsumi, H.; Tardif, S.; Shibuya, K.; Yumoto, H.; Koyama, T.; Ohashi, H.; Takata, M.; Kawasaki, M.; Tokura, Y.; Iwasa, Y.; Arima, T.

    2014-01-01

    We examined the impact of electric field on crystal lattice of vanadium dioxide (VO 2 ) in a field-effect transistor geometry by in-situ synchrotron x-ray diffraction measurements. Whereas the c-axis lattice parameter of VO 2 decreases through the thermally induced insulator-to-metal phase transition, the gate-induced metallization was found to result in a significant increase of the c-axis length by almost 1% from that of the thermally stabilized insulating state. We also found that this gate-induced gigantic lattice deformation occurs even at the thermally stabilized metallic state, enabling dynamic control of c-axis lattice parameter by more than 1% at room temperature

  2. Dissipation of the electronic excitation energy in fluorides with different type of a crystal lattice

    International Nuclear Information System (INIS)

    Lisitsyn, V.M.; Grechkina, T. V.; Korepanov, V.I.; Lisitsyna, L.A.

    2004-01-01

    Full text: In this paper we present results of comparison of efficiency creations of primary defects in crystals of fluorides of two different lattice structures: stone salt - LiF and rutile MgF 2 . We have used the methods with nanosecond time-resolved of pulse spectroscopy and found laws of creation and evolution self-trapped exciton (STE) and the F centers in a temperature range from 12.5 to 500 K and a time interval from 10 -8 to 10 -1 s after the ending of influence of a pulse electron. The density of excitation of crystals in a pulse is no more than 0.1 J·cm -3 , average energy electrons made 200 keV, duration electron pulse - 7 ns. It is established, that in crystal LiF under action of radiation are created STE two types which have various spectral-kinetic parameters absorption and emission transitions, various values of activation energy of processes of a post-industrial relaxation and different character of temperature dependences of creation efficiency under action electron pulse. In the field of low temperatures (12.5 K) created on center STE has absorption bands on 5.5 and 5.1 eV and emission band on 5.8 eV. Off-center STE has absorption on 5.3 and 4.75 eV and emission on 4.4 eV bands and are created in the interval 12.5-170 K with peak efficiency h area 60 K. In crystal MgF 2 at low temperatures (20 K) under action of radiation one STE with a nucleus occupying off-center configuration, having luminescence band on 3.2 eV and a series absorption transitions in area 4-5.5 eV is created. Concurrently with STE in both crystals under action of a pulse electron the F-centers with efficiency, not dependent on temperature of a crystal in area 20-100 K are created. There are two alternative processes under action of an irradiation with growth of temperature higher 100 K: reducing of STE creation and increasing of F centers creation. In both crystals quenching temperature of luminescence STE at T>60 K which is not accompanied by growth of efficiency of creation

  3. Equilibrium properties of the fluxoid lattice in single-crystal niobium

    International Nuclear Information System (INIS)

    Kerchner, H.R.; Christen, D.K.; Sekula, S.T.; Thorel, P.

    1979-06-01

    The dimensions and symmetry of the fluxoid lattice in a single-crystal sphere of niobium have been measured by using a double-perfect-crystal small-angle neutron-scattering technique (DCSANS). The bulk magnetization of the same sample has been measured by a field-sweep technique. In addition, the misalignment between the fluxoids and the applied magnetic field was observed by DCSANS. The experimental methods and most of the results are reported elsewhere. The findings are reported here, and the measurements are compared with realistic microscopic theory where it is available

  4. Crystal Engineering on Industrial Diaryl Pigments Using Lattice Energy Minimizations and X-ray Powder Diffraction

    International Nuclear Information System (INIS)

    Schmidt, M.; Dinnebier, R.; Kalkhof, H.

    2007-01-01

    Diaryl azo pigments play an important role as yellow pigments for printing inks, with an annual pigment production of more than 50,000 t. The crystal structures of Pigment Yellow 12 (PY12), Pigment Yellow 13 (PY13), Pigment Yellow 14 (PY14), and Pigment Yellow 83 (PY83) were determined from X-ray powder data using lattice energy minimizations and subsequent Rietveld refinements. Details of the lattice energy minimization procedure and of the development of a torsion potential for the biphenyl fragment are given. The Rietveld refinements were carried out using rigid bodies, or constraints. It was also possible to refine all atomic positions individually without any constraint or restraint, even for PY12 having 44 independent non-hydrogen atoms per asymmetric unit. For PY14 (23 independent non-hydrogen atoms), additionally all atomic isotropic temperature factors could be refined individually. PY12 crystallized in a herringbone arrangement with twisted biaryl fragments. PY13 and PY14 formed a layer structure of planar molecules. PY83 showed a herringbone structure with planar molecules. According to quantum mechanical calculations, the twisting of the biaryl fragment results in a lower color strength of the pigments, whereas changes in the substitution pattern have almost no influence on the color strength of a single molecule. Hence, the experimentally observed lower color strength of PY12 in comparison with that of PY13 and PY83 can be explained as a pure packing effect. Further lattice energy calculations explained that the four investigated pigments crystallize in three different structures because these structures are the energetically most favorable ones for each compound. For example, for PY13, PY14, or PY83, a PY12-analogous crystal structure would lead to considerably poorer lattice energies and lower densities. In contrast, lattice energy calculations revealed that PY12 could adopt a PY13-type structure with only slightly poorer energy. This structure was

  5. Square-lattice large-pitch hollow-core photonic crystal fiber

    DEFF Research Database (Denmark)

    Couny, F.; Roberts, John; Birks, T.A.

    2008-01-01

    We report on the design, fabrication and characterization of silica square-lattice hollow core photonic crystal fibers optimized for low loss guidance over an extended frequency range in the mid-IR region of the optical spectrum. The fiber's linear optical properties include an ultra-low group...... velocity dispersion and a polarization cross-coupling as low as -13.4dB over 10m of fiber....

  6. X-ray characteristic temperature of Fe-Ni alloys with different crystal lattices

    International Nuclear Information System (INIS)

    Krasnikova, G.N.; Ushakov, A.I.; Kazakov, V.G.; Bochkarev, V.F.; Gorovoj, A.M.

    1978-01-01

    Investigated has been the temperature dependence of the thermal expansion coefficient and the characteristic Debye temperature of the ferronickel films, having a body-centered (cubic) and a face-centered (cubic) lattice. In case of the body-centered lattice films the tests have been staged in the 100-200 deg C range, and in case of the face c.entered lattice films - in the 20-300 deg C range. The study of temperature dependence of the thermal expansion coefficient has revealed that a non-linear growth of the thermal expansion coefficient occurs in α-phase samples when approaching the phase transition temperature. The phase transition in the Invar composition Fe-Ni films is conductive to a considerable variation of the Debye temperature. Approaching the phase transition temperature, the crystal lattice dynamic characteristics vary

  7. Gate-tunable gigantic lattice deformation in VO{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Okuyama, D., E-mail: okuyama@riken.jp, E-mail: nakano@imr.tohoku.ac.jp, E-mail: iwasa@ap.t.u-tokyo.ac.jp; Hatano, T. [RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198 (Japan); Nakano, M., E-mail: okuyama@riken.jp, E-mail: nakano@imr.tohoku.ac.jp, E-mail: iwasa@ap.t.u-tokyo.ac.jp [RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198 (Japan); Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); Takeshita, S.; Ohsumi, H.; Tardif, S. [RIKEN SPring-8 Center, Hyogo 679-5148 (Japan); Shibuya, K. [National Institute of Advanced Industrial Science and Technology, Tsukuba 305-8562 (Japan); Yumoto, H.; Koyama, T.; Ohashi, H. [Japan Synchrotron Radiation Research Institute, SPring-8, Hyogo 679-5198 (Japan); Takata, M. [RIKEN SPring-8 Center, Hyogo 679-5148 (Japan); Japan Synchrotron Radiation Research Institute, SPring-8, Hyogo 679-5198 (Japan); Kawasaki, M.; Tokura, Y.; Iwasa, Y., E-mail: okuyama@riken.jp, E-mail: nakano@imr.tohoku.ac.jp, E-mail: iwasa@ap.t.u-tokyo.ac.jp [RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198 (Japan); Quantum-Phase Electronics Center and Department of Applied Physics, University of Tokyo, Tokyo 113-8656 (Japan); Arima, T. [RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198 (Japan); RIKEN SPring-8 Center, Hyogo 679-5148 (Japan); Department of Advanced Materials Science, University of Tokyo, Kashiwa 277-8561 (Japan)

    2014-01-13

    We examined the impact of electric field on crystal lattice of vanadium dioxide (VO{sub 2}) in a field-effect transistor geometry by in-situ synchrotron x-ray diffraction measurements. Whereas the c-axis lattice parameter of VO{sub 2} decreases through the thermally induced insulator-to-metal phase transition, the gate-induced metallization was found to result in a significant increase of the c-axis length by almost 1% from that of the thermally stabilized insulating state. We also found that this gate-induced gigantic lattice deformation occurs even at the thermally stabilized metallic state, enabling dynamic control of c-axis lattice parameter by more than 1% at room temperature.

  8. Dynamics of Spontaneous Emission Controlled by Local Density of States in Photonic Crystals

    DEFF Research Database (Denmark)

    Lodahl, Peter; Nikolaev, Ivan S.; van Driel, A. Floris

    2006-01-01

    We have measured time-resolved spontaneous emission from quantum dots in 3D photonic crystals. Due to the spatially dependent local density of states, the distribution of decay rates varies strongly with the photonic crystal lattice parameter.......We have measured time-resolved spontaneous emission from quantum dots in 3D photonic crystals. Due to the spatially dependent local density of states, the distribution of decay rates varies strongly with the photonic crystal lattice parameter....

  9. A new crystal lattice structure of Helicobacter pylori neutrophil-activating protein (HP-NAP)

    International Nuclear Information System (INIS)

    Tsuruta, Osamu; Yokoyama, Hideshi; Fujii, Satoshi

    2012-01-01

    A new crystal lattice structure of H. pylori neutrophil-activating protein has been determined. Iron loading causes a series of conformational changes at the ferroxidase centre. A new crystal lattice structure of Helicobacter pylori neutrophil-activating protein (HP-NAP) has been determined in two forms: the native state (Apo) at 2.20 Å resolution and an iron-loaded form (Fe-load) at 2.50 Å resolution. The highly solvated packing of the dodecameric shell is suitable for crystallographic study of the metal ion-uptake pathway. Like other bacterioferritins, HP-NAP forms a spherical dodecamer with 23 symmetry including two kinds of channels. Iron loading causes a series of conformational changes of amino-acid residues (Trp26, Asp52 and Glu56) at the ferroxidase centre

  10. Investigations on critical parameters, growth, structural and spectral studies of beta-alaninium picrate (BAP) single crystals

    International Nuclear Information System (INIS)

    Shanthi, D; Selvarajan, P; Perumal, S

    2014-01-01

    Beta-alaninium picrate (BAP) salt has been synthesized and the solubility of the synthesized sample in double distilled water was determined at different temperatures. Solution stability was studied by observing the metastable zone width by employing the polythermal method. Induction period values for different supersaturation ratios at room temperature were determined based on the isothermal method. The nucleation parameters such as critical radius, critical free energy change, interfacial tension, and nucleation rate have been estimated for BAP salt on the basis of the classical nucleation theory. The lattice parameters of the grown BAP crystal were determined using the x-ray diffraction (XRD) technique. The reflection planes of the sample were confirmed by the powder XRD study and diffraction peaks were indexed. Fourier transform infrared spectroscopy and Fourier transform–Raman studies were used to confirm the presence of various functional groups in the BAP crystal. The nonlinear optical property of the grown crystal was studied using the Kurtz–Perry powder technique. UV–visible spectral studies were carried out to understand optical transparency and the type of band gap of the grown BAP crystal. (paper)

  11. Tunable multi-wavelength polymer laser based on a triangular-lattice photonic crystal structure

    International Nuclear Information System (INIS)

    Huang, Wenbin; Pu, Donglin; Qiao, Wen; Wan, Wenqiang; Liu, Yanhua; Ye, Yan; Wu, Shaolong; Chen, Linsen

    2016-01-01

    A continuously tunable multi-wavelength polymer laser based on a triangular-lattice photonic crystal cavity is demonstrated. The triangular-lattice resonator was initially fabricated through multiple interference exposure and was then replicated into a low refractive index polymer via UV-nanoimprinting. The blend of a blue-emitting conjugated polymer and a red-emitting one was used as the gain medium. Three periods in the scalene triangular-lattice structure yield stable tri-wavelength laser emission (625.5 nm, 617.4 nm and 614.3 nm) in six different directions. A uniformly aligned liquid crystal (LC) layer was incorporated into the cavity as the top cladding layer. Upon heating, the orientation of LC molecules and thus the effective refractive index of the lasing mode changes which continuously shifts the lasing wavelength. A maximum tuning range of 12.2 nm was observed for the lasing mode at 625.5 nm. This tunable tri-wavelength polymer laser is simple constructed and cost-effective. It may find application in the fields of biosensors and photonic integrated circuits. (paper)

  12. Numerical study of slip system activity and crystal lattice rotation under wedge nanoindents in tungsten single crystals

    Science.gov (United States)

    Volz, T.; Schwaiger, R.; Wang, J.; Weygand, S. M.

    2018-05-01

    Tungsten is a promising material for plasma facing components in future nuclear fusion reactors. In the present work, we numerically investigate the deformation behavior of unirradiated tungsten (a body-centered cubic (bcc) single crystal) underneath nanoindents. A finite element (FE) model is presented to simulate wedge indentation. Crystal plasticity finite element (CPFE) simulations were performed for face-centered and body-centered single crystals accounting for the slip system family {110} in the bcc crystal system and the {111} slip family in the fcc system. The 90° wedge indenter was aligned parallel to the [1 ¯01 ]-direction and indented the crystal in the [0 1 ¯0 ]-direction up to a maximum indentation depth of 2 µm. In both, the fcc and bcc single crystals, the activity of slip systems was investigated and compared. Good agreement with the results from former investigations on fcc single crystals was observed. Furthermore, the in-plane lattice rotation in the material underneath an indent was determined and compared for the fcc and bcc single crystals.

  13. Lattice effects in HoVo3 single crystal

    International Nuclear Information System (INIS)

    Sikora, M.; Marquina, C.; Ibarra, M.R.; Nugroho, A.A.; Palstra, T.T.M.

    2007-01-01

    We report the study of lattice effects in the Mott insulator HoVO 3 performed by means of linear thermal expansion on a single crystal in the temperature range 10-290 K. The holmium orthovanadate HoVO 3 reveals gradual orbital ordering (OO) below T OO =200 K and orders antiferromagnetically at T N =113 K. A first-order structural phase transition takes place at T S ∼38 K, which is probably accompanied by change of the OO type and hence the type of antiferromagnetic spin ordering

  14. Lattice location studies of deuterium in Pdsub(0.8)Ausub(0.2) and Ta crystals by ion channeling

    International Nuclear Information System (INIS)

    Takahashi, J.; Yamaguchi, S.; Koiwa, M.; Fujino, Y.; Yoshinari, O.; Hirabayashi, M.

    1978-01-01

    The channelling of 300 to 400 KeV deuterons combined with the D(d,p)T reaction has been used to study the lattice location of deuterium in a fcc crystal of (Pdsub(0.8)Ausub(0.2))Dsub(0.04) and a bcc crystal of TaDsub(0.10). The channelling angular distributions are measured for , , axial and brace 100 brace, brace 110 brace, brace 111 brace planar directions. It is concluded that deuterium in Pdsub(0.8)Ausub(0.2) occupies the octahedral interstice of the fcc lattice, while that in Ta occupies the tetrahedral interstice of the bcc lattice. (author)

  15. Anisotropic lattice softening near the structural phase transition in the thermosalient crystal 1,2,4,5-tetrabromobenzene.

    Science.gov (United States)

    Zakharov, Boris A; Michalchuk, Adam A L; Morrison, Carole A; Boldyreva, Elena V

    2018-03-28

    The thermosalient effect (crystal jumping on heating) attracts much attention as both an intriguing academic phenomenon and in relation to its potential for the development of molecular actuators but its mechanism remains unclear. 1,2,4,5-Tetrabromobenzene (TBB) is one of the most extensively studied thermosalient compounds that has been shown previously to undergo a phase transition on heating, accompanied by crystal jumping and cracking. The difference in the crystal structures and intermolecular interaction energies of the low- and high-temperature phases is, however, too small to account for the large stress that arises over the course of the transformation. The energy is released spontaneously, and crystals jump across distances that exceed the crystal size by orders of magnitude. In the present work, the anisotropy of lattice strain is followed across the phase transition by single-crystal X-ray diffraction, focusing on the structural evolution from 273 to 343 K. A pronounced lattice softening is observed close to the transition point, with the structure becoming more rigid immediately after the phase transition. The diffraction studies are further supported by theoretical analysis of pairwise intermolecular energies and zone-centre lattice vibrations. Only three modes are found to monotonically soften up to the phase transition, with complex behaviour exhibited by the remaining lattice modes. The thermosalient effect is delayed with respect to the structural transformation itself. This can originate from the martensitic mechanism of the transformation, and the accumulation of stress associated with vibrational switching across the phase transition. The finding of this study sheds more light on the nature of the thermosalient effect in 1,2,4,5-tetrabromobenzene and can be applicable also to other thermosalient compounds.

  16. Extremely Low Loss THz Guidance Using Kagome Lattice Porous Core Photonic Crystal Fiber

    DEFF Research Database (Denmark)

    Hossain, Anwar; Hasanuzzaman, G.K.M.; Habib, Selim

    2015-01-01

    A novel porous core Kagome lattice photonic crystal fiber is proposed for extremely low loss THz waves guiding. It has been reported that 82.5% of bulk effective material loss of Topas can be reduced...

  17. Low crosstalk waveguide intersections in honeycomb lattice photonic crystals for TM-polarized light

    International Nuclear Information System (INIS)

    Ma, P; Jäckel, H

    2011-01-01

    We present the design of a low crosstalk, high throughput waveguide intersection for transverse-magnetic-polarized light. The design is based on two orthogonal photonic crystal waveguides and a resonant photonic crystal cavity in honeycomb lattice geometry. The results of our numerical simulation validate the concept of the design and demonstrate a crosstalk smaller than 0.1% and throughput transmission of more than 80% for both orthogonal waveguide branches

  18. Change in lattice parameter of tantalum due to dissolved hydrogen

    Directory of Open Access Journals (Sweden)

    Gyanendra P. Tiwari

    2012-06-01

    Full Text Available The volume expansion of tantalum due to the dissolved hydrogen has been determined using Bragg equation. The hydrogen was dissolved in the pure tantalum metal at constant temperature (360 °C and constant pressure (132 mbar by varying the duration of hydrogen charging. The amount of dissolved hydrogen was within the solid solubility limit. The samples with different hydrogen concentration were analyzed by X-ray diffraction technique. Slight peak shifts as well as peak broadening were observed. The relative changes of lattice parameters plotted against the hydrogen concentration revealed that the lattice parameters varied linearly with the hydrogen concentration.

  19. Multiscale crystal defect dynamics: A coarse-grained lattice defect model based on crystal microstructure

    Science.gov (United States)

    Lyu, Dandan; Li, Shaofan

    2017-10-01

    Crystal defects have microstructure, and this microstructure should be related to the microstructure of the original crystal. Hence each type of crystals may have similar defects due to the same failure mechanism originated from the same microstructure, if they are under the same loading conditions. In this work, we propose a multiscale crystal defect dynamics (MCDD) model that models defects by considering its intrinsic microstructure derived from the microstructure or material genome of the original perfect crystal. The main novelties of present work are: (1) the discrete exterior calculus and algebraic topology theory are used to construct a scale-up (coarse-grained) dual lattice model for crystal defects, which may represent all possible defect modes inside a crystal; (2) a higher order Cauchy-Born rule (up to the fourth order) is adopted to construct atomistic-informed constitutive relations for various defect process zones, and (3) an hierarchical strain gradient theory based finite element formulation is developed to support an hierarchical multiscale cohesive (process) zone model for various defects in a unified formulation. The efficiency of MCDD computational algorithm allows us to simulate dynamic defect evolution at large scale while taking into account atomistic interaction. The MCDD model has been validated by comparing of the results of MCDD simulations with that of molecular dynamics (MD) in the cases of nanoindentation and uniaxial tension. Numerical simulations have shown that MCDD model can predict dislocation nucleation induced instability and inelastic deformation, and thus it may provide an alternative solution to study crystal plasticity.

  20. Elimination of spurious lattice fermion solutions and noncompact lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    Lee, T.D.

    1997-09-22

    It is well known that the Dirac equation on a discrete hyper-cubic lattice in D dimension has 2{sup D} degenerate solutions. The usual method of removing these spurious solutions encounters difficulties with chiral symmetry when the lattice spacing l {ne} 0, as exemplified by the persistent problem of the pion mass. On the other hand, we recall that in any crystal in nature, all the electrons do move in a lattice and satisfy the Dirac equation; yet there is not a single physical result that has ever been entangled with a spurious fermion solution. Therefore it should not be difficult to eliminate these unphysical elements. On a discrete lattice, particle hop from point to point, whereas in a real crystal the lattice structure in embedded in a continuum and electrons move continuously from lattice cell to lattice cell. In a discrete system, the lattice functions are defined only on individual points (or links as in the case of gauge fields). However, in a crystal the electron state vector is represented by the Bloch wave functions which are continuous functions in {rvec {gamma}}, and herein lies one of the essential differences.

  1. BK-parameter from Nf=2 twisted mass lattice QCD

    International Nuclear Information System (INIS)

    Constantinou, M.; Dimopoulos, P.; Frezzotti, R.; INFN, Rome

    2011-01-01

    We present an unquenched N f = 2 lattice computation of the B K parameter which controls K 0 - anti K 0 oscillations. A partially quenched setup is employed with two maximally twisted dynamical (sea) light Wilson quarks, and valence quarks of both the maximally twisted and the Osterwalder-Seiler variety. Suitable combinations of these two kinds of valence quarks lead to a lattice definition of the B K parameter which is both multiplicatively renormalizable and O(a) improved. Employing the non-perturbative RI-MOM scheme, in the continuum limit and at the physical value of the pion mass we get B RGI K =0.729±0.030, a number well in line with the existing quenched and unquenched determinations. (orig.)

  2. Sensitivity analysis on various parameters for lattice analysis of DUPIC fuel with WIMS-AECL code

    Energy Technology Data Exchange (ETDEWEB)

    Roh, Gyu Hong; Choi, Hang Bok; Park, Jee Won [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of)

    1998-12-31

    The code WIMS-AECL has been used for the lattice analysis of DUPIC fuel. The lattice parameters calculated by the code is sensitive to the choice of number of parameters, such as the number of tracking lines, number of condensed groups, mesh spacing in the moderator region, other parameters vital to the calculation of probabilities and burnup analysis. We have studied this sensitivity with respect to these parameters and recommend their proper values which are necessary for carrying out the lattice analysis of DUPIC fuel.

  3. Sensitivity analysis on various parameters for lattice analysis of DUPIC fuel with WIMS-AECL code

    Energy Technology Data Exchange (ETDEWEB)

    Roh, Gyu Hong; Choi, Hang Bok; Park, Jee Won [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of)

    1997-12-31

    The code WIMS-AECL has been used for the lattice analysis of DUPIC fuel. The lattice parameters calculated by the code is sensitive to the choice of number of parameters, such as the number of tracking lines, number of condensed groups, mesh spacing in the moderator region, other parameters vital to the calculation of probabilities and burnup analysis. We have studied this sensitivity with respect to these parameters and recommend their proper values which are necessary for carrying out the lattice analysis of DUPIC fuel.

  4. X-ray topographic studies and measurement of lattice parameter differences within synthetic diamonds grown by the reconstitution technique

    Science.gov (United States)

    Wierzchowski, W.; Moore, M.; Makepeace, A. P. W.; Yacoot, A.

    1991-10-01

    A 4 x 4 x 1.5 cu mm cuboctahedral diamond and two 0.7 mm thick slabs cut from a truncated octahedral diamond grown by the reconstitution technique were studied in different double-crystal arrangements with both conventional and synchrotron X-ray sources. The back-reflection double crystal topographs of large polished 001-plane-oriented faces intersecting different growth sectors, together with cathodoluminescence patterns, allowed identification of these sectors. A double-crystal arrangement, employing the -3 2 5 quartz reflection matching the symmetrical 004 diamond reflection in CuK(alpha 1) radiation, was used for measurement of lattice parameter differences with an accuracy of one and a half parts per million. The simultaneous investigation by means of Lang projection and section topography provided complementary information about the crystallographic defects and internal structures of growth sectors. Observation of the cuboctahedral diamond with a filter of peak transmittance at 430 nm revealed a 'Maltese cross' growth feature in the central (001) growth sector, which also affected the birefringence pattern. However, this feature only very slightly affected the double-crystal topographs.

  5. Investigating the large degeneracy Kondo lattice metamagnet CeTiGe: Crystal growth and doping studies

    Energy Technology Data Exchange (ETDEWEB)

    Gruner, T.; Caroca-Canales, N.; Deppe, M.; Geibel, C. [MPI fuer Chemische Physik fester Stoffe, 01187, Dresden (Germany); Sereni, J. [Centro Atomico Bariloche, 8400, S. C. de Bariloche (Argentina)

    2011-07-01

    CeTiGe is a paramagnetic Kondo lattice system with a large orbital degeneracy involved in the formation of the heavy Fermion ground state. Recently we discovered that this compound presents a huge metamagnetic transition at B{sub MMT} {approx} 13 T, with much larger anomalies in magnetization, magnetoresistance and magnetostriction than in the archetypical Kondo lattice metamagnet CeRu{sub 2}Si{sub 2}. Since CeTiGe forms in a pronounced peritectic reaction the growth of single crystals is difficult. We therefore studied the Ce-Ti-Ge ternary metallographic phase diagram to get a sound basis for future crystal growth attempts. Preliminary results of growth experiments based on these studies are promising and shall be discussed. Furthermore, Ti-rich CeTiGe was recently reported to present a high temperature phase crystallizing in the closely related CeScSi structure type. In order to study this structural instability and the effect on the physical properties, we studied the effect of substituting Sc for Ti, since pure CeScGe crystallizes in the CeScSi structure type. In well annealed samples we observed a two phase region in the range 10% - 25%-Sc-substitution. Preliminary investigations of the CeSc{sub x}Ti{sub 1-x}Ge alloy suggest it is a promising candidate for the observation of a ferromagnetic quantum critical point in a large degeneracy Kondo lattice system.

  6. Effect of naturally-occurring uranium and thorium on the level of crystal lattice damage of Malaysian Zircon

    International Nuclear Information System (INIS)

    Meor Yusoff Sulaiman; Khangoankar, P.R.; Kamarudin Husin

    1999-01-01

    Malaysian zircon is classified as a radioactive mineral due to its high uranium and thorium content. Recoil α, which is produce from the decay process of these radioactive elements, could results to the damage of the crystal. Metamictization or crystal lattice damage level of this mineral can be determined from their crystallise size and lattice strain values. Results for two local zircon samples with different uranium and thorium content seem to suggest that there is some relationship between the concentration of these elements and its metamictization level. Comparison of the lattice strain value with previous results conducted on zircon from different country shows that the value is still within the range obtained. Microstructure analysis was also done on the samples. Fractures and pores formed on the mineral surface support the lattice expansion phenomena obtained from the crystallographic analysis. Production of a clean, white non-radioactive zircon pigment is among the commercial potential that could be derived from this study. (Author)

  7. Crystal structure and magnetic susceptibility of UOSe single crystals

    International Nuclear Information System (INIS)

    Kaczorowski, D.; Muenster Univ.; Poettgen, R.; Jeitschko, W.; Gajek, Z.; Zygmunt, A.

    1993-01-01

    The crystal structure and magnetic susceptibility behaviour of UOSe single crystals have been studied. UOSe crystalizes in the tetragonal PbFC1-type structure (space group P4/nmm) with the lattice parameters: a = 390.38(5) pm and c = 698.05(9) pm. It orders antiferromagnetically at T N =100±2 K and exhibits a very strong anisotropy in the susceptibility vs temperature variation. The magnetic and thermodynamic properties of UOSe are successfully interpreted in the framework of a perturbative ab initio crystal field approach. (Author)

  8. Crystal structure and magnetic susceptibility of UOSe single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Kaczorowski, D. (Polish Academy of Sciences, Wroclaw (Poland). Inst. for Low Temperature and Structure Research Muenster Univ. (Germany). Anorganisch-Chemisches Inst.); Poettgen, R.; Jeitschko, W. (Muenster Univ. (Germany). Anorganisch-Chemisches Inst.); Gajek, Z.; Zygmunt, A. (Polish Academy of Sciences, Wroclaw (Poland). Inst. for Low Temperature and Structure Research)

    1993-01-01

    The crystal structure and magnetic susceptibility behaviour of UOSe single crystals have been studied. UOSe crystalizes in the tetragonal PbFC1-type structure (space group P4/nmm) with the lattice parameters: a = 390.38(5) pm and c = 698.05(9) pm. It orders antiferromagnetically at T[sub N]=100[+-]2 K and exhibits a very strong anisotropy in the susceptibility vs temperature variation. The magnetic and thermodynamic properties of UOSe are successfully interpreted in the framework of a perturbative ab initio crystal field approach. (Author).

  9. A novel optical beam splitter based on photonic crystal with hybrid lattices

    International Nuclear Information System (INIS)

    Zhu Qing-Yi; Fu Yong-Qi; Zhang Zhi-Min; Hu De-Qing

    2012-01-01

    A novel optical beam splitter constructed on the basis of photonic crystal (PC) with hybrid lattices is proposed in this paper. The band gap of square-lattice PC is so designed that the incident light is divided into several branch beams. Triangular-lattice graded-index PCs are combined for focusing each branch. Computational calculations are carried out on the basis of finite-different time-domain algorithm to prove the feasibility of our design. The waveguide is unnecessary in the design. Thus the device has functions of both splitting and focusing beams. Size of the divided beam at site of full-width at half-maximum is of the order of λ/2. The designed splitter has the advantages that it has a small volume and can be integrated by conventional semiconductor manufacturing process. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)

  10. Lattice Boltzmann Simulation of Kinetic Isotope Effect During Snow Crystal Formation

    Science.gov (United States)

    Lu, G.; Depaolo, D. J.; Kang, Q.; Zhang, D.

    2007-12-01

    The isotopic composition of precipitation, especially that of snow, plays a special role in the global hydrological cycle and in reconstruction of past climates using polar ice cores. The fractionation of the major water isotope species (HHO, HDO, HHO-18) during ice crystal formation is critical to understanding the global distribution of isotopes in precipitation. Ice crystal growth in clouds is traditionally treated with a spherically-symmetric steady state diffusion model, with semi-empirical modifications added to account for ventilation and for complex crystal morphology. Although it is known that crystal growth rate, which depends largely on the degree of vapor over- saturation, determines crystal morphology, there are no quantitative models that relate morphology to the vapor saturation factor. Since kinetic (vapor phase diffusion-controlled) isotopic fractionation also depends on growth rate, there should be direct relationships between vapor saturation, crystal morphology, and crystal isotopic composition. We use a 2D lattice Boltzmann model to simulate diffusion-controlled ice crystal growth from vapor- oversaturated air. In the model, crystals grow solely according to the diffusive fluxes just above the crystal surfaces, and hence crystal morphology arises from the initial and boundary conditions in the model and does not need to be specified a priori. Crystal growth patterns can be varied between random growth and deterministic growth (along the maximum concentration gradient for example). The input parameters needed are the isotope- dependent vapor deposition rate constant (k) and the water vapor diffusivity in air (D). The values of both k and D can be computed from kinetic theory, and there are also experimentally determined values of D. The deduced values of k are uncertain to the extent that the condensation coefficient for ice is uncertain. The ratio D/k is a length (order 1 micron) that determines the minimum scale of dendritic growth features

  11. TRICE - A program for reconstructing 3D reciprocal space and determining unit-cell parameters

    International Nuclear Information System (INIS)

    Zou Xiaodong; Hovmoeller, Anders; Hovmoeller, Sven

    2004-01-01

    A program system-Trice-for reconstructing the 3D reciprocal lattice from an electron diffraction tilt series is described. The unit-cell parameters can be determined from electron diffraction patterns directly by Trice. The unit cell can be checked and the lattice type and crystal system can be determined from the 3D reciprocal lattice. Trice can be applied to all crystal systems and lattice types

  12. Geometric treatment of conduction electron scattering by crystal lattice strains and dislocations

    Energy Technology Data Exchange (ETDEWEB)

    Viswanathan, Koushik, E-mail: kviswana@purdue.edu [Department of Physics, Purdue University, West Lafayette, Indiana 47907 (United States); Center for Materials Processing and Tribology, Purdue University, West Lafayette, Indiana 47907 (United States); Chandrasekar, Srinivasan [Center for Materials Processing and Tribology, Purdue University, West Lafayette, Indiana 47907 (United States)

    2014-12-28

    The problem of conduction electron scattering by inhomogeneous crystal lattice strains is addressed using a tight-binding formalism and the differential geometric treatment of deformations in solids. In this approach, the relative positions of neighboring atoms in a strained lattice are naturally taken into account, even in the presence of crystal dislocations, resulting in a fully covariant Schrödinger equation in the continuum limit. Unlike previous work, the developed formalism is applicable to cases involving purely elastic strains as well as discrete and continuous distributions of dislocations—in the latter two cases, it clearly demarcates the effects of the dislocation strain field and core. It also differentiates between elastic and plastic strain contributions, respectively. The electrical resistivity due to the strain field of edge dislocations is then evaluated and the resulting numerical estimate for Cu shows good agreement with reported experimental values. This indicates that the electrical resistivity of edge dislocations in metals is not entirely due to the core, contrary to current models. Application to the study of strain effects in constrained quantum systems is also discussed.

  13. Influence of crystal orientation on the formation of femtosecond laser-induced periodic surface structures and lattice defects accumulation

    Energy Technology Data Exchange (ETDEWEB)

    Sedao, Xxx; Garrelie, Florence, E-mail: florence.garrelie@univ-st-etienne.fr; Colombier, Jean-Philippe; Reynaud, Stéphanie; Pigeon, Florent [Université de Lyon, CNRS, UMR5516, Laboratoire Hubert Curien, Université de Saint Etienne, Jean Monnet, F-42023 Saint-Etienne (France); Maurice, Claire; Quey, Romain [Ecole Nationale Supérieure des Mines de Saint-Etienne, CNRS, UMR5307, Laboratoire Georges Friedel, F-42023 Saint-Etienne (France)

    2014-04-28

    The influence of crystal orientation on the formation of femtosecond laser-induced periodic surface structures (LIPSS) has been investigated on a polycrystalline nickel sample. Electron Backscatter Diffraction characterization has been exploited to provide structural information within the laser spot on irradiated samples to determine the dependence of LIPSS formation and lattice defects (stacking faults, twins, dislocations) upon the crystal orientation. Significant differences are observed at low-to-medium number of laser pulses, outstandingly for (111)-oriented surface which favors lattice defects formation rather than LIPSS formation.

  14. Contributions to the study of elementary excitations in crystal lattice of real solids

    International Nuclear Information System (INIS)

    Vamanu, V.D.

    1978-01-01

    Two methods for the determination of magnon and phonon elementary excitation spectrum in crystal lattices of certain real solid models have been proposed, tracing down their efficiency in interpreting and predicting certain macroscopic characteristics and behaviour of the materials from the technological point of view, such as saturation magnetization, stability of magnetic phases, spin wave resonance spectra, specific heat, radiation emission and absorbtion etc. The models selected for the real solid are created by supplying the ideal solid model - i.e.a. boundless, periodic solid crystal - with limits, shape and inner defects. Therefore, the paper investigates two typical varieties: the thin monocrystal layer and the crystal itself characterized by impurities. (author)

  15. New Crystal-Growth Methods for Producing Lattice-Matched Substrates for High-Temperature Superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Boatner, L.A.

    2008-06-24

    This effort addressed the technical problem of identifying and growing, on a commercial scale, suitable single-crystal substrates for the subsequent deposition of epitaxial thin films of high temperature semiconductors such as GaN/AlN. The lack of suitable lattice-matched substrate materials was one of the major problem areas in the development of semiconducting devices for use at elevated temperatures as well as practical opto-electronic devices based on Al- and GaN technology. Such lattice-matched substrates are necessary in order to reduce or eliminate high concentrations of defects and dislocations in GaN/AlN and related epitaxial thin films. This effort concentrated, in particular, on the growth of single crystals of ZnO for substrate applications and it built on previous ORNL experience in the chemical vapor transport growth of large single crystals of zinc oxide. This combined expertise in the substrate growth area was further complemented by the ability of G. Eres and his collaborators to deposit thin films of GaN on the subject substrates and the overall ORNL capability for characterizing the quality of such films. The research effort consisted of research on the growth of two candidate substrate materials in conjunction with concurrent research on the growth and characterization of GaN films, i.e. the effort combined bulk crystal growth capabilities in the area of substrate production at both ORNL and the industrial partner, Commercial Crystal Growth Laboratories (CCL), Naples, Florida, with the novel thin-film deposition techniques previously developed in the ORNL SSD.

  16. Thermal restoration of the lattice parameter of weakly irradiated UO2 (1962)

    International Nuclear Information System (INIS)

    Bloch, J.

    1962-01-01

    Weak irradiations of uranium dioxide lead to an expansion of the cristal lattice. We have studied the restoration of the lattice parameter after successive isochronous annealings. The process occurs in two main stages, one starting at 200 deg. C and the other at 500 deg. C. (author) [fr

  17. Nanoscale size dependence parameters on lattice thermal conductivity of Wurtzite GaN nanowires

    International Nuclear Information System (INIS)

    Mamand, S.M.; Omar, M.S.; Muhammad, A.J.

    2012-01-01

    Graphical abstract: Temperature dependence of calculated lattice thermal conductivity of Wurtzite GaN nanowires. Highlights: ► A modified Callaway model is used to calculate lattice thermal conductivity of Wurtzite GaN nanowires. ► A direct method is used to calculate phonon group velocity for these nanowires. ► 3-Gruneisen parameter, surface roughness, and dislocations are successfully investigated. ► Dislocation densities are decreases with the decrease of wires diameter. -- Abstract: A detailed calculation of lattice thermal conductivity of freestanding Wurtzite GaN nanowires with diameter ranging from 97 to 160 nm in the temperature range 2–300 K, was performed using a modified Callaway model. Both longitudinal and transverse modes are taken into account explicitly in the model. A method is used to calculate the Debye and phonon group velocities for different nanowire diameters from their related melting points. Effect of Gruneisen parameter, surface roughness, and dislocations as structure dependent parameters are successfully used to correlate the calculated values of lattice thermal conductivity to that of the experimentally measured curves. It was observed that Gruneisen parameter will decrease with decreasing nanowire diameters. Scattering of phonons is assumed to be by nanowire boundaries, imperfections, dislocations, electrons, and other phonons via both normal and Umklapp processes. Phonon confinement and size effects as well as the role of dislocation in limiting thermal conductivity are investigated. At high temperatures and for dislocation densities greater than 10 14 m −2 the lattice thermal conductivity would be limited by dislocation density, but for dislocation densities less than 10 14 m −2 , lattice thermal conductivity would be independent of that.

  18. Nanoscale size dependence parameters on lattice thermal conductivity of Wurtzite GaN nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Mamand, S.M., E-mail: soran.mamand@univsul.net [Department of Physics, College of Science, University of Sulaimani, Sulaimanyah, Iraqi Kurdistan (Iraq); Omar, M.S. [Department of Physics, College of Science, University of Salahaddin, Arbil, Iraqi Kurdistan (Iraq); Muhammad, A.J. [Department of Physics, College of Science, University of Kirkuk, Kirkuk (Iraq)

    2012-05-15

    Graphical abstract: Temperature dependence of calculated lattice thermal conductivity of Wurtzite GaN nanowires. Highlights: Black-Right-Pointing-Pointer A modified Callaway model is used to calculate lattice thermal conductivity of Wurtzite GaN nanowires. Black-Right-Pointing-Pointer A direct method is used to calculate phonon group velocity for these nanowires. Black-Right-Pointing-Pointer 3-Gruneisen parameter, surface roughness, and dislocations are successfully investigated. Black-Right-Pointing-Pointer Dislocation densities are decreases with the decrease of wires diameter. -- Abstract: A detailed calculation of lattice thermal conductivity of freestanding Wurtzite GaN nanowires with diameter ranging from 97 to 160 nm in the temperature range 2-300 K, was performed using a modified Callaway model. Both longitudinal and transverse modes are taken into account explicitly in the model. A method is used to calculate the Debye and phonon group velocities for different nanowire diameters from their related melting points. Effect of Gruneisen parameter, surface roughness, and dislocations as structure dependent parameters are successfully used to correlate the calculated values of lattice thermal conductivity to that of the experimentally measured curves. It was observed that Gruneisen parameter will decrease with decreasing nanowire diameters. Scattering of phonons is assumed to be by nanowire boundaries, imperfections, dislocations, electrons, and other phonons via both normal and Umklapp processes. Phonon confinement and size effects as well as the role of dislocation in limiting thermal conductivity are investigated. At high temperatures and for dislocation densities greater than 10{sup 14} m{sup -2} the lattice thermal conductivity would be limited by dislocation density, but for dislocation densities less than 10{sup 14} m{sup -2}, lattice thermal conductivity would be independent of that.

  19. Integral parameters of crystal field for RE spectra

    International Nuclear Information System (INIS)

    Kustov, E.F.; Maketov, T.K.; Prgevudsky, A.K.; Steczko, G.

    1980-01-01

    The integral parameters of the crystal field are introduced for the interpretation of the spectra of RE ions in various crystals. The main formula of the method, the expression of the parameters for various states of Ce, Pr, Nd, Eu, Tb, Er, Tu, and Yb are determined. Integral parameters of A 2 , A 4 , A 6 and parameter of the spin-orbit interaction xi are calculated for 40 laser crystals with Nd, Er. An interpretation of the symmetry of the Eu 3+ centres of the NaBaZn silicate glass is given using integral parameters A 2 , A 4 . (author)

  20. Debye–Einstein approximation approach to calculate the lattice specific heat and related parameters for a Si nanowire

    Directory of Open Access Journals (Sweden)

    A. KH. Alassafee

    2017-11-01

    Full Text Available The modified Debye–Einstein approximation model is used to calculate nanoscale size-dependent values of Gruneisen parameters and lattice specific heat capacity for Si nanowires. All parameters forming the model, including Debye temperatures, bulk moduli, the lattice thermal expansion and the lattice volume, are calculated according to their nanoscale size dependence. Values for lattice volume Gruneisen parameters increase with the decrease of the nanowires’ diameter, while all other parameters decrease. The nanosize dependence of lattice thermal parameters agree with other reported theoretical results. Keywords: Lattice specific heat capacity, Gruneisen parameter, Debye–Einstein model, Si nanowires

  1. Negative refractions by triangular lattice sonic crystals in partial band gaps

    International Nuclear Information System (INIS)

    Alagoz, S.; Sahin, A.; Alagoz, B. B.; Nur, S.

    2015-01-01

    This study numerically demonstrates the effects of partial band gaps on the negative refraction properties of sonic crystal. The partial band gap appearing at the second band edge leads to the efficient transmissions of scattered wave envelopes in the transverse directions inside triangular lattice sonic crystal, and therefore enhances the refraction property of sonic crystal. Numerical simulation results indicate a diagonal guidance of coupled scattered wave envelopes inside crystal structure at the partial band gap frequencies and then output waves are restored in the vicinity of the output interface of sonic crystal by combining phase coherent scattered waves according to Huygens’ principles. This mechanism leads to two operations for wavefront engineering: one is spatial wavefront shifting operation and the other is convex–concave wavefront inversion operation. The effects of this mechanism on the negative refraction and wave focalization are investigated by using the finite difference time domain (FDTD) simulations. This study contributes to a better understanding of negative refraction and wave focusing mechanisms at the band edge frequencies, and shows the applications of the slab corner beam splitting and SC-air multilayer acoustic system. (paper)

  2. Nematic quantum liquid crystals of bosons in frustrated lattices

    Science.gov (United States)

    Zhu, Guanyu; Koch, Jens; Martin, Ivar

    2016-04-01

    The problem of interacting bosons in frustrated lattices is an intricate one due to the absence of a unique minimum in the single-particle dispersion where macroscopic number of bosons can condense. Here, we consider a family of tight-binding models with macroscopically degenerate lowest energy bands, separated from other bands by a gap. We predict the formation of exotic states that spontaneously break rotational symmetry at relatively low filling. These states belong to three nematic phases: Wigner crystal, supersolid, and superfluid. The Wigner crystal phase is established exactly at low filling. Supersolid and superfluid phases, at larger filling, are obtained by making use of a projection onto the flat band, construction of an appropriate Wannier basis, and subsequent mean-field treatment. The nematic superfluid that we predict is uniform in real space but has an anisotropic momentum distribution, providing a novel scenario for Bose condensation with an additional nematic order. Our findings open up a promising direction of studying microscopic quantum liquid crystalline phases of bosons.

  3. Anyonic order parameters for discrete gauge theories on the lattice

    International Nuclear Information System (INIS)

    Bais, F.A.; Romers, J.C.

    2009-01-01

    We present a new family of gauge invariant non-local order parameters Δ α A for (non-abelian) discrete gauge theories on a Euclidean lattice, which are in one-to-one correspondence with the excitation spectrum that follows from the representation theory of the quantum double D(H) of the finite group H. These combine magnetic flux-sector labeled by a conjugacy class with an electric representation of the centralizer subgroup that commutes with the flux. In particular, cases like the trivial class for magnetic flux, or the trivial irrep for electric charge, these order parameters reduce to the familiar Wilson and the 't Hooft operators, respectively. It is pointed out that these novel operators are crucial for probing the phase structure of a class of discrete lattice models we define, using Monte Carlo simulations.

  4. Analysis of polytype stability in PVT grown silicon carbide single crystal using competitive lattice model Monte Carlo simulations

    Directory of Open Access Journals (Sweden)

    Hui-Jun Guo

    2014-09-01

    Full Text Available Polytype stability is very important for high quality SiC single crystal growth. However, the growth conditions for the 4H, 6H and 15R polytypes are similar, and the mechanism of polytype stability is not clear. The kinetics aspects, such as surface-step nucleation, are important. The kinetic Monte Carlo method is a common tool to study surface kinetics in crystal growth. However, the present lattice models for kinetic Monte Carlo simulations cannot solve the problem of the competitive growth of two or more lattice structures. In this study, a competitive lattice model was developed for kinetic Monte Carlo simulation of the competition growth of the 4H and 6H polytypes of SiC. The site positions are fixed at the perfect crystal lattice positions without any adjustment of the site positions. Surface steps on seeds and large ratios of diffusion/deposition have positive effects on the 4H polytype stability. The 3D polytype distribution in a physical vapor transport method grown SiC ingot showed that the facet preserved the 4H polytype even if the 6H polytype dominated the growth surface. The theoretical and experimental results of polytype growth in SiC suggest that retaining the step growth mode is an important factor to maintain a stable single 4H polytype during SiC growth.

  5. The role of diffusion measurements in the study of crystal lattice defects

    Energy Technology Data Exchange (ETDEWEB)

    Kidson, G V

    1965-07-15

    Measurements of atomic mobility in solids are frequently of direct interest to those concerned with the design, development and utilization of materials in engineering. Increasing attention, however, is currently devoted to an under standing of such properties in terms of the occurrence and nature of point and line defects in the crystals. This paper reviews some recent diffusion studies conducted at C.R,N.L. that provide, in addition to data of interest in nuclear technology, a means of gaining some insight into the more fundamental nature of the lattice defects occurring in the materials. The systems discussed are (i) self diffusion in the high temperature phase of pure zirconium (ii) solute diffusion in lead and (iii) interdiffusion of aluminum and zirconium The unusual and at present incompletely understood results described in (i) are briefly reviewed. Evidence is given to suggest that diffusion occurs either through a dense dislocation network produced as a result of a martensitic phase transformation, or, alternatively, by excess vacancies introduced into the crystal by impurities. In (ii) the extraordinarily rapid diffusion of noble metal solutes in high purity lead single crystals will be discussed n terms of the state of solution of the solute atoms. It will be shown that their diffusion behaviour can be understood by assuming that a fraction f{sub i} of the dissolved solute atoms occupy interstitial sites, The measured diffusion coefficient D{sub m} is related to the interstitial diffusion coefficient by D{sub m} = f{sub i} D{sub i}. In (iii) the formation and rapid growth of single intermetallic compound ZrAl{sub 3} in the diffusion zone formed between pure zirconium and pure aluminum is described and the diffusion mechanism is interpreted in terms of the structure of the compound lattice. The results indicate that ZrAl{sub 3} forms a defect lattice, leading to the relatively rapid migration of aluminum atoms. (author)

  6. Effect of Metal Dopant on Ninhydrin—Organic Nonlinear Optical Single Crystals

    Directory of Open Access Journals (Sweden)

    R. S. Sreenivasan

    2013-01-01

    Full Text Available In the present work, metal (Cu2+-substituted ninhydrin single crystals were grown by slow evaporation method. The grown crystals have been subjected to single crystal XRD, powder X-ray diffraction, FTIR, dielectric and SHG studies. Single crystal X-ray diffraction analysis reveals that the compound crystallizes in monoclinic system with noncentrosymmetric space group P21 with lattice parameters a=11.28 Å, b=5.98 Å, c=5.71 Å, α=90∘, β=98.57, γ=90∘, and V=381 (Å3, which agrees very well with the reported value. The sharp and strong peaks in the powder X-ray diffraction pattern confirm the good crystallinity of the grown crystals. The presence of dopants marginally altered the lattice parameters without affecting the basic structure of the crystal. The UV-Vis transmittance spectrum shows that the crystal has a good optical transmittance in the entire visible region with lower cutoff wavelength 314 nm. The vibrational frequencies of various functional groups in the crystals have been derived from FT-IR analysis. Based on the shifts in the vibrations, the presence of copper in the lattice of the grown crystal is clearly established from the pure ninhydrin crystals. Both dielectric constant and dielectric loss decrease with the increase in frequency. The second harmonic generation efficiency was measured by employing powder Kurtz method.

  7. Anisotropic lattice expansion of three-dimensional colloidal crystals and its impact on hypersonic phonon band gaps.

    Science.gov (United States)

    Wu, Songtao; Zhu, Gaohua; Zhang, Jin S; Banerjee, Debasish; Bass, Jay D; Ling, Chen; Yano, Kazuhisa

    2014-05-21

    We report anisotropic expansion of self-assembled colloidal polystyrene-poly(dimethylsiloxane) crystals and its impact on the phonon band structure at hypersonic frequencies. The structural expansion was achieved by a multistep infiltration-polymerization process. Such a process expands the interplanar lattice distance 17% after 8 cycles whereas the in-plane distance remains unaffected. The variation of hypersonic phonon band structure induced by the anisotropic lattice expansion was recorded by Brillouin measurements. In the sample before expansion, a phononic band gap between 3.7 and 4.4 GHz is observed; after 17% structural expansion, the gap is shifted to a lower frequency between 3.5 and 4.0 GHz. This study offers a facile approach to control the macroscopic structure of colloidal crystals with great potential in designing tunable phononic devices.

  8. Localized electromagnetic modes and transmission spectrum of one-dimensional photon crystal with lattice defects

    CERN Document Server

    Vetrov, S Y

    2001-01-01

    The properties of the localized electromagnetic modes in the one-dimensional photon crystal with a structural defective layer are studied. The anisotropic layer of the nematic liquid layer is considered as the defect. It is shown that the frequency and coefficient of the defective modes attenuation essentially depend on the defective layer thickness and nematic optical axis orientation. The spectrum of the photon crystal transmittance with one or two defects in the lattice is studied. The possibility of controlling the the photon crystal transmittance spectrum on the count of changing the orientation of the nematic optical axis, for example, through the external electric field is shown with an account of strong anisotropy of the dielectric permittivity

  9. Lattice dynamics of a crystal with a molecular impurity

    International Nuclear Information System (INIS)

    Sahoo, D.; Venkataraman, G.

    1975-01-01

    The dynamics of a crystal containing a molecular impurity is discussed with allowance for the effects of internal vibrations of the molecule. Cartesian coordinates are used to describe internal vibrations, angular oscillations and centre of mass translations of the impurity, and the displacement of atoms of the host lattice. Next the Hamiltonian is set up and the equations of motion derived. In this process, use is made of Dirac brackets when dealing with vibrational coordinates (of the molecule) which have redundancy and constraints. A method of solution of the normal modes of the system is indicated by using the defect space matrixpartitioning technique. The special case of a rigid molecular impurity is then discussed along with the relevance of the present formalism in the interpretation of a recent neutron scattering experiment. It is also shown how the results of crystal-field approximation model and those of the molecular model approximation are obtained as further special cases of the present formalism. A comparison of the present work with those of others has been made. (author)

  10. Experimental evidence for a chiral symmetry-breaking mechanism in aspartic acid: Lattice and sub-lattice matching

    Science.gov (United States)

    Teschke, Omar; Soares, David Mendez

    2017-10-01

    A mother crystal formed from a transient molecular structure of (D+L) aspartic acid in solution is reported. Hexagonal structures with a lattice constant of 1.04 nm were crystallized from a solution in which three aspartic acid species coexist: right- and left-handed enantiomorphs, denoted D-aspartic and L-aspartic, respectively, and transitory (D+L) aspartic acid specie. Atomic force microscopy images of the crystalline deposits reveal domains of the transitory (D+L) aspartic acid crystal forming the substrate deposit on silicon wafers, and on top of this hexagonal lattice only L-aspartic acid is observed to conform and crystallize. A preferential crystallization mechanism is then observed for (D+L) aspartic acid crystals that seed only L-aspartic deposits by the geometrical matching of their multiple hexagonal lattice structures with periodicities of 1.04 nm and 0.52 nm, respectively.

  11. Holographic Fabrication of Designed Functional Defect Lines in Photonic Crystal Lattice Using a Spatial Light Modulator

    Directory of Open Access Journals (Sweden)

    Jeffrey Lutkenhaus

    2016-04-01

    Full Text Available We report the holographic fabrication of designed defect lines in photonic crystal lattices through phase engineering using a spatial light modulator (SLM. The diffracted beams from the SLM not only carry the defect’s content but also the defect related phase-shifting information. The phase-shifting induced lattice shifting in photonic lattices around the defects in three-beam interference is less than the one produced by five-beam interference due to the alternating shifting in lattice in three beam interference. By designing the defect line at a 45 degree orientation and using three-beam interference, the defect orientation can be aligned with the background photonic lattice, and the shifting is only in one side of the defect line, in agreement with the theory. Finally, a new design for the integration of functional defect lines in a background phase pattern reduces the relative phase shift of the defect and utilizes the different diffraction efficiency between the defect line and background phase pattern. We demonstrate that the desired and functional defect lattice can be registered into the background lattice through the direct imaging of designed phase patterns.

  12. Single-crystal growth of ceria-based materials

    International Nuclear Information System (INIS)

    Ulbrich, Gregor

    2015-01-01

    In this work it could be shown that Skull-Melting is a suitable method for growing ceria single crystals. Twenty different ceria-based single crystals could be manufactured. It was possible to dope ceria single crystals with Gd, Sm, Y, Zr, Ti, Ta, and Pr in different concentrations. Also co-doping with the named metals was realized. However, there remain some problems for growing ceria-based single crystals by Skull-Melting. As ignition metal zirconium was used because no ceria-based material works well. For that reason all single crystals show small zirconium contamination. Another problem is the formation of oxygen by the heat-induced reduction of ceria during the melting process. Because of that the skull of sintered material is often destroyed by gas pressure. This problem had to be solved individually for every single crystal. The obtained single crystals were characterized using different methods. To ensure the single crystal character the y were examined by Laue diffraction. All manufactured crystals are single crystals. Also powder diffraction patterns of the milled and oxidized samples were measured. For the determination of symmetry and metric the structural parameters were analyzed by the Rietveld method. All synthesized materials crystallize in space group Fm-3m known from calcium fluoride. The cubic lattice parameter a was determined for all crystals. In the case of series with different cerium and zirconium concentrations a linear correlation between cerium content and cubic lattice parameter was detected. The elemental composition was determined by WDX. All crystals show a homogeneous elemental distribution. The oxygen content was calculated because the WDX method isn't useful for determination.

  13. Calculation of Optical Parameters of Liquid Crystals

    Science.gov (United States)

    Kumar, A.

    2007-12-01

    Validation of a modified four-parameter model describing temperature effect on liquid crystal refractive indices is being reported in the present article. This model is based upon the Vuks equation. Experimental data of ordinary and extraordinary refractive indices for two liquid crystal samples MLC-9200-000 and MLC-6608 are used to validate the above-mentioned theoretical model. Using these experimental data, birefringence, order parameter, normalized polarizabilities, and the temperature gradient of refractive indices are determined. Two methods: directly using birefringence measurements and using Haller's extrapolation procedure are adopted for the determination of order parameter. Both approches of order parameter calculation are compared. The temperature dependences of all these parameters are discussed. A close agreement between theory and experiment is obtained.

  14. Lattice parameters and Raman-active phonon modes of β-(AlxGa1−x)2O3

    International Nuclear Information System (INIS)

    Kranert, Christian; Jenderka, Marcus; Lenzner, Jörg; Lorenz, Michael; Wenckstern, Holger von; Schmidt-Grund, Rüdiger; Grundmann, Marius

    2015-01-01

    We present X-ray diffraction and Raman spectroscopy investigations of a (100)-oriented (Al x Ga 1–x ) 2 O 3 thin film on MgO (100) and bulk-like ceramics in dependence on their composition. The thin film grown by pulsed laser deposition has a continuous lateral composition spread allowing to determine precisely the dependence of the phonon mode properties and lattice parameters on the chemical composition. For x < 0.4, we observe the single-phase β-modification. Its lattice parameters and phonon energies depend linearly on the composition. We determined the slopes of these dependencies for the individual lattice parameters and for nine Raman lines, respectively. While the lattice parameters of the ceramics follow Vegard's rule, deviations are observed for the thin film. This deviation has only a small effect on the phonon energies, which show a reasonably good agreement between thin film and ceramics

  15. Influence of hydrostatic pressure on BCC-lattice parameter in molybdenum, niobium and vanadium with rhenium solid solutions

    International Nuclear Information System (INIS)

    Smol'yaninova, Eh.A.; Stribuk, E.K.; Tyavlovskij, V.I.

    1987-01-01

    Data on the effect of 1.8GPa hydrostatic pressure on bcc lattice parameters of solid solutions in Mo-Re, Nb-Re, V-re systems are presented. It is shown that after the application hydrostatic pressure a decrease in bcc lattice parameter is observed and the greatest change in the lattice parameter takes place in bcc of solid solutions in the Nb-Re system (DELTA A ∼ 0.0035 nm). Analysis of the experimental data obtained on the basis of calculations made for packing density change in the above-mentioned solid solutions under the pressure is carried out

  16. Elastic lattice in an incommensurate background

    International Nuclear Information System (INIS)

    Dickman, R.; Chudnovsky, E.M.

    1995-01-01

    We study a harmonic triangular lattice, which relaxes in the presence of an incommensurate short-wavelength potential. Monte Carlo simulations reveal that the elastic lattice exhibits only short-ranged translational correlations, despite the absence of defects in either lattice. Extended orientational order, however, persists in the presence of the background. Translational correlation lengths exhibit approximate power-law dependence upon cooling rate and background strength. Our results may be relevant to Wigner crystals, atomic monolayers on crystals surfaces, and flux-line and magnetic bubble lattices

  17. Analysis of crystallite size and microdeformation crystal lattice the tungsten carbide milling in mill high energy

    International Nuclear Information System (INIS)

    Silva, F.T. da; Nunes, M.A.M.; Souza, C.P. de; Gomes, U.U.

    2010-01-01

    The tungsten carbide (WC) has wide application due to its properties like high melting point, high hardness, wear resistance, oxidation resistance and good electrical conductivity. The microstructural characteristics of the starting powders influences the final properties of the carbide. In this context, the use of nanoparticle powders is an efficient way to improve the final properties of the WC. The high energy milling stands out from other processes to obtain nanometric powders due to constant microstructural changes caused by this process. Therefore, the objective is to undertake an analysis of microstructural characteristics on the crystallite size and microdeformations of the crystal lattice using the technique of X-ray diffraction (XRD) using the Rietveld refinement. The results show an efficiency of the milling process to reduce the crystallite size, leading to a significant deformation in the crystal lattice of WC from 5h milling. (author)

  18. Spin-phonon and lattice contributions to the ground-state splitting of Gd3+ and Eu2+ in scheelite crystals

    Science.gov (United States)

    Gorlov, A. D.

    2015-07-01

    The EPR spectra of Gd3+ in CaWO4 single crystals have been studied at temperatures T = 1.8, 4.2, and 114-300 K, and the temperature dependence of the parameters b {/n m } ( T) of the spin Hamiltonian has been found. The behavior of b {2/0}( T) has been analyzed. The spin-phonon and static lattice contributions b {2/0}( F) and b {2/0}( L) to b {2/0}( T) have been revealed. For this purpose, the variation of b {2/0}( L) has been calculated taking into account the thermal shifts of oxygen ions in CaWO4. Similar analysis has been carried out for CaWO4: Eu2+ based on the EPR data of other authors (Bronstein, Voterra and Harvey, Kiefte). It has been shown that at b {2/0}( F) > 0, the variation of b {2/0}( F) as a function of T for these impurity centers is described well by the Pfister model and a sign change of b {2/0}( T) for Eu2+ is determined by thermal expansion of the lattice.

  19. Adjoint Parameter Sensitivity Analysis for the Hydrodynamic Lattice Boltzmann Method with Applications to Design Optimization

    DEFF Research Database (Denmark)

    Pingen, Georg; Evgrafov, Anton; Maute, Kurt

    2009-01-01

    We present an adjoint parameter sensitivity analysis formulation and solution strategy for the lattice Boltzmann method (LBM). The focus is on design optimization applications, in particular topology optimization. The lattice Boltzmann method is briefly described with an in-depth discussion...

  20. Composition dependence of the thermodynamic activity and lattice parameter of zeta nickel-indium

    International Nuclear Information System (INIS)

    Bhattacharya, B.; Masson, D.B.

    1976-01-01

    The vapor pressure of indium over six alloys in the zeta phase of the nickel-indium system was measured by the method of atomic absorption. Values of thermodynamic activity were calculated from the vapor pressure, and partial heat and entropy of indium were calculated from the temperature coefficients. The lattice parameters of the hexagonal B8 2 unit cell of all alloys were calculated from X-ray diffraction powder patterns. It was found that the a lattice parameter passed through a minimum at the same composition that the excess chemical potential showed a sharp change of slope, when graphed as a function of composition. These effects were similar to those observed previously which have been attributed to overlap by the Fermi surface of a Brillouin zone face. In the present case they were attributed to overlap of the Fermi surface across faces tentatively identified as the [110] faces of the Brillouin zone of the B8 2 structure. The influence of substitutional disorder was also considered as a cause of the thermodynamic effects, but this was rejected because it does not explain the minimum in lattice parameter. (Auth.)

  1. Piezoelectricity and pyroelectricity in polyvinylidene fluoride - Influence of the lattice structure

    Science.gov (United States)

    Purvis, C. K.; Taylor, P. L.

    1983-01-01

    Piezoelectric and pyroelectric responses of beta-phase (Phase I) polyvinylidene fluoride are predicted for a model system of polarizable point dipoles. The model incorporates the influence of the orthorhombic crystal structure by including the dependence of the internal electric field on the lattice parameters. Strong anisotropy in the piezoelectric response under uniaxial stress is predicted as a consequence of the orthorhombic lattice structure. Predictions are found to be in reasonable agreement with room-temperature experimental data.

  2. Application of Powder Diffraction Methods to the Analysis of Short- and Long-Range Atomic Order in Nanocrystalline Diamond and SiC: The Concept of the Apparent Lattice Parameter (alp)

    Science.gov (United States)

    Palosz, B.; Grzanka, E.; Gierlotka, S.; Stelmakh, S.; Pielaszek, R.; Bismayer, U.; Weber, H.-P.; Palosz, W.

    2003-01-01

    Two methods of the analysis of powder diffraction patterns of diamond and SiC nanocrystals are presented: (a) examination of changes of the lattice parameters with diffraction vector Q ('apparent lattice parameter', alp) which refers to Bragg scattering, and (b), examination of changes of inter-atomic distances based on the analysis of the atomic Pair Distribution Function, PDF. Application of these methods was studied based on the theoretical diffraction patterns computed for models of nanocrystals having (i) a perfect crystal lattice, and (ii), a core-shell structure, i.e. constituting a two-phase system. The models are defined by the lattice parameter of the grain core, thickness of the surface shell, and the magnitude and distribution of the strain field in the shell. X-ray and neutron experimental diffraction data of nanocrystalline SiC and diamond powders of the grain diameter from 4 nm up to micrometers were used. The effects of the internal pressure and strain at the grain surface on the structure are discussed based on the experimentally determined dependence of the alp values on the Q-vector, and changes of the interatomic distances with the grain size determined experimentally by the atomic Pair Distribution Function (PDF) analysis. The experimental results lend a strong support to the concept of a two-phase, core and the surface shell structure of nanocrystalline diamond and SiC.

  3. Crystal Systems.

    Science.gov (United States)

    Schomaker, Verner; Lingafelter, E. C.

    1985-01-01

    Discusses characteristics of crystal systems, comparing (in table format) crystal systems with lattice types, number of restrictions, nature of the restrictions, and other lattices that can accidently show the same metrical symmetry. (JN)

  4. Lattice parameters and electrical resistivity of Ceria-Yttria solid solutions

    International Nuclear Information System (INIS)

    Rey, Jose Fernando Queiruga

    2002-01-01

    Ce0 2 :u mol% Y 2 O 3 (u=0, 4, 6, 8, 10 and 12) solid solutions were prepared by the conventional powder mixture technique. The main purposes of this work are: the study of the dependence of the lattice parameter of the Ceria cubic phase on the Yttria content, comparing the experimental data with data calculated according to the existing theoretical models; to determine the dependence of the ionic conductivity on the Yttria content; and to study the stability of the cubic fluorite phase after extensive thermal treatments (aging) of the Ceria-Yttria specimens. The results show that the lattice parameter of the solid solutions follows the Vegard's law and can be described by the two reported theoretical models. The 8 mol% Yttria-doped Ceria was found to present the largest value of ionic conductivity. Preliminary results show that a large decrease is found for only 1 h aging at 700 deg C and that the ionic conductivity decreases for ceramic specimens aged for times up to 10 h. (author)

  5. Growth and Characterization of ZnTe Crystal

    International Nuclear Information System (INIS)

    Nann Thazin

    2011-12-01

    High quality ZnTe crystals have been synthesized by vapor Transport method. The grown crystals were p-type. The concentration and mobility were 2.5 x 10 16 cm-3 and 23 cm2/Vs at 300K, according to Hall effect measurements. Surface morphology of the crystal was investigated by scanning electron microscope (SEM). Crystal orientation and lattice parameters of the crystals were also analysed by XRD. From X-ray diffraction studies the structure of the grown crystals were found to be zinc-blende. The crystal emitted light in the visible range at room temperature.

  6. Tunable all-angle negative refraction and photonic band gaps in two-dimensional plasma photonic crystals with square-like Archimedean lattices

    International Nuclear Information System (INIS)

    Zhang, Hai-Feng; Liu, Shao-Bin; Jiang, Yu-Chi

    2014-01-01

    In this paper, the tunable all-angle negative refraction and photonic band gaps (PBGs) in two types of two-dimensional (2D) plasma photonic crystals (PPCs) composed of homogeneous plasma and dielectric (GaAs) with square-like Archimedean lattices (ladybug and bathroom lattices) for TM wave are theoretically investigated based on a modified plane wave expansion method. The type-1 structure is dielectric rods immersed in the plasma background, and the complementary structure is named as type-2 PPCs. Theoretical simulations demonstrate that the both types of PPCs with square-like Archimedean lattices have some advantages in obtaining the higher cut-off frequency, the larger PBGs, more number of PBGs, and the relative bandwidths compared to the conventional square lattices as the filling factor or radius of inserted rods is same. The influences of plasma frequency and radius of inserted rod on the properties of PBGs for both types of PPCs also are discussed in detail. The calculated results show that PBGs can be manipulated by the parameters as mentioned above. The possibilities of all-angle negative refraction in such two types of PPCs at low bands also are discussed. Our calculations reveal that the all-angle negative phenomena can be observed in the first two TM bands, and the frequency range of all-angle negative refraction can be tuned by changing plasma frequency. Those properties can be used to design the optical switching and sensor

  7. Optical NOR logic gate design on square lattice photonic crystal platform

    Energy Technology Data Exchange (ETDEWEB)

    D’souza, Nirmala Maria, E-mail: nirmala@cukerala.ac.in; Mathew, Vincent, E-mail: vincent@cukerala.ac.in [Department of Physics, Central University of Kerala, Kasaragod, Kerala-671 314 (India)

    2016-05-06

    We numerically demonstrate a new configuration of all-optical NOR logic gate with square lattice photonic crystal (PhC) waveguide using finite difference time domain (FDTD) method. The logic operations are based on interference effect of optical waves. We have determined the operating frequency range by calculating the band structure for a perfectly periodic PhC using plane wave expansion (PWE) method. Response time of this logic gate is 1.98 ps and it can be operated with speed about 513 GB/s. The proposed device consists of four linear waveguides and a square ring resonator waveguides on PhC platform.

  8. Effect of process parameters on crystal size and morphology of lactose in ultrasound-assisted crystallization

    Energy Technology Data Exchange (ETDEWEB)

    Patel, S.R.; Murthy, Z.V.P. [Chemical Engineering Department, S.V. National Institute of Technology, Surat - 395 007, Gujarat (India)

    2011-03-15

    {alpha}-lactose monohydrate is widely used as a pharmaceutical excipient. Drug delivery system requires the excipient to be of narrow particle size distribution with regular particle shape. Application of ultrasound is known to increase or decrease the growth rate of certain crystal faces and controls the crystal size distribution. In the present paper, effect of process parameters such as sonication time, anti-solvent concentration, initial lactose concentration and initial pH of sample on lactose crystal size, shape and thermal transition temperature was studied. The parameters were set according to the L{sub 9}-orthogonal array method at three levels and recovered lactose from whey by sonocrystallization. The recovered lactose was analyzed by particle size analyzer, scanning electron microscopy and differential scanning calorimeter. It was found that the morphology of lactose crystal was rod/needle like shape. Crystal size distribution of lactose was observed to be influenced by different process parameters. From the results of analysis of variance, the sonication time interval was found to be the most significant parameter affecting the volume median diameter of lactose with the highest percentage contribution (74.28%) among other parameters. (copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  9. Lattice mechanics of ionic crystals - unified study

    International Nuclear Information System (INIS)

    Sengupta, S.; Roy, D.; Basu, A.N.

    1979-01-01

    The up-to-date situation in the understanding of the mechanical properties of ionic solids is reviewed. These properties are determined by the Born-Oppenheimer (B-O) potential energy function. For ionic crystals this potential energy function can be written down with some precision. To keep the expression tractable, the dominant electron deformation, the dipolar deformation, is treated as an adiabatic variable and the energy then becomes a function of both the nuclear coordinates and the ionic dipole moments. All the well known models for ionic crystals are discussed in terms of the energy expression they imply. This makes the comparison straight forward and brings out the essential difference between the models clearly. Next various quantum mechanical treatments for ionic crystals are reviewed. An attempt is made to obtain the B-O potential energy expression using a Heitler-London approach. By comparing the various models one can arrive at some definitive conclusions about the degree of validity and the assumptions underlying these models. Finally a comprehensive review of the results of actual computation on various ionic crystals done by different authors is undertaken. The crucial quantitative results are examined and the success and shortcoming of each calculation are critically analysed. The guiding principle in this part is the unified approach. i.e. to see how far a model with a given set of parameters accounts for both the dynamic and static properties. The discussion is divided in three sections for crystals with sodium chloride, cesium chloride and zinc sulfide structures. Outstanding problems and difficulties in the present understanding are pointed out. (auth.)

  10. Band structure of semiconductor compounds of Mg sub 2 Si and Mg sub 2 Ge with strained crystal lattice

    CERN Document Server

    Krivosheeva, A V; Shaposhnikov, V L; Krivosheev, A E; Borisenko, V E

    2002-01-01

    The effect of isotopic and unaxial deformation of the crystal lattice on the electronic band structure of indirect band gap semiconductors Mg sub 2 Si and Mg sub 2 Ge has been simulated by means of the linear augmented plane wave method. The reduction of the lattice constant down to 95 % results in a linear increase of the direct transition in magnesium silicide by 48%. The stresses arising under unaxial deformation shift the bands as well as result in splitting of degenerated states. The dependence of the interband transitions on the lattice deformation is nonlinear in this case

  11. New methods for indexing multi-lattice diffraction data

    International Nuclear Information System (INIS)

    Gildea, Richard J.; Waterman, David G.; Parkhurst, James M.; Axford, Danny; Sutton, Geoff; Stuart, David I.; Sauter, Nicholas K.; Evans, Gwyndaf; Winter, Graeme

    2014-01-01

    A new indexing method is presented which is capable of indexing multiple crystal lattices from narrow wedges of data. The efficacy of this method is demonstrated with both semi-synthetic multi-lattice data and real multi-lattice data recorded from microcrystals of ∼1 µm in size. A new indexing method is presented which is capable of indexing multiple crystal lattices from narrow wedges of diffraction data. The method takes advantage of a simplification of Fourier transform-based methods that is applicable when the unit-cell dimensions are known a priori. The efficacy of this method is demonstrated with both semi-synthetic multi-lattice data and real multi-lattice data recorded from crystals of ∼1 µm in size, where it is shown that up to six lattices can be successfully indexed and subsequently integrated from a 1° wedge of data. Analysis is presented which shows that improvements in data-quality indicators can be obtained through accurate identification and rejection of overlapping reflections prior to scaling

  12. Lattice Boltzmann Simulation of Water Isotope Fractionation During Growth of Ice Crystals in Clouds

    Science.gov (United States)

    Lu, G.; Depaolo, D.; Kang, Q.; Zhang, D.

    2006-12-01

    The isotopic composition of precipitation, especially that of snow, plays a special role in the global hydrological cycle and in reconstruction of past climates using polar ice cores. The fractionation of the major water isotope species (HHO, HDO, HHO-18) during ice crystal formation is critical to understanding the global distribution of isotopes in precipitation. Ice crystal growth in clouds is traditionally treated with a spherically- symmetric steady state diffusion model, with semi-empirical modifications added to account for ventilation and for complex crystal morphology. Although it is known that crystal growth rate, which depends largely on the degree of vapor over-saturation, determines crystal morphology, there are no existing quantitative models that directly relate morphology to the vapor saturation factor. Since kinetic (vapor phase diffusion-controlled) isotopic fractionation also depends on growth rate, there should be a direct relationship between vapor saturation, crystal morphology, and crystal isotopic composition. We use a 2D Lattice-Boltzmann model to simulate diffusion-controlled ice crystal growth from vapor- oversaturated air. In the model, crystals grow solely according to the diffusive fluxes just above the crystal surfaces, and hence crystal morphology arises from the initial and boundary conditions in the model and does not need to be specified a priori. The input parameters needed are the isotope-dependent vapor deposition rate constant (k) and the water vapor diffusivity in air (D). The values of both k and D can be computed from kinetic theory, and there are also experimentally determined values of D. The deduced values of k are uncertain to the extent that the sticking coefficient (or accommodation coefficient) for ice is uncertain. The ratio D/k is a length that determines the minimum scale of dendritic growth features and allows us to scale the numerical calculations to atmospheric conditions using a dimensionless Damkohler number

  13. Diffusion in Coulomb crystals.

    Science.gov (United States)

    Hughto, J; Schneider, A S; Horowitz, C J; Berry, D K

    2011-07-01

    Diffusion in Coulomb crystals can be important for the structure of neutron star crusts. We determine diffusion constants D from molecular dynamics simulations. We find that D for Coulomb crystals with relatively soft-core 1/r interactions may be larger than D for Lennard-Jones or other solids with harder-core interactions. Diffusion, for simulations of nearly perfect body-centered-cubic lattices, involves the exchange of ions in ringlike configurations. Here ions "hop" in unison without the formation of long lived vacancies. Diffusion, for imperfect crystals, involves the motion of defects. Finally, we find that diffusion, for an amorphous system rapidly quenched from Coulomb parameter Γ=175 to Coulomb parameters up to Γ=1750, is fast enough that the system starts to crystalize during long simulation runs. These results strongly suggest that Coulomb solids in cold white dwarf stars, and the crust of neutron stars, will be crystalline and not amorphous.

  14. Rho resonance parameters from lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Dehua; Alexandru, Andrei; Molina, Raquel; Döring, Michael

    2016-08-01

    We perform a high-precision calculation of the phase shifts for $\\pi$-$\\pi$ scattering in the I = 1, J = 1 channel in the elastic region using elongated lattices with two mass-degenerate quark favors ($N_f = 2$). We extract the $\\rho$ resonance parameters using a Breit-Wigner fit at two different quark masses, corresponding to $m_{\\pi} = 226$MeV and $m_{\\pi} = 315$MeV, and perform an extrapolation to the physical point. The extrapolation is based on a unitarized chiral perturbation theory model that describes well the phase-shifts around the resonance for both quark masses. We find that the extrapolated value, $m_{\\rho} = 720(1)(15)$MeV, is significantly lower that the physical rho mass and we argue that this shift could be due to the absence of the strange quark in our calculation.

  15. Experimental investigation of the EPR parameters and molecular orbital bonding coefficients for VO{sup 2+} ion in NaH{sub 2}PO{sub 4}·2H{sub 2}O single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Kalfaoğlu, Emel [Ondokuz Mayıs University, Faculty of Sciences, Department of Physics, 55139 Kurupelit-Samsun (Turkey); Karabulut, Bünyamin, E-mail: bbulut@omu.edu.tr [Ondokuz Mayıs University, Faculty of Engineering, Department of Computer Engineering, 55139 Kurupelit-Samsun (Turkey)

    2016-09-15

    Electron paramagnetic resonance (EPR) spectra of VO{sup 2+} ions in NaH{sub 2}PO{sub 4}·2H{sub 2}O single crystal have been studied. The spin-Hamiltonian parameters and molecular orbital bonding coefficients were calculated. The angular variation of the EPR spectra shows two different VO{sup 2+} complexes. These are located in different chemical environment and each environment contains four magnetically inequivalent VO{sup 2+} sites. The crystal field around VO{sup 2+} ion is approximately axially symmetric since a strong V=O bond distorts the crystal lattice. Spin Hamiltonian parameters and molecular orbital bonding coefficients were calculated from the EPR data and the nature of bonding in the complex was discussed together.

  16. Annealing effect of H+ -implanted single crystal silicon on strain and crystal structure

    International Nuclear Information System (INIS)

    Duo Xinzhong; Liu Weili; Zhang Miao; Gao Jianxia; Fu Xiaorong; Lin Chenglu

    2000-01-01

    The work focuses on the rocking curves of H + -implanted single silicon crystal detected by Four-Crystal X-ray diffractometer. The samples were annealed under different temperatures. Lattice defect in H + -implanted silicon crystals was detected by Rutherford Backscattering Spectrometry. It appeared that H-related complex did not crush until annealing temperature reached about 400 degree C. At that temperature H 2 was formed, deflated in silicon lattice and strained the lattice. But defects did not come into being in large quantity. The lattice was undamaged. When annealing temperature reached 500 degree C, strain induced by H 2 deflation crashed the silicon lattice. A large number of defects were formed. At the same time bubbles in the crystal and blister/flaking on the surface could be observed

  17. X-ray diffraction studies of NbTe 2 single crystal

    Indian Academy of Sciences (India)

    The composition of the grown crystals was confirmed on the basis of energy dispersive analysis by X-ray (EDAX) and remaining structural characterization was also accomplished by X-ray diffraction (XRD) studies. Lattice parameters, volume and X-ray density have been carried out for the grown crystals. The particle size ...

  18. Vacancies in quantal Wigner crystals near melting

    International Nuclear Information System (INIS)

    Barraza, N.; Colletti, L.; Tosi, M.P.

    1999-04-01

    We estimate the formation energy of lattice vacancies in quantal Wigner crystals of charged particles near their melting point at zero temperature, in terms of the crystalline Lindemann parameter and of the static dielectric function of the fluid phase near freezing. For both 3D and 2D crystals of electrons our results suggest the presence of vacancies in the ground state at the melting density. (author)

  19. Effect of lattice-level adjoint-weighting on the kinetics parameters of CANDU reactors

    International Nuclear Information System (INIS)

    Nichita, Eleodor

    2009-01-01

    Space-time kinetics calculations for CANDU reactors are routinely performed using the Improved Quasistatic (IQS) method. The IQS method calculates kinetics parameters such as the effective delayed-neutron fraction and generation time using adjoint weighting. In the current implementation of IQS, the direct flux, as well as the adjoint, is calculated using a two-group cell-homogenized reactor model which is inadequate for capturing the effect of the softer energy spectrum of the delayed neutrons. Additionally, there may also be fine spatial effects that are lost because the intra-cell adjoint shape is ignored. The purpose of this work is to compare the kinetics parameters calculated using the two-group cell-homogenized model with those calculated using lattice-level fine-group heterogeneous adjoint weighting and to assess whether the differences are large enough to justify further work on incorporating lattice-level adjoint weighting into the IQS method. A second goal is to evaluate whether the use of a fine-group cell-homogenized lattice-level adjoint, such as is the current practice for Light Water Reactors (LWRs), is sufficient to capture the lattice effects in question. It is found that, for CANDU lattices, the generation time is almost unaffected by the type of adjoint used to calculate it, but that the effective delayed-neutron fraction is affected by the type of adjoint used. The effective delayed-neutron fraction calculated using the two-group cell-homogenized adjoint is 5.2% higher than the 'best' effective delayed-neutron fraction value obtained using the detailed lattice-level fine-group heterogeneous adjoint. The effective delayed-neutron fraction calculated using the fine-group cell-homogenized adjoint is only 1.7% higher than the 'best' effective delayed-neutron fraction value but is still not equal to it. This situation is different from that encountered in LWRs where weighting by a fine-group cell-homogenized adjoint is sufficient to calculate the

  20. Lattice parameters and thermal expansion of delta-VNsub(1-x) from 298-1000 K

    International Nuclear Information System (INIS)

    Lengauer, W.; Ettmayer, P.

    1986-01-01

    The thermal expansion of VNsub(1-x) was determined from measurements of the lattice parameters in the temperature range of 298-1000 K and in the composition range of VNsub(0.707) - VNsub(0.996). Within the accuracy of the results the expansion of the lattice parameter with temperature is not dependent on the composition. The lattice parameter as a function of composition ([N]/[V] = 0.707-0.996) and temperature (198-1000 K) is given by a([N]/[V], T) = 0.38872+0.02488 ([N]/[V]) - (1.083+-0.021) x 10 -4 Tsup(1/2) + (6.2+-0.1) x 10 - sup6T. The coefficient of linear thermal expansion as a function of temperature (in the same range) is given by α(T) = a([N]/[V], T) -1 [(-5.04+-0.01) x 10 -5 Tsup(1/2) + (6.2+-0.1) x 10 -6 ]. The average linear thermal expansion coefficient is αsub(av) = 9.70 +- 0.15 x 10 -6 K -1 (298-1000 K). The data are compared with those of several fcc transition metal nitrides collected and evaluated from the literature. (Author)

  1. B{sub K}-parameter from N{sub f}=2 twisted mass lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    Constantinou, M. [Cyprus Univ., Nicosia (Cyprus). Dept. of Physics; Dimopoulos, P. [Roma Univ. (Italy). Dipt. di Fisica; Frezzotti, R. [Roma ' ' Tor Vergata' ' Univ. (Italy). Dipt. di Fisica; INFN, Rome (IT). Dipt. di Fisica] (and others)

    2011-01-07

    We present an unquenched N{sub f} = 2 lattice computation of the B{sub K} parameter which controls K{sup 0}- anti K{sup 0} oscillations. A partially quenched setup is employed with two maximally twisted dynamical (sea) light Wilson quarks, and valence quarks of both the maximally twisted and the Osterwalder-Seiler variety. Suitable combinations of these two kinds of valence quarks lead to a lattice definition of the B{sub K} parameter which is both multiplicatively renormalizable and O(a) improved. Employing the non-perturbative RI-MOM scheme, in the continuum limit and at the physical value of the pion mass we get B{sup RGI}{sub K}=0.729{+-}0.030, a number well in line with the existing quenched and unquenched determinations. (orig.)

  2. Boron lattice location in room temperature ion implanted Si crystal

    International Nuclear Information System (INIS)

    Piro, A.M.; Romano, L.; Mirabella, S.; Grimaldi, M.G.

    2005-01-01

    The B lattice location in presence of a Si-self-interstitial (I Si ) supersaturation, controlled by energetic proton bombardment, has been studied by means of ion channelling and massive Monte Carlo simulations. B-doped layers of Si crystals with a B concentration of 1 x 10 2 B/cm 3 were grown by Molecular Beam Epitaxy. Point defect engineering techniques, with light energetic ion implants, have been applied to generate an I Si uniform injection in the electrically active layer. The displacement of B atoms out of substitutional lattice sites was induced by 650 keV proton irradiations at room temperature (R.T.) and the resultant defect configuration was investigated by ion channelling and Nuclear Reaction Analysis (NRA) techniques. Angular scans were measured both through and axes along the (1 0 0) plane using the 11 B(p,α) 8 Be nuclear reaction at 650 keV proton energy. Monte Carlo simulated angular scans were calculated considering a variety of theoretical defect configurations, supported by literature, and compared with experimental data. Our experimental scans can be fitted by a linear combination of small (0.3 A) and large B displacements (1.25 A) along the direction, compatible with the B-dumbbell oriented along as proposed by ab initio calculations

  3. Lattice thermal expansion and solubility limits of neodymium-doped ceria

    International Nuclear Information System (INIS)

    Zhang, Jinhua; Ke, Changming; Wu, Hongdan; Yu, Jishun; Wang, Jingran

    2016-01-01

    Nd x Ce 1−x O 2−0.5x (x=0–1.0) powders were prepared by reverse coprecipitation-calcination method and characterized by XRD. The crystal structure of product powders transformed from single fluorite structure to the complex of fluorite and C-type cubic structure, and finally to trigonal structure with the increase of x-value. An empirical equation simulating the lattice parameter of neodymium doped ceria was established based on the experimental data. The lattice parameters of the fluorite structure solid solutions increased with extensive adoption of Nd 3+ , and the heating temperature going up. The average thermal expansion coefficients of neodymium doped ceria with fluorite structure are higher than 13.5×10 −6 °C −1 from room temperature to 1200 °C. - Graphical abstract: The crystal structure of Nd x Ce 1−x O 2−0.5x (x=0–1.0) powders transformed from single fluorite structure to the complex of fluorite and C-type cubic structure, and finally to trigonal structure with the increase of x-value.

  4. Method of storing radioactive rare gas. [gas occupies spaces in the zeolite crystal lattice

    Energy Technology Data Exchange (ETDEWEB)

    Nagao, H; Miharada, H; Takiguchi, Y; Kanazawa, T; Soya, M

    1975-05-15

    A method is provided to prevent dispersion of radioactive rare gas atoms by sealing them in a pressurised state within zeolite and thereby confining them in position within the zeolite crystal lattice. Radioactive rare gas is separated from exhaust gas and concentrated by using a low temperature adsorption means or liquefaction distillation means and necessary accessory means, and then it is temporarily stored in a gas holder. When a predetermined quantity of storage is reached, the gas is led to a sealing tank containing zeolite heated to 300 to 400/sup 0/C and held at 3,000 to 4,000 atmospheres, and under this condition radioactive rare gas is brought to occupy the spaces in the zeolite crystal lattice. After equilibrium pressure is reached by the pressure in the tank at that temperature, the gas is cooled in the pressurised state down to room temperature. Subsequently, the rare gas remaining in the tank and duct is recovered by a withdrawal pump into the gas holder. Thereafter, the zeolite with radioactive rare gas sealed in it is taken out from the tank and sealed within a long period storage container, which is then housed in a predetermined place for storage.

  5. Investigation on lattice parameters and superconducting properties in Fe(Te, Se, S) ternary-chalcogen system

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Zhongnan; Zhang, Huanhuan; Han, Bingling; Yuan, Wenxia, E-mail: wxyuanwz@163.com

    2015-02-15

    Highlights: • A series sample of Fe{sub 1.02}Te{sub 0.85}Se{sub 0.15−x}S{sub x} has been synthesised. • The lattice parameters is basically unchanged with the S doping. • The superconductivity is clearly suppressed with the S substitution of Se. • The solid solubility region of the tetragonal phase in this system is discussed. - Abstract: A series of samples with the nominal compositions Fe{sub 1.02}Te{sub 0.85}Se{sub 0.15−x}S{sub x} (x = 0, 0.0375, 0.075, 0.1125 and 0.15) have been synthesized to study the influence of the S substitution of Se on the lattice parameters and superconducting properties. It has been found that the S substitution basically has no effect on the lattice parameters a and c of the tetragonal phase. However, T{sub c} of Fe{sub 1.02}(Te{sub 0.85}Se{sub 0.15−x}S{sub x}) superconductors clearly decreases with S doping.

  6. A study on the microstructural parameters of 550 keV electron irradiated Lexan polymer films

    International Nuclear Information System (INIS)

    Hareesh, K.; Pramod, R.; Petwal, V. C.; Dwivedi, Jishnu; Sangappa; Sanjeev, Ganesh

    2012-01-01

    Lexan polymer films irradiated with 550 keV Electron Beam (EB) were characterized using Wide Angle Xray Scattering (WAXS) data to study the microstructural parameters. The crystal imperfection parameters like crystal size , lattice strain (g in %) and enthalpy (α) have been determined by Line Profile Analysis (LPA) using Fourier method of Warren.

  7. Observation of a commensurate array of flux chains in tilted flux lattices in Bi-Sr-Ca-Cu-O single crystals

    International Nuclear Information System (INIS)

    Bolle, C.A.; Gammel, P.L.; Grier, D.G.; Murray, C.A.; Bishop, D.J.; Mitzi, D.B.; Kapitulnik, A.

    1991-01-01

    We report the observation of a novel flux-lattice structure, a commensurate array of flux-line chains. Our experiments consist of the magnetic decoration of the flux lattices in single crystals of Ba-Sr-Ca-Cu-O where the magnetic field is applied at an angle with respect to the conducting planes. For a narrow range of angles, the equilibrium structure is one with uniformly spaced chains with a higher line density of vortices than the background lattice. Our observations are in qualitative agreement with theories which suggest that, in strongly anisotropic materials the vortices develop an attractive interaction in tilted magnetic fields

  8. Effect of ion nitriding on the crystal structure of 3 mol% Y2O3-doped ZrO2 thin-films prepared by the sol-gel method

    International Nuclear Information System (INIS)

    Ortiz, A.L.; Diaz-Parralejo, A.; Borrero-Lopez, O.; Guiberteau, F.

    2006-01-01

    We investigated the effect of ion nitriding on the crystal structure of 3 mol% Y 2 O 3 -doped ZrO 2 (3YSZ) thin-films prepared by the sol-gel method. For this purpose, we used X-ray diffractometry to determine the crystalline phases, the lattice parameters, the crystal sizes, and the lattice microstrains, and glow discharge-optical emission spectroscopy to obtain the depth profiles of the elemental chemical composition. We found that nitrogen atoms substitute oxygen atoms in the 3YSZ crystal, thus leading to the formation of unsaturated-substitutional solid solutions with reduced lattice parameters and Zr 0.94 Y 0.06 O 1.72 N 0.17 stoichiometric formula. We also found that ion nitriding does not affect the grain size, but does generate lattice microstrains due to the increase in point defects in the crystalline lattice

  9. A Lattice-Misfit-Dependent Damage Model for Non-linear Damage Accumulations Under Monotonous Creep in Single Crystal Superalloys

    Science.gov (United States)

    le Graverend, J.-B.

    2018-05-01

    A lattice-misfit-dependent damage density function is developed to predict the non-linear accumulation of damage when a thermal jump from 1050 °C to 1200 °C is introduced somewhere in the creep life. Furthermore, a phenomenological model aimed at describing the evolution of the constrained lattice misfit during monotonous creep load is also formulated. The response of the lattice-misfit-dependent plasticity-coupled damage model is compared with the experimental results obtained at 140 and 160 MPa on the first generation Ni-based single crystal superalloy MC2. The comparison reveals that the damage model is well suited at 160 MPa and less at 140 MPa because the transfer of stress to the γ' phase occurs for stresses above 150 MPa which leads to larger variations and, therefore, larger effects of the constrained lattice misfit on the lifetime during thermo-mechanical loading.

  10. Numerical investigation of flows in Czochralski crystal growth by an axisymmetric lattice Boltzmann method

    CERN Document Server

    Peng, Y; Chew, Y T; Qiu, J

    2003-01-01

    An alternative new method called lattice Boltzmann method (LBM) is applied in this work to simulate the flows in Czochralski crystal growth, which is one of the widely used prototypical systems for melt-crystal growth. The standard LBM can only be used in Cartesian coordinate system and we extend it to be applicable to this axisymmetric thermal flow problem, avoiding the use of three-dimensional LBM on Cartesian coordinate system. The extension is based on the following idea. By inserting position and time dependent source terms into the evolution equation of standard LBM, the continuity and NS equations on the cylindrical coordinate system can be recovered. Our extension is validated by its application to the benchmark problem suggested by Wheeler .

  11. Numerical investigation of flows in Czochralski crystal growth by an axisymmetric lattice Boltzmann method

    Science.gov (United States)

    Peng, Y.; Shu, C.; Chew, Y. T.; Qiu, J.

    2003-03-01

    An alternative new method called lattice Boltzmann method (LBM) is applied in this work to simulate the flows in Czochralski crystal growth, which is one of the widely used prototypical systems for melt-crystal growth. The standard LBM can only be used in Cartesian coordinate system and we extend it to be applicable to this axisymmetric thermal flow problem, avoiding the use of three-dimensional LBM on Cartesian coordinate system. The extension is based on the following idea. By inserting position and time dependent source terms into the evolution equation of standard LBM, the continuity and NS equations on the cylindrical coordinate system [1] can be recovered. Our extension is validated by its application to the benchmark problem suggested by Wheeler [2].

  12. Numerical investigation of flows in Czochralski crystal growth by an axisymmetric lattice Boltzmann method

    International Nuclear Information System (INIS)

    Peng, Y.; Shu, C.; Chew, Y.T.; Qiu, J.

    2003-01-01

    An alternative new method called lattice Boltzmann method (LBM) is applied in this work to simulate the flows in Czochralski crystal growth, which is one of the widely used prototypical systems for melt-crystal growth. The standard LBM can only be used in Cartesian coordinate system and we extend it to be applicable to this axisymmetric thermal flow problem, avoiding the use of three-dimensional LBM on Cartesian coordinate system. The extension is based on the following idea. By inserting position and time dependent source terms into the evolution equation of standard LBM, the continuity and NS equations on the cylindrical coordinate system can be recovered. Our extension is validated by its application to the benchmark problem suggested by Wheeler

  13. A simple method for determining the lattice parameter and chemical composition in ternary bcc-Fe rich nanocrystals

    International Nuclear Information System (INIS)

    Moya, Javier A.; Gamarra Caramella, Soledad; Marta, Leonardo J.; Berejnoi, Carlos

    2015-01-01

    Highlights: • A method for determining composition in ternary nanocrystals is presented. • X-ray diffraction and Mössbauer spectroscopy data were employed. • We perform theoretical charts for lattice parameter of Fe-rich ternary alloys. • A linear relationship in lattice parameter for binary alloys is evaluated. • A parabolic relationship is proposed for the Fe–Co–Si alloy. - Abstract: Charts containing lattice parameters of Fe 1−x (M,N) x ternary systems with M and N = Si, Al, Ge or Co, and 0 ⩽ x ⩽ ∼0.3, were developed by implementing a linear relationship between the respective binary alloys with the same solute content of the ternary one. Charts were validated with experimental data obtained from literature. For the Fe–Co–Si system, the linear relationship does not fit the experimental data. For the other systems (except the Fe–Co–Ge one where no experimental data was found), the lineal relationship constitute a very good approximation. Using these charts and the lattice parameter data obtained from X-ray diffraction technique combining with the solute content data obtained from Mössbauer spectroscopy technique it is possible to determine the chemical composition of nanograins in soft magnetic nanocomposite materials and some examples are provided

  14. A simple method for determining the lattice parameter and chemical composition in ternary bcc-Fe rich nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Moya, Javier A., E-mail: jmoya.fi.uba@gmail.com [Grupo Interdisciplinario en Materiales-IESIING, Universidad Católica de Salta, INTECIN UBA-CONICET, Salta (Argentina); Gamarra Caramella, Soledad; Marta, Leonardo J. [Grupo Interdisciplinario en Materiales-IESIING, Universidad Católica de Salta, INTECIN UBA-CONICET, Salta (Argentina); Berejnoi, Carlos [Universidad Nacional de Salta, Facultad de Ingeniería, Salta (Argentina)

    2015-05-15

    Highlights: • A method for determining composition in ternary nanocrystals is presented. • X-ray diffraction and Mössbauer spectroscopy data were employed. • We perform theoretical charts for lattice parameter of Fe-rich ternary alloys. • A linear relationship in lattice parameter for binary alloys is evaluated. • A parabolic relationship is proposed for the Fe–Co–Si alloy. - Abstract: Charts containing lattice parameters of Fe{sub 1−x}(M,N){sub x} ternary systems with M and N = Si, Al, Ge or Co, and 0 ⩽ x ⩽ ∼0.3, were developed by implementing a linear relationship between the respective binary alloys with the same solute content of the ternary one. Charts were validated with experimental data obtained from literature. For the Fe–Co–Si system, the linear relationship does not fit the experimental data. For the other systems (except the Fe–Co–Ge one where no experimental data was found), the lineal relationship constitute a very good approximation. Using these charts and the lattice parameter data obtained from X-ray diffraction technique combining with the solute content data obtained from Mössbauer spectroscopy technique it is possible to determine the chemical composition of nanograins in soft magnetic nanocomposite materials and some examples are provided.

  15. 'Ionic crystals' consisting of trinuclear macrocations and ...

    Indian Academy of Sciences (India)

    T Arumuganathan

    )(ClCH2COO)6(H2O)3]4. [SiW12O40] ... solid state properties to obtain new materials in appli- ... Reflections Collected/unique ... covalent bonds in the relevant crystal lattice having ...... the relevant parameters are given in Tables 5 and 6,.

  16. Stacking faults and microstructural parameters in non-mulberry silk ...

    Indian Academy of Sciences (India)

    rameters like crystal size (〈N〉), lattice strain (g) and stacking faults in polymer materials ... metal oxide compounds, but may be inadequate for describing diffraction patterns .... Further, with these model parameters for individual Bragg reflec-.

  17. Physical Realization of von Neumann Lattices in Rotating Bose Gases with Dipole Interatomic Interactions.

    Science.gov (United States)

    Cheng, Szu-Cheng; Jheng, Shih-Da

    2016-08-22

    This paper reports a novel type of vortex lattice, referred to as a bubble crystal, which was discovered in rapidly rotating Bose gases with long-range interactions. Bubble crystals differ from vortex lattices which possess a single quantum flux per unit cell, while atoms in bubble crystals are clustered periodically and surrounded by vortices. No existing model is able to describe the vortex structure of bubble crystals; however, we identified a mathematical lattice, which is a subset of coherent states and exists periodically in the physical space. This lattice is called a von Neumann lattice, and when it possesses a single vortex per unit cell, it presents the same geometrical structure as an Abrikosov lattice. In this report, we extend the von Neumann lattice to one with an integral number of flux quanta per unit cell and demonstrate that von Neumann lattices well reproduce the translational properties of bubble crystals. Numerical simulations confirm that, as a generalized vortex, a von Neumann lattice can be physically realized using vortex lattices in rapidly rotating Bose gases with dipole interatomic interactions.

  18. Fluorescence lifetime of emitters with broad homogeneous linewidths modified in opal photonic crystals

    DEFF Research Database (Denmark)

    Nikolaev, Ivan S.; Lodahl, Peter; Vos, Willem L.

    2008-01-01

    We have investigated the dynamics of spontaneous emission from dye molecules embedded in opal photonic crystals. Fluorescence lifetimes of Rhodamine 6G (R6G) dye were measured as a function of both optical frequency and crystal lattice parameter of the polystyrene opals. Due to the broad...

  19. Crystal structure of vanadite: Refinement of anisotropic displacement parameters

    Czech Academy of Sciences Publication Activity Database

    Laufek, F.; Skála, Roman; Haloda, J.; Císařová, I.

    2006-01-01

    Roč. 51, 3-4 (2006), s. 271-275 ISSN 1210-8197 Institutional research plan: CEZ:AV0Z30130516 Keywords : anisotropic displacement parameter * crystal structure * single-crystal X-ray refinement * vanadinite Subject RIV: DB - Geology ; Mineralogy

  20. Method for fitting crystal field parameters and the energy level fitting for Yb3+ in crystal SC2O3

    International Nuclear Information System (INIS)

    Qing-Li, Zhang; Kai-Jie, Ning; Jin, Xiao; Li-Hua, Ding; Wen-Long, Zhou; Wen-Peng, Liu; Shao-Tang, Yin; Hai-He, Jiang

    2010-01-01

    A method to compute the numerical derivative of eigenvalues of parameterized crystal field Hamiltonian matrix is given, based on the numerical derivatives the general iteration methods such as Levenberg–Marquardt, Newton method, and so on, can be used to solve crystal field parameters by fitting to experimental energy levels. With the numerical eigenvalue derivative, a detailed iteration algorithm to compute crystal field parameters by fitting experimental energy levels has also been described. This method is used to compute the crystal parameters of Yb 3+ in Sc 2 O 3 crystal, which is prepared by a co-precipitation method and whose structure was refined by Rietveld method. By fitting on the parameters of a simple overlap model of crystal field, the results show that the new method can fit the crystal field energy splitting with fast convergence and good stability. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  1. THERMODYNAMIC PARAMETERS OF LEAD SULFIDE CRYSTALS IN THE CUBIC PHASE

    Directory of Open Access Journals (Sweden)

    T. O. Parashchuk

    2016-07-01

    Full Text Available Geometric and thermodynamic parameters of cubic PbS crystals were obtained using the computer calculations of the thermodynamic parameters within density functional theory method DFT. Cluster models for the calculation based on the analysis of the crystal and electronic structure. Temperature dependence of energy ΔE and enthalpy ΔH, Gibbs free energy ΔG, heat capacity at constant pressure CP and constant volume CV, entropy ΔS were determined on the basis of ab initio calculations of the crystal structure of molecular clusters. Analytical expressions of temperature dependences of thermodynamic parameters which were approximated with quantum-chemical calculation points have been presented. Experimental results compared with theoretically calculated data.

  2. The focusing effect of electromagnetic waves in two-dimensional photonic crystals with gradually varying lattice constant

    Directory of Open Access Journals (Sweden)

    F Bakhshi Garmi

    2016-02-01

    Full Text Available In this paper we studied the focusing effect of electromagnetic wave in the two-dimensional graded photonic crystal consisting of Silicon rods in the air background with gradually varying lattice constant. The results showed that graded photonic crystal can focus wide beams on a narrow area at frequencies near the lower edge of the band gap, where equal frequency contours are not concave. For calculation of photonic band structure and equal frequency contours, we have used plane wave expansion method and revised plane wave expansion method, respectively. The calculation of the electric and magnetic fields was performed by finite difference time domain method.

  3. Determination of D2O - 2% enriched uranium lattice parameters by means of a critical system

    International Nuclear Information System (INIS)

    Raisic, N.; Takac, S.; Markovic, H.; Bosevski, T.

    1963-01-01

    In order to specify experimental procedures for few standard measurements sufficient to provide consistent set of lattice parameters, a series of experiments were performed at the RB reactor using 2% enriched tubular fuel elements. Obtained results were compared to standard two-group diffusion calculation indicating high degree of accuracy for a broad variety of reactor lattice configurations

  4. Lattice thermal expansion and solubility limits of neodymium-doped ceria

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Jinhua, E-mail: jhzhang1212@126.com [The State Key Laboratory of Refractories and Metallurgy, Wuhan University of Science and Technology, Wuhan 430081 (China); State Key laboratory of Geological Process and Mineral Resources, China University of Geosciences, Wuhan 430074 (China); Ke, Changming [The State Key Laboratory of Refractories and Metallurgy, Wuhan University of Science and Technology, Wuhan 430081 (China); Wu, Hongdan [College of Resources and Enviromental Engineering, Wuhan University of Science and Technology, Wuhan 430081 (China); Yu, Jishun [State Key laboratory of Geological Process and Mineral Resources, China University of Geosciences, Wuhan 430074 (China); Wang, Jingran [The State Key Laboratory of Refractories and Metallurgy, Wuhan University of Science and Technology, Wuhan 430081 (China)

    2016-11-15

    Nd{sub x}Ce{sub 1−x}O{sub 2−0.5x} (x=0–1.0) powders were prepared by reverse coprecipitation-calcination method and characterized by XRD. The crystal structure of product powders transformed from single fluorite structure to the complex of fluorite and C-type cubic structure, and finally to trigonal structure with the increase of x-value. An empirical equation simulating the lattice parameter of neodymium doped ceria was established based on the experimental data. The lattice parameters of the fluorite structure solid solutions increased with extensive adoption of Nd{sup 3+}, and the heating temperature going up. The average thermal expansion coefficients of neodymium doped ceria with fluorite structure are higher than 13.5×10{sup −6} °C{sup −1} from room temperature to 1200 °C. - Graphical abstract: The crystal structure of Nd{sub x}Ce{sub 1−x}O{sub 2−0.5x} (x=0–1.0) powders transformed from single fluorite structure to the complex of fluorite and C-type cubic structure, and finally to trigonal structure with the increase of x-value.

  5. Irradiation effects on c-axis lattice parameter in EuBa{sub 2}Cu{sub 3}O{sub y} irradiated with energetic ions

    Energy Technology Data Exchange (ETDEWEB)

    Ishikawa, Norito; Chimi, Yasuhiro; Iwase, Akihiro; Maeta, Hiroshi [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment; Tsuru, Koji; Michikami, Osamu

    1997-03-01

    We report an irradiation effect on c-axis lattice parameter in EuBa{sub 2}Cu{sub 3}O{sub y} oxide superconductors when irradiated with ions of energy ranging from 0.85 to 200 MeV. For the irradiation with low energy (0.85-2 MeV) ions, the defect production and the resultant c-axis lattice expansion were dominated by elastic collisions. On the other hand, for the irradiation with high energy (120-200 MeV) ions, the change in the c-axis lattice parameter was found to be much greater than that expected from the elastic displacement of target atoms. For high energy ion irradiation we could observe the excessive increase of c-axis lattice parameter reflecting additional production of defects which can be attributed to the electronic excitation. The large increase in c-axis lattice parameter due to high energy ion irradiation should be taken into account for the study on the interaction between vortices and irradiation-induced defects. (author)

  6. Investigation of fuel lattice pitch changes influence on reactor performance through evaluate the neutronic parameters

    International Nuclear Information System (INIS)

    Zareian Ronizi, F.; Fadaei, A.H.; Setayeshi, S.; Shahidi, A.R.

    2015-01-01

    Highlights: • One of the most complex issues that Nu-engineers deal with is the design of NR core. • Numerous factors in nuclear core design depend on Fuel-to-Moderator volume ratio. • Aim of this research is to investigate RX performance for different lattice pitches. - Abstract: Nuclear reactor core design is one of the most complex issues that nuclear engineers deal with. The number and complexity of effective parameters and their impact on reactor design, which makes the problem difficult to solve, require precise knowledge of these parameters and their influence on the reactor operation. Numerous factors in a nuclear reactor core design depend on the Fuel-to-Moderator volume ratio, V F /V M , in a fuel cell. This ratio can be modified by changing the lattice pitch which is the thickness of water channels between fuels plates while keeping fuel slab dimensions fixed. Cooling and moderating properties of water are affected by such a change in a reactor core, and hence some parameters related to these properties might be changed. The aim of this research is to provide the suitable knowledge for nuclear core designing. To reach this goal, the first operating core of Tehran Research Reactor (TRR) with different lattice pitches is simulated, and the effect of different lattice pitches on some parameters such as effective multiplication factor (K eff ), reactor life time, distribution of neutron flux and power density in the core, as well as moderator temperature and density coefficient of reactivity are evaluated. The nuclear reactor analysis code, MTR-PC package is employed to carry out the considered calculation. Finally, the results are presented in some tables and graphs that provide useful information for nuclear engineers in the nuclear reactor core design

  7. Thermal expansion and lattice parameters of shaped metal deposited Ti-6Al-4V

    Energy Technology Data Exchange (ETDEWEB)

    Swarnakar, Akhilesh Kumar; Van der Biest, Omer [Katholieke Universiteit Leuven, MTM, Kasteelpark Arenberg 44, 3001 Leuven (Belgium); Baufeld, Bernd, E-mail: b.baufeld@sheffield.ac.uk [Katholieke Universiteit Leuven, MTM, Kasteelpark Arenberg 44, 3001 Leuven (Belgium)

    2011-02-10

    Research highlights: > Measurement of thermal expansion and of the lattice parameters of Ti-6Al-4V fabricated by shaped metal deposition up to 1100 {sup o}C. > The observation of alpha to beta transformation not reflected in the expansion but in the contraction curve is explained by non-equilibrium alpha phase of the SMD material. > Denuding of the {alpha} phase and enrichment of the {beta} phase of Vanadium due to high temperature experiments. > The unit cell volumes derived from lattice parameters measured by X-ray diffraction are at room temperature larger for the {alpha} than for the {beta} phase. With increasing temperature the unit cell volume of the {beta} phase increases stronger than the one of the {alpha} phase resulting in a similar unit cell volume at the {beta} transus temperature. - Abstract: Thermal expansion and lattice parameters are investigated up to 1100 deg. C for Ti-6Al-4V components, fabricated by shaped metal deposition. This is a novel additive layer manufacturing technique where near net-shape components are built by tungsten inert gas welding. The as-fabricated SMD Ti-6Al-4V components exhibit a constant coefficient of thermal expansion of 1.17 x 10{sup -5} K{sup -1} during heating up to 1100 {sup o}C, not reflecting the {alpha} to {beta} phase transformation. During cooling a stalling of the contraction is observed starting at the {beta} transus temperature. These high temperature experiments denude the {alpha} phase of V and enrich the {beta} phase. The development of the lattice parameters in dependence on temperature are observed with high temperature X-ray diffraction. The unit cell volumes derived from these parameters are at room temperature larger for the {alpha} than for the {beta} phase. With increasing temperature the unit cell volume of the {beta} phase increases stronger than the one of the {alpha} phase resulting in a similar unit cell volume at the {beta} transus temperature. These observations are interpreted as an

  8. Synthesizing lattice structures in phase space

    International Nuclear Information System (INIS)

    Guo, Lingzhen; Marthaler, Michael

    2016-01-01

    In one dimensional systems, it is possible to create periodic structures in phase space through driving, which is called phase space crystals (Guo et al 2013 Phys. Rev. Lett. 111 205303). This is possible even if for particles trapped in a potential without periodicity. In this paper we discuss ultracold atoms in a driven optical lattice, which is a realization of such a phase space crystals. The corresponding lattice structure in phase space is complex and contains rich physics. A phase space lattice differs fundamentally from a lattice in real space, because its coordinate system, i.e., phase space, has a noncommutative geometry, which naturally provides an artificial gauge (magnetic) field. We study the behavior of the quasienergy band structure and investigate the dissipative dynamics. Synthesizing lattice structures in phase space provides a new platform to simulate the condensed matter phenomena and study the intriguing phenomena of driven systems far away from equilibrium. (paper)

  9. Effect of ion nitriding on the crystal structure of 3 mol% Y{sub 2}O{sub 3}-doped ZrO{sub 2} thin-films prepared by the sol-gel method

    Energy Technology Data Exchange (ETDEWEB)

    Ortiz, A.L. [Departamento de Electronica e Ingenieria Electromecanica, Escuela de Ingenierias Industriales, Universidad de Extremadura, Badajoz 06071 (Spain)]. E-mail: alortiz@unex.es; Diaz-Parralejo, A. [Departamento de Electronica e Ingenieria Electromecanica, Escuela de Ingenierias Industriales, Universidad de Extremadura, Badajoz 06071 (Spain); Borrero-Lopez, O. [Departamento de Electronica e Ingenieria Electromecanica, Escuela de Ingenierias Industriales, Universidad de Extremadura, Badajoz 06071 (Spain); Guiberteau, F. [Departamento de Electronica e Ingenieria Electromecanica, Escuela de Ingenierias Industriales, Universidad de Extremadura, Badajoz 06071 (Spain)

    2006-06-30

    We investigated the effect of ion nitriding on the crystal structure of 3 mol% Y{sub 2}O{sub 3}-doped ZrO{sub 2} (3YSZ) thin-films prepared by the sol-gel method. For this purpose, we used X-ray diffractometry to determine the crystalline phases, the lattice parameters, the crystal sizes, and the lattice microstrains, and glow discharge-optical emission spectroscopy to obtain the depth profiles of the elemental chemical composition. We found that nitrogen atoms substitute oxygen atoms in the 3YSZ crystal, thus leading to the formation of unsaturated-substitutional solid solutions with reduced lattice parameters and Zr{sub 0.94}Y{sub 0.06}O{sub 1.72}N{sub 0.17} stoichiometric formula. We also found that ion nitriding does not affect the grain size, but does generate lattice microstrains due to the increase in point defects in the crystalline lattice.

  10. Synthesis and structural characterization of Na 2 MnP 2 O 7 crystal

    Indian Academy of Sciences (India)

    Na2MnP2O7 crystals were synthesized by hydrothermal technique. Crystals obtained are in the form of single crystals of rhombohedral morphology with lattice parameters as follows: triclinic, 1 ¯ , = 0.71069 Å, = 6.657(3) Å, = 6.714(6) Å, = 6.518(4) Å, = 112.31(6)°, = 92.14(4)°, = 83.89(5)°, = 268.0(3) Å3, ...

  11. Program LATTICE for Calculation of Parameters of Targets with Heterogeneous (Lattice) Structure

    CERN Document Server

    Bznuni, S A; Soloviev, A G; Sosnin, A N

    2002-01-01

    Program LATTICE, with which help it is possible to describe lattice structure for the program complex CASCAD, is created in the C++ language. It is shown that for model-based electronuclear system on a basis of molten salt reactor with graphite moderator at transition from homogeneous structure to heterogeneous at preservation of a chemical compound there is a growth of k_{eff} by approximately 6 %.

  12. Vortex lattice structures in YNi2B2C

    International Nuclear Information System (INIS)

    Yethiraj, M.; Paul, D.M.; Tomy, C.V.; Forgan, E.M.

    1997-01-01

    The authors observe a flux lattice with square symmetry in the superconductor YNi 2 B 2 C when the applied field is parallel to the c-axis of the crystal. A square lattice observed previously in the isostructural magnetic analog ErNi 2 B 2 C was attributed to the interaction between magnetic order in that system and the flux lattice. Since the Y-based compound does not order magnetically, it is clear that the structure of the flux lattice is unrelated to magnetic order. In fact, they show that the flux lines have a square cross-section when the applied field is parallel to the c-axis of the crystal, since the measured penetration depth along the 100 crystal direction is larger than the penetration depth along the 110 by approximately 60%. This is the likely reason for the square symmetry of the lattice. Although they find considerable disorder in the arrangement of the flux lines at 2.5T, no melting of the vortex lattice was observed

  13. Tunable alumina 2D photonic-crystal structures via biomineralization of peacock tail feathers

    Science.gov (United States)

    Jiang, Yonggang; Wang, Rui; Feng, Lin; Li, Jian; An, Zhonglie; Zhang, Deyuan

    2018-04-01

    Peacock tail feathers with subtle periodic nanostructures exhibit diverse striking brilliancy, which can be applied as natural templates to fabricate artificial photonic crystals (PhCs) via a biomineralization method. Alumina photonic-crystal structures are successfully synthesized via an immersion and two-step calcination process. The lattice constants of the artificial PhCs are greatly reduced compared to their natural matrices. The lattice constants are tunable by modifying the final annealing conditions in the biomineralization process. The reflection spectra of the alumina photonic-crystal structures are measured, which is related to their material and structural parameters. This work suggests a facile fabrication process to construct alumina PhCs with a high-temperature resistance.

  14. Synchrotron Bragg diffraction imaging characterization of synthetic diamond crystals for optical and electronic power device applications.

    Science.gov (United States)

    Tran Thi, Thu Nhi; Morse, J; Caliste, D; Fernandez, B; Eon, D; Härtwig, J; Barbay, C; Mer-Calfati, C; Tranchant, N; Arnault, J C; Lafford, T A; Baruchel, J

    2017-04-01

    Bragg diffraction imaging enables the quality of synthetic single-crystal diamond substrates and their overgrown, mostly doped, diamond layers to be characterized. This is very important for improving diamond-based devices produced for X-ray optics and power electronics applications. The usual first step for this characterization is white-beam X-ray diffraction topography, which is a simple and fast method to identify the extended defects (dislocations, growth sectors, boundaries, stacking faults, overall curvature etc. ) within the crystal. This allows easy and quick comparison of the crystal quality of diamond plates available from various commercial suppliers. When needed, rocking curve imaging (RCI) is also employed, which is the quantitative counterpart of monochromatic Bragg diffraction imaging. RCI enables the local determination of both the effective misorientation, which results from lattice parameter variation and the local lattice tilt, and the local Bragg position. Maps derived from these parameters are used to measure the magnitude of the distortions associated with polishing damage and the depth of this damage within the volume of the crystal. For overgrown layers, these maps also reveal the distortion induced by the incorporation of impurities such as boron, or the lattice parameter variations associated with the presence of growth-incorporated nitrogen. These techniques are described, and their capabilities for studying the quality of diamond substrates and overgrown layers, and the surface damage caused by mechanical polishing, are illustrated by examples.

  15. Effect of a Nitrogen Impurity on the Fundamental Raman Band of Diamond Single Crystals

    Science.gov (United States)

    Gusakov, G. A.; Samtsov, M. P.; Voropay, E. S.

    2018-05-01

    The effect of nitrogen defects in natural and synthetic diamond single crystals on the position and half-width of the fundamental Raman band was investigated. Samples containing the main types of nitrogen lattice defects at impurity contents of 1-1500 ppm were studied. The parameters of the Stokes and anti-Stokes components in Raman spectra of crystals situated in a cell with distilled water to minimize the influence of heating by the exciting laser radiation were analyzed to determine the effect of a nitrogen impurity in the diamond crystal lattice. It was shown that an increase of impurity atoms in the crystals in the studied concentration range resulted in broadening of the Raman band from 1.61 to 2.85 cm-1 and shifting of the maximum to lower frequency from 1332.65 to 1332.3 cm-1. The observed effect was directly proportional to the impurity concentration and depended on the form of the impurity incorporated into the diamond lattice. It was found that the changes in the position and half-width of the fundamental Raman band for diamond were consistent with the magnitude of crystal lattice distortions due to the presence of impurity defects and obeyed the Gruneisen law.

  16. Determination of D{sub 2}O - 2% enriched uranium lattice parameters by means of a critical system

    Energy Technology Data Exchange (ETDEWEB)

    Raisic, N; Takac, S; Markovic, H; Bosevski, T [Boris Kidric Institute of Nuclear Sciences Belgrade (Yugoslavia)

    1963-07-01

    In order to specify experimental procedures for few standard measurements sufficient to provide consistent set of lattice parameters, a series of experiments were performed at the RB reactor using 2% enriched tubular fuel elements. Obtained results were compared to standard two-group diffusion calculation indicating high degree of accuracy for a broad variety of reactor lattice configurations.

  17. Lattice vibrations in α-boron

    International Nuclear Information System (INIS)

    Richter, W.

    1976-01-01

    α-rhombohedral boron is the simplest boron modification, with only 12 atoms per unit cell. The boron atoms are arranged in B 12 icosahedra, which are centered at the lattice points of a primitive rhombohedral lattice. The icosahedra are slightly deformed, as the five-fold symmetry of the ideal icosahedron is incompatible with any crystal structure. The lattice dynamics of α-boron are discussed in terms of the model developed by Weber and Thorpe. (Auth.)

  18. Calculation of dynamic and electronic properties of perfect and defect crystals by semiempirical quantum mechanical methods

    International Nuclear Information System (INIS)

    Zunger, A.

    1975-07-01

    Semiempirical all-valence-electron LCAO methods, that were previously used to study the electronic structure of molecules are applied to three problems in solid state physics: the electronic band structure of covalent crystals, point defect problems in solids and lattice dynamical study of molecular crystals. Calculation methods for the electronic band structure of regular solids are introduced and problems regarding the computation of the density matrix in solids are discussed. Three models for treating the electronic eigenvalue problem in the solid, within the proposed calculation schemes, are discussed and the proposed models and calculation schemes are applied to the calculation of the electronic structure of several solids belonging to different crystal types. The calculation models also describe electronic properties of deep defects in covalent insulating crystals. The possible usefulness of the semieipirical LCAO methods in determining the first order intermolecular interaction potential in solids and an improved model for treating the lattice dynamics and related thermodynamical properties of molecular solids are presented. The improved lattice dynamical is used to compute phonon dispersion curves, phonon density of states, stable unit cell structure, lattice heat capacity and thermal crystal parameters, in α and γ-N 2 crystals, using the N 2 -N 2 intermolecular interaction potential that has been computed from the semiempirical LCAO methods. (B.G.)

  19. Three-dimensional Random Voronoi Tessellations: From Cubic Crystal Lattices to Poisson Point Processes

    OpenAIRE

    Lucarini, Valerio

    2008-01-01

    We perturb the SC, BCC, and FCC crystal structures with a spatial Gaussian noise whose adimensional strength is controlled by the parameter a, and analyze the topological and metrical properties of the resulting Voronoi Tessellations (VT). The topological properties of the VT of the SC and FCC crystals are unstable with respect to the introduction of noise, because the corresponding polyhedra are geometrically degenerate, whereas the tessellation of the BCC crystal is topologically stable eve...

  20. Simultaneous effect of crystal lattice and non magnetic substitution on magnetic properties of barium hexaferrite

    Science.gov (United States)

    Kumar, Sunil; Supriya, Sweety; Pradhan, Lagen Kumar; Pandey, Rabichandra; Kar, Manoranjan

    2018-05-01

    The aluminium doped barium hexaferrite BaFe12-xAlxO19 with x =0.0, 1.0, 2.0, 4.0 and 6.0 have been synthesized by the sol-gel method to modify the magnetic properties for technological applications. The crystal structure and phase purity of all the samples have been explored by employing the X-ray diffraction (XRD) technique. It confirms that the sample is nanocrystalline, hexagonal symmetry and all the intense peaks could be indexed to the P63/mmc space group. The obtained lattice parameters from the XRD analysis decrease with the increase in Al3+ content in the samples. The microstructural morphology and particle sizes of all samples were studied by using the Field Emission Scanning Electron Microscopy (FESEM-Hitachi-S4800) technique. The magnetic hysteresis (M-H) loops measurement has been carried out at room temperature by employing the vibrating sample magnetometer (VSM) over a field range of +20 kOe to -20 kOe. The magnetic hysteresis (M-H) loops revealed the ferromagnetic (hard magnetic materials) nature of the samples and, analyzed by using the Law of Approach to Saturation.

  1. Experimental determination of lattice parameters for 2% enriched uranium heavy water reactor cores

    Energy Technology Data Exchange (ETDEWEB)

    Raisic, N; Takac, S; Markovic, H; Bosevski, T [Boris Kidric Institute of Nuclear Sciences Vinca, Belgrade (Yugoslavia)

    1963-04-15

    Systematic measurements of the buckling, infinite multiplication factor and the thermal utilization factor were made on a series of lattices for 2% enriched uranium tubular fuel elements in heavy water. This work represents the first phase of experimental verification of standard theoretical methods used for the determination of reactor parameters.

  2. Deformed lattice states in a Zn{sub 0.9}V{sub 0.1}Se cubic crystal

    Energy Technology Data Exchange (ETDEWEB)

    Maksimov, V. I., E-mail: kokailo@rambler.ru; Dubinin, S. F.; Surkova, T. P.; Parkhomenko, V. D. [Russian Academy of Sciences, Institute of Metal Physics, Ural Branch (Russian Federation)

    2016-01-15

    Neutron scattering patterns have been recorded for a bulk Zn{sub 0.9}V{sub 0.1}Se cubic crystal at room temperature; they are indicative of macroscopic deformation in the material and its significant inhomogeneity. Specific features of the previously found state, preceding the fcc ↔ hcp structural transformation of the sphalerite lattice upon strong destabilization induced by vanadium ions in the doped ZnSe matrix, are discussed taking into account the data obtained.

  3. Growth and microtopographic study of CuInSe{sub 2} single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Chauhan, Sanjaysinh M.; Chaki, Sunil, E-mail: sunilchaki@yahoo.co.in; Deshpande, M. P. [Department of Physics, Sardar Patel University, Vallabh Vidyanagar, Gujarat - 388120 (India); Tailor, J. P. [Applied Physics Department, S.V.N.I.T., Surat, Gujarat - 395007 (India)

    2016-05-23

    The CuInSe{sub 2} single crystals were grown by chemical vapour transport (CVT) technique using iodine as transporting agent. The elemental composition of the as-grown CuInSe{sub 2} single crystals was determined by energy dispersive analysis of X-ray (EDAX). The unit cell crystal structure and lattice parameters were determined by X-ray diffraction (XRD) technique. The surface microtopographic study of the as-grown CuInSe{sub 2} single crystals surfaces were done to study the defects, growth mechanism, etc. of the CVT grown crystals.

  4. Lattice Waves, Spin Waves, and Neutron Scattering

    Science.gov (United States)

    Brockhouse, Bertram N.

    1962-03-01

    Use of neutron inelastic scattering to study the forces between atoms in solids is treated. One-phonon processes and lattice vibrations are discussed, and experiments that verified the existence of the quantum of lattice vibrations, the phonon, are reviewed. Dispersion curves, phonon frequencies and absorption, and models for dispersion calculations are discussed. Experiments on the crystal dynamics of metals are examined. Dispersion curves are presented and analyzed; theory of lattice dynamics is considered; effects of Fermi surfaces on dispersion curves; electron-phonon interactions, electronic structure influence on lattice vibrations, and phonon lifetimes are explored. The dispersion relation of spin waves in crystals and experiments in which dispersion curves for spin waves in Co-Fe alloy and magnons in magnetite were obtained and the reality of the magnon was demonstrated are discussed. (D.C.W)

  5. Dispersive photonic crystals from the plane wave method

    Energy Technology Data Exchange (ETDEWEB)

    Guevara-Cabrera, E.; Palomino-Ovando, M.A. [Facultad de Ciencias Físico Matemáticas, Benemérita Universidad Autónoma de Puebla, Apdo. Post. 165, Puebla, Pue. 72000, México (Mexico); Flores-Desirena, B., E-mail: bflores@fcfm.buap.mx [Facultad de Ciencias Físico Matemáticas, Benemérita Universidad Autónoma de Puebla, Apdo. Post. 165, Puebla, Pue. 72000, México (Mexico); Gaspar-Armenta, J.A. [Departamento de Investigación en Física de la Universidad de Sonora Apdo, Post 5-088, Hermosillo Sonora 83190, México (Mexico)

    2016-03-01

    Nowadays photonic crystals are widely used in many different applications. One of the most used methods to compute their band structure is the plane wave method (PWM). However, it can only be applied directly to non-dispersive media and be extended to systems with a few model dielectric functions. We explore an extension of the PWM to photonic crystals containing dispersive materials, that solves an eigenvalue equation for the Bloch wave vectors. First we compare our calculation with analytical results for one dimensional photonic crystals containing Si using experimental values of its optical parameters, and obtainig very well agreement, even for the spectrum region with strong absorption. Then, using the same method, we computed the band structure for a two dimensional photonic crystal without absorption, formed by an square array of MgO cylinders in air. The optical parameters for MgO were modeled with the Lorentz dielectric function. Finally, we studied an array of MgO cylinders in a metal, using Drude model without absorption, for the metal dielectric function. For this last case, we study the gap–midgap ratio as a function of the filling fraction for both the square and triangular lattice. The gap–midgap ratio is larger for the triangular lattice, with a maximum value of 10% for a filling fraction of 0.6. Our results show that the method can be applied to dispersive materials, and then to a wide range of applications where photonic crystals can be used.

  6. Lattice-parameter-difference measurement of heteroepitaxial structures by means of extremely asymmetrical Bragg diffraction

    International Nuclear Information System (INIS)

    Pietsch, U.; Borchard, W.

    1987-01-01

    The sensitivity of measurements of the lattice-parameter difference in monocrystalline heterostructures can be enhanced by use of an extremely asymmetrical diffraction geometry. If the angle of incidence is somewhat higher than the critical angle for total external reflection, the Bragg peak is shifted from the position calculated by kinematic theory. The amount of shift depends on the angle of incidence as well as on the mass density of the material used. For heteroepitaxial structures both the layer and the substrate peaks are shifted but by different amounts. Therefore it becomes possible to characterize layers of totally lattice-matched structures also. (orig.)

  7. Physical Realization of von Neumann Lattices in Rotating Bose Gases with Dipole Interatomic Interactions

    OpenAIRE

    Cheng, Szu-Cheng; Jheng, Shih-Da

    2016-01-01

    This paper reports a novel type of vortex lattice, referred to as a bubble crystal, which was discovered in rapidly rotating Bose gases with long-range interactions. Bubble crystals differ from vortex lattices which possess a single quantum flux per unit cell, while atoms in bubble crystals are clustered periodically and surrounded by vortices. No existing model is able to describe the vortex structure of bubble crystals; however, we identified a mathematical lattice, which is a subset of coh...

  8. Epitaxial Ge-crystal arrays for X-ray detection

    International Nuclear Information System (INIS)

    Kreiliger, T; Falub, C V; Müller, E; Känel, H von; Isa, F; Isella, G; Chrastina, D; Bergamaschini, R; Marzegalli, A; Miglio, L; Kaufmann, R; Niedermann, P; Neels, A; Dommann, A; Meduňa, M

    2014-01-01

    Monolithic integration of an X-ray absorber layer on a Si CMOS chip might be a potentially attractive way to improve detector performance at acceptable costs. In practice this requires, however, the epitaxial growth of highly mismatched layers on a Si-substrate, both in terms of lattice parameters and thermal expansion coefficients. The generation of extended crystal defects, wafer bowing and layer cracking have so far made it impossible to put the simple concept into practice. Here we present a way in which the difficulties of fabricating very thick, defect-free epitaxial layers may be overcome. It consists of an array of densely packed, three-dimensional Ge-crystals on a patterned Si(001) substrate. The finite gap between neighboring micron-sized crystals prevents layer cracking and substrate bowing, while extended defects are driven to the crystal sidewalls. We show that the Ge-crystals are indeed defect-free, despite the lattice misfit of 4.2%. The electrical characteristics of individual Ge/Si heterojunction diodes are obtained from in-situ measurements inside a scanning electron microscope. The fabrication of monolithically integrated detectors is shown to be compatible with Si-CMOS processing

  9. Crystal growth, characterization and theoretical studies of alkaline earth metal-doped tetrakis(thiourea)nickel(II) chloride.

    Science.gov (United States)

    Agilandeshwari, R; Muthu, K; Meenatchi, V; Meena, K; Rajasekar, M; Aditya Prasad, A; Meenakshisundaram, S P

    2015-02-25

    The influence of Sr(II)-doping on the properties of tetrakis(thiourea)nickel(II) chloride (TTNC) has been described. The reduction in the intensity observed in powder X-ray diffraction of doped specimen and slight shifts in vibrational frequencies of doped specimens confirm the lattice stress as a result of doping. Surface morphological changes due to doping of the Sr(II) are observed by scanning electron microscopy. The incorporation of metal into the host crystal lattice was confirmed by energy dispersive X-ray spectroscopy. Lattice parameters are determined by single crystal XRD analysis. The thermogravimetric and differential thermal analysis studies reveal the purity of the materials and no decomposition is observed up to the melting point. The nonlinear optical properties of the doped and undoped specimens were studied. Theoretical calculations were performed using the Density functional theory (DFT) method with B3LYP/LANL2DZ as the basis set. The molecular geometry and vibrational frequencies of TTNC in the ground state were calculated and the observed structural parameters of TTNC are compared with parameters obtained from single crystal X-ray studies. The atomic charge distributions are obtained by Mulliken charge population analysis. The first-order molecular hyperpolarizability, polarizability and dipole moment were derived. Copyright © 2014 Elsevier B.V. All rights reserved.

  10. Lattice parameters and Raman-active phonon modes of β-(Al{sub x}Ga{sub 1−x}){sub 2}O{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Kranert, Christian, E-mail: christian.kranert@uni-leipzig.de; Jenderka, Marcus; Lenzner, Jörg; Lorenz, Michael; Wenckstern, Holger von; Schmidt-Grund, Rüdiger; Grundmann, Marius [Institut für Experimentelle Physik II, Universität Leipzig, Halbleiterphysik, Linnéstr. 5, 04103 Leipzig (Germany)

    2015-03-28

    We present X-ray diffraction and Raman spectroscopy investigations of a (100)-oriented (Al{sub x}Ga{sub 1–x}){sub 2}O{sub 3} thin film on MgO (100) and bulk-like ceramics in dependence on their composition. The thin film grown by pulsed laser deposition has a continuous lateral composition spread allowing to determine precisely the dependence of the phonon mode properties and lattice parameters on the chemical composition. For x < 0.4, we observe the single-phase β-modification. Its lattice parameters and phonon energies depend linearly on the composition. We determined the slopes of these dependencies for the individual lattice parameters and for nine Raman lines, respectively. While the lattice parameters of the ceramics follow Vegard's rule, deviations are observed for the thin film. This deviation has only a small effect on the phonon energies, which show a reasonably good agreement between thin film and ceramics.

  11. Phase Transformation and Lattice Parameter Changes of Non-trivalent Rare Earth-Doped YSZ as a Function of Temperature

    Science.gov (United States)

    Jiang, Shengli; Huang, Xiao; He, Zhang; Buyers, Andrew

    2018-05-01

    To examine the effect of doping/co-doping on high-temperature phase compositions of YSZ, stand-alone YSZ and CeO2 and Nb2O5 co-doped YSZ samples were prepared using mechanical alloy and high-temperature sintering. XRD analysis was performed on these samples from room temperature to 1100 °C. The results show that the structure for the co-doped samples tends to be thermally stable when the test temperature is higher than a critical value. Monoclinic phase was dominant in Nb2O5 co-doped YSZ at temperatures lower than 600 °C, while for the YSZ and CeO2 co-doped YSZ, cubic/tetragonal phase was dominant in the whole test temperature range. The lattice parameters for all the samples increase with increasing test temperature generally. The lattice parameters for the two non-trivalent rare earth oxides co-doped YSZ show that the lattice parameter a for the cubic phase of the Ce4+ co-doped YSZ is consistently greater than that of 7YSZ which is related to the presence of larger radius of Ce4+ in the matrix. The lattice parameters a, b, c for the monoclinic phase of Ce4+ co-doped YSZ are much closer to each other than that of the Nb5+ co-doped YSZ, indicating the former has better tendency to form cubic/tetragonal phase, which is desired for vast engineering applications.

  12. Thermal conductivity prediction of nanoscale phononic crystal slabs using a hybrid lattice dynamics-continuum mechanics technique

    Directory of Open Access Journals (Sweden)

    Charles M. Reinke

    2011-12-01

    Full Text Available Recent work has demonstrated that nanostructuring of a semiconductor material to form a phononic crystal (PnC can significantly reduce its thermal conductivity. In this paper, we present a classical method that combines atomic-level information with the application of Bloch theory at the continuum level for the prediction of the thermal conductivity of finite-thickness PnCs with unit cells sized in the micron scale. Lattice dynamics calculations are done at the bulk material level, and the plane-wave expansion method is implemented at the macrosale PnC unit cell level. The combination of the lattice dynamics-based and continuum mechanics-based dispersion information is then used in the Callaway-Holland model to calculate the thermal transport properties of the PnC. We demonstrate that this hybrid approach provides both accurate and efficient predictions of the thermal conductivity.

  13. Synthesis of spatially variant lattices.

    Science.gov (United States)

    Rumpf, Raymond C; Pazos, Javier

    2012-07-02

    It is often desired to functionally grade and/or spatially vary a periodic structure like a photonic crystal or metamaterial, yet no general method for doing this has been offered in the literature. A straightforward procedure is described here that allows many properties of the lattice to be spatially varied at the same time while producing a final lattice that is still smooth and continuous. Properties include unit cell orientation, lattice spacing, fill fraction, and more. This adds many degrees of freedom to a design such as spatially varying the orientation to exploit directional phenomena. The method is not a coordinate transformation technique so it can more easily produce complicated and arbitrary spatial variance. To demonstrate, the algorithm is used to synthesize a spatially variant self-collimating photonic crystal to flow a Gaussian beam around a 90° bend. The performance of the structure was confirmed through simulation and it showed virtually no scattering around the bend that would have arisen if the lattice had defects or discontinuities.

  14. Crystal orientation and sample preparation effects on sputtering and lattice damage in 100 keV self-irradiated copper

    International Nuclear Information System (INIS)

    Sprague, J.A.; Malmberg, P.R.; Reynolds, G.W.; Lambert, J.M.; Treado, P.A.; Vincenz, A.M.

    1987-01-01

    Sputtering yields and angular distributions have been measured as functions of sample preparation techniques and incident ion-beam orientation with respect to the crystal axes for 100 keV Cu-ion beams on Cu crystals and polycrystalline samples. The angular distributions have structure requiring an nth order cosine with two Gaussians superimposed to fit the data; strong peaking is observed near the backscatter direction. The yield is dependent on the beam to crystal and beam to polycrystalline-rod axis orientation, on the grain size of the polycrystals and on sample-preparation techniques. Yield measurements vary by as much as a factor of 4. Lattice-damage differences, measured with alpha particle channeling, are much smaller and seem to be saturated by fluences of the order of 1x10 16 /cm 2 . (orig.)

  15. Two modifications of Y2Piv6(HPiv)6 crystals: synthesis and structures

    International Nuclear Information System (INIS)

    Kiseleva, E.A.; Troyanov, S.I.; Korenev, Yu.M.

    2006-01-01

    Crystal structure of solvate of yttrium pivalate YPiv 3 ·3HPiv is studied. Existing of two polymorphous modifications of the compound is detected. It is shown that α- and β-modifications of yttrium pivalate solvate have molecular crystal structures and are built of Y 2 Piv 6 (HPiv) 6 dimers. Difference of these two modifications is in package of dimer molecules and in center-symmetricity of dimers in α-modification structure. Molecular and crystal structure, crystal lattice parameters are determined [ru

  16. Single-crystal growth of ceria-based materials; Einkristallzuechtung von Materialien auf der Basis von Cerdioxid

    Energy Technology Data Exchange (ETDEWEB)

    Ulbrich, Gregor

    2015-07-23

    In this work it could be shown that Skull-Melting is a suitable method for growing ceria single crystals. Twenty different ceria-based single crystals could be manufactured. It was possible to dope ceria single crystals with Gd, Sm, Y, Zr, Ti, Ta, and Pr in different concentrations. Also co-doping with the named metals was realized. However, there remain some problems for growing ceria-based single crystals by Skull-Melting. As ignition metal zirconium was used because no ceria-based material works well. For that reason all single crystals show small zirconium contamination. Another problem is the formation of oxygen by the heat-induced reduction of ceria during the melting process. Because of that the skull of sintered material is often destroyed by gas pressure. This problem had to be solved individually for every single crystal. The obtained single crystals were characterized using different methods. To ensure the single crystal character the y were examined by Laue diffraction. All manufactured crystals are single crystals. Also powder diffraction patterns of the milled and oxidized samples were measured. For the determination of symmetry and metric the structural parameters were analyzed by the Rietveld method. All synthesized materials crystallize in space group Fm-3m known from calcium fluoride. The cubic lattice parameter a was determined for all crystals. In the case of series with different cerium and zirconium concentrations a linear correlation between cerium content and cubic lattice parameter was detected. The elemental composition was determined by WDX. All crystals show a homogeneous elemental distribution. The oxygen content was calculated because the WDX method isn't useful for determination.

  17. The development of a computer technique for the investigation of reactor lattice parameters

    International Nuclear Information System (INIS)

    Joubert, W.R.

    1982-01-01

    An integrated computer technique was developed whereby all the computer programmes needed to calculate reactor lattice parameters from basic neutron data, could be combined in one system. The theory of the computer programmes is explained in detail. Results are given and compared with experimental values as well as those calculated with a standard system

  18. Effect of gamma irradiation on microstrain and lattice parameter of Co3O4 loaded on Al2O3

    International Nuclear Information System (INIS)

    El-Shobaky, G.A.; El-Shabiny, A.M.; Ramadan, A.A.

    1987-01-01

    Cobaltic oxide, Co 3 O 4 loaded on an amorphous alumina sample and precalcined in air at 650 0 C was exposed to different doses of γ-irradiation ranging between 7 and 60 Mrad. The change in residual microstrain and lattice parameter due to the irradiation process were investigated by X-ray diffraction analyses. The results revealed that γ-irradiation brought about a progressive decrease in both microstrain and lattice parameter to an extent proportional to the dose employed falling to minimum values at a dose of 30 Mrad then increased slightly at doses above this limit. The observed decrease in lattice parameter was attributed to removal of the excess oxygen in Co 3 O 4 samples with subsequent decrease in the concentration of lattice defects (trivalent cobalt ions). The decrease in residual microstrain due to exposure to γ-rays was related to splitting of Co 3 O 4 crystallites. The splitting process resulted in remarkable increase in the catalytic activity (2-6 fold) of the irradiated solid samples. (author)

  19. Pinning potentials of the vortex lattice in YBCO crystals in the peak effect region

    International Nuclear Information System (INIS)

    Pasquini, G.; Bekeris, V.

    2004-01-01

    Memory effects in the dynamic response of the vortex lattice (VL) in type II superconductors and its relationship with the controversial peak effect, have attracted great interest for a long time. In the last years, these features have been observed in YBCO single crystals, with the DC magnetic field tilted away from the twin planes and were related with robust dynamical states characterized by different degrees of mobility. Recently, we reported that the previous dynamical history of the VL can modify not only its dynamic response, but can even modify its static properties as well. In the present work, we try to understand the nature of the peak effect in YBCO crystals by sensing the effective AC penetration depth in the linear Campbell regime. We report history dependent effective pinning potential well curvatures and study the stability of the different static configurations. Interestingly, we observe that the more pinned VL configuration is not the more stable. Results agree with a dynamic scenario undergoing the Peak Effect

  20. Localized structures in Kagome lattices

    Energy Technology Data Exchange (ETDEWEB)

    Saxena, Avadh B [Los Alamos National Laboratory; Bishop, Alan R [Los Alamos National Laboratory; Law, K J H [UNIV OF MASSACHUSETTS; Kevrekidis, P G [UNIV OF MASSACHUSETTS

    2009-01-01

    We investigate the existence and stability of gap vortices and multi-pole gap solitons in a Kagome lattice with a defocusing nonlinearity both in a discrete case and in a continuum one with periodic external modulation. In particular, predictions are made based on expansion around a simple and analytically tractable anti-continuum (zero coupling) limit. These predictions are then confirmed for a continuum model of an optically-induced Kagome lattice in a photorefractive crystal obtained by a continuous transformation of a honeycomb lattice.

  1. Dispersion of low frequency vibrations in the deuterated naphthalene crystal

    International Nuclear Information System (INIS)

    Bokhenkov, E.L.; Sheka, E.; Natkaniec, I.

    1977-01-01

    The dispersion curves of the lattice vibrations and of the two lowest intramolecular vibrations in d 8 -naphthalene (C 10 D 8 ) crystal have been measured by coherent inelastic neutron scattering for the [010] and the [100] directions at the temperature of 98 K and partially at 5 K. The results are compared with calculations based on the Kitaigorodskii parameters for C-C, C-H and H-H interactions in organic molecular crystals. (author)

  2. Study of the lattice parameter evolution of PWR irradiated MOX fuel by X-Ray diffraction

    International Nuclear Information System (INIS)

    Clavier, B.

    1995-01-01

    Fuel irradiation leads to a swelling resulting from the formation of gaseous (Kr, Xe) or solid fission products which are found either in solution or as solid inclusions in the matrix. This phenomena has to be evaluated to be taken into account in fuel cladding Interaction. Fuel swelling was studied as a function of burn up by measuring the corresponding cell constant evolution by X-Ray diffraction. This study was realized on Mixed Oxide Fuels (MOX) irradiated in a Pressurized Water Reactor (PWR) at different burn-up for 3 initial Pu contents. Lattice parameter evolutions were followed as a function of burn-up for the irradiated fuel with and without an annealing thermal treatment. These experimental evolutions are compared to the theoretical evolutions calculated from the hard sphere model, using the fission product concentrations determined by the APPOLO computer code. Contribution of varying parameters influencing the unit cell value is discussed. Thermal treatment effects were checked by metallography, X-Ray diffraction and microprobe analysis. After thermal treatment, no structural change was observed but a decrease of the lattice parameter was measured. This modification results essentially from self-irradiation defect annealing and not from stoichiometry variations. Microprobe analysis showed that about 15% of the formed Molybdenum is in solid solution In the oxide matrix. Micrographs showed the existence of Pu packs in the oxide matrix which induces a broadening of diffraction lines. The RIETVELD method used to analyze the X-Ray patterns did not allow to characterize independently the Pu packs and the oxide matrix lattice parameters. Nevertheless, with this method, the presence of micro-strains in the irradiated nuclear fuel could be confirmed. (author)

  3. Spatially resolved resistivity near the vortex lattice phase transition in Bi 2Sr 2CaCu 2O 8+δ single crystals

    Science.gov (United States)

    Berseth, V.; Indenbom, M. V.; van der Beek, C. J.; D'Anna, G.; Benoit, W.

    1997-08-01

    Using a multiterminal contact configuration, we investigate the local variations of the resistivity drop near the vortex lattice first order phase transition in a very homogeneous Bi2Sr2CaCu2O8+δ (BSCCO) single crystal.

  4. Crystal structure of the binder phase in a model HfC-TiC-Ni material

    International Nuclear Information System (INIS)

    Heiligers, Christiane; Neethling, Johannes H.

    2008-01-01

    The crystal structure of the binder phase in a model HfC-TiC-Ni sample produced by hot pressing is investigated. The nature of the binder depends on the amount of Hf and Ti that remains in solution with Ni after cooling. Four different crystal structures are identified by analysis of electron diffraction patterns obtained using transmission electron microscopy techniques and the composition of the phases determined by energy dispersive X-ray spectrometry. Three of the phases are cubic; Ni, Ni 3 (Ti,Hf) and Ni 23 (Ti,Hf) 6 with lattice parameters of 3.52 ± 0.05, 3.52 ± 0.03 and 10.70 ± 0.40 A, respectively. The hexagonal phase is an intermetallic Ni 3 Ti phase, with lattice parameters of a = b = 5.00 ± 0.20 A and c = 8.16 ± 0.20 A. The crystal structures are confirmed by simulations of the electron diffraction patterns using JEMS software

  5. Unexpected behavior of an order parameter for lattice gauge theories with matter fields

    International Nuclear Information System (INIS)

    Meyer, H.

    1983-07-01

    I consider a slightly modified definition of an order parameter that was recently suggested by DeTar and McLerran. It is supposed to test for confinement in lattice gauge theories when arbitrary matter fields are present, at finite physical temperature β -1 > 0. Its definition is quite directly related to confinement in the sense that no physical states with fractional baryon number can be observed. We test the parameter for different ranges of the coupling constants in the Z(2) Higgs model, whose phase structure is well known at zero temperature. It is found that the order parameter always shows the behavior characteristic of confinement, for all values of the coupling constants and arbitrary nonzero temperature. (orig.)

  6. Band gap of two-dimensional fiber-air photonic crystals

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Shu, E-mail: yangshu5678@163.com; Li, Masha

    2016-04-15

    A two-dimensional photonic crystal (PC) composed of textile fiber and air is initially discussed in this paper. Textile materials are so called soft materials, which are different from the previous PCs composed of rigid materials. The plain wave expansion method is used to calculate band structure of different PCs by altering component properties or structural parameters. Results show that the dielectric constant of textile fibers, fiber filling ratio and lattice arrangement are effective factors which influence PCs' band gap. Yet lattice constant and fiber diameter make inconspicuous influence on the band gap feature.

  7. Multiphysical simulation analysis of the dislocation structure in germanium single crystals

    Science.gov (United States)

    Podkopaev, O. I.; Artemyev, V. V.; Smirnov, A. D.; Mamedov, V. M.; Sid'ko, A. P.; Kalaev, V. V.; Kravtsova, E. D.; Shimanskii, A. F.

    2016-09-01

    To grow high-quality germanium crystals is one of the most important problems of growth industry. The dislocation density is an important parameter of the quality of single crystals. The dislocation densities in germanium crystals 100 mm in diameter, which have various shapes of the side surface and are grown by the Czochralski technique, are experimentally measured. The crystal growth is numerically simulated using heat-transfer and hydrodynamics models and the Alexander-Haasen dislocation model in terms of the CGSim software package. A comparison of the experimental and calculated dislocation densities shows that the dislocation model can be applied to study lattice defects in germanium crystals and to improve their quality.

  8. Effects of Cr 3+ impurity concentration on the crystallography of synthetic emerald crystals

    Science.gov (United States)

    Lee, Pei-Lun; Huang, Eugene; Lee, Jan-Shing; Yu, Shu-Cheng

    2011-06-01

    Flux method has been adopted for the synthesis of emerald crystals using PbO-V 2O 5 as a flux in order to study the crystallography of the synthetic crystals. In general, the hue of green color of emerald deepens with the addition of Cr 3+. The molar volume of the synthesized crystals was found to increase with the incorporation of Cr 2O 3 dopant. The substitution of Cr 3+ for Al 3+ in the octahedral sites of beryl results in the expansion of a-axis, while c-axis remains nearly unchanged. The maximum Cr 2O 3-content allowed in the crystal lattice of emerald has been found to be about 3.5 wt%. When the doping Cr 2O 3-content exceeds 3.5 wt%, a significant anomaly in lattice parameters starts to take place, accompanying the precipitation of an unknown phase in the emerald matrix.

  9. Lattice sums then and now

    CERN Document Server

    Borwein, J M; McPhedran, R C

    2013-01-01

    The study of lattice sums began when early investigators wanted to go from mechanical properties of crystals to the properties of the atoms and ions from which they were built (the literature of Madelung's constant). A parallel literature was built around the optical properties of regular lattices of atoms (initiated by Lord Rayleigh, Lorentz and Lorenz). For over a century many famous scientists and mathematicians have delved into the properties of lattices, sometimes unwittingly duplicating the work of their predecessors. Here, at last, is a comprehensive overview of the substantial body of

  10. HQE parameters from unquenched lattice data on pseudoscalar and vector heavy-light meson masses

    Science.gov (United States)

    Gambino, Paolo; Melis, Aurora; Simula, Silvano

    2018-03-01

    We present a new lattice determination of some of the parameters appearing both in the Operator Product Expansion (OPE) analysis of the inclusive semileptonic B-meson decays and in the Heavy Quark Expansion (HQE) of the pseudoscalar (PS) and vector (V) heavy-light meson masses. We perform a lattice QCD (LQCD) computation of PS and V heavy-light meson masses for heavy-quark masses mh in the range from mcphys to ≃ 4mbphys. We employed the Nf = 2 + 1 + 1 gauge configurations of the European Twisted Mass Collaboration (ETMC) at three values of the lattice spacing a ≃ (0.062,0.082,0.089) fm with pion masses in the range Mπ ≃ (210 - 450) MeV. The heavy-quark mass is simulated directly on the lattice up to ≃ 3mcphys. The interpolation to the physical mbphys is performed using the ETMC ratio method and adopting the kinetic mass scheme. We obtain mbkin (1 GeV) = 4.61(20) GeV (m̅b(m̅b) = 4.26(18) GeV in the MS scheme). The lattice data are analyzed in terms of the HQE and the matrix elements of dimension-4 and dimension-5 operators are extracted with good precision, namely: Λ¯ = 0.552(26) GeV, μπ2 = 0.321(32) GeV2 and μG2(mb) = 0.253(25)GeV2. The data also allow for an estimate of the dimension-6 operator matrix elements.

  11. Atomistic modelling study of lanthanide incorporation in the crystal lattice of an apatite

    International Nuclear Information System (INIS)

    Louis-Achille, V.

    1999-01-01

    Studies of natural and synthetic apatites allow to propose such crystals as matrix for nuclear waste storage. The neodymium substituted britholite, Ca 9 Nd(PO 4 ) 5 (SiO 4 )F 2 . is a model for the trivalent actinide storage Neodymium can be substituted in two types of sites. The aim of this thesis is to compare the chemical nature of this two sites in fluoro-apatite Ca 9 (PO 4 ) 6 F 2 and then in britholite, using ab initio atomistic modeling. Two approaches are used: one considers the infinite crystals and the second considers clusters. The calculations of the electronic structure for both were performed using Kohn and Sham density functional theory in the local approximation. For solids, pseudopotentials were used, and wave functions are expanded in plane waves. For clusters, a frozen core approximation was used, and the wave functions are expanded in a linear combination of Slater type atomic orbitals. The pseudopotential is semi-relativistic for neodymium, and the Hamiltonian is scalar relativistic for the clusters. The validation of the solid approach is performed using two test cases: YPO 4 and ScPO 4 . Two numerical tools were developed to compute electronic deformation density map, and calculate partial density of stases. A full optimisation of the lattice parameters with a relaxation of the atomic coordinates leads to correct structural and thermodynamic properties for the fluoro-apatite, compared to experience. The electronic deformation density maps do not show any significant differences. between the two calcium sites. but Mulliken analysis on the solid and on the clusters point out the more ionic behavior of the calcium in site 2. A neodymium substituted britholite is then studied. Neodymium location only induces local modifications in; the crystalline structure and few changes in the formation enthalpy. The electronic study points out an increase of the covalent character the bonding involving neodymium compared with the one related to calcium

  12. Great Disparity in Photoluminesence Quantum Yields of Colloidal CsPbBr3 Nanocrystals with Varied Shape: The Effect of Crystal Lattice Strain.

    Science.gov (United States)

    Zhao, Jiangtao; Liu, Mei; Fang, Li; Jiang, Shenlong; Zhou, Jingtian; Ding, Huaiyi; Huang, Hongwen; Wen, Wen; Luo, Zhenlin; Zhang, Qun; Wang, Xiaoping; Gao, Chen

    2017-07-06

    Understanding the big discrepancy in the photoluminesence quantum yields (PLQYs) of nanoscale colloidal materials with varied morphologies is of great significance to its property optimization and functional application. Using different shaped CsPbBr 3 nanocrystals with the same fabrication processes as model, quantitative synchrotron radiation X-ray diffraction analysis reveals the increasing trend in lattice strain values of the nanocrystals: nanocube, nanoplate, nanowire. Furthermore, transient spectroscopic measurements reveal the same trend in the defect quantities of these nanocrystals. These experimental results unambiguously point out that large lattice strain existing in CsPbBr 3 nanoparticles induces more crystal defects and thus decreases the PLQY, implying that lattice strain is a key factor other than the surface defect to dominate the PLQY of colloidal photoluminesence materials.

  13. Angle-resolved imaging of single-crystal materials with MeV helium ions

    Energy Technology Data Exchange (ETDEWEB)

    Strathman, M D; Baumann, S [Charles Evans and Associates, Redwood City, CA (United States)

    1992-02-01

    The simplest form of angle-resolved mapping for single-crystal materials is the creation of a channeling angular scan. Several laboratories have expanded this simple procedure to include mapping as a function of two independent tilts. These angle-resolved images are particularly suited to the assessment of crystal parameters including disorder, lattice location of impurities, and lattice stress. This paper will describe the use of the Charles Evans and Associates RBS-400 scattering chamber for acquisition, display, and analysis of angle-resolved images obtained from backscattered helium ions. Typical data acquisition times are 20 min for a {+-}2deg X-Y tilt scan with 2500 pixels (8/100deg resolution), and 10 nC per pixel. In addition, we will present a method for automatically aligning crystals for channeling measurements based on this imaging technology. (orig.).

  14. Angle-resolved imaging of single-crystal materials with MeV helium ions

    International Nuclear Information System (INIS)

    Strathman, M.D.; Baumann, S.

    1992-01-01

    The simplest form of angle-resolved mapping for single-crystal materials is the creation of a channeling angular scan. Several laboratories have expanded this simple procedure to include mapping as a function of two independent tilts. These angle-resolved images are particularly suited to the assessment of crystal parameters including disorder, lattice location of impurities, and lattice stress. This paper will describe the use of the Charles Evans and Associates RBS-400 scattering chamber for acquisition, display, and analysis of angle-resolved images obtained from backscattered helium ions. Typical data acquisition times are 20 min for a ±2deg X-Y tilt scan with 2500 pixels (8/100deg resolution), and 10 nC per pixel. In addition, we will present a method for automatically aligning crystals for channeling measurements based on this imaging technology. (orig.)

  15. Repulsive energy and the Grueneisen parameter of alkali halides calculated on the basis of a quantum-statistical ab initio theory

    International Nuclear Information System (INIS)

    Kucharczyk, M.; Olszewski, S.

    1982-01-01

    The Grueneisen parameter of alkali halides is calculated by an ab initio quantum-statistical method and then compared with the experimental data. The crystal model applied assumes the crystal ions to be compressible but impenetrable spheres. The ions are described with the aid of a modified Thomas-Fermi theory with exchange. At the next step it is possible to calculate the energy needed to transform the system of the non-interacting ions into the ionic system represented by the crystal lattice. This calculation allows for an ab initio estimate of the parameters entering the Born, or the Born-Mayer, repulsive part of the crystal energy. The parameters are then used in the calculation of the Grueneisen parameter and its dependence on the crystal compression. (author)

  16. Synchrotron Bragg diffraction imaging characterization of synthetic diamond crystals for optical and electronic power device applications1 1

    Science.gov (United States)

    Tran Thi, Thu Nhi; Morse, J.; Caliste, D.; Fernandez, B.; Eon, D.; Härtwig, J.; Mer-Calfati, C.; Tranchant, N.; Arnault, J. C.; Lafford, T. A.; Baruchel, J.

    2017-01-01

    Bragg diffraction imaging enables the quality of synthetic single-crystal diamond substrates and their overgrown, mostly doped, diamond layers to be characterized. This is very important for improving diamond-based devices produced for X-ray optics and power electronics applications. The usual first step for this characterization is white-beam X-ray diffraction topography, which is a simple and fast method to identify the extended defects (dislocations, growth sectors, boundaries, stacking faults, overall curvature etc.) within the crystal. This allows easy and quick comparison of the crystal quality of diamond plates available from various commercial suppliers. When needed, rocking curve imaging (RCI) is also employed, which is the quantitative counterpart of monochromatic Bragg diffraction imaging. RCI enables the local determination of both the effective misorientation, which results from lattice parameter variation and the local lattice tilt, and the local Bragg position. Maps derived from these parameters are used to measure the magnitude of the distortions associated with polishing damage and the depth of this damage within the volume of the crystal. For overgrown layers, these maps also reveal the distortion induced by the incorporation of impurities such as boron, or the lattice parameter variations associated with the presence of growth-incorporated nitrogen. These techniques are described, and their capabilities for studying the quality of diamond substrates and overgrown layers, and the surface damage caused by mechanical polishing, are illustrated by examples. PMID:28381981

  17. Crystal growth and mechanical hardness of In{sub 2}Se{sub 2.7}Sb{sub 0.3} single crystal

    Energy Technology Data Exchange (ETDEWEB)

    Patel, Piyush, E-mail: piyush-patel130@yahoo.com; Vyas, S. M., E-mail: s-m-vyas-gu@hotmail.com; Patel, Vimal; Pavagadhi, Himanshu [Department of Physics, School of Science, Gujarat University, Ahmedabad, Gujarat, India-380009 (India); Solanki, Mitesh [panditdindayal Petroleum University, Gandhinagar. Gujarat (India); Jani, Maunik P. [BITS Edu Campus, Varnama, Vadodara, Gujarat (India)

    2015-08-28

    The III-VI compound semiconductors is important for the fabrication of ionizing radiation detectors, solid-state electrodes, and photosensitive heterostructures, solar cell and ionic batteries. In this paper, In{sub 2}Se{sub 2.7} Sb{sub 0.3} single crystals were grown by the Bridgman method with temperature gradient of 60 °C/cm and the growth velocity 0.5cm/hr. The as-grown crystals were examined under the optical microscope for surface study, a various growth features observed on top free surface of the single crystal which is predominant of layers growth mechanism. The lattice parameters of as-grown crystal was determined by the XRD analysis. A Vickers’ projection microscope were used for the study of microhardness on the as-cleaved, cold-worked and annealed samples of the crystals, the results were discussed, and reported in detail.

  18. Symmetry Groups of the Austenite Lattice and Construction of Self-Accommodation Complexes of Martensite Crystals in Alloys with the Shape-Memory Effect

    Science.gov (United States)

    Khundjua, A. G.; Ptitsin, A. G.; Brovkina, E. A.

    2018-01-01

    The internal structure of experimentally observed self-accommodation complexes of martensite crystals, which is determined by the system of twinning planes, is studied in this work. The direct correlation of the construction type of the complexes with the subgroups of the austenite lattice symmetry group is shown.

  19. The edition of a personal computer program for determining lattice constants and its application in materials for storage of hydrogen

    International Nuclear Information System (INIS)

    Chen Yongzhong; Bai Chaomao; Lang Dingmu; Zhang Youshou

    1998-01-01

    The equations for finding lattice constants of the 7 crystal systems were completely deduced using the M.U.Cohen least square method. From the deduction process it is obvious that the equation forms had nothing to do with the extrapolation functions so any of them can be used. (But in practice, cos 2 θ and cos 2 θ(1/sinθ + 1/θ) were generally performed.) After a personal computer program was finished using above mathematic model, the lattice constants of materials for storage of hydrogen ZrCo and LaNi 5-x M x (M = Mn, Al) were determined. The results showed that the program is very good for finding lattice parameters and can be used in the 7 crystal systems. The results also showed to the LaNi 5 alloy its lattice constants increase when the elements (such as Mn, Al, etc.) whose atomic radii are larger than that of Ni are substituted for Ni and when the content of the same substitutional element Al goes up. This phenomenon is in accordance with the theory

  20. Design and optical characterization of high-Q guided-resonance modes in the slot-graphite photonic crystal lattice.

    Science.gov (United States)

    Martínez, Luis Javier; Huang, Ningfeng; Ma, Jing; Lin, Chenxi; Jaquay, Eric; Povinelli, Michelle L

    2013-12-16

    A new photonic crystal structure is generated by using a regular graphite lattice as the base and adding a slot in the center of each unit cell to enhance field confinement. The theoretical Q factor in an ideal structure is over 4 × 10(5). The structure was fabricated on a silicon-on-insulator wafer and optically characterized by transmission spectroscopy. The resonance wavelength and quality factor were measured as a function of slot height. The measured trends show good agreement with simulation.

  1. Crystal structure of a novel cerium indide Ce{sub 6}Pt{sub 11}In{sub 14}

    Energy Technology Data Exchange (ETDEWEB)

    Stepien-Damm, J.; Bukowski, Z.; Zaremba, V.I.; Pikul, A.P.; Kaczorowski, D

    2004-10-06

    The crystal structure of a new intermetallic compound Ce{sub 6}Pt{sub 11}In{sub 14} has been determined from single crystal X-ray data and was refined by a full-matrix least-squares method down to R{sub 1}=0.0497 for 1215 structure factors and 96 parameters. The unit cell is monoclinic, space group C2/m, Z=2 with the lattice parameters: a=22.729(5) A, b=4.3960(10) A, c=14.780(3) A and {beta}=118.35(3) deg. . It represents a new type of crystal structure of intermetallic compounds.

  2. Crystal Structure of Chicken γS-Crystallin Reveals Lattice Contacts with Implications for Function in the Lens and the Evolution of the βγ-Crystallins.

    Science.gov (United States)

    Sagar, Vatsala; Chaturvedi, Sumit K; Schuck, Peter; Wistow, Graeme

    2017-07-05

    Previous attempts to crystallize mammalian γS-crystallin were unsuccessful. Native L16 chicken γS crystallized avidly while the Q16 mutant did not. The X-ray structure for chicken γS at 2.3 Å resolution shows the canonical structure of the superfamily plus a well-ordered N arm aligned with a β sheet of a neighboring N domain. L16 is also in a lattice contact, partially shielded from solvent. Unexpectedly, the major lattice contact matches a conserved interface (QR) in the multimeric β-crystallins. QR shows little conservation of residue contacts, except for one between symmetry-related tyrosines, but molecular dipoles for the proteins with QR show striking similarities while other γ-crystallins differ. In γS, QR has few hydrophobic contacts and features a thin layer of tightly bound water. The free energy of QR is slightly repulsive and analytical ultracentrifugation confirms no dimerization in solution. The lattice contacts suggest how γ-crystallins allow close packing without aggregation in the crowded environment of the lens. Published by Elsevier Ltd.

  3. Lattice location of platinum ions implanted into single crystal zirconia and their annealing behaviour

    Energy Technology Data Exchange (ETDEWEB)

    Cao, D X [Royal Melbourne Inst. of Tech., VIC (Australia); Sood, D K [Academia Sinica, Shanghai, SH (China). Shanghai Inst. of Nuclear Research; Brown, I G [Lawrence Berkeley Lab., CA (United States)

    1994-12-31

    Single crystal samples of (100) oriented cubic zirconia stabilised with 9.5 mol % yttria were implanted with platinum ions, using a metal vapour vacuum arc (MEVVA) high current ion implanter, to a nominal dose of 1x10{sup 17} ions/cm{sup 2}. The implanted samples were annealed isothermally in air ambient at 1200 deg C, from 1-24 hours. Rutherford Backscattering Spectrometry and Channeling (RBSC) of 2 MeV He ions are employed to determine depth distributions of ion damage, Pt ions and substitutionality of Pt ions before and after annealing. The damage behaviour, Pt migration and lattice location are discussed in terms of metastable phase formation and solid solubility considerations. 7 refs., 3 figs.

  4. Lattice location of platinum ions implanted into single crystal zirconia and their annealing behaviour

    Energy Technology Data Exchange (ETDEWEB)

    Cao, D.X. [Royal Melbourne Inst. of Tech., VIC (Australia); Sood, D.K. [Academia Sinica, Shanghai, SH (China). Shanghai Inst. of Nuclear Research; Brown, I.G. [Lawrence Berkeley Lab., CA (United States)

    1993-12-31

    Single crystal samples of (100) oriented cubic zirconia stabilised with 9.5 mol % yttria were implanted with platinum ions, using a metal vapour vacuum arc (MEVVA) high current ion implanter, to a nominal dose of 1x10{sup 17} ions/cm{sup 2}. The implanted samples were annealed isothermally in air ambient at 1200 deg C, from 1-24 hours. Rutherford Backscattering Spectrometry and Channeling (RBSC) of 2 MeV He ions are employed to determine depth distributions of ion damage, Pt ions and substitutionality of Pt ions before and after annealing. The damage behaviour, Pt migration and lattice location are discussed in terms of metastable phase formation and solid solubility considerations. 7 refs., 3 figs.

  5. Lattice continuum and diffusional creep.

    Science.gov (United States)

    Mesarovic, Sinisa Dj

    2016-04-01

    Diffusional creep is characterized by growth/disappearance of lattice planes at the crystal boundaries that serve as sources/sinks of vacancies, and by diffusion of vacancies. The lattice continuum theory developed here represents a natural and intuitive framework for the analysis of diffusion in crystals and lattice growth/loss at the boundaries. The formulation includes the definition of the Lagrangian reference configuration for the newly created lattice, the transport theorem and the definition of the creep rate tensor for a polycrystal as a piecewise uniform, discontinuous field. The values associated with each crystalline grain are related to the normal diffusional flux at grain boundaries. The governing equations for Nabarro-Herring creep are derived with coupled diffusion and elasticity with compositional eigenstrain. Both, bulk diffusional dissipation and boundary dissipation accompanying vacancy nucleation and absorption, are considered, but the latter is found to be negligible. For periodic arrangements of grains, diffusion formally decouples from elasticity but at the cost of a complicated boundary condition. The equilibrium of deviatorically stressed polycrystals is impossible without inclusion of interface energies. The secondary creep rate estimates correspond to the standard Nabarro-Herring model, and the volumetric creep is small. The initial (primary) creep rate is estimated to be much larger than the secondary creep rate.

  6. The X-ray powder diffraction pattern and lattice parameters of perovskite

    International Nuclear Information System (INIS)

    Ball, C.J.; Napier, J.G.

    1988-02-01

    The interplanar spacings and intensities of all lines appearing in the X-ray powder diffraction pattern of perovskite have been calculated. Many of the lines occur in groups with a large amount of overlap. As an aid to identifying the lines which are observed, the intensity profiles of the major groups have been plotted. Those lines which are relatively free of overlap and can be identified unambiguously have been used to calculate the lattice parameters, with the results a=5.4424 ± 0.0001 A, b=7.6417 ± 0.0002 A, c=5.3807 ± 0.0001 A

  7. Lattice location of O{sup 18} in ion implanted Fe crystals by Rutherford backscattering spectrometry, channeling and nuclear reaction analysis

    Energy Technology Data Exchange (ETDEWEB)

    Vairavel, Mathayan; Sundaravel, Balakrishnan, E-mail: bsundar@igcar.gov.in; Panigrahi, Binaykumar

    2016-09-15

    There are contradictory theoretical predictions of lattice location of oxygen interstitial atom at tetrahedral and octahedral interstices in bcc Fe. For validating these predictions, 300 keV O{sup 18} ions with fluence of 5 × 10{sup 15} ions/cm{sup 2} are implanted into bcc Fe single crystals at room temperature and annealed at 400 °C. The Rutherford backscattering spectrometry (RBS) and nuclear reaction analysis (NRA)/channeling measurements are carried out with 850 keV protons. The lattice location of implanted O{sup 18} is analysed using the α-particles yield from O{sup 18}(p,α)N{sup 15} nuclear reaction. The tilt angular scans of α-particle yield along 〈110〉 and 〈100〉 axial directions are performed at room temperature. Lattice location of O{sup 18} is found to be at tetrahedral interstitial site by comparing the experimental scan with simulated scans using FLUX7 software.

  8. Single Crystals Grown Under Unconstrained Conditions

    Science.gov (United States)

    Sunagawa, Ichiro

    Based on detailed investigations on morphology (evolution and variation in external forms), surface microtopography of crystal faces (spirals and etch figures), internal morphology (growth sectors, growth banding and associated impurity partitioning) and perfection (dislocations and other lattice defects) in single crystals, we can deduce how and by what mechanism the crystal grew and experienced fluctuation in growth parameters through its growth and post-growth history under unconstrained condition. The information is useful not only in finding appropriate way to growing highly perfect and homogeneous single crystals, but also in deciphering letters sent from the depth of the Earth and the Space. It is also useful in discriminating synthetic from natural gemstones. In this chapter, available methods to obtain molecular information are briefly summarized, and actual examples to demonstrate the importance of this type of investigations are selected from both natural minerals (diamond, quartz, hematite, corundum, beryl, phlogopite) and synthetic crystals (SiC, diamond, corundum, beryl).

  9. Prediction of molecular crystal structures

    International Nuclear Information System (INIS)

    Beyer, Theresa

    2001-01-01

    The ab initio prediction of molecular crystal structures is a scientific challenge. Reliability of first-principle prediction calculations would show a fundamental understanding of crystallisation. Crystal structure prediction is also of considerable practical importance as different crystalline arrangements of the same molecule in the solid state (polymorphs)are likely to have different physical properties. A method of crystal structure prediction based on lattice energy minimisation has been developed in this work. The choice of the intermolecular potential and of the molecular model is crucial for the results of such studies and both of these criteria have been investigated. An empirical atom-atom repulsion-dispersion potential for carboxylic acids has been derived and applied in a crystal structure prediction study of formic, benzoic and the polymorphic system of tetrolic acid. As many experimental crystal structure determinations at different temperatures are available for the polymorphic system of paracetamol (acetaminophen), the influence of the variations of the molecular model on the crystal structure lattice energy minima, has also been studied. The general problem of prediction methods based on the assumption that the experimental thermodynamically stable polymorph corresponds to the global lattice energy minimum, is that more hypothetical low lattice energy structures are found within a few kJ mol -1 of the global minimum than are likely to be experimentally observed polymorphs. This is illustrated by the results for molecule I, 3-oxabicyclo(3.2.0)hepta-1,4-diene, studied for the first international blindtest for small organic crystal structures organised by the Cambridge Crystallographic Data Centre (CCDC) in May 1999. To reduce the number of predicted polymorphs, additional factors to thermodynamic criteria have to be considered. Therefore the elastic constants and vapour growth morphologies have been calculated for the lowest lattice energy

  10. Prediction of molecular crystal structures

    Energy Technology Data Exchange (ETDEWEB)

    Beyer, Theresa

    2001-07-01

    The ab initio prediction of molecular crystal structures is a scientific challenge. Reliability of first-principle prediction calculations would show a fundamental understanding of crystallisation. Crystal structure prediction is also of considerable practical importance as different crystalline arrangements of the same molecule in the solid state (polymorphs)are likely to have different physical properties. A method of crystal structure prediction based on lattice energy minimisation has been developed in this work. The choice of the intermolecular potential and of the molecular model is crucial for the results of such studies and both of these criteria have been investigated. An empirical atom-atom repulsion-dispersion potential for carboxylic acids has been derived and applied in a crystal structure prediction study of formic, benzoic and the polymorphic system of tetrolic acid. As many experimental crystal structure determinations at different temperatures are available for the polymorphic system of paracetamol (acetaminophen), the influence of the variations of the molecular model on the crystal structure lattice energy minima, has also been studied. The general problem of prediction methods based on the assumption that the experimental thermodynamically stable polymorph corresponds to the global lattice energy minimum, is that more hypothetical low lattice energy structures are found within a few kJ mol{sup -1} of the global minimum than are likely to be experimentally observed polymorphs. This is illustrated by the results for molecule I, 3-oxabicyclo(3.2.0)hepta-1,4-diene, studied for the first international blindtest for small organic crystal structures organised by the Cambridge Crystallographic Data Centre (CCDC) in May 1999. To reduce the number of predicted polymorphs, additional factors to thermodynamic criteria have to be considered. Therefore the elastic constants and vapour growth morphologies have been calculated for the lowest lattice energy

  11. Influence of dislocations in solid-phase crystal lattices on structure and properties of an WC-9Co alloy

    International Nuclear Information System (INIS)

    Grewe, H.

    1976-01-01

    After theoretical considerations about evaluation of degree of dislocation concentration in crystal lattices two tungsten-carbide-powders are characterized by chemical reaction behaviour. The hard metal grades produced from the two carbide powders are tested by material and tool life investigation. The tungsten carbide powder with lower level of dislocation-concentration leads to a hardmetall-alloy with an equal microstructure and with favourable properties, especially with a good toughness and with an interesting tool life. (orig.) [de

  12. Quantum simulation and quantum information processing with molecular dipolar crystals

    International Nuclear Information System (INIS)

    Ortner, M.

    2011-01-01

    In this thesis interactions between dipolar crystals and neutral atoms or separated molecules have been investigated. They were motivated to realize new kinds of lattice models in mixtures of atoms and polar molecules where an MDC functions as an underlying periodic lattice structure for the second species. Such models bring out the peculiar features of MDC's, that include a controllable, potentially sub-optical wavelength periodicity and strong particle phonon interactions. Only stable collisional configurations have been investigated, excluding chemical reactions between the substituents, and crystal distortions beyond the scope of perturbation theory. The system was treated in the polaron picture where particles of the second species are dressed by surrounding crystal phonons. To describe the competition between coherent and incoherent dynamics of the polarons, a master equation in the Brownian motion limit was used with phonons treated as a thermal heat bath. It was shown analytically that in a wide range of realistic parameters the corrections to the coherent time evolution are small, and that the dynamics of the dressed particles can be described by an effective extended Hubbard model with controllable system parameters. The last chapter of this thesis contains a proposal for QIP with cold polar molecules that, in contrast to previous works, uses an MDC as a quantum register. It was motivated by the unique features of dipolar molecules and to exploit the peculiar physical conditions in dipolar crystals. In this proposal the molecular dipole moments were tailored by non-local fields to include a small, switchable, state-dependent dipole moment in addition to the large internal state independent moment that stabilizes the crystal. It was shown analytically that a controllable, non-trivial phonon-mediated interaction can be generated that exceeds non-trivial, direct dipole-dipole couplings. The addressability problem due to high crystal densities was overcome by

  13. Growth and optical characterizations on 3-aminophenol perchlorate (3-AMPP) crystal

    Energy Technology Data Exchange (ETDEWEB)

    Boopathi, K., E-mail: ramasamyp@ssn.edu.in; Ramasamy, P., E-mail: ramasamyp@ssn.edu.in [Centre for Crystal Growth, SSN College of Engineering, Kalavakkam-603110 (India)

    2014-04-24

    A single crystal of organic nonlinear optical material 3-aminophenol perchlorate (3-AMP) was successfully grown by the slow evaporation solution method. Single-crystal X-ray diffractrometer was utilized to measure unit cell parameters and to confirm lattice parameter. 3-aminophenol perchlorate belongs to monoclinic space group P2{sub 1}. The optical transparency window in the UV-vis-NIR region is found to be good for nonlinear optical applications second harmonic studies were carried out. The second harmonic output intensity was tested using the Kurtz and Perry powder method and was found to be 1.1 times that of potassium dihydrogen phosphate (KDP)

  14. Rapid synthesis of nitrogen doped titania with mixed crystal lattice via microwave-assisted hydrothermal method

    International Nuclear Information System (INIS)

    Zhang Peilin; Liu Bin; Yin Shu; Wang Yuhua; Petrykin, Valery; Kakihana, Masato; Sato, Tsugio

    2009-01-01

    A microwave-assisted hydrothermal method was employed to synthesize nitrogen doped titania nanoparticles. Due to the high heating efficiency of microwave, rapid synthesis could be achieved in comparison with the conventional oven. Mixed crystal lattice was found existing in the obtained product, and the phase transformation behaviour under calcination was studied by XRD measurement together with Raman spectroscopy in details. The obtained nitrogen doped titania showed high specific surface area, about 300 m 2 g -1 . Photocatalytic activity in destructing NO x gas by the prepared sample exceeded that of commercial titania (P 25) or nitrogen doped titania synthesized by conventional hydrothermal method, under both visible-light and ultraviolet-light irradiation.

  15. Magnetic field effects on ultrafast lattice compression dynamics of Si(111) crystal when excited by linearly-polarized femtosecond laser pulses

    Science.gov (United States)

    Hatanaka, Koji; Odaka, Hideho; Ono, Kimitoshi; Fukumura, Hiroshi

    2007-03-01

    Time-resolved X-ray diffraction measurements of Si (111) single crystal are performed when excited by linearly-polarized femtosecond laser pulses (780 nm, 260 fs, negatively-chirped, 1 kHz) under a magnetic field (0.47 T). Laser fluence on the sample surface is 40 mJ/cm^2, which is enough lower than the ablation threshold at 200 mJ/cm^2. Probing X-ray pulses of iron characteristic X-ray lines at 0.193604 and 0.193998 nm are generated by focusing femtosecond laser pulses onto audio-cassette tapes in air. Linearly-polarized femtosecond laser pulse irradiation onto Si(111) crystal surface induces transient lattice compression in the picosecond time range, which is confirmed by transient angle shift of X-ray diffraction to higher angles. Little difference of compression dynamics is observed when the laser polarization is changed from p to s-pol. without a magnetic field. On the other hand, under a magnetic field, the lattice compression dynamics changes when the laser is p-polarized which is vertical to the magnetic field vector. These results may be assigned to photo-carrier formation and energy-band distortion.

  16. Crystal structure and crystal growth of the polar ferrimagnet CaBaFe4O7

    Science.gov (United States)

    Perry, R. S.; Kurebayashi, H.; Gibbs, A.; Gutmann, M. J.

    2018-05-01

    Magnetic materials are a cornerstone for developing spintronic devices for the transport of information via magnetic excitations. To date, relatively few materials have been investigated for the purpose of spin transport, mostly due to the paucity of suitable candidates as these materials are often chemically complex and difficult to synthesize. We present the crystal growth and a structure solution on the high-temperature crystal structure of the layered, polar ferrimagnet CaBaFe4O7 , which is a possible new contender for spintronics research. The space group is identified as P 3 by refinement of single crystal and powder neutron diffraction data. At 400 K, the trigonal lattice parameters are a =11.0114 (11 )Å and c =10.330 (3 )Å . The structure is similar to the low-temperature phase with alternating layers of triangular and Kagome-arranged Fe-O tetrahedra. We also present details of the crystal growth by traveling solvent method.

  17. Electronic bandstructure of an incommensurate crystal

    International Nuclear Information System (INIS)

    Rasing, T.

    1984-06-01

    The consequences of an incommensurate lattice modulation on the electronic energy levels have been studied by optical transmission experiments on Rb 2 ZnBr 4 . The results are analyzed with a simple tight-binding model in which the superspace symmetry of the crystal is taken into account. The lattice translational symmetry of crystalline matter leads to the well known concepts of the Brillouin zones, Bloch electrons, phonons and the like. In a crystal where the lattice is periodically distorted with a period that is incommensurate with the underlying lattice, this translational symmetry is broken. Nonetheless, incommensurate crystals are perfectly ordered and can be described by higher dimensional so-called superspace groups. In this paper we will show how this superspace approach provides a natural framework to understand their electronic bandstructure as well. 5 references, 3 figures

  18. Laser guiding of cold atoms in photonic crystals

    International Nuclear Information System (INIS)

    Tarasishin, A V; Magnitskiy, Sergey A; Shuvaev, V A; Zheltikov, Aleksei M

    2000-01-01

    The possibility of using photonic crystals with a lattice defect for the laser guiding of cold atoms is analysed. We have found a configuration of a photonic-crystal lattice and a defect ensuring the distribution of a potential in the defect mode of the photonic crystal allowing the guiding of cold atoms along the defect due to the dipole force acting on atoms. Based on quantitative estimates, we have demonstrated that photonic crystals with a lattice defect permit the guiding of atoms with much higher transverse temperatures and a much higher transverse localisation degree than in the case of hollow-core fibres. (laser applications and other topics in quantum electronics)

  19. Structural properties and stability of the bcc and omega phases in the Zr-Nb system. Pt. II. Composition dependence of the lattice parameters

    International Nuclear Information System (INIS)

    Grad, G.B.; Guillermet, A.F.; Pieres, J.J.; Cuello, G.J.; Consejo Nacional de Investigaciones Cientificas y Tecnicas, Buenos Aires; Universidad Nacional del Comahue

    1996-01-01

    For pt.I see Guillermet, A.F., J. Nucl. Mater., vol.218, p.236-46, 1995. This paper deals with the composition dependence of the lattice parameters of the bcc and omega phases of the Zr-Nb system. The experimental part of the work comprises neutron scattering experiments on a Zr-10 at.% Nb alloy in the as-quenched state and after successive aging treatments at 773 K. This new information is combined with an extensive review of the available data, and a detailed analysis is performed of the effects of composition and heat-treatment upon the lattice parameters a Ω and c Ω of the omega phase and the lattice-parameter relations between bcc and omega. A striking behaviour is detected in the variation of a Ω with composition in low-Nb alloys. (orig.)

  20. On the effect of the lattice asymmetry parameter on the phase structure of SU(N) pure gauge theories

    International Nuclear Information System (INIS)

    Averchenkova, L.A.; Petrov, K.V.; Petrov, V.K.; Zinovjev, G.M.

    1998-01-01

    The role of the lattice asymmetry parameter ξ in the phase structure description of the SU(2) and SU(3) gluodynamics at finite temperature has been studied analytically in the SU(N)∼Z(N) approach. The properties of thermodynamic quantities have been investigated near the physical border. The effective action which includes the first non-trivial order from the space-like part allows estimates to be made of the phase structure not only close to the physical border but in the whole area of couplings. We find that thermodynamic quantities depend on ξ and this dependence may be strong enough, up to discontinuity over this parameter for some of them. The Hamiltonian formulation of the SU(2) gauge theory on the asymmetric lattice is presented. (orig.)

  1. First-Principles Lattice Dynamics Method for Strongly Anharmonic Crystals

    Science.gov (United States)

    Tadano, Terumasa; Tsuneyuki, Shinji

    2018-04-01

    We review our recent development of a first-principles lattice dynamics method that can treat anharmonic effects nonperturbatively. The method is based on the self-consistent phonon theory, and temperature-dependent phonon frequencies can be calculated efficiently by incorporating recent numerical techniques to estimate anharmonic force constants. The validity of our approach is demonstrated through applications to cubic strontium titanate, where overall good agreement with experimental data is obtained for phonon frequencies and lattice thermal conductivity. We also show the feasibility of highly accurate calculations based on a hybrid exchange-correlation functional within the present framework. Our method provides a new way of studying lattice dynamics in severely anharmonic materials where the standard harmonic approximation and the perturbative approach break down.

  2. Crystal and molecular structure of tetrathiocyanato tetrakis (triphenylphosphine oxide)uranium(IV)

    Energy Technology Data Exchange (ETDEWEB)

    Bombieri, G; De Paoli, G; Forsellini, E [Consiglio Nazionale delle Ricerche, Padua (Italy). Lab. di Chimica e Tecnologia dei Radioelementi; Brown, D

    1979-01-01

    The crystal structure of the title compound has been determined from three dimensional X-ray diffraction data. The space group and lattice parameters are given. The asymmetric unit comprises two independent U(NCS)/sub 4/(tppo)/sub 4/ molecules in each of which the coordination polyhedron around the uranium atom is close to square antiprismatic.

  3. Morphology and parameters of crystallization the blend PE/Epoxy/PE-co-PEG

    International Nuclear Information System (INIS)

    Becker, Daniela; Coelho, Luiz Antonio Ferreira; Nack, Fernanda; Silva, Bruna Louise

    2014-01-01

    This study aims to evaluate the morphology and crystallization parameters of high density polyethylene (HDPE) with different concentrations of epoxy (DGEBA / OTBG), and the compatibility of this system was used and the copolymer polyethylene-block-poly (ethylene glycol) (PEG-co-PE). The blends were obtained by mechanical mixing on a torque rheometer (Haake). Determined the crystallization parameters of the test matrix differential scanning calorimetry (DSC) and by X-ray diffraction (XRD). The morphology of the system was analyzed by transmission electron microscopy (TEM). It was observed by XRD analysis that the addition of compatibilizer and epoxy resins do not interfere with the crystal structure of HDPE, indicating that the increase in crystallinity associated with the crystallization kinetics. It was observed that the compatibilizing helped the adhesion, reducing the size of the dispersed phase becomes a more stable morphology and obtaining a distribution of the dispersed epoxy phase. (author)

  4. Waveguiding in supported phononic crystal plates

    International Nuclear Information System (INIS)

    Vasseur, J; Hladky-Hennion, A-C; Deymier, P; Djafari-Rouhani, B; Duval, F; Dubus, B; Pennec, Y

    2007-01-01

    We investigate, with the help of the finite element method, the existence of absolute band gaps in the band structure of a free-standing phononic crystal plate and of a phononic crystal slab deposited on a substrate. The two-dimensional phononic crystal is constituted by a square array of holes drilled in an active piezoelectric (PZT5A or AlN) matrix. For both matrix materials, an absolute band gap occurs in the band structure of the free-standing plate provided the thickness of the plate is on the order of magnitude of the lattice parameter. When the plate is deposited on a Si substrate, the absolute band gap still remains when the matrix of the phononic crystal is made of PZT5A. The AlN phononic crystal plate losses its gap when supported by the Si substrate. In the case of the PZT5A matrix, we also study the possibility of localized modes associated with a linear defect created by removing one row of air holes in the deposited phononic crystal plate

  5. Reflectance properties of one-dimensional metal-dielectric ternary photonic crystal

    Energy Technology Data Exchange (ETDEWEB)

    Pandey, G. N., E-mail: gnpandey2009@gmail.com [Department of Physics, Amity Institute of Applied Sciences, AmityUniversity, Noida (U.P.) (India); Kumar, Narendra [Department of Physics (CASH), Modi University of Science and Technology, Lakshmangarh, Sikar, Rajsthan (India); Thapa, Khem B. [Department of Physics, U I E T, ChhatrapatiShahu Ji Maharaj University, Kanpur- (UP) (India); Ojha, S. P. [Department of Physics IIT, Banaras Hindu University (India)

    2016-05-06

    Metallic photonic crystal has a very important application in absorption enhancement in solar cells. It has been found that an ultra-thin metallic layer becomes transparent due to internal scattering of light through the each interface of the dielectric and metal surfaces. The metal has absorption due to their surface plasmon and the plasmon has important parameters for changing optical properties of the metal. We consider ternary metallic-dielectric photonic crystal (MDPC) for having large probabilities to change the optical properties of the MDPC and the photonic crystals may be changed by changing dimensionality, symmetry, lattice parameters, Filling fraction and effective refractive index refractive index contrast. In this present communication, we try to show that the photonic band gap in ternary metal-dielectric photonic crystal can be significantly enlarged when air dielectric constant is considered. All the theoretical analyses are made based on the transfer matrix method together with the Drude model of metal.

  6. Applications of X-ray fluorescence holography to determine local lattice distortions

    International Nuclear Information System (INIS)

    Hayashi, Kouichi; Happo, Naohisa; Hosokawa, Shinya

    2014-01-01

    Highlights: • We summarized topics of X-ray fluorescence holography focused on the local lattice distortions. • We found details of behaviors of nearest neighbor atoms around dopants. • We found the average distributions of the atoms at the individual sites in mixed crystals. • Distorted and undistorted sires sometimes coexist in a same mixed crystal. - Abstract: X-ray fluorescence holography (XFH) is a method for investigating atomic order up to the medium ranges, and can provide 3D atomic images around specific elements within a radius of nm order. In addition to these characteristics, XFH is sensitive to positional fluctuations of atoms, and therefore it is useful for characterizing the local lattice distortions around specific elements. We have applied XFH to dopants and mixed crystals. We found interesting features in local lattice distortions, such as the displacements of first-neighbor atoms around dopants, far-sighted views of the atomistic fluctuations in mixed crystals, and the coexistence of distorted/undistorted sites in the same material

  7. Properties of melt-grown single crystals of 'YB/sub 68/'

    Energy Technology Data Exchange (ETDEWEB)

    Slack, G A; Oliver, D W; Brower, G D; Young, J D [General Electric Co., Schenectady, N.Y. (USA). Research and Development Center

    1977-01-01

    Single crystals of yttrium boride YB/sub n/ with n = 61 +- 3 were grown from the melt. Precision density and lattice parameter measurements indicate a congruent melting point at n = 61.7 and a stoichiometric composition at n = 68. Measurements of elastic constants, acoustic attenuation, electrical resistivity and optical absorption are presented. High resolution transmission electron microscopy reveals a complex crystal structure similar to that found by using X-rays. A comparison of the properties of YB/sub n/ with those of ..beta..-boron show that there are many similarities.

  8. Energy flow in photonic crystal waveguides

    DEFF Research Database (Denmark)

    Søndergaard, Thomas; Dridi, Kim

    2000-01-01

    Theoretical and numerical investigations of energy flow in photonic crystal waveguides made of line defects and branching points are presented. It is shown that vortices of energy flow may occur, and the net energy flow along: the line defect is described via the effective propagation velocity....... Single-mode and multimode operations are studied, and dispersion relations are computed for different waveguide widths. Both strong positive, strong negative, and zero dispersion an possible. It is shown that geometric parameters such as the nature of the lattice, the line defect orientation, the defect...... width, and the branching-point geometry have a significant influence on the electrodynamics. These are important issues for the fabrication of photonic crystal structures....

  9. Convergence of surface diffusion parameters with model crystal size

    Science.gov (United States)

    Cohen, Jennifer M.; Voter, Arthur F.

    1994-07-01

    A study of the variation in the calculated quantities for adatom diffusion with respect to the size of the model crystal is presented. The reported quantities include surface diffusion barrier heights, pre-exponential factors, and dynamical correction factors. Embedded atom method (EAM) potentials were used throughout this effort. Both the layer size and the depth of the crystal were found to influence the values of the Arrhenius factors significantly. In particular, exchange type mechanisms required a significantly larger model than standard hopping mechanisms to determine adatom diffusion barriers of equivalent accuracy. The dynamical events that govern the corrections to transition state theory (TST) did not appear to be as sensitive to crystal depth. Suitable criteria for the convergence of the diffusion parameters with regard to the rate properties are illustrated.

  10. Predicting lattice thermal conductivity with help from ab initio methods

    Science.gov (United States)

    Broido, David

    2015-03-01

    The lattice thermal conductivity is a fundamental transport parameter that determines the utility a material for specific thermal management applications. Materials with low thermal conductivity find applicability in thermoelectric cooling and energy harvesting. High thermal conductivity materials are urgently needed to help address the ever-growing heat dissipation problem in microelectronic devices. Predictive computational approaches can provide critical guidance in the search and development of new materials for such applications. Ab initio methods for calculating lattice thermal conductivity have demonstrated predictive capability, but while they are becoming increasingly efficient, they are still computationally expensive particularly for complex crystals with large unit cells . In this talk, I will review our work on first principles phonon transport for which the intrinsic lattice thermal conductivity is limited only by phonon-phonon scattering arising from anharmonicity. I will examine use of the phase space for anharmonic phonon scattering and the Grüneisen parameters as measures of the thermal conductivities for a range of materials and compare these to the widely used guidelines stemming from the theory of Liebfried and Schölmann. This research was supported primarily by the NSF under Grant CBET-1402949, and by the S3TEC, an Energy Frontier Research Center funded by the US DOE, office of Basic Energy Sciences under Award No. DE-SC0001299.

  11. Anomalous transparency in photonic crystals and its application to point-by-point grating inscription in photonic crystal fibers.

    Science.gov (United States)

    Baghdasaryan, Tigran; Geernaert, Thomas; Chah, Karima; Caucheteur, Christophe; Schuster, Kay; Kobelke, Jens; Thienpont, Hugo; Berghmans, Francis

    2018-04-03

    It is common belief that photonic crystals behave similarly to isotropic and transparent media only when their feature sizes are much smaller than the wavelength of light. Here, we counter that belief and we report on photonic crystals that are transparent for anomalously high normalized frequencies up to 0.9, where the crystal's feature sizes are comparable with the free space wavelength. Using traditional photonic band theory, we demonstrate that the isofrequency curves can be circular in the region above the first stop band for triangular lattice photonic crystals. In addition, by simulating how efficiently a tightly focused Gaussian beam propagates through the photonic crystal slab, we judge on the photonic crystal's transparency rather than on isotropy only. Using this approach, we identified a wide range of photonic crystal parameters that provide anomalous transparency. Our findings indicate the possibility to scale up the features of photonic crystals and to extend their operational wavelength range for applications including optical cloaking and graded index guiding. We applied our result in the domain of femtosecond laser micromachining, by demonstrating what we believe to be the first point-by-point grating inscribed in a multi-ring photonic crystal fiber.

  12. Dramatic Improvement of Crystal Quality for Low-temperature-grown Rabbit Muscle Aldolase

    Energy Technology Data Exchange (ETDEWEB)

    Park, H.; Rangarajan, E; Sygusch, J; Izard, T

    2010-01-01

    Rabbit muscle aldolase (RMA) was crystallized in complex with the low-complexity domain (LC4) of sorting nexin 9. Monoclinic crystals were obtained at room temperature that displayed large mosaicity and poor X-ray diffraction. However, orthorhombic RMA-LC4 crystals grown at 277 K under similar conditions exhibited low mosaicity, allowing data collection to 2.2 {angstrom} Bragg spacing and structure determination. It was concluded that the improvement of crystal quality as indicated by the higher resolution of the new RMA-LC4 complex crystals was a consequence of the introduction of new lattice contacts at lower temperature. The lattice contacts corresponded to an increased number of interactions between high-entropy side chains that mitigate the lattice strain incurred upon cryocooling and accompanying mosaic spread increases. The thermodynamically unfavorable immobilization of high-entropy side chains used in lattice formation was compensated by an entropic increase in the bulk-solvent content owing to the greater solvent content of the crystal lattice.

  13. Dramatic improvement of crystal quality for low-temperature-grown rabbit muscle aldolase.

    Science.gov (United States)

    Park, Hajeung; Rangarajan, Erumbi S; Sygusch, Jurgen; Izard, Tina

    2010-05-01

    Rabbit muscle aldolase (RMA) was crystallized in complex with the low-complexity domain (LC4) of sorting nexin 9. Monoclinic crystals were obtained at room temperature that displayed large mosaicity and poor X-ray diffraction. However, orthorhombic RMA-LC4 crystals grown at 277 K under similar conditions exhibited low mosaicity, allowing data collection to 2.2 A Bragg spacing and structure determination. It was concluded that the improvement of crystal quality as indicated by the higher resolution of the new RMA-LC4 complex crystals was a consequence of the introduction of new lattice contacts at lower temperature. The lattice contacts corresponded to an increased number of interactions between high-entropy side chains that mitigate the lattice strain incurred upon cryocooling and accompanying mosaic spread increases. The thermodynamically unfavorable immobilization of high-entropy side chains used in lattice formation was compensated by an entropic increase in the bulk-solvent content owing to the greater solvent content of the crystal lattice.

  14. Microprobe channeling analysis of pyrite crystals

    International Nuclear Information System (INIS)

    Jamieson, D.N.; Ryan, C.G.

    1992-01-01

    Nuclear microprobe analysis has provided much useful information about the composition of microscopic inclusions in minerals, mainly through the use of Particle Induced X-ray Emission (PIXE). However this technique, while powerful, does not provide any direct information about the chemical state, in particular the lattice location, of the elements in the mineral. This information is often of crucial importance in understanding the ore genesis. The technique of ion channeling may be used to identify lattice location, but many minerals occur as microscopic crystals. Therefore it is necessary to utilize a nuclear microprobe with the technique of Channeling Contrast Microscopy (CCM). As many minerals contain interesting trace elements, it is necessary to measure both the yield of backscattered particles and the induced x-rays to get a clear picture of the lattice location of the elements in the crystal. CCM with PIXE was used to analyse natural pyrite crystals containing a variety of substitutional and non-substitutional elements and natural pyrite crystals from a gold bearing ore. In the latter case, evidence was obtained for two habits for Au in the 400 μm crystals: one as inclusions of Au rich minerals, the other substituted on the pyrite lattice sites. 31 refs., 3 tabs., 6 figs

  15. Internal space decimation for lattice gauge theories

    International Nuclear Information System (INIS)

    Flyvbjerg, H.

    1984-01-01

    By a systematic decimation of internal space lattice gauge theories with continuous symmetry groups are mapped into effective lattice gauge theories with finite symmetry groups. The decimation of internal space makes a larger lattice tractable with the same computational resources. In this sense the method is an alternative to Wilson's and Symanzik's programs of improved actions. As an illustrative test of the method U(1) is decimated to Z(N) and the results compared with Monte Carlo data for Z(4)- and Z(5)-invariant lattice gauge theories. The result of decimating SU(3) to its 1080-element crystal-group-like subgroup is given and discussed. (orig.)

  16. Crystal Growth of Ca3Nb(Ga1−xAlx3Si2O14 Piezoelectric Single Crystals with Various Al Concentrations

    Directory of Open Access Journals (Sweden)

    Yuui Yokota

    2015-08-01

    Full Text Available Ca3Nb(Ga1−xAlx3Si2O14 (CNGAS single crystals with various Al concentrations were grown by a micro-pulling-down (µ-PD method and their crystal structures, chemical compositions, crystallinities were investigated. CNGAS crystals with x = 0.2, 0.4 and 0.6 indicated a single phase of langasite-type structure without any secondary phases. In contrast, the crystals with x = 0.8 and 1 included some secondary phases in addition to the langasite-type phase. Lattice parameters, a- and c-axes lengths, of the langasite-type phase systematically decreased with an increase of Al concentration. The results of chemical composition analysis revealed that the actual Al concentrations in as-grown crystals were almost consistent with the nominal compositions. In addition, there was no large segregation of each cation along the growth direction.

  17. Preliminary morphological and X-ray diffraction studies of the crystals of the DNA cetyltrimethylammonium salt.

    Science.gov (United States)

    Osica, V D; Pyatigorskaya, T L; Polyvtsev, O F; Dembo, A T; Kliya, M O; Vasilchenko, V N; Verkin, B I; Sukharevskya, B Y

    1977-04-01

    Double-stranded DNA molecules (molecular weight 2.5 X 10(5) - 5 X 10(5) daltons) have been crystallized from water-salt solutions as cetyltrimethylammonium salts (CTA-DNA). Variation of crystallization conditions results in a production of different types of CTA-DNA crystals: spherulits, dendrites, needle-shaped and faceted rhombic crystals, the latter beeing up to 0.3 mm on a side. X-ray diffraction data indicate that DNA molecules in the crystals form a hexagonal lattice which parameters vary slightly with the morphological type of the crystal. Comparison of the melting curves of the DNA preparation before and after crystallization suggests that DNA molecules are partially fractionated in the course of crystallization. Crystals of the CTA-DNA-proflavine complex have also been obtained.

  18. Electron paramagnetic resonance and optical spectroscopy of Yb sup 3 sup + ions in SrF sub 2 and BaF sub 2; an analysis of distortions of the crystal lattice near Yb sup 3 sup +

    CERN Document Server

    Falin, M L; Latypov, V A; Leushin, A M

    2003-01-01

    SrF sub 2 and BaF sub 2 crystals, doped with the Yb sup 3 sup + ions, have been investigated by electron paramagnetic resonance and optical spectroscopy. As-grown crystals of SrF sub 2 and BaF sub 2 show the two paramagnetic centres for the cubic (T sub c) and trigonal (T sub 4) symmetries of the Yb sup 3 sup + ions. Empirical diagrams of the energy levels were established and the potentials of the crystal field were determined. Information was obtained on the SrF sub 2 and BaF sub 2 phonon spectra from the electron-vibrational structure of the optical spectra. The crystal field parameters were used to analyse the crystal lattice distortions in the vicinity of the impurity ion and the F sup - ion compensating for the excess positive charge in T sub 4. Within the frames of a superposition model, it is shown that three F sup - ions from the nearest surrounding cube, located symmetrically with respect to the C sub 3 axis from the side of the ion-compensator, approach the impurity ion and cling to the axis of the...

  19. Ground and excited state absorption of Ni{sup 2+} ions in MgAl{sub 2}O{sub 4}: Crystal field analysis

    Energy Technology Data Exchange (ETDEWEB)

    Brik, M.G. [Fukui Institute for Fundamental Chemistry, Kyoto University, 34-4 Takano Nishihiraki-cho, Sakyo-ku, Kyoto 606-8103 (Japan) and Department of Chemistry, School of Science and Technology, Kwansei Gakuin University, 2-1 Gakuen, Sanda, Hyogo 669-1337 (Japan)]. E-mail: brik@fukui.kyoto-u.ac.jp; Avram, N.M. [Department of Physics, West University of Timisoara, Bd. V. Parvan No. 4, 300223 Timisoara (Romania); Avram, C.N. [Department of Physics, West University of Timisoara, Bd. V. Parvan No. 4, 300223 Timisoara (Romania); Rudowicz, C. [Institute of Physics, Szczecin University of Technology, Al. Piastow 17, 70-310 Szczecin (Poland); Yeung, Y.Y. [Department of Mathematics, Science, Social Sciences and Technology, The Hong Kong Institute of Education, 10 Lo Ping Road, Tai Po, New Territories (Hong Kong); Gnutek, P. [Institute of Physics, Szczecin University of Technology, Al. Piastow 17, 70-310 Szczecin (Poland)

    2007-04-25

    The exchange charge model (ECM) of crystal field is utilized to provide the theoretical explanation of the ground state absorption and the excited state absorption observed for the octahedrally coordinated Ni{sup 2+} ions in the spinel MgAl{sub 2}O{sub 4}. The ECM enables modeling of the crystal field parameters (CFPs) for the impurity ions based on the crystal structure data of the host lattice. To ensure the reliability of the CFPs, the convergence of the CFP values with the increasing number of the coordination spheres taken into account in the ECM calculations is considered. The trigonal CFPs B{sub 2}{sup 0},B{sub 4}{sup 0}andB{sub 4}{sup -3} determined by the ECM, together with the appropriate Racah parameters B and C, serve as input to two crystal field analysis computer packages, which compute the energy level schemes within the whole 3d{sup 8} configuration. The cubic approximation utilizing only one CFP Dq is also discussed. Basic features of the ground and excited state absorption spectra observed for MgAl{sub 2}O{sub 4}:Ni{sup 2+} are satisfactorily explained by our crystal field analysis. In order to model the pressure dependence of the CFPs (and thus of the absorption spectra when relevant experimental data become available), the variation of the CFPs induced by possible distortions of the lattice due to, e.g. overall relaxation of the ions or accommodation of the impurity ions in the lattice, is studied. Analysis of the experimental absorption spectra enables us to evaluate also the Huang-Rhys parameter, the effective phonon energy, and the zero-phonon line position.

  20. Nuclear reaction analysis of Ge ion-implanted ZnO bulk single crystals: The evaluation of the displacement in oxygen lattices

    Science.gov (United States)

    Kamioka, K.; Oga, T.; Izawa, Y.; Kuriyama, K.; Kushida, K.; Kinomura, A.

    2014-08-01

    The displacement of oxygen lattices in Ge ion-implanted ZnO bulk single crystals is studied by nuclear reaction analysis (NAR), photoluminescence (PL), and Van der Pauw methods. The Ge ion-implantation (net concentration: 2.6 × 1020 cm-3) into ZnO is performed using a multiple-step energy. The high resistivity of ∼103 Ω cm in un-implanted samples remarkably decreased to ∼10-2 Ω cm after implanting Ge-ion and annealing subsequently. NRA measurements of as-implanted and annealed samples suggest the existence of the lattice displacement of O atoms acting as acceptor defects. As O related defects still remain after annealing, these defects are not attributed to the origin of the low resistivity in 800 and 1000 °C annealed ZnO.

  1. The Effect of Anisotropy on Light Extraction of Organic Light-Emitting Diodes with Photonic Crystal Structure

    Directory of Open Access Journals (Sweden)

    Wei Xu

    2013-01-01

    Full Text Available The light extraction efficiency of organic light-emitting diodes (OLED is greatly limited due to the difference in refractive indexes between materials of OLED. We fabricated OLED with photonic crystal microstructures in the interface between the glass substrate and the ITO anode. The light extraction efficiency can be improved by utilizing photonic crystals; however, the anisotropy effect of light extraction was clearly observed in experiment. To optimize the device performance, the effect of photonic crystal on both light extraction and angular distribution was investigated using finite-difference time domain (FDTD method. We simulated the photonic crystals with the structure of square lattice and triangle lattice. We analyzed the improvement of these structures in the light extraction efficiency of the OLED and the influence of arrangement, depth, period, and diameter on anisotropy. The optimized geometric parameters were provided, which will provide the theoretical support for designing the high performance OLED.

  2. Photon-phonon interaction in photonic crystals

    International Nuclear Information System (INIS)

    Ueta, T

    2010-01-01

    Photon-phonon interaction on the analogy of electron-phonon interaction is considered in one-dimensional photonic crystal. When lattice vibration is artificially introduced to the photonic crystal, a governing equation of electromagnetic field is derived. A simple model is numerically analysed and the following novel phenomena are found out. The lattice vibration generates the light of frequency which added the integral multiple of the vibration frequency to that of the incident wave and also amplifies the incident wave resonantly. On a resonance, the amplification factor increases very rapidly with the number of layers increases. Resonance frequencies change with the phases of lattice vibration. The amplification phenomenon is analytically discussed for low frequency of the lattice vibration.

  3. Photonic Crystal Laser-Driven Accelerator Structures

    International Nuclear Information System (INIS)

    Cowan, B

    2004-01-01

    The authors discuss simulated photonic crystal structure designs for laser-driven particle acceleration. They focus on three-dimensional planar structures based on the so-called ''woodpile'' lattice, demonstrating guiding of a speed-of-light accelerating mode by a defect in the photonic crystal lattice. They introduce a candidate geometry and discuss the properties of the accelerating mode. They also discuss the linear beam dynamics in the structure present a novelmethod for focusing the beam. In addition they describe ongoing investigations of photonic crystal fiber-based structures

  4. Improved reproducibility of unit-cell parameters in macromolecular cryocrystallography by limiting dehydration during crystal mounting.

    Science.gov (United States)

    Farley, Christopher; Burks, Geoffry; Siegert, Thomas; Juers, Douglas H

    2014-08-01

    In macromolecular cryocrystallography unit-cell parameters can have low reproducibility, limiting the effectiveness of combining data sets from multiple crystals and inhibiting the development of defined repeatable cooling protocols. Here, potential sources of unit-cell variation are investigated and crystal dehydration during loop-mounting is found to be an important factor. The amount of water lost by the unit cell depends on the crystal size, the loop size, the ambient relative humidity and the transfer distance to the cooling medium. To limit water loss during crystal mounting, a threefold strategy has been implemented. Firstly, crystal manipulations are performed in a humid environment similar to the humidity of the crystal-growth or soaking solution. Secondly, the looped crystal is transferred to a vial containing a small amount of the crystal soaking solution. Upon loop transfer, the vial is sealed, which allows transport of the crystal at its equilibrated humidity. Thirdly, the crystal loop is directly mounted from the vial into the cold gas stream. This strategy minimizes the exposure of the crystal to relatively low humidity ambient air, improves the reproducibility of low-temperature unit-cell parameters and offers some new approaches to crystal handling and cryoprotection.

  5. Multiplicative congruential generators, their lattice structure, its relation to lattice-sublattice transformations and applications in crystallography

    Science.gov (United States)

    Hornfeck, W.; Harbrecht, B.

    2009-11-01

    An analysis of certain types of multiplicative congruential generators - otherwise known for their application to the sequential generation of pseudo-random numbers - reveals their relation to lattice-sublattice transformations and the coordinate description of crystal structures.

  6. Radiation induced color in topaz crystals

    International Nuclear Information System (INIS)

    Castagnet, A.C.; Rocca, H.C.C.; Rostilato, M.E.C.M.

    1989-08-01

    The presence of defects and impurities in the crystal lattice alters the eletric field distribution within the crystal, allowing the electrons to occupy energy levels in the forbbiden band. Ionizing radiation supply the required energy to permit the electrons originaly bound to lattice atoms, to occupy effectively those intermediate levels, forming color centers. Dependig upon the nature and energy of the radiation, it is possible to produce defects in regions of the crystal, generating color centers. Based on these premises, a technique to induce color in originally colorless topaz, by using the IEA-R1 nuclear reactor, was developed at Engineering and Industrial Application Department (TE). Samples were irradiated inside iron capsules coated with cadmium foils. The iron, and principaly the cadmium, absorb the thermal neutrons that could activate crystal impurities generating long-lived radioisotopes. The epithermal neutrons that overpass the iron and cadmium barriers interact with the crystal atoms, causing lattice defects which give rise to color center, by subsequent ionization processes. The procedure used at TE induces permanent blue color, in natural colorless topaz. (author) [pt

  7. The Raman spectrum and lattice parameters of MgB2 as a function of temperature

    International Nuclear Information System (INIS)

    Shi Lei; Zhang Huarong; Chen Lin; Feng Yong

    2004-01-01

    The temperature dependences of the Raman spectrum and lattice parameters of polycrystalline MgB 2 have been investigated by means of Raman spectroscopy and x-ray diffraction. It is found that the lattice parameters show an approximately linear change with the temperature decrease, giving different thermal expansions along the a- and c-axes, which is caused by the comparatively weak metal-boron bonding in MgB 2 . The grain size of MgB 2 determined by means of x-ray diffraction is around 45 nm for both [100] and [001] directions. There is no evidence for any structural transition while the temperature changes from 300 K down to 12 K. An anomalous Raman band at 603 cm -1 is observed, which is consistent with the theoretical prediction for the E 2g in-plane boron stretching mode. The Raman frequency increases and the linewidth decreases as the temperature decreases. A possible origin of the temperature dependences of the Raman frequency and the linewidth is discussed. It is suggested that the grain size effect of MgB 2 on the nanometric scale will have a clear influence on the frequency and the linewidth of the Raman spectrum

  8. Dramatic improvement of crystal quality for low-­temperature-grown rabbit muscle aldolase

    Science.gov (United States)

    Park, HaJeung; Rangarajan, Erumbi S.; Sygusch, Jurgen; Izard, Tina

    2010-01-01

    Rabbit muscle aldolase (RMA) was crystallized in complex with the low-complexity domain (LC4) of sorting nexin 9. Monoclinic crystals were obtained at room temperature that displayed large mosaicity and poor X-ray diffraction. However, orthorhombic RMA–LC4 crystals grown at 277 K under similar conditions exhibited low mosaicity, allowing data collection to 2.2 Å Bragg spacing and structure determination. It was concluded that the improvement of crystal quality as indicated by the higher resolution of the new RMA–LC4 complex crystals was a consequence of the introduction of new lattice contacts at lower temperature. The lattice contacts corresponded to an increased number of interactions between high-entropy side chains that mitigate the lattice strain incurred upon cryocooling and accompanying mosaic spread increases. The thermodynamically unfavorable immobilization of high-entropy side chains used in lattice formation was compensated by an entropic increase in the bulk-solvent content owing to the greater solvent content of the crystal lattice. PMID:20445268

  9. Grain dynamics and inter-grain coupling in dusty plasma Coulomb crystals

    International Nuclear Information System (INIS)

    Rahman, H.U.; Mohideen, U.; Smith, M.A.; Rosenberg, M.; Mendis, D.A.

    2001-01-01

    We review our results on the lattice structure and the lattice dynamics of dusty plasma Coulomb crystals formed in rectangular conductive grooves. The basic structure appears to be made of mutually repulsive columns of grains confined by the walls of the groove. The columns are oriented along the direction of the electrode sheath electric field. Inter-grain coupling as a function of plasma temperature and density were investigated by measurement of these parameters. A simple phenomenological model wherein the inter-grain spacing along the column results from an attractive electric field induced dipole-dipole force balanced by a repulsive monopole Coulomb force is consistent with observed features of the Coulomb crystal. In addition, here we present some preliminary measurements of the vibration and rotation dynamics of the individual grains in the Coulomb crystal. The thermal energy of the dust grain thus calculated is much less than the inter-grain Coulomb potential energy as required for the formation of stable structures. Also the observed rotational frequency is consistent with the assumption of thermal equilibrium between the dust grains and the neutral gas. (orig.)

  10. Calculations of the electronic levels, spin-Hamiltonian parameters and vibrational spectra for the CrCl{sub 3} layered crystals

    Energy Technology Data Exchange (ETDEWEB)

    Avram, C.N. [Faculty of Physics, West University of Timisoara, Bd. V. Parvan No. 4, 300223 Timisoara (Romania); Gruia, A.S., E-mail: adigruia@yahoo.com [Faculty of Physics, West University of Timisoara, Bd. V. Parvan No. 4, 300223 Timisoara (Romania); Brik, M.G. [College of Sciences, Chongqing University of Posts and Telecommunications, Chongqing 400065 (China); Institute of Physics, University of Tartu, Ravila 14C, Tartu 50411 (Estonia); Institute of Physics, Jan Dlugosz University, Armii Krajowej 13/15, PL-42200 Czestochowa (Poland); Institute of Physics, Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warsaw (Poland); Barb, A.M. [Faculty of Physics, West University of Timisoara, Bd. V. Parvan No. 4, 300223 Timisoara (Romania)

    2015-12-01

    Calculations of the Cr{sup 3+} energy levels, spin-Hamiltonian parameters and vibrational spectra for the layered CrCl{sub 3} crystals are reported for the first time. The crystal field parameters and the energy level scheme were calculated in the framework of the Exchange Charge Model of crystal field. The spin-Hamiltonian parameters (zero-field splitting parameter D and g-factors) for Cr{sup 3+} ion in CrCl{sub 3} crystals were obtained using two independent techniques: i) semi-empirical crystal field theory and ii) density functional theory (DFT)-based model. In the first approach, the spin-Hamiltonian parameters were calculated from the perturbation theory method and the complete diagonalization (of energy matrix) method. The infrared (IR) and Raman frequencies were calculated for both experimental and fully optimized geometry of the crystal structure, using CRYSTAL09 software. The obtained results are discussed and compared with the experimental available data.

  11. Degenerate Ising model for atomistic simulation of crystal-melt interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Schebarchov, D., E-mail: Dmitri.Schebarchov@gmail.com [University Chemical Laboratories, Lensfield Road, Cambridge CB2 1EW (United Kingdom); Schulze, T. P., E-mail: schulze@math.utk.edu [Department of Mathematics, University of Tennessee, Knoxville, Tennessee 37996-1300 (United States); Hendy, S. C. [The MacDiarmid Institute for Advanced Materials and Nanotechnology, School of Chemical and Physical Sciences, Victoria University of Wellington, Wellington 6140 (New Zealand); Department of Physics, University of Auckland, Auckland 1010 (New Zealand)

    2014-02-21

    One of the simplest microscopic models for a thermally driven first-order phase transition is an Ising-type lattice system with nearest-neighbour interactions, an external field, and a degeneracy parameter. The underlying lattice and the interaction coupling constant control the anisotropic energy of the phase boundary, the field strength represents the bulk latent heat, and the degeneracy quantifies the difference in communal entropy between the two phases. We simulate the (stochastic) evolution of this minimal model by applying rejection-free canonical and microcanonical Monte Carlo algorithms, and we obtain caloric curves and heat capacity plots for square (2D) and face-centred cubic (3D) lattices with periodic boundary conditions. Since the model admits precise adjustment of bulk latent heat and communal entropy, neither of which affect the interface properties, we are able to tune the crystal nucleation barriers at a fixed degree of undercooling and verify a dimension-dependent scaling expected from classical nucleation theory. We also analyse the equilibrium crystal-melt coexistence in the microcanonical ensemble, where we detect negative heat capacities and find that this phenomenon is more pronounced when the interface is the dominant contributor to the total entropy. The negative branch of the heat capacity appears smooth only when the equilibrium interface-area-to-volume ratio is not constant but varies smoothly with the excitation energy. Finally, we simulate microcanonical crystal nucleation and subsequent relaxation to an equilibrium Wulff shape, demonstrating the model's utility in tracking crystal-melt interfaces at the atomistic level.

  12. Degenerate Ising model for atomistic simulation of crystal-melt interfaces

    International Nuclear Information System (INIS)

    Schebarchov, D.; Schulze, T. P.; Hendy, S. C.

    2014-01-01

    One of the simplest microscopic models for a thermally driven first-order phase transition is an Ising-type lattice system with nearest-neighbour interactions, an external field, and a degeneracy parameter. The underlying lattice and the interaction coupling constant control the anisotropic energy of the phase boundary, the field strength represents the bulk latent heat, and the degeneracy quantifies the difference in communal entropy between the two phases. We simulate the (stochastic) evolution of this minimal model by applying rejection-free canonical and microcanonical Monte Carlo algorithms, and we obtain caloric curves and heat capacity plots for square (2D) and face-centred cubic (3D) lattices with periodic boundary conditions. Since the model admits precise adjustment of bulk latent heat and communal entropy, neither of which affect the interface properties, we are able to tune the crystal nucleation barriers at a fixed degree of undercooling and verify a dimension-dependent scaling expected from classical nucleation theory. We also analyse the equilibrium crystal-melt coexistence in the microcanonical ensemble, where we detect negative heat capacities and find that this phenomenon is more pronounced when the interface is the dominant contributor to the total entropy. The negative branch of the heat capacity appears smooth only when the equilibrium interface-area-to-volume ratio is not constant but varies smoothly with the excitation energy. Finally, we simulate microcanonical crystal nucleation and subsequent relaxation to an equilibrium Wulff shape, demonstrating the model's utility in tracking crystal-melt interfaces at the atomistic level

  13. Lattice Entertain You: Paper Modeling of the 14 Bravais Lattices on Youtube

    Science.gov (United States)

    Sein, Lawrence T., Jr.; Sein, Sarajane E.

    2015-01-01

    A system for the construction of double-sided paper models of the 14 Bravais lattices, and important crystal structures derived from them, is described. The system allows the combination of multiple unit cells, so as to better represent the overall three-dimensional structure. Students and instructors can view the models in use on the popular…

  14. On calculation of lattice parameters of refractory metal solid solutions

    International Nuclear Information System (INIS)

    Barsukov, A.D.; Zhuravleva, A.D.; Pedos, A.A.

    1995-01-01

    Technique for calculating lattice periods of solid solutions is suggested. Experimental and calculation values of lattice periods of some solid solutions on the basis of refractory metals (V-Cr, Nb-Zr, Mo-W and other) are presented. Calculation error was correlated with experimental one. 7 refs.; 2 tabs

  15. Theoretical explanation of EPR parameters for Cu2+ ion in TiO2 crystal

    International Nuclear Information System (INIS)

    Dong, H.N.; Wu, S.Y.; Li, P.

    2004-01-01

    The EPR parameters anisotropic g-factors g x , g y and g z for Cu 2+ ion and hyperfine structure constants A x , A y and A z for 63 Cu 2+ and 65 Cu 2+ isotopes in rutile (TiO 2 ) crystal are calculated by the method of diagonalizing the full Hamiltonian matrix. The crystal-field parameters contact with the crystal structure by the aid of the superposition model. The calculated results are in reasonable agreement with the observed values. The results are discussed. (copyright 2004 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  16. Parameters of heavy quark effective theory from N{sub f}=2 lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    Blossier, Benoit [CNRS, Orsay (France). LPT; Paris-11 Univ., 91 - Orsay (France); Della Morte, Michele [Mainz Univ. (Germany). Inst. fuer Kernphysik; Fritzsch, Patrick [Humboldt-Universitaet, Berlin (Germany). Inst. fuer Physik; Garron, Nicolas [Edinburgh Univ. (United Kingdom). School of Physics and Astronomy; Heitger, Jochen [Muenster Univ. (Germany). Inst. fuer Theoretische Physik 1; Simma, Hubert; Sommer, Rainer [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC; Tantalo, Nazario [Rome-3 Univ. (Italy). Dipt. di Fisica; INFN, Sezione di Roma (Italy)

    2012-07-15

    We report on a non-perturbative determination of the parameters of the lattice Heavy Quark Effective Theory (HQET) Lagrangian and of the time component of the heavy-light axial-vector current with N{sub f} = 2 flavors of massless dynamical quarks. The effective theory is considered at the 1/m{sub h} order, and the heavy mass m{sub h} covers a range from slightly above the charm to beyond the beauty region. These HQET parameters are needed to compute, for example, the b-quark mass, the heavy-light spectrum and decay constants in the static approximation and to order 1/m{sub h} in HQET. The determination of the parameters is done non-perturbatively. The computation reported in this paper uses the plaquette gauge action and two different static actions for the heavy quark described by HQET. For the light-quark action we choose non-perturbatively O(a)-improved Wilson fermions.

  17. Nuclear reaction analysis of Ge ion-implanted ZnO bulk single crystals: The evaluation of the displacement in oxygen lattices

    Energy Technology Data Exchange (ETDEWEB)

    Kamioka, K.; Oga, T.; Izawa, Y. [College of Engineering and Research Center of Ion Beam Technology, Hosei University, Koganei, Tokyo 184-8584 (Japan); Kuriyama, K., E-mail: kuri@ionbeam.hosei.ac.jp [College of Engineering and Research Center of Ion Beam Technology, Hosei University, Koganei, Tokyo 184-8584 (Japan); Kushida, K. [Department of Arts and Science, Osaka Kyouiku University, Kashiwara, Osaka 582-8582 (Japan); Kinomura, A. [National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki 305-8568 (Japan)

    2014-08-01

    The displacement of oxygen lattices in Ge ion-implanted ZnO bulk single crystals is studied by nuclear reaction analysis (NAR), photoluminescence (PL), and Van der Pauw methods. The Ge ion-implantation (net concentration: 2.6 × 10{sup 20} cm{sup −3}) into ZnO is performed using a multiple-step energy. The high resistivity of ∼10{sup 3} Ω cm in un-implanted samples remarkably decreased to ∼10{sup −2} Ω cm after implanting Ge-ion and annealing subsequently. NRA measurements of as-implanted and annealed samples suggest the existence of the lattice displacement of O atoms acting as acceptor defects. As O related defects still remain after annealing, these defects are not attributed to the origin of the low resistivity in 800 and 1000 °C annealed ZnO.

  18. Photographic appraisal of crystal lattice growth technique

    Directory of Open Access Journals (Sweden)

    Kapoor D

    2005-01-01

    Full Text Available Concept of creating mechanical retention for bonding through crystal growth has been successfully achieved in the present study. By using polyacrylic acid, sulphated with sulphuric acid as etchant, abundant crystal growth was demonstrated. Keeping in view the obvious benefits of crystal growth technique, the present SEM study was aimed to observe and compare the changes brought about by different etching agents (phosphoric acid, polyacrylic acid and polyacrylic acid sulphated and to evaluate their advantages and disadvantages in an attempt to reduce iatrogenic trauma caused due to surface enamel alteration. Control and experimental groups were made of 24 and 30 premolars, respectively, for scanning electron microscopic appraisal of normal unetched and etched enamel surface and fracture site and finished surface evaluation. When compared with conventional phosphoric acid and weaker polyacrylic acid, investigations indicated that crystal growth treatment on enamel surface caused minimal iatrogenic trauma and surface alteration were restored to the original untreated condition to a large extent.

  19. Lattice gauge theories

    International Nuclear Information System (INIS)

    Creutz, M.

    1983-04-01

    In the last few years lattice gauge theory has become the primary tool for the study of nonperturbative phenomena in gauge theories. The lattice serves as an ultraviolet cutoff, rendering the theory well defined and amenable to numerical and analytical work. Of course, as with any cutoff, at the end of a calculation one must consider the limit of vanishing lattice spacing in order to draw conclusions on the physical continuum limit theory. The lattice has the advantage over other regulators that it is not tied to the Feynman expansion. This opens the possibility of other approximation schemes than conventional perturbation theory. Thus Wilson used a high temperature expansion to demonstrate confinement in the strong coupling limit. Monte Carlo simulations have dominated the research in lattice gauge theory for the last four years, giving first principle calculations of nonperturbative parameters characterizing the continuum limit. Some of the recent results with lattice calculations are reviewed

  20. Dramatic improvement of crystal quality for low-temperature-grown rabbit muscle aldolase

    International Nuclear Information System (INIS)

    Park, HaJeung; Rangarajan, Erumbi S.; Sygusch, Jurgen; Izard, Tina

    2010-01-01

    Rabbit muscle aldolase (RMA) was crystallized in complex with the low-complexity domain (LC4) of sorting nexin 9. Monoclinic crystals were obtained at room temperature that displayed large mosaicity and poor X-ray diffraction. However, orthorhombic RMA–LC4 crystals grown at 277 K under similar conditions exhibited low mosaicity, allowing data collection to 2.2 Å Bragg spacing and structure determination. Rabbit muscle aldolase (RMA) was crystallized in complex with the low-complexity domain (LC4) of sorting nexin 9. Monoclinic crystals were obtained at room temperature that displayed large mosaicity and poor X-ray diffraction. However, orthorhombic RMA–LC4 crystals grown at 277 K under similar conditions exhibited low mosaicity, allowing data collection to 2.2 Å Bragg spacing and structure determination. It was concluded that the improvement of crystal quality as indicated by the higher resolution of the new RMA–LC4 complex crystals was a consequence of the introduction of new lattice contacts at lower temperature. The lattice contacts corresponded to an increased number of interactions between high-entropy side chains that mitigate the lattice strain incurred upon cryocooling and accompanying mosaic spread increases. The thermodynamically unfavorable immobilization of high-entropy side chains used in lattice formation was compensated by an entropic increase in the bulk-solvent content owing to the greater solvent content of the crystal lattice

  1. Spin-1 and -2 bilayer Bethe lattice: A Monte Carlo study

    International Nuclear Information System (INIS)

    Masrour, R.; Jabar, A.; Benyoussef, A.; Hamedoun, M.

    2016-01-01

    The magnetic behaviors of bilayer with spin-1 and 2 Ising model on the Bethe lattice are investigated using the Monte Carlo simulations. The thermal magnetizations, the magnetic susceptibilities and the transition temperature of the bilayer spin-1 and 2 on the Bethe lattice are studied for different values of crystal field and intralayer coupling constants of the two layers and interlayer coupling constant between the layers. The thermal and magnetic hysteresis cycles are given for different values of the crystal field, for different temperatures and for different exchange interactions. - Highlights: • The magnetic properties of bilayer on the Bethe lattice have been investigated. • The transition temperature has been deduced. • The magnetic coercive filed has been established.

  2. Spin-1 and -2 bilayer Bethe lattice: A Monte Carlo study

    Energy Technology Data Exchange (ETDEWEB)

    Masrour, R., E-mail: rachidmasrour@hotmail.com [Laboratory of Materials, Processes, Environment and Quality, Cady Ayyed University, National School of Applied Sciences, 63 46000 Safi (Morocco); Laboratoire de Magnétisme et Physique des Hautes Energies L.M.P.H.E.URAC 12, Université Mohammed V, Faculté des Sciences, B.P. 1014 Rabat (Morocco); Jabar, A. [Laboratoire de Magnétisme et Physique des Hautes Energies L.M.P.H.E.URAC 12, Université Mohammed V, Faculté des Sciences, B.P. 1014 Rabat (Morocco); Benyoussef, A. [Laboratoire de Magnétisme et Physique des Hautes Energies L.M.P.H.E.URAC 12, Université Mohammed V, Faculté des Sciences, B.P. 1014 Rabat (Morocco); Institute of Nanomaterials and Nanotechnologies, MAScIR, Rabat (Morocco); Hassan II Academy of Science and Technology, Rabat (Morocco); Hamedoun, M. [Institute of Nanomaterials and Nanotechnologies, MAScIR, Rabat (Morocco)

    2016-03-01

    The magnetic behaviors of bilayer with spin-1 and 2 Ising model on the Bethe lattice are investigated using the Monte Carlo simulations. The thermal magnetizations, the magnetic susceptibilities and the transition temperature of the bilayer spin-1 and 2 on the Bethe lattice are studied for different values of crystal field and intralayer coupling constants of the two layers and interlayer coupling constant between the layers. The thermal and magnetic hysteresis cycles are given for different values of the crystal field, for different temperatures and for different exchange interactions. - Highlights: • The magnetic properties of bilayer on the Bethe lattice have been investigated. • The transition temperature has been deduced. • The magnetic coercive filed has been established.

  3. Two mechanisms of disorder-induced localization in photonic-crystal waveguides

    Science.gov (United States)

    García, P. D.; KiršanskÄ--, G.; Javadi, A.; Stobbe, S.; Lodahl, P.

    2017-10-01

    Unintentional but unavoidable fabrication imperfections in state-of-the-art photonic-crystal waveguides lead to the spontaneous formation of Anderson-localized modes thereby limiting slow-light propagation and its potential applications. On the other hand, disorder-induced cavities offer an approach to cavity-quantum electrodynamics and random lasing at the nanoscale. The key statistical parameter governing the disorder effects is the localization length, which together with the waveguide length determines the statistical transport of light through the waveguide. In a disordered photonic-crystal waveguide, the localization length is highly dispersive, and therefore, by controlling the underlying lattice parameters, it is possible to tune the localization of the mode. In the present work, we study the localization length in a disordered photonic-crystal waveguide using numerical simulations. We demonstrate two different localization regimes in the dispersion diagram where the localization length is linked to the density of states and the photon effective mass, respectively. The two different localization regimes are identified in experiments by recording the photoluminescence from quantum dots embedded in photonic-crystal waveguides.

  4. The spin-3/2 Ising model AFM/AFM two-layer lattice with crystal field

    International Nuclear Information System (INIS)

    Yigit, A.; Albayrak, E.

    2010-01-01

    The spin-3/2 Ising model is investigated for the case of antiferromagnetic (AFM/AFM) interactions on the two-layer Bethe lattice by using the exact recursion relations in a pairwise approach for given coordination numbers q=3, 4 and 6 when the layers are under the influences of equal external magnetic and equal crystal fields. The ground state (GS) phase diagrams are obtained on the different planes in detail and then the temperature dependent phase diagrams of the system are calculated accordingly. It is observed that the system presents both second- and first-order phase transitions for all q, therefore, tricritical points. It was also found that the system exhibits double-critical end points and isolated points. The model also presents two Neel temperatures, TN, and the existence of which leads to the reentrant behavior.

  5. Engineering the near-field imaging of a rectangular-lattice photonic-crystal slab in the second band

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Imaging properties of a two-dimensional rectangular-lattice photonic crystal (PC) slab consisting of air holes immersed in a dielectric are studied in this work. The field patterns of electromagnetic waves radiated from a point source through the PC slab are calculated with the finite-difference time-domain method. Comparing the field patterns with the corresponding equifrequency-surface contours simulated by the plane-wave expansion method, we find that an excellent-quality near-field image may be formed through the PC slab by the mechanisms of the simultaneous action of the self-collimation effect and the negative-refraction effect. Near-field imaging may be obtained within two different frequency regions in two vertical directions of the PC slab.

  6. Monte Carlo study of the double and super-exchange model with lattice distortion

    Energy Technology Data Exchange (ETDEWEB)

    Suarez, J R; Vallejo, E; Navarro, O [Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico, Apartado Postal 70-360, 04510 Mexico D. F. (Mexico); Avignon, M, E-mail: jrsuarez@iim.unam.m [Institut Neel, Centre National de la Recherche Scientifique (CNRS) and Universite Joseph Fourier, BP 166, 38042 Grenoble Cedex 9 (France)

    2009-05-01

    In this work a magneto-elastic phase transition was obtained in a linear chain due to the interplay between magnetism and lattice distortion in a double and super-exchange model. It is considered a linear chain consisting of localized classical spins interacting with itinerant electrons. Due to the double exchange interaction, localized spins tend to align ferromagnetically. This ferromagnetic tendency is expected to be frustrated by anti-ferromagnetic super-exchange interactions between neighbor localized spins. Additionally, lattice parameter is allowed to have small changes, which contributes harmonically to the energy of the system. Phase diagram is obtained as a function of the electron density and the super-exchange interaction using a Monte Carlo minimization. At low super-exchange interaction energy phase transition between electron-full ferromagnetic distorted and electron-empty anti-ferromagnetic undistorted phases occurs. In this case all electrons and lattice distortions were found within the ferromagnetic domain. For high super-exchange interaction energy, phase transition between two site distorted periodic arrangement of independent magnetic polarons ordered anti-ferromagnetically and the electron-empty anti-ferromagnetic undistorted phase was found. For this high interaction energy, Wigner crystallization, lattice distortion and charge distribution inside two-site polarons were obtained.

  7. Variable valence ion spectra in a crystal field

    International Nuclear Information System (INIS)

    Ghiordanescu, V.

    1979-01-01

    Using the Cadmium chloride as a host lattice, the optical spectra and RES of Mnsup(2+) were studied and the following results were obtained: a) By controlled dopings, the absorbtion and excitation spectra of ion Mnsup(2+) in CdCl 2 within the concentration range between 0.01 M and 25 M were plotted. Thus, the band structure for small concentrations was pointed out to differ from the structure observed for high concentrations. In the literature, this effect has not been observed on similar compounds, due to the small intensity values of the absorbtion spectra. b) Considering that for CdCl 2 :Mnsup(2+) 0.1 M, the optical spectra correspond to the isolated ion in the lattice, the energy levels were evaluated using electrostatic and spin-orbit terms in a perturbation calculation of the crystal field approximation. c) The calculation of parameter a which represents the effect of the cubic field in the spjn Hamiltonian of Mnsup(2+), is closer to the experjmental value -0.5.10 -4 cm -1 of the crystal field Dq and zeta parameters are used, respectively, parameters of the spin-orbit interaction obtained under b). d) The coupling effects of spins into more concentrated crystals with Mn 2+ are a function of temperature. The emjssion yield was given a quasi-cantitative evaluation in thjs paper as a function of temperature and concentratjon on the basis of which the isolated centers of Mn 2+ were found to display ectra whose intensity vary with temperature according to the Laporte forbidden transitions and spin rule theory, and the clusters including Mn 2+ - Mn 2+ pairs provide spectra whose intensity vary with the strength of the spin-spin coupling. (author)

  8. Spin and lattice structures of single-crystalline SrFe2As2

    Science.gov (United States)

    Zhao, Jun; Ratcliff, W., II; Lynn, J. W.; Chen, G. F.; Luo, J. L.; Wang, N. L.; Hu, Jiangping; Dai, Pengcheng

    2008-10-01

    We use neutron scattering to study the spin and lattice structure of single-crystal SrFe2As2 , the parent compound of the FeAs-based superconductor (Sr,K)Fe2As2 . We find that SrFe2As2 exhibits an abrupt structural phase transition at 220 K, where the structure changes from tetragonal with lattice parameters c>a=b to orthorhombic with c>a>b . At almost the same temperature, Fe spins develop a collinear antiferromagnetic structure along the orthorhombic a axis with spin direction parallel to this a axis. These results are consistent with earlier work on the RFeAsO ( R=rare earth) families of materials and on BaFe2As2 , and therefore suggest that static antiferromagnetic order is ubiquitous for the parent compounds of these FeAs-based high-transition temperature superconductors.

  9. Structural, spectroscopic and Thermal Studies of Potassium Di-hydrogen Citrate Crystal

    Directory of Open Access Journals (Sweden)

    N.D. Pandya

    2017-04-01

    Full Text Available Potassium dihydrogen citrate (KDC finds wide applications in food products. Pure potassium dihydrogen citrate crystal was grown by slow solvent evaporation technique at room temperature. Grown crystal exhibited needle like morphology. The powder XRD shows triclinic structure symmetry with lattice parameters a=11.820 Å, b=14.970 Å, c=9.442 Å with angles α = 91.60°, β = 93.35°, γ = 110°. The presence of various functional groups of grown crystal was confirmed by using FT-IR spectroscopy. The thermogram indicates the thermal stability of the sample up to 100oC and then decomposes slowly into oxide stage through two stages. The results are discussed here.

  10. Crystal Structure of Tetragonal Form of La2NiO4+x

    Science.gov (United States)

    Kajitani, Tsuyoshi; Hosoya, Syoichi; Hirabayashi, Makoto; Fukuda, Tsuguo; Onozuka, Takashi

    1989-10-01

    The crystal structure of the title oxide was studied by means of the X-ray and neutron single crystal diffraction measurements. At room temperature, the tetragonal crystal structure is P42/ncm-type (No. 138), which is one of the subgroup of the space group I4/mmm. The lattice parameters of a sample annealed and slowly cooled in oxygen atmosphere from 673 K are a{=}b{=}5.4640(1) Å and c{=}12.6719(2) Å, while the oxygen content, x{=}0.10(4), was determined from obtained neutron data. The title oxide undergoes a tetragonal (P42/ncm)/tetragonal (I4/mmm) phase transition at about 560 K. The transition temperature is almost identical both in the annealed and as-grown crystals.

  11. Design parameters of transmission curved crystal spectrometer for hard X-ray diagnoses

    International Nuclear Information System (INIS)

    Qian Feng; Cao Leifeng; Zhou Weimin; Zhao Zongqing; Gu Yuqiu; Yan Yonghong; Wei Lai; Xiao Shali

    2013-01-01

    The high resolving measurement of hard X-ray spectra generated in laser-produced plasma is usually performed using a cylindrically curved crystal spectrometer. In this paper, theoretical analysis and numerical simulation are performed to investigate the dependence of the energy range and resolving power on various design parameters, including crystal bending radius, source to crystal standoff distance, source size, location of the detector, etc. The investigation provides a means to design and develop cylindrically transmission curved crystal spectrometer which is used in hard X-ray diagnostics. The results show that crystal bending radius has a great influence on energy range of spectra and resolving power, and the separation between the spectral lines increases with the distance behind the focal circle faster than the line width, resulting in increased resolving power with distance. (authors)

  12. Creation of tunable absolute bandgaps in a two-dimensional anisotropic photonic crystal modulated by a nematic liquid crystal

    International Nuclear Information System (INIS)

    Liu Chenyang

    2008-01-01

    Photonic crystals (PCs) have many potential applications because of their ability to control light-wave propagation. We have investigated the tunable absolute bandgap in a two-dimensional anisotropic photonic crystal structures modulated by a nematic liquid crystal. The PC structure composed of an anisotropic-dielectric cylinder in the liquid crystal medium is studied by solving Maxwell's equations using the plane wave expansion method. The photonic band structures are found to exhibit absolute bandgaps for the square and triangular lattices. Numerical simulations show that the absolute bandgaps can be continuously tuned in the square and triangular lattices consisting of anisotropic-dielectric cylinders by infiltrating nematic liquid crystals. Such a mechanism of bandgap adjustment should open up a new application for designing components in photonic integrated circuits

  13. Lattice parameters and stability of the spinel compounds in relation to the ionic radii and electronegativities of constituting chemical elements.

    Science.gov (United States)

    Brik, Mikhail G; Suchocki, Andrzej; Kamińska, Agata

    2014-05-19

    A thorough consideration of the relation between the lattice parameters of 185 binary and ternary spinel compounds, on one side, and ionic radii and electronegativities of the constituting ions, on the other side, allowed for establishing a simple empirical model and finding its linear equation, which links together the above-mentioned quantities. The derived equation gives good agreement between the experimental and modeled values of the lattice parameters in the considered group of spinels, with an average relative error of about 1% only. The proposed model was improved further by separate consideration of several groups of spinels, depending on the nature of the anion (oxygen, sulfur, selenium/tellurium, nitrogen). The developed approach can be efficiently used for prediction of lattice constants for new isostructural materials. In particular, the lattice constants of new hypothetic spinels ZnRE2O4, CdRE2S4, CdRE2Se4 (RE = rare earth elements) are predicted in the present Article. In addition, the upper and lower limits for the variation of the ionic radii, electronegativities, and their certain combinations were established, which can be considered as stability criteria for the spinel compounds. The findings of the present Article offer a systematic overview of the structural properties of spinels and can serve as helpful guides for synthesis of new spinel compounds.

  14. GaAs, AlAs, and AlxGa1-xAs: Material parameters for use in research and device applications

    Science.gov (United States)

    Adachi, Sadao

    1985-08-01

    The AlxGa1-xAs/GaAs heterostructure system is potentially useful material for high-speed digital, high-frequency microwave, and electro-optic device applications. Even though the basic AlxGa1-xAs/GaAs heterostructure concepts are understood at this time, some practical device parameters in this system have been hampered by a lack of definite knowledge of many material parameters. Recently, Blakemore has presented numerical and graphical information about many of the physical and electronic properties of GaAs [J. S. Blakemore, J. Appl. Phys. 53, R123 (1982)]. The purpose of this review is (i) to obtain and clarify all the various material parameters of AlxGa1-xAs alloy from a systematic point of view, and (ii) to present key properties of the material parameters for a variety of research works and device applications. A complete set of material parameters are considered in this review for GaAs, AlAs, and AlxGa1-xAs alloys. The model used is based on an interpolation scheme and, therefore, necessitates known values of the parameters for the related binaries (GaAs and AlAs). The material parameters and properties considered in the present review can be classified into sixteen groups: (1) lattice constant and crystal density, (2) melting point, (3) thermal expansion coefficient, (4) lattice dynamic properties, (5) lattice thermal properties, (6) electronic-band structure, (7) external perturbation effects on the band-gap energy, (8) effective mass, (9) deformation potential, (10) static and high-frequency dielectric constants, (11) magnetic susceptibility, (12) piezoelectric constant, (13) Fröhlich coupling parameter, (14) electron transport properties, (15) optical properties, and (16) photoelastic properties. Of particular interest is the deviation of material parameters from linearity with respect to the AlAs mole fraction x. Some material parameters, such as lattice constant, crystal density, thermal expansion coefficient, dielectric constant, and elastic constant

  15. Static magnetic susceptibility, crystal field and exchange interactions in rare earth titanate pyrochlores.

    Science.gov (United States)

    Malkin, B Z; Lummen, T T A; van Loosdrecht, P H M; Dhalenne, G; Zakirov, A R

    2010-07-14

    The experimental temperature dependence (T = 2-300 K) of single crystal bulk and site susceptibilities of rare earth titanate pyrochlores R(2)Ti(2)O(7) (R = Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb) is analyzed in the framework of crystal field theory and a mean field approximation. Analytical expressions for the site and bulk susceptibilities of the pyrochlore lattice are derived taking into account long range dipole-dipole interactions and anisotropic exchange interactions between the nearest neighbor rare earth ions. The sets of crystal field parameters and anisotropic exchange coupling constants have been determined and their variations along the lanthanide series are discussed.

  16. 3D DNA Origami Crystals.

    Science.gov (United States)

    Zhang, Tao; Hartl, Caroline; Frank, Kilian; Heuer-Jungemann, Amelie; Fischer, Stefan; Nickels, Philipp C; Nickel, Bert; Liedl, Tim

    2018-05-18

    3D crystals assembled entirely from DNA provide a route to design materials on a molecular level and to arrange guest particles in predefined lattices. This requires design schemes that provide high rigidity and sufficiently large open guest space. A DNA-origami-based "tensegrity triangle" structure that assembles into a 3D rhombohedral crystalline lattice with an open structure in which 90% of the volume is empty space is presented here. Site-specific placement of gold nanoparticles within the lattice demonstrates that these crystals are spacious enough to efficiently host 20 nm particles in a cavity size of 1.83 × 10 5 nm 3 , which would also suffice to accommodate ribosome-sized macromolecules. The accurate assembly of the DNA origami lattice itself, as well as the precise incorporation of gold particles, is validated by electron microscopy and small-angle X-ray scattering experiments. The results show that it is possible to create DNA building blocks that assemble into lattices with customized geometry. Site-specific hosting of nano objects in the optically transparent DNA lattice sets the stage for metamaterial and structural biology applications. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Na2TiGeO5: Crystal structure stability at low temperature and high pressure

    DEFF Research Database (Denmark)

    Waskowska, A.; Gerward, Leif; Olsen, J.S.

    2008-01-01

    The temperature evolution of the lattice parameters measured from 295 to 125 K exhibits a small instability below T-c approximate to 278 K, indicating ferroelastic properties of Na2TiGeO5. The behavior is related to the specific crystal structure built of polyhedral layers with shared TiO5 pyrami...

  18. LATTICE/hor ellipsis/a beam transport program

    International Nuclear Information System (INIS)

    Staples, J.

    1987-06-01

    LATTICE is a computer program that calculates the first order characteristics of synchrotrons and beam transport systems. The program uses matrix algebra to calculate the propagation of the betatron (Twiss) parameters along a beam line. The program draws on ideas from several older programs, notably Transport and Synch, adds many new ones and incorporates them into an interactive, user-friendly program. LATTICE will calculate the matched functions of a synchrotron lattice and display them in a number of ways, including a high resolution Tektronix graphics display. An optimizer is included to adjust selected element parameters so the beam meets a set of constraints. LATTICE is a first order program, but the effect of sextupoles on the chromaticity of a synchrotron lattice is included, and the optimizer will set the sextupole strengths for zero chromaticity. The program will also calculate the characteristics of beam transport systems. In this mode, the beam parameters, defined at the start of the transport line, are propagated through to the end. LATTICE has two distinct modes: the lattice mode which finds the matched functions of a synchrotron, and the transport mode which propagates a predefined beam through a beam line. However, each mode can be used for either type of problem: the transport mode may be used to calculate an insertion for a synchrotron lattice, and the lattice mode may be used to calculate the characteristics of a long periodic beam transport system

  19. Introduction to Louis Michel's lattice geometry through group action

    CERN Document Server

    Zhilinskii, Boris

    2015-01-01

    Group action analysis developed and applied mainly by Louis Michel to the study of N-dimensional periodic lattices is the central subject of the book. Different basic mathematical tools currently used for the description of lattice geometry are introduced and illustrated through applications to crystal structures in two- and three-dimensional space, to abstract multi-dimensional lattices and to lattices associated with integrable dynamical systems. Starting from general Delone sets the authors turn to different symmetry and topological classifications including explicit construction of orbifolds for two- and three-dimensional point and space groups. Voronoï and Delone cells together with positive quadratic forms and lattice description by root systems are introduced to demonstrate alternative approaches to lattice geometry study. Zonotopes and zonohedral families of 2-, 3-, 4-, 5-dimensional lattices are explicitly visualized using graph theory approach. Along with crystallographic applications, qualitative ...

  20. Ultratight crystal packing of a 10 kDa protein

    Energy Technology Data Exchange (ETDEWEB)

    Trillo-Muyo, Sergio [Molecular Biology Institute of Barcelona, Spanish Research Council CSIC, Barcelona Science Park, c/Baldiri Reixac 15-21, 08028 Barcelona (Spain); Jasilionis, Andrius [Vilnius University, M. K. Čiurlionio 21/27, 03101 Vilnius (Lithuania); Domagalski, Marcin J. [University of Virginia, 1340 Jefferson Park Avenue, Charlottesville, VA 22908-0736 (United States); Chruszcz, Maksymilian [University of South Carolina, 631 Sumter Street, Columbia, SC 29208 (United States); Minor, Wladek [University of Virginia, 1340 Jefferson Park Avenue, Charlottesville, VA 22908-0736 (United States); Kuisiene, Nomeda [Vilnius University, M. K. Čiurlionio 21/27, 03101 Vilnius (Lithuania); Arolas, Joan L.; Solà, Maria; Gomis-Rüth, F. Xavier, E-mail: xgrcri@ibmb.csic.es [Molecular Biology Institute of Barcelona, Spanish Research Council CSIC, Barcelona Science Park, c/Baldiri Reixac 15-21, 08028 Barcelona (Spain)

    2013-03-01

    The crystal structure of the C-terminal domain of a putative U32 peptidase from G. thermoleovorans is reported; it is one of the most tightly packed protein structures reported to date. While small organic molecules generally crystallize forming tightly packed lattices with little solvent content, proteins form air-sensitive high-solvent-content crystals. Here, the crystallization and full structure analysis of a novel recombinant 10 kDa protein corresponding to the C-terminal domain of a putative U32 peptidase are reported. The orthorhombic crystal contained only 24.5% solvent and is therefore among the most tightly packed protein lattices ever reported.

  1. Magnetic properties of checkerboard lattice: a Monte Carlo study

    Science.gov (United States)

    Jabar, A.; Masrour, R.; Hamedoun, M.; Benyoussef, A.

    2017-12-01

    The magnetic properties of ferrimagnetic mixed-spin Ising model in the checkerboard lattice are studied using Monte Carlo simulations. The variation of total magnetization and magnetic susceptibility with the crystal field has been established. We have obtained a transition from an order to a disordered phase in some critical value of the physical variables. The reduced transition temperature is obtained for different exchange interactions. The magnetic hysteresis cycles have been established. The multiples hysteresis cycle in checkerboard lattice are obtained. The multiples hysteresis cycle have been established. The ferrimagnetic mixed-spin Ising model in checkerboard lattice is very interesting from the experimental point of view. The mixed spins system have many technological applications such as in domain opto-electronics, memory, nanomedicine and nano-biological systems. The obtained results show that that crystal field induce long-range spin-spin correlations even bellow the reduced transition temperature.

  2. Crystal-field investigations of rare-earth-doped wide band gap semiconductors

    CERN Multimedia

    Muller, S; Wahl, U

    Crystal field investigations play a central role in the studies of rare earth doped semiconductors. Optical stark level spectroscopy and lattice location studies of radioactive rare earth isotopes implanted at ISOLDE have provided important insight into these systems during the last years. It has been shown that despite a major site preference of the probe atoms in the lattice, several defect configurations do exist. These sites are visible in the optical spectra but their origin and nature aren't deducible from these spectra alone. Hyperfine measurements on the other hand should reveal these defect configurations and yield the parameters necessary for a description of the optical properties at the atomic scale. In order to study the crystal field with this alternative approach, we propose a new concept for perturbed $\\gamma\\gamma$-angular correlation (PAC) experiments at ISOLDE based on digital signal processing in contrast to earlier analog setups. The general functionality of the spectrometer is explained ...

  3. Trace element distribution in geological crystals

    Energy Technology Data Exchange (ETDEWEB)

    Den Besten, J.L.; Jamieson, D.N.; Weiser, P.S. [Melbourne Univ., Parkville, VIC (Australia). School of Physics

    1996-12-31

    Channelling is a useful microprobe technique for determining the structure of crystals, but until now has not been performed on geological crystals. The composition has been investigated rather than the structure, which can further explain the origin of the crystal and provide useful information on the substitutionality of trace elements. This may then lead to applications of extraction of valuable metals and semiconductor electronics. Natural crystals of pyrite, FeS{sub 2}, which contains a substantial concentration of gold were channeled and examined to identify the channel axis orientation. Rutherford Backscattering (RBS) and Particle Induced X-Ray Emission (PIXE) spectra using MeV ions were obtained in the experiment to provide a comparison of lattice and non-lattice trace elements. 3 figs.

  4. Trace element distribution in geological crystals

    Energy Technology Data Exchange (ETDEWEB)

    Den Besten, J L; Jamieson, D N; Weiser, P S [Melbourne Univ., Parkville, VIC (Australia). School of Physics

    1997-12-31

    Channelling is a useful microprobe technique for determining the structure of crystals, but until now has not been performed on geological crystals. The composition has been investigated rather than the structure, which can further explain the origin of the crystal and provide useful information on the substitutionality of trace elements. This may then lead to applications of extraction of valuable metals and semiconductor electronics. Natural crystals of pyrite, FeS{sub 2}, which contains a substantial concentration of gold were channeled and examined to identify the channel axis orientation. Rutherford Backscattering (RBS) and Particle Induced X-Ray Emission (PIXE) spectra using MeV ions were obtained in the experiment to provide a comparison of lattice and non-lattice trace elements. 3 figs.

  5. High resolution electron microscopy. Visualization of crystal lattices and of their defects

    International Nuclear Information System (INIS)

    Desseaux, J.

    1981-10-01

    A great number of fault characterization results may be obtained without calculations simply by observing the pictures: determination of Burgers' vector of dislocations, dissociation of the dislocations, presence of precipitates in the heart of the dislocations, presence of micro-twin-crystals, phase boundaries, etc. Determining the position of the atoms will be facilitated if the phase system approximation can be applied. In those cases where it is necessary to use the calculated image-experimental image comparison, it is fundamental to check the parameters on which the image depends. For the simplicity of the interpretation it is always necessary to obtain images taken in conditions where the structure is the most directly projected and where the image contrast is as stable as possible for a small variation in the parameters: thickness, focusing and crystalline parameters. A few examples are given on silicon [fr

  6. Lidar inelastic multiple-scattering parameters of cirrus particle ensembles determined with geometrical-optics crystal phase functions.

    Science.gov (United States)

    Reichardt, J; Hess, M; Macke, A

    2000-04-20

    Multiple-scattering correction factors for cirrus particle extinction coefficients measured with Raman and high spectral resolution lidars are calculated with a radiative-transfer model. Cirrus particle-ensemble phase functions are computed from single-crystal phase functions derived in a geometrical-optics approximation. Seven crystal types are considered. In cirrus clouds with height-independent particle extinction coefficients the general pattern of the multiple-scattering parameters has a steep onset at cloud base with values of 0.5-0.7 followed by a gradual and monotonic decrease to 0.1-0.2 at cloud top. The larger the scattering particles are, the more gradual is the rate of decrease. Multiple-scattering parameters of complex crystals and of imperfect hexagonal columns and plates can be well approximated by those of projected-area equivalent ice spheres, whereas perfect hexagonal crystals show values as much as 70% higher than those of spheres. The dependencies of the multiple-scattering parameters on cirrus particle spectrum, base height, and geometric depth and on the lidar parameters laser wavelength and receiver field of view, are discussed, and a set of multiple-scattering parameter profiles for the correction of extinction measurements in homogeneous cirrus is provided.

  7. Optimizing solubility and permeability of a biopharmaceutics classification system (BCS) class 4 antibiotic drug using lipophilic fragments disturbing the crystal lattice.

    Science.gov (United States)

    Tehler, Ulrika; Fagerberg, Jonas H; Svensson, Richard; Larhed, Mats; Artursson, Per; Bergström, Christel A S

    2013-03-28

    Esterification was used to simultaneously increase solubility and permeability of ciprofloxacin, a biopharmaceutics classification system (BCS) class 4 drug (low solubility/low permeability) with solid-state limited solubility. Molecular flexibility was increased to disturb the crystal lattice, lower the melting point, and thereby improve the solubility, whereas lipophilicity was increased to enhance the intestinal permeability. These structural changes resulted in BCS class 1 analogues (high solubility/high permeability) emphasizing that simple medicinal chemistry may improve both these properties.

  8. Multi-parameter variational calculations for the (2+1)-dimensional U(1) lattice gauge theory and the XY model

    International Nuclear Information System (INIS)

    Heys, D.W.; Stump, D.R.

    1987-01-01

    Variational calculations are described that use multi-parameter trial wave functions for the U(1) lattice gauge theory in two space dimensions, and for the XY model. The trial functions are constructed as the exponential of a linear combination of states from the strong-coupling basis of the model, with the coefficients treated as variational parameters. The expectation of the hamiltonian is computed by the Monte Carlo method, using a reweighting technique to evaluate expectation values in finite patches of the parameter space. The trial function for the U(1) gauge theory involves six variational parameters, and its weak-coupling behaviour is in reasonable agreement with theoretical expectations. (orig.)

  9. Validation of CENDL and JEFF evaluated nuclear data files for TRIGA calculations through the analysis of integral parameters of TRX and BAPL benchmark lattices of thermal reactors

    International Nuclear Information System (INIS)

    Uddin, M.N.; Sarker, M.M.; Khan, M.J.H.; Islam, S.M.A.

    2009-01-01

    The aim of this paper is to present the validation of evaluated nuclear data files CENDL-2.2 and JEFF-3.1.1 through the analysis of the integral parameters of TRX and BAPL benchmark lattices of thermal reactors for neutronics analysis of TRIGA Mark-II Research Reactor at AERE, Bangladesh. In this process, the 69-group cross-section library for lattice code WIMS was generated using the basic evaluated nuclear data files CENDL-2.2 and JEFF-3.1.1 with the help of nuclear data processing code NJOY99.0. Integral measurements on the thermal reactor lattices TRX-1, TRX-2, BAPL-UO 2 -1, BAPL-UO 2 -2 and BAPL-UO 2 -3 served as standard benchmarks for testing nuclear data files and have also been selected for this analysis. The integral parameters of the said lattices were calculated using the lattice transport code WIMSD-5B based on the generated 69-group cross-section library. The calculated integral parameters were compared to the measured values as well as the results of Monte Carlo Code MCNP. It was found that in most cases, the values of integral parameters show a good agreement with the experiment and MCNP results. Besides, the group constants in WIMS format for the isotopes U-235 and U-238 between two data files have been compared using WIMS library utility code WILLIE and it was found that the group constants are identical with very insignificant difference. Therefore, this analysis reflects the validation of evaluated nuclear data files CENDL-2.2 and JEFF-3.1.1 through benchmarking the integral parameters of TRX and BAPL lattices and can also be essential to implement further neutronic analysis of TRIGA Mark-II research reactor at AERE, Dhaka, Bangladesh.

  10. Optics of globular photonic crystals

    International Nuclear Information System (INIS)

    Gorelik, V S

    2007-01-01

    The results of experimental and theoretical studies of the optical properties of globular photonic crystals - new physical objects having a crystal structure with the lattice period exceeding considerably the atomic size, are presented. As globular photonic crystals, artificial opal matrices consisting of close-packed silica globules of diameter ∼200 nm were used. The reflection spectra of these objects characterising the parameters of photonic bands existing in these crystals in the visible spectral region are presented. The idealised models of the energy band structure of photonic crystals investigated in the review give analytic dispersion dependences for the group velocity and the effective photon mass in a globular photonic crystal. The characteristics of secondary emission excited in globular photonic crystals by monochromatic and broadband radiation are presented. The results of investigations of single-photon-excited delayed scattering of light observed in globular photonic crystals exposed to cw UV radiation and radiation from a repetitively pulsed copper vapour laser are presented. The possibilities of using globular photonic crystals as active media for lasing in different spectral regions are considered. It is proposed to use globular photonic crystals as sensitive sensors in optoelectronic devices for molecular analysis of organic and inorganic materials by the modern methods of laser spectroscopy. The results of experimental studies of spontaneous and stimulated globular scattering of light are discussed. The conditions for observing resonance and two-photon-excited delayed scattering of light are found. The possibility of accumulation and localisation of the laser radiation energy inside a globular photonic crystal is reported. (review)

  11. Studying The Effect of Various Parameters on The Characteristics of The Dielectric and Metallic Photonic Crystals

    International Nuclear Information System (INIS)

    Ismail, M.; Badawy, Z.M.; Abdel-Rahman, E.

    2015-01-01

    Transmittance characteristics of two types of photonic crystals have been analysed using the transfer matrix method. The first one is the dielectric photonic crystal (DPC), and the second is the metallic photonic crystal (MPC). The effect of the most parameters on the transmission spectra of the dielectric and metallic photonic crystals has been studied

  12. Construction of Capacity Achieving Lattice Gaussian Codes

    KAUST Repository

    Alghamdi, Wael

    2016-04-01

    We propose a new approach to proving results regarding channel coding schemes based on construction-A lattices for the Additive White Gaussian Noise (AWGN) channel that yields new characterizations of the code construction parameters, i.e., the primes and dimensions of the codes, as functions of the block-length. The approach we take introduces an averaging argument that explicitly involves the considered parameters. This averaging argument is applied to a generalized Loeliger ensemble [1] to provide a more practical proof of the existence of AWGN-good lattices, and to characterize suitable parameters for the lattice Gaussian coding scheme proposed by Ling and Belfiore [3].

  13. Thermal evolution of the crystal structure of the orthorhombic perovskite LaFeO3

    International Nuclear Information System (INIS)

    Dixon, Charlotte A.L.; Kavanagh, Christopher M.; Knight, Kevin S.; Kockelmann, Winfried; Morrison, Finlay D.; Lightfoot, Philip

    2015-01-01

    The thermal evolution of the crystal structure of the prototypical orthorhombic perovskite LaFeO 3 has been studied in detail by powder neutron diffraction in the temperature range 25lattice metrics in the perovskite LaFeO 3 is rationalized from a detailed powder neutron diffraction study. - Highlights: • Crystal structure of the perovskite LaFeO 3 studied in detail by powder neutron diffraction. • Unusual thermal evolution of lattice metrics rationalized. • Contrasting behavior to Bi-doped LaFeO 3 . • Octahedral distortion/tilt parameters explain unusual a and c lattice parameter behavior

  14. Making sense of nanocrystal lattice fringes

    International Nuclear Information System (INIS)

    Fraundorf, P.; Qin Wentao; Moeck, Peter; Mandell, Eric

    2005-01-01

    The orientation dependence of thin-crystal lattice fringes can be gracefully quantified using fringe-visibility maps, a direct-space analog of Kikuchi maps [Nishikawa and Kikuchi, Nature (London) 121, 1019 (1928)]. As in navigation of reciprocal space with the aid of Kikuchi lines, fringe-visibility maps facilitate acquisition of crystallographic information from lattice images. In particular, these maps can help researchers to determine the three-dimensional lattice of individual nanocrystals, to 'fringe-fingerprint' collections of randomly oriented particles, and to measure local specimen thickness with only a modest tilt. Since the number of fringes in an image increases with maximum spatial-frequency squared, these strategies (with help from more precise goniometers) will be more useful as aberration correction moves resolutions into the subangstrom range

  15. Lattice dynamics of fcc helium at high pressure

    International Nuclear Information System (INIS)

    Eckert, J.; Thomlinson, W.; Shirane, G.

    1977-01-01

    The neutron-inelastic-scattering technique was used to measure the phonon dispersion relations in a high-density crystal of fcc He at 38 K. The crystal was grown at a pressure of 4.93 kbar and a temperature of 38.5 K in a high-pressure sample holder. Its lattice parameter was determined to be 3.915 +- 0.002 A, equivalent to a molar volume of 9.03 cm 3 /mol. The measured dispersion curves were found to be in good agreement with a recent calculation by Goldman using the first-order self-consistent phonon theory without short-range correlation functions. The strong anharmonic effects observed in earlier measurements on the crystals of 21 cm 3 /mol were found to be much less prominent in this He crystal. The magnitude of the multiphonon interference effects on the one-phonon intensities is shown to be less than half of that observed in the low-density crystals. Thermodynamic analysis of the data yielded THETA/sup M//sub D/ = 154 K which indicates that the ratio of mean amplitude of vibration to the nearest-neighbor distance is 8.6%, as opposed to nearly 30% for the lowest-density He crystals. The dependence of the phonon energies on volume is discussed with reference to the earlier work of Traylor et al. on an fcc crystal at 11.7 cm 3 /mol. Limited measurements were also made at 22 K to determine the temperature dependence of the phonon energies. Unusually large isochoric temperature shifts of as much as 15% for some phonons close to the zone center were found over the range of 22--38 K

  16. Molecular morphology and crystallization in the quantum limit

    DEFF Research Database (Denmark)

    Bohr, Jakob

    2002-01-01

    The effects of phonons on crystallization and crystal morphology are investigated. It is shown that the commensuration of the lattice vibrations with the lattice will favor certain crystal morphologies. Vibrational effects can also be important for the molecular structure of chain molecules...... protein are estimated to differ by several electron volts. For a biomolecule, such energy is significant and may contribute to cold denaturing as seen for proteins. This is consistent with the empirical observation that cold denaturation is exothermic and hot denaturation endothermic....

  17. Hamiltonian approach to the lattice massive Schwinger model

    International Nuclear Information System (INIS)

    Sidorov, A.V.; Zastavenko, L.G.

    1996-01-01

    The authors consider the limit e 2 /m 2 much-lt 1 of the lattice massive Schwinger model, i.e., the lattice massive QED in two space-time dimensions, up to lowest order in the effective coupling constant e 2 /m 2 . Here, m is the fermion mass parameter and e is the electron charge. They compare their lattice QED model with the analogous continuous space and lattice space models, (CSM and LSM), which do not take account of the zero momentum mode, z.m.m., of the vector potential. The difference is that (due to extra z.m.m. degree of freedom) to every eigenstate of the CSM and LSM there corresponds a family of eigenstates of the authors lattice QED with the parameter λ. They restrict their consideration to small values of the parameter λ. Then, the energies of the particle states of their lattice QED and LSM do coincide (in their approximation). In the infinite periodicity length limit the Hamiltonian of the authors lattice QED (as well as the Hamiltonian of the LSM) possesses two different Hilbert spaces of eigenfunctions. Thus, in this limit the authors lattice QED model (as well as LSM) describes something like two connected, but different, worlds

  18. Structural elucidation and physicochemical properties of an organic NLO crystal: 4-Nitrotoluene-2-sulphonic acid dihydrate

    Science.gov (United States)

    Sangeetha, K.; Guru Prasad, L.; Mathammal, R.

    2018-03-01

    4-nitrotoluene-2-sulphonic acid dihydrate single crystals have been developed using slow evaporation technique in methanol. Lattice parameters of the NTSAD crystal have been calculated and it confirms the grown material. The intermolecular interactions are studied from the 3D Hirshfeld surface analysis and 2D fingerprint plots. The NMR spectral analysis has been carried out to confirm the molecular structure of the grown material. Optical properties have been obtained from UV-VIS spectral analysis and photoluminescence studies. Frequency conversion property of the NTSAD crystal was investigated with the aid of Kurtz and Perry method.

  19. Theoretical calculations of spin-Hamiltonian parameters for the rhombic-like Mo5+ centers in KTiOPO4 crystal

    International Nuclear Information System (INIS)

    Yang, Mei; Wen-Chen, Zheng; Hong-Gang, Liu

    2013-01-01

    The spin-Hamiltonian parameters (g factors g i and hyperfine structure constants A i , were i=x, y and z) for Mo 5+ ion occupying the Ti(1) site with approximately rhombic symmetry in KTiOPO 4 crystal are calculated from the high-order perturbation formulas based on the two-mechanism model. In the model, not only the contribution due to the conventional crystal-field (CF) mechanism, but also those due to the charge-transfer (CT) mechanism are included. The six calculated spin-Hamiltonian parameters with four adjustable parameters are in reasonable agreement with the experimental values. The calculations show that for more accurate calculations of spin-Hamiltonian parameters of the high valence d n ions (e.g., Mo 5+ considered here) in crystals, the contribution from CT mechanism, which is ignored in the conventional crystal field theory, should be taken into account. The reasonable crystal field energy levels of Mo 5+ in KTiOPO 4 are also predicted from calculations

  20. Crystal structure of the new ternary thorium indide Th{sub 4}Pd{sub 10}In{sub 21}

    Energy Technology Data Exchange (ETDEWEB)

    Hlukhyy, V.; Zaremba, V.; Stepien-Damm, J.; Troc, R

    2003-03-24

    The structure of Th{sub 4}Pd{sub 10}In{sub 21} was refined from single crystal X-ray diffraction data. The compound crystallizes in the monoclinic system, space group C2/m, mC70; with lattice parameters a=23.024(5) A, b=4.512(1) A, c=17.224(3) A, {beta}=124.57(3) deg. The crystal structure was refined using the SHELXL-97 program (R{sub 1}=0.0477, 2561 F{sup 2} values for 108 variables). This compound adopts the Ho{sub 4}Ni{sub 10}Ga{sub 21}-type structure. The crystal chemistry and relationships of this phase to other ones are briefly discussed.

  1. Entropy-driven crystal formation on highly strained substrates

    KAUST Repository

    Savage, John R.

    2013-05-20

    In heteroepitaxy, lattice mismatch between the deposited material and the underlying surface strongly affects nucleation and growth processes. The effect of mismatch is well studied in atoms with growth kinetics typically dominated by bond formation with interaction lengths on the order of one lattice spacing. In contrast, less is understood about how mismatch affects crystallization of larger particles, such as globular proteins and nanoparticles, where interparticle interaction energies are often comparable to thermal fluctuations and are short ranged, extending only a fraction of the particle size. Here, using colloidal experiments and simulations, we find particles with short-range attractive interactions form crystals on isotropically strained lattices with spacings significantly larger than the interaction length scale. By measuring the free-energy cost of dimer formation on monolayers of increasing uniaxial strain, we show the underlying mismatched substrate mediates an entropy-driven attractive interaction extending well beyond the interaction length scale. Remarkably, because this interaction arises from thermal fluctuations, lowering temperature causes such substrate-mediated attractive crystals to dissolve. Such counterintuitive results underscore the crucial role of entropy in heteroepitaxy in this technologically important regime. Ultimately, this entropic component of lattice mismatched crystal growth could be used to develop unique methods for heterogeneous nucleation and growth of single crystals for applications ranging from protein crystallization to controlling the assembly of nanoparticles into ordered, functional superstructures. In particular, the construction of substrates with spatially modulated strain profiles would exploit this effect to direct self-assembly, whereby nucleation sites and resulting crystal morphology can be controlled directly through modifications of the substrate.

  2. High-resolution mapping of two-dimensional lattice distortions in ion-implanted crystals from X-ray diffractometry data

    International Nuclear Information System (INIS)

    Nikulin, A.Y.; Gureyev, T.E.; Stevenson, A.W.; Wilkins, S.W.; Hashizume, H.; Cookson, D.

    1996-01-01

    The triple-crystal synchrotron X-ray diffractometry data described in Nikulin, Stevenson, Hashizume, Wilkins, Foran, Cookson and Garrett (J. Appl. Cryst. 28, 57-60 (1995)) has been analyzed to map out two-dimensional (2D) lattice distortions in silicon (111) crystals implanted with B + ions of 100 keV energy through a periodic SiO 2 strip pattern. The lateral periodic structure produced a series of satellite reflections associated with the 111 Bragg peak. The 2D reconstruction incorporates the use of the Petrashen-Chukhovskii method, which retrieves the phases of the Bragg waves for these satellite reflections, together with that for the fundamental. The finite Fourier series is then synthesized with the relative phases determined. Localized distortions perpendicular to the surface arising from deposited B + ions in near-surface layers of the crystal are clearly displayed with spatial resolutions of 0.016 and 0.265 μm in the depth and lateral directions respectively. For a sample with the oxide layer removed from the surface, two equally plausible strain maps have been obtained by assigning relative phases to eleven satellites using a sequential trial method and a minimum-energy method. Failed map reconstructions for the oxide-covered sample are discussed in terms of the non-unique solutions of the Petrashen-Chukhovskii phase-recovery algorithm and the ambiguous phases determined for the satellites. 16 refs., 8 figs

  3. Structural Characterization of Doped GaSb Single Crystals by X-ray Topography

    Energy Technology Data Exchange (ETDEWEB)

    Honnicke, M.G.; Mazzaro, I.; Manica, J.; Benine, E.; M da Costa, E.; Dedavid, B. A.; Cusatis, C.; Huang, X. R.

    2009-09-13

    We characterized GaSb single crystals containing different dopants (Al, Cd and Te), grown by the Czochralski method, by x-ray topography and high angular resolution x-ray diffraction. Lang topography revealed dislocations parallel and perpendicular to the crystal's surface. Double-crystal GaSb 333 x-ray topography shows dislocations and vertical stripes than can be associated with circular growth bands. We compared our high-angular resolution x-ray diffraction measurements (rocking curves) with the findings predicted by the dynamical theory of x-ray diffraction. These measurements show that our GaSb single crystals have a relative variation in the lattice parameter ({Delta}d/d) on the order of 10{sup -5}. This means that they can be used as electronic devices (detectors, for example) and as x-ray monochromators.

  4. Three-dimensional function photonic crystals

    Science.gov (United States)

    Zhang, Hai-Feng

    2017-11-01

    In this paper, the properties of the photonic band gaps (PBGs) of three-dimensional (3D) function photonic crystals (PCs) are theoretically investigated by a modified plane wave expansion (PWE) method, whose equations for computations are deduced. The configuration of 3D function PCs is the dielectric spheres inserted in the air background with simple-cubic (SC) lattices whose dielectric constants are the functions of space coordinates, which can be realized by the electro-optical or optical Kerr effect in the practice. The influences of the parameter for 3D function PCs on the PBGs also are discussed. The calculated results show that the bandwidths and number of PBGs can be tuned with different distributions of function dielectrics. Compared with the conventional 3D dielectric PCs with SC lattices, the larger and more PBGs can be obtained in the 3D function PCs. Those results provide a new way to design the novel practical devices.

  5. KBr-Li Br and KBr-LiBr doped with Ti mixed single crystal by Czochralski method and glow curve studies

    International Nuclear Information System (INIS)

    Faripour, H.; Faripour, N.

    2003-01-01

    Mixed-single Crystals: pure KBr-LiBr and KBr-LiBr with Ti dopant were grown by Czochralski method. Because of difference between lattice parameters of KBr and LiBr, the growth speed of crystals were relatively low, and they were annealed in a special temperature condition providing some cleavages. They were exposed by β radiation and the glow curve was analysed for each crystal. Analysing of glow curve, showed that Ti impurity has been the curves of main peak curve appearance temperature decreasing

  6. Kinetic models for irreversible processes on a lattice

    Energy Technology Data Exchange (ETDEWEB)

    Wolf, N.O.

    1979-04-01

    The development and application of kinetic lattice models are considered. For the most part, the discussions are restricted to lattices in one-dimension. In Chapter 1, a brief overview of kinetic lattice model formalisms and an extensive literature survey are presented. A review of the kinetic models for non-cooperative lattice events is presented in Chapter 2. The development of cooperative lattice models and solution of the resulting kinetic equations for an infinite and a semi-infinite lattice are thoroughly discussed in Chapters 3 and 4. The cooperative models are then applied to the problem of theoretically dtermining the sticking coefficient for molecular chemisorption in Chapter 5. In Chapter 6, other possible applications of these models and several model generalizations are considered. Finally, in Chapter 7, an experimental study directed toward elucidating the mechanistic factors influencing the chemisorption of methane on single crystal tungsten is reported. In this it differs from the rest of the thesis which deals with the statistical distributions resulting from a given mechanism.

  7. DFT-Assisted Polymorph Identification from Lattice Raman Fingerprinting.

    Science.gov (United States)

    Bedoya-Martínez, Natalia; Schrode, Benedikt; Jones, Andrew O F; Salzillo, Tommaso; Ruzié, Christian; Demitri, Nicola; Geerts, Yves H; Venuti, Elisabetta; Della Valle, Raffaele Guido; Zojer, Egbert; Resel, Roland

    2017-08-03

    A combined experimental and theoretical approach, consisting of lattice phonon Raman spectroscopy and density functional theory (DFT) calculations, is proposed as a tool for lattice dynamics characterization and polymorph phase identification. To illustrate the reliability of the method, the lattice phonon Raman spectra of two polymorphs of the molecule 2,7-dioctyloxy[1]benzothieno[3,2-b]benzothiophene are investigated. We show that DFT calculations of the lattice vibrations based on the known crystal structures, including many-body dispersion van der Waals (MBD-vdW) corrections, predict experimental data within an accuracy of ≪5 cm -1 (≪0.6 meV). Due to the high accuracy of the simulations, they can be used to unambiguously identify different polymorphs and to characterize the nature of the lattice vibrations and their relationship to the structural properties. More generally, this work implies that DFT-MBD-vdW is a promising method to describe also other physical properties that depend on lattice dynamics like charge transport.

  8. Kinetic models for irreversible processes on a lattice

    International Nuclear Information System (INIS)

    Wolf, N.O.

    1979-04-01

    The development and application of kinetic lattice models are considered. For the most part, the discussions are restricted to lattices in one-dimension. In Chapter 1, a brief overview of kinetic lattice model formalisms and an extensive literature survey are presented. A review of the kinetic models for non-cooperative lattice events is presented in Chapter 2. The development of cooperative lattice models and solution of the resulting kinetic equations for an infinite and a semi-infinite lattice are thoroughly discussed in Chapters 3 and 4. The cooperative models are then applied to the problem of theoretically dtermining the sticking coefficient for molecular chemisorption in Chapter 5. In Chapter 6, other possible applications of these models and several model generalizations are considered. Finally, in Chapter 7, an experimental study directed toward elucidating the mechanistic factors influencing the chemisorption of methane on single crystal tungsten is reported. In this it differs from the rest of the thesis which deals with the statistical distributions resulting from a given mechanism

  9. radiation and electric field induced effects on the order-disorder phase in lithium sodium sulphate crystals

    Science.gov (United States)

    Hamed, A. E.; Kassem, M. E.; El-Wahidy, E. F.; El-Abshehy, M. A.

    1995-03-01

    The temperature dependence of specific heat at constant pressure, Cp(T), has been measured for lithium sodium sulphate, LiNaSo4 crystals, at different ?-radiation doses and external bias electric field (Eb), in the temperature range 300-900 K. A nonlinear dependence of transition temperature, T1 and a remarkable change in the thermodynamic parameters, were obtained as the effect of both electric field and ?-radiation. The effect of ?-radiation doses on the phase transition in LiNaSO4 crystals was explained as due to an internal bias field, Eb, originating from the interaction of polar defects with the order parameter of the host lattice. The internal bias field effect on the behaviour of Cp(T) in LiNaSO4 crystals was similar to that of the external electric field (E).

  10. Lattice location of diffused Zn atoms in GaAs and InP single crystals

    International Nuclear Information System (INIS)

    Chan, L.Y.; Yu, K.M.; Ben-Tzur, M.; Haller, E.E.; Jaklevic, J.M.; Walukiewicz, W.; Hanson, C.M.

    1991-01-01

    We have investigated the saturation phenomenon of the free carrier concentration in p-type GaAs and InP single crystals doped by zinc diffusion. The free hole saturation occurs at 10 20 cm -3 for GaAs, but the maximum concentration for InP appears at mid 10 18 cm -3 . The difference in the saturation hole concentrations for these materials is investigated by studying the incorporation and the lattice location of the impurity zinc, an acceptor when located on a group III atom site. Zinc is diffused into the III-V wafers in a sealed quartz ampoule. Particle-induced x-ray emission with ion-channeling techniques are employed to determine the exact lattice location of the zinc atoms. We have found that over 90% of all zinc atoms occupy Ga sites in the diffused GaAs samples, while for the InP case, the zinc substitutionality is dependent on the cooling rate of the sample after high-temperature diffusion. For the slowly cooled sample, a large fraction (∼90%) of the zinc atoms form random precipitates of Zn 3 P 2 and elemental Zn. However, when rapidly cooled only 60% of the zinc forms such precipitates while the rest occupies specific sites in the InP. We analyze our results in terms of the amphoteric native defect model. We show that the difference in the electrical activity of the Zn atoms in GaAs and InP is a consequence of the different location of the Fermi level stabilization energy in these two materials

  11. Comparison of functional parameters of CsI:Tl crystals and thick films

    International Nuclear Information System (INIS)

    Fedorov, A.; Gektin, A.; Lebedynskiy, A.; Mateychenko, P.; Shkoropatenko, A.

    2013-01-01

    500 mkm thick CsI:Tl columnar films can be produced using thermal evaporation in vacuum by sublimation of the same bulk crystal. Comparison of afterglow and radiation stability of deposited CsI:Tl films with source crystal was the aim of current work. It is shown that the afterglow in the films is always below its level in initial single crystal. It was ascertained that the annealing atmospheres influence the processes leading to the activator depletion of the films during the thermal processing. -- Highlights: ► Thick CsI:Tl columnar films were obtained by thermal evaporation in vacuum. ► Radiation stability of such CsI:Tl films appears to be better than that of crystal. ► CsI:Tl film parameters can be modified by annealing in different atmospheres

  12. Universality in the mixed SU(2) lattice gauge theory. Nonperturbative approach to the ratio of Λ parameters

    International Nuclear Information System (INIS)

    Makeenko, Yu.M.; Polikarpov, M.I.; Zhelonkin, A.V.

    1983-01-01

    The mixed SU(2) lattice gauge theory (LGT) is approximately represented as an effective SU(2) LGT with Wilson's action. This approach is applied to the nonperturbative calculation of the ratio of Λ-parameters in the mixed SU(2) LGT. It is shown that the formulas obtained fairly describe the Monte Carlo data so that universality holds in the mixed SU(2) LGT

  13. Unconventional superconductivity in honeycomb lattice

    Directory of Open Access Journals (Sweden)

    P Sahebsara

    2013-03-01

    Full Text Available   ‎ The possibility of symmetrical s-wave superconductivity in the honeycomb lattice is studied within a strongly correlated regime, using the Hubbard model. The superconducting order parameter is defined by introducing the Green function, which is obtained by calculating the density of the electrons ‎ . In this study showed that the superconducting order parameter appears in doping interval between 0 and 0.5, and x=0.25 is the optimum doping for the s-wave superconductivity in honeycomb lattice.

  14. An improved strategy for the crystallization of Leishmania mexicana pyruvate kinase

    International Nuclear Information System (INIS)

    Morgan, Hugh P.; McNae, Iain W.; Hsin, Kun-Yi; Michels, Paul A. M.; Fothergill-Gilmore, Linda A.; Walkinshaw, Malcolm D.

    2010-01-01

    The first crystal structure of Leishmania mexicana pyruvate kinase (LmPYK) obtained at a neutral pH. LmPYK was co-crystallized with the small molecule 1,3,6,8-pyrenetetrasulfonic acid, which provides a helpful intermolecular bridge between macromolecules. The inclusion of novel small molecules in crystallization experiments has provided very encouraging results and this method is now emerging as a promising alternative strategy for crystallizing ‘problematic’ biological macromolecules. These small molecules have the ability to promote lattice formation through stabilizing intermolecular interactions in protein crystals. Here, the use of 1,3,6,8-pyrenetetrasulfonic acid (PTS), which provides a helpful intermolecular bridge between Leishmania mexicana PYK (LmPYK) macromolecules in the crystal, is reported, resulting in the rapid formation of a more stable crystal lattice at neutral pH and greatly improved X-ray diffraction results. The refined structure of the LmPYK–PTS complex revealed the negatively charged PTS molecule to be stacked between positively charged (surface-exposed) arginine side chains from neighbouring LmPYK molecules in the crystal lattice

  15. An Enhanced Plane Wave Expansion Method to Solve Piezoelectric Phononic Crystal with Resonant Shunting Circuits

    Directory of Open Access Journals (Sweden)

    Ziyang Lian

    2016-01-01

    Full Text Available An enhanced plane wave expansion (PWE method is proposed to solve piezoelectric phononic crystal (PPC connected with resonant shunting circuits (PPC-C, which is named as PWE-PPC-C. The resonant shunting circuits can not only bring about the locally resonant (LR band gap for the PPC-C but also conveniently tune frequency and bandwidth of band gaps through adjusting circuit parameters. However, thus far, more than one-dimensional PPC-C has been studied just by Finite Element method. Compared with other methods, the PWE has great advantages in solving more than one-dimensional PC as well as various lattice types. Nevertheless, the conventional PWE cannot accurately solve coupling between the structure and resonant shunting circuits of the PPC-C since only taking one-way coupling from displacements to electrical parameters into consideration. A two-dimensional PPC-C model of orthorhombic lattice is established to demonstrate the whole solving process of PWE-PPC-C. The PWE-PPC-C method is validated by Transfer Matrix method as well as Finite Element method. The dependence of band gaps on circuit parameters has been investigated in detail by PWE-PPC-C. Its advantage in solving various lattice types is further illustrated by calculating the PPC-C of triangular and hexagonal lattices, respectively.

  16. Lattice QCD on fine lattices

    Energy Technology Data Exchange (ETDEWEB)

    Schaefer, Stefan [DESY (Germany). Neumann Inst. for Computing

    2016-11-01

    These configurations are currently in use in many on-going projects carried out by researchers throughout Europe. In particular this data will serve as an essential input into the computation of the coupling constant of QCD, where some of the simulations are still on-going. But also projects computing the masses of hadrons and investigating their structure are underway as well as activities in the physics of heavy quarks. As this initial project of gauge field generation has been successful, it is worthwhile to extend the currently available ensembles with further points in parameter space. These will allow to further study and control systematic effects like the ones introduced by the finite volume, the non-physical quark masses and the finite lattice spacing. In particular certain compromises have still been made in the region where pion masses and lattice spacing are both small. This is because physical pion masses require larger lattices to keep the effects of the finite volume under control. At light pion masses, a precise control of the continuum extrapolation is therefore difficult, but certainly a main goal of future simulations. To reach this goal, algorithmic developments as well as faster hardware will be needed.

  17. Optimal numerical methods for determining the orientation averages of single-scattering properties of atmospheric ice crystals

    International Nuclear Information System (INIS)

    Um, Junshik; McFarquhar, Greg M.

    2013-01-01

    The optimal orientation averaging scheme (regular lattice grid scheme or quasi Monte Carlo (QMC) method), the minimum number of orientations, and the corresponding computing time required to calculate the average single-scattering properties (i.e., asymmetry parameter (g), single-scattering albedo (ω o ), extinction efficiency (Q ext ), scattering efficiency (Q sca ), absorption efficiency (Q abs ), and scattering phase function at scattering angles of 90° (P 11 (90°)), and 180° (P 11 (180°))) within a predefined accuracy level (i.e., 1.0%) were determined for four different nonspherical atmospheric ice crystal models (Gaussian random sphere, droxtal, budding Bucky ball, and column) with maximum dimension D=10μm using the Amsterdam discrete dipole approximation at λ=0.55, 3.78, and 11.0μm. The QMC required fewer orientations and less computing time than the lattice grid. The calculations of P 11 (90°) and P 11 (180°) required more orientations than the calculations of integrated scattering properties (i.e., g, ω o , Q ext , Q sca , and Q abs ) regardless of the orientation average scheme. The fewest orientations were required for calculating g and ω o . The minimum number of orientations and the corresponding computing time for single-scattering calculations decreased with an increase of wavelength, whereas they increased with the surface-area ratio that defines particle nonsphericity. -- Highlights: •The number of orientations required to calculate the average single-scattering properties of nonspherical ice crystals is investigated. •Single-scattering properties of ice crystals are calculated using ADDA. •Quasi Monte Carlo method is more efficient than lattice grid method for scattering calculations. •Single-scattering properties of ice crystals depend on a newly defined parameter called surface area ratio

  18. Low-temperature embrittlement and fracture of metals with different crystal lattices – Dislocation mechanisms

    Directory of Open Access Journals (Sweden)

    V.M. Chernov

    2016-12-01

    Full Text Available The state of a low-temperature embrittlement (cold brittleness and dislocation mechanisms for formation of the temperature of a ductile-brittle transition and brittle fracture of metals (mono- and polycrystals with various crystal lattices (BCC, FCC, HCP are considered. The conditions for their formation connected with a stress-deformed state and strength (low temperature yield strength as well as the fracture breaking stress and mobility of dislocations in the top of a crack of the fractured metal are determined. These conditions can be met for BCC and some HCP metals in the initial state (without irradiation and after a low-temperature damaging (neutron irradiation. These conditions are not met for FCC and many HCP metals. In the process of the damaging (neutron irradiation such conditions are not met also and the state of low-temperature embrittlement of metals is absent (suppressed due to arising various radiation dynamic processes, which increase the mobility of dislocations and worsen the strength characteristics.

  19. Lattice Boltzmann simulation of asymmetric flow in nematic liquid crystals with finite anchoring

    Science.gov (United States)

    Zhang, Rui; Roberts, Tyler; Aranson, Igor S.; de Pablo, Juan J.

    2016-02-01

    Liquid crystals (LCs) display many of the flow characteristics of liquids but exhibit long range orientational order. In the nematic phase, the coupling of structure and flow leads to complex hydrodynamic effects that remain to be fully elucidated. Here, we consider the hydrodynamics of a nematic LC in a hybrid cell, where opposite walls have conflicting anchoring boundary conditions, and we employ a 3D lattice Boltzmann method to simulate the time-dependent flow patterns that can arise. Due to the symmetry breaking of the director field within the hybrid cell, we observe that at low to moderate shear rates, the volumetric flow rate under Couette and Poiseuille flows is different for opposite flow directions. At high shear rates, the director field may undergo a topological transition which leads to symmetric flows. By applying an oscillatory pressure gradient to the channel, a net volumetric flow rate is found to depend on the magnitude and frequency of the oscillation, as well as the anchoring strength. Taken together, our findings suggest several intriguing new applications for LCs in microfluidic devices.

  20. Lattice dynamics of impurity clusters : application to pairs

    International Nuclear Information System (INIS)

    Chandralekha Devi, N.; Behera, S.N.

    1979-01-01

    A general solution is obtained for the lattice dynamics of a cluster of n-impurity atoms using the double-time Green's function formalism. The cluster is characterized by n-mass defect and m-force constant change parameters. It is shown that this general solution for the Green's function for the n-impurity cluster can also be expressed in terms of the Green's function for the (n-1)-impurity cluster. As an application, the cluster impurity modes for a pair are calculated using the Debye model for the host lattice dynamics. The splitting of the high frequency local modes and nearly zero frequency resonant modes due to pairs show an oscillatory behaviour on varying the distance of separation between the two impurity atoms. These oscillations are most prominent for two similar impurities and get damped for two dissimilar impurities or if one of the impurities produces a force constant change. The predictions of the calculation provide qualitative explanation of the data obtained from the infrared measurements of the resonant modes in mixed crystal system of KBrsub(1-c)Clsub(c):Lisup(+) and KBrsub(1-c)Isub(c):Lisup(+). (author)

  1. Thermodynamic and lattice parameter calculation of TiC x produced from Al-Ti-C powders by laser igniting self-propagating high-temperature synthesis

    International Nuclear Information System (INIS)

    Li, Y.X.; Hu, J.D.; Wang, H.Y.; Guo, Z.X.; Chumakov, A.N.

    2007-01-01

    TiC x has been formed by self-propagating high-temperature synthesis (SHS) from elemental powder mixtures with a range of C/Ti ratios. The combusting behavior of the powder mixtures was investigated. The effect of the processing variables on the lattice parameter and the composition of TiC were examined. The results show that lattice parameters of TiC x increase with the increase of C/Ti ratio. The variation of Gibbs free energy in Al-Ti-C system was studied based on the thermodynamics theory. The results show that TiC and Al 3 Ti phases are easier to form than Al 4 C 3 phase

  2. Frequency distribution of the reduced unit cells of centred lattices from the Protein Data Bank.

    Science.gov (United States)

    Swaminathan, Kunchithapadam

    2012-03-01

    In crystallography, a centred conventional lattice unit cell has its corresponding reduced primitive unit cell. This study presents the frequency distribution of the reduced unit cells of all centred lattice entries of the Protein Data Bank (as of 23 August 2011) in four unit-cell-dimension-based groups and seven interaxial-angle-based subgroups. This frequency distribution is an added layer of support during space-group assignment in new crystals. In addition, some interesting patterns of distribution are discussed as well as how some reduced unit cells could be wrongly accepted as primitive lattices in a different crystal system.

  3. Crystal structure and magnetic properties of Tb6FeSb2

    International Nuclear Information System (INIS)

    Cai Gemei; Zhang Jiliang; He Wei; Qin Pingli; Zeng Lingmin

    2006-01-01

    The crystal structure and magnetic properties of Tb 6 FeSb 2 has been investigated for the first time. The compound crystallizes in the hexagonal, space group P6-bar 2m (No. 189) with the Ho 6 FeSb 2 structure type and lattice parameters a=8.1942(5)A, c=4.1758(3)A, z=1 and D calc =8.564g/cm 3 . Its magnetic properties were measured between 85 and 420K. The Curie temperature T c =256K was obtained using the method of intersecting tangents, and the effective paramagnetic moment was μ eff =9.32μ B per Tb atom

  4. Melting of the moving vortex lattice in the presence of disorder

    International Nuclear Information System (INIS)

    Koshelev, A.E.; Vinokur, V.M.

    1994-07-01

    The authors investigate the melting of the two-dimensional vortex lattice moving in an inhomogeneous environment under the applied current j. They predict the existence of a dynamic phase transition at some current j = j t (crystallization current) from the motion of the amorphous configuration at j t to the motion of the crystal at j > j t . j t exceeds essentially the critical current j c for strongly disordered systems and approaches j c with the decrease of the degree of disorder. They find that j t diverges as temperature approaches the melting temperature of the undisturbed lattice

  5. Clar sextets in square graphene antidot lattices

    DEFF Research Database (Denmark)

    Petersen, Rene; Pedersen, Thomas Garm; Jauho, Antti-Pekka

    2011-01-01

    A periodic array of holes transforms graphene from a semimetal into a semiconductor with a band gap tuneable by varying the parameters of the lattice. In earlier work only hexagonal lattices have been treated. Using atomistic models we here investigate the size of the band gap of a square lattice...

  6. Advanced x-ray stress analysis method for a single crystal using different diffraction plane families

    International Nuclear Information System (INIS)

    Imafuku, Muneyuki; Suzuki, Hiroshi; Sueyoshi, Kazuyuki; Akita, Koichi; Ohya, Shin-ichi

    2008-01-01

    Generalized formula of the x-ray stress analysis for a single crystal with unknown stress-free lattice parameter was proposed. This method enables us to evaluate the plane stress states with any combination of diffraction planes. We can choose and combine the appropriate x-ray sources and diffraction plane families, depending on the sample orientation and the apparatus, whenever diffraction condition is satisfied. The analysis of plane stress distributions in an iron single crystal was demonstrated combining with the diffraction data for Fe{211} and Fe{310} plane families

  7. Computer modeling of liquid crystals

    International Nuclear Information System (INIS)

    Al-Barwani, M.S.

    1999-01-01

    In this thesis, we investigate several aspects of the behaviour of liquid crystal molecules near interfaces using computer simulation. We briefly discuss experiment, theoretical and computer simulation studies of some of the liquid crystal interfaces. We then describe three essentially independent research topics. The first of these concerns extensive simulations of a liquid crystal formed by long flexible molecules. We examined the bulk behaviour of the model and its structure. Studies of a film of smectic liquid crystal surrounded by vapour were also carried out. Extensive simulations were also done for a long-molecule/short-molecule mixture, studies were then carried out to investigate the liquid-vapour interface of the mixture. Next, we report the results of large scale simulations of soft-spherocylinders of two different lengths. We examined the bulk coexistence of the nematic and isotropic phases of the model. Once the bulk coexistence behaviour was known, properties of the nematic-isotropic interface were investigated. This was done by fitting order parameter and density profiles to appropriate mathematical functions and calculating the biaxial order parameter. We briefly discuss the ordering at the interfaces and make attempts to calculate the surface tension. Finally, in our third project, we study the effects of different surface topographies on creating bistable nematic liquid crystal devices. This was carried out using a model based on the discretisation of the free energy on a lattice. We use simulation to find the lowest energy states and investigate if they are degenerate in energy. We also test our model by studying the Frederiks transition and comparing with analytical and other simulation results. (author)

  8. Synthesis, growth, morphology and characterization of ferroelectric glycine phosphite single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Devi, K. Renuka; Srinivasan, K. [Crystal Growth Laboratory, Department of Physics, School of Physical Sciences, Bharathiar University, Tamil Nadu (India)

    2011-12-15

    Glycine phosphite (NH{sub 3}CH{sub 2}COO.H{sub 3}PO{sub 3}), a potential ferroelectric material, was grown as single crystals from aqueous solutions by slow evaporation and slow cooling methods. Laboratory synthesized title compound was purified by recrystallization method and confirmed by Fourier transform infrared and Laser Raman studies. Temperature dependent solubility in double distilled water in the range between 288 and 328 K was determined by gravimetric method. Morphological importance of various growth faces were studied by optical goniometry. Powder x-ray diffraction study performed on the grown crystals confirms the crystal system and lattice parameters of the unit cell. Optical transparency of the grown crystals in the ultraviolet-visible -near infrared region was studied by spectroscopic method. Thermal stability of the grown crystals in the temperature region above ambient until melting was studied using differential scanning calorimetry. (copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  9. Evaluating variability with atomistic simulations: the effect of potential and calculation methodology on the modeling of lattice and elastic constants

    Science.gov (United States)

    Hale, Lucas M.; Trautt, Zachary T.; Becker, Chandler A.

    2018-07-01

    Atomistic simulations using classical interatomic potentials are powerful investigative tools linking atomic structures to dynamic properties and behaviors. It is well known that different interatomic potentials produce different results, thus making it necessary to characterize potentials based on how they predict basic properties. Doing so makes it possible to compare existing interatomic models in order to select those best suited for specific use cases, and to identify any limitations of the models that may lead to unrealistic responses. While the methods for obtaining many of these properties are often thought of as simple calculations, there are many underlying aspects that can lead to variability in the reported property values. For instance, multiple methods may exist for computing the same property and values may be sensitive to certain simulation parameters. Here, we introduce a new high-throughput computational framework that encodes various simulation methodologies as Python calculation scripts. Three distinct methods for evaluating the lattice and elastic constants of bulk crystal structures are implemented and used to evaluate the properties across 120 interatomic potentials, 18 crystal prototypes, and all possible combinations of unique lattice site and elemental model pairings. Analysis of the results reveals which potentials and crystal prototypes are sensitive to the calculation methods and parameters, and it assists with the verification of potentials, methods, and molecular dynamics software. The results, calculation scripts, and computational infrastructure are self-contained and openly available to support researchers in performing meaningful simulations.

  10. REVIEW: Optics of globular photonic crystals

    Science.gov (United States)

    Gorelik, V. S.

    2007-05-01

    The results of experimental and theoretical studies of the optical properties of globular photonic crystals - new physical objects having a crystal structure with the lattice period exceeding considerably the atomic size, are presented. As globular photonic crystals, artificial opal matrices consisting of close-packed silica globules of diameter ~200 nm were used. The reflection spectra of these objects characterising the parameters of photonic bands existing in these crystals in the visible spectral region are presented. The idealised models of the energy band structure of photonic crystals investigated in the review give analytic dispersion dependences for the group velocity and the effective photon mass in a globular photonic crystal. The characteristics of secondary emission excited in globular photonic crystals by monochromatic and broadband radiation are presented. The results of investigations of single-photon-excited delayed scattering of light observed in globular photonic crystals exposed to cw UV radiation and radiation from a repetitively pulsed copper vapour laser are presented. The possibilities of using globular photonic crystals as active media for lasing in different spectral regions are considered. It is proposed to use globular photonic crystals as sensitive sensors in optoelectronic devices for molecular analysis of organic and inorganic materials by the modern methods of laser spectroscopy. The results of experimental studies of spontaneous and stimulated globular scattering of light are discussed. The conditions for observing resonance and two-photon-excited delayed scattering of light are found. The possibility of accumulation and localisation of the laser radiation energy inside a globular photonic crystal is reported.

  11. Reorientation of molecules in a Cl3P/Dirac h/NCCl2CF3 crystal according to NQR data

    International Nuclear Information System (INIS)

    Kyuntsel', I.A.; Mokeeva, V.A.; Soifer, G.B.

    1988-01-01

    The structural-dynamic inequivalence of the molecules in solid Cl 3 P/Dirac h/NCCl 2 CF 3 has been established, and their rotational mobility has been studied with the aid of the temperature dependence of the resonance frequency and of the spin-lattice relaxation time of the 35 Cl nuclei. The observed motion has been interpreted with consideration of the molecular structure as reorientation between unequal potential wells in the crystal lattice, and the corresponding activation parameters have been determined from the 35 Cl NQR data

  12. X-ray diffraction patterns of single crystals implanted with high-energy light ions

    International Nuclear Information System (INIS)

    Wieteska, K.

    1998-01-01

    X-ray diffraction patterns of silicon and gallium arsenide single crystals implanted with high-energy protons and α-particles were studied. A various models of lattice parameter changes were analysed. The agreement between the simulation and experiment proves that the lattice parameter depth-distribution can be assumed to be proportional to vacancy distribution obtained by Monte-Carlo method and from the Biersack-Ziegler theory. Most of the X-ray experiments were performed using synchrotron source of X-ray radiation in particular in the case of back-reflection and transmission section topographic methods. The new method of direct determination of the implanted ion ranges was proposed using synchrotron radiation back-reflection section topography. A number of new interference phenomena was revealed and explained. These interferences are important in the applications of diffraction theory in studying of the real structure of implanted layers. (author)

  13. Adsorption, Desorption, Surface Diffusion, Lattice Defect Formation, and Kink Incorporation Processes of Particles on Growth Interfaces of Colloidal Crystals with Attractive Interactions

    Directory of Open Access Journals (Sweden)

    Yoshihisa Suzuki

    2016-07-01

    Full Text Available Good model systems are required in order to understand crystal growth processes because, in many cases, precise incorporation processes of atoms or molecules cannot be visualized easily at the atomic or molecular level. Using a transmission-type optical microscope, we have successfully observed in situ adsorption, desorption, surface diffusion, lattice defect formation, and kink incorporation of particles on growth interfaces of colloidal crystals of polystyrene particles in aqueous sodium polyacrylate solutions. Precise surface transportation and kink incorporation processes of the particles into the colloidal crystals with attractive interactions were observed in situ at the particle level. In particular, contrary to the conventional expectations, the diffusion of particles along steps around a two-dimensional island of the growth interface was not the main route for kink incorporation. This is probably due to the number of bonds between adsorbed particles and particles in a crystal; the number exceeds the limit at which a particle easily exchanges its position to the adjacent one along the step. We also found novel desorption processes of particles from steps to terraces, attributing them to the assistance of attractive forces from additionally adsorbing particles to the particles on the steps.

  14. Crystal structure of the Hg4SiS6 and Hg4SiSe6 compounds

    International Nuclear Information System (INIS)

    Gulay, L.D.; Olekseyuk, I.D.; Parasyuk, O.V.

    2002-01-01

    The crystal structures of Hg 4 SiS 6 and Hg 4 SiSe 6 compounds were investigated using X-ray powder diffraction. These compounds crystallize in the monoclinic Cc space group with the lattice parameters a=1.23020(5), b=0.71031(4), c=1.22791(4) nm, β=109.721(3) deg. for Hg 4 SiS 6 and a=1.28110(4), b=0.74034(4), c=1.27471(1) nm, β=109.605(3) deg. for Hg 4 SiSe 6 . Atomic parameters were refined in the isotropic approximation (R I =0.0571 and R I =0.0555 for the Hg 4 SiS 6 and Hg 4 SiSe 6 , respectively)

  15. Immobilizing Water into Crystal Lattice of Calcium Sulfate for its Separation from Water-in-Oil Emulsion.

    Science.gov (United States)

    Jiang, Guangming; Li, Junxi; Nie, Yunliang; Zhang, Sen; Dong, Fan; Guan, Baohong; Lv, Xiaoshu

    2016-07-19

    This work report a facile approach to efficiently separate surfactant-stabilized water (droplet diameter of around 2.0 μm) from water-in-oil emulsion via converting liquid water into solid crystal water followed by removal with centrifugation. The liquid-solid conversion is achieved through the solid-to-solid phase transition of calcium sulfate hemihydrate (CaSO4. 0.5H2O, HH) to dihydrate (CaSO4·2H2O, DH), which could immobilize the water into crystal lattice of DH. For emulsion of 10 mg mL(-1) water, the immobilization-separation process using polycrystalline HH nanoellipsoids could remove 95.87 wt % water at room temperature. The separation efficiency can be further improved to 99.85 wt % by optimizing the HH dosage, temperature, HH size and crystalline structure. Property examination of the recycled oil confirms that our method has neglectable side-effect on oil quality. The byproduct DH was recycled to alpha-HH (a valuable cemetitious material widely used in construction and binding field), which minimizes the risk of secondary pollution and promotes the practicality of our method. With the high separation efficiency, the "green" feature and the recyclability of DH byproduct, the HH-based immobilization-separation approach is highly promising in purifying oil with undesired water contamination.

  16. Strain relaxation of GaAs/Ge crystals on patterned Si substrates

    International Nuclear Information System (INIS)

    Taboada, A. G.; Kreiliger, T.; Falub, C. V.; Känel, H. von; Isa, F.; Isella, G.; Salvalaglio, M.; Miglio, L.; Wewior, L.; Fuster, D.; Alén, B.; Richter, M.; Uccelli, E.; Niedermann, P.; Neels, A.; Dommann, A.; Mancarella, F.

    2014-01-01

    We report on the mask-less integration of GaAs crystals several microns in size on patterned Si substrates by metal organic vapor phase epitaxy. The lattice parameter mismatch is bridged by first growing 2-μm-tall intermediate Ge mesas on 8-μm-tall Si pillars by low-energy plasma enhanced chemical vapor deposition. We investigate the morphological evolution of the GaAs crystals towards full pyramids exhibiting energetically stable (111) facets with decreasing Si pillar size. The release of the strain induced by the mismatch of thermal expansion coefficients in the GaAs crystals has been studied by X-ray diffraction and photoluminescence measurements. The strain release mechanism is discussed within the framework of linear elasticity theory by Finite Element Method simulations, based on realistic geometries extracted from scanning electron microscopy images

  17. Strain relaxation of GaAs/Ge crystals on patterned Si substrates

    Energy Technology Data Exchange (ETDEWEB)

    Taboada, A. G., E-mail: gonzalez@phys.ethz.ch; Kreiliger, T.; Falub, C. V.; Känel, H. von [Laboratory for Solid State Physics, ETH Zürich, Otto-Stern-Weg 1, CH-8093 Zürich (Switzerland); Isa, F.; Isella, G. [L-NESS, Department of Physics, Politecnico di Milano, via Anzani 42, I-22100 Como (Italy); Salvalaglio, M.; Miglio, L. [L-NESS, Department of Materials Science, Università di Milano-Bicocca, via Cozzi 55, I-20125 Milano (Italy); Wewior, L.; Fuster, D.; Alén, B. [IMM, Instituto de Microelectrónica de Madrid (CNM, CSIC), C/Isaac Newton 8, E-28760 Tres Cantos, Madrid (Spain); Richter, M.; Uccelli, E. [Functional Materials Group, IBM Research-Zürich, Säumerstrasse 4, CH-8803 Rüschlikon (Switzerland); Niedermann, P.; Neels, A.; Dommann, A. [Centre Suisse d' Electronique et Microtechnique, Jaquet-Droz 1, CH-2002 Neuchatel (Switzerland); Mancarella, F. [CNR-IMM of Bologna, Via Gobetti 101, I-40129 Bologna (Italy)

    2014-01-13

    We report on the mask-less integration of GaAs crystals several microns in size on patterned Si substrates by metal organic vapor phase epitaxy. The lattice parameter mismatch is bridged by first growing 2-μm-tall intermediate Ge mesas on 8-μm-tall Si pillars by low-energy plasma enhanced chemical vapor deposition. We investigate the morphological evolution of the GaAs crystals towards full pyramids exhibiting energetically stable (111) facets with decreasing Si pillar size. The release of the strain induced by the mismatch of thermal expansion coefficients in the GaAs crystals has been studied by X-ray diffraction and photoluminescence measurements. The strain release mechanism is discussed within the framework of linear elasticity theory by Finite Element Method simulations, based on realistic geometries extracted from scanning electron microscopy images.

  18. Characterization of monoclinic crystals in tablets by pattern-fitting procedure using X-ray powder diffraction data.

    Science.gov (United States)

    Yamamura, Shigeo; Momose, Yasunori

    2003-06-18

    The purpose of this study is to characterize the monoclinic crystals in tablets by using X-ray powder diffraction data and to evaluate the deformation feature of crystals during compression. The monoclinic crystals of acetaminophen and benzoic acid were used as the samples. The observed X-ray diffraction intensities were fitted to the analytic expression, and the fitting parameters, such as the lattice parameters, the peak-width parameters, the preferred orientation parameter and peak asymmetric parameter were optimized by a non-linear least-squares procedure. The Gauss and March distribution functions were used to correct the preferred orientation of crystallites in the tablet. The March function performed better in correcting the modification of diffraction intensity by preferred orientation of crystallites, suggesting that the crystallites in the tablets had fiber texture with axial orientation. Although a broadening of diffraction peaks was observed in acetaminophen tablets with an increase of compression pressure, little broadening was observed in the benzoic tablets. These results suggest that "acetaminophen is a material consolidating by fragmentation of crystalline particles and benzoic acid is a material consolidating by plastic deformation then occurred rearrangement of molecules during compression". A pattern-fitting procedure is the superior method for characterizing the crystalline drugs of monoclinic crystals in the tablets, as well as orthorhombic isoniazid and mannitol crystals reported in the previous paper.

  19. Effect of processing parameters of rotary ultrasonic machining on surface integrity of potassium dihydrogen phosphate crystals

    Directory of Open Access Journals (Sweden)

    Jianfu Zhang

    2015-09-01

    Full Text Available Potassium dihydrogen phosphate is an important optical crystal. However, high-precision processing of large potassium dihydrogen phosphate crystal workpieces is difficult. In this article, surface roughness and subsurface damage characteristics of a (001 potassium dihydrogen phosphate crystal surface produced by traditional and rotary ultrasonic machining are studied. The influence of process parameters, including spindle speed, feed speed, type and size of sintered diamond wheel, ultrasonic power, and selection of cutting fluid on potassium dihydrogen phosphate crystal surface integrity, was analyzed. The surface integrity, especially the subsurface damage depth, was affected significantly by the ultrasonic power. Metal-sintered diamond tools with high granularity were most suitable for machining potassium dihydrogen phosphate crystal. Cutting fluid played a key role in potassium dihydrogen phosphate crystal machining. A more precise surface can be obtained in machining with a higher spindle speed, lower feed speed, and using kerosene as cutting fluid. Based on the provided optimized process parameters for machining potassium dihydrogen phosphate crystal, a processed surface quality with Ra value of 33 nm and subsurface damage depth value of 6.38 μm was achieved.

  20. Ising antiferromagnet on the Archimedean lattices

    Science.gov (United States)

    Yu, Unjong

    2015-06-01

    Geometric frustration effects were studied systematically with the Ising antiferromagnet on the 11 Archimedean lattices using the Monte Carlo methods. The Wang-Landau algorithm for static properties (specific heat and residual entropy) and the Metropolis algorithm for a freezing order parameter were adopted. The exact residual entropy was also found. Based on the degree of frustration and dynamic properties, ground states of them were determined. The Shastry-Sutherland lattice and the trellis lattice are weakly frustrated and have two- and one-dimensional long-range-ordered ground states, respectively. The bounce, maple-leaf, and star lattices have the spin ice phase. The spin liquid phase appears in the triangular and kagome lattices.

  1. Thermal expansion of crystals of the N2 type

    International Nuclear Information System (INIS)

    Tolkachev, A.M.; Manzhelii, V.G.; Azarenkov, V.P.; Jezowski, A.; Kosobutskaya, E.A.

    1981-01-01

    Linear expansion coefficients of low temperature crystals with linear molecules and Pa3 lattice N 2 (2-21 K), CO(2-28 K), CO 2 (2-25 K), N 2 O(2-90 K) were measured. A version of the law of corresponding states to describe the translational component of the thermal expansion of the substances studied and other low temperature crystals with close-packed lattices is proposed. In the thermal properties of crystals consisting of molecules without inversion centre, we have found anomalies interpreted as the evidence of a partial dipole ordering. (orig.)

  2. Phenomenology Using Lattice QCD

    Science.gov (United States)

    Gupta, R.

    2005-08-01

    This talk provides a brief summary of the status of lattice QCD calculations of the light quark masses and the kaon bag parameter BK. Precise estimates of these four fundamental parameters of the standard model, i.e., mu, md, ms and the CP violating parameter η, help constrain grand unified models and could provide a window to new physics.

  3. Crystal lattice desolvation effects on the magnetic quantum tunneling of single-molecule magnets

    Science.gov (United States)

    Redler, G.; Lampropoulos, C.; Datta, S.; Koo, C.; Stamatatos, T. C.; Chakov, N. E.; Christou, G.; Hill, S.

    2009-09-01

    High-frequency electron paramagnetic resonance (HFEPR) and alternating current (ac) susceptibility measurements are reported for a new high-symmetry Mn12 complex, [Mn12O12(O2CCH3)16(CH3OH)4]ṡCH3OH . The results are compared to those of other high-symmetry spin S=10Mn12 single-molecule magnets (SMMs), including the original acetate, [Mn12(O2CCH3)16(H2O)4]ṡ2CH3CO2Hṡ4H2O , and the [Mn12O12(O2CCH2Br)16(H2O)4]ṡ4CH2Cl2 and [Mn12O12(O2CCH2But)16(CH3OH)4]ṡCH3OH complexes. These comparisons reveal important insights into the factors that influence the values of the effective barrier to magnetization reversal, Ueff , deduced on the basis of ac susceptibility measurements. In particular, we find that variations in Ueff can be correlated with the degree of disorder in a crystal which can be controlled by desolvating (drying) samples. This highlights the importance of careful sample handling when making measurements on SMM crystals containing volatile lattice solvents. The HFEPR data additionally provide spectroscopic evidence suggesting that the relatively weak disorder induced by desolvation influences the quantum tunneling interactions and that it is under-barrier tunneling that is responsible for a consistent reduction in Ueff that is found upon drying samples. Meanwhile, the axial anisotropy deduced from HFEPR is found to be virtually identical for all four Mn12 complexes, with no measurable reduction upon desolvation.

  4. Light crystals for ultracold quantum degenerate bosonic gases

    International Nuclear Information System (INIS)

    Arimondo, E.

    2009-01-01

    Full text follows. The experimental realization of quantum degenerate states in ultracold atomic gases has opened the possibility to realize few body systems isolated from external perturbations and at temperatures close to absolute zero. Under these conditions counterintuitive phenomena characteristic of the quantum mechanical evolution may be assessed experimentally. Matter quantum-mechanical waves inside periodic potentials investigated in solid-state physics, where electrons propagate within a crystal lattice. Interfering laser beams create a light-induced spatial periodic potential for ultracold atoms called an 'optical lattice'. Atoms hopping between the lattice periodic potential minima emulate the motion of electrons in a crystal. The creation of one-, two-, and three-dimensional periodic structures in which atoms can be trapped and accelerated, with the possibility of switching or modulating the lattice at will, gives a great flexibility. In addition atomic physicists can tune the lattice's geometry, the rate of hopping, and the push and pull between atoms within the light crystals. So they hope to map the various behaviors of solid-state models. On the basis of the research work performed at Pisa, several processes of quantum mechanics evolution within a spatial periodic potential and associated to the solid-state physics will be presented

  5. Stability of void lattices under irradiation: a kinetic model

    International Nuclear Information System (INIS)

    Benoist, P.; Martin, G.

    1975-01-01

    Voids are imbedded in a homogeneous medium where point defects are uniformly created and annihilated. As shown by a perturbation calculation, the proportion of the defects which are lost on the cavities goes through a maximum, when the voids are arranged on a translation lattice. If a void is displaced from its lattice site, its growth rate becomes anisotropic and is larger in the direction of the vacant site. The relative efficiency of BCC versus FCC void lattices for the capture of point defects is shown to depend on the relaxation length of the point defects in the surrounding medium. It is shown that the rate of energy dissipation in the crystal under irradiation is maximum when the voids are ordered on the appropriate lattice

  6. Stability of void lattices under irradiation: a kinetic model

    International Nuclear Information System (INIS)

    Benoist, P.; Martin, G.

    1975-01-01

    Voids are imbedded in a homogeneous medium where point defects are uniformly created and annihilated. As shown by a perturbation calculation, the proportion of the defects which are lost on the cavities goes through a maximum, when the voids are arranged on a translation lattice. If a void is displaced from its lattice site, its growth the rate becomes anisotropic and is larger in the direction of the vacant site. The relative efficiency of BCC versus FCC void lattices for the capture of point defects is shown to depend on the relaxation length of the point defects in the surrounding medium. It is shown that the rate of energy dissipation in the crystal under irradiation is maximum when the voids are ordered on the appropriate lattice [fr

  7. Optical properties of Sulfur doped InP single crystals

    Science.gov (United States)

    El-Nahass, M. M.; Youssef, S. B.; Ali, H. A. M.

    2014-05-01

    Optical properties of InP:S single crystals were investigated using spectrophotometric measurements in the spectral range of 200-2500 nm. The absorption coefficient and refractive index were calculated. It was found that InP:S crystals exhibit allowed and forbidden direct transitions with energy gaps of 1.578 and 1.528 eV, respectively. Analysis of the refractive index in the normal dispersion region was discussed in terms of the single oscillator model. Some optical dispersion parameters namely: the dispersion energy (Ed), single oscillator energy (Eo), high frequency dielectric constant (ɛ∞), and lattice dielectric constant (ɛL) were determined. The volume and the surface energy loss functions (VELF & SELF) were estimated. Also, the real and imaginary parts of the complex conductivity were calculated.

  8. Theoretical explanation of EPR parameters for Cu{sup 2+} ion in TiO{sub 2} crystal

    Energy Technology Data Exchange (ETDEWEB)

    Dong, H.N. [Institute of Applied Physics and College of Electronic Engineering, Chongqing University of Posts and Telecommunications, Chongqing 400065 (China); International Centre for Materials Physics, Chinese Academy of Sciences, Shenyang 110016 (China); Wu, S.Y. [International Centre for Materials Physics, Chinese Academy of Sciences, Shenyang 110016 (China); Department of Applied Physics, University of Electronic Science and Technology of China, Chengdu 610054 (China); Li, P. [Department of Physics, The University of Hong Kong, Pokfulam Road, Hong Kong (China)

    2004-07-01

    The EPR parameters anisotropic g-factors g{sub x}, g{sub y} and g{sub z} for Cu{sup 2+} ion and hyperfine structure constants A{sub x}, A{sub y} and A{sub z} for {sup 63}Cu{sup 2+} and {sup 65}Cu{sup 2+} isotopes in rutile (TiO{sub 2}) crystal are calculated by the method of diagonalizing the full Hamiltonian matrix. The crystal-field parameters contact with the crystal structure by the aid of the superposition model. The calculated results are in reasonable agreement with the observed values. The results are discussed. (copyright 2004 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  9. Spectral Gaps in Graphene Antidot Lattices

    DEFF Research Database (Denmark)

    Barbaroux, Jean-Marie; Cornean, Decebal Horia; Stockmeyer, Edgardo

    2017-01-01

    We consider the gap creation problem in an antidot graphene lattice, i.e. a sheet of graphene with periodically distributed obstacles. We prove several spectral results concerning the size of the gap and its dependence on different natural parameters related to the antidot lattice....

  10. Non-Abelian vortex lattices

    Science.gov (United States)

    Tallarita, Gianni; Peterson, Adam

    2018-04-01

    We perform a numerical study of the phase diagram of the model proposed in [M. Shifman, Phys. Rev. D 87, 025025 (2013)., 10.1103/PhysRevD.87.025025], which is a simple model containing non-Abelian vortices. As per the case of Abrikosov vortices, we map out a region of parameter space in which the system prefers the formation of vortices in ordered lattice structures. These are generalizations of Abrikosov vortex lattices with extra orientational moduli in the vortex cores. At sufficiently large lattice spacing the low energy theory is described by a sum of C P (1 ) theories, each located on a vortex site. As the lattice spacing becomes smaller, when the self-interaction of the orientational field becomes relevant, only an overall rotation in internal space survives.

  11. Ion beam modification of thermal stress resistance of MgO single crystals with different crystallographic faces

    International Nuclear Information System (INIS)

    Gurarie, V.N.; Otsuka, P.H.; Williams, J.S.; Conway, M.J.

    2000-01-01

    Ion beam modification of thermal shock stress resistance of MgO single crystals with various crystallographic faces is investigated. The most stable crystal faces in terms of stress and damage resistance are established. Ion implantation is shown to reduce the temperature threshold of fracture for all crystal faces tested. The (111) face is demonstrated to be of highest stability compared to (110) and (100) faces in both implanted and unimplanted crystals. At the same time ion implantation substantially increases the microcrack density for all the faces tested and reduces the degree of fracture damage following thermal shock. The theoretical resistance parameters for various crystal faces are calculated using the continuum mechanics approach. The results are discussed on the basis of fracture mechanics principles and the effect of the implantation-induced lattice damage on crack nucleation

  12. Analysis of neutron parameters in light water moderated lattices of ThO2 and UO2 fuel rods

    International Nuclear Information System (INIS)

    Onusic Junior, J.; Oosterkamp, W.J.

    1977-01-01

    A large number of light water moderated lattices of UO 2 and ThO 2 fuel rods were analyzed with the code HAMMER. The purpose of the study was to compare experimental results with computer calculated values. The model employed is described and some modification were introduced in the resonance parameters of Th-232 to increase the agreement with the experimental value [pt

  13. Crystal growth and scintillation properties of multi-component oxide single crystals: Ce:GGAG and Ce:La-GPS

    Energy Technology Data Exchange (ETDEWEB)

    Yoshikawa, A., E-mail: yoshikawa@imr.tohoku.ac.jp [Institute for Materials Research (IMR), Tohoku University, Sendai 980-8577 (Japan); New Industry Creation Hatchery Center (NICHe), Tohoku University, Sendai 980-8579 (Japan); C& A Corporation, 6-6-40 Aramaki Aza Aoba, Aoba-ku, Sendai 980-8579 (Japan); Kamada, K. [New Industry Creation Hatchery Center (NICHe), Tohoku University, Sendai 980-8579 (Japan); C& A Corporation, 6-6-40 Aramaki Aza Aoba, Aoba-ku, Sendai 980-8579 (Japan); Kurosawa, S. [Institute for Materials Research (IMR), Tohoku University, Sendai 980-8577 (Japan); New Industry Creation Hatchery Center (NICHe), Tohoku University, Sendai 980-8579 (Japan); Shoji, Y. [Institute for Materials Research (IMR), Tohoku University, Sendai 980-8577 (Japan); C& A Corporation, 6-6-40 Aramaki Aza Aoba, Aoba-ku, Sendai 980-8579 (Japan); Yokota, Y. [New Industry Creation Hatchery Center (NICHe), Tohoku University, Sendai 980-8579 (Japan); Chani, V.I. [Institute for Materials Research (IMR), Tohoku University, Sendai 980-8577 (Japan); Nikl, M. [Institute of Physics, AS CR, Cukrovarnická 10, 162 53 Prague (Czech Republic)

    2016-01-15

    Crystal growth by micro-pulling-down, Czochralski, and floating zone methods and scintillation properties of Ce:Gd{sub 3}(Ga,Al){sub 5}O{sub 12} (Ce:GGAG) multi-component oxide garnets, and Ce:Gd{sub 2}Si{sub 2}O{sub 7} (Ce:GPS) or Ce:(La,Gd){sub 2}Si{sub 2}O{sub 7} (Ce:La-GPS) pyro-silicates are reviewed. GGAG crystals demonstrated practically linear dependences of some of the parameters including lattice constant, emission wavelength, and band gap on Ga content. However, emission intensity, light yield and energy resolution showed maxima for intermediate compositions. GGAG crystals had the highest light yield of 56,000 photon/MeV for Ga content of 2.7 atoms per garnet formula unit. Similarly the light yield and energy resolution of La-GPS showed the highest values of 40,000 photon/MeV and 4.4%@662 keV, respectively, for La-GPS containing 10% of La. Moreover, La-GPS demonstrated stable scintillation performance up to 200 °C.

  14. RAHAB calculation of lattice parameters for CANDU-type lattices using Monte Carlo calculations for resolved resonance capture

    International Nuclear Information System (INIS)

    Craig, D.S.; Festarini, G.L.

    1986-07-01

    The Monte Carlo code, REPC, has been used to calculate resonance reaction rates for the thermal test lattices TRX-1 and MIT-4, and for the CRNL lattices ZEEP-1, 19 UO 2 and 37 UO 2 . These reaction rates were used in the RAHAB cell code to calculate k eff , conversion ratios, and fast fission ratios, for comparison with experimental values. The calculations used the cluster geometry for the 19-, 28-, and 37-element clusters. Calculations were also made using annular representations of the cluster for comparison of the rates with those obtained using the discrete ordinate code OZMA

  15. Structure and lattice dynamics in non-centrosymmetric borates

    International Nuclear Information System (INIS)

    Stein, W.D.R.

    2007-01-01

    This thesis deals with a study of structural and lattice dynamical properties of some noncentrosymmetric borates with outstanding non-linear optical properties. The focus was on the compound bismuth triborate (BiB 3 O 6 ). The structure of the tetraborates MB 4 O 7 (M=Pb,Sr,Ba) was also investigated. The structural investigations in bismuth triborate include powder and single crystal diffraction experiments on X-ray and neutron sources. The crystal structure was under examination in the temperature range from 100 K to room temperature and the lattice constants in the temperature range from 20 K to 800 K. The lattice constants show a nearly linear dependency from temperature. Our observations are in good agreement with investigations of the thermal expansion, which shows a strong anisotropy within the layer-like structure of bismuth triborate. Within the borate layers, along the polar axis a strong positive and in the orthogonal direction a negative thermal expansion is observed. This effect can be explained by a zig-zag effect within the borate layers. The lone electron pair at the bismuth atom is discussed to be possibly the origin of the temperature dependency of the coordination environment of the bismuth atom. The influence of the lone electron pair on the crystal structure is raising by lowering the temperature. At the bismuth atom distinct anharmonic effects are observed, where the maximum points along the direction of the polar axis and therefore along the direction of the lone electron pair. The phonon dispersion of bismuth triborate has been investigated by inelastic neutron scattering. The low symmetry of the crystal structure depicts to be a special challenge. The dispersion was observed along the three reciprocal lattice constants. Along the polar axis the dispersion could be characterized to a maximum energy of 20 THz. The low energy acoustic branch along the polar axis shows a softening at the zone boundary. In the orthogonal directions the dispersion

  16. Polymorphism of felodipine co-crystals with 4,4'-bipyridine

    DEFF Research Database (Denmark)

    Surov, Artem Olegovich; Solanko, Katarzyna A.; Bond, Andrew

    2014-01-01

    -crystal is the most thermodynamically stable phase. The difference in the crystal lattice energies between different polymorphs of the co-crystal is found to be comparable with that between the polymorphic forms of pure felodipine. The enthalpies of formation of the co-crystals are small, which indicates...

  17. Lattice Boltzmann simulations of liquid crystalline fluids: active gels and blue phases

    OpenAIRE

    Cates, M. E.; Henrich, O.; Marenduzzo, D.; Stratford, K.

    2010-01-01

    Lattice Boltzmann simulations have become a method of choice to solve the hydrodynamic equations of motion of a number of complex fluids. Here we review some recent applications of lattice Boltzmann to study the hydrodynamics of liquid crystalline materials. In particular, we focus on the study of (a) the exotic blue phases of cholesteric liquid crystals, and (b) active gels - a model system for actin plus myosin solutions or bacterial suspensions. In both cases lattice Boltzmann studies have...

  18. Nanoimprinted polymer photonic crystal dye lasers

    DEFF Research Database (Denmark)

    Christiansen, Mads Brøkner; Smith, Cameron; Buss, Thomas

    2010-01-01

    Optically pumped polymer photonic crystal band-edge dye lasers are presented. The photonic crystal is a rectangular lattice providing laser feedback as well as an optical resonance for the pump light. The lasers are defined in a thin film of photodefinable Ormocore hybrid polymer, doped...

  19. Development of polarization magneto-optics of paramagnetic crystals

    International Nuclear Information System (INIS)

    Zapasskij, V.S.; Feofilov, P.P.

    1975-01-01

    The present status of the polarization magnetooptics of crystals containing paramagnetic ion impurities is reviewed. The paper discusses methods of measurement of circular magnetic anisotropy and results obtained in recent years in the field of conventional magnetooptical studies, e.g., magnetooptical activity in absorption spectra for intrinsic and impurity defects in crystals, luminescence magnetic circular polarization, anisotropy of magnetooptical activity in cubic crystals. The main emphasis is placed on new trends in polarization magnetooptics: studies of interactions of a spin system with a lattice, in particular, spin-lattice relaxation and spin memory effect, experiments in the double radiooptical resonance, studies of optical spin relaxation, nonlinear magnetooptical effects, etc

  20. Quantitative analysis of thermal diffuse X-ray scattering on single crystals. Communication 2. FCC metals

    International Nuclear Information System (INIS)

    Najsh, V.E.; Novoselova, T.V.; Sagaradze, I.V.; Kvyatkovskij, B.E.; Fedorov, V.I.; Chernenkov, Yu.P.

    1994-01-01

    With the use of X-ray diffractometer a study was made into the intensity of diffuse scattering in Ni crystals with FCC lattice. Earlier accomplished quantitative analysis for BCC crystals was extended to FCC lattices. Comparative evaluation was made for cooperative thermal oscillation patterns and corresponding diffuse scattering in crystals of various structures. Measurements on FCC crystals were carried out at room temperature using AgK a lpha-radiation in 96 points of Ni crystal. 8 refs., 4 figs

  1. Superconductivity in the Penson-Kolb Model on a Triangular Lattice

    Science.gov (United States)

    Ptok, A.; Mierzejewski, M.

    2008-07-01

    We investigate properties of the two-dimensional Penson-Kolb model with repulsive pair hopping interaction. In the case of a bipartite square lattice this interaction may lead to the η-type pairing, when the phase of superconducting order parameter changes from one lattice site to the neighboring one. We show that this interaction may be responsible for the onset of superconductivity also for a triangular lattice. We discuss the spatial dependence of the superconducting order parameter and demonstrate that the total momentum of the paired electrons is determined by the lattice geometry.

  2. Orientation of quartz nanocrystallites in the silicon lattice

    International Nuclear Information System (INIS)

    Kalanov, M.U.; Ibragimova, E.M.; Khamraeva, R.N.; Rustamova, V.M.; Ummatov, Kh.D.

    2006-01-01

    Full text: Basing on the study of medium angle diffuse X-ray scattering from silicon single crystals, it was supposed to be due to rod like oxygen precipitates. It was shown by us later, that depending on the growth conditions, as-grown silicon single crystals contain quartz crystal inclusions at an amount of 0.3 / 0.5 wt. % . Since it has not been done before, the aim of this work was to study the shape and orientation of quartz inclusions relative to a chosen axis of the silicon crystal lattice. We studied p-Si single crystals of one crucible origin with the specific resistance ρ 0 ≅ 1/10 Ohm· cm with different cut surfaces parallel to the crystal planes (100), (110) and (111). All the samples were cut and polished in the bar form with the sizes of 20x12x1.5 mm 3 . The dislocation density was N D ≅ 10 1 /10 3 cm -2 , the concentrations of oxygen and boron were N O ≅ 2/ 4 x10 17 cm -3 and N B ≅ 3· 10 1 5 c m -3 . Structure was analyzed at the set-up DRON-3M ( λ Cu K∝ = 0.1542 nm) at the room temperature in the angle range of angles 2Θ = 10/70 deg. The diffraction spectrum of the sample cut in (111) includes 5 selective reflections and the only diffuse one at 2Θ≅ 20 deg (d/n≅ 0.3136 nm), having a large width 0.1032 rad, which is due to presence of amorphous SiO x precipitate in the surface layer of silicon single crystal. The dominative selective line with d/n≅ 0.3136 nm at 2Θ≅ 28.5 deg belongs to reflection from (111) planes of the silicon lattice and the second less intensive one comes from the same planes with Cu K β radiation. Another selective reflection of a medium intensity at 2Θ≅ 59 deg with d/n≅ 0.1568 nm is its second order (222) and forbidden by the weakening laws. The rest narrow but weak lines with d/n≅ 0.3345 nm at 2Θ≅ 26.6 deg and 0.2468 nm at≅36.6 deg correspond to the diffraction reflections (101) and (110) from the crystal quartz lattice SiO 2 . It means that they are caused by optimally oriented quartz

  3. Phases, lattice parameters and thermal expansion of HoNi5-xAlx, 3≥x≥0

    International Nuclear Information System (INIS)

    Grzeta, B.; Sorgic, B.; Blazina, Z.

    1998-01-01

    The phases, lattice parameters and linear coefficient of thermal expansion were determined by X-ray powder diffraction between room temperature and 873 K for the system HoNi 5-x Al x (3 ≥ x ≥ 0). Alloys were hexagonal, in the space group P6/mmm; for 2 ≥ x ≥ 0 they were isostructural with CaCu 5 , and for 3 ≥ x ≥ 2 they were isostructural with YCo 3 Ga 2 . In both cases, the unit-cell parameters a and c increased as the Al content increased. The linear thermal expansion coefficient was composition dependent. Each of the investigated alloys exhibited an anisotropy in thermal expansion, the linear expansion coefficient along the a axis being larger than along the c axis. (orig.)

  4. Single crystal growth and characterization of kagomé-lattice shandites Co3Sn2-xInxS2

    Science.gov (United States)

    Kassem, Mohamed A.; Tabata, Yoshikazu; Waki, Takeshi; Nakamura, Hiroyuki

    2015-09-01

    Single crystals of the shandite-type half metallic ferromagnet Co3Sn2S2, and its In-substituted compounds, Co3Sn2-xInxS2 (0crystals. Single crystals of the two end members, Co3Sn2S2 and Co3In2S2, and solid solutions with low In concentrations (x≤0.35) were grown out of Sn and In self flux. Solid solution single crystals with higher In concentrations were grown out of Sn, In and Pb mixture flux. Grown crystals were characterized using the powder x-ray diffraction, wavelength-dispersive x-ray spectroscopy and magnetization measurements. The shandite structure with R3¯m symmetry was confirmed and crystal structure parameters of the obtained plate-shaped hexagonal crystals were refined using the Rietveld analysis. Magnetization measurements show suppression of the ferromagnetic ordering, observed in Co3Sn2S2, by In-substitution as reported for polycrystalline samples. The obtained crystals are useful to study anisotropy in magnetic and transport properties and further interesting magnetotransport properties of the layered compounds.

  5. Dark Solitons in FPU Lattice Chain

    Science.gov (United States)

    Wang, Deng-Long; Yang, Ru-Shu; Yang, You-Tian

    2007-11-01

    Based on multiple scales method, we study the nonlinear properties of a new Fermi-Pasta-Ulam lattice model analytically. It is found that the lattice chain exhibits a novel nonlinear elementary excitation, i.e. a dark soliton. Moreover, the modulation depth of dark soliton is increasing as the anharmonic parameter increases.

  6. Dark Solitons in FPU Lattice Chain

    International Nuclear Information System (INIS)

    Wang Denglong; Yang Youtian; Yang Rushu

    2007-01-01

    Based on multiple scales method, we study the nonlinear properties of a new Fermi-Pasta-Ulam lattice model analytically. It is found that the lattice chain exhibits a novel nonlinear elementary excitation, i.e. a dark soliton. Moreover, the modulation depth of dark soliton is increasing as the anharmonic parameter increases.

  7. On the construction of capacity-achieving lattice Gaussian codes

    KAUST Repository

    Alghamdi, Wael Mohammed Abdullah

    2016-08-15

    In this paper, we propose a new approach to proving results regarding channel coding schemes based on construction-A lattices for the Additive White Gaussian Noise (AWGN) channel that yields new characterizations of the code construction parameters, i.e., the primes and dimensions of the codes, as functions of the block-length. The approach we take introduces an averaging argument that explicitly involves the considered parameters. This averaging argument is applied to a generalized Loeliger ensemble [1] to provide a more practical proof of the existence of AWGN-good lattices, and to characterize suitable parameters for the lattice Gaussian coding scheme proposed by Ling and Belfiore [3]. © 2016 IEEE.

  8. On the construction of capacity-achieving lattice Gaussian codes

    KAUST Repository

    Alghamdi, Wael; Abediseid, Walid; Alouini, Mohamed-Slim

    2016-01-01

    In this paper, we propose a new approach to proving results regarding channel coding schemes based on construction-A lattices for the Additive White Gaussian Noise (AWGN) channel that yields new characterizations of the code construction parameters, i.e., the primes and dimensions of the codes, as functions of the block-length. The approach we take introduces an averaging argument that explicitly involves the considered parameters. This averaging argument is applied to a generalized Loeliger ensemble [1] to provide a more practical proof of the existence of AWGN-good lattices, and to characterize suitable parameters for the lattice Gaussian coding scheme proposed by Ling and Belfiore [3]. © 2016 IEEE.

  9. Electron paramagnetic resonance of the ns1 centers in crystals

    International Nuclear Information System (INIS)

    Nistor, S.V.; Ursu, I.

    1993-05-01

    The results of the EPR studies concerning the paramagnetic centers with ns 1 (N=n>2) outer electronic configuration contained in crystals are reviewed. Such centers, with 2 S 1/2 ground state, are produced by electron trapping at impurities of the IB and IIB group or by hole trapping at impurities of the IIIB and IV group of elements. The production and structural properties of such centers consisting of ns 1 ions (atoms) at various sites in the crystal lattice with different configurations of neighbouring defects are discussed in connection with their EPR characteristics. Tables containing the spin Hamiltonian parameters of all ns 1 centers reported in the literature until the end of year 1992 are given. (author). 146 refs, 14 tabs

  10. Vortex lattices in superconducting niobium and skyrmion lattices in chiral MnSi. An investigation by neutron scattering

    International Nuclear Information System (INIS)

    Muehlbauer, Sebastian C.

    2009-01-01

    In this thesis, we present a comprehensive small angle neutron scattering study of the vortex lattice (VL) in an ultra-pure Nb single crystal sample, characterized by a residual resistivity ratio of ∝ 10 4 . We systematically investigate the morphology of vortex structures with the magnetic field applied along a four-fold left angle 100 right angle axis. We succeed to deconvolute the general morphology of the VL and its orientation to three dominant mechanisms: First, non-local contributions, second, the transition between open and closed Fermi surface sheets and, third, the intermediate mixed state (IMS) between the Meissner and the Shubnikov phase. We present first time microscopic measurements of the intrinsic bulk VL tilt modulus c 44 by means of time resolved stroboscopic small angle neutron scattering in combination with a tailored magnetic field setup. In our study we find that the VL in Nb responds to an external force - in the form of a changed magnetic field - with an exponential relaxation. As expected, the relaxation process shows increasing VL stiffness with increasing magnetic field and reduced damping with increasing temperature. Besides this general trend, we observe a dramatic changeover of the relaxation process associated with the non-trivial VL morphology in the IMS and the crossover from attractive to repulsive vortex-vortex interaction. Furthermore we use small angle neutron scattering to establish the existence of a skyrmion lattice in the A-phase of MnSi. Due to a parallel alignment of the magnetic field with respect to the neutron beam, we are able to resolve the complete magnetic structure of the A-phase: The structure in the A-phase, reminiscent of a vortex lattice, consists of topological knots of the magnetization with particle-like properties, arranged in a regular six-fold lattice. The orientation of this lattice is strictly driven by the orientation of the applied magnetic field, regardless of the underlying crystal symmetry. The

  11. Vortex lattices in superconducting niobium and skyrmion lattices in chiral MnSi. An investigation by neutron scattering

    Energy Technology Data Exchange (ETDEWEB)

    Muehlbauer, Sebastian C

    2009-12-10

    In this thesis, we present a comprehensive small angle neutron scattering study of the vortex lattice (VL) in an ultra-pure Nb single crystal sample, characterized by a residual resistivity ratio of {proportional_to} 10{sup 4}. We systematically investigate the morphology of vortex structures with the magnetic field applied along a four-fold left angle 100 right angle axis. We succeed to deconvolute the general morphology of the VL and its orientation to three dominant mechanisms: First, non-local contributions, second, the transition between open and closed Fermi surface sheets and, third, the intermediate mixed state (IMS) between the Meissner and the Shubnikov phase. We present first time microscopic measurements of the intrinsic bulk VL tilt modulus c{sub 44} by means of time resolved stroboscopic small angle neutron scattering in combination with a tailored magnetic field setup. In our study we find that the VL in Nb responds to an external force - in the form of a changed magnetic field - with an exponential relaxation. As expected, the relaxation process shows increasing VL stiffness with increasing magnetic field and reduced damping with increasing temperature. Besides this general trend, we observe a dramatic changeover of the relaxation process associated with the non-trivial VL morphology in the IMS and the crossover from attractive to repulsive vortex-vortex interaction. Furthermore we use small angle neutron scattering to establish the existence of a skyrmion lattice in the A-phase of MnSi. Due to a parallel alignment of the magnetic field with respect to the neutron beam, we are able to resolve the complete magnetic structure of the A-phase: The structure in the A-phase, reminiscent of a vortex lattice, consists of topological knots of the magnetization with particle-like properties, arranged in a regular six-fold lattice. The orientation of this lattice is strictly driven by the orientation of the applied magnetic field, regardless of the underlying

  12. Magnetization plateaus and ground-state phase diagrams of the S=1 Ising model on the Shastry Sutherland lattice

    Science.gov (United States)

    Deviren, Seyma Akkaya

    2017-02-01

    In this research, we have investigated the magnetic properties of the spin-1 Ising model on the Shastry Sutherland lattice with the crystal field interaction by using the effective-field theory with correlations. The effects of the applied field on the magnetization are examined in detail in order to obtain the magnetization plateaus, thus different types of magnetization plateaus, such as 1/4, 1/3, 1/2, 3/5, 2/3 and 7/9 of the saturation, are obtained for strong enough magnetic fields (h). Magnetization plateaus exhibit single, triple, quintuplet and sextuple forms according to the interaction parameters, hence the magnetization plateaus originate from the competition between the crystal field (D) and exchange interaction parameters (J, J‧). The ground-state phase diagrams of the system are presented in three varied planes, namely (h/J, J‧/J), (h/J, D/J) and (D/J, J‧/J) planes. These phase diagrams display the Néel (N), collinear (C) and ferromagnetic (F) phases for certain values of the model parameters. The obtained results are in good agreement with some theoretical and experimental studies.

  13. Band structures in two-dimensional phononic crystals with periodic Jerusalem cross slot

    Science.gov (United States)

    Li, Yinggang; Chen, Tianning; Wang, Xiaopeng; Yu, Kunpeng; Song, Ruifang

    2015-01-01

    In this paper, a novel two-dimensional phononic crystal composed of periodic Jerusalem cross slot in air matrix with a square lattice is presented. The dispersion relations and the transmission coefficient spectra are calculated by using the finite element method based on the Bloch theorem. The formation mechanisms of the band gaps are analyzed based on the acoustic mode analysis. Numerical results show that the proposed phononic crystal structure can yield large band gaps in the low-frequency range. The formation mechanism of opening the acoustic band gaps is mainly attributed to the resonance modes of the cavities inside the Jerusalem cross slot structure. Furthermore, the effects of the geometrical parameters on the band gaps are further explored numerically. Results show that the band gaps can be modulated in an extremely large frequency range by the geometry parameters such as the slot length and width. These properties of acoustic waves in the proposed phononic crystals can potentially be applied to optimize band gaps and generate low-frequency filters and waveguides.

  14. Large-area photonic crystals

    Science.gov (United States)

    Ruhl, Tilmann; Spahn, Peter; Hellmann, Gotz P.; Winkler, Holger

    2004-09-01

    Materials with a periodically modulated refractive index, with periods on the scale of light wavelengths, are currently attracting much attention because of their unique optical properties which are caused by Bragg scattering of the visible light. In nature, 3d structures of this kind are found in the form of opals in which monodisperse silica spheres with submicron diameters form a face-centered-cubic (fcc) lattice. Artificial opals, with the same colloidal-crystalline fcc structure, have meanwhile been prepared by crystallizing spherical colloidal particles via sedimentation or drying of dispersions. In this report, colloidal crystalline films are introduced that were produced by a novel technique based on shear flow in the melts of specially designed submicroscopic silica-polymer core-shell hybrid spheres: when the melt of these spheres flows between the plates of a press, the spheres crystallize along the plates, layer by layer, and the silica cores assume the hexagonal order corresponding to the (111) plane of the fcc lattice. This process is fast and yields large-area films, thin or thick. To enhance the refractive index contrast in these films, the colloidal crystalline structure was inverted by etching out the silica cores with hydrofluoric acid. This type of an inverse opal, in which the fcc lattice is formed by mesopores, is referred to as a polymer-air photonic crystal.

  15. A study on new types of metallic photonic crystals

    International Nuclear Information System (INIS)

    Ahmed, M.I.

    2013-01-01

    In this thesis, I tried to synthesize a one dimension dielectric photonic crystal. I have succeeded in depositing single layers of zinc oxide and magnesium oxide on glass substrates. Each single layer was characterized by a scanning electron microscope, X-ray diffraction, A Mirue interferometer, and a spectrophotometer. The refractive indices, extinction coefficients, and absorption coefficients of each single layer were calculated from the measured transmittance, reflectance, and thickness data. Using the calculated parameters (refractive indices) and measured parameters (thicknesses) the transmission spectrum of the one dimension photonic crystal composed of zinc oxide and magnesium oxide was modelled. Using the transfer matrix method, a comparative study of the one dimension-dielectric and metallic photonic crystals was done. Effect of the refractive index difference, filling factor, number of periods, Plasmon frequency, damping coefficient, and incidence angle on the transmittance of the dielectric and metallic photonic crystal was carried out. A multilayered structure composed of Silver and Gallium Nitride was designed to transmit in the visible region, block UV frequencies, and reflect the IR and microwave frequencies. Using a combination of MaxwellGarnett Approximation and the transfer matrix method; the properties of a nanocomposite photonic crystal consisting of Cryolite and spherical nanoparticles of silver distributed in a dielectric matrix of titanium dioxide was studied. Effect of the nanoparticle concentration, lattice constant and incidence angle on the polaritonic and structure photonic band gap were studied.

  16. Heavy water critical experiments on plutonium lattice

    International Nuclear Information System (INIS)

    Miyawaki, Yoshio; Shiba, Kiminori

    1975-06-01

    This report is the summary of physics study on plutonium lattice made in Heavy Water Critical Experiment Section of PNC. By using Deuterium Critical Assembly, physics study on plutonium lattice has been carried out since 1972. Experiments on following items were performed in a core having 22.5 cm square lattice pitch. (1) Material buckling (2) Lattice parameters (3) Local power distribution factor (4) Gross flux distribution in two region core (5) Control rod worth. Experimental results were compared with theoretical ones calculated by METHUSELAH II code. It is concluded from this study that calculation by METHUSELAH II code has acceptable accuracy in the prediction on plutonium lattice. (author)

  17. Comment on 'Magic strains in face-centered and body-centered cubic lattices'

    Energy Technology Data Exchange (ETDEWEB)

    Waal, B.W. van de (Technische Hogeschool Twente, Enschede (Netherlands). Dept. of Physics)

    1990-03-01

    The six symmetry-related so-called magic strain tensors that transform a f.c.c. lattice (or a b.c.c. lattice) into itself, which have been reported recently by Boyer are not unique: An infinite number of displacement tensors can be constructed that transform one lattice into another, or into itself. There is no connection with fivefold symmetry, other than that in any f.c.c. crystal. (orig.).

  18. Rotation of dust plasma crystals in an axial magnetic field

    International Nuclear Information System (INIS)

    Cheung, F.; Prior, N.; Mitchell, L.

    2000-01-01

    Full text: Micron-sized melamine formaldehyde particles were introduced into argon plasma. As a result, the particles were negatively charged due to collision with the electrons within the plasma. With the right conditions, these particles formed a stable macroscopic crystal lattice, known as dust plasma crystal. In our experiment we conduct at Flinders University, we apply an external axial magnetic field to various configurations of dust plasma crystal. These configurations include small crystal lattices consisting of one to several particles, and large crystal lattices with many hundreds of particles. The magnetic field strength ranged from 0-32G and was uniform over the extent of the crystal. The crystals were observed to be rotating collectively in the left-handed direction under the influence of the axial magnetic field. In the case of the large crystals, the angular velocity was about 2 complete rotations per minute and was proportional to the applied magnetic field. The angular velocity changes only slightly depending on the plasma conditions. Neither radial variance in the angular velocity nor shear velocity in the vertical direction was observed in the crystal's rotational motion. In the case of the small crystals, we managed to rotate 2-6 particles (whether they are planar, 2 layers or tetrahedral). We discovered that the ease and the uniformity of the rotation of the different crystals increase as its rotational symmetry increases. Also an increase in the magnetic field strength will correspond to an increase in the angular velocity. Crystals in the shape of an annulus were also tested for theoretical reasons. The poster presentation will contain the experimental procedures, a detailed analysis and an explanation for such dust plasma crystal rotational motion

  19. Order parameters in smectic liquid crystals

    International Nuclear Information System (INIS)

    Beldon, Stephen M.

    2001-01-01

    This thesis explores some of the important mechanisms for switching in smectic liquid crystals. It is mainly concerned with the interaction of the electric field and various order parameters in smectic phases. Distortion of these order parameters and also the layer structures associated with smectics are discussed in depth. Initial work is concentrated on the electroclinic effect of commercially available FLC mixtures, where experimental results suggest the presence of non-uniformity in the molecular director profile. Two possible models are suggested assuming a variation of the order parameter θ through the cell. The first model assumes that the smectic layers remain bookshelf-like, and the second that the layers tilt in a vertical chevron structure when a cone angle is induced electroclinically or otherwise. The latter model is the first 'order parameter' model of an electric field induced vertical chevron. The presence of non-uniformity in the director profile is sensed by a method similar to wavelength extinction spectroscopy. Investigations are undertaken on racemic smectic materials with high dielectric biaxiality. Modelling of such a material reveals a new electroclinic effect which shows a discrete second order phase transition on application of a field. It is suggested that a bistable electroclinic effect stabilised with a high frequency ac field may be realised if a residual polarisation is present in the high biaxiality material, and that this might be useful in the displays industry. Experimental investigations of such a material confirm the above effects close to the smectic A-C transition. Finally a higher order smectic phase, the smectic I* phase, is considered. The distortion of the hexagonal bond orientational order is investigated experimentally during application of an electric field. The first dynamic model of the switching process is presented, showing good agreement with the experimental results. It is suggested that the bond orientational

  20. Entropy-driven crystal formation on highly strained substrates

    KAUST Repository

    Savage, John R.; Hopp, Stefan F.; Ganapathy, Rajesh; Gerbode, Sharon J.; Heuer, Andreas; Cohen, Itai

    2013-01-01

    the crucial role of entropy in heteroepitaxy in this technologically important regime. Ultimately, this entropic component of lattice mismatched crystal growth could be used to develop unique methods for heterogeneous nucleation and growth of single crystals

  1. Crystal nucleation in binary hard-sphere mixtures: the effect of order parameter on the cluster composition

    NARCIS (Netherlands)

    Ni, R.; Smallenburg, F.; Filion, L.C.; Dijkstra, M.

    2011-01-01

    We study crystal nucleation in a binary mixture of hard spheres and investigate the composition and size of the (non)critical clusters using Monte Carlo simulations. In order to study nucleation of a crystal phase in computer simulations, a one-dimensional order parameter is usually defined to

  2. Preparation and properties of crystals of mixed refractory oxides with perovskite structure

    Energy Technology Data Exchange (ETDEWEB)

    Melekh, B T; Andreev, A A; Kartenko, N F; Pevtsov, A B; Trepakov, V A; Filin, Yu N [AN SSSR, Moscow. Fiziko-Tekhnicheskij Inst.

    1982-10-01

    Peculiar features of crystal growth of some complex refractory oxides with perovskite structure using the method of direct high-frequency melting in a cold container are studied. Melting, synthesis and directed crystallization have been conducted in the air. X-ray diffraction investigations of the prepared SrTiO/sub 3/, CaZrO/sub 3/, BaZrO/sub 3/, BaHFO/sub 3/, LaCrO/sub 3/, YCrO/sub 3/, ErCrO/sub 3/, La/sub 2/Ti/sub 2/O/sub 7/, LaTaO/sub 3/ and other oxides are conducted, lattice parameters are given. Optical spectra of absorption, photo- and thermoluminescence and thermostimulated currents are studied.

  3. Imperfection and radiation damage in protein crystals studied with coherent radiation

    Energy Technology Data Exchange (ETDEWEB)

    Nave, Colin, E-mail: colin.nave@diamond.ac.uk [Diamond Light Source Ltd, Harwell Science and Innovation Campus, Didcot OX11 0DE (United Kingdom); Sutton, Geoff [Wellcome Trust Centre for Human Genetics, Roosevelt Drive, Oxford OX3 7BN (United Kingdom); Evans, Gwyndaf; Owen, Robin; Rau, Christoph [Diamond Light Source Ltd, Harwell Science and Innovation Campus, Didcot OX11 0DE (United Kingdom); Robinson, Ian [University College London, 17–19 Gordon Street, London WC1H 0AH (United Kingdom); Stuart, David Ian [Wellcome Trust Centre for Human Genetics, Roosevelt Drive, Oxford OX3 7BN (United Kingdom); Diamond Light Source Ltd, Harwell Science and Innovation Campus, Didcot OX11 0DE (United Kingdom)

    2016-01-01

    Coherent diffraction observations from polyhedra crystals at cryotemperature are reported. Information is obtained about the lattice strain and the changes with radiation damage. Fringes and speckles occur within diffraction spots when a crystal is illuminated with coherent radiation during X-ray diffraction. The additional information in these features provides insight into the imperfections in the crystal at the sub-micrometre scale. In addition, these features can provide more accurate intensity measurements (e.g. by model-based profile fitting), detwinning (by distinguishing the various components), phasing (by exploiting sampling of the molecular transform) and refinement (by distinguishing regions with different unit-cell parameters). In order to exploit these potential benefits, the features due to coherent diffraction have to be recorded and any change due to radiation damage properly modelled. Initial results from recording coherent diffraction at cryotemperatures from polyhedrin crystals of approximately 2 µm in size are described. These measurements allowed information about the type of crystal imperfections to be obtained at the sub-micrometre level, together with the changes due to radiation damage.

  4. Imperfection and radiation damage in protein crystals studied with coherent radiation

    International Nuclear Information System (INIS)

    Nave, Colin; Sutton, Geoff; Evans, Gwyndaf; Owen, Robin; Rau, Christoph; Robinson, Ian; Stuart, David Ian

    2016-01-01

    Coherent diffraction observations from polyhedra crystals at cryotemperature are reported. Information is obtained about the lattice strain and the changes with radiation damage. Fringes and speckles occur within diffraction spots when a crystal is illuminated with coherent radiation during X-ray diffraction. The additional information in these features provides insight into the imperfections in the crystal at the sub-micrometre scale. In addition, these features can provide more accurate intensity measurements (e.g. by model-based profile fitting), detwinning (by distinguishing the various components), phasing (by exploiting sampling of the molecular transform) and refinement (by distinguishing regions with different unit-cell parameters). In order to exploit these potential benefits, the features due to coherent diffraction have to be recorded and any change due to radiation damage properly modelled. Initial results from recording coherent diffraction at cryotemperatures from polyhedrin crystals of approximately 2 µm in size are described. These measurements allowed information about the type of crystal imperfections to be obtained at the sub-micrometre level, together with the changes due to radiation damage

  5. Supersymmetry on the noncommutative lattice

    International Nuclear Information System (INIS)

    Nishimura, Jun; Rey, Soo-Jong; Sugino, Fumihiko

    2003-01-01

    Built upon the proposal of Kaplan et al. (heplat{0206109}), we construct noncommutative lattice gauge theory with manifest supersymmetry. We show that such theory is naturally implementable via orbifold conditions generalizing those used by Kaplan et al. We present the prescription in detail and illustrate it for noncommutative gauge theories latticized partially in two dimensions. We point out a deformation freedom in the defining theory by a complex-parameter, reminiscent of discrete torsion in string theory. We show that, in the continuum limit, the supersymmetry is enhanced only at a particular value of the deformation parameter, determined solely by the size of the noncommutativity. (author)

  6. Lattice misfit during ageing of a polycrystalline nickel-base superalloy

    International Nuclear Information System (INIS)

    Collins, D.M.; Yan, L.; Marquis, E.A.; Connor, L.D.; Ciardiello, J.J.; Evans, A.D.; Stone, H.J.

    2013-01-01

    The temporal evolution of the lattice parameters and lattice misfit of an advanced polycrystalline nickel-base superalloy have been studied in situ during an ageing heat treatment using synchrotron X-ray diffraction. During ageing, the γ and γ′ lattice parameters were both observed to decrease, a trend that cannot be attributed to a loss of coherency alone. Phase-extracted γ′ replicated this behaviour. Atom probe tomography was used to measure the compositional changes between the start and end of the ageing heat treatment. Using these data, a thermodynamic assessment was made using the software ThermoCalc of the structural change across the interface between γ and γ′. Subsequently, the unconstrained lattice parameters were estimated and were shown to be in good agreement with the X-ray diffraction measurements. Thus, the observed anomalous lattice misfit behaviour was concluded to be dominated by elemental exchange between the γ and γ′ phases during ageing

  7. Finite element method analysis of band gap and transmission of two-dimensional metallic photonic crystals at terahertz frequencies.

    Science.gov (United States)

    Degirmenci, Elif; Landais, Pascal

    2013-10-20

    Photonic band gap and transmission characteristics of 2D metallic photonic crystals at THz frequencies have been investigated using finite element method (FEM). Photonic crystals composed of metallic rods in air, in square and triangular lattice arrangements, are considered for transverse electric and transverse magnetic polarizations. The modes and band gap characteristics of metallic photonic crystal structure are investigated by solving the eigenvalue problem over a unit cell of the lattice using periodic boundary conditions. A photonic band gap diagram of dielectric photonic crystal in square lattice array is also considered and compared with well-known plane wave expansion results verifying our FEM approach. The photonic band gap designs for both dielectric and metallic photonic crystals are consistent with previous studies obtained by different methods. Perfect match is obtained between photonic band gap diagrams and transmission spectra of corresponding lattice structure.

  8. Ellipsometry study of optical parameters of AgIn5S8 crystals

    Science.gov (United States)

    Isik, Mehmet; Gasanly, Nizami

    2015-12-01

    AgIn5S8 crystals grown by Bridgman method were characterized for optical properties by ellipsometry measurements. Spectral dependence of optical parameters; real and imaginary parts of the pseudodielectric function, pseudorefractive index, pseudoextinction coefficient, reflectivity and absorption coefficient were obtained from ellipsometry experiments carried out in the 1.2-6.2 eV range. Direct band gap energy of 1.84 eV was found from the analysis of absorption coefficient vs. photon energy. The oscillator energy, dispersion energy and zero-frequency refractive index, high-frequency dielectric constant values were found from the analysis of the experimental data using Wemple-DiDomenico and Spitzer-Fan models. Crystal structure and atomic composition ratio of the constituent elements in the AgIn5S8 crystal were revealed from structural characterization techniques of X-ray diffraction and energy dispersive spectroscopy.

  9. A benchmark comparison of the Canadian Supercritical Water-Cooled Reactor (SCWR) 64-element fuel lattice cell parameters using various computer codes

    Energy Technology Data Exchange (ETDEWEB)

    Sharpe, J.; Salaun, F.; Hummel, D.; Moghrabi, A., E-mail: sharpejr@mcmaster.ca [McMaster University, Hamilton, ON (Canada); Nowak, M. [McMaster University, Hamilton, ON (Canada); Institut National Polytechnique de Grenoble, Phelma, Grenoble (France); Pencer, J. [McMaster University, Hamilton, ON (Canada); Canadian Nuclear Laboratories, Chalk River, ON, (Canada); Novog, D.; Buijs, A. [McMaster University, Hamilton, ON (Canada)

    2015-07-01

    Discrepancies in key lattice physics parameters have been observed between various deterministic (e.g. DRAGON and WIMS-AECL) and stochastic (MCNP, KENO) neutron transport codes in modeling previous versions of the Canadian SCWR lattice cell. Further, inconsistencies in these parameters have also been observed when using different nuclear data libraries. In this work, the predictions of k∞, various reactivity coefficients, and relative ring-averaged pin powers have been re-evaluated using these codes and libraries with the most recent 64-element fuel assembly geometry. A benchmark problem has been defined to quantify the dissimilarities between code results for a number of responses along the fuel channel under prescribed hot full power (HFP), hot zero power (HZP) and cold zero power (CZP) conditions and at several fuel burnups (0, 25 and 50 MW·d·kg{sup -1} [HM]). Results from deterministic (TRITON, DRAGON) and stochastic codes (MCNP6, KENO V.a and KENO-VI) are presented. (author)

  10. A benchmark comparison of the Canadian Supercritical Water-Cooled Reactor (SCWR) 64-element fuel lattice cell parameters using various computer codes

    International Nuclear Information System (INIS)

    Sharpe, J.; Salaun, F.; Hummel, D.; Moghrabi, A.; Nowak, M.; Pencer, J.; Novog, D.; Buijs, A.

    2015-01-01

    Discrepancies in key lattice physics parameters have been observed between various deterministic (e.g. DRAGON and WIMS-AECL) and stochastic (MCNP, KENO) neutron transport codes in modeling previous versions of the Canadian SCWR lattice cell. Further, inconsistencies in these parameters have also been observed when using different nuclear data libraries. In this work, the predictions of k∞, various reactivity coefficients, and relative ring-averaged pin powers have been re-evaluated using these codes and libraries with the most recent 64-element fuel assembly geometry. A benchmark problem has been defined to quantify the dissimilarities between code results for a number of responses along the fuel channel under prescribed hot full power (HFP), hot zero power (HZP) and cold zero power (CZP) conditions and at several fuel burnups (0, 25 and 50 MW·d·kg"-"1 [HM]). Results from deterministic (TRITON, DRAGON) and stochastic codes (MCNP6, KENO V.a and KENO-VI) are presented. (author)

  11. Lattice expansion of carbon-stabilized expanded austenite

    DEFF Research Database (Denmark)

    Hummelshøj, Thomas Strabo; Christiansen, Thomas; Somers, Marcel A. J.

    2010-01-01

    The lattice parameter of expanded austenite was determined as a function of the content of interstitially dissolved carbon in homogeneous, carburized thin stainless steel foils. For the first time this expansion of the face-centered cubic lattice is determined on unstrained austenite. It is found...

  12. Buried Porous Silicon-Germanium Layers in Monocrystalline Silicon Lattices

    Science.gov (United States)

    Fathauer, Robert W. (Inventor); George, Thomas (Inventor); Jones, Eric W. (Inventor)

    1998-01-01

    Monocrystalline semiconductor lattices with a buried porous semiconductor layer having different chemical composition is discussed and monocrystalline semiconductor superlattices with a buried porous semiconductor layers having different chemical composition than that of its monocrystalline semiconductor superlattice are discussed. Lattices of alternating layers of monocrystalline silicon and porous silicon-germanium have been produced. These single crystal lattices have been fabricated by epitaxial growth of Si and Si-Ge layers followed by patterning into mesa structures. The mesa structures are strain etched resulting in porosification of the Si-Ge layers with a minor amount of porosification of the monocrystalline Si layers. Thicker Si-Ge layers produced in a similar manner emitted visible light at room temperature.

  13. Low-cost spray-processed Ag{sub 1−x}Cu{sub x}InS{sub 2} nano-films: Structural and functional investigation within the Lattice Compatibility Theory framework

    Energy Technology Data Exchange (ETDEWEB)

    Gherouel, D. [Unité de Physique des Dispositifs à Semi-conducteurs, Faculté des Sciences de Tunis, Tunis El Manar University, 2092 Tunis (Tunisia); Yumak, A. [Physics Department, The Faculty of Arts and Science,Marmara University, 34722 Göztepe, Istanbul (Turkey); Znaidi, M. [Institut Préparatoire Aux Etudes d’Ingénieurs de Nabeul, Merazka, 8000 Nabeul (Tunisia); Bouzidi, A. [Unité de Physique des Dispositifs à Semi-conducteurs, Faculté des Sciences de Tunis, Tunis El Manar University, 2092 Tunis (Tunisia); Boubaker, K., E-mail: mmbb11112000@yahoo.fr [Unité de Physique des Dispositifs à Semi-conducteurs, Faculté des Sciences de Tunis, Tunis El Manar University, 2092 Tunis (Tunisia); Yacoubi, N. [Institut Préparatoire Aux Etudes d’Ingénieurs de Nabeul, Merazka, 8000 Nabeul (Tunisia); Amlouk, M. [Unité de Physique des Dispositifs à Semi-conducteurs, Faculté des Sciences de Tunis, Tunis El Manar University, 2092 Tunis (Tunisia)

    2015-08-15

    Highlights: • Cu{sub x}Ag{sub 1−x}InS{sub 2} with a minimal lattice mismatch between absorbers and buffers. • The lattice compatibility for understanding silver–copper kinetics. • Controlled and enhanced spray pyrolisis method as a low-cost synthesis protocol. - Abstract: This work deals with some structural and optical investigations about Cu{sub x}Ag{sub 1−x}InS{sub 2} alloys sprayed films and the beneficial effect of copper incorporation in AgInS{sub 2} ternary matrices. The main purpose of this work is to obtain the band gap energy E{sub g} as well as different lattice parameters. The studied properties led to reaching minimum of lattice mismatch between absorber and buffer layers within solar cell devices. As a principal and original finding, the lattice compatibility between both silver and copper indium disulfide structures has been proposed as a guide for understanding kinetics of these materials crystallization.

  14. Scanning tunneling microscopy of the atomically smooth (001) surface of vanadium pentoxide V_2O_5 crystals

    International Nuclear Information System (INIS)

    Muslimov, A. E.; Butashin, A. V.; Kanevsky, V. M.

    2017-01-01

    The (001) cleavage surface of vanadium pentoxide (V_2O_5) crystal has been studied by scanning tunneling spectroscopy (STM). It is shown that the surface is not reconstructed; the STM image allows geometric lattice parameters to be determined with high accuracy. The nanostructure formed on the (001) cleavage surface of crystal consists of atomically smooth steps with a height multiple of unit-cell parameter c = 4.37 Å. The V_2O_5 crystal cleavages can be used as references in calibration of a scanning tunneling microscope under atmospheric conditions both along the (Ñ…, y) surface and normally to the sample surface (along the z axis). It is found that the terrace surface is not perfectly atomically smooth; its roughness is estimated to be ~0.5 Å. This circumstance may introduce an additional error into the microscope calibration along the z coordinate.

  15. Electrostatic instability of some jellium model lattices of high symmetry to their plane cleavage

    International Nuclear Information System (INIS)

    Kholopov, Eugene V; Kalashnikova, Vita V

    2007-01-01

    Jellium model structures composed of regular lattices of equal point charges immersed in a neutralizing uniform background are considered. The symmetric description eliminating the effect of potentials without transverse structural modulation is extended to the events specified by alternating distances between point-charge planes. Based on modulated potentials typical of plane-wise lattice summation, the energy of interaction between two semi-infinite hemi-crystals divided by a plane is obtained for cubic and hexagonal crystals, where all the characteristic orientations of the cleavage plane are taken into account. We found that simple cubic and hexagonal lattices, as well as cubic and hexagonal diamond structures, turn out to be unstable for certain cleavage planes. The most favourable cleavage planes for the bcc, fcc and hcp structures are also emphasized

  16. High-pressure synthesis and crystal structure of α-Y{sub 2}B{sub 4}O{sub 9}

    Energy Technology Data Exchange (ETDEWEB)

    Schmitt, Martin K.; Huppertz, Hubert [Innsbruck Univ. (Austria). Inst. fuer Allgemeine, Anorganische und Theoretische Chemie

    2017-07-01

    α-Y{sub 2}B{sub 4}O{sub 9} was synthesized in a high-pressure/high-temperature experiment at 12.3 GPa/1020 C. The crystal structure has been determined via single-crystal X-ray diffraction. α-Y{sub 2}B{sub 4}O{sub 9} is isotypic to the lanthanide borates α-Ln{sub 2}B{sub 4}O{sub 9} (Ln = Sm-Ho) and crystallizes in the monoclinic space group C2/c (no. 15) with the following lattice parameters: a = 25.084(2), b = 4.3913(2), c = 24.726(2) Aa, and β = 99.97(1) . The compound was further characterized via X-ray powder diffraction as well as IR and Raman spectroscopy.

  17. Electronic relaxations of radiative defects of the anion sublattice in cesium bromide crystals and exoemission of electrons

    CERN Document Server

    Galyij, P V

    2002-01-01

    The paper presents the results of investigations of thermostimulated exoelectron emission (TSEE) from CsBr crystal, excited by moderate doses (D <= 10 sup 4 Gy) of ultraviolet (h nu <= 7 eV) that selectively creates anion excitons and radiative defects in the anion sublattice. Having used the previously established connection between thermoactivated processes such as thermostimulated exoemission, electroconductivity, and luminescence in the irradiated crystal lattice, the concentrations of exoemission-active centers (EAC) and kinetics parameters of TSEE are calculated. The EAC concentration calculated on a base of the bulk, thermoactivated-recombinational, and band-gap Auger-like exoemission mechanisms, are in satisfactory agreement with the concentration of electron color centers in the irradiated crystals.

  18. Thermal, Dielectric Studies on Pure and Amino Acid L-Glutamic Acid, L-Histidine L-Valine Doped Potassium Dihydrogen Phosphate Single Crystals

    Science.gov (United States)

    Kumaresan, P.; Babu, S. Moorthy; Anbarasan, P. M.

    Amino acids (L-Glutamic acid, L-Histidine, L-Valine) doped potassium dihydrogen phosphate crystals were grown by the solution growth technique. Slow cooling as well as slow evaporation methods were employed to grow these crystals. The concentration of dopants in the mother solution was varied from 0.1 mole % to 10 mole %. The solubility data for all dopant concentrations were determined. The variation in pH and the corresponding habit modification of the grown crystals were characterized with UV - VIS, FT-IR and SHG trace elements, and dielectric studies reveal slight distortion of lattice parameter for the heavily doped KDP crystals. TGA-DTA studies reveal good thermal stability. The dopants increase the hardness value of the material, which also depends on the concentration of the dopants. Amino acids doping improved the NLO properties. The detailed results on the spectral parameters, habit modifications and constant values will be presented.

  19. Intrinsic magnetism of a series of Co substituted ZnO single crystals

    International Nuclear Information System (INIS)

    Lv Peiwen; Huang Feng; Chu Wangsheng; Lin Zhang; Chen Dagui; Li Wei; Chen Dongliang; Wu Ziyu

    2008-01-01

    Magnetic properties of a series of well-substituted Zn 1-x Co x O (x = 0.018,0.036 and 0.05) single crystals were studied. A typical paramagnetic anisotropy property, which strengthens when x decreases, was found. A magnetization step was observed at 2 K when the magnetic field is parallel to the c axis, indicating that paramagnetic anisotropy is the origin of the strong crystal field effect on Co 2+ ions in ZnO lattices. The Co 2+ single-ion anisotropy parameter 2D is obtained as 7.5 K. The effective moment of Co 2+ takes the values 2.7 μ B , 1.82 μ B , 1.49 μ B when x = 0.018, 0.036 and 0.05, revealing that more antiferromagnetic coupling between Co 2+ ions arises in the perfect crystal when x increases

  20. Mixed spin Ising model with four-spin interaction and random crystal field

    International Nuclear Information System (INIS)

    Benayad, N.; Ghliyem, M.

    2012-01-01

    The effects of fluctuations of the crystal field on the phase diagram of the mixed spin-1/2 and spin-1 Ising model with four-spin interactions are investigated within the finite cluster approximation based on a single-site cluster theory. The state equations are derived for the two-dimensional square lattice. It has been found that the system exhibits a variety of interesting features resulting from the fluctuation of the crystal field interactions. In particular, for low mean value D of the crystal field, the critical temperature is not very sensitive to fluctuations and all transitions are of second order for any value of the four-spin interactions. But for relatively high D, the transition temperature depends on the fluctuation of the crystal field, and the system undergoes tricritical behaviour for any strength of the four-spin interactions. We have also found that the model may exhibit reentrance for appropriate values of the system parameters.

  1. Superconductivity in Sm-doped CaFe2As2 single crystals

    Science.gov (United States)

    Dong-Yun, Chen; Bin-Bin, Ruan; Jia, Yu; Qi, Guo; Xiao-Chuan, Wang; Qing-Ge, Mu; Bo-Jin, Pan; Tong, Liu; Gen-Fu, Chen; Zhi-An, Ren

    2016-06-01

    In this article, the Sm-doping single crystals Ca1 - x Sm x Fe2As2 (x = 0 ˜ 0.2) were prepared by the CaAs flux method, and followed by a rapid quenching treatment after the high temperature growth. The samples were characterized by structural, resistive, and magnetic measurements. The successful Sm-substitution was revealed by the reduction of the lattice parameter c, due to the smaller ionic radius of Sm3+ than Ca2+. Superconductivity was observed in all samples with onset T c varying from 27 K to 44 K upon Sm-doping. The coexistence of a collapsed phase transition and the superconducting transition was found for the lower Sm-doping samples. Zero resistivity and substantial superconducting volume fraction only happen in higher Sm-doping crystals with the nominal x > 0.10. The doping dependences of the c-axis length and onset T c were summarized. The high-T c observed in these quenched crystals may be attributed to simultaneous tuning of electron carriers doping and strain effect caused by lattice reduction of Sm-substitution. Project supported by the National Natural Science Foundation of China (Grant No. 11474339), the National Basic Research Program of China (Grant Nos. 2010CB923000 and 2011CBA00100), and the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDB07020100).

  2. Photonic crystals: features and applications (physics research and technology)

    CERN Document Server

    2013-01-01

    The present book is focused on the study of unprecedented control and manipulation of light by photonic crystals (PCs) and their applications. These are micro- or usually nano-structures composed of periodic indexes of refraction of dielectrics with high refractive index contrast. They exhibit optical frequency band gaps in analogy to electronic bands for a periodic potential of a semiconductor crystal lattice. The gemstone opal and butterflys feathers colours are already referred to as natural examples of photonic crystals. The characteristics of such supper-lattices were first reported by Yablonovitch in 1987. The exploitation of photonic crystals is a promising tool in communication, sensors, optical computing, and nanophotonics. Discussed are the various features of one-dimensional (1D) and two-dimensional (2D) photonic crystals, photonic quasi crystals, heterostuctures and PC fibres under a variety of conditions using several materials, and metamaterials. It also focuses on the applications of PCs in opt...

  3. Study of wide band-gap crystal LiCaAlF6 by IR-reflection spectroscopy and ab initio calculations

    International Nuclear Information System (INIS)

    Novikova, N.N.; Klimin, S.A.; Mavrin, B.N.

    2017-01-01

    Polarized IR-reflection spectra and results of ab initio calculations of vibrational and electronic properties of LiCaAlF6 single crystal are presented. It is shown that the crystal band gap is direct. Experimental and theoretical parameters are obtained for dipole-active and all phonons, respectively, including silent modes. Experimental IR-reflection and Raman spectra are well described in the frame of results obtained by ab initio calculations. The peculiarities are discussed concerning the structure of electronic bands, the interatomic interactions, the character of lattice vibrations, and the phonon dispersion.

  4. Density of states model for the lattice transformation in A-15 compounds

    International Nuclear Information System (INIS)

    Pietrass, B.; Handstein, A.; Behr, G.

    1980-01-01

    The cubic-tetragonal lattice transformation in A-15 compounds is described by an empirical model in which the density of states function near the Fermi energy is characterized by a two-parametric peak in addition to the constant part. Two types of peak splitting under tetragonal deformation are considered, leading to qualitatively different results about the phase transition. Results are given for the order parameter, the phase stability, the soft elastic modulus, and the paramagnetic spin susceptibility. Comparing with measurements of the magnetic susceptibility of V 3 Si single crystals near the phase transition a better agreement is obtained for a twofold degenerate density of states peak than for a threefold degenerate one. (author)

  5. Experimental evidence for flux-lattice melting. [in high-Tc superconductors

    Science.gov (United States)

    Farrell, D. E.; Rice, J. P.; Ginsberg, D. M.

    1991-01-01

    A low-frequency torsional oscillator has been used to search for flux-lattice melting in an untwinned single crystal of YBa2Cu3O(7-delta). The damping of the oscillator was measured as a function of temperature, for applied magnetic fields in the range H = 0.1-2.3 T. A remarkably sharp damping peak has been located. It is suggested that the temperature of the peak corresponds to the melting point of the Abrikosov flux lattice.

  6. A lattice-based Monte Carlo evaluation of Canada Deuterium Uranium-6 safety parameters

    International Nuclear Information System (INIS)

    Kim, Yong Hee; Hartanto, Donny; Kim, Woo Song

    2016-01-01

    Important safety parameters such as the fuel temperature coefficient (FTC) and the power coefficient of reactivity (PCR) of the CANada Deuterium Uranium (CANDU-6) reactor have been evaluated using the Monte Carlo method. For accurate analysis of the parameters, the Doppler broadening rejection correction scheme was implemented in the MCNPX code to account for the thermal motion of the heavy uranium-238 nucleus in the neutron-U scattering reactions. In this work, a standard fuel lattice has been modeled and the fuel is depleted using MCNPX. The FTC value is evaluated for several burnup points including the mid-burnup representing a near-equilibrium core. The Doppler effect has been evaluated using several cross-section libraries such as ENDF/B-VI.8, ENDF/B-VII.0, JEFF-3.1.1, and JENDL-4.0. The PCR value is also evaluated at mid-burnup conditions to characterize the safety features of an equilibrium CANDU-6 reactor. To improve the reliability of the Monte Carlo calculations, we considered a huge number of neutron histories in this work and the standard deviation of the k-infinity values is only 0.5-1 pcm

  7. Lattice dynamics of cubic Cs2NaLnX6 and CsNaLn1-xLn'xX6 elpasolites

    International Nuclear Information System (INIS)

    Acevedo, R.; Poblete, V.; Alzamora, R.; Venegas, R.; Navarro, G.; Henriquez, C.

    1999-01-01

    Crystal lattice dynamics of stoichiometric Cs 2 NaLnX 6 and nonstoichiometric CsNaLn 1-x Ln' x X 6 , 0.01 ≤ x ≤ 0.10, Ln and Ln' are trivalent positive lanthanide ions and X is chlorine or bromine, were studied.. Phonon dispersion relations were computed for similar compound, Cs 2 UBr 6 , and vibronic absorption spectra with reduced number of required input parameters are considered on the basis of proposed model. (author)

  8. Experimental investigation on dependency of interparticle distance in Coulomb crystal on various parameters

    OpenAIRE

    Adachi, Satoshi; Takayanagi, Masahiro; 足立 聡; 高柳 昌弘

    2007-01-01

    Dependency of interparticle distance in Coulomb crystal on various parameters such as plasma density, electron temperature, plasma potential and the Debye length are experimentally investigated. From the investigation, it is found that the interparticle distance is proportional to the Debye length.

  9. Reconstruction of lattice parameters and beam momentum distribution from turn-by-turn beam position monitor readings in circular accelerators

    Directory of Open Access Journals (Sweden)

    C. S. Edmonds

    2014-05-01

    Full Text Available In high chromaticity circular accelerators, rapid decoherence of the betatron motion of a particle beam can make the measurement of lattice and bunch values, such as Courant-Snyder parameters and betatron amplitude, difficult. A method for reconstructing the momentum distribution of a beam from beam position measurements is presented. Further analysis of the same beam position monitor data allows estimates to be made of the Courant-Snyder parameters and the amplitude of coherent betatron oscillation of the beam. The methods are tested through application to data taken on the linear nonscaling fixed field alternating gradient accelerator, EMMA.

  10. Information flow between weakly interacting lattices of coupled maps

    Energy Technology Data Exchange (ETDEWEB)

    Dobyns, York [PEAR, Princeton University, Princeton, NJ 08544-5263 (United States); Atmanspacher, Harald [Institut fuer Grenzgebiete der Psychologie und Psychohygiene, Wilhelmstr. 3a, 79098 Freiburg (Germany)]. E-mail: haa@igpp.de

    2006-05-15

    Weakly interacting lattices of coupled maps can be modeled as ordinary coupled map lattices separated from each other by boundary regions with small coupling parameters. We demonstrate that such weakly interacting lattices can nevertheless have unexpected and striking effects on each other. Under specific conditions, particular stability properties of the lattices are significantly influenced by their weak mutual interaction. This observation is tantamount to an efficacious information flow across the boundary.

  11. Information flow between weakly interacting lattices of coupled maps

    International Nuclear Information System (INIS)

    Dobyns, York; Atmanspacher, Harald

    2006-01-01

    Weakly interacting lattices of coupled maps can be modeled as ordinary coupled map lattices separated from each other by boundary regions with small coupling parameters. We demonstrate that such weakly interacting lattices can nevertheless have unexpected and striking effects on each other. Under specific conditions, particular stability properties of the lattices are significantly influenced by their weak mutual interaction. This observation is tantamount to an efficacious information flow across the boundary

  12. Structural changes induced by lattice-electron interactions: SiO2 stishovite and FeTiO3 ilmenite.

    Science.gov (United States)

    Yamanaka, Takamitsu

    2005-09-01

    The bright source and highly collimated beam of synchrotron radiation offers many advantages for single-crystal structure analysis under non-ambient conditions. The structure changes induced by the lattice-electron interaction under high pressure have been investigated using a diamond anvil pressure cell. The pressure dependence of electron density distributions around atoms is elucidated by a single-crystal diffraction study using deformation electron density analysis and the maximum entropy method. In order to understand the bonding electrons under pressure, diffraction intensity measurements of FeTiO3 ilmenite and gamma-SiO2 stishovite single crystals at high pressures were made using synchrotron radiation. Both diffraction studies describe the electron density distribution including bonding electrons and provide the effective charge of the cations. In both cases the valence electrons are more localized around the cations with increasing pressure. This is consistent with molecular orbital calculations, proving that the bonding electron density becomes smaller with pressure. The thermal displacement parameters of both samples are reduced with increasing pressure.

  13. Growth, crystal structure, spectral properties and laser performance of Yb3+:NaLu(MoO4)2 crystal

    International Nuclear Information System (INIS)

    Yu, Yi; Zhang, Lizhen; Huang, Yisheng; Lin, Zhoubin; Wang, Guofu

    2013-01-01

    A double molybdate Yb 3+ :NaLu(MoO 4 ) 2 crystal was successfully grown from a flux of Na 2 Mo 2 O 7 by the top-seeded solution growth method, for the first time to our knowledge. The crystal belongs to the tetragonal system with space group I4 1 /a, and the unit-cell parameters are a = b = 5.159 Å, c = 11.246 Å. Na and Lu atoms co-occupy the same lattice site, which leads to the disordered structure of NaLu(MoO 4 ) 2 crystal. The thermal expansion coefficients of the crystal are 1.35 × 10 −5 K −1 along the c-axis, and 1.01 × 10 −5 K −1 along the a-axis. The full-width at half-maximum of the emission bands are 67 nm for the σ-polarization and 50 nm for the π-polarization at about 1020 nm. The maximum emission cross-sections for the σ- and π-polarizations are 2.79 × 10 −20 cm 2 and 2.94 × 10 −20 cm 2 , respectively. 0.3 W output power at 1025 nm was obtained at an absorbed pump power of 1.7 W, with a slope efficiency of 24%. (paper)

  14. Growth, crystal structure, spectral properties and laser performance of Yb3+:NaLu(MoO4)2 crystal

    Science.gov (United States)

    Yu, Yi; Zhang, Lizhen; Huang, Yisheng; Lin, Zhoubin; Wang, Guofu

    2013-10-01

    A double molybdate Yb3+:NaLu(MoO4)2 crystal was successfully grown from a flux of Na2Mo2O7 by the top-seeded solution growth method, for the first time to our knowledge. The crystal belongs to the tetragonal system with space group I41/a, and the unit-cell parameters are a = b = 5.159 Å, c = 11.246 Å. Na and Lu atoms co-occupy the same lattice site, which leads to the disordered structure of NaLu(MoO4)2 crystal. The thermal expansion coefficients of the crystal are 1.35 × 10-5 K-1 along the c-axis, and 1.01 × 10-5 K-1 along the a-axis. The full-width at half-maximum of the emission bands are 67 nm for the σ-polarization and 50 nm for the π-polarization at about 1020 nm. The maximum emission cross-sections for the σ- and π-polarizations are 2.79 × 10-20 cm2 and 2.94 × 10-20 cm2, respectively. 0.3 W output power at 1025 nm was obtained at an absorbed pump power of 1.7 W, with a slope efficiency of 24%.

  15. Calculations of spin Hamiltonian parameters and analysis of trigonal distortions in LiSr(Al,Ga)F6:Cr3+ crystals

    International Nuclear Information System (INIS)

    Brik, M.G.; Avram, C.N.; Avram, N.M.

    2006-01-01

    The effective spin-Hamiltonian (SH) parameters (zero-field splitting D and g factors g - parallel and g - perpendicular ) for Cr 3+ ions in LiSr(Al,Ga)F 6 crystals are calculated from the complete high-order perturbation formulae for a d 3 ion. Parameters of trigonal crystal field acting on the Cr 3+ ion are calculated. The magnitude of trigonal distortion of the [CrF 6 ] 3- clusters is related to the experimental measurements of the spin-Hamiltonian parameters in the considered systems. Since in both crystals g parallel perpendicular , [CrF 6 ] 3- clusters undergo an axial compression along the C 3 axis. Experimental values of the hyperfine structure constants A parallel and A perpendicular are used to evaluate the core polarization constant κ for Cr 3+ ion in both crystals

  16. Calculation Of A Lattice Physics Parameter For SBWR Fuel Bundle Design

    International Nuclear Information System (INIS)

    Sardjono, Y.

    1996-01-01

    The maximum power peaking factor for Nuclear Power Plant SBWR type is 1.5. The precision for that calculation is related with the result of unit cell analysis each rod in the fuel bundles. This analysis consist of lattice eigenvalue, lattice average diffusion cross section as well as relative power peaking factor in the fuel rod for each fuel bundles. The calculation by using TGBLA computer code which is based on the transport and 168 group diffusion theory. From this calculation can be concluded that the maximum relative power peaking factor is 1.304 and lower than design limit

  17. About some practical aspects of X-ray diffraction : From single crystal to powders

    Energy Technology Data Exchange (ETDEWEB)

    Giacovazzo, C [Bari Univ. (Italy). Dip. Geomineralogico

    1996-09-01

    An ideal polycrystalline material or power is an ensemble of a very large number of randomly oriented crystallites. It is shown the effect that this random orientation has on the diffraction of a specimen assumed to contain only one reciprocal lattice node. The most remarkable difference with the single-crystal case is that now must think of scattering vectors not as lying on discrete nodes of reciprocal lattice vectors, the distances from the single-crystal reciprocal lattice nodes to the origin of reciprocal space.

  18. About some practical aspects of X-ray diffraction : From single crystal to powders

    International Nuclear Information System (INIS)

    Giacovazzo, C.

    1996-01-01

    An ideal polycrystalline material or power is an ensemble of a very large number of randomly oriented crystallites. It is shown the effect that this random orientation has on the diffraction of a specimen assumed to contain only one reciprocal lattice node. The most remarkable difference with the single-crystal case is that now must think of scattering vectors not as lying on discrete nodes of reciprocal lattice vectors, the distances from the single-crystal reciprocal lattice nodes to the origin of reciprocal space

  19. Synthesis and crystal structure of lithium beryllium deuteride Li2BeD4.

    Science.gov (United States)

    Bulychev, Boris M; Shpanchenko, Roman V; Antipov, Evgeny V; Sheptyakov, Denis V; Bushmeleva, Svetlana N; Balagurov, Anatoly M

    2004-10-04

    Single-phase ternary deuteride Li(2)BeD(4) was synthesized by a high-pressure high-temperature technique from LiD and BeD(2). The crystal structure of Li(2)BeD(4) was solved from X-ray and neutron powder diffraction data. The compound crystallizes in the monoclinic space group P2(1)/c with lattice parameters a = 7.06228(9) A, b = 8.3378(1) A, c = 8.3465(1) A, beta =93.577(1) degrees, and Z = 8. Its structure contains isolated BeD(4) tetrahedra and Li atoms that are located in the structure interstices. Li(2)BeD(4) does not undergo any structural phase transitions at temperatures down to 8 K.

  20. Random crystal field effects on the integer and half-integer mixed-spin system

    Science.gov (United States)

    Yigit, Ali; Albayrak, Erhan

    2018-05-01

    In this work, we have focused on the random crystal field effects on the phase diagrams of the mixed spin-1 and spin-5/2 Ising system obtained by utilizing the exact recursion relations (ERR) on the Bethe lattice (BL). The distribution function P(Di) = pδ [Di - D(1 + α) ] +(1 - p) δ [Di - D(1 - α) ] is used to randomize the crystal field.The phase diagrams are found to exhibit second- and first-order phase transitions depending on the values of α, D and p. It is also observed that the model displays tricritical point, isolated point, critical end point and three compensation temperatures for suitable values of the system parameters.

  1. Experimental and theoretical investigation of lattice defect structures in a series of Zn, Fe-doped nonstoichiometric lithium niobate

    International Nuclear Information System (INIS)

    Guo Fengyun; Lue Qiang; Sun Liang; Li Hongtao; Zhen Xihe; Xu Yuheng; Zhao Liancheng

    2006-01-01

    A series of the double doped lithium niobate (LiNbO 3 , LN) single crystals had been grown by Czochralski method. The Curie temperatures of various concentrations doped or [Li]/[Nb] ratio LN crystals measured by differential thermal analysis (DTA) were discussed to investigate their defect structures with Safaryan et al. new approach about LN lattice defect structure using Curie temperatures calculated. Infrared transmission spectra of various concentrations doped were used to compare the investigation above. The results show that the lithium vacancy model is the more probable to describe the lattice defect structure of the doped LN single crystal

  2. Simulation and design of the photonic crystal microwave accelerating structure

    International Nuclear Information System (INIS)

    Song Ruiying; Wu Congfeng; He Xiaodong; Dong Sai

    2007-01-01

    The authors have derived the global band gaps for general two-dimensional (2D) photonic crystal microwave accelerating structures formed by square or triangular arrays of metal posts. A coordinate-space, finite-difference code was used to calculate the complete dispersion curves for the lattices. The fundamental and higher frequency global photonic band gaps were determined numerically. The structure formed by triangular arrays of metal posts with a missing rod at the center has advantages of higher-order-modes (HOM) suppression and main mode restriction under the condition of a/b<0.2. The relationship between the RF properties and the geometrical parameters have been studied for the 9.37 GHz photonic crystal accelerating structure. The Rs, Q, Rs/Q of the new structure may be comparable to the disk-loaded accelerating structure. (authors)

  3. Solid solutions of gadolinium doped zinc oxide nanorods by combined microwave-ultrasonic irradiation assisted crystallization

    Science.gov (United States)

    Kiani, Armin; Dastafkan, Kamran; Obeydavi, Ali; Rahimi, Mohammad

    2017-12-01

    Nanocrystalline solid solutions consisting of un-doped and gadolinium doped zinc oxide nanorods were fabricated by a modified sol-gel process utilizing combined ultrasonic-microwave irradiations. Polyvinylpyrrolidone, diethylene glycol, and triethylenetetramine respectively as capping, structure directing, and complexing agents were used under ultrasound dynamic aging and microwave heating to obtain crystalline nanorods. Crystalline phase monitoring, lattice parameters and variation, morphology and shape, elemental analysis, functional groups, reducibility, and the oxidation state of emerged species were examined by PXRD, FESEM, TEM, EDX, FTIR, micro Raman, H2-TPR, and EPR techniques. Results have verified that irradiation mechanism of gelation and crystallization reduces the reaction time, augments the crystal quality, and formation of hexagonal close pack structure of Wurtzite morphology. Besides, dissolution of gadolinium within host lattice involves lattice deformation, unit cell distortion, and angular position variation. Structure related shape and growth along with compositional purity were observed through microscopic and spectroscopic surveys. Furthermore, TPR and EPR studies elucidated more detailed behavior upon exposure to the exerted irradiations and subsequent air-annealing including the formed oxidation states and electron trapping centers, presence of gadolinium, zinc, and oxygen disarrays and defects, as well as alteration in the host unit cell via gadolinium addition.

  4. Moessbauer effect in lattice dynamics. Experimental techniques and applications

    International Nuclear Information System (INIS)

    Chen, Yi-Long; Yang, De-Ping

    2007-01-01

    This up-to-date review closes an important gap in the existing literature by providing a comprehensive description of the applications of Moessbauer effect in lattice dynamics, along with a collection of applications in metals, alloys, amorphous solids, molecular crystals, thin films, and nanocrystals. It is the first book to systematically compare Moessbauer spectroscopy using synchrotron radiation to conventional Moessbauer spectroscopy, discussing in detail its advantages and capabilities, backed by the latest theoretical developments and experimental examples. Intended as a self-contained volume that may be used as a complete reference or textbook, 'Moessbauer Effect in Lattice Dynamics' adopts new pedagogical approaches with several non-traditional and refreshing theoretical expositions, while all quantitative relations are derived with the necessary details so as to be easily followed by the reader. Two entire chapters are devoted to the study of the dynamics of impurity atoms in solids, while a thorough description of the Mannheim model as a theoretical method is presented and its predictions compared to experimental results. Finally, an in-depth analysis of absorption of Moessbauer radiation is presented, based on recent research by one of the authors, resulting in an exact expression of fractional absorption and a method to determine the optimal thickness of an absorber. Supplemented by elaborate appendices containing constants and parameters. (orig.)

  5. Quality control on pre-serial Bridgman production of PbWO{sub 4} scintillating crystals by means of photoelasticity

    Energy Technology Data Exchange (ETDEWEB)

    Rinaldi, D., E-mail: d.rinaldi@univpm.i [Dipartimento di Fisica e Ingegneria dei Materiali e del Territorio, Universita Politecnica delle Marche, via Brecce Bianche, 60131 Ancona (Italy); INFN section of Perugia (Italy); Ciriaco, A. [Dipartimento di Fisica e Ingegneria dei Materiali e del Territorio, Universita' Politecnica delle Marche, via Brecce Bianche, 60131 Ancona (Italy); Lebeau, M. [CERN PH department, 1211 Geneva 23 (Switzerland); Paone, N. [Dipartimento di Meccanica, Universita' Politecnica delle Marche, via Brecce Bianche, 60131 Ancona (Italy)

    2010-04-11

    Residual internal stresses in PbWO{sub 4} (PWO) scintillating crystals grown by Bridgman method have been systematically studied. Residual stresses induced during growth play an important role in production yield. Cracking probability during mechanical processing as well as stable mechanical properties in finished crystal are closely related to internal stress levels. A regular production of good-quality crystals requires a fast and easy feed-back on growth parameters. Samples from a pre-serial production were analyzed in order to give the producer a quality feed-back for process optimization. By means of photoelasticity, we measured residual stress distribution in several sections along the growth axis and for typical positions in every section. The stress analysis revealed defects occurring during the crystallization process, attributed to dislocations, lattice disorientation and poly-crystallinity. This work had been prompted by the need for quality monitoring of a pre-serial production of PWO for the CMS experiment at CERN's LHC. Mapping stress levels inside the ingot volume and proposing a synthetic parameter to be used as a quality indicator, the resulting analysis should contribute to parameter optimization and improve the growth performance. The proposed method may be useful in conventional crystal production.

  6. Synthesis and crystal structure of Mg0.5NbO2: An ion-exchange reaction with Mg2+ between trigonal [NbO2]- layers

    Science.gov (United States)

    Miura, Akira; Takei, Takahiro; Kumada, Nobuhiro

    2013-01-01

    A new layered niobate, Mg0.5NbO2, was synthesized from LiNbO2 through a cation-exchange reaction with Mg2+ at 450-550 °C. This is the first example of a topotactic reaction with an aliovalent cation between trigonal [NbO2]- layers. It is proposed to be isostructural with LiNbO2 (space group; P63/mmc) with lattice parameters of a=2.9052(6) Å, c=10.625(15) Å. The lattice parameters and formation energy of Mg0.5NbO2 crystallized in LiNbO2 form and other layered CaNb2O4 one were calculated by density functional theory.

  7. Ultrasonic characterization of Cu-Al-Ni single crystals lattice stability in the vicinity of the phase transition.

    Science.gov (United States)

    Landa, Michal; Novák, Václav; Sedlák, Petr; Sittner, Petr

    2004-04-01

    Measurements of elastic constants of the austenite phase when approaching the phase transformation either upon cooling or stressing is of the crucial interest for the shape memory alloy field. Acoustic properties (wave velocity and also attenuation changes) of the Cu-Al-Ni single crystal were investigated in situ during stress-induced martensitic transformation at constant (room) temperature. The parent austenite cubic lattice of the Cu-Al-Ni exhibits very high elastic anisotropy (anisotropy factor A approximately 12). The measurements were made using nine combinations of (i) applied uniaxial compression in a given crystal direction, (ii) the wave propagation and (iii) polarization vectors. The chosen configurations are sufficient for evaluation of all independent third order elastic constants (TOEC). The longitudinal modes were also measured by the immersion technique, using the transducer pair in a water tank installed on the testing machine. The device works as "a ultrasonic extensometer" measuring a transverse strain of the specimen. The dependencies of both natural and initial wave velocities on the applied stress may be evaluated. Three elastic constants of the stress-induced martensite were determined. The elastic properties were found to vary with the increasing stress above the Ms transformation temperature, which is interpreted as a precursor for the martensitic transformation. The onset of the transformation was additionally identified from the acoustic emission measurement.

  8. Inelastic light scattering in crystals

    Science.gov (United States)

    Sushchinskii, M. M.

    The papers presented in this volume are concerned with a variety of problems in optics and solid state physics, such as Raman scattering of light in crystals and disperse media, Rayleigh and inelastic scattering during phase transitions, characteristics of ferroelectrics in relation to the general soft mode concept, and inelastic spectral opalescence. A group-theory approach is used to classify the vibrational spectra of the crystal lattice and to analyze the properties of idealized crystal models. Particular attention is given to surface vibrational states and to the study of the surface layers of crystals and films by light scattering methods.

  9. Topological magnon bands in ferromagnetic star lattice

    International Nuclear Information System (INIS)

    Owerre, S A

    2017-01-01

    The experimental observation of topological magnon bands and thermal Hall effect in a kagomé lattice ferromagnet Cu(1–3, bdc) has inspired the search for topological magnon effects in various insulating ferromagnets that lack an inversion center allowing a Dzyaloshinskii–Moriya (DM) spin–orbit interaction. The star lattice (also known as the decorated honeycomb lattice) ferromagnet is an ideal candidate for this purpose because it is a variant of the kagomé lattice with additional links that connect the up-pointing and down-pointing triangles. This gives rise to twice the unit cell of the kagomé lattice, and hence more interesting topological magnon effects. In particular, the triangular bridges on the star lattice can be coupled either ferromagnetically or antiferromagnetically which is not possible on the kagomé lattice ferromagnets. Here, we study DM-induced topological magnon bands, chiral edge modes, and thermal magnon Hall effect on the star lattice ferromagnet in different parameter regimes. The star lattice can also be visualized as the parent material from which topological magnon bands can be realized for the kagomé and honeycomb lattices in some limiting cases. (paper)

  10. Topological magnon bands in ferromagnetic star lattice.

    Science.gov (United States)

    Owerre, S A

    2017-05-10

    The experimental observation of topological magnon bands and thermal Hall effect in a kagomé lattice ferromagnet Cu(1-3, bdc) has inspired the search for topological magnon effects in various insulating ferromagnets that lack an inversion center allowing a Dzyaloshinskii-Moriya (DM) spin-orbit interaction. The star lattice (also known as the decorated honeycomb lattice) ferromagnet is an ideal candidate for this purpose because it is a variant of the kagomé lattice with additional links that connect the up-pointing and down-pointing triangles. This gives rise to twice the unit cell of the kagomé lattice, and hence more interesting topological magnon effects. In particular, the triangular bridges on the star lattice can be coupled either ferromagnetically or antiferromagnetically which is not possible on the kagomé lattice ferromagnets. Here, we study DM-induced topological magnon bands, chiral edge modes, and thermal magnon Hall effect on the star lattice ferromagnet in different parameter regimes. The star lattice can also be visualized as the parent material from which topological magnon bands can be realized for the kagomé and honeycomb lattices in some limiting cases.

  11. X-ray determination of mean square amplitudes of lattice oscillations in compounds with ZnS structure

    International Nuclear Information System (INIS)

    Deus, P.; Schneider, H.A.; Voland, U.

    1980-01-01

    A general method of determination of the mean square amplitudes of lattice oscillations (MSA) for crystals with sphalerite structure is described and applied to InP. The linearity of suitable functions of the measured integral BRAGG intensities of sin 2 theta/lambda 2 is used for the verification of the parameters selected for the correction of extinction and DTS. In this way the accuracy of the results is increased. The MSAs of the InP-sublattices are evaluated. According to theoretical expectations the MSAs of the P-sublattice are larger because of the greater contributions of optical phonons. (author)

  12. Non-conservative dynamics of lattice sites near a migrating interface in a diffusional phase transformation

    International Nuclear Information System (INIS)

    Yang, T.; Gao, Y.; Wang, D.; Shi, R.P.; Chen, Z.; Nie, J.F.; Li, J.; Wang, Y.

    2017-01-01

    Migration of phase boundaries in crystalline solids eliminates one set of lattice sites and establishes another. Using a combination of phase field crystal modeling and crystallographic analysis, we present here a complete atomistic description of the migration mechanism of a high-index planar interface during a diffusional hexagon to square phase transformation. In particular we show that a terrace-step interface advances macroscopically in the form of growth ledges, while microscopically its migration occurs by opposite shearing on the terraces and a one-to-two splitting of lattice sites, giving a new class of lattice site correspondence and superabundant vacancies. In addition, a new approach capable of finding a critical nucleus with atomic resolution is developed by combining the phase field crystal energetics with the free-end nudged elastic band algorithm.

  13. All optical detection of picosecond spin-wave dynamics in 2D annular antidot lattice

    Science.gov (United States)

    Porwal, Nikita; Mondal, Sucheta; Choudhury, Samiran; De, Anulekha; Sinha, Jaivardhan; Barman, Anjan; Datta, Prasanta Kumar

    2018-02-01

    Novel magnetic structures with precisely controlled dimensions and shapes at the nanoscale have potential applications in spin logic, spintronics and other spin-based communication devices. We report the fabrication of 2D bi-structure magnonic crystal in the form of embedded nanodots in a periodic Ni80Fe20 antidot lattice structure (annular antidot) by focused ion-beam lithography. The spin-wave spectra of the annular antidot sample, studied for the first time by a time-resolved magneto-optic Kerr effect microscopy show a remarkable variation with bias field, which is important for the above device applications. The optically induced spin-wave spectra show multiple modes in the frequency range 14.7 GHz-3.5 GHz due to collective interactions between the dots and antidots as well as the annular elements within the whole array. Numerical simulations qualitatively reproduce the experimental results, and simulated mode profiles reveal the spatial distribution of the spin-wave modes and internal magnetic fields responsible for these observations. It is observed that the internal field strength increases by about 200 Oe inside each dot embedded within the hole of annular antidot lattice as compared to pure antidot lattice and pure dot lattice. The stray field for the annular antidot lattice is found to be significant (0.8 kOe) as opposed to the negligible values of the same for the pure dot lattice and pure antidot lattice. Our findings open up new possibilities for development of novel artificial crystals.

  14. Crystal structure and magnetism of UOsAl

    Energy Technology Data Exchange (ETDEWEB)

    Andreev, A.V., E-mail: andreev@fzu.cz [Institute of Physics, Academy of Sciences, Na Slovance 2, 182 21 Prague (Czech Republic); Daniš, S. [Department of Condensed Matter Physics, Charles University, Ke Karlovu 5, 121 16 Prague (Czech Republic); Šebek, J.; Henriques, M.S.; Vejpravová, J. [Institute of Physics, Academy of Sciences, Na Slovance 2, 182 21 Prague (Czech Republic); Gorbunov, D.I. [Institute of Physics, Academy of Sciences, Na Slovance 2, 182 21 Prague (Czech Republic); Dresden High Magnetic Field Laboratory (HLD-EMFL), Helmholtz-Zentrum, Dresden-Rossendorf, D-01314 Dresden (Germany); Havela, L. [Department of Condensed Matter Physics, Charles University, Ke Karlovu 5, 121 16 Prague (Czech Republic)

    2017-04-15

    Crystal structure, magnetization, and specific heat were studied on single crystal of uranium intermetallic compound UOsAl. It is a hexagonal Laves phase of MgZn{sub 2} type, space group P6{sub 3}/mmc, with lattice parameters a=536.4 pm, c=845.3 pm. Shortest inter-uranium distance 313 pm (along the c-axis) is considerably smaller than the Hill limit (340 pm). The compound is a weakly temperature-dependent paramagnet with magnetic susceptibility of ≈1.5*10{sup −8} m{sup 3} mol{sup −1} (at T=2 K), which is slightly higher with magnetic field along the a-axis compared to the c-axis. The Sommerfeld coefficient of electronic specific heat has moderate value of γ=36 mJ mol{sup −1} K{sup −2}. - Highlights: • Crystal structure and magnetic properties were studied on single crystal of UOsAl with hexagonal structure of MgZn{sub 2} type. • Shortest inter-uranium distance 313 pm (along the c-axis) is considerably smaller than the Hill limit (340 pm). • UOsAl has paramagnetic ground state as the compounds with T=Fe and Ru, i.e. 3d and 4d analogues of Os.

  15. Relationship between changes in the crystal lattice strain and thermal conductivity of high burnup UO{sub 2} pellets

    Energy Technology Data Exchange (ETDEWEB)

    Amaya, Masaki, E-mail: amaya.masaki@jaea.go.j [Fuel Safety Research Group, Nuclear Safety Research Center, Japan Atomic Energy Agency, Tokai-mura, Naka-gun, Ibaraki 319-1195 (Japan); Nakamura, Jinichi; Fuketa, Toyoshi [Fuel Safety Research Group, Nuclear Safety Research Center, Japan Atomic Energy Agency, Tokai-mura, Naka-gun, Ibaraki 319-1195 (Japan); Kosaka, Yuji [Nuclear Development Corporation, 622-12, Funaishikawa, Tokai-mura, Naka-gun, Ibaraki 319-1111 (Japan)

    2010-01-01

    Two kinds of disk-shaped UO{sub 2} samples (4 mm in diameter and 1 mm in thickness) were irradiated in a test reactor up to about 60 and 130 GWd/t, respectively. The microstructures of the samples were investigated by means of optical microscopy, scanning electron microscopy/ electron probe micro-analysis (SEM/EPMA) and micro-X-ray diffractometry. The measured lattice parameters tended to be considerably smaller than the reported values, and the typical cauliflower structure which is often observed in high burnup fuel pellet is hardly seen in these samples. Thermal diffusivities of the samples were also measured by using a laser flash method, and their thermal conductivities were evaluated by multiplying the heat capacity of unirradiated UO{sub 2} and sample densities. While the thermal conductivities of sample 2 showed recovery after being annealed at 1500 K, those of sample 4 were not clearly observed even after being annealed at 1500 K. These trends suggest that the amount of accumulated irradiation-induced defects depends on the irradiation condition of each sample. From the comparison of the changes in the lattice parameter and strain energy density before and after the thermal diffusivity measurements, it is likely that the thermal conductivity recovery in the temperature region from 1200 to 1500 K is related to the migration of dislocation.

  16. Multiple x-ray diffraction applied to the study of crystal impurities

    International Nuclear Information System (INIS)

    Cardoso, L.P.

    1983-06-01

    The x-ray multiple diffraction technique is used in the study of impurities concentration and localization in the crystal lattice, implemented with the fundamental observation that the impurities cannot be distributed with the same spatial group symmetry of the crystal. This fact could introduce scattered intensity in the crystal reciprocal lattice forbidden nodes. This effect was effectively observed in multiple diffraction diagrams, where a reinforcement of the scattered intensity in the pure crystal is produced, when choosing conveniently the involved reflections. The reflectivity theory was developed in the kinematic case, which take into account the scattering by the impurities atoms, and the analysis showed that, in the first approximation, the impurities can influence both in the allowed and forbidden positions for the pure crystal. (L.C.J.A.)

  17. Size dependences of crystal structure and magnetic properties of DyMnO{sub 3} nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Tajiri, T., E-mail: tajiri@fukuoka-u.ac.jp [Faculty of Science, Fukuoka University, Fukuoka 814-0180 (Japan); Terashita, N.; Hamamoto, K.; Deguchi, H.; Mito, M. [Faculty of Engineering, Kyushu Institute of Technology, Kitakyushu 804-8550 (Japan); Morimoto, Y.; Konishi, K. [Graduate School of Science and Engineering, Ehime University, Matsuyama 790-8577 (Japan); Kohno, A. [Faculty of Science, Fukuoka University, Fukuoka 814-0180 (Japan)

    2013-11-15

    We synthesized DyMnO{sub 3} nanoparticles with particle sizes of about 7.5–15.3 nm in the pores of mesoporous silica and investigated their crystal structure and magnetic properties. As the particle size decreased, the lattice constants of the DyMnO{sub 3} nanoparticles deviated from those of the bulk crystal, and the Jahn–Teller distortion in the nanoparticle systems decreased. In addition, the estimated lattice strain increased with decreasing particle size. The DyMnO{sub 3} nanoparticles showed superparamagnetic behavior. The blocking temperature and the coercive field increased with decreasing particle size, and this behavior was contrary to the usual magnetic size effects. It is deduced that these unique size dependences of the magnetic properties for the DyMnO{sub 3} nanoparticles were derived from the changes in lattice constants and lattice strain. The anisotropic lattice deformation in the crystal structure of the nanoparticles induces an enhancement of the magnetic anisotropy, which results in the increase in blocking temperature and coercive field with decreasing particle size. - Highlights: • We successfully synthesized DyMnO{sub 3} nanoparticles with particle size of 7.5–15.3 nm. • Lattice strain increases with decreasing particle size. • Lattice constants exhibit anisotropic change with decreasing particle size. • Distortion of crystal structure leads to enhancement of magnetic anisotropy constant. • Blocking temperature and coercive field increases with decreasing particle size.

  18. Thermal, dielectric studies on pure and amino acid ( L-glutamic acid, L-histidine, L-valine) doped KDP single crystals

    Science.gov (United States)

    Kumaresan, P.; Moorthy Babu, S.; Anbarasan, P. M.

    2008-05-01

    Amino acids ( L-glutamic acid, L-histidine, L-valine) doped potassium dihydrogen phospate crystals are grown by solution growth technique. Slow cooling as well as slow evaporation methods were employed to grow these crystals. The concentration of dopants in the mother solution was varied from 0.1 mol% to 10 mol%. The solubility data for all dopants concentration were determined. There is variation in pH value and hence, there is habit modification of the grown crystals were characterized with UV-VIS, FT-IR studies, SHG trace elements and dielectric studies reveal slight distortion of lattice parameter for the heavily doped KDP crystals. UV-Visible spectra confirm the improvement in the transparency of these crystals on doping metal ions. FT-IR spectra reveal strong absorption band between 1400 and 1600 cm -1 for metal ion doped crystals. TGA-DTA studies reveal good thermal stability. The dopants increase the hardness value of the material and it also depends on the concentration of the dopants. Amino acids doping improved the NLO properties. The detailed results on the spectral parameters, habit modifications and constant values will be presented.

  19. Effect of reactor neutron radiation and temperature on the structure of InP single crystals

    International Nuclear Information System (INIS)

    Bojko, V.M.; Kolin, N.G.; Merkurisov, D.I.; Bublik, V.T.; Voronova, M.I.; Shcherbachev, K.D.

    2006-01-01

    The structural characteristics of InP single crystals have been investigated depending on the radiation effects produced by fast and full spectrum neutrons and subsequent heat treatment. A lattice period in InP single crystals decreases under neutron irradiation. Fast neutrons make the main contribution into the change of the lattice period. Availability of the thermal neutrons initiates the formation of Sn atoms, but does not make a significant influence on the change of the lattice period. Heat treatment of the irradiated samples up to 600 deg C causes the annealing of radiation defects and recovery of the lattice period. With increasing neutron fluences a lattice period becomes even higher than before irradiation [ru

  20. Discrete-to-continuum modelling of weakly interacting incommensurate two-dimensional lattices.

    Science.gov (United States)

    Español, Malena I; Golovaty, Dmitry; Wilber, J Patrick

    2018-01-01

    In this paper, we derive a continuum variational model for a two-dimensional deformable lattice of atoms interacting with a two-dimensional rigid lattice. The starting point is a discrete atomistic model for the two lattices which are assumed to have slightly different lattice parameters and, possibly, a small relative rotation. This is a prototypical example of a three-dimensional system consisting of a graphene sheet suspended over a substrate. We use a discrete-to-continuum procedure to obtain the continuum model which recovers both qualitatively and quantitatively the behaviour observed in the corresponding discrete model. The continuum model predicts that the deformable lattice develops a network of domain walls characterized by large shearing, stretching and bending deformation that accommodates the misalignment and/or mismatch between the deformable and rigid lattices. Two integer-valued parameters, which can be identified with the components of a Burgers vector, describe the mismatch between the lattices and determine the geometry and the details of the deformation associated with the domain walls.

  1. Lattice Transparency of Graphene.

    Science.gov (United States)

    Chae, Sieun; Jang, Seunghun; Choi, Won Jin; Kim, Youn Sang; Chang, Hyunju; Lee, Tae Il; Lee, Jeong-O

    2017-03-08

    Here, we demonstrated the transparency of graphene to the atomic arrangement of a substrate surface, i.e., the "lattice transparency" of graphene, by using hydrothermally grown ZnO nanorods as a model system. The growth behaviors of ZnO nanocrystals on graphene-coated and uncoated substrates with various crystal structures were investigated. The atomic arrangements of the nucleating ZnO nanocrystals exhibited a close match with those of the respective substrates despite the substrates being bound to the other side of the graphene. By using first-principles calculations based on density functional theory, we confirmed the energetic favorability of the nucleating phase following the atomic arrangement of the substrate even with the graphene layer present in between. In addition to transmitting information about the atomic lattice of the substrate, graphene also protected its surface. This dual role enabled the hydrothermal growth of ZnO nanorods on a Cu substrate, which otherwise dissolved in the reaction conditions when graphene was absent.

  2. Influence of radiation-damages on parameters of lattice oscillations in crystalline and vitreous SiO2

    International Nuclear Information System (INIS)

    Abdukadyrova, I.Kh.

    2008-01-01

    Using IR reflection spectroscopy, the influence of radiation-induced disturbances on a number of parameters of lattice oscillations in two SiO 2 modifications was investigated. Radiation kinetics of changes in spectral characteristics of fundamental oscillations in SiO 2 crystalline and glassy states was determined. Dose dependences of both reflectivity and degenerate mode vibrational frequency were found to show minima whose locations were governed by a type of a sample. Under higher doses of neutron radiation (10 21 cm -2 ), certain characteristics of bands were observed to be of the same values for the both materials modified. The features of radiation kinetics were found for dynamic parameters of the samples. It was deduced that specific character of radiation-induced changes observed in spectral and dynamic parameters of oscillations in the region of degenerate modes was due to both the accumulation of radiation damages and a change in the force field surrounding bridge-type bonds which was related with the change in the SiO 2 structure. (authors)

  3. Scanning tunneling microscopy of the atomically smooth (001) surface of vanadium pentoxide V{sub 2}O{sub 5} crystals

    Energy Technology Data Exchange (ETDEWEB)

    Muslimov, A. E., E-mail: amuslimov@mail.ru; Butashin, A. V.; Kanevsky, V. M. [Russian Academy of Sciences, Shubnikov Institute of Crystallography, Federal Research Centre “Crystallography and Photonics” (Russian Federation)

    2017-01-15

    The (001) cleavage surface of vanadium pentoxide (V{sub 2}O{sub 5}) crystal has been studied by scanning tunneling spectroscopy (STM). It is shown that the surface is not reconstructed; the STM image allows geometric lattice parameters to be determined with high accuracy. The nanostructure formed on the (001) cleavage surface of crystal consists of atomically smooth steps with a height multiple of unit-cell parameter c = 4.37 Å. The V{sub 2}O{sub 5} crystal cleavages can be used as references in calibration of a scanning tunneling microscope under atmospheric conditions both along the (Ñ…, y) surface and normally to the sample surface (along the z axis). It is found that the terrace surface is not perfectly atomically smooth; its roughness is estimated to be ~0.5 Å. This circumstance may introduce an additional error into the microscope calibration along the z coordinate.

  4. Combined measurement of surface, grain boundary and lattice diffusion coefficients on olivine bi-crystals

    Science.gov (United States)

    Marquardt, Katharina; Dohmen, Ralf; Wagner, Johannes

    2014-05-01

    Diffusion along interface and grain boundaries provides an efficient pathway and may control chemical transport in rocks as well as their mechanical strength. Besides the significant relevance of these diffusion processes for various geologic processes, experimental data are still very limited (e.g., Dohmen & Milke, 2010). Most of these data were measured using polycrystalline materials and the formalism of LeClaire (1951) to fit integrated concentration depth profiles. To correctly apply this formalism, certain boundary conditions of the diffusion problem need to be fulfilled, e.g., surface diffusion is ignored, and furthermore the lattice diffusion coefficient has to be known from other studies or is an additional fitting parameter, which produces some ambiguity in the derived grain boundary diffusion coefficients. We developed an experimental setup where we can measure the lattice and grain boundary diffusion coefficients simultaneously but independent and demonstrate the relevance of surface diffusion for typical grain boundary diffusion experiments. We performed Mg2SiO4 bicrystal diffusion experiments, where a single grain boundary is covered by a thin-film of pure Ni2SiO4 acting as diffusant source, produced by pulsed laser deposition. The investigated grain boundary is a 60° (011)/[100]. This specific grain boundary configuration was modeled using molecular dynamics for comparison with the experimental observations in the transmission electron microscope (TEM). Both, experiment and model are in good agreement regarding the misorientation, whereas there are still some disagreements regarding the strain fields along the grain boundary that are of outmost importance for the strengths of the material. The subsequent diffusion experiments were carried out in the temperature range between 800° and 1450° C. The inter diffusion profiles were measured using the TEMs energy dispersive x-ray spectrometer standardized using the Cliff-Lorimer equation and EMPA

  5. Study of the size effect by accurately determining the crystal parameters

    International Nuclear Information System (INIS)

    Seguin, Remy

    1973-01-01

    The size factor η = da/adC was measured by comparing the variations in the crystal parameter as a function of the concentration, samples of Al of various degrees of purity and Al - V and Al - Cu alloys with concentrations of less than 1 000 ppm being used. The results confirm the experimental results obtained with alloys supersaturated by ultra-rapid tempering but are not consistent with theoretical values, which appear to be too large for the case of transition elements in solution in Al. The parameter was determined from Kossel diagrams obtained using an electron probe microanalyzer. The measurement methods were developed and generalized by plotting curves representing the variation of the parameter as a function of temperature between 20 and 60 deg. C. Values were obtained for the parameter at given temperatures (± 0.1 deg. C) with an accuracy of Δa/a ≅ 8.10 -6 . (author) [fr

  6. Intrinsic magnetism of a series of Co substituted ZnO single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Lv Peiwen [Laboratory of Materials Chemistry and Physics, Fujian Institute of Research on the Structure of Matter, National Engineering Research Center for Optoelectronic Crystalline Materials, Chinese Academy of Sciences, Fuzhou, Fujian 350002 (China); Huang Feng [Laboratory of Materials Chemistry and Physics, Fujian Institute of Research on the Structure of Matter, National Engineering Research Center for Optoelectronic Crystalline Materials, Chinese Academy of Sciences, Fuzhou, Fujian 350002 (China); Chu Wangsheng [Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Academy of Sciences, 100049 Beijing (China); Lin Zhang [Laboratory of Materials Chemistry and Physics, Fujian Institute of Research on the Structure of Matter, National Engineering Research Center for Optoelectronic Crystalline Materials, Chinese Academy of Sciences, Fuzhou, Fujian 350002 (China); Chen Dagui [Laboratory of Materials Chemistry and Physics, Fujian Institute of Research on the Structure of Matter, National Engineering Research Center for Optoelectronic Crystalline Materials, Chinese Academy of Sciences, Fuzhou, Fujian 350002 (China); Li Wei [Laboratory of Materials Chemistry and Physics, Fujian Institute of Research on the Structure of Matter, National Engineering Research Center for Optoelectronic Crystalline Materials, Chinese Academy of Sciences, Fuzhou, Fujian 350002 (China); Chen Dongliang [Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Academy of Sciences, 100049 Beijing (China); Wu Ziyu [Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Academy of Sciences, 100049 Beijing (China)

    2008-01-23

    Magnetic properties of a series of well-substituted Zn{sub 1-x}Co{sub x}O (x = 0.018,0.036 and 0.05) single crystals were studied. A typical paramagnetic anisotropy property, which strengthens when x decreases, was found. A magnetization step was observed at 2 K when the magnetic field is parallel to the c axis, indicating that paramagnetic anisotropy is the origin of the strong crystal field effect on Co{sup 2+} ions in ZnO lattices. The Co{sup 2+} single-ion anisotropy parameter 2D is obtained as 7.5 K. The effective moment of Co{sup 2+} takes the values 2.7 {mu}{sub B}, 1.82 {mu}{sub B}, 1.49 {mu}{sub B} when x = 0.018, 0.036 and 0.05, revealing that more antiferromagnetic coupling between Co{sup 2+} ions arises in the perfect crystal when x increases.

  7. Temperature effect on phase states of quartz nano-crystals in silicon single crystal

    International Nuclear Information System (INIS)

    Kalanov, M.U.; Ibragimova, E.M.; Khamraeva, R.N.; Rustamova, V.M.; Ummatov, Kh.D.

    2006-01-01

    Full text: Oxygen penetrates into the silicon lattice up to the concentration of 2·10 18 cm -3 in the course of growing [1]. By the author's opinion at a low oxygen content the formation of solid solution is possible in the local defect places of the silicon single crystal lattice due to the difference in effective ion radius of oxygen and silicon (r O 0.176 and r Si = 0.065 nm). Upon reaching some critical content (∼ 10 17 cm -3 ), it becomes favorable energetically for oxygen ions to form precipitates (SiO x ) and finally a dielectric layer (stoichiometric inclusions of SiO 2 ). It was shown later that depending on the growth conditions, indeed the quartz crystal inclusions are formed in the silicon single crystals at an amount of 0.3 /0.5 wt. % [2]. However the authors did not study a phase state of the quartz inclusions. Therefore the aim of this work was to study a phase state of the quartz inclusions in silicon crystal at various temperatures. We examined the silicon single crystals grown by Czochralski technique, which were cut in (111) plane in the form of disk of 20 mm diameter and 1.5 thickness and had hole conductivity with the specific resistance ρ o ≅ 1/10 Ohm cm. The dislocation density was N D ≅ 10 1 /10 3 cm -2 , the concentrations of oxygen and boron were N 0 ≅ 2/ 4·10 17 cm -3 and N B ≅ 3*10 15 cm -3 . Structure was analyzed at the set-up DRON-UM1 with high temperature supply UVD-2000 ( CuK = 0.1542 nm) at the temperatures of 300, 1173 and 1573 K measured with platinum-platinum-rhodium thermocouple. The high temperature diffraction spectrum measured at 1573 K in the angle range (2Θ≅10/70 d egree ) there is only one main structure reflection (111) with a high intensity and d/n ≅ 0.3136 nm (2 Θ≅ 28.5 d egree ) from the matrix lattice of silicon single crystal. The weak line at 2 Θ≅ 25.5 d egree ( d/n≅0.3136 nm) is β component of the main reflection (111), and the weak structure peak at 2Θ≅59 d egree ( d/n≅ 0.1568 nm

  8. Crystal field analysis of Pm$^{3+}$ (4$^{f4}) and Sm$^{3+}$ (4$^{f5}) and lattice location studies of $^{147}$Nd and $^{147}$Pm in w-AlN

    CERN Document Server

    Vetter, Ulrich; Nijjar, Anmol S; Zandi, Bahram; Öhl, Gregor; Wahl, Ulrich; De Vries, Bart; Hofsäss, Hans; Dietrich, Marc

    2006-01-01

    We report a detailed crystal field analysis of Pm3+ and Sm3+ as well as lattice location studies of 147Pm and 147Nd in 2H-aluminum nitride (w-AlN). The isotopes of mass 147 were produced by nuclear fission and implanted at an energy of 60 keV. The decay chain of interest in this work is 147Nd→147Pm→147Sm (stable). Lattice location studies applying the emission channeling technique were carried out using the β− particles and conversion electrons emitted in the radioactive decay of 147Nd→147Pm. The samples were investigated as implanted, and also they were investigated after annealing to temperatures of 873 K as well as 1373 K. The main fraction of about 60% of both 147Pm as well as 147Nd atoms was located on substitutional Al sites in the AlN lattice; the remainder of the ions were located randomly within the AlN lattice. Following radioactive decay of 147Nd, the cathodoluminescence spectra of Pm3+ and Sm3+ were obtained between 500 nm and 1050 nm at sample temperatures between 12 K and 300 K. High-re...

  9. Lattice damage assessment and optical waveguide properties in LaAlO3 single crystal irradiated with swift Si ions

    Science.gov (United States)

    Liu, Y.; Crespillo, M. L.; Huang, Q.; Wang, T. J.; Liu, P.; Wang, X. L.

    2017-02-01

    As one of the representative ABO3 perovskite-structured oxides, lanthanum aluminate (LaAlO3) crystal has emerged as one of the most valuable functional-materials, and has attracted plenty of fundamental research and promising applications in recent years. Electronic, magnetic, optical and other properties of LaAlO3 strongly depend on its crystal structure, which could be strongly modified owing to the nuclear or electronic energy loss deposited in an ion irradiation environment and, therefore, significantly affecting the performance of LaAlO3-based devices. In this work, utilizing swift (tens of MeV) Si-ion irradiation, the damage behavior of LaAlO3 crystal induced by nuclear or electronic energy loss has been studied in detail utilizing complementary characterization techniques. Differing from other perovskite-structured crystals in which the electronic energy loss could lead to the formation of an amorphous region based on the thermal spike mechanism, in this case, intense electronic energy loss in LaAlO3 will not induce any obvious structural damage. The effects of ion irradiation on the mechanical properties, including hardness increase and elastic modulus decrease, have been confirmed. On the other hand, considering the potential applications of LaAlO3 in the field of integrated optoelectronics, the optical-waveguide properties of the irradiation region have been studied. The significant correspondence (symmetrical inversion) between the iWKB-reconstructed refractive-index profile and SRIM-simulated dpa profile further proves the effects (irradiation-damage production and refractive-index decrease) of nuclear energy loss during the swift-ion penetration process in LaAlO3 crystal. In the case of the rather-thick damage layer produced by swift-ion irradiation, obtaining a damage profile will be constrained owing to the analysis-depth limitation of the characterization techniques (RBS/channeling), and our analysis process (optical guided-mode measurement and

  10. Magnetic properties in kagomé lattice with RKKY interaction: A Monte Carlo study

    Energy Technology Data Exchange (ETDEWEB)

    Masrour, R., E-mail: rachidmasrour@hotmail.com [Laboratory of Materials, Processes, Environment and Quality, Cady Ayyed University, National School of Applied Sciences, 63, 46000 Safi (Morocco); Laboratoire de Magnétisme et Physique des Hautes Energies L.M.P.H.E.URAC 12, Université Mohammed V, Faculté des Sciences, B.P. 1014, Rabat (Morocco); Jabar, A. [Laboratoire de Magnétisme et Physique des Hautes Energies L.M.P.H.E.URAC 12, Université Mohammed V, Faculté des Sciences, B.P. 1014, Rabat (Morocco); Benyoussef, A. [Laboratoire de Magnétisme et Physique des Hautes Energies L.M.P.H.E.URAC 12, Université Mohammed V, Faculté des Sciences, B.P. 1014, Rabat (Morocco); Institute of Nanomaterials and Nanotechnologies, MAScIR, Rabat (Morocco); Hassan II Academy of Science and Technology, Rabat (Morocco); Hamedoun, M. [Institute of Nanomaterials and Nanotechnologies, MAScIR, Rabat (Morocco)

    2016-03-01

    The magnetic properties of the kagomé lattice have been studied with Ruderman–Kittel–Kasuya–Yosida (RKKY) exchange interactions in a spin-7/2 Ising model using Monte Carlo simulations. The RKKY interaction between the two magnetic layers is considered for different distances. The magnetizations and magnetic susceptibilities of this lattice are given for different triquadratic interactions around each triangular face. The critical temperature is obtained for a fixed size. The magnetic hysteresis cycle of kagomé lattice with RKKY interactions is obtained for different temperatures and for different crystal field with a fixed size of nonmagnetic layer. - Highlights: • We study the RKKY interaction in kagomé lattice using the Monte Carlo simulations. • The transition temperature is obtained for kagomé lattice with RKKY interaction. • The coercive field is obtained for kagomé lattice with RKKY interaction.

  11. Strontium ranelate changes the composition and crystal structure of the biological bone-like apatite produced in osteoblast cell cultures.

    Science.gov (United States)

    Querido, William; Campos, Andrea P C; Martins Ferreira, Erlon H; San Gil, Rosane A S; Rossi, Alexandre M; Farina, Marcos

    2014-09-01

    We evaluate the effects of strontium ranelate on the composition and crystal structure of the biological bone-like apatite produced in osteoblast cell cultures, a system that gave us the advantage of obtaining mineral samples produced exclusively during treatment. Cells were treated with strontium ranelate at concentrations of 0.05 and 0.5 mM Sr(2+). Mineral substances were isolated and analyzed by using a combination of methods: Fourier transform infrared spectroscopy, solid-state (1)H nuclear magnetic resonance, X-ray diffraction, micro-Raman spectroscopy and energy dispersive X-ray spectroscopy. The minerals produced in all cell cultures were typical bone-like apatites. No changes occurred in the local structural order or crystal size of the minerals. However, we noticed several relevant changes in the mineral produced under 0.5 mM Sr(2+): (1) increase in type-B CO3 (2-) substitutions, which often lead to the creation of vacancies in Ca(2+) and OH(-) sites; (2) incorporation of Sr(2+) by substituting slightly less than 10 % of Ca(2+) in the apatite crystal lattice, resulting in an increase in both lattice parameters a and c; (3) change in the PO4 (3-) environments, possibly because of the expansion of the lattice; (4) the Ca/P ratio of this mineral was reduced, but its (Ca+Sr)/P ratio was the same as that of the control, indicating that its overall cation/P ratio was preserved. Thus, strontium ranelate changes the composition and crystal structure of the biological bone-like apatite produced in osteoblast cell cultures.

  12. EPR and optical absorption studies of paramagnetic molecular ion (VO2+) in Lithium Sodium Acid Phthalate single crystal

    Science.gov (United States)

    Subbulakshmi, N.; Kumar, M. Saravana; Sheela, K. Juliet; Krishnan, S. Radha; Shanmugam, V. M.; Subramanian, P.

    2017-12-01

    Electron Paramagnetic Resonance (EPR) spectroscopic studies of VO2+ ions as paramagnetic impurity in Lithium Sodium Acid Phthalate (LiNaP) single crystal have been done at room temperature on X-Band microwave frequency. The lattice parameter values are obtained for the chosen system from Single crystal X-ray diffraction study. Among the number of hyperfine lines in the EPR spectra only two sets are reported from EPR data. The principal values of g and A tensors are evaluated for the two different VO2+ sites I and II. They possess the crystalline field around the VO2+ as orthorhombic. Site II VO2+ ion is identified as substitutional in place of Na1 location and the other site I is identified as interstitial location. For both sites in LiNaP, VO2+ are identified in octahedral coordination with tetragonal distortion as seen from the spin Hamiltonian parameter values. The ground state of vanadyl ion in the LiNaP single crystal is dxy. Using optical absorption data the octahedral and tetragonal parameters are calculated. By correlating EPR and optical data, the molecular orbital bonding parameters have been discussed for both sites.

  13. Dynamic hysteresis behaviors in the kinetic Ising system on triangular lattice

    Science.gov (United States)

    Kantar, Ersin; Ertaş, Mehmet

    2018-04-01

    We studied dynamic hysteresis behaviors of the spin-1 Blume-Capel (BC) model in a triangular lattice by means of the effective-field theory (EFT) with correlations and using Glauber-type stochastic dynamics. The effects of the exchange interaction (J), crystal field (D), temperature (T) and oscillating frequency (w) on the hysteresis behaviors of the BC model in a triangular lattice are investigated in detail. Results are compared with some other dynamic studies and quantitatively good agreement is found.

  14. The nature of γ-hydride in crept zirconium single crystals

    International Nuclear Information System (INIS)

    Akhtar, A.

    1977-01-01

    Single crystals prepared from crystal bar zirconium have been subjected to uniaxial tensile-creep under a vacuum of 10 -4 Pa for 160 h. Transmission electron microscopy of crept crystals has revealed the presence of thin fct γ-zirconium hydride platelets lying parallel to (1100) planes and elongated along the [1120]sub(α) direction. The platelets maintain the following lattice relationship with the hcp (α) matrix: [1120]sub(α)//[110]sub(γ), (0001)sub(α)//(001)sub(γ). This relationship is different from that obtained for needle γ-hydride generally observed in quenched samples. Lattice misfit calculations indicate that the platelets have a large positive misfit normal to the plane of the disc and a small misfit in the plane of the disc, which remains parallel to (1010)sub(α). Displacement fringe contrast is observed inside the platelets under conditions consistent with the lattice misfit. It is proposed that the nucleation of these precipitates occurs at stacking faults in the presence of applied stress. (Auth.)

  15. Indexing in single-crystal diffractometry with an obstinate list of reflections

    International Nuclear Information System (INIS)

    Duisenberg, A.J.M.

    1992-01-01

    An indexing method for single-crystal diffractometry is described which is applicable to especially difficult cases such as twin lattices, incommensurate structures, fragmented crystals, long axes and unreliable data. Finding the reciprocal lattice from a cloud of reciprocal-lattice points (reflections) is reduced to finding elementary periods in one-dimensional rows, obtained by projecting all observed points onto the normal to the plane formed by any three of these points. Row periodicity and offending reflections are easily recognized. Each row, by its direction and (reciprocal) spacing, defines one direct axis vector, based upon all cooperating observations. From the direct vectors so obtained a primitive direct cell is chosen and refined against the fitting reflections. The result is one main lattice, or a main lattice and a set of alien reflections. The method operates semi-automatically in the program DIRAX and has been tested, without failure, on hundreds of CAD4 reflection files, among which there were many auto-indexing-resistant lists. (orig.)

  16. Monte Carlo simulation of continuous-space crystal growth

    International Nuclear Information System (INIS)

    Dodson, B.W.; Taylor, P.A.

    1986-01-01

    We describe a method, based on Monte Carlo techniques, of simulating the atomic growth of crystals without the discrete lattice space assumed by conventional Monte Carlo growth simulations. Since no lattice space is assumed, problems involving epitaxial growth, heteroepitaxy, phonon-driven mechanisms, surface reconstruction, and many other phenomena incompatible with the lattice-space approximation can be studied. Also, use of the Monte Carlo method circumvents to some extent the extreme limitations on simulated timescale inherent in crystal-growth techniques which might be proposed using molecular dynamics. The implementation of the new method is illustrated by studying the growth of strained-layer superlattice (SLS) interfaces in two-dimensional Lennard-Jones atomic systems. Despite the extreme simplicity of such systems, the qualitative features of SLS growth seen here are similar to those observed experimentally in real semiconductor systems

  17. Adjustment of a two-block X-ray interferometer and absolute measurement of lattice spacing

    International Nuclear Information System (INIS)

    Nakayama, Kan

    1994-01-01

    X-ray interferometer was invented in 1965 by Bonse and Hart, and it uses the lattice surface of a silicon single crystal as a three-dimensional diffraction lattice. It divides X-ray coherently, changes direction, combines and causes interference. It made for the first time the interference effect of X-ray into the usable form in macroscopic world. As an example of the application of X-ray interferometers to basic science, there is the absolute measurement of lattice spacing. This is the method of simultaneously measuring the same displacement with an X-ray interferometer and a light wave interferometer, and doing the absolute measurement of the lattice spacing of crystals with light wavelength. Avogadro constant is the constant that becomes the foundation of chemistry, and its relation with other basic constants is shown. The principle of X-ray interferometers is explained. As the elementary technologies for the absolute measurement of lattice spacing, the adjustment of X-ray interferometers, parallel movement table and angular adjustment table, light wave interferometer and the prevention of vibration and temperature change are described. The example of the measurement is reported. In order to improve the accuracy, the improvement of the equipment and the measurement in vacuum are prepared at present. (K.I.)

  18. Interactions of molecules and the properties of crystals

    Science.gov (United States)

    McConnell, Thomas Daniel Leigh

    In this thesis the basic theory of the lattice dynamics of molecular crystals is considered, with particular reference to the specific case of linear molecules. The objective is to carry out a critical investigation of a number of empirical potentials as models for real systems. Suitable coordinates are introduced, in particular vibrational coordinates which are used to describe the translational and rotational modes of the free molecule. The Taylor expansion of the intermolecular potential is introduced and its terms considered, in particular the (first-order) equilibrium conditions for such a system and the (second-order) lattice vibrations. The elastic properties are also considered, in particular with reference to the specific case of rhombohedral crystals. The compressibility and a number of conditions for elastic stability are introduced. The total intermolecular interaction potential is divided into three components using perturbation methods, the electrostatic energy, the repulsion energy and the dispersion energy. A number of models are introduced for these various components. The induction energy is neglected. The electrostatic interaction is represented by atomic multipole and molecular multipole models. The repulsion and dispersion energies are modelled together in a central interaction potential, either the Lennard-Jones atom-atom potential or the anisotropic Berne-Pechukas molecule-molecule potential. In each case, the Taylor expansion coefficients, used to calculate the various molecular properties, are determined. An algorithm is described which provides a relatively simple method for calculating cartesian tensors, which are found in the Taylor expansion coefficients of the multipolar potentials. This proves to be particularly useful from a computational viewpoint, both in terms of programming and calculating efficiency. The model system carbonyl sulphide is introduced and its lattice properties are described. Suitable parameters for potentials used

  19. Optimization of the scintillation parameters of the lead tungstate crystals for their application in high precision electromagnetic calorimetry

    International Nuclear Information System (INIS)

    Drobychev, G.

    2000-01-01

    In the frame of this dissertation work scintillation properties of the lead tungstate crystals PWO) and possibilities of their use were studied foreseeing their application for electromagnetic calorimetry in extreme radiation environment conditions of new colliders. The results of this work can be summarized in the following way. 1. A model of the scintillations origin in the lead tungstate crystals which includes processes influencing on the crystals radiation hardness and presence of slow components in scintillations was developed. 2. An analysis of the influences of the PWO scintillation properties changes on the parameters of the electromagnetic calorimeter was done. 3. Methods of the light collection from the large scintillation elements of complex shape made of the birefringent scintillation crystal with high refraction index and low light yield in case of signal registration by a photodetector with sensitive surface small in compare with the output face of scintillator were Studied. 4. Physical principles of the methodology of the scintillation crystals certification during their mass production foreseeing their installation into a calorimeter electromagnetic were developed. Correlations between the results of measurements of the PWO crystals parameters by different methods were found. (author)

  20. Crystals in the LHC

    CERN Multimedia

    Antonella Del Rosso

    2012-01-01

    Bent crystals can be used to deflect charged particle beams. Their use in high-energy accelerators has been investigated for almost 40 years. Recently, a bent crystal was irradiated for the first time in the HiRadMat facility with an extreme particle flux, which crystals would have to withstand in the LHC. The results were very encouraging and confirmed that this technology could play a major role in increasing the beam collimation performance in future upgrades of the machine.   UA9 bent crystal tested with a laser. Charged particles interacting with a bent crystal can be trapped in channelling states and deflected by the atomic planes of the crystal lattice (see box). The use of bent crystals for beam manipulation in particle accelerators is a concept that has been well-assessed. Over the last three decades, a large number of experimental findings have contributed to furthering our knowledge and improving our ability to control crystal-particle interactions. In modern hadron colliders, su...

  1. EPR and optical investigation of Mn2+ doped L-histidine-4-nitrophenolate 4-nitrophenol single crystal

    Science.gov (United States)

    Prabakaran, R.; Subramanian, P.

    2018-04-01

    Single crystals of L-histidine-4-nitrophenolate 4-nitrophenol[LHFNP] complex doped with Mn2+ were grown by the slow evaporation method at room temperature. The EPR spectrum reveals the entry of one Mn2+ ion in the lattice. The angular variation plot was drawn between the angles and the magnetic field position. The spin Hamiltonian parameters were obtained by EPR-NMR program. The D and E values show the rhombic field around the ion and is an interstitial one. The g value obtained here suggests that the Mn2+ ion experiences a strong field and there is a transfer of electron from the metal ion to the ligand atom. The optical absorption study shows various bands and are assigned to the transition from the ground state 6A1g(S). The Racah and crystal field parameters have also been evaluated and fitted to the experimental values. The Racah parameter shows the covalent bonding between the metal ion to the ligand.

  2. Origin of gigantic magnetostriction and crystal field effects in terbium dititanate

    International Nuclear Information System (INIS)

    Aleksandrov, I.V.; Lidskij, B.V.; Mamsurova, L.G.

    1985-01-01

    The temperature and magnetic field dependences of the magnetostriction and magnetization and the temperature dependences of the magnetic susceptibility, specific heat and lattice parameter are investigated experimentally in a broad range of temperature and field strength for polycrystalline and single crystal Tb 2 Ti 2 O 7 . A conclusion is drawn regarding the structure of the energy levels of Tb 3+ in Tb 2 Ti 2 O 7 . A qualitative and quantitative explanation of all observed magnetic effects, and in particular of gigantic magnetostriction in Tb 2 Ti 2 O 7 , is presented which is based on the crystal field theory. It is shown that the huge magnitude of the magnetostriction in terbium dititanate is due to the specificity of the energy spectrum of Tb 3+ in Tb 2 Ti 2 O 7

  3. First principles crystal engineering of nonlinear optical materials. I. Prototypical case of urea

    Science.gov (United States)

    Masunov, Artëm E.; Tannu, Arman; Dyakov, Alexander A.; Matveeva, Anastasia D.; Freidzon, Alexandra Ya.; Odinokov, Alexey V.; Bagaturyants, Alexander A.

    2017-06-01

    The crystalline materials with nonlinear optical (NLO) properties are critically important for several technological applications, including nanophotonic and second harmonic generation devices. Urea is often considered to be a standard NLO material, due to the combination of non-centrosymmetric crystal packing and capacity for intramolecular charge transfer. Various approaches to crystal engineering of non-centrosymmetric molecular materials were reported in the literature. Here we propose using global lattice energy minimization to predict the crystal packing from the first principles. We developed a methodology that includes the following: (1) parameter derivation for polarizable force field AMOEBA; (2) local minimizations of crystal structures with these parameters, combined with the evolutionary algorithm for a global minimum search, implemented in program USPEX; (3) filtering out duplicate polymorphs produced; (4) reoptimization and final ranking based on density functional theory (DFT) with many-body dispersion (MBD) correction; and (5) prediction of the second-order susceptibility tensor by finite field approach. This methodology was applied to predict virtual urea polymorphs. After filtering based on packing similarity, only two distinct packing modes were predicted: one experimental and one hypothetical. DFT + MBD ranking established non-centrosymmetric crystal packing as the global minimum, in agreement with the experiment. Finite field approach was used to predict nonlinear susceptibility, and H-bonding was found to account for a 2.5-fold increase in molecular hyperpolarizability to the bulk value.

  4. Chimera states in Gaussian coupled map lattices

    Science.gov (United States)

    Li, Xiao-Wen; Bi, Ran; Sun, Yue-Xiang; Zhang, Shuo; Song, Qian-Qian

    2018-04-01

    We study chimera states in one-dimensional and two-dimensional Gaussian coupled map lattices through simulations and experiments. Similar to the case of global coupling oscillators, individual lattices can be regarded as being controlled by a common mean field. A space-dependent order parameter is derived from a self-consistency condition in order to represent the collective state.

  5. How robust will the RHIC lattice be during commissioning?

    International Nuclear Information System (INIS)

    Ohnuma, S.

    1991-09-01

    The question raised here is whether the RHIC lattice is robust enough to make all these commissioning manipulations possible. There are of course many factors involved in answering this question in a definitive manner. The purpose of this note is to see if there are any fundamental and serious shortcomings basic to the lattice. The lattice considered here is the one presented to the workshop by Steve Tepikian and called RHIC91. More specifically, we fix nine quadrupole parameters in all insertions except in the 6 o'clock insertion where the independent parameters is sixteen. The so-called perfect matching may require fourteen parameters instead of nine but the difference is insignificant. On the other hand, if the number of parameters is reduced from sixteen to nine in the 6 o'clock insertion, the mismatch in the arc beta function becomes non-trivial. For example, the horizontal beta may vary between 40m to 60m at QF locations

  6. Solid-Liquid equilibrium of n-alkanes using the Chain Delta Lattice Parameter model

    DEFF Research Database (Denmark)

    Coutinho, João A.P.; Andersen, Simon Ivar; Stenby, Erling Halfdan

    1996-01-01

    The formation of a solid phase in liquid mixtures with large paraffinic molecules is a phenomenon of interest in the petroleum, pharmaceutical, and biotechnological industries among onters. Efforts to model the solid-liquid equilibrium in these systems have been mainly empirical and with different...... degrees of success.An attempt to describe the equilibrium between the high temperature form of a paraffinic solid solution, commonly known as rotator phase, and the liquid phase is performed. The Chain Delta Lattice Parameter model (CDLP) is developed allowing a successful description of the solid-liquid...... equilibrium of n-alkanes ranging from n-C_20 to n-C_40.The model is further modified to achieve a more correct temperature dependence because it severely underestimates the excess enthalpy. It is shown that the ratio of excess enthalpy and entropy for n-alkane solid solutions, as happens for other solid...

  7. SU(N) gauge theory couplings on asymmetric lattices

    International Nuclear Information System (INIS)

    Karsch, F.

    1982-01-01

    The connection between euclidean and hamiltonian lattice QCD requires the use of asymmetric lattices, which in turn implies the necessity of two coupling parameters. We analyse the dependence of space- and time-like couplings gsub(sigma) and gsub(tau) on the different lattice spacings a and asub(tau) in space and time directions. Using the background field method we determine the derivatives of the couplings with respect to the asymmetry factor xi = a/asub(tau) in the weak coupling limit, obtaining for xi = 1 the values (deltag -2 sub(sigma)/deltaxi)sub(xi = 1) = 0.11403, N = 2, 0.20161, N = 3, (deltag -2 sub(tau)/deltaxi)sub(xi = 1) = -0.06759, N = 2, -0.13195, N = 3. We argue that the sum of these derivatives has to be equal to b 0 = 11N/48π 2 and determine the Λ parameter for asymmetric lattices. In the limit xi → infinity all our results agree with those of A. and P. Hasenfratz. (orig.)

  8. Restoring the lattice of Si-based atom probe reconstructions for enhanced information on dopant positioning.

    Science.gov (United States)

    Breen, Andrew J; Moody, Michael P; Ceguerra, Anna V; Gault, Baptiste; Araullo-Peters, Vicente J; Ringer, Simon P

    2015-12-01

    The following manuscript presents a novel approach for creating lattice based models of Sb-doped Si directly from atom probe reconstructions for the purposes of improving information on dopant positioning and directly informing quantum mechanics based materials modeling approaches. Sophisticated crystallographic analysis techniques are used to detect latent crystal structure within the atom probe reconstructions with unprecedented accuracy. A distortion correction algorithm is then developed to precisely calibrate the detected crystal structure to the theoretically known diamond cubic lattice. The reconstructed atoms are then positioned on their most likely lattice positions. Simulations are then used to determine the accuracy of such an approach and show that improvements to short-range order measurements are possible for noise levels and detector efficiencies comparable with experimentally collected atom probe data. Copyright © 2015 Elsevier B.V. All rights reserved.

  9. Acid indium strontium phosphate SrIn2[PO3(OH)]4: synthesis and crystal structure

    International Nuclear Information System (INIS)

    Rusakov, D.A.; Bobylev, A.P.; Komissarova, L.N.; Filaretov, A.A.; Danilov, V.P.

    2007-01-01

    Acid indium-strontium phosphate SrIn 2 [PO 3 (OH)] 4 is synthesized and characterized. Crystal structure and lattice parameters ate determined. In atoms in SrIn 2 [PO 3 (OH)] 4 structure are in distorted InO 6 octahedrons and form with PO 3 (OH) tetrahedrons mixed paraskeleton {In 2 [PO 3 (OH)] 4 } 3∞ 2- with emptinesses occupied by big Sr 2+ cations. The compound is thermally stable up to 400 Deg C [ru

  10. Crystal structure and anisotropic magnetic properties of new ferromagnetic Kondo lattice compound Ce(Cu,Al,Si){sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Maurya, A.; Thamizhavel, A.; Dhar, S.K. [Department of Condensed Matter Physics & Materials Science, Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400 005 (India); Provino, A.; Pani, M.; Costa, G.A. [Department of Chemistry, University of Genova, Via Dodecaneso 31, 16146 Genova (Italy); Institute SPIN-CNR, Corso Perrone 24, 16152 Genova (Italy)

    2017-03-15

    Single crystals of the new compound CeCu{sub 0.18}Al{sub 0.24}Si{sub 1.58} have been grown by high-temperature solution growth method using a eutectic Al-Si mixture as flux. This compound is derived from the binary CeSi{sub 2} (tetragonal α-ThSi{sub 2}-type, Pearson symbol tI12, space group I4{sub 1}/amd) obtained by partial substitution of Si by Cu and Al atoms but showing full occupation of the Si crystal site (8e). While CeSi{sub 2} is a well-known valence-fluctuating paramagnetic compound, the CeCu{sub 0.18}Al{sub 0.24}Si{sub 1.58} phase orders ferromagnetically at T{sub C}=9.3 K. At low temperatures the easy-axis of magnetization is along the a-axis, which re-orients itself along the c-axis above 30 K. The presence of hysteresis in the magnetization curve, negative temperature coefficient of resistivity at high temperatures, reduced jump in the heat capacity and a relatively lower entropy released up to the ordering temperature, and enhanced Sommerfeld coefficient (≈100 mJ/mol K{sup 2}) show that CeCu{sub 0.18}Al{sub 0.24}Si{sub 1.58} is a Kondo lattice ferromagnetic, moderate heavy fermion compound. Analysis of the high temperature heat capacity data in the paramagnetic region lets us infer that the crystal electric field split doublet levels are located at 178 and 357 K, respectively, and Kondo temperature (8.4 K) is of the order of T{sub C} in CeCu{sub 0.18}Al{sub 0.24}Si{sub 1.58}.

  11. Fuel lattice design using heuristics and new strategies

    Energy Technology Data Exchange (ETDEWEB)

    Ortiz S, J. J.; Castillo M, J. A.; Torres V, M.; Perusquia del Cueto, R. [ININ, Carretera Mexico-Toluca s/n, Ocoyoacac 52750, Estado de Mexico (Mexico); Pelta, D. A. [ETS Ingenieria Informatica y Telecomunicaciones, Universidad de Granada, Daniel Saucedo Aranda s/n, 18071 Granada (Spain); Campos S, Y., E-mail: juanjose.ortiz@inin.gob.m [IPN, Escuela Superior de Fisica y Matematicas, Unidad Profesional Adolfo Lopez Mateos, Edif. 9, 07738 Mexico D. F. (Mexico)

    2010-10-15

    This work show some results of the fuel lattice design in BWRs when some allocation pin rod rules are not taking into account. Heuristics techniques like Path Re linking and Greedy to design fuel lattices were used. The scope of this work is to search about how do classical rules in design fuel lattices affect the heuristics techniques results and the fuel lattice quality. The fuel lattices quality is measured by Power Peaking Factor and Infinite Multiplication Factor at the beginning of the fuel lattice life. CASMO-4 code to calculate these parameters was used. The analyzed rules are the following: pin rods with lowest uranium enrichment are only allocated in the fuel lattice corner, and pin rods with gadolinium cannot allocated in the fuel lattice edge. Fuel lattices with and without gadolinium in the main diagonal were studied. Some fuel lattices were simulated in an equilibrium cycle fuel reload, using Simulate-3 to verify their performance. So, the effective multiplication factor and thermal limits can be verified. The obtained results show a good performance in some fuel lattices designed, even thought, the knowing rules were not implemented. A fuel lattice performance and fuel lattice design characteristics analysis was made. To the realized tests, a dell workstation was used, under Li nux platform. (Author)

  12. Fuel lattice design using heuristics and new strategies

    International Nuclear Information System (INIS)

    Ortiz S, J. J.; Castillo M, J. A.; Torres V, M.; Perusquia del Cueto, R.; Pelta, D. A.; Campos S, Y.

    2010-10-01

    This work show some results of the fuel lattice design in BWRs when some allocation pin rod rules are not taking into account. Heuristics techniques like Path Re linking and Greedy to design fuel lattices were used. The scope of this work is to search about how do classical rules in design fuel lattices affect the heuristics techniques results and the fuel lattice quality. The fuel lattices quality is measured by Power Peaking Factor and Infinite Multiplication Factor at the beginning of the fuel lattice life. CASMO-4 code to calculate these parameters was used. The analyzed rules are the following: pin rods with lowest uranium enrichment are only allocated in the fuel lattice corner, and pin rods with gadolinium cannot allocated in the fuel lattice edge. Fuel lattices with and without gadolinium in the main diagonal were studied. Some fuel lattices were simulated in an equilibrium cycle fuel reload, using Simulate-3 to verify their performance. So, the effective multiplication factor and thermal limits can be verified. The obtained results show a good performance in some fuel lattices designed, even thought, the knowing rules were not implemented. A fuel lattice performance and fuel lattice design characteristics analysis was made. To the realized tests, a dell workstation was used, under Li nux platform. (Author)

  13. The effect of correlated and point defects on the vortex lattice melting transition in single crystal YBa2Cu3O7-δ

    International Nuclear Information System (INIS)

    Kwok, W.K.; Fleshler, S.; Welp, U.; Downey, J.; Crabtree, G.W.; Fendrich, J. Giapintzakis, J.

    1993-08-01

    The vortex melting transition T m in several untwinned and twinned crystals measured resistively in fields up to 8 Tesla. A Lindemann criterion for vortex lattice melting is obtained in addition to a sharp hysteresis in the magnetoresistance at B m supporting a first order phase transition. The anisotropy of twin boundary pinning and its reduction of the ''kink'' in ρ(T) associated with the first order melting transition is discussed in samples with very dilute twin boundaries. We also report on direct suppression of melting transition by intrinsic pinning for H parallel ab and by electron-irradiation-induced point defects

  14. Crystallization of carbonate hydroxyapatite in the presence of strontium ranelate

    Science.gov (United States)

    Izmailov, R. R.; Golovanova, O. A.

    2015-11-01

    The influence of strontium ranelate on the crystallization of carbonate hydroxyapatite from a prototype of synovial fluid of humans has been investigated. The synthesis products are studied by IR Fourier spectroscopy, X-ray diffraction, and differential thermal analysis. The amount of strontium in the samples is determined by atomic emission analysis. The sizes of crystallites in the synthesized phases are calculated from the Selyakov-Scherrer formula; the lattice parameters are also determined. The phases obtained are found to be species of calcium-deficient strontium-containing carbonate hydroxyapatite of mixed A and B types. Schemes of chemical reactions occurring during heat treatment are proposed.

  15. La5M3X (M=Sn, Bi; X=Cl, Br, I): exploring the limit of the Mn5Si3-type hosting lattice

    International Nuclear Information System (INIS)

    Zheng Chong; Mattausch, Hansjuergen; Simon, Arndt

    2002-01-01

    Three new compounds add to the family of the Mn 5 Si 3 type host-guest lattice. These are La 5 Sn 3 X (X=Cl, Br, I) synthesized from stoichiometric mixtures of La, LaX 3 and Sn heated under Ar atmosphere in sealed Ta ampoules at 850-990 deg. C for 13-62 days. La 5 Sn 3 X crystallize in the space group P6 3 /mcm (No. 193) with lattice parameters a=9.603(1) A, 9.637(1) A and 9.673(1) A; c=6.890(1) A, 6.931(1) A and 6.987(1) A, respectively, for X=Cl, Br and I. Computational analysis using both the extended Hueckel and the local density functional methods showed that the Sn and La site acts as electron reservoir, providing electrons to the interstitials as necessary. This gives rise to a metallic behavior. Susceptibility and conductivity measurements confirmed these predictions. The single crystal structure of La 5 Bi 3 Br is also reported

  16. Effect of shape of scatterers and plasma frequency on the complete photonic band gap properties of two-dimensional dielectric-plasma photonic crystals

    Energy Technology Data Exchange (ETDEWEB)

    Fathollahi Khalkhali, T., E-mail: tfathollahi@aeoi.org.ir; Bananej, A.

    2016-12-16

    In this study, we analyze complete photonic band gap properties of two-dimensional dielectric-plasma photonic crystals with triangular and square lattices, composed of plasma rods with different geometrical shapes in the anisotropic tellurium background. Using the finite-difference time-domain method we discuss the maximization of the complete photonic band gap width as a function of plasma frequency and plasma rods parameters with different shapes and orientations. The numerical results demonstrate that our proposed structures represent significantly wide complete photonic band gaps in comparison to previously studied dielectric-plasma photonic crystals. - Highlights: • In this paper, we have investigated plasma photonic crystals. • Plasma is a kind of dispersive medium with its equivalent refractive index related to the frequency of an incident EM wave. • In this work, our simulations are performed using the Meep implementation of the finite-difference time-domain (FDTD) method. • For this study, the lattice structures investigated are triangular and square. • Extensive calculations reveal that almost all of these structures represent wide complete band gaps.

  17. Effect of shape of scatterers and plasma frequency on the complete photonic band gap properties of two-dimensional dielectric-plasma photonic crystals

    International Nuclear Information System (INIS)

    Fathollahi Khalkhali, T.; Bananej, A.

    2016-01-01

    In this study, we analyze complete photonic band gap properties of two-dimensional dielectric-plasma photonic crystals with triangular and square lattices, composed of plasma rods with different geometrical shapes in the anisotropic tellurium background. Using the finite-difference time-domain method we discuss the maximization of the complete photonic band gap width as a function of plasma frequency and plasma rods parameters with different shapes and orientations. The numerical results demonstrate that our proposed structures represent significantly wide complete photonic band gaps in comparison to previously studied dielectric-plasma photonic crystals. - Highlights: • In this paper, we have investigated plasma photonic crystals. • Plasma is a kind of dispersive medium with its equivalent refractive index related to the frequency of an incident EM wave. • In this work, our simulations are performed using the Meep implementation of the finite-difference time-domain (FDTD) method. • For this study, the lattice structures investigated are triangular and square. • Extensive calculations reveal that almost all of these structures represent wide complete band gaps.

  18. Non-Covalent Interactions in the Crystal Structure of Methyl 4-Hydroxy-3-Nitrobenzoate

    Directory of Open Access Journals (Sweden)

    Jim Simpson

    2012-06-01

    Full Text Available Methyl 4-hydroxy-3-nitrobenzoate, (I, C8H7NO5, crystallizes with two unique molecules, A and B, in the asymmetric unit of the triclinic unit cell. The space group was assigned as P-1, with lattice parameters a = 0.72831(15, b = 1.0522(2, c = 1.1410(2 nm, α = 83.38(3, β = 80.83(3, γ = 82.02(3°, Z = 4, V = 0.8510(3 nm3, Mr = 197.15, Dc = 1.539 g/m3, µ= 0.131 mm−1, F(000 = 408, R = 0.1002 and wR = 0.2519. In the crystal structure, 12 hydrogen bonding and two p-stacking interactions link the molecules into infinite stacked sheets parallel to (101.

  19. High-resolution lattice-spacing comparator using SR

    International Nuclear Information System (INIS)

    Zhang, Xiaowei; Sugiyama, Hiroshi; Ando, Masami

    2004-01-01

    A novel lattice spacing measurement using a high-resolution self-reference d-spacing comparator has been described. Self selection of monochromatic synchrotron x-rays by a monolithic double channel-cut-crystal monochromator (MDCM) comprising silicon 2,6,4 and 6,2,4 reflections may lead to a stable, highly-collimated and narrow bandwidth beam. Also if utilizing 2,6,4 and 6,2,4 Bragg planes of a silicon sample, the interval between two associated Bragg peaks for the X-rays with wavelength of 0.13438 nm can be extremely small, so that the diffraction angle can be determined with high precision and the traveling time from one peak to the other can be marvelously reduced by the order of at least three compared to the established classical methods such as the Bond method. Thus this so-called self-reference comparator method can dramatically save measurement time and provide an absolute measurement on the basis of the x-ray wavelength of the MDCM, therefore a lattice spacing measurement with uncertainty of 10 -8 , for the 1mm 2 area on a silicon crystal within measurement time of a few ten seconds and has been achieved. (author)

  20. Studies on the effect of different operational parameters on the crystallization kinetics of α-lactose monohydrate single crystals in aqueous solution

    Science.gov (United States)

    Parimaladevi, P.; Srinivasan, K.

    2014-09-01

    Supersaturation dependent nucleation, size and morphology of alpha-lactose monohydrate (α-LM) crystals from aqueous solution were investigated by adopting two different crystallization methods, slow evaporation and fast evaporation, in the supersaturation range between σ=0.05 and 1.30. The induction period of nucleation is comparatively long in case of slow evaporation and is very short in case of fast evaporation process as the interconversion between α-L and β-L is uncontrollable in the former and is under control in the latter case. Moreover α-LM crystals with tomahawk morphology were obtained throughout the supersaturation range by slow evaporation method whereas crystals with tomahawk, triangular and needle-like morphologies were obtained in supersaturation ranges σ=0.05-0.5, σ=0.5-0.9 and σ=0.9-1.30 respectively by fast evaporation method. Experimentally observed nucleation parameters were verified with theoretically deuced values. It is realized that the fast evaporation method employed in the present study is found to be highly efficient in controlling the interconversion between α-L and β-L as well as in suppressing the inhibitory activity of β molecule on the nucleation and growth of α-LM crystals when compared to conventional slow evaporation method and is successful in producing the industrially preferred needle-like crystals at high supersaturation ranges.