WorldWideScience

Sample records for cubic crystal field

  1. Crystal field effects on interionic distance in cubic MgO crystal doped with Fe{sup 2+} ions

    Energy Technology Data Exchange (ETDEWEB)

    Ivascu, S.; Gruia, A.S. [Faculty of Physics, West University of Timisoara, Bd. V. Parvan 4, 300223-Timisoara (Romania); Avram, N.M., E-mail: avram@physics.uvt.ro [Faculty of Physics, West University of Timisoara, Bd. V. Parvan 4, 300223-Timisoara (Romania); Academy of Romanian Scientists, Independentei 54, 050094-Bucharest (Romania)

    2014-10-01

    The exchange charge model of crystal field was applied to determine the dependence of the crystal field strength 10Dq on interionic distances R between the Fe{sup 2+} impurity ion and O{sup 2−} ligands in cubic MgO:Fe{sup 2+}. The obtained results were extrapolated by the power law and was shown that 10Dq depends on R as 1/R{sup n}, with n=6.3486. The deviations of these values from the value n=5 (predicted by the simple point charge model of crystal field) is explained by the covalent and exchange effects between impurity ion and ligands; the contribution of these effects into the total crystal field strength was considered separately. The 10Dq functions obtained as a result of our calculations were used for estimations of the electron–vibrational constants, Huang–Rhys parameters, and Jahn–Teller stabilization energy, and compared with available literature data.

  2. Crystal field effects on interionic distance in cubic MgO crystal doped with Fe2+ ions

    Science.gov (United States)

    Ivascu, S.; Gruia, A. S.; Avram, N. M.

    2014-10-01

    The exchange charge model of crystal field was applied to determine the dependence of the crystal field strength 10Dq on interionic distances R between the Fe2+ impurity ion and O2- ligands in cubic MgO:Fe2+. The obtained results were extrapolated by the power law and was shown that 10Dq depends on R as 1/R, with n=6.3486. The deviations of these values from the value n=5 (predicted by the simple point charge model of crystal field) is explained by the covalent and exchange effects between impurity ion and ligands; the contribution of these effects into the total crystal field strength was considered separately. The 10Dq functions obtained as a result of our calculations were used for estimations of the electron-vibrational constants, Huang-Rhys parameters, and Jahn-Teller stabilization energy, and compared with available literature data.

  3. Influence of spin-orbit interactions on the cubic crystal-field states of the d4 system*

    OpenAIRE

    Radwanski, R. J.; Ropka, Z.

    2002-01-01

    It has been shown that for the highly-correlated d4 electronic system the spin-orbit interactions produce, even in case of the cubic crystal-field interactions, a singlet ground state. Its magnetic moment grows rapidly with the applied magnetic field approaching 4 uB for the Eg state, but only 3 uB for the T2g state. The applicability of the present results to the Mn3+ ion in LaMnO3 is discussed. Keywords: crystal-field, spin-orbit, orbital moment. PACS: 71.70.E, 75.10.D

  4. Crystal field excitations in the cubic compound Ce{sub 3}Rh{sub 4}Sn{sub 13}

    Energy Technology Data Exchange (ETDEWEB)

    Adroja, D.T. [ISIS Facility, Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire OX11 0QX (United Kingdom)], E-mail: d.t.adroja@rl.ac.uk; Strydom, A.M. [Department of Physics APK, University of Johannesburg (South Africa); Murani, A.P. [Institut Laue Langevin, F-38042 Grenoble Cedex (France); Kockelmann, W.A. [ISIS Facility, Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire OX11 0QX (United Kingdom); Fraile, A. [Laboratorio de Magnetismo, Dpto de Fisica de Materia Condensada and Instituto de Ciencia de Materiales de Aragon, Universidad de Zaragoza, 50009 Zaragoza (Spain)

    2008-04-01

    The recent heat capacity measurements of Ce{sub 3}Rh{sub 4}Sn{sub 13} have revealed a broad peak at 1 K with an entropy of 3R ln(2) per f.u., but no clear sign of any magnetic ordering down to 100 mK. In order to understand this anomalous heat capacity behaviour of Ce{sub 3}Rh{sub 4}Sn{sub 13}, we have carried out low- and high-energy inelastic neutron scattering measurements. Our high-energy studies reveal two well-resolved crystal field (CF) excitations at {approx}9 meV and 38 meV. The observation of two CF excitations in the cubic structure of Ce{sub 3}Rh{sub 4}Sn{sub 13} could be explained on the basis of tetragonal point symmetry of the Ce ions. Interestingly, the low-energy measurements apparently show, or are best described by, a quasi-elastic peak and an inelastic peak at {approx}0.2 meV at 1.5 K, both of Lorentzian shape. We attribute the low-energy peak to Zeeman splitting of the ground state doublet, in the presence of short range magnetic ordering. Further, the low-energy peak explains the observed anomaly in the heat capacity.

  5. Orientational phase transition in cubic liquid crystals with positional order

    OpenAIRE

    Pokrovsky, V.L.; Saidachmetov, P.A.

    1988-01-01

    An electric field can give rise to a shear deformation of a cubic liquid crystal with long-range positional order fixed by two plates. The critical value of the field does not depend on the size of the system and depends crucially on the orientation.

  6. Tame Kernels of Pure Cubic Fields

    Institute of Scientific and Technical Information of China (English)

    Xiao Yun CHENG

    2012-01-01

    In this paper,we study the p-rank of the tame kernels of pure cubic fields.In particular,we prove that for a fixed positive integer m,there exist infinitely many pure cubic fields whose 3-rank of the tame kernel equal to m.As an application,we determine the 3-rank of their tame kernels for some special pure cubic fields.

  7. Polarization conversion in cubic Raman crystals

    Science.gov (United States)

    McKay, Aaron; Sabella, Alexander; Mildren, Richard P.

    2017-01-01

    Nonlinear conversion of unpolarized beams to lower frequencies is generally inefficient in c(2) materials, as it is challenging to achieve phase-matching for input ordinary and extraordinary beams simultaneously in the normal dispersion regime. Here, we show that cubic Raman crystals having doubly and triply degenerate (E and F type) modes provide a method for efficient nonlinear frequency downconversion of an unpolarized beam and yield a linearly polarized output state. Using Mueller calculus, optimal crystal directions for such polarization conversion are determined. Using diamond, an example of an F-class Raman crystal, we have verified that such conversion is possible with near quantum-defect-limited slope efficiency and a linear polarization contrast of more than 23.9 dB. PMID:28169327

  8. CLASSIFICATION OF CUBIC PARAMETERIZED HOMOGENEOUS VECTOR FIELDS

    Institute of Scientific and Technical Information of China (English)

    Karnal H.Yasir; TANG Yun

    2002-01-01

    In this paper the cubic homogeneous parameterized vector fields are studied.The classification of the phase portrait near the critical point is presented. This classification is an extension of the result given by Takens to the cubic homogeneous parameterized vector fields with six parameters.

  9. CLASSIFICATION OF CUBIC PARAMETERIZED HOMOGENEOUS VECTOR FIELDS

    Institute of Scientific and Technical Information of China (English)

    KamalH.Yasir; TNAGYun

    2002-01-01

    In this paper the cubic homogeneous parameterized vector fields are studied.The classification of the phase portrait near the critical point is presented.This classification is an extension of the result given by takens to the cubic homogeneous parameterized vector fields with six parameters.

  10. Use of Pom Pons to Illustrate Cubic Crystal Structures.

    Science.gov (United States)

    Cady, Susan G.

    1997-01-01

    Describes a method that uses olefin pom pons to illustrate cubic crystal structure. Facilitates hands-on examination of different packing arrangements such as hexagonal close-packed and cubic close-packed structures. (JRH)

  11. Theoretical and Experimental Study of Time Reversal in Cubic Crystals

    Institute of Scientific and Technical Information of China (English)

    陆铭慧; 张碧星; 汪承灏

    2004-01-01

    The self-adaptive focusing of the time reversal in anisotropic media is studied theoretically and experimentally. It is conducted for the compressional wave field in the cubic crystal silicon. The experimental result is in agreement with our theoretical analysis. The focusing gain and the displacement distributions of the time reversal field are analysed in detail. It is shown that the waves from different elements of the transducer array arrive at the original place of the source simultaneously after the time reversal operation. The waveform distortions caused by the velocity anisotropy can automatically be compensated for after the time reversal processing.

  12. An effective packing density of binary cubic crystals

    Science.gov (United States)

    Eremin, I. E.; Eremina, V. V.; Sychev, M. S.; Moiseenko, V. G.

    2015-04-01

    The methodology of effective macroscopic calculation of numerical values of internuclear distances in binary crystals of a cubic crystal system is based on the use of coefficients of the structural packing density of the crystal lattice. The possibility of combining the reference data on the main physicochemical parameters of the substance is implemented by synthesis of the corresponding mathematical models.

  13. Binomial Squares in Pure Cubic Number Fields

    CERN Document Server

    Lemmermeyer, Franz

    2011-01-01

    Let K = Q(\\omega) with \\omega^3 = m be a pure cubic number field. We show that the elements\\alpha \\in K^\\times whose squares have the form a - \\omega form a group isomorphic to the group of rational points on the elliptic curve E_m: y^2= x^3 - m.

  14. Purely cubic action for string field theory

    Science.gov (United States)

    Horowitz, G. T.; Lykken, J.; Rohm, R.; Strominger, A.

    1986-01-01

    It is shown that Witten's (1986) open-bosonic-string field-theory action and a closed-string analog can be written as a purely cubic interaction term. The conventional form of the action arises by expansion around particular solutions of the classical equations of motion. The explicit background dependence of the conventional action via the Becchi-Rouet-Stora-Tyutin operator is eliminated in the cubic formulation. A closed-form expression is found for the full nonlinear gauge-transformation law.

  15. Purely cubic action for string field theory

    Science.gov (United States)

    Horowitz, G. T.; Lykken, J.; Rohm, R.; Strominger, A.

    1986-01-01

    It is shown that Witten's (1986) open-bosonic-string field-theory action and a closed-string analog can be written as a purely cubic interaction term. The conventional form of the action arises by expansion around particular solutions of the classical equations of motion. The explicit background dependence of the conventional action via the Becchi-Rouet-Stora-Tyutin operator is eliminated in the cubic formulation. A closed-form expression is found for the full nonlinear gauge-transformation law.

  16. Elastic interaction of point defects in crystals with cubic symmetry

    Science.gov (United States)

    Kuz'michev, S. V.; Kukushkin, S. A.; Osipov, A. V.

    2013-07-01

    The energy of elastic mechanical interaction between point defects in cubic crystals is analyzed numerically. The finite-element complex ANSYS is used to investigate the character of interaction between point defects depending on their location along the crystallographic directions , , and on the distance from the free boundary of the crystal. The numerical results are compared with the results of analytic computations of the energy of interaction between two point defects in an infinite anisotropic medium with cubic symmetry. The interaction between compressible and incompressible defects of general type is studied. Conditions for onset of elastic attraction between the defects, which leads to general relaxation of the crystal elastic energy, are obtained.

  17. Extended temperature dependence of elastic constants in cubic crystals.

    Science.gov (United States)

    Telichko, A V; Sorokin, B P

    2015-08-01

    To extend the theory of the temperature dependence of the elastic constants in cubic crystals beyond the second- and third-order elastic constants, the fourth-order elastic constants, as well as the non-linearity in the thermal expansion temperature dependence, have been taken into account. Theoretical results were represented as temperature functions of the effective elastic constants and compared with experimental data for a number of cubic crystals, such as alkali metal halides, and elements gold and silver. The relations obtained give a more accurate description of the experimental temperature dependences of second-order elastic constants for a number of cubic crystals, including deviations from linear behavior. A good agreement between theoretical estimates and experimental data has been observed.

  18. Tachyon Vacuum in Cubic Superstring Field Theory

    CERN Document Server

    Erler, Theodore

    2008-01-01

    In this paper we give an exact analytic solution for tachyon condensation in the modified (picture 0) cubic superstring field theory. We prove the absence of cohomology and, crucially, reproduce the correct value for the D-brane tension. The solution is surprising for two reasons: First, the existence of a tachyon vacuum in this theory has not been definitively established in the level expansion. Second, the solution {\\it vanishes} in the GSO$(-)$ sector, implying a ``tachyon vacuum'' solution exists even for a {\\it BPS} D-brane.

  19. Reversible Nanoparticle Cubic Lattices in Blue Phase Liquid Crystals.

    Science.gov (United States)

    Gharbi, Mohamed Amine; Manet, Sabine; Lhermitte, Julien; Brown, Sarah; Milette, Jonathan; Toader, Violeta; Sutton, Mark; Reven, Linda

    2016-03-22

    Blue phases (BPs), a distinct class of liquid crystals (LCs) with 3D periodic ordering of double twist cylinders involving orthogonal helical director twists, have been theoretically studied as potential templates for tunable colloidal crystals. Here, we report the spontaneous formation of thermally reversible, cubic crystal nanoparticle (NP) assemblies in BPs. Gold NPs, functionalized to be highly miscible in cyanobiphenyl-based LCs, were dispersed in BP mixtures and characterized by polarized optical microscopy and synchrotron small-angle X-ray scattering (SAXS). The NPs assemble by selectively migrating to periodic strong trapping sites in the BP disclination lines. The NP lattice, remarkably robust given the small particle size (4.5 nm diameter), is commensurate with that of the BP matrix. At the BP I to BP II phase transition, the NP lattice reversibly switches between two different cubic structures. The simultaneous presence of two different symmetries in a single material presents an interesting opportunity to develop novel dynamic optical materials.

  20. Photonic Crystal Cavities in Cubic Polytype Silicon Carbide Films

    CERN Document Server

    Radulaski, Marina; Buckley, Sonia; Rundquist, Armand; Provine, J; Alassaad, Kassem; Ferro, Gabriel; Vučković, Jelena

    2013-01-01

    We present the design, fabrication, and characterization of high quality factor and small mode volume planar photonic crystal cavities from cubic (3C) thin films (thickness ~ 200 nm) of silicon carbide (SiC) grown epitaxially on a silicon substrate. We demonstrate cavity resonances across the telecommunications band, with wavelengths from 1250 - 1600 nm. Finally, we discuss possible applications in nonlinear optics, optical interconnects, and quantum information science.

  1. Assembly of body-centered cubic crystals in hard spheres.

    Science.gov (United States)

    Xu, W-S; Sun, Z-Y; An, L-J

    2011-05-01

    We investigate the crystallization of monodisperse hard spheres confined by two square patterned substrates (possessing the basic character of the body-centered cubic (bcc) crystal structure) at varying substrate separations via molecular dynamics simulation. Through slowly increasing the density of the system, we find that crystallization under the influence of square patterned substrates can set in at lower densities compared with the homogeneous crystallization. As the substrate separation decreases, the density, where crystallization occurs (i.e., pressure drops), becomes small. Moreover, two distinct regimes are identified in the plane of bcc particle fraction and density for the separation range investigated. For large substrate separations, the bcc particle fraction displays a local maximum as the density is increased, and the resulting formed crystals have a polycrystalline structure. However, and more importantly, another situation emerges for small substrate separations: the capillary effects (stemming from the presence of two substrates) overwhelm the bulk driving forces (stemming from the spontaneous thermal fluctuations in the bulk) during the densification, eventually resulting in the formation of a defect-free bcc crystal (unstable with respect to the bulk hard-sphere crystals) by using two square patterned substrates.

  2. 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.

  3. Slanted stacking faults and persistent face centered cubic crystal growth in sedimentary colloidal hard sphere crystals

    NARCIS (Netherlands)

    Hilhorst, J.; Wolters, J. R.; Petukhov, A.V.

    2010-01-01

    Hard sphere crystal growth is a delicate interplay between kinetics and thermodynamics, where the former is commonly thought to favour a random hexagonal close packed structure and the latter leads to a face centered cubic crystal. In this article, we discuss the influence of slanted stacking faults

  4. Cubic to tetragonal crystal lattice reconstruction during ordering or decomposition

    Energy Technology Data Exchange (ETDEWEB)

    Cheong, Byung-kl [Carnegie-Mellon Univ., Pittsburgh, PA (United States). Dept. of Materials Science and Engineering

    1992-09-01

    This thesis studied thermodynamic stability and morphology of product phases in diffusional phase transformations involving cubic-to-tetragonal crystal lattice reconstructions. Two different kinds of diffusional transformations were examined: L1{sub 0} ordering (fcc to fct lattice change) and decomposition of off-stoichiometric B2 ordering alloys accompanying bcc to fcc Bain transformation. In the first case, Fe-45 at.% Pd alloys were studied by TEM; in the second, the Bain strain relaxation during decomposition of hyper-eutectoid Cu-9.04 wt% Be alloy was studied. CuAu and InMg were also studied.

  5. Tensor tomography of stresses in cubic single crystals

    Directory of Open Access Journals (Sweden)

    Dmitry D. Karov

    2015-03-01

    Full Text Available The possibility of optical tomography applying to investigation of a two-dimensional and a three-dimensional stressed state in single cubic crystals has been studied. Stresses are determined within the framework of the Maxwell piezo-optic law (linear dependence of the permittivity tensor on stresses and weak optical anisotropy. It is shown that a complete reconstruction of stresses in a sample is impossible both by translucence it in the parallel planes system and by using of the elasticity theory equations. For overcoming these difficulties, it is offered to use a method of magnetophotoelasticity.

  6. Curvature properties of the slowness surface of the system of crystal acoustics for cubic crystals

    OpenAIRE

    LIESS, Otto

    2008-01-01

    In this paper we study geometric properties of the slowness surface of the system of crystal acoustics for cubic crystals. In particular we shall study curvature properties of the surface and the behaviour of the surface near singular points. The main result is that in the generic nearly isotropic case there are no planes which are tangent to the surface along entire curves. This is in contrast with what happens for the slowness surface of the system of crystal optics for...

  7. On the magnetization process and the associated probability in anisotropic cubic crystals

    Science.gov (United States)

    Khedr, D. M.; Aly, Samy H.; Shabara, Reham M.; Yehia, Sherif

    2017-05-01

    We present a theoretical method to calculate specific magnetic properties, e.g. magnetization curves, magnetic susceptibility and probability landscapes along the [100], [110] and [111] crystallographic directions of a crystal of cubic symmetry. The probability landscape displays the evolution of the most probable angular orientation of the magnetization vector, for selected temperatures and magnetic fields. Our method is based on the premises of classical statistical mechanics. The energy density, used in the partition function, is the sum of magnetic anisotropy and Zeeman energies, however no other energies e.g. elastic or magnetoelastic terms are considered in the present work. Model cubic systems of diverse anisotropies are analyzed first, and subsequently material magnetic systems of cubic symmetry; namely iron, nickel and Cox Fe100-x compounds, are discussed. We highlight a correlation between magnetization curves and the associated probability landscapes. In addition, determination of easiest axes of magnetization, using energy consideration, is done and compared with the results of the present method.

  8. On cubic equations over $P-$adic field

    CERN Document Server

    Mukhamedov, Farrukh; Saburov, Mansoor

    2012-01-01

    We provide a solvability criteria for a depressed cubic equation in domains $\\bz_p^{*},\\bz_p,\\bq_p$. We show that, in principal, the Cardano method is not always applicable for such equations. Moreover, the numbers of solutions of the depressed cubic equation in domains $\\bz_p^{*},\\bz_p,\\bq_p$ are provided. Since $\\bbf_p\\subset\\bq_p,$ we generalize J.-P. Serre's \\cite{JPSJ} and Z.H.Sun's \\cite{ZHS1,ZHS3} results concerning with depressed cubic equations over the finite field $\\bbf_p$. Finally, all depressed cubic equations, for which the Cardano method could be applied, are described and the $p-$adic Cardano formula is provided for those cubic equations.

  9. Curvature properties of the slowness surface of the system of crystal acoustics for cubic crystals II

    OpenAIRE

    LIESS, Otto; Sonobe, Tetsuya

    2012-01-01

    In this paper we study geometric properties of the slowness surface of the system of crystal acoustics for cubic crystals in the special case when the stiffness constants satisfy the condition $a = -2b$. The paper is a natural continuation of the paper [9] in which related properties were studied for general constants $a$ and $b$, but assuming that we were in the nearly isotropic case, in which case $a - b$ has to be small. We also take this opportunity to correct a state...

  10. Cubic ideal ferromagnets at low temperature and weak magnetic field

    Science.gov (United States)

    Hofmann, Christoph P.

    2017-04-01

    The low-temperature series for the free energy density, pressure, magnetization and susceptibility of cubic ideal ferromagnets in weak external magnetic fields are discussed within the effective Lagrangian framework up to three loops. The structure of the simple, body-centered, and face-centered cubic lattice is taken into account explicitly. The expansion involves integer and half-integer powers of the temperature. The corresponding coefficients depend on the magnetic field and on low-energy effective constants that can be expressed in terms of microscopic quantities. Our formulas may also serve as efficiency or consistency check for other techniques like Green's function methods, where spurious terms in the low-temperature expansion have appeared. We explore the sign and magnitude of the spin-wave interaction in the pressure, magnetization and susceptibility, and emphasize that our effective field theory approach is fully systematic and rigorous.

  11. Arithmetic Problems in Cubic and Quartic Function Fields

    CERN Document Server

    Bembom, Tobias

    2010-01-01

    One of the main themes in this thesis is the description of the signature of both the infinite place and the finite places in cubic function fields of any characteristic and quartic function fields of characteristic at least 5. For these purposes, we provide a new theory which can be applied to cubic and quartic function fields and to even higher dimensional function fields. One of the striking advantages of this theory to other existing methods is that is does not use the concept of p-adic completions and we can dispense of Cardano's formulae. Another key result comprises the construction of cubic function fields of unit rank 1 and 2, with an obvious fundamental system. One of the main ingredients for such constructions is the definition of the maximum value. This definition is new and very prolific in the context of finding fundamental systems. We conclude the thesis with miscellaneous results on the divisor class number h, including a new approach for finding divisors of h.

  12. Industrial growth of yttria-stabilized cubic zirconia crystals by skull melting process

    Institute of Scientific and Technical Information of China (English)

    徐家跃; 雷秀云; 蒋新; 何庆波; 房永征; 张道标; 何雪梅

    2009-01-01

    We reported the development of a Ф100 cm growth apparatus for skull melting growth of yttria-stabilized cubic zirconia(YSZ) crystals and more than 1000 kg crystals have been grown in the furnace each time.The growth conditions were optimized and the structure of the as-grown crystals was characterized by X-ray diffraction.The transmittance of 15 mol.% yttria-stabilized cubic zirconia crystal was nearly 80% in the range of 400-1600 nm.The refractive indices were measured and fitted the Sellmeier equation whi...

  13. Superconductivity in cubic noncentrosymmetric PdBiSe Crystal

    Science.gov (United States)

    Joshi, B.; Thamizhavel, A.; Ramakrishnan, S.

    2015-03-01

    Mixing of spin singlet and spin triplet superconducting pairing state is expected in noncentrosymmetric superconductors (NCS) due to the inherent presence of Rashba-type antisymmetric spin-orbit coupling. Unlike low symmetry (tetragonal or monoclinic) NCS, parity is isotropicaly broken in space for cubic NCS and can additionally lead to the coexistence of magnetic and superconducting state under certain conditions. Motivated with such enriched possibility of unconventional superconducting phases in cubic NCS we are reporting successful formation of single crystalline cubic noncentrosymmetric PdBiSe with lattice parameter a = 6.4316 Å and space group P21 3 (space group no. 198) which undergoes to superconducting transition state below 1.8 K as measured by electrical transport and AC susceptibility measurements. Significant strength of Rashba-type antisymmetric spin-orbit coupling can be expected for PdBiSe due to the presence of high Z (atomic number) elements consequently making it potential candidate for unconventional superconductivity.

  14. Field-effect transistors based on cubic indium nitride.

    Science.gov (United States)

    Oseki, Masaaki; Okubo, Kana; Kobayashi, Atsushi; Ohta, Jitsuo; Fujioka, Hiroshi

    2014-02-04

    Although the demand for high-speed telecommunications has increased in recent years, the performance of transistors fabricated with traditional semiconductors such as silicon, gallium arsenide, and gallium nitride have reached their physical performance limits. Therefore, new materials with high carrier velocities should be sought for the fabrication of next-generation, ultra-high-speed transistors. Indium nitride (InN) has attracted much attention for this purpose because of its high electron drift velocity under a high electric field. Thick InN films have been applied to the fabrication of field-effect transistors (FETs), but the performance of the thick InN transistors was discouraging, with no clear linear-saturation output characteristics and poor on/off current ratios. Here, we report the epitaxial deposition of ultrathin cubic InN on insulating oxide yttria-stabilized zirconia substrates and the first demonstration of ultrathin-InN-based FETs. The devices exhibit high on/off ratios and low off-current densities because of the high quality top and bottom interfaces between the ultrathin cubic InN and oxide insulators. This first demonstration of FETs using a ultrathin cubic indium nitride semiconductor will thus pave the way for the development of next-generation high-speed electronics.

  15. Coulomb crystals in the magnetic field

    CERN Document Server

    Baiko, D A

    2009-01-01

    The body-centered cubic Coulomb crystal of ions in the presence of a uniform magnetic field is studied using the rigid electron background approximation. The phonon mode spectra are calculated for a wide range of magnetic field strengths and for several orientations of the field in the crystal. The phonon spectra are used to calculate the phonon contribution to the crystal energy, entropy, specific heat, Debye-Waller factor of ions, and the rms ion displacements from the lattice nodes for a broad range of densities, temperatures, chemical compositions, and magnetic fields. Strong magnetic field dramatically alters the properties of quantum crystals. The phonon specific heat increases by many orders of magnitude. The ion displacements from their equilibrium positions become strongly anisotropic. The results can be relevant for dusty plasmas, ion plasmas in Penning traps, and especially for the crust of magnetars (neutron stars with superstrong magnetic fields $B \\gtrsim 10^{14}$ G). The effect of the magnetic ...

  16. Optimization of the gain in Yb3+-doped cubic laser crystals of 99.99% purity

    Institute of Scientific and Technical Information of China (English)

    Georges Boulon; Yannick Guyot; Akira Yoshikawa

    2009-01-01

    This was an outlook on the prediction of the infrared laser potentiality from concentration dependences of the 2F5/2 experimental decay time in Yb3+-doped solid-state crystals mainly on cubic crystals with 99.99% purity which could be extended to laser ceramics of the same composition.

  17. Body-centered cubic dissipative crystal formation in a dispersive and diffractive optical parametric oscillator.

    Science.gov (United States)

    Tlidi, M; Pieroux, D; Mandel, Paul

    2003-09-15

    We show that coupling diffraction and chromatic dispersion lead to body-centered cubic and hexagonally packed cylinders of dissipative optical crystals in a degenerate optical parametric oscillator. The stabilization of these crystals is a direct consequence of the interaction between the modulational and the quasi-neutral modes.

  18. Gauge Fixing of Modified Cubic Open Superstring Field Theory

    CERN Document Server

    Kohriki, Maiko; Kunitomo, Hiroshi

    2011-01-01

    The gauge-fixing problem of modified cubic open superstring field theory is discussed in detail both for the Ramond and Neveu-Schwarz sectors in the Batalin-Vilkovisky (BV) framework. We prove for the first time that the same form of action as the classical gauge-invariant one with the ghost-number constraint on the string field relaxed gives the master action satisfying the BV master equation. This is achieved by identifying independent component fields based on the analysis of the kernel structure of the inverse picture changing operator. The explicit gauge-fixing conditions for the component fields are discussed. In a kind of $b_0=0$ gauge, we explicitly obtain the NS propagator which has poles at the zeros of the Virasoro operator $L_0$.

  19. Exotic Universal Solutions in Cubic Superstring Field Theory

    CERN Document Server

    Erler, Theodore

    2010-01-01

    We present a class of analytic solutions of cubic superstring field theory in the universal sector on a non-BPS D-brane. Computation of the action and gauge invariant overlap reveal that the solutions carry half the tension of a non-BPS D-brane. However, the solutions do not satisfy the reality condition. In fact, they display an intriguing topological structure: We find evidence that conjugation of the solutions is equivalent to a gauge transformation that cannot be continuously deformed to the identity.

  20. Epitaxial Growth of Cubic Crystalline Semiconductor Alloys on Basal Plane of Trigonal or Hexagonal Crystal

    Science.gov (United States)

    Park, Yeonjoon (Inventor); Choi, Sang H. (Inventor); King, Glen C. (Inventor)

    2011-01-01

    Hetero-epitaxial semiconductor materials comprising cubic crystalline semiconductor alloys grown on the basal plane of trigonal and hexagonal substrates, in which misfit dislocations are reduced by approximate lattice matching of the cubic crystal structure to underlying trigonal or hexagonal substrate structure, enabling the development of alloyed semiconductor layers of greater thickness, resulting in a new class of semiconductor materials and corresponding devices, including improved hetero-bipolar and high-electron mobility transistors, and high-mobility thermoelectric devices.

  1. Rotation-limited growth of three-dimensional body-centered-cubic crystals.

    Science.gov (United States)

    Tarp, Jens M; Mathiesen, Joachim

    2015-07-01

    According to classical grain growth laws, grain growth is driven by the minimization of surface energy and will continue until a single grain prevails. These laws do not take into account the lattice anisotropy and the details of the microscopic rearrangement of mass between grains. Here we consider coarsening of body-centered-cubic polycrystalline materials in three dimensions using the phase field crystal model. We observe, as a function of the quenching depth, a crossover between a state where grain rotation halts and the growth stagnates and a state where grains coarsen rapidly by coalescence through rotation and alignment of the lattices of neighboring grains. We show that the grain rotation per volume change of a grain follows a power law with an exponent of -1.25. The scaling exponent is consistent with theoretical considerations based on the conservation of dislocations.

  2. Equation of state for charge-doping-induced deformation and hardening in cubic crystals

    Science.gov (United States)

    Li, Yao; Liu, Xiaofei; Guo, Wanlin

    2017-08-01

    Charge doping would inevitably induce strain, which can significantly influence device performance but cannot be directly predicted by classical mechanical laws. Here we present a set of equations of states for deformable cubic crystals subjected to charge doping by introducing the quantum electronic stress at fixed lattice as equivalent mechanical pressure into the classical hydrostatic pressure-vs-deformation equations. The equations are proved to be efficient for all the cubic crystals considered in this work (diamond, Si, Ge, GaAs, Al, and ZrO2) by first-principles calculations. The proposed method and presented equations should pave a convenient way to predict doping effects on device performance.

  3. Anelastic Relaxation of Point Defects in Cubic Crystals

    OpenAIRE

    Weller, M.

    1996-01-01

    Point defects in solids can give rise to anelastic relaxation provided that the defects behave as elastic dipoles. Experiments with single crystals give information on the atomic configuration of the point defects. Measurements of the orientation dependence of the relaxation strength allow determination of the defect symmetry and the dipole shape factor δλ=|λ1-λ2|. This is demonstrated for two examples : (i) The Snoek relaxation of O and N in Nb and Ta single crystals : The δλ values for O an...

  4. Rheological Properties of Cubic Liquid Crystals Formed from Monoglyceride/H2O Systems

    Institute of Scientific and Technical Information of China (English)

    水玲玲; 王志宁; 郑利强

    2005-01-01

    Monoglyceride (MO) can form various liquid crystalline phases spontaneously in the presence of various amount of water at room temperature. The appropriate compositions from binary phase diagram of MO/H2O were selected to form cubic phases. The selected systems were studied at different salt concentrations and pH value using rheological methods. There was a weak effect of salt on viscoelastic properties of cubic phases formed from MO/H2O system. Hexagonal phase was formed when pH value was decreased or increased. The viscoelasticity of cubic phases was different from that of hexagonal liquid crystals. Rheological properties of MO/H2O cubic phases were stable at pH and salt concentration similar to physiological condition.

  5. GREEN'S FUNCTION AND EFFECTIVE ELASTIC STIFFNESS TENSOR FOR ARBITRARY AGGREGATES OF CUBIC CRYSTALS

    Institute of Scientific and Technical Information of China (English)

    HuangMojia; ZhengChaomei

    2004-01-01

    A closed but approximate formula of Green's function for an arbitrary aggregate of cubic crystallites is given to derive the effective elastic stiffness tensor of the polycrystal. This formula, which includes three elastic constants of single cubic crystal and five texture coefficients,accounts for the effects of the orientation distribution function (ODF) up to terms linear in the texture coefficients. Thus it is expected that our formula would be applicable to arbitrary aggregates with weak texture or to materials such as aluminum whose single crystal has weak anisotropy.Three examples are presented to compare predictions from our formula with those from Nishioka and Lothe's formula and Synge's contour integral through numerical integration. As an application of Green's function, we briefly describe the procedure of deriving the effective elastic stiffness tensor for an orthorhombic aggregate of cubic crystallites. The comparison of the computational results given by the finite element method and our effective elastic stiffness tensor is made by an example.

  6. Cubic Single Crystal Representations in Classical and Size-dependent Couple Stress Elasticity

    CERN Document Server

    Bansal, Dipanshu; Aref, Amjad J; Hadjesfandiari, Ali R

    2015-01-01

    Beginning with Cosserat theory in the early 20th century, there have been several different formulations for size-dependent elastic response. In this paper, we concentrate on the application of classical Cauchy theory and the recent parsimonious consistent couple stress theory to model a homogeneous linear elastic solid, exemplified by a pure single crystal with cubic structure. The focus is on an examination of elastodynamic response based upon wave velocities from ultrasonic excitation and phonon dispersion curves, along with adiabatic bulk moduli measurements. In particular, we consider in detail elastic parameter estimation within classical elasticity and consistent couple stress theory for four different cubic single crystals (NaCl, KCl, Cu, CuZn). The classical theory requires the estimation of three independent material parameters, while only one additional parameter relating skew-symmetric mean curvature to skew-symmetric couple-stress is needed for the size-dependent consistent couple stress theory. ...

  7. Formation and properties of reverse micellar cubic liquid crystals and derived emulsions.

    Science.gov (United States)

    Rodríguez-Abreu, Carlos; Shrestha, Lok Kumar; Varade, Dharmesh; Aramaki, Kenji; Maestro, Alicia; Quintela, Arturo López; Solans, Conxita

    2007-10-23

    The structure of the reverse micellar cubic (I2) liquid crystal and the adjacent micellar phase in amphiphilic block copolymer/water/oil systems has been studied by small-angle X-ray scattering (SAXS), rheometry, and differential scanning calorimetry (DSC). Upon addition of water to the copolymer/oil mixture, spherical micelles are formed and grow in size until a disorder-order transition takes place, which is related to a sudden increase in the viscosity and shear modulus. The transition is driven by the packing of the spherical micelles into a Fd3m cubic lattice. The single-phase I2 liquid crystals show gel-like behavior and elastic moduli higher than 104 Pa, as determined by oscillatory measurements. Further addition of water induces phase separation, and it is found that reverse water-in-oil emulsions with high internal phase ratio and stabilized by I2 liquid crystals can be prepared in the two-phase region. Contrary to liquid-liquid emulsions, both the elastic modulus and the viscosity decrease with the fraction of dispersed water, due to a decrease in the crystalline fraction in the sample, although the reverse emulsions remain gel-like even at high volume fractions of the dispersed phase. A temperature induced order-disorder transition can be detected by calorimetry and rheometry. Upon heating the I2 liquid crystals, two thermal events associated with small enthalpy values were detected: one endothermic, related to the "melting" of the liquid crystal, and the other exothermic, attributed to phase separation. The melting of the liquid crystal is associated with a sudden drop in viscosity and shear moduli. Results are relevant for understanding the formation of cubic-phase-based reverse emulsions and for their application as templates for the synthesis of structured materials.

  8. Effective-Field Theory on High Spin Systems with Biaxial Crystal Field

    Institute of Scientific and Technical Information of China (English)

    JIANG Wei; GUO An-Bang; LI Xin; WANG Xi-Kun; BAI Bao-Dong

    2006-01-01

    Based on the effective-field theory with self-spin correlations and the differential operator technique,physical properties of the spin-2 system with biaxial crystal field on the simple cubic, body-centered cubic, as well as faced-centered lattice have been studied. The influences of the external longitudinal magnetic field on the magnetization,internal energy, specific heat, and susceptibility have been discussed in detail. The phenomenon that the magnetization in the ground state shows quantum effects produced by the biaxial transverse crystal field has been found.

  9. Dual Effect of the Cubic Ag₃PO₄ Crystal on Pseudomonas syringae Growth and Plant Immunity

    Directory of Open Access Journals (Sweden)

    Mi Kyung Kim

    2016-04-01

    Full Text Available We previously found that the antibacterial activity of silver phosphate crystals on Escherichia coli depends on their structure. We here show that the cubic form of silver phosphate crystal (SPC can also be applied to inhibit the growth of a plant-pathogenic Pseudomonas syringae bacterium. SPC pretreatment resulted in reduced in planta multiplication of P. syringae. Induced expression of a plant defense marker gene PR1 by SPC alone is suggestive of its additional plant immunity-stimulating activity. Since SPC can simultaneously inhibit P. syringae growth and induce plant defense responses, it might be used as a more effective plant disease-controlling agent.

  10. N2 plasma etching processes of microscopic single crystals of cubic boron nitride

    Science.gov (United States)

    Tamura, Takahiro; Takami, Takuya; Yanase, Takashi; Nagahama, Taro; Shimada, Toshihiro

    2017-06-01

    We studied the N2 plasma etching of cubic boron nitride (cBN). We have developed experimental techniques for handling 200-µm-size single crystals for the preparation of surfaces with arbitrary crystal indexes, plasma processes, and surface analyses. We successfully prepared smooth surfaces of cBN with roughness smaller than 10 nm and found that the etching behavior was strongly influenced by the surface indexes. The morphology of the etched surfaces can be explained by the chemical stability of (111)B surfaces.

  11. Dislocation kink-pair energetics and pencil glide in body-centered-cubic crystals.

    Science.gov (United States)

    Ngan, A H; Wen, M

    2001-08-13

    When body-centered-cubic crystals undergo plastic deformation, the slip planes are often noncrystallographic. By performing atomistic simulation on the activation pathway of dislocation jumps in bcc iron, we show that the main reason for bcc crystals to exhibit this phenomenon is that one type of kink pair has significantly lower energy than all the other types on the same slip plane. Dislocation motion therefore cannot continue on the same slip plane, and the dislocation has to cross slip onto an intersecting slip plane after each atomic jump. Thus in the long run, the average slip plane would be zigzag and noncrystallographic.

  12. Visualization of membrane protein crystals in lipid cubic phase using X-ray imaging

    Energy Technology Data Exchange (ETDEWEB)

    Warren, Anna J. [Diamond Light Source, Harwell Science and Innovation Campus, Didcot OX11 0DE (United Kingdom); Armour, Wes [Diamond Light Source, Harwell Science and Innovation Campus, Didcot OX11 0DE (United Kingdom); Oxford e-Research Centre, 7 Keble Road, Oxford OX1 3QG (United Kingdom); Axford, Danny; Basham, Mark; Connolley, Thomas; Hall, David R. [Diamond Light Source, Harwell Science and Innovation Campus, Didcot OX11 0DE (United Kingdom); Horrell, Sam [Diamond Light Source, Harwell Science and Innovation Campus, Didcot OX11 0DE (United Kingdom); University of Liverpool, Liverpool L69 3BX (United Kingdom); McAuley, Katherine E.; Mykhaylyk, Vitaliy; Wagner, Armin; Evans, Gwyndaf, E-mail: gwyndaf.evans@diamond.ac.uk [Diamond Light Source, Harwell Science and Innovation Campus, Didcot OX11 0DE (United Kingdom)

    2013-07-01

    A comparison of X-ray diffraction and radiographic techniques for the location and characterization of protein crystals is demonstrated on membrane protein crystals mounted within lipid cubic phase material. The focus in macromolecular crystallography is moving towards even more challenging target proteins that often crystallize on much smaller scales and are frequently mounted in opaque or highly refractive materials. It is therefore essential that X-ray beamline technology develops in parallel to accommodate such difficult samples. In this paper, the use of X-ray microradiography and microtomography is reported as a tool for crystal visualization, location and characterization on the macromolecular crystallography beamlines at the Diamond Light Source. The technique is particularly useful for microcrystals and for crystals mounted in opaque materials such as lipid cubic phase. X-ray diffraction raster scanning can be used in combination with radiography to allow informed decision-making at the beamline prior to diffraction data collection. It is demonstrated that the X-ray dose required for a full tomography measurement is similar to that for a diffraction grid-scan, but for sample location and shape estimation alone just a few radiographic projections may be required.

  13. Evaluation method of multiaxial low cycle fatigue life for cubic single crystal material

    Institute of Scientific and Technical Information of China (English)

    CHEN Jiping; DING Zhiping

    2007-01-01

    The coupling effect of normal stress and shear stress on orthotropic materials happens when applied loading deflects from the directions of the principal axes of the material coordinate system.By taking account of the coupling effects,formulas of equivalent stress and strain for cubic single crystal materials are cited.Using the equivalent strain and equivalent stress for such material and a variable k,which is introduced to express the effect of asymmetrical cyclic loading on fatigue life,a low cycle fatigue (LCF) life prediction model for such material in multiaxial stress starts is proposed.On the basis of the yield criterion and constitutive model of cubic single crystal materials,a subroutine to calculate the thermo elastic-plastic stress-strain of the material on an ANSYS platform was developed.The cyclic stress-strain of DD3 notched specimens under asymmetrical loading at 680℃ was analyzed.Low cycle fatigue test data of the single crystal nickel-based superalloy are used to fit the different parameters of the power law with multiple linear regression analysis.The equivalent stress and strain for a cubic single crystal material as failure parameters have the largest correlation coefficient.A power law exists between k and the failure cycle.The model was validated with LCF test data of CMSX-2 and DD3 single crystal nickel-based superalloys.All the test data fall into the factor of 2.5 for CMSX-2 hollow cylinder specimens and 2.0 scatter band for DD3 notched specimens,respectively.

  14. Luminescence enhancement in nanocrystalline Eu2O3 nanorods - Microwave hydrothermal crystallization and thermal degradation of cubic phase

    Science.gov (United States)

    Kaszewski, Jarosław; Witkowski, Bartłomiej S.; Wachnicki, Łukasz; Przybylińska, Hanka; Kozankiewicz, Bolesław; Mijowska, Ewa; Godlewski, Marek

    2016-09-01

    Thermally induced crystallization of cubic Eu2O3 obtained with the microwave hydrothermal method has been investigated. The starting material crystallized in the form of needle-shaped agglomerates of nanocrystalline hexagonal Eu(OH)3. Thermal treatment up to 800 °C induced the crystallization of cubic Eu2O3, after further calcination at 1200 °C in the air a monoclinic phase appeared. The phase transformation caused abnormal reduction of Eu3+ ions, related to the oxygen vacancy creation during sintering of the oxide crystallites. The crystallization process of cubic Eu2O3 occurred within the agglomerates without change of their shapes. The cubic form exhibited bright emission of Eu3+ related luminescence with intensity increasing with the size of crystallites.

  15. Crystal-field effects in fluoride crystals for optical refrigeration

    Energy Technology Data Exchange (ETDEWEB)

    Hehlen, Markus P [Los Alamos National Laboratory

    2010-01-01

    thermal energy from the solid and carries it away as high-entropy light, thereby cooling the material. In the ideal case, the respective laser-cooling power is given by the pump wavelength ({lambda}{sub p}), the mean fluorescence wavelength ({bar {lambda}}{sub L}), and the absorption coefficient (a{sub r}) of the pumped transition. These quantities are solely determined by crystal field interactions. On one hand, a large crystal-field splitting offers a favorably large difference of {lambda}{sub p} - {bar {lambda}}{sub L} and thus a high cooling efficiency {eta}{sub cool} = ({lambda}{sub p} - {bar {lambda}}{sub L})/{bar {lambda}}{sub L}. On the other hand, a small crystal-field splitting offers a high thermal population (n{sub i}) of the initial state of the pumped transition, giving a high pump absorption coefficient and thus high laser cooling power, particularly at low temperatures. A quantitative description of crystal-field interactions is therefore critical to the understanding and optimization of optical refrigeration. In the case of Yb3+ as the laser cooling ion, however, development of a crystal-field model is met with substantial difficulties. First, Yb3+ has only two 4/multiplets, {sup 2}F{sub 7/2} and {sup 2}F{sub 5/2}, which lead to at most 7 crystal-field levels. This makes it difficult, and in some cases impossible, to evaluate the crystal-field Hamiltonian, which has at least 4 parameters for any Yb3+ point symmety lower than cubic. Second, {sup 2}F{sub 7/2}{leftrightarrow}{sup 2}F{sub 5/2} transitions exhibit an exceptionally strong electron-phonon coupling compared to 4f transitions of other rare earths. This makes it difficult to distinguish electronic from vibronic transitions in the absorption and luminescence spectra and to reliably identify the crystal-field levels. Yb3+ crystal-field splittings reported in the literature should thus generally be viewed with caution. This paper explores the effects of crystal-field interactions on the laser cooling

  16. pH-responsive lyotropic liquid crystals for the preparation of pure cubic zirconia nanoparticles

    Science.gov (United States)

    He, Wei Yan; Liu, Jin Rong; He, Zhang; Cao, Zhen Zhu; Li, Cai Hong; Gao, Yan Fang

    2016-07-01

    We present a lyotropic liquid crystal system consisting of SDS/Triton X-100/water at 25 °C. This system is respond to pH variations with a phase switch. When pH is altered from alkaline (pH 13) to acidic (pH 2) conditions, phase change occurs from a bicontinuous hexagonal phase to a partially hexagonal phase until it disappears. The hexagonal phase under alkaline conditions is stable. Thus, this system is an ideal candidate for the preparation of pure cubic ZrO2 nanoparticles. XRD results confirm that the as-synthesized powder is composed of pure cubic ZrO2. These nanoparticles also exhibit a thermal stability of up to 800 °C. The size and morphological characteristics of the nanoparticles are greatly affected by ZrOCl2 concentration. The mechanism of zirconia nanoparticle synthesis in a lyotropic hexagonal phase was proposed.

  17. pH-responsive lyotropic liquid crystals for the preparation of pure cubic zirconia nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    He, Wei Yan; Liu, Jin Rong; He, Zhang; Cao, Zhen Zhu; Li, Cai Hong; Gao, Yan Fang [Inner Mongolia University of Technology, School of Chemical Engineering, Hohhot (China)

    2016-07-15

    We present a lyotropic liquid crystal system consisting of SDS/Triton X-100/water at 25 C. This system is respond to pH variations with a phase switch. When pH is altered from alkaline (pH 13) to acidic (pH 2) conditions, phase change occurs from a bicontinuous hexagonal phase to a partially hexagonal phase until it disappears. The hexagonal phase under alkaline conditions is stable. Thus, this system is an ideal candidate for the preparation of pure cubic ZrO{sub 2} nanoparticles. XRD results confirm that the as-synthesized powder is composed of pure cubic ZrO{sub 2}. These nanoparticles also exhibit a thermal stability of up to 800 C. The size and morphological characteristics of the nanoparticles are greatly affected by ZrOCl{sub 2} concentration. The mechanism of zirconia nanoparticle synthesis in a lyotropic hexagonal phase was proposed. (orig.)

  18. Cesium hafnium chloride: A high light yield, non-hygroscopic cubic crystal scintillator for gamma spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Burger, Arnold, E-mail: aburger@fisk.edu [Department of Life and Physical Sciences, Fisk University, Nashville, Tennessee 37208 (United States); Department of Physics and Astronomy, Vanderbilt University, Nashville, Tennessee 37235 (United States); Rowe, Emmanuel; Groza, Michael; Morales Figueroa, Kristle [Department of Life and Physical Sciences, Fisk University, Nashville, Tennessee 37208 (United States); Cherepy, Nerine J.; Beck, Patrick R.; Hunter, Steven; Payne, Stephen A. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)

    2015-10-05

    We report on the scintillation properties of Cs{sub 2}HfCl{sub 6} (cesium hafnium chloride or CHC) as an example of a little-known class of non-hygroscopic compounds having the generic cubic crystal structure of K{sub 2}PtCl{sub 6}. The crystals are easily growable from the melt using the Bridgman method with minimal precursor treatments or purification. CHC scintillation is centered at 400 nm, with a principal decay time of 4.37 μs and a light yield of up to 54 000 photons/MeV when measured using a silicon CCD photodetector. The light yield is the highest ever reported for an undoped crystal, and CHC also exhibits excellent light yield nonproportionality. These desirable properties allowed us to build and test CHC gamma-ray spectrometers providing energy resolution of 3.3% at 662 keV.

  19. Compression Stress Effect on Dislocations Movement and Crack propagation in Cubic Crystal

    CERN Document Server

    Suprijadi,; Yusfi, Meiqorry

    2012-01-01

    Fracture material is seriously problem in daily life, and it has connection with mechanical properties itself. The mechanical properties is belief depend on dislocation movement and crack propagation in the crystal. Information about this is very important to characterize the material. In FCC crystal structure the competition between crack propagation and dislocation wake is very interesting, in a ductile material like copper (Cu) dislocation can be seen in room temperature, but in a brittle material like Si only cracks can be seen observed. Different techniques were applied to material to study the mechanical properties, in this study we did compression test in one direction. Combination of simulation and experimental on cubic material are reported in this paper. We found that the deflection of crack direction in Si caused by vacancy of lattice,while compression stress on Cu cause the atoms displacement in one direction. Some evidence of dislocation wake in Si crystal under compression stress at high tempera...

  20. Rhombohedral cubic semiconductor materials on trigonal substrate with single crystal properties and devices based on such materials

    Science.gov (United States)

    Park, Yeonjoon (Inventor); Choi, Sang Hyouk (Inventor); King, Glen C. (Inventor); Elliott, James R. (Inventor)

    2012-01-01

    Growth conditions are developed, based on a temperature-dependent alignment model, to enable formation of cubic group IV, group II-V and group II-VI crystals in the [111] orientation on the basal (0001) plane of trigonal crystal substrates, controlled such that the volume percentage of primary twin crystal is reduced from about 40% to about 0.3%, compared to the majority single crystal. The control of stacking faults in this and other embodiments can yield single crystalline semiconductors based on these materials that are substantially without defects, or improved thermoelectric materials with twinned crystals for phonon scattering while maintaining electrical integrity. These methods can selectively yield a cubic-on-trigonal epitaxial semiconductor material in which the cubic layer is substantially either directly aligned, or 60 degrees-rotated from, the underlying trigonal material.

  1. Descriptors for predicting the lattice constant of body centered cubic crystal

    Science.gov (United States)

    Takahashi, Keisuke; Takahashi, Lauren; Baran, Jakub D.; Tanaka, Yuzuru

    2017-05-01

    The prediction of the lattice constant of binary body centered cubic crystals is performed in terms of first principle calculations and machine learning. In particular, 1541 binary body centered cubic crystals are calculated using density functional theory. Results from first principle calculations, corresponding information from periodic table, and mathematically tailored data are stored as a dataset. Data mining reveals seven descriptors which are key to determining the lattice constant where the contribution of descriptors is also discussed and visualized. Support vector regression (SVR) technique is implemented to train the data where the predicted lattice constants have the mean score of 83.6% accuracy via cross-validation and maximum error of 4% when compared to experimentally determined lattice constants. In addition, trained SVR is successful in predicting material combinations from a desired lattice constant. Thus, a set of descriptors for determining the lattice constant is identified and can be used as a base descriptor for lattice constants of further complex crystals. This would allow for the acceleration of the search for lattice constants of desired atomic compositions as well as the prediction of new materials based on a specified lattice constant.

  2. Distorted asymmetric cubic nanostructure of soluble fullerene crystals in efficient polymer:fullerene solar cells.

    Science.gov (United States)

    Kim, Youngkyoo; Nelson, Jenny; Zhang, Tong; Cook, Steffan; Durrant, James R; Kim, Hwajeong; Park, Jiho; Shin, Minjung; Nam, Sungho; Heeney, Martin; McCulloch, Iain; Ha, Chang-Sik; Bradley, Donal D C

    2009-09-22

    We found that 1-(3-methoxycarbonyl)propyl-1-phenyl-(6,6)C(61) (PCBM) molecules make a distorted asymmetric body-centered cubic crystal nanostructure in the bulk heterojunction films of reigoregular poly(3-hexylthiophene) and PCBM. The wider angle of distortion in the PCBM nanocrystals was approximately 96 degrees , which can be assigned to the influence of the attached side group to the fullerene ball of PCBM to bestow solubility. Atom concentration analysis showed that after thermal annealing the PCBM nanocrystals do preferentially distribute above the layer of P3HT nanocrystals inside devices.

  3. Stabilizing the body centered cubic crystal in titanium alloys by a nano-scale concentration modulation

    Energy Technology Data Exchange (ETDEWEB)

    Wang, H. L.; Shah, S. A. A.; Hao, Y. L.; Prima, F.; Li, T.; Cairney, J. M.; Wang, Y. D.; Wang, Y.; Obbard, E. G.; Li, S. J.; Yang, R.

    2017-04-01

    It is well-known that the body centered cubic (bcc) crystal in titanium alloys reaches its stability limit as the electron-to-atom (e/a) ratio of the alloy drops down to ~4.24. This critical value, however, is much higher than that of a multifunctional bcc type alloy (e/a = 4.15). Here we demonstrate that a nano-scale concentration modulation created by spinodal decomposition is what stabilizes the bcc crystal of the alloy. Aided by such a nano-scale concentration heterogeneity, unexpected properties from its chemically homogeneous counterpart are obtained. This provides a new strategy to design functional titanium alloys by tuning the spinodal decomposition.

  4. Investigation on quality of cubic GaN/GaAs (100) by double-crystal X-ray diffraction

    Institute of Scientific and Technical Information of China (English)

    徐大鹏; 王玉田; 杨辉; 郑联喜; 李建斌; 段俐宏; 吴荣汉

    1999-01-01

    Cubic GaN was grown on GaAs (100) by low pressure metal organic chemical vapor deposition (MOCVD). X-ray diffraction, scanning electron microscope (SEM) and photoluminescence (PL) spectra were performed to characterize the quality of the GaN film. The PL spectra of cubic GaN thin films being thicker than 1.5 μm were reported. Triple-crystal diffraction to analyze orientation distributions and strain of the thin films was also demonstrated.

  5. Measurement of the linear electro-optic tensor of cubic boron nitride single crystals

    Institute of Scientific and Technical Information of China (English)

    Shuang Wang; Gang Jia; Xiuhuan Liu; Shipeng Chi; Jingcheng Zhu; Yanjun Gao; Pingwei Zhou; Zhanguo Chen

    2012-01-01

    The transverse electro-optic (EO) modulation system is built based on cubic boron nitride (cBN) single crystals unintentionally doped and synthesized at a high pressure and high temperature.The photoelectric output of the system includes two parts that can be measured respectively and the value of elements in the linear EO tensor of the cBN crystal can be obtained.This method does not need to measure the absolute light intensity.All of the surfaces of the tiny cBN crystals whose hardness is next to the hardest diamonds are {111} planes.The rectangular parallelepiped cBN samples are obtained by cleaving along {110} planes and subsequently grinding and polishing {112} planes of the tiny octahedral cBN flakes.Three identical non-zero elements of the EO tensor of the cBN crystal are measured via two sample configurations,and the measured results are very close,about 3.68 and 3.95 pm/V,respectively,which are larger than the linear EO coefficients of the general Ⅲ-Ⅴ compounds.

  6. Deformation twinning in small-sized face-centred cubic single crystals: Experiments and modelling

    Science.gov (United States)

    Liang, Z. Y.; Huang, M. X.

    2015-12-01

    Small-sized crystals generally show deformation behaviour distinct from their bulk counterparts. In addition to dislocation slip, deformation twinning in small-sized face-centred cubic (FCC) single crystals has been reported to follow a different mechanism which involves coherent emission of partial dislocations on successive { 111 } planes from free surface. The present work employed a twinning-induced plasticity (TWIP) steel with a low stacking fault energy to systematically investigate the twin evolution in small-sized FCC single crystals. Micrometre-sized single crystal pillars of TWIP steel were fabricated by focus ion beam and then strained to different levels by compression experiments. Detailed transmission electron microscopy characterization was carried out to obtain a quantitative evaluation of the deformation twins, which contribute to most of the plastic strain. Emissions of partial dislocations from free surface (surface sources) and pre-existing perfect dislocations inside the pillar (inner sources) are found as the essential processes for the formation of deformation twins. Accordingly, a physically-based model, which integrates source introduction methods and source activation criterions for partial dislocation emission, is developed to quantitatively predict the twin evolution. The model is able to reproduce the experimental twin evolution, in terms of the total twin formation, the twin morphology and the occurrence of twinning burst.

  7. Finite Element Treatment of Vortex States in 3D Cubic Superconductors in a Tilted Magnetic Field

    Science.gov (United States)

    Peng, Lin; Cai, Chuanbing

    2017-03-01

    The time-dependent Ginzburg-Landau equations have been solved numerically by a finite element analysis for superconducting samples with a cubic shape in a tilted magnetic field. We obtain different vortex patterns as a function of the external magnetic field. With a magnetic field not parallel to the x- or y-axis, the vortices attempt to change their orientation accordingly. Our analysis of the corresponding changes in the magnetic response in different directions can provide information not only about vorticity but also about the three-dimensional vortex arrangement, even about the very subtle changes for the superconducting samples with a cubic shape in a tilted magnetic field.

  8. Understanding the Cubic Phase Stabilization and Crystallization Kinetics in Mixed Cations and Halides Perovskite Single Crystals.

    Science.gov (United States)

    Xie, Li-Qiang; Chen, Liang; Nan, Zi-Ang; Lin, Hai-Xin; Wang, Tan; Zhan, Dong-Ping; Yan, Jia-Wei; Mao, Bing-Wei; Tian, Zhong-Qun

    2017-03-08

    The spontaneous α-to-δ phase transition of the formamidinium-based (FA) lead halide perovskite hinders its large scale application in solar cells. Though this phase transition can be inhibited by alloying with methylammonium-based (MA) perovskite, the underlying mechanism is largely unexplored. In this Communication, we grow high-quality mixed cations and halides perovskite single crystals (FAPbI3)1-x(MAPbBr3)x to understand the principles for maintaining pure perovskite phase, which is essential to device optimization. We demonstrate that the best composition for a perfect α-phase perovskite without segregation is x = 0.1-0.15, and such a mixed perovskite exhibits carrier lifetime as long as 11.0 μs, which is over 20 times of that of FAPbI3 single crystal. Powder XRD, single crystal XRD and FT-IR results reveal that the incorporation of MA(+) is critical for tuning the effective Goldschmidt tolerance factor toward the ideal value of 1 and lowering the Gibbs free energy via unit cell contraction and cation disorder. Moreover, we find that Br incorporation can effectively control the perovskite crystallization kinetics and reduce defect density to acquire high-quality single crystals with significant inhibition of δ-phase. These findings benefit the understanding of α-phase stabilization behavior, and have led to fabrication of perovskite solar cells with highest efficiency of 19.9% via solvent management.

  9. Visualization of membrane protein crystals in lipid cubic phase using X-ray imaging.

    Science.gov (United States)

    Warren, Anna J; Armour, Wes; Axford, Danny; Basham, Mark; Connolley, Thomas; Hall, David R; Horrell, Sam; McAuley, Katherine E; Mykhaylyk, Vitaliy; Wagner, Armin; Evans, Gwyndaf

    2013-07-01

    The focus in macromolecular crystallography is moving towards even more challenging target proteins that often crystallize on much smaller scales and are frequently mounted in opaque or highly refractive materials. It is therefore essential that X-ray beamline technology develops in parallel to accommodate such difficult samples. In this paper, the use of X-ray microradiography and microtomography is reported as a tool for crystal visualization, location and characterization on the macromolecular crystallography beamlines at the Diamond Light Source. The technique is particularly useful for microcrystals and for crystals mounted in opaque materials such as lipid cubic phase. X-ray diffraction raster scanning can be used in combination with radiography to allow informed decision-making at the beamline prior to diffraction data collection. It is demonstrated that the X-ray dose required for a full tomography measurement is similar to that for a diffraction grid-scan, but for sample location and shape estimation alone just a few radiographic projections may be required.

  10. Science Letters: New solutions of shear waves in piezoelectric cubic crystals

    Institute of Scientific and Technical Information of China (English)

    ZAKHARENKO A.A.

    2007-01-01

    Acoustic wave propagation in piezoelectric crystals of classes 43m and 23 is studied. The crystals Tl3VS4 and Tl3TaSe4 (-43m) of the Chalcogenide family and the crystal Bi12TiO20 (23) possess strong piezoelectric effect. Because the surface Bleustein-Gulyaev waves cannot exist in piezoelectric cubic crystals, it was concluded that new solutions for shear-horizontal surface acoustic waves (SH-SAWs) are found in the monocrystals using different electrical boundary conditions such as electrically "short" and "open" free-surfaces for the unique [ 101] direction of wave propagation. For the crystal Tl3TaSe4 with coefficient of electromechanical coupling (CEMC) Ke2=e2/(C×g)~1/3, the phase velocity Vph for the new SH-SAWs can be calculated with the following formula: Vph=(Va+Vt)/2, where Vt is the speed of bulk SH-wave, Vt=Vt4(1+Ke2)1/2, Va=aKVt4, aK=2[Ke(1+Ke2)1/2-Ke2]1/2,and Vt4=(C44/ρ)1/2. It was found that the CEMC K2 evaluation for Tl3TaSe4 gave the value of K2=2(Vf-Vm)/Vf~O.047 (~4.7%),where Vf~848 m/s and Vm~828 m/s are the new-SAW velocities for the free and metallized surfaces, respectively. This high value of K2(Tl3TaSe4) is significantly greater than K2(Tl3VS4)~3% and about five times that of K2(Bi12TiO20).

  11. Growth and characterization of cubic SiC single-crystal films on Si

    Science.gov (United States)

    Powell, J. Anthony; Matus, L. G.; Kuczmarski, Maria A.

    1987-01-01

    Morphological and electrical characterization results are presented for cubic SiC films grown by chemical vapor deposition on single-crystal Si substrates. The films, up to 40 microns thick, were characterized by optical microscopy, (SEM), (TEM), electron channeling, surface profilometry, and Hall measurements. A variety of morphological features observed on the SiC films are described. Electrical measurements showed a decrease in the electron mobility with increasing electron carrier concentration, similar to that observed in Si. Room-temperature electron mobilities up to 520 sq cm/V-s (at an electron carrier concentration of 5 x 10 to the 16th/cu cm) were measured. Finally, a number of parameters believed to be important in the growth process were investigated, and some discussion is given of their possible effects on the film characteristics.

  12. Magnetic, magnetocaloric and magnetoresistive properties of cubic Laves phase HoAl2 single crystal.

    Science.gov (United States)

    Patra, M; Majumdar, S; Giri, S; Xiao, Y; Chatterji, T

    2014-01-29

    We report the magnetization (M) and magnetoresistance (MR) results of HoAl2 single crystals oriented along the ⟨100⟩ and ⟨110⟩ directions. Although HoAl2 has cubic Laves phase structure, a large anisotropy is observed in M and MR below the Curie temperature (TC). A satisfactory correlation between magnetic entropy change (ΔSM) and MR could be established along ⟨110⟩ and also ⟨100⟩, except for the temperature (T) region around which spin reorientation takes place. Large inverse magnetocaloric effect is observed at low T, which is associated with the spin reorientation process in the ⟨100⟩ direction. A theoretical model based on the Landau theory of phase transition can describe the T-variation of -ΔSM for T > TC.

  13. Directional dependence of nonlinear surface acoustic waves in the (001) plane of cubic crystals.

    Science.gov (United States)

    Kumon, R E; Hamilton, M F

    2002-05-01

    Spectral evolution equations are used to perform analytical and numerical studies of nonlinear surface acoustic waves in the (001) plane of a variety of nonpiezoelectric cubic crystals. The basic theory underlying the model equations is outlined, and quasilinear solutions of the equations are presented. Expressions are also developed for a characteristic length scale for nonlinear distortion and a nonlinearity coefficient. A time-domain equation corresponding to the spectral equations is derived. Numerical calculations based on measured second- and third-order elastic constants taken from the literature are performed to predict the evolution of initially monofrequency surface waves. Nonlinearity matrix elements that indicate the coupling strength of harmonic interactions are shown to provide a useful tool for characterizing waveform distortion. The formation of compression or rarefaction shocks can be strongly dependent on the direction of propagation, and harmonic generation is suppressed or increased in certain directions.

  14. Mathemimetics II. Demonstratio Mirabilis of FLT by infinitely ascending cubical crystal growth

    Science.gov (United States)

    Trell, Erik

    2012-09-01

    Emulating Nature by observation and ground-up application of its patterns, structures and processes is a classical scientific practice which under the designation of Biomimetics has now been brought to the Nanotechnology scale where even highly complex systems can be realized by continuous or cyclically reiterated assembly of the respective self-similar eigen-elements, modules and algorithms right from their infinitesimal origin. This is actually quite akin to the genuine mathematical art and can find valuable renewed use as here exemplified by the tentatively original Demonstratio Mirabilis of FLT (Fermat's Last Theorem, or, in that case, Triumph) by infinitely ascending sheet-wise cubical crystal growth leading to the binomial `magic triangle' of his close fellow Blaise Pascal.

  15. Potassium doped barium bismuthates coexisting near the tetra (ortho) and cubic phases boundary: crystal growth and properties

    Energy Technology Data Exchange (ETDEWEB)

    Barilo, S.N. [Institute of Solid State and Semiconductors Physics, Minsk 220072 (Belarus). E-mail: bars at ifttp.bas-net.by; Shiryaev, S.V.; Soldatov, A.G.; Smirnova, T.V.; Gatalskaya, V.I. [Institute of Solid State and Semiconductors Physics, Minsk 220072 (Belarus); Reichardt, W. [Foschungszentrum Karlsruhe, INFP, 3640-76021, Karlsruhe (Germany); Braden, M. [Laboratoire Leon Brillouin, CE-Saclay, CEA, Cedex 91191, Gif sur Yvette (France); Szymczak, H.; Szymczak, R.; Baran, M. [Institute of Physics, PL02-668, Warsaw (Poland)

    2000-08-01

    We report on the seeded growth of large (up to 2 cm{sup 3}) single crystals of the cubic and orthorhombic phases of Ba{sub 1-x}K{sub x}BiO{sub 3}. The shape of the crystals varies with potassium content from a cube to a cube-octahedron shape at x{approx}0.2. The flux saturated by Bi{sub 2}O{sub 3} alone with an anode potential of +740 mV were selected to grow cubic Ba{sub 1-x}K{sub x}BiO{sub 3} crystals with x 0.67, T{sub c}{approx}4.5 K. We found that a new cubic phase (x = 0.51, a = 4.266 A) of crystals could be grown under +970 mV potential and reduced Bi{sub 2}O{sub 3} content in the flux. The crystals grown at {approx}250 deg. C acquired a cube-octahedron shape. In turn, crystals of the tetragonal Ba{sub 1.7}K{sub 1.3}Bi{sub 2}O{sub 7} phase (a = 4.25 A, c = 21.91 A) up to several mm{sup 3} in size were grown at the same temperature but lower potential and higher Bi{sub 2O}3 concentration in the flux. Surprisingly the crystals exhibited a weak superconductor-like magnetization. (author)

  16. Growth Defects in Cubic KTa1-xNbxO3 Crystal

    Institute of Scientific and Technical Information of China (English)

    WANG Xu-Ping; WANG Ji-Yang; WU-Jian; YU Yong-Gui; ZHANG Huai-Jin

    2008-01-01

    Potassium tantalate niobate(KTa1-x NbxO3,KTN)crystals with different dimensions and quality situations were grown by Czochralski method.Crystal growth process and morphology properties of KTN are presented in this paper.It was found that some defects,such as bubble,inclusion,crack,dislocation etc.,can all appear if the crystal is grown in an improper condition.The character and formation mechanism of such defects in macro growth are discussed.We consider that the CO2,which Was not released absolutely during the sintering process and dissolved in the melt,led to bubbles.The composition of the inclusion caused by high pulling and rotation rates is KTN polycrystalline.The crack and dislocation in KTN crystal mainly come from improper temperature field.Etching and high-resolution X-ray diffraction(HRXRD)experiment results indicate that the central area is the defects concentrated.

  17. On the 3-rank of tame kernels of certain pure cubic number fields

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    In this paper,we present some explicit formulas for the 3-rank of the tame kernels of certain pure cubic number fields,and give the density results concerning the 3-rank of the tame kernels.Numerical examples are given in Tables 1 and 2.

  18. Equilibrium shapes and faceting for ionic crystals of body-centered cubic type

    NARCIS (Netherlands)

    Carlon, E.; van Beijeren, H.

    2000-01-01

    A mean-field theory is developed for a calculation of the surface free energy of the staggered body-centered solid-on-solid (or six vertex) model as function of the surface orientation and temperature. The model approximately describes surfaces of crystals with nearest neighbor attractions, and next

  19. Structural, elastic and electronic Properties of isotropic cubic crystals of carbon and silicon nanotubes : Density functional based tight binding calculations.

    Directory of Open Access Journals (Sweden)

    Alexander L. Ivanovskii

    2008-01-01

    Full Text Available Atomic models of cubic crystals (CC of carbon and graphene-like Si nanotubes are offered and their structural, cohesive, elastic and electronic properties are predicted by means of the DFTB method. Our main findings are that the isotropic crystals of carbon nanotubes adopt a very high elastic modulus B and low compressibility β, namely B = 650 GPa, β = 0.0015 1/GPa. In addition, these crystals preserve the initial conductivity type of their “building blocks”, i.e. isolated carbon and Si nanotubes. This feature may be important for design of materials with the selected conductivity type.

  20. Characteristics of plate-like and color-zoning cubic boron nitride crystals

    Energy Technology Data Exchange (ETDEWEB)

    Feng, Shuang [State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, 2699 Qianjin Street, Changchun 130012 (China); Hou, Lixin, E-mail: houlixin_2000@126.com [College of Information and Technology, Jilin Agricultural University, 2888 Xincheng Street, Changchun 130118 (China); Liu, Xiuhuan [College of Telecommunication Engineering, Jilin University, 5372 Nanhu Road, Changchun 130012 (China); Gao, Yanjun; Li, Xinlu; Wang, Qi [State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, 2699 Qianjin Street, Changchun 130012 (China); Chen, Zhanguo, E-mail: czg@jlu.edu.cn [State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, 2699 Qianjin Street, Changchun 130012 (China); Jia, Gang; Zheng, Jie [State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, 2699 Qianjin Street, Changchun 130012 (China)

    2013-11-15

    The polarities of a kind of plate-like and color-zoning cubic boron nitride (cBN) crystal were extensively investigated by microscopy, chemical etching, XPS, Raman scattering, and current–voltage measurements. The {1 1 1}B faces and {1"¯1"¯1"¯}N faces of the cBN samples can be easily distinguished by optical microscope as there are a lot of defects incorporate in {1"¯1"¯1"¯}N sectors serving as the color centers, while the {1 1 1}B sectors have less defects and are nearly colorless. Both XPS and Raman spectra also revealed the uneven distributions of N vacancies and substitutional impurities in cBN crystals. The determination of {1 1 1}B faces and {1"¯1"¯1"¯}N faces can also be verified by the results of the chemical etching because the {1"¯1"¯1"¯}N faces have much faster etch rates than the {1 1 1}B faces. According to XPS, the {1 1 1}B faces have more C and O contaminations than the {1"¯1"¯1"¯}N faces, however the {1"¯1"¯1"¯}N faces have larger atomic ratio of B:N after surface cleaning by Ar{sup +} sputtering. In the Raman spectra of the {1"¯1"¯1"¯}N sectors of cBN, several small broad infrared-active phonon bands emerge nearby TO and LO modes because of the disorder-activated Raman scattering. As for the {1 1 1}B sectors, this phenomenon disappears. In addition, the {1 1 1}B faces have much smaller leakage current than the {1"¯1"¯1"¯}N faces, which indicates that the {1 1 1}B sectors have higher crystalline quality.

  1. Investigation on cubic boron nitride crystals doped with Si by high temperature thermal diffusion

    Science.gov (United States)

    Li, Xinlu; Feng, Shuang; Liu, Xiuhuan; Hou, Lixin; Gao, Yanjun; Wang, Qi; Liu, Nian; Zhang, Hai; Chen, Zhanguo; Zheng, Jie; Jia, Gang

    2014-07-01

    The method of high temperature thermal diffusion was successfully applied for doping Si impurities into cubic boron nitride (cBN) crystals. X-ray photoelectron spectra (XPS) and the current-voltage (I-V) characteristics at different temperatures were respectively used for analyzing the chemical states and the activation energy of Si impurity in cBN. According to the XPS results, Si impurities mainly replace B atoms bonding with the adjacent N atoms and become donors in cBN. Without surface cleaning, there are a lot of C and O contaminations on the surface of cBN, so a small quantity of C-Si and Si-N-O bonds also exist at the surface of cBN. Most Si impurities distribute in the shallow layer underneath the surface of cBN. Based on the electric measurement, Si impurities in cBN usually have the activation energy beyond 0.4 eV, and they can only be slightly ionized at room temperature, therefore the resistivity of Si-doped cBN is still high, and the space charge limited current becomes the main conductive mechanism in cBN. However, the conductivity of Si-doped cBN can rapidly increase with the temperature. In addition, the activation energy and the concentration of Si impurity in cBN can be affected by the temperature and the time of thermal diffusion, which needs to be verified further.

  2. Single-crystal cubic silicon carbide: an in vivo biocompatible semiconductor for brain machine interface devices.

    Science.gov (United States)

    Frewin, Christopher L; Locke, Christopher; Saddow, Stephen E; Weeber, Edwin J

    2011-01-01

    Single crystal silicon carbide (SiC) is a wide band-gap semiconductor which has shown both bio- and hemo-compatibility [1-5]. Although single crystalline SiC has appealing bio-sensing potential, the material has not been extensively characterized. Cubic silicon carbide (3C-SiC) has superior in vitro biocompatibility compared to its hexagonal counterparts [3, 5]. Brain machine interface (BMI) systems using implantable neuronal prosthetics offer the possibility of bi-directional signaling, which allow sensory feedback and closed loop control. Existing implantable neural interfaces have limited long-term reliability, and 3C-SiC may be a material that may improve that reliability. In the present study, we investigated in vivo 3C-SiC biocompatibility in the CNS of C56BL/6 mice. 3C-SiC was compared against the known immunoreactive response of silicon (Si) at 5, 10, and 35 days. The material was examined to detect CD45, a protein tyrosine phosphatase (PTP) expressed by activated microglia and macrophages. The 3C-SiC surface revealed limited immunoresponse and significantly reduced microglia compared to Si substrate.

  3. Singular orientations and faceted motion of dislocations in body-centered cubic crystals.

    Science.gov (United States)

    Kang, Keonwook; Bulatov, Vasily V; Cai, Wei

    2012-09-18

    Dislocation mobility is a fundamental material property that controls strength and ductility of crystals. An important measure of dislocation mobility is its Peierls stress, i.e., the minimal stress required to move a dislocation at zero temperature. Here we report that, in the body-centered cubic metal tantalum, the Peierls stress as a function of dislocation orientation exhibits fine structure with several singular orientations of high Peierls stress-stress spikes-surrounded by vicinal plateau regions. While the classical Peierls-Nabarro model captures the high Peierls stress of singular orientations, an extension that allows dislocations to bend is necessary to account for the plateau regions. Our results clarify the notion of dislocation kinks as meaningful only for orientations within the plateau regions vicinal to the Peierls stress spikes. These observations lead us to propose a Read-Shockley type classification of dislocation orientations into three distinct classes-special, vicinal, and general-with respect to their Peierls stress and motion mechanisms. We predict that dislocation loops expanding under stress at sufficiently low temperatures, should develop well defined facets corresponding to two special orientations of highest Peierls stress, the screw and the M111 orientations, both moving by kink mechanism. We propose that both the screw and the M111 dislocations are jointly responsible for the yield behavior of BCC metals at low temperatures.

  4. Photonic bandgap properties of void-based body-centered-cubic photonic crystals in polymer.

    Science.gov (United States)

    Zhou, Guangyong; Ventura, Michael; Gu, Min; Matthews, Aaron; Kivshar, Yuri

    2005-06-13

    We report on the fabrication and characterization of void-based body-centered-cubic (bcc) photonic crystals in a solidified transparent polymer by the use of a femtosecond laser-driven microexplosion method. The change in the refractive index in the region surrounding the void dots that form the bcc structures is verified by presenting confocal microscope images, and the bandgap properties are characterized by using a Fourier transform infrared spectrometer. The effect of the angle of incidence on the photonic bandgaps is also studied. We observe multiple stop gaps with a suppression rate of the main gap of 47% for a bcc structure with a lattice constant of 2.77 microm, where the first and second stop gaps are located at 3.7 microm and 2.2 microm, respectively. We also present a theoretical approach to characterize the refractive index of the material for calculating the bandgap spectra, and confirm that the wavelengths of the observed bandgaps are in good correlation with the analytical predictions.

  5. Lipidic cubic phase injector is a viable crystal delivery system for time-resolved serial crystallography.

    Science.gov (United States)

    Nogly, Przemyslaw; Panneels, Valerie; Nelson, Garrett; Gati, Cornelius; Kimura, Tetsunari; Milne, Christopher; Milathianaki, Despina; Kubo, Minoru; Wu, Wenting; Conrad, Chelsie; Coe, Jesse; Bean, Richard; Zhao, Yun; Båth, Petra; Dods, Robert; Harimoorthy, Rajiv; Beyerlein, Kenneth R; Rheinberger, Jan; James, Daniel; DePonte, Daniel; Li, Chufeng; Sala, Leonardo; Williams, Garth J; Hunter, Mark S; Koglin, Jason E; Berntsen, Peter; Nango, Eriko; Iwata, So; Chapman, Henry N; Fromme, Petra; Frank, Matthias; Abela, Rafael; Boutet, Sébastien; Barty, Anton; White, Thomas A; Weierstall, Uwe; Spence, John; Neutze, Richard; Schertler, Gebhard; Standfuss, Jörg

    2016-08-22

    Serial femtosecond crystallography (SFX) using X-ray free-electron laser sources is an emerging method with considerable potential for time-resolved pump-probe experiments. Here we present a lipidic cubic phase SFX structure of the light-driven proton pump bacteriorhodopsin (bR) to 2.3 Å resolution and a method to investigate protein dynamics with modest sample requirement. Time-resolved SFX (TR-SFX) with a pump-probe delay of 1 ms yields difference Fourier maps compatible with the dark to M state transition of bR. Importantly, the method is very sample efficient and reduces sample consumption to about 1 mg per collected time point. Accumulation of M intermediate within the crystal lattice is confirmed by time-resolved visible absorption spectroscopy. This study provides an important step towards characterizing the complete photocycle dynamics of retinal proteins and demonstrates the feasibility of a sample efficient viscous medium jet for TR-SFX.

  6. Bifurcation and Isochronicity at Infinity in a Class of Cubic Polynomial Vector Fields

    Institute of Scientific and Technical Information of China (English)

    Qin-long Wang; Yi-rong Liu

    2007-01-01

    In this paper, we study the appearance of limit cycles from the equator and isochronicity of infinity in polynomial vector fields with no singular points at infinity. We give a recursive formula to compute the singular point quantities of a class of cubic polynomial systems, which is used to calculate the first seven singular point quantities. Further, we prove that such a cubic vector field can have maximal seven limit cycles in the neighborhood of infinity. We actually and construct a system that has seven limit cycles. The positions of these limit cycles can be given exactly without constructing the Poincare cycle fields. The technique employed in this work is essentially different from the previously widely used ones. Finally, the isochronous center conditions at infinity are given.

  7. The Electric Field of a Uniformly Charged Non-Conducting Cubic Surface

    CERN Document Server

    McCreery, Kaitlin

    2016-01-01

    As an integrative and insightful example for undergraduates learning about electrostatics, we discuss how to use symmetry, Coulomb's Law, superposition, Gauss's law, and visualization to understand the electric field produced by a non-conducting cubic surface that is covered with a uniform surface charge density. We first discuss how to deduce qualitatively, using only elementary physics, the surprising fact that the electric field inside the cubic surface is nonzero and has a complex structure, pointing inwards towards the cube center from the midface of each cube and pointing outwards towards each edge and corner. We then discuss how to understand the quantitative features of the electric field by plotting an analytical expression for E along symmetry lines and on symmetry surfaces. This example would be a good choice for group problem solving in a recitation or flipped classroom.

  8. Synthesis and photonic band calculations of NCP face-centered cubic photonic crystals of TiO2 hollow spheres.

    Science.gov (United States)

    Zhu, Yong-zheng; Cao, Yan-ling; Li, Zhi-hui; Ding, Juan; Liu, Jun-song; Chi, Yuan-bin

    2007-02-01

    With the help of self-assembly, thermal sintering, selective etching techniques and sol-gel process, the non-close packed (ncp) face-centered cubic (fcc) photonic crystals of titanium dioxide (TiO2) hollow spheres connected by TiO2 cylindrical tubes have been fabricated using silica template. The photonic bandgap calculations indicate that the ncp structure of TiO2 hollow spheres was easier to open the pseudogaps than close packed system at the lowest energy.

  9. 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.

  10. On Gauge Equivalence of Tachyon Solutions in Cubic Neveu-Schwarz String Field Theory

    CERN Document Server

    Aref'eva, I Ya

    2010-01-01

    Simple analytic solution to cubic Neveu-Schwarz String Field Theory including the $GSO(-)$ sector is presented. This solution is an analog of the Erler-Schnabl solution for bosonic case and one of the authors solution for the pure $GSO(+)$ case. Gauge transformations of the new solution to others known solutions for the $NS$ string tachyon condensation are constructed explicitly. This gauge equivalence manifestly supports the early observed fact that these solutions have the same value of the action density.

  11. The effective crystal field potential

    CERN Document Server

    Mulak, J

    2000-01-01

    As it results from the very nature of things, the spherical symmetry of the surrounding of a site in a crystal lattice or an atom in a molecule can never occur. Therefore, the eigenfunctions and eigenvalues of any bound ion or atom have to differ from those of spherically symmetric respective free ions. In this way, the most simplified concept of the crystal field effect or ligand field effect in the case of individual molecules can be introduced. The conventional notion of the crystal field potential is narrowed to its non-spherical part only through ignoring the dominating spherical part which produces only a uniform energy shift of gravity centres of the free ion terms. It is well understood that the non-spherical part of the effective potential "seen" by open-shell electrons localized on a metal ion plays an essential role in most observed properties. Light adsorption, electron paramagnetic resonance, inelastic neutron scattering and basic characteristics derived from magnetic and thermal measurements, ar...

  12. Heavy-atom derivatives in lipidic cubic phases: results on hen egg-white lysozyme tetragonal derivative crystals with Gd-HPDO3A complex.

    Science.gov (United States)

    Girard, Eric; Pebay-Peyroula, Eva; Vicat, Jean; Kahn, Richard

    2004-08-01

    Gd-HPDO3A, a neutral gadolinium complex, is a good candidate for obtaining heavy-atom-derivative crystals by the lipidic cubic phase crystallization method known to be effective for membrane proteins. Gadolinium-derivative crystals of hen egg-white lysozyme were obtained by co-crystallizing the protein with 100 mM Gd-HPDO3A in a monoolein cubic phase. Diffraction data were collected to a resolution of 1.7 A using Cu Kalpha radiation from a rotating-anode generator. Two binding sites of the gadolinium complex were located from the strong gadolinium anomalous signal. The Gd-atom positions and their refined occupancies were found to be identical to those found in derivative crystals of hen egg-white lysozyme obtained by co-crystallizing the protein with 100 mM Gd-HPDO3A using the hanging-drop technique. Moreover, the refined structures are isomorphous. The lipidic cubic phase is not disturbed by the high concentration of Gd-HPDO3A. This experiment demonstrates that a gadolinium complex, Gd-HPDO3A, can be used to obtain derivative crystals by the lipidic cubic phase crystallization method. Further studies with membrane proteins that are known to crystallize in lipidic cubic phases will be undertaken with Gd-HPDO3A and other Gd complexes to test whether derivative crystals with high Gd-site occupancies can be obtained.

  13. Investigation of atom-attaching pro cess of three-dimensional b o dy-center-cubic dendritic growth by phase-field crystal mo del%BCC枝晶生长原子堆垛过程的晶体相场研究∗

    Institute of Scientific and Technical Information of China (English)

    郭灿; 王锦程; 王志军; 李俊杰; 郭耀麟; 唐赛

    2015-01-01

    通过在自由能泛函中引入各向异性参数得到了一个基于高斯内核的改进晶体相场模型,并采用该模型研究了体心立方结构(BCC)枝晶生长的原子堆垛过程。结果表明,在BCC由正十二面体平衡形貌演化为枝晶组织过程中,形核位置经历了由面心({110}面)到尖端(⟨100⟩取向)的转移,进而发生界面失稳形成枝晶组织;枝晶生长过程中,新的固相原子首先在枝晶尖端附近形核,并快速向尖端及根部生长,枝晶尖端被新原子完全包覆后将再次诱发液相原子附着形核及生长;随初始液相密度的增加,固-液界面移动速率增加,速率系数的各向异性也增强。%On the basis of the Gaussian kernel phase field crystal model (PFC), we propose a modified PFC model. The atom-attaching process of three-dimensional body-center-cubic (BCC) dendritic growth is examined by using the modified PFC model. Our simulations indicate that in the process of the morphology evolution from regular dodecahedron to dendrite shape, the nucleation position of new layer is transferred from the center of {110} planes into the region of{110}plane near the⟨100⟩tips, and then the BCC dendritic morphology is obtained. In the process of dendritic growth, first, new solid atom absorption takes place near dendrite tips, then liquid atoms start to grow up on the existing solid phase rapidly. After the dendrite tips are completely occupied by new atoms, new nuclei begin to form again. Increasing the initial atom density n will increase the velocity coefficient C and the anisotropy of C.

  14. Characteristics of plate-like and color-zoning cubic boron nitride crystals

    Science.gov (United States)

    Feng, Shuang; Hou, Lixin; Liu, Xiuhuan; Gao, Yanjun; Li, Xinlu; Wang, Qi; Chen, Zhanguo; Jia, Gang; Zheng, Jie

    2013-11-01

    The polarities of a kind of plate-like and color-zoning cubic boron nitride (cBN) crystal were extensively investigated by microscopy, chemical etching, XPS, Raman scattering, and current-voltage measurements. The {1 1 1}B faces and {1¯ 1¯ 1¯}N faces of the cBN samples can be easily distinguished by optical microscope as there are a lot of defects incorporate in {1¯ 1¯ 1¯}N sectors serving as the color centers, while the {1 1 1}B sectors have less defects and are nearly colorless. Both XPS and Raman spectra also revealed the uneven distributions of N vacancies and substitutional impurities in cBN crystals. The determination of {1 1 1}B faces and {1¯ 1¯ 1¯}N faces can also be verified by the results of the chemical etching because the {1¯ 1¯ 1¯}N faces have much faster etch rates than the {1 1 1}B faces. According to XPS, the {1 1 1}B faces have more C and O contaminations than the {1¯ 1¯ 1¯}N faces, however the {1¯ 1¯ 1¯}N faces have larger atomic ratio of B:N after surface cleaning by Ar+ sputtering. In the Raman spectra of the {1¯ 1¯ 1¯}N sectors of cBN, several small broad infrared-active phonon bands emerge nearby TO and LO modes because of the disorder-activated Raman scattering. As for the {1 1 1}B sectors, this phenomenon disappears. In addition, the {1 1 1}B faces have much smaller leakage current than the {1¯ 1¯ 1¯}N faces, which indicates that the {1 1 1}B sectors have higher crystalline quality.

  15. Hysteresis Loops and Phase Diagrams of the Spin-1 Ising Model in a Transverse Crystal Field

    Institute of Scientific and Technical Information of China (English)

    S. Bouhou; I. Essaoudi; A. Ainane; M. Saber; J. J. de Miguel; M. Kerouad1

    2012-01-01

    Within the framework of the effective-Geld theory with a probability distribution technique, which accounts for the self-spin correlation functions, the ferromagnetic spin-l Ising model with a transverse crystal field on honeycomb, square and simple cubic lattices is studied. We have investigated the effect of the transverse crystal field on the phase diagrams, magnetization, hysteresis loops and χz,h of the system. A number of interesting phenomena of the system are discussed.%Within the framework of the effective-field theory with a probability distribution technique,which accounts for the self-spin correlation functions,the ferromagnetic spin-1 Ising model with a transverse crystal field on honeycomb,square and simple cubic lattices is studied.We have investigated the effect of the transverse crystal field on the phase diagrams,magnetization,hysteresis loops and xz,h of the system.A number of interesting phenomena of the system are discussed.

  16. Generating Erler-Schnabl-type Solution for Tachyon Vacuum in Cubic Superstring Field Theory

    CERN Document Server

    Arroyo, E Aldo

    2010-01-01

    We analyze a new class of identity-based solutions in open bosonic string field theory and cubic superstring field theory. Even though these solutions seem to be trivial, it turns out that after performing a suitable gauge transformation, we are left with the known Erler-Schnabl-type solutions which correctly reproduce the value for the D-brane tension. This important result shows explicitly that how a seemingly trivial solution can generate a non-trivial configuration which precisely represents the tachyon vacuum.

  17. Generating Erler-Schnabl-type solution for the tachyon vacuum in cubic superstring field theory

    Science.gov (United States)

    Aldo Arroyo, E.

    2010-11-01

    We study a new set of identity-based solutions to analyze the problem of tachyon condensation in open bosonic string field theory and cubic superstring field theory. Even though these identity-based solutions seem to be trivial, it turns out that after performing a suitable gauge transformation, we are left with the known Erler-Schnabl-type solutions which correctly reproduce the value of the D-brane tension. This result shows explicitly that a seemingly trivial solution can generate a non-trivial configuration which precisely represents the tachyon vacuum.

  18. Synthesis of indium oxide cubic crystals by modified hydrothermal route for application in room temperature flexible ethanol sensors

    Energy Technology Data Exchange (ETDEWEB)

    Seetha, M., E-mail: seetha.phy@gmail.com [Department of Physics, SRM University, Kattankulathur, Kancheepuram Dt 603 203 (India); Meena, P. [Department of Physics, PSGR Krishnammal College for Women, Coimbatore 641 046 (India); Mangalaraj, D., E-mail: dmraj800@yahoo.com [DRDO-BU Centre for Life Sciences, Bharathiar University Campus, Coimbatore (India); Department of Nanoscience and Technology, Bharathiar University, Coimbatore 641 014 (India); Masuda, Yoshitake [National Institute of Advanced Industrial Science and Technology (AIST), Nagoya 463-8560 (Japan); Senthil, K. [School of Advanced Materials Science and Engineering, Sungkyunkwan University (Suwon Campus), Cheoncheon-dong 300, Jangan-gu, Suwon 440-746 (Korea, Republic of)

    2012-03-15

    Highlights: Black-Right-Pointing-Pointer For the first time HMT is used in the preparation of indium oxide. Black-Right-Pointing-Pointer HMT itself acts as base for the precursor and results in cubic indium hydroxide. Black-Right-Pointing-Pointer Modified hydrothermal route used for the preparation of cubic indium oxide crystals. Black-Right-Pointing-Pointer As a new approach a composite film synthesized with prepared indium oxide. Black-Right-Pointing-Pointer Film showed good response to ethanol vapours with quick response and recovery times. - Abstract: Indium oxide cubic crystals were prepared by using hexamethylenetetramine and indium chloride without the addition of any structure directing agents. The chemical route followed in the present work was a modified hydrothermal synthesis. The average crystallite size of the prepared cubes was found to be 40 nm. A blue emission at 418 nm was observed at room temperature when the sample was excited with a 380 nm Xenon lamp. This emission due to oxygen vacancies made the material suitable for gas sensing applications. The synthesized material was made as a composite film with polyvinyl alcohol which was more flexible than the films prepared on glass substrates. This flexible film was used as a sensing element and tested with ethanol vapours at room temperature. The film showed fast response as well as recovery to ethanol vapours with a sensor response of about 1.4 for 100 ppm of the gas.

  19. Equilibrium shapes and faceting for ionic crystals of body-centered-cubic type

    Science.gov (United States)

    Carlon; van Beijeren H

    2000-12-01

    A mean-field theory is developed for a calculation of the surface free energy of the staggered body-centered solid-on-solid (or six vertex) model as function of the surface orientation and temperature. The model approximately describes surfaces of crystals with nearest neighbor attractions, and next nearest neighbor repulsions. The mean-field free energy is calculated by expressing the model in terms of interacting directed walks on a lattice. The resulting equilibrium shape is very rich with facet boundaries and boundaries between reconstructed and unreconstructed regions, which can be either sharp (first order) or smooth (continuous). In addition, there are tricritical points where a smooth boundary changes into a sharp one, and triple points where three sharp boundaries meet. Finally our numerical results strongly suggest the existence of conical points, at which tangent planes of a finite range of orientations all intersect each other. The thermal evolution of the equilibrium shape in this model shows a strong similarity to that seen experimentally for ionic crystals.

  20. Superstructures in cubic A{sup II}B{sup VI} crystals heavily doped with Ni and V ions

    Energy Technology Data Exchange (ETDEWEB)

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

    2016-01-15

    Specific features of the crystal structure of bulk sphalerite-type Zn{sub 0.9}Ni{sub 0.1}S, Zn{sub 0.9}V{sub 0.1}Se, and Zn{sub 0.997}Ni{sub 0.003}Te crystals have been investigated in detail by thermal-neutron diffraction at room temperature. Fine effects (indicative of the existence of distortion microdomains, nucleation of long- and short-wavelength modulations, and tendencies toward local lowering of the symmetry based on the initial cubic structure) can be observed in the obtained scattering patterns. Various states preceding the fcc ↔ hcp phase transition have been revealed in these crystals. They depend on the elemental composition and are formed upon the reaction of the initial lattice to perturbations induced by foreign ions with an incomplete 3d shell.

  1. Optical properties of GaAs 2D hexagonal and cubic photonic crystal

    Energy Technology Data Exchange (ETDEWEB)

    Arab, F., E-mail: farab@CDTA.DZ; Assali, A.; Grain, R.; Kanouni, F. [Centre for Development of Advanced Technologies (CDTA) Research Unit in Optics and Photonics (UROP), University of Setif 1, El Bez, 19000 Setif (Algeria)

    2015-03-30

    In this paper we present our theoretical study of 2D hexagonal and cubic rods GaAs in air, with plan wave expansion (PWE) and finite difference time domain (FDTD) by using BandSOLVE and FullWAVE of Rsoft photonic CAD package. In order to investigate the effect of symmetry and radius, we performed calculations of the band structures for both TM and TE polarization, contour and electromagnetic propagation and transmission spectra. Our calculations show that the hexagonal structure gives a largest band gaps compare to cubic one for a same filling factor.

  2. Gauge equivalence of Tachyon solutions in the cubic Neveu—Schwarz string field theory

    Science.gov (United States)

    Aref'eva, I. Ya.; Gorbachev, R. V.

    2010-11-01

    We construct a simple analytic solution of the cubic Neveu—Schwarz (NS) string field theory including the GSO(-) sector. This solution is analogous to the Erler—Schnabl solution in the bosonic case and to the solution in the pure GSO(+) case previously proposed by one of us. We construct exact gauge transformations of the new solution to other known solutions for the NS string tachyon condensation. This gauge equivalence manifestly supports the previous observation that the Erler solution for the pure GSO(+) sector and our solution containing both the GSO(+) and the GSO(-) sectors have the same value of the action density.

  3. A Finer Classification of the Unit Sum Number of the Ring of Integers of Quadratic Fields and Complex Cubic Fields

    Indian Academy of Sciences (India)

    Nahid Ashrafi

    2009-06-01

    The unit sum number, $u(R)$, of a ring is the least such that every element is the sum of units; if there is no such then $u(R)$ is or ∞ depending on whether the units generate additively or not. Here we introduce a finer classification for the unit sum number of a ring and in this new classification we completely determine the unit sum number of the ring of integers of a quadratic field. Further we obtain some results on cubic complex fields which one can decide whether the unit sum number is or ∞. Then we present some examples showing that all possibilities can occur.

  4. A novel microseeding method for the crystallization of membrane proteins in lipidic cubic phase.

    Science.gov (United States)

    Kolek, Stefan Andrew; Bräuning, Bastian; Stewart, Patrick Douglas Shaw

    2016-04-01

    Random microseed matrix screening (rMMS), in which seed crystals are added to random crystallization screens, is an important breakthrough in soluble protein crystallization that increases the number of crystallization hits that are available for optimization. This greatly increases the number of soluble protein structures generated every year by typical structural biology laboratories. Inspired by this success, rMMS has been adapted to the crystallization of membrane proteins, making LCP seed stock by scaling up LCP crystallization conditions without changing the physical and chemical parameters that are critical for crystallization. Seed crystals are grown directly in LCP and, as with conventional rMMS, a seeding experiment is combined with an additive experiment. The new method was used with the bacterial integral membrane protein OmpF, and it was found that it increased the number of crystallization hits by almost an order of magnitude: without microseeding one new hit was found, whereas with LCP-rMMS eight new hits were found. It is anticipated that this new method will lead to better diffracting crystals of membrane proteins. A method of generating seed gradients, which allows the LCP seed stock to be diluted and the number of crystals in each LCP bolus to be reduced, if required for optimization, is also demonstrated.

  5. Spatiotemporal light bullets and supercontinuum generation in β-BBO crystal with competing quadratic and cubic nonlinearities.

    Science.gov (United States)

    Šuminas, R; Tamošauskas, G; Valiulis, G; Dubietis, A

    2016-05-01

    We experimentally study filamentation and supercontinuum generation in a birefringent medium [beta-barium borate (β-BBO) crystal] pumped by intense 90 fs, 1.8 μm laser pulses whose carrier wavelength falls in the range of anomalous group velocity dispersion of the crystal. We demonstrate that the competition between the intrinsic cubic and cascaded-quadratic nonlinearities may serve as a useful tool for controlling the self-action effects via phase matching condition. In particular, we found that spectral superbroadening of the ordinary polarization is linked to three-dimensional self-focusing and formation of self-compressed spatiotemporal light bullets that could be accessed within a certain range of either positive or negative phase mismatch. In the extraordinary polarization, we detect giant spectral shifts of the second harmonic radiation, which are attributed to a light bullet-induced self-phase matching.

  6. Bragg reflection band width and optical rotatory dispersion of cubic blue-phase liquid crystals

    Science.gov (United States)

    Yoshida, Hiroyuki; Anucha, Konkanok; Ogawa, Yasuhiro; Kawata, Yuto; Ozaki, Masanori; Fukuda, Jun-ichi; Kikuchi, Hirotsugu

    2016-10-01

    The Bragg reflection band width and optical rotatory dispersion of liquid crystalline cholesteric blue phases (BPs) I and II are compared by numerical simulations. Attention is paid to the wavelength regions for which the reflection bands with lowest photon energies appear, i.e., the [110 ] direction for BP I and the [100 ] direction for BP II. Finite difference time domain and 4 ×4 matrix calculations performed on the theoretical director tensor distribution of BPs with the same material parameters show that BP II, which has simple cubic symmetry, has a wider photonic band gap than BP I, which has body centered cubic symmetry, possibly due to the fact that the density of the double-twist cylinders in BP II are twice that in BP I. The theoretical results on the Bragg reflection band width are supported by reflectance measurements performed on BPs I and II for light incident along the [110 ] and [100 ] directions, respectively.

  7. Studies on the second-harmonic generations in cubical quantum dots with applied electric field

    Energy Technology Data Exchange (ETDEWEB)

    Shao Shuai [Department of Physics, College of Physics and Electronic Engineering, Guangzhou University, Guangzhou 510006 (China); Guo Kangxian, E-mail: axguo@sohu.co [Department of Physics, College of Physics and Electronic Engineering, Guangzhou University, Guangzhou 510006 (China); Zhang Zhihai; Li Ning; Peng Chao [Department of Physics, College of Physics and Electronic Engineering, Guangzhou University, Guangzhou 510006 (China)

    2011-02-01

    The second-harmonic generation (SHG) coefficient for cubical quantum dots (CQDs) with the applied electric field is theoretically investigated. Using the compact density-matrix approach and the iterative method, we get the analytical expression of the SHG coefficient. And the numerical calculations for the typical GaAs/AlAs CQDs are presented. The results show that the SHG coefficient can reach the magnitude of 10{sup -5} m/V, about two orders higher than that in spherical quantum dot system. More importantly, the SHG coefficient is not a monotonic function of the length L of CQDs as well as the applied field F. If we select suitable values of F and L, we will get a higher value of the SHG coefficient. In addition, the relaxation rate also affects the SHG coefficient obviously.

  8. The electrical characteristics of metal-oxide-semiconductor field effect transistors fabricated on cubic silicon carbide

    CERN Document Server

    Ohshima, T; Ishida, Y

    2003-01-01

    The n-channel metal-oxide-semiconductor field effect transistors (MOSFETs) were fabricated on cubic silicon carbide (3C-SiC) epitaxial layers grown on 3C-SiC substrates. The gate oxide of the MOSFETs was formed using pyrogenic oxidation at 1100 degC. The 3C-SiC MOSFETs showed enhancement type behaviors after annealing at 200degC for 30 min in argon atmosphere. The maximum value of the effective channel mobility of the 3C-SiC MOSFETs was 260cm sup 2 /V centre dot s. The leakage current of gate oxide was of a few tens of nA/cm sup 2 at an electric field range below 8.5 MV/cm, and breakdown began around 8.5MV/cm. (author)

  9. Multiplicity factor and diffraction geometry factor for single crystal X-ray diffraction analysis and measurement of phase content in cubic GaN/GaAs(001) epilayers

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    On the basis of integrated intensity of rocking curves, the multiplicity factor and the diffraction geometry factor for single crystal X-ray diffraction (XRD) analysis were proposed and a general formula for calculating the content of mixed phases was obtained. With a multifunction four-circle X-ray double-crystal diffractometer, pole figures of cubic (002), {111} and hexagonal {1010} and reciprocal space mapping were measured to investigate the distributive character of mixed phases and to obtain their multiplicity factors and diffraction geometry factors. The contents of cubic twins and hexagonal inclusions were calculated by the integrated intensities of rocking curves of cubic (002), cubic twin {111}, hexagonal {1010} and {1011}.

  10. BV analysis of tachyon fluctuation around multi-brane solutions in cubic string field theory

    Science.gov (United States)

    Hata, Hiroyuki

    2016-05-01

    We study whether the tachyon mode exists as a physical fluctuation on the 2-brane solution and on the tachyon vacuum solution in cubic open string field theory. Our analysis is based on the Batalin-Vilkovisky formalism. We first construct a set of six string states which corresponds to the set of fields and anti-fields containing the tachyon field. Whether the tachyon field can exist as a physical fluctuation is determined by the 6 × 6 matrix defining the anti-bracket in the present sector. If the matrix is degenerate/non-degenerate, the tachyon field is physical/unphysical. Calculations for the pure-gauge type solutions in the framework of the KBc algebra and using the K ɛ -regularization lead to the expected results. Namely, the matrix for the anti-bracket is degenerate/non-degenerate in the case of the 2-brane/tachyon-vacuum solution. Our analysis is not complete, in particular, in that we have not identified the four-fold degeneracy of tachyon fluctuation on the 2-brane solution, and moreover that the present six states do not satisfy the hermiticity condition.

  11. A comprehensive review of the lipid cubic phase or in meso method for crystallizing membrane and soluble proteins and complexes

    Energy Technology Data Exchange (ETDEWEB)

    Caffrey, Martin, E-mail: martin.caffrey@tcd.ie [Trinity College Dublin, Dublin (Ireland)

    2015-01-01

    A comprehensive and up-to-date review of the lipid cubic phase or in meso method for crystallizing membrane and soluble proteins and complexes is reported. Recent applications of the method for in situ serial crystallography at X-ray free-electron lasers and synchrotrons are described. The lipid cubic phase or in meso method is a robust approach for crystallizing membrane proteins for structure determination. The uptake of the method is such that it is experiencing what can only be described as explosive growth. This timely, comprehensive and up-to-date review introduces the reader to the practice of in meso crystallogenesis, to the associated challenges and to their solutions. A model of how crystallization comes about mechanistically is presented for a more rational approach to crystallization. The possible involvement of the lamellar and inverted hexagonal phases in crystallogenesis and the application of the method to water-soluble, monotopic and lipid-anchored proteins are addressed. How to set up trials manually and automatically with a robot is introduced with reference to open-access online videos that provide a practical guide to all aspects of the method. These range from protein reconstitution to crystal harvesting from the hosting mesophase, which is noted for its viscosity and stickiness. The sponge phase, as an alternative medium in which to perform crystallization, is described. The compatibility of the method with additive lipids, detergents, precipitant-screen components and materials carried along with the protein such as denaturants and reducing agents is considered. The powerful host and additive lipid-screening strategies are described along with how samples that have low protein concentration and cell-free expressed protein can be used. Assaying the protein reconstituted in the bilayer of the cubic phase for function is an important element of quality control and is detailed. Host lipid design for crystallization at low temperatures and for

  12. Crystal fields and conduction electrons in praseodymium

    DEFF Research Database (Denmark)

    Clausen, K.N.; Aagaard Sørensen, S.; McEwen, K.A.

    1995-01-01

    The interactions between the crystal-field excitations, the phonons and the conduction electrons in Pr have been studied further. The low-energy satellites to the crystal-field excitations, which are believed to be associated with propagating paramagnon modes in the conduction-electron gas, appear...

  13. A Cubic B-Spline Approach for Inter-Transformation Between Potential Field and Gradient Data

    Science.gov (United States)

    Wang, B.; Gao, S. S.

    2008-12-01

    Traditionally, algorithms involving Fast Fourier Transforms (FFT) are used to calculate gradients from field data and vise versa. Because the popular FFT differentiation algorithms are prone to noise, expensive field campaigns are increasingly utilized to obtain gradient data. In areas with both field and gradient data, transformation facilitates comparison. In areas with only one kind of data, transformation facilitates interpretation by transforming the measured data into another form of data. We advance unified formulae for interpolation, differentiation and integration using cubic B-splines, and propose new space-domain approaches for 2D and 3D transformations from potential field data to potential-field gradient data and vice versa. We also advance spline-based continuation techniques. In the spline-based algorithms, the spacing can be either regular or irregular. Analyses using synthetic and real gravity and magnetic data show that the new algorithms have higher accuracy, are more noise-tolerant and thus provide better insights into understanding the nature of the sources than the traditional FFT techniques.

  14. Crystal fields of porphyrins and phthalocyanines

    Science.gov (United States)

    Johnson, P. S.; Boukahil, I.; Himpsel, F. J.; Kennedy, C.; Jersett, N.; Cook, P. L.; Garcia-Lastra, J. M.

    2014-03-01

    Polarization-dependent X-ray absorption spectroscopy at the N 1s and metal 2p edges is combined with density functional and atomic multiplet calculations to determine the crystal field parameters 10Dq, Ds, and Dt of transition metal (Mn, Fe, Co, Ni) phthalocyanines and octaethylporphyrins. Octaethyl porphyrins are observed to lie flat on Si with native oxide, while phthalocyanines lie on edge. Strong polarization dependence is found at all edges, which facilitates a unique determination of the crystal field parameters. Crystal field values from PBE density functional calculations provide helpful starting values, which are refined by fitting atomic multiplet calculations to the data. Since the crystal field affects electron-hole separation in solar cells, the systematic set of crystal field parameters obtained here can be useful for optimizing dyes for solar cells.

  15. Phase portraits of cubic polynomial vector fields of Lotka-Volterra type having a rational first integral of degree 2

    Energy Technology Data Exchange (ETDEWEB)

    Cairo, Laurent [MAPMO/CNRS-Departement de Mathematiques, Universite d' Orleans, 45067 Orleans, Cedex 2 (France); Llibre, Jaume [Departament de Matematiques, Universitat Autonoma de Barcelona, 08193 Bellaterra, Barcelona (Spain)

    2007-06-15

    We classify all the global phase portraits of the cubic polynomial vector fields of Lotka-Volterra type having a rational first integral of degree 2. For such vector fields there are exactly 28 different global phase portraits in the Poincare disc up to a reversal of sense of all orbits.

  16. Acousto-optical phonon excitation in cubic piezoelectric slabs and crystal growth orientation effects

    DEFF Research Database (Denmark)

    Willatzen, Morten; Duggen, Lars

    2017-01-01

    mode density in GaAs can change by a factor of approximately 2–3 at qx a = 1 for different crystal-growth directions relative to the slab thickness direction. In particular, it is found that optical and acoustic phonon modes are always piezoelectrically coupled, independent of the crystal......-growth direction, and will be jointly excited by electrical stimulus. We demonstrate this for an electrically excited freestanding slab for two cases of high-symmetry crystal-growth directions and finally show the impact of the Drude model for permittivity on the phonon dispersion. In particular, it is verified...

  17. BDA: A novel method for identifying defects in body-centered cubic crystals.

    Science.gov (United States)

    Möller, Johannes J; Bitzek, Erik

    2016-01-01

    The accurate and fast identification of crystallographic defects plays a key role for the analysis of atomistic simulation output data. For face-centered cubic (fcc) metals, most existing structure analysis tools allow for the direct distinction of common defects, such as stacking faults or certain low-index surfaces. For body-centered cubic (bcc) metals, on the other hand, a robust way to identify such defects is currently not easily available. We therefore introduce a new method for analyzing atomistic configurations of bcc metals, the BCC Defect Analysis (BDA). It uses existing structure analysis algorithms and combines their results to uniquely distinguish between typical defects in bcc metals. In essence, the BDA method offers the following features:•Identification of typical defect structures in bcc metals.•Reduction of erroneously identified defects by iterative comparison to the defects in the atom's neighborhood.•Availability as ready-to-use Python script for the widespread visualization tool OVITO [http://ovito.org].

  18. Crystal field parameters and crystal field linewidths in the (REY)Pd/sub 3/ and (REY)Al/sub 2/ alloys

    Energy Technology Data Exchange (ETDEWEB)

    Walter, U.; Holland-Moritz, E.

    1981-12-01

    The LLW-parameters x and W of dilute rare earth impurities (RE = Pr, Nd, Tb, Dy, Ho, Er, Tm; c approx. equal to 0.05) in the cubic matrices YPd/sub 3/ and YAl/sub 2/ could be determined unequivocally in the crystal field scheme of Lea, Leask and Wolf by inelastic neutron scattering. The crystal field parameters derived from x and W are not consistent with the point charge model. The ratio of N(Esub(F))Jsub(ex) for the (REY)Al/sub 2/ extracted from the RE-linewidths correlates with the corresponding ratio extracted from their magnetic ordering temperatures.

  19. Optical anisotropy of cubic photonic crystals under conditions of multiple-mode light propagation

    Science.gov (United States)

    Ukleev, T. A.; Yurasova, D. I.; Shevchenko, N. N.; Sel'kin, A. V.

    2016-11-01

    Bragg reflection spectra of light are studied for opal-like photonic crystals made of polystyrene spheres. A resonant enhancement of reflectivity is observed in cross-polarization configuration of the analyzer and polarizer when varying the azimuthal orientation of a sample in respect to the incidence plane. The cross-polarization effect takes place at oblique incidence of light on the lateral (111) crystal plane with the plane of incidence being non-perpendicular to the inclined (11-1) crystal plane. The effect is shown to be due to the multiple Bragg diffraction of light when the resonant Bragg conditions are fulfilled at a certain angle of incidence and azimuth for the lateral and inclined crystal planes simultaneously.

  20. Compression Stress Effect on Dislocations Movement and Crack propagation in Cubic Crystal

    OpenAIRE

    Suprijadi; Ely, Aprilia; Meiqorry, Yusfi

    2011-01-01

    Fracture material is seriously problem in daily life, and it has connection with mechanical properties itself. The mechanical properties is belief depend on dislocation movement and crack propagation in the crystal. Information about this is very important to characterize the material. In FCC crystal structure the competition between crack propagation and dislocation wake is very interesting, in a ductile material like copper (Cu) dislocation can be seen in room temperature, but in a brittle ...

  1. Cubic modification crystal structure of cesium neodymium tetrametaphosphates,. beta. -CsNd(POsub(3))sub(4) (CsNdP/sub 4/O/sub 12/)

    Energy Technology Data Exchange (ETDEWEB)

    Palkina, K.K.; Maksimova, S.I.; Chibiskova, N.T. (AN SSSR, Moscow. Inst. Obshchej i Neorganicheskoj Khimii)

    1981-01-01

    A complete X-ray structural investigation into ..beta..-CsNd (PO/sub 3/)/sub 4/ crystallites is presented. ..beta..-CsNd (PO/sub 3/)/sub 4/ is crystallized in the cubic crystal system; space group is 143 d; the parameters of the elementary cell are a=15.233 (3)A; Z=12, V=3535 4A/sup 3/, dsub(roent)=3.34 g/cm/sup 3/. Interatomic distances and valent angles of crystals are presented. It is shown that ..beta..- CsNd(NO/sub 3/)/sub 4/ noncentrosymmetric crystals are isotropic, as they belong to cubic crystal structure and must obviously combine simultaneously luminescent, optic non-linear and piezoelectric properties.

  2. In-depth investigation of EPR spectra of Mn(2+) ions in ZnS single crystals with pure cubic structure.

    Science.gov (United States)

    Nistor, S V; Stefan, M

    2009-04-01

    The X (9.8 GHz)-band electron paramagnetic resonance (EPR) properties of substitutional Mn(2+) ions in high quality cubic ZnS single crystals grown from PbCl(2) flux have been thoroughly investigated. Accurate spin Hamiltonian (SH) parameters: g = 2.002 25 ± 0.000 06; a = (7.987 ± 0.008) × 10(-4) cm(-1) and A = -(63.88 ± 0.02) × 10(-4) cm(-1) were obtained by simulation and fitting to the experimentally allowed transitions recorded for the magnetic field aligned within ± 0.25° along the main crystal axes. The normally forbidden hyperfine [Formula: see text], Δm = ± 1 transitions were also observed. Their position was found to be in agreement, within the experimental accuracy of ΔH = ± 0.01 mT, with calculations using the same SH parameters. The angular variation of the ratios of the intensities of the central forbidden to the allowed transitions could be accounted for only by including an additional constant contribution. The observed line broadening of the [Formula: see text] and [Formula: see text] fine structure transitions and their line width variation in a (110) plane have been quantitatively described by considering a random distribution of lattice strains at the Mn(2+) impurity ions. The influence of the forbidden transitions and line broadening on the EPR spectra line shape of the Mn(2+) ions in cubic ZnS crystalline powders is also examined.

  3. Enhanced coercivity in Co-doped α-Fe2O3 cubic nanocrystal assemblies prepared via a magnetic field-assisted hydrothermal synthesis

    Directory of Open Access Journals (Sweden)

    Kinjal Gandha

    2017-05-01

    Full Text Available Ferromagnetic Co-doped α-Fe2O3 cubic shaped nanocrystal assemblies (NAs with a high coercivity of 5.5 kOe have been synthesized via a magnetic field (2 kOe assisted hydrothermal process. The X-ray diffraction pattern and Raman spectra of α-Fe2O3 and Co-doped α-Fe2O3 NAs confirms the formation of single-phase α-Fe2O3 with a rhombohedral crystal structure. Electron microscopy analysis depict that the Co-doped α-Fe2O3 NAs synthesized under the influence of the magnetic field are consist of aggregated nanocrystals (∼30 nm and of average assembly size 2 μm. In contrast to the NAs synthesized with no magnetic field, the average NAs size and coercivity of the Co-doped α-Fe2O3 NAs prepared with magnetic field is increased by 1 μm and 1.4 kOe, respectively. The enhanced coercivity could be related to the well-known spin–orbit coupling strength of Co2+ cations and the redistribution of the cations. The size increment indicates that the small ferromagnetic nanocrystals assemble into cubic NAs with increased size in the magnetic field that also lead to the enhanced coercivity.

  4. Theoretical Strength of Face-Centred-Cubic Single Crystal Copper Based on a Continuum Model

    Institute of Scientific and Technical Information of China (English)

    LIU Xiao-Ming; LIU Zhan-Li; YOU Xiao-Chuan; NIE Jun-Feng; ZHUANG Zhuo

    2009-01-01

    The constitutive relation of single crystal copper based on atomistic potential is implemented to capture the nonlinear inter-atomic interactions. Uniaxial loading tests of single crystal copper with inter-atomic potential finite-element model are carried out to determine the corresponding ideal strength using the modified Born stability criteria. Dependence of the ideal strength on the crystallographic orientation is studied, and tension-compression asymmetry in ideal strength is also investigated. The results suggest that asymmetry for yielding strength of nano-materials may result from anisotropic character of crystal instability. Moreover, the results also reveal that the critical resolved shear stress in the direction of slip is not an accurate criterion for the ideal strength since it could not capture the dependence on the loading conditions and hydrostatic stress components for the ideal strength.

  5. Acousto-optical phonon excitation in cubic piezoelectric slabs and crystal growth orientation effects

    DEFF Research Database (Denmark)

    Duggen, Lars; Willatzen, Morten

    2017-01-01

    In this paper we investigate theoretically the influence of piezoelectric coupling on phonon dispersion relations. Specifically we solve dispersion relations for a fully coupled zinc-blende freestanding quantum well for different orientations of the crystal unit cell. It is shown that the phonon ...

  6. Acoustic band gaps of the woodpile sonic crystal with the simple cubic lattice

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Liang-Yu; Chen, Lien-Wen, E-mail: chenlw@mail.ncku.edu.t [Department of Mechanical Engineering, National Cheng Kung University, Tainan 70101, Taiwan (China)

    2011-02-02

    This study theoretically and experimentally investigates the acoustic band gap of a three-dimensional woodpile sonic crystal. Such crystals are built by blocks or rods that are orthogonally stacked together. The adjacent layers are perpendicular to each other. The woodpile structure is embedded in air background. Their band structures and transmission spectra are calculated using the finite element method with a periodic boundary condition. The dependence of the band gap on the width of the stacked rods is discussed. The deaf bands in the band structure are observed by comparing with the calculated transmission spectra. The experimental transmission spectra for the {Gamma}-X and {Gamma}-X' directions are also presented. The calculated results are compared with the experimental results.

  7. Crystal Field Splittings of NdN

    DEFF Research Database (Denmark)

    Warming, E.; Bak, Poul Erik

    1975-01-01

    The crystal field levels of the Nd (J=9/2) ion in NdN have been determined by inelastic neutron scattering. The crystal field parameters obtained by a least-squares fit to the spectra at 80K are: B4=-0.042+or-0.002K and B6=-0.00042+or-0.00002K. This result contrasts with the point charge model used...

  8. Gravitational cubic interactions for a simple mixed-symmetry gauge field in AdS and flat backgrounds

    Energy Technology Data Exchange (ETDEWEB)

    Boulanger, Nicolas [Service de Mecanique et Gravitation, Universite de Mons-UMONS, 20 Place du Parc, 7000 Mons (Belgium); Skvortsov, E D [P. N. Lebedev Physical Institute, Leninsky Prospect 53, 119991 Moscow (Russian Federation); Zinoviev, Yu M, E-mail: nicolas.boulanger@umons.ac.be, E-mail: skvortsov@lpi.ru, E-mail: Yurii.Zinoviev@ihep.ru [Institute for High Energy Physics Protvino, Moscow Region 142280 (Russian Federation)

    2011-10-14

    Cubic interactions between the simplest mixed-symmetry gauge field and gravity are constructed in anti-de Sitter (AdS) and flat backgrounds. Non-Abelian cubic interactions are obtained in AdS following various perturbative methods including the Fradkin-Vasiliev construction, with and without Stueckelberg fields. The action that features the maximal number of Stueckelberg fields can be considered in the flat limit without loss of physical degrees of freedom. The resulting interactions in flat space are compared with a classification of vertices obtained via the antifield cohomological perturbative method. It is shown that the gauge algebra becomes Abelian in the flat limit, in contrast to what happens for totally symmetric gauge fields in AdS. (paper)

  9. Theory of electrolyte crystallization in magnetic field

    DEFF Research Database (Denmark)

    Madsen, Hans Erik Lundager

    2007-01-01

    Crystallization from aqueous solution of a sparingly soluble electrolyte is accelerated by magnetic field if the crystalizing phase is a diamagnetic salt of a weak acid, and crystallization is from neutral or acid solution in ordinary (not heavy) water. Since the effect of Lorentz force...... is negligible, if not absent, the key property is likely to be the spin of protons which, by virtue of their half-integral spin, are fermions. An effect on crystal growth kinetics has been demonstrated, and the apparent effect on nucleation concerns the growth rate of nuclei. We are thus dealing with surface...... phenomena. The basis of the theory is a crystal model of a sparingly soluble salt with NaCl structure, where the ions are divalent, and the anion is a base. It is assumed that almost all the anions in the surface layer are protonized, and that an approaching metal ion pushes the proton away...

  10. Non-cubic crystal symmetry of CaSiO 3 perovskite up to 18 GPa and 1600 K

    Science.gov (United States)

    Uchida, Takeyuki; Wang, Yanbin; Nishiyama, Norimasa; Funakoshi, Ken-ichi; Kaneko, Hiroshi; Nozawa, Akifumi; Von Dreele, Robert B.; Rivers, Mark L.; Sutton, Steve R.; Yamada, Akihiro; Kunimoto, Takehiro; Irifune, Tetsuo; Inoue, Toru; Li, Baosheng

    2009-05-01

    In situ synchrotron X-ray diffraction experiments have been conducted on CaSiO 3 perovskite (CaPv) in a double-stage multianvil apparatus up to 18 GPa and 1600 K using a newly developed step-scan diffraction technique, which utilizes an energy-dispersive setup with a solid-state detector and collimator assemblies to collect angle-dispersive diffraction data over a wide range of photon energies. Superlattice reflections were resolved throughout the pressure ( P) and temperature ( T) range of the experiments, confirming that the crystal symmetry of CaPv is neither cubic nor tetragonal. A combination of analyses of the complete two-dimensional intensity datasets (photon energy from 20 to 160 keV and 2 θ angle from 3.0° to 9.0°) and Rietveld refinements at selected wavelengths revealed that the most likely space group of CaPv in the experimental P- T range, and therefore in the Earth's transition zone, is either Pbnm or Cmcm. The difference between these two space groups was too small to resolve with our technique.

  11. Crystal fields in UO2 - revisited

    Energy Technology Data Exchange (ETDEWEB)

    Nakotte, Heinz [Los Alamos National Laboratory; Rajatram, R [NMSU/UNIV OF N.C.; Kern, S [COLORADO STATE UNIV; Mcqueeney, R J [AMES LAB; Lander, G H [EUROPEAN COMMISIONS, JRC; Robinson, R A [BRAGG INSTITUTE

    2009-01-01

    We performed inelastic neutron scattering (INS) in order to re-investigate the crystal-field ground state and the level splitting in UO{sub 2}. Previous INS studies on UO{sub 2} by Amorelli et al. [Physical Review B 15, 1989, 1856] uncovered four excitations at low temperatures in the 150-180 meV range. Considering the dipole-allowed transitions, only three of these transitions could be explained by the published crystal-field model. Our INS results on a different UO{sub 2} sample revealed that the unaccounted peak at about 180 meV is a spurious one, and thus not intrinsic to UO{sub 2}. In good agreement with Amoretti's results, we corroborated that the ground-state of UO{sub 2} is the {Lambda}{sub 5} triplet, and we computed that the fourth- and six-order crystal field parameters are V{sub 4} = -116 meV and V{sub 6} = 26 meV, respectively. We also studied the INS response of the non-magnetic U{sub 0.4}Th{sub 0.6}O{sub 2}. The splitting for this thorium-doped compound is similar to the one of UO{sub 2}, which orders antiferromagnetically at low temperatures. Therefore, we can conclude that magnetic interactions only weakly perturb the energy level splitting, which is dominated by strong crystal fields.

  12. High Field Magnetization of Tb Single Crystals

    DEFF Research Database (Denmark)

    Roeland, L. W.; Cock, G. J.; Lindgård, Per-Anker

    1975-01-01

    The magnetization of Tb single crystals was measured in magnetic fields to 34T along the hard direction at temperature of 1.8, 4.2, 65.5 and 77K, and along with easy direction at 4.2 and 77K. The data are compared with the results of a self-consistent spin wave calculation using a phenomenological...

  13. Analytic cubic and quartic force fields using density-functional theory

    Energy Technology Data Exchange (ETDEWEB)

    Ringholm, Magnus; Gao, Bin; Thorvaldsen, Andreas J.; Ruud, Kenneth [Centre for Theoretical and Computational Chemistry (CTCC), Department of Chemistry, University of Tromsø—The Arctic University of Norway, 9037 Tromsø (Norway); Jonsson, Dan [Centre for Theoretical and Computational Chemistry (CTCC), Department of Chemistry, University of Tromsø—The Arctic University of Norway, 9037 Tromsø (Norway); High Performance Computing Group, University of Tromsø—The Arctic University of Norway, 9037 Tromsø (Norway); Bast, Radovan [Theoretical Chemistry and Biology, School of Biotechnology, Royal Institute of Technology, AlbaNova University Center, S-10691 Stockholm, Sweden and PDC Center for High Performance Computing, Royal Institute of Technology, S-10044 Stockholm (Sweden); Ekström, Ulf; Helgaker, Trygve [Center for Theoretical and Computational Chemistry (CTCC), Department of Chemistry, University of Oslo, P.O. Box 1033, Blindern, 0315 Oslo (Norway)

    2014-01-21

    We present the first analytic implementation of cubic and quartic force constants at the level of Kohn–Sham density-functional theory. The implementation is based on an open-ended formalism for the evaluation of energy derivatives in an atomic-orbital basis. The implementation relies on the availability of open-ended codes for evaluation of one- and two-electron integrals differentiated with respect to nuclear displacements as well as automatic differentiation of the exchange–correlation kernels. We use generalized second-order vibrational perturbation theory to calculate the fundamental frequencies of methane, ethane, benzene, and aniline, comparing B3LYP, BLYP, and Hartree–Fock results. The Hartree–Fock anharmonic corrections agree well with the B3LYP corrections when calculated at the B3LYP geometry and from B3LYP normal coordinates, suggesting that the inclusion of electron correlation is not essential for the reliable calculation of cubic and quartic force constants.

  14. Mean-field models for disordered crystals

    CERN Document Server

    Cancès, Eric; Lewin, Mathieu

    2012-01-01

    In this article, we set up a functional setting for mean-field electronic structure models of Hartree-Fock or Kohn-Sham types for disordered crystals. The electrons are quantum particles and the nuclei are classical point-like articles whose positions and charges are random. We prove the existence of a minimizer of the energy per unit volume and the uniqueness of the ground state density of such disordered crystals, for the reduced Hartree-Fock model (rHF). We consider both (short-range) Yukawa and (long-range) Coulomb interactions. In the former case, we prove in addition that the rHF ground state density matrix satisfies a self-consistent equation, and that our model for disordered crystals is the thermodynamic limit of the supercell model.

  15. Crystal field in ErGa sub 3 - a neutron spectroscopy study

    CERN Document Server

    Murasik, A; Clementyev, E; Schefer, J

    2000-01-01

    The splitting of the J=15/2 multiplet of Er sup 3 sup + in a cubic crystal field has been determined by inelastic scattering from a polycrystalline sample of ErGa sub 3. On the basis of the observed intensities and their temperature variation we have been able to determine two crystal electric field (CEF) parameters required for cubic symmetry. Least-squares fits applied to the observed spectra taken at various temperatures gave crystal field parameters: B sub 4 =(7.15+-0.05)x10 sup - sup 5 and B sub 6 =(1.28+-0.05)x10 sup - sup 6 meV yielding the GAMMA sub 7 doublet as a ground level with the overall splitting of 10.92 meV. The results are used to calculate the temperature-dependant zero-field magnetisation, the Schottky anomaly of the specific heat associated with the CEF splitting of Er sup 3 sup + in ErGa sub 3 , and the high-field magnetisation.

  16. XPS analysis for cubic boron nitride crystal synthesized under high pressure and high temperature using Li{sub 3}N as catalysis

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Xiaofei [School of Materials Science and Engineering, Shandong Jianzhu University, Ji’nan 250101 (China); School of Materials Science and Engineering, Shandong University, Ji’nan 250061 (China); Xu, Bin, E-mail: xubin@sdjzu.edu.cn [School of Materials Science and Engineering, Shandong Jianzhu University, Ji’nan 250101 (China); Zhang, Wen [School of Materials Science and Engineering, Shandong Jianzhu University, Ji’nan 250101 (China); Cai, Zhichao [School of Materials Science and Engineering, Shandong University, Ji’nan 250061 (China); Wen, Zhenxing [School of Materials Science and Engineering, Shandong Jianzhu University, Ji’nan 250101 (China)

    2014-12-01

    Highlights: • The cBN was synthesized by Li{sub 3}N as catalyst under high pressure and high temperature (HPHT). • The film coated on the as-grown cBN crystals was studied by XPS. • The electronic structure variation in the film was investigated. • The growth mechanism of cubic boron nitride crystal was analyzed briefly. - Abstract: Cubic boron nitride (cBN) single crystals are synthesized with lithium nitride (Li3N) as catalyst under high pressure and high temperature. The variation of electronic structures from boron nitride of different layers in coating film on the cBN single crystal has been investigated by X-ray photoelectron spectroscopy. Combining the atomic concentration analysis, it was shown that from the film/cBN crystal interface to the inner, the sp{sup 2} fractions are decreasing, and the sp{sup 3} fractions are increasing in the film at the same time. Moreover, by transmission electron microscopy, a lot of cBN microparticles are found in the interface. For there is no Li{sub 3}N in the film, it is possible that Li{sub 3}N first reacts with hexagonal boron nitride to produce Li{sub 3}BN{sub 2} during cBN crystals synthesis under high pressure and high temperature (HPHT). Boron and nitrogen atoms, required for cBN crystals growth, could come from the direct conversion from hexagonal boron nitride with the catalysis of Li{sub 3}BN{sub 2} under high pressure and high temperature, but not directly from the decomposition of Li{sub 3}BN{sub 2}.

  17. Non-Born-Oppenheimer self-consistent field calculations with cubic scaling

    Energy Technology Data Exchange (ETDEWEB)

    Moncada, Felix, E-mail: areyesv@unal.edu.co [Departamento de Quimica, Universidad Nacional de Colombia, Av. Cra. 30 45-03, Bogota (Colombia); Posada, Edwin [Departamento de Quimica, Universidad Nacional de Colombia, Av. Cra. 30 45-03, Bogota (Colombia); Flores-Moreno, Roberto [Departamento de Quimica, Universidad de Guadalajara, Blvd. Marcelino Garcia Barragan 1421, Guadalajara Jal., C.P. 44430 (Mexico); Reyes, Andres [Departamento de Quimica, Universidad Nacional de Colombia, Av. Cra. 30 45-03, Bogota (Colombia)

    2012-05-25

    Highlights: Black-Right-Pointing-Pointer It is possible to perform cubic-scaling Non-Born-Oppenheimer calculations. Black-Right-Pointing-Pointer The errors introduced by the approximations used in this methodology are small. Black-Right-Pointing-Pointer This method makes possible calculations of molecules with more than a hundred atoms. - Abstract: An efficient nuclear molecular orbital methodology is presented. This approach combines an auxiliary density functional theory for electrons (ADFT) and a localized Hartree product (LHP) representation for the nuclear wave function. A series of test calculations conducted on small molecules exposed that energy and geometry errors introduced by the use of ADFT and LHP approximations are small and comparable to those obtained by the use of electronic ADFT. In addition, sample calculations performed on (HF){sub n} chains disclosed that the combined ADFT/LHP approach scales cubically with system size (n) as opposed to the quartic scaling of Hartree-Fock/LHP or DFT/LHP methods. Even for medium size molecules the improved scaling of the ADFT/LHP approach resulted in speedups of at least 5x with respect to Hartree-Fock/LHP calculations. The ADFT/LHP method opens up the possibility of studying nuclear quantum effects on large size systems that otherwise would be impractical.

  18. Eighth-order phase-field-crystal model for two-dimensional crystallization

    OpenAIRE

    Jaatinen, A.; Ala-Nissila, T.

    2010-01-01

    We present a derivation of the recently proposed eighth order phase field crystal model [Jaatinen et al., Phys. Rev. E 80, 031602 (2009)] for the crystallization of a solid from an undercooled melt. The model is used to study the planar growth of a two dimensional hexagonal crystal, and the results are compared against similar results from dynamical density functional theory of Marconi and Tarazona, as well as other phase field crystal models. We find that among the phase field crystal models...

  19. The growth of a cubic, single phase, Cd 0.6Mn 0.4Te single crystal by the vertical gradient freeze method

    Science.gov (United States)

    Azoulay, M.; Raizman, A.; Weingarten, R.; Shacham, H.; Feldstein, H.

    1993-03-01

    The growth of CdMnTe single crystals faces some difficulties due to the phase transition in the solid state at high temperatures, just after solidification. To overcome this problem, it has been suggested to grow the crystals from a Te-rich solution by the traveling heater method at a lower temperature than that of growth from the melt, or alternatively to grow the crystal from the melt at high axial thermal gradient near the interface. In this paper, we present for the first time the growth of cubic, single phase, CdxMn1-xTe single crystals by the vertical gradient freeze technique under a very low axial thermal gradient in the melt (3°C/cm) and high manganese content (x ≈ 40%). The solidification stage is characterized by a rapid cooling of the crystal through the phase transition temperature region, followed by annealing at about 800°C. The crystal exhibits a very high crystalline perfection, as measured by the double-crystal X-ray rocking curves with a full width at half maximum of 30 arc sec and low optical losses of about 1 dB/mm between 650 and 820 nm with λ-cutoff at 630 nm. Further magneto-optical properties are currently examined for a possible application in devices.

  20. Electric Field-Controlled Crystallizing CaCO3 Nanostructures from Solution.

    Science.gov (United States)

    Qi, Jian Quan; Guo, Rui; Wang, Yu; Liu, Xuan Wen; Chan, Helen Lai Wah

    2016-12-01

    The role of electric field is investigated in determining the structure, morphology, and crystallographic characteristics of CaCO3 nanostructures crystallized from solution. It is found that the lattice structure and crystalline morphology of CaCO3 can be tailed by the electric field applied to the solution during its crystallization. The calcite structure with cubic-like morphology can be obtained generally without electric field, and the vaterite structure with the morphology of nanorod is formed under the high electric field. The vaterite nanorods can be piled up to the petaliform layers. Both the nanorod and the petaliform layer can have mesocrystal structures which are piled up by much fine units of the rods with the size of several nanometers. Beautiful rose-like nanoflowers can be self-arranged by the petaliform layers. These structures can have potential application as carrier for medicine to involve into metabolism of living cell.

  1. Multiple twinning in cubic crystals: geometric/algebraic study and its application for the identification of the Σ3{sup n} grain boundaries

    Energy Technology Data Exchange (ETDEWEB)

    Cayron, Cyril, E-mail: cyril.cayron@cea.fr [CEA-Grenoble DRT/LITEN/DTH, 17 rue des Martyrs, 38054 Grenoble (France)

    2007-01-01

    Multiple twinning in cubic crystals is represented geometrically by three-dimensional fractals and algebraically by groupoids. The groupoid composition table can be used to identify the Σ3{sup n} grain boundaries in EBSD maps. Multiple twinning in cubic crystals is represented geometrically by a three-dimensional fractal and algebraically by a groupoid. In this groupoid, the variant crystals are the objects, the misorientations between the variants are the operations, and the Σ3{sup n} operators are the different types of operations (expressed by sets of equivalent operations). A general formula gives the number of variants and the number of Σ3{sup n} operators for any twinning order. Different substructures of this groupoid (free group, semigroup) can be equivalently introduced to encode the operations with strings. For any coding substructure, the operators are expressed by sets of equivalent strings. The composition of two operators is determined without any matrix calculation by string concatenations. It is multivalued due to the groupoid structure. The composition table of the operators is used to identify the Σ3{sup n} grain boundaries and to reconstruct the twin related domains in the electron back-scattered diffraction maps.

  2. Characterization and evaluation of Y{sub 2}O{sub 3}-stabilized cubic ZrO{sub 2} for single crystal fibers. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Heuer, A.H.

    1993-06-20

    The goal of this research was to develop the understanding of the structure/property relations in Y{sub 2}O{sub 3}-stabilized cubic ZrO{sub 2} (Y-CSZ) single crystals with emphasis on the potential use of these materials as a fibrous reinforcement for high temperature structural applications. In particular, the issues addressed include: (i) determination of the structure of as-grown Y-CSZ and its relation to the deformation behavior and (ii) initial fiber growth and evaluation. Selected papers are indexed separately for inclusion in the Energy Science and Technology Database.

  3. Temperature fields in a growing solar silicon crystal

    Directory of Open Access Journals (Sweden)

    Kondrik A. I.

    2012-06-01

    Full Text Available The optimal thermal terms for growing by Czochralski method Si single-crystals, suitable for making photoelectric energy converters, has been defined by the computer simulation method. Dependences of temperature fields character and crystallization front form on the diameter of the crystal, stage and speed of growing, and also on correlation between diameter and height of the crystal has been studied.

  4. Atomic density functional and diagram of structures in the phase field crystal model

    Science.gov (United States)

    Ankudinov, V. E.; Galenko, P. K.; Kropotin, N. V.; Krivilyov, M. D.

    2016-02-01

    The phase field crystal model provides a continual description of the atomic density over the diffusion time of reactions. We consider a homogeneous structure (liquid) and a perfect periodic crystal, which are constructed from the one-mode approximation of the phase field crystal model. A diagram of 2D structures is constructed from the analytic solutions of the model using atomic density functionals. The diagram predicts equilibrium atomic configurations for transitions from the metastable state and includes the domains of existence of homogeneous, triangular, and striped structures corresponding to a liquid, a body-centered cubic crystal, and a longitudinal cross section of cylindrical tubes. The method developed here is employed for constructing the diagram for the homogeneous liquid phase and the body-centered iron lattice. The expression for the free energy is derived analytically from density functional theory. The specific features of approximating the phase field crystal model are compared with the approximations and conclusions of the weak crystallization and 2D melting theories.

  5. Formalism of gauge-invariant curvatures and constructing the cubic vertices for massive spin-(3)/(2) field in AdS{sub 4} space

    Energy Technology Data Exchange (ETDEWEB)

    Buchbinder, I.L. [Tomsk State Pedagogical University, Department of Theoretical Physics, Tomsk (Russian Federation); National Research Tomsk State University, Tomsk (Russian Federation); Snegirev, T.V. [Tomsk State Pedagogical University, Department of Theoretical Physics, Tomsk (Russian Federation); Zinoviev, Yu.M. [Institute for High Energy Physics, Protvino, Moscow Region (Russian Federation)

    2014-11-15

    We study the interaction of a massive spin-3/2 field with electromagnetic and gravitational fields in the four dimensional AdS space and construct the corresponding cubic vertices. The construction is based on a generalization of Fradkin-Vasiliev formalism, developed for massless higher spin fields, to massive fermionic higher spin fields. The main ingredients of this formalism are the gauge-invariant curvatures. We build such curvatures for the massive theory under consideration and show how the cubic vertices are written in their terms. (orig.)

  6. Oxidation and crystal field effects in uranium

    Energy Technology Data Exchange (ETDEWEB)

    Tobin, J. G. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Booth, C. H. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Shuh, D. K. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); van der Laan, G. [Diamond Light Source, Didcot (United Kingdom); Sokaras, D. [Stanford Synchrotron Radiation Lightsource, Stanford, CA (United States); Weng, T. -C. [Stanford Synchrotron Radiation Lightsource, Stanford, CA (United States); Yu, S. W. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Bagus, P. S. [Univ. of North Texas, Denton, TX (United States); Tyliszczak, T. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Nordlund, D. [Stanford Synchrotron Radiation Lightsource, Stanford, CA (United States)

    2015-07-06

    An extensive investigation of oxidation in uranium has been pursued. This includes the utilization of soft x-ray absorption spectroscopy, hard x-ray absorption near-edge structure, resonant (hard) x-ray emission spectroscopy, cluster calculations, and a branching ratio analysis founded on atomic theory. The samples utilized were uranium dioxide (UO2), uranium trioxide (UO3), and uranium tetrafluoride (UF4). As a result, a discussion of the role of non-spherical perturbations, i.e., crystal or ligand field effects, will be presented.

  7. Variable-temperature single-crystal X-ray diffraction study of tetragonal and cubic perovskite-type barium titanate phases.

    Science.gov (United States)

    Nakatani, Tomotaka; Yoshiasa, Akira; Nakatsuka, Akihiko; Hiratoko, Tatsuya; Mashimo, Tsutomu; Okube, Maki; Sasaki, Satoshi

    2016-02-01

    A variable-temperature single-crystal X-ray diffraction study of a synthetic BaTiO3 perovskite has been performed over the temperature range 298-778 K. A transition from a tetragonal (P4mm) to a cubic (Pm3m) phase has been revealed near 413 K. In the non-centrosymmetric P4mm symmetry group, both Ti and O atoms are displaced along the c-axis in opposite directions with regard to the Ba position fixed at the origin, so that Ti(4+) and Ba(2+) cations occupy off-center positions in the TiO6 and BaO12 polyhedra, respectively. Smooth temperature-dependent changes of the atomic coordinates become discontinuous with the phase transition. Our observations imply that the cations remain off-center even in the high-temperature cubic phase. The temperature dependence of the mean-square displacements of Ti in the cubic phase includes a significant static component which means that Ti atoms are statistically distributed in the off-center positions.

  8. High-temperature single-crystal X-ray diffraction study of tetragonal and cubic perovskite-type PbTiO3 phases.

    Science.gov (United States)

    Yoshiasa, Akira; Nakatani, Tomotaka; Nakatsuka, Akihiko; Okube, Maki; Sugiyama, Kazumasa; Mashimo, Tsutomu

    2016-06-01

    A high-temperature single-crystal X-ray diffraction study of a synthetic PbTiO3 perovskite was carried out over the wide temperature range 298-928 K. A transition from a tetragonal (P4mm) to a cubic (Pm \\bar 3 m) phase has been revealed near 753 K. In the non-centrosymmetric P4mm symmetry group, the difference in relative displacement between Pb and O along the c-axis is much larger than that between Ti and O. The Pb and Ti cations contribute sufficiently to polarization being shifted in the opposite direction compared with the shift of O atoms. Deviation from the linear changes in Debye-Waller factors and bonding distances in the tetragonal phases can be interpreted as a precursor phenomenon before the phase transition. Disturbance of the temperature factor Ueq for O is observed in the vicinity of the transition point, while Ueq values for Pb and Ti are continuously changing with increasing temperature. The O site includes the clear configurational disorder in the cubic phase. The polar local positional distortions remain in the cubic phase and are regarded as the cause of the paraelectricity. Estimated values of the Debye temperature ΘD for Pb and Ti are 154 and 467 K in the tetragonal phase and decrease 22% in the high-temperature phase. Effective potentials for Pb and Ti change significantly and become soft after the phase transition.

  9. Icosahedral quasicrystals of intermetallic compounds are icosahedral twins of cubic crystals of three kinds, consisting of large (about 5000 atoms) icosahedral complexes in either a cubic body-centered or a cubic face-centered arrangement or smaller (about 1350 atoms) icosahedral complexes in the beta-tungsten arrangement.

    Science.gov (United States)

    Pauling, L

    1989-11-01

    The twofold-axis electron-diffraction photographs of icosahedral quasicrystals are of three kinds, reflecting three different structures of the cubic crystals that by icosahedral twinning form the quasicrystals. The first kind, represented by Al(13)Cu(4)Fe(3), contains two very large icosahedral complexes, each of about 4680 atoms, in the body-centered arrangement, with six smaller icosahedral complexes (104 atoms each) in the principal interstices. The second kind, represented by Al(5)Mn, contains four of the very large complexes in the face-centered arrangement (cubic close packing), with four of the smaller clusters in the interstices. The third kind, represented by Al(6)CuLi(3), contains eight icosahedral complexes, each of about 1350 atoms, in the beta-W arrangement. The supporting evidence for these cubic structures is discussed as well as other evidence showing that the simple quasicrystal theory, which states that quasicrystals do not involve any translational identity operations, has to be modified.

  10. Magnetic Field in Superlattices Semiconductors of Crystals

    Directory of Open Access Journals (Sweden)

    Luciano Nascimento

    2015-05-01

    Full Text Available In this work we present a study on the super-semiconductor networks, using the Kronig-Penney model for the effective mass approximation, and then the calculations for the application of the magnetic field perpendicular and parallel to the layers of super lattices crystals. The magnetic field applied parallel to the layers, was used to adjust the resonance of a higher energy subband of a well by thermal excitation with a lower energy subband of the adjacent well, increasing energy levels in its tunneling rate. We use the formalism of Schrödinger equation of quantum mechanics. Introducing the calculations in a systematic way in superlattices for each semiconductor quantum well to assess their energy spectrum systematically studied.

  11. High-strength, creep-resistant Y{sub 2}O{sub 3}-stabilized cubic ZrO{sub 2} single crystal fibers

    Energy Technology Data Exchange (ETDEWEB)

    McClellan, K.J.; Sayir, H.; Heuer, A.H. [Case Western Reserve Univ., Cleveland, OH (United States)] [and others

    1993-06-20

    Y{sub 2}O{sub 3}-stabilized cubic ZrO{sub 2} (Y-CSZ) single crystal fibers have much higher thermal expansion coefficients than other possible oxide fibers and thus can serve as viable reinforcements for metallic- and intermetallic-matrix composites; furthermore, they offer good isotropic creep resistance. Data is presented for [001] ZrO{sub 2} single crystal fibers (9.5-21 m/o Y{sub 2}O{sub 3}) grown by the laser heated floating zone process; high temperature strengths were measured as a function of composition and the variation in tensile strength with temperature was measured for 21 m/o Y-CSZ fibers. Strengths of {approximately}2.0 GPa at -196{degrees}C, {approximately}1.5 GPa at room temperature and {approximately}500 MPa at 1400{degrees}C were achieved. All fibers failed in a brittle manner from surface or near-surface flaws.

  12. Effect of magnetic field on the wave dispersion relation in three-dimensional dusty plasma crystals

    Energy Technology Data Exchange (ETDEWEB)

    Yang Xuefeng [School of Mathematical Sciences, Dalian University of Technology, Dalian 116024 (China); Wang Zhengxiong [School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024 (China)

    2012-07-15

    Three-dimensional plasma crystals under microgravity condition are investigated by taking into account an external magnetic field. The wave dispersion relations of dust lattice modes in the body centered cubic (bcc) and the face centered cubic (fcc) plasma crystals are obtained explicitly when the magnetic field is perpendicular to the wave motion. The wave dispersion relations of dust lattice modes in the bcc and fcc plasma crystals are calculated numerically when the magnetic field is in an arbitrary direction. The numerical results show that one longitudinal mode and two transverse modes are coupled due to the Lorentz force in the magnetic field. Moreover, three wave modes, i.e., the high frequency phonon mode, the low frequency phonon mode, and the optical mode, are obtained. The optical mode and at least one phonon mode are hybrid modes. When the magnetic field is neither parallel nor perpendicular to the primitive wave motion, all the three wave modes are hybrid modes and do not have any intersection points. It is also found that with increasing the magnetic field strength, the frequency of the optical mode increases and has a cutoff at the cyclotron frequency of the dust particles in the limit of long wavelength, and the mode mixings for both the optical mode and the high frequency phonon mode increase. The acoustic velocity of the low frequency phonon mode is zero. In addition, the acoustic velocity of the high frequency phonon mode depends on the angle of the magnetic field and the wave motion but does not depend on the magnetic field strength.

  13. Coherent isotropic averaging in zero-field nuclear magnetic resonance. II. Cubic sequences and time-reversal of spin couplings

    Energy Technology Data Exchange (ETDEWEB)

    Llor, A.; Olejniczak, Z.; Pines, A. [Materials Sciences Division, Lawrence Berkeley Laboratory, and Department of Chemistry, University of California, Berkeley, California 94720 (United States)

    1995-09-08

    We present a special case of the theory of coherent isotropic averaging in zero-field NMR, given in part I of this work. In a zero external field, combinations of the magnetic-field pulses restricted to {pi}/2 rotations along the three coordinate axes can selectively average internal spin Hamiltonians while preserving the intrinsic invariance of the spectrum with respect to the sample orientation. Compared with the general case, the limits of the allowed scaling factors of first- and second-rank interactions are slightly reduced. For instance, time reversal is possible for second-rank tensors with a {minus}1/5 scaling factor, instead of {minus}1/4 in general. Finite pulse compensations are analyzed and experimental illustrations are given for two optimum time-reversal sequences. The cubic sequences, though less efficient than the icosahedral sequences, are technically more feasible and may be used in zero-field experiments such as decoupling (by rank or nuclear species), time reversal or multipolar experiments (the zero-field equivalent of multiple-quantum NMR). {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

  14. Incorporation of the dopamine D2L receptor and bacteriorhodopsin within bicontinuous cubic lipid phases. 2. Relevance to in meso crystallization of integral membrane proteins in novel lipid systems

    Energy Technology Data Exchange (ETDEWEB)

    Conn, Charlotte E.; Darmanin, Connie; Sagnella, Sharon M.; Mulet, Xavier; Greaves, Tamar L.; Varghese, Joseph N.; Drummond, Calum J.

    2014-09-24

    The dopamine D2 long (D2L) receptor and bacteriorhodopsin (bR), which are integral membraneproteins, have been incorporated within bicontinuous cubic mesophases formed by the lipids anandamide and H-farnesoyl monoethanolamide, which have been specifically investigated by us for use as in mesocrystallization media. We show that the incorporated membraneprotein affects the structure of the cubic phases with the particular effect observed dependent on the geometry of the underlying cubic phase. The results are complementary to those obtained in Part 1 of this series, where we demonstrated that the structural effects observed depend on the structure of the membraneprotein. Importantly protein concentrations commonly used for crystallization can destroy the cubic phase matrix, particularly where there is a large discrepancy between the hydrophilic and the hydrophobic spans of the membraneprotein, and the hydrophilic and hydrophobic domain sizes of the cubic phase.

  15. Ferromagnetism and crystalline electric field effects in cubic UX2Zn20 (X=Co, Rh, Ir)

    Science.gov (United States)

    Bauer, E. D.; Thompson, J. D.; Sarrao, J. L.; Hundley, M. F.

    2007-03-01

    The physical properties of a new family of cubic UX2Zn20 (X=Co, Rh, Ir) heavy-fermion compounds are presented. Both UCo2Zn20 and URh2Zn20 show peaks in specific heat and magnetic susceptibility at ˜5-10 K suggesting the presence of crystalline electric field (CEF) effects in these materials, i.e., a localized 5f2 configuration of uranium. UIr2Zn20 exhibits a first-order ferromagnetic transition at Tc=2.1 K with a saturation moment μsat=0.4 μB at 2 K indicating itinerant ferromagnetism. All compounds in this series are heavy-fermion materials with enhanced electronic specific heat coefficients γ˜100-450 mJ/mol K2.

  16. Field assisted sintering of dense Al-substituted cubic phase Li7La3Zr2O12 solid electrolytes

    Science.gov (United States)

    Zhang, Yanhua; Chen, Fei; Tu, Rong; Shen, Qiang; Zhang, Lianmeng

    2014-12-01

    High performance lithium ion conducting Li7La3Zr2O12 solid electrolytes are prepared for the first time by field assisted sintering technology (FAST). The effect of sintering temperature on the phase compositions, microstructure and Li ionic conductivity is systematically investigated. The results show that pure cubic phase LLZO can be obtained at a range of temperatures from 1100 to 1180 °C for no more than 10 min. For the sample sintered at 1150 °C, a maximum relative density of 99.8% with a total ionic conductivity as high as 5.7 × 10-4 S cm-1 are obtained at room temperature. This value is the highest among the present research. Compared with the traditional preparation methods, the current FAST is very promising to obtain high performance LLZO for its advantages of very short sintering time, a single preparation step of reaction-densification processing, and relatively lower sintering temperature.

  17. The body-centered cubic structure of methyllithium tetramer crystal: staggered methyl conformation by electrostatic stabilization via intratetramer multipolarization.

    Science.gov (United States)

    Ohta, Yusuke; Demura, Akimitsu; Okamoto, Takuya; Hitomi, Haruko; Nagaoka, Masataka

    2006-06-29

    The methyllithium tetramer (CH3Li)4 structure in the bcc crystal has been theoretically optimized with the use of density functional theory calculations under the periodic boundary condition. The X-ray structure shows that the methyl-group conformation in tetramer in crystal takes the staggered form rather than the eclipsed form that is taken in the isolated tetramer, i.e., the crystal packing effect, and this has been reproduced for the first time. It is concluded that the staggered form is advantageous in crystal, as a whole, due to the larger electrostatic stabilization via the induced intratetramer multipolarization, although it should cause, simultaneously, smaller destabilization in intratetramer electronic energy.

  18. Peculiarities of Crystal Structure of the Cubic System Compounds with T 4 and T 5 Space Groups

    Science.gov (United States)

    Zolotarev, M. L.; Poplavnoi, A. S.

    2016-09-01

    We study symmetry peculiarities of crystalline compounds of a cubic system with the space groups T 4 and T 5 caused by the absence of point Wyckoff-sets in the unit cells of these groups. Due to the high multiplicity of the available Wyckoff positions, such compounds possess unit cells of complex composition. In these compounds, pseudosymmetry is realized with high probability when some group of atoms is located in positions close to the positions of higher-symmetry groups. We provide examples of crystalline compounds showing predicted specific structural features.

  19. Eighth-order phase-field-crystal model for two-dimensional crystallization

    OpenAIRE

    Jaatinen, A.; Ala-Nissilä, Tapio

    2010-01-01

    We present a derivation of the recently proposed eighth-order phase-field crystal model [A. Jaatinen et al., Phys. Rev. E 80, 031602 (2009)] for the crystallization of a solid from an undercooled melt. The model is used to study the planar growth of a two-dimensional hexagonal crystal, and the results are compared against similar results from dynamical density functional theory of Marconi and Tarazona, as well as other phase-field crystal models. We find that among the phase-field crystal mod...

  20. Numerical analysis of natural convection in thermoelectrically conducting fluids in a cubic cavity under a constant magnetic field. 2nd Report. Effect of direction of magnetic field on thermal and velocity field on thermal and velocity fields; Jibaka ni okeru denji netsuryutai no rippotai cavity nai shizen tairyu kaiseki. 2. Inka jiba hoko no netsuryudoba eno eikyo

    Energy Technology Data Exchange (ETDEWEB)

    Nakai, T.; Tanahashi, T. [Keio University, Tokyo (Japan). Faculty of Science and Technology

    1996-01-25

    In a previous paper, we investigated the natural convection in thermoelectrically conducting fluids in a cubic cavity under a magnetic field applied in the gravitational direction, and complicated fluid phenomena were clarified. Particularly in the case of mercury (Pr=0.025, Gr=3.75{times}10{sup 7}), the numerical results agreed well with the observed experimental results obtained using a thermosensitive liquid crystal sheet. In the present paper, we aim to explain the fundamental behavior of thermoelectrically conducting fluids, and numerically determine the natural convection by considering a different direction for the applied magnetic field. The direction of the applied magnetic field is chosen as either the +x, -y or +z direction (see Fig. 1). The convective inhibitory effect of the Lorentz force increases in the order of the +x, -y and +z-directions. 11 refs., 7 figs., 2 tabs.

  1. A singular one-parameter family of solutions in cubic superstring field theory

    Science.gov (United States)

    Arroyo, E. Aldo

    2016-05-01

    Performing a gauge transformation of a simple identity-like solution of superstring field theory, we construct a one-parameter family of solutions, and by evaluating the energy associated to this family, we show that for most of the values of the parameter the solution represents the tachyon vacuum, except for two isolated singular points where the solution becomes the perturbative vacuum and the half brane solution.

  2. Diffusion-controlled anisotropic growth of stable and metastable crystal polymorphs in the phase-field crystal model.

    Science.gov (United States)

    Tegze, G; Gránásy, L; Tóth, G I; Podmaniczky, F; Jaatinen, A; Ala-Nissila, T; Pusztai, T

    2009-07-17

    We use a simple density functional approach on a diffusional time scale, to address freezing to the body-centered cubic (bcc), hexagonal close-packed (hcp), and face-centered cubic (fcc) structures. We observe faceted equilibrium shapes and diffusion-controlled layerwise crystal growth consistent with two-dimensional nucleation. The predicted growth anisotropies are discussed in relation with results from experiment and atomistic simulations. We also demonstrate that varying the lattice constant of a simple cubic substrate, one can tune the epitaxially growing body-centered tetragonal structure between bcc and fcc, and observe a Mullins-Sekerka-Asaro-Tiller-Grinfeld-type instability.

  3. Influence of a strong magnetic field on paramagnetic fluid's flow in cubical enclosure

    Science.gov (United States)

    Kraszewska, A.; Pyrda, L.; Donizak, J.

    2016-10-01

    The fluid behaviour in thermo-magnetic convection of paramagnetic fluid in a strong magnetic field was studied. The fluid was 50% volume aqueous solution of glycerol with an addition of gadolinium nitrate hexahydrate (Gd(NO3)3-6H2O). Experimental enclosure - a vessel with aspect ratio (AR=height/width) equal to 1.0 - was heated from the bottom, and cooled from the top. Temperature difference between top and bottom walls was kept constant at ΔT = 5 and 11 [°C]. The magnetic induction was increased stepwise from 1 to 10 [T] and thermocouples placed inside the enclosures measured temperature changes of the fluid. On the basis of temperature measurements, analysis of the fluid flow was performed.

  4. Phonon softening and superconductivity triggered by spin-orbit coupling in simple-cubic α-polonium crystals

    Science.gov (United States)

    Kang, Chang-Jong; Kim, Kyoo; Min, B. I.

    2012-08-01

    We have investigated the mechanism of stabilizing the simple-cubic (sc) structure in polonium (α-Po), based on the phonon dispersion calculations using the first-principles all-electron band method. We have demonstrated that the stable sc structure results from the suppression of the Peierls instability due to the strong spin-orbit coupling (SOC) in α-Po. We have also discussed the structural chirality realized in β-Po, as a consequence of the phonon instability. Further, we have explored the possible superconductivity in α-Po, and predicted that it becomes a superconductor with Tc˜4 K. The transverse soft phonon mode at q≈(2)/(3)R, which is greatly influenced by the SOC, plays an important role both in the structural stability and the superconductivity in α-Po.

  5. Anisotropic surface melting in lyotropic cubic crystals. Part 1: Pn3m/L1 interface, poor faceting.

    Science.gov (United States)

    Grenier, J; Plötzing, T; Rohe, D; Pieranski, P

    2006-02-01

    From experiments with ice or metal crystals, in the vicinity of their crystal/liquid/vapor triple points, it is known that melting of crystals starts on their surfaces and is anisotropic. It is shown here by direct observations under an optical microscope that this anisotropic surface melting phenomenon occurs also in lyotropic systems. In the case of C12EO2/water mixture, it takes place in the vicinity of the peritectic Pn3m/L3/L1 triple point. Above the peritectic triple point, where the Pn3m and L1 phases coexist in the bulk, the surface of a Pn3m-in-L1 crystal is composed of (111)-type facets surrounded by rough surfaces. The angular junction suggests that rough surfaces are wet by a L3-like layer while facets stay "dry". This is analogous to the pre-melting at rough surfaces in solid crystals. Upon cooling below the peritectic triple point, where L3 and L1 phases coexist in the bulk, a thick layer of the L3 phase grows from the pre-melted, rough Pn3m/L1 interface. Simultaneously, facets stay dry and their radius decreases. In this tri-phasic configuration, stable in a narrow temperature range, the L3/L1 and L3/Pn3m interfaces have shapes of constant mean curvature surfaces having common borders: edges of facets.

  6. Magnetism and crystal field in TmCu sub 2

    Energy Technology Data Exchange (ETDEWEB)

    Sima, V.; Smetana, Z.; Divis, M.; Svoboda, P.; Zajac, S. (Karlova Univ., Prague (CS)); Bischof, J.; (Vyzkummy Ustav Silmoproude Elektrotechniky, Bechovice (CS)); Lebech, B. (Risoe National Lab., Roskilde (DK)); Kayzel, F. (Amsterdam Univ. (NL). Natuurkundig Lab.)

    1988-12-01

    The crystal field energies and Gruneisen parameters of the individual crystal field levels of Tm{sup 3+} in TmCu{sub 2} were determined from specific heat and thermal expansion data above T{sub N}. The magnetic phase transitions are discussed with respect to magnetic entropy and molar volume.

  7. Synthesis, crystal structure, and bonding analysis of the hypoelectronic cubic phase Ca5Pd6Ge6.

    Science.gov (United States)

    Doverbratt, Isa; Ponou, Siméon; Wang, Fei; Lidin, Sven

    2015-09-21

    The title compound, Ca5Pd6Ge6, was obtained during a systematic investigation of the Ca-Pd-Ge ternary phase diagram. The crystal structure was determined and refined from single-crystal X-ray diffraction data. It crystallizes in a new structure variant of the Y4PdGa12-type structure (Im3̅m, a = 8.7764(4) Å) that features an arrangement of vertex-sharing body-centered cubes of calcium, Ca@Ca8, with a hierarchical bcc network, interpenetrating a second (Pd6Ge6) network consisting of Ge2 dumbbells surrounded by Pd in a strongly flattened octahedron with Pd(μ(2)-η(2),η(4)-Ge2)-like motifs. These octahedra are condensed through the Pd to form a 3D open fcc network. Theoretical band structure calculations suggested that the compound is hypoelectronic with predominantly multicenter-type interatomic interactions involving all three elements and essentially a Hume-Rothery-like regime of electronic stabilization. The similar electronegativity between germanium and palladium atoms has a decisive impact on the bonding picture of the system.

  8. Effects of magnetic fields on dissolution of arthritis causing crystals

    Science.gov (United States)

    Takeuchi, Y.; Iwasaka, M.

    2015-05-01

    The number of gout patients has rapidly increased because of excess alcohol and salt intake. The agent responsible for gout is the monosodium urate (MSU) crystal. MSU crystals are found in blood and consist of uric acid and sodium. As a substitute for drug dosing or excessive water intake, physical stimulation by magnetic fields represents a new medical treatment for gout. In this study, we investigated the effects of a magnetic field on the dissolution of a MSU crystal suspension. The white MSU crystal suspension was dissolved in an alkaline solution. We measured the light transmission of the MSU crystal suspension by a transmitted light measuring system. The magnetic field was generated by a horizontal electromagnet (maximum field strength was 500 mT). The MSU crystal suspension that dissolved during the application of a magnetic field of 500 mT clearly had a higher dissolution rate when compared with the control sample. We postulate that the alkali solution promoted penetration upon diamagnetic rotation and this magnetic field orienting is because of the pronounced diamagnetic susceptibility anisotropy of the MSU crystal. The results indicate that magnetic fields represent an effective gout treatment approach.

  9. Enhancement of crystal homogeneity of protein crystals under application of an external alternating current electric field

    Energy Technology Data Exchange (ETDEWEB)

    Koizumi, H.; Uda, S.; Fujiwara, K.; Nozawa, J. [Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, 980-8577 (Japan); Tachibana, M. [Graduate School of Nanobioscience, Yokohama City University, 22-2 Seto, Kanazawa-ku, Yokohama, 236-0027 (Japan); Kojima, K. [Department of Education, Yokohama Soei University, 1 Miho-tyou, Midori-ku, Yokohama, 226-0015 (Japan)

    2014-10-06

    X-ray diffraction rocking-curve measurements were performed on tetragonal hen egg white (HEW) lysozyme crystals grown with and without the application of an external alternating current (AC) electric field. The crystal quality was assessed by the full width at half maximum (FWHM) value for each rocking curve. For two-dimensional maps of the FWHMs measured on the 440 and the 12 12 0 reflection, the crystal homogeneity was improved under application of an external electric field at 1 MHz, compared with that without. In particular, the significant improvement of the crystal homogeneity was observed for the 12 12 0 reflection.

  10. Bicritical universality of the anisotropic Heisenberg model in a crystal field.

    Science.gov (United States)

    Freire, R T S; Plascak, J A

    2015-03-01

    The bicritical properties of the three-dimensional classical anisotropic Heisenberg model in a crystal field are investigated through extensive Monte Carlo simulations on a simple cubic lattice, using Metropolis and Wolff algorithms. Field-mixing and multidimensional histogram techniques were employed in order to compute the probability distribution function of the extensive conjugate variables of interest and, using finite-size scaling analysis, the first-order transition line of the model was precisely located. The fourth-order cumulant of the order parameter was then calculated along this line and the bicritical point located with good precision from the cumulant crossings. The bicritical properties of this point were further investigated through the measurement of the universal probability distribution function of the order parameter. The results lead us to conclude that the studied bicritical point belongs in fact to the three-dimensional Heisenberg universality class.

  11. Effect of magnetic field on the crystallization of zinc sulfate

    Directory of Open Access Journals (Sweden)

    Freitas A. M. B.

    2000-01-01

    Full Text Available The effect of magnetic field on the crystallization of diamagnetic zinc sulfate was investigated in a series of controlled batch cooling experiments. Zinc sulfate solutions were exposed to magnetic fields of different intensities, up to a maximum of 0.7T. A clear influence of magnetic field on the following zinc sulfate crystallization parameters was found: an increase in saturation temperature, a decrease in metastable zone width, and an increase in growth rate and average crystal size. These effects were observed for the diamagnetic zinc sulfate, but not in similar, previously reported experiments for paramagnetic copper sulfate.

  12. Crystal-Field Engineering of Solid-State Laser Materials

    Science.gov (United States)

    Henderson, Brian; Bartram, Ralph H.

    2005-08-01

    This book examines the underlying science and design of laser materials. It emphasizes the principles of crystal-field engineering and discusses the basic physical concepts that determine laser gain and nonlinear frequency conversion in optical crystals. Henderson and Bartram develop the predictive capabilities of crystal-field engineering to show how modification of the symmetry and composition of optical centers can improve laser performance. They also discuss applications of the principles of crystal-field engineering to a variety of optical crystals in relation to the performances of laser devices. This book will be of considerable interest to physical, chemical and material scientists and to engineers involved in the science and technology of solid state lasers.

  13. Crystal structure of monoclinic samarium and cubic europium sesquioxides and bound coherent neutron scattering lengths of the isotopes {sup 154}Sm and {sup 153}Eu

    Energy Technology Data Exchange (ETDEWEB)

    Kohlmann, Holger [Leipzig Univ. (Germany). Inst. of Inorganic Chemistry; Hein, Christina; Kautenburger, Ralf [Saarland Univ., Saarbruecken (Germany). Inorganic Solid State Chemistry; Hansen, Thomas C.; Ritter, Clemens [Institut Laue-Langevin, Grenoble (France); Doyle, Stephen [Karlsruhe Institute of Technology, Eggenstein-Leopoldshafen (Germany). Inst. for Synchrotron Radiation (ISS)

    2016-11-01

    The crystal structures of monoclinic samarium and cubic europium sesquioxide, Sm{sub 2}O{sub 3} and Eu{sub 2}O{sub 3}, were reinvestigated by powder diffraction methods (laboratory X-ray, synchrotron, neutron). Rietveld analysis yields more precise structural parameters than previously known, especially for oxygen atoms. Interatomic distances d(Sm-O) in Sm{sub 2}O{sub 3} range from 226.3(4) to 275.9(2) pm [average 241.6(3) pm] for the monoclinic B type Sm{sub 2}O{sub 3} [space group C2/m, a = 1418.04(3) pm, b = 362.660(7) pm, c = 885.48(2) pm, β = 100.028(1) ], d(Eu-O) in Eu{sub 2}O{sub 3} from 229.9(2) to 238.8(2) pm for the cubic bixbyite (C) type [space group Ia anti 3, a = 1086.87(1) pm]. Neutron diffraction at 50 K and 2 K did not show any sign for magnetic ordering in Sm{sub 2}O{sub 3}. Isotopically enriched {sup 154}Sm{sub 2}O{sub 3} and {sup 153}Eu{sub 2}O{sub 3} were used for the neutron diffraction work because of the enormous absorption cross section of the natural isotopic mixtures for thermal neutrons. The isotopic purity was determined by inductively coupled plasma - mass spectrometry to be 98.9% for {sup 154}Sm and 99.8% for {sup 153}Eu. Advanced analysis of the neutron diffraction data suggest that the bound coherent scattering lengths of {sup 154}Sm and {sup 153}Eu need to be revised. We tentatively propose b{sub c}({sup 154}Sm) = 8.97(6) fm and b{sub c}({sup 153}Eu) = 8.85(3) fm for a neutron wavelength of 186.6 pm to be better values for these isotopes, showing up to 8% deviation from accepted literature values. It is shown that inaccurate scattering lengths may result in severe problems in crystal structure refinements causing erroneous structural details such as occupation parameters, which might be critically linked to physical properties like superconductivity in multinary oxides.

  14. Eighth-order phase-field-crystal model for two-dimensional crystallization

    Science.gov (United States)

    Jaatinen, A.; Ala-Nissila, T.

    2010-12-01

    We present a derivation of the recently proposed eighth-order phase-field crystal model [A. Jaatinen , Phys. Rev. E 80, 031602 (2009)10.1103/PhysRevE.80.031602] for the crystallization of a solid from an undercooled melt. The model is used to study the planar growth of a two-dimensional hexagonal crystal, and the results are compared against similar results from dynamical density functional theory of Marconi and Tarazona, as well as other phase-field crystal models. We find that among the phase-field crystal models studied, the eighth-order fitting scheme gives results in good agreement with the density functional theory for both static and dynamic properties, suggesting it is an accurate and computationally efficient approximation to the density functional theory.

  15. Near-field probing of photonic crystals

    NARCIS (Netherlands)

    Flück, E.; Hammer, M.; Vos, W.L.; Hulst, van N.F.; Kuipers, L.

    2004-01-01

    Photonic crystals form an exciting new class of optical materials that can greatly affect optical propagation and light emission. As the relevant length scale is smaller than the wavelength of light, sub-wavelength detection forms an important ingredient to obtain full insight in the physical proper

  16. Goethite liquid crystals and magnetic field effects

    NARCIS (Netherlands)

    van den Pol, E

    2010-01-01

    In this thesis the liquid crystal phase behavior of colloidal, boardlike, goethite (alpha-FeOOH) particles is described. Apart from the nematic phase, a smectic A phase is formed in systems with a low and high polydispersity. Strong fractionation occurs which is able to reduce the local length polyd

  17. Crystal field effects in TmCu2 compound

    Science.gov (United States)

    Zajac, Š.; Šíma, V.; Smetana, Z.

    1987-01-01

    The splitting of the3H6 multiplet has been estimated for the Tm3+ ion in the crystal electric field of the orthorhombic TmCu2 compound. Using the energy levels and appropriate eigenfunctions the crystal field only susceptibility has been calculated along the principal orthorhombic axes at temperatures 10 to 300 K. The obtained results are compared with our measurements of specific heat and paramagnetic susceptibility on polycrystalline sample.

  18. Intermittent dislocation density fluctuations in crystal plasticity from a phase-field crystal model

    DEFF Research Database (Denmark)

    Tarp, Jens M.; Angheluta, Luiza; Mathiesen, Joachim;

    2014-01-01

    Plastic deformation mediated by collective dislocation dynamics is investigated in the two-dimensional phase-field crystal model of sheared single crystals. We find that intermittent fluctuations in the dislocation population number accompany bursts in the plastic strain-rate fluctuations. Disloc...

  19. Forming limit prediction using a self-consistent crystal plasticity framework: a case study for body-centered cubic materials

    Science.gov (United States)

    Jeong, Youngung; Pham, Minh-Son; Iadicola, Mark; Creuziger, Adam; Foecke, Timothy

    2016-06-01

    A rate-dependent self-consistent crystal plasticity model was incorporated with the Marciniak-Kuczyński model in order to study the effects of anisotropy on the forming limits of BCC materials. The computational speed of the model was improved by a factor of 24 when running the simulations for several strain paths in parallel. This speed-up enabled a comprehensive investigation of the forming limits of various BCC textures, such as γ , σ , α , η and ɛ fibers and a uniform (random) texture. These simulations demonstrate that the crystallographic texture has significant (both positive and negative) effects on the resulting forming limit diagrams. For example, the γ fiber texture, which is often sought through thermo-mechanical processing due to a high r-value, had the highest forming limit in the balanced biaxial strain path but the lowest forming limit under the plane strain path among the textures under consideration. A systematic investigation based on the results produced by the current model, referred to as ‘VPSC-FLD’, suggests that the r-value does not serve as a good measure of forming limit strain. However, model predictions show a degree of correlation between the r-value and the forming limit stress.

  20. Mapping individual electromagnetic field components inside a photonic crystal

    CERN Document Server

    Denis, T; Lee, J H H; van der Slot, P J M; Vos, W L; Boller, K -J

    2012-01-01

    We present a method to map the absolute electromagnetic field strength inside photonic crystals. We apply the method to map the electric field component Ez of a two-dimensional photonic crystal slab at microwave frequencies. The slab is placed between two mirrors to select Bloch standing waves and a subwavelength spherical scatterer is scanned inside the resulting resonator. The resonant Bloch frequencies shift depending on the electric field at the position of the scatterer. To map the electric field component Ez we measure the frequency shift in the reflection and transmission spectrum of the slab versus the scatterer position. Very good agreement is found between measurements and calculations without any adjustable parameters.

  1. Crystal structure and optical properties of the [Ag62S12(SBu(t))32](2+) nanocluster with a complete face-centered cubic kernel.

    Science.gov (United States)

    Jin, Shan; Wang, Shuxin; Song, Yongbo; Zhou, Meng; Zhong, Juan; Zhang, Jun; Xia, Andong; Pei, Yong; Chen, Man; Li, Peng; Zhu, Manzhou

    2014-11-05

    The crystal structure of the [Ag62S12(SBu(t))32](2+) nanocluster (denoted as NC-I) has been successfully determined, and it shows a complete face-centered-cubic (FCC) Ag14 core structure with a Ag48(SBu(t))32 shell configuration interconnected by 12 sulfide ions, which is similar to the [Ag62S13(SBu(t))32](4+) structure (denoted as NC-II for short) reported by Wang. Interestingly, NC-I exhibits prominent differences in the optical properties in comparison with the case of the NC-II nanocluster. We employed femtosecond transient absorption spectroscopy to further identify the differences between the two nanoclusters. The results show that the quenching of photoluminescence in NC-I in comparison to that of NC-II is caused by the free valence electrons, which dramatically change the ligand to metal charge transfer (LMCT, S 3p → Ag 5s). To get further insight into these, we carried out time-dependent density functional theory (TDDFT) calculations on the electronic structure and optical absorption spectra of NC-I and NC-II. These findings offer a new insight into the structure and property evolution of silver cluster materials.

  2. Field renormalization in photonic crystal waveguides

    DEFF Research Database (Denmark)

    Colman, Pierre

    2015-01-01

    A novel strategy is introduced in order to include variations of the nonlinearity in the nonlinear Schro¨dinger equation. This technique, which relies on renormalization, is in particular well adapted to nanostructured optical systems where the nonlinearity exhibits large variations up to two...... Schro¨dinger equation is an occasion for physics-oriented considerations and unveils the potential of photonic crystal waveguides for the study of new nonlinear propagation phenomena....

  3. Field induced heliconical structure of cholesteric liquid crystal

    Science.gov (United States)

    Lavrentovich, Oleg D.; Shiyanovsii, Sergij V.; Xiang, Jie; Kim, Young-Ki

    2017-06-27

    A diffraction grating comprises a liquid crystal (LC) cell configured to apply an electric field through a cholesteric LC material that induces the cholesteric LC material into a heliconical state with an oblique helicoid director. The applied electric field produces diffracted light from the cholesteric LC material within the visible, infrared or ultraviolet. The axis of the heliconical state is in the plane of the liquid crystal cell or perpendicular to the plane, depending on the application. A color tuning device operates with a similar heliconical state liquid crystal material but with the heliconical director axis oriented perpendicular to the plane of the cell. A power generator varies the strength of the applied electric field to adjust the wavelength of light reflected from the cholesteric liquid crystal material within the visible, infrared or ultraviolet.

  4. Nucleation of lysozyme crystals under external electric and ultrasonic fields

    Science.gov (United States)

    Nanev, Christo N.; Penkova, Anita

    2001-11-01

    Preferred orientation along c-axis of hen-egg-white lysozyme (HEWL) crystals has been observed in an external electric field. Besides, the HEWL crystals grew predominantly on the cathode side of the glass cell. These facts were explained on the basis of a concept for specific spatial distribution of the positive electric charges on the individual HEWL molecules, and thus attributed to the (preferred) orientation of individual HEWL molecules in the solution, under these conditions. Ultrasonic field redoubles the nucleation rate of HEWL crystals, but does not change the number of building units in the critical nucleus. Taking into account the intermolecular binding energy, we conclude that ultrasonic field accelerates nucleation due to breaking of the protein crystals.

  5. Optical properties of 3d-ions in crystals spectroscopy and crystal field analysis

    CERN Document Server

    Brik, Mikhail

    2013-01-01

    "Optical Properties of 3d-Ions in Crystals: Spectroscopy and Crystal Field Analysis" discusses spectral, vibronic and magnetic properties of 3d-ions in a wide range of crystals, used as active media for solid state lasers and potential candidates for this role. Crystal field calculations (including first-principles calculations of energy levels and absorption spectra) and their comparison with experimental spectra, the Jahn-Teller effect, analysis of vibronic spectra, materials science applications are systematically presented. The book is intended for researchers and graduate students in crystal spectroscopy, materials science and optical applications. Dr. N.M. Avram is an Emeritus Professor at the Physics Department, West University of Timisoara, Romania; Dr. M.G. Brik is a Professor at the Institute of Physics, University of Tartu, Estonia.

  6. The Magnetic Ordering in Diluted Crystal Magnets with Indirect Exchange Interaction

    OpenAIRE

    Belokon, V. I.; Nefedev, K. V.; Savunov, M. A.

    2006-01-01

    The closed system of equations for a determination of parameters distribution function for random interaction fields was calculated analytically. The estimations of critical concentrations for phase transitions in diluted crystal magnets with face centered cubic (fcc), volume centered cubic (vcc) and simple cubic (sc) lattices with interaction of Ruderman-Kittel-Kasua-Yosida between spins were made.

  7. Mapping the absolute electromagnetic field strength of individual field components inside a photonic crystal

    NARCIS (Netherlands)

    Denis, T.; Reijnders, B.; Lee, J.H.H.; Vos, Willem L.; Boller, Klaus J.; van der Slot, Petrus J.M.

    2013-01-01

    We present a method to map the absolute electromagnetic field strength inside photonic crystals. We demonstrate our method by applying it to map the electric field component Ez of a two-dimensional photonic crystal slab at microwave frequencies. The slab is placed between two mirrors to create a

  8. Strain field of interstitial hydrogen atom in body-centered cubic iron and its effect on hydrogen-dislocation interaction

    OpenAIRE

    Wang, Shuai; Takahashi, Keisuke; Hashimoto, Naoyuki; Isobe, Shigehito; Ohnuki, Somei

    2013-01-01

    Effect of hydrogen in body-centered cubic iron is explored by using the density function theory. Hydrogen atoms increase the concentration of free electrons in the simulation cell and have bonding interaction with Fe atom. Caused by anisotropic strain components of hydrogen atoms in the tetrahedral sites, elastic interaction for hydrogen with screw dislocation has been found. The dependence of hydrogen-screw dislocation interaction on hydrogen concentration is confirmed by repeated stress rel...

  9. Critical line of the Φ4 scalar field theory on a 4D cubic lattice in the local potential approximation

    Directory of Open Access Journals (Sweden)

    J.-M. Caillol

    2013-01-01

    Full Text Available We establish the critical line of the one-component Φ4 (or Landau-Ginzburg model on a simple four dimensional cubic lattice. Our study is performed in the framework of the non-perturbative renormalization group in the local potential approximation with a soft infra-red regulator. The transition is found to be of second order even in the Gaussian limit where first order would be expected according to some recent theoretical predictions.

  10. Fiber field-effect device via in situ channel crystallization.

    Science.gov (United States)

    Danto, Sylvain; Sorin, Fabien; Orf, Nicholas D; Wang, Zheng; Speakman, Scott A; Joannopoulos, John D; Fink, Yoel

    2010-10-01

    The in situ crystallization of the incorporated amorphous semiconductor within the multimaterial fiber device yields a large decrease in defect density and a concomitant five-order-of-magnitude decrease in resistivity of the novel metal-insulator-crystalline semiconductor structure. Using a post-drawing crystallization process, the first tens-of-meters-long single-fiber field-effect device is demonstrated. This work opens significant opportunities for incorporating higher functionality in functional fibers and fabrics.

  11. Phase Field Modeling of Twinning in Indentation of Transparent Crystals

    Science.gov (United States)

    2011-09-01

    twin boundaries . Equilibrium configurations of deformed and twinned crystals are attained via direct energy minimization. The theory is framed in the...phases: (i) the original crystal (the parent) and (ii) the twin. Interfaces between phases are twin boundaries . Order parameter η generally exhibits the...following values: η(X, •) = 0∀X ∈ parent, = 1∀X ∈ twin, ∈ (0, 1)∀X ∈ twin boundaries . (1) In linear elasticity, kinematic field variables are

  12. Magnetic Fields and the Crystallization of White Dwarfs

    Science.gov (United States)

    Isern, J.; García-Berro, E.; Külebi, B.; Lorén-Aguilar, P.

    2017-03-01

    The evolution of white dwarfs can be described as a cooling process. When the temperature is low enough, the interior experiences a phase transition and crystallizes. Crystallization introduces two new sources of energy, latent heat and chemical sedimentation, and induces the formation of a convective mantle around the solid core. This structure, which is analogous to that of the Earth, could induce the formation of a magnetic field via dynamo mechanism. In this work we discuss the viability of such mechanism, and its use as a diagnostic tool of crystallization.

  13. Crystal field spectra of lunar pyroxenes.

    Science.gov (United States)

    Burns, R. G.; Abu-Eid, R. M.; Huggins, F. E.

    1972-01-01

    Absorption spectra in the visible and near infrared regions have been obtained for pyroxene single crystals in rocks from the Apollo 11, 12, 14, and 15 missions. The polarized spectra are compared with those obtained from terrestrial calcic clinopyroxenes, subcalcic augites, pigeonites, and orthopyroxenes. The lunar pyroxenes contain several broad, intense absorption bands in the near infrared, the positions of which are related to bulk composition, Fe(2+) site occupancy and structure type of the pyroxene. The visible spectra contain several sharp, weak peaks mainly due to spin-forbidden transitions in Fe(2+). Additional weak bands in this region in Apollo 11 pyroxenes are attributed to Ti(3+) ions. Spectral features from Fe(3+), Mn(2+), Cr(3+), and Cr(2+) were not observed.

  14. Magnetic Field Applications in Semiconductor Crystal Growth and Metallurgy

    Science.gov (United States)

    Mazuruk, Konstantin; Ramachandran, Narayanan; Grugel, Richard; Curreri, Peter A. (Technical Monitor)

    2002-01-01

    The Traveling Magnetic Field (TMF) technique, recently proposed to control meridional flow in electrically conducting melts, is reviewed. In particular, the natural convection damping capability of this technique has been numerically demonstrated with the implication of significantly improving crystal quality. Advantages of the traveling magnetic field, in comparison to the more mature rotating magnetic field method, are discussed. Finally, results of experiments with mixing metallic alloys in long ampoules using TMF is presented

  15. Correlation theory of crystal field and anisotropic exchange effects

    DEFF Research Database (Denmark)

    Lindgård, Per-Anker

    1985-01-01

    A general theory for including correlation effects in static and dynamic properties is presented in terms of Raccah or Stevens operators. It is explicitly developed for general crystal fields and anisotropic interactions and systems with several sublattices, like the rare earth compounds. The the......A general theory for including correlation effects in static and dynamic properties is presented in terms of Raccah or Stevens operators. It is explicitly developed for general crystal fields and anisotropic interactions and systems with several sublattices, like the rare earth compounds....... The theory gives explicitly a temperature dependent renormalization of both the crystal field and the interactions, and a damping of the excitations and in addition a central park component. The general theory is illustrated by a discussion of the singlet-doublet system. The correlation effects...... on the susceptibility, the first and second moment frequencies and the line shape are calculated self-consistently....

  16. Relaxation Dynamics of Ferroelectric Liquid Crystals in Pulsed Electric Field

    Science.gov (United States)

    Kudreyko, A. A.; Migranov, N. G.; Migranova, D. N.

    2016-11-01

    In this contribution we report a theoretical study of relaxation processes in surface-stabilized ferroelectric liquid crystals with spontaneous polarization. The influence of pulsed electric field on the behavior of ferroelectric liquid crystal in the SmC* phase, which is placed in a thin cell with strong anchoring of SmC* molecules with the boundary substrate, is studied. In the vicinity of the substrate interface, temporal dependence of the azimuthal motion of the director induced by electric field is obtained. The response to the external distortion of ferroelectric liquid crystal confined between two microstructured substrates is the occurrence of periodic temporal formation of solitons connected with the distortion of the director field n in the sample bulk. The interplay between microstructured substrates and director distribution of the ferroelectric SmC* phase is explained by the Frenkel-Kontorova model for a chain of atoms, but adapted for the continuum problem.

  17. Physical modelling of Czochralski crystal growth in horizontal magnetic field

    Science.gov (United States)

    Grants, Ilmārs; Pal, Josef; Gerbeth, Gunter

    2017-07-01

    This study addresses experimentally the heat transfer, the temperature azimuthal non-uniformity and the onset of oscillations in a low temperature physical model of a medium-sized Czochralski crystal growth process with a strong horizontal magnetic field (HMF). It is observed that under certain conditions the integral heat flux may decrease with increasing magnetic field strength at the same time as the flow velocity increases. The azimuthal non-uniformity of the temperature field in the melt near the crystal model rim is only little influenced by its rotation rate outside of a narrow range where the centrifugal force balances the buoyant one. The flow oscillation onset has been observed for two values of the HMF strength. Conditions of this onset are little influenced by the crystal rotation. The critical temperature difference of the oscillation onset considerably exceeds that of the Rayleigh-Bénard (RB) cell in a strong HMF.

  18. CRYSTAL-FIELD AND TRANSVERSE-FIELD EFFECTS OF THE SPIN-ONE ISING MODEL

    Institute of Scientific and Technical Information of China (English)

    宋为基; 杨传章

    1993-01-01

    A mean-field approximation (MFA) is used to treat the crystal-field and transverse-field effects of the spin-1 Ising modle in the presence of longitudinal field. In spite of its simplicity, this scheme still gives the satisfied results.

  19. Organic single-crystal field-effect transistors

    Directory of Open Access Journals (Sweden)

    Colin Reese

    2007-03-01

    Full Text Available Organic molecular crystals hold great promise for the rational development of organic semiconductor materials. Their long-range order not only reveals the performance limits of organic materials, but also provides unique insight into their intrinsic transport properties. The field-effect transistor (FET has served as a versatile tool for electrical characterization of many facets of their performance. In the last few years, breakthroughs in single-crystal FET fabrication techniques have enabled the realization of field-effect mobilities far surpassing amorphous Si, observation of the Hall effect in an organic material, and the study of transport as an explicit function of molecular packing and chemical structure.

  20. Fine structure of fields in 2D photonic crystal waveguides

    DEFF Research Database (Denmark)

    Lavrinenko, Andrei; Volkov, V. S.; Bozhevolnyi, S. I.

    2006-01-01

    We resolve fine structure of fields in a single-row missing photonic crystal waveguide by finite-difference time-domain modelling and SNOM measurements. Both linear dispersion and slow-light regimes in proximity of the cutoff are addressed in the analysis.......We resolve fine structure of fields in a single-row missing photonic crystal waveguide by finite-difference time-domain modelling and SNOM measurements. Both linear dispersion and slow-light regimes in proximity of the cutoff are addressed in the analysis....

  1. Electromagnetic Field Effects in Semiconductor Crystal Growth

    Science.gov (United States)

    Dulikravich, George S.

    1996-01-01

    This proposed two-year research project was to involve development of an analytical model, a numerical algorithm for its integration, and a software for the analysis of a solidification process under the influence of electric and magnetic fields in microgravity. Due to the complexity of the analytical model that was developed and its boundary conditions, only a preliminary version of the numerical algorithm was developed while the development of the software package was not completed.

  2. Electromagnetic field patterning or crystal light

    Science.gov (United States)

    Słupski, Piotr; Wymysłowski, Artur; Czarczyński, Wojciech

    2016-12-01

    Using the orbital angular momentum of light for the development of a vortex interferometer, the underlying physics requires microwave/RF models,1 as well as quantum mechanics for light1, 2 and fluid flow for semiconductor devices.3, 4 The combination of the aforementioned physical models yields simulations and results such as optical lattices,1 or an Inverse Farday effect.5 The latter is explained as the absorption of optical angular momentum, generating extremely high instantenous magnetic fields due to radiation friction. An algorithmic reduction across the computational methods used in microwaves, lasers, quantum optics and holography is performed in order to explain electromagnetic field interactions in a single computational framework. This work presents a computational model for photon-electron interactions, being a simplified gauge theory described using differentials or disturbances (photons) instead of integrals or fields. The model is based on treating the Z-axis variables as a Laplace fluid with spatial harmonics, and the XY plane as Maxwell's equations on boundaries. The result is a unified, coherent, graphical computational method of describing the photon qualitatively, quantitatively and with proportion. The model relies on five variables and is described using two equations, which use emitted power, cavity wavelength, input frequency, phase and time. Phase is treated as a rotated physical dimension under gauge theory of Feynmann's QED. In essence, this model allows the electromagnetic field to be treated with it's specific crystallography. The model itself is described in Python programming language. PACS 42.50.Pq, 31.30.J-, 03.70.+k, 11.10.-z, 67.10.Hk

  3. Improving NASICON Sinterability through Crystallization under High Frequency Electrical Fields

    Directory of Open Access Journals (Sweden)

    Ilya eLisenker

    2016-03-01

    Full Text Available The effect of high frequency (HF electric fields on the crystallization and sintering rates of a lithium aluminum germanium phosphate (LAGP ion conducting ceramic was investigated. LAGP with the nominal composition Li1.5Al0.5Ge1.5(PO43 was crystallized and sintered, both conventionally and under effect of electrical field. Electrical field application, of 300V/cm at 1MHz, produced up to a 40% improvement in sintering rate of LAGP that was crystallized and sintered under the HF field. Heat sink effect of the electrodes appears to arrest thermal runaway and subsequent flash behavior. Sintered pellets were characterized using XRD, SEM, TEM and EIS to compare conventionally and field sintered processes. The as-sintered structure appears largely unaffected by the field as the sintering curves tend to converge beyond initial stages of sintering. Differences in densities and microstructure after 1 hour of sintering were minor with measured sintering strains of 31% vs. 26% with and without field, respectively . Ionic conductivity of the sintered pellets was evaluated and no deterioration due to the use of HF field was noted, though capacitance of grain boundaries due to secondary phases was significantly increased.

  4. Crystallization of Calcium Carbonate in a Large Scale Field Study

    Science.gov (United States)

    Ueckert, Martina; Wismeth, Carina; Baumann, Thomas

    2017-04-01

    The long term efficiency of geothermal facilities and aquifer thermal energy storage in the carbonaceous Malm aquifer in the Bavarian Molasse Basin is seriously affected by precipitations of carbonates. This is mainly caused by pressure and temperature changes leading to oversaturation during production. Crystallization starts with polymorphic nuclei of calcium carbonate and is often described as diffusion-reaction controlled. Here, calcite crystallization is favoured by high concentration gradients while aragonite crystallization is occurring at high reaction rates. The factors affecting the crystallization processes have been described for simplified, well controlled laboratory experiments, the knowledge about the behaviour in more complex natural systems is still limited. The crystallization process of the polymorphic forms of calcium carbonate were investigated during a heat storage test at our test site in the eastern part of the Bavarian Molasse Basin. Complementary laboratory experiments in an autoclave were run. Both, field and laboratory experiments were conducted with carbonaceous tap water. Within the laboratory experiments additionally ultra pure water was used. To avoid precipitations of the tap water, a calculated amount of {CO_2} was added prior to heating the water from 45 - 110°C (laboratory) resp. 65 - 110°C (field). A total water volume of 0.5 L (laboratory) resp. 1 L (field) was immediately sampled and filtrated through 10 - 0.1

  5. Crystal Field Parameters and Phase Transitions in ErSb

    DEFF Research Database (Denmark)

    Shapiro, S. M.; Bak, P.

    1975-01-01

    The crystal field levels of the Er ion in a single crystal of ErSb have been measured by inelastic neutron scattering. The crystal field parameters obtained by a least squares fit to the spectra at several temperatures are: B4 = (0·473 ± 0·005) × 10−2°K and B6 = (0·59 ± 0·06) × 10−5°K, which differ...... considerably from the values o by interpolation from measurements on other compounds. In addition the temperature dependence of the magnetic scattering in the vicinity of the Néel temperature (TN = 3·55°K) clearly demonstrates that the transition is second order in contrast to the first order behavior...

  6. Tailor-made force fields for crystal-structure prediction.

    Science.gov (United States)

    Neumann, Marcus A

    2008-08-14

    A general procedure is presented to derive a complete set of force-field parameters for flexible molecules in the crystalline state on a case-by-case basis. The force-field parameters are fitted to the electrostatic potential as well as to accurate energies and forces generated by means of a hybrid method that combines solid-state density functional theory (DFT) calculations with an empirical van der Waals correction. All DFT calculations are carried out with the VASP program. The mathematical structure of the force field, the generation of reference data, the choice of the figure of merit, the optimization algorithm, and the parameter-refinement strategy are discussed in detail. The approach is applied to cyclohexane-1,4-dione, a small flexible ring. The tailor-made force field obtained for cyclohexane-1,4-dione is used to search for low-energy crystal packings in all 230 space groups with one molecule per asymmetric unit, and the most stable crystal structures are reoptimized in a second step with the hybrid method. The experimental crystal structure is found as the most stable predicted crystal structure both with the tailor-made force field and the hybrid method. The same methodology has also been applied successfully to the four compounds of the fourth CCDC blind test on crystal-structure prediction. For the five aforementioned compounds, the root-mean-square deviations between lattice energies calculated with the tailor-made force fields and the hybrid method range from 0.024 to 0.053 kcal/mol per atom around an average value of 0.034 kcal/mol per atom.

  7. Fine structure of fields in 2D photonic crystal waveguides

    DEFF Research Database (Denmark)

    Lavrinenko, Andrei; Volkov, V. S.; Bozhevolnyi, S. I.

    2006-01-01

    We resolve fine structure of fields in a single-row missing photonic crystal waveguide by finite-difference time-domain modelling and SNOM measurements. Both linear dispersion and slow-light regimes in proximity of the cutoff are addressed in the analysis....

  8. Control over colloidal crystallization by shear and electric fields

    NARCIS (Netherlands)

    Wu, Y.L.

    2007-01-01

    We used shear flow and an electric field to control colloidal crystallization. The structures were examined in situ with confocal microscopy. For experiments under shear, a new parallel plate shear cell was designed. It had a zero-velocity plane that was stationary with respect to the microscope. Th

  9. Density functional theory of the crystal field in dioxides

    Science.gov (United States)

    Diviš, M.; Kuriplach, J.; Richter, M.; Steinbeck, L.

    1996-04-01

    Presented are the results of ab-initio density functional calculations for PrO2 and UO2 using the general potential LAPW and optimized LCAO method in the local density approximation. The crystal field splitting of ionic Pr4+ and U4+ ground states was calculated and compared with predictions of a superposition model.

  10. Crystal orientation effects on wurtzite quantum well electromechanical fields

    DEFF Research Database (Denmark)

    Duggen, Lars; Willatzen, Morten

    2010-01-01

    A one-dimensional continuum model for calculating strain and electric field in wurtzite semiconductor heterostructures with arbitrary crystal orientation is presented and applied to GaN/AlGaN and ZnO/MgZnO heterostructure combinations. The model is self-consistent involving feedback couplings of ...

  11. Field-effect transistors on tetracene single crystals

    NARCIS (Netherlands)

    De Boer, R.W.I.; Klapwijk, T.M.; Morpurgo, A.F

    2003-01-01

    We report on the fabrication and electrical characterization of field-effect transistors at the surface of tetracene single crystals. We find that the mobility of these transistors reaches the room-temperature value of 0.4 cm2/V s. The nonmonotonous temperature dependence of the mobility, its weak g

  12. Phase field simulations of ice crystal growth in sugar solutions

    NARCIS (Netherlands)

    Sman, Van Der R.G.M.

    2016-01-01

    We present the first model ever, that describes explicitly ice crystal growth in a sugar solution during freezing. This 2-D model uses the phase field method, supplemented with realistic, and predictive theories on the thermodynamics and (diffusion) kinetics of this food system. We have to make u

  13. Field stability of piezoelectric shear properties in PIN-PMN-PT crystals under large drive field.

    Science.gov (United States)

    Zhang, Shujun; Li, Fei; Luo, Jun; Xia, Ru; Hackenberger, Wesley; Shrout, Thomas

    2011-02-01

    The coercive fields (E(C)) of Pb(In₀.₅Nb₀.₅)O₃-Pb(Mg(¹/₃)Nb(²/₃)O₃-PbTiO₃ (PIN-PMN-PT) ternary single crystals were found to be 5 kV/cm, double the value of binary Pb(Mg(¹/₃)Nb(²/₃)O₃-PbTiO₃ (PMNT) crystals, further increased to 6 to 9 kV/cm using Mn modifications. In addition to an increased EC, the acceptor modification resulted in the developed internal bias (E(int)), on the order of ~1 kV/cm. The piezoelectric shear properties of unmodified and Mn-modified PIN-PMN-PT crystals with various domain configurations were investigated. The shear piezoelectric coefficients and electromechanical coupling factors for different domain configurations were found to be >2000 pC/N and >0.85, respectively, with slightly reduced properties observed in Mn-modified tetragonal crystals. Fatigue/cycling tests performed on shearmode samples as a function of ac drive field level demonstrated that the allowable ac field levels (the maximum applied ac field before the occurrence of depolarization) were only ~2 kV/cm for unmodified crystals, less than half of their coercive field. Allowable ac drive levels were on the order of 4 to 6 kV/cm for Mn-modified crystals with rhombohedral/orthorhombic phase, further increased to 5 to 8 kV/cm in tetragonal crystals, because of their higher coercive fields. It is of particular interest that the allowable ac drive field level for Mn-modified crystals was found to be ≥ 60% of their coercive fields, because of the developed E(int), induced by the acceptor-oxygen vacancy defect dipoles.

  14. Crystal Structure of Garnet-Related Li-Ion Conductor Li7-3x Ga x La3Zr2O12: Fast Li-Ion Conduction Caused by a Different Cubic Modification?

    Science.gov (United States)

    Wagner, Reinhard; Redhammer, Günther J; Rettenwander, Daniel; Senyshyn, Anatoliy; Schmidt, Walter; Wilkening, Martin; Amthauer, Georg

    2016-03-22

    Li-oxide garnets such as Li7La3Zr2O12 (LLZO) are among the most promising candidates for solid-state electrolytes to be used in next-generation Li-ion batteries. The garnet-structured cubic modification of LLZO, showing space group Ia-3d, has to be stabilized with supervalent cations. LLZO stabilized with Ga(3+) shows superior properties compared to LLZO stabilized with similar cations; however, the reason for this behavior is still unknown. In this study, a comprehensive structural characterization of Ga-stabilized LLZO is performed by means of single-crystal X-ray diffraction. Coarse-grained samples with crystal sizes of several hundred micrometers are obtained by solid-state reaction. Single-crystal X-ray diffraction results show that Li7-3x Ga x La3Zr2O12 with x > 0.07 crystallizes in the acentric cubic space group I-43d. This is the first definite record of this cubic modification for LLZO materials and might explain the superior electrochemical performance of Ga-stabilized LLZO compared to its Al-stabilized counterpart. The phase transition seems to be caused by the site preference of Ga(3+). (7)Li NMR spectroscopy indicates an additional Li-ion diffusion process for LLZO with space group I-43d compared to space group Ia-3d. Despite all efforts undertaken to reveal structure-property relationships for this class of materials, this study highlights the potential for new discoveries.

  15. Crystal Structure of Garnet-Related Li-Ion Conductor Li7–3xGaxLa3Zr2O12: Fast Li-Ion Conduction Caused by a Different Cubic Modification?

    Science.gov (United States)

    2016-01-01

    Li-oxide garnets such as Li7La3Zr2O12 (LLZO) are among the most promising candidates for solid-state electrolytes to be used in next-generation Li-ion batteries. The garnet-structured cubic modification of LLZO, showing space group Ia-3d, has to be stabilized with supervalent cations. LLZO stabilized with Ga3+ shows superior properties compared to LLZO stabilized with similar cations; however, the reason for this behavior is still unknown. In this study, a comprehensive structural characterization of Ga-stabilized LLZO is performed by means of single-crystal X-ray diffraction. Coarse-grained samples with crystal sizes of several hundred micrometers are obtained by solid-state reaction. Single-crystal X-ray diffraction results show that Li7–3xGaxLa3Zr2O12 with x > 0.07 crystallizes in the acentric cubic space group I-43d. This is the first definite record of this cubic modification for LLZO materials and might explain the superior electrochemical performance of Ga-stabilized LLZO compared to its Al-stabilized counterpart. The phase transition seems to be caused by the site preference of Ga3+. 7Li NMR spectroscopy indicates an additional Li-ion diffusion process for LLZO with space group I-43d compared to space group Ia-3d. Despite all efforts undertaken to reveal structure–property relationships for this class of materials, this study highlights the potential for new discoveries. PMID:27019548

  16. Organic field-effect transistors using single crystals

    Directory of Open Access Journals (Sweden)

    Tatsuo Hasegawa and Jun Takeya

    2009-01-01

    Full Text Available Organic field-effect transistors using small-molecule organic single crystals are developed to investigate fundamental aspects of organic thin-film transistors that have been widely studied for possible future markets for 'plastic electronics'. In reviewing the physics and chemistry of single-crystal organic field-effect transistors (SC-OFETs, the nature of intrinsic charge dynamics is elucidated for the carriers induced at the single crystal surfaces of molecular semiconductors. Materials for SC-OFETs are first reviewed with descriptions of the fabrication methods and the field-effect characteristics. In particular, a benchmark carrier mobility of 20–40 cm2 Vs−1, achieved with thin platelets of rubrene single crystals, demonstrates the significance of the SC-OFETs and clarifies material limitations for organic devices. In the latter part of this review, we discuss the physics of microscopic charge transport by using SC-OFETs at metal/semiconductor contacts and along semiconductor/insulator interfaces. Most importantly, Hall effect and electron spin resonance (ESR measurements reveal that interface charge transport in molecular semiconductors is properly described in terms of band transport and localization by charge traps.

  17. TOPICAL REVIEW: Organic field-effect transistors using single crystals

    Science.gov (United States)

    Hasegawa, Tatsuo; Takeya, Jun

    2009-04-01

    Organic field-effect transistors using small-molecule organic single crystals are developed to investigate fundamental aspects of organic thin-film transistors that have been widely studied for possible future markets for 'plastic electronics'. In reviewing the physics and chemistry of single-crystal organic field-effect transistors (SC-OFETs), the nature of intrinsic charge dynamics is elucidated for the carriers induced at the single crystal surfaces of molecular semiconductors. Materials for SC-OFETs are first reviewed with descriptions of the fabrication methods and the field-effect characteristics. In particular, a benchmark carrier mobility of 20-40 cm2 Vs-1, achieved with thin platelets of rubrene single crystals, demonstrates the significance of the SC-OFETs and clarifies material limitations for organic devices. In the latter part of this review, we discuss the physics of microscopic charge transport by using SC-OFETs at metal/semiconductor contacts and along semiconductor/insulator interfaces. Most importantly, Hall effect and electron spin resonance (ESR) measurements reveal that interface charge transport in molecular semiconductors is properly described in terms of band transport and localization by charge traps.

  18. Augmented 3D super-resolution of fluorescence-free nanoparticles using enhanced dark-field illumination based on wavelength-modulation and a least-cubic algorithm

    Science.gov (United States)

    Zhang, Peng; Kim, Kyungsoo; Lee, Seungah; Chakkarapani, Suresh Kumar; Fang, Ning; Kang, Seong Ho

    2016-09-01

    Augmented three-dimensional (3D) subdiffraction-limited resolution of fluorescence-free single-nanoparticles was achieved with wavelength-dependent enhanced dark-field (EDF) illumination and a least-cubic algorithm. Various plasmonic nanoparticles on a glass slide (i.e., gold nanoparticles, GNPs; silver nanoparticles, SNPs; and gold nanorods, GNRs) were imaged and sliced in the z-direction to a thickness of 10 nm. Single-particle images were then compared with simulation data. The 3D coordinates of individual GNP, SNP, and GNR nanoparticles (x, y, z) were resolved by fitting the data with 3D point spread functions using a least-cubic algorithm and collation. Final, 3D super-resolution microscopy (SRM) images were obtained by resolving 3D coordinates and their Cramér-Rao lower bound-based localization precisions in an image space (530 nm × 530 nm × 300 nm) with a specific voxel size (2.5 nm × 2.5 nm × 5 nm). Compared with the commonly used least-square method, the least-cubic method was more useful for finding the center in asymmetric cases (i.e., nanorods) with high precision and accuracy. This novel 3D fluorescence-free SRM technique was successfully applied to resolve the positions of various nanoparticles on glass and gold nanospots (in vitro) as well as in a living single cell (in vivo) with subdiffraction limited resolution in 3D.

  19. Near-field probing of photonic crystal directional couplers

    DEFF Research Database (Denmark)

    Volkov, V. S.; Bozhevolnyi, S. I.; Borel, Peter Ingo

    2006-01-01

    . By comparing the near-field optical images recorded in and after the directional coupler area, the features of light distribution are analyzed. Finally, the scanning near-field optical microscope observations are found to be in agreement with the transmission measurements conducted with the same sample.......We report the design, fabrication and characterization of a photonic crystal directional with a size of ~20 x 20 mm2 fabricated in silicon-on-insulator material. Using a scanning near-field optical microscope we demonstrate a high coupling efficiency for TM polarized light at telecom wavelengths...

  20. High frequency (208 GHz) determination of the cubic spin Zeeman term for the U{sup 3+} ion in the dilute magnetic semiconductor crystals of Pb{sub 1−x}U{sub x}Te and Pb{sub 1−x}U{sub x}Se at 5 K by electron paramagnetic resonance

    Energy Technology Data Exchange (ETDEWEB)

    Misra, Sushil K., E-mail: skmisra@alcor.concordia.ca; Michaels, Adam

    2015-03-15

    A high-frequency (208 GHz) Electron Paramagnetic Resonance (EPR) study on the U{sup 3+} ion (5f{sup 3}, {sup 4}I{sub 9/2}, S=3/2) embedded with 3% concentration in the dilute magnetic semiconductor crystals of PbTe and PbSe, each characterized by cubic symmetry, has been performed at ∼5 K, especially in view to determine the value of the Zeeman cubic spin term parameter u, and the site symmetry of the U{sup 3+} ion (radius 0.089 nm), substituting for the Pb{sup 2+} ion (radius 0.119 nm). The experimental spectra reveal the presence of only one set of EPR lines from U{sup 3+} ions in these host crystals, exhibiting cubic symmetry, whose magnetic axes are oriented along the crystal axes. The spin-Hamiltonian parameters are for both crystals: g=1.9811, u=-0.0257. - Highlights: • EPR studies of U{sup 3+} ion done at 208 GHz at 5 K embedded in PbTe and PbSe crystals. • Site symmetry at U{sup 3+} ion is determined to be cubic from EPR data. • Zeeman cubic spin term parameter u=-0.0257 determined for both crystals. • g=1.9811 Determined for both crystals.

  1. Multiplicity factor and diffraction geometry factor for single crystal X-ray diffraction analysis and measurement of phase content in cubic GaN/GaAs(001) epilayers

    Institute of Scientific and Technical Information of China (English)

    QU; Bo

    2001-01-01

    [1] Yang, H., Zheng, L.X., Li, J.B. et al., Cubic-phase GaN light-emitting diode, Appl. Phys. Lett., 1999, 74(17): 2498.[2] Trampert, A., Brandt, O., Yang, H. et al., Direct observation of the initial nucleation and epitaxial growth of metastable cubic GaN on GaAs(001), Appl. Phys. Lett., 1997, 70(5): 583.[3] Balakrishnan, K., Feuillet, G., Ohta, K. et al., Structural analysis of cubic GaN through X-ray pole figure generation, Jpn. J. Appl. Phys., 1997, 36(10, part 1): 6221.[4] Basu, S.N., Lei, T., Moustakas, T.D., Microstructures of GaN films deposited on (001) and (111) Si substrates using electron cyclotron resonance assisted-molecular beam epitaxy, J. Mater. Res., 1994, 9(9): 2370.[5] Powell, R.C., Lee, N.E., Kim, Y.W. et al., Heteroepitaxial wurtzite and zinc-blende structure GaN grown by reactive-ion molecular-beam epitaxy: growth kinetics, microstructure, and properties, J. Appl. Phys., 1993, 73(1): 189.[6] Camassel, J., Vicente, P., Planes, N. et al., Experimental investigation of cubic to hexagonal ratio for GaN layers deposited on 3C-SiC/Si, Phys. Stat. Sol. (b), 1999, 216: 253.[7] Sun, X.L., Yang, H., Zheng, L.X., Stability investigation of cubic GaN films grown by MOCVD on GaAs(100), Appl. Phys. Lett., 1999, 74(19 ): 2827.[8] Moret, M., Ruttenach-clur, S., Moreaud, N. et al., MOCVD growth of cubic gallium nitride: effect of V/III ratio, Phys. Stat. Sol. (a), 1999, 176: 493.[9] Qin, Z.X., Nagano, H., Sugure, Y. et al., High-resolution X-ray diffraction analysis of cubic GaN grown on (001)GaAs by RF-radical source molecular beam epitaxy, J. Crys. Growth, 1998, 189/190: 425.[10] Qin Zhixin, Kobayashi, M., Yoshikawa, A., X-ray diffraction reciprocal space and pole figure characterization of cubic GaN epitaxial layers grown on (001)GaAs by molecular beam epitaxy, J. Mater. Sci., 1999,109: 199.[11] Trampert, A., Brandt, O., Ploog, K. H., Phase transformations and phase stability in epitaxial

  2. Orientation ordering in J = 1 solid hydrogens at crystal fields

    CERN Document Server

    Antsygina, T N; Freimann, Y A; Hemley, R J

    2003-01-01

    A system of quantum linear rotators with a rotational quantum number J 1 is considered at a crystal field. An equation for orientation order parameter is derived, and the critical parameters, the phase separation curve and the lines of overheating and overcooling points are obtained. It is shown that in terms of the thermodynamics the behavior of the above linear rotators in the classical case and in the extremely quantum (J = 1) one is identical. For positive values of the crystal field there also exist parallels between orientation phase transitions in a system of rotators with J = 1 and phase transitions in a liquid-vapor system. It is shown that the consideration of J > 1 states results in a radical change of the phase transition behavior in a system of rotators: instead of the sole critical point typical for the J = 1 system, there appears a line of critical points.

  3. Magnetic Field Measurements Based on Terfenol Coated Photonic Crystal Fibers

    Directory of Open Access Journals (Sweden)

    Carla C. Kato

    2011-11-01

    Full Text Available A magnetic field sensor based on the integration of a high birefringence photonic crystal fiber and a composite material made of Terfenol particles and an epoxy resin is proposed. An in-fiber modal interferometer is assembled by evenly exciting both eigenemodes of the HiBi fiber. Changes in the cavity length as well as the effective refractive index are induced by exposing the sensor head to magnetic fields. The magnetic field sensor has a sensitivity of 0.006 (nm/mT over a range from 0 to 300 mT with a resolution about ±1 mT. A fiber Bragg grating magnetic field sensor is also fabricated and employed to characterize the response of Terfenol composite to the magnetic field.

  4. Magnetic field measurements based on Terfenol coated photonic crystal fibers.

    Science.gov (United States)

    Quintero, Sully M M; Martelli, Cicero; Braga, Arthur M B; Valente, Luiz C G; Kato, Carla C

    2011-01-01

    A magnetic field sensor based on the integration of a high birefringence photonic crystal fiber and a composite material made of Terfenol particles and an epoxy resin is proposed. An in-fiber modal interferometer is assembled by evenly exciting both eigenemodes of the HiBi fiber. Changes in the cavity length as well as the effective refractive index are induced by exposing the sensor head to magnetic fields. The magnetic field sensor has a sensitivity of 0.006 (nm/mT) over a range from 0 to 300 mT with a resolution about ±1 mT. A fiber Bragg grating magnetic field sensor is also fabricated and employed to characterize the response of Terfenol composite to the magnetic field.

  5. Low-frequency electromagnetic field in a Wigner crystal

    CERN Document Server

    Stupka, Anton

    2016-01-01

    Long-wave low-frequency oscillations are described in a Wigner crystal by generalization of the reverse continuum model for the case of electronic lattice. The internal self-consistent long-wave electromagnetic field is used to describe the collective motions in the system. The eigenvectors and eigenvalues of the obtained system of equations are derived. The velocities of longitudinal and transversal sound waves are found.

  6. Semiconductor Crystal Growth in Static and Rotating Magnetic fields

    Science.gov (United States)

    Volz, Martin

    2004-01-01

    Magnetic fields have been applied during the growth of bulk semiconductor crystals to control the convective flow behavior of the melt. A static magnetic field established Lorentz forces which tend to reduce the convective intensity in the melt. At sufficiently high magnetic field strengths, a boundary layer is established ahead of the solid-liquid interface where mass transport is dominated by diffusion. This can have a significant effect on segregation behavior and can eliminate striations in grown crystals resulting from convective instabilities. Experiments on dilute (Ge:Ga) and solid solution (Ge-Si) semiconductor systems show a transition from a completely mixed convective state to a diffusion-controlled state between 0 and 5 Tesla. In HgCdTe, radial segregation approached the diffusion limited regime and the curvature of the solid-liquid interface was reduced by a factor of 3 during growth in magnetic fields in excess of 0.5 Tesla. Convection can also be controlled during growth at reduced gravitational levels. However, the direction of the residual steady-state acceleration vector can compromise this effect if it cannot be controlled. A magnetic field in reduced gravity can suppress disturbances caused by residual transverse accelerations and by random non-steady accelerations. Indeed, a joint program between NASA and the NHMFL resulted in the construction of a prototype spaceflight magnet for crystal growth applications. An alternative to the suppression of convection by static magnetic fields and reduced gravity is the imposition of controlled steady flow generated by rotating magnetic fields (RMF)'s. The potential benefits of an RMF include homogenization of the melt temperature and concentration distribution, and control of the solid-liquid interface shape. Adjusting the strength and frequency of the applied magnetic field allows tailoring of the resultant flow field. A limitation of RMF's is that they introduce deleterious instabilities above a

  7. Order by virtual crystal field fluctuations in pyrochlore XY antiferromagnets

    Science.gov (United States)

    Rau, Jeffrey G.; Petit, Sylvain; Gingras, Michel J. P.

    2016-05-01

    Conclusive evidence of order by disorder is scarce in real materials. Perhaps one of the strongest cases presented has been for the pyrochlore XY antiferromagnet Er2Ti2O7 , with the ground state selection proceeding by order by disorder induced through the effects of quantum fluctuations. This identification assumes the smallness of the effect of virtual crystal field fluctuations that could provide an alternative route to picking the ground state. Here we show that this order by virtual crystal field fluctuations is not only significant, but competitive with the effects of quantum fluctuations. Further, we argue that higher-multipolar interactions that are generically present in rare-earth magnets can dramatically enhance this effect. From a simplified bilinear-biquadratic model of these multipolar interactions, we show how the virtual crystal field fluctuations manifest in Er2Ti2O7 using a combination of strong-coupling perturbation theory and the random-phase approximation. We find that the experimentally observed ψ2 state is indeed selected and the experimentally measured excitation gap can be reproduced when the bilinear and biquadratic couplings are comparable while maintaining agreement with the entire experimental spin-wave excitation spectrum. Finally, we comment on possible tests of this scenario and discuss implications for other order-by-disorder candidates in rare-earth magnets.

  8. Introduction to Phase-Field Model and Its Applications in the Fields of Crystal Growth and Planetary Science

    Science.gov (United States)

    Miura, Hitoshi; Yokoyama, Etsuro; Tsukamoto, Katsuo

    2010-07-01

    The growth of crystal induces a change of ambient environment (temperature, concentration, etc.), and the environmental change gives some feedback to the growth of crystal. The interaction between the crystal growth and ambient environment is important to be taken into consideration, also in the crystallization process of cosmic crystals observed in chondritic meteorites. In this lecture, we will introduce the phase-field simulation, which is one of the powerful numerical methods to treat the crystal growth and diffusion fields (temperature, concentration, etc.) simultaneously. Participants can experience some phase-field simulations on their own laptop by using a newly developed Java program, which will be distributed at the school.

  9. The structural phase transition and loss of magnetic moments in NpO2: ab initio approach to the crystal and mean field

    OpenAIRE

    Nikolaev, A. V.; Michel, K.H.

    2002-01-01

    We discuss the triple-$\\vec{q}^X$ structures for the ordered cubic phase of NpO$_2$, which are $Pn{\\bar 3}m$ and $Pa{\\bar 3}$. A special care should be taken to discriminate between these two cases. We analyze the relevant structure-factor amplitudes and the effect of domains on resonant X-ray scattering experiments. We formulate the technique of multipole expansion of the Coulomb interaction and use it to study the crystal electric field and mean field for a number of neptunium many electron...

  10. Phase-field-crystal model for fcc ordering.

    Science.gov (United States)

    Wu, Kuo-An; Adland, Ari; Karma, Alain

    2010-06-01

    We develop and analyze a two-mode phase-field-crystal model to describe fcc ordering. The model is formulated by coupling two different sets of crystal density waves corresponding to and reciprocal lattice vectors, which are chosen to form triads so as to produce a simple free-energy landscape with coexistence of crystal and liquid phases. The feasibility of the approach is demonstrated with numerical examples of polycrystalline and (111) twin growth. We use a two-mode amplitude expansion to characterize analytically the free-energy landscape of the model, identifying parameter ranges where fcc is stable or metastable with respect to bcc. In addition, we derive analytical expressions for the elastic constants for both fcc and bcc. Those expressions show that a nonvanishing amplitude of [200] density waves is essential to obtain mechanically stable fcc crystals with a nonvanishing tetragonal shear modulus (C11-C12)/2. We determine the model parameters for specific materials by fitting the peak liquid structure factor properties and solid-density wave amplitudes following the approach developed for bcc [K.-A. Wu and A. Karma, Phys. Rev. B 76, 184107 (2007)]. This procedure yields reasonable predictions of elastic constants for both bcc Fe and fcc Ni using input parameters from molecular dynamics simulations. The application of the model to two-dimensional square lattices is also briefly examined.

  11. Magnetic properties of a three layer superlattice with a crystal field

    Institute of Scientific and Technical Information of China (English)

    Jiang Wei; Li Xin; Wang Xi-Kun; Guo An-Bang

    2006-01-01

    In this paper the magnetic properties of a three layer superlattice with the crystal field on the honeycomb and square lattice have been studied based on the effective-field theory with self-spin correlations and the differential operator technique. The effects of the crystal field and longitudinal magnetic field on the susceptibility are discussed in detail. A number of interesting phenomena, originating from the competition between the longitudinal magnetic field, crystal-field,and coordination number, have been found.

  12. Optical characterization and crystal field calculations for some erbium based solid state materials for laser refrigeration

    Science.gov (United States)

    Hasan, Z.; Qiu, Z.; Johnson, Jackie; Homerick, Uwe

    2009-02-01

    The potential of three erbium based solids hosts has been investigated for laser cooling. Absorption and emission spectra have been studied for the low lying IR transitions of erbium that are relevant to recent reports of cooling using the 4I15/2-4I9/2 and4I15/2 -4I13/2 transitions. Experimental studies have been performed for erbium in three hosts; ZBLAN glass and KPb2Cl5 and Cs2NaYCl6 crystals. In order to estimate the efficiencies of cooling, theoretical calculations have been performed for the cubic Elpasolite (Cs2NaYCl6 ) crystal. These calculations also provide a first principle insight into the cooling efficiency for non-cubic and glassy hosts where such calculations are not possible.

  13. Anisotropic cubic curvature couplings

    CERN Document Server

    Bailey, Quentin G

    2016-01-01

    To complement recent work on tests of spacetime symmetry in gravity, cubic curvature couplings are studied using an effective field theory description of spacetime-symmetry breaking. The associated mass dimension 8 coefficients for Lorentz violation studied do not result in any linearized gravity modifications and instead are revealed in the first nonlinear terms in an expansion of spacetime around a flat background. We consider effects on gravitational radiation through the energy loss of a binary system and we study two-body orbital perturbations using the post-Newtonian metric. Some effects depend on the internal structure of the source and test bodies, thereby breaking the Weak Equivalence Principle for self-gravitating bodies. These coefficients can be measured in solar-system tests, while binary-pulsar systems and short-range gravity tests are particularly sensitive.

  14. Near-field characterization of photonic crystal Y-splitters

    DEFF Research Database (Denmark)

    Volkov, V. S.; Bozhevolnyi, S. I.; Borel, Peter Ingo

    2005-01-01

    -1570 nm. The recorded intensity distribution exhibit highly wavelength (and polarization) dependent intensity variations along the propagation direction, especially around the fork and bend regions. By comparing the SNOM images recorded in and after the PC Y-splitter area, the features of light......A scanning near-field optical microscope (SNOM) is used to directly map the propagation of light in a specially designed 50/50 photonic crystal (PC) Y-splitter fabricated on silicon-on-insulator (SOI) wafers. SNOM images are obtained for TE- and TM-polarized light in the wavelength range 1425...

  15. Charge Penetration Effects in Rare-Earth Crystal Fields.

    Science.gov (United States)

    1982-06-01

    Interactions, 3. Three-Parameter Theory of Crystal Fields, Harry Diamond Laboratories HDL-TR-1673 (June 1975). 2R. M. Sternheimer , Phys. Rev., 84 (1951...R. M. Sternheimer , Phys. Rev., 84 (1951), 244. (3) R. E. Watson and A. J. Freeman, Phys. Rev., 135 (1964), A1209. (4) D. Sengupta and J. 0. Artman...A RARE-EARTH ION INTO THE CHARGE DI! THE RESULTS ARE CAST INTO A FORM REMINISCENT OF THE STERNHEIMER SHIELDING FA( A PRIME NM(R TO THE NTH POWER) TO

  16. A cubic interpolation pipeline for fast computation of 3D deformation fields modeled using B-splines

    Science.gov (United States)

    Castro-Pareja, Carlos R.; Shekhar, Raj

    2006-02-01

    Fast computation of 3D deformation fields is critical to bringing the application of automated elastic image registration algorithms to routine clinical practice. However, it lies beyond the computational power of current microprocessors; therefore requiring implementations using either massively parallel computers or application-specific hardware accelerators. The use of massively parallel computers in a clinical setting is not practical or cost-effective, therefore making the use of hardware accelerators necessary. We present a hardware pipeline that allows accelerating the computation of 3D deformation fields to speeds up to two orders of magnitude faster than software implementations on current workstations and about 64 times faster than other previously reported architectures. The pipeline implements a version of the free-form deformation calculation algorithm, which is optimized to minimize the number of arithmetic operations required to calculate the transformation of a given set of neighboring voxels, thereby achieving an efficient and compact implementation in hardware which allows its use as part of a larger system.

  17. Organic single-crystal light-emitting field-effect transistors

    NARCIS (Netherlands)

    Hotta, Shu; Yamao, Takeshi; Bisri, Satria Zulkarnaen; Takenobu, Taishi; Iwasa, Yoshihiro

    2014-01-01

    Growth and characterisation of single crystals constitute a major field of materials science. In this feature article we overview the characteristics of organic single-crystal light-emitting field-effect transistors (OSCLEFETs). The contents include the single crystal growth of organic semiconductor

  18. 从含锑烟灰中湿法提取立方晶型三氧化二锑%Extraction of Cubic Crystal Antimony Trioxide from Dusts Containing Antimony

    Institute of Scientific and Technical Information of China (English)

    张荣良; 史宝良; 史爱波; 鞠洪博; 姜大伟; 王伟; 颜平

    2011-01-01

    以含锑烟尘为原料,采用HCI浸出-锑粉还原-Na2CO3中和-氨水添加EDTA水解工艺回收立方晶型Sb2O3产品.对回收工艺过程和条件进行了研究.重点探讨了浸出温度、浸出时间、HCI摩尔浓度、浸出液固比对Sb浸出率的影响,以及不同的SbCl3与EDTA摩尔比对产品Sb2O3晶型的影响.结果表明,采用该工艺Sb的浸出率为98.50%,Sb的回收率为90.35%,产品为纯的立方晶型Sb2O3.%With dusts containing antimony as raw material, the cubic crystal antimony trioxide was recovered by the processes including leaching in hydrochloric acid, antimony powder reduction, sodium carbonate-neutralization, and hydrolysis with EDTA as an additive in ammonia.The influences of leaching temperature, leaching time, hydrochloric acid concentrate, and ratio of liquid to solid on the leaching rate of Sb, and the molar ratio of SbCl3 to EDTA on the crystal of the antimony trioxide product were investigated.The results indicated that the leaching rate of Sb was 98.50%, the recovery of Sb was 90.35%, and the purity of product with cubic crystal antimony trioxide was 99.5%.

  19. Atomic orbital-based cubic response theory for one-, two-, and four-component relativistic self-consistent field models

    Science.gov (United States)

    Bast, Radovan; Thorvaldsen, Andreas J.; Ringholm, Magnus; Ruud, Kenneth

    2009-02-01

    We present the first analytic calculations of the second hyperpolarizability in a relativistic framework. The calculations are made possible by our recent developments of a response theory built on a quasienergy formalism, in which the basis set may be both time and perturbation dependent. The approach is formulated for an arbitrary self-consistent field state in the atomic orbital basis. The implementation consists of a stand-alone code that only requires the unperturbed density in the atomic orbital basis as input, as well as a linear response solver by which we can determine the perturbed density matrices to different orders, at each new order solving equations that have the same structure as the linear response equation. Using these features of our formalism, we extend in this paper our approach to the relativistic domain, utilizing both two- and four-component relativistic wave functions. We apply the formalism to the calculation of the electronic and pure vibrational contributions to the second hyperpolarizability tensor for the hydrogen halides. Our results demonstrate that relativistic effects can be substantial for frequency-dependent second hyperpolarizabilities. Due to changes in the pole structure when going to the relativistic domain, the relativistic corrections to the hyperpolarizabilities are not transferable between different optical processes, except for very low frequencies.

  20. Atomic orbital-based cubic response theory for one-, two-, and four-component relativistic self-consistent field models

    Energy Technology Data Exchange (ETDEWEB)

    Bast, Radovan; Thorvaldsen, Andreas J.; Ringholm, Magnus [Centre for Theoretical and Computational Chemistry (CTCC), Department of Chemistry, University of Tromso, N-9037 Tromso (Norway); Ruud, Kenneth [Centre for Theoretical and Computational Chemistry (CTCC), Department of Chemistry, University of Tromso, N-9037 Tromso (Norway)], E-mail: kenneth.ruud@chem.uit.no

    2009-02-17

    We present the first analytic calculations of the second hyperpolarizability in a relativistic framework. The calculations are made possible by our recent developments of a response theory built on a quasienergy formalism, in which the basis set may be both time and perturbation dependent. The approach is formulated for an arbitrary self-consistent field state in the atomic orbital basis. The implementation consists of a stand-alone code that only requires the unperturbed density in the atomic orbital basis as input, as well as a linear response solver by which we can determine the perturbed density matrices to different orders, at each new order solving equations that have the same structure as the linear response equation. Using these features of our formalism, we extend in this paper our approach to the relativistic domain, utilizing both two- and four-component relativistic wave functions. We apply the formalism to the calculation of the electronic and pure vibrational contributions to the second hyperpolarizability tensor for the hydrogen halides. Our results demonstrate that relativistic effects can be substantial for frequency-dependent second hyperpolarizabilities. Due to changes in the pole structure when going to the relativistic domain, the relativistic corrections to the hyperpolarizabilities are not transferable between different optical processes, except for very low frequencies.

  1. Crystal-field theoretical approach to second harmonic generation on antiferromagnetic NiO(001), CoO(001), and FeO(001) surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Ney, O [Department of Physics, Kaiserslautern University of Technology, Box 3049, D-67653 Kaiserslautern (Germany); Trzeciecki, M [Hans Guentner GmbH, Industriestrasse 14, D-82256 Fuerstenfeldbruck (Germany); Huebner, W [Department of Physics, Kaiserslautern University of Technology, Box 3049, D-67653 Kaiserslautern (Germany)

    2005-12-07

    Using an extended Hubbard model, we calculate the many-body states of various transition-metal (TM) ions in the full spherical symmetry, thus accounting for the electronic correlations in TM oxides (TMOs). The influence of the symmetry of the bulk (cubic) crystal and of an (001) surface is described by a ligand-field procedure. The Slater integrals are fitted to gas phase data, EELS experiments, and low-lying states from ab initio theory. We present spectra of second harmonic generation from the bulk states and from the (001) surfaces.

  2. Crystal field excitations of YbMn2Si2

    Science.gov (United States)

    Mole, R. A.; Hofmann, M.; Adroja, D. T.; Moze, O.; Campbell, S. J.

    2013-12-01

    The crystal field excitations of the rare earth intermetallic compound YbMn2Si2 have been measured by inelastic neutron scattering over the temperature range 2.5-50 K. The YbMn2Si2 spectra exhibit three low energy excitations (~3-7 meV) in the antiferromagnetic AFil region above the magnetic phase transition at TN2 = 30(5) K. The crystal field parameters have been determined for YbMn2Si2 in the antiferromagnetic AFil region. A further two inelastic excitations (~9 meV, 17 meV) are observed below TN2=30(5) K, the temperature at which the high temperature antiferromagnetic structure is reported to exhibit doubling of the magnetic cell. Energy level diagrams have been determined for Yb3+ ions in the different sites above (single site) and below the magnetic transition temperature (two sites). The excitation energies for both sites are shown to be temperature independent with the temperature dependences of the transition intensities for the two sites described well by a simple Boltzmann model. The spectra below TN2 cannot be described fully in terms of molecular field models based on either a single Yb3+ site or two Yb3+ sites. This indicates that the magnetic behaviour of YbMn2Si2 is more complicated than previously considered. The inability to account fully for excitations below the magnetic phase transition may be due to an, as yet, unresolved structural transition associated with the magnetic transition.

  3. Crystal field splittings of PrX 2 compounds (X=Pt, Rh, Ir, Ru, Ni) studied by inelastic neutron scattering

    Science.gov (United States)

    Greidanus, F. J. A. M.; De Jongh, L. J.; Huiskamp, W. J.; Furrer, A.; Buschow, K. H. J.

    1983-01-01

    Neutron inelastic scattering experiments have been performed on polycrystalline samples of the cubic Laves phase compounds PrX 2(X=Pt, Rh, Ir, Ni). Measurements in the paramagnetic state yield LLW parameters 0.6< x<1 and W<0. In this region various levels cross at an x value 0.86 and as a consequence the electronic ground state in the paramagnetic regime is either the singlet Γ 1, or the non-magnetic doublet Γ 3. Measurements in the ferromagnetic state support these conclusions. The crystal-field parameters obtained can be used in model calculations of some macroscopic quantities, in particular the specific heat and the spontaneous magnetization. The variation of the x values in the present series of Laves phase compounds evidences the presence of a contribution by conduction electrons to the crystal field.

  4. Hysteresis behaviors of the crystal field diluted general spin-S Ising model

    Science.gov (United States)

    Akıncı, Ümit

    2017-10-01

    Hysteresis characteristics of the crystal field diluted general Spin-S (S > 1) Blume-Capel model have been studied within the effective field approximation. Particular emphasis has been paid on the large negative valued crystal field and low temperature region and it has been demonstrated for this region that, rising dilution of the crystal field results in decreasing number of windowed hysteresis loops. The evolution of the multiple hysteresis loop with the dilution of the crystal field has been investigated and physical mechanism behind this evolution has been given.

  5. The Effects of a Magnetic Field on the Crystallization of a Fluorozirconate Glass

    Science.gov (United States)

    Tucker, Dennis S.; Lapointe, Michael R.; Jia, Zhiyong

    2006-01-01

    An axial magnetic field of 0.1T was applied to ZrF4-BaF2-LaF3-AlF3-NaF (ZBLAN) fibers during heating to the glass crystallization temperature. Scanning electron microscopy and x-ray diffraction were used to identify crystal phases. It was shown that fibers exposed to the magnetic field did not crystallize while fibers not exposed to the field did crystallize. A hypothesis based on magnetic work was proposed to explain the results and tested by measuring the magnetic susceptibilities of the glass and crystal.

  6. Influence of crystals fields on the magnetic form factor of samarium

    NARCIS (Netherlands)

    Wijn, H.W. de; Diepen, A.M. van; Buschow, K.H.J.

    1974-01-01

    It is calculated that crstal fields, with inclusion of mixing of higher multiplets into the ground J = 5/2 state, have a substantial effect on the magnetic form factor of Sm3+. From the neutron diffraction data obtained by Koehler and Moon for the cubic site in Sm metal it follows that the quartet Γ

  7. Experimental investigation and crystal-field modeling of Er{sup 3+} energy levels in GSGG crystal

    Energy Technology Data Exchange (ETDEWEB)

    Gao, J.Y., E-mail: jygao1985@sina.com [Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei 230031 (China); Sun, D.L.; Zhang, Q.L. [Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei 230031 (China); Wang, X.F. [Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei 230031 (China); Graduate School of the Chinese Academy of Sciences, Beijing 100049 (China); Liu, W.P.; Luo, J.Q.; Sun, G.H.; Yin, S.T. [Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei 230031 (China)

    2016-06-25

    The Er{sup 3+}-doped Gd{sub 3}Sc{sub 2}Ga{sub 3}O{sub 12} (Er{sup 3+}:GSGG) single crystal, a excellent medium of the mid-infrared and anti-radiation solid state laser pumped by laser diode, was grown by Czochralski method successfully. The absorption spectra were measured and analyzed in a wider spectral wavelength range of 350–1700 nm at different temperatures of 7.6, 77, 200 and 300 K. The free-ions and crystal-field parameters were fitted to the experimental energy levels with the root mean square deviation of 9.86 cm{sup −1}. According to the crystal-field calculations, 124 degenerate energy levels of Er{sup 3+} in GSGG host crystals were assigned. The fitting results of free-ions and crystal-field parameters were compared with those already reported of Er{sup 3+}:YSGG. The results indicated that the free-ions parameters for Er{sup 3+} in GSGG host are similar to those in YSGG host crystals, and the crystal-field interaction of GSGG is weaker than that of YSGG, which may result in the better laser characterization of Er{sup 3+}:GSGG crystal. - Highlights: • The efficient diode-end-pumped laser crystal Er:GSGG has been grown successfully. • The absorption spectra of Er:GSGG have been measured in range of 350–1700 nm. • The fitting result is very well for the root mean square deviation is 9.86 cm{sup −1}. • The 124 levels of Er:GSGG have been assigned from the crystal-field calculations.

  8. Spin-1 Blume-Capel model with longitudinal random crystal and transverse magnetic fields:A mean-field approach

    Institute of Scientific and Technical Information of China (English)

    Erhan Albayrak

    2013-01-01

    The spin-1 Blume-Capel model with transverse Ω and longitudinal external magnetic fields h,in addition to a longitudinal random crystal field D,is studied in the mean-field approximation.It is assumed that the crystal field is either turned on with probability p or turned off with probability 1-p on the sites of a square lattice.Phase diagrams are then calculated on the reduced temperature crystal field planes for given values of γ =-Ω/J and p at zero h.Thus,the effect of changing γ and p are illustrated on the phase diagrams in great detail and interesting results are observed.

  9. Reductive renormalization of the phase-field crystal equation.

    Science.gov (United States)

    Oono, Y; Shiwa, Y

    2012-12-01

    It has been known for some time that singular perturbation and reductive perturbation can be unified from the renormalization-group theoretical point of view: Reductive extraction of space-time global behavior is the essence of singular perturbation methods. Reductive renormalization was proposed to make this unification practically accessible; actually, this reductive perturbation is far simpler than most reduction methods, such as the rather standard scaling expansion. However, a rather cryptic exposition of the method seems to have been the cause of some trouble. Here, an explicit demonstration of the consistency of the reductive renormalization-group procedure is given for partial differentiation equations (of a certain type, including time-evolution semigroup type equations). Then, the procedure is applied to the reduction of a phase-field crystal equation to illustrate the streamlined reduction method. We conjecture that if the original system is structurally stable, the reductive renormalization-group result and that of the original equation are diffeomorphic.

  10. Raman spectrum of plutonium dioxide: Vibrational and crystal field modes

    Science.gov (United States)

    Naji, M.; Magnani, N.; Bonales, L. J.; Mastromarino, S.; Colle, J.-Y.; Cobos, J.; Manara, D.

    2017-03-01

    The Raman spectrum of plutonium dioxide is studied both experimentally and theoretically. Particular attention has been devoted to the identification of high-energy modes at 2110 and 2620 c m-1 , whose attribution has so far been controversial. The temperature dependence of both modes suggests an electronic origin for them. Original crystal field (CF) calculations reported in this work show that these two modes can be respectively assigned to the Γ1→Γ5 and Γ1→Γ3 CF transitions within the I54 manifold. These two modes, together with the only vibrational line foreseen by the group theory for the F m -3 m Pu O2 symmetry—the T2 gPu -O stretching mode observed at 478 c m-1 —can thus be used as a Raman fingerprint of fcc plutonium dioxide.

  11. The Strength of PIN-PMN-PT Single Crystals under Bending with a Longitudinal Electric Field

    Science.gov (United States)

    2011-04-06

    The strength of PIN– PMN – PT single crystals under bending with a longitudinal electric field This article has been downloaded from IOPscience. Please...COVERED 00-00-2011 to 00-00-2011 4. TITLE AND SUBTITLE The Strength Of PIN- PMN - PT Single Crystals Under Bending With A Longitudinal Electric Field... PMN ? PT ) single crystals was measured using a four point bending apparatus with a longitudinal electric field applied to the bar during bending. The

  12. An Example of Body-Centered Cubic Crystal Structure: The Atomium in Brussels as an Educative Tool for Introductory Materials Chemistry

    Science.gov (United States)

    Pinto, Gabriel

    2012-01-01

    When students are introduced to the ways in which atoms are arranged in crystal structures, transposing the textbook illustrations into three-dimensional structures is difficult for some of them. To facilitate this transition, this article describes an approach to the study of the structure of solids through a well-known monument, the Atomium in…

  13. An Example of Body-Centered Cubic Crystal Structure: The Atomium in Brussels as an Educative Tool for Introductory Materials Chemistry

    Science.gov (United States)

    Pinto, Gabriel

    2012-01-01

    When students are introduced to the ways in which atoms are arranged in crystal structures, transposing the textbook illustrations into three-dimensional structures is difficult for some of them. To facilitate this transition, this article describes an approach to the study of the structure of solids through a well-known monument, the Atomium in…

  14. Cubic Subalgebras and Cubic Closed Ideals of B-algebras

    Directory of Open Access Journals (Sweden)

    Tapan Senapati

    2015-06-01

    Full Text Available In this paper, the concept of cubic set to subalgebras, ideals and closed ideals of B-algebras are introduced. Relations among cubic subalgebras with cubic ideals and cubic closed ideals of B-algebras investigated. The homomorphic image and inverse image of cubic subalgebras, ideals are studied and some related properties are investigated. Also, the product of cubic B-algebras are investigated.

  15. Vector magneto-optical sensor based on transparent magnetic films with cubic crystallographic symmetry

    Science.gov (United States)

    Rogachev, A. E.; Vetoshko, P. M.; Gusev, N. A.; Kozhaev, M. A.; Prokopov, A. R.; Popov, V. V.; Dodonov, D. V.; Shumilov, A. G.; Shaposhnikov, A. N.; Berzhansky, V. N.; Zvezdin, A. K.; Belotelov, V. I.

    2016-10-01

    The concept of vector magneto-optical magnetometry is proposed and experimentally demonstrated. The key element of the vector magnetometer is a transparent high Faraday activity magnetic film with a cubic crystal lattice. Magnetocrystalline anisotropy of the film leads to the three dimensional trajectory of the film magnetization when the magnetization is rotated by the control magnetic field. It makes the magnetization sensitive to all three components of the external magnetic field. This field can be found from the harmonic composition of the Faraday rotation dependence on the azimuth angle of the control magnetic field. The demonstrated vector magnetometer is promising for mapping and visualization of ultra small magnetic fields.

  16. An Overview of Hardware for Protein Crystallization in a Magnetic Field

    Directory of Open Access Journals (Sweden)

    Er-Kai Yan

    2016-11-01

    Full Text Available Protein crystallization under a magnetic field is an interesting research topic because a magnetic field may provide a special environment to acquire improved quality protein crystals. Because high-quality protein crystals are very useful in high-resolution structure determination using diffraction techniques (X-ray, neutron, and electron diffraction, research using magnetic fields in protein crystallization has attracted substantial interest; some studies have been performed in the past two decades. In this research field, the hardware is especially essential for successful studies because the environment is special and the design and utilization of the research apparatus in such an environment requires special considerations related to the magnetic field. This paper reviews the hardware for protein crystallization (including the magnet systems and the apparatus designed for use in a magnetic field and progress in this area. Future prospects in this field will also be discussed.

  17. Phase-field modeling on morphological landscape of isotactic polystyrene single crystals.

    Science.gov (United States)

    Xu, Haijun; Matkar, Rushikesh; Kyu, Thein

    2005-07-01

    Spatio-temporal growth of isotactic polystyrene single crystals during isothermal crystallization has been investigated theoretically based on the phase field model by solving temporal evolution of a nonconserved phase order parameter coupled with a heat conduction equation. In the description of the total free energy, an asymmetric double-well local free energy density has been adopted to represent the metastable melt and the stable solid crystal. Unlike the small molecule systems, polymer crystallization rarely reaches thermodynamic equilibrium; most polymer crystals are kinetically stabilized in some metastable states. To capture various metastable polymer crystals, the phase field crystal order parameter at the solidification potential has been treated to be supercooling dependent such that it can assume an intermediate value between zero (melt) and unity (perfect crystal), reflecting imperfect polycrystalline nature of polymer crystals. Two-dimensional simulations exhibit various single crystal morphologies of isotactic polystyrene crystals such as faceted hexagonal patterns transforming to nonfaceted snowflakes with increasing supercooling. Of particular interest is that heat liberation from the crystallizing front influences the curvature of the crystal-melt interface, leading to directional growth of lamellar tips and side branches. The landscape of these morphological textures has been established as a function of anisotropy of surface energy and supercooling. With increasing supercooling and decreasing anisotropy, the hexagonal single crystal transforms to the dense lamellar branching morphology in conformity with the experimental findings.

  18. Description of hard-sphere crystals and crystal-fluid interfaces: a comparison between density functional approaches and a phase-field crystal model.

    Science.gov (United States)

    Oettel, M; Dorosz, S; Berghoff, M; Nestler, B; Schilling, T

    2012-08-01

    In materials science the phase-field crystal approach has become popular to model crystallization processes. Phase-field crystal models are in essence Landau-Ginzburg-type models, which should be derivable from the underlying microscopic description of the system in question. We present a study on classical density functional theory in three stages of approximation leading to a specific phase-field crystal model, and we discuss the limits of applicability of the models that result from these approximations. As a test system we have chosen the three-dimensional suspension of monodisperse hard spheres. The levels of density functional theory that we discuss are fundamental measure theory, a second-order Taylor expansion thereof, and a minimal phase-field crystal model. We have computed coexistence densities, vacancy concentrations in the crystalline phase, interfacial tensions, and interfacial order parameter profiles, and we compare these quantities to simulation results. We also suggest a procedure to fit the free parameters of the phase-field crystal model. Thereby it turns out that the order parameter of the phase-field crystal model is more consistent with a smeared density field (shifted and rescaled) than with the shifted and rescaled density itself. In brief, we conclude that fundamental measure theory is very accurate and can serve as a benchmark for the other theories. Taylor expansion strongly affects free energies, surface tensions, and vacancy concentrations. Furthermore it is phenomenologically misleading to interpret the phase-field crystal model as stemming directly from Taylor-expanded density functional theory.

  19. The g-value of Er3 doped unfilled skutterudite CoSb3 (Th) reveals the existence of an additional sixth order term in the crystal field Hamiltonian

    Science.gov (United States)

    Vargas, J. M.; Garcia, F. A.; Rettori, C.; Garcia, D. J.; Sales, B.; Schlottmann, P.; Oseroff, S. B.

    2009-10-01

    Electron spin resonance (ESR) experiments have been carried out in single crystals of the unfilled skutterudite CoSb3 doped with Er ions. The X- (9.5 GHz) and Q- (34.4 GHz) band spectra obtained at low temperature (4-20 K) shown a temperature independent g-value of 6.21(5). This g-value can only be explained with the addition of a second sixth order B6t(O62-O66) term to the usual cubic crystal field Hamiltonian. The ESR of Er show the typical temperature dependence of the line-shape and line-width expected for insulating host.

  20. Cubic Curves, Finite Geometry and Cryptography

    CERN Document Server

    Bruen, A A; Wehlau, D L

    2011-01-01

    Some geometry on non-singular cubic curves, mainly over finite fields, is surveyed. Such a curve has 9,3,1 or 0 points of inflexion, and cubic curves are classified accordingly. The group structure and the possible numbers of rational points are also surveyed. A possible strengthening of the security of elliptic curve cryptography is proposed using a `shared secret' related to the group law. Cubic curves are also used in a new way to construct sets of points having various combinatorial and geometric properties that are of particular interest in finite Desarguesian planes.

  1. Generalized Vaidya spacetime for cubic gravity

    CERN Document Server

    Ruan, Shan-Ming

    2015-01-01

    We present a kind of generalized Vaidya solutions of a new cubic gravity in five dimensions whose field equations in spherically spacetime are always second order like the Lovelock gravity. We also study the thermodynamics of its apparent horizon and get its entropy expression and generalized Misner-Sharp energy. Finally we present the first law and second law hold in this gravity. Although all the results are analogue to those in Lovelock gravity, we in fact introduce the contribution of new cubic term in five dimensions where cubic Lovelock term is just zero.

  2. Crystal Fields in Dilute Rare-Earth Metals Obtained from Magnetization Measurements on Dilute Rare-Earth Alloys

    DEFF Research Database (Denmark)

    Touborg, P.; Høg, J.

    1974-01-01

    Crystal field parameters of Tb, Dy, and Er in Sc, Y, and Lu are summarized. These parameters are obtained from magnetization measurements on dilute single crystals, and successfully checked by a number of different methods. The crystal field parameters vary unpredictably with the rare-earth solute....... B40, B60, and B66 are similar in Y and Lu. Crystal field parameters for the pure metals Tb, Dy, and Er are estimated from the crystal fields in Y and Lu....

  3. SOLIDIFICATION OF NICKEL-BASED SINGLE CRYSTAL SUPERALLOY BY ELECTRIC FIELD

    Institute of Scientific and Technical Information of China (English)

    Y.S. Yang; X.H. Feng; G.F. Cheng; Y.J. Li; Z.Q. Hu

    2005-01-01

    The crystal growth of a nickel-based single crystal superalloy DD3 was researched via controlled directional solidification under the action of a DC electric field. The cellular or dendrite spacing of the single crystal superalloy is refined and microsegregation of alloying elements Al,Ti, Mo and W, is reduced by the electric field. The electric field decreases the interface stability and reduces the critical growth rate of the cellular-dendritic translation because of Thomson effect and Joule heating. The precipitation of the γ' phase is more uniform and the size of the γ'phase is smaller with the electric field than that without the electric field.

  4. Estimation of the Birefringence Change in Crystals Induced by Gravitation Field

    OpenAIRE

    Vlokh R.; Kostyrko M.

    2007-01-01

    The effect of gravitation field of spherically symmetric mass on the birefringent properties of crystals has been analysed. It has been shown that the gravitation field with spherical symmetry can lead to a change of birefringence in anisotropic media.

  5. Single-crystal organic field-effect transistors based on dibenzo-tetrathiafulvalene

    NARCIS (Netherlands)

    Mas-Torrent, M.; Hadley, P.; Bromley, S.T.; Crivillers, N.; Veciana, J.; Rovira, C.

    2004-01-01

    We report on the fabrication and characterization of field-effect transistors based on single crystals of the organic semiconductor dibenzo-tetrathiafulvalene (DB-TTF). We demonstrate that it is possible to prepare very-good-quality DB-TTF crystals from solution. These devices show high field-effect

  6. Method to map individual electromagnetic field components inside a photonic crystal

    NARCIS (Netherlands)

    Denis, T.; Reijnders, B.; Lee, J.H.H.; van der Slot, Petrus J.M.; Vos, Willem L.; Boller, Klaus J.

    2012-01-01

    We present a method to map the absolute electromagnetic field strength inside photonic crystals. We apply the method to map the dominant electric field component Ez of a two-dimensional photonic crystal slab at microwave frequencies. The slab is placed between two mirrors to select Bloch standing

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

    NARCIS (Netherlands)

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

    2010-01-01

    The experimental temperature dependence (T = 2-300 K) of single crystal bulk and site susceptibilities of rare earth titanate pyrochlores R2Ti2O7 (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 s

  8. Crystal fields at light rare-earth ions in Y and Lu

    DEFF Research Database (Denmark)

    Touborg, P.; Nevald, Rolf; Johansson, Torben

    1978-01-01

    Crystal-field parameters have been deduced for the light rare-earth solutes Ce, Pr, and Nd in Y or Lu hosts from measurements of the paramagnetic susceptibilities. In the analysis all multiplets in the lowest LS term were included. For a given host, crystal-field parameters divided by Stevens fac...

  9. Effect of axial magnetic field on the shape of copper ribbon crystal grown by Czochralski method

    OpenAIRE

    Shen, Zhe; Zhong, Yunbo; Dong, Licheng; FAN, Lijun; Wang, Huai; Li, Chuanjun; Ren, Weili; Lei, Zuosheng; Ren, Zhongming

    2015-01-01

    International audience; During the process of growing ribbon crystal by Czochralski method, Turbulent convection in copper melt was effectively suppressed by applying an axial magnetic field (magnetic induction B≤57mT). The changes of thermal fluctuation and flow field were measured and modeled. With the magnetic field increased gradually (from 0 to 57mT), the shape of ribbon crystal became regularly wider. We concluded that the axial magnetic field could promote to form a suitable temperatur...

  10. Phonon and crystal field excitations in geometrically frustrated rare earth titanates

    Science.gov (United States)

    Lummen, T. T. A.; Handayani, I. P.; Donker, M. C.; Fausti, D.; Dhalenne, G.; Berthet, P.; Revcolevschi, A.; van Loosdrecht, P. H. M.

    2008-06-01

    The phonon and crystal field excitations in several rare earth titanate pyrochlores are investigated. Magnetic measurements on single crystals of Gd2Ti2O7 , Tb2Ti2O7 , Dy2Ti2O7 , and Ho2Ti2O7 are used for characterization, while Raman spectroscopy and terahertz time domain spectroscopy are employed to probe the excitations in the materials. The lattice excitations are found to be analogous across the compounds over the whole temperature range investigated (295-4 K). The resulting full phononic characterization of the R2Ti2O7 pyrochlore structure is then used to identify crystal field excitations observed in the materials. Several crystal field excitations have been observed in Tb2Ti2O7 in Raman spectroscopy, among which all of the previously reported excitations. The presence of additional crystal field excitations, however, suggests the presence of two inequivalent Tb3+ sites in the low-temperature structure. Furthermore, the crystal field level at approximately 13cm-1 is found to be both Raman and dipole active, indicating broken inversion symmetry in the system and thus undermining its current symmetry interpretation. In addition, evidence is found for a significant crystal field-phonon coupling in Tb2Ti2O7 . The additional crystal field information on Tb2Ti2O7 adds to the recent discussion on the low temperature symmetry of this system and may serve to improve its theoretical understanding.

  11. Thermodynamical Properties of Spin-3/2 Ising Model in a Longitudinal Random Field with Crystal Field

    Institute of Scientific and Technical Information of China (English)

    LIANGYa-Qiu; WEIGuo-Zhu; ZHANGHong; SONGGuo-Li

    2004-01-01

    A theoretical study of a spin-3/2 Ising model in a longitudinal random field with crystal field is studied by using of the effective-field theory with correlations. The phase diagrams and the behavior of the tricritical point are investigated numerically for the honeycomb lattice when the random field is bimodal. In particular, the specific heat and the internal energy are examined in detail for the system with a crystal-field constant in the critical region where the ground-state configuration may change from the spin-3/2 state to the spin-1/2 state. We find many interesting phenomena in the system.

  12. Thermodynamical Properties of Spin-3/2 Ising Model in a Longitudinal Random Field with Crystal Field

    Institute of Scientific and Technical Information of China (English)

    LIANG Ya-Qiu; WEI Guo-Zhu; ZHANG Hong; SONG Guo-Li

    2004-01-01

    A theoretical study of a spin-3/2 Ising model in a longitudinal random field with crystal field is studiedby using of the effective-field theory with correlations. The phase diagrams and the behavior of the tricritical point areinvestigated numerically for the honeycomb lattice when the randorm field is bimodal. In particular, the specific heatand the internal energy are examined in detail for the system with a crystal-field constant in the critical region wherethe ground-state configuration may change from the spin-3/2 state to the spin-1/2 state. We find many interestingphenomena in the system.

  13. The anisotropic Ising superantiferromagnet on a simple cubic lattice in the presence of a magnetic field: Effective-field theory analysis

    Energy Technology Data Exchange (ETDEWEB)

    Ricardo de Sousa, J. [Universidade Federal do Amazonas, Departamento de Física, 3000, Japiim, 69077-000 Manaus, AM (Brazil); National Institute of Science and Technology for Complex Systems, 3000, Japiim, 69077-000 Manaus, AM (Brazil); Neto, Minos A., E-mail: minos@pq.cnpq.br [Universidade Federal do Amazonas, Departamento de Física, 3000, Japiim, 69077-000 Manaus, AM (Brazil); Padilha, Igor T.; Salmon, Octavio D.R.; Viana, J. Roberto [Universidade Federal do Amazonas, Departamento de Física, 3000, Japiim, 69077-000 Manaus, AM (Brazil)

    2013-12-15

    We have studied the anisotropic three-dimensional nearest-neighbor Ising model with competitive interactions in an uniform longitudinal magnetic field H. The model consists of ferromagnetic interactions J{sub z}=λ{sub 2}J{sub x} in the x(z) direction and antiferromagnetic interactions J{sub y}=λ{sub 1}J{sub x} in the y direction (Ising superantiferromagnet). For the particular case λ{sub 1}=λ{sub 2}=1 we obtain the phase diagram in the H−T plane, using the framework of the differential operator technique in the effective-field theory with finite cluster of N=4 spins (EFT-4). It was observed first- and second-order transitions in the low and high temperature limits, respectively, with the presence of a tricritical point and a reentrant behavior is observed at low temperature. The critical curve in the classical approach is also obtained and the results are compared.

  14. Einsteinian cubic gravity

    Science.gov (United States)

    Bueno, Pablo; Cano, Pablo A.

    2016-11-01

    We drastically simplify the problem of linearizing a general higher-order theory of gravity. We reduce it to the evaluation of its Lagrangian on a particular Riemann tensor depending on two parameters, and the computation of two derivatives with respect to one of those parameters. We use our method to construct a D -dimensional cubic theory of gravity which satisfies the following properties: (1) it shares the spectrum of Einstein gravity, i.e., it only propagates a transverse and massless graviton on a maximally symmetric background; (2) it is defined in the same way in general dimensions; (3) it is neither trivial nor topological in four dimensions. Up to cubic order in curvature, the only previously known theories satisfying the first two requirements are the Lovelock ones. We show that, up to cubic order, there exists only one additional theory satisfying requirements (1) and (2). Interestingly, this theory is, along with Einstein gravity, the only one which also satisfies (3).

  15. Superhard BC(3) in cubic diamond structure.

    Science.gov (United States)

    Zhang, Miao; Liu, Hanyu; Li, Quan; Gao, Bo; Wang, Yanchao; Li, Hongdong; Chen, Changfeng; Ma, Yanming

    2015-01-01

    We solve the crystal structure of recently synthesized cubic BC(3) using an unbiased swarm structure search, which identifies a highly symmetric BC(3) phase in the cubic diamond structure (d-BC(3)) that contains a distinct B-B bonding network along the body diagonals of a large 64-atom unit cell. Simulated x-ray diffraction and Raman peaks of d-BC(3) are in excellent agreement with experimental data. Calculated stress-strain relations of d-BC(3) demonstrate its intrinsic superhard nature and reveal intriguing sequential bond-breaking modes that produce superior ductility and extended elasticity, which are unique among superhard solids. The present results establish the first boron carbide in the cubic diamond structure with remarkable properties, and these new findings also provide insights for exploring other covalent solids with complex bonding configurations.

  16. Transparent polycrystalline cubic silicon nitride

    Science.gov (United States)

    Nishiyama, Norimasa; Ishikawa, Ryo; Ohfuji, Hiroaki; Marquardt, Hauke; Kurnosov, Alexander; Taniguchi, Takashi; Kim, Byung-Nam; Yoshida, Hidehiro; Masuno, Atsunobu; Bednarcik, Jozef; Kulik, Eleonora; Ikuhara, Yuichi; Wakai, Fumihiro; Irifune, Tetsuo

    2017-01-01

    Glasses and single crystals have traditionally been used as optical windows. Recently, there has been a high demand for harder and tougher optical windows that are able to endure severe conditions. Transparent polycrystalline ceramics can fulfill this demand because of their superior mechanical properties. It is known that polycrystalline ceramics with a spinel structure in compositions of MgAl2O4 and aluminum oxynitride (γ-AlON) show high optical transparency. Here we report the synthesis of the hardest transparent spinel ceramic, i.e. polycrystalline cubic silicon nitride (c-Si3N4). This material shows an intrinsic optical transparency over a wide range of wavelengths below its band-gap energy (258 nm) and is categorized as one of the third hardest materials next to diamond and cubic boron nitride (cBN). Since the high temperature metastability of c-Si3N4 in air is superior to those of diamond and cBN, the transparent c-Si3N4 ceramic can potentially be used as a window under extremely severe conditions. PMID:28303948

  17. TL and PL studies on cubic fluoroperovskite single crystal (KMgF{sub 3}: Eu{sup 2+}, Ce{sup 3+})

    Energy Technology Data Exchange (ETDEWEB)

    Daniel, D. Joseph, E-mail: josephd@ssn.edu.in; Ramasamy, P. [Centre for Crystal Growth, SSN College of Engineering, Kalavakkam, Tamilnadu-603110 (India); Madhusoodanan, U.; Annalakshmi, O. [Radiological Safety Division, Indira Gandhi Centre for Atomic Research, Kalpakkam, Tamilnadu - 603102 (India)

    2014-04-24

    The perovskite-like KMgF{sub 3} polycrystalline compounds were synthesized by standard solid state reaction technique. Phase purity of the synthesized compounds was analyzed by powder X-ray diffraction technique. Single crystals of (0.2 mol% of EuF{sub 3} and CeF{sub 3}) Co-doped KMgF{sub 3} have been grown from melt by using a vertical Bridgman-Stockbarger method. Thermoluminescence (TL) characteristics of KMgF{sub 3} samples doped with Eu{sub 2+} and Ce{sub 3+} have been studied after β-ray irradiation. At ambient conditions the photoluminescence spectra consisted of sharp line peaked of Eu{sub 2+} at 360 nm attributed to the f → f transition ({sup 6}P{sub 7/2}→{sup 8}S{sub 7/2}) could only be observed due to the energy transfer from Ce{sub 3+} to Eu{sub 2+}.

  18. The Symmetry of Optical Field in Photonic Crystal Fibre with Trigonal Symmetry

    Directory of Open Access Journals (Sweden)

    Ivan Turek

    2006-01-01

    Full Text Available Some photographs of intensity of optical field of a photonic crystal fibre are presented in the contribution. Presented photographs document that the symmetry of photonic crystal creating the cladding of fibre is manifested in the symmetry of distribution of the optical field intensity. In case when more modes are excited in the fibre the symmetry of the generated field can be different as the symmetry of the eventual modes. How the symmetry may be changed is illustrated by amodel example.

  19. Method of synthesizing cubic system boron nitride

    Energy Technology Data Exchange (ETDEWEB)

    Yuzu, S.; Sumiya, H.; Degawa, J.

    1987-10-13

    A method is described for synthetically growing cubic system boron nitride crystals by using boron nitride sources, solvents for dissolving the boron nitride sources, and seed crystals under conditions of ultra-high pressure and high temperature for maintaining the cubic system boron nitride stable. The method comprises the following steps: preparing a synthesizing vessel having at least two chambers, arrayed in order in the synthesizing vessel so as to be heated according to a temperature gradient; placing the solvents having different eutectic temperatures in each chamber with respect to the boron nitride sources according to the temperature gradient; placing the boron nitride source in contact with a portion of each of the solvents heated at a relatively higher temperature and placing at least a seed crystal in a portion of each of the solvents heated at a relatively lower temperature; and growing at least one cubic system boron nitride crystal in each of the solvents in the chambers by heating the synthesizing vessel for establishing the temperature gradient while maintaining conditions of ultra-high pressure and high temperature.

  20. Influence of magnetic field on the growth and properties of calcium tartrate crystals

    Energy Technology Data Exchange (ETDEWEB)

    Saban, K.V. E-mail: sabanvarkey@rediffmail.com; Jini, T.; Varghese, G

    2003-10-01

    The growth of calcium tartrate crystals in hydrosilica gel, in the presence of static magnetic fields has been investigated. Crystal formation at the free surface of the gel was studied under fields of strength up to 3 T. Weak magnetic fields created by permanent ferrite magnets were used to study the crystal formation in the gel column over long duration. The XRD spectra of the samples grown under magnetic fields exhibit increase in d values of most of the diffraction peaks and noticeable change in the intensity of reflections from certain planes. Application of the field resulted in the appearance of two additional absorption peaks in the IR spectrum of the material. Samples grown under fields of strength 1 and 3 T show paramagnetism up to 6 and 7 T, respectively, of the probing field strength. For stronger probing fields, the samples start exhibiting diamagnetism.

  1. Probing the sheath electric field with a crystal lattice by using thermophoresis in dusty plasma

    CERN Document Server

    Land, Victor; Matthews, Lorin; Hyde, Truell

    2010-01-01

    A two-dimensional dust crystal levitated in the sheath of a modified Gaseous Electronics Conference (GEC) reference cell is manipulated by heating or cooling the lower electrode. The dust charge is obtained by measuring global characteristics of the levitated crystal obtained from top-view pictures. From the force balance, the electric field in the sheath is reconstructed. From the Bohm criterion, we conclude that the dust crystal is levitated mainly above and just below the classical Bohm point.

  2. Patterning technology for solution-processed organic crystal field-effect transistors

    OpenAIRE

    Yun Li; Huabin Sun; Yi Shi; Kazuhito Tsukagoshi

    2014-01-01

    Organic field-effect transistors (OFETs) are fundamental building blocks for various state-of-the-art electronic devices. Solution-processed organic crystals are appreciable materials for these applications because they facilitate large-scale, low-cost fabrication of devices with high performance. Patterning organic crystal transistors into well-defined geometric features is necessary to develop these crystals into practical semiconductors. This review provides an update on recent development...

  3. Characterizing configurable transmission modes in plasma photonic crystals using scanning field mapping

    Science.gov (United States)

    Wang, Benjamin; Cappelli, Mark

    2016-10-01

    A fully tunable plasma photonic crystal is used to control the propagation of free space electromagnetic waves in the S to X band of the microwave spectrum. A structured array of discharge plasma tubes are arranged in a square crystal lattice with the individual plasma dielectric constant tuned through variation in the plasma density. Microwave field-mapping is used to characterize the transmitted electromagnetic fields of the tunable device operating in waveguiding and bending modes. These modes are obtained by introducing appropriate line defects in the photonic crystal structure by controlling the activity of individual plasma tubes. Comparisons are made of the measured fields to those simulated using commercially-available software.

  4. 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.

  5. The effect of magnetic field on the shape of etch pits of paracetamol crystals

    Energy Technology Data Exchange (ETDEWEB)

    Ivashchenko, V.E. [Kemerovo State University, Novosibirsk (Russian Federation); Research and Educational Center, Novosibirsk State University (Russian Federation); Boldyrev, V.V.; Shakhtshneider, T.P. [Institute of Solid State Chemistry and Mechanochemistry, RAS, Novosibirsk (Russian Federation); Zakharov, Yu.A.; Krasheninin, V.I. [Kemerovo State University, Novosibirsk (Russian Federation); Ermakov, A.E. [Institute of Physics of Metals, Ural Branch of RAS, Ekaterinburg (Russian Federation)

    2002-04-01

    In the present study we investigate the effect of magnetic field on the shape of etch pits of the crystals of p-hydroxyacetanilide (paracetamol), which is widely used in pharmacy as antipyretic, antiphlogistic medicine. It was discovered that the magnetic field (H=0.5 T, {tau}=15 min) changes the morphology of etch pits and shifts dislocations in paracetamol crystal. Activation energy of the changes induced by the action of the magnetic field was determined to be 63 kJ/mol, which is comparable with the energy of hydrogen bonds in crystal lattice. (orig.)

  6. Anisotropy of a cubic ferromagnet at criticality

    Science.gov (United States)

    Kudlis, A.; Sokolov, A. I.

    2016-10-01

    Critical fluctuations change the effective anisotropy of cubic ferromagnet near the Curie point. If the crystal undergoes phase transition into orthorhombic phase and the initial anisotropy is not too strong, reduced anisotropy of nonlinear susceptibility acquires at Tc the universal value δ4*=2/v* 3 (u*+v*) where u* and v* are coordinates of the cubic fixed point on the flow diagram of renormalization group equations. In the paper, the critical value of the reduced anisotropy is estimated within the pseudo-ɛ expansion approach. The six-loop pseudo-ɛ expansions for u*, v*, and δ4* are derived for the arbitrary spin dimensionality n . For cubic crystals (n =3 ) higher-order coefficients of the pseudo-ɛ expansions obtained turn out to be so small that use of simple Padé approximants yields reliable numerical results. Padé resummation of the pseudo-ɛ series for u*, v*, and δ4* leads to the estimate δ4*=0.079 ±0.006 , indicating that detection of the anisotropic critical behavior of cubic ferromagnets in physical and computer experiments is certainly possible.

  7. Anisotropic magnetic properties and crystal electric field studies on CePd2Ge2 single crystal.

    Science.gov (United States)

    Maurya, Arvind; Kulkarni, R; Dhar, S K; Thamizhavel, A

    2013-10-30

    The anisotropic magnetic properties of the antiferromagnetic compound CePd2Ge2, crystallizing in the tetragonal crystal structure have been investigated in detail on a single crystal grown by the Czochralski method. From the electrical transport, magnetization and heat capacity data, the Néel temperature is confirmed to be 5.1 K. Anisotropic behaviour of the magnetization and resistivity is observed along the two principal crystallographic directions-namely, [100] and [001]. The isothermal magnetization measured in the magnetically ordered state at 2 K exhibits a spin reorientation at 13.5 T for the field applied along the [100] direction, whereas the magnetization is linear along the [001] direction attaining a value of 0.94 μ(B)/Ce at 14 T. The reduced value of the magnetization is attributed to the crystalline electric field (CEF) effects. A sharp jump in the specific heat at the magnetic ordering temperature is observed. After subtracting the phononic contribution, the jump in the heat capacity amounts to 12.5 J K(-1)mol(-1) which is the expected value for a spin ½ system. From the CEF analysis of the magnetization data the excited crystal field split energy levels were estimated to be at 120 K and 230 K respectively, which quantitatively explains the observed Schottky anomaly in the heat capacity. A magnetic phase diagram has been constructed based on the field dependence of magnetic susceptibility and the heat capacity data.

  8. Guarded Cubical Type Theory

    DEFF Research Database (Denmark)

    Birkedal, Lars; Bizjak, Aleš; Clouston, Ranald;

    2016-01-01

    This paper improves the treatment of equality in guarded dependent type theory (GDTT), by combining it with cubical type theory (CTT). GDTT is an extensional type theory with guarded recursive types, which are useful for building models of program logics, and for programming and reasoning with co...

  9. Growth, structure, spectral properties and crystal-field analysis of monoclinic Nd:YNbO4 single crystal

    Science.gov (United States)

    Ding, Shoujun; Zhang, Qingli; Gao, Jinyun; Liu, Wenpeng; Luo, Jianqiao; Sun, Dunlu; Sun, Guihua; Wang, Xiaofei

    2016-12-01

    A Nd:YNbO4 single crystal was successfully grown by Czochralski (Cz) method, its structural and spectroscopic properties were investigated. The X-ray rocking curve of the (010) diffraction face of Nd:YNbO4 crystal was measured, the full width at half maximum (FWHM) of this diffraction peak is 0.05°, which indicates a high crystalline quality of the as-grown crystal. Its lattice parameters, atomic coordinates and so on were obtained by Rietvield refinement to X-ray diffraction data. According to the Archimedes drainage method, the crystal density of Nd:YNbO4 is calculated to be 5.4 g/cm3. The Mohr‧s hardness value along (010) face was determined to be 6.0. The transmission spectrum along (010) face at room temperature was recorded and the excitation and emission spectra at 8 K were measured. Photoluminescence peaks of Nd:YNbO4 were assigned, and the crystal-field splitting of Nd3+ in YNbO4 was obtained. The fluorescence lifetime of the 4F3/2→4I11/2 transition of Nd3+ in YNbO4 is fitted to be 152 μs These spectroscopic and energy splitting data give an important reference for the research of laser property of Nd:YNbO4 crystal.

  10. Growth, structure, spectral properties and crystal-field analysis of monoclinic Nd:YNbO{sub 4} single crystal

    Energy Technology Data Exchange (ETDEWEB)

    Ding, Shoujun [Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Key Laboratory of Photonic Devices and Materials, Hefei 230031 (China); University of Science and Technology of China, Hefei 230026 (China); Zhang, Qingli, E-mail: zql@aiofm.ac.cn [Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Key Laboratory of Photonic Devices and Materials, Hefei 230031 (China); Gao, Jinyun; Liu, Wenpeng; Luo, Jianqiao; Sun, Dunlu; Sun, Guihua; Wang, Xiaofei [Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Key Laboratory of Photonic Devices and Materials, Hefei 230031 (China)

    2016-12-15

    A Nd:YNbO{sub 4} single crystal was successfully grown by Czochralski (Cz) method, its structural and spectroscopic properties were investigated. The X-ray rocking curve of the (010) diffraction face of Nd:YNbO{sub 4} crystal was measured, the full width at half maximum (FWHM) of this diffraction peak is 0.05°, which indicates a high crystalline quality of the as-grown crystal. Its lattice parameters, atomic coordinates and so on were obtained by Rietvield refinement to X-ray diffraction data. According to the Archimedes drainage method, the crystal density of Nd:YNbO{sub 4} is calculated to be 5.4 g/cm{sup 3}. The Mohr′s hardness value along (010) face was determined to be 6.0. The transmission spectrum along (010) face at room temperature was recorded and the excitation and emission spectra at 8 K were measured. Photoluminescence peaks of Nd:YNbO{sub 4} were assigned, and the crystal-field splitting of Nd{sup 3+} in YNbO{sub 4} was obtained. The fluorescence lifetime of the {sup 4}F{sub 3/2}→{sup 4}I{sub 11/2} transition of Nd{sup 3+} in YNbO{sub 4} is fitted to be 152 μs These spectroscopic and energy splitting data give an important reference for the research of laser property of Nd:YNbO{sub 4} crystal.

  11. Influence of Superconductivity on Crystal Electric Field Transitions in La1-xTbxAl2

    DEFF Research Database (Denmark)

    Feile, R.; Loewenhaupt, M.; Kjems, Jørgen

    1981-01-01

    Inelastic neutron scattering from the crystal electric field transitions in La1-xTbxAl2 single crystals has revealed an abrupt increase in the lifetimes of these transitions when the system becomes superconducting. An increase in the integrated intensities is also observed. The lifetime effects...

  12. Spectroscopy of Charge Carriers and Traps in Field-Doped Single Crystal Organic Semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Xiaoyang [Columbia Univ., New York, NY (United States); Frisbie, Daniel [Univ. of Minnesota, Minneapolis, MN (United States)

    2017-03-31

    The proposed research aims to achieve quantitative, molecular level understanding of charge carriers and traps in field-doped crystalline organic semiconductors via in situ linear and nonlinear optical spectroscopy, in conjunction with transport measurements and molecular/crystal engineering.

  13. Mixed spin Ising model with four-spin interaction and random crystal field

    Energy Technology Data Exchange (ETDEWEB)

    Benayad, N., E-mail: n.benayad@fsac.ac.ma [Groupe de Mecanique Statistique, Laboratoire de physique theorique et appliquee, Faculte des sciences-Aien Chock, Universite Hassan II-Casablanca, B.P 5366 Maarif, Casablanca 20100 (Morocco); Laboratoire de physique des hautes energies et de la matiere condensee, Faculte des sciences-Aien Chock, Universite Hassan II-Casablanca, B.P 5366 Maarif, Casablanca 20100 (Morocco); Ghliyem, M. [Groupe de Mecanique Statistique, Laboratoire de physique theorique et appliquee, Faculte des sciences-Aien Chock, Universite Hassan II-Casablanca, B.P 5366 Maarif, Casablanca 20100 (Morocco); Laboratoire de physique des hautes energies et de la matiere condensee, Faculte des sciences-Aien Chock, Universite Hassan II-Casablanca, B.P 5366 Maarif, Casablanca 20100 (Morocco)

    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.

  14. Imposed Orientation of Dye Molecules by Liquid Crystals and an Electric Field.

    Science.gov (United States)

    Sadlej-Sosnowska, Nina

    1980-01-01

    Describes experiments using dye solutions in liquid crystals in which polar molecules are oriented in an electrical field and devices are constructed to change their color in response to an electric signal. (CS)

  15. Analytical solutions for anisotropic time-dependent heat equations with Robin boundary condition for cubic-shaped solid-state laser crystals.

    Science.gov (United States)

    Sabaeian, Mohammad

    2012-10-20

    The problem of finding analytical solutions for time-dependent or time-independent heat equations, especially for solid-state laser media, has required a lot of work in the field of thermal effects. However, to calculate the temperature distributions analytically, researchers often have to make some approximations or employ complex methods. In this work, we present full analytical solutions for anisotropic time-dependent heat equations in the Cartesian coordinates with various source terms corresponding to various pumping schemes. Moreover, the most general boundary condition of Robin (or impedance boundary condition), corresponding to the convection cooling mechanism, was applied. This general condition can be easily switched to constant temperature and thermal insulation as special cases. To this end, we first proposed a general approach to solving time-dependent heat equations with an arbitrary heat source. We then applied our approach to explore the temperature distribution for three cases: steady-state pumping or long transient, single-shot pumping or short transient, and repetitively pulsed pumping. Our results show the possibility of an easier and more accurate approach to analytical calculations of the thermal dispersion, thermal stresses (strains), thermal bending, thermal phase shift, and other thermal effects.

  16. Calculation of electrostatic fields in ionic crystals by a Bertaut method

    NARCIS (Netherlands)

    Weenk, J.W.; Harwig, H.A.

    1975-01-01

    A method to calculate the electrostatic field strength in ionic crystals is evaluated according to a model by Bertaut. Formulae for the self potential and the field strength at an ion site are derived. The practical use is demonstrated by calculations of field vectors in TiO2 (rutile, anatase, brook

  17. Low field investigations of single crystal Bi(2212): DC magnetization

    Energy Technology Data Exchange (ETDEWEB)

    Shaw, G.; Murphy, S.D.; Bhagat, S.M. (Center for Superconductivity Research and Dept. of Physics and Astronomy, Univ. of Maryland, College Park (USA))

    1989-12-01

    DC Magnetization measurements on micaceous Bi(2212) single crystals suggest that; 1. for T< or approx.25 K the material is a bulk Superconductor (SC), 2. as T is increased, the interlayer coupling weakens, until for T> or approx.55 K the lamina become independent. (orig.).

  18. Study of Fluid Flow Control in Protein Crystallization using Strong Magnetic Fields

    Science.gov (United States)

    Ramachandran, Narayanan; Leslie, Fred; Ciszak, Ewa

    2002-01-01

    An important component in biotechnology, particularly in the area of protein engineering and rational drug design is the knowledge of the precise three-dimensional molecular structure of proteins. The quality of structural information obtained from X-ray diffraction methods is directly dependent on the degree of perfection of the protein crystals. As a consequence, the growth of high quality macromolecular crystals for diffraction analyses has been the central focus for biochemists, biologists, and bioengineers. Macromolecular crystals are obtained from solutions that contain the crystallizing species in equilibrium with higher aggregates, ions, precipitants, other possible phases of the protein, foreign particles, the walls of the container, and a likely host of other impurities. By changing transport modes in general, i.e., reduction of convection and sedimentation, as is achieved in "microgravity", researchers have been able to dramatically affect the movement and distribution of macromolecules in the fluid, and thus their transport, formation of crystal nuclei, and adsorption to the crystal surface. While a limited number of high quality crystals from space flights have been obtained, as the recent National Research Council (NRC) review of the NASA microgravity crystallization program pointed out, the scientific approach and research in crystallization of proteins has been mainly empirical yielding inconclusive results. We postulate that we can reduce convection in ground-based experiments and we can understand the different aspects of convection control through the use of strong magnetic fields and field gradients. Whether this limited convection in a magnetic field will provide the environment for the growth of high quality crystals is still a matter of conjecture that our research will address. The approach exploits the variation of fluid magnetic susceptibility with concentration for this purpose and the convective damping is realized by appropriately

  19. Guarded Cubical Type Theory

    DEFF Research Database (Denmark)

    Birkedal, Lars; Bizjak, Aleš; Clouston, Ranald;

    2016-01-01

    This paper improves the treatment of equality in guarded dependent type theory (GDTT), by combining it with cubical type theory (CTT). GDTT is an extensional type theory with guarded recursive types, which are useful for building models of program logics, and for programming and reasoning...... with coinductive types. We wish to implement GDTT with decidable type-checking, while still supporting non-trivial equality proofs that reason about the extensions of guarded recursive constructions. CTT is a variation of Martin-L\\"of type theory in which the identity type is replaced by abstract paths between...... terms. CTT provides a computational interpretation of functional extensionality, is conjectured to have decidable type checking, and has an implemented type-checker. Our new type theory, called guarded cubical type theory, provides a computational interpretation of extensionality for guarded recursive...

  20. Guarded Cubical Type Theory

    DEFF Research Database (Denmark)

    Birkedal, Lars; Bizjak, Aleš; Clouston, Ranald;

    2016-01-01

    This paper improves the treatment of equality in guarded dependent type theory (GDTT), by combining it with cubical type theory (CTT). GDTT is an extensional type theory with guarded recursive types, which are useful for building models of program logics, and for programming and reasoning...... with coinductive types. We wish to implement GDTT with decidable type checking, while still supporting non-trivial equality proofs that reason about the extensions of guarded recursive constructions. CTT is a variation of Martin-L\\"of type theory in which the identity type is replaced by abstract paths between...... terms. CTT provides a computational interpretation of functional extensionality, enjoys canonicity for the natural numbers type, and is conjectured to support decidable type-checking. Our new type theory, guarded cubical type theory (GCTT), provides a computational interpretation of extensionality...

  1. Crystal Fields in Er0.2Y0.98 Studied by Neutron Scattering

    DEFF Research Database (Denmark)

    Rathmann, Ole; Als-Nielsen, Jens Aage; Bak, Poul Erik;

    1974-01-01

    The splitting of the J=15/2 multiplet of Er in an hcp crystal field has been determined by inelastic neutron scattering from a single crystal of Er0.02Y0.98. Least-squares fits to the spectra gave crystal-field parameters B20=-0.34±0.04, B40=(0.7±0.2)×10-3, B60=(0.21±0.02)×10-4, and B66=(-0.30±0....

  2. Phase field crystal study of deformation and plasticity in nanocrystalline materials.

    Science.gov (United States)

    Stefanovic, Peter; Haataja, Mikko; Provatas, Nikolas

    2009-10-01

    We introduce a modified phase field crystal (MPFC) technique that self-consistently incorporates rapid strain relaxation alongside the usual plastic deformation and multiple crystal orientations featured by the traditional phase field crystal (PFC) technique. Our MPFC formalism can be used to study a host of important phase transformation phenomena in material processing that require rapid strain relaxation. We apply the MPFC model to study elastic and plastic deformations in nanocrystalline materials, focusing on the "reverse" Hall-Petch effect. Finally, we introduce a multigrid algorithm for efficient numerical simulations of the MPFC model.

  3. Models of Mass Transport During Microgravity Crystal Growth of Alloyed Semiconductors in a Magnetic Field

    Science.gov (United States)

    Ma, Nancy

    2003-01-01

    Alloyed semiconductor crystals, such as germanium-silicon (GeSi) and various II-VI alloyed crystals, are extremely important for optoelectronic devices. Currently, high-quality crystals of GeSi and of II-VI alloys can be grown by epitaxial processes, but the time required to grow a certain amount of single crystal is roughly 1,000 times longer than the time required for Bridgman growth from a melt. Recent rapid advances in optoelectronics have led to a great demand for more and larger crystals with fewer dislocations and other microdefects and with more uniform and controllable compositions. Currently, alloyed crystals grown by bulk methods have unacceptable levels of segregation in the composition of the crystal. Alloyed crystals are being grown by the Bridgman process in space in order to develop successful bulk-growth methods, with the hope that the technology will be equally successful on earth. Unfortunately some crystals grown in space still have unacceptable segregation, for example, due to residual accelerations. The application of a weak magnetic field during crystal growth in space may eliminate the undesirable segregation. Understanding and improving the bulk growth of alloyed semiconductors in microgravity is critically important. The purpose of this grant to to develop models of the unsteady species transport during the bulk growth of alloyed semiconductor crystals in the presence of a magnetic field in microgravity. The research supports experiments being conducted in the High Magnetic Field Solidification Facility at Marshall Space Flight Center (MSFC) and future experiments on the International Space Station.

  4. Dependence of magnetization on crystal fields and exchange interactions in magnetite

    Energy Technology Data Exchange (ETDEWEB)

    Ouaissa, Mohamed, E-mail: m.ouaissa@yahoo.fr [Laboratoire de Génie Physique et Environnement, Faculté des Sciences, Université Ibn Tofail, Campus Universitaire BP 133, Kénitra 14000 (Morocco); Benyoussef, Abdelilah [Laboratory of Magnetism and Physics of High Energy, Faculty of Science, Mohammed V-Agdal University, Rabat (Morocco); Abo, Gavin S. [Department of Electrical and Computer Engineering and MINT Center, The University of Alabama, Tuscaloosa, AL 35487 (United States); Ouaissa, Samia; Hafid, Mustapha [Laboratoire de Génie Physique et Environnement, Faculté des Sciences, Université Ibn Tofail, Campus Universitaire BP 133, Kénitra 14000 (Morocco); Belaiche, Mohammed [Laboratoire de Magnétisme, Matériaux Magnétiques, Microonde et Céramique, Ecole Normale Supérieure, Université Mohammed V-Agdal, B.P. 9235, Océan, Rabat (Morocco)

    2015-11-15

    In this work, we study the magnetization of magnetite (Fe{sub 3}O{sub 4}) with different exchange interactions and crystal fields using variational method based on the Bogoliubov inequality for the Gibbs free energy within the mean field theory. The magnetic behavior was investigated in the absence and presence of crystal fields. The investigations also revealed that the transition temperature depends on the crystal fields of the octahedral and tetrahedral sites. Magnetite exhibits ferrimagnetic phase with second order transition to paramagnetic phase at 850 K. This result is confirmed using the mean field theory within the Heisenberg model. Important factors that can affect the magnetic behavior of the system are exchange interactions and crystal field. Indeed, a new magnetic behavior was observed depending on these parameters. A first order phase transition from ferrimagnetic to ferromagnetic was found at low temperature, and a second order transition from ferromagnetic to paramagnetic was observed at high temperature. - Highlights: • Magnetization of magnetite versus temperature was studied by mean field theory. • The critical temperature of magnetite (Fe{sub 3}O{sub 4}) was approximately obtained. • Effect of sublattice crystal fields on the magnetization of Fe{sub 3}O{sub 4} was investigated.

  5. Influence of Acoustic Field Structure on Polarization Characteristics of Acousto-optic Interaction in Crystals

    Science.gov (United States)

    Muromets, A. V.; Trushin, A. S.

    Influence of acoustic field structure on polarization characteristics of acousto-optic interaction is investigated. It is shown that inhomogeneity of acoustic field and mechanism of ultrasound excitation causes changes in values of acousto-optic figure of merit for ordinary and extraordinary light beams in comparison with theoretic values. The theoretic values were derived under assumption that acoustic wave is homogeneous. Experimental analysis was carried out in acousto-optic cell based on lithium niobate crystal where the acoustic wave propagates at the angle 13 degrees to Z axis of the crystal. We used three different methods of ultrasound generation in the crystal: by means of external piezotransducer, by interdigital transducer and by two sets of electrodes placed on top of the crystal surface. In the latter case, the first pair of the electrodes was directed along X crystal axis, while the second pair of the electrodes was directed orthogonally to X crystal axis and the direction of ultrasound. Obtained values for diffraction efficiencies for ordinary and extraordinary polarized optical beams were qualitatively different which may be caused by spatial inhomogeneity of the generated acoustic waves in the crystal. Structure of acoustic field generated by these sets of electrodes was examined by laser probing. We performed the analysis of the acoustic field intensity using acousto-optic method. A relation of diffraction efficiencies for ordinary and extraordinary light waves was measured during each iteration of the laser probing.

  6. Ground-State Phase Diagram of Transverse Spin-2 Ising Model with Longitudinal Crystal-Field

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The transverse spin-2 Ising ferromagnetic model with a longitudinal crystal-field is studied within the mean-field theory based on Bogoliubov inequality for the Gibbs free energy. The ground-state phase diagram and the tricritical point are obtained in the transverse field Ω/z J-longitudinal crystal D/zJ field plane. We find that there are the first order-order phase transitions in a very smallrange of D/zJ besides the usual first order-disorder phase transitions and the second order-disorder phase transitions.

  7. Two-dimensional cubic convolution.

    Science.gov (United States)

    Reichenbach, Stephen E; Geng, Frank

    2003-01-01

    The paper develops two-dimensional (2D), nonseparable, piecewise cubic convolution (PCC) for image interpolation. Traditionally, PCC has been implemented based on a one-dimensional (1D) derivation with a separable generalization to two dimensions. However, typical scenes and imaging systems are not separable, so the traditional approach is suboptimal. We develop a closed-form derivation for a two-parameter, 2D PCC kernel with support [-2,2] x [-2,2] that is constrained for continuity, smoothness, symmetry, and flat-field response. Our analyses, using several image models, including Markov random fields, demonstrate that the 2D PCC yields small improvements in interpolation fidelity over the traditional, separable approach. The constraints on the derivation can be relaxed to provide greater flexibility and performance.

  8. Hidden local symmetry of Eu{sup 3+} in xenotime-like crystals revealed by high magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Han, Yibo; Ma, Zongwei; Zhang, Junpei; Wang, Junfeng; Du, Guihuan; Xia, Zhengcai; Han, Junbo, E-mail: junbo.han@mail.hust.edu.cn; Li, Liang [Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology, Wuhan 430074 (China); Yu, Xuefeng [Department of Physics, Key Laboratory of Artificial Micro- and Nanostructures of Ministry of Education and School of Physics and Technology, Wuhan University, Wuhan 430072 (China)

    2015-02-07

    The excellent optical properties of europium-doped crystals in visible and near infrared wavelength regions enable them to have broad applications in optoelectronics, laser crystals and sensing devices. The local site crystal fields can affect the intensities and peak positions of the photo-emission lines strongly, but they are usually difficult to be clarified due to magnetically degenerate 4f electronic levels coupling with the crystal fields. Here, we provide an effective way to explore the hidden local symmetry of the Eu{sup 3+} sites in different hosts by taking photoluminescence measurements under pulsed high magnetic fields up to 46 T. The zero-field photoluminescence peaks split further at high magnetic fields when the Zeeman splitting energy is comparable to or larger than that of the crystal field induced zero-field splitting. In particular, a magnetic field induced crossover of the local crystal fields has been observed in the GdVO{sub 4}:Eu{sup 3+} crystal, which resulted from the alignment of Gd{sup 3+} magnetic moment in high magnetic fields; and a hexagonally symmetric local crystal fields was observed in the YPO{sub 4} nanocrystals at the Eu{sup 3+} sites characterized by the special axial and rhombic crystal field terms. These distinct Zeeman splitting behaviors uncover the crystal fields-related local symmetry of luminescent Eu{sup 3+} centers in different hosts or magnetic environments, which are significant for their applications in optics and optoelectronics.

  9. Change in crystal structure and physical properties of the Multiferroics YMnO3 single crystals by Strong gravitational field

    Science.gov (United States)

    Tokuda, M.; Weijian, M.; Hayami, S.; Yoshiasa, A.; Mashimo, T.

    2017-04-01

    Many researchers have studied the multiferroicity of the hexagonal RMnO3 (R: rare-earth element) for both applications and fundamental studies. To investigate the relationship between the structure and physical properties of materials, some people apply the chemical pressure effect. The procedure of chemical pressure effect involves substituting rare-earth elements for ones which have a different ionic radius. Mashimo et al. have developed a high-temperature ultracentrifuge apparatus that can generate extended duration strong gravitational field in excess of 106 G under a wide range of temperatures (up to 500°C). Strong gravitational fields directly act on each atom as a different body force. This can cause the change in crystal structure. Thus, we subjected YMnO3 single crystal to strong gravity experiments (0.78×106 G, 400°C, 2 h) and investigated the resulting changes in the crystal structure and physical properties of the gravity sample. The single crystal four-circle X-ray diffraction measurements revealed the change in the nearest neighboring Mn-Mn and M-O bond distances. The temperature dependence of magnetic susceptibility by SQUID showed the change in the magnetic anisotropy of gravity sample.

  10. Composite Fermion Theory for the High Field Wigner Crystal State

    Science.gov (United States)

    Narevich, Romanas; Murthy, Ganpathy; Fertig, Herbert

    2001-03-01

    The low filling fraction Quantum Hall Effect is reexamined using the hamiltonian composite fermion theory developed by Shankar and Murthy(R. Shankar and G. Murthy, Phys. Rev. Lett. 79), 4437 (1997). We address the experiment by Jiang et. al.(H. W. Jiang et. al., Phys. Rev. B 44), 8107 (1991) where the insulating phase surrounding the ν=1/5 quantum liquid was observed and its activation energies (gaps) measured. Previous studies either found gaps that were off by few orders of magnitude (Hartree-Fock calculations of the electronic Wigner crystal(D. Yoshioka and H. Fukuyama, J. Phys. Soc. Japan 47), 394 (1979)) or were unable to calculate them because of the computational complexity (Monte-Carlo studies of the correlated crystal(H. Yi and H. A. Fertig, Phys. Rev. B 58), 4019 (1998)). We use the Hartree-Fock approximation for the periodic density state of composite fermions and find gaps that have a correct order of magnitude and reproduce the experimental dependence on the filling factor. We also report the results of the shear modulus calculation relevant for the collective pinning of the crystal.

  11. High-Field Magnetization in PrCo2Si2 Single Crystals

    Science.gov (United States)

    Shigeoka, Toru; Fujii, Hironobu; Yonenobu, Kenji; Sugiyama, Kiyohiro; Date, Muneyuki

    1989-02-01

    Magnetic properties of PrCo2Si2 single crystals have been studied by measurements of high-field magnetization, magnetic susceptibility and electrical resistivity. Anomalous behaviors in the resistivity appear at three successive magnetic phase transition temperatures of 9, 17 and 30K. The magnetic susceptibility is highly anisotropic and is analyzed using the single-ion Hamiltonian, including the crystal-field and molecular-field effects. The thermal variations of the susceptibilities can be well reproduced by the crystal-field parameters estimated from the point-charge model. Metamagnetic transitions with four steps are observable in the c-axis magnetization process up to 300 kOe. The magnetization process is discussed in terms of the incommensurate exchange field model in the Ising system proposed by Date.

  12. Phase diagrams of mixtures of a polymer and a cholesteric liquid crystal under an external field.

    Science.gov (United States)

    Matsuyama, Akihiko

    2014-11-14

    We present a mean field theory to describe phase behaviors in mixtures of a polymer and a cholesteric liquid crystal under an external magnetic or electric field. Taking into account a chiral coupling between a polymer and a liquid crystal under the external field, we examine twist-untwist phase transitions and phase separations in the mixtures. It is found that a cholesteric-nematic phase transition can be induced by not only the external field but also concentration and temperature. Depending on the strength of the external field, we predict cholesteric-paranematic (Ch+pN), nematic-paranematic (N+pN), cholesteric-nematic (Ch+N) phase separations, etc., on the temperature-concentration plane. We also discuss mixtures of a non-chiral nematic liquid crystal and a chiral dopant.

  13. Exchange field effect in the crystal field ground state of CeMAl{sub 4}Si{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Kai; Strigari, Fabio; Sundermann, Martin; Severing, Andrea [University of Cologne, Cologne (Germany); Agrestini, Stefano [Max Planck Institute for Chemical Physics of Solids, Dresden (Germany); Bauer, Eric D.; Sarrao, John L.; Thompson, Joe D. [Los Alamos National Laboratory, Los Alamos, NM (United States); Otero, Edwige [Synchrotron Soleil, Gif-sur-Yvette (France); Tanaka, Arata [Hiroshima University, Higashi-Hiroshima (Japan)

    2016-07-01

    The crystal-field ground state wave functions of the tetragonal Kondo lattice materials CeMAl{sub 4}Si{sub 2}(M = Rh, Ir and Pt), as well as the crystal-field splittings, are determined with low temperature linear polarized soft x-ray absorption spectroscopy. Surprisingly, at T < 20 K, which is far below the first excited crystal-field level at 200 K, a change in linear dichroism was observed that cannot be accounted for by population of crystal-field states. Adding an exchange field to the ionic full multiplet calculations below 20 K leads to a splitting to the ground state doublet and modification of J{sub z} admixture, thus accounting for the change in low temperature linear dichroism. The direction of the required exchange field is parallel along c-axis for the antiferromagnetic Rh and Ir compounds, and perpendicular to c-axis for ferromagnetic CePtAl{sub 4}Si{sub 2}.

  14. Magnetic field controlled single crystal growth and surface modification of titanium alloys exposed for biocompatibility

    Science.gov (United States)

    Hermann, Regina; Uhlemann, Margitta; Wendrock, Horst; Gerbeth, Gunter; Büchner, Bernd

    2011-03-01

    The aim of this work is growth and characterisation of Ti55Nb45 (wt%) single crystals by floating-zone single crystal growth of intermetallic compounds using two-phase radio-frequency (RF) electromagnetic heating. Thereby, the process and, in particular, the flow field in the molten zone is influenced by additional magnetic fields. The growth of massive intermetallic single crystals is very often unsuccessful due to an unfavourable solid-liquid interface geometry enclosing concave fringes. It is generally known that the crystallization process stability is enhanced if the crystallization interface is convex. For this, a tailored magnetic two-phase stirrer system has been developed, which enables a controlled influence on the melt ranging from intensive inwards to outwards flows. Since Ti is favourably light, strong and biocompatible, it is one of the few materials that naturally match the requirements for implantation in the human body. Therefore, the magnetic system was applied to crystal growth of Ti alloys. The grown crystals were oriented and cut to cubes with the desired crystallographic orientations [1 0 0] and [1 0 1] normally on a plane. The electron backscatter diffraction (EBSD) technique was applied to clearly determine crystal orientation and to localize grain boundaries. The formation of oxidic nanotubes on Ti surfaces in dependence of the grain orientation was investigated, performed electrochemically by anodic oxidation from fluoride containing electrolyte.

  15. Light field distribution of general function photonic crystals

    CERN Document Server

    Wu, Xiang-Yao; Liu, Xiao-Jing; Zhang, Si-Qi; Wang, Jing; Ba, Nuo; Xiao, Li; Li, Hong

    2012-01-01

    In this paper, We have presented a new general function photonic crystals (GFPCs), which refractive indexes are line functions of space position in two mediums $A$ and $B$, and obtain new results: (1) when the line function of refractive indexes is up or down, the transmissivity can be far larger or smaller than 1. (2) when the refractive indexes function increase or decrease along the direction of incident light, the light intensity should be magnified or weaken, which can be made optical magnifier or attenuator. (3) The GFPCs can be made optical diode when the light positive and negative incident the GFPCs.

  16. Scientists summit at Shanghai in the field of polymer crystallization

    Institute of Scientific and Technical Information of China (English)

    Wenbing HU

    2009-01-01

    @@ From Aug. 12 to 15 at Galaxy Hotel, Shanghai, more than 100 scientists and graduate students from macromolecular phy-sics, engineering and chemistry met together in the Interna-tional Discussion Meeting of Polymer Crystallization (IDMPC). The participants were coming from China, Japan, United States, Germany, England, France, Netherlands, Italy, Korea and Canada. The meeting was initiated by the Ministry of Education of China and European Physical Society, sponsored by the National Natural Science Foundation of China and Donghua University, and organized by the State Key Laboratory for Modification of Chemical Fibers and Chemical Materials.

  17. Magnetic properties of Ce{sup 3+} in Pb{sub 1{minus}x}Ce{sub x}Se: Kondo and crystal-field effect

    Energy Technology Data Exchange (ETDEWEB)

    Gratens, X.; Charar, S.; Averous, M. [Groupe dEtude des Semiconducteurs URA 357, Universite Montpellier II, Place Eugene Bataillon, 34095 Montpellier Cedex 5 (France); Isber, S. [Department of Physic, Concordia University, 1455 de Maisonneuve Boulevard West, Montreal, Quebec, H3G 1M8 (CANADA); Deportes, J. [Laboratoire Louis Neel, Avenue des Martyres, BP 166X, 38042 Grenoble Cedex 9 (France); Golacki, Z. [Institute of Physics, Polish Academy of Sciences, Pl. 02-668, Warsaw (Poland)

    1997-10-01

    Electron paramagnetic resonance (EPR) experiments were performed on a Pb{sub 1{minus}x}Ce{sub x}Se crystal at liquid-helium temperatures and show very clearly that the doublet {Gamma}{sub 7} is the ground state for cerium ions. The cubic symmetry is shown and the effective Land{acute e} factor for the Ce{sup 3+} is determined to be 1.354{plus_minus}0.003. An orbital reduction factor is introduced to explain the g experimental value. High-field magnetization results are in good agreement with the EPR results. The nominal Ce composition in PbSe deduced from saturation of the magnetization, x=0.0405{plus_minus}0.0003, is very closed to the value determined by microprobe analysis (x=0.04). At 1.5 K, an antiferromagnetic interaction between the nearest-neighbor cerium atoms is found, J{sub ex}/k{sub B}={minus}0.715thinspK. The low-field magnetic-susceptibility results show that the magnetic moment of cerium impurities is strongly temperature dependent, explained by the presence of the crystal-field effect and the Kondo effect. {copyright} {ital 1997} {ital The American Physical Society}

  18. Electric-field variations within a nematic-liquid-crystal layer.

    Science.gov (United States)

    Cummings, L J; Mema, E; Cai, C; Kondic, L

    2014-07-01

    A thin layer of nematic liquid crystal (NLC) across which an electric field is applied is a setup of great industrial importance in liquid crystal display devices. There is thus a large literature modeling this situation and related scenarios. A commonly used assumption is that an electric field generated by electrodes at the two bounding surfaces of the layer will produce a field that is uniform: that is, the presence of NLC does not affect the electric field. In this paper, we use calculus of variations to derive the equations coupling the electric potential to the orientation of the NLC's director field, and use a simple one-dimensional model to investigate the limitations of the uniform field assumption in the case of a steady applied field. The extension of the model to the unsteady case is also briefly discussed.

  19. Reorientation of single-wall carbon nanotubes in negative anisotropy liquid crystals by an electric field

    Directory of Open Access Journals (Sweden)

    Amanda García-García

    2016-06-01

    Full Text Available Single-wall carbon nanotubes (SWCNT are anisotropic nanoparticles that can cause modifications in the electrical and electro-optical properties of liquid crystals. The control of the SWCNT concentration, distribution and reorientation in such self-organized fluids allows for the possibility of tuning the liquid crystal properties. The alignment and reorientation of CNTs are studied in a system where the liquid crystal orientation effect has been isolated. Complementary studies including Raman spectroscopy, microscopic inspection and impedance studies were carried out. The results reveal an ordered reorientation of the CNTs induced by an electric field, which does not alter the orientation of the liquid crystal molecules. Moreover, impedance spectroscopy suggests a nonnegligible anchoring force between the CNTs and the liquid crystal molecules.

  20. Excess vibrational modes of a crystal in an external non-affine field

    Indian Academy of Sciences (India)

    SASWATI GANGULY; SURAJIT SENGUPTA

    2017-07-01

    Thermal displacement fluctuations in a crystal may be classified as either “affine” or “non-affine”. While the former couples to external stress with familiar consequences, the response of a crystal when nonaffine displacements are enhanced using the thermodynamically conjugate field, is relatively less studied. We examine this using a simple model of a crystal in two dimensions for which analytical calculations are possible. Enhancing non-affine fluctuations destabilises the crystal. The population of small frequency phonon modesincreases, with the phonon density of states shifting, as a whole, towards zero frequency. Even though the crystal is free of disorder, we observe growing length and time scales. Our results, which may have implications for the glass transition and structural phase transitions in solids, are compared to molecular dynamics simulations. Possibility of experimental verification of these results is also discussed.

  1. Reorientation of single-wall carbon nanotubes in negative anisotropy liquid crystals by an electric field

    Science.gov (United States)

    García-García, Amanda; Vergaz, Ricardo; Algorri, José F; Zito, Gianluigi; Cacace, Teresa; Marino, Antigone; Otón, José M

    2016-01-01

    Summary Single-wall carbon nanotubes (SWCNT) are anisotropic nanoparticles that can cause modifications in the electrical and electro-optical properties of liquid crystals. The control of the SWCNT concentration, distribution and reorientation in such self-organized fluids allows for the possibility of tuning the liquid crystal properties. The alignment and reorientation of CNTs are studied in a system where the liquid crystal orientation effect has been isolated. Complementary studies including Raman spectroscopy, microscopic inspection and impedance studies were carried out. The results reveal an ordered reorientation of the CNTs induced by an electric field, which does not alter the orientation of the liquid crystal molecules. Moreover, impedance spectroscopy suggests a nonnegligible anchoring force between the CNTs and the liquid crystal molecules. PMID:27547599

  2. Tunable defect modes in 2D photonic crystals by means of external magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Soltani Vala, A., E-mail: asoltani@tabrizu.ac.i [Physics Department, University of Tabriz, Tabriz (Iran, Islamic Republic of); Research Institute for Applied Physics and Astronomy, University of Tabriz, Tabriz (Iran, Islamic Republic of); Rezaei, B. [Research Institute for Applied Physics and Astronomy, University of Tabriz, Tabriz (Iran, Islamic Republic of); Kalafi, M. [Physics Department, University of Tabriz, Tabriz (Iran, Islamic Republic of); Research Institute for Applied Physics and Astronomy, University of Tabriz, Tabriz (Iran, Islamic Republic of)

    2010-07-15

    We investigate the tunable defect modes in 2D photonic crystal of silicon rods in air background in which one of the rods is replaced by ferrite material and an external static magnetic field is applied in the ferrite rod direction. Using the supercell method, the dependence of E-polarized defect modes on the magnetic field has been reported.

  3. Spin-orbit qubits of rare-earth-metal ions in axially symmetric crystal fields.

    Science.gov (United States)

    Bertaina, S; Shim, J H; Gambarelli, S; Malkin, B Z; Barbara, B

    2009-11-27

    Contrary to the well-known spin qubits, rare-earth-metal qubits are characterized by a strong influence of crystal field due to large spin-orbit coupling. At low temperature and in the presence of resonance microwaves, it is the magnetic moment of the crystal-field ground state which nutates (for several micros) and the Rabi frequency Omega(R) is anisotropic. Here, we present a study of the variations of Omega(R)(H(0)) with the magnitude and direction of the static magnetic field H(0) for the odd 167Er isotope in a single crystal CaWO(4):Er(3+). The hyperfine interactions split the Omega(R)(H(0)) curve into eight different curves which are fitted numerically and described analytically. These "spin-orbit qubits" should allow detailed studies of decoherence mechanisms which become relevant at high temperature and open new ways for qubit addressing using properly oriented magnetic fields.

  4. Interpolation by two-dimensional cubic convolution

    Science.gov (United States)

    Shi, Jiazheng; Reichenbach, Stephen E.

    2003-08-01

    This paper presents results of image interpolation with an improved method for two-dimensional cubic convolution. Convolution with a piecewise cubic is one of the most popular methods for image reconstruction, but the traditional approach uses a separable two-dimensional convolution kernel that is based on a one-dimensional derivation. The traditional, separable method is sub-optimal for the usual case of non-separable images. The improved method in this paper implements the most general non-separable, two-dimensional, piecewise-cubic interpolator with constraints for symmetry, continuity, and smoothness. The improved method of two-dimensional cubic convolution has three parameters that can be tuned to yield maximal fidelity for specific scene ensembles characterized by autocorrelation or power-spectrum. This paper illustrates examples for several scene models (a circular disk of parametric size, a square pulse with parametric rotation, and a Markov random field with parametric spatial detail) and actual images -- presenting the optimal parameters and the resulting fidelity for each model. In these examples, improved two-dimensional cubic convolution is superior to several other popular small-kernel interpolation methods.

  5. CRACK PROBLEM UNDER SHEAR LOADING IN CUBIC QUASICRYSTAL

    Institute of Scientific and Technical Information of China (English)

    周旺民; 范天佑; 尹姝媛

    2003-01-01

    The axisymmetric elasticity problem of cubic quasicrystal is reduced to a single higher-order partial differential equation by introducing a displacement function. Based on the work, the analytic solutions of elastic field of cubic quasicrystal with a penny-shaped crack under the shear loading are found, and the stress intensity factor and strain energy release rate are determined.

  6. Two Beam Energy Exchange in Hybrid Liquid Crystal Cells with Photorefractive Field Controlled Boundary Conditions (Postprint)

    Science.gov (United States)

    2016-09-12

    AFRL-RX-WP-JA-2017-0209 TWO BEAM ENERGY EXCHANGE IN HYBRID LIQUID CRYSTAL CELLS WITH PHOTOREFRACTIVE FIELD CONTROLLED BOUNDARY...DATES COVERED (From - To) 29 August 2016 Interim 26 October 2015 – 29 July 2016 4. TITLE AND SUBTITLE TWO BEAM ENERGY EXCHANGE IN HYBRID LIQUID... energy gain when two light beams intersect in a hybrid nematic liquid crystal (LC) cell with photorefractive crystalline substrates. A periodic space

  7. Liquid crystal cell design of VGA field sequential color LCoS display

    Science.gov (United States)

    Liu, Yanyan; Geng, Weidong; Dai, Yongping

    2009-07-01

    The design of liquid crystal cell is an important factor to determine the display quality of LCoS display device. The goal of this paper is to gain VGA field sequential color (FSC) LCoS device used for near-to-eye system. The characteristics of optics and electrooptics for the twist nematic liquid crystal material and the material requirements of the FSC LCoS were studied. The LCOS liquid crystal cell optimized by dynamic parameter space method had an uniform reflectivity (about 90%) for the light with wave length from 450nm to 650nm. Both considering the electrooptic response curve of liquid crystal and the relationship between the contrast ratio and pixel size, we determined to use high speed twist nematic liquid crystal working in normally white mode. The liquid crystal cell gap and the pixel size were determined as 2.5um and 12um, respectively. The VGA FSC LCoS device was fabricated with SMIC 0.35um CMOS process and filled with LC-A liquid crystal of Merck in Varitronix. The measurement showed that the response time of liquid crystal from light to dark was 1.8ms and from dark to light was 4.4ms. The contrast ratio is bigger than 50:1. The LCoS displays well.

  8. Semiconductor crystal growth in crossed electric and magnetic fields: Center Director's Discretionary Fund

    Science.gov (United States)

    Mazuruk, K.; Volz, M. P.

    1996-01-01

    A unique growth cell was designed in which crossed electric and magnetic fields could be separately or simultaneously applied during semiconductor crystal growth. A thermocouple was inserted into an InSb melt inside the growth cell to examine the temperature response of the fluid to applied electromagnetic fields. A static magnetic field suppressed time-dependent convection when a destabilizing thermal field was applied. The simultaneous application of electric and magnetic fields resulted in forced convection in the melt. The InSb ingots grown in the cell were polycrystalline. An InGaSb crystal, 0.5 cm in diameter and 23-cm long, was grown without electromagnetic fields applied. The axial composition results indicated that complete mixing in the melt occurred for this large aspect ratio.

  9. Stress Intensity of Antiplane Conjugate Cracks in Cubic Quasicrystal

    Institute of Scientific and Technical Information of China (English)

    ZHANG Lei

    2008-01-01

    Based on the theory of Muskhelishvili, the general solutions for stress and strain of conjugate cracks in cubic quasicrystal are obtained, with which the stress intensity factors of cubic quasicrystal at crack tips and the stress distribution functions of phonon and phason fields are given. The results show that though phason field is coupled with phonon field by constitutive equations, the stress intensity factors are not coupled with any other factors.

  10. Random crystal field effect on the magnetic and hysteresis behaviors of a spin-1 cylindrical nanowire

    Science.gov (United States)

    Zaim, N.; Zaim, A.; Kerouad, M.

    2017-02-01

    In this work, the magnetic behavior of the cylindrical nanowire, consisting of a ferromagnetic core of spin-1 atoms surrounded by a ferromagnetic shell of spin-1 atoms is studied in the presence of a random crystal field interaction. Based on Metropolis algorithm, the Monte Carlo simulation has been used to investigate the effects of the concentration of the random crystal field p, the crystal field D and the shell exchange interaction Js on the phase diagrams and the hysteresis behavior of the system. Some characteristic behaviors have been found, such as the first and second-order phase transitions joined by tricritical point for appropriate values of the system parameters, triple and isolated critical points can be also found. Depending on the Hamiltonian parameters, single, double and para hysteresis regions are explicitly determined.

  11. Crystal fields of Pr sup 3 sup + in LiYF sub 4 under pressure

    CERN Document Server

    Tröster, T

    2003-01-01

    Fluorescence spectra of LiYF sub 4 :Pr sup 3 sup + have been measured between 12,000 and 22,000 cm sup - sup 1 under pressures up to 10 GPa. In total, 25 crystal field energy levels were obtained and used for the determination of free-ion and crystal field parameters under pressure. According to the nephelauxetic effect, the free-ion parameters decrease with increasing pressure. The relative decrease is larger for the Slater than for the spin-orbit coupling parameter. This behavior is consistent with former studies on Pr sup 3 sup + in different crystals and can be explained by a special covalency model. According to an effective D sub 2 sub d symmetry, five crystal field parameters B sub 0 sup 2 (f,f), B sub 0 sup 4 (f,f), B sub 4 sup 4 (f,f), B sub 0 sup 6 (f,f), and B sub 4 sup 6 (f,f) are non-zero. The pressure-induced changes of these parameters have been determined up to the maximum pressure of 10 GPa. In order to improve the calculation of the crystal field levels, the configuration interactions with t...

  12. Zero-field nuclear magnetic resonance of a nematic liquid crystal

    Energy Technology Data Exchange (ETDEWEB)

    Thayer, A.M.; Millar, J.M.; Luzar, M.; Jarvie, T.P.; Pines, A.

    1986-04-10

    The molecular order parameter of CH/sub 2/Cl/sub 2/ in a nematic liquid crystal was measured by using a version of zero-field NMR employing pulsed dc magnetic fields. Spectral frequencies and intensities are shown to reflect the ordering on a molecular and macroscopic scale, respectively. Samples oriented in high magnetic field did not significantly change their state of alignment during the time scale of the field cycle. Zero-field measurements of the order parameter yielded values within experimental error of those measured in high field. A zero-field echo experiment was performed to decrease the effect of residual fields on line width. Dipolar order was created in zero field by using a pulsed dc field analogue of the Jeener-Brokaert experiment. 26 references, 8 figures.

  13. An optimized intermolecular force field for hydrogen-bonded organic molecular crystals using atomic multipole electrostatics

    Science.gov (United States)

    Pyzer-Knapp, Edward O.; Thompson, Hugh P. G.; Day, Graeme M.

    2016-01-01

    We present a re-parameterization of a popular intermolecular force field for describing intermolecular interactions in the organic solid state. Specifically we optimize the performance of the exp-6 force field when used in conjunction with atomic multipole electrostatics. We also parameterize force fields that are optimized for use with multipoles derived from polarized molecular electron densities, to account for induction effects in molecular crystals. Parameterization is performed against a set of 186 experimentally determined, low-temperature crystal structures and 53 measured sublimation enthalpies of hydrogen-bonding organic molecules. The resulting force fields are tested on a validation set of 129 crystal structures and show improved reproduction of the structures and lattice energies of a range of organic molecular crystals compared with the original force field with atomic partial charge electrostatics. Unit-cell dimensions of the validation set are typically reproduced to within 3% with the re-parameterized force fields. Lattice energies, which were all included during parameterization, are systematically underestimated when compared with measured sublimation enthalpies, with mean absolute errors of between 7.4 and 9.0%. PMID:27484370

  14. Crystal field of Dy in non-magnetic metals

    NARCIS (Netherlands)

    Kikkert, Pieter Jan Willem

    1980-01-01

    Many investigations carried out during the last 15 years have demonstrated that the crystalline electric field (CEF) has a great influence on the low temperature magnetic behaviour of rare earth ions in metallic systems (see e.g. /1/) . It is therefore important to understand the origin of the CEF i

  15. Relation between stabilization energy, crystal field coefficient and themagnetic exchange interaction for Tb3+ ion

    Institute of Scientific and Technical Information of China (English)

    ZHANG Xiangmu; MA Wenjuan; CUI Shuwen; WANG Lihua

    2006-01-01

    Based on a single ion model, Hamiltonian of the simplest form about magnetocrystalline anisotropy for Tb3+ ion was solved by using the numerical method. The relation between the stabilization energy, crystal field coefficient B20 and the magnetic exchange interaction was studied as temperature approaches to 0K. The results show that the stabilization energy contributed by Tb3+ is linear with crystal field coefficient B20 approximately, but it is insensitive to the change of magnetic exchange interaction for the strong magnetic substancessuch as TbCo5, Tb2Co17 and Tb2Fe14B compounds.

  16. Organic single crystals or crystalline micro/nanostructures: Preparation and field-effect transistor applications

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Organic single crystals hold great promise for the development of organic semiconductor materials,because they could reveal the intrinsic electronic properties of these materials,providing high-performance electronic devices and probing the structureproperty relationships.This article reviews the preparation methods for organic single crystals or crystalline micro/nanostructures,including vapor phase growth methods and solution-processed methods,and summarizes a few methods employed in the fabrication of field-effect transistors along with dozens of examples concerning both small molecules and polymers with high field-effect performance.

  17. Electric field-induced optical second harmonic generation in nematic liquid crystal 5CB

    Science.gov (United States)

    Torgova, S. I.; Shigorin, V. D.; Maslyanitsyn, I. A.; Todorova, L.; Marinov, Y. G.; Hadjichristov, G. B.; Petrov, A. G.

    2014-12-01

    Electric field-induced second harmonic generation (EFISH) was studied for the liquid crystal 4-cyano-4'-pentylbiphenyl (5CB) (a nematic phase material at room temperature). The intensity of coherent SHG from 5CB cells upon DC electric field was measured for various initial orientations of the liquid crystal. The dependence of the SHG intensity on the pump beam incidence angle was obtained in transmission geometry using sample rotation method. The experimental results (the registered light intensity in the output SHG interference patterns) were theoretically modelled and analyzed.

  18. Crystal field and magnetism with Wannier functions:rare-earth doped aluminum garnets

    Institute of Scientific and Technical Information of China (English)

    Eva Mihóková; Pavel Novák; Valentin V. Laguta

    2015-01-01

    Using the recently developed method we calculated the crystal field parameters in yttrium and lutetium aluminum garnets doped with seven trivalent Kramers rare-earth ions. We then inserted calculated parameters into the atomic-like Hamiltonian taking into account the electron-electron, spin-orbit and Zeeman interactions and determined the multiplet splitting by the crystal field as well as magneticĝ tensors. We compared calculated results with available experimental data. Very good agreement with the spectro-scopic data and qualitative agreement with experimentalĝ tensors was found.

  19. A single-gap transflective liquid crystal driven by fringe and vertical electric fields

    Energy Technology Data Exchange (ETDEWEB)

    Lim, Young Jin; Chin, Mi Hyung; Kim, Jin Ho; Her, Jung Hwa; Lee, Seung Hee [Polymer BIN Fusion Research Center, Department of Polymer Nano-Science and Technology, Chonbuk National University, Chonju, Chonbuk 561-756 (Korea, Republic of); Jin, Hyun Suk; Kim, Byeong Koo, E-mail: lsh1@chonbuk.ac.k [Mobile Product Development Department, LG Display Co., Ltd., Gumi, Gyungbuk 730-350 (Korea, Republic of)

    2009-07-21

    A single-gap transflective liquid-crystal display driven by a fringe electric field in the transmissive (T) region and a vertical electric field in the reflective (R) region was designed. In the device, a homogeneously aligned liquid crystal (LC) rotates almost in plane by a fringe field in the T-region whereas the LC tilts upwards by a vertical field in the R-region. A high surface pre-tilt angle of the LC in the R-region is achieved through polymerization of an UV curable reactive mesogen monomer at the surfaces and thus the effective cell retardation in the R-region becomes half of that in the T-region. Consequently, a transflective display driven by a vertical and a fringe electric field with a single cell gap and single gamma curves is realized.

  20. Striations in CZ silicon crystals grown under various axial magnetic field strengths

    Science.gov (United States)

    Kim, K. M.; Smetana, P.

    1985-10-01

    Inhibition of fluid flow instabilities in the melt by the axial magnetic field in Czochralski silicon crystal growth (AMCZ) is investigated precisely by a high-sensitivity striation etch in conjunction with temperature measurements. The magnetic field strength (B) was varied up to 4.0 kG, incremented mostly in 0.5-kG/2.5-cm crystal length. The convection flow was substantially suppressed at B greater than or equal to 1.0 kG. A low oxygen level of 2-3 ppm and a high resistivity of 400 ohm-cm is achieved in the AMCZ silicon crystals at B greater than or equal to 1.0 kG. Random striations at B = O, characteristic of turbulent convection, assumed progressively a periodicity, indicative of oscillatory convection at B from 0.35-4.0 kG. The striation contrast or 'intensity' decreased steadily with the increase in B. At B = 4 kG, most of the crystal was free of striations, although some weak, localized periodic striations persisted near the crystal periphery. Spreading-resistance measurement shows, however, a uniform dopant distribution in all crystal sections grown at B from 0.35-4.0 kG within a few percent.

  1. Study of Fluid Flow Control in Protein Crystallization using Strong Magnetic Fields

    Science.gov (United States)

    Ramachandran, Narayanan; Leslie, Fred; Ciszak, Ewa

    2002-11-01

    An important component in biotechnology, particularly in the area of protein engineering and rational drug design is the knowledge of the precise three-dimensional molecular structure of proteins. The quality of structural information obtained from X-ray diffraction methods is directly dependent on the degree of perfection of the protein crystals. As a consequence, the growth of high quality macromolecular crystals for diffraction analyses has been the central focus for biochemists, biologists, and bioengineers. Macromolecular crystals are obtained from solutions that contain the crystallizing species in equilibrium with higher aggregates, ions, precipitants, other possible phases of the protein, foreign particles, the walls of the container, and a likely host of other impurities. By changing transport modes in general, i.e., reduction of convection and sedimentation, as is achieved in "microgravity", researchers have been able to dramatically affect the movement and distribution of macromolecules in the fluid, and thus their transport, formation of crystal nuclei, and adsorption to the crystal surface. While a limited number of high quality crystals from space flights have been obtained, as the recent National Research Council (NRC) review of the NASA microgravity crystallization program pointed out, the scientific approach and research in crystallization of proteins has been mainly empirical yielding inconclusive results. We postulate that we can reduce convection in ground-based experiments and we can understand the different aspects of convection control through the use of strong magnetic fields and field gradients. Whether this limited convection in a magnetic field will provide the environment for the growth of high quality crystals is still a matter of conjecture that our research will address. The approach exploits the variation of fluid magnetic susceptibility with concentration for this purpose and the convective damping is realized by appropriately

  2. Dark-field transmission electron microscopy of cortical bone reveals details of extrafibrillar crystals.

    Science.gov (United States)

    Schwarcz, Henry P; McNally, Elizabeth A; Botton, Gianluigi A

    2014-12-01

    In a previous study we showed that most of the mineral in bone is present in the form of "mineral structures", 5-6nm-thick, elongated plates which surround and are oriented parallel to collagen fibrils. Using dark-field transmission electron microscopy, we viewed mineral structures in ion-milled sections of cortical human bone cut parallel to the collagen fibrils. Within the mineral structures we observe single crystals of apatite averaging 5.8±2.7nm in width and 28±19nm in length, their long axes oriented parallel to the fibril axis. Some appear to be composite, co-aligned crystals as thin as 2nm. From their similarity to TEM images of crystals liberated from deproteinated bone we infer that we are viewing sections through platy crystals of apatite that are assembled together to form the mineral structures.

  3. Analyses of crystal field and exchange interaction of Dy3Ga5O12 under extreme conditions

    Institute of Scientific and Technical Information of China (English)

    Wang Wei; Qi Xin; Yue Yuan

    2011-01-01

    This paper theoretically investigates the effects of crystal field and exchange interaction field on magnetic properties in dysprosium gallium garnet under extreme conditions (low temperatures and high magnetic fields) based on quantum theory. Here, five sets of crystal field parameters are discussed and compared. It demonstrates that, only considering the crystal field effect, the experiments can not be successfully explained. Thus, referring to the molecular field theory,an effective exchange field associated with the Dy-Dy exchange interaction is further taken into account. Under special consideration of crystal field and the exchange interaction field, it obtains an excellent agreement between the theoretical results and experiments, and further confirms that the exchange interaction field between rare-earth ions has great importance to magnetic properties in paramagnetic rare-earth gallium garnets.

  4. Electric-field-induced weakly chaotic transients in ferroelectric liquid crystals

    Science.gov (United States)

    Śliwa, I.; JeŻewski, W.; Kuczyński, W.

    2016-01-01

    Nonlinear dynamics induced in surface stabilized ferroelectric liquid crystals by strong alternating external electric fields is studied both theoretically and experimentally. As has already been shown, molecular reorientations induced by sufficiently strong fields of high-enough frequencies can reveal a long transient behavior that has a weakly chaotic character. The resulting complex dynamics of ferroelectric liquid crystals can be considered not only as a consequence of irregular motions of particular molecules but also as a repercussion of a surface-enforced partial decorrelation of nonlinear molecular motions within smectic layers. To achieve more insight into the nature of this phenomenon and to show that the underlying complex field-induced behavior of smectic liquid crystals is not exceptional, ranges of system parameters for which the chaotic behavior occurs are determined. It is proved that there exists a large enough set of initial phase trajectory points, for which weakly chaotic long-time transitory phenomena occur, and, thereby, it is demonstrated that such a chaotic behavior can be regarded as being typical for strongly field-driven thin liquid crystal systems. Additionally, the influence of low-amplitude random noise on the duration of the transient processes is numerically studied. The strongly nonlinear contribution to the electro-optic response, experimentally determined for liquid crystal samples at frequencies lower than the actual field frequency, is also analyzed for long-time signal sequences. Using a statistical approach to distinguish numerically response signals of samples from noise generated by measuring devices, it is shown that the distribution of sample signals distinctly differs from the device noise. This evidently corroborates the occurrence of the nonlinear low-frequency effect, found earlier for different surface stabilized liquid crystal samples.

  5. Electric-field-induced weakly chaotic transients in ferroelectric liquid crystals.

    Science.gov (United States)

    Śliwa, I; Jeżewski, W; Kuczyński, W

    2016-01-01

    Nonlinear dynamics induced in surface stabilized ferroelectric liquid crystals by strong alternating external electric fields is studied both theoretically and experimentally. As has already been shown, molecular reorientations induced by sufficiently strong fields of high-enough frequencies can reveal a long transient behavior that has a weakly chaotic character. The resulting complex dynamics of ferroelectric liquid crystals can be considered not only as a consequence of irregular motions of particular molecules but also as a repercussion of a surface-enforced partial decorrelation of nonlinear molecular motions within smectic layers. To achieve more insight into the nature of this phenomenon and to show that the underlying complex field-induced behavior of smectic liquid crystals is not exceptional, ranges of system parameters for which the chaotic behavior occurs are determined. It is proved that there exists a large enough set of initial phase trajectory points, for which weakly chaotic long-time transitory phenomena occur, and, thereby, it is demonstrated that such a chaotic behavior can be regarded as being typical for strongly field-driven thin liquid crystal systems. Additionally, the influence of low-amplitude random noise on the duration of the transient processes is numerically studied. The strongly nonlinear contribution to the electro-optic response, experimentally determined for liquid crystal samples at frequencies lower than the actual field frequency, is also analyzed for long-time signal sequences. Using a statistical approach to distinguish numerically response signals of samples from noise generated by measuring devices, it is shown that the distribution of sample signals distinctly differs from the device noise. This evidently corroborates the occurrence of the nonlinear low-frequency effect, found earlier for different surface stabilized liquid crystal samples.

  6. Use of the Primitive Unit Cell in Understanding Subtle Features of the Cubic Closest-Packed Structure

    Science.gov (United States)

    Hawkins, John A.; Rittenhouse, Jeffrey L.; Soper, Linda M.; Rittenhouse, Robert C.

    2008-01-01

    One of the most important crystal structures adopted by metals is characterized by the "abcabc"...stacking of close-packed layers. This structure is commonly referred to in textbooks as the cubic close-packed (ccp) or face-centered cubic (fcc) structure, since the entire lattice can be generated by replication of a face-centered cubic unit cell…

  7. Electric quadrupole interaction in cubic BCC α-Fe

    Energy Technology Data Exchange (ETDEWEB)

    Błachowski, A.; Komędera, K. [Mössbauer Spectroscopy Division, Institute of Physics, Pedagogical University, ul. Podchorążych 2, PL-30-084 Kraków (Poland); Ruebenbauer, K., E-mail: sfrueben@cyf-kr.edu.pl [Mössbauer Spectroscopy Division, Institute of Physics, Pedagogical University, ul. Podchorążych 2, PL-30-084 Kraków (Poland); Cios, G.; Żukrowski, J. [AGH University of Science and Technology, Academic Center for Materials and Nanotechnology, Av. A. Mickiewicza 30, PL-30-059 Kraków (Poland); Górnicki, R. [RENON, ul. Gliniana 15/15, PL-30-732 Kraków (Poland)

    2016-07-15

    Mössbauer transmission spectra for the 14.41-keV resonant line in {sup 57}Fe have been collected at room temperature by using {sup 57}Co(Rh) commercial source and α-Fe strain-free single crystal as an absorber. The absorber was magnetized to saturation in the absorber plane perpendicular to the γ-ray beam axis applying small external magnetic field. Spectra were collected for various orientations of the magnetizing field, the latter lying close to the [110] crystal plane. A positive electric quadrupole coupling constant was found practically independent on the field orientation. One obtains the following value V{sub zz} = +1.61(4) × 10{sup 19} Vm{sup −2} for the (average) principal component of the electric field gradient (EFG) tensor under assumption that the EFG tensor is axially symmetric and the principal axis is aligned with the magnetic hyperfine field acting on the {sup 57}Fe nucleus. The nuclear spectroscopic electric quadrupole moment for the first excited state of the {sup 57}Fe nucleus was adopted as +0.17 b. Similar measurement was performed at room temperature using as-rolled polycrystalline α-Fe foil of high purity in the zero external field. Corresponding value for the principal component of the EFG was found as V{sub zz} = +1.92(4) × 10{sup 19} Vm{sup −2}. Hence, it seems that the origin of the EFG is primarily due to the local (atomic) electronic wave function distortion caused by the spin–orbit interaction between effective electronic spin S and incompletely quenched electronic angular momentum L. It seems as well that the lowest order term proportional to the product L·λ·S dominates, as no direction dependence of the EFG principal component is seen. The lowest order term is isotropic for a cubic symmetry as one has λ=λ 1 for cubic systems with the symbol 1 denoting unit operator and λ being the coupling parameter. - Highlights: • Precision of MS the same as MAPON • Real scans versus magnetization direction • A challenge

  8. Solid-state 13C NMR study of banana liquid crystals - 3: Alkyl-tail-group packing environments of an acute-angle bent-core molecule in the hexagonal columnar and cubic phases

    Science.gov (United States)

    Kurosu, Hiromichi; Endo, Yumi; Kimura, Saori; Hashimoto, Tomoko; Harada, Motoi; Lee, Eun-Woo; Sone, Masato; Watanabe, Junji; Kang, Sungmin

    2016-02-01

    Solid-state 13C nuclear magnetic resonance (NMR) measurements were performed on the hexagonal columnar and cubic phases of an acute-angle banana-shaped molecule, N(1,7)-S30. In the hexagonal columnar phase, three peaks appear at the NMR chemical shifts assigned to the internal methylene carbons of alkyl tails, indicating that the two alkyl tails have different packing structures, and one of the tails has two different conformations within a single molecule. Combined cross-polarization/magic-angle spinning and pulse saturation transfer/magic-angle spinning measurements show that one of the alkyl chains is located inside and the other is located outside the columnar structure. In the cubic phase, pulse saturation transfer/magic-angle spinning measurement shows that only one peak appears at the NMR chemical shifts assigned to the internal methylene carbons of alkyl tails, indicating that both of the alkyl chains are located outside the cubic structure.

  9. Deformations of charge-density wave crystals under electric field

    Energy Technology Data Exchange (ETDEWEB)

    Pokrovskii, V.Ya. [Kotel' nikov Institute of Radioengineering and Electronics of RAS, Mokhovaya 11, 125009 Moscow (Russian Federation)], E-mail: pok@cplire.ru; Zybtsev, S.G.; Loginov, V.B. [Kotel' nikov Institute of Radioengineering and Electronics of RAS, Mokhovaya 11, 125009 Moscow (Russian Federation); Timofeev, V.N. [Baikov Institute of Metallurgy of RAS, Leninsky prosp. 49, 119991 Moscow (Russian Federation); Kolesov, D.V.; Yaminsky, I.V. [Advanced Technologies Center, Department of Physics, Moscow State University, Leninskie Gori, 119991 Moscow (Russian Federation); Gorlova, I.G. [Kotel' nikov Institute of Radioengineering and Electronics of RAS, Mokhovaya 11, 125009 Moscow (Russian Federation)

    2009-03-01

    We report the effects of electric field induced deformations of quasi one-dimensional conductors with charge-density wave (CDW). The most pronounced sort of deformation is torsional strain (TS). The TS is found to comprise two contributions. The features of the 1st-the larger one-are threshold hysteretic dependence on electric field and high relaxation time {tau}: For o-TaS{sub 3}{tau}{approx}10{sup -2} s at T=80 K and falls as exp(900 K/T) with increasing T. The 2nd contribution is linear in electric field and does not drop with frequency increase. The amplitude of this contribution falls abruptly with T approaching the Peierls transition temperature T{sub P} from below. Similar features of TS are demonstrated for other CDW compounds: (TaSe{sub 4}){sub 2}I, K{sub 0.3}MoO{sub 3} and NbS{sub 3} type II, for which T{sub P}{approx}360 K. We attribute the 1st and the 2nd contributions to large (hysteretic) and small (near-equilibrium) CDW deformations, respectively, likely-shear at the surface. The TS is observed also above T{sub P}: For TaS{sub 3} and (TaSe{sub 4}){sub 2}I typical torsional amplitude is 10{sup -1} deg./V in the resonance regimes, corresponding to the piezomodulus {approx}10{sup -9} m/V. A separate study of TS was performed at room temperature with AFM technique. Apart from this ('intrinsic') effect, we observe electrostatic contribution to the TS. In contrast to the intrinsic response, the electrostatic one is proportional to the potential either over the sample, or over an additional electrode ('gate') placed nearby, but not to the difference of potentials between the sample ends. It is typically 2 orders of magnitude less. The intrinsic TS reveals a new electromechanical effect at room temperature, presumably associated with the excitations of the pinned mode of the CDW fluctuations. Its observation opens prospects for application of quasi one-dimensional conductors as micro- and nano-actuators. Basing on the electrostatic

  10. Dependence of image flicker on dielectric anisotropy of liquid crystal in a fringe field switching liquid crystal cell

    Science.gov (United States)

    Oh, Seung-Won; Baek, Jong-Min; Kim, Jung-Wook; Yoon, Tae-Hoon

    2016-09-01

    Two types of image flicker, which are caused by the flexoelectric effect of liquid crystals (LCs), are observed when a fringe-field switching (FFS) LC cell is driven by a low frequency electric field. Static image flicker, observed because of the transmittance difference between neighboring frames, has been reported previously. On the other hand, research on dynamic image flicker has been minimal until now. Dynamic image flicker is noticeable because of the brief transmittance drop when the sign of the applied voltage is reversed. We investigated the dependence of the image flicker in an FFS LC cell on dielectric anisotropy of the LCs in terms of both the static and dynamic flicker. Experimental results show that small dielectric anisotropy of the LC can help suppress not only the static but also dynamic flicker for positive LCs. We found that both the static and dynamic flicker in negative LCs is less evident than in positive LCs.

  11. Crystal fields of dilute Tb, Dy, or Er in Sc obtained by magnetization measurements

    DEFF Research Database (Denmark)

    Høg, J.; Touborg, P.

    1976-01-01

    Crystal-field parameters for dilute Sc-Tb, Sc-Dy, and Sc-Er alloys have been obtained by fitting theoretical expressions to the experimentally measured paramagnetic susceptibility. The initial susceptibility was measured and corrected for the effects of ordering at the lowest temperatures in the ...

  12. Tuning the Colloidal Crystal Structure of Magnetic Particles by External Field

    NARCIS (Netherlands)

    Pal, Antara; Malik, Vikash; He, Le; Erne, Ben H.; Yin, Yadong; Kegel, Willem K.; Petukhov, A. V.

    2015-01-01

    Manipulation of the self-assembly of magnetic colloidal particles by an externally applied magnetic field paves a way toward developing novel stimuli responsive photonic structures. Using microradian X-ray scattering technique we have investigated the different crystal structures exhibited by self-a

  13. Ambipolar Cu- and Fe-phthalocyanine single-crystal field-effect transistors

    NARCIS (Netherlands)

    De Boer, R.W.I.; Stassen, A.F.; Craciun, M.F.; Mulder, C.L.; Molinari, A.; Rogge, S.; Morpurgo, A.F.

    2005-01-01

    We report the observation of ambipolar transport in field-effect transistors fabricated on single crystals of copper- and iron-phthalocyanine, using gold as a high work-function metal for the fabrication of source and drain electrodes. In these devices, the room-temperature mobility of holes reaches

  14. Reproducible low contact resistance in rubrene single-crystal field-effect transistors with nickel electrodes

    NARCIS (Netherlands)

    Hulea, I.N.; Russo, S.; Molinari, A.; Morpurgo, A.F.

    2006-01-01

    We have investigated the contact resistance of rubrene single-crystal field-effect transistors (FETs) with nickel electrodes by performing scaling experiments on devices with channel length ranging from 200 nm up to 300 μm. We find that the contact resistance can be as low as 100 Ω cm with narrowly

  15. Bias-dependent contact resistance in rubrene single-crystal field-effect transistors

    NARCIS (Netherlands)

    Molinari, A.; Gutiérrez, I.; Hulea, I.N.; Russo, S.; Morpurgo, A.F.

    2007-01-01

    The authors report a systematic study of the bias-dependent contact resistance in rubrene single-crystal field-effect transistors with Ni, Co, Cu, Au, and Pt electrodes. They show that the reproducibility in the values of contact resistance strongly depends on the metal, ranging from a factor of 2 f

  16. Ambipolar Cu- and Fe-phthalocyanine single-crystal field-effect transistors

    NARCIS (Netherlands)

    De Boer, R.W.I.; Stassen, A.F.; Craciun, M.F.; Mulder, C.L.; Molinari, A.; Rogge, S.; Morpurgo, A.F.

    2005-01-01

    We report the observation of ambipolar transport in field-effect transistors fabricated on single crystals of copper- and iron-phthalocyanine, using gold as a high work-function metal for the fabrication of source and drain electrodes. In these devices, the room-temperature mobility of holes reaches

  17. Effect of electrical field on crystallization and ferroelectric properties of Ge:Sb:Te films

    Energy Technology Data Exchange (ETDEWEB)

    Gervacio Arciniega, J.J.; Prokhorov, E.; Espinoza Beltran, F.J.; Trapaga Martinez, L.G. [CINVESTAV, Unidad Queretaro (Mexico); Gonzalez-Hernandez, J. [Centro de Investigacion en Materiales Avanzados, S.C. and Laboratorio Nacional de Nanotecnologia, Chihuahua (Mexico)

    2011-11-15

    In this work impedance spectroscopy has been used to investigate of the NaCl type-hexagonal transition in stoichiometric Ge{sub 2}Sb{sub 2}Te{sub 5} and in non-stoichiometric (Ge{sub 24}Sb{sub 15}Te{sub 61}) films. The temperature dependence of capacitance in all films shows an abrupt change (about 4-6 times) at the temperature corresponding to the end of the NaCl type-hexagonal transition. Additional, impedance measurements were carried out in films which have been crystallized with an external DC electric field. Comparing the results in the films crystallized with and without the external electric field, it is observed that in films crystallized with an external electric field, the capacitance increases during the NaCl type-hexagonal transition for about 9-15 times and that the piezoresponse force microscopy measurements have shown ferroelectric domains in the NaCl type phase. External electrical field changes significantly the onset of amorphous-NaCl type crystallization temperature which could be related with an increase in atomic diffusion, promoting the growth of the crystalline phase. (copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  18. Capability of the free-ion eigenstates for crystal-field splitting

    CERN Document Server

    Mulak, Jacek

    2011-01-01

    Any electron eigenstate |\\Psi>of the paramagnetic ion open-shell is characterized by the three independent multipole asphericities A_{k}= for k=2,4 and 6 related to the second moments of the relevant crystal-field splittings by \\sigma_{k}^{2}=]A_{k}^{2}S_{k}^{2}, where S_{k}^{2}=]\\sum_{q}|B_{kq}|^{2}. The A_{k} can serve as a reliable measure of the state |\\Psi>capability for the splitting produced by the k-rank component of the crystal-field Hamiltonian and allow one to verify any fitted crystal-field parameter set directly comparing the calculated and the experimental second moments of the relevant crystal-field splittings. We present the multipole characteristics A_{k} for the extensive set of eigenstates from the lower parts of energy spectra of the tripositive 4f^{N} ions applying in the calculations the advanced eigenfunctions of the free lanthanide ions obtained based on the M. Reid f-shell programs. Such amended asphericities are compared with those achieved for the simplified Russell-Saunders states....

  19. Scaling of crystal field parameters between Pd 2REIn and Pd 2RESn

    Science.gov (United States)

    Babateen, M.; Neumann, K.-U.; Ziebeck, K. R. A.

    1995-02-01

    Experimentally it is found that crystal field (CF) parameters between the same rare earth compounds in the alloy series Pd 2REIn and Pd 2RESn (RE = rare earth element) exhibit scaling properties. A phenomenological model is put forward to explain this observation.

  20. Near-field imaging of out-of-plane light scattering in photonic crystal slabs

    DEFF Research Database (Denmark)

    Volkov, Valentyn; Bozhevolnyi, Sergey; Taillaert, Dirk

    2003-01-01

    A collection scanning near-field optical microscope (SNOM) is used to image the propagating of light at telecommunication wavelengths (1520-1570 nm) along photonic crystal (PC) slabs, which combine slab waveguides with in-plane PCs consisting of one- and two-dimensional gratings. The efficient out...

  1. Magnetic-Field-Induced Weak Order in Nematic Liquid Crystals Formed by Biaxial Molecules

    Institute of Scientific and Technical Information of China (English)

    ZHANG Zhi-Dong; ZHANG De-Xian; SUN Yu-Bao

    2000-01-01

    Nematic liquid crystal system of interacting biaxial particles via dispersion forces is studied. The molecular orienting potential form in a magnetic field is given for the first time. Weakly ordered isotropic phase is treated in the two-particle cluster approximation. Taking account of the molecular biaxiality, it is found that the ratio of the lowest supercooling temperature T* to the nematic-isotropic phase transition temperature TC approaches the observed value, and the validity of the mean field theory is clarified.

  2. Bridging the terahertz near-field and far-field observations of liquid crystal based metamaterial absorbers

    Science.gov (United States)

    Wang, Lei; Ge, Shijun; Chen, Zhaoxian; Hu, Wei; Lu, Yanqing

    2016-09-01

    Metamaterial-based absorbers play a significant role in applications ranging from energy harvesting and thermal emitters to sensors and imaging devices. The middle dielectric layer of conventional metamaterial absorbers has always been solid. Researchers could not detect the near field distribution in this layer or utilize it effectively. Here, we use anisotropic liquid crystal as the dielectric layer to realize electrically fast tunable terahertz metamaterial absorbers. We demonstrate strong, position-dependent terahertz near-field enhancement with sub-wavelength resolution inside the metamaterial absorber. We measure the terahertz far-field absorption as the driving voltage increases. By combining experimental results with liquid crystal simulations, we verify the near-field distribution in the middle layer indirectly and bridge the near-field and far-field observations. Our work opens new opportunities for creating high-performance, fast, tunable, terahertz metamaterial devices that can be applied in biological imaging and sensing. Project supported by the National Basic Research Program of China (Grant No. 2012CB921803), the National Natural Science Foundation of China (Grants Nos. 61225026, 61490714, 11304151, and 61435008), the Natural Science Foundation of Jiangsu Province, China (Grant Nos. BK20150845 and 15KJB140004), the Open Foundation Project of National Laboratory of Solid State Microstructures, China (Grant No. M28003), and the Research Center of Optical Communications Engineering & Technology, Jiangsu Province, China.

  3. Effect of non-uniform magnetic field on crystal growth by floating-Zone method in microgravity

    Institute of Scientific and Technical Information of China (English)

    LI; Kai(

    2001-01-01

    [1]Markov, E. V., Antropov, V. Yu, Biryukov, V. M. et al., Space materials for microelectronics, in Proceedings of the Joint Xth European and VIth Russian Symposium on Physical Sciences in Microgravity, St. Petersburg, Russia (eds. Av-duyevsky, V. S., Polezhaev, V. I.), Moscow: RAS, 1997, Vol. 2, 11-20.[2]Croll, A., Dold, P., Benz, K. W., Segregation in Si floating-zone crystals grown under microgravity and in a magnetic field, J. Crystal Growth, 1994, 137: 95-101.[3]Leon de, N., Guldberg, J., Sailing, J. , Growth of homogeneous high resistivity FZ silicon crystals under magnetic field bias, J. Crystal Growth, 1981, 55: 406-408.[4]Robertson, D. G., O' connor Jr., D. J., Magnetic field effects on float-zone Si crystal growth: strong axial fields, J. Crystal Growth, 1986, 76: 111-122.[5]Series, R. W., Hurle, D. T. J., The use of magnetic field in semiconductor crystal growth, J. Crystal Growth, 1991, 113:305-328.[6]Lan, C. W. , Effect of axisymmetric magnetic fields on radial dopant segregation of floating-zone silicon growth in a mirror fur-nace, J. Crystal Growth, 1996, 169: 269-278.[7]Li, K., Hu, W. R. , Numerical simulation of magnetic field design for damping thermocapillary convection in a floating half zone, J. Crystal Growth, 2001, 222: 677-684.[8]Li. K., Hu, W. R., Magnetic design for crystal growth, 3rd International Workshop on Modeling in Crystal Growth, New York, USA, 2000, to be published in J. Crystal Growth.[9]Patankar, S. V., Advanced Computational Heat Transfer and Fluid Flow, Graduate Student Course 8352 of Mechanical Engi-neering Department at Univ. of Minnesota, USA.

  4. Electrical properties and electrical field in depletion layer for CZT crystals

    Institute of Scientific and Technical Information of China (English)

    LI Qiang; JIE Wan-qi; FU Li; YANG Ge; ZHA Gang-qiang; WANG Tao; BAI Xu-xu

    2006-01-01

    Current—voltage (I—V) and capacitance-voltage (C—V) characteristics of Au/p-CZT contacts with different surface treatments on cadmium zinc telluride (CZT) wafer's surface were measured with Agilent 4339B high resistance meter and Agilent 4294A precision impedance analyzer,respectively. The Schottky barrier height was 0.85±0.05,0.96±0.05 eV for non-passivated and passivated CZT crystals by I—V measurement. By C—V measurement,the Schottky barrier height was 1.39±0.05,1.51±0.05 eV for non-passivated and passivated CZT crystals. The results show that the passivation treatment can increase the barrier height of the Au/p-CZT contact and decrease the leakage current. The main reason is that the higher barrier height of Au/p-CZT contacts can decrease the possibility for electrons to pass through the native TeO2 film. Most of the applied voltage appears on the depleted layer and there is only a negligible voltage drops across the nearly undepleted region. Furthermore,the electric field in the depleted layer is not uniform and can be calculated by the depletion approximation. The maximum electric field of CZT crystals is Em1=133 V/cm at x=0 for non-passivated CZT crystal and Em2=55 V/cm for passivated CZT crystal,respectively.

  5. Patterning technology for solution-processed organic crystal field-effect transistors

    Science.gov (United States)

    Li, Yun; Sun, Huabin; Shi, Yi; Tsukagoshi, Kazuhito

    2014-04-01

    Organic field-effect transistors (OFETs) are fundamental building blocks for various state-of-the-art electronic devices. Solution-processed organic crystals are appreciable materials for these applications because they facilitate large-scale, low-cost fabrication of devices with high performance. Patterning organic crystal transistors into well-defined geometric features is necessary to develop these crystals into practical semiconductors. This review provides an update on recent development in patterning technology for solution-processed organic crystals and their applications in field-effect transistors. Typical demonstrations are discussed and examined. In particular, our latest research progress on the spin-coating technique from mixture solutions is presented as a promising method to efficiently produce large organic semiconducting crystals on various substrates for high-performance OFETs. This solution-based process also has other excellent advantages, such as phase separation for self-assembled interfaces via one-step spin-coating, self-flattening of rough interfaces, and in situ purification that eliminates the impurity influences. Furthermore, recommendations for future perspectives are presented, and key issues for further development are discussed.

  6. Patterning technology for solution-processed organic crystal field-effect transistors

    Directory of Open Access Journals (Sweden)

    Yun Li

    2014-04-01

    Full Text Available Organic field-effect transistors (OFETs are fundamental building blocks for various state-of-the-art electronic devices. Solution-processed organic crystals are appreciable materials for these applications because they facilitate large-scale, low-cost fabrication of devices with high performance. Patterning organic crystal transistors into well-defined geometric features is necessary to develop these crystals into practical semiconductors. This review provides an update on recent development in patterning technology for solution-processed organic crystals and their applications in field-effect transistors. Typical demonstrations are discussed and examined. In particular, our latest research progress on the spin-coating technique from mixture solutions is presented as a promising method to efficiently produce large organic semiconducting crystals on various substrates for high-performance OFETs. This solution-based process also has other excellent advantages, such as phase separation for self-assembled interfaces via one-step spin-coating, self-flattening of rough interfaces, and in situ purification that eliminates the impurity influences. Furthermore, recommendations for future perspectives are presented, and key issues for further development are discussed.

  7. Ionization of Atoms and the Thomas-Fermi Model for the Electric Field in Crystal Planar Channels

    Institute of Scientific and Technical Information of China (English)

    LIU Ying-Tai; ZHANG Qi-Ren; GAO Chun-Yuan

    2002-01-01

    The electric field in the crystal planar channels is studied by the Thomas Fermi method. The Thomas-Fermi equation and the corresponding boundary conditions are derived for the crystal planar channels. The numericalsolution for the electric field in the channels between (110) planes of the single crystal silicon and the critical angles ofchannelling protons in them are shown. Reasonable agreements with the experimental data are obtained. The resultsshow that the Thomas-Fermi method for the crystal works well in this study, and a microscopic research of the channelelectric field with the contribution of all atoms and the atomic ionization being taken into account is practical.

  8. The g-value of Er{sup 3+} doped unfilled skutterudite CoSb{sub 3} (T{sub h}) reveals the existence of an additional sixth order term in the crystal field Hamiltonian

    Energy Technology Data Exchange (ETDEWEB)

    Vargas, J.M.; Garcia, F.A. [Instituto de Fisica ' Gleb Wataghin' , UNICAMP, Campinas-SP 13083-970 (Brazil); Rettori, C., E-mail: rettori@ifi.unicamp.b [Instituto de Fisica ' Gleb Wataghin' , UNICAMP, Campinas-SP 13083-970 (Brazil); Garcia, D.J. [Consejo Nacional de Investigaciones Cientificas y Tecnicas and Centro Atomico Bariloche, S.C. de Bariloche, RN (Argentina); Sales, B. [Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Schlottmann, P. [Department of Physics, Florida State University, Tallahassee, FL 32306 (United States); Oseroff, S.B. [San Diego State University, San Diego, CA 92182 (United States)

    2009-10-15

    Electron spin resonance (ESR) experiments have been carried out in single crystals of the unfilled skutterudite CoSb{sub 3} doped with Er ions. The X- (9.5 GHz) and Q- (34.4 GHz) band spectra obtained at low temperature (4-20 K) shown a temperature independent g-value of 6.21(5). This g-value can only be explained with the addition of a second sixth order B{sub 6}{sup t}(O{sub 6}{sup 2}-O{sub 6}{sup 6}) term to the usual cubic crystal field Hamiltonian. The ESR of Er{sup 3+} show the typical temperature dependence of the line-shape and line-width expected for insulating host.

  9. Thermodynamic properties of the magnetized Coulomb crystal lattices

    Science.gov (United States)

    Kozhberov, A. A.

    2016-08-01

    It is thought that Coulomb crystals of ions with hexagonal close-packed lattice may form in the crust of strongly-magnetized neutron stars (magnetars). In this work we are trying to verify this prediction assuming that the direction of the magnetic field corresponds to the minimum of the zero-point energy. We also continue a detailed study of vibration modes and thermodynamic properties of magnetized Coulomb crystals in a wide range of temperatures and magnetic fields. It is demonstrated that the total Helmholtz free energy of the body-centered cubic Coulomb crystal is always lower than that of the Coulomb crystal with hexagonal close-packed or face-centered cubic lattice, which casts doubt on the hypothesis above.

  10. Crystal-field spectra of 3d super n impurities in II-VI and III-V compound semiconductors.

    Science.gov (United States)

    Allen, J. W.; Baranowski, J. M.; Pearson, G. L.

    1967-01-01

    Impurity crystal-field spectra in II-VI and III- V compound semiconductors used to predict unexplored systems spectra impurity crystal-field spectra in II-VI and III-V compound semiconductors used to predict unexplored systems spectra

  11. Lipidic cubic phase injector facilitates membrane protein serial femtosecond crystallography.

    Science.gov (United States)

    Weierstall, Uwe; James, Daniel; Wang, Chong; White, Thomas A; Wang, Dingjie; Liu, Wei; Spence, John C H; Bruce Doak, R; Nelson, Garrett; Fromme, Petra; Fromme, Raimund; Grotjohann, Ingo; Kupitz, Christopher; Zatsepin, Nadia A; Liu, Haiguang; Basu, Shibom; Wacker, Daniel; Han, Gye Won; Katritch, Vsevolod; Boutet, Sébastien; Messerschmidt, Marc; Williams, Garth J; Koglin, Jason E; Marvin Seibert, M; Klinker, Markus; Gati, Cornelius; Shoeman, Robert L; Barty, Anton; Chapman, Henry N; Kirian, Richard A; Beyerlein, Kenneth R; Stevens, Raymond C; Li, Dianfan; Shah, Syed T A; Howe, Nicole; Caffrey, Martin; Cherezov, Vadim

    2014-01-01

    Lipidic cubic phase (LCP) crystallization has proven successful for high-resolution structure determination of challenging membrane proteins. Here we present a technique for extruding gel-like LCP with embedded membrane protein microcrystals, providing a continuously renewed source of material for serial femtosecond crystallography. Data collected from sub-10-μm-sized crystals produced with less than 0.5 mg of purified protein yield structural insights regarding cyclopamine binding to the Smoothened receptor.

  12. The Exact Limit of Some Cubic Towers

    DEFF Research Database (Denmark)

    Anbar Meidl, Nurdagül; Beelen, Peter; Nguyen, Nhut

    2016-01-01

    Recently, a new explicit tower of function fields was introduced by Bassa, Beelen, Garcia and Stichtenoth (BBGS). This resulted in currently the best known lower bound for Ihara’s constant in the case of non-prime finite fields. In particular over cubic fields, the tower’s limit is at least as good...... as Zink’s bound; i.e. λ(BBGS/Fq3 ) ≥ 2(q2 - 1)/(q + 2). In this paper, the exact value of λ(BBGS/Fq3 ) is computed. We also settle a question stated by Ihara....

  13. Wide-field-of-view narrow-band spectral filters based on photonic crystal nanocavities.

    Science.gov (United States)

    Nakagawa, Wataru; Sun, Pang-Chen; Chen, Chyong-Hua; Fainman, Yeshaiahu

    2002-02-01

    We describe a novel approach to implementing wide-field-of-view narrow-band spectral filters, using an array of resonant nanocavities consisting of periodic defects in a two-dimensional three-material photonic-crystal nanostructure. We analyze the transmissivity of this type of filter for a range of wavelengths and in-plane incidence angles as a function of the defect's refractive index, the number of layers in the photonic-crystal reflectors, and the period of the defects and find that this structure diminishes the angular sensitivity of the resonance condition relative to that of a standard multilayer filter.

  14. Optical study of the molecular alignment in a nematic liquid crystal in an oblique magnetic field

    OpenAIRE

    Oldano, C.; Miraldi, E.; Strigazzi, A.; Taverna Valabrega, P.; Trossi, L.

    1984-01-01

    The light intensity I transmitted through a homeotropically oriented nematic liquid crystal slab held between crossed polarizers, as a function of the angle θH of an applied magnetic field, is calculated for oblique light incidence. The presence of singular points in the I vs. θ H curve which are related to the elastic constants of the liquid crystal is demonstrated One of these points, found here for the first time, for small angles of incidence depends only on the ratio K33/Χ a, and allows ...

  15. An energy-stable convex splitting for the phase-field crystal equation

    KAUST Repository

    Vignal, P.

    2015-10-01

    Abstract The phase-field crystal equation, a parabolic, sixth-order and nonlinear partial differential equation, has generated considerable interest as a possible solution to problems arising in molecular dynamics. Nonetheless, solving this equation is not a trivial task, as energy dissipation and mass conservation need to be verified for the numerical solution to be valid. This work addresses these issues, and proposes a novel algorithm that guarantees mass conservation, unconditional energy stability and second-order accuracy in time. Numerical results validating our proofs are presented, and two and three dimensional simulations involving crystal growth are shown, highlighting the robustness of the method. © 2015 Elsevier Ltd.

  16. Phase diagrams and synthesis of cubic boron nitride

    CERN Document Server

    Turkevich, V Z

    2002-01-01

    On the basis of phase equilibria, the lowest temperatures, T sub m sub i sub n , above which at high pressures cubic boron nitride crystallization from melt solution is allowable in terms of thermodynamics have been found for a number of systems that include boron nitride.

  17. Creating physically-based three-dimensional microstructures: Bridging phase-field and crystal plasticity models.

    Energy Technology Data Exchange (ETDEWEB)

    Lim, Hojun [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Owen, Steven J. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Abdeljawad, Fadi F. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Hanks, Byron [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Battaile, Corbett Chandler [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2015-09-01

    In order to better incorporate microstructures in continuum scale models, we use a novel finite element (FE) meshing technique to generate three-dimensional polycrystalline aggregates from a phase field grain growth model of grain microstructures. The proposed meshing technique creates hexahedral FE meshes that capture smooth interfaces between adjacent grains. Three dimensional realizations of grain microstructures from the phase field model are used in crystal plasticity-finite element (CP-FE) simulations of polycrystalline a -iron. We show that the interface conformal meshes significantly reduce artificial stress localizations in voxelated meshes that exhibit the so-called "wedding cake" interfaces. This framework provides a direct link between two mesoscale models - phase field and crystal plasticity - and for the first time allows mechanics simulations of polycrystalline materials using three-dimensional hexahedral finite element meshes with realistic topological features.

  18. Neutron investigations of magnetic properties of crystal substances with use of a pulsed magnetic field

    CERN Document Server

    Nitts, V V

    2001-01-01

    Bases for neutron researches of magnetic properties of crystal substances with use of a pulsed magnetic field and analysis of possible application of various neutron sources in this area are submitted. The review of the most interesting physical results is presented. Main investigations on pulsed reactors of JINR are researches on kinetics of the first order reorientational phase transitions induced in single crystals, and also measurements of antiferromagnetic ordering induced by an external magnetic field. Magnetic phase transitions, induced by a field up to 160 kOe in several magnetic ordering substances, were studied in KEK (Japan). Experiment on observation of spin-flop transition in MnF sub 2 was carried out on TRIGA-reactor in a mode of single flashes of power

  19. Resistive memory effects in BiFeO3 single crystals controlled by transverse electric fields

    Science.gov (United States)

    Kawachi, S.; Kuroe, H.; Ito, T.; Miyake, A.; Tokunaga, M.

    2016-04-01

    The effects of electric fields perpendicular to the c-axis of the trigonal cell in single crystals of BiFeO3 are investigated through magnetization and resistance measurements. Magnetization and resistance exhibit hysteretic changes under applied electric fields, which can be ascribed to the reorientation of the magnetoelectric domains. Samples are repetitively switched between high- and low-resistance states by changing the polarity of the applied electric fields over 20 000 cycles at room temperature. These results demonstrate the potential of BiFeO3 for use in non-volatile memory devices.

  20. Molecular Field Calculation of Magnetization on NdRh2Ge2 Single Crystal

    Directory of Open Access Journals (Sweden)

    A. Himori

    2008-01-01

    Full Text Available Calculation of magnetization of the ternary single crystal compound NdRh2Ge2 has been carried out by using the wave-like molecular field model to explain the complex magnetic behavior. The field-induced magnetic structures having the propagation vectors, 2=(0,0,39/40, 3=(0,0,35/40, 4=(0,0,31/40, and 5=(0,0,0/40 (= the field-induced ferromagnetic phase were proposed. Calculation on the basis of these structures and the antiferromagnetic phase with 1=(0,0,1 well reproduces the experimental magnetization processes and - magnetic phase diagram.

  1. Optical near-field microscopy of light focusing through a photonic crystal flat lens.

    Science.gov (United States)

    Fabre, Nathalie; Lalouat, Loïc; Cluzel, Benoit; Mélique, Xavier; Lippens, Didier; de Fornel, Frédérique; Vanbésien, Olivier

    2008-08-15

    We report here the direct observation by using a scanning near-field microscopy technique of the light focusing through a photonic crystal flat lens designed and fabricated to operate at optical frequencies. The lens is fabricated using a III-V semiconductor slab, and we directly visualize the propagation of the electromagnetic waves by using a scanning near-field optical microscope. We directly evidence spatially, as well as spectrally, the focusing operating regime of the lens. At last, in light of the experimental scanning near-field optical microscope pictures, we discuss the lens ability to focus light at a subwavelength scale.

  2. Enhancement of local electromagnetic fields in plasmonic crystals of coaxial metallic nanostructures

    Science.gov (United States)

    Iwanaga, Masanobu; Ikeda, Naoki; Sugimoto, Yoshimasa

    2012-01-01

    We have experimentally and numerically examined resonant modes in plasmonic crystals (PlCs) of coaxial metallic nanostructures. Resonance enhancements of local electromagnetic (EM) fields were evaluated quantitatively. We clarified that a local mode induced in the coaxial metallic structure shows the most significant field enhancement. The enhancement factors are comprehensively discussed by comparison with other PlCs, indicating that the coaxial PlC provides a locally intense electric field and EM power flux in the annular slit of 50-nm metallic gaps.

  3. Near-Field Optical Microscopy of Defects in Cholesteric Oligomeric Liquid Crystal Films

    Energy Technology Data Exchange (ETDEWEB)

    Lukishova, S.G.; Schmid, A.W.

    2006-08-18

    This paper describes formation of 2-D hexagonal structures with a periodicity ~0.5-0.8 um in the defects of thin films of cholesteric oligomeric liquid crystals prepared by the evaporation of the solvent from the oligomer solution on the substrate. These regular arrays were observed by scanning near-field optical and concurrent atomic force microscopy. The mechanisms considered are both Benard-Marangoni and buoyancy conventions induced by solvent evaporation and air-bubble creation around the condensed water droplets from the air during evaporative cooling. Hexagonal structures prepared by this method can be used in photonic devices for emission enhancement, for instance, in liquid crystal lasers and single photon sources with oligomeric liquid crystal hosts.

  4. Phase-field simulations of faceted Ge/Si-crystal arrays, merging into a suspended film

    Science.gov (United States)

    Salvalaglio, Marco; Bergamaschini, Roberto; Backofen, Rainer; Voigt, Axel; Montalenti, Francesco; Miglio, Leo

    2017-01-01

    We simulate the morphological evolution of Ge microcrystals, grown out-of-equilibrium on deeply patterned Si substrates, as resulting from surface diffusion driven by the tendency toward the minimization of the surface energy. In particular, we report three-dimensional phase-field simulations accounting for the realistic surface energy anisotropy of Ge/Si crystals. In Salvalaglio et al. (2015) [10] it has been shown both by experiments and simulations that annealing of closely spaced crystals leads to a coalescence process with the formation of a suspended film. However, this was explained only by considering an isotropic surface energy. Here, we extend such a study by showing first the morphological changes of faceted isolated crystals. Then, the evolution of dense arrays is considered, describing their coalescence along with the evolution of facets. Combined with the previous results without anisotropy in the surface energy, this work allows us to confirm and assess the key features of the coalescence process.

  5. Role of internal demagnetizing field for the dynamics of a surface-modulated magnonic crystal

    Science.gov (United States)

    Langer, M.; Röder, F.; Gallardo, R. A.; Schneider, T.; Stienen, S.; Gatel, C.; Hübner, R.; Bischoff, L.; Lenz, K.; Lindner, J.; Landeros, P.; Fassbender, J.

    2017-05-01

    This work aims to demonstrate and understand the key role of local demagnetizing fields in hybrid structures consisting of a continuous thin film with a stripe modulation on top. To understand the complex spin dynamics of these structures, the magnonic crystal was reconstructed in two different ways—performing micromagnetic simulations based on the structural shape as well as based on the internal demagnetizing field, which both are mapped on the nanoscale using electron holography. The simulations yield the frequency-field dependence as well as the angular dependence revealing the governing role of the internal field landscape around the backward-volume geometry. Simple rules for the propagation vector and the mode localization are formulated in order to explain the calculated mode profiles. Treating internal demagnetizing fields equivalent to anisotropies, the complex angle-dependent spin-wave behavior is described for an in-plane rotation of the external field.

  6. Pinning features of the magnetic flux trapped by YBCO single crystals in weak constant magnetic fields

    Science.gov (United States)

    Monarkha, V. Yu.; Paschenko, V. A.; Timofeev, V. P.

    2013-02-01

    The dynamics of Abrikosov vortices and their bundles was experimentally investigated in weak constant magnetic fields, in the range of Earth's magnetic field. Characteristics of the isothermal magnetization relaxation in YBCO single-crystal samples with strong pinning centers were studied for different sample-field orientation. The obtained values of normalized relaxation rate S allowed us to estimate the effective pinning potential U in the bulk of the YBCO sample and its temperature dependence, as well as the critical current density Jc. A comparison between the data obtained and the results of similar measurements in significantly higher magnetic fields was performed. To compare different techniques for evaluation of Jc, the magnetization loop measurements M(H), which relate the loop width to the critical current, were carried out. These measurements provided important parameters of the samples under study (penetration field Hp and first critical field Hc1), which involve the geometrical configuration of the samples.

  7. Cubic-scaling algorithm and self-consistent field for the random-phase approximation with second-order screened exchange.

    Science.gov (United States)

    Moussa, Jonathan E

    2014-01-07

    The random-phase approximation with second-order screened exchange (RPA+SOSEX) is a model of electron correlation energy with two caveats: its accuracy depends on an arbitrary choice of mean field, and it scales as O(n(5)) operations and O(n(3)) memory for n electrons. We derive a new algorithm that reduces its scaling to O(n(3)) operations and O(n(2)) memory using controlled approximations and a new self-consistent field that approximates Brueckner coupled-cluster doubles theory with RPA+SOSEX, referred to as Brueckner RPA theory. The algorithm comparably reduces the scaling of second-order Mo̸ller-Plesset perturbation theory with smaller cost prefactors than RPA+SOSEX. Within a semiempirical model, we study H2 dissociation to test accuracy and Hn rings to verify scaling.

  8. Cubic-scaling algorithm and self-consistent field for the random-phase approximation with second-order screened exchange

    Energy Technology Data Exchange (ETDEWEB)

    Moussa, Jonathan E., E-mail: godotalgorithm@gmail.com [Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States)

    2014-01-07

    The random-phase approximation with second-order screened exchange (RPA+SOSEX) is a model of electron correlation energy with two caveats: its accuracy depends on an arbitrary choice of mean field, and it scales as O(n{sup 5}) operations and O(n{sup 3}) memory for n electrons. We derive a new algorithm that reduces its scaling to O(n{sup 3}) operations and O(n{sup 2}) memory using controlled approximations and a new self-consistent field that approximates Brueckner coupled-cluster doubles theory with RPA+SOSEX, referred to as Brueckner RPA theory. The algorithm comparably reduces the scaling of second-order Møller-Plesset perturbation theory with smaller cost prefactors than RPA+SOSEX. Within a semiempirical model, we study H{sub 2} dissociation to test accuracy and H{sub n} rings to verify scaling.

  9. Theoretical innovation and technical progress will usher in a production period of gas fields with an annual capacity of ten billion cubic meters

    Directory of Open Access Journals (Sweden)

    Zhenwei Gan

    2017-01-01

    Full Text Available Challenged by the increasing complexity of targets and the tense situation of turning losses into profits during the 12th Five-Year Plan, by virtue of technological innovation, Sinopec Southwest Oil & Gas Company proposed the theories of gas exploration in continental clastic rock and marine carbonate rock, and developed the development technologies for reef, channel sandstone and tight sandstone reservoirs. Moreover, it innovatively formed a series of engineering technologies, including intelligent sliding sleeve staged fracturing, blasting–packing–fracturing stimulation, impulse fracturing, and drilling, completion and production technologies for ultra-deep horizontal wells with high sulfur contents. With these innovated theories and improved technologies, great discoveries have been made in the continental clastic rocks and marine carbonate rocks in West Sichuan Basin, the marine shale in South Sichuan Basin, and the marine carbonate rocks in Yuanba area of NE Sichuan Basin, and three 100 billion-m3 class commercial gas reserves zones were discovered. Moreover, two medium- and large-sized gas fields were proved, and three medium- and large-sized gas fields were completely constructed. Both reserves and production reached a new record in history. During the 13th Five-Year Plan, Sinopec Southwest Oil & Gas Company will focus on the exploration and development of deep marine carbonate reservoirs, commercial development of deep shale gas, safe development of gas fields with high sulfur, and enhancement of recovery in mature gas fields. By the end of the 13th Five-Year Plan, it is expected that the annual gas production of (10–12 × 109 m3 will be achieved.

  10. Influence of electromagnetic field intensity on the metastable zone width of CaCO3 crystallization in circulating water

    Science.gov (United States)

    Wang, Jianguo; Liang, Yandong; Chen, Si

    2016-09-01

    In this study, changes in the metastable zone width of CaCO3 crystallization was determined through conductivity titration by altering electromagnetic field parameters applied to the circulating water system. The critical conductivity value and metastable zone curves of CaCO3 crystallization were determined under different solution concentrations and electromagnetic field intensities. Experimental results indicate that the effect of the electromagnetic field intensity on the critical conductivity value intensifies with the increase of solution concentration. Moreover, the metastable zone width of CaCO3 crystallization increases with the increase of electromagnetic field intensity within 200 Gs, thereby prolonging the induction period of nucleation.

  11. A Cubic Tree Taper Model

    National Research Council Canada - National Science Library

    Goodwin, Adrian N

    2009-01-01

    A flexible tree taper model based on a cubic polynomial is described. It is algebraically invertible and integrable, and can be constrained by one or two diameters, neither of which need be diameter at breast height (DBH...

  12. Milestone in the History of Field-Effect Liquid Crystal Displays and Materials

    Science.gov (United States)

    Schadt, Martin

    2009-03-01

    The history of digital electronics would have been very different without the invention of field-effect liquid crystal displays (LCDs) in 1970 and their sophisticated development and implementation into numerous products. Transmissive and reflective LCDs have become a key interface between man and machine. After almost 40 years of interdisciplinary R+D and engineering, today's LCDs enable virtually all display applications, including high definition television. Field-effect LCDs are characterized by flat design, low weight, low driving voltage, design flexibility, compatibility with silicon-on-glass and very low power consumption, especially in reflection. Their polarization-sensitive layer concept is the basis for sandwiching and integration of optical and electronic thin-film functions. The liquid crystal technology has become a fast growing industry over the past 38 years, today surpassing 100 billion, with many spin-offs into new areas. Prerequisite for field-effect LCDs and their large diversification potential is the unique self-organization of liquid crystals. New applications beyond displays based on self-organisation, smart boundary alignment, dedicated liquid crystalline materials and the ability of LCs to respond to electromagnetic fields, including light, are being developed. Examples for new applications are LC polymer thin-film optics, or synergies between LCDs and solid state back-lighting, such as inorganic and organic light emitting diodes (LEDs/OLEDs).

  13. Hyperfine and crystal field interactions in multiferroic HoCrO3

    Science.gov (United States)

    Kumar, C. M. N.; Xiao, Y.; Nair, H. S.; Voigt, J.; Schmitz, B.; Chatterji, T.; Jalarvo, N. H.; Brückel, Th

    2016-11-01

    We report a comprehensive specific heat and inelastic neutron scattering study to explore the possible origin of multiferroicity in HoCrO3. We have performed specific heat measurements in the temperature range 100 mK-290 K and inelastic neutron scattering measurements were performed in the temperature range 1.5-200 K. From the specific heat data we determined hyperfine splitting at 22.5(2) μeV and crystal field transitions at 1.379(5) meV, 10.37(4) meV, 15.49(9) meV and 23.44(9) meV, indicating the existence of strong hyperfine and crystal field interactions in HoCrO3. Further, an effective hyperfine field is determined to be 600(3) T. The quasielastic scattering observed in the inelastic scattering data and a large linear term γ =6.3(8) mJ mol-1  K-2 in the specific heat is attributed to the presence of short range exchange interactions, which is understood to be contributing to the observed ferroelectricity. Further the nuclear and magnetic entropies were computed to be, ˜17.2 Jmol-1 K-1 and  ˜34 Jmol-1 K-1, respectively. The entropy values are in excellent agreement with the limiting theoretical values. An anomaly is observed in the peak position of the temperature dependent crystal field spectra around 60 K, at the same temperature an anomaly in the pyroelectric current is reported. From this we could elucidate a direct correlation between the crystal electric field excitations of Ho3+ and ferroelectricity in HoCrO3. Our present study, along with recent reports, confirm that HoCrO3, and RCrO3 (R  =  rare earth) in general, possess more than one driving force for the ferroelectricity and multiferroicity.

  14. Neutron diffraction investigations of zero-field and field-induced magnetic structures of DyNiSn single crystal

    Energy Technology Data Exchange (ETDEWEB)

    Murogaki, K. [Graduate School of Science, Kyoto University, Kyoto 606-8502 (Japan)]. E-mail: murogaki@fiberbit.net; Kawano, S. [Research Reactor Institute, Kyoto University, Osaka 590-0494 (Japan); Andoh, Y. [Faculty of Regional Sciences, Tottori University, Tottori 680-8551 (Japan); Takahashi, M. [Institute of Materials Science, University of Tsukuba, Ibaraki 305-8573 (Japan); Kurisu, M. [Japan Advanced Institute of Science and Technology, Ishikawa 923-1292 (Japan); Nakamoto, G. [Japan Advanced Institute of Science and Technology, Ishikawa 923-1292 (Japan); Anh, D.T. Kim [Japan Advanced Institute of Science and Technology, Ishikawa 923-1292 (Japan); Tsutaoka, T. [Graduate School of Education, Hiroshima University, Hiroshima 739-8524 (Japan)

    2006-02-09

    Single crystal neutron diffraction studies have been performed on the rare-earth ternary compound, DyNiSn. This crystal exhibits an incommensurate magnetic structure expressed by the propagation vector, Q = (0.662 0.352 0) with its third harmonics at low temperatures. In an external magnetic field applied along the c-axis DyNiSn shows incommensurate modulation with Q = (1 0.315 0) at 1.6 K, while along the easy magnetization direction of the b-axis a commensurate modulation with Q = (2/3 0 0) develops at 2 K. The results along the b-axis are fully consistent with the magnetization curve.

  15. Self-consistent density functional calculations of the crystal field levels in lanthanide and actinide dioxides

    Science.gov (United States)

    Zhou, Fei; Ozoliņš, Vidvuds

    2012-02-01

    Using a recently developed method combining a nonspherical self-interaction corrected LDA + U scheme and an on-site multibody Hamiltonian [Phys. Rev. BPRBMDO1098-012110.1103/PhysRevB.83.085106 83, 085106 (2011)], we calculate the crystal field parameters and crystal field (CF) excitation levels of f-element dioxides in the fluorite structure with fn electronic configurations, including n=1 (PaO2, PrO2), n=2 (UO2), n=3 (NpO2), and n=4 (PuO2). It is shown that good agreement with experimental data (within approximately 10-20 meV) can be obtained in all cases. The properties of the multielectron CF ground states are analyzed.

  16. 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 ...

  17. Phase Transition for a Mixed Spin-1/2 and Spin-sB System with a Transverse Crystal Field

    Institute of Scientific and Technical Information of China (English)

    JIANG Wei; XIAO Gui-Bin; WEI Guo-Zhu; DU An; ZHANG Qi

    2004-01-01

    The critical behaviors of a mixed spin-1/2 and spin-sB Ising system with a transverse crystal field are studied by use of the effective-field theory with correlations. The effect of the transverse crystal field on transition temperatures is investigated numerically for the honeycomb (z = 3) and square (z = 4) lattices. The results show that there is no tricritical point for the system.

  18. Tunable extended depth of field using a liquid crystal annular spatial filter.

    Science.gov (United States)

    Klapp, Iftach; Solodar, Asi; Abdulhalim, Ibrahim

    2014-03-15

    A tunable extended depth of field (EDOF) imaging is presented using temporal multiplexing and a low-cost eight-ring, annular liquid crystal spatial light modulator. By changing between different phase profiles in the pupil plane of a lens we perform several levels of EDOF. Using these levels as a "database" it is shown by temporal multiplexing how to decompose tunable levels of EDOF.

  19. Longitudinal magnetoresistance of layered crystals in a quantizing magnetic field taking into account the spin splitting

    Science.gov (United States)

    Askerov, B. M.; Figarova, S. R.; Mahmudov, M. M.

    2006-07-01

    The magnetoresistance of layered crystals in a longitudinal quantizing magnetic field by taking into account the spin splitting is theoretically investigated. The general expression for the electrical conductivity of a quasi two-dimensional electron gas at the deformation-potential scattering has been obtained. In the behavior of the specific resistance, peaks have been revealed, and a number and positions of the peaks are dictated by the spin splitting magnitude.

  20. Evaluation of the exchange interaction and crystal fields in a prototype Dy2 SMM

    Science.gov (United States)

    Zhang, Qing; Sarachik, Myriam; Baker, Michael; Chen, Yizhang; Kent, Andrew; Pineda, Eufemio; McInnes, Eric

    In order to gain an understanding of the INS and magnetization data obtained for Dy2, the simplest member of a newly synthesized family of dysprosium-based molecular magnets, we report on calculations of the magnetic behavior of a Dy2 cluster with the formula [hqH2][Dy2(hq)4(NO3)3].MeOH. The molecular complex contains one high symmetry Dy(III) ion and one low symmetry Dy(III) ion. Our calculations suggest that exchange coupling between the two ions controls the behavior of the magnetization at low temperature, while the crystal field of the low symmetry Dy(III) ion controls the behavior at higher temperature. A point charge electrostatic model, based on crystallographic coordinates, provides a starting point for the determination of the crystal field. Parameters in these calculations are adjusted to provide best fits to inelastic neutron scattering data (INS) and low temperature magnetometry: the INS measurements access crystal field energies and low temperature magnetization probes the Dy-Dy exchange interaction. Work supported by ARO W911NF-13-1-1025 (CCNY) and NSF-DMR-1309202 (NYU).

  1. Crystal-field and covalency effects in uranates: an X-ray spectroscopic study

    Energy Technology Data Exchange (ETDEWEB)

    Butorin, Sergei M. [Molecular and Condensed Matter Physics, Department of Physics and Astronomy, Uppsala University, Uppsala (Sweden); Kvashnina, Kristina O. [European Synchrotron Radiation Facility, CS40220, Grenoble (France); Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Institute of Resource Ecology, Dresden (Germany); Smith, Anna L. [Department of Radiation Science and Technology, TU Delft (Netherlands); Popa, Karin [European Commission, Joint Research Centre, Institute for Transuranium Elements, Karlsruhe (Germany); Martin, Philippe M. [CEA Marcoule, CEA, DEN, DTEC/SECA/LCC, Bagnols-sur-Ceze (France)

    2016-07-04

    The electronic structure of U{sup V}- and U{sup VI}-containing uranates NaUO{sub 3} and Pb{sub 3}UO{sub 6} was studied by using an advanced technique, namely X-ray absorption spectroscopy (XAS) in high-energy-resolution fluorescence-detection (HERFD) mode. Due to a significant reduction in core-hole lifetime broadening, the crystal-field splittings of the 5f shell were probed directly in HERFD-XAS spectra collected at the U 3d edge, which is not possible by using conventional XAS. In addition, the charge-transfer satellites that result from U 5f-O 2p hybridization were clearly resolved. The crystal-field parameters, 5f occupancy, and degree of covalency of the chemical bonding in these uranates were estimated by using the Anderson impurity model by calculating the U 3d HERFD-XAS, conventional XAS, core-to-core (U 4f-3d transitions) resonant inelastic X-ray scattering (RIXS), and U 4f X-ray photoelectron spectra. The crystal field was found to be strong in these systems and the 5f occupancy was determined to be 1.32 and 0.84 electrons in the ground state for NaUO{sub 3} and Pb{sub 3}UO{sub 6}, respectively, which indicates a significant covalent character for these compounds. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  2. Local symmetry lowering in the cubic intermetallics YbPdBi and YbNiSb

    Energy Technology Data Exchange (ETDEWEB)

    LeBras, G.; Bonville, P.; Hodges, J.A.; Hammann, J.; Besnus, M.J.; Schmerber, G.; Dhar, S.K.; Aliev, F.G.; Andre, G. [DRECAM/SPEC, CE Saclay, Gif-sur-Yvette (France)

    1995-07-10

    A microscopic investigation of the cubic ternary alloys YbPdBi and YbNiSb, using {sup 170}Yb Mossbauer spectroscopy, reveals that the point symmetry at the site of the Yb{sup 3+} is far from cubic in both compounds. An analysis of the thermal variation of the quadrupolar 4f moment shows that the energy of the first crystal electric field transition is close to 20 K in YbPdBi and to 10 K in YbNiSb. Specific heat measurements are also presented in YbPdBi, and magnetic ordering is detected below 1 K in YbPdBi, with saturated Yb{sup 3+} moments of 1.25 {mu}{sub B}, and below 0.85 K in YbNiSb, with saturated moments of 1 {mu}{sub B}. A tentative explanation of the Yb site symmetry breaking is made in terms of a Jahn-Teller distortion within the {gamma}{sub 8} cubic quartet. (author)

  3. Beta tricalcium phosphate ceramics with controlled crystal orientation fabricated by application of external magnetic field during the slip casting process.

    Science.gov (United States)

    Hagio, Takeshi; Yamauchi, Kazushige; Kohama, Takenori; Matsuzaki, Toshiya; Iwai, Kazuhiko

    2013-07-01

    Beta tricalcium phosphate (β-TCP) is a resorbable bioceramic that has hitherto been utilized in the medical field. Since it crystallizes in the anisotropic hexagonal system, properties such as chemical and physical ones are expected to depend on its crystal axis direction and/or on its crystal plane (anisotropy). Control of crystal orientation is thus important when used in polycrystalline form. Meanwhile, application of a strong magnetic field has been found to be a promising technique to control crystal orientation of anisotropic shape or structured crystals. In this work, we attempted to fabricate β-TCP ceramics with controlled crystal orientation by applying an external magnetic field during the slip casting process and subsequently sintering them at 1050°C, below the β-α transition temperature. Application of a vertical magnetic field increased intensities of planes perpendicular to c-plane on the top surface, while a horizontal one with simultaneous mechanical mold rotation decreased it. These results indicated that crystal orientation of β-TCP ceramics were successfully controlled by the external magnetic field and together that the magnetic susceptibility of β-TCP is χ(c[perpendicular])>χ(c//).

  4. Phase Diagrams and Tricritical Behaviour of the Spin-2 Ising Model in a Longitudinal Random Field

    Institute of Scientific and Technical Information of China (English)

    LIANG Ya-Qiu; WEI Guo-Zhu; ZHANG Qi; SONG Guo-Li

    2004-01-01

    @@ Within the framework of the effective-field theory with correlations, we study the ferromagnetic spin-2 randomfield Ising model (RFIM) in the presence of a crystal field on honeycomb (z = 3), square (z = 4) and simple cubic (z = 6) lattices. The effects of the crystal field and the longitudinal random field on the phase diagrams are investigated. Some characteristic features of the phase diagrams, such as the tricritical phenomena, reentrant phenomena and existence of two tricritical points, are found.

  5. The double-end-pumped cubic Nd:YVO4 laser: Temperature distribution and thermal stress

    Indian Academy of Sciences (India)

    P Elahi; S Morshedi

    2010-01-01

    Thermal effects of a double-end-pumped cubic Nd:YVO4 laser crystal are investigated in this paper. A detailed analysis of temperature distribution and thermal stress in cubic crystal with circular shape pumping is discussed. It has been shown that by considering the total input powers as constant, the double-end-pumped configurations with equal pump power can be considered as having a minimum thermal effect with respect to the other end-pumped configuration.

  6. Computational Strain Gradient Crystal Plasticity

    DEFF Research Database (Denmark)

    Niordson, Christian Frithiof; Kysar, Jeffrey W.

    2011-01-01

    A model for strain gradient crystal visco-plasticity is formulated along the lines proposed by Fleck andWillis (2009) for isotropic plasticity. Size-effects are included in the model due to the addition of gradient terms in both the free energy as well as through a dissipation potential. A finite...... element solution method is presented, which delivers the slip-rate field and the velocity-field based on two minimum principles. Some plane deformation problems relevant for certain specific orientations of a face centered cubic crystal under plane loading conditions are studied, and effective in......-plane parameters are developed based on the crystallographic properties of the material. The problem of cyclic shear of a single crystal between rigid platens is studied as well as void growth of a cylindrical void....

  7. Novel colloidal system: Magnetite-polymer particles/lyotropic liquid crystal under magnetic field

    Science.gov (United States)

    Mănăilă-Maximean, D.; Cîrtoaje, C.; Dănilă, O.; Donescu, D.

    2017-09-01

    We obtained a new highly ordered colloidal composite using specially manufactured magnetite-polymer nanoparticles and lyotropic liquid crystal. A good compatibility between the components was ensured by the functionalization of the particles during their synthesis. We studied the laser light transmission for the mixtures filled in sandwich-glass cells with homeotropic and planar treatment of the surfaces under external magnetic field. The Fréedericksz transition critical field was estimated, and its' behavior was compared to our new theoretical model based on the Brochard-de Gennes one.

  8. A photonic-crystal optical antenna for extremely large local-field enhancement.

    Science.gov (United States)

    Chang, Hyun-Joo; Kim, Se-Heon; Lee, Yong-Hee; Kartalov, Emil P; Scherer, Axel

    2010-11-08

    We propose a novel design of an all-dielectric optical antenna based on photonic-band-gap confinement. Specifically, we have engineered the photonic-crystal dipole mode to have broad spectral response (Q~70) and well-directed vertical-radiation by introducing a plane mirror below the cavity. Considerably large local electric-field intensity enhancement~4,500 is expected from the proposed design for a normally incident planewave. Furthermore, an analytic model developed based on coupled-mode theory predicts that the electric-field intensity enhancement can easily be over 100,000 by employing reasonably high-Q (~10,000) resonators.

  9. Magnetism of Rare-Earth Compounds with Non-Magnetic Crystal-Field Ground Levels

    Institute of Scientific and Technical Information of China (English)

    LIU Zhao-Sen

    2007-01-01

    @@ Among rare-earth compounds, there are many materials having non-magnetic crystal-field (CF) ground levels.To understand their magnetic behaviour at low temperatures, we study the effects of the CF levels and the Heisenberg-like coupling on the magnetic process of such a crystalline with mean-field and CF theory. It is found that the material can be magnetically ordered if the Heisenberg exchange is sufficiently strong. Additionally we obtain a condition for initial magnetic ordering, and derive a formula for estimating the Curie temperature if the ordering occurs.

  10. Crystal fields of porphyrins and phthalocyanines from polarization-dependent 2p-to-3d multiplets

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, Phillip S.; Boukahil, Idris; Himpsel, F. J., E-mail: fhimpsel@wisc.edu [Department of Physics, University of Wisconsin-Madison, 1150 University Ave., Madison, Wisconsin 53706 (United States); García-Lastra, J. M. [Department of Energy Conversion and Storage, Technical University of Denmark, 4000 Roskilde (Denmark); Kennedy, Colton K.; Jersett, Nathan J.; Cook, Peter L. [Natural Sciences Department, University of Wisconsin-Superior, Belknap and Catlin, Superior, Wisconsin 54880 (United States)

    2014-03-21

    Polarization-dependent X-ray absorption spectroscopy is combined with density functional calculations and atomic multiplet calculations to determine the crystal field parameters 10Dq, Ds, and Dt of transition metal phthalocyanines and octaethylporphyrins (Mn, Fe, Co, Ni). The polarization dependence facilitates the assignment of the multiplets in terms of in-plane and out-of-plane orbitals and avoids ambiguities. Crystal field values from density functional calculations provide starting values close to the optimum fit of the data. The resulting systematics of the crystal field can be used for optimizing electron-hole separation in dye-sensitized solar cells.

  11. Crystal fields of porphyrins and phthalocyanines from polarization-dependent 2p-to-3d multiplets

    Science.gov (United States)

    Johnson, Phillip S.; García-Lastra, J. M.; Kennedy, Colton K.; Jersett, Nathan J.; Boukahil, Idris; Himpsel, F. J.; Cook, Peter L.

    2014-03-01

    Polarization-dependent X-ray absorption spectroscopy is combined with density functional calculations and atomic multiplet calculations to determine the crystal field parameters 10Dq, Ds, and Dt of transition metal phthalocyanines and octaethylporphyrins (Mn, Fe, Co, Ni). The polarization dependence facilitates the assignment of the multiplets in terms of in-plane and out-of-plane orbitals and avoids ambiguities. Crystal field values from density functional calculations provide starting values close to the optimum fit of the data. The resulting systematics of the crystal field can be used for optimizing electron-hole separation in dye-sensitized solar cells.

  12. Theory of crystal field states for heavy rare-earth impurities in MgB sub 2

    CERN Document Server

    Welsch, F; Faehnle, M

    2002-01-01

    For isolated rare-earth impurities substituting for Mg atoms in the superconductor MgB sub 2 the crystal field parameters are calculated by the ab initio density functional electron theory with constraints for the 4f charge and spin density. The crystal field parameter A sub 6 sup 6 is extremely small due to the structure and bonding properties of MgB sub 2 , and therefore the crystal field levels are nearly exclusively determined by one magnetic quantum number M. Implications for the pair-breaking mechanism of the superconductivity in MgB sub 2 are discussed.

  13. Magnetic field induced strain assisted by stress in Ni-Fe-GaCo single crystals

    Directory of Open Access Journals (Sweden)

    Chumlyakov Y.

    2010-06-01

    Full Text Available Ferromagnetic shape memory alloys (FSMA have the possibility to induced a strain by applying a magnetic field. The main advantage of the FSMA is that the strain cycling frequency is two orders of magnitude higher than coventional shape memory alloys. The best alloy showing this effect is the Ni-Mn-Ga system, with a high mobility of its martensite variants and high magnetocrystalline anisotropy constant. Nevertheless, due to the high brittleness of this alloy, other systems (Ni-Fe-Ga, Co-Ni-Al, Co-Ni-Ga, ... are being investigated as an alternative to Ni-Mn-Ga. In the current work, Ni-Fe-Ga-Co single crystals have been studied. In spite of the formation of L10 martensite (low mobility of the variants, the [001] crystals exhibited magnetic-field-induced strains (in tension larger than 2%, under an assisting tensile stress around 16 MPa and fields below 15 kOe. In martensitic samples previously compressed, application of a constant tensile stress along the same axis together with a perpendicular magnetic field produces the elongation of the sample by variant reorientation, as one of the variants rotates its c axis from the field direction to the stress-axis direction. An estimated magnetostress of ~0.8 MPa is in good agreement with the theoretical value given by the ratio of magnetocrystalline anisotropy constant and twinning shear.

  14. The Structure of the Cubic Coincident Site Lattice Rotation Group

    Energy Technology Data Exchange (ETDEWEB)

    Reed, B W; Minich, R W; Rudd, R E; Kumar, M

    2004-01-13

    This work is intended to be a mathematical underpinning for the field of grain boundary engineering and its relatives. The interrelationships within the set of rotations producing coincident site lattices in cubic crystals are examined in detail. Besides combining previously established but widely scattered results into a unified context, the present work details newly developed representations of the group structure in terms of strings of generators (based on quaternionic number theory, and including uniqueness proofs and rules for algebraic manipulation) as well as an easily visualized topological network model. Important results that were previously obscure or not universally understood (e.g. the {Sigma} combination rule governing triple junctions) are clarified in these frameworks. The methods also facilitate several general observations, including the very different natures of twin-limited structures in two and three dimensions, the inadequacy of the {Sigma} combination rule to determine valid quadruple nodes, and a curious link between allowable grain boundary assignments and the four-color map theorem. This kind of understanding is essential to the generation of realistic statistical models of grain boundary networks (particularly in twin-dominated systems) and is especially applicable to the field of grain boundary engineering.

  15. Anisotropies of the lower and upper critical fields in MgB2 single crystals.

    Science.gov (United States)

    Lyard, L; Szabó, P; Klein, T; Marcus, J; Marcenat, C; Kim, K H; Kang, B W; Lee, H S; Lee, S I

    2004-02-01

    The temperature dependence of the upper (H(c2)) and lower (H(c1)) critical fields has been deduced from Hall probe magnetization measurements of high quality MgB2 single crystals along the two main crystallographic directions. We show that Gamma(H(c2))=H(c2 axially ab)/H(c2 axially c) and Gamma(H(c1))=H(c1 axially c)/H(c1 axially ab) differ significantly at low temperature (being approximately 5 and approximately 1, respectively) and have opposite temperature dependencies. We suggest that MgB2 can be described by a single field dependent anisotropy parameter gamma(H) (=lambda(c)/lambda(ab)=xi(ab)/xi(c)) that increases from Gamma(H(c1)) at low field to Gamma(H(c2)) at high field.

  16. Near-field lithography on the azobenzene polymer liquid crystal films

    Institute of Scientific and Technical Information of China (English)

    Douguo Zhang; Jian Liu; Zebo Zhang; Li Cao; Anlian Pan; Pei Wang; Yonghua Lu; Ming Bai; Jun Yang; Lin Tang; Jiangying Zhang; Hai Ming; Qijin Zhang

    2005-01-01

    @@ In this article, we reported near-field research on azobenzene polymer liquid crystal films using scanning near-field optical microscopy (SNOM). Optical writing and subsequently topographic reading of the patterns with subwavelength resolution were carried out in our experiments. Nanometer scale dots and lines were successfully fabricated on the films and the smallest dot diameter is about 120 nm. The width of the line fabricated is about 250 nm. This method is also a choice for nanolithography. The mechanism of the surface deformation on the polymer films was briefly analyzed from the viewpoint of gradient force in the optical near field. The intensity distribution of the electric field near the tip aperture was numerically simulated using finite-difference time-domain (FDTD) method and the numerical simulation results were consistent with the experimental results.

  17. Crystallization Behavior of Anatase Films in Applied Electric Field Heating Process

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    In this research the TiO2 thin films were prepared by sol-gel dip coating. The crystallization of the films in the applied electric field heating process was thoroughly studied by many technique, differential thermal analysis (DTA), Raman spectroscopy and atomic force microscope (AFM). Furthermore the phase formation, microstructure and photo-catalytic activity of TiO2 film were studied under the condition of an electric field heating-treatment. It is found that the existence of applied electric field promotes the phase transformation from anatase to rutile. Studies on photo-catalytic degradation show that the photo-catalytic activity of TiO2 thin films in an applied electric field is higher.

  18. Theoretically informed Monte Carlo simulation of liquid crystals by sampling of alignment-tensor fields.

    Energy Technology Data Exchange (ETDEWEB)

    Armas-Perez, Julio C.; Londono-Hurtado, Alejandro; Guzman, Orlando; Hernandez-Ortiz, Juan P.; de Pablo, Juan J.

    2015-07-27

    A theoretically informed coarse-grained Monte Carlo method is proposed for studying liquid crystals. The free energy functional of the system is described in the framework of the Landau-de Gennes formalism. The alignment field and its gradients are approximated by finite differences, and the free energy is minimized through a stochastic sampling technique. The validity of the proposed method is established by comparing the results of the proposed approach to those of traditional free energy minimization techniques. Its usefulness is illustrated in the context of three systems, namely, a nematic liquid crystal confined in a slit channel, a nematic liquid crystal droplet, and a chiral liquid crystal in the bulk. It is found that for systems that exhibit multiple metastable morphologies, the proposed Monte Carlo method is generally able to identify lower free energy states that are often missed by traditional approaches. Importantly, the Monte Carlo method identifies such states from random initial configurations, thereby obviating the need for educated initial guesses that can be difficult to formulate.

  19. Theoretically informed Monte Carlo simulation of liquid crystals by sampling of alignment-tensor fields

    Energy Technology Data Exchange (ETDEWEB)

    Armas-Pérez, Julio C.; Londono-Hurtado, Alejandro [Institute for Molecular Engineering, University of Chicago, Chicago, Illinois 60637 (United States); Guzmán, Orlando [Departamento de Física, Universidad Autónoma Metropolitana, Iztapalapa, DF 09340, México (Mexico); Hernández-Ortiz, Juan P. [Departamento de Materiales y Minerales, Universidad Nacional de Colombia, Sede Medellín, Medellín (Colombia); Institute for Molecular Engineering, University of Chicago, Chicago, Illinois 60637 (United States); Pablo, Juan J. de, E-mail: depablo@uchicago.edu [Institute for Molecular Engineering, University of Chicago, Chicago, Illinois 60637 (United States); Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States)

    2015-07-28

    A theoretically informed coarse-grained Monte Carlo method is proposed for studying liquid crystals. The free energy functional of the system is described in the framework of the Landau-de Gennes formalism. The alignment field and its gradients are approximated by finite differences, and the free energy is minimized through a stochastic sampling technique. The validity of the proposed method is established by comparing the results of the proposed approach to those of traditional free energy minimization techniques. Its usefulness is illustrated in the context of three systems, namely, a nematic liquid crystal confined in a slit channel, a nematic liquid crystal droplet, and a chiral liquid crystal in the bulk. It is found that for systems that exhibit multiple metastable morphologies, the proposed Monte Carlo method is generally able to identify lower free energy states that are often missed by traditional approaches. Importantly, the Monte Carlo method identifies such states from random initial configurations, thereby obviating the need for educated initial guesses that can be difficult to formulate.

  20. Local atomic structure in cubic stabilized zirconia

    Energy Technology Data Exchange (ETDEWEB)

    Villella, P.; Conradson, S. D.; Espinosa-Faller, F. J.; Foltyn, S. R.; Sickafus, K. E.; Valdez, J. A.; Degueldre, C. A.

    2001-09-01

    X-ray-absorption fine structure measurements have been used to elucidate the local atomic structure of quaternary Zr, Y, Er, Ce/U cubic stabilized zirconia. These compounds display more complicated local environments than those reported for simpler binary systems. While the shortest cation-O distances are similar to those found in the binary cubic stabilized compounds, responding to the different sizes of the cations, we have identified large distortions in the first-shell oxygen distribution involving long, 2.8--3.2 {angstrom} cation-O distances that are similar to those found in the amorphous phase of zirconium. The cation-cation distributions are also found to be quite complicated (non-Gaussian) and element specific. The U-near neighbor distances are expanded relative to the Ce ions for which it substitutes, consistent with the larger size of the actinide, and the U-cation distribution is also more complicated. In terms of the effects of this substitution on the other cation sites, the local environment around Y is altered while the Zr and Er local environments remain unchanged. These results point out the importance of collective and correlated interactions between the different pairs of cations and the host lattice that are mediated by the local strain fields generated by the different cations. The presence of pair-specific couplings has not been commonly included in previous analyses and may have implications for the stabilization mechanisms of cubic zirconia.

  1. The special symplectic structure of binary cubics

    CERN Document Server

    Slupinski, Marcus

    2009-01-01

    Let $k$ be a field of characteristic not 2 or 3. Let $V$ be the $k$-space of binary cubic polynomials. The natural symplectic structure on $k^2$ promotes to a symplectic structure $\\omega$ on $V$ and from the natural symplectic action of $\\textrm{Sl}(2,k)$ one obtains the symplectic module $(V,\\omega)$. We give a complete analysis of this symplectic module from the point of view of the associated moment map, its norm square $Q$ (essentially the classical discriminant) and the symplectic gradient of $Q$. Among the results are a symplectic derivation of the Cardano-Tartaglia formulas for the roots of a cubic, detailed parameters for all $\\textrm{Sl}(2,k)$ and $\\textrm{Gl}(2,k)$-orbits, in particular identifying a group structure on the set of $\\textrm{Sl}(2,k)$-orbits of fixed nonzero discriminant, and a purely symplectic generalization of the classical Eisenstein syzygy for the covariants of a binary cubic. Such fine symplectic analysis is due to the special symplectic nature inherited from the ambient excepti...

  2. Crystal Structure of Garnet-Related Li-Ion Conductor Li7–3x Ga x La3Zr2O12: Fast Li-Ion Conduction Caused by a Different Cubic Modification?

    OpenAIRE

    Wagner, Reinhard; Redhammer, Günther J.; Rettenwander, Daniel; Senyshyn, Anatoliy; Schmidt, Walter; Wilkening, Martin; Amthauer, Georg

    2016-01-01

    Li-oxide garnets such as Li7La3Zr2O12 (LLZO) are among the most promising candidates for solid-state electrolytes to be used in next-generation Li-ion batteries. The garnet-structured cubic modification of LLZO, showing space group Ia-3d, has to be stabilized with supervalent cations. LLZO stabilized with Ga3+ shows superior properties compared to LLZO stabilized with similar cations; however, the reason for this behavior is still unknown. In this study, a comprehensive structural characteriz...

  3. High magnetic-field scales and critical currents in SmFeAs(O, F) crystals

    Science.gov (United States)

    Moll, Philip J. W.; Puzniak, Roman; Balakirev, Fedor; Rogacki, Krzysztof; Karpinski, Janusz; Zhigadlo, Nikolai D.; Batlogg, Bertram

    2010-08-01

    With the discovery of new superconducting materials, such as the iron pnictides, exploring their potential for applications is one of the foremost tasks. Even if the critical temperature Tc is high, intrinsic electronic properties might render applications difficult, particularly if extreme electronic anisotropy prevents effective pinning of vortices and thus severely limits the critical current density, a problem well known for cuprates. Although many questions concerning microscopic electronic properties of the iron pnictides have been successfully addressed and estimates point to a very high upper critical field, their application potential is less clear. Thus, we focus here on the critical currents, their anisotropy and the onset of electrical dissipation in high magnetic fields up to 65T. Our detailed study of the transport properties of SmFeAsO0.7F0.25 single crystals reveals a promising combination of high (>2×106Acm-2) and nearly isotropic critical current densities along all crystal directions. This favourable intragrain current transport in SmFeAs(O, F), which shows the highest Tc of 54K at ambient pressure, is a crucial requirement for possible applications. Essential in these experiments are four-probe measurements on focused-ion-beam-cut single crystals with a sub-square-micrometre cross-section, with current along and perpendicular to the crystallographic c axis.

  4. Direct current electric field assembly of colloidal crystals displaying reversible structural color.

    Science.gov (United States)

    Shah, Aayush A; Ganesan, Mahesh; Jocz, Jennifer; Solomon, Michael J

    2014-08-26

    We report the application of low-voltage direct current (dc) electric fields to self-assemble close-packed colloidal crystals in nonaqueous solvents from colloidal spheres that vary in size from as large as 1.2 μm to as small as 0.1 μm. The assemblies are created rapidly (∼2 min) from an initially low volume fraction colloidal particle suspension using a simple capacitor-like electric field device that applies a steady dc electric voltage. Confocal microscopy is used to observe the ordering that is produced by the assembly method. This spatial evidence for ordering is consistent with the 6-fold diffraction patterns identified by light scattering. Red, green, and blue structural color is observed for the ordered assemblies of colloids with diameters of 0.50, 0.40, and 0.29 μm, respectively, consistent with spectroscopic measurements of reflectance. The diffraction and spectrophotometry results were found to be consistent with the theoretical Bragg's scattering expected for closed-packed crystals. By switching the dc electric field from on to off, we demonstrate reversibility of the structural color response on times scales ∼60 s. The dc electric field assembly method therefore represents a simple method to produce reversible structural color in colloidal soft matter.

  5. Imaging the oblique propagation of electrons in germanium crystals at low temperature and low electric field

    Energy Technology Data Exchange (ETDEWEB)

    Moffatt, R. A., E-mail: rmoffatt@stanford.edu; Cabrera, B.; Corcoran, B. M.; Kreikebaum, J. M.; Redl, P.; Shank, B.; Yen, J. J. [Department of Physics, Stanford University, Stanford, California 94305 (United States); Young, B. A. [Department of Physics, Stanford University, Stanford, California 94305 (United States); Department of Physics, Santa Clara University, Santa Clara, California 95053 (United States); Brink, P. L.; Cherry, M.; Tomada, A. [SLAC National Accelerator Facility, Menlo Park, California 94025 (United States); Phipps, A.; Sadoulet, B.; Sundqvist, K. M. [Department of Physics, University of California, Berkeley, California 94720 (United States)

    2016-01-11

    Excited electrons in the conduction band of germanium collect into four energy minima, or valleys, in momentum space. These local minima have highly anisotropic mass tensors which cause the electrons to travel in directions which are oblique to an applied electric field at sub-Kelvin temperatures and low electric fields, in contrast to the more isotropic behavior of the holes. This experiment produces a full two-dimensional image of the oblique electron and hole propagation and the quantum transitions of electrons between valleys for electric fields oriented along the [0,0,1] direction. Charge carriers are excited with a focused laser pulse on one face of a germanium crystal and then drifted through the crystal by a uniform electric field of strength between 0.5 and 6 V/cm. The pattern of charge density arriving on the opposite face is used to reconstruct the trajectories of the carriers. Measurements of the two-dimensional pattern of charge density are compared in detail with Monte Carlo simulations developed for the Cryogenic Dark Matter Search (SuperCDMS) to model the transport of charge carriers in high-purity germanium detectors.

  6. Magnetostrictive behaviors of Fe-Al(001 single-crystal films under rotating magnetic fields

    Directory of Open Access Journals (Sweden)

    Tetsuroh Kawai

    2016-05-01

    Full Text Available Magnetostrictive behaviors of Fe100−x − Alx(x = 0 − 30 at.%(001 single-crystal films under rotating magnetic fields are investigated along the two different crystallographic orientations, [100] and [110]. The behaviors of Fe and Fe90Al10 films show bath-tub like waveform along [100], easy magnetization axis, and triangular waveform along [110], hard magnetization axis, with respect to their four-fold magnetic anisotropy. On the other hand, the behaviors of Fe80Al20 film are different from those of Fe or Fe90Al10 film. The output of the film along [100] shows a strong magnetic field dependence. The Fe70Al30 film shows similar magnetostrictive behaviors along both [100] and [110] reflecting its magnetic properties, which are almost same for the both directions. The growth of ordered phase (B2 in Fe80Al20 and Fe70Al30 films is considered to have affected their magnetostrictive behaviors. The Al content dependence on λ100 and λ111 values shows similar tendency to that reported for the bulk samples but the values are slightly different. The Fe90Al10(001 single-crystal film shows a large magnetostriction along [100] under a very small magnetic field of 0.02 kOe, which is comparable to the saturated one, and changes the value abruptly in relation to the angle of applied magnetic field.

  7. Universal Reconfiguration of (Hyper-)cubic Robots

    OpenAIRE

    Abel, Zachary; Kominers, Scott D.

    2008-01-01

    We study a simple reconfigurable robot model which has not been previously examined: cubic robots comprised of three-dimensional cubic modules which can slide across each other and rotate about each others' edges. We demonstrate that the cubic robot model is universal, i.e., that an n-module cubic robot can reconfigure itself into any specified n-module configuration. Additionally, we provide an algorithm that efficiently plans and executes cubic robot motion. Our results directly extend to a...

  8. Orientation of growing crystals of Co- or Gd-containing L-threonine dehydrogenase by magnetic fields

    Science.gov (United States)

    Maki, Syou; Ishikawa, Kazuhiko; Ataka, Mitsuo

    2009-12-01

    L-Threonine dehydrogenase from Pyrococcus horikoshii (TDH) is a water-soluble metalloenzyme, the molecular structure of which has been unknown until recently. The Zn 2+ ion in the native TDH, prepared as a recombinant protein, is replaced artificially with Co 2+, Ni 2+ or Gd 3+. These samples are crystallized in homogeneous magnetic fields of 2-10 T. Half of the Co- or Gd-substituted crystals show magnetic orientation in a field of 2 T at 278 K whereas the crystals of the native TDH require a 4 T magnetic field for half orientation. The sensitivity to magnetic orientation can thus be increased by metal substitution. On the other hand, we cannot assign clear changes in the size, number, and quality of the native and metal-substituted crystals with and without the presence of the magnetic field.

  9. Anisotropy and Magnetostriction in Cobalt-Modified Magnetite: A Crystal Field Approach

    Science.gov (United States)

    Nlebedim, Cajetan; Jiles, David

    2013-03-01

    The anisotropy and magnetostrictive properties of magnetite are altered by the introduction of cobalt ions into the spinel crystal lattice. 4% of Co2+ substituted for Fe2+ changes both the sign and magnitude of magnetocrystalline anisotropy coefficient. Such strong dependence can be useful for tailoring the properties of cobalt-iron oxides for applications. This is especially important, considering that cobalt ferrite materials prepared for magnetostrictive, multiferroic and other related applications often deviate from targeted or stoichiometric compositions. In this study, magnetite has been systematically modified by substitution of cobalt. The changes in anisotropy and magnetostriction have been studied and can be explained using the single ion model. The agreement between the trend observed in this experimental investigation and previous theoretical studies is noteworthy. The variation in anisotropy and magnetostriction will be presented on the basis of two competing factors; the unquenched orbital angular momentum of Co2+ and changes in the crystal field due to Co2+ substitution.

  10. Deflecting Easy-axis of Fe304 Single Crystal Nanowires by Magnetic-field-induced Method

    Institute of Scientific and Technical Information of China (English)

    W. Wang; S. Y. Wang

    2012-01-01

    In order to control the orientation of easy-axis of magnetic nanowires, FesO4 single crystal nanowires with easy-axis perpendicular to wire-axis were prepared successfully by means of a magnetic-field-induced method. Analysis of X-ray diffraction and electron diffraction pattern showed that there was a wide-angle deflection of easy-axis in the prepared Fe304 nanowires. A high saturation magnetization (82 emu/g) of the FesO4 nanowires was achieved at room temperature. The benefits and mechanism of the deflection of easy-axis from its wire-axis in FesO4 single crystal nanowires were discussed. The results are expected to broaden the magnetic properties of traditional ferrite nanowires.

  11. Development of specialized modelling tools for crystal growth processes with magnetic fields

    Science.gov (United States)

    Rudevics, A.; Muiznieks, A.; Nacke, B.

    2007-06-01

    The present paper is devoted to some aspects of the development of specialized software for the modelling of crystal growth processes with magnetic fields. Due to the complexity of the mathematical models for such processes, the modern technology of software design and implementation has to be used. Our experience in numerical modelling of crystal growth processes has shown that such approach facilitates the development of complex software systems. It involves the so-called object-oriented design and programming as well as the use of powerful software libraries in order to benefit from its functionality. To illustrate the programs created by our group, some examples are briefly described in this paper. Figs 7, Refs 13.

  12. On the binding of small polarons in a mean-field quantum crystal

    CERN Document Server

    Lewin, Mathieu

    2012-01-01

    We consider a small multi-polaron model obtained by coupling the many-body Schr\\"odinger equation for N interacting electrons with the energy functional of a mean- field crystal with a localized defect, obtaining a highly non linear many-body problem. The physical picture is that the electrons constitue a charge defect in an otherwise perfect periodic crystal. A remarkable feature of such a system is the possibility to form a bound state of electrons via their interaction with the polarizable background. We first prove that a single polaron always binds, i.e. the energy functional has a minimizer for N = 1. Then we discuss the case of multi-polarons containing two electrons or more. We show that their existence is guaranteed when certain quantized binding inequalities of HVZ type are satisfied.

  13. Crystal field-phonon coupling in the Kondo lattice CeCu2

    Science.gov (United States)

    Witte, U.; Kramp, S.; Braden, M.; Svoboda, P.; Loewenhaupt, M.

    CeCu2 is a Kondo lattice and shows antiferromagnetic order below 3.5K. In earlier neutron-scattering experiments on a polycrystalline sample an anomaly in the inelastic neutron spectra at about 14 meV and at temperatures between 100 and 150K was observed. This has led to the assumption of a coupling between a crystal field transition between two excited levels and phonons. Inelastic neutron measurements on a single crystal confirm this assumption. We find an unusual strong energy shift (up to 15%) of certain phonons with increasing temperature, depending on their symmetry. At the same time the magnetic response is strongly broadened due to the coupling to the phonons.

  14. Crystal field-phonon coupling in the Kondo lattice CeCu{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Witte, U. [TU Dresden, Institut fuer Angewandte Physik (IAPD), 01062 Dresden (Germany); HMI Berlin, Glienicker Str. 100, 14109 Berlin (Germany); Kramp, S. [HMI Berlin, Glienicker Str. 100, 14109 Berlin (Germany); Braden, M. [LLB Saclay, 91191 Gif-Sur-Yvette Cedex (France); Svoboda, P. [Charles University, 12116 Praha (Czech Republic); Loewenhaupt, M. [TU Dresden, Institut fuer Angewandte Physik (IAPD), 01062 Dresden (Germany)

    2002-07-01

    CeCu{sub 2} is a Kondo lattice and shows antiferromagnetic order below 3.5 K. In earlier neutron-scattering experiments on a polycrystalline sample an anomaly in the inelastic neutron spectra at about 14 meV and at temperatures between 100 and 150 K was observed. This has led to the assumption of a coupling between a crystal field transition between two excited levels and phonons. Inelastic neutron measurements on a single crystal confirm this assumption. We find an unusual strong energy shift (up to 15%) of certain phonons with increasing temperature, depending on their symmetry. At the same time the magnetic response is strongly broadened due to the coupling to the phonons. (orig.)

  15. Crystal fields of porphyrins and phthalocyanines from polarization-dependent 2p-to-3d multiplets

    OpenAIRE

    Johnson, Phillip S.; García Lastra, Juan Maria; Kennedy, Colton K.; Jersett, Nathan J.; Boukahil, Idris; Himpsel, F. J.; Cook, Peter L.

    2014-01-01

    Polarization-dependent X-ray absorption spectroscopy is combined with density functional calculations and atomic multiplet calculations to determine the crystal field parameters 10Dq, Ds, and Dt of transition metal phthalocyanines and octaethylporphyrins (Mn, Fe, Co, Ni). The polarization dependence facilitates the assignment of the multiplets in terms of in-plane and out-of-plane orbitals and avoids ambiguities. Crystal field values from density functional calculations provide starting value...

  16. Melt Motion Due to Peltier Marking During Bridgman Crystal Growth with an Axial Magnetic Field

    Science.gov (United States)

    Sellers, C. C.; Walker, John S.; Szofran, Frank R.; Motakef, Shariar

    2000-01-01

    This paper treats a liquid-metal flow inside an electrically insulating cylinder with electrically conducting solids above and below the liquid region. There is a uniform axial magnetic field, and there is an electric current through the liquid and both solids. Since the lower liquid-solid interface is concave into the solid and since the liquid is a better electrical conductor than the adjacent solid, the electric current is locally concentrated near the centerline. The return to a uniform current distribution involves a radial electric current which interacts with the axial magnetic field to drive an azimuthal flow. The axial variation of the centrifugal force due to the azimuthal velocity drives a meridional circulation with radial and axial velocities. This problem models the effects of Peltier marking during the vertical Bridgman growth of semiconductor crystals with an externally applied magnetic field, where the meridional circulation due to the Peltier Current may produce important mixing in the molten semiconductor.

  17. Enhanced electrocaloric cooling in ferroelectric single crystals by electric field reversal

    Science.gov (United States)

    Ma, Yang-Bin; Novak, Nikola; Koruza, Jurij; Yang, Tongqing; Albe, Karsten; Xu, Bai-Xiang

    2016-09-01

    An improved thermodynamic cycle is validated in ferroelectric single crystals, where the cooling effect of an electrocaloric refrigerant is enhanced by applying a reversed electric field. In contrast to the conventional adiabatic heating or cooling by on-off cycles of the external electric field, applying a reversed field is significantly improving the cooling efficiency, since the variation in configurational entropy is increased. By comparing results from computer simulations using Monte Carlo algorithms and experiments using direct electrocaloric measurements, we show that the electrocaloric cooling efficiency can be enhanced by more than 20% in standard ferroelectrics and also relaxor ferroelectrics, like Pb (Mg1 /3 /Nb2 /3)0.71Ti0.29O3 .

  18. Bifurcation properties of nematic liquid crystals exposed to an electric field: Switchability, bistability, and multistability

    KAUST Repository

    Cummings, L. J.

    2013-07-01

    Bistable liquid crystal displays (LCDs) offer the potential for considerable power savings compared with conventional (monostable) LCDs. The existence of two (or more) stable field-free states that are optically distinct means that contrast can be maintained in a display without an externally applied electric field. An applied field is required only to switch the device from one state to the other, as needed. In this paper we examine the basic physical principles involved in generating multiple stable states and the switching between these states. We consider a two-dimensional geometry in which variable surface anchoring conditions are used to control the steady-state solutions and explore how different anchoring conditions can influence the number and type of solutions and whether or not switching is possible between the states. We find a wide range of possible behaviors, including bistability, tristability, and tetrastability, and investigate how the solution landscape changes as the boundary conditions are tuned. © 2013 American Physical Society.

  19. Field analysis of TE and TM modes in photonic crystal Bragg fibers by transmission matrix method

    Directory of Open Access Journals (Sweden)

    M Hosseini Farzad

    2010-03-01

    Full Text Available In this article, we considered the field analysis in photonic crystal Bragg fibers. We apply the method of transmission matrix to calculater the dispersion curves, the longitudinal wave number over wave number versus incident wavelength, and the field distributions of TE and TM modes in the Bragg fiber. Our analysis shows that the field of guided modes is confined in the core and can exist only in particular wavelength bands corresponding to the band-gap of the periodic structure of the clad. From another point of view, light confinement is due to Bragg reflection from high-and low-refractive index layers of the clad. Also, the diagram of average angular frequency with respect to average longitudinal wave number is plotted so that the band gap regions of the clad are clearly observed.

  20. Near-field characterization of low-loss photonic crystal waveguides

    DEFF Research Database (Denmark)

    Volkov, V. S.; Bozhevolnyi, S. I.; Borel, Peter Ingo

    2005-01-01

    A scanning near-field optical microscope is used to directly map the propagation of light in the wavelength range of 1500-1630 nm along straight photonic crystal waveguides (PCWs) fabricated on silicon-on-insulator wafers. The PVWs were formed by removing a single row of holes in the triangular 428......-nm-period lattices with different filling factors (0.76 and 0.82) and connected to access ridge waveguides. Using the near-field optical images we investigate the light propagation along PCWs for TM and TE polarization (the electric field is perpendicular/parallel to the sample surface). Efficient...... guiding (for both samples) of the TM-polarized radiation is observed in the whole range of laser tunability. For TE polarization, the efficient guiding is limited to the wavelengths shorter than 1552 or 1570 nm for the PCW with the filling factor of 0.76 or 0.82, respectively. For longer wavelengths, we...

  1. 3D global analysis of CZ-Si growth in a transverse magnetic field with rotating crucible and crystal

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Lijun; Kakimoto, Koichi [Research Institute for Applied Mechanics, Kyushu University, 6-1, Kasuga-Koen, Kasuga 816-8580 (Japan)

    2005-04-01

    Three-dimensional global simulations were carried out for a small Czochralski furnace for silicon crystal growth with a recently developed global model. The furnace is placed in a transverse magnetic field with rotating crucible and crystal. The convective, conductive and radiative heat transfers in the entire furnace were solved in a three-dimensionally conjugated way. Three-dimensional distributions of temperature and velocity were analyzed. The melt-crystal interface was found to have nearly rotational symmetry, and the azimuthal non-uniformity of temperature is much weaker on the crystal and crucible sidewalls in the case of high rotation rates of crucible and crystal than in the case of non-rotating crucible and crystal. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  2. Interpolating solutions in cubic superstring field theory

    CERN Document Server

    Arroyo, E Aldo

    2016-01-01

    Performing a gauge transformation of an identity based solution, we construct a one-parameter family of solutions, and by evaluating the energy associated to these solutions, we show that depending on the value of the parameter, the solution interpolates between three distinct gauge orbits corresponding to the perturbative vacuum, the half brane and the tachyon vacuum solution.

  3. Optical electric-field sensor based on angular optical bias using single β-BaB2O4 crystal.

    Science.gov (United States)

    Li, Changsheng; Shen, Xiaoli; Zeng, Rong

    2013-11-01

    A novel optical electric-field sensor is proposed and demonstrated in experiment by use of a single beta barium borate (β-BaB2O4, BBO) crystal. The optical sensing unit is only composed of one BBO crystal and two polarizers. An optical phase bias of 0.5π is provided by using natural birefringence in the BBO crystal itself. A small angle (e.g., 0.6°) between the sensing light beam and principal axis of the crystal is required in order to produce the above optical bias. Thus the BBO crystal is used as the electric-field-sensing element and quarter waveplate. The ac electric field in the range of (1.4-703.2) kV/m has been measured with measurement sensitivity of 1.39 mV/(kV/m) and nonlinear error of 0.6%. Compared with lithium niobate crystal used as an electric-field sensor, main advantages of the BBO crystal include higher measurement sensitivity, compact configuration, and no ferroelectric ringing effect.

  4. Large field-induced-strain at high temperature in ternary ferroelectric crystals

    Science.gov (United States)

    Wang, Yaojin; Chen, Lijun; Yuan, Guoliang; Luo, Haosu; Li, Jiefang; Viehland, D.

    2016-10-01

    The new generation of ternary Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 ferroelectric single crystals have potential applications in high power devices due to their surperior operational stability relative to the binary system. In this work, a reversible, large electric field induced strain of over 0.9% at room temperature, and in particular over 0.6% above 380 K was obtained. The polarization rotation path and the phase transition sequence of different compositions in these ternary systems have been determined with increasing electric field applied along [001] direction based on x-ray diffraction data. Thereafter, composition dependence of field-temperature phase diagrams were constructed, which provide compositional and thermal prospectus for the electromechanical properties. It was found the structural origin of the large stain, especially at higher temperature is the lattice parameters modulated by dual independent variables in composition of these ternary solid solution crystals.

  5. Cubication of Conservative Nonlinear Oscillators

    Science.gov (United States)

    Belendez, Augusto; Alvarez, Mariela L.; Fernandez, Elena; Pascual, Immaculada

    2009-01-01

    A cubication procedure of the nonlinear differential equation for conservative nonlinear oscillators is analysed and discussed. This scheme is based on the Chebyshev series expansion of the restoring force, and this allows us to approximate the original nonlinear differential equation by a Duffing equation in which the coefficients for the linear…

  6. Cryptographic Analysis in Cubic Time

    DEFF Research Database (Denmark)

    Nielson, Flemming; Nielson, Hanne Riis; Seidl, H.

    2004-01-01

    The spi-calculus is a variant of the polyadic pi-calculus that admits symmetric cryptography and that admits expressing communication protocols in a precise though still abstract way. This paper shows that context-independent control flow analysis can be calculated in cubic time despite the fact ...

  7. The diagonalization of cubic matrices

    Science.gov (United States)

    Cocolicchio, D.; Viggiano, M.

    2000-08-01

    This paper is devoted to analysing the problem of the diagonalization of cubic matrices. We extend the familiar algebraic approach which is based on the Cardano formulae. We rewrite the complex roots of the associated resolvent secular equation in terms of transcendental functions and we derive the diagonalizing matrix.

  8. Phase field theory of interfaces and crystal nucleation in a eutectic system of fcc structure: I. Transitions in the one-phase liquid region.

    Science.gov (United States)

    Tóth, Gyula I; Gránásy, László

    2007-08-21

    The phase field theory (PFT) has been applied to predict equilibrium interfacial properties and nucleation barrier in the binary eutectic system Ag-Cu using double well and interpolation functions deduced from a Ginzburg-Landau expansion that considers fcc (face centered cubic) crystal symmetries. The temperature and composition dependent free energies of the liquid and solid phases are taken from CALculation of PHAse Diagrams-type calculations. The model parameters of PFT are fixed so as to recover an interface thickness of approximately 1 nm from molecular dynamics simulations and the interfacial free energies from the experimental dihedral angles available for the pure components. A nontrivial temperature and composition dependence for the equilibrium interfacial free energy is observed. Mapping the possible nucleation pathways, we find that the Ag and Cu rich critical fluctuations compete against each other in the neighborhood of the eutectic composition. The Tolman length is positive and shows a maximum as a function of undercooling. The PFT predictions for the critical undercooling are found to be consistent with experimental results. These results support the view that heterogeneous nucleation took place in the undercooling experiments available at present. We also present calculations using the classical droplet model [classical nucleation theory (CNT)] and a phenomenological diffuse interface theory (DIT). While the predictions of the CNT with a purely entropic interfacial free energy underestimate the critical undercooling, the DIT results appear to be in a reasonable agreement with the PFT predictions.

  9. Calculation of crystal-field parameters for rare-earth noble metal alloys

    Energy Technology Data Exchange (ETDEWEB)

    Steinbeck, L. [MPG Research Group `Electron Systems`, Department of Physics, University of Technology, Mommsenstr. 13, D-01062, Dresden (Germany); Richter, M. [MPG Research Group `Electron Systems`, Department of Physics, University of Technology, Mommsenstr. 13, D-01062, Dresden (Germany); Eschrig, H. [MPG Research Group `Electron Systems`, Department of Physics, University of Technology, Mommsenstr. 13, D-01062, Dresden (Germany); Nitzsche, U. [MPG Research Group `Electron Systems`, Department of Physics, University of Technology, Mommsenstr. 13, D-01062, Dresden (Germany)

    1995-02-09

    The crystal-field (CF) parameters for 4f electrons of a series of rare-earth impurities in Ag and Au have been evaluated from first-principles density functional calculations of the charge distribution which are based on an optimized LCAO scheme. The localized 4f states are treated as `open core shell`. By including the self-interaction correction for the 4f states, artificial constraints on the 4f charge density employed in earlier density functional CF calculations are avoided. The calculated parameters are compared with recent neutron scattering data. ((orig.)).

  10. Calculation of crystal-field parameters for rare-earth noble metal alloys

    Science.gov (United States)

    Steinbeck, L.; Richter, M.; Eschrig, H.; Nitzsche, U.

    1995-02-01

    The crystal-field (CF) parameters for 4f electrons of a series of rare earth impurities in Ag and Au have been evaluated from first-principles density functional calculations of the charge distribution which are based on an optimized LCAO scheme. The localized 4f states are treated as 'open core shell'. By including the self-interaction correction for the 4f states, artificial constraints on the 4f charge density employed in earlier density functional CF calculations are avoided. The calculated parameters are compared with recent neutron scattering data.

  11. Linearly first- and second-order, unconditionally energy stable schemes for the phase field crystal model

    Science.gov (United States)

    Yang, Xiaofeng; Han, Daozhi

    2017-02-01

    In this paper, we develop a series of linear, unconditionally energy stable numerical schemes for solving the classical phase field crystal model. The temporal discretizations are based on the first order Euler method, the second order backward differentiation formulas (BDF2) and the second order Crank-Nicolson method, respectively. The schemes lead to linear elliptic equations to be solved at each time step, and the induced linear systems are symmetric positive definite. We prove that all three schemes are unconditionally energy stable rigorously. Various classical numerical experiments in 2D and 3D are performed to validate the accuracy and efficiency of the proposed schemes.

  12. Light quasiparticles dominate electronic transport in molecular crystal field-effect transistors

    Energy Technology Data Exchange (ETDEWEB)

    Li, Z. Q.; Podzorov, V.; Sai, N.; Martin, Michael C.; Gershenson, M. E.; Di Ventra, M.; Basov, D. N.

    2007-03-01

    We report on an infrared spectroscopy study of mobile holes in the accumulation layer of organic field-effect transistors based on rubrene single crystals. Our data indicate that both transport and infrared properties of these transistors at room temperature are governed by light quasiparticles in molecular orbital bands with the effective masses m[small star, filled]comparable to free electron mass. Furthermore, the m[small star, filled]values inferred from our experiments are in agreement with those determined from band structure calculations. These findings reveal no evidence for prominent polaronic effects, which is at variance with the common beliefs of polaron formation in molecular solids.

  13. Electrical Impact of SiC Structural Crystal Defects on High Electric Field Devices (Invited)

    Science.gov (United States)

    Neudeck, Philip G.

    1999-01-01

    As illustrated by the invited paper at this conference and other works, SiC wafers and epilayers contain a variety of crystallographic imperfections, including micropipes, closed-core screw dislocations, grain boundaries, basal plane dislocations, heteropolytypic inclusions, and surfaces that are often damaged and contain atomically rough features like step bunching and growth pits or hillocks. Present understanding of the operational impact of various crystal imperfections on SiC electrical devices is reviewed, with an emphasis placed on high-field SiC power devices and circuits.

  14. Ambipolar Cu- and Fe-Phthalocyanine single-crystal field-effect transistors

    OpenAIRE

    de Boer, R. W. I.; Stassen, A. F.; Craciun, M. F.; Mulder, C. L.; Molinari, A; Rogge, S.; Morpurgo, A. F.

    2005-01-01

    We report the observation of ambipolar transport in field-effect transistors fabricated on single crystals of Copper- and Iron-Phthalocyanine, using gold as a high work-function metal for the fabrication of source and drain electrodes. In these devices, the room-temperature mobility of holes reaches 0.3 cm$^2$/Vs in both materials. The highest mobility for electrons is observed for Iron-Phthalocyanines and is approximately one order of magnitude lower. Our measurements indicate that these val...

  15. Electric field induced domain formation in surface stabilized ferroelectric liquid crystal cells

    OpenAIRE

    Dierking, Ingo; Gießelmann, Frank; Schacht, Jochen; Zugenmaier, Peter

    1994-01-01

    Two types of domains have been observed for S sub(C) ferroelectric liquid crystals in surface stabilized cells (SSFLC) by application of a high electric field with the smectic layers tilted by the amount of the chevron angle with respect to the normal of the rubbing direction in the substrate plane. The layer structure resembles that of a chevron configuration in the plane of the substrate similar to the recently reported stripe-shaped SSFLC structure. The two domain types 'appear' to switch ...

  16. Field induced microwave absorption in single crystal Bi (2212): Evidence for a superconductive glass state

    Energy Technology Data Exchange (ETDEWEB)

    Tyagi, S.; Gould, A.; Bhagat, S.M. (Centre for Research on Superconductivity, Dept. of Physics, Univ. of Maryland, College Park (USA)); Manheimer, M.A. (Lab. for Physical Sciences, College Park, MD (USA))

    1989-12-01

    The field induced microwave absorption P(H) at 35 GHz in Bi 2212 micaceous single crystals exhibits remarkable variations as temperature is increased from 1.3 K to Tc. For T< or approx.16 K, the hysteresis loops are highly reminiscent of those observed in spin glasses. At 30< or approx.T< or approx.50 K, they resemble those of a Type II superconductor. As suggested by the magnetization data, the micaceous nature causes a large enhancement in P(H) for 50

  17. Tunable far-field acoustic imaging by two-dimensional sonic crystal with concave incident surface

    Science.gov (United States)

    Shen, Feng-Fu; Lu, Dan-Feng; Zhu, Hong-Wei; Ji, Chang-Ying; Shi, Qing-Fan

    2017-01-01

    An additional concave incident surface comprised of two-dimensional (2D) sonic crystals (SCs) is employed to tune the acoustic image in the far-field region. The tunability is realized through changing the curvature of the concave surface. To explain the tuning mechanism, a simple ray-trace analysis is demonstrated based on the wave-beam negative refractive law. Then, a numerical confirmation is carried out. Results show that both the position and the intensity of the image can be tuned by the introduced concave surface.

  18. Rigorous analysis of an electric-field-driven liquid crystal lens for 3D displays

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Bong-Sik; Lee, Seung-Chul; Park, Woo-Sang [Inha University, Incheon (Korea, Republic of)

    2014-08-15

    We numerically analyzed the optical performance of an electric field driven liquid crystal (ELC) lens adopted for 3-dimensional liquid crystal displays (3D-LCDs) through rigorous ray tracing. For the calculation, we first obtain the director distribution profile of the liquid crystals by using the Erickson-Leslie motional equation; then, we calculate the transmission of light through the ELC lens by using the extended Jones matrix method. The simulation was carried out for a 9 view 3D-LCD with a diagonal of 17.1 inches, where the ELC lens was slanted to achieve natural stereoscopic images. The results show that each view exists separately according to the viewing position at an optimum viewing distance of 80 cm. In addition, our simulation results provide a quantitative explanation for the ghost or blurred images between views observed from a 3D-LCD with an ELC lens. The numerical simulations are also shown to be in good agreement with the experimental results. The present simulation method is expected to provide optimum design conditions for obtaining natural 3D images by rigorously analyzing the optical functionalities of an ELC lens.

  19. Numerical analysis of near and far field patterns of second-harmonic generation with tiling nonlinear optical crystals

    Energy Technology Data Exchange (ETDEWEB)

    Harimoto, T [Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, 4-3-11 Kofu, Yamanashi 400-8511 (Japan); Shiraga, H [Institute of Laser Engineering, Osaka University, Suita, Osaka (Japan)], E-mail: harimoto@yamanashi.ac.jp

    2008-05-01

    We report numerical analysis of near- and far-field patterns of the second-harmonic wave in a large-scale high-power laser used in the laser fusion with type I KDP crystals arranged in a tiling style. The thickness and phase-matching angle of the tiling crystals are designed based on the near-field pattern of the second-harmonic wave. The tilting angle error and thickness difference of the tiling crystals are evaluated by the energy distribution included in the Airy spot of the far-field pattern at the focal point. The parallelism and flatness of the tiling crystals can also be estimated with the same method.

  20. Ionization of Atoms and the Thomas-Fermi Model for the Electric Field in Crystal Planar Channels

    Institute of Scientific and Technical Information of China (English)

    LIUYing-Tai; ZHANGQi-Ren; 等

    2002-01-01

    The electric field in the crystal planar channels is studied by the Thomas-Fermi method.The ThomasFermi equation and the corresponding boundary conditions are derived for the crystal palanar channels,The numerical solution for the elctric field in the channels between(110) Planes of the single crystal silicaon and the critical angles of channelling protons in them are shown.Reasonable agreements with the experimental data are obtained.The results show that the Thomas-Fermi method for the crystal works well in this study,and a microscopic research of the channel electric field with the contribution of all atoms and the atomic ionization being taken into account is practical.

  1. Black holes in a cubic Galileon universe

    CERN Document Server

    Babichev, Eugeny; Lehébel, Antoine; Moskalets, Tetiana

    2016-01-01

    We find and study the properties of black hole solutions for a subclass of Horndeski theory including the cubic Galileon term. The theory under study has shift symmetry but not reflection symmetry for the scalar field. The Galileon is assumed to have linear time dependence characterized by a velocity parameter. We give analytic 3-dimensional solutions that are akin to the BTZ solutions but with a non-trivial scalar field that modifies the effective cosmological constant. We then study the 4-dimensional asymptotically flat and de Sitter solutions. The latter present three different branches according to their effective cosmological constant. For two of these branches, we find families of black hole solutions, parametrized by the velocity of the scalar field. These spherically symmetric solutions, obtained numerically, are different from GR solutions close to the black hole event horizon, while they have the same de-Sitter asymptotic behavior. The velocity parameter represents black hole primary hair.

  2. EMR-related problems at the interface between the crystal field Hamiltonians and the zero-field splitting Hamiltonians

    Directory of Open Access Journals (Sweden)

    Rudowicz Czesław

    2015-07-01

    Full Text Available The interface between optical spectroscopy, electron magnetic resonance (EMR, and magnetism of transition ions forms the intricate web of interrelated notions. Major notions are the physical Hamiltonians, which include the crystal field (CF (or equivalently ligand field (LF Hamiltonians, and the effective spin Hamiltonians (SH, which include the zero-field splitting (ZFS Hamiltonians as well as to a certain extent also the notion of magnetic anisotropy (MA. Survey of recent literature has revealed that this interface, denoted CF (LF ↔ SH (ZFS, has become dangerously entangled over the years. The same notion is referred to by three names that are not synonymous: CF (LF, SH (ZFS, and MA. In view of the strong need for systematization of nomenclature aimed at bringing order to the multitude of different Hamiltonians and the associated quantities, we have embarked on this systematization. In this article, we do an overview of our efforts aimed at providing a deeper understanding of the major intricacies occurring at the CF (LF ↔ SH (ZFS interface with the focus on the EMR-related problems for transition ions.

  3. A Phase Field Technique for Modeling and Predicting Flow Induced Crystallization Morphology of Semi-Crystalline Polymers

    Directory of Open Access Journals (Sweden)

    Xiaodong Wang

    2016-06-01

    Full Text Available Flow induced crystallization of semi-crystalline polymers is an important issue in polymer science and engineering because the changes in morphology strongly affect the properties of polymer materials. In this study, a phase field technique considering polymer characteristics was established for modeling and predicting the resulting morphologies. The considered crystallization process can be divided into two stages, which are nucleation upon the flow induced structures and subsequent crystal growth after the cessation of flow. Accordingly, the proposed technique consists of two parts which are a flow induced nucleation model based on the calculated information of molecular orientation and stretch, and a phase field crystal growth model upon the oriented nuclei. Two-dimensional simulations are carried out to predict the crystallization morphology of isotactic polystyrene under an injection molding process. The results of these simulations demonstrate that flow affects crystallization morphology mainly by producing oriented nuclei. Specifically, the typical skin-core structures along the thickness direction can be successfully predicted. More importantly, the results reveal that flow plays a dominant part in generating oriented crystal morphologies compared to other parameters, such as anisotropy strength, crystallization temperature, and physical noise.

  4. Preparation of AgCl Nano-Crystal Embedded Tellurite Nonlinear Optical Glasses under Electric Field Accompanied Heat Treatment

    Institute of Scientific and Technical Information of China (English)

    Jian LIN; Wenhai HUANG; Bofang LI; Chong JIN; Changcheng LIU; Shuhua LEI; Zhenrong SUN

    2008-01-01

    The quantum effect of nano-crystals is an important factor to improve nonlinear optical performance of nano-crystal embedded glasses,while controlling the size distribution and content of nano-crystals in the glass accurately is a key to obtain good quality.The auxiliary direct current electric field,accompanied with heat treatment,was applied on AgCl containing niobic tellurite glass sheet.The nucleation and crystallization of the glass were well controlled under auxiliary electric field.It was found that the average size of AgCl nano-crystal particles in the glass is smaller than that under single heat treatment,and the content of nano-crystals is higher.Therefore the third-order nonlinear optical performance of the glass was increased a lot.The local-area distributed AgCl nano-crystal particles can also be embedded into a glass sheet by using locally applied electric field.

  5. Electrostimulation of the magnetoplastic effect in LiF crystals by an "internal" electric field induced during indentation

    Science.gov (United States)

    Galustashvili, M. V.; Driaev, D. G.; Akopov, F. Kh.; Tsakadze, S. D.

    2013-08-01

    Indented LiF crystals demonstrate a change in the length of the dislocation rosette rays during their exposure to jointly acting dc magnetic and electric fields. It is shown that magnetic field with induction B = 1 T causes the electrostimulation or electrosuppression depending on the magnitude and direction of the external electric field with respect to the "internal" electric field induced by the charge transfer due to dislocations moving during the indentation.

  6. High-mobility field-effect transistors from large-area solution-grown aligned C60 single crystals.

    Science.gov (United States)

    Li, Hanying; Tee, Benjamin C-K; Cha, Judy J; Cui, Yi; Chung, Jong Won; Lee, Sang Yoon; Bao, Zhenan

    2012-02-08

    Field-effect transistors based on single crystals of organic semiconductors have the highest reported charge carrier mobility among organic materials, demonstrating great potential of organic semiconductors for electronic applications. However, single-crystal devices are difficult to fabricate. One of the biggest challenges is to prepare dense arrays of single crystals over large-area substrates with controlled alignment. Here, we describe a solution processing method to grow large arrays of aligned C(60) single crystals. Our well-aligned C(60) single-crystal needles and ribbons show electron mobility as high as 11 cm(2)V(-1)s(-1) (average mobility: 5.2 ± 2.1 cm(2)V(-1)s(-1) from needles; 3.0 ± 0.87 cm(2)V(-1)s(-1) from ribbons). This observed mobility is ~8-fold higher than the maximum reported mobility for solution-grown n-channel organic materials (1.5 cm(2)V(-1)s(-1)) and is ~2-fold higher than the highest mobility of any n-channel organic material (~6 cm(2)V(-1)s(-1)). Furthermore, our deposition method is scalable to a 100 mm wafer substrate, with around 50% of the wafer surface covered by aligned crystals. Hence, our method facilitates the fabrication of large amounts of high-quality semiconductor crystals for fundamental studies, and with substantial improvement on the surface coverage of crystals, this method might be suitable for large-area applications based on single crystals of organic semiconductors.

  7. Near-field imaging of light propagation in photonic crystal waveguides: Explicit role of Bloch harmonics

    DEFF Research Database (Denmark)

    Bozhevolnyi, Sergey I.; Volkov, V.S.; Søndergaard, Thomas;

    2002-01-01

    We employ a collection scanning near-field optical microscope (SNOM) to image the propagation of light at telecommunication wavelengths along straight and bent regions of silicon-on-insulator photonic crystal waveguides (PCWs) formed by removing a single row of holes in the triangular 410-nm......-period lattice along the GammaM direction of the irreducible Brillouin zone. We obtain high quality SNOM images of PCWs excited in the wavelength range of 1520-1570 nm, which indicate good PCW mode confinement and low propagation loss. Using averaged cross sections of the intensity distributions before and after...... the interference between a quasihomogeneous background field and Bloch harmonics of the PCW mode, we account for spatial frequency spectra of the intensity variations and determine the propagation constant of the PCW mode at 1520 nm. The possibilities and limitations of SNOM imaging for the characterization...

  8. Extensional flow of nematic liquid crystal with an applied electric field

    KAUST Repository

    CUMMINGS, L. J.

    2013-10-17

    Systematic asymptotic methods are used to formulate a model for the extensional flow of a thin sheet of nematic liquid crystal. With no external body forces applied, the model is found to be equivalent to the so-called Trouton model for Newtonian sheets (and fibres), albeit with a modified \\'Trouton ratio\\'. However, with a symmetry-breaking electric field gradient applied, behaviour deviates from the Newtonian case, and the sheet can undergo finite-time breakup if a suitable destabilizing field is applied. Some simple exact solutions are presented to illustrate the results in certain idealized limits, as well as sample numerical results to the full model equations. Copyright © Cambridge University Press 2013.

  9. Nonlinear response and dynamical transitions in a phase-field crystal model for adsorbed overlayers

    Energy Technology Data Exchange (ETDEWEB)

    Ramos, J A P [Departamento de Ciencias Exatas, Universidade Estadual do Sudoeste da Bahia, 45000-000 Vitoria da Conquista, BA (Brazil); Granato, E [Laboratorio Associado de Sensores e Materiais, Instituto Nacional de Pesquisas Espaciais, 12245-970 Sao Jose dos Campos, SP (Brazil); Ying, S C; Ala-Nissila, T [Department of Physics, PO Box 1843, Brown University, Providence, RI 02912-1843 (United States); Achim, C V [Department of Applied Physics, Aalto University School of Science and Technology, PO Box 11000, FI-00076 Aalto, Espoo (Finland); Elder, K R, E-mail: Jorge@las.inpe.b [Department of Physics, Oakland University, Rochester, Michigan 48309-4487 (United States)

    2010-09-01

    The nonlinear response and sliding friction behavior of a phase-field crystal model for driven adsorbed atomic layers is determined numerically. The model describes the layer as a continuous density field coupled to the pinning potential of the substrate and under an external driving force. Dynamical equations which take into account both thermal fluctuations and inertial effects are used for numerical simulations of commensurate and incommensurate layers. At low temperatures, the velocity response of an initially commensurate layer shows hysteresis with dynamical melting and freezing transitions at different critical forces. The main features of the sliding friction behavior are similar to the results obtained previously from molecular dynamics simulations of particle models. However, the dynamical transitions correspond to nucleations of stripes rather than closed domains.

  10. Long-wavelength properties of phase-field-crystal models with second-order dynamics

    Science.gov (United States)

    Heinonen, V.; Achim, C. V.; Ala-Nissila, T.

    2016-05-01

    The phase-field-crystal (PFC) approach extends the notion of phase-field models by describing the topology of the microscopic structure of a crystalline material. One of the consequences is that local variation of the interatomic distance creates an elastic excitation. The dynamics of these excitations poses a challenge: pure diffusive dynamics cannot describe relaxation of elastic stresses that happen through phonon emission. To this end, several different models with fast dynamics have been proposed. In this article we use the amplitude expansion of the PFC model to compare the recently proposed hydrodynamic PFC amplitude model with two simpler models with fast dynamics. We compare these different models analytically and numerically. The results suggest that in order to have proper relaxation of elastic excitations, the full hydrodynamical description of the PFC amplitudes is required.

  11. Mean-Field Limit and Phase Transitions for Nematic Liquid Crystals in the Continuum

    Science.gov (United States)

    Bachmann, Sven; Genoud, François

    2017-08-01

    We discuss thermotropic nematic liquid crystals in the mean-field regime. In the first part of this article, we rigorously carry out the mean-field limit of a system of N rod-like particles as N→ ∞, which yields an effective `one-body' free energy functional. In the second part, we focus on spatially homogeneous systems, for which we study the associated Euler-Lagrange equation, with a focus on phase transitions for general axisymmetric potentials. We prove that the system is isotropic at high temperature, while anisotropic distributions appear through a transcritical bifurcation as the temperature is lowered. Finally, as the temperature goes to zero we also prove, in the concrete case of the Maier-Saupe potential, that the system converges to perfect nematic order.

  12. Nanoscale mechanical actuation and near-field read-out of photonic crystal molecules

    Science.gov (United States)

    Petruzzella, M.; La China, F.; Intonti, F.; Caselli, N.; De Pas, M.; van Otten, F. W. M.; Gurioli, M.; Fiore, A.

    2016-09-01

    We employed the contact forces induced by a near-field tip to tune and probe the optical resonances of a mechanically compliant photonic crystal molecule. Here, the pressure induced by the near-field tip is exploited to control the spectral proprieties of the coupled cavities in an ultrawide spectral range, demonstrating a reversible mode shift of 37.5 nm . Besides, by monitoring the coupling strength variation due to the vertical nanodeformation of the dielectric structure, distinct tip-sample interaction regimes have been unambiguously reconstructed with a nano-Newton sensitivity. These results demonstrate an optical method for mapping mechanical forces at the nanoscale with a lateral spatial resolution below 100 nm.

  13. Sternheimer Factors and Electric-Field-Gradient Hyperpolarisabilities for Ions in Crystals

    Science.gov (United States)

    Fowler, P. W.; Kelly, H. M.

    1994-02-01

    Analytic coupled Hartree-Fock calculations of the electric field gradient response properties y (the Sternheimer shielding factor) and e (the dipole-dipole-electric field gradient hyperpolarisability) have been carried out on anions in clusters that simulate that crystal environment. The systems studied are F- in LiF and NaF, Cl- in LiCl and NaCl, O2-in MgO, S2- in MgS, and H- in LiH. Both properties show large reductions from free-ion values and significant variation with lattice parameter, and the results indicate that damped values of anion Sternheimer factors will be necessary in accurate simulation of N Q R data or modelling of properties of ion-pairs.

  14. Large piezoelectricity in electric-field modified single crystals of SrTiO3

    Science.gov (United States)

    Khanbabaee, B.; Mehner, E.; Richter, C.; Hanzig, J.; Zschornak, M.; Pietsch, U.; Stöcker, H.; Leisegang, T.; Meyer, D. C.; Gorfman, S.

    2016-11-01

    Defect engineering is an effective and powerful tool to control the existing material properties and produce completely new ones, which are symmetry-forbidden in a defect-free crystal. For example, the application of a static electric field to a single crystal of SrTiO3 forms a strained near-surface layer through the migration of oxygen vacancies out of the area beneath the positively charged electrode. While it was previously shown that this near-surface phase holds pyroelectric properties, which are symmetry-forbidden in centrosymmetric bulk SrTiO3, this paper reports that the same phase is strongly piezoelectric. We demonstrate the piezoelectricity of this phase through stroboscopic time-resolved X-ray diffraction under alternating electric field and show that the effective piezoelectric coefficient d33 ranges between 60 and 100 pC/N. The possible atomistic origins of the piezoelectric activity are discussed as a coupling between the electrostrictive effect and spontaneous polarization of this near-surface phase.

  15. Precise Patterning of Organic Single Crystals via Capillary-Assisted Alternating-Electric Field.

    Science.gov (United States)

    Zhang, Yedong; Jie, Jiansheng; Sun, Yuning; Jeon, Seok-Gy; Zhang, Xiujuan; Dai, Gaole; Lee, Cheol Jin; Zhang, Xiaohong

    2017-07-01

    Owing to the extraordinary properties, organic micro/nanocrystals are important building blocks for future low-cost and high-performance organic electronic devices. However, integrated device application of the organic micro/nanocrystals is hampered by the difficulty in high-throughput, high-precision patterning of the micro/nanocrystals. In this study, the authors demonstrate, for the first time, a facile capillary-assisted alternating-electric field method for the large-scale assembling and patterning of both 0D and 1D organic crystals. These crystals can be precisely patterned at the photolithography defined holes/channels at the substrate with the yield up to 95% in 1 mm(2) . The mechanism of assembly kinetics is systematically studied by the electric field distribution simulation and experimental investigations. By using the strategy, various organic micro/nanocrystal patterns are obtained by simply altering the geometries of the photoresist patterns on substrates. Moreover, ultraviolet photodetectors based on the patterned Alq3 micro/nanocrystals exhibit visible-blind photoresponse with high sensitivity as well as excellent stability and reproducibility. This work paves the way toward high-integration, high-performance organic electronic, and optoelectronic devices from the organic micro/nanocrystals. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Spectroscopic and crystal-field analysis of new Yb-doped laser materials

    Energy Technology Data Exchange (ETDEWEB)

    Haumesser, Paul-Henri; Gaume, Romain; Antic-Fidancev, Elisabeth; Vivien, Daniel; Viana, Bruno [Laboratoire de Chimie Appliquee de l' Etat Solide UMR 75 74, ENSCP, Paris (France)]. E-mail: viana@ext.jussieu.fr

    2001-06-11

    Crystal-field effects are very important as far as laser performances of Yb-doped materials are concerned. In order to simplify the interpretation of low-temperature spectra, two tools derived from a careful examination of crystal-field interaction are presented. Both approaches are successfully applied in the case of new Yb-doped materials, namely Ca{sub 3}Y{sub 2}(BO{sub 3}){sub 4} (CYB), Ca{sub 3}Gd{sub 2}(BO{sub 3}){sub 4} (CaGB), Sr{sub 3}Y(BO{sub 3}){sub 3} (SrYBO), Ba{sub 3}Lu(BO{sub 3}){sub 3} (BLuB), Y{sub 2}SiO{sub 5} (YSO), Ca{sub 2}Al{sub 2}SiO{sub 7} (CAS) and SrY{sub 4}(SiO{sub 4}){sub 3}O (SYS). The {sup 2}F{sub 7/2} splitting is particularly large in these materials and favourable to a quasi-three-level laser operating scheme. Calculations performed using the point charge electrostatic model for these compounds and using a consistent set of effective atomic charges confirm the experimental results. This should permit to use this model in a predictive approach. (author)

  17. Fluctuations in the Microwave Conductivity of YBCO Single Crystals in Zero DC Magnetic Field

    Science.gov (United States)

    Anlage, Steven; Mao, Jian; Booth, James; Wu, Dong-Ho; Peng, J. L.

    1996-03-01

    We present a quantitative analysis of finite frequency fluctuation conductivity above and below Tc in cuprate superconductors in zero dc magnetic field.(S. M. Anlage, J. Mao, J. C. Booth, D. H. Wu, and J. L. Peng, Phys. Rev. B 53), Feb. 1, 1996. In a YBa_2Cu_3O_7-δ crystal showing a linear in temperature increase of the magnetic penetration depth at low temperatures, we find that two-dimensional finite-frequency Gaussian conductivity fluctuations above Tc cross over into a slower divergence of the conductivity as Tc is approached from above. We find that the critical regime above Tc is less than about 0.6 K wide, although inhomogeneities in the crystal may also dominate the conductivity in this temperature range. At and below T_c, 3D fluctuations dominate the conductivity, with evidence of 3D XY critical scaling of the imaginary part of the conductivity down to 5 K below T_c. Supported by the NSF NYI program (DMR-9258183), and NSF grant DMR-9123198.

  18. Exchange and crystal field in Sm-based magnets. II. Phenomenological analysis and density functional calculations

    Science.gov (United States)

    Kuz'Min, Michael D.; Steinbeck, Lutz; Richter, Manuel

    2002-02-01

    A technique of determining the exchange field Bex on the 4f shell of Sm atoms in Sm-based magnets is proposed. It makes use of the 4f intermultiplet transition in Sm, observed in inelastic neutron scattering (INS) experiments. The method is used to analyze previously published data for a number of Sm-Fe and Sm-Co intermetallics, for all of which Bex is determined. Additional information on intramultiplet transitions in SmCo5 and Sm2Co17 makes it possible to obtain more accurate Bex values as well as to estimate the leading crystal field parameter (CFP) A02 for these compounds. For the same systems an independent determination of A02 is carried out using published magnetization curves and the Bex values found from the INS spectra. The two ``experimental'' values of A02 (INS and magnetization) agree well. For comparison, theoretical Sm-Co exchange fields and CFP for SmCo5 and Sm2Co17 are obtained from full-potential density-functional calculations. The theoretical A02 are shifted toward more negative values with respect to their experimental counterparts by a few millielectronvolts. The calculated Sm-Co exchange fields are in fair agreement with the experimentally determined values of the total exchange field on Sm, Bex, the weak Sm-Sm exchange interaction being accountable for the remaining small discrepancies.

  19. Synchrotron radiation topographic observation of KTiOPO4 crystals under an electric field

    Institute of Scientific and Technical Information of China (English)

    1999-01-01

    In situ white-beam synchrotron radiation topographic observations under an electric field have been made on the KTiOPO4(KTP) family of crystals.The investigation shows a strong enhancement of diffracted intensity for hkl reflections(l≠0) and topographic contrast in the form of fine striations when the external electric field is parallel to the polar axis.Severalk kinds of doped and undoped samples with various grown-in defects,such as domain boundaries.growth striations,growth-sector boundaries.dislocations.etc.,have been studied in detail.The results suggest that these defects have very little effect on the field-induced striations,It is believed that the movement of K+ ions driven by the electric field leads to a local accumulation of charges and a lattice distortion.The stronly anisotropic conductivity is a governing factor in the explanation of the field-related phenomena in this kind of quasi-one-dimensional conductor.

  20. Cubication of conservative nonlinear oscillators

    Energy Technology Data Exchange (ETDEWEB)

    Belendez, Augusto; Alvarez, Mariela L [Departamento de Fisica, Ingenieria de Sistemas y Teoria de la Senal, Universidad de Alicante, Apartado 99, E-03080 Alicante (Spain); Fernandez, Elena; Pascual, Inmaculada [Departamento de Optica, FarmacologIa y Anatomia, Universidad de Alicante, Apartado 99, E-03080 Alicante (Spain)], E-mail: a.belendez@ua.es

    2009-09-15

    A cubication procedure of the nonlinear differential equation for conservative nonlinear oscillators is analysed and discussed. This scheme is based on the Chebyshev series expansion of the restoring force, and this allows us to approximate the original nonlinear differential equation by a Duffing equation in which the coefficients for the linear and cubic terms depend on the initial amplitude, A, while in a Taylor expansion of the restoring force these coefficients are independent of A. The replacement of the original nonlinear equation by an approximate Duffing equation allows us to obtain an approximate frequency-amplitude relation as a function of the complete elliptic integral of the first kind. Some conservative nonlinear oscillators are analysed to illustrate the usefulness and effectiveness of this scheme.

  1. High-resolution magnetic field imaging with a nitrogen-vacancy diamond sensor integrated with a photonic-crystal fiber.

    Science.gov (United States)

    Fedotov, I V; Blakley, S M; Serebryannikov, E E; Hemmer, P; Scully, M O; Zheltikov, A M

    2016-02-01

    We demonstrate high-resolution magnetic field imaging with a scanning fiber-optic probe which couples nitrogen-vacancy (NV) centers in diamond to a high-numerical-aperture photonic-crystal fiber integrated with a two-wire microwave transmission line. Magnetic resonance excitation of NV centers driven by the microwave field is read out through optical interrogation through the photonic-crystal fiber to enable high-speed, high-sensitivity magnetic field imaging with sub 30 μm spatial resolution.

  2. In-Situ Alignment of MnBi Crystals Induced by High Magnetic Field above Curie Temperature

    Institute of Scientific and Technical Information of China (English)

    LIU Yong-Sheng; ZHANG Jin-Cang; REN Zhong-Ming; CAO Shi-Xun

    2007-01-01

    @@ Above Curie temperature, MnBi crystals are aligned in situ along the c-axis in a Bi matrix by a high fabrication magnetic field Hf of 10 T. Magnetic testing shows a pronounced anisotropy in magnetization in directions normal and parallel to the fabrication field, resulting from the alignment. The successful alignment may result from the fact that the easy magnetization direction is along the c-axis of MnBi and the high fabrication field of 10 T is large enough to rotate the MnBi crystal to this direction even though the temperature is above the Curie temperature.

  3. A Photonic Crystal Magnetic Field Sensor Using a Shoulder-Coupled Resonant Cavity Infiltrated with Magnetic Fluid.

    Science.gov (United States)

    Su, Delong; Pu, Shengli; Mao, Lianmin; Wang, Zhaofang; Qian, Kai

    2016-12-16

    A kind of photonic crystal magnetic field sensor is proposed and investigated numerically. The shoulder-coupled resonant cavity is introduced in the photonic crystal, which is infiltrated with magnetic fluid. Through monitoring the shift of resonant wavelength, the magnetic field sensing is realized. According to the designed infiltration schemes, both the magnetic field sensitivity and full width at half maximum increase with the number of infiltrated air holes. The figure of merit of the structure is defined to evaluate the sensing performance comprehensively. The best structure corresponding to the optimal infiltration scheme with eight air holes infiltrated with magnetic fluid is obtained.

  4. Cubic Matrix, Nambu Mechanics and Beyond

    OpenAIRE

    Kawamura, Y

    2002-01-01

    We propose a generalization of cubic matrix mechanics by introducing a canonical triplet and study its relation to Nambu mechanics. The generalized cubic matrix mechanics we consider can be interpreted as a “quantum” generalization of Nambu mechanics.

  5. Cubical sets and the topological topos

    DEFF Research Database (Denmark)

    Spitters, Bas

    2016-01-01

    Coquand's cubical set model for homotopy type theory provides the basis for a computational interpretation of the univalence axiom and some higher inductive types, as implemented in the cubical proof assistant. This paper contributes to the understanding of this model. We make three contributions...... show that it can also be a target for cubical realization by showing that Coquand's cubical sets classify the geometric theory of flat distributive lattices. As a side result, we obtain a simplicial realization of a cubical set. 2. Using the internal `interval' in the topos of cubical sets, we...... construct a Moore path model of identity types. 3. We construct a premodel structure internally in the cubical type theory and hence on the fibrant objects in cubical sets....

  6. Properties of the ground state in a spin-2 transverse Ising model with the presence of a crystal field

    Institute of Scientific and Technical Information of China (English)

    姜伟; 魏国柱; 杜安; 张起

    2002-01-01

    The properties of the ground state in the spin-2 transverse Ising model with the presence of a crystal field arestudied by using the effective-field theory with correlations. The longitudinal and transverse magnetizations, the phasediagram and the internal energy in the ground state are given numerically for a honeycomb lattice (z=3).

  7. Viewing angle switching of liquid crystal display using fringe-field switching to control off-axis phase retardation

    Energy Technology Data Exchange (ETDEWEB)

    Lim, Young Jin; Kim, Jin Ho; Her, Jung Hwa; Lee, Seung Hee [Polymer BIN Fusion Research Center, Department of Polymer Nano-Science and Technology, Chonbuk National University, Chonju, Chonbuk 561-756 (Korea, Republic of); Park, Kyoung Ho; Lee, Joun Ho; Kim, Byeong Koo [Mobile Product Development Department, LG Display Company, Ltd, Gumi, Gyungbuk 730-350 (Korea, Republic of); Kang, Wan-Seok; Lee, Gi-Dong, E-mail: gdlee@dau.ac.k, E-mail: lsh1@chonbuk.ac.k [Department of Electronics Engineering, Dong-A University, Pusan 604-714 (Korea, Republic of)

    2010-03-03

    A viewing angle switchable liquid crystal display associated with fringe-field switching mode is proposed. In the device, one pixel is composed of a main pixel and a sub-pixel, in which both pixels are formed to generate a fringe electric field. However, the field directions are different from each other so that in the main pixel, the fringe field rotates the liquid crystal for displaying the main image, whereas it controls only the tilt angle of the liquid crystal without rotating in the sub-pixel region. In this way, phase retardation to cause leakage of light at the off-normal axis can be generated in the sub-pixel, and by utilizing the light, the main displayed image in the normal direction can be blocked in the oblique viewing direction.

  8. Tunable Lamb wave band gaps in two-dimensional magnetoelastic phononic crystal slabs by an applied external magnetostatic field.

    Science.gov (United States)

    Zhou, Changjiang; Sai, Yi; Chen, Jiujiu

    2016-09-01

    This paper theoretically investigates the band gaps of Lamb mode waves in two-dimensional magnetoelastic phononic crystal slabs by an applied external magnetostatic field. With the assumption of uniformly oriented magnetization, an equivalent piezomagnetic material model is used. The effects of magnetostatic field on phononic crystals are considered carefully in this model. The numerical results indicate that the width of the first band gap is significantly changed by applying the external magnetic field with different amplitude, and the ratio between the maximum and minimum gap widths reaches 228%. Further calculations demonstrate that the orientation of the magnetic field obviously affects the width and location of the first band gap. The contactless tunability of the proposed phononic crystal slabs shows many potential applications of vibration isolation in engineering. Copyright © 2016 Elsevier B.V. All rights reserved.

  9. Cubic interactions of Maxwell-like higher spins

    CERN Document Server

    Francia, Dario; Mkrtchyan, Karapet

    2016-01-01

    We study the cubic vertices for Maxwell-like higher-spins in flat space. Reducibility of their free spectra implies that a single cubic vertex involving any three fields subsumes a number of couplings among different particles of various spins. The resulting vertices do not involve traces of the fields and in this sense are simpler than their Fronsdal counterparts. We propose an extension of both the free theory and of its cubic deformation to a more general class of partially reducible systems, that one can obtain from the original theory upon imposing trace constraints of various orders. The key to our results is a version of the Noether procedure allowing to systematically account for the deformations of the transversality conditions to be imposed on the gauge parameters at the free level.

  10. Numbers for reducible cubic scrolls

    Directory of Open Access Journals (Sweden)

    Israel Vainsencher

    2004-12-01

    Full Text Available We show how to compute the number of reducible cubic scrolls of codimension 2 in (math blackboard symbol Pn incident to the appropriate number of linear spaces.Mostramos como calcular o número de rolos cúbicos redutíveis de codimensão 2 em (math blackboard symbol Pn incidentes a espaços lineares apropriados.

  11. Investigation of the linear and second-order nonlinear optical properties of molecular crystals within the local field theory.

    Science.gov (United States)

    Seidler, Tomasz; Stadnicka, Katarzyna; Champagne, Benoît

    2013-09-21

    In this paper it is shown that modest calculations combining first principles evaluations of the molecular properties with electrostatic interaction schemes to account for the crystal environment effects are reliable for predicting and interpreting the experimentally measured electric linear and second-order nonlinear optical susceptibilities of molecular crystals within the experimental error bars. This is illustrated by considering two molecular crystals, namely: 2-methyl-4-nitroaniline and 4-(N,N-dimethylamino)-3-acetamidonitrobenzene. Three types of surrounding effects should be accounted for (i) the polarization due to the surrounding molecules, described here by static electric fields originating from their electric dipoles or charge distributions, (ii) the intermolecular interactions, which affect the geometry and particularly the molecular conformation, and (iii) the screening of the external electric field by the constitutive molecules. This study further highlights the role of electron correlation on the linear and nonlinear responses of molecular crystals and the challenge of describing frequency dispersion.

  12. Ferroelectric Single-Crystal Gated Graphene/Hexagonal-BN/Ferroelectric Field-Effect Transistor.

    Science.gov (United States)

    Park, Nahee; Kang, Haeyong; Park, Jeongmin; Lee, Yourack; Yun, Yoojoo; Lee, Jeong-Ho; Lee, Sang-Goo; Lee, Young Hee; Suh, Dongseok

    2015-11-24

    The effect of a ferroelectric polarization field on the charge transport in a two-dimensional (2D) material was examined using a graphene monolayer on a hexagonal boron nitride (hBN) field-effect transistor (FET) fabricated using a ferroelectric single-crystal substrate, (1-x)[Pb(Mg1/3Nb2/3)O3]-x[PbTiO3] (PMN-PT). In this configuration, the intrinsic properties of graphene were preserved with the use of an hBN flake, and the influence of the polarization field from PMN-PT could be distinguished. During a wide-range gate-voltage (VG) sweep, a sharp inversion of the spontaneous polarization affected the graphene channel conductance asymmetrically as well as an antihysteretic behavior. Additionally, a transition from antihysteresis to normal ferroelectric hysteresis occurred, depending on the V(G) sweep range relative to the ferroelectric coercive field. We developed a model to interpret the complex coupling among antihysteresis, current saturation, and sudden conductance variation in relation with the ferroelectric switching and the polarization-assisted charge trapping, which can be generalized to explain the combination of 2D structured materials with ferroelectrics.

  13. Cubic colloids : Synthesis, functionalization and applications

    NARCIS (Netherlands)

    Castillo, S.I.R.

    2015-01-01

    This thesis is a study on cubic colloids: micron-sized cubic particles with rounded corners (cubic superballs). Owing to their shape, particle packing for cubes is more efficient than for spheres and results in fascinating phase and packing behavior. For our cubes, the particle volume fraction when

  14. Cubic colloids : Synthesis, functionalization and applications

    NARCIS (Netherlands)

    Castillo, S.I.R.

    2015-01-01

    This thesis is a study on cubic colloids: micron-sized cubic particles with rounded corners (cubic superballs). Owing to their shape, particle packing for cubes is more efficient than for spheres and results in fascinating phase and packing behavior. For our cubes, the particle volume fraction when

  15. Solving Cubic Equations by Polynomial Decomposition

    Science.gov (United States)

    Kulkarni, Raghavendra G.

    2011-01-01

    Several mathematicians struggled to solve cubic equations, and in 1515 Scipione del Ferro reportedly solved the cubic while participating in a local mathematical contest, but did not bother to publish his method. Then it was Cardano (1539) who first published the solution to the general cubic equation in his book "The Great Art, or, The Rules of…

  16. Cubic Icosahedra? A Problem in Assigning Symmetry

    Science.gov (United States)

    Lloyd, D. R.

    2010-01-01

    There is a standard convention that the icosahedral groups are classified separately from the cubic groups, but these two symmetry types have been conflated as "cubic" in some chemistry textbooks. In this note, the connection between cubic and icosahedral symmetries is examined, using a simple pictorial model. It is shown that octahedral and…

  17. Faraday isolator based on a TSAG single crystal with compensation of thermally induced depolarization inside magnetic field

    Science.gov (United States)

    Snetkov, Ilya; Palashov, Oleg

    2015-04-01

    A Faraday isolator based on a terbium scandium aluminum garnet (TSAG) single crystal with compensation of thermally induced depolarization inside magnetic field was demonstrated. An isolation ratio of 32 dB at 350 W cw laser radiation power was achieved. Thermally induced depolarization and thermal lens were studied and compared with similar thermal effects arising in the widely used terbium gallium garnet crystal (TGG) for the first time.

  18. High-performance single crystal organic field-effect transistors based on two dithiophene-tetrathiafulvalene (DT-TTF) polymorphs.

    Science.gov (United States)

    Pfattner, Raphael; Mas-Torrent, Marta; Bilotti, Ivano; Brillante, Aldo; Milita, Silvia; Liscio, Fabiola; Biscarini, Fabio; Marszalek, Tomasz; Ulanski, Jacek; Nosal, Andrzej; Gazicki-Lipman, Maciej; Leufgen, Michael; Schmidt, Georg; Molenkamp, Laurens W; Laukhin, Vladimir; Veciana, Jaume; Rovira, Concepció

    2010-10-01

    Solution prepared single crystal organic field-effect transistors (OFETs) combine low-cost with high performance due to structural ordering of molecules. However, in organic crystals polymorphism is a known phenomenon, which can have a crucial influence on charge transport. Here, the performance of solution-prepared single crystal OFETs based on two different polymorphs of dithiophene-tetrathiafulvalene, which were investigated by confocal Raman spectroscopy and X-ray diffraction, are reported. OFET devices prepared using different configurations show that both polymorphs exhibited excellent device performance, although the -phase revealed charge carrier mobility between two and ten times higher in accordance to the closer stacking of the molecules.

  19. Liquid crystal tunable photonic crystal dye laser

    DEFF Research Database (Denmark)

    Buss, Thomas; Christiansen, Mads Brøkner; Smith, Cameron

    2010-01-01

    We present a dye-doped liquid crystal laser using a photonic crystal cavity. An applied electric field to the liquid crystal provides wavelength tunability. The photonic crystal enhances resonant interaction with the gain medium....

  20. Wide-field imaging of birefringent synovial fluid crystals using lens-free polarized microscopy for gout diagnosis

    Science.gov (United States)

    Zhang, Yibo; Lee, Seung Yoon Celine; Zhang, Yun; Furst, Daniel; Fitzgerald, John; Ozcan, Aydogan

    2016-06-01

    Gout is a form of crystal arthropathy where monosodium urate (MSU) crystals deposit and elicit inflammation in a joint. Diagnosis of gout relies on identification of MSU crystals under a compensated polarized light microscope (CPLM) in synovial fluid aspirated from the patient’s joint. The detection of MSU crystals by optical microscopy is enhanced by their birefringent properties. However, CPLM partially suffers from the high-cost and bulkiness of conventional lens-based microscopy, and its relatively small field-of-view (FOV) limits the efficiency and accuracy of gout diagnosis. Here we present a lens-free polarized microscope which adopts a novel differential and angle-mismatched polarizing optical design achieving wide-field and high-resolution holographic imaging of birefringent objects with a color contrast similar to that of a standard CPLM. The performance of this computational polarization microscope is validated by imaging MSU crystals made from a gout patient’s tophus and steroid crystals used as negative control. This lens-free polarized microscope, with its wide FOV (>20 mm2), cost-effectiveness and field-portability, can significantly improve the efficiency and accuracy of gout diagnosis, reduce costs, and can be deployed even at the point-of-care and in resource-limited clinical settings.