All-electron ab initio calculations of YBa2Cu3O7 with self-consistence crystal field
Institute of Scientific and Technical Information of China (English)
刘洪霖; 陈念贻
1995-01-01
The quantum chemical calculations of cluster YBa2Cu3O7 considering all electrons have been per-formed by using the ab initio HF method with self-consistence crystal field.A Hartree-Fork surface potentialis proposed to make an asymmetric duster model possess a relatively symmetric potential field and to obtaina relatively symmetric electronic structure,electronic distributions,frontier orbitals,and bond order,etc.Thesuggestions that there exists a covalent bonding complex,[CuO2-O-CuO-O-Cu2]6,8-,in the cell unit ofthe crystal,and the cell units are connected with each other by ionic bonds along the c direction of the crys-tal lattice are offered based on the chemical bonding characteristics from the calculated results.The importantcontribution of the apical oxygen to superconductivities is emphasized as well.
National Oceanic and Atmospheric Administration, Department of Commerce — The Magnetic Field Calculator will calculate the total magnetic field, including components (declination, inclination, horizontal intensity, northerly intensity,...
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National Oceanic and Atmospheric Administration, Department of Commerce — The Magnetic Field Properties Calculator will computes the estimated values of Earth's magnetic field(declination, inclination, vertical component, northerly...
Lu, Shih-I.
2018-01-01
We use the discrete solvent reaction field model to evaluate the linear and second-order nonlinear optical susceptibilities of 3-methyl-4-nitropyridine-1-oxyde crystal. In this approach, crystal environment is created by supercell architecture. A self-consistent procedure is used to obtain charges and polarizabilities for environmental atoms. Impact of atomic polarizabilities on the properties of interest is highlighted. This approach is shown to give the second-order nonlinear optical susceptibilities within error bar of experiment as well as the linear optical susceptibilities in the same order as experiment. Similar quality of calculations are also applied to both 4-N,N-dimethylamino-3-acetamidonitrobenzene and 2-methyl-4-nitroaniline crystals.
International Nuclear Information System (INIS)
Gajek, Z.; Lahalle, M.P.; Krupa, J.C.; Mulak, J.
1988-01-01
Simple ab initio model perturbation calculations of the crystal-field parameters for the U 4+ ion in UO 2 crystals are reported. The crystal-field parameters obtained, B 0 4 = -7130 cm -1 and B 0 6 = 2890 cm -1 , turn out to be much lower in value, particularly the first one, than those usually assumed for this compound. They are found, however, to agree with new spectroscopic data and recent inelastic neutron scattering measurements. (orig.)
Zimmermann, Patric; Green, Robert J; Haverkort, Maurits W; de Groot, Frank M F
2018-05-01
Some initial instructions for the Quanty4RIXS program written in MATLAB ® are provided. The program assists in the calculation of 1s 2p RIXS and 1s 2p RIXS-MCD spectra using Quanty. Furthermore, 1s XAS and 2p 3d RIXS calculations in different symmetries can also be performed. It includes the Hartree-Fock values for the Slater integrals and spin-orbit interactions for several 3d transition metal ions that are required to create the .lua scripts containing all necessary parameters and quantum mechanical definitions for the calculations. The program can be used free of charge and is designed to allow for further adjustments of the scripts. open access.
2D director calculation for liquid crystal optical phased array
International Nuclear Information System (INIS)
Xu, L; Zhang, J; Wu, L Y
2005-01-01
A practical numerical model for a liquid crystal cell is set up based on the geometrical structure of liquid crystal optical phased arrays. Model parameters include width and space of electrodes, thickness of liquid crystal layer, alignment layers and glass substrates, pre-tilted angles, dielectric constants, elastic constants and so on. According to electrostatic field theory and Frank-Oseen elastic continuum theory, 2D electric potential distribution and 2D director distribution are calculated by means of the finite difference method on non-uniform grids. The influence of cell sizes on director distribution is analyzed. The fringe field effect between electrodes is also discussed
Energy Technology Data Exchange (ETDEWEB)
Gajek, Z.; Mulak, J.; Faucher, M.
1987-01-01
A practical crystal field model allowing one to estimate the crystal field parameters from first principles is presented and applied to the actinide compounds. The model results directly from the renormalization (and reduction) procedure of the true Schroedinger equation for an effective Hamiltonian acting on the 5f spin-orbitals only. In practice this approach becomes convergent with the ab initio model of Newman. Three ionic uranium compounds: CsUF/sub 6/, Cs/sub 2/UCl/sub 6/ and UCl/sub 4/ have served as examples of the application. The results obtained, particularly for the first two compounds, are in good agreement with the experimental data. The contributions of different mechanisms responsible for the crystal field effect are discussed.
Crystal field effect in the uranium compounds - model calculations for CsUF6, Cs2UCl6 and UCl4
International Nuclear Information System (INIS)
Gajek, Z.; Mulak, J.
1987-01-01
A practical crystal field model allowing one to estimate the crystal field parameters from first principles is presented and applied to the actinide compounds. The model results directly from the renormalization (and reduction) procedure of the true Schroedinger equation for an effective Hamiltonian acting on the 5f spin-orbitals only. In practice this approach becomes convergent with the ab initio model of Newman. Three ionic uranium compounds: CsUF 6 , Cs 2 UCl 6 and UCl 4 have served as examples of the application. The results obtained, particularly for the first two compounds, are in good agreement with the experimental data. The contributions of different mechanisms responsible for the crystal field effect are discussed. (author)
Transient anisotropic magnetic field calculation
International Nuclear Information System (INIS)
Jesenik, Marko; Gorican, Viktor; Trlep, Mladen; Hamler, Anton; Stumberger, Bojan
2006-01-01
For anisotropic magnetic material, nonlinear magnetic characteristics of the material are described with magnetization curves for different magnetization directions. The paper presents transient finite element calculation of the magnetic field in the anisotropic magnetic material based on the measured magnetization curves for different magnetization directions. For the verification of the calculation method some results of the calculation are compared with the measurement
Calculation of Optical Parameters of Liquid Crystals
Kumar, A.
2007-12-01
Validation of a modified four-parameter model describing temperature effect on liquid crystal refractive indices is being reported in the present article. This model is based upon the Vuks equation. Experimental data of ordinary and extraordinary refractive indices for two liquid crystal samples MLC-9200-000 and MLC-6608 are used to validate the above-mentioned theoretical model. Using these experimental data, birefringence, order parameter, normalized polarizabilities, and the temperature gradient of refractive indices are determined. Two methods: directly using birefringence measurements and using Haller's extrapolation procedure are adopted for the determination of order parameter. Both approches of order parameter calculation are compared. The temperature dependences of all these parameters are discussed. A close agreement between theory and experiment is obtained.
Phase-field crystal simulation facet and branch crystal growth
Chen, Zhi; Wang, Zhaoyang; Gu, Xinrui; Chen, Yufei; Hao, Limei; de Wit, Jos; Jin, Kexin
2018-05-01
Phase-field crystal model with one mode is introduced to describe morphological transition. The relationship between growth morphology and smooth density distribution was investigated. The results indicate that the pattern selection of dendrite growth is caused by the competition between interface energy anisotropy and interface kinetic anisotropy based on the 2D phase diagram. When the calculation time increases, the crystal grows to secondary dendrite at the dimensionless undercooling equal to - 0.4. Moreover, when noise is introduced in the growth progress, the symmetry is broken in the growth mode, and there becomes irregular fractal-like growth morphology. Furthermore, the single crystal shape develops into polycrystalline when the noise amplitude is large enough. When the dimensionless undercooling is less than - 0.3, the noise has a significant effect on the growth shape. In addition, the growth velocity of crystal near to liquid phase line is slow, while the shape far away from the liquid adapts to fast growth. Based on the simulation results, the method was proved to be effective, and it can easily obtain different crystal shapes by choosing the different points in 2D phase diagram.
Local fields in ionic crystals
International Nuclear Information System (INIS)
Claro, F.
1981-08-01
Local fields arising from the electronic distortion in perfect ionic crystals are described in terms of multipolar excitations. Field factors for the alkali halides and chalcogenide ions are found to differ significantly from the Lorentz value of 4π/3, the correction size following an exponential dependence on the difference in ionic radii. Local fields are only slightly modified by these corrections however, and together with the Clausius-Mossotti relation may be regarded as accurate to within 2% if the Lorentz value is adopted. (author)
Methods for magnetostatic field calculation
International Nuclear Information System (INIS)
Vorozhtsov, S.B.
1984-01-01
Two methods for magnetostatic field calculation: differential and integrat are considered. Both approaches are shown to have certain merits and drawbacks, choice of the method depend on the type of the solved problem. An opportunity of combination of these tWo methods in one algorithm (hybrid method) is considered
The effective crystal field potential
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...
Energy Technology Data Exchange (ETDEWEB)
Brik, M.G., E-mail: mikhail.brik@ut.ee [College of Sciences, Chongqing University of Posts and Telecommunications, Chongqing 400065 (China); Institute of Physics, University of Tartu, W. Ostwald Str. 1, Tartu 50411 (Estonia); Institute of Physics, Jan Dlugosz University, Al. Armii Krajowej 13/15, Czestochowa PL-42200 (Poland); Papan, J.; Jovanović, D.J. [University of Belgrade, Vinča Institute of Nuclear Sciences, P.O. Box 522, Belgrade 11001 (Serbia); Dramićanin, M.D., E-mail: dramican@vinca.rs [University of Belgrade, Vinča Institute of Nuclear Sciences, P.O. Box 522, Belgrade 11001 (Serbia)
2016-09-15
Details of preparation, spectroscopic and structural studies along with crystal field calculations for two Cr{sup 3+} doped spinels MgAl{sub 2}O{sub 4} and ZnAl{sub 2}O{sub 4} are given in the present paper. Both compounds show efficient red emission at about 685 nm, which is due to the {sup 2}E{sub g} → {sup 4}A{sub 2g} spin-forbidden transition of Cr{sup 3+} ions located at the sites with D{sub 3d} local symmetry. Analysis of structure of the CrO{sub 6} clusters was performed; comparison of the crystal field effects in both compounds revealed that the low-symmetry splitting of the orbital triplet states is more pronounced in ZnAl{sub 2}O{sub 4}. Both compounds show potential for applications as red-emitting phosphors. - Highlights: • Cr{sup 3+}-doped MgAl{sub 2}O{sub 4} and ZnAl{sub 2}O{sub 4} spinels were synthesized. • Excitation/emission spectra were recorded and analyzed. • Symmetry properties of the Cr-sites were analyzed. • Cr{sup 3+} energy levels in trigonal crystal field were calculated. • Cr{sup 3+}-doped MgAl{sub 2}O{sub 4} and ZnAl{sub 2}O{sub 4} spinels can be used as red phosphors.
International Nuclear Information System (INIS)
Ahn, Sang Woon; Oh, Se Woung; Ro, Seung Woo
1986-01-01
The NMR chemical shift arising from 4d electron angular momentum and 4d electron angular momentum and 4d electron spin dipolar-nuclear spin angular momentum interactions for a 4d 1 system in a strong crystal field environment of trigonal symmetry, where the threefold axis is chosen to be the axis of quantization axis, has been examined. A general expression using the nonmultipole expansion method (exact method) is derived for the NMR chemical shift. From this expression all the multipolar terms are determined. we observe that along the (100), (010), (110), and (111) axes the NMR chemical shifts are positive while along the (001) axis, it is negative. We observe that the dipolar term (1/R 3 ) is the dominant contribution to the NMR chemical shift except for along the (111) axis. A comparison of the multipolar terms with the exact values shows also that the multipolar results are exactly in agreement with the exact values around R≥0.2 nm. The temperature dependence analysis on the NMR chemical shifts may imply that along the (111) axis the contribution to the NMR chemical shift is dominantly pseudo contact interaction. Separation of the contributions of the Fermi and the pseudo contact interactions would correctly imply that the dipolar interaction is the dominant contribution to the NMR chemical shifts along the (100), (010), (001), and (110) axes, but along the (111) axis the Fermi contact interaction is incorrectly the dominant contribution to the NMR chemical shift. (Author)
Theory of electrolyte crystallization in magnetic field
DEFF Research Database (Denmark)
Madsen, Hans Erik Lundager
2007-01-01
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...... enter an excited state due to its momentum. Spin relaxation in magnetic field may remove hindrances to proton transfer. The theory is supported by numerical results from model calculations....
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 (UO_{2}), uranium trioxide (UO_{3}), and uranium tetrafluoride (UF_{4}). As a result, a discussion of the role of non-spherical perturbations, i.e., crystal or ligand field effects, will be presented.
Pankrats, A I; Demidov, A A; Ritter, C; Velikanov, D A; Semenov, S V; Tugarinov, V I; Temerov, V L; Gudim, I A
2016-10-05
The magnetic structure of the mixed rare-earth system Pr x Y1-x Fe3(BO3)4 (x = 0.75, 0.67, 0.55, 0.45, 0.25) was studied via magnetic and resonance measurements. These data evidence the successive spin reorientation from the easy-axis antiferromagnetic structure formed in PrFe3(BO3)4 to the easy-plane one of YFe3(BO3)4 associated with the weakening of the magnetic anisotropy of the Pr subsystem due to its diamagnetic dilution by nonmagnetic Y. This reorientation occurs through the formation of an inclined magnetic structure, as was confirmed by our previous neutron research in the range of x = 0.67 ÷ 0.45. In the compounds with x = 0.75 and 0.67 whose magnetic structure is close to the easy-axis one, a two-step spin reorientation takes place in the magnetic field H||c. Such a peculiarity is explained by the formation of an interjacent inclined magnetic structure with magnetic moments of Fe ions located closer to the basal plane than in the initial state, with these intermediate states remaining stable in some ranges of the magnetic field. An approach based on a crystal field model for the Pr(3+) ion and the molecular-field approximation is used to describe the magnetic characteristics of the system Pr x Y1-x Fe3(BO3)4. With the parameters of the d-d and f-d exchange interactions, of the magnetic anisotropy of the iron subsystem and of the crystal field parameters of praseodymium thus determined, it is possible to achieve a good agreement between the experimental and calculated temperature and field dependences of the magnetization curves (up to 90 kOe) and magnetic susceptibilities (2-300 K).
ATLAS cavern magnetic field calculations
International Nuclear Information System (INIS)
Vorojtsov, S.B.; Vorozhtsov, A.S.; Butin, F.; Price, M.
2000-01-01
A new approach has been adopted in an attempt to produce a complete ATLAS cavern B-field map using a more precise methodological approach (variable magnetisation, depending on the external field) and the latest design taking into account of the structural elements. The basic idea was to produce a dedicated basic TOSCA model and then to insert a series of ferromagnetic structure elements to monitor the perturbative effect on the basic field map. Eventually, it was found: the bedplate field perturbation is an order of magnitude above the permissible level; manufacturing of the bedplates from nonmagnetic material or careful evaluation of their field contribution in the event reconstruction codes is required; the field value at the rack positions is higher than the permissible one; the final position of racks should be chosen taking into account the detailed magnetic field distribution
A novel lattice energy calculation technique for simple inorganic crystals
Energy Technology Data Exchange (ETDEWEB)
Kaya, Cemal [Department of Chemistry, Faculty of Science, Cumhuriyet University, 58140 Sivas (Turkey); Kaya, Savaş, E-mail: savaskaya@cumhuriyet.edu.tr [Department of Chemistry, Faculty of Science, Cumhuriyet University, 58140 Sivas (Turkey); Banerjee, Priyabrata [Surface Engineering and Tribology Group, CSIR-Central Mechanical Engineering Research Institute, Mahatma Gandhi Avenue, Durgapur 713209 (India)
2017-01-01
In this pure theoretical study, a hitherto unexplored equation based on Shannon radii of the ions forming that crystal and chemical hardness of any crystal to calculate the lattice energies of simple inorganic ionic crystals has been presented. To prove the credibility of this equation, the results of the equation have been compared with experimental outcome obtained from Born-Fajans-Haber- cycle which is fundamentally enthalpy-based thermochemical cycle and prevalent theoretical approaches proposed for the calculation of lattice energies of ionic compounds. The results obtained and the comparisons made have demonstrated that the new equation is more useful compared to other theoretical approaches and allows to exceptionally accurate calculation of lattice energies of inorganic ionic crystals without doing any complex calculations.
Crystal field and magnetocrystalline anisotropy in various crystalline systems
International Nuclear Information System (INIS)
Adam, S.A.
1983-01-01
Systematic derivation of the one-perticle crystal field Hamiltonians is given for all possible site symmetries in crystals. Distinct parametrizations are found to occur for the eleven Laue-symmetry groups. The functional dependence of the Hamiltonian on the choice of the coordinate axes is also investigated. A general method is developed for the derivation of the one-particle crYstal field potential characteristic of a given crystallographic symmetry, for arbitrary effective interatomic forces. Calculations performed for cubic and hexagonal structures lead to the standard representations in spherical harmonics with the coefficients given, however, by power series of rsup(n) rather than by simgle rsup(n) terms as obtained within the usual hypothesis of Coulombian interatomic forces. This result has implications on the interpretation of some theoretical and experimental data. Theoretical results are obtained for the crystal field coefficients which enable us to develop an approach to the use of the crystal field data for the derivation of information on the effective interatomic forces in crystals. The method is applied to the magnetic Sm 3+ ion in SmCo 5 , and it is shown to provide valuable results both for the effective interatomic potential and for the consistency of various sets of crystal field parameters previously proposed in the literature. Maqnetocrystalline anisotropy of the rare-earth intermetallic compounds are discussed. Single-ion anisotropy model is used for SmCo 5 and the theoreticalpr predictions are compared with the experimental data. (author)
Non-perturbative background field calculations
International Nuclear Information System (INIS)
Stephens, C.R.; Department of Physics, University of Utah, Salt Lake City, Utah 84112)
1988-01-01
New methods are developed for calculating one loop functional determinants in quantum field theory. Instead of relying on a calculation of all the eigenvalues of the small fluctuation equation, these techniques exploit the ability of the proper time formalism to reformulate an infinite dimensional field theoretic problem into a finite dimensional covariant quantum mechanical analog, thereby allowing powerful tools such as the method of Jacobi fields to be used advantageously in a field theory setting. More generally the methods developed herein should be extremely valuable when calculating quantum processes in non-constant background fields, offering a utilitarian alternative to the two standard methods of calculation: perturbation theory in the background field or taking the background field into account exactly. The formalism developed also allows for the approximate calculation of covariances of partial differential equations from a knowledge of the solutions of a homogeneous ordinary differential equation. copyright 1988 Academic Press, Inc
Crystal growth under external electric fields
International Nuclear Information System (INIS)
Uda, Satoshi; Koizumi, Haruhiko; Nozawa, Jun; Fujiwara, Kozo
2014-01-01
This is a review article concerning the crystal growth under external electric fields that has been studied in our lab for the past 10 years. An external field is applied electrostatically either through an electrically insulating phase or a direct injection of an electric current to the solid-interface-liquid. The former changes the chemical potential of both solid and liquid and controls the phase relationship while the latter modifies the transport and partitioning of ionic solutes in the oxide melt during crystallization and changes the solute distribution in the crystal
Crystal growth under external electric fields
Energy Technology Data Exchange (ETDEWEB)
Uda, Satoshi; Koizumi, Haruhiko; Nozawa, Jun; Fujiwara, Kozo [Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577 (Japan)
2014-10-06
This is a review article concerning the crystal growth under external electric fields that has been studied in our lab for the past 10 years. An external field is applied electrostatically either through an electrically insulating phase or a direct injection of an electric current to the solid-interface-liquid. The former changes the chemical potential of both solid and liquid and controls the phase relationship while the latter modifies the transport and partitioning of ionic solutes in the oxide melt during crystallization and changes the solute distribution in the crystal.
Integral parameters of crystal field for RE spectra
International Nuclear Information System (INIS)
Kustov, E.F.; Maketov, T.K.; Prgevudsky, A.K.; Steczko, G.
1980-01-01
The integral parameters of the crystal field are introduced for the interpretation of the spectra of RE ions in various crystals. The main formula of the method, the expression of the parameters for various states of Ce, Pr, Nd, Eu, Tb, Er, Tu, and Yb are determined. Integral parameters of A 2 , A 4 , A 6 and parameter of the spin-orbit interaction xi are calculated for 40 laser crystals with Nd, Er. An interpretation of the symmetry of the Eu 3+ centres of the NaBaZn silicate glass is given using integral parameters A 2 , A 4 . (author)
Non-perturbative background field calculations
Stephens, C. R.
1988-01-01
New methods are developed for calculating one loop functional determinants in quantum field theory. Instead of relying on a calculation of all the eigenvalues of the small fluctuation equation, these techniques exploit the ability of the proper time formalism to reformulate an infinite dimensional field theoretic problem into a finite dimensional covariant quantum mechanical analog, thereby allowing powerful tools such as the method of Jacobi fields to be used advantageously in a field theory setting. More generally the methods developed herein should be extremely valuable when calculating quantum processes in non-constant background fields, offering a utilitarian alternative to the two standard methods of calculation—perturbation theory in the background field or taking the background field into account exactly. The formalism developed also allows for the approximate calculation of covariances of partial differential equations from a knowledge of the solutions of a homogeneous ordinary differential equation.
Numerical calculations in quantum field theories
International Nuclear Information System (INIS)
Rebbi, C.
1984-01-01
Four lecture notes are included: (1) motivation for numerical calculations in Quantum Field Theory; (2) numerical simulation methods; (3) Monte Carlo studies of Quantum Chromo Dynamics; and (4) systems with fermions. 23 references
Internal bias field in glycine phosphite crystal
International Nuclear Information System (INIS)
Nayeem, Jannatul; Wakabayashi, Hiroshi; Kikuta, Toshio; Yamazaki, Toshinari; Nakatani, Noriyuki
2003-01-01
The distributions of internal bias field E b have been investigated under the carbon-powder pattern and mercury electrode techniques in GPI ferroelectric crystals. Polarity and intensity of E b are distributed depending on crystal growth sectors. Crystal symmetry 2/m is observed obviously in the distribution of E b . The polarities of E b are head-to-head manner in those growth sectors where a surface is growing parallel to the crystallographic a-axis and tail-to-tail manner in the other growth sectors in the crystal. The maximum intensity of E b is found in the sectors (010) where the growing surfaces are perpendicular to the ferroelectric b-axis
International Nuclear Information System (INIS)
Yang Tao; Chen Zheng; Zhang Jing; Wang Yongxin; Lu Yanli
2016-01-01
By employing the phase-field-crystal models, the atomic crystallization process of hexagonal and square crystals is investigated with the emphasis on the growth mechanism and morphological change. A unified regime describing the crystallization behavior of both crystals is obtained with the thermodynamic driving force varying. By increasing the driving force, both crystals (in the steady-state) transform from a faceted polygon to an apex-bulged polygon, and then into a symmetric dendrite. For the faceted polygon, the interface advances by a layer-by-layer (LL) mode while for the apex-bulged polygonal and the dendritic crystals, it first adopts the LL mode and then transits into the multi-layer (ML) mode in the later stage. In particular, a shift of the nucleation sites from the face center to the area around the crystal tips is detected in the early growth stage of both crystals and is rationalized in terms of the relation between the crystal size and the driving force distribution. Finally, a parameter characterizing the complex shape change of square crystal is introduced. (paper)
Calculation of the band gap energy of ionic crystals
International Nuclear Information System (INIS)
Aguado, A.; Lopez, J.M.; Alonso, J.A.; Ayuela, A.; Rivas S, J.F.; Berrondo, M.
1998-01-01
The band gap of alkali halides, alkaline-earth oxides, Al 2 O 3 and SiO 2 crystals has been calculated using the perturbed-ion model supplemented with some assumptions for the treatment of excited states. The gap is calculated in several ways: as a difference between one-electron energy eigenvalues and as a difference between the total energies of appropriate electronic states of the crystal, both at the HF level and with inclusion of Coulomb correlation effects. The results compare well with experimental band gap energies and with other theoretical calculations, suggesting that the picture of bonding and excitation given by the model can be useful in ionic materials. (Author)
Molecular-Field Calculation of the Magnetic Structure in Erbium
DEFF Research Database (Denmark)
Jensen, J.
1976-01-01
A molecular-field calculation of the magnetic configurations in Er is found to reproduce the neutron diffraction results of the three different magnetic phases and to give a reasonable fit to the magnetization data at 4.2K. The two-ion coupling is considered to be described by the inter......-planar coupling parameters deduced from the dispersion of the spin waves in the low temperature conical phases. The four (effective) crystal-field parameters are determined by the fit to the experimental data. Projecting the magnetic moments present in the intermediate phase of Er (18-52.4K) to a common origin...
Optical spectroscopy and crystal-field analysis of U3+: Ba2YCl7
International Nuclear Information System (INIS)
Karbowiak, M.; Mech, A.; Drozdzyndki, J.; Gajek, Z.; Edelstein, N.M.
2002-01-01
High resolution absorption spectra of a U 3+ (0.3%): Ba 2 YCl 7 single crystal were recorded in the 4000-50 000 cm -1 range at 7 K. The observed crystal-field levels were assigned and fit to the parameters of the simplified angular overlap model (AOM) as well as a semi-empirical Hamiltonian representing the combined atomic and one-electron crystal-field interactions. The starting values of the AOM parameters were obtained from ab initio calculations. The analysis of the spectra allowed the assignment of 65 crystal-field levels with a relatively small rms deviation of 25 cm -1 and has shown that the AOM approach can predict quite well the B q k crystal-field parameters. The value determined for the crystal-field strength parameter, N v , corresponds well with those determined for U 3+ in other chloride single crystals. (authors)
Poloidal field equilibrium calculations for JET
International Nuclear Information System (INIS)
Khalafallah, A.K.
1976-01-01
The structure of the JET 2D Poloidal Field Analysis Package is discussed. The ability to cope with different plasma current density distributions (skin, flat or peaked), each with a range of Beta poloidal values and varying plasma shapes is a new feature of these calculations. It is possible to construct instant-by-instant pictures of equilibrium configurations for various plasma build up scenarios taking into account the level of flux in the iron core and return limbs. The equilibrium configurations are calculated for two possible sequences of plasma build up. Examples of the magnetic field calculations being carried out under contract to JET at the Rutherford Laboratory, using a 3D code, are also given
Crystal orientation effects on wurtzite quantum well electromechanical fields
DEFF Research Database (Denmark)
Duggen, Lars; Willatzen, Morten
2010-01-01
in the literature for semiconductors, is inaccurate for ZnO/MgZnO heterostructures where shear-strain components play an important role. An interesting observation is that a growth direction apart from [1̅ 21̅ 0] exists for which the electric field in the quantum well region becomes zero. This is important for, e......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 spontaneous polarization, strain, and electric field. Significant differences between fully coupled and semicoupled models are found for the longitudinal and shear-strain components as a function of the crystal-growth direction. In particular, we find that the semicoupled model, typically used...
On standardization of low symmetry crystal fields
Gajek, Zbigniew
2015-07-01
Standardization methods of low symmetry - orthorhombic, monoclinic and triclinic - crystal fields are formulated and discussed. Two alternative approaches are presented, the conventional one, based on the second-rank parameters and the standardization based on the fourth-rank parameters. Mainly f-electron systems are considered but some guidelines for d-electron systems and the spin Hamiltonian describing the zero-field splitting are given. The discussion focuses on premises for choosing the most suitable method, in particular on inadequacy of the conventional one. Few examples from the literature illustrate this situation.
Calculation of rf fields in axisymmetric cavities
International Nuclear Information System (INIS)
Iwashita, Y.
1985-01-01
A new code, PISCES, has been developed for calculating a complete set of rf electromagnetic modes in an axisymmetric cavity. The finite-element method is used with up to third-order shape functions. Although two components are enough to express these modes, three components are used as unknown variables to take advantage of the symmetry of the element matrix. The unknowns are taken to be either the electric field components or the magnetic field components. The zero-divergence condition will be satisfied by the shape function within each element
Energy Technology Data Exchange (ETDEWEB)
Avram, C.N. [Faculty of Physics, West University of Timisoara, Bd. V. Parvan No. 4, 300223 Timisoara (Romania); Gruia, A.S., E-mail: adigruia@yahoo.com [Faculty of Physics, West University of Timisoara, Bd. V. Parvan No. 4, 300223 Timisoara (Romania); Brik, M.G. [College of Sciences, Chongqing University of Posts and Telecommunications, Chongqing 400065 (China); Institute of Physics, University of Tartu, Ravila 14C, Tartu 50411 (Estonia); Institute of Physics, Jan Dlugosz University, Armii Krajowej 13/15, PL-42200 Czestochowa (Poland); Institute of Physics, Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warsaw (Poland); Barb, A.M. [Faculty of Physics, West University of Timisoara, Bd. V. Parvan No. 4, 300223 Timisoara (Romania)
2015-12-01
Calculations of the Cr{sup 3+} energy levels, spin-Hamiltonian parameters and vibrational spectra for the layered CrCl{sub 3} crystals are reported for the first time. The crystal field parameters and the energy level scheme were calculated in the framework of the Exchange Charge Model of crystal field. The spin-Hamiltonian parameters (zero-field splitting parameter D and g-factors) for Cr{sup 3+} ion in CrCl{sub 3} crystals were obtained using two independent techniques: i) semi-empirical crystal field theory and ii) density functional theory (DFT)-based model. In the first approach, the spin-Hamiltonian parameters were calculated from the perturbation theory method and the complete diagonalization (of energy matrix) method. The infrared (IR) and Raman frequencies were calculated for both experimental and fully optimized geometry of the crystal structure, using CRYSTAL09 software. The obtained results are discussed and compared with the experimental available data.
Calculations in external fields in quantum chromodynamics
International Nuclear Information System (INIS)
Novikov, V.A.; Shifman, M.A.; Vairshtejn, A.I.; Zakharov, V.I.
1983-01-01
The technique of calculation of operator expansion coefficients is reviewed. The main emphasis is put on gluon operators which appear in expansion of n-point functions induced by colourless quark currents. Two convenient schemes are discussed in detail: the abstract operator method and the method based on the Fock-Schwinger gauge for the vacuum gluon field. A large number of instructive examples important from the point of view of physical applications is considered
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.
High Field Magnetization of Tb Single Crystals
DEFF Research Database (Denmark)
Roeland, L. W.; Cock, G. J.; Lindgård, Per-Anker
1975-01-01
Hamiltonian including isotropic exchange interactions, effective single-ion anisotropy and magnetoelastic contributions. The parameters of this Hamiltonian were determined by fitting the theoretical results for the spin wave dispersion and energy gap as a function of temperature and magnetic field to existing...... data on Tb. The conduction-electron polarization at zero field and temperature is (0.33+or-0.05) mu B/ion, and the susceptibility is greater than the Pauli susceptibility calculated from the band-structure....
Crystal field parameters in UCl4: Experiment versus theory
International Nuclear Information System (INIS)
Zolnierek, Z.; Gajek, Z.; Khan Malek, C.
1984-01-01
Crystal field effect on U 4+ ion with the 3 H 4 ground term in tetragonal ligand field of UCl 4 has been studied in detail. Crystal field parameters determined experimentally from optical spectroscopy and magnetic susceptibility are in good agreement with CEP sets derived from the modified point charge model and the ab initio method. Theoretical calculations lead to overestimating the A 4 4 4 > and lowering the A 2 0 2 > values in comparison to those found in the experiments. The discrepancies are, however, within an accuracy of calculations. A large reduction of expectation values of the magnetic moment operator for the eigenvectors of lowest CF levels (17.8%), determined from magnetic susceptibility, cannot be attributed to the overlap and covalency effects only. The detailed calculations have shown that the latter effects provide about 4.6% reduction of respective matrix elements, and the applied J-J mixing procedure increases this factor up to 6.5%. Since similar, as in UCl 4 , reduction factor (proportional15%) has already been observed in a number of different uranium compounds, it seems to be likely that this feature is involved in the intrinsic properties of the U 4+ ion. We endeavor to explain this effect in terms of configuration interaction mechanisms. (orig.)
Crystal field parameters in UCI 4: Experiment versus theory
Zolnierek, Z.; Gajek, Z.; Malek, Ch. Khan
1984-08-01
Crystal field effect on U 4+ ion with the 3H 4 ground term in tetragonal ligand field of UCl 4 has been studied in detail. Crystal field parameters determined experimentally from optical spectroscopy and magnetic susceptibility are in good agreement with CFP sets derived from the modified point charge model and the ab initio method. Theoretical calculations lead to overestimating the A44 and lowering the A02 values in comparison to those found in the experiments. The discrepancies are, however, within an accuracy of calculations. A large reduction of expectation values of the magnetic moment operator for the eigenvectors of lowest CF levels (17.8%), determined from magnetic susceptibility, cannot be attributed to the overlap and covalency effects only. The detailed calculations have shown that the latter effects provide about 4.6% reduction of respective matrix elements, and the applied J-J mixing procedure increases this factor up to 6.5%. Since similar, as in UCl 4, reduction factor(≈15%) has already been observed in a number of different uranium compounds, it seems likely that this feature is involved in the intrinsic properties of the U 4+ ion. We endeavor to explain this effect in terms of configuration interaction mechanisms.
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.
International Nuclear Information System (INIS)
Worgan, K.; Shaw, W.
1992-02-01
In Project-90, the far-field transport of nuclides is assumed to take place in a 200 m long section of rock mass, which starts at the outer boundary of the near-field and ends in a fracture zone. The nuclides are eventually discharged to the biosphere. This document provides an overview of the results obtained with the far-field model CRYSTAL developed by Intera Environmental Division for the Swedish Nuclear Power Inspectorate (SKI). It reports on the results of a series of calculation that have been performed within the SKIs Project-90, and provides some indication of the key parameters for the far field. A more thorough discussion of the implications for performance assessment is given in the Project-90 reports. (au)
Absorption measurement s in InSe single crystal under an applied electric field
International Nuclear Information System (INIS)
Ates, A.; Guerbulak, B.; Guer, E.; Yildirim, T.; Yildirim, M.
2002-01-01
InSe single crystal was grown by Bridgman-Stockberger method. Electric field effect on the absorption measurements have been investigated as a function of temperature in InSe single crystal. The absorption edge shifted towards longer wavelengths and decreased of intensity in absorption spectra under an electric field. Using absorption measurements, Urbach energy was calculated under an electric field. Applied electric field caused a increasing in the Urbach energy. At 10 K and 320 K, the first exciton energies were calculated as 1.350 and 1.311 eV for zero voltage and 1.334 and 1.301 eV for electric field respectively
International Nuclear Information System (INIS)
Karbowiak, M.; Gnutek, P.; Rudowicz, C.; Ryba-Romanowski, W.
2011-01-01
Graphical abstract: In this paper we report a detailed analysis of spectroscopic data obtained from low temperature absorption spectra, which enabled assignment of energy levels, and subsequently their analysis in terms of the free-ion and crystal field (CF) parameters. Highlights: → Polarized absorption spectra measured for Nd 3+ and Tm 3+ ions in ABC 3 O 7 crystals. → Energy levels analyzed in terms of the free-ion and crystal-field (CF) parameters. → The combined ADS/SPM procedure have been successfully applied. → The B-bar k parameters and the power law exponents t k of SPM model are determined. → The energies of levels are important for evaluation of the emission cross-section. - Abstract: Low temperature polarized absorption spectra are analyzed to achieve assignments of energy levels for Nd 3+ and Tm 3+ ions at monoclinic C s site symmetry in ABC 3 O 7 crystals. Based on the concept of average optical center, the experimental energy levels for single crystals of SrLaGa 3 O 7 :Nd 3+ (SLG:Nd), BaLaGa 3 O 7 :Nd 3+ (BLG:Nd), and SrGdGa 3 O 7 :Tm 3+ (SGG:Tm) were analyzed in terms of the free-ion parameters and the crystal field (CF) ones, B kq . Assignments of the energy levels resolved in the spectra were done in stages applying the ascent/descent in symmetry method in CF analysis. The actual monoclinic C s site symmetry at the metal centers in ABC 3 O 7 crystals and the approximated orthorhombic C 2v and tetragonal C 4v symmetry were considered. The starting values of B kq 's for SLG:Nd and BLG:Nd crystals were obtained from superposition model (SPM) analysis. The final fitted crystal field parameters show high compatibility with the existing data for structurally similar ion-host systems. The obtained values of the intrinsic parameters provide basis for SPM analysis of CF parameters for rare earth ions in other similar systems, especially those exhibiting low-symmetry sites. The SPM parameters derived for SLG:Nd are used for simulation and
Calculation of effective impedance of polycrystals in weak magnetic fields
International Nuclear Information System (INIS)
Kaganova, I.M.
2006-01-01
We present results for the effective surface impedance tensor (EIT) of polycrystals of metals in a weak uniform magnetic field H. The frequency region corresponds to the region in which the local impedance boundary conditions are applicable. We suppose that the resistivity tensor ρ ik (H) of the single crystal grains out of which the polycrystal is composed, is known up to the terms of O(H 2 ). For polycrystals of metals of arbitrary symmetry, the elements of the EIT can be calculated to the same order in H, even if the tensor ρ ik (H) is strongly anisotropic. As examples, we write down the EIT of polycrystals of (i) cubic metals (ii) metals with ellipsoidal Fermi surfaces, and (iii) metals of tetragonal symmetry whose tensor ρ ik (0) is strongly anisotropic. Although polycrystals are metals that are isotropic on average, in the presence of a uniform magnetic field the structure of the EIT is not the same as the structure of the impedance tensor of an isotropic metal with a spherical Fermi surface. The results cannot be improved either by taking into account higher powers of H, or with respect to the anisotropy of the single crystal grains
Variable valence ion spectra in a crystal field
International Nuclear Information System (INIS)
Ghiordanescu, V.
1979-01-01
Using the Cadmium chloride as a host lattice, the optical spectra and RES of Mnsup(2+) were studied and the following results were obtained: a) By controlled dopings, the absorbtion and excitation spectra of ion Mnsup(2+) in CdCl 2 within the concentration range between 0.01 M and 25 M were plotted. Thus, the band structure for small concentrations was pointed out to differ from the structure observed for high concentrations. In the literature, this effect has not been observed on similar compounds, due to the small intensity values of the absorbtion spectra. b) Considering that for CdCl 2 :Mnsup(2+) 0.1 M, the optical spectra correspond to the isolated ion in the lattice, the energy levels were evaluated using electrostatic and spin-orbit terms in a perturbation calculation of the crystal field approximation. c) The calculation of parameter a which represents the effect of the cubic field in the spjn Hamiltonian of Mnsup(2+), is closer to the experjmental value -0.5.10 -4 cm -1 of the crystal field Dq and zeta parameters are used, respectively, parameters of the spin-orbit interaction obtained under b). d) The coupling effects of spins into more concentrated crystals with Mn 2+ are a function of temperature. The emjssion yield was given a quasi-cantitative evaluation in thjs paper as a function of temperature and concentratjon on the basis of which the isolated centers of Mn 2+ were found to display ectra whose intensity vary with temperature according to the Laporte forbidden transitions and spin rule theory, and the clusters including Mn 2+ - Mn 2+ pairs provide spectra whose intensity vary with the strength of the spin-spin coupling. (author)
The diluted tri-dimensional spin-one Ising model with crystal field interactions
International Nuclear Information System (INIS)
Saber, M.
1988-09-01
3D spin-one Ising models with nearest-neighbour ferromagnetic interactions with crystal-field exhibit tricritical behaviour. A new method that applies to a wide class of random systems is used to study the influence of site and bond dilution on this behaviour. We have calculated temperature-crystal-field-concentration phase diagrams and determined, in particular, the influence of dilution on the zero temperature tricritical temperature. (author). 10 refs, 8 figs
Tricritical behavior in the diluted transverse spin-1 Ising model with a longitudinal crystal field
International Nuclear Information System (INIS)
Htoutou, K.; Oubelkacem, A.; Ainane, A.; Saber, M.
2005-01-01
The transverse spin-1 Ising model with a longitudinal crystal field exhibits a tricritical behavior. Within the effective field theory with a probability distribution technique that accounts for the self-spin correlations, we have studied the influence of site dilution on this behavior and have calculated the temperature-transverse field-longitudinal crystal field-concentration phase diagrams and determined, in particular, the influence of the concentration of magnetic atoms c on the tricritical behavior. We have found that the tricritical point appears for large values of the concentration c of magnetic atoms and disappears with the increase in dilution (small values of c). Results for square lattice are calculated numerically and some interesting results are obtained. In certain ranges of values of the strength of the longitudinal crystal field D/J when it becomes sufficiently negative, we found re-entrant phenomenon, which disappears with increase in the value of the strength of the transverse field
Magnetic islands modelled by a phase-field-crystal approach
Faghihi, Niloufar; Mkhonta, Simiso; Elder, Ken R.; Grant, Martin
2018-03-01
Using a minimal model based on the phase-field-crystal formalism, we study the coupling between the density and magnetization in ferromagnetic solids. Analytical calculations for the square phase in two dimensions are presented and the small deformation properties of the system are examined. Furthermore, numerical simulations are conducted to study the influence of an external magnetic field on various phase transitions, the anisotropic properties of the free energy functional, and the scaling behaviour of the growth of the magnetic domains in a crystalline solid. It is shown that the energy of the system can depend on the direction of the magnetic moments, with respect to the crystalline direction. Furthermore, the growth of the magnetic domains in a crystalline solid is studied and is shown that the growth of domains is in agreement with expected behaviour.
Unified calculations of the optical band positions and EPR g factors for NaCrS2 crystal
International Nuclear Information System (INIS)
Mei, Yang; Zheng, Wen-Chen; Zhang, Lin
2014-01-01
Six optical band positions and EPR g factors g || , g ⊥ for the trigonal Cr 3+ octahedral clusters in NaCrS 2 crystal are calculated together through the complete diagonalization (of energy matrix) method based on the two-spin–orbit-parameter model, where besides the contribution due to the spin–orbit parameter of central d n ion in the conventional crystal-field theory, the contribution due to the spin–orbit parameter of ligand ion via the covalence effect is also considered. In the calculations, the crystal-field parameters B kl are obtained from the superposition model with the structural data of Cr 3+ octahedral clusters in NaCrS 2 crystal measured exactly by the X-ray diffraction method. The calculated optical and EPR spectral data are in a reasonable agreement with the observed values. So, the reliability of the superposition model in the studies of crystal-field parameters for d n ions in crystals is confirmed, and the complete diagonalization (of energy matrix) method based on the two-spin–orbit-model is effective in the unified calculations of optical and EPR spectral data for d n ions in crystals. - Highlights: • Six optical band positions and g factors g || , g ⊥ of NaCrS 2 are calculated together. • Calculation is using the complete diagonalization (of energy matrix) method. • The diagonalization method is based on the two-spin–orbit-parameter model. • Reliability of superposition model in the studies of CF parameters is confirmed
Pretest Calculations of Temperature Changes for Field Thermal Conductivity Tests
International Nuclear Information System (INIS)
N.S. Brodsky
2002-01-01
A large volume fraction of the potential monitored geologic repository at Yucca Mountain may reside in the Tptpll (Tertiary, Paintbrush Group, Topopah Spring Tuff, crystal poor, lower lithophysal) lithostratigraphic unit. This unit is characterized by voids, or lithophysae, which range in size from centimeters to meters. A series of thermal conductivity field tests are planned in the Enhanced Characterization of the Repository Block (ECRB) Cross Drift. The objective of the pretest calculation described in this document is to predict changes in temperatures in the surrounding rock for these tests for a given heater power and a set of thermal transport properties. The calculation can be extended, as described in this document, to obtain thermal conductivity, thermal capacitance (density x heat capacity, J · m -3 · K -1 ), and thermal diffusivity from the field data. The work has been conducted under the ''Technical Work Plan For: Testing and Monitoring'' (BSC 2001). One of the outcomes of this analysis is to determine the initial output of the heater. This heater output must be sufficiently high that it will provide results in a reasonably short period of time (within several weeks or a month) and be sufficiently high that the heat increase is detectable by the instruments employed in the test. The test will be conducted in stages and heater output will be step increased as the test progresses. If the initial temperature is set too high, the experiment will not have as many steps and thus fewer thermal conductivity data points will result
Energy Technology Data Exchange (ETDEWEB)
Kripal, Ram, E-mail: ram_kripal2001@rediffmail.com; Yadav, Awadhesh Kumar, E-mail: aky.physics@gmail.com
2015-06-15
Zero field splitting parameters (ZFSPs) D and E of Cr{sup 3+} ion doped ammonium oxalate monohydrate (AOM) are calculated with formula using the superposition model. The theoretically calculated ZFSPs for Cr{sup 3+} in AOM crystal are compared with the experimental value obtained by electron paramagnetic resonance (EPR). Theoretical ZFSPs are in good agreement with the experimental ones. The energy band positions of optical absorption spectra of Cr{sup 3+} in AOM crystal calculated with CFA package are in good match with the experimental values.
International Nuclear Information System (INIS)
Lino, A.T.; Takahashi, E.K.; Leite, J.R.; Ferraz, A.C.
1988-01-01
The band structure of metallic sodium is calculated, using for the first time the self-consistent field variational cellular method. In order to implement the self-consistency in the variational cellular theory, the crystal electronic charge density was calculated within the muffin-tin approximation. The comparison between our results and those derived from other calculations leads to the conclusion that the proposed self-consistent version of the variational cellular method is fast and accurate. (author) [pt
Rotation of dust plasma crystals in an axial magnetic field
International Nuclear Information System (INIS)
Cheung, F.; Prior, N.; Mitchell, L.
2000-01-01
Full text: Micron-sized melamine formaldehyde particles were introduced into argon plasma. As a result, the particles were negatively charged due to collision with the electrons within the plasma. With the right conditions, these particles formed a stable macroscopic crystal lattice, known as dust plasma crystal. In our experiment we conduct at Flinders University, we apply an external axial magnetic field to various configurations of dust plasma crystal. These configurations include small crystal lattices consisting of one to several particles, and large crystal lattices with many hundreds of particles. The magnetic field strength ranged from 0-32G and was uniform over the extent of the crystal. The crystals were observed to be rotating collectively in the left-handed direction under the influence of the axial magnetic field. In the case of the large crystals, the angular velocity was about 2 complete rotations per minute and was proportional to the applied magnetic field. The angular velocity changes only slightly depending on the plasma conditions. Neither radial variance in the angular velocity nor shear velocity in the vertical direction was observed in the crystal's rotational motion. In the case of the small crystals, we managed to rotate 2-6 particles (whether they are planar, 2 layers or tetrahedral). We discovered that the ease and the uniformity of the rotation of the different crystals increase as its rotational symmetry increases. Also an increase in the magnetic field strength will correspond to an increase in the angular velocity. Crystals in the shape of an annulus were also tested for theoretical reasons. The poster presentation will contain the experimental procedures, a detailed analysis and an explanation for such dust plasma crystal rotational motion
Reliability of conventional crystal field models in f-electron systems
Energy Technology Data Exchange (ETDEWEB)
Gajek, Z. [Polska Akademia Nauk, Wroclaw (Poland). Inst. Niskich Temperatur i Badan Strukturalnych
1995-03-15
Crystal field models commonly applied to explain the electronic properties of solid f-electron compounds are discussed from the point of view of their inherent limitations and the false conclusions they may lead to. Both phenomenological and ab initio approximate models are considered. The discussion is based on generalized perturbation model calculations of the crystal field parameters for europium, uranium, plutonium and neptunium ions in various crystals. The results reveal the inadequacy of various electrostatic approaches and the correctness of models based on renormalization terms. ((orig.))
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.
Calculations in perturbative string field theory
International Nuclear Information System (INIS)
Thorn, C.B.
1987-01-01
The author discusses methods for evaluating the Feynman diagrams of string field theory, with particular emphasis on Witten's version of open string field theory. It is explained in some detail how the rules states by Giddings and Martinec for relating a given diagram to a Polyakov path integral emerge from the Feynman rules
How to estimate hardness of crystals on a pocket calculator
International Nuclear Information System (INIS)
Simunek, Antonin
2007-01-01
A generalization of the semiempirical microscopic model of hardness is presented and applied to currently studied borides, carbides, and nitrides of heavy transition metals. The hardness of OsB, OsC, OsN, PtN, RuC, RuB 2 , ReB 2 , OsB 2 , IrN 2 , PtN 2 , and OsN 2 crystals in various structural phases is predicted. It is found that none of the transition metal crystals is superhard, i.e., with hardness greater than 40 GPa. The presented method provides materials researchers with a practical tool in the search for new hard materials
Vertical field and equilibrium calculation in ETE
International Nuclear Information System (INIS)
Montes, Antonio; Shibata, Carlos Shinya.
1996-01-01
The free-boundary MHD equilibrium code HEQ is used to study the plasma behaviour in the tokamak ETE, with optimized compensations coils and vertical field coils. The changes on the equilibrium parameters for different plasma current values are also investigated. (author). 5 refs., 4 figs., 2 tabs
The two-wave X-ray field calculated by means of integral-equation methods
International Nuclear Information System (INIS)
Bremer, J.
1984-01-01
The problem of calculating the two-wave X-ray field on the basis of the Takagi-Taupin equations is discussed for the general case of curved lattice planes. A two-dimensional integral equation which incorporates the nature of the incoming radiation, the form of the crystal/vacuum boundary, and the curvature of the structure, is deduced. Analytical solutions for the symmetrical Laue case with incoming plane waves are obtained directly for perfect crystals by means of iteration. The same method permits a simple derivation of the narrow-wave Laue and Bragg cases. Modulated wave fronts are discussed, and it is shown that a cut-off in the width of an incoming plane wave leads to lateral oscillations which are superimposed on the Pendelloesung fringes. Bragg and Laue shadow fields are obtained. The influence of a non-zero kernel is discussed and a numerical procedure for calculating wave amplitudes in curved crystals is presented. (Auth.)
Some approximate calculations in SU2 lattice mean field theory
International Nuclear Information System (INIS)
Hari Dass, N.D.; Lauwers, P.G.
1981-12-01
Approximate calculations are performed for small Wilson loops of SU 2 lattice gauge theory in mean field approximation. Reasonable agreement is found with Monte Carlo data. Ways of improving these calculations are discussed. (Auth.)
Analyzed method for calculating the distribution of electrostatic field
International Nuclear Information System (INIS)
Lai, W.
1981-01-01
An analyzed method for calculating the distribution of electrostatic field under any given axial gradient in tandem accelerators is described. This method possesses satisfactory accuracy compared with the results of numerical calculation
Calculation of magnetic fields for engineering devices
International Nuclear Information System (INIS)
Colonias, J.S.
1976-06-01
The methodology of magnet technology and its application to various engineering devices are discussed. Magnet technology has experienced a rigid growth in the past few years as a result of the advances made in superconductivity, numerical methods and computational techniques. Included are discussions on: (1) mathematical models for solving magnetic field problems; (2) the applicability, usefulness, and limitations of computer programs that utilize these models; (3) examples of application in various engineering disciplines; and (4) areas where further contributions are needed
Numerical challenges of short range wake field calculations
Energy Technology Data Exchange (ETDEWEB)
Lau, Thomas; Gjonaj, Erion; Weiland, Thomas [Technische Universitaet Darmstadt (Germany). Institut fuer Theorie Elektromagnetischer Felder (TEMF)
2011-07-01
For present and future accelerator projects with ultra short bunches the accurate and reliable calculation of short range wake fields is an important issue. However, the numerical calculation of short range wake fields is a numerical challenging task. The presentation gives an overview over the numerical challenges and techniques for short range wake field calculations. Finally, some simulation results obtained by the program PBCI developed at the TU Darmstadt are presented.
Massively parallel self-consistent-field calculations
International Nuclear Information System (INIS)
Tilson, J.L.
1994-01-01
The advent of supercomputers with many computational nodes each with its own independent memory makes possible extremely fast computations. The author's work, as part of the US High Performance Computing and Communications Program (HPCCP), is focused on the development of electronic structure techniques for the solution of Grand Challenge-size molecules containing hundreds of atoms. Their efforts have resulted in a fully scalable Direct-SCF program that is portable and efficient. This code, named NWCHEM, is built around a distributed-data model. This distributed data is managed by a software package called Global Arrays developed within the HPCCP. They present performance results for Direct-SCF calculations of interest to the consortium
Energy Technology Data Exchange (ETDEWEB)
Strindehag, O; Tollander, B
1968-08-15
Calculated values of the absolute total detection efficiencies of cylindrical scintillation crystals viewing spherical sources of various sizes are presented. The calculation is carried out for 2 x 2 inch and 3 x 3 inch Nal(Tl) crystals and for sources which have the radii 1/4, 1/2, 3/4 and 1 times the crystal radius. Source-detector distances of 5-20 cm and gamma energies in the range 0.1 - 5 MeV are considered. The correction factor for absorption in the sample container wall and in the detector housing is derived and calculated for a practical case.
Efficient Calculation of Near Fields in the FDTD Method
DEFF Research Database (Denmark)
Franek, Ondrej
2011-01-01
When calculating frequency-domain near fields by the FDTD method, almost 50 % reduction in memory and CPU operations can be achieved if only E-fields are stored during the main time-stepping loop and H-fields computed later. An improved method of obtaining the H-fields from Faraday's Law is prese...
Crystal field and magnetism with Wannier functions: rare-earth dopedaluminum garnets
Czech Academy of Sciences Publication Activity Database
Mihóková, Eva; Novák, Pavel; Laguta, Valentyn
2015-01-01
Roč. 33, č. 12 (2015), 1316-1323 ISSN 1002-0721 R&D Projects: GA ČR GA13-09876S Institutional support: RVO:68378271 Keywords : crystal field * ab initio calculations * garnets * rare earths Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.188, year: 2015
Nonperturbative calculation of symmetry breaking in quantum field theory
Bender, Carl M.; Milton, Kimball A.
1996-01-01
A new version of the delta expansion is presented, which, unlike the conventional delta expansion, can be used to do nonperturbative calculations in a self-interacting scalar quantum field theory having broken symmetry. We calculate the expectation value of the scalar field to first order in delta, where delta is a measure of the degree of nonlinearity in the interaction term.
Classical nucleation theory in the phase-field crystal model.
Jreidini, Paul; Kocher, Gabriel; Provatas, Nikolas
2018-04-01
A full understanding of polycrystalline materials requires studying the process of nucleation, a thermally activated phase transition that typically occurs at atomistic scales. The numerical modeling of this process is problematic for traditional numerical techniques: commonly used phase-field methods' resolution does not extend to the atomic scales at which nucleation takes places, while atomistic methods such as molecular dynamics are incapable of scaling to the mesoscale regime where late-stage growth and structure formation takes place following earlier nucleation. Consequently, it is of interest to examine nucleation in the more recently proposed phase-field crystal (PFC) model, which attempts to bridge the atomic and mesoscale regimes in microstructure simulations. In this work, we numerically calculate homogeneous liquid-to-solid nucleation rates and incubation times in the simplest version of the PFC model, for various parameter choices. We show that the model naturally exhibits qualitative agreement with the predictions of classical nucleation theory (CNT) despite a lack of some explicit atomistic features presumed in CNT. We also examine the early appearance of lattice structure in nucleating grains, finding disagreement with some basic assumptions of CNT. We then argue that a quantitatively correct nucleation theory for the PFC model would require extending CNT to a multivariable theory.
Classical nucleation theory in the phase-field crystal model
Jreidini, Paul; Kocher, Gabriel; Provatas, Nikolas
2018-04-01
A full understanding of polycrystalline materials requires studying the process of nucleation, a thermally activated phase transition that typically occurs at atomistic scales. The numerical modeling of this process is problematic for traditional numerical techniques: commonly used phase-field methods' resolution does not extend to the atomic scales at which nucleation takes places, while atomistic methods such as molecular dynamics are incapable of scaling to the mesoscale regime where late-stage growth and structure formation takes place following earlier nucleation. Consequently, it is of interest to examine nucleation in the more recently proposed phase-field crystal (PFC) model, which attempts to bridge the atomic and mesoscale regimes in microstructure simulations. In this work, we numerically calculate homogeneous liquid-to-solid nucleation rates and incubation times in the simplest version of the PFC model, for various parameter choices. We show that the model naturally exhibits qualitative agreement with the predictions of classical nucleation theory (CNT) despite a lack of some explicit atomistic features presumed in CNT. We also examine the early appearance of lattice structure in nucleating grains, finding disagreement with some basic assumptions of CNT. We then argue that a quantitatively correct nucleation theory for the PFC model would require extending CNT to a multivariable theory.
Cohesion energy calculations for ternary ionic novel crystals
International Nuclear Information System (INIS)
Vazquez P, G.; Cabrera, E.; Mijangos, R.R.; Valdez, E.; Duarte, C.
2001-01-01
The present work calculates the value of the link energy of a crystalline ternary structure newly formed by alkali halides. The ternary structure prepared with different concentrations of KCl x KBrRbCl 2 maintains a very good miscibility and stability. The calculation is based on the use of a generalization of the Vegard law (which generally is valid for binary compounds) for calculating the values of the lattice constant and the repulsive m exponent. The value of the lattice parameter given by X-ray diffractometry agrees with the close approximation of the calculated value of the method used. It also compares the value of energy cohesion obtained by the Born expression with more complex approximations. (Author)
Simultaneous near field imaging of electric and magnetic field in photonic crystal nanocavities
Vignolini, S.; Intonti, F.; Riboli, F.; Wiersma, D.S.; Balet, L.P.; Li, L.H.; Francardi, M.; Gerardino, A.; Fiore, A.; Gurioli, M.
2012-01-01
The insertion of a metal-coated tip on the surface of a photonic crystal microcavity is used for simultaneous near field imaging of electric and magnetic fields in photonic crystal nanocavities, via the radiative emission of embedded semiconductor quantum dots (QD). The photoluminescence intensity
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
International Nuclear Information System (INIS)
Agamaliyev, Z.A.; Tahirov, V.I.; Hasanov, Z.Y.; Quliyev, A.F.
2007-01-01
A binary solid solution single crystal growth method has been worked out. Cylinder feeding alloy with complex content distribution and truncated cone crucible are used. Second component distribution coefficient is more than unit. Content distribution along grown crystal is found by solving continuity equation. After reaching dynamic equilibrium state second component concentration in grown crystal is saturated the value of which is less than the average ona in the feeding alloy. Using the method Ge-Si perfect single crystals has been grown. Calculation method of melt surface displacement velocity has been offered as well
Calculation of the quadrupole-lense fringing field
International Nuclear Information System (INIS)
Arzumanov, A.A.
1978-01-01
With the aim of decreasing the scattering field effect at electrode edge or quadrupole lens poles with conformal transformations the scattering fields of electric quadrupole lens, two-electrode lens with the electrodes in a hyperbola form, as well as magnetic lens with hyperbolic poles are calculated. For the two-electrode system with kappa=0.1 (kappa - is coefficient, characterizing the rate of field intensity change in the lens) field distortion equals 1.8%. The comparison of experimental data with the calculation data has shown that with a rather high accuracy the scattering field effect in electric and magnetic lenses with hyperbolic poles may be taken into account
On the laws of disordering of the Ln3+ -ion crystal field in insulating crystals
International Nuclear Information System (INIS)
Kaminskij, A.A.
1988-01-01
Results of the study of fundamental regularities, which cause crystal field (CF) disordering on Ln 3+ ions in dielectric crystals are summed up. Analysis and systematization of the investigation results of atomic structure of disordered laser crystals and conducted investigations on spectroscopic properties and induced radiation (IR) permitted to come to the conclusion that the nature of disordering on CF is related to two fundamental regularities. The first regularity- the structural-dynamic one- is pronounced in numerous nonstoichiometric phases; the second one - determines spectroscopic properties and IR character
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...... propose a simple stochastic model of dislocation reaction kinetics that is able to capture these statistical properties of the dislocation density fluctuations as a function of shear rate....
Magnetic Field Applications in Semiconductor Crystal Growth and Metallurgy
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
On the neutron diffraction in a crystal in the field of a standing laser wave
International Nuclear Information System (INIS)
Grigoryan, K.K.; Hayrapetyan, A.G.; Petrosyan, R.G.
2010-01-01
The possibility of high-energy neutron diffraction in a crystal is shown by applying the solution of time-dependent Schroedinger equation for a neutron in the field of a standing laser wave. The scattering picture is examined within the framework of non-stationary S-matrix theory, where the neutron-laser field interaction is considered exactly and the neutron-crystal interaction is considered as a perturbation described by Fermi pseudopotential (Farri representation). The neutron-crystal interaction is elastic, and the neutron-laser field interaction has both inelastic and elastic behaviors which results in the observation of an analogous to the Kapitza-Dirac effect for neutrons. The neutron scattering probability is calculated and the analysis of the results are adduced. Both inelastic and elastic diffraction conditions are obtained and the formation of a 'sublattice' is illustrated in the process of neutron-photon-phonon elastic interaction.
3D electric field calculation with surface charge method
International Nuclear Information System (INIS)
Yamada, S.
1992-01-01
This paper describes an outline and some examples of three dimensional electric field calculations with a computer code developed at NIRS. In the code, a surface charge method is adopted because of it's simplicity in the mesh establishing procedure. The charge density in a triangular mesh is assumed to distribute with a linear function of the position. The electric field distribution is calculated for a pair of drift tubes with the focusing fingers on the opposing surfaces. The field distribution in an acceleration gap is analyzed with a Fourier-Bessel series expansion method. The calculated results excellently reproduces the measured data with a magnetic model. (author)
International Nuclear Information System (INIS)
Zunger, A.
1975-07-01
Semiempirical all-valence-electron LCAO methods, that were previously used to study the electronic structure of molecules are applied to three problems in solid state physics: the electronic band structure of covalent crystals, point defect problems in solids and lattice dynamical study of molecular crystals. Calculation methods for the electronic band structure of regular solids are introduced and problems regarding the computation of the density matrix in solids are discussed. Three models for treating the electronic eigenvalue problem in the solid, within the proposed calculation schemes, are discussed and the proposed models and calculation schemes are applied to the calculation of the electronic structure of several solids belonging to different crystal types. The calculation models also describe electronic properties of deep defects in covalent insulating crystals. The possible usefulness of the semieipirical LCAO methods in determining the first order intermolecular interaction potential in solids and an improved model for treating the lattice dynamics and related thermodynamical properties of molecular solids are presented. The improved lattice dynamical is used to compute phonon dispersion curves, phonon density of states, stable unit cell structure, lattice heat capacity and thermal crystal parameters, in α and γ-N 2 crystals, using the N 2 -N 2 intermolecular interaction potential that has been computed from the semiempirical LCAO methods. (B.G.)
Crystal field in rare-earth metals and intermetallic compounds
International Nuclear Information System (INIS)
Ray, D.K.
1978-01-01
Reasons for the success of the crystal-field model for the rare-earth metals and intermetallic compounds are discussed. A review of some of the available experimental results is made with emphasis on cubic intermetallic compounds. Various sources of the origin of the crystal field in these metals are discussed in the background of the recent APW picture of the conduction electrons. The importance of the non-spherical part of the muffin-tin potential on the single-ion anisotropy is stressed. (author)
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 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...
Crystal field in ErGa3 - a neutron spectroscopy study
International Nuclear Information System (INIS)
Murasik, A.; Czopnik, A.; Clementyev, E.; Schefer, J.
2000-01-01
The splitting of the J = 15/2 multiplet of Er in a cubic crystal field has been determined by inelastic scattering from a polycrystalline sample of ErGa 3 . On the base of observed intensities and their temperature variation we have been able to determine two crystal electric fields (CEF) parameters required for cubic symmetry. Least-squares fits of calculated crystal field transitions of the observed neutron inelastic scattering spectra taken at 12, 24, 32, 40, 50 and 80 K, gave the crystal field parameters: B 4 (7.15±0.05) x 10 -5 and B 6 = (1.28±0.05) x 1- -6 MeV yielding the Γ 7 doublet as a ground level with the overall splitting of 10.92 MeV. The results are used to calculate the temperature-depended zero field magnetization and the Schottky anomaly of the heat capacity of the ErGa 3 which yield reasonable agreement with experimental data obtained earlier. (author)
Thermal conductivity of niobium single crystals in a magnetic field
International Nuclear Information System (INIS)
Gladun, C.; Vinzelberg, H.
1980-01-01
The thermal conductivity in longitudinal magnetic fields up to 5 T and in the temperature range 3.5 to 15 K is measured in two high purity niobium single crystals having residual resistivity ratios of 22700 and 19200 and orientations of the rod axis [110] and [100]. The investigations show that by means of the longitudinal magnetic field the thermal conductivity may decrease only to a limiting value. In the crystal directions [110] and [100] for the ratio of the thermal conductivity in zero field and the thermal conductivity in the saturation field the temperature-independent factors 1.92 and 1.27, respectively, are determined. With the aid of these factors the thermal conductivity in the normal state is evaluated from the measured values of thermal conductivity below Tsub(c) in the magnetic field. The different conduction and scattering mechanisms are discussed. (author)
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.
Verification, validation, and field testing the USEPA National Stormwater Calculator
U.S. Environmental Protection Agency — We used this dataset to verify and validate functions in the USEPA National Stormwater Calculator, and then applied field data and commonly-available datasets to...
Comparison of different dose calculation methods for irregular photon fields
International Nuclear Information System (INIS)
Zakaria, G.A.; Schuette, W.
2000-01-01
In this work, 4 calculation methods (Wrede method, Clarskon method of sector integration, beam-zone method of Quast and pencil-beam method of Ahnesjoe) are introduced to calculate point doses in different irregular photon fields. The calculations cover a typical mantle field, an inverted Y-field and different blocked fields for 4 and 10 MV photon energies. The results are compared to those of measurements in a water phantom. The Clarkson and the pencil-beam method have been proved to be the methods of equal standard in relation to accuracy. Both of these methods are being distinguished by minimum deviations and applied in our clinical routine work. The Wrede and beam-zone methods deliver useful results to central beam and yet provide larger deviations in calculating points beyond the central axis. (orig.) [de
International Nuclear Information System (INIS)
Ehvarestov, R.A.; Panin, A.I.; Bandura, A.V.
2008-01-01
Account of relativistic effects on the properties of uranium hexafluoride is testified. Detailed comparison of single electron energies spectrum revealed in nonrelativistic (by Hartree-Fock method), relativistic (by Dirac-Fock method), and scalar-relativistic (using relativistic potential of atomic uranium frame) has been conducted. Optimization procedures of atomic basis in LCAO calculations of molecules and crystals permissive taking into account distortion of atomic orbitals when chemical bonding are discussed, and optimization effect of atomic basis on the results of scalar-relativistic calculations of UF 6 molecule properties is analyzed. Calculations of electronic structure and properties of UO 2 crystal having relativistic and nonrelativistic pseudopotentials have been realized [ru
Field calculations. Part I: Choice of variables and methods
International Nuclear Information System (INIS)
Turner, L.R.
1981-01-01
Magnetostatic calculations can involve (in order of increasing complexity) conductors only, material with constant or infinite permeability, or material with variable permeability. We consider here only the most general case, calculations involving ferritic material with variable permeability. Variables suitable for magnetostatic calculations are the magnetic field, the magnetic vector potential, and the magnetic scalar potential. For two-dimensional calculations the potentials, which each have only one component, have advantages over the field, which has two components. Because it is a single-valued variable, the vector potential is perhaps the best variable for two-dimensional calculations. In three dimensions, both the field and the vector potential have three components; the scalar potential, with only one component,provides a much smaller system of equations to be solved. However the scalar potential is not single-valued. To circumvent this problem, a calculation with two scalar potentials can be performed. The scalar potential whose source is the conductors can be calculated directly by the Biot-Savart law, and the scalar potential whose source is the magnetized material is single valued. However in some situations, the fields from the two potentials nearly cancel; and the numerical accuracy is lost. The 3-D magnetostatic program TOSCA employs a single total scalar potential; the program GFUN uses the magnetic field as its variable
Calculation Of Multicenter Electric Field Integrals Over Slater Type Orbitals
International Nuclear Information System (INIS)
Zaim, N.
2010-01-01
Using the properties of complete orthonormal sets of Ψ α -exponential type orbitals (α1,0,-1,-2, ...) and the relations for overlap integrals, the calculations for the multicenter electric field integrals of Slater type orbitals are performed. The results of computer calculations are presented. The convergence of the series is tested by calculating concrete cases for the arbitrary values of quantum numbers, orbital parameters and internuclear distances.
Redshift of A 1(longitudinal optical) mode for GaN crystals under strong electric field
Gu, Hong; Wu, Kaijie; Zheng, Shunan; Shi, Lin; Zhang, Min; Liu, Zhenghui; Liu, Xinke; Wang, Jianfeng; Zhou, Taofei; Xu, Ke
2018-01-01
We investigated the property of GaN crystals under a strong electric field. The Raman spectra of GaN were measured using an ultraviolet laser, and a remarkable redshift of the A 1(LO) mode was observed. The role of the surface depletion layer was discussed, and the interrelation between the electric field and phonons was revealed. First-principles calculations indicated that, in particular, the phonons that vibrate along the [0001] direction are strongly influenced by the electric field. This effect was confirmed by a surface photovoltage experiment. The results revealed the origin of the redshift and presented the phonon property of GaN under a strong electric field.
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....
Phase field simulations of ice crystal growth in sugar solutions
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
Near-field characterization of photonic crystal Y-splitters
DEFF Research Database (Denmark)
Volkov, V. S.; Bozhevolnyi, S. I.; Borel, Peter Ingo
2005-01-01
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...
Calculation of thermal deformations in water-cooled monochromator crystals
International Nuclear Information System (INIS)
Nakamura, Ario; Hashimoto, Shinya; Motohashi, Haruhiko
1994-11-01
Through calculation of temperature distribution and thermal deformation of monochromators, optical degradation by the heat loads in SPring-8 have been discussed. Cooling experiments were made on three models of copper structures with the JAERI Electron Beam Irradiation Stand (JEBIS) and the results were used to estimate heat transfer coefficients in the models. The heat transfer coefficients have been adopted to simulate heating processes on silicon models of the same structures as the copper models, for which radiations from the SPring-8 bending magnet and the JAERI prototype undulator (WPH-33J) were considered. It has been concluded that, in the case of bending magnet (with power density of 0.27[MW/m 2 ] on monochromator surface), the temperature at the surface center reaches about 30[degC] from the initial temperature of 27[degC] in all the models. In the case of WPH-33J (with power density of 8.2[MW/m 2 ]), the temperature reaches about 200 to 280[degC] depending on the models. The radiation from WPH-33J yields slope errors bigger than the Darwin's width(23[μrad]). (author)
Accurate Calculation of Fringe Fields in the LHC Main Dipoles
Kurz, S; Siegel, N
2000-01-01
The ROXIE program developed at CERN for the design and optimization of the superconducting LHC magnets has been recently extended in a collaboration with the University of Stuttgart, Germany, with a field computation method based on the coupling between the boundary element (BEM) and the finite element (FEM) technique. This avoids the meshing of the coils and the air regions, and avoids the artificial far field boundary conditions. The method is therefore specially suited for the accurate calculation of fields in the superconducting magnets in which the field is dominated by the coil. We will present the fringe field calculations in both 2d and 3d geometries to evaluate the effect of connections and the cryostat on the field quality and the flux density to which auxiliary bus-bars are exposed.
Method for fitting crystal field parameters and the energy level fitting for Yb3+ in crystal SC2O3
International Nuclear Information System (INIS)
Qing-Li, Zhang; Kai-Jie, Ning; Jin, Xiao; Li-Hua, Ding; Wen-Long, Zhou; Wen-Peng, Liu; Shao-Tang, Yin; Hai-He, Jiang
2010-01-01
A method to compute the numerical derivative of eigenvalues of parameterized crystal field Hamiltonian matrix is given, based on the numerical derivatives the general iteration methods such as Levenberg–Marquardt, Newton method, and so on, can be used to solve crystal field parameters by fitting to experimental energy levels. With the numerical eigenvalue derivative, a detailed iteration algorithm to compute crystal field parameters by fitting experimental energy levels has also been described. This method is used to compute the crystal parameters of Yb 3+ in Sc 2 O 3 crystal, which is prepared by a co-precipitation method and whose structure was refined by Rietveld method. By fitting on the parameters of a simple overlap model of crystal field, the results show that the new method can fit the crystal field energy splitting with fast convergence and good stability. (condensed matter: electronic structure, electrical, magnetic, and optical properties)
Crystal-field-modulated magnon squeezing states in a ferromagnet
International Nuclear Information System (INIS)
Peng Feng
2003-01-01
The magnon squeezing states in some magnetic crystals allow a reduction in the quantum fluctuations of the spin component to below the zero-point quantum noise level of the coherent magnon states. It is known that there are the magnon squeezing states in an antiferromagnet. However, their generating mechanism is not suitable for the ferromagnet. In this paper, we discuss the possibility of generating the magnon squeezing states in a ferromagnet, and discuss the effect of the crystal field on the magnon squeezing states
Organic field-effect transistors using single crystals
International Nuclear Information System (INIS)
Hasegawa, Tatsuo; Takeya, Jun
2009-01-01
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 cm 2 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. (topical review)
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.
Far-field coupling in nanobeam photonic crystal cavities
Energy Technology Data Exchange (ETDEWEB)
Rousseau, Ian, E-mail: ian.rousseau@epfl.ch; Sánchez-Arribas, Irene; Carlin, Jean-François; Butté, Raphaël; Grandjean, Nicolas [Institute of Physics, École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne (Switzerland)
2016-05-16
We optimized the far-field emission pattern of one-dimensional photonic crystal nanobeams by modulating the nanobeam width, forming a sidewall Bragg cross-grating far-field coupler. By setting the period of the cross-grating to twice the photonic crystal period, we showed using three-dimensional finite-difference time-domain simulations that the intensity extracted to the far-field could be improved by more than three orders of magnitude compared to the unmodified ideal cavity geometry. We then experimentally studied the evolution of the quality factor and far-field intensity as a function of cross-grating coupler amplitude. High quality factor (>4000) blue (λ = 455 nm) nanobeam photonic crystals were fabricated out of GaN thin films on silicon incorporating a single InGaN quantum well gain medium. Micro-photoluminescence spectroscopy of sets of twelve identical nanobeams revealed a nine-fold average increase in integrated far-field emission intensity and no change in average quality factor for the optimized structure compared to the unmodulated reference. These results are useful for research environments and future nanophotonic light-emitting applications where vertical in- and out-coupling of light to nanocavities is required.
Near-field probing of photonic crystal directional couplers
DEFF Research Database (Denmark)
Volkov, V. S.; Bozhevolnyi, S. I.; Borel, Peter Ingo
2006-01-01
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....... 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....
Off disk-center potential field calculations using vector magnetograms
Venkatakrishnan, P.; Gary, G. Allen
1989-01-01
A potential field calculation for off disk-center vector magnetograms that uses all the three components of the measured field is investigated. There is neither any need for interpolation of grid points between the image plane and the heliographic plane nor for an extension or a truncation to a heliographic rectangle. Hence, the method provides the maximum information content from the photospheric field as well as the most consistent potential field independent of the viewing angle. The introduction of polarimetric noise produces a less tolerant extrapolation procedure than using the line-of-sight extrapolation, but the resultant standard deviation is still small enough for the practical utility of this method.
International Nuclear Information System (INIS)
Brik, M.G.; Avram, C.N.; Avram, N.M.
2006-01-01
The effective spin-Hamiltonian (SH) parameters (zero-field splitting D and g factors g - parallel and g - perpendicular ) for Cr 3+ ions in LiSr(Al,Ga)F 6 crystals are calculated from the complete high-order perturbation formulae for a d 3 ion. Parameters of trigonal crystal field acting on the Cr 3+ ion are calculated. The magnitude of trigonal distortion of the [CrF 6 ] 3- clusters is related to the experimental measurements of the spin-Hamiltonian parameters in the considered systems. Since in both crystals g parallel perpendicular , [CrF 6 ] 3- clusters undergo an axial compression along the C 3 axis. Experimental values of the hyperfine structure constants A parallel and A perpendicular are used to evaluate the core polarization constant κ for Cr 3+ ion in both crystals
Examples of 3-D field calculations using GFUN
International Nuclear Information System (INIS)
Lari, R.J.
1981-01-01
Magnets are described that were calculated using GFUN. A four-step procedure is used to calculate magnets using GFUN. First, the interactive TSO system is used to draw the geometry of the magnet on a Tektronix 4012 graphic display unit. When the geometry is correct, it is stored on a disc file that is shared by the batch computers 3033 and 195. A file JCL and data can be created on TSO and submitted to the batch computers to calculate the magnetization of the steel tetrahedron elements. The results of this approx. 1 hour batch job are stored on disc. In the same job, or in a separate one, the fields can be calculated at desired points and stored on a shared disc. The fourth step is to plot these fields interactively in TSO
International Nuclear Information System (INIS)
Yang, Mei; Wen-Chen, Zheng; Hong-Gang, Liu
2013-01-01
The spin-Hamiltonian parameters (g factors g i and hyperfine structure constants A i , were i=x, y and z) for Mo 5+ ion occupying the Ti(1) site with approximately rhombic symmetry in KTiOPO 4 crystal are calculated from the high-order perturbation formulas based on the two-mechanism model. In the model, not only the contribution due to the conventional crystal-field (CF) mechanism, but also those due to the charge-transfer (CT) mechanism are included. The six calculated spin-Hamiltonian parameters with four adjustable parameters are in reasonable agreement with the experimental values. The calculations show that for more accurate calculations of spin-Hamiltonian parameters of the high valence d n ions (e.g., Mo 5+ considered here) in crystals, the contribution from CT mechanism, which is ignored in the conventional crystal field theory, should be taken into account. The reasonable crystal field energy levels of Mo 5+ in KTiOPO 4 are also predicted from calculations
Molecular dynamics on diffusive time scales from the phase-field-crystal equation.
Chan, Pak Yuen; Goldenfeld, Nigel; Dantzig, Jon
2009-03-01
We extend the phase-field-crystal model to accommodate exact atomic configurations and vacancies by requiring the order parameter to be non-negative. The resulting theory dictates the number of atoms and describes the motion of each of them. By solving the dynamical equation of the model, which is a partial differential equation, we are essentially performing molecular dynamics simulations on diffusive time scales. To illustrate this approach, we calculate the two-point correlation function of a fluid.
ptchg: A FORTRAN program for point-charge calculations of electric field gradients (EFGs)
Spearing, Dane R.
1994-05-01
ptchg, a FORTRAN program, has been developed to calculate electric field gradients (EFG) around an atomic site in crystalline solids using the point-charge direct-lattice summation method. It uses output from the crystal structure generation program Atoms as its input. As an application of ptchg, a point-charge calculation of the EFG quadrupolar parameters around the oxygen site in SiO 2 cristobalite is demonstrated. Although point-charge calculations of electric field gradients generally are limited to ionic compounds, the computed quadrupolar parameters around the oxygen site in SiO 2 cristobalite, a highly covalent material, are in good agreement with the experimentally determined values from nuclear magnetic resonance (NMR) spectroscopy.
Calculation of accelerating electric fields in the CO2 injector
International Nuclear Information System (INIS)
Baron, E.
1999-01-01
The accelerating structure in the injecting cyclotron for O.A.E. can be divided, if one takes the inflector exit as departure point, into the following two regions: 1. the relatively complex central zone comprising three accelerating gaps which is flanked by vertical pillars destined to increase the transit time factor and, at the same time, to reduce the influence of electric field vertical components; 2. the so-called 'large radius' subsequent zone where the gaps are no longer radially delimited. To study the behavior of the individual trajectories in these fields, the equations of motion must be integrated step by step (for instance by Runge-Kutta method) what implies the knowledge of field (or at least of potential) in every point. This is the method for the calculation of potential contour maps which is presented here; the potentials are static, and a sinusoidal time variation is subsequently applied to perform dynamical calculations. The paper has the following sections: 1. Introduction; 2. Potential and large radius field components; 2.1. Calculation of median plane potential; 2.2. Calculation of the off-median-plane potential and field; 3. Potential in the central region; 4. Further Developments
Relativistic mean field calculations in neutron-rich nuclei
Energy Technology Data Exchange (ETDEWEB)
Gangopadhyay, G.; Bhattacharya, Madhubrata [Department of Physics, University of Calcutta, 92 Acharya Prafulla Chandra Road, Kolkata 700 009 (India); Roy, Subinit [Saha Institute of Nuclear Physics, Block AF, Sector 1, Kolkata- 700 064 (India)
2014-08-14
Relativistic mean field calculations have been employed to study neutron rich nuclei. The Lagrange's equations have been solved in the co-ordinate space. The effect of the continuum has been effectively taken into account through the method of resonant continuum. It is found that BCS approximation performs as well as a more involved Relativistic Continuum Hartree Bogoliubov approach. Calculations reveal the possibility of modification of magic numbers in neutron rich nuclei. Calculation for low energy proton scattering cross sections shows that the present approach reproduces the density in very light neutron rich nuclei.
Evaluation of the exchange interaction and crystal fields in a prototype Dy2 SMM
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).
Low-frequency electromagnetic field in a Wigner crystal
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.
Pulsed zero field NMR of solids and liquid crystals
International Nuclear Information System (INIS)
Thayer, A.M.
1987-02-01
This work describes the development and applications to solids and liquid crystals of zero field nuclear magnetic resonance (NMR) experiments with pulsed dc magnetic fields. Zero field NMR experiments are one approach for obtaining high resolution spectra of amorphous and polycrystalline materials which normally (in high field) display broad featureless spectra. The behavior of the spin system can be coherently manipulated and probed in zero field with dc magnetic field pulses which are employed in a similar manner to radiofrequency pulses in high field NMR experiments. Nematic phases of liquid crystalline systems are studied in order to observe the effects of the removal of an applied magnetic field on sample alignment and molecular order parameters. In nematic phases with positive and negative magnetic susceptibility anisotropies, a comparison between the forms of the spin interactions in high and low fields is made. High resolution zero field NMR spectra of unaligned smectic samples are also obtained and reflect the symmetry of the liquid crystalline environment. These experiments are a sensitive measure of the motionally induced asymmetry in biaxial phases. Homonuclear and heteronuclear solute spin systems are compared in the nematic and smectic phases. Nonaxially symmetric dipolar couplings are reported for several systems. The effects of residual fields in the presence of a non-zero asymmetry parameter are discussed theoretically and presented experimentally. Computer programs for simulations of these and other experimental results are also reported. 179 refs., 75 figs
Calculation of the Magnetic Fields of the Electric Power Line
Directory of Open Access Journals (Sweden)
Patsiuk V.
2016-12-01
Full Text Available The task of calculation of per unit length parameters of multi-conductor electrical overhead transmission lines has been treated in the paper. The calculation of distribution of electric and magnetic fields has been performed by means of the finite volume method for entire span of the line. The theoretical justification of the method for calculation the parameters of electromagnetic field taking into account the change of the vector of magnetic potential along the line has been given. The problems of electrostatic and magnetostatic for a single electric conductor and unlimited long conductor with current have been solved. For the inner and total inductivities of a single conductor under the current have been obtained relationships and drawn dependences. Dependence between the speeds of light and of electromagnetic wave’s propagation has been presented. Based on the characteristics of distribution of electric and magnetic fields of multi-conductor lines has been provided the method of calculation of the matrix of own and mutual capacitances and inductivities the calculated values of per unit length parameters of compact 110 kV electric line which is in concordance with one of basic physical constant – the speed of light.
Calculating Casimir energies in renormalizable quantum field theory
International Nuclear Information System (INIS)
Milton, Kimball A.
2003-01-01
Quantum vacuum energy has been known to have observable consequences since 1948 when Casimir calculated the force of attraction between parallel uncharged plates, a phenomenon confirmed experimentally with ever increasing precision. Casimir himself suggested that a similar attractive self-stress existed for a conducting spherical shell, but Boyer obtained a repulsive stress. Other geometries and higher dimensions have been considered over the years. Local effects, and divergences associated with surfaces and edges were studied by several authors. Quite recently, Graham et al. have reexamined such calculations, using conventional techniques of perturbative quantum field theory to remove divergences, and have suggested that previous self-stress results may be suspect. Here we show that the examples considered in their work are misleading; in particular, it is well known that in two space dimensions a circular boundary has a divergence in the Casimir energy for massless fields, while for general spatial dimension D not equal to an even integer the corresponding Casimir energy arising from massless fields interior and exterior to a hyperspherical shell is finite. It has also long been recognized that the Casimir energy for massive fields is divergent for curved boundaries. These conclusions are reinforced by a calculation of the relevant leading Feynman diagram in D and in three dimensions. There is therefore no doubt of the validity of the conventional finite Casimir calculations
Advances in computational methods for Quantum Field Theory calculations
Ruijl, B.J.G.
2017-01-01
In this work we describe three methods to improve the performance of Quantum Field Theory calculations. First, we simplify large expressions to speed up numerical integrations. Second, we design Forcer, a program for the reduction of four-loop massless propagator integrals. Third, we extend the R*
Quantization of fermions in external soliton fields and index calculation
International Nuclear Information System (INIS)
Grosse, H.
1986-01-01
We review recent results on the quantization of fermions in external fields, discuss equivalent and inequivalent representations of the canonical anticommutation relations, indicate how the requirement of implementability of gauge transformations leads to quantization conditions, determine the algebra of charges, identify the Schwinger term and remark finally how one may calculate a ground state charge. (Author)
Analytical relativistic self-consistent-field calculations for atoms
International Nuclear Information System (INIS)
Barthelat, J.C.; Pelissier, M.; Durand, P.
1980-01-01
A new second-order representation of the Dirac equation is presented. This representation which is exact for a hydrogen atom is applied to approximate analytical self-consistent-field calculations for atoms. Results are given for the rare-gas atoms from helium to radon and for lead. The results compare favorably with numerical Dirac-Hartree-Fock solutions
Electric field calculations in brain stimulation based on finite elements
DEFF Research Database (Denmark)
Windhoff, Mirko; Opitz, Alexander; Thielscher, Axel
2013-01-01
The need for realistic electric field calculations in human noninvasive brain stimulation is undisputed to more accurately determine the affected brain areas. However, using numerical techniques such as the finite element method (FEM) is methodologically complex, starting with the creation...... of accurate head models to the integration of the models in the numerical calculations. These problems substantially limit a more widespread application of numerical methods in brain stimulation up to now. We introduce an optimized processing pipeline allowing for the automatic generation of individualized...... the successful usage of the pipeline in six subjects, including field calculations for transcranial magnetic stimulation and transcranial direct current stimulation. The quality of the head volume meshes is validated both in terms of capturing the underlying anatomy and of the well-shapedness of the mesh...
Crystal-field magnetic anisotropy of dilute dysprosium or erbium in yttrium single crystals
DEFF Research Database (Denmark)
Høg, J.; Touborg, P.
1974-01-01
Magnetization measurements have been performed between 1.3 and 300 K in fields up to 50 × 105 A/m in the a, b, and c directions of hcp crystals of pure Y and Y doped with 0.14-at.% Dy or 0.14-at.% Er, using the Faraday method and a vibrating-sample method. The characteristic behavior of both...
Magnetic field calculation of the Na-4 muon spectrometer
International Nuclear Information System (INIS)
Cvach, J.; Il'yushchenko, V.I.; Savin, I.A.; Vorozhtsov, S.B.
1980-01-01
A NA-4 muon spectrometer is described. Preliminary results of calculating a magnetic field in a toroidal magnetic detector are given. The spectrometer includes 10 similar supermodules each of which consists of 32 iron discs with 275 cm outer diameter magnetized up to saturation. Each module is an independent detector. The POISSON program is used for calculating magnetic field distribution in a toroidal spectrometer magnet. The results obtained show that a magnetic field of iron is a toroidal one and drops approximately according to the logarithmic law from 21.1 kGs on an inner magnet rig to 17.7 kGs on an outer. Magnet support gives approximately 2 % error
Properties of the localized field emitted from degenerate Λ-type atoms in photonic crystals
International Nuclear Information System (INIS)
Foroozani, N.; Golshan, M. M.; Mahjoei, M.
2007-01-01
The spontaneous emission from a degenerate Λ-type three-level atom, embedded in a photonic crystal, is studied. The emitted field, as a function of time and position, is calculated by solving the three coupled differential equations governing the amplitudes. We show that the spontaneously emitted field is characterized by three components (as in the case of two-level and V-type atoms): a localized part, a traveling part, and a t -3/2 decaying part. Our calculations indicate that under specific conditions the atoms do not emit propagating fields, while the localized field, having shorter localization length and time, is intensified. As a consequence, the population of the upper level, after a short period of oscillations, approaches a constant value. It is also shown that this steady value, under the same conditions, is much larger than its counterpart in V-type atoms
Role of internal demagnetizing field for the dynamics of a surface-modulated magnonic crystal
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.
The theoretical tensile strength of fcc crystals predicted from shear strength calculations
International Nuclear Information System (INIS)
Cerny, M; Pokluda, J
2009-01-01
This work presents a simple way of estimating uniaxial tensile strength on the basis of theoretical shear strength calculations, taking into account its dependence on a superimposed normal stress. The presented procedure enables us to avoid complicated and time-consuming analyses of elastic stability of crystals under tensile loading. The atomistic simulations of coupled shear and tensile deformations in cubic crystals are performed using first principles computational code based on pseudo-potentials and the plane wave basis set. Six fcc crystals are subjected to shear deformations in convenient slip systems and a special relaxation procedure controls the stress tensor. The obtained dependence of the ideal shear strength on the normal tensile stress seems to be almost linearly decreasing for all investigated crystals. Taking these results into account, the uniaxial tensile strength values in three crystallographic directions were evaluated by assuming a collapse of the weakest shear system. Calculated strengths for and loading were found to be mostly lower than previously calculated stresses related to tensile instability but rather close to those obtained by means of the shear instability analysis. On the other hand, the strengths for loading almost match the stresses related to tensile instability.
Two dimensional magnetic field calculations for the SSC dipole magnets
International Nuclear Information System (INIS)
Krefta, M.P.; Pavlik, D.
1991-01-01
In this work two-dimensional methods are used to calculate the magnetic fields throughout the cross section of a SSC dipole magnet. Analytic techniques, which are based on closed form solutions to the defining field equations, are used to calculate the multipole content for any specified conductor positioning. The method is extended to investigate the effects of radial slots or keyways in the iron yoke. The multipole components of field, directly attributable to the slots or keyways, are examined as a function of size and location. It is shown that locating the slots or keyways at the magnet pole centers has a large effect on the multipole components; whereas, locating the keyways between the magnet poles has little effect on any of the multipoles. The investigation of nonlinear effects such as ferromagnetic saturation or superconductor magnetization relies on the use of numerical methods such as the finite element method. The errors associated with these codes are explained in terms of numerical round-off, spatial discretization error and the representation of distant boundaries. A method for increasing the accuracy of the multipole calculation from finite element solutions is set forth. It is shown that calculated multipole coefficients are sensitive to boundary conditions external to the cold mass during conditions of magnetic saturation
Optical spectroscopy and crystal-field analysis of U{sup 3+}: Ba{sub 2}YCl{sub 7}
Energy Technology Data Exchange (ETDEWEB)
Karbowiak, M.; Mech, A.; Drozdzyndki, J. [Wroclaw Univ., Faculty of Chemistry (Poland); Gajek, Z. [Polish Academy of Sciences, W. Trzebiatowski Institute of Low Temperature and Structure Research, Wroclaw (Poland); Edelstein, N.M. [Lawrence Berkeley National Lab., Chemical Sciences Div., CA (United States)
2002-11-01
High resolution absorption spectra of a U{sup 3+}(0.3%): Ba{sub 2}YCl{sub 7} single crystal were recorded in the 4000-50 000 cm{sup -1} range at 7 K. The observed crystal-field levels were assigned and fit to the parameters of the simplified angular overlap model (AOM) as well as a semi-empirical Hamiltonian representing the combined atomic and one-electron crystal-field interactions. The starting values of the AOM parameters were obtained from ab initio calculations. The analysis of the spectra allowed the assignment of 65 crystal-field levels with a relatively small rms deviation of 25 cm{sup -1} and has shown that the AOM approach can predict quite well the B{sub q}{sup k} crystal-field parameters. The value determined for the crystal-field strength parameter, N{sub v}, corresponds well with those determined for U{sup 3+} in other chloride single crystals. (authors)
Strong crystal field effect in ? - optical absorption study
Gajek, Z.; Krupa, J. C.
1998-12-01
=-1 Results of optical absorption measurements in polarized light on tetravalent neptunium diluted in a 0953-8984/10/50/021/img6 single crystal are reported. The recorded spectra are complex, pointing to the presence of an 0953-8984/10/50/021/img7 impurity. The electronic transitions assigned to the 0953-8984/10/50/021/img8 ion are interpreted in terms of the usual model, following the actual understanding of the neptunium electronic structure and independent theoretical predictions. R.m.s. deviations of the order of 0953-8984/10/50/021/img9 have been obtained for 42 levels fitted with 11 free parameters. The crystal field effect resulting from the fitting is considerably larger than that observed for the uranium ion in the same host.
Actual and Idealized Crystal Field Parameterizations for the Uranium Ions in UF 4
Gajek, Z.; Mulak, J.; Krupa, J. C.
1993-12-01
The crystal field parameters for the actual coordination symmetries of the uranium ions in UF 4, C2 and C1, and for their idealizations to D2, C2 v , D4, D4 d , and the Archimedean antiprism point symmetries are given. They have been calculated by means of both the perturbative ab initio model and the angular overlap model and are referenced to the recent results fitted by Carnall's group. The equivalency of some different sets of parameters has been verified with the standardization procedure. The adequacy of several idealized approaches has been tested by comparison of the corresponding splitting patterns of the 3H 4 ground state. Our results support the parameterization given by Carnall. Furthermore, the parameterization of the crystal field potential and the splitting diagram for the symmetryless uranium ion U( C1) are given. Having at our disposal the crystal field splittings for the two kinds of uranium ions in UF 4, U( C2) and U( C1), we calculate the model plots of the paramagnetic susceptibility χ( T) and the magnetic entropy associated with the Schottky anomaly Δ S( T) for UF 4.
Synthesis, Crystal Structure, and DFT Calculations of 1,3-Diisobutyl Thiourea
Directory of Open Access Journals (Sweden)
Ataf A. Altaf
2015-01-01
Full Text Available 1,3-Diisobutyl thiourea was synthesized and characterized by single crystal X-ray diffraction. It gives a monoclinic (α = γ = 90 and β ≠ 90 structure with the space group P21/c. The unit cell dimensions are a = 11.5131 (4 Å, b = 9.2355 (3 Å, c = 11.3093 (5 Å, α = 90°, β = 99.569° (2, γ = 90°, V = 1185.78 (8 Å3, and Z = 4. The crystal packing is stabilized by intermolecular (N–H⋯S hydrogen bonding in the molecules. The optimized geometry and Mullikan's charges of the said molecule calculated with the help of DFT using B3LYP-6-311G model support the crystal structure.
Eddy current calculations for the Tore Supra toroidal field magnet
International Nuclear Information System (INIS)
Blum, J.
1983-01-01
An outline is given of the calculation of the eddy currents in the magnetic structures of a Tokamak, which can be assimilated to thin conductors, so that the three-dimensional problem can be reduced mathematically to a two-dimensional one, the variables being two orthogonal coordinates of the considered surface. A finite element method has been used in order to treat the complicated geometry of the set of the 18 toroidal field coil casings and mechanical structures of Tore Supra. This eddy current code has been coupled with an axisymmetric equilibrium code in order to simulate typical phases of a Tokamak discharge (plasma current rise, additional heating, disruption, cleaning discharge) and the losses in the toroidal field magnet have thus been calculated. (author)
Uniform angular overlap model interpretation of the crystal field effect in U(5+) fluoride compounds
Energy Technology Data Exchange (ETDEWEB)
Gajek, Z.; Mulak, J. (W. Trzebiatowski Inst. of Low Temperature and Structure Research, Polish Academy of Sciences, Wroclaw (Poland))
1990-11-01
The uniform interpretation of the crystal field effect in three different U(5+) fluoride compounds: CsUF{sub 6}, {alpha}-UF{sub 5} and {beta}-UF{sub 5} within the angular overlap model (AOM) is given. Some characteristic relations between the AOM parameters and their distance dependencies resulting from ab initio calculations are introduced and examined from a phenomenological point of view. The traditional simplest approach with only one independent parameter, i.e. e{sub {sigma}} with e{sub {pi}}:e{sub {sigma}} = 0.32 and e{sub {delta}} = 0, is shown to provide a consistent interpretation of the crystal field effect of the whole class of the compounds. The parameters obtained for one compound are easily and successfully extrapolated to others. The specificity and importance of the e{sub {delta}} parameter for 5f{sup 1} systems is discussed. (orig.).
Theoretical modeling of zircon's crystal morphology according to data of atomistic calculations
Gromalova, Natalia; Nikishaeva, Nadezhda; Eremin, Nikolay
2017-04-01
Zircon is an essential mineral that is used in the U-Pb dating. Moreover, zircon is highly resistant to radioactive exposure. It is of great interest in solving both fundamental and applied problems associated with the isolation of high-level radioactive waste. There is significant progress in forecasting of the most energetically favorable crystal structures at the present time. Unfortunately, the theoretical forecast of crystal morphology at high technological level is under-explored nowadays, though the estimation of crystal equilibrium habit is extremely important in studying the physical and chemical properties of new materials. For the first time, the thesis about relation of the equilibrium shape of a crystal with its crystal structure was put forward in the works by O.Brave. According to it, the idealized habit is determined in the simplest case by a correspondence with the reticular densities Rhkl of individual faces. This approach, along with all subsequent corrections, does not take into account the nature of atoms and the specific features of the chemical bond in crystals. The atomistic calculations of crystal surfaces are commonly performed using the energetic characteristics of faces, namely, the surface energy (Esurf), which is a measure of the thermodynamic stability of the crystal face. The stable crystal faces are characterized by small positive values of Esurf. As we know from our previous research (Gromalova et al.,2015) one of the constitutive factors affecting the value of the surface energy in calculations is a choice of potentials model. In this regard, we studied several sets of parameters of atomistic interatomic potentials optimized previously. As the first test model («Zircon 1») were used sets of interatomic potentials of interaction Zr-O, Si-O and O-O in the form of Buckingham potentials. To improve playback properties of zircon additionally used Morse potential for a couple of Zr-Si, as well as the three-particle angular harmonic
HTSL massive motor. Project: Motor field calculation. Final report
International Nuclear Information System (INIS)
Gutt, H.J.; Gruener, A.
2003-01-01
HTS motors up to 300 kW were to be developed and optimized. For this, specific calculation methods were enhanced to include superconducting rotor types (hysteresis, reluctance and permanent magnet HTS rotors). The experiments were carried out in a SHM70-45 hysteresis motor. It was shown how static and dynamic trapped field magnetisation of the rotor with YBCO rings will increase flux in the air gap motor, increasing the motor capacity to twice its original level. (orig.) [de
Calculation of gas gain fluctuations in uniform fields
Schindler, H; Veenhof, R
2010-01-01
Fluctuations of the charge amplification factor (gain) are a key element for assessing the performance of gas-based particle detectors In this report we present Monte Carlo calculations of electron avalanches based on the Magboltz program In terms of a simple model extracted from the simulation an intuitive explanation for the impact of the gas mixture and the electric field on the gain spectrum is proposed.
Choi, Tae-Hoon; Oh, Seung-Won; Park, Young-Jin; Choi, Yeongyu; Yoon, Tae-Hoon
2016-01-01
We report a simple method for reducing the response time of a fringe-field switching liquid crystal cell by using two-dimensional confinement of the liquid crystals. Through both numerical calculations and experiments, we show that the switching speed can be increased by several fold in a fringe-field switching cell by simply using a rubbing angle of zero, which causes virtual walls to be built when an electric field is applied between the interdigitated electrodes and the common electrode, w...
Emdadi, M.; Poursamad, J. B.; Sahrai, M.; Moghaddas, F.
2018-06-01
A planar nematic liquid crystal cell (NLC) doped with spherical ferroelectric nanoparticles is considered. Polarisation of the nanoparticles are assumed to be along the NLC molecules parallel and antiparallel to the director with equal probability. The NLC molecules anchoring to the cell walls are considered to be strong, while soft anchoring at the nanoparticles surface is supposed. Behaviour of the NLC molecules and nanoparticles in the presence of a perpendicular electric field to the NLC cell is theoretically investigated. The electric field of the nanoparticles is taken into account in the calculations. Freedericksz transition (FT) threshold field in the presence of nanoparticles is found. Then, the director and particles reorientations for the electric fields larger than the threshold field are studied. Measuring the onset of the nanoparticles reorientation is proposed as a new method for the FT threshold measurement.
Energy Technology Data Exchange (ETDEWEB)
Krupa, J.C. (Paris-11 Univ., 91 - Orsay (FR). Inst. de Physique Nucleaire); Gajek, Z. (Polska Akademia Nauk, Wroclaw (PL). Inst. Niskich Temperatur i Badan Strukturalnych)
1991-01-01
Crystal-field parameters resulting from analysis of optical spectroscopy and neutron diffraction data recorded on UO{sub 2} and NpO{sub 2} as well as ab-initio calculated parameters were used to calculate the crystal-field eigenfunctions and eigenvalues for the J ground-state manifold of U{sup 4+}, Np{sup 4+} and Pu{sup 4+} in UO{sub 2}, NpO{sub 2} and PuO{sub 2}.
Crystal field levels of tetravalent actinide ions in actinide dioxides UO2, NpO2 and PuO2
International Nuclear Information System (INIS)
Krupa, J.C.; Gajek, Z.
1991-01-01
Crystal-field parameters resulting from analysis of optical spectroscopy and neutron diffraction data recorded on UO 2 and NpO 2 as well as ab-initio calculated parameters were used to calculate the crystal-field eigenfunctions and eigenvalues for the J ground-state manifold of U 4+ , Np 4+ and Pu 4+ in UO 2 , NpO 2 and PuO 2
Calculated and measured fields in superferric wiggler magnets
Energy Technology Data Exchange (ETDEWEB)
Blum, E.B.; Solomon, L. [Brookhaven National Lab., Upton, NY (United States)
1995-02-01
Although Klaus Halbach is widely known and appreciated as the originator of the computer program POISSON for electromagnetic field calculation, Klaus has always believed that analytical methods can give much more insight into the performance of a magnet than numerical simulation. Analytical approximations readily show how the different aspects of a magnet`s design such as pole dimensions, current, and coil configuration contribute to the performance. These methods yield accuracies of better than 10%. Analytical methods should therefore be used when conceptualizing a magnet design. Computer analysis can then be used for refinement. A simple model is presented for the peak on-axis field of an electro-magnetic wiggler with iron poles and superconducting coils. The model is applied to the radiator section of the superconducting wiggler for the BNL Harmonic Generation Free Electron Laser. The predictions of the model are compared to the measured field and the results from POISSON.
The use of Wannier function in the calculations of band structure of covalent crystals
International Nuclear Information System (INIS)
Lu Dong; Yang Guang
1985-10-01
A variational procedure has been used to build up Wannier functions to study the energy bands of diamond, silicon and α-tin. For the case of silicon the Wannier function, density of charge and band structure are calculated self-consistently and a simple method in a non-self-consistent way has been used to compute the band structure of diamond, silicon and α-tin. The method seems to be effective to describe the electronic properties of covalent crystals. (author)
Dipolar local field in homogeneously magnetized quasi-two-dimensional crystals
International Nuclear Information System (INIS)
Leon, H; Estevez-Rams, E
2009-01-01
A formalism to calculate the dipolar local field in homogeneously magnetized quasi-two-dimensional (Q2D) crystals is comprehensively presented. Two fundamental tests for this formalism are accomplished: the transition from the Q2D quantities to the corresponding 3D ones; and the recovering of the macroscopic quantities of the 3D continuum theory. The additive separation between lattice and shape contributions to the local field allows an unambiguous interpretation of the respective effects. Calculated demagnetization tensors for square and circular lateral geometries of dipole layers show that for a single crystal layer an extremely thin film, but still with a finite thickness, is a better physical representation than a strictly 2D plane. Distinct close-packed structures are simulated and calculations of the local field at the nodes of the stacked 2D lattices allow one to establish the number of significantly coupled dipole layers, depending on the ratio between the interlayer distance and the 2D lattice constant. The conclusions drawn are of interest for the study of the dipolar interaction in magnetic ultrathin films and other nanostructured materials, where magnetic nanoparticles are embedded in non-magnetic matrices.
Crystal field parameters in UCl/sub 4/: Experiment versus theory
Energy Technology Data Exchange (ETDEWEB)
Zolnierek, Z.; Gajek, Z. (Polska Akademia Nauk, Wroclaw. Inst. Niskich Temperatur i Badan Strukturalnych); Khan Malek, C. (Paris-11 Univ., 91 - Orsay (France). Inst. de Physique Nucleaire)
1984-08-01
Crystal field effect on U/sup 4 +/ ion with the /sup 3/H/sub 4/ ground term in tetragonal ligand field of UCl/sub 4/ has been studied in detail. Crystal field parameters determined experimentally from optical spectroscopy and magnetic susceptibility are in good agreement with CEP sets derived from the modified point charge model and the ab initio method. Theoretical calculations lead to overestimating the A/sub 4//sup 4/
Calculation of optical second-harmonic susceptibilities and optical activity for crystals
International Nuclear Information System (INIS)
Levine, Z.H.
1994-01-01
A new generation of nearly first-principles calculations predicts both the linear and second-harmonic susceptibilities for a variety of insulating crystals, including GaAs, GaP, AlAs, AlP, Se, α-quartz, and c-urea. The results are typically in agreement with experimental measurements. The calculations have been extended to optical activity, with somewhat less success to date. The theory, based on a simple self-energy correction to the local density approximation, and results are reviewed herein
Yu, Yi; Huang, Yisheng; Zhang, Lizhen; Lin, Zhoubin; Sun, Shijia; Wang, Guofu
2014-07-01
A Nd3+:Na2La4(WO4)7 crystal with dimensions of ϕ 17 × 30 mm3 was grown by the Czochralski method. The thermal expansion coefficients of Nd3+:Na2La4(WO4)7 crystal are 1.32 × 10-5 K-1 along c-axis and 1.23 × 10-5 K-1 along a-axis, respectively. The spectroscopic characteristics of Nd3+:Na2La4(WO4)7 crystal were investigated. The Judd-Ofelt theory was applied to calculate the spectral parameters. The absorption cross sections at 805 nm are 2.17 × 10-20 cm2 with a full width at half maximum (FWHM) of 15 nm for π-polarization, and 2.29 × 10-20 cm2 with a FWHM of 14 nm for σ-polarization. The emission cross sections are 3.19 × 10-20 cm2 for σ-polarization and 2.67 × 10-20 cm2 for π-polarization at 1,064 nm. The fluorescence quantum efficiency is 67 %. The quasi-cw laser of Nd3+:Na2La4(WO4)7 crystal was performed. The maximum output power is 80 mW. The slope efficiency is 7.12 %. The results suggest Nd3+:Na2La4(WO4)7 crystal as a promising laser crystal fit for laser diode pumping.
Using Quartz Crystal Microbalance for Field Measurement of Liquid Viscosities
Directory of Open Access Journals (Sweden)
Qingsong Bai
2016-01-01
Full Text Available The field measurement of liquid viscosities, especially the high viscous liquids, is challenging and often requires expensive equipment, long processing time, and lots of reagent. We use quartz crystal microbalances (QCMs operating in solution which are also sensitive to the viscosity and density of the contacting solution. QCMs are typically investigated for sensor applications in which one surface of QCM completely immersed in Newtonian liquid, but the viscous damping in liquids would cause not only large frequency shifts but also large losses in the quality factor Q leading to instability and even cessation of oscillation. A novel mass-sensitivity-based method for field measurement of liquid viscosities using a QCM is demonstrated in this paper and a model describing the influence of the liquid properties on the oscillation frequency is established as well. Two groups of verified experiments were performed and the experimental results show that the presented method is effective and possesses potential applications.
Effect of magnetic field on the wave dispersion relation in three-dimensional dusty plasma crystals
International Nuclear Information System (INIS)
Yang Xuefeng; Wang Zhengxiong
2012-01-01
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.
A calculational scheme for nonequilibrium quantum field system
International Nuclear Information System (INIS)
Yamanaka, Y.
1991-01-01
A new calculational scheme is presented for interacting nonequi-librium time dependent quantum field systems within the framework of thermo field dynamics (TFD), taking account of the fact that the thermal vacuum should go through many inequivalent state vector spaces. A para-meter parametrizing various state vector spaces has to be introduced and plays a role of new time-variable. Thus we have double-time TFD. The 2 requirements in this double-time TFD are imposed to establish a quasi-particle picture to get an attainable scheme of perturbative calculation : the existence of the spectral representation for the full propagator and the diagonalization of the quasi-particle Hamiltonian. The 1st condition turns out to amount to the existence of local-time tempera-ture. The 2nd condition leads to the master equation for the number density. This formalism is applied to high-energy heavy ion collision process. The very fundamental question is then how the thermodynamical properties such as heat and temperature appear in such an isolated system. This double-time TFD, suitable for isolated thermal systems of quantum fields, can handle the situation from the beginning of the process. (author). 24 refs.; 1 fig
Calculation of the internal electric field within doped semiconductors
International Nuclear Information System (INIS)
Phelps, G J
2012-01-01
A detailed model for the calculation of the internal potential and electric field profile within doped semiconductors is developed from a first-principles approach and presented in this paper. The model utilizes Poisson's equation and basic Boltzmann statistics to develop a standard nonlinear Poisson–Boltzmann equation (NPBE) for doped semiconductors. The resultant NPBE links the internal electrostatic potential within the doped semiconductor to the doping concentration profile of the semiconductor device under consideration. The NPBE is solved by the application of numerical methods, is general in formulation, supporting multiple simultaneous dopant configurations, and may be applied to any semiconductor type. Calculated results of the electric field profile for various semiconductor dopant structures derived using the model are additionally presented in this paper. The electric field results predicted by the model are shown to be in excellent agreement with those found by other methods. The model may be expanded to accommodate effects involving internal substrate electron–hole pair generation (gemination) caused by photo-ionization for application to and the modeling of solar cell device structures. (paper)
Average cross sections calculated in various neutron fields
International Nuclear Information System (INIS)
Shibata, Keiichi
2002-01-01
Average cross sections have been calculated for the reactions contained in the dosimetry files, JENDL/D-99, IRDF-90V2, and RRDF-98 in order to select the best data for the new library IRDF-2002. The neutron spectra used in the calculations are as follows: 1) 252 Cf spontaneous fission spectrum (NBS evaluation), 2) 235 U thermal fission spectrum (NBS evaluation), 3) Intermediate-energy Standard Neutron Field (ISNF), 4) Coupled Fast Reactivity Measurement Facility (CFRMF), 5) Coupled thermal/fast uranium and boron carbide spherical assembly (ΣΣ), 6) Fast neutron source reactor (YAYOI), 7) Experimental fast reactor (JOYO), 8) Japan Material Testing Reactor (JMTR), 9) d-Li neutron spectrum with a 2-MeV deuteron beam. The items 3)-7) represent fast neutron spectra, while JMTR is a light water reactor. The Q-value for the d-Li reaction mentioned above is 15.02 MeV. Therefore, neutrons with energies up to 17 MeV can be produced in the d-Li reaction. The calculated average cross sections were compared with the measurements. Figures 1-9 show the ratios of the calculations to the experimental data which are given. It is found from these figures that the 58 Fe(n, γ) cross section in JENDL/D-99 reproduces the measurements in the thermal and fast reactor spectra better than that in IRDF-90V2. (author)
Monte Carlo calculations for intermediate-energy standard neutron field
International Nuclear Information System (INIS)
Joneja, O.P.; Subbukutty, K.; Iyengar, S.B.D.; Navalkar, M.P.
Intermediate-Energy Standard Neutron Field (ISNF) which produces a well characterised spectrum in the energy range of interest for fast reactors including breeders, has been set up at NBS using thin enriched 235 U fission sources. A proposal has been made for setting up a similar facility at BARC using however, easily available natural U instead of enriched U sources, to start with. In order to simulate the neutronics of such a facility Monte Carlo method of calculations has been adopted and developed. The results of these calculations have been compared with those of NBS and it is found that there may be a maximum difference of 10% in spectrum characteristics for the two cases of using thick and thin fission sources. (K.B.)
Electric field influence on exciton absorption of Er doped and undoped InSe single crystals
International Nuclear Information System (INIS)
Guerbulak, B; Kundakci, M; Ates, A; Yildirim, M
2007-01-01
Undoped InSe and Er doped InSe (InSe:Er) single crystals were grown by using the Stockbarger method. Ingots had no cracks and voids on the surface. The absorption measurements were carried out in InSe and InSe:Er samples for U=0 and U=30 V in the temperature range 10-320 K with a step of 10 K. Electric field effects on excitons are observed in InSe and InSe:Er single crystals. The absorption edge shifted towards longer wavelengths and decreased intensity in absorption spectra under an electric field E≅5.9 kV cm -1 . The applied electric field caused a shifting and a decreasing of intensity in the absorption spectra. The shifting of the absorption edge can be explained on the basis of the Franz-Keldysh effect (FKE) or thermal heating of the sample under the electric field. At 10 and 320 K, the first exciton energies for InSe were calculated as 1.336 and 1.291 eV for zero voltage and 1.331 and 1.280 eV for electric field and InSe:Er as 1.329 and 1.251 eV for zero voltage and 1.318 and 1.248 eV for electric field, respectively
High-field Transport in Low Symmetry β-Ga2O3 Crystal
Ghosh, Krishnendu; Singisetti, Uttam
High-field carrier transport plays an important role in many disciplines of electronics. Conventional transport theories work well on high-symmetry materials but lacks insight as the crystal symmetry goes down. Newly emerging materials, many of which possess low symmetry, demand more rigorous treatment of charge transport. We will present a comprehensive study of high-field transport using ab initio electron-phonon interaction (EPI) elements in a full-band Monte Carlo (FBMC) algorithm. We use monoclinic β-Ga2O3 as a benchmark low-symmetry material which is also an emerging wide-bandgap semiconductor. β-Ga2O3 has a C2m space group and a 10 atom primitive cell. In this work the EPIs are calculated under density-functional perturbation theory framework. We will focus on the computational challenges arising from many phonon modes and low crystal symmetry. Significant insights will be presented on the details of energy relaxation by the hot electrons mediated by different phonon modes. We will also show the velocity-field curves of electrons in different crystal directions. The authors acknowledge the support from the National Science Foundation Grant (ECCS 1607833). The authors also acknowledge the computing support provided by the Center for Computational Research at the University at Buffalo.
Muon contact hyperfine field in metals: A DFT calculation
Onuorah, Ifeanyi John; Bonfà, Pietro; De Renzi, Roberto
2018-05-01
In positive muon spin rotation and relaxation spectroscopy it is becoming customary to take advantage of density functional theory (DFT) based computational methods to aid the experimental data analysis. DFT-aided muon site determination is especially useful for measurements performed in magnetic materials, where large contact hyperfine interactions may arise. Here we present a systematic analysis of the accuracy of the ab initio estimation of muon's hyperfine contact field on elemental transition metals, performing state-of-the-art spin-polarized plane-wave DFT and using the projector-augmented pseudopotential approach, which allows one to include the core state effects due to the spin ordering. We further validate this method in not-so-simple, noncentrosymmetric metallic compounds, presently of topical interest for their spiral magnetic structure giving rise to skyrmion phases, such as MnSi and MnGe. The calculated hyperfine fields agree with experimental values in all cases, provided the spontaneous spin magnetization of the metal is well reproduced within the approach. To overcome the known limits of the conventional mean-field approximation of DFT on itinerant magnets, we adopt the so-called reduced Stoner theory [L. Ortenzi et al., Phys. Rev. B 86, 064437 (2012), 10.1103/PhysRevB.86.064437]. We establish the accuracy of the estimated muon contact field in metallic compounds with DFT and our results show improved agreement with experiments compared to those of earlier publications.
Accurate calculation of field and carrier distributions in doped semiconductors
Directory of Open Access Journals (Sweden)
Wenji Yang
2012-06-01
Full Text Available We use the numerical squeezing algorithm(NSA combined with the shooting method to accurately calculate the built-in fields and carrier distributions in doped silicon films (SFs in the micron and sub-micron thickness range and results are presented in graphical form for variety of doping profiles under different boundary conditions. As a complementary approach, we also present the methods and the results of the inverse problem (IVP - finding out the doping profile in the SFs for given field distribution. The solution of the IVP provides us the approach to arbitrarily design field distribution in SFs - which is very important for low dimensional (LD systems and device designing. Further more, the solution of the IVP is both direct and much easy for all the one-, two-, and three-dimensional semiconductor systems. With current efforts focused on the LD physics, knowing of the field and carrier distribution details in the LD systems will facilitate further researches on other aspects and hence the current work provides a platform for those researches.
Chen, Kexun; Zhang, Xingyuan; Pan, Jian; Zhang, Wencheng; Yong, Ji; Yin, Wenhong
2003-10-01
In this paper, a supercritical fluid extraction-crystallization of andrographolide, a kind of Chinese traditional medicine, was investigated. We have studied the extraction-crystallization process with or without magnet in the extractor, respectively. It was found that the presence of magnetic field is an important factor influencing the quality of the products. SEM images showed that the crystal was slice-like in shape, and many slices reunited together in the absence of magnet. Further research showed that pressure had a certain effect on the morphology of the crystal.
International Nuclear Information System (INIS)
Ran, Zhang; Jun, He; Zeng-Hui, Peng; Li, Xuan
2009-01-01
This paper investigates the average dielectric permittivity (ε-bar ) in the Maier–Meier theory for calculating the dielectric anisotropy (Δε) of nematic liquid crystals. For the reason that ε-bar of nematics has the same expression as the dielectric permittivity of the isotropic state, the Onsager equation for isotropic dielectric was used to calculate it. The computed ε-bar shows reasonable agreement with the results of the numerical methods used in the literature. Molecular parameters, such as the polarizability and its anisotropy, the dipole moment and its angle with the molecular long axis, were taken from semi-empirical quantum chemistry (MOCPAC/AM1) modeling. The calculated values of Δε according to the Maier–Meier equation are in good agreement with the experimental results for the investigated compounds having different core structures and polar substituents. (condensed matter: structure, thermal and mechanical properties)
Coupling-reducing k-points for photonic crystal fibre calculations
DEFF Research Database (Denmark)
Albertsen, Maja; Lægsgaard, Jesper; Barkou Libori, Stig Eigil
2003-01-01
When describing localized electromagnetic modes in dielectric waveguides by the planewave method, a supercell geometry must necessarily be adopted. We demonstrate in the present work that the convergence of the calculations with respect to supercell size depends strongly on the choice of the tran......When describing localized electromagnetic modes in dielectric waveguides by the planewave method, a supercell geometry must necessarily be adopted. We demonstrate in the present work that the convergence of the calculations with respect to supercell size depends strongly on the choice...... of the transverse Bloch wave vector, k. We describe a method to derive k-points that minimize the coupling between repeated images of the guided modes in real space. Calculations have been done for a quadratic and a triangular photonic crystal fiber structure. With the new coupling reducing (CR) k...
Phase-field-crystal model for magnetocrystalline interactions in isotropic ferromagnetic solids
Faghihi, Niloufar; Provatas, Nikolas; Elder, K. R.; Grant, Martin; Karttunen, Mikko
2013-09-01
An isotropic magnetoelastic phase-field-crystal model to study the relation between morphological structure and magnetic properties of pure ferromagnetic solids is introduced. Analytic calculations in two dimensions were used to determine the phase diagram and obtain the relationship between elastic strains and magnetization. Time-dependent numerical simulations in two dimensions were used to demonstrate the effect of grain boundaries on the formation of magnetic domains. It was shown that the grain boundaries act as nucleating sites for domains of reverse magnetization. Finally, we derive a relation for coercivity versus grain misorientation in the isotropic limit.
Quantum Monte Carlo calculations with chiral effective field theory interactions
Energy Technology Data Exchange (ETDEWEB)
Tews, Ingo
2015-10-12
The neutron-matter equation of state connects several physical systems over a wide density range, from cold atomic gases in the unitary limit at low densities, to neutron-rich nuclei at intermediate densities, up to neutron stars which reach supranuclear densities in their core. An accurate description of the neutron-matter equation of state is therefore crucial to describe these systems. To calculate the neutron-matter equation of state reliably, precise many-body methods in combination with a systematic theory for nuclear forces are needed. Chiral effective field theory (EFT) is such a theory. It provides a systematic framework for the description of low-energy hadronic interactions and enables calculations with controlled theoretical uncertainties. Chiral EFT makes use of a momentum-space expansion of nuclear forces based on the symmetries of Quantum Chromodynamics, which is the fundamental theory of strong interactions. In chiral EFT, the description of nuclear forces can be systematically improved by going to higher orders in the chiral expansion. On the other hand, continuum Quantum Monte Carlo (QMC) methods are among the most precise many-body methods available to study strongly interacting systems at finite densities. They treat the Schroedinger equation as a diffusion equation in imaginary time and project out the ground-state wave function of the system starting from a trial wave function by propagating the system in imaginary time. To perform this propagation, continuum QMC methods require as input local interactions. However, chiral EFT, which is naturally formulated in momentum space, contains several sources of nonlocality. In this Thesis, we show how to construct local chiral two-nucleon (NN) and three-nucleon (3N) interactions and discuss results of first QMC calculations for pure neutron systems. We have performed systematic auxiliary-field diffusion Monte Carlo (AFDMC) calculations for neutron matter using local chiral NN interactions. By
Phase field modeling of twinning in indentation of transparent crystals
International Nuclear Information System (INIS)
Clayton, J D; Knap, J
2011-01-01
Continuum phase field theory is applied to study elastic twinning in calcite and sapphire single crystals subjected to indentation loading by wedge-shaped indenters. An order parameter is associated with the magnitude of stress-free twinning shear. Geometrically linear and nonlinear theories are implemented and compared, the latter incorporating neo-Hookean elasticity. Equilibrium configurations of deformed and twinned crystals are attained numerically via direct energy minimization. Results are in qualitative agreement with experimental observations: a long thin twin forms asymmetrically under one side of the indenter, the tip of the twin is sharp and the length of the twin increases with increasing load. Qualitatively similar results are obtained using isotropic and anisotropic elastic constants, though the difference between isotropic and anisotropic results is greater in sapphire than in calcite. Similar results are also obtained for nanometer-scale specimens and millimeter-scale specimens. Indentation forces are greater in the nonlinear model than the linear model because of the increasing tangent bulk modulus with increasing pressure in the former. Normalized relationships between twin length and indentation force are similar for linear and nonlinear theories at both nanometer and millimeter scales. Twin morphologies are similar for linear and nonlinear theories for indentation with a 90° wedge. However, in the nonlinear model, indentation with a 120° wedge produces a lamellar twin structure between the indenter and the long sharp primary twin. This complex microstructure is not predicted by the linear theory
International Nuclear Information System (INIS)
Sen, Pinar; Yildiz, S. Zeki; Atalay, Yusuf; Dege, Necmi; Demirtas, Günes
2014-01-01
A novel 4-(2-meso-BOBIPY-phenoxy)phthalonitrile (6) derivative has been synthesized starting from BF 3 –OEt 2 complex and 4-(2-meso-dipyrromethene-phenoxy)phthalonitrile (5) which was prepared by the oxidation of 4-(2-meso-dipyrromethane-phenoxy)phthalonitrile (4). The final product exhibit noticeable spectroscopic properties which were examined by its absorption and fluorescence emission spectra. The original compounds prepared in the reaction pathway were characterized by the combination of FT-IR, 1 H and 13 C NMR, UV–vis, MS and HRMS spectral data. The final product (6) was obtained as single crystal which crystallized in the triclinic space group P-1 with a=7.9411 (6) Å, b=9.0150 (6) Å, c=14.419 (1) Å, α=74.917 (5)°, β=86.824 (6)°, γ=84.109 (5)° and Z=2. The crystal structure has intermolecular C–H···F–B and C–H···N interactions. These interactions construct bifurcated hydrogen bonds in the crystal structure. In this study, It has been calculated; molecular structure, vibrational frequencies, 1 H and 13 C NMR chemical shifts and HOMO and LUMO energies of the title compound by using B3LYP method with 6–311++G(dp) basis set, and the electronic spectral characterization was investigated for the target product, as well. - Highlights: • A novel 4-(2-meso-BOBIPY-phenoxy)phthalonitrile derivative has been synthesized. • The title product exhibit noticeable spectroscopic properties which were examined by its absorption and fluorescence emission spectra. • The final product (6) was obtained as single crystal which crystallized in the triclinic space group. • Molecular structure, vibrational frequencies, 1 H and 13 C NMR chemical shifts and HOMO and LUMO energies of the title compound were calculated theoretically. • The electronic spectral characterization was investigated, as well. • The title compound is also open to prepare further BODIPY substituted oligomeric molecules via on it
International Nuclear Information System (INIS)
Tikhonirov, V.V.
1993-01-01
The results of calculations of the intensity and polarization of radiation from channeled and unchanneled e +- are presented. The Fourier transformation (FT) is used to calculate numerous matrix elements. The calculations for channeled e + showed fast approach of spectral intensity to its value calculated in the approximation of self-consistent field (ASCF) with growing photon energy. In the case of 150 GeV unchanneled e - in Ge at T=293 K the ASCF gives a significantly higher value as compared to the FT. 4 refs., 3 figs
Flood field uniformity testing - effects of crystal hydration
International Nuclear Information System (INIS)
Dimcheva, M.; Sergieva, S.; Doldurova, M.; Jovanovska, A.
2012-01-01
The most basic and sensitive routine quality control (QC) of gamma camera is that of intrinsic flood-field uniformity. The routine QC test must be assessed daily and any nonuniformity must be eliminated before patient testing to eliminate artifacts and false positive or false-negative patient results. The purpose of this study was to compare uniformity analysis results for scintillation crystal hydration with symmetric and asymmetric energy window on the Siemens Symbia T2 SPECTCT camera. Integral and differential uniformity analysis was performed by placing a point source 99m Tc in front of the detector with removed collimator to measure the effect of correction matrix, a count rate and activity volume on intrinsic uniformity. A 15% energy window set symmetrically over the 99m Tc photo peak is equivalent to 140±10% keV or a window spanning 126-154 keV. The results, received from Detector 2 gave the following uniformity parameter values: Both asymmetric energy window images show clearly multiple focal spots due to crystal hydration: discrete hot spots in the asymmetric low window image and discrete cold spots in the asymmetric high window image. The above results are not seen yet on the symmetric window image. We had replaced Detector 2 in order to avoid spots become visible in flood images obtained with the clinical energy window. The uniformity of a gamma camera is maybe the most important parameter that expresses the quality of the camera's performance. Non uniform areas in the field of view can result in misdiagnosed patients and low quality of clinical services. (authors)
International Nuclear Information System (INIS)
Tonkonogov, M.P.; Medvedev, V.Ya.
2003-01-01
The formulas for volume charge distribution, complex permittivity, static dielectric constant for the crystals with hydrogen bonds are proposed. With help of the formulas the structure defect concentration, relaxation energy of relaxators were calculated for important electronic and optoelectronic materials as mica, KDP and DKDP crystals, gypsum, talk
The use of single-crystal iron frames in transient field measurements
International Nuclear Information System (INIS)
Zalm, P.C.; Laan, J. van der; Middelkoop, G. van
1979-01-01
Single-crystal Fe frames have been investigated for use as a ferromagnetic backing in transient magnetic field experiments. For this purpose the surface magnetization as a function of applied magnetic field has been determined with the magneto-optical Kerr effect. The frames, which have two sides parallel to the crystal axis, can be fully magnetized at low external fields such that fringing fields are negligibly small. These single-crystal Fe backings have been used in several transient magnetic field experiments. Comparison of the measured precession angles with previous results, obtained in polycrystalline Fe foils at high external magnetic fields, shows that the single-crystal backings are satisfactory. After extended periods of heavy-ion bombardment the crystals exhibited no radiation damage effects. The absence of fringing fields leads to a reduction of a factor of four in the measuring time for transient field experiments. (Auth.)
International Nuclear Information System (INIS)
Baryshevskii, V.G.; Skadorov, V.V.
1986-01-01
A dynamical theory is developed of the Moessbauer radiation diffraction by crystals being subjected to an variable external field action. Equations describing the dynamical diffraction by nonstationary crystals are obtained. It is shown that the resonant interaction between Moessbauer radiation and shift field induced in the crystal by a variable external field giving rise to an effective conversion of the incident wave into a wave with changed frequency. (author)
Calculation of magnetic error fields in hybrid insertion devices
International Nuclear Information System (INIS)
Savoy, R.; Halbach, K.; Hassenzahl, W.; Hoyer, E.; Humphries, D.; Kincaid, B.
1989-08-01
The Advanced Light Source (ALS) at the Lawrence Berkeley Laboratory requires insertion devices with fields sufficiently accurate to take advantage of the small emittance of the ALS electron beam. To maintain the spectral performance of the synchrotron radiation and to limit steering effects on the electron beam these errors must be smaller than 0.25%. This paper develops a procedure for calculating the steering error due to misalignment of the easy axis of the permanent magnet material. The procedure is based on a three dimensional theory of the design of hybrid insertion devices developed by one of us. The acceptable tolerance for easy axis misalignment is found for a 5 cm period undulator proposed for the ALS. 11 refs., 5 figs
Quantum theory of gauge fields and rigid processes calculation
International Nuclear Information System (INIS)
Andreev, I.V.
1981-01-01
Elementary statement of the basic data on the nature of quark interactions and their role in the high energy processes is presented in the first part of the paper. The second part of the paper deals with gauge theory (GT) of strong interactions (chromodynamics (CD)) and its application in calculation of rigid processes with quark participation. It is based on the method of functional integration (MFI). A comparatively simple representation of the MFI in the quantum theory and formulation of the perturbation theory for gauge fields are given. A derivation of the rules of diagram technique is presented. Renormalization invariance of the theory and the basic for CD phenomenon of asymptotical freedom are discussed. Theory application in calculation of certain effects at high energies is considered. From the CD view point considered is a parton model on the base of which ''rigid'' stage of evolution of quark and gluon jets produced at high energies can be quantitatively described and some quantitative experimental tests of the CD are suggested [ru
Crystal-fields at rare-earth sites in R2Fe14B compounds
International Nuclear Information System (INIS)
Adam, S.; Adam, G.; Burzo, E.
1985-12-01
Crystal-field effects are expected to be important in R 2 Fe 14 B compounds. Within a model-independent approach, it is proved that four distinct rare-earth sites exist with respect to the crystalline electric fields, namely, R(4f; z=0), R(4f; z=0.5 c), R(4g; z=0), and R(4g; z=0.5 c), and relationships are established between the corresponding crystal-fields coefficients. Further, generalized Stevens parametrizations of the crystal field coefficients are derived at three levels of approximation for the interatomic forces inside the crystal. A crystal lattice dressing effect upon the radial electronic integrals is found to occur, the magnitude of which depends on the deviation of the interatomic forces from Coulombian. Finally, computation of crystal-field coefficients in Nd 2 Fe 14 B leads to results which raise questions about the validity of the simple Coulomb point-charge model. (author)
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.
Project-90 Near-field calculations using CALIBRE
International Nuclear Information System (INIS)
Worgan, K.; Robinson, P.
1992-02-01
A comprehensive set of near-field calculations for the Swedish Nuclear Power Inspectorates Project-90 safety assessment has been performed using the CALIBRE model. In the majority of cases considered the redox front migrates through the bentonite buffer and into the rock, where it becomes effectively immobilised. The fracture remains in a reducing state, which means that for solubility-limited nuclides, the concentration at the bentonite/fracture interface can never be greater than the reducing solubility limit. The calculations also show that significant retardation occurs for nuclides which are even moderately sorbed. The effect is less pronounced in the wider fracture and high flow cases, as the opportunity for diffusion from the fracture to the rock matrix is reduced. In contrast, the release from the near-field of poorly-sorbed nuclides which are not solubility limited is governed by the release rate from the fuel, the diffusive mass transfer resistance of the buffer, rock matrix and fracture, the initial inventories and the nuclide half-lives. In the reference case, the maximum dose potential of nuclides emerging from the near-field occur for I-129 and was 3.2 x 10 -7 Sv per canister-year, assuming the flux to be discharged directly into the wall receptor biosphere. The parameters which have the most impact on the reference base results are high flow, wide aperture and poor chemistry (i.e. high solubility limits and low sorption distribution coefficients). The effects of combining extreme values of parameters does not give results which are in proportion to their effect when applied in isolation. In the worst case variant (early canister failure high flow, wide aperture and poor chemistry) the maximum dose potential is 1.0 x 10 -4 Sv per canister-year, compared with 8.9 x 10 -6 Sv in the high flow case, 4.5 x 10 -7 in the wide aperture case, 2.3 x 10 -6 in the poor chemistry case and 3.9 x 10 -6 in the early failure, wide aperture and high flow case. (au)
Hamiltonian lattice field theory: Computer calculations using variational methods
International Nuclear Information System (INIS)
Zako, R.L.
1991-01-01
I develop a variational method for systematic numerical computation of physical quantities -- bound state energies and scattering amplitudes -- in quantum field theory. An infinite-volume, continuum theory is approximated by a theory on a finite spatial lattice, which is amenable to numerical computation. I present an algorithm for computing approximate energy eigenvalues and eigenstates in the lattice theory and for bounding the resulting errors. I also show how to select basis states and choose variational parameters in order to minimize errors. The algorithm is based on the Rayleigh-Ritz principle and Kato's generalizations of Temple's formula. The algorithm could be adapted to systems such as atoms and molecules. I show how to compute Green's functions from energy eigenvalues and eigenstates in the lattice theory, and relate these to physical (renormalized) coupling constants, bound state energies and Green's functions. Thus one can compute approximate physical quantities in a lattice theory that approximates a quantum field theory with specified physical coupling constants. I discuss the errors in both approximations. In principle, the errors can be made arbitrarily small by increasing the size of the lattice, decreasing the lattice spacing and computing sufficiently long. Unfortunately, I do not understand the infinite-volume and continuum limits well enough to quantify errors due to the lattice approximation. Thus the method is currently incomplete. I apply the method to real scalar field theories using a Fock basis of free particle states. All needed quantities can be calculated efficiently with this basis. The generalization to more complicated theories is straightforward. I describe a computer implementation of the method and present numerical results for simple quantum mechanical systems
Hamiltonian lattice field theory: Computer calculations using variational methods
International Nuclear Information System (INIS)
Zako, R.L.
1991-01-01
A variational method is developed for systematic numerical computation of physical quantities-bound state energies and scattering amplitudes-in quantum field theory. An infinite-volume, continuum theory is approximated by a theory on a finite spatial lattice, which is amenable to numerical computation. An algorithm is presented for computing approximate energy eigenvalues and eigenstates in the lattice theory and for bounding the resulting errors. It is shown how to select basis states and choose variational parameters in order to minimize errors. The algorithm is based on the Rayleigh-Ritz principle and Kato's generalizations of Temple's formula. The algorithm could be adapted to systems such as atoms and molecules. It is shown how to compute Green's functions from energy eigenvalues and eigenstates in the lattice theory, and relate these to physical (renormalized) coupling constants, bound state energies and Green's functions. Thus one can compute approximate physical quantities in a lattice theory that approximates a quantum field theory with specified physical coupling constants. The author discusses the errors in both approximations. In principle, the errors can be made arbitrarily small by increasing the size of the lattice, decreasing the lattice spacing and computing sufficiently long. Unfortunately, the author does not understand the infinite-volume and continuum limits well enough to quantify errors due to the lattice approximation. Thus the method is currently incomplete. The method is applied to real scalar field theories using a Fock basis of free particle states. All needed quantities can be calculated efficiently with this basis. The generalization to more complicated theories is straightforward. The author describes a computer implementation of the method and present numerical results for simple quantum mechanical systems
High-pressure Raman spectra and DFT calculations of L-tyrosine hydrochloride crystal
dos Santos, C. A. A. S. S.; Carvalho, J. O.; da Silva Filho, J. G.; Rodrigues, J. L.; Lima, R. J. C.; Pinheiro, G. S.; Freire, P. T. C.; Façanha Filho, P. F.
2018-02-01
High-pressure Raman spectra of L-tyrosine hydrochloride crystal were obtained from 1.0 atm to 7.0 GPa in the 90-1800 cm-1 spectral region. At atmospheric pressure, the Raman spectrum was obtained in the 50-3200 cm-1 spectral range and the assignment of the normal modes based on density functional theory calculations was provided. We found good correspondence between the calculated and the observed intramolecular geometry parameters. This confirms the correct assignment of the normal modes, since it was crucial to understand the meaning of the changes observed in particular Raman active modes. Here we show that bands associated with internal modes undergo slight modifications during compression. However, an inversion of the relative intensity of bands around 125 cm-1 as well as a change of slope dω/dP from 1.0 to 1.5 GPa was understood as a conformational change involving a torsion of the L-tyrosine molecule. As a consequence, it is possible to conclude that the crystal remained in the same monoclinic structure in the 1 atm-7.0 GPa interval, although conformational change of the molecule was verified. A comparison of our results with other selected studies provided insights about the role of the amino acid side chain on the arrangement of hydrogen bonds. Finally, when the pressure was released back to 1 atm, the Raman spectrum was recovered and no hysteresis was observed.
Tight-binding calculation of radiation loss in photonic crystal CROW.
Ma, Jing; Martínez, Luis Javier; Fan, Shanhui; Povinelli, Michelle L
2013-01-28
The tight binding approximation (TBA) is used to relate the intrinsic, radiation loss of a coupled resonator optical waveguide (CROW) to that of a single constituent resonator within a light cone picture. We verify the validity of the TBA via direct, full-field simulation of CROWs based on the L2 photonic crystal cavity. The TBA predicts that the quality factor of the CROW increases with that of the isolated cavity. Moreover, our results provide a method to design CROWs with low intrinsic loss across the entire waveguide band.
International Nuclear Information System (INIS)
Brandow, B.H.
1985-01-01
Evidence is now quite strong that the elementary hybridization model is the correct way to understand the lattice-coherent Fermi liquid regime at very low temperatures. Many-body theory leads to significant renormalizations of the input parameters, and many of the band-theoretic channels for hybridization are suppressed by the combined effects of Hund's-rule coupling, crystal-field splitting, and the f-f Coulomb repulsion U. Some exploratory calculations based on this picture are described, and some inferences are drawn about the band structures of several heavy-fermion materials. These inferences can and should be tested by suitably modified band-theoretic calculations. We find evidence for a significant Baber-scattering contribution in the very-low-temperature resistivity. A new mechanism is proposed for crossover from the coherent Fermi-liquid regime to the incoherent dense-Kondo regime. 28 refs
Ab inito calculations of Hubbard parameters for NiO and Gd crystals
Directory of Open Access Journals (Sweden)
A. R Faghihi and S Jalali Asadabadi
2008-07-01
Full Text Available In this research the Hubbard parameters have been calculated for NiO and Gd crystals, as two strongly correlated systems with partially full 3d and 4f levels, respectively. The calculations were performed within the density functional theory (DFT using the augmented plane waves plus the local orbitat (APW+lo method. We constructed a suitable supercell and found that the Hubbard parameters for the NiO and Gd compounds are equal to 5.9 eV and 5.7 eV, respectively. Our results are in good agreement with experimental data and results of other computational methods. Then we used the obtained parameters to study the structural properties of NiO and Gd by means of LDA+U approximation. Our results calculated by the LDA+U method which are in better agreement with the experiment show a significant improvement compared to the GGA approximation. The result shows that our method for calculating U parameter can be considered as a satisfactory method to study a strongly correlated system.
International Nuclear Information System (INIS)
Ravindran, P.; Fast, L.; Korzhavyi, P.A.; Johansson, B.; Wills, J.; Eriksson, O.
1998-01-01
A theoretical formalism to calculate the single crystal elastic constants for orthorhombic crystals from first principle calculations is described. This is applied for TiSi 2 and we calculate the elastic constants using a full potential linear muffin-tin orbital method using the local density approximation (LDA) and generalized gradient approximation (GGA). The calculated values compare favorably with recent experimental results. An expression to calculate the bulk modulus along crystallographic axes of single crystals, using elastic constants, has been derived. From this the calculated linear bulk moduli are found to be in good agreement with the experiments. The shear modulus, Young's modulus, and Poisson's ratio for ideal polycrystalline TiSi 2 are also calculated and compared with corresponding experimental values. The directional bulk modulus and the Young's modulus for single crystal TiSi 2 are estimated from the elastic constants obtained from LDA as well as GGA calculations and are compared with the experimental results. The shear anisotropic factors and anisotropy in the linear bulk modulus are obtained from the single crystal elastic constants. From the site and angular momentum decomposed density of states combined with a charge density analysis and the elastic anisotropies, the chemical bonding nature between the constituents in TiSi 2 is analyzed. The Debye temperature is calculated from the average elastic wave velocity obtained from shear and bulk modulus as well as the integration of elastic wave velocities in different directions of the single crystal. The calculated elastic properties are found to be in good agreement with experimental values when the generalized gradient approximation is used for the exchange and correlation potential. copyright 1998 American Institute of Physics
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....
Elastic constants of stressed and unstressed materials in the phase-field crystal model
Wang, Zi-Le; Huang, Zhi-Feng; Liu, Zhirong
2018-04-01
A general procedure is developed to investigate the elastic response and calculate the elastic constants of stressed and unstressed materials through continuum field modeling, particularly the phase-field crystal (PFC) models. It is found that for a complete description of system response to elastic deformation, the variations of all the quantities of lattice wave vectors, their density amplitudes (including the corresponding anisotropic variation and degeneracy breaking), the average atomic density, and system volume should be incorporated. The quantitative and qualitative results of elastic constant calculations highly depend on the physical interpretation of the density field used in the model, and also importantly, on the intrinsic pressure that usually pre-exists in the model system. A formulation based on thermodynamics is constructed to account for the effects caused by constant pre-existing stress during the homogeneous elastic deformation, through the introducing of a generalized Gibbs free energy and an effective finite strain tensor used for determining the elastic constants. The elastic properties of both solid and liquid states can be well produced by this unified approach, as demonstrated by an analysis for the liquid state and numerical evaluations for the bcc solid phase. The numerical calculations of bcc elastic constants and Poisson's ratio through this method generate results that are consistent with experimental conditions, and better match the data of bcc Fe given by molecular dynamics simulations as compared to previous work. The general theory developed here is applicable to the study of different types of stressed or unstressed material systems under elastic deformation.
Schmitt, Regina; Kuhn, Charlotte; Müller, Ralf
2017-07-01
A continuum phase field model for martensitic transformations is introduced, including crystal plasticity with different slip systems for the different phases. In a 2D setting, the transformation-induced eigenstrain is taken into account for two martensitic orientation variants. With aid of the model, the phase transition and its dependence on the volume change, crystal plastic material behavior, and the inheritance of plastic deformations from austenite to martensite are studied in detail. The numerical setup is motivated by the process of cryogenic turning. The resulting microstructure qualitatively coincides with an experimentally obtained martensite structure. For the numerical calculations, finite elements together with global and local implicit time integration scheme are employed.
Effect of pressure on the crystal field splitting in rare earth pnictides and chalcogenides
International Nuclear Information System (INIS)
Schirber, J.E.; Weaver, H.T.
1978-01-01
The experimental situation for the pressure dependence of the crystal field of praseodymium pnictides and chalcogenides is reviewed and compared with the predictions of the point charge model. The problem of separating exchange and crystal field contributions from the measured NMR frequency shift or susceptibility measurements is discussed as well as problems explaining these effects with conduction electron related models
International Nuclear Information System (INIS)
Iannarella, L.; Guimaraes, A.P.; Silva, X.A. da.
1990-01-01
The magnetic behavior at T = O K of a system consisting of conduction electrons coupled to localized electrons, the latter submitted to an inhomogeneous crystal field distribution, is studied. The study implies that the inhomogeneity of the crystal field attenuates the quenching effects. The model is interesting to the study of disordered rare-earth intermetallic compounds. (A.C.A.S.) [pt
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...
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
Method to map individual electromagnetic field components inside a photonic crystal
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
International Nuclear Information System (INIS)
Hua Manyu; Li Yimin; Long Chunguang; Li Xia
2012-01-01
The structural, electronic and elastic properties of potassium hexatitanate (K 2 Ti 6 O 13 ) whisker were investigated using first-principles calculations. The calculated cell parameters of K 2 Ti 6 O 13 including lattice constants and atomic positions are in good agreement with the experimental data. The obtained formation enthalpy (-61.1535 eV/atom) and cohesive energy (-137.4502 eV/atom) are both negative, showing its high structural stability. Further analysis of the electronic structures shows that the potassium hexatitanate is a wide-band semiconductor. Within K 2 Ti 6 O 13 crystal, the Ti---O bonding interactions are stronger than that of K---O, while no apparent K---Ti bonding interactions can be observed. The structural stability of K 2 Ti 6 O 13 was closely associated with the covalent bond interactions between Ti (d) and O (p) orbits. Further calculations on elastic properties show that K 2 Ti 6 O 13 is a high stiffness and brittle material with small anisotropy in shear and compression.
Directory of Open Access Journals (Sweden)
FANG FANG JIAN
2010-09-01
Full Text Available The main aim of this study was to investigate the relationship between mIn tA new Ni(II complex of bisglycinato-bis[p-(hydroxylmethylpy-ridine] was synthesized and characterized by elemental analysis, IR, UV–Vis spectroscopy and X-ray single crystal diffraction analysis. The thermal stability of the title complex was also determined. The complex adopts a distorted octahedral geometry and possesses inversion symmetry with the Ni(II ion as the center of inversion. Density function theory (DFT calculations of the structure, electronic absorption spectra, electron structure and natural population analysis (NPA at the B3LYP/LANL2DZ level of theory were performed. The predicted geometric parameters and electronic spectra were compared with the experimental values and they supported each other. The NPA results indicate that the electronic transitions were mainly derived from the contribution of an intra-ligand (IL transition, a ligand-to-metal charge transfer (LMCT transition and a d-d transition. The electron structure calculations suggest that the central Ni(II ion uses its 4s and 3d orbitals to form covalent bonds with coordinated N and O atoms. The calculated bond orders are also consistent with the thermal decomposition results. Based on vibrational analysis, the thermodynamic properties of the title complex were predicted and the correlative equations between these thermodynamic properties and temperature are also reported.
Energy Technology Data Exchange (ETDEWEB)
Nascimento, Josenaide P. do; Santos, Lourivaldo S.; Carmo, Maria Carolina L. do; Brasil, Davi S.B.; Alves, Claudio N., E-mail: nahum@ufpa.b [Universidade Federal do Para (UFPA), Belem, PA (Brazil). Inst. de Ciencias Exatas e Naturais; Santos, Regina Helena A.; Tozzo, Erica; Ferreira, Janaina G. [Universidade de Sao Paulo (IQSC/USP), Sao Carlos, SP (Brazil). Inst. de Quimica
2010-07-01
The synthesis and X-ray crystal diffraction structure of two analogues of neolignans, 2-(4-chlorophenyl)-1-phenylethanone (20) and 2-[(4-chlorophenyl)thio]-1-(3,4-dimethoxyphenyl) propan-1-one (12) is described. The compound 12 presents activity against intracellular Leishmania donovani and Leishmania amazonensis amastigotes that cause cutaneous and visceral leishmaniasis. In addition, the density functional theory (DFT) with the B3LYP hybrid functional was employed to calculate a set of molecular descriptors for nineteen synthetic analogues of neolignans with antileishmanial activities. Afterwards, the stepwise discriminant analysis was performed to investigate possible relationship between the molecular descriptors and biological activities. Through this analysis the compounds were classified into two groups active and inactive according to their degree of biological activities, and the more important properties were charges on some key atoms, electronic affinity and ClogP. (author)
International Nuclear Information System (INIS)
Nascimento, Josenaide P. do; Santos, Lourivaldo S.; Carmo, Maria Carolina L. do; Brasil, Davi S.B.; Alves, Claudio N.; Santos, Regina Helena A.; Tozzo, Erica; Ferreira, Janaina G.
2010-01-01
The synthesis and X-ray crystal diffraction structure of two analogues of neolignans, 2-(4-chlorophenyl)-1-phenylethanone (20) and 2-[(4-chlorophenyl)thio]-1-(3,4-dimethoxyphenyl) propan-1-one (12) is described. The compound 12 presents activity against intracellular Leishmania donovani and Leishmania amazonensis amastigotes that cause cutaneous and visceral leishmaniasis. In addition, the density functional theory (DFT) with the B3LYP hybrid functional was employed to calculate a set of molecular descriptors for nineteen synthetic analogues of neolignans with antileishmanial activities. Afterwards, the stepwise discriminant analysis was performed to investigate possible relationship between the molecular descriptors and biological activities. Through this analysis the compounds were classified into two groups active and inactive according to their degree of biological activities, and the more important properties were charges on some key atoms, electronic affinity and ClogP. (author)
International Nuclear Information System (INIS)
Du Yanjun; Liu Qingcheng; Liu Hongzhang; Qin Guoxiu
2009-01-01
In order to find the feasibility of calculating mine radiation dose based on γ field theory, this paper calculates the γ radiation dose of a mine by means of γ field theory based calculation method. The results show that the calculated radiation dose is of small error and can be used to monitor mine environment of nuclear radiation. (authors)
Study of the accuracy of radiation field calculations in media
International Nuclear Information System (INIS)
Bolyatko, V.V.; Vyrskij, M.Yu.; Ilyushkin, A.I.; Mashkovich, V.P.; Sakharov, V.K.; Stroganov, A.A.
1981-01-01
The sensitivity p of the radiation transport calculations to variations of input parameters Xsub(i) is theoretically analyzed, and the calculational errors induced by uncertainties of initial data are evaluated. Two calculational methods are considered: the direct substitution method using the ROZ-5 code and method using the linear perturbation theory. In order to calculate p(Xsub(i)) and bilinear convolutions of the conjugated transport equations the ZAKAT code has been developed. The calculations use the ZAKAT, ROZ-11 and APAMAKO-2F codes. As an example of practical use of the method proposed a shielding composition characteristic for fast reactors was analyzed. A plane monodirectional neutron beam of the BR-10 reactor falls onto a 5-layer stainless steel (1Kh18N10T)-carbon barrier. The sensitivily of the neutron dose absorbed in tissue to the cross sections of all the shielding constituents and to the source and detector representation functions has been calculated. A comparison of the calculations with experimental data proves the validity of the calculational method [ru
Meshed doped silicon photonic crystals for manipulating near-field thermal radiation
Elzouka, Mahmoud; Ndao, Sidy
2018-01-01
The ability to control and manipulate heat flow is of great interest to thermal management and thermal logic and memory devices. Particularly, near-field thermal radiation presents a unique opportunity to enhance heat transfer while being able to tailor its characteristics (e.g., spectral selectivity). However, achieving nanometric gaps, necessary for near-field, has been and remains a formidable challenge. Here, we demonstrate significant enhancement of the near-field heat transfer through meshed photonic crystals with separation gaps above 0.5 μm. Using a first-principle method, we investigate the meshed photonic structures numerically via finite-difference time-domain technique (FDTD) along with the Langevin approach. Results for doped-silicon meshed structures show significant enhancement in heat transfer; 26 times over the non-meshed corrugated structures. This is especially important for thermal management and thermal rectification applications. The results also support the premise that thermal radiation at micro scale is a bulk (rather than a surface) phenomenon; the increase in heat transfer between two meshed-corrugated surfaces compared to the flat surface (8.2) wasn't proportional to the increase in the surface area due to the corrugations (9). Results were further validated through good agreements between the resonant modes predicted from the dispersion relation (calculated using a finite-element method), and transmission factors (calculated from FDTD).
Sink efficiency calculation of dislocations in irradiated materials by phase-field modelling
International Nuclear Information System (INIS)
Rouchette, Adrien
2015-01-01
The aim of this work is to develop a modelling technique for diffusion of crystallographic migrating defects in irradiated metals and absorption by sinks to better predict the microstructural evolution in those materials.The phase field technique is well suited for this problem, since it naturally takes into account the elastic effects of dislocations on point defect diffusion in the most complex cases. The phase field model presented in this work has been adapted to simulate the generation of defects by irradiation and their absorption by the dislocation cores by means of a new order parameter associated to the sink morphology. The method has first been validated in different reference cases by comparing the sink strengths obtained numerically with analytical solutions available in the literature. Then, the method has been applied to dislocations with different orientations in zirconium, taking into account the anisotropic properties of the crystal and point defects, obtained by state-of-the-art atomic calculations.The results show that the shape anisotropy of the point defects promotes the vacancy absorption by basal loops, which is consistent with the experimentally observed zirconium growth under irradiation. Finally, the rigorous investigation of the dislocation loop case proves that phase field simulations give more accurate results than analytical solutions in realistic loop density ranges. (author)
Crystal-field analysis of U3+ ions in K2LaX5 (X=Cl, Br or I) single crystals
Karbowiak, M.; Edelstein, N.; Gajek, Z.; Drożdżyński, J.
1998-11-01
An analysis of low temperature absorption spectra of U3+ ions doped in K2LaX5 (X=Cl, Br or I) single crystals is reported. The energy levels of the U3+ ion in the single crystals were assigned and fitted to a semiempirical Hamiltonian representing the combined atomic and crystal-field interactions at the Cs symmetry site. An analysis of the nephelauxetic effect and crystal-field splittings in the series of compounds is also reported.
Piezo-optic tensor of crystals from quantum-mechanical calculations.
Erba, A; Ruggiero, M T; Korter, T M; Dovesi, R
2015-10-14
An automated computational strategy is devised for the ab initio determination of the full fourth-rank piezo-optic tensor of crystals belonging to any space group of symmetry. Elastic stiffness and compliance constants are obtained as numerical first derivatives of analytical energy gradients with respect to the strain and photo-elastic constants as numerical derivatives of analytical dielectric tensor components, which are in turn computed through a Coupled-Perturbed-Hartree-Fock/Kohn-Sham approach, with respect to the strain. Both point and translation symmetries are exploited at all steps of the calculation, within the framework of periodic boundary conditions. The scheme is applied to the determination of the full set of ten symmetry-independent piezo-optic constants of calcium tungstate CaWO4, which have recently been experimentally reconstructed. Present calculations unambiguously determine the absolute sign (positive) of the π61 constant, confirm the reliability of 6 out of 10 experimentally determined constants and provide new, more accurate values for the remaining 4 constants.
Broken symmetry phase transition in solid p-H 2, o-D 2 and HD: crystal field effects
Freiman, Yu. A.; Hemley, R. J.; Jezowski, A.; Tretyak, S. M.
1999-04-01
We report the effect of the crystal field (CF) on the broken symmetry phase transition (BSP) in solid parahydrogen, orthodeuterium, and hydrogen deuteride. The CF was calculated taking into account a distortion from the ideal HCP structure. We find that, in addition to the molecular field generated by the coupling terms in the intermolecular potential, the Hamiltonian of the system contains a crystal-field term, originating from single-molecular terms in the intermolecular potential. Ignoring the CF is the main cause of the systematic underestimation of the transition pressure, characteristic of published theories of the BSP transition. The distortion of the lattice that gives rise to the negative CF in response to the applied pressure is in accord with the general Le Chatelier-Braun principle.
Kim, Seonah; Orendt, Anita M; Ferraro, Marta B; Facelli, Julio C
2009-10-01
This article describes the application of our distributed computing framework for crystal structure prediction (CSP) the modified genetic algorithms for crystal and cluster prediction (MGAC), to predict the crystal structure of flexible molecules using the general Amber force field (GAFF) and the CHARMM program. The MGAC distributed computing framework includes a series of tightly integrated computer programs for generating the molecule's force field, sampling crystal structures using a distributed parallel genetic algorithm and local energy minimization of the structures followed by the classifying, sorting, and archiving of the most relevant structures. Our results indicate that the method can consistently find the experimentally known crystal structures of flexible molecules, but the number of missing structures and poor ranking observed in some crystals show the need for further improvement of the potential. Copyright 2009 Wiley Periodicals, Inc.
Dielectric properties of layered FeGaInS{sub 4} single crystals in an alternating electric field
Energy Technology Data Exchange (ETDEWEB)
Mammadov, F. M. [Azerbaijan National Academy of Sciences, Nagiyev Institute of Catalysis and Inorganic Chemistry (Azerbaijan); Niftiyev, N. N., E-mail: namiq7@bk.ru [Azerbaijan State Pedagogical University (Azerbaijan)
2016-09-15
The results of investigations of the frequency and temperature dependences of dielectric losses and the imaginary part of the dielectric permittivity in FeGaInS{sub 4} single crystals are presented. Their experimental values are determined. It is established that the loss tangent and the imaginary part of the permittivity of FeGaInS{sub 4} single crystals in a field with frequencies of 10{sup 4}–10{sup 6} Hz decrease inversely proportional to the frequency (tanδ ~ 1/ω), and the conductivity is characterized by the band–hopping mechanism. For FeGaInS{sub 4}, the relaxation time is calculated, and it is established that there is a mechanism of electron polarization caused by thermal motion in this crystal.
Inductive crystal field control in layered metal oxides with correlated electrons
International Nuclear Information System (INIS)
Balachandran, P. V.; Cammarata, A.; Rondinelli, J. M.; Nelson-Cheeseman, B. B.; Bhattacharya, A.
2014-01-01
We show that the NiO 6 crystal field energies can be tailored indirectly via heterovalent A cation ordering in layered (La,A)NiO 4 Ruddlesden–Popper (RP) oxides, where A = Sr, Ca, or Ba, using density functional calculations. We leverage as a driving force the electrostatic interactions between charged [LaO] 1+ and neutral [AO] 0 planes to inductively tune the Ni–O bond distortions, without intentional doping or epitaxial strain, altering the correlated d-orbital energies. We use this strategy to design cation ordered LaCaNiO 4 and LaBaNiO 4 with distortions favoring enhanced Ni e g orbital polarization, and find local electronic structure signatures analogous to those in RP La-cuprates, i.e., parent phases of the high-temperature superconducting oxides
Inductive crystal field control in layered metal oxides with correlated electrons
Energy Technology Data Exchange (ETDEWEB)
Balachandran, P. V.; Cammarata, A.; Rondinelli, J. M., E-mail: jrondinelli@nortwestern.edu [Department of Materials Science and Engineering, Drexel University, Philadelphia, Pennsylvania 19104 (United States); Nelson-Cheeseman, B. B. [School of Engineering, University of St. Thomas, St. Paul, Minnesota 55105 (United States); Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Bhattacharya, A. [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Center for Nanoscale Materials, Argonne National Laboratory, Argonne, Illinois 60439 (United States)
2014-07-01
We show that the NiO{sub 6} crystal field energies can be tailored indirectly via heterovalent A cation ordering in layered (La,A)NiO{sub 4} Ruddlesden–Popper (RP) oxides, where A = Sr, Ca, or Ba, using density functional calculations. We leverage as a driving force the electrostatic interactions between charged [LaO]{sup 1+} and neutral [AO]{sup 0} planes to inductively tune the Ni–O bond distortions, without intentional doping or epitaxial strain, altering the correlated d-orbital energies. We use this strategy to design cation ordered LaCaNiO{sub 4} and LaBaNiO{sub 4} with distortions favoring enhanced Ni e{sub g} orbital polarization, and find local electronic structure signatures analogous to those in RP La-cuprates, i.e., parent phases of the high-temperature superconducting oxides.
Energy Technology Data Exchange (ETDEWEB)
Gajek, Z. E-mail: gajek@int.pan.wroc.pl
2004-05-01
The electronic properties of the actinide ions in the series of semi-conducting, antiferromagnetic compounds: dioxides, AnO{sub 2} and oxychalcogenides, AnOY, where An=U, Np and Y=S, Se, are re-examined from the point of view of the consistency of the crystal field (CF) model. The discussion is based on the supposition that the effective metal-ligand interaction solely determines the net CF effect in non-metallic compounds. The main question we address here is, whether a reliable, consistent description of the CF effect in terms of the intrinsic parameters can be achieved for this particular family of compounds. Encouraging calculations reported previously for the AnO{sub 2} and UOY series serve as a reference data in the present estimation of electronic structure parameters for neptunium oxychalcogenides.
Gajek, Z.
2004-05-01
The electronic properties of the actinide ions in the series of semi-conducting, antiferromagnetic compounds: dioxides, AnO2 and oxychalcogenides, AnOY, where An=U, Np and Y=S, Se, are re-examined from the point of view of the consistency of the crystal field (CF) model. The discussion is based on the supposition that the effective metal-ligand interaction solely determines the net CF effect in non-metallic compounds. The main question we address here is, whether a reliable, consistent description of the CF effect in terms of the intrinsic parameters can be achieved for this particular family of compounds. Encouraging calculations reported previously for the AnO2 and UOY series serve as a reference data in the present estimation of electronic structure parameters for neptunium oxychalcogenides.
International Nuclear Information System (INIS)
Gajek, Z.
2004-01-01
The electronic properties of the actinide ions in the series of semi-conducting, antiferromagnetic compounds: dioxides, AnO 2 and oxychalcogenides, AnOY, where An=U, Np and Y=S, Se, are re-examined from the point of view of the consistency of the crystal field (CF) model. The discussion is based on the supposition that the effective metal-ligand interaction solely determines the net CF effect in non-metallic compounds. The main question we address here is, whether a reliable, consistent description of the CF effect in terms of the intrinsic parameters can be achieved for this particular family of compounds. Encouraging calculations reported previously for the AnO 2 and UOY series serve as a reference data in the present estimation of electronic structure parameters for neptunium oxychalcogenides
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.)
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.
Global mean-field phase diagram of the spin-1 Ising ferromagnet in a random crystal field
Borelli, M. E. S.; Carneiro, C. E. I.
1996-02-01
We study the phase diagram of the mean-field spin-1 Ising ferromagnet in a uniform magnetic field H and a random crystal field Δi, with probability distribution P( Δi) = pδ( Δi - Δ) + (1 - p) δ( Δi). We analyse the effects of randomness on the first-order surfaces of the Δ- T- H phase diagram for different values of the concentration p and show how these surfaces are affected by the dilution of the crystal field.
Crystal fields of dilute Tb, Dy, Ho, or Er in Lu obtained by magnetization measurements
International Nuclear Information System (INIS)
Touborg, P.; Hog, J.
1975-01-01
Magnetization measurements are reported on single crystals of dilute Tb, Dy, Ho, or Er in Lu. These measurements were performed in the temperature range 1.5--100 K and field range 0--6 T and include measurements of initial susceptibility, isothermal and isofield magnetization, and basal-plane anisotropy. The results show features similar to the corresponding Y-R alloys, where R is a rare earth. Crystal-field and molecular-field parameters could be unabiguously deduced from the experimental data. The effects of crystal-field level broadening were investigated and demonstrated for Ho. Comparison of the Y-R and Lu-R results makes possible an estimate of the crystal-field parameters in the pure-rare-earth metals
Kim, Jaekyun; Kang, Jingu; Cho, Sangho; Yoo, Byungwook; Kim, Yong-Hoon; Park, Sung Kyu
2014-11-01
High-performance microrod single crystal organic transistors based on a p-type 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT) semiconductor are fabricated and the effects of grain boundaries on the carrier transport have been investigated. The spin-coating of C8-BTBT and subsequent solvent vapor annealing process enabled the formation of organic single crystals with high aspect ratio in the range of 10 - 20. It was found that the organic field-effect transistors (OFETs) based on these single crystals yield a field-effect mobility and an on/off current ratio of 8.04 cm2/Vs and > 10(5), respectively. However, single crystal OFETs with a kink, in which two single crystals are fused together, exhibited a noticeable drop of field-effect mobility, and we claim that this phenomenon results from the carrier scattering at the grain boundary.
Dennis Raj, A.; Jeeva, M.; Shankar, M.; Venkatesa Prabhu, G.; Vimalan, M.; Vetha Potheher, I.
2017-11-01
2-Naphthol substituted Mannich base 1-morpholino(phenyl)methyl)naphthalen-2-ol (MPMN), a potential NLO active organic single crystal was developed using acetonitrile as a solvent by slow evaporation method. The experimental and theoretical analysis made towards the exploitation in the field of electro-optic and NLO applications. The cubic structure with non-centrosymmetric space group Cc was confirmed and cell dimensions of the grown crystal were obtained from single crystal X-ray diffraction (XRD) study. The formation of the Csbnd Nsbnd C vibrational band at 1115 cm-1 in Fourier Transform Infra-Red (FTIR) analysis confirms the formation of MPMN compound. The placement of protons and carbons of MPMN were identified from Nuclear Magnetic Resonance Spectroscopy (NMR) analysis. The wide optical absorption window and the lower cutoff wavelength of MPMN show the suitability of the material for the various laser related applications. The presence of dislocations and growth pattern of crystal were analyzed using chemical etching technique. The Second Harmonic Generation (SHG) of MPMN was found to be 1.57 times greater than the standard KDP crystal. The laser damage threshold was measured by using Nd: YAG laser beam passed through the sample and it was found to be 1.006 GW/cm2. The electronic structure of the molecular system and the optical properties were also studied from quantum chemical calculations using Density Functional Theory (DFT) and reported for the first time.
Home Field Advantage Calculation for Physical Education and Sport Students
Inan, Tugbay
2018-01-01
It is a well-established fact that playing at home field is an advantageous condition for professional sport teams. For this reason, the home field advantage in team sports is an important issue to be explored. It is also one of the different topics that physical education and sports students can use when they want to perform performance analysis…
Model calculation of the scanned field enhancement factor of CNTs
International Nuclear Information System (INIS)
Ahmad, Amir; Tripathi, V K
2006-01-01
The field enhancement factor of a carbon nanotube (CNT) placed in a cluster of CNTs is smaller than an isolated CNT because the electric field on one tube is screened by neighbouring tubes. This screening depends on the length of the CNTs and the spacing between them. We have derived an expression to compute the field enhancement factor of CNTs under any positional distribution of CNTs using a model of a floating sphere between parallel anode and cathode plates. Using this expression we can compute the field enhancement factor of a CNT in a cluster (non-uniformly distributed CNTs). This expression is used to compute the field enhancement factor of a CNT in an array (uniformly distributed CNTs). Comparison has been shown with experimental results and existing models
International Nuclear Information System (INIS)
Snowman, Daniel P.
2009-01-01
Phase diagrams have been produced and critical exponents calculated for a Blume-Emery-Griffiths system with competing biquadratic and crystal-field interactions with uniform ferromagnetic bilinear interactions. This competition directly effects the clustering and density of nonmagnetic impurities. These results have been produced using renormalization-group methods with a hierarchical lattice. A series of planes of constant, repulsive biquadratic coupling have been probed while varying the temperature and concentration of annealed vacancies in the system. The sinks have been analyzed and interpreted, and critical exponents calculated for the higher order transitions.
Energy Technology Data Exchange (ETDEWEB)
Zaitseva, E. V.; Markelov, A. S.; Trushin, V. N., E-mail: trushin@phys.unn.ru; Chuprunov, E. V. [Nizhni Novgorod State University (Russian Federation)
2013-12-15
The features of formation of thermal fields in potassium dihydrophosphate crystal doped with potassium permanganate under a 532-nm laser beam passing through it have been investigated. Data on the influence of birefringence on the temperature distribution in an anisotropic crystal whose surface is illuminated by a spatially modulated light beam are presented.
Monte Carlo Calculation of the Radiation Field at Aircraft Altitudes
Energy Technology Data Exchange (ETDEWEB)
Roesler, Stefan
2001-08-24
Energy spectra of secondary cosmic rays are calculated for aircraft altitudes and a discrete set of solar modulation parameters and rigidity cutoff values covering all possible conditions. The calculations are based on the Monte Carlo code FLUKA and on the most recent information on the interstellar cosmic ray flux including a detailed model of solar modulation. Results are compared to a large variety of experimental data obtained on ground and aboard of aircrafts and balloons, such as neutron, proton, and muon spectra and yields of charged particles. Furthermore, particle fluence is converted into ambient dose equivalent and effective dose and the dependence of these quantities on height above sea level, solar modulation, and geographic location is studied. Finally, calculated dose equivalent is compared to results of comprehensive measurements performed aboard of aircrafts.
Large Field Visualization with Demand-Driven Calculation
Moran, Patrick J.; Henze, Chris
1999-01-01
We present a system designed for the interactive definition and visualization of fields derived from large data sets: the Demand-Driven Visualizer (DDV). The system allows the user to write arbitrary expressions to define new fields, and then apply a variety of visualization techniques to the result. Expressions can include differential operators and numerous other built-in functions, ail of which are evaluated at specific field locations completely on demand. The payoff of following a demand-driven design philosophy throughout becomes particularly evident when working with large time-series data, where the costs of eager evaluation alternatives can be prohibitive.
Accurate magnetic field calculations for contactless energy transfer coils
Sonntag, C.L.W.; Spree, M.; Lomonova, E.A.; Duarte, J.L.; Vandenput, A.J.A.
2007-01-01
In this paper, a method for estimating the magnetic field intensity from hexagon spiral windings commonly found in contactless energy transfer applications is presented. The hexagonal structures are modeled in a magneto-static environment using Biot-Savart current stick vectors. The accuracy of the models are evaluated by mapping the current sticks and the hexagon spiral winding tracks to a local twodimensional plane, and comparing their two-dimensional magnetic field intensities. The accurac...
Transverse magnetic field impact on waveguide modes of photonic crystals.
Sylgacheva, Daria; Khokhlov, Nikolai; Kalish, Andrey; Dagesyan, Sarkis; Prokopov, Anatoly; Shaposhnikov, Alexandr; Berzhansky, Vladimir; Nur-E-Alam, Mohammad; Vasiliev, Mikhail; Alameh, Kamal; Belotelov, Vladimir
2016-08-15
This Letter presents a theoretical and experimental study of waveguide modes of one-dimensional magneto-photonic crystals magnetized in the in-plane direction. It is shown that the propagation constants of the TM waveguide modes are sensitive to the transverse magnetization and the spectrum of the transverse magneto-optical Kerr effect has resonant features at mode excitation frequencies. Two types of structures are considered: a non-magnetic photonic crystal with an additional magnetic layer on top and a magneto-photonic crystal with a magnetic layer within each period. We found that the magneto-optical non-reciprocity effect is greater in the first case: it has a magnitude of δ∼10-4, while the second structure type demonstrates δ∼10-5 only, due to the higher asymmetry of the claddings of the magnetic layer. Experimental observations show resonant features in the optical and magneto-optical Kerr effect spectra. The measured dispersion properties are in good agreement with the theoretical predictions. An amplitude of light intensity modulation of up to 2.5% was observed for waveguide mode excitation within the magnetic top layer of the non-magnetic photonic crystal structure. The presented theoretical approach may be utilized for the design of magneto-optical sensors and modulators requiring pre-determined spectral features.
Accounting for chemical kinetics in field scale transport calculations
International Nuclear Information System (INIS)
Bryan, N.D.
2005-01-01
The modelling of column experiments has shown that the humic acid mediated transport of metal ions is dominated by the non-exchangeable fraction. Metal ions enter this fraction via the exchangeable fraction, and may transfer back again. However, in both directions these chemical reactions are slow. Whether or not a kinetic description of these processes is required during transport calculations, or an assumption of local equilibrium will suffice, will depend upon the ratio of the reaction half-time to the residence time of species within the groundwater column. If the flow rate is sufficiently slow or the reaction sufficiently fast then the assumption of local equilibrium is acceptable. Alternatively, if the reaction is sufficiently slow (or the flow rate fast), then the reaction may be 'decoupled', i.e. removed from the calculation. These distinctions are important, because calculations involving chemical kinetics are computationally very expensive, and should be avoided wherever possible. In addition, column experiments have shown that the sorption of humic substances and metal-humate complexes may be significant, and that these reactions may also be slow. In this work, a set of rules is presented that dictate when the local equilibrium and decoupled assumptions may be used. In addition, it is shown that in all cases to a first approximation, the behaviour of a kinetically controlled species, and in particular its final distribution against distance at the end of a calculation, depends only upon the ratio of the reaction first order rate to the residence time, and hence, even in the region where the simplifications may not be used, the behaviour is predictable. In this way, it is possible to obtain an estimate of the migration of these species, without the need for a complex transport calculation. (orig.)
International Nuclear Information System (INIS)
Lim, Young Jin; Lee, Myong-Hoon; Lee, Gi-Dong; Jang, Won-Gun; Lee, Seung Hee
2007-01-01
There is considerable difficulty in fabricating a reflector with embossing in an array substrate using a conventional single gap transflective fringe-field switching nematic liquid-crystal display. In order to solve this problem, we propose a new structure, which consists of a reflector on a colour filter substrate. The newly proposed structure with a complex field direction has problems such that the voltage-dependent transmittance and reflectance curves do not match each other, which necessitate a dual driving circuit. This paper reports the optimized electrode structure and calculated electro-optical results realizing a single gamma curve and high light efficiency
Crystal field and site deformation in spinels and pentavalent uranium compounds
International Nuclear Information System (INIS)
Drifford, M.; Soulie, E.
1976-01-01
Magnesium aluminates with different alumina contents have the spinel structure. The optical absorption spectra of doped spinel compounds (Cr 3+ , Ni 2+ , Co 2+ ) or E.S.R. spectra (Cr 3+ , Mn 2+ ) are used for the investigation of the position of the doping materials and the deformation of the crystal sites, and give information on the structural disorders. The local structural information given by the doping materials are compared with the mean structure parameters obtained from X-ray diffraction. The optical absorption spectrum and the principal components of the g tensor for UF 6 Cs and the thermal variation in the magnetic susceptibility for UF 8 Cs 3 and UF 8 (NH 4 ) are used for determining the parameters of the electron Hamiltonian for the f 1 configuration. A rather significant covalent aspect is evidenced for UF 6 Cs, in the framework of the model of Eisenstein and Pryce, this property being weaker for the other two complex compounds. The three parameters giving the crystal field at a deformed cubic site with Dsub(3d) symmetry in the Newman superposition model are noticeably weaker for the 8-coordination than for the 6-coordination. As for UF 8 Cs 3 and UF 8 (NH 4 ) 3 a calculation predicts an electronic levels with a very low excitation, at about 110 and 70cm -1 respectively [fr
Electric-field gradient characterization at 181Ta impurities in sapphire single crystals
International Nuclear Information System (INIS)
Renteria, M.; Darriba, G.N.; Errico, L.A.; Munoz, E.L.; Eversheim, P.D.
2005-01-01
We report Perturbed-Angular-Correlation (PAC) experiments on corundum Al 2 O 3 single crystals implanted with 181 Hf/ 181 Ta ions at the ISKP at Bonn and measured at La Plata with high efficiency and time-resolution. The magnitude, asymmetry, and orientation (with respect to the crystalline axes) of the electric-field gradient (EFG) tensor were determined measuring the spin-rotation curves as a function of different orientations of the single crystals relative to the detector system. These results are analyzed in the framework of point-charge model and ab initio Full-Potential Linearized-Augmented Plane Wave calculations, and compared with EFG results coming from PAC experiments with 111 In/ 111 Cd impurities. This combined study enables the determination of lattice relaxations induced by the presence of the impurity and the state of charge of a deep impurity donor level in the band gap of the semiconductor. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)
Electric-field gradient characterization at {sup 181}Ta impurities in sapphire single crystals
Energy Technology Data Exchange (ETDEWEB)
Renteria, M.; Darriba, G.N.; Errico, L.A.; Munoz, E.L. [Departamento de Fisica, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, CC 67, 1900 La Plata (Argentina); Eversheim, P.D. [Helmholtz-Institut fuer Strahlen-und Kernphysik (ISKP), Universitaet Bonn, Nussallee 14-16, 53115 Bonn (Germany)
2005-07-01
We report Perturbed-Angular-Correlation (PAC) experiments on corundum Al{sub 2}O{sub 3} single crystals implanted with {sup 181}Hf/{sup 181}Ta ions at the ISKP at Bonn and measured at La Plata with high efficiency and time-resolution. The magnitude, asymmetry, and orientation (with respect to the crystalline axes) of the electric-field gradient (EFG) tensor were determined measuring the spin-rotation curves as a function of different orientations of the single crystals relative to the detector system. These results are analyzed in the framework of point-charge model and ab initio Full-Potential Linearized-Augmented Plane Wave calculations, and compared with EFG results coming from PAC experiments with {sup 111}In/{sup 111}Cd impurities. This combined study enables the determination of lattice relaxations induced by the presence of the impurity and the state of charge of a deep impurity donor level in the band gap of the semiconductor. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)
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.
Mixed spin Ising model with four-spin interaction and random crystal field
International Nuclear Information System (INIS)
Benayad, N.; Ghliyem, M.
2012-01-01
The effects of fluctuations of the crystal field on the phase diagram of the mixed spin-1/2 and spin-1 Ising model with four-spin interactions are investigated within the finite cluster approximation based on a single-site cluster theory. The state equations are derived for the two-dimensional square lattice. It has been found that the system exhibits a variety of interesting features resulting from the fluctuation of the crystal field interactions. In particular, for low mean value D of the crystal field, the critical temperature is not very sensitive to fluctuations and all transitions are of second order for any value of the four-spin interactions. But for relatively high D, the transition temperature depends on the fluctuation of the crystal field, and the system undergoes tricritical behaviour for any strength of the four-spin interactions. We have also found that the model may exhibit reentrance for appropriate values of the system parameters.
Mendoza, Carlos I.; Reyes, J. Adrian
2006-08-01
The authors present a geometrical approach to calculate the transmission of light in a hybrid-aligned nematic cell under the influence of an applied electric field. Using the framework of geometrical optics they present results for the ray tracing as well as the transmission of light as a function of the applied low frequency voltage. Dispersion effects are included through a wavelength dependent dielectric function. Their results for the transmittance as a function of the applied voltage show oscillations that are in good qualitative agreement with previously obtained experimental measurements.
Mrozek, A.; Karolak-Wojciechowska, J.; Amiel, P.; Barbe, J.
2000-06-01
Crystal structures of four bisubstituted 1,3,4-thiadiazole derivatives were determined. Detailed description of the five-membered heteroring geometry is enabled thorough analysis of ring aromaticity. For this purpose the HOMA index was used as a quantitative measure of aromaticity. The calculated HOMA indices evidenced the role of substituents. In particular, increase in the substituent electrophilicity brings about increase in aromaticity.
AOM reconciling of crystal field parameters for UCl 3, UBr 3, UI 3 series
Gajek, Z.; Mulak, J.
1990-07-01
Available inelastic neutron scattering interpretations of crystal field effect in the uranium trihalides have been verified in terms of Angular Overlap Model. For UCl 3 a good reconciling of both INS and optical interpretations of crystal field effect has been obtained. On the contrary, the parameterizations for UBr 3 and UI 3 were found to be highly artificial and suggestion is given to experimentalists to reinterpret their INS spectra.
AOM reconciling of crystal field parameters for UCl3, UBr3, Ul3 series
International Nuclear Information System (INIS)
Gajek, Z.; Mulak, J.
1990-01-01
Available inelastic neutron scattering interpretations of crystal field effect in the uranium trihalides have been verified in terms of Angular Overlap Model. For UCl 3 a good reconciling of both INS and optical interpretations of crystal field effect has been obtained. On the contrary, the parameterizations for UBr 3 and UI 3 were found to be highly artificial and suggestion is given to experimentalists to reinterpret their INS spectra
Magnetic fields in a residential neighbourhood by network analysis and field calculation
International Nuclear Information System (INIS)
Mader, D.L.
1992-01-01
A magnetic field research facility has been used for validation of a method to compute 60-Hz magnetic fields in a residential neighbourhood. Network analysis is used to solve for currents in a mathematical model of the electric power distribution system including grounding conductors and metallic water supply pipes. Then, magnetic fields are calculated using the currents and the locations of all conductors. The critical role of joint resistance was highlighted by this study as follows. With initial estimates of resistances in the model, a fitting algorithm was able to obtain excellent agreement between the model and measurements, and provide confidence in its predictive capability. Simulations are then done to illustrate the effects of a poor joint, multiple unbalanced loads, heavy balanced loads, a heavy feeder line going through the neighbourhood, injection of current into the local neutral from an adjacent neighbourhood, use of plastic water pipes instead of metal, wet soil, increasing the distance from the power line, changing from twisted wires to an open secondary bus, and primary current loops caused by poor joints in the interconnected system neutral. 8 refs., 24 figs., 8 tabs
Accurate magnetic field calculations for contactless energy transfer coils
Sonntag, C.L.W.; Spree, M.; Lomonova, E.A.; Duarte, J.L.; Vandenput, A.J.A.
2007-01-01
In this paper, a method for estimating the magnetic field intensity from hexagon spiral windings commonly found in contactless energy transfer applications is presented. The hexagonal structures are modeled in a magneto-static environment using Biot-Savart current stick vectors. The accuracy of the
Effective and efficient method of calculating Bessel beam fields
CSIR Research Space (South Africa)
Litvin, IA
2005-01-01
Full Text Available Bessel beams have gathered much interest of late due to their properties of near diffraction free propagation and self reconstruction after obstacles. Such laser beams have already found applications in fields such as optical tweezers and as pump...
A Navier-Stokes phase-field crystal model for colloidal suspensions.
Praetorius, Simon; Voigt, Axel
2015-04-21
We develop a fully continuous model for colloidal suspensions with hydrodynamic interactions. The Navier-Stokes Phase-Field Crystal model combines ideas of dynamic density functional theory with particulate flow approaches and is derived in detail and related to other dynamic density functional theory approaches with hydrodynamic interactions. The derived system is numerically solved using adaptive finite elements and is used to analyze colloidal crystallization in flowing environments demonstrating a strong coupling in both directions between the crystal shape and the flow field. We further validate the model against other computational approaches for particulate flow systems for various colloidal sedimentation problems.
Nanomechanical control of optical field and quality factor in photonic crystal structures
Cotrufo, Michele; Midolo, Leonardo; Zobenica, Žarko; Petruzzella, Maurangelo; van Otten, Frank W. M.; Fiore, Andrea
2018-03-01
Actively controlling the properties of localized optical modes is crucial for cavity quantum electrodynamics experiments. While several methods to tune the optical frequency have been demonstrated, the possibility of controlling the shape of the modes has scarcely been investigated. Yet an active manipulation of the mode pattern would allow direct control of the mode volume and the quality factor and therefore of the radiative processes. In this work, we propose and demonstrate a nano-optoelectromechanical device in which a mechanical displacement affects the spatial pattern of the electromagnetic field. The device is based on a double-membrane photonic crystal waveguide which, upon bending, creates a spatial modulation of the effective refractive index, resulting in an effective potential well or antiwell for the optical modes. The change in the field pattern drastically affects the optical losses: large modulations of the quality factors and dissipative coupling rates larger than 1 GHz/nm are predicted by calculations and confirmed by experiments. This concept opens new avenues in solid-state cavity quantum electrodynamics in which the field, instead of the frequency, is coupled to the mechanical motion.
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.
Liquid crystal blue phases: stability, field effects and alignment
Gleeson, HF; Miller, RJ; Tian, L; Görtz, V; Goodby, JW
2015-01-01
The blue phases are fascinating structures in liquid crystals, fluids that exhibit cubic structures that have true crystalline order. The blue phases were discovered in the 1970s and were the subject of extensive research in the 1980s, when a deep understanding of many of their properties was established. The discovery that the blue phases could be stabilised to exist over wide temperature ranges meant that they became more than scientific curiosities and led to a recent resurgence in researc...
Numerical calculation of transient field effects in quenching superconducting magnets
Schwerg, Nikolai; Russenschuck, Stephan
2009-01-01
The maximum obtainable magnetic induction of accelerator magnets, relying on normal conducting cables and iron poles, is limited to around 2 T because of ohmic losses and iron saturation. Using superconducting cables, and employing permeable materials merely to reduce the fringe field, this limit can be exceeded and fields of more than 10 T can be obtained. A quench denotes the sudden transition from the superconducting to the normal conducting state. The drastic increase in electrical resistivity causes ohmic heating. The dissipated heat yields a temperature rise in the coil and causes the quench to propagate. The resulting high voltages and excessive temperatures can result in an irreversible damage of the magnet - to the extend of a cable melt-down. The quench behavior of a magnet depends on numerous factors, e.g. the magnet design, the applied magnet protection measures, the external electrical network, electrical and thermal material properties, and induced eddy current losses. The analysis and optimizat...
The exergy fields in transport processes: Their calculation and use
Energy Technology Data Exchange (ETDEWEB)
Lior, N.; Sarmiento-Darkin, W.; Al-Sharqawi, H.S. [University of Penn, Philadelphia, PA (United States). Dept. of Mechanical Engineering & Applied Mechanics
2006-04-15
This paper is a brief review of the method for analyzing the space and time dependent exergy and irreversibility fields in processes. It presents the basic equations, the method for their use, major literature sources, and three examples from the authors' work: flow desiccation, combustion of oil droplets, and combustion of pulverized coal. Conclusions from this Second Law analysis are used to attempt process improvement suggestions.
Velocity field calculation for non-orthogonal numerical grids
Energy Technology Data Exchange (ETDEWEB)
Flach, G. P. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)
2015-03-01
Computational grids containing cell faces that do not align with an orthogonal (e.g. Cartesian, cylindrical) coordinate system are routinely encountered in porous-medium numerical simulations. Such grids are referred to in this study as non-orthogonal grids because some cell faces are not orthogonal to a coordinate system plane (e.g. xy, yz or xz plane in Cartesian coordinates). Non-orthogonal grids are routinely encountered at the Savannah River Site in porous-medium flow simulations for Performance Assessments and groundwater flow modeling. Examples include grid lines that conform to the sloping roof of a waste tank or disposal unit in a 2D Performance Assessment simulation, and grid surfaces that conform to undulating stratigraphic surfaces in a 3D groundwater flow model. Particle tracking is routinely performed after a porous-medium numerical flow simulation to better understand the dynamics of the flow field and/or as an approximate indication of the trajectory and timing of advective solute transport. Particle tracks are computed by integrating the velocity field from cell to cell starting from designated seed (starting) positions. An accurate velocity field is required to attain accurate particle tracks. However, many numerical simulation codes report only the volumetric flowrate (e.g. PORFLOW) and/or flux (flowrate divided by area) crossing cell faces. For an orthogonal grid, the normal flux at a cell face is a component of the Darcy velocity vector in the coordinate system, and the pore velocity for particle tracking is attained by dividing by water content. For a non-orthogonal grid, the flux normal to a cell face that lies outside a coordinate plane is not a true component of velocity with respect to the coordinate system. Nonetheless, normal fluxes are often taken as Darcy velocity components, either naively or with accepted approximation. To enable accurate particle tracking or otherwise present an accurate depiction of the velocity field for a non
International Nuclear Information System (INIS)
Streek, Jacco van de; Neumann, Marcus A.
2010-01-01
The accuracy of a dispersion-corrected density functional theory method is validated against 241 experimental organic crystal structures from Acta Cryst. Section E. This paper describes the validation of a dispersion-corrected density functional theory (d-DFT) method for the purpose of assessing the correctness of experimental organic crystal structures and enhancing the information content of purely experimental data. 241 experimental organic crystal structures from the August 2008 issue of Acta Cryst. Section E were energy-minimized in full, including unit-cell parameters. The differences between the experimental and the minimized crystal structures were subjected to statistical analysis. The r.m.s. Cartesian displacement excluding H atoms upon energy minimization with flexible unit-cell parameters is selected as a pertinent indicator of the correctness of a crystal structure. All 241 experimental crystal structures are reproduced very well: the average r.m.s. Cartesian displacement for the 241 crystal structures, including 16 disordered structures, is only 0.095 Å (0.084 Å for the 225 ordered structures). R.m.s. Cartesian displacements above 0.25 Å either indicate incorrect experimental crystal structures or reveal interesting structural features such as exceptionally large temperature effects, incorrectly modelled disorder or symmetry breaking H atoms. After validation, the method is applied to nine examples that are known to be ambiguous or subtly incorrect
A thermal model for czochralski silicon crystal growth with an axial magnetic field
Hjellming, L. N.
1990-07-01
This paper presents a thermal model for molten silicon in a Czochralski crystal puller system with an applied uniform axial magnetic field. The melt depth is treated as continually decreasing, which affects the thermal environment of the melt and crystal. The radiative heat loss and the input heat flux are treated as functions of time, with a constraint placed on the heat lost to the crystal from the melt. As the melt motion reaches a steady state rapidly, the temperature and flow fields are treated as instantaneously steady at each melt depth. The heat transport is a mixture of conduction and convection, and by considering the crystal and crucible to be rotating with the same angular velocity, the flows driven by buoyancy and thermocapillarity are isolated and provide the convective heat transport in the melt for the range of magnetic field strengths 0.2 ≤ B ≤ 1.0T.
Stroboscopic topographies on iron borate crystal in 9.6 MHz rf magnetic field
International Nuclear Information System (INIS)
Mitsui, Takaya; Imai, Yasuhiko; Kikuta, Seishi
2003-01-01
The influence of magnetoacoustic wave on the crystal deformation was studied by stroboscopic double crystal X-ray topography. The acoustic wave was excited by the rf magnetic field, which was synchronized with synchrotron radiation X-ray pulse. In measured rocking curves of FeBO 3 (4 4 4) reflection, we observed, for the first time, that the application of rf magnetic field (|H rf | max >8.4 Oe) brought about the extreme narrowing of full width at half maximum (FWHM). Recorded topographs showed that the narrowing of FWHM was due to the magnetoacoustic standing wave which is excited in FeBO 3 crystal. In our experiments, the influence of additional static magnetic field on the magnetoacoustic standing wave of FeBO 3 crystal was investigated too
Pavlova, Anna; Parks, Jerry M; Gumbart, James C
2018-02-13
Corrinoid cofactors such as cobalamin are used by many enzymes and are essential for most living organisms. Therefore, there is broad interest in investigating cobalamin-protein interactions with molecular dynamics simulations. Previously developed parameters for cobalamins are based mainly on crystal structure data. Here, we report CHARMM-compatible force field parameters for several corrinoids developed from quantum mechanical calculations. We provide parameters for corrinoids in three oxidation states, Co 3+ , Co 2+ , and Co 1+ , and with various axial ligands. Lennard-Jones parameters for the cobalt center in the Co(II) and Co(I) states were optimized using a helium atom probe, and partial atomic charges were obtained with a combination of natural population analysis (NPA) and restrained electrostatic potential (RESP) fitting approaches. The Force Field Toolkit was used to optimize all bonded terms. The resulting parameters, determined solely from calculations of cobalamin alone or in water, were then validated by assessing their agreement with density functional theory geometries and by analyzing molecular dynamics simulation trajectories of several corrinoid proteins for which X-ray crystal structures are available. In each case, we obtained excellent agreement with the reference data. In comparison to previous CHARMM-compatible parameters for cobalamin, we observe a better agreement for the fold angle and lower RMSD in the cobalamin binding site. The approach described here is readily adaptable for developing CHARMM-compatible force-field parameters for other corrinoids or large biomolecules.
Full 3D FDTD analysis of Electromagnetic Field in Photonic Crystal VCSEL
International Nuclear Information System (INIS)
Liu Fa; Xu Chen; Xie Yiyang; Zhao Zhenbo; Zhou Kang; Wang Baoqiang; Liu Yingming; Shen Guangdi
2011-01-01
The effect of etch damage to the mode characteristics of photonic crystal vertical cavity surface emitting lasers was simulated in this paper. The devices simulated in this paper are 850-nm GaAs-based VCSELs with photonic crystal. And the devices were simulated by using finite difference time domain (FDTD) method. Limited to the computer resource, the top DBR was simulated only, and the traverse size was smaller than the real size. In order to highlight the impact of the etch damage, several kinds of light sources and photonic crystal structures were simulated separately, and each situation is calculated in the condition of ideal photonic crystal and photonic crystal with etch damage respectively. All parameters of device and light feature are referred to the real condition.
Full 3D FDTD analysis of Electromagnetic Field in Photonic Crystal VCSEL
Energy Technology Data Exchange (ETDEWEB)
Liu Fa; Xu Chen; Xie Yiyang; Zhao Zhenbo; Zhou Kang; Wang Baoqiang; Liu Yingming; Shen Guangdi, E-mail: liufa20719@126.com [Key Laboratory of Opto-electronics Technology (Beijing University of Technology), Ministry of Education, Beijing University of Technology, 100 Ping Le Yuan, Chaoyang District, Beijing 100124 (China)
2011-02-01
The effect of etch damage to the mode characteristics of photonic crystal vertical cavity surface emitting lasers was simulated in this paper. The devices simulated in this paper are 850-nm GaAs-based VCSELs with photonic crystal. And the devices were simulated by using finite difference time domain (FDTD) method. Limited to the computer resource, the top DBR was simulated only, and the traverse size was smaller than the real size. In order to highlight the impact of the etch damage, several kinds of light sources and photonic crystal structures were simulated separately, and each situation is calculated in the condition of ideal photonic crystal and photonic crystal with etch damage respectively. All parameters of device and light feature are referred to the real condition.
Magnetic field optimisation and orbit calculation for VEC superconducting cyclotron
International Nuclear Information System (INIS)
Debnath, J.; Dey, M.K.; Mallik, C.; Bhandari, R.K.
2003-01-01
At VECC, Kolkata preparations are underway to measure the magnetic field of the cyclotron. Also once the superconducting cyclotron is assembled prediction of beam related parameters will be a very important exercise to carry out. Considering this the beam behaviour in the cyclotron will be crucial to achieve these goals. The present paper deals with the efforts in this direction and using a test beam of He 1+ 20 MeV/n the trim coil currents, the tune variation and the (r,Pr) behaviour of the central trajectory
Surface incompressibility from semiclassical relativistic mean field calculations
International Nuclear Information System (INIS)
Patra, S.K.; Centelles, M.; Vinas, X.; Estal, M. del
2002-01-01
By using the scaling method and the Thomas-Fermi and extended Thomas-Fermi approaches to relativistic mean field theory the surface contribution to the leptodermous expansion of the finite nuclei incompressibility K A has been self-consistently computed. The validity of the simplest expansion, which contains volume, volume-symmetry, surface, and Coulomb terms, is examined by comparing it with self-consistent results of K A for some currently used nonlinear σ-ω parameter sets. A numerical estimate of higher-order contributions to the leptodermous expansion, namely, the curvature and surface-symmetry terms, is made
On the use of quartic force fields in variational calculations
Fortenberry, Ryan C.; Huang, Xinchuan; Yachmenev, Andrey; Thiel, Walter; Lee, Timothy J.
2013-06-01
Quartic force fields (QFFs) have been shown to be one of the most effective ways to efficiently compute vibrational frequencies for small molecules. In this letter we discuss how the simple-internal or bond-length bond-angle (BLBA) coordinates can be transformed into Morse-cosine (-sine) coordinates which produce potential energy surfaces from QFFs that possess proper limiting behavior and can describe the vibrational (or rovibrational) energy levels of an arbitrary molecular system to 5 cm-1 or better compared to experiment. We investigate parameter scaling in the Morse coordinate, symmetry considerations, and examples of transformed QFFs making use of the MULTIMODE, TROVE, and VTET variational vibrational methods.
International Nuclear Information System (INIS)
Pyzer-Knapp, Edward O.; Thompson, Hugh P. G.; Day, Graeme M.
2016-01-01
An empirically parameterized intermolecular force field is developed for crystal structure modelling and prediction. The model is optimized for use with an atomic multipole description of electrostatic interactions. 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%
International Nuclear Information System (INIS)
Mokhtari, F.; Bouabdallah, A.; Merah, A.; Oualli, H.
2012-01-01
The effect of axial magnetic field of different intensities on pressure in silicon Czochralski crystal growth is investigated in cylindrical and hemispherical geometries with rotating crystal and crucible and thermocapillary convection. As one important thermodynamic variable, the pressure is found to be more sensitive than temperature to magnetic field with strong dependence upon the vorticity field. The pressure at the triple point is proposed as a convenient parameter to control the homogeneity of the grown crystal. With a gradual increase of the magnetic field intensity the convection effect can be reduced without thermal fluctuations in the silicon melt. An evaluation of the magnetic interaction parameter critical value corresponding to flow, pressure and temperature homogenization leads to the important result that a relatively low axial magnetic field is required for the spherical system comparatively to the cylindrical one. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
Energy Technology Data Exchange (ETDEWEB)
Mokhtari, F. [Universite Mouloud Mammeri de Tizi Ouzou (Algeria); LTSE Laboratory, University of Science and Technology. BP 32 Elalia, Babezzouar, Algiers (Algeria); Bouabdallah, A. [LTSE Laboratory, University of Science and Technology. BP 32 Elalia, Babezzouar, Algiers (Algeria); Merah, A. [LTSE Laboratory, University of Science and Technology. BP 32 Elalia, Babezzouar, Algiers (Algeria); M' hamed Bougara University, Boumerdes (Algeria); Oualli, H. [EMP, Bordj ElBahri, Algiers (Algeria)
2012-12-15
The effect of axial magnetic field of different intensities on pressure in silicon Czochralski crystal growth is investigated in cylindrical and hemispherical geometries with rotating crystal and crucible and thermocapillary convection. As one important thermodynamic variable, the pressure is found to be more sensitive than temperature to magnetic field with strong dependence upon the vorticity field. The pressure at the triple point is proposed as a convenient parameter to control the homogeneity of the grown crystal. With a gradual increase of the magnetic field intensity the convection effect can be reduced without thermal fluctuations in the silicon melt. An evaluation of the magnetic interaction parameter critical value corresponding to flow, pressure and temperature homogenization leads to the important result that a relatively low axial magnetic field is required for the spherical system comparatively to the cylindrical one. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
Calculation of pressure fields from arbitrarily shaped, apodized, and excited ultrasound transducers
DEFF Research Database (Denmark)
Jensen, Jørgen Arendt; Svendsen, Niels Bruun
1992-01-01
A method for simulation of pulsed pressure fields from arbitrarily shaped, apodized and excited ultrasound transducers is suggested. It relies on the Tupholme-Stepanishen method for calculating pulsed pressure fields, and can also handle the continuous wave and pulse-echo case. The field...... is calculated by dividing the surface into small rectangles and then Summing their response. A fast calculation is obtained by using the far-field approximation. Examples of the accuracy of the approach and actual calculation times are given...
van de Streek, Jacco; Neumann, Marcus A
2010-10-01
This paper describes the validation of a dispersion-corrected density functional theory (d-DFT) method for the purpose of assessing the correctness of experimental organic crystal structures and enhancing the information content of purely experimental data. 241 experimental organic crystal structures from the August 2008 issue of Acta Cryst. Section E were energy-minimized in full, including unit-cell parameters. The differences between the experimental and the minimized crystal structures were subjected to statistical analysis. The r.m.s. Cartesian displacement excluding H atoms upon energy minimization with flexible unit-cell parameters is selected as a pertinent indicator of the correctness of a crystal structure. All 241 experimental crystal structures are reproduced very well: the average r.m.s. Cartesian displacement for the 241 crystal structures, including 16 disordered structures, is only 0.095 Å (0.084 Å for the 225 ordered structures). R.m.s. Cartesian displacements above 0.25 A either indicate incorrect experimental crystal structures or reveal interesting structural features such as exceptionally large temperature effects, incorrectly modelled disorder or symmetry breaking H atoms. After validation, the method is applied to nine examples that are known to be ambiguous or subtly incorrect.
Parallel computation of automatic differentiation applied to magnetic field calculations
International Nuclear Information System (INIS)
Hinkins, R.L.; Lawrence Berkeley Lab., CA
1994-09-01
The author presents a parallelization of an accelerator physics application to simulate magnetic field in three dimensions. The problem involves the evaluation of high order derivatives with respect to two variables of a multivariate function. Automatic differentiation software had been used with some success, but the computation time was prohibitive. The implementation runs on several platforms, including a network of workstations using PVM, a MasPar using MPFortran, and a CM-5 using CMFortran. A careful examination of the code led to several optimizations that improved its serial performance by a factor of 8.7. The parallelization produced further improvements, especially on the MasPar with a speedup factor of 620. As a result a problem that took six days on a SPARC 10/41 now runs in minutes on the MasPar, making it feasible for physicists at Lawrence Berkeley Laboratory to simulate larger magnets
International Nuclear Information System (INIS)
Kosztyla, Robert; Pierce, Greg; Ploquin, Nicolas; Roumeliotis, Michael; Schinkel, Colleen
2016-01-01
Purpose: To determine the source of systematic monitor unit (MU) calculation discrepancies between RadCalc and Eclipse treatment planning software for three-dimensional conformal radiotherapy field-in-field breast treatments. Methods: Data were reviewed for 28 patients treated with a field-in-field breast technique with MU calculations from RadCalc that were larger than MU calculations from Eclipse for at least one field. The distance of the calculation point from the jaws was measured in each field’s beam’s-eye-view and compared with the percentage difference in MU (%ΔMU) between RadCalc and Eclipse. 10×10, 17×13 and 20×20 cm 2 beam profiles were measured using the Profiler 2 diode array for 6-MV photon beams and compared with profiles calculated with Eclipse and RadCalc using a gamma analysis (3%, 3 mm). Results: The mean %ΔMU was 1.3%±0.3%. There was a statistically-significant correlation between %ΔMU and the distance of the calculation point from the Y jaw (r=−0.43, p<0.001). RadCalc profiles differed from measured profiles, especially near the jaws. The gamma pass rate for 6-MV fields of 17×13 cm 2 field size was 95%±1% for Eclipse-generated profiles and 53%±20% for RadCalc-generated profiles (p=0.01). Conclusions: Calculations using RadCalc for field-in-field breast plans resulted in MUs that were larger than expected from previous clinical experience with wedged plans with calculation points far from the jaws due to the position of the calculation point near the jaws in the beam’s-eye-view of each field.
Energy Technology Data Exchange (ETDEWEB)
Kosztyla, Robert; Pierce, Greg; Ploquin, Nicolas; Roumeliotis, Michael; Schinkel, Colleen [Tom Baker Cancer Centre, Calgary, AB, Tom Baker Cancer Centre, Tom Baker Cancer Centre, Tom Baker Cancer Centre, Calgary, AB, Tom Baker Cancer Centre, Calgary, AB (Canada)
2016-08-15
Purpose: To determine the source of systematic monitor unit (MU) calculation discrepancies between RadCalc and Eclipse treatment planning software for three-dimensional conformal radiotherapy field-in-field breast treatments. Methods: Data were reviewed for 28 patients treated with a field-in-field breast technique with MU calculations from RadCalc that were larger than MU calculations from Eclipse for at least one field. The distance of the calculation point from the jaws was measured in each field’s beam’s-eye-view and compared with the percentage difference in MU (%ΔMU) between RadCalc and Eclipse. 10×10, 17×13 and 20×20 cm{sup 2} beam profiles were measured using the Profiler 2 diode array for 6-MV photon beams and compared with profiles calculated with Eclipse and RadCalc using a gamma analysis (3%, 3 mm). Results: The mean %ΔMU was 1.3%±0.3%. There was a statistically-significant correlation between %ΔMU and the distance of the calculation point from the Y jaw (r=−0.43, p<0.001). RadCalc profiles differed from measured profiles, especially near the jaws. The gamma pass rate for 6-MV fields of 17×13 cm{sup 2} field size was 95%±1% for Eclipse-generated profiles and 53%±20% for RadCalc-generated profiles (p=0.01). Conclusions: Calculations using RadCalc for field-in-field breast plans resulted in MUs that were larger than expected from previous clinical experience with wedged plans with calculation points far from the jaws due to the position of the calculation point near the jaws in the beam’s-eye-view of each field.
Crystal-field splittings in rare-earth-based hard magnets: An ab initio approach
Delange, Pascal; Biermann, Silke; Miyake, Takashi; Pourovskii, Leonid
2017-10-01
We apply the first-principles density functional theory + dynamical mean-field theory framework to evaluate the crystal-field splitting on rare-earth sites in hard magnetic intermetallics. An atomic (Hubbard-I) approximation is employed for local correlations on the rare-earth 4 f shell and self-consistency in the charge density is implemented. We reduce the density functional theory self-interaction contribution to the crystal-field splitting by properly averaging the 4 f charge density before recalculating the one-electron Kohn-Sham potential. Our approach is shown to reproduce the experimental crystal-field splitting in the prototypical rare-earth hard magnet SmCo5. Applying it to R Fe12 and R Fe12X hard magnets (R =Nd , Sm and X =N , Li), we obtain in particular a large positive value of the crystal-field parameter A20〈r2〉 in NdFe12N resulting in a strong out-of-plane anisotropy observed experimentally. The sign of A20〈r2〉 is predicted to be reversed by substituting N with Li, leading to a strong out-of-plane anisotropy in SmFe12Li . We discuss the origin of this strong impact of N and Li interstitials on the crystal-field splitting on rare-earth sites.
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.
Crystallization of inorganic salts from aqueous solutions in a microwave field
International Nuclear Information System (INIS)
Kochetkov, S. E.; Kuznetsov, V. A.; Lyashenko, A. V.; Bakshutov, V. S.
2006-01-01
The crystallization of some inorganic salts (KH 2 PO 4 , NaCl, Sr(NO 3 ) 2 , KNO 2 , Ca(OH) 2 ) by the thermal-gradient (with decreasing temperature) and solvent-evaporation methods using microwave heating of solutions is investigated. It is established that the growth rates of single crystals in a microwave field are an order of magnitude higher than obtained in other known techniques at comparable crystallization temperatures and supersaturations. For example, the growth rate of prismatic faces {100} of KH 2 PO 4 crystals is as high as 11 mm/day at supersaturations of ∼1.2%. The results obtained are discussed in the context of the effect of microwave radiation on the adsorption surface layers of crystals. Fine-grained phases of the salts under study are obtained by evaporation of the solvent
International Nuclear Information System (INIS)
Beckman, S.P.; Chelikowsky, James R.
2007-01-01
The structure and properties of vacancies in a 2 nm Si nano-crystal are studied using a real space density functional theory/pseudopotential method. It is observed that a vacancy's electronic properties and energy of formation are directly related to the local symmetry of the vacancy site. The formation energy for vacancies and Frenkel pair are calculated. It is found that both defects have lower energy in smaller crystals. In a 2 nm nano-crystal the energy to form a Frenkel pair is 1.7 eV and the energy to form a vacancy is no larger than 2.3 eV. The energy barrier for vacancy diffusion is examined via a nudged elastic band algorithm
Engineering the near-field imaging of a rectangular-lattice photonic-crystal slab in the second band
Institute of Scientific and Technical Information of China (English)
无
2009-01-01
Imaging properties of a two-dimensional rectangular-lattice photonic crystal (PC) slab consisting of air holes immersed in a dielectric are studied in this work. The field patterns of electromagnetic waves radiated from a point source through the PC slab are calculated with the finite-difference time-domain method. Comparing the field patterns with the corresponding equifrequency-surface contours simulated by the plane-wave expansion method, we find that an excellent-quality near-field image may be formed through the PC slab by the mechanisms of the simultaneous action of the self-collimation effect and the negative-refraction effect. Near-field imaging may be obtained within two different frequency regions in two vertical directions of the PC slab.
High-field magnetization of UCuGe single crystal
Czech Academy of Sciences Publication Activity Database
Andreev, Alexander V.; Mushnikov, N. V.; Gozo, T.; Honda, F.; Sechovský, V.; Prokeš, K.
346-347, - (2004), s. 132-136 ISSN 0921-4526 R&D Projects: GA ČR GA202/02/0739 Institutional research plan: CEZ:AV0Z1010914 Keywords : uranium intermetallics * UCuGe * high fields * magnetic anisotropy * field-induced phase transition Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.679, year: 2004
A simple localized-itinerant model for PrAl3: crystal field and exchange effects
International Nuclear Information System (INIS)
Ranke, P.J. von; Palermo, L.
1990-01-01
We present a simple magnetic model for PrAl sub(3). The effects of crystal field are treated using a reduced set of levels and the corresponding wave functions are extracted from the actual crystal field levels of Pr sup(+3) in a hexagonal symmetry. The exchange between 4f- and conduction electrons are dealt within a molecular field approximation. An analytical magnetic state equation is derived and the magnetic behaviour discussed. The parameters of the model are estimated from a fitting of the inverse susceptibility of PrAl sub(3) given in the literature. (author)
Spin-Orbit Qubits of Rare-Earth-Metal Ions in Axially Symmetric Crystal Fields
Bertaina, S.; Shim, J. H.; Gambarelli, S.; Malkin, B. Z.; Barbara, B.
2009-11-01
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 μs) and the Rabi frequency ΩR is anisotropic. Here, we present a study of the variations of ΩR(H→0) with the magnitude and direction of the static magnetic field H→0 for the odd Er167 isotope in a single crystal CaWO4:Er3+. The hyperfine interactions split the ΩR(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.
Numerical calculation of transient field effects in quenching superconducting magnets
International Nuclear Information System (INIS)
Schwerg, Juljan Nikolai
2010-01-01
The maximum obtainable magnetic induction of accelerator magnets, relying on normal conducting cables and iron poles, is limited to around 2 T because of ohmic losses and iron saturation. Using superconducting cables, and employing permeable materials merely to reduce the fringe field, this limit can be exceeded and fields of more than 10 T can be obtained. A quench denotes the sudden transition from the superconducting to the normal conducting state. The drastic increase in electrical resistivity causes ohmic heating. The dissipated heat yields a temperature rise in the coil and causes the quench to propagate. The resulting high voltages and excessive temperatures can result in an irreversible damage of the magnet - to the extend of a cable melt-down. The quench behavior of a magnet depends on numerous factors, e.g. the magnet design, the applied magnet protection measures, the external electrical network, electrical and thermal material properties, and induced eddy current losses. The analysis and optimization of the quench behavior is an integral part of the construction of any superconducting magnet. The dissertation is divided in three complementary parts, i.e. the thesis, the detailed treatment and the appendix. In the thesis the quench process in superconducting accelerator magnets is studied. At first, we give an overview over features of accelerator magnets and physical phenomena occurring during a quench. For all relevant effects numerical models are introduced and adapted. The different models are weakly coupled in the quench algorithm and solved by means of an adaptive time-stepping method. This allows to resolve the variation of material properties as well as time constants. The quench model is validated by means of measurement data from magnets of the Large Hadron Collider. In a second step, we show results of protection studies for future accelerator magnets. The thesis ends with a summary of the results and a critical outlook on aspects which could
Numerical calculation of transient field effects in quenching superconducting magnets
Energy Technology Data Exchange (ETDEWEB)
Schwerg, Juljan Nikolai
2010-07-01
The maximum obtainable magnetic induction of accelerator magnets, relying on normal conducting cables and iron poles, is limited to around 2 T because of ohmic losses and iron saturation. Using superconducting cables, and employing permeable materials merely to reduce the fringe field, this limit can be exceeded and fields of more than 10 T can be obtained. A quench denotes the sudden transition from the superconducting to the normal conducting state. The drastic increase in electrical resistivity causes ohmic heating. The dissipated heat yields a temperature rise in the coil and causes the quench to propagate. The resulting high voltages and excessive temperatures can result in an irreversible damage of the magnet - to the extend of a cable melt-down. The quench behavior of a magnet depends on numerous factors, e.g. the magnet design, the applied magnet protection measures, the external electrical network, electrical and thermal material properties, and induced eddy current losses. The analysis and optimization of the quench behavior is an integral part of the construction of any superconducting magnet. The dissertation is divided in three complementary parts, i.e. the thesis, the detailed treatment and the appendix. In the thesis the quench process in superconducting accelerator magnets is studied. At first, we give an overview over features of accelerator magnets and physical phenomena occurring during a quench. For all relevant effects numerical models are introduced and adapted. The different models are weakly coupled in the quench algorithm and solved by means of an adaptive time-stepping method. This allows to resolve the variation of material properties as well as time constants. The quench model is validated by means of measurement data from magnets of the Large Hadron Collider. In a second step, we show results of protection studies for future accelerator magnets. The thesis ends with a summary of the results and a critical outlook on aspects which could
Calculation of near-field concentrations of hydrogen sulphide
International Nuclear Information System (INIS)
Baynes, C.J.
1985-03-01
This report provides simulations of the near-field dispersion in the atmosphere of postulated releases of hydrogen sulphide gas (H2S) at a heavy water plant. The size and extent of the flammable or detonable gas clouds which might result are estimated. This work was undertaken to support experimental studies of the detonability of H2S releases. Thirty-six different cases were simulated involving the catastrophic failure of a liquid H2S storage tank or tank car of H2S. The major variables were the size of the release, the initial mixing ratio of gas with ambient air, and the wind speed. Since the gas/air mixture is initially heavier than air, an existing heavy gas mathematical model (DENZ) was used for these simulations. The model was modified to provide the outputs needed to support the experimental studies. The outputs were the mass of H2S in the cloud, the mass and volume of the cloud, its radius at ground level and its temperature, all as functions of distance and time from release. The edge of the cloud was defined by a given concentration of H2S in air. The simulations were repeated for ten different values of this parameter, ranging between 3% and 40% H2S by volume. Simulations were also performed using a simple 'top-hat' mixing model to predict the length of the flammable or detonable jet formed at the break in a pipe carrying H2S vapour under pressure. The analysis was conducted for four postulated pipe break diameters and repeated for the same ten concentration levels used in the storage tank studies. The report presents a summary of the results. The complete outputs from the 36 storage tank failure simulations are available on floppy disks in a format suitable for detailed examination using any IBM-PC compatible microcomputer system
Dose Measurement and Calculation of Asymmetric X-Ray Fields from Therapeutic Linac
International Nuclear Information System (INIS)
El-Attar, A. L.; Abdel-Wanees, M. E.; Hashem, M. A.
2011-01-01
Linear accelerators with x-ray collimators that move independently are becoming increasingly common for treatment with asymmetric fields. In this paper we present a simplified approach to the calculation of dose for asymmetric fields. A method is described for calculating the beam profiles, depth doses and output factors for asymmetric fields of radiation produced by linear accelerators (siemens mevatron M2) with independent jaws. Values are calculated from data measured for symmetric fields. Symmetric field data are modified using opened off-axis factors (OAFs) and primary off-centre ratios (POCRs) which are obtained from in air measurements of the largest possible opened field. Beam hardening occurring within the flattening filter is taken into account using of attenuation coefficients for opened field and used to generate the opened POCR at different depths. A full investigation to compare measured and calculated profiles demonstrates favorable agreement.
International Nuclear Information System (INIS)
Bergeret, G.; Abon, M.; Tardy, B.; Teichner, S.J.
1974-01-01
A probe-hole field emission microscope was used to determine the work function of clean molybdenum single crystal planes relative to the average work function of the field emitter, assumed to be 4.20 eV. Results are compared with other available data
Dislocation motion in InSb crystals under a magnetic field
Darinskaya, E V; Erofeeva, S A
2002-01-01
Dislocation displacements under the action of a permanent magnetic field without mechanical loading in differently doped InSb crystals are investigated. The dependences of the mean dislocation path length and the relative number of divergence and tightening half-loops on the magnetic induction and preliminary load are obtained. Experiments on n-InSb crystals with Te impurities and on p-InSb crystals with Ge impurities have shown a sensitivity of the magnetoplasticity to the conductivity type and the dopant content. Study of the magnetoplastic effect in the initial deformed InSb crystals shows that internal stresses decrease the lengths of divergence dislocation paths and simultaneously increase the threshold magnetic field above which the magnetoplastic effect exists. Possible reasons for the observed phenomena are discussed.
Magnetic properties and crystal field effects in TlLnX2 compounds (X=S, Se, Te)
International Nuclear Information System (INIS)
Duczmal, M.; Pawlak, L.
1997-01-01
Ternary thallium lanthanide chalcogenides TlLnX 2 (X=S, Se or Te) crystallize in the α-NaFeO 2 type of structure (R anti 3m). Each kind of the metal ions, surrounded by the distorted chalcogenide octahedra, forms separate layers. The TlX 6 octahedra are strongly elongated and the LnX 6 octahedra slightly shrunk along the threefold axis. The deformations of the coordination polyhedra and the cell volumes change regularly with the lanthanide ionic radii. The difference between the experimental and the calculated M-X distances increases on going from sulphides to tellurides, as a result of the growing covalent character of the bonds. The crystal field parameters were estimated from the high field magnetization (0-14 T) assuming trigonal distortion of the octahedral symmetry of LnX 6 polyhedra. The second-order crystal field parameters were found to correlate with the deformation of the lanthanide ions' environments. No magnetic transition was observed down to 4.2 K. (orig.)
Sabanskis, A.; Virbulis, J.
2018-05-01
Mathematical modelling is employed to numerically analyse the dynamics of the Czochralski (CZ) silicon single crystal growth. The model is axisymmetric, its thermal part describes heat transfer by conduction and thermal radiation, and allows to predict the time-dependent shape of the crystal-melt interface. Besides the thermal field, the point defect dynamics is modelled using the finite element method. The considered process consists of cone growth and cylindrical phases, including a short period of a reduced crystal pull rate, and a power jump to avoid large diameter changes. The influence of the thermal stresses on the point defects is also investigated.
Calculation of the radiation force on a cylinder in a standing wave acoustic field
Energy Technology Data Exchange (ETDEWEB)
Haydock, David [Unilever R and D Colworth, Sharnbrook, Bedford MK44 1LQ (United Kingdom); Department of Physics, Theoretical Physics, University of Oxford, 1 Keble Road, Oxford OX1 3NP (United Kingdom)
2005-04-15
We present a new calculation of the radiation force on a cylinder in a standing wave acoustic field. We use the formula to calculate the force on a cylinder which is free to move in the field and one which is fixed in space.
Calculation of the radiation force on a cylinder in a standing wave acoustic field
International Nuclear Information System (INIS)
Haydock, David
2005-01-01
We present a new calculation of the radiation force on a cylinder in a standing wave acoustic field. We use the formula to calculate the force on a cylinder which is free to move in the field and one which is fixed in space
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...... are quantitatively reproduced by existing theories, which take into account the reduced scattering of the conduction electrons by the magnetic ions due to the creation of the superconducting energy gap 2Δ(T)....
Self-Aligned Growth of Organic Semiconductor Single Crystals by Electric Field.
Kotsuki, Kenji; Obata, Seiji; Saiki, Koichiro
2016-01-19
We proposed a novel but facile method for growing organic semiconductor single-crystals via solvent vapor annealing (SVA) under electric field. In the conventional SVA growth process, nuclei of crystals appeared anywhere on the substrate and their crystallographic axes were randomly distributed. We applied electric field during the SVA growth of 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT) on the SiO2/Si substrate on which a pair of electrodes had been deposited beforehand. Real-time observation of the SVA process revealed that rodlike single crystals grew with their long axes parallel to the electric field and bridged the prepatterned electrodes. As a result, C8-BTBT crystals automatically formed a field effect transistor (FET) structure and the mobility reached 1.9 cm(2)/(V s). Electric-field-assisted SVA proved a promising method for constructing high-mobility single-crystal FETs at the desired position by a low-cost solution process.
Generalized monitor unit calculation for the Varian enhanced dynamic wedge field
International Nuclear Information System (INIS)
Liu Chihray; Kim, Siyong; Kahler, Darren L.; Palta, Jatinder R.
2003-01-01
The generalized monitor unit (MU) calculation equation for the Varian enhanced dynamic wedge (EDW) is derived. The assumption of this MU calculation method is that the wedge factor of the EDW at the center of the field is a function of field size, the position of the center of the field in the wedge direction, and the final position of the moving jaw. The wedge factors at the center of the field in both symmetric and asymmetric fields are examined. The difference between calculated and measured wedge factors is within 1.0%. The method developed here is easy to implement. The only datum required in addition to the standard set of conventional physical wedge implementation data is the off-axis output factor for the open field in the reference condition. The off-center point calculation is also examined. For the off-center point calculation, the dose profile in the wedge direction for the largest EDW field is used to obtain the relative off-center ratio in any smaller wedge field. The accuracy of the off-center point calculation decreases when the point of calculation is too close to the field edge
Chauvin, Nicolas; Mavel, Amaury; Jaffal, Ali; Patriarche, Gilles; Gendry, Michel
2018-02-01
Excitation photoluminescence spectroscopy is usually used to extract the crystal field splitting (ΔCR) and spin orbit coupling (ΔSO) parameters of wurtzite (Wz) InP nanowires (NWs). However, the equations expressing the valence band splitting are symmetric with respect to these two parameters, and a choice ΔCR > ΔSO or ΔCR InP NWs grown on silicon. The experimental results combined with a theoretical model and finite difference time domain calculations allow us to conclude that ΔCR > ΔSO in Wz InP.
Energy Technology Data Exchange (ETDEWEB)
Zhang, Zhen [School of Electrical Engineering and Automation, Tianjin University, Tianjin 300072 (China); Xia, Changliang [School of Electrical Engineering and Automation, Tianjin University, Tianjin 300072 (China); Tianjin Engineering Center of Electric Machine System Design and Control, Tianjin 300387 (China); Yan, Yan, E-mail: yanyan@tju.edu.cn [School of Electrical Engineering and Automation, Tianjin University, Tianjin 300072 (China); Geng, Qiang [Tianjin Engineering Center of Electric Machine System Design and Control, Tianjin 300387 (China); Shi, Tingna [School of Electrical Engineering and Automation, Tianjin University, Tianjin 300072 (China)
2017-08-01
Highlights: • A hybrid analytical model is developed for field calculation of multilayer IPM machines. • The rotor magnetic field is calculated by the magnetic equivalent circuit method. • The field in the stator and air-gap is calculated by subdomain technique. • The magnetic scalar potential on rotor surface is modeled as trapezoidal distribution. - Abstract: Due to the complicated rotor structure and nonlinear saturation of rotor bridges, it is difficult to build a fast and accurate analytical field calculation model for multilayer interior permanent magnet (IPM) machines. In this paper, a hybrid analytical model suitable for the open-circuit field calculation of multilayer IPM machines is proposed by coupling the magnetic equivalent circuit (MEC) method and the subdomain technique. In the proposed analytical model, the rotor magnetic field is calculated by the MEC method based on the Kirchhoff’s law, while the field in the stator slot, slot opening and air-gap is calculated by subdomain technique based on the Maxwell’s equation. To solve the whole field distribution of the multilayer IPM machines, the coupled boundary conditions on the rotor surface are deduced for the coupling of the rotor MEC and the analytical field distribution of the stator slot, slot opening and air-gap. The hybrid analytical model can be used to calculate the open-circuit air-gap field distribution, back electromotive force (EMF) and cogging torque of multilayer IPM machines. Compared with finite element analysis (FEA), it has the advantages of faster modeling, less computation source occupying and shorter time consuming, and meanwhile achieves the approximate accuracy. The analytical model is helpful and applicable for the open-circuit field calculation of multilayer IPM machines with any size and pole/slot number combination.
International Nuclear Information System (INIS)
Song, Linze; Shi, Qiang
2015-01-01
We present a new non-perturbative method to calculate the charge carrier mobility using the imaginary time path integral approach, which is based on the Kubo formula for the conductivity, and a saddle point approximation to perform the analytic continuation. The new method is first tested using a benchmark calculation from the numerical exact hierarchical equations of motion method. Imaginary time path integral Monte Carlo simulations are then performed to explore the temperature dependence of charge carrier delocalization and mobility in organic molecular crystals (OMCs) within the Holstein and Holstein-Peierls models. The effects of nonlocal electron-phonon interaction on mobility in different charge transport regimes are also investigated
International Nuclear Information System (INIS)
Gnutek, P; Rudowicz, C; Yang, Z Y
2009-01-01
The local structure and the spin Hamiltonian (SH) parameters, including the zero-field-splitting (ZFS) parameters D and (a+2F/3), and the Zeeman g factors g || and g perpendicular , are theoretically investigated for the Fe K 3+ -O I 2- center in KTaO 3 crystal. The microscopic SH (MSH) parameters are modeled within the framework of the crystal field (CF) theory employing the CF analysis (CFA) package, which also incorporates the MSH modules. Our approach takes into account the spin-orbit interaction as well as the spin-spin and spin-other-orbit interactions omitted in previous studies. The superposition model (SPM) calculations are carried out to provide input CF parameters for the CFA/MSH package. The combined SPM-CFA/MSH approach is used to consider various structural models for the Fe K 3+ -O I 2- defect center in KTaO 3 . This modeling reveals that the off-center displacement of the Fe 3+ ions, Δ 1 (Fe 3+ ), combined with an inward relaxation of the nearest oxygen ligands, Δ 2 (O 2- ), and the existence of the interstitial oxygen O I 2- give rise to a strong tetragonal crystal field. This finding may explain the large ZFS experimentally observed for the Fe K 3+ -O I 2- center in KTaO 3 . Matching the theoretical MSH predictions with the available structural data as well as electron magnetic resonance (EMR) and optical spectroscopy data enables predicting reasonable ranges of values of Δ 1 (Fe 3+ ) and Δ 2 (O 2- ) as well as the possible location of O I 2- ligands around Fe 3+ ions in KTaO 3 . The defect structure model obtained using the SPM-CFA/MSH approach reproduces very well the ranges of the experimental SH parameters D, g || and g perpendicular and importantly yields not only the correct magnitude of D but also the sign, unlike previous studies. More reliable predictions may be achieved when experimental data on (a+2F/3) and/or crystal field energy levels become available. Comparison of our results with those arising from alternative models existing
A methodology for calculating photovoltaic field output and effect of solar tracking strategy
International Nuclear Information System (INIS)
Hu, Yeguang; Yao, Yingxue
2016-01-01
Highlights: • A new methodology for calculating PV field output is proposed. • The reduction of diffuse radiation and albedo due to shading is considered. • The shadow behavior is accurately analyzed at a cell level. • Several simplified measures are taken to reduce the calculation work. • The field outputs with different solar tracking strategies are compared. - Abstract: This paper proposes an effective methodology for calculating the photovoltaic field output. A combination of two methods is first presented for optical performance calculation: point projection method for direction radiation, and Monte Carlo ray-tracing method for both diffuse radiation and albedo radiation. Based on the optical calculation, an accurate output of the photovoltaic field can be obtained through a cell-level simulation of PV system. Several simplified measures are taken to reduce the large amount of calculation work. The proposed methodology has been validated for accurate and fast calculation of field output. With the help of the developed code, this paper deals with the performance comparison between four typical tracking strategies. Through the comparative analysis, the field output is proved to be related to the tracking strategy. For a regular photovoltaic field, the equatorial and elevation-rolling tracking show the superior performance in annual field output to the azimuth-elevation and rolling-elevation tracking. A reasonable explanation for this difference has been presented in this paper.
Measurement and calculation of radiation fields of the Sandia irradiator for dried sewage solids
International Nuclear Information System (INIS)
Morris, M.E.
1981-03-01
The radiation field of the Sandia Irradiator for Dried Sewage Solids was measured. The results of the measurement are given in this report. In addition, theoretical calculations of the fields are given and then compared with the measured values. Elementary models of the radiation source geometry and irradiated product are found to be adequate and thus allow us to duplicate (through calculation) the important features of the measured fields
Crystal field of Dy in non-magnetic metals
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
Neutron Crystal-Field Spectroscopy and Susceptibility in ErcY1-cA1
DEFF Research Database (Denmark)
Heer, H.; Furrer, A.; Walker, E.
1974-01-01
Inelastic neutron scattering experiments and susceptibility measurements have been carried out on polycrystalline ErcY1-cAl2. A least-squares fitting procedure has been applied to the neutron data which favours four sets of crystal-field parameters. The results are compared with the measured...... susceptibility and other bulk magnetic properties. From this it is concluded that the crystal-field parameters x=-0.54 and W=-0.018 meV are the most probable ones....
Resource-saving application of FDTD technique in 3D photonic crystal waveguide calculations
DEFF Research Database (Denmark)
Lavrinenko, Andrei; Tromborg, Bjarne
2002-01-01
This paper presents an algorithm based on the well-known FDTD numerical method which is adapted for 3D problems of transmission and reflection of photonic crystal waveguides, and which effectively saves memory and computing resources. Specific examples showing its validity and effectiveness...
Hybrid excitations due to crystal field, spin-orbit coupling, and spin waves in LiFePO4
Yiu, Yuen; Le, Manh Duc; Toft-Peterson, Rasmus; Ehlers, Georg; McQueeney, Robert J.; Vaknin, David
2017-03-01
We report on the spin waves and crystal field excitations in single crystal LiFePO4 by inelastic neutron scattering over a wide range of temperatures, below and above the antiferromagnetic transition of this system. In particular, we find extra excitations below TN=50 K that are nearly dispersionless and are most intense around magnetic zone centers. We show that these excitations correspond to transitions between thermally occupied excited states of Fe2 + due to splitting of the S =2 levels that arise from the crystal field and spin-orbit interactions. These excitations are further amplified by the highly distorted nature of the oxygen octahedron surrounding the iron atoms. Above TN, magnetic fluctuations are observed up to at least 720 K, with an additional inelastic excitation around 4 meV, which we attribute to single-ion effects, as its intensity weakens slightly at 720 K compared to 100 K, which is consistent with the calculated cross sections using a single-ion model. Our theoretical analysis, using the MF-RPA model, provides both detailed spectra of the Fe d shell and estimates of the average ordered magnetic moment and TN. By applying the MF-RPA model to a number of existing spin-wave results from other Li M PO4 (M =Mn , Co, and Ni), we are able to obtain reasonable predictions for the moment sizes and transition temperatures.
A modified method of calculating the lateral build-up ratio for small electron fields
International Nuclear Information System (INIS)
Tyner, E; McCavana, P; McClean, B
2006-01-01
This note outlines an improved method of calculating dose per monitor unit values for small electron fields using Khan's lateral build-up ratio (LBR). This modified method obtains the LBR directly from the ratio of measured, surface normalized, electron beam percentage depth dose curves. The LBR calculated using this modified method more accurately accounts for the change in lateral scatter with decreasing field size. The LBR is used along with Khan's dose per monitor unit formula to calculate dose per monitor unit values for a set of small fields. These calculated dose per monitor unit values are compared to measured values to within 3.5% for all circular fields and electron energies examined. The modified method was further tested using a small triangular field. A maximum difference of 4.8% was found. (note)
Error Propagation dynamics: from PIV-based pressure reconstruction to vorticity field calculation
Pan, Zhao; Whitehead, Jared; Richards, Geordie; Truscott, Tadd; USU Team; BYU Team
2017-11-01
Noninvasive data from velocimetry experiments (e.g., PIV) have been used to calculate vorticity and pressure fields. However, the noise, error, or uncertainties in the PIV measurements would eventually propagate to the calculated pressure or vorticity field through reconstruction schemes. Despite the vast applications of pressure and/or vorticity field calculated from PIV measurements, studies on the error propagation from the velocity field to the reconstructed fields (PIV-pressure and PIV-vorticity are few. In the current study, we break down the inherent connections between PIV-based pressure reconstruction and PIV-based vorticity calculation. The similar error propagation dynamics, which involve competition between physical properties of the flow and numerical errors from reconstruction schemes, are found in both PIV-pressure and PIV-vorticity reconstructions.
International Nuclear Information System (INIS)
Korlyukov, Alexander A; Antipin, Mikhail Yu
2012-01-01
The review generalizes the results of structural studies of crystals of organic and organometallic compounds by modern quantum chemical calculations within the framework of the density functional theory reported in the last decade. Features of the software for such calculations are discussed. Examples of the use of quantum chemical calculations for the studies of the electronic structure, spectroscopic and other physicochemical properties of molecular crystals are presented. The bibliography includes 223 references.
Directory of Open Access Journals (Sweden)
P. K. Choudhury
2013-01-01
Full Text Available The paper presents the analysis of the electromagnetic wave propagation through liquid crystal optical fibers (LCOFs of two different types—conventional guides loaded with liquid crystals (addressed as LCOFs and those with additional twists due to conducting helical windings (addressed as HCLCOFs. More precisely, the three-layer optical waveguide structures are considered along with its outermost region being loaded with radially anisotropic liquid crystal material and the inner regions being made of usual silica, as used in conventional optical fibers. In addition to that, LCOF with twists introduced in the form of conducting helical windings at the interface of the silica core and the liquid crystal clad is also taken into account. Emphasis has been put on the power confinements by the lower-order TE modes sustained in the different sections of the LCOF structure. The results demonstrate useful applications of these guides in integrated optics as the power sustained in the liquid crystal section by the excited TE modes remains very high. In the case of twisted clad liquid crystal guides, descriptions are limited to the nature of dispersion relation only under the TE mode excitation, and corresponding to the cases of helix orientations being parallel and perpendicular to the optical axis.
A simple model for localized-itinerant magnetic systems: crystal field effects
International Nuclear Information System (INIS)
Iannarella, L.; Silva, X.A. da; Guimarares, A.P.
1989-01-01
The magnetic behavior of a system consisting of localized electrons coupled to conduction electrons and submitted to an axial crystral field at T=0 K is ivestigated within the framework of the molecular field approximation. An analytical ionic magnetic state equation is deduced; it shows how the magnetization depends on the model parameters (exchange, crystal field, band occupation) and external magnetic field. A condition for the onset of spontaneous magnetic order is obtained and the ferro - and paramagnetic phases are studied. This study displays several features of real magnetic systems, including quenching or total suppression of the magnetic moments (depending on the relative value of the crystal field parameter) and exchange enhacement. The relevance of such model for the description of rare-earth intermetallic compounds is discussed. (author) [pt
Zhang, Zhen; Xia, Changliang; Yan, Yan; Geng, Qiang; Shi, Tingna
2017-08-01
Due to the complicated rotor structure and nonlinear saturation of rotor bridges, it is difficult to build a fast and accurate analytical field calculation model for multilayer interior permanent magnet (IPM) machines. In this paper, a hybrid analytical model suitable for the open-circuit field calculation of multilayer IPM machines is proposed by coupling the magnetic equivalent circuit (MEC) method and the subdomain technique. In the proposed analytical model, the rotor magnetic field is calculated by the MEC method based on the Kirchhoff's law, while the field in the stator slot, slot opening and air-gap is calculated by subdomain technique based on the Maxwell's equation. To solve the whole field distribution of the multilayer IPM machines, the coupled boundary conditions on the rotor surface are deduced for the coupling of the rotor MEC and the analytical field distribution of the stator slot, slot opening and air-gap. The hybrid analytical model can be used to calculate the open-circuit air-gap field distribution, back electromotive force (EMF) and cogging torque of multilayer IPM machines. Compared with finite element analysis (FEA), it has the advantages of faster modeling, less computation source occupying and shorter time consuming, and meanwhile achieves the approximate accuracy. The analytical model is helpful and applicable for the open-circuit field calculation of multilayer IPM machines with any size and pole/slot number combination.
Improving NASICON Sinterability through Crystallization under High-Frequency Electrical Fields
Energy Technology Data Exchange (ETDEWEB)
Lisenker, Ilya; Stoldt, Conrad R., E-mail: stoldt@colorado.edu [Department of Mechanical Engineering, University of Colorado Boulder, Boulder, CO (United States)
2016-03-31
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 Li{sub 1.5}Al{sub 0.5}Ge{sub 1.5}(PO{sub 4}){sub 3} was crystallized and sintered, both conventionally and under effect of electrical field. Electrical field application, of 300 V/cm at 1 MHz, 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 X-ray diffraction, scanning electron microscope, TEM, and electrochemical impedance spectroscopy 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 h 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.
Palmesi, P.; Abert, C.; Bruckner, F.; Suess, D.
2018-05-01
Fast stray field calculation is commonly considered of great importance for micromagnetic simulations, since it is the most time consuming part of the simulation. The Fast Multipole Method (FMM) has displayed linear O(N) parallelization behavior on many cores. This article investigates the error of a recent FMM approach approximating sources using linear—instead of constant—finite elements in the singular integral for calculating the stray field and the corresponding potential. After measuring performance in an earlier manuscript, this manuscript investigates the convergence of the relative L2 error for several FMM simulation parameters. Various scenarios either calculating the stray field directly or via potential are discussed.
International Nuclear Information System (INIS)
Elamain, Omaima; Komitov, Lachezar; Hegde, Gurumurthy; Fodor-Csorba, Katalin
2013-01-01
The behaviour of bent core (BC) nematic liquid crystals was investigated under dc applied electric field. The optically isotropic state of a sample containing BC nematic was observed under application of low dc electric fields. The quality of the dark state when the sample was inserted between two crossed polarizers was found to be superb and it did not change when rotating the sample between the polarizers. The coupling between the net molecular dipole moment and the applied dc electric field was considered as the origin of the out-of-plane switching of the BC molecules resulting in switching from the field-off bright state to the field-on dark state. The field-induced optically isotropic state is an unambiguous proof of the field-induced biaxiality in the BC nematic liquid crystal. A simple model explaining the appearance of the isotropic optical state in BC nematics and the switching of the sample slow axis between three mutually orthogonal directions under dc applied electric field is proposed. (paper)
Calculation of electromagnetic fields and forces in coil systems of arbitrary geometry
International Nuclear Information System (INIS)
Sackett, S.J.
1975-01-01
A computer program, EFFI, is described which calculates the electric and magnetic fields due to an arbitrary spatial distribution of current-carrying circular loops, circular arcs, and straight lines. The electric field is assumed to arise solely from the time variation of the magnetic field, and the magnetic field due to the changing electric field is assumed to be negligible. In addition, the conductor bundle elements (loops, arcs, lines) are assumed to be absent. Electric and magnetic flux lines and magnetic forces and inductances are also calculated by the program. The algorithm used in the code, which is based on a combination of direct and numerical integration using the Biot-Savart law, is discussed. The methods used to maintain accuracy in calculating fields within the conductor bundle, in particular, are detailed. Several examples are then presented to illustrate the input and output features as well as the accuracy obtained and the running time required
Comparison of measured and calculated doses for narrow MLC defined fields
International Nuclear Information System (INIS)
Lydon, J.; Rozenfeld, A.; Lerch, M.
2002-01-01
Full text: The introduction of Intensity Modulated Radiotherapy (IMRT) has led to the use of narrow fields in the delivery of radiation doses to patients. Such fields are not well characterized by calculation methods commonly used in radiotherapy treatment planning systems. The accuracy of the dose calculation algorithm must therefore be investigated prior to clinical use. This study looked at symmetrical and asymmetrical 0.1 to 3cm wide fields delivered with a Varian CL2100C 6MV photon beam. Measured doses were compared to doses calculated using Pinnacle, the ADAC radiotherapy treatment planning system. Two high resolution methods of measuring dose were used. A MOSFET detector in a water phantom and radiographic film in a solid water phantom with spatial resolutions of 10 and 89μm respectively. Dose calculations were performed using the collapsed cone convolution algorithm in Pinnacle with a 0.1cm dose calculation grid in the MLC direction. The effect of Pinnacle not taking into account the rounded leaf ends was simulated by offsetting the leaves by 0.1cm in the dose calculation. Agreement between measurement and calculation is good for fields of 1cm and wider. However, fields of less than 1cm width can show a significant difference between measurement and calculation
Analyses of crystal field and exchange interaction of Dy3Ga5O12 under extreme conditions
International Nuclear Information System (INIS)
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. (condensed matter: electronic structure, electrical, magnetic, and optical properties)
Crystal-field tuning of photoluminescence in two-dimensional materials with embedded lanthanide ions
Energy Technology Data Exchange (ETDEWEB)
Xu, Ding; Chen, Weiyin; Zeng, Mengqi; Xue, Haifeng; Chen, Yunxu; Xiao, Yao; Zhang, Tao; Fu, Lei [College of Chemistry and Molecular Sciences, Institute for Advanced Studies, Wuhan University, Wuhan (China); Sang, Xiahan; Unocic, Raymond R.; Xiao, Kai [Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN (United States)
2018-01-15
Lanthanide (Ln) group elements have been attracting considerable attention owing to the distinct optical properties. The crystal-field surroundings of Ln ions in the host materials can determine their energy level splitting, which is of vital importance to tailor their optical properties. 2D MoS{sub 2} single crystals were utilized as the host material to embed Eu{sup 3+} and energy-level splitting was achieved for tuning its photoluminescence (PL). The high anisotropy of the 2D host materials makes them distort the degenerate orbitals of the Ln ions more efficiently than the symmetrical bulk host materials. A significant red-shift of the PL peak for Eu{sup 3+} was observed. The strategy for tailoring the energy level splitting of Ln ions by the highly designable 2D material crystal field provides a new method to extend their optical properties. (copyright 2018 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)
Waveguide modes of 1D photonic crystals in a transverse magnetic field
Energy Technology Data Exchange (ETDEWEB)
Sylgacheva, D. A., E-mail: sylgacheva.darjja@physics.msu.ru; Khokhlov, N. E.; Kalish, A. N.; Belotelov, V. I. [Moscow State University, Physics Department (Russian Federation)
2016-11-15
We analyze waveguide modes in 1D photonic crystals containing layers magnetized in the plane. It is shown that the magnetooptical nonreciprocity effect emerges in such structures during the propagation of waveguide modes along the layers and perpendicularly to the magnetization. This effect involves a change in the phase velocity of the mode upon reversal of the direction of magnetization. Comparison of the effects in a nonmagnetic photonic crystal with an additional magnetic layer and in a photonic crystal with magnetic layers shows that the magnitude of this effect is several times larger in the former case in spite of the fact that the electromagnetic field of the modes in the latter case is localized in magnetic regions more strongly. This is associated with asymmetry of the dielectric layers contacting with the magnetic layer in the former case. This effect is important for controlling waveguide structure modes with the help of an external magnetic field.
Dual gauge field theory of quantum liquid crystals in three dimensions
International Nuclear Information System (INIS)
Beekman, Aron J.; Nissinen, Jaakko; Wu, Kai; Zaanen, Jan
2017-01-01
The dislocation-mediated quantum melting of solids into quantum liquid crystals is extended from two to three spatial dimensions, using a generalization of boson-vortex or Abelian-Higgs duality. Dislocations are now Burgers-vector-valued strings that trace out worldsheets in space-time while the phonons of the solid dualize into two-form (Kalb-Ramond) gauge fields. We propose an effective dual Higgs potential that allows for restoring translational symmetry in either one, two, or three directions, leading to the quantum analogues of columnar, smectic, or nematic liquid crystals. In these phases, transverse phonons turn into gapped, propagating modes, while compressional stress remains massless. Rotational Goldstone modes emerge whenever translational symmetry is restored. Lastly, we also consider the effective electromagnetic response of electrically charged quantum liquid crystals, and find among other things that as a hard principle only two out of the possible three rotational Goldstone modes are observable using propagating electromagnetic fields.
Dual gauge field theory of quantum liquid crystals in three dimensions
Beekman, Aron J.; Nissinen, Jaakko; Wu, Kai; Zaanen, Jan
2017-10-01
The dislocation-mediated quantum melting of solids into quantum liquid crystals is extended from two to three spatial dimensions, using a generalization of boson-vortex or Abelian-Higgs duality. Dislocations are now Burgers-vector-valued strings that trace out worldsheets in space-time while the phonons of the solid dualize into two-form (Kalb-Ramond) gauge fields. We propose an effective dual Higgs potential that allows for restoring translational symmetry in either one, two, or three directions, leading to the quantum analogues of columnar, smectic, or nematic liquid crystals. In these phases, transverse phonons turn into gapped, propagating modes, while compressional stress remains massless. Rotational Goldstone modes emerge whenever translational symmetry is restored. We also consider the effective electromagnetic response of electrically charged quantum liquid crystals, and find among other things that as a hard principle only two out of the possible three rotational Goldstone modes are observable using propagating electromagnetic fields.
International Nuclear Information System (INIS)
Derenzo, S.E.; Riles, J.K.
1981-10-01
The high density and atomic number of bismuth germanate (Bi 4 Ge 3 O 12 or BGO) make it a very useful detector for positron emission tomography. Modern tomograph designs use large numbers of small, closely-packed crystals for high spatial resolution and high sensitivity. However, the low light output, the high refractive index (n=2.15), and the need for accurate timing make it important to optimize the transfer of light to the photomultiplier tube (PMT). We describe the results of a Monte Carlo computer program developed to study the effect of crystal shape, reflector type, and the refractive index of the PMT window on coupling efficiency. The program simulates total internal, external, and Fresnel reflection as well as internal absorption and scattering by bubbles
DEFF Research Database (Denmark)
Kleis, Jesper; Schröder, Elsebeth; Hyldgaard, Per
2008-01-01
calculations, the vdW-DF study predicts an intertube vdW bonding with a strength that is consistent with recent observations for the interlayer binding in graphitics. It also produces a nanotube wall-to-wall separation, which is in very good agreement with experiments. Moreover, we find that the vdW-DF result...... for the nanotube-crystal binding energy can be approximated by a sum of nanotube-pair interactions when these are calculated in vdW-DR This observation suggests a framework for an efficient implementation of quantum-physical modeling of the carbon nanotube bundling in more general nanotube bundles, including......The dispersive interaction between nanotubes is investigated through ab initio theory calculations and in an analytical approximation. A van der Waals density functional (vdW-DF) [M. Dion et al., Phys. Rev. Lett. 92, 246401 (2004)] is used to determine and compare the binding of a pair of nanotubes...
Energy Technology Data Exchange (ETDEWEB)
Kenneth D. Wright
1997-09-03
The purpose of this design analysis is to document the SAS2H depletion calculations of certain rodded fuel assemblies from batches 1, 2, 3, and 1X of the Crystal River Unit 3 pressurized water reactor (PWR) that are required for Commercial Reactor Critical (CRC) evaluations to support the development of the disposal criticality methodology. A rodded assembly is one that contains a control rod assembly (CRA) or an axial power shaping rod assembly (APSRA) for some period of time during its irradiation history. The objective of this analysis is to provide SAS2H calculated isotopic compositions of depleted fuel and depleted burnable poison for each fuel assembly to be used in subsequent CRC reactivity calculations containing the fuel assemblies.
International Nuclear Information System (INIS)
Wright, Kenneth D.
1997-01-01
The purpose of this design analysis is to document the SAS2H depletion calculations of certain rodded fuel assemblies from batches 1, 2, 3, and 1X of the Crystal River Unit 3 pressurized water reactor (PWR) that are required for Commercial Reactor Critical (CRC) evaluations to support the development of the disposal criticality methodology. A rodded assembly is one that contains a control rod assembly (CRA) or an axial power shaping rod assembly (APSRA) for some period of time during its irradiation history. The objective of this analysis is to provide SAS2H calculated isotopic compositions of depleted fuel and depleted burnable poison for each fuel assembly to be used in subsequent CRC reactivity calculations containing the fuel assemblies
Lunt, A. J. G.; Xie, M. Y.; Baimpas, N.; Zhang, S. Y.; Kabra, S.; Kelleher, J.; Neo, T. K.; Korsunsky, A. M.
2014-08-01
Yttria Stabilised Zirconia (YSZ) is a tough, phase-transforming ceramic that finds use in a wide range of commercial applications from dental prostheses to thermal barrier coatings. Micromechanical modelling of phase transformation can deliver reliable predictions in terms of the influence of temperature and stress. However, models must rely on the accurate knowledge of single crystal elastic stiffness constants. Some techniques for elastic stiffness determination are well-established. The most popular of these involve exploiting frequency shifts and phase velocities of acoustic waves. However, the application of these techniques to YSZ can be problematic due to the micro-twinning observed in larger crystals. Here, we propose an alternative approach based on selective elastic strain sampling (e.g., by diffraction) of grain ensembles sharing certain orientation, and the prediction of the same quantities by polycrystalline modelling, for example, the Reuss or Voigt average. The inverse problem arises consisting of adjusting the single crystal stiffness matrix to match the polycrystal predictions to observations. In the present model-matching study, we sought to determine the single crystal stiffness matrix of tetragonal YSZ using the results of time-of-flight neutron diffraction obtained from an in situ compression experiment and Finite Element modelling of the deformation of polycrystalline tetragonal YSZ. The best match between the model predictions and observations was obtained for the optimized stiffness values of C11 = 451, C33 = 302, C44 = 39, C66 = 82, C12 = 240, and C13 = 50 (units: GPa). Considering the significant amount of scatter in the published literature data, our result appears reasonably consistent.
Spectral element method for band-structure calculations of 3D phononic crystals
International Nuclear Information System (INIS)
Shi, Linlin; Liu, Na; Zhou, Jianyang; Zhou, Yuanguo; Wang, Jiamin; Liu, Qing Huo
2016-01-01
The spectral element method (SEM) is a special kind of high-order finite element method (FEM) which combines the flexibility of a finite element method with the accuracy of a spectral method. In contrast to the traditional FEM, the SEM exhibits advantages in the high-order accuracy as the error decreases exponentially with the increase of interpolation degree by employing the Gauss–Lobatto–Legendre (GLL) polynomials as basis functions. In this study, the spectral element method is developed for the first time for the determination of band structures of 3D isotropic/anisotropic phononic crystals (PCs). Based on the Bloch theorem, we present a novel, intuitive discretization formulation for Navier equation in the SEM scheme for periodic media. By virtue of using the orthogonal Legendre polynomials, the generalized eigenvalue problem is converted to a regular one in our SEM implementation to improve the efficiency. Besides, according to the specific geometry structure, 8-node and 27-node hexahedral elements as well as an analytic mesh have been used to accurately capture curved PC models in our SEM scheme. To verify its accuracy and efficiency, this study analyses the phononic-crystal plates with square and triangular lattice arrangements, and the 3D cubic phononic crystals consisting of simple cubic (SC), bulk central cubic (BCC) and faced central cubic (FCC) lattices with isotropic or anisotropic scatters. All the numerical results considered demonstrate that SEM is superior to the conventional FEM and can be an efficient alternative method for accurate determination of band structures of 3D phononic crystals. (paper)
Energy Technology Data Exchange (ETDEWEB)
Lunt, A. J. G., E-mail: alexander.lunt@eng.ox.ac.uk; Xie, M. Y.; Baimpas, N.; Korsunsky, A. M. [Department of Engineering Science, University of Oxford, Parks Road, Oxford OX1 3PJ (United Kingdom); Zhang, S. Y.; Kabra, S.; Kelleher, J. [ISIS Neutron and Muon Source, Rutherford Appleton Laboratory, Harwell, Oxford OX11 0QX (United Kingdom); Neo, T. K. [Specialist Dental Group, Mount Elizabeth Orchard, 3 Mount Elizabeth, #08-03/08-08/08-10, Singapore 228510 (Singapore)
2014-08-07
Yttria Stabilised Zirconia (YSZ) is a tough, phase-transforming ceramic that finds use in a wide range of commercial applications from dental prostheses to thermal barrier coatings. Micromechanical modelling of phase transformation can deliver reliable predictions in terms of the influence of temperature and stress. However, models must rely on the accurate knowledge of single crystal elastic stiffness constants. Some techniques for elastic stiffness determination are well-established. The most popular of these involve exploiting frequency shifts and phase velocities of acoustic waves. However, the application of these techniques to YSZ can be problematic due to the micro-twinning observed in larger crystals. Here, we propose an alternative approach based on selective elastic strain sampling (e.g., by diffraction) of grain ensembles sharing certain orientation, and the prediction of the same quantities by polycrystalline modelling, for example, the Reuss or Voigt average. The inverse problem arises consisting of adjusting the single crystal stiffness matrix to match the polycrystal predictions to observations. In the present model-matching study, we sought to determine the single crystal stiffness matrix of tetragonal YSZ using the results of time-of-flight neutron diffraction obtained from an in situ compression experiment and Finite Element modelling of the deformation of polycrystalline tetragonal YSZ. The best match between the model predictions and observations was obtained for the optimized stiffness values of C11 = 451, C33 = 302, C44 = 39, C66 = 82, C12 = 240, and C13 = 50 (units: GPa). Considering the significant amount of scatter in the published literature data, our result appears reasonably consistent.
Campelo, M. J. M.; Freire, P. T. C.; Mendes Filho, J.; de Toledo, T. A.; Teixeira, A. M. R.; da Silva, L. E.; Bento, R. R. F.; Faria, J. L. B.; Pizani, P. S.; Gusmão, G. O. M.; Coutinho, H. D. M.; Oliveira, M. T. A.
2017-10-01
A new derivative of Meldrum's acid 5-((5-chloropyridin-2-ylamino)methylene)-2,2-dimethyl-1,3-dioxane-4,6-dione (CYMM) of molecular formula C12H11ClN2O4 was synthesized and structurally characterized using single crystal X-ray diffraction technique. The vibrational properties of the crystal were studied by Fourier Transform infrared (FT-IR), Fourier Transform Raman (FT-Raman) techniques and theoretical calculations of quantum chemistry using Density functional theory (DFT) and Density functional perturbation theory (DFPT). A comparison with experimental spectra allowed the assignment of all the normal modes. The descriptions of the normal modes were carried by means of potential energy distribution (PED). Additionally, analysis of the antimicrobial activity and antibiotic resistance modulatory activity was carried out to evaluate the antibacterial potential of the CYMM.
Energy Technology Data Exchange (ETDEWEB)
Djouder, M., E-mail: djouder-madjid@ummto.dz; Kermoun, F.; Mitiche, M. D.; Lamrous, O. [Laboratoire de Physique et Chimie Quantique, Université Mouloud Mammeri Tizi-Ouzou, BP 17 RP, 15000 Tizi-Ouzou (Algeria)
2016-01-15
Dust particles observed in universe as well as in laboratory and technological plasma devices are still under investigation. At low temperature, these particles are strongly negatively charged and are able to form a 2D or 3D coulomb crystal. In this work, our aim was to check the ideal gas law validity for a 2D single-layer dust crystal recently reported in the literature. For this purpose, we have simulated, using the molecular dynamics method, its thermodynamic properties for different values of dust particles number and confinement parameters. The obtained results have allowed us to invalidate the ideal gas behaviour and to propose an effective equation of state which assumes a near zero dust temperature. Furthermore, the value of the calculated sound velocity was found to be in a good agreement with experimental data published elsewhere.
International Nuclear Information System (INIS)
Djouder, M.; Kermoun, F.; Mitiche, M. D.; Lamrous, O.
2016-01-01
Dust particles observed in universe as well as in laboratory and technological plasma devices are still under investigation. At low temperature, these particles are strongly negatively charged and are able to form a 2D or 3D coulomb crystal. In this work, our aim was to check the ideal gas law validity for a 2D single-layer dust crystal recently reported in the literature. For this purpose, we have simulated, using the molecular dynamics method, its thermodynamic properties for different values of dust particles number and confinement parameters. The obtained results have allowed us to invalidate the ideal gas behaviour and to propose an effective equation of state which assumes a near zero dust temperature. Furthermore, the value of the calculated sound velocity was found to be in a good agreement with experimental data published elsewhere
Classical calculation of radiative lifetimes of atomic hydrogen in a homogeneous magnetic field
International Nuclear Information System (INIS)
Horbatsch, M.W.; Hessels, E.A.; Horbatsch, M.
2005-01-01
Radiative lifetimes of hydrogenic atoms in a homogeneous magnetic field of moderate strength are calculated on the basis of classical radiation. The modifications of the Keplerian orbits due to the magnetic field are incorporated by classical perturbation theory. The model is complemented by a classical radiative decay calculation using the radiated Larmor power. A recently derived highly accurate formula for the transition rate of a field-free hydrogenic state is averaged over the angular momentum oscillations caused by the magnetic field. The resulting radiative lifetimes for diamagnetic eigenstates classified by n,m and the diamagnetic energy shift C compare well with quantum results
Energy Technology Data Exchange (ETDEWEB)
Gendron, Frederic; Pritchard, Ben; Autschbach, Jochen [Department of Chemistry, University at Buffalo, State University of New York, Buffalo, NY (United States); Paez-Hernandez, Dayan; Bolvin, Helene [Laboratoire de Physique et de Chimie Quantiques, Universite Toulouse 3 (France); Notter, Francois-Paul [Laboratoire de Chimie Quantique, Universite de Strasbourg (France)
2014-06-23
The electronic structure and magnetic properties of neptunyl(VI), NpO{sub 2}{sup 2+}, and two neptunyl complexes, [NpO{sub 2}(NO{sub 3}){sub 3}]{sup -} and [NpO{sub 2}Cl{sub 4}]{sup 2-}, were studied with a combination of theoretical methods: ab initio relativistic wavefunction methods and density functional theory (DFT), as well as crystal-field (CF) models with parameters extracted from the ab initio calculations. Natural orbitals for electron density and spin magnetization from wavefunctions including spin-orbit coupling were employed to analyze the connection between the electronic structure and magnetic properties, and to link the results from CF models to the ab initio data. Free complex ions and systems embedded in a crystal environment were studied. Of prime interest were the electron paramagnetic resonance g-factors and their relation to the complex geometry, ligand coordination, and nature of the nonbonding 5f orbitals. The g-factors were calculated for the ground and excited states. For [NpO{sub 2}Cl{sub 4}]{sup 2-}, a strong influence of the environment of the complex on its magnetic behavior was demonstrated. Kohn-Sham DFT with standard functionals can produce reasonable g-factors as long as the calculation converges to a solution resembling the electronic state of interest. However, this is not always straightforward. (copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
Low field Monte-Carlo calculations in heterojunctions and quantum wells
Hall, van P.J.; Rooij, de R.; Wolter, J.H.
1990-01-01
We present results of low-field Monte-Carlo calculations and compare them with experimental results. The negative absolute mobility of minority electrons in p-type quantum wells, as found in recent experiments, is described quite well.
Calculation of an axisymmetric current coil field with the bounding contour integration method
Energy Technology Data Exchange (ETDEWEB)
Telegin, Alexander P.; Klevets, Nickolay I. E-mail: pmsolution@mail.ru
2004-06-01
Method for the economic and stable (in the sense of calculation errors) analysis of an induction of a magnetic field created with axisymmetric coils in arbitrary points of space, including points located inside a coil or on its border, is obtained. The basic idea of the method is to replace a current coil with continuous distribution of current density by magnetization distributed in the volume of the coil and creating the equivalent magnetic field. This allows to use field surface sources at calculation of the fields. Consequently, the range of integration is reduced resulting in reduction of calculation volume by an order in most cases. Besides, the calculation of improper integrals in internal points and on the border is completely excluded.
Calculation of an axisymmetric current coil field with the bounding contour integration method
International Nuclear Information System (INIS)
Telegin, Alexander P.; Klevets, Nickolay I.
2004-01-01
Method for the economic and stable (in the sense of calculation errors) analysis of an induction of a magnetic field created with axisymmetric coils in arbitrary points of space, including points located inside a coil or on its border, is obtained. The basic idea of the method is to replace a current coil with continuous distribution of current density by magnetization distributed in the volume of the coil and creating the equivalent magnetic field. This allows to use field surface sources at calculation of the fields. Consequently, the range of integration is reduced resulting in reduction of calculation volume by an order in most cases. Besides, the calculation of improper integrals in internal points and on the border is completely excluded
Crystal-field splitting in coadsorbate systems: c (2x2) CO/K/Ni (100)
Hasselström, J.; Föhlisch, A.; Denecke, R.; Nilsson, A.; Groot, F.M.F. de
2000-01-01
It is demonstrated how the crystal field splitting (CFS) fine structure can be used to characterize a coadsor-bate system. We have applied K 2p x-ray absorption spectroscopy (XAS) to the c(2x2) CO/K/Ni(100) system. The CFS fine structure is shown to be sensitive to the the local atomic
Crystal field effect in YbMnO.sub.3./sub..
Czech Academy of Sciences Publication Activity Database
Diviš, M.; Hölsä, J.; Lastusaari, M.; Litvinchuk, A. P.; Nekvasil, Vladimír
2008-01-01
Roč. 451, 1-2 (2008), s. 662-665 ISSN 0925-8388 R&D Projects: GA AV ČR IAA100100627 Institutional research plan: CEZ:AV0Z10100521 Keywords : ytterbium * manganites * IR spectroscopy * crystal field Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.510, year: 2008
Energy Technology Data Exchange (ETDEWEB)
Zaim, N.; Zaim, A., E-mail: ah_zaim@yahoo.fr; Kerouad, M., E-mail: kerouad@fs-umi.ac.ma
2017-02-15
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 J{sub s} 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. - Highlights: • Phase diagrams of a ferromagnetic nanowire are examined by the Monte Carlo simulation. • Different types of the phase diagrams are obtained. • The effect of the random crystal field on the hysteresis loops is studied. • Single, double and para hysteresis regions are explicitly determined.
Ambipolar Cu- and Fe-phthalocyanine single-crystal field-effect transistors
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
Crystal field and magnetism with Wannier functions: Orthorhombic rare-earth manganites
Czech Academy of Sciences Publication Activity Database
Novák, Pavel; Nekvasil, Vladimír; Knížek, Karel
358-359, MAY (2014), s. 228-232 ISSN 0304-8853 R&D Projects: GA ČR GA13-25251S Institutional support: RVO:68378271 Keywords : crystal field * rare- earth magnetism Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.970, year: 2014
The optics of gyrotropic crystals in the field of two counter-propagating ultrasound waves
International Nuclear Information System (INIS)
Gevorgyan, A H; Harutyunyan, E M; Hovhannisyan, M A; Matinyan, G K
2014-01-01
We consider oblique light propagation through a layer of a gyrotropic crystal in the field of two counter-propagating ultrasound waves. The problem is solved by Ambartsumyan's layer addition modified method. The results of the reflection spectra for different values of the problem parameters are presented. The possibilities of such system applications are discussed.
Tellurium adsorption on single crystal faces of molybdenum and tungsten field emitters
International Nuclear Information System (INIS)
Collins, R.A.; Kiwanga, C.A.
1978-01-01
The purpose of this letter is to report the extension of previous studies of Te adsorption on Mo and W field emitters to measurements on single crystal planes. The adsorption of semiconductors on metallic emitters has been found to be characterized by simultaneous decreases in emission current and the Fowler-Nordheim work function for adsorbate coverages of less than a monolayer. (Auth.)
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...
Electrical resistance of flaky crystals in the longitudinal quantizing magnetic field
International Nuclear Information System (INIS)
Askerov, B.M.; Figarova, S.R.; Makhmudov, M.M.
2005-01-01
Specific resistance of the quasi-two-dimensional electrical gas in the longitudinal quantizing magnetic field is investigated in this work. Common expression for resistivity in the flaky crystals was received. In quantum limit was analyzed dependence of the resistivity from the size of magnetic field and parameters energetic spectra in case of strong degenerate gas. It was tagged that, the conduct of specific resistance is formed by the dependence of chemical potential from the size of magnetic field. At the defined value of the chemical potential and size of magnetic field obtains inflation of the specific resistance. (author)
Dose discrepancies in the buildup region and their impact on dose calculations for IMRT fields
International Nuclear Information System (INIS)
Hsu, Shu-Hui; Moran, Jean M.; Chen Yu; Kulasekere, Ravi; Roberson, Peter L.
2010-01-01
Purpose: Dose accuracy in the buildup region for radiotherapy treatment planning suffers from challenges in both measurement and calculation. This study investigates the dosimetry in the buildup region at normal and oblique incidences for open and IMRT fields and assesses the quality of the treatment planning calculations. Methods: This study was divided into three parts. First, percent depth doses and profiles (for 5x5, 10x10, 20x20, and 30x30 cm 2 field sizes at 0 deg., 45 deg., and 70 deg. incidences) were measured in the buildup region in Solid Water using an Attix parallel plate chamber and Kodak XV film, respectively. Second, the parameters in the empirical contamination (EC) term of the convolution/superposition (CVSP) calculation algorithm were fitted based on open field measurements. Finally, seven segmental head-and-neck IMRT fields were measured on a flat phantom geometry and compared to calculations using γ and dose-gradient compensation (C) indices to evaluate the impact of residual discrepancies and to assess the adequacy of the contamination term for IMRT fields. Results: Local deviations between measurements and calculations for open fields were within 1% and 4% in the buildup region for normal and oblique incidences, respectively. The C index with 5%/1 mm criteria for IMRT fields ranged from 89% to 99% and from 96% to 98% at 2 mm and 10 cm depths, respectively. The quality of agreement in the buildup region for open and IMRT fields is comparable to that in nonbuildup regions. Conclusions: The added EC term in CVSP was determined to be adequate for both open and IMRT fields. Due to the dependence of calculation accuracy on (1) EC modeling, (2) internal convolution and density grid sizes, (3) implementation details in the algorithm, and (4) the accuracy of measurements used for treatment planning system commissioning, the authors recommend an evaluation of the accuracy of near-surface dose calculations as a part of treatment planning commissioning.
A solution algorithm for calculating photon radiation fields with the aid of the Monte Carlo method
International Nuclear Information System (INIS)
Zappe, D.
1978-04-01
The MCTEST program and its subroutines for the solution of the Boltzmann transport equation is presented. The program renders possible to calculate photon radiation fields of point or plane gamma sources. After changing two subroutines the calculation can also be carried out for the case of directed incidence of radiation on plane shields of iron or concrete. (author)
Program system for calculating streaming neutron radiation field in reactor cavity
International Nuclear Information System (INIS)
He Zhongliang; Zhao Shu.
1986-01-01
The A23 neutron albedo data base based on Monte Carlo method well agrees with SAIL albedo data base. RSCAM program system, using Monte Carlo method with albedo approach, is used to calculate streaming neutron radiation field in reactor cavity and containment operating hall. The dose rate distributions calculated with RSCAM in square concrete duct well agree with experiments
Drift of nonequilibrium charge carriers in GaAs-crystals with traps in ultrasonic fields
International Nuclear Information System (INIS)
Zaveryukhina, N.N.; Zaveryukhin, B.N.; Zaveryukhina, E.B.
2007-01-01
Full text: The drift of nonequilibrium charge carriers in a semiconductor is one of the basic processes determining the efficiency of semiconductor photodetectors. Gallium arsenide possesses certain advantages to other semiconductors in this respect, which allow GaAs-photodetectors to be obtained which possess the maximum efficiency in comparison with all other systems. The purpose of this study was to deepen and expand our knowledge about the acoustic-drift processes in GaAs- crystals. As is known, the drift of nonequilibrium charge carriers in a semiconductor is determined either by external electric fields and/or by internal (built-in) electrostatic fields related to an impurity concentration gradient in the semiconductor. Gallium arsenide is a piezoelectric semiconductor with a structure possessing no center of symmetry. An electric field applied to such a crystal produces deformation of the crystal, and vice versa, any deformation of the crystal leads to the appearance of an induced electric field. Therefore, investigation of the effect of deformation on the drift of nonequilibrium charge carriers is a very important task. One of the possible straining factors is ultrasonic wave. Interaction of the charge carriers with ultrasonic waves in piezo-semiconductors is mediated by piezo exertion. Straining a semiconductor by an ultrasonic wave field gives rise to a force acting upon the charge carriers, which is proportional to the wave vector and the piezoelectric constant of the crystal. The physics of interaction between an ultrasonic wave and nonequilibrium charge carriers in GaAs, as well as in non-polar semiconductors (Si, Ge), consists in the energy and momentum exchange between the wave and the carriers. Besides the ultrasonic waves interact with the traps of carriers and devastate them. These both acoustic effects lead to rise of amplitude of signal of GaAs-photodetectors. (authors)
Energy Technology Data Exchange (ETDEWEB)
Urata, Kazuhiro [Japan Atomic Energy Research Inst., Naka, Ibaraki (Japan). Naka Fusion Research Establishment
2003-03-01
In design of the future fusion devises in which low activation ferritic steel is planned to use as the plasma facing material and/or the inserts for ripple reduction, the appreciation of the error field effect against the plasma as well as the optimization of ferritic plate arrangement to reduce the toroidal field ripple require calculation of magnetic field generated by ferritic steel. However iterative calculations concerning the non-linearity in B-H curve of ferritic steel disturbs high-speed calculation required as the design tool. In the strong toroidal magnetic field that is characteristic in the tokamak fusion devices, fully magnetic saturation of ferritic steel occurs. Hence a distribution of magnetic charges as magnetic field source is determined straightforward and any iteration calculation are unnecessary. Additionally objective ferritic steel geometry is limited to the thin plate and ferritic plates are installed along the toroidal magnetic field. Taking these special conditions into account, high-speed calculation code ''FEMAG'' has been developed. In this report, the formalization of 'FEMAG' code, how to use 'FEMAG', and the validity check of 'FEMAG' in comparison with a 3D FEM code, with the measurements of the magnetic field in JFT-2M are described. The presented examples are numerical results of design studies for JT-60 modification. (author)
International Nuclear Information System (INIS)
El Bounagui, O.; Erramli, H.
2010-01-01
In this work, we report on calculations of the electronic channelling energy loss of hydrogen and helium ions along Si and Si axial directions for the low energy range by using the Monte Carlo simulation code. Simulated and experimental data are compared for protons and He ions in the and axis of silicon. A reasonable agreement was found. Computer simulation was also employed to study the angular dependence of energy loss for 0.5, 0.8, 1, and 2 MeV channelled 4 He ions transmitted through a silicon crystal of 3 μm thickness along the axis.
Vibrational multiconfiguration self-consistent field theory: implementation and test calculations.
Heislbetz, Sandra; Rauhut, Guntram
2010-03-28
A state-specific vibrational multiconfiguration self-consistent field (VMCSCF) approach based on a multimode expansion of the potential energy surface is presented for the accurate calculation of anharmonic vibrational spectra. As a special case of this general approach vibrational complete active space self-consistent field calculations will be discussed. The latter method shows better convergence than the general VMCSCF approach and must be considered the preferred choice within the multiconfigurational framework. Benchmark calculations are provided for a small set of test molecules.
Quark number density and susceptibility calculation with one correction in mean field potential
International Nuclear Information System (INIS)
Singh, S. Somorendro
2016-01-01
We calculate quark number density and susceptibility of a model which has one loop correction in mean field potential. The calculation shows continuous increasing in the number density and susceptibility up to the temperature T = 0.4 GeV. Then the value of number density and susceptibility approach to the lattice result for higher value of temperature. The result indicates that the calculated values of the model fit well and the result increase the temperature to reach the lattice data with the one loop correction in the mean field potential. (author)
International Nuclear Information System (INIS)
Perrin, Andre; Caillet, Paul
1976-01-01
Vibrational spectra of anhydrous uranyl chloride UO 2 Cl 2 and so called basic uranyl chloride: dihydroxodiuranyl chloride tetrahydrate /UO 2 (OH) 2 UO 2 /Cl 2 (H 2 O) 4 are reported. Factor group method analysis leads for the first time to complete and comprehensive interpretation of their spectra. Two extreme examples of crystal field influence on vibrational spectra are pointed out: for UO 2 Cl 2 , one is unable to explain spectra without taking into account all the elements of primitive crystalline cell, whilst for dihydroxodiuranyl dichloride tetrahydrate the crystal packing has very little effect on vibrational spectra [fr
An energy-stable convex splitting for the phase-field crystal equation
Vignal, P.; Dalcin, L.; Brown, D. L.; Collier, N.; Calo, V. M.
2015-01-01
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.
Wave dispersion relation of two-dimensional plasma crystals in a magnetic field
International Nuclear Information System (INIS)
Uchida, G.; Konopka, U.; Morfill, G.
2004-01-01
The wave dispersion relation in a two-dimensional strongly coupled plasma crystal is studied by theoretical analysis and molecular dynamics simulation taking into account a constant magnetic field parallel to the crystal normal. The expression for the wave dispersion relation clearly shows that high-frequency and low-frequency branches exist as a result of the coupling of longitudinal and transverse modes due to the Lorenz force acting on the dust particles. The high-frequency and the low-frequency branches are found to belong to right-hand and left-hand polarized waves, respectively
An energy-stable convex splitting for the phase-field crystal equation
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.
Dose calculations for irregular fields using three-dimensional first-scatter integration
International Nuclear Information System (INIS)
Boesecke, R.; Scharfenberg, H.; Schlegel, W.; Hartmann, G.H.
1986-01-01
This paper describes a method of dose calculations for irregular fields which requires only the mean energy of the incident photons, the geometrical properties of the irregular field and of the therapy unit, and the attenuation coefficient of tissue. The method goes back to an approach including spatial aspects of photon scattering for inhomogeneities for the calculation of dose reduction factors as proposed by Sontag and Cunningham (1978). It is based on the separation of dose into a primary component and a scattered component. The scattered component can generally be calculated for each field by integration over dose contributions from scattering in neighbouring volume elements. The quotient of this scattering contribution in the irregular field and the scattering contribution in the equivalent open field is then the correction factor for scattering in an irregular field. A correction factor for the primary component can be calculated if the attenuation of the photons in the shielding block is properly taken into account. The correction factor is simply given by the quotient of primary photons of the irregular field and the primary photons of the open field. (author)
Far-Field Focus and Dispersionless Anticrossing Bands in Two-Dimensional Photonic Crystals
Directory of Open Access Journals (Sweden)
Xiaoshuang Chen
2007-01-01
Full Text Available We review the simulation work for the far-field focus and dispersionless anticrossing bands in two-dimensional (2D photonic crystals. In a two-dimensional photonic-crystal-based concave lens, the far-field focus of a plane wave is given by the distance between the focusing point and the lens. Strong and good-quality far-field focusing of a transmitted wave, explicitly following the well-known wave-beam negative refraction law, can be achieved. The spatial frequency information of the Bloch mode in multiple Brillouin zones (BZs is investigated in order to indicate the wave propagation in two different regions. When considering the photonic transmission in a 2D photonic crystal composed of a negative phase-velocity medium (NPVM, it is shown that the dispersionless anticrossing bands are generated by the couplings among the localized surface polaritons of the NPVM rods. The photonic band structures of the NPVM photonic crystals are characterized by a topographical continuous dispersion relationship accompanied by many anticrossing bands.
Environment-dependent crystal-field tight-binding based on density-functional theory
International Nuclear Information System (INIS)
Urban, Alexander
2012-01-01
systematic derivation of Slater-Koster parameters from the results of DFT calculations. In our approach, the DFT wave functions (Kohn-Sham orbitals) in a numerically converged basis of atom-centered functions and plane waves are mapped onto a minimal basis of atomic orbitals (AOs) using a projection formalism. This allows the computation of the minimal basis representation of the converged DFT Hamiltonian. The quality of TB parameters obtained using the projection methodology crucially depends on the choice of the minimal AO basis. We have therefore developed several schemes for the optimization of AO basis sets, which are discussed in detail in this thesis. The projection formalism described above is not limited to the calculation of conventional TB parameters, i.e., to bond and overlap integrals over two orbitals that are located at two different atomic sites. It also can be used to analyze crystal field interactions. We introduce an extended crystal-field tight-binding (CF-TB) method, which includes an environment-dependent on-site parametrization. It is demonstrated that the CF-TB method is substantially more accurate for low-symmetry structures. A common potential energy reference is a necessary condition to be able to compare Hamilton matrices and eigenvalues from different structures. We point out that the structure-dependent on-site parameters of a CF-TB model are suitable to gauge eigenvalues and bond integrals of different atomic and molecular structures. Most importantly, with an appropriate choice of potential energy reference, the structure sensitivity of bond integrals can be significantly reduced, thus leading to a substantial increase of the transferability of the TB models. In addition to the Slater-Koster parametrization of the electronic structure, for the calculation of cohesion energies and atomic forces in TB, a description of the ionic core repulsion and the double-counting corrections is required. We have explored various options for the partitioning
Directory of Open Access Journals (Sweden)
Jian Cheng
2016-03-01
Full Text Available Rapid growth and ultra-precision machining of large-size KDP (KH2PO4 crystals with high laser damage resistance are tough challenges in the development of large laser systems. It is of high interest and practical significance to have theoretical models for scientists and manufacturers to determine the laser-induced damage threshold (LIDT of actually prepared KDP optics. Here, we numerically and experimentally investigate the laser-induced damage on KDP crystals in ultra-short pulse laser regime. On basis of the rate equation for free electron generation, a model dedicated to predicting the LIDT is developed by considering the synergistic effect of photoionization, impact ionization and decay of electrons. Laser damage tests are performed to measure the single-pulse LIDT with several testing protocols. The testing results combined with previously reported experimental data agree well with those calculated by the model. By taking the light intensification into consideration, the model is successfully applied to quantitatively evaluate the effect of surface flaws inevitably introduced in the preparation processes on the laser damage resistance of KDP crystals. This work can not only contribute to further understanding of the laser damage mechanisms of optical materials, but also provide available models for evaluating the laser damage resistance of exquisitely prepared optical components used in high power laser systems.
Energy Technology Data Exchange (ETDEWEB)
Orlando, Roberto, E-mail: roberto.orlando@unito.it; Erba, Alessandro; Dovesi, Roberto [Dipartimento di Chimica, Università di Torino and NIS, Nanostructured Interfaces and Surfaces, Centre of Excellence, Via P. Giuria 7, 10125 Torino (Italy); De La Pierre, Marco [Dipartimento di Chimica, Università di Torino and NIS, Nanostructured Interfaces and Surfaces, Centre of Excellence, Via P. Giuria 7, 10125 Torino (Italy); Nanochemistry Research Institute, Department of Chemistry, Curtin University, GPO Box U1987, Perth, WA 6845 (Australia); Zicovich-Wilson, Claudio M. [Facultad de Ciencias, Universidad Autónoma del Estado de Morelos, Av. Universidad, 1001, Col. Chamilpa, 62209 Cuernavaca (Morelos) (Mexico)
2014-09-14
Use of symmetry can dramatically reduce the computational cost (running time and memory allocation) of self-consistent-field ab initio calculations for molecular and crystalline systems. Crucial for running time is symmetry exploitation in the evaluation of one- and two-electron integrals, diagonalization of the Fock matrix at selected points in reciprocal space, reconstruction of the density matrix. As regards memory allocation, full square matrices (overlap, Fock, and density) in the Atomic Orbital (AO) basis are avoided and a direct transformation from the packed AO to the symmetry adapted crystalline orbital basis is performed, so that the largest matrix to be handled has the size of the largest sub-block in the latter basis. Quantitative examples, referring to the implementation in the CRYSTAL code, are given for high symmetry families of compounds such as carbon fullerenes and nanotubes.
Lattice distortion under an electric field in BaTiO3 piezoelectric single crystal
International Nuclear Information System (INIS)
Tazaki, Ryoko; Fu Desheng; Daimon, Masahiro; Koshihara, Shin-ya; Itoh, Mitsuru
2009-01-01
Lattice distortions under an electric field in a mono-domain of BaTiO 3 ferroelectric crystal have been detected with synchrotron x-ray radiation. The variation of the lattice constant with an electric field observed with high angle diffraction shows a linear response nature of the piezoelectric effect. When an electric field is applied along the spontaneous polarization direction, the c-axis of the lattice elongates and the a-axis of the lattice shrinks at a rate of d 33 = 149 ± 54 pm V -1 and d 31 = -82 ± 61 pm V -1 ; these represent the longitudinal and transverse piezoelectric coefficients of BaTiO 3 crystal, respectively. These results give an insight into the intrinsic piezoelectric response on the lattice scale in BaTiO 3 that has been widely used to explore high performance lead-free piezoelectric alloys.
A Cosserat crystal plasticity and phase field theory for grain boundary migration
Ask, Anna; Forest, Samuel; Appolaire, Benoit; Ammar, Kais; Salman, Oguz Umut
2018-06-01
The microstructure evolution due to thermomechanical treatment of metals can largely be described by viscoplastic deformation, nucleation and grain growth. These processes take place over different length and time scales which present significant challenges when formulating simulation models. In particular, no overall unified field framework exists to model concurrent viscoplastic deformation and recrystallization and grain growth in metal polycrystals. In this work a thermodynamically consistent diffuse interface framework incorporating crystal viscoplasticity and grain boundary migration is elaborated. The Kobayashi-Warren-Carter (KWC) phase field model is extended to incorporate the full mechanical coupling with material and lattice rotations and evolution of dislocation densities. The Cosserat crystal plasticity theory is shown to be the appropriate framework to formulate the coupling between phase field and mechanics with proper distinction between bulk and grain boundary behaviour.
Origin of gigantic magnetostriction and crystal field effects in terbium dititanate
International Nuclear Information System (INIS)
Aleksandrov, I.V.; Lidskij, B.V.; Mamsurova, L.G.
1985-01-01
The temperature and magnetic field dependences of the magnetostriction and magnetization and the temperature dependences of the magnetic susceptibility, specific heat and lattice parameter are investigated experimentally in a broad range of temperature and field strength for polycrystalline and single crystal Tb 2 Ti 2 O 7 . A conclusion is drawn regarding the structure of the energy levels of Tb 3+ in Tb 2 Ti 2 O 7 . A qualitative and quantitative explanation of all observed magnetic effects, and in particular of gigantic magnetostriction in Tb 2 Ti 2 O 7 , is presented which is based on the crystal field theory. It is shown that the huge magnitude of the magnetostriction in terbium dititanate is due to the specificity of the energy spectrum of Tb 3+ in Tb 2 Ti 2 O 7
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.
On the stress calculation within phase-field approaches: a model for finite deformations
Schneider, Daniel; Schwab, Felix; Schoof, Ephraim; Reiter, Andreas; Herrmann, Christoph; Selzer, Michael; Böhlke, Thomas; Nestler, Britta
2017-08-01
Numerical simulations based on phase-field methods are indispensable in order to investigate interesting and important phenomena in the evolution of microstructures. Microscopic phase transitions are highly affected by mechanical driving forces and therefore the accurate calculation of the stresses in the transition region is essential. We present a method for stress calculations within the phase-field framework, which satisfies the mechanical jump conditions corresponding to sharp interfaces, although the sharp interface is represented as a volumetric region using the phase-field approach. This model is formulated for finite deformations, is independent of constitutive laws, and allows using any type of phase inherent inelastic strains.
Fast Near-Field Calculation for Volume Integral Equations for Layered Media
DEFF Research Database (Denmark)
Kim, Oleksiy S.; Meincke, Peter; Breinbjerg, Olav
2005-01-01
. Afterwards, the scattered electric field can be easily computed at a regular rectangular grid on any horizontal plane us-ing a 2-dimensional FFT. This approach provides significant speedup in the near-field calculation in comparison to a straightforward numerical evaluation of the ra-diation integral since......An efficient technique based on the Fast Fourier Transform (FFT) for calculating near-field scattering by dielectric objects in layered media is presented. A higher or-der method of moments technique is employed to solve the volume integral equation for the unknown induced volume current density...
International Nuclear Information System (INIS)
Nieves, Jose F.; Pal, Palash B.
2006-01-01
We consider the calculation of amplitudes for processes that take place in a constant background magnetic field, first using the standard method for the calculation of an amplitude in an external field, and second utilizing the Schwinger propagator for charged particles in a magnetic field. We show that there are processes for which the Schwinger-propagator method does not yield the total amplitude. We explain why the two methods yield equivalent results in some cases and indicate when we can expect the equivalence to hold. We show these results in fairly general terms and illustrate them with specific examples as well
Review of MFTF yin-yang magnet displacement and magnetic field measurements and calculations
International Nuclear Information System (INIS)
Hanson, C.L.; Myall, J.O.; Wohlwend, J.W.
1983-01-01
During the recent testing of the MFTF yin-yang magnet, measurements of coil position, structural case strain, and magnetic field were made to verify calculated values. Measurements to detect magnet movement were taken throughout cooldown and during the operation of the magnet. The magnetic field at the mirror points was measured by Hall-effect probes. The magnet position, structural case strain, and magnetic field measurements indicated a reasonably close correlation with calculated values. Information obtained from the yin-yang test has been very useful in setting realistic mechanical alignment values for the new MFTF-B magnet system
Review of MFTF yin-yang magnet displacement and magnetic field measurements and calculations
International Nuclear Information System (INIS)
Hanson, C.L.; Myall, J.O.; Wohlwend, J.W.
1983-01-01
During the recent testing of the MFTF yin-yang magnet, measurements of coil position, structural case strain, and magnetic field were made to verify calculated values. Measurements to detect magnet movement were taken throughout cooldown and during the operation of the magnet. The magnetic field at the mirror points was measured by Hall-effect probes. The magnet position, structural case strain, and magntic field measurements indicated a reasonably close correlation with calculated values. Information obtained from the yin-yang test has been very useful in setting realistic mechanical alignment values for the new MFTF-B magnet system
Calculation of one-loop anomalous dimensions by means of the background field method
International Nuclear Information System (INIS)
Morozov, A.Yu.
1983-01-01
The knowledge of propagators in background fields makes calculation of anomalous dimensions (AD) straightforward and brief. The paper illustrates this statement by calculation of AD of many spin-zero and one QCD operators up to the eighth dimension included. The method presented does not simplify calculations in case of four-quark operators, therefore these are not discussed. Together with calculational difficulties arising for operators with derivatives this limits capacities of the whole approach and leads to incompleteness of some mixing matrices found in the article
Temperature field calculation for a metal charge of large cylindrical billets
Energy Technology Data Exchange (ETDEWEB)
Korovina, V M; Gurenko, V A; Bashnin, Yu A; Gordeeva, L I; Mernik, E B; Varakin, P I
1979-09-01
The temperature field of cylindrical blanks of 35KhN3MFA steel, cooled separately in the air and as-charged on rolled-out hearth was calculated. The temperature curves of the blanks cooled in the as-charged state were calculated with allowance for the variation of the external temperature with the time. The comparison of the experimental and of the calculated data has shown their satisfactory agreement for all practical purposes. This method of calculation can be used for any other problems with different linear, thermal and physical parameters of blanks.
A magnetostatic calculation of fringing field for the Rogowski pole boundary with floating snake
International Nuclear Information System (INIS)
Yan Chen; Fan Ming-Wu
1984-01-01
A boundary integral method has been used to calculate the fringing field distribution of Rogowski pole boundary with floating snake for QMG2 type of QDDD magnetic spectrograph and the experimental EFB is nearly reproduced from BIM calculation. As a further criteria, a calculation for clamped Rogowski pole but without snake is also performed and the calculated EFB shows perfect identity with the experiment. For evaluating the effect of snake quantitatively, this work also predicts the EFB values for two different positions of snake
Magnetostatic calculation of fringing field for the Rogowski pole boundary with floating snake
Energy Technology Data Exchange (ETDEWEB)
Chen, Yan; Ming-Wu, Fan [Institute of Atomic Energy, Peking (China)
1984-01-01
A boundary integral method has been used to calculate the fringing field distribution of Rogowski pole boundary with floating snake for QMG2 type of QDDD magnetic spectrograph and the experimental EFB is nearly reproduced from BIM calculation. As a further criteria, a calculation for clamped Rogowski pole but without snake is also performed and the calculated EFB shows perfect identity with the experiment. For evaluating the effect of snake quantitatively, this work also predicts the EFB values for two different positions of snake.
CRC DEPLETION CALCULATIONS FOR THE NON-RODDED ASSEMBLIES IN BATCHES 4 AND 5 OF CRYSTAL RIVER UNIT 3
Energy Technology Data Exchange (ETDEWEB)
Kenneth D. Wright
1997-07-30
The purpose of this design analysis is to document the SAS2H depletion calculations of certain non-rodded fuel assemblies from batches 4 and 5 of the Crystal River Unit 3 pressurized water reactor (PWR) that are required for commercial Reactor Critical (CRC) evaluations to support the development of the disposal criticality methodology. A non-rodded assembly is one which never contains a control rod assembly (CRA) or an axial power shaping rod assembly (APSRA) during its irradiation history. The objective of this analysis is to provide SAS2H generated isotopic compositions for each fuel assembly's depleted fuel and depleted burnable poison materials. These SAS2H generated isotopic compositions are acceptable for use in CRC benchmark reactivity calculations containing the various fuel assemblies.
CRC DEPLETION CALCULATIONS FOR THE NON-RODDED ASSEMBLIES IN BATCHES 8 AND 9 CRYSTAL RIVER UNIT 3
International Nuclear Information System (INIS)
Wilson, Michael L.
2001-01-01
The purpose of this design analysis is to document the SAS2H depletion calculations of certain non-rodded fuel assemblies from batches 8 and 9 of the Crystal River Unit 3 pressurized water reactor (PWR) that are required for Commercial Reactor Critical (CRC) evaluations to support the development of the disposal criticality methodology. A non-rodded assembly is one which never contains a control rod assembly (CRA) or an axial power shaping rod assembly (APSRA) during its irradiation history. The objective of this analysis is to provide SAS2H generated isotopic compositions for each fuel assembly's depleted fuel and depleted burnable poison materials. These SAS2H generated isotopic compositions are acceptable for use in CRC benchmark reactivity calculations containing the various fuel assemblies
CRC DEPLETION CALCULATIONS FOR THE NON-RODDED ASSEMBLIES IN BATCHES 4 AND 5 OF CRYSTAL RIVER UNIT 3
International Nuclear Information System (INIS)
Wright, Kenneth D.
1997-01-01
The purpose of this design analysis is to document the SAS2H depletion calculations of certain non-rodded fuel assemblies from batches 4 and 5 of the Crystal River Unit 3 pressurized water reactor (PWR) that are required for commercial Reactor Critical (CRC) evaluations to support the development of the disposal criticality methodology. A non-rodded assembly is one which never contains a control rod assembly (CRA) or an axial power shaping rod assembly (APSRA) during its irradiation history. The objective of this analysis is to provide SAS2H generated isotopic compositions for each fuel assembly's depleted fuel and depleted burnable poison materials. These SAS2H generated isotopic compositions are acceptable for use in CRC benchmark reactivity calculations containing the various fuel assemblies
International Nuclear Information System (INIS)
Wright, Kenneth D.
1997-01-01
The purpose of this design analysis is to document the SAS2H depletion calculations of certain non-rodded fuel assemblies from batches 1, 2, and 3 of the Crystal River Unit 3 pressurized water reactor (PWR) that are required for Commercial Reactor Critical (CRC) evaluations to support development of the disposal criticality methodology. A non-rodded assembly is one which never contains a control rod assembly (CRA) or an axial power shaping rod assembly (APSRA) during its irradiation history. The objective of this analysis is to provide SAS2H generated isotopic compositions for each fuel assembly's depleted fuel and depleted burnable poison materials. These SAS2H generated isotopic compositions are acceptable for use in CRC benchmark reactivity calculations containing the various fuel assemblies
Optical properties of alkali halide crystals from all-electron hybrid TD-DFT calculations
Energy Technology Data Exchange (ETDEWEB)
Webster, R., E-mail: ross.webster07@imperial.ac.uk; Harrison, N. M. [Thomas Young Centre, Department of Chemistry, Imperial College London, South Kensington, London SW7 2AZ (United Kingdom); Bernasconi, L. [Rutherford Appleton Laboratory, STFC, Harwell Oxford, Didcot OX11 0QX (United Kingdom)
2015-06-07
We present a study of the electronic and optical properties of a series of alkali halide crystals AX, with A = Li, Na, K, Rb and X = F, Cl, Br based on a recent implementation of hybrid-exchange time-dependent density functional theory (TD-DFT) (TD-B3LYP) in the all-electron Gaussian basis set code CRYSTAL. We examine, in particular, the impact of basis set size and quality on the prediction of the optical gap and exciton binding energy. The formation of bound excitons by photoexcitation is observed in all the studied systems and this is shown to be correlated to specific features of the Hartree-Fock exchange component of the TD-DFT response kernel. All computed optical gaps and exciton binding energies are however markedly below estimated experimental and, where available, 2-particle Green’s function (GW-Bethe-Salpeter equation, GW-BSE) values. We attribute this reduced exciton binding to the incorrect asymptotics of the B3LYP exchange correlation ground state functional and of the TD-B3LYP response kernel, which lead to a large underestimation of the Coulomb interaction between the excited electron and hole wavefunctions. Considering LiF as an example, we correlate the asymptotic behaviour of the TD-B3LYP kernel to the fraction of Fock exchange admixed in the ground state functional c{sub HF} and show that there exists one value of c{sub HF} (∼0.32) that reproduces at least semi-quantitatively the optical gap of this material.
International Nuclear Information System (INIS)
Velez Juarez, Esteban; Rodriguez Garciapinna, Jorge L.; Ostrovsky, Andrey S.
2016-01-01
A technique for experimental determining the coherent-mode structure of electromagnetic field is proposed. This technique is based on the coherence measurements of the field in some reference basis and represents a nontrivial vector generalization of the dual-mode field correlation method recently reported by F. Ferreira and M. Belsley. The justifiability and efficiency of the proposed technique is illustrated by an example of determining the coherent-mode structure of some specially generated and experimentally characterized secondary electromagnetic source using a spatial modulator of light of liquid crystal (SLM-LC). (Author)
Angular and magnetic field dependences of critical current in irradiated YBaCuO single crystals
International Nuclear Information System (INIS)
Petrusenko, Yu.
2010-01-01
The investigation of mechanisms responsible for the current-carrying capability of irradiated high-temperature superconductors (HTSC) was realized. For the purpose, experiments were made to investigate the effect of point defects generated by high-energy electron irradiation on the critical temperature and the critical current in high-Tc superconducting single crystals YBa 2 Cu 3 O 7-x . The transport current density measured in HTSC single crystals YBa 2 Cu 3 O 7-x by the dc-method was found to exceed 80000 A/cm 2 . The experiments have demonstrated a more than 30-fold increase in the critical current density in single crystals irradiated with 2.5 MeV electrons to a dose of 3·10 18 el/cm 2 . Detailed studies were made into the anisotropy of critical current and the dependence of critical current on the external magnetic field strength in irradiated single crystals. A high efficiency of point defects as centers of magnetic vortex pinning in HTSC single crystals was first demonstrated.
Energy Technology Data Exchange (ETDEWEB)
Ismayilova, N. A., E-mail: ismayilova-narmin-84@mail.ru; Orudjev, H. S.; Jabarov, S. H. [Azerbaijan National Academy of Sciences, Institute of Physics (Azerbaijan)
2017-04-15
The results of ab initio calculations of the electron spectrum of TlFeS{sub 2} and TlFeSe{sub 2} crystals in the antiferromagnetic phase are reported. Calculations are carried out in the context of the density functional theory. The origin of the bands of s, p, and d electron states of Tl, Fe, S, and Se atoms is studied. It is established that, in the antiferromagnetic phase, the crystals possess semiconductor properties. The band gaps are found to be 0.05 and 0.34 eV for TlFeS{sub 2} and TlFeSe{sub 2} crystals, respectively.
Synthesis, crystal structure and DFT calculations of a new Hg (II) metal-organic polymer
Czech Academy of Sciences Publication Activity Database
Mirtamizdoust, B.; Roodsari, M.S.; Shaabani, B.; Dušek, Michal; Fejfarová, Karla
2016-01-01
Roč. 15, č. 3 (2016), s. 257-266 ISSN 1024-1221 Grant - others:AV ČR(CZ) Praemium Academiae Institutional support: RVO:68378271 Keywords : mercury (II) iodide * coordination polymer * square planar * tetrahedral geometry * density functional calculation Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.565, year: 2016
CCSD(T)/CBS fragment-based calculations of lattice energy of molecular crystals
Czech Academy of Sciences Publication Activity Database
Červinka, C.; Fulem, Michal; Růžička, K.
2016-01-01
Roč. 144, č. 6 (2016), 1-15, č. článku 064505. ISSN 0021-9606 Institutional support: RVO:68378271 Keywords : density-functional theory * organic oxygen compounds * quantum -mechanical calculations Subject RIV: BJ - Thermodynamics Impact factor: 2.965, year: 2016
Reply to comment on 'Model calculation of the scanned field enhancement factor of CNTs'
International Nuclear Information System (INIS)
Ahmad, Amir; Tripathi, V K
2010-01-01
In the paper (Ahmad and Tripathi 2006 Nanotechnology 17 3798), we derived an expression to compute the field enhancement factor of CNTs under any positional distribution of CNTs by using the model of a floating sphere between parallel anode and cathode plates. Using this expression we can compute the field enhancement factor of a CNT in a cluster (non-uniformly distributed CNTs). This expression was used to compute the field enhancement factor of a CNT in an array (uniformly distributed CNTs). We used an approximation to calculate the field enhancement factor. Hence, our expressions are correct in that assumption only. Zhbanov et al (2010 Nanotechnology 21 358001) suggest a correction that can calculate the field enhancement factor without using the approximation. Hence, this correction can improve the applicability of this model. (reply)
Crystal-field excitations in PrAl sub 3 and NdAl sub 3 at ambient and elevated pressure
Straessle, T; Rusz, J; Janssen, S; Juranyi, F; Sadykov, R; Furrer, A
2003-01-01
The crystal fields (CFs) of the binary rare-earth compounds PrAl sub 3 and NdAl sub 3 have been examined at ambient pressure by means of inelastic neutron scattering. The CF of the latter compound has also been measured under hydrostatic pressure (p = 0.84 GPa). The observed substantial changes of the CF under pressure are discussed within the framework of first-principles density functional theory calculations.
Phase field modeling of rapid crystallization in the phase-change material AIST
Tabatabaei, Fatemeh; Boussinot, Guillaume; Spatschek, Robert; Brener, Efim A.; Apel, Markus
2017-07-01
We carry out phase field modeling as a continuum simulation technique in order to study rapid crystallization processes in the phase-change material AIST (Ag4In3Sb67Te26). In particular, we simulate the spatio-temporal evolution of the crystallization of a molten area of the phase-change material embedded in a layer stack. The simulation model is adapted to the experimental conditions used for recent measurements of crystallization rates by a laser pulse technique. Simulations are performed for substrate temperatures close to the melting temperature of AIST down to low temperatures when an amorphous state is involved. The design of the phase field model using the thin interface limit allows us to retrieve the two limiting regimes of interface controlled (low temperatures) and thermal transport controlled (high temperatures) dynamics. Our simulations show that, generically, the crystallization velocity presents a maximum in the intermediate regime where both the interface mobility and the thermal transport, through the molten area as well as through the layer stack, are important. Simulations reveal the complex interplay of all different contributions. This suggests that the maximum switching velocity depends not only on material properties but also on the precise design of the thin film structure into which the phase-change material is embedded.
The use of single-crystal iron frames in transient field measurements, ch. 3
International Nuclear Information System (INIS)
Zalm, P.C.
1977-01-01
An experimental technique for measuring g-factors of short-lived states (tausub(m)=0.1-10 ps) is discussed. In this method, one uses the strong hyperfine interaction caused by the transient magnetic field. The transient field method dates from 1967. A gain in measuring time of at least a factor of four is shown to be obtained by the use of a single crystal iron frame as a ferromagnetic target backing in which the excited nuclei, formed in a nuclear reaction, recoil. Such frames can be fully magnetized with low external fields as shown by magneto-optical Kerr-effect measurements. The important improvement is that the associated magnetic fringing field near the target is negligible. This is in contrast to the conventional set-up in which strong external fields, with corresponding large disturbing fringing fields, were necessary. The single-crystal set-up is compared to the conventional set-up in several transient field experiments and proves to be successful
Directory of Open Access Journals (Sweden)
Dongjia Cao
2017-12-01
Full Text Available Phase-field simulation serves as an effective tool for quantitative characterization of microstructure evolution in single-crystal Ni-based superalloys during solidification nowadays. The classic unit cell is either limited to γ dendrites along crystal orientation or too ideal to cover complex morphologies for γ dendrites. An attempt to design the unit cell for two-dimensional (2-D phase-field simulations of microstructure evolution in single-crystal Ni-based superalloys during solidification was thus performed by using the MICRESS (MICRostructure Evolution Simulation Software in the framework of the multi-phase-field (MPF model, and demonstrated in a commercial TMS-113 superalloy. The coupling to CALPHAD (CALculation of PHAse Diagram thermodynamic database was realized via the TQ interface and the experimental diffusion coefficients were utilized in the simulation. Firstly, the classic unit cell with a single γ dendrite along crystal orientation was employed for the phase-field simulation in order to reproduce the microstructure features. Then, such simple unit cell was extended into the cases with two other different crystal orientations, i.e., and . Thirdly, for crystal orientations, the effect of γ dendritic orientations and unit cell sizes on microstructure and microsegregation was comprehensively studied, from which a new unit cell with multiple γ dendrites was proposed. The phase-field simulation with the newly proposed unit cell was further performed in the TMS-113 superalloy, and the microstructure features including the competitive growth of γ dendrites, microsegregation of different solutes and distribution of γ′ grains, can be nicely reproduced.
Reciprocity relationships in vector acoustics and their application to vector field calculations.
Deal, Thomas J; Smith, Kevin B
2017-08-01
The reciprocity equation commonly stated in underwater acoustics relates pressure fields and monopole sources. It is often used to predict the pressure measured by a hydrophone for multiple source locations by placing a source at the hydrophone location and calculating the field everywhere for that source. A similar equation that governs the orthogonal components of the particle velocity field is needed to enable this computational method to be used for acoustic vector sensors. This paper derives a general reciprocity equation that accounts for both monopole and dipole sources. This vector-scalar reciprocity equation can be used to calculate individual components of the received vector field by altering the source type used in the propagation calculation. This enables a propagation model to calculate the received vector field components for an arbitrary number of source locations with a single model run for each vector field component instead of requiring one model run for each source location. Application of the vector-scalar reciprocity principle is demonstrated with analytic solutions for a range-independent environment and with numerical solutions for a range-dependent environment using a parabolic equation model.
Directory of Open Access Journals (Sweden)
Seied R Mahdavi
2012-01-01
Full Text Available Aims: The objective of this study is to evaluate the accuracy of a treatment planning system (TPS for calculating the dose distribution parameters in conformal fields (CF. Dosimetric parameters of CF′s were compared between measurement, Monte Carlo simulation (MCNP4C and TPS calculation. Materials and Methods: Field analyzer water phantom was used for obtaining percentage depth dose (PDD curves and beam profiles (BP of different conformal fields. MCNP4C was used to model conformal fields dose specification factors and head of linear accelerator varian model 2100C/D. Results: Results showed that the distance to agreement (DTA and dose difference (DD of our findings were well within the acceptance criteria of 3 mm and 3%, respectively. Conclusions: According to this study it can be revealed that TPS using equivalent tissue air ratio calculation method is still convenient for dose prediction in non small conformal fields normally used in prostate radiotherapy. It was also showed that, since there is a close correlation with Monte Carlo simulation, measurements and TPS, Monte Carlo can be further confirmed for implementation and calculation dose distribution in non standard and complex conformal irradiation field for treatment planning systems.
Electric-field-induced internal deformation in piezoelectric BiB{sub 3}O{sub 6} crystals
Energy Technology Data Exchange (ETDEWEB)
Schmidt, O.; Gorfman, S.; Pietsch, U. [Solid State Physics Department, University of Siegen (Germany)
2008-11-15
For the first time electric-field-induced atomic displacements (internal strains) in non-ferroelectric polar BiB{sub 3}O{sub 6} single crystal plates (point symmetry 2) were investigated using X-ray diffraction technique. The intensity variations of selected Bragg reflections were collected for three different orientations of the applied external electric field vector with respect to the crystal lattice and used for calculating the microscopic structural response of BiB{sub 3}O{sub 6}. Due to the limited number of the reflections providing measurable changes in Bragg intensities we restricted ourselves in analyzing the shift of the B{sub 3}O{sub 6} sublattice relative to the Bi one. In addition, we considered the deformation of the Bi-O, B(1)-O and B(2)-O bond lengths and identified the [B(2)O{sub 3}] group as the most sensitive structural unit to an external electric perturbation. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)
Calculation about a modification to the toroidal magnetic field of the Tokamak Novillo. Part I
International Nuclear Information System (INIS)
Chavez A, E.; Melendez L, L.; Colunga S, S.; Valencia A, R.; Lopez C, R.; Gaytan G, E.
1991-07-01
The charged particles that constitute the plasma in the tokamaks are located in magnetic fields that determine its behavior. The poloidal magnetic field of the plasma current and the toroidal magnetic field of the tokamak possess relatively big gradients, which produce drifts on these particles. These drifts are largely the cause of the continuous lost of particles and of energy of the confinement region. In this work the results of numerical calculations of a modification to the 'traditional' toroidal magnetic field that one waits it diminishes the drifts by gradient and improve the confinement properties of the tokamaks. (Author)
Palmesi, P.; Exl, L.; Bruckner, F.; Abert, C.; Suess, D.
2017-11-01
The long-range magnetic field is the most time-consuming part in micromagnetic simulations. Computational improvements can relieve problems related to this bottleneck. This work presents an efficient implementation of the Fast Multipole Method [FMM] for the magnetic scalar potential as used in micromagnetics. The novelty lies in extending FMM to linearly magnetized tetrahedral sources making it interesting also for other areas of computational physics. We treat the near field directly and in use (exact) numerical integration on the multipole expansion in the far field. This approach tackles important issues like the vectorial and continuous nature of the magnetic field. By using FMM the calculations scale linearly in time and memory.
Relativistic deformed mean-field calculation of binding energy differences of mirror nuclei
International Nuclear Information System (INIS)
Koepf, W.; Barreiro, L.A.
1996-01-01
Binding energy differences of mirror nuclei for A=15, 17, 27, 29, 31, 33, 39 and 41 are calculated in the framework of relativistic deformed mean-field theory. The spatial components of the vector meson fields and the photon are fully taken into account in a self-consistent manner. The calculated binding energy differences are systematically smaller than the experimental values and lend support to the existence of the Okamoto-Nolen-Schiffer anomaly found decades ago in nonrelativistic calculations. For the majority of the nuclei studied, however, the results are such that the anomaly is significantly smaller than the one obtained within state-of-the-art nonrelativistic calculations. (author). 35 refs
First-principles calculation on dilute magnetic alloys in zinc blend crystal structure
International Nuclear Information System (INIS)
Ullah, Hamid; Inayat, Kalsoom; Khan, S.A; Mohammad, S.; Ali, A.; Alahmed, Z.A.; Reshak, A.H.
2015-01-01
Ab-initio calculations are performed to investigate the structural, electronic and magnetic properties of spin-polarized diluted magnetic alloys in zinc blende structure. The first-principles study is carried out on Mn doped III–V semiconductors. The calculated band structures, electronic properties and magnetic properties of Ga 1−x Mn x X (X=P, As) compounds reveal that Ga 0.75 Mn 0.25 P is half metallic turned to be metallic with increasing x to 0.5 and 0.75, whereas substitute P by As cause to maintain the half-metallicity nature in both of Ga 0.75 Mn 0.25 As and Ga 0.5 Mn 0.5 As and tune Ga 0.25 Mn 0.75 As to be metallic. Calculated total magnetic moments and the robustness of half-metallicity of Ga 0.75 Mn 0.25 P, Ga 0.75 Mn 0.25 As and Ga 0.5 Mn 0.5 As with respect to the variation in lattice parameters are also discussed. The predicted theoretical evidence shows that some Mn-doped III–V semiconductors can be effectively used in spintronic devices
First-principles calculation on dilute magnetic alloys in zinc blend crystal structure
Energy Technology Data Exchange (ETDEWEB)
Ullah, Hamid, E-mail: hamidullah@yahoo.com [Department of Physics, Government Post Graduate Jahanzeb College, Saidu Sharif Swat (Pakistan); Inayat, Kalsoom [Department of Physics, Government Post Graduate Jahanzeb College, Saidu Sharif Swat (Pakistan); Khan, S.A; Mohammad, S. [Department of Physics, Materials Modeling Laboratory, Hazara University, Mansehra 21300 (Pakistan); Ali, A. [Department of Advanced Materials Science & Engineering, Hanseo University, Seosan-si, Chungnam-do 356-706 (Korea, Republic of); Alahmed, Z.A. [Department of Physics and Astronomy, King Saud University, Riyadh 11451 (Saudi Arabia); Reshak, A.H. [New Technologies-Research Center, University of West Bohemia, Univerzitni 8, 306 14 Pilsen (Czech Republic); Center of Excellence Geopolymer and Green Technology, School of Material Engineering, University Malaysia Perlis, 01007 Kangar, Perlis (Malaysia)
2015-07-01
Ab-initio calculations are performed to investigate the structural, electronic and magnetic properties of spin-polarized diluted magnetic alloys in zinc blende structure. The first-principles study is carried out on Mn doped III–V semiconductors. The calculated band structures, electronic properties and magnetic properties of Ga{sub 1−x}Mn{sub x}X (X=P, As) compounds reveal that Ga{sub 0.75}Mn{sub 0.25}P is half metallic turned to be metallic with increasing x to 0.5 and 0.75, whereas substitute P by As cause to maintain the half-metallicity nature in both of Ga{sub 0.75}Mn{sub 0.25}As and Ga{sub 0.5}Mn{sub 0.5}As and tune Ga{sub 0.25}Mn{sub 0.75}As to be metallic. Calculated total magnetic moments and the robustness of half-metallicity of Ga{sub 0.75}Mn{sub 0.25}P, Ga{sub 0.75}Mn{sub 0.25}As and Ga{sub 0.5}Mn{sub 0.5}As with respect to the variation in lattice parameters are also discussed. The predicted theoretical evidence shows that some Mn-doped III–V semiconductors can be effectively used in spintronic devices.
International Nuclear Information System (INIS)
Bube, W.; Michel-Beyerle, M.E.; Haberkorn, R.; Steffens, E.
1977-01-01
The magnetic field (H approximately 50 Oe) dependence of the rhodamine sensitized triplet exciton density in anthracene crystals is influenced by isotopic substitution. This confirms the hyperfine interaction as mechanism explaining the change of the spin multiplicity in the initially formed singlet state of the radical pair. The isotope effect occurs in the sensitizing dye ( 14 N/ 15 N) rather than at the molecular site of the injected charge within the crystal. This can be understood in terms of the high hopping frequency of the charge carriers as compared to the time constant of the hyperfine induced singlet-triplet transition. Since the dye molecules adsorb in an oriented fashion, the angular dependence of the magnetic field modulation of the triplet exciton density can be interpreted without assuming any additional interactions. (Auth.)
Random crystal field effects on the integer and half-integer mixed-spin system
Yigit, Ali; Albayrak, Erhan
2018-05-01
In this work, we have focused on the random crystal field effects on the phase diagrams of the mixed spin-1 and spin-5/2 Ising system obtained by utilizing the exact recursion relations (ERR) on the Bethe lattice (BL). The distribution function P(Di) = pδ [Di - D(1 + α) ] +(1 - p) δ [Di - D(1 - α) ] is used to randomize the crystal field.The phase diagrams are found to exhibit second- and first-order phase transitions depending on the values of α, D and p. It is also observed that the model displays tricritical point, isolated point, critical end point and three compensation temperatures for suitable values of the system parameters.
Crystal-field investigations of rare-earth-doped wide band gap semiconductors
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 ...
Comment on 'New ansatz for metric operator calculation in pseudo-Hermitian field theory'
International Nuclear Information System (INIS)
Bender, Carl M.; Benincasa, Gregorio; Jones, H. F.
2009-01-01
In a recent Brief Report by Shalaby, a new first-order perturbative calculation of the metric operator for an iφ 3 scalar field theory is given. It is claimed that the incorporation of derivative terms in the ansatz for the metric operator results in a local solution, in contrast to the nonlocal solution previously obtained by Bender, Brody, and Jones. Unfortunately, Shalaby's calculation is not valid because of sign errors.
Calculating infrared contributions to vacuum expectation values of gluonic and quark fields
International Nuclear Information System (INIS)
Arbuzov, B.A.; Boos, E.E.; Turashvili, K.Sh.
1986-01-01
Based on the infrared asymptotics of the lower QCD Green's functions obtained before, we propose a definition and elaborate a technique for calculating non-perturbative vacuum expectations of gluon and quark fields. In our calculations, we use only the known QCD parameters: constituent quark masses, the confining potential slope and the QCD parameter Λ. The values obtained for the vacuum expectations agree well with experiment. (orig.)
Troć, R.; Gajek, Z.; Pikul, A.; Misiorek, H.; Colineau, E.; Wastin, F.
2013-07-01
The transport properties described previously [Troć , Phys. Rev. BPRBMDO1098-012110.1103/PhysRevB.85.224434 85, 224434 (2012)] as well as the magnetic and thermal properties presented in this paper, observed for single-crystalline UCu2Si2, are discussed by assuming a dual (localized-itinerant) scenario. The electronic states of the localized 5f electrons in UCu2Si2 are constructed using the effective Hamiltonian known for ionic systems, allowing us to treat the Coulomb, spin-orbital, and crystal-field interactions on equal footing. The space of parameters has been restricted in the initial steps with the aid of the angular overlap model approximation. The final crystal-field parameters, obtained from the refined steps of calculations, are relatively large (in absolute values), which we attribute to the hybridization characteristic of the metallic systems on the verge of localization. The proposed crystal-field model reproduces correctly with satisfactory accuracy the magnetic and thermal properties of UCu2Si2 in agreement also with the transport properties reported previously. Considerable crystal-field splitting of the ground multiplet of 2760 K is responsible for a large anisotropy in the magnetic behavior, observed in the whole temperature range explored.
Symmetry-adaptation and selection rules for effective crystal field Hamiltonians
International Nuclear Information System (INIS)
Tuszynski, J.A.
1986-01-01
The intention of this paper is to systematically derive an effective Hamiltonian in the presence of crystal fields in such a way as to incorporate relativistic effects and higher order perturbation corrections including configuration mixing. This Hamiltonian will then be conveniently represented as a symmetry-adapted series of one- and two-body double tensor operators whose matrix elements will be analyzed for selection rules. 16 references, 4 tables
Crystal field parameters with Wannier functions: application to rare-earth aluminates
Czech Academy of Sciences Publication Activity Database
Novák, Pavel; Knížek, Karel; Kuneš, Jan
2013-01-01
Roč. 87, č. 20 (2013), "205139-1"-"205139-7" ISSN 1098-0121 R&D Projects: GA ČR(CZ) GAP204/11/0713 Institutional support: RVO:68378271 Keywords : crystal-field * rare earths * Wannier functions Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.664, year: 2013 http://link.aps.org/doi/10.1103/PhysRevB.87.205139
Magnetic field effect on microplastic strain rate in C690 single crystals
International Nuclear Information System (INIS)
Smirnov, B.I.; Shpejzman, V.V.; Peschanskaya, N.N.; Nikolaev, R.K.
2002-01-01
Microplastic strain in magnetic field and beyond it, as well as, subsequent to preliminary exposure of C 60 crystals to magnetic field was investigated by means of laser interferometer enabling to measure rate of strain on the basis of 0.15 μm linear shifting. It is shown that introduction and removal of specimen from 0.2 T induction field immediately during deformation of specimen result in variation of its rate, and at reduction of rate one observes discontinuous interruption of deformation. Sign of effect depends on temperature: at room temperature magnetic field promotes deformation, at 100 K - shows it down. Effect of preliminary exposure within 0.2 and 2T induction field turned to be analogous one. One analyzed possible reasons of the observed manifestation of magnetoplastic effect in C 60 and relation of its sign with phase transition under 260 K temperature [ru
Directory of Open Access Journals (Sweden)
Adela Rodríguez-Romero
2017-06-01
Full Text Available The first part of this research was devoted to investigating the effect of alternate current (AC using four different types of wave modes (pulse-wave at 2 Hz on the crystal growth of lysozyme in solution. The best results, in terms of size and crystal quality, were obtained when protein crystals were grown under the influence of electric fields in a very specific wave mode (“breathing” wave, giving the highest resolution up to 1.34 Å in X-ray diffraction analysis compared with controls and with those crystals grown in gel. In the second part, we evaluated the effect of a strong magnetic field of 16.5 Tesla combined with radiofrequency pulses of 0.43 μs on the crystal growth in gels of tetragonal hen egg white (HEW lysozyme. The lysozyme crystals grown, both in solution applying breathing-wave and in gel under the influence of this strong magnetic field with pulses of radio frequencies, produced the larger-in-size crystals and the highest resolution structures. Data processing and refinement statistics are very good in terms of the resolution, mosaicity and Wilson B factor obtained for each crystal. Besides, electron density maps show well-defined and distinctly separated atoms at several selected tryptophan residues for the crystal grown using the “breathing wave pulses”.
Investigation and Calculation of Magnetic Field in Tubular Linear Reluctance Motor Using FEM
Directory of Open Access Journals (Sweden)
MOSALLANEJAD, A.
2010-11-01
Full Text Available In this paper the magnetic flux density of tubular linear reluctance motor (TLRM in open type magnetic circuit is studied. Also, all magnetic flux density calculation methods in winding of tubular linear reluctance motor are described. The effect of structure parameters on magnetic flux density is also discussed. Electromagnetic finite-element analysis is used for simulation of magnetic field, and simulation results of the magnetic field analysis with DC voltage excitation are compared with results obtained from calculation methods. The comparison yields a good agreement.
Superconducting transition and low-field magnetoresistance of a niobium single crystal at 4.2 deg. K
International Nuclear Information System (INIS)
Perriot, G.
1967-01-01
We report the study of the electrical resistance of a niobium single crystal, at 4.2 deg. K, from the beginning of the superconductive transition to 80 kilo oersteds. Critical fieldsH c2 and H c3 have been determined. Influences on superconductive transition of current density, field-current angle, crystal orientation and magnetoresistance have been studied. Variation laws of low-field transverse and longitudinal magneto-resistances have been determined. (author) [fr
Scanning near-field optical microscopy of quantum dots in photonic crystal cavities
Energy Technology Data Exchange (ETDEWEB)
Skacel, Matthias; Fiore, Andrea [COBRA Research Institute, Technical University Eindhoven, Den Dolech 2, 5600 MB Eindhoven (Netherlands); Prancardi, Marco; Gerardino, Annamaria [Institute of Photonics and Nanotechnology, CNR, via del Cineto Romano 42, 00156 Roma (Italy); Alloing, Blandine; Li Lianhe, E-mail: m.s.skacel@tue.n [Institute of Photonics and Quantum Electronics, EPFL, CH-1015 Lausanne (Switzerland)
2010-09-01
Nanophotonic devices are of major interest for research and future quantum communication applications. Due to their nanometer feature size the resolution limit of far-field microscopy poses a limitation on the characterization of their optical properties. A method to overcome the resolution limit is the Scanning Near-Field Optical Microscope (SNOM). By approaching a fiber tip into the close vicinity of the sample the optical emission in the near-field regime is collected. This way of collecting the light is not affected by the diffraction limit. We employ a low temperature SNOM to investigate the photoluminescence of InAs QDs emitting at 1300nm wavelength embedded in photonic crystal cavities. At each location of an image scan the tip is stopped and a spectrum is acquired. We then plot maps of the photoluminescence for each wavelength. With this instrument it is now possible to directly observe the coupling of QDs to photonic crystal cavities both spectrally and spatially. We show first results of photoluminescence mapping of InAs QDs in photonic crystal cavities.
Mechanical stress calculations for toroidal field coils by the finite element method
International Nuclear Information System (INIS)
Soell, M.; Jandl, O.; Gorenflo, H.
1976-09-01
After discussing fundamental relationships of the finite element method, this report describes the calculation steps worked out for mechanical stress calculations in the case of magnetic forces and forces produced by thermal expansion or compression of toroidal field coils using the SOLID SAP IV computer program. The displacement and stress analysis are based on the 20-node isoparametric solid element. The calculation of the nodal forces produced by magnetic body forces are discussed in detail. The computer programs, which can be used generally for mesh generation and determination of the nodal forces, are published elsewhere. (orig.) [de
Chinnaraja, D; Rajalakshmi, R; Srinivasan, T; Velmurugan, D; Jayabharathi, J
2014-04-24
A series of biologically active N-thiocarbamoyl pyrazoline derivatives have been synthesized using anhydrous potassium carbonate as the catalyst. All the synthesized compounds were characterized by FT-IR, (1)H NMR, (13)C NMR spectral studies, LCMS, CHN Analysis and X-ray diffraction analysis (compound 7). In order to supplement the XRD parameters, molecular modelling was carried out by Gaussian 03W. From the optimized structure, the energy, dipolemoment and HOMO-LUMO energies of all the systems were calculated. Copyright © 2014 Elsevier B.V. All rights reserved.
International Nuclear Information System (INIS)
Bax, D.P.; Verlinde, P.H.; Storchi, P.; Woudstra, E.; Puurunen, H.
1995-01-01
In the Cadplan external beam planning system, irregular fields are calculated using the pencil beam convolution model. This model uses measured PDDs, profiles, and peak scatter factor data to extract pencil beam kernels. The scatter kernel is convolved with a matrix describing the field shape to calculate the PDD of the irregular field. The boundary kernel is used in the calculation of the off-axis ratios. The field matrix used in the convolution has a value of 1 in the open parts of the field a value of zero outside the field and equals the transmission in the blocked part. The evaluation of the model was done using two test cases. Both test cases are based on a 20x20 cm 2 field. In the first case, the central part of the field is blocked by an 8x8 cm 2 block. On one side this block is connected to the field edge by another block with a width of 3 cm. In the second case, two corners of the field are blocked by an 8x8.5 cm 2 block. There is a gap of 3 cm between the two blocks. The two cases were measured in a waterphantom for open and 45 deg. wedged beams of 4 different energies. 4, 6 and 23 MV were measured on conventional accelerators using customized blocks. 25 MV was measured on a scanned beam MM50 using a multileaf collimator. For all fields PDDs, and profiles were measured centrally and at 2 or more off-axis distances. All the measured doses are relative to the normalisation dose of a 20x20 cm 2 open field at d max . The PDDs and profiles measured for the two test cases were compared to results of the calculation of the pencil beam convolution model. The profiles were compared at four depths: d max , 5, 10, and 20 cm. The difference found between measurement and calculation was within acceptable limits, making it possible to use the model in routine clinical planning
Calculation of induced modes of magnetic field in the geodynamo problem
International Nuclear Information System (INIS)
Yokoyama, Yukiko; Yukutake, Takesi
1989-01-01
In the dynamo problem, the calculation of induced modes is of vital importance, because the interaction of fluid motions with the magnetic field induces specific types of fields which are, in many cases, different either from the type of velocity field or from the original magnetic field. This special induction relationship, known as 'selection rules', has so far been derived by calculating Adams-Gaunt integrals and Elsasser integrals. In this paper, we calculate the induced modes in a more direct way, expressing the magnetic fields and the velocity in a spherical harmonic series. By linearizing the product terms of spherical harmonic functions, which appear in interaction terms between the velocity and the magnetic field, into a simple spherical harmonic series, we have derived the induced magnetic modes in a simple general form. When the magnetic field and the velocity are expressed by toroidal and poloidal modes, four kinds of interaction are conceivable between the velocity and the magnetic field. By each interaction, two modes, the poloidal and toroidal, are induced, except in the interaction of the toroidal velocity with the toroidal magnetic field, which induces only the toroidal mode. In spite of the diversity of interaction processes, the induced modes have been found to be expressed simply by two types. For a velocity of degree l and order k interacting with a magnetic field of degree n and order m, one type is the mode with degree and order of n+l-2t, |m±k| for an integer t, and the other with n+l-2t-1, |m±k|. (author)
International Nuclear Information System (INIS)
Han, H.C.; Davey, K.R.; Turner, L.
1985-08-01
The transient eddy current problem is characteristically computationally intensive. The motivation for this research was to realize an efficient, accurate, solution technique involving small matrices via an eigenvalue approach. Such a technique is indeed realized and tested using the null field integral technique. Using smart (i.e., efficient, global) basis functions to represent unknowns in terms of a minimum number of unknowns, homogeneous eigenvectors and eigenvalues are first determined. The general excitatory response is then represented in terms of these eigenvalues/eigenvectors. Excellent results are obtained for the Argonne Felix cylinder experiments using a 4 x 4 matrix. Extension to the 3-D problem (short cylinder) is set up in terms of an 8 x 8 matrix
Directory of Open Access Journals (Sweden)
A.V. Erisov
2016-05-01
Full Text Available Purpose. Simplification of accounting ratio to determine the magnetic field strength of electric power lines, and assessment of their environmental safety. Methodology. Description of the transmission lines of the magnetic field by using techniques of spatial harmonic analysis in the cylindrical coordinate system is carried out. Results. For engineering calculations of electric power lines magnetic field with sufficient accuracy describes their first spatial harmonic magnetic field. Originality. Substantial simplification of the definition of the impact of the construction of transmission line poles on the value of its magnetic field and the bands of land alienation sizes. Practical value. The environmentally friendly projection electric power lines on the level of the magnetic field.
Hyperfine field calculations: search for muon stopping sites in Fe3O4
International Nuclear Information System (INIS)
Boekema, C.; Denison, A.B.; Cooke, D.W.; Heffner, R.H.; Hutson, R.L.; Leon, M.; Schillaci, M.E.
1983-01-01
Muon Spin Rotation (μSR) results for magnetite (Fe 3 O 4 ) are analyzed and discussed. At room temperature, a μSR signal is observed due to the presence of an internal magnetic field (Bsub(int)) at the muon site. External transverse field measurements show that Bsub(int) is parallel to the magnetic spin direction, the direction in zero applied field. Calculations of the hyperfine field to pinpoint muon stopping sites in magnetite show that the local field contains supertransfer (covalent) and dipolar field contributions. The implanted muons appear to stop at sites structurally similar to those reported for hematite (α-Fe 2 O 3 ), where muon-oxygen bond formation was strongly indicated. (Auth.)
Energy Technology Data Exchange (ETDEWEB)
Kneur, J.L
2006-06-15
This document is divided into 2 parts. The first part describes a particular re-summation technique of perturbative series that can give a non-perturbative results in some cases. We detail some applications in field theory and in condensed matter like the calculation of the effective temperature of Bose-Einstein condensates. The second part deals with the minimal supersymmetric standard model. We present an accurate calculation of the mass spectrum of supersymmetric particles, a calculation of the relic density of supersymmetric black matter, and the constraints that we can infer from models.
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...... 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...
Self-field calculation of CICC with fast direct Biot–Savart integration
Energy Technology Data Exchange (ETDEWEB)
Wang, Xu; Li, Yingxu [Key Laboratory of Mechanics on Environment and Disaster in Western China, The Ministry of Education of China, Lanzhou, Gansu 730000 (China); Department of Mechanics and Engineering Science, College of Civil Engineering and Mechanics, Lanzhou University, Lanzhou, Gansu 730000 (China); Gao, Yuanwen, E-mail: ywgao@lzu.edu.cn [Key Laboratory of Mechanics on Environment and Disaster in Western China, The Ministry of Education of China, Lanzhou, Gansu 730000 (China); Department of Mechanics and Engineering Science, College of Civil Engineering and Mechanics, Lanzhou University, Lanzhou, Gansu 730000 (China); Zhou, Youhe [Key Laboratory of Mechanics on Environment and Disaster in Western China, The Ministry of Education of China, Lanzhou, Gansu 730000 (China); Department of Mechanics and Engineering Science, College of Civil Engineering and Mechanics, Lanzhou University, Lanzhou, Gansu 730000 (China)
2014-04-15
Highlights: • An algorithm of fast direct Biot–Savart integration (FDBS) is proposed. • FDBS calculates the self-field of ITER cable-in-conduit conductor (CICC). • FDBS is more effective and easier to implement. • This new method will benefit future magnet design. - Abstract: ITER magnetic device (Tokamak) requires a strong magnetic field produced by charged cable conductors and external sources to arrive at stable and reliable magnetic confinement performance. Before manufacturing and assembling conductors, preliminary analysis of self-field induction is helpful for reducing the cost of varying-parameter experiments. Spatial helix shape of numerous strand elements and multi-level twist of the finalized cable, known as CICC type, make it unpractical to direct use finite-element methods and other numerical procedures for self-field calculation. An algorithm FDBS (fast direct Biot–Savart integration) is proposed to surmount this difficulty, which improves the traditional method (DBS, direct implementing Biot–Savart law for all strand sources) in terms of computational effort. As such the complexity reduces to O(N) from the original O(N{sup 2}) and speed enhancement is achieved in the parallel computation environment. FDBS calculates out a detailed self-field profile for the uncompressed ITER TF conductors carrying uniform current at each cabling level; the layered self-field distribution becomes more indistinct for higher level subcable.
Self-field calculation of CICC with fast direct Biot–Savart integration
International Nuclear Information System (INIS)
Wang, Xu; Li, Yingxu; Gao, Yuanwen; Zhou, Youhe
2014-01-01
Highlights: • An algorithm of fast direct Biot–Savart integration (FDBS) is proposed. • FDBS calculates the self-field of ITER cable-in-conduit conductor (CICC). • FDBS is more effective and easier to implement. • This new method will benefit future magnet design. - Abstract: ITER magnetic device (Tokamak) requires a strong magnetic field produced by charged cable conductors and external sources to arrive at stable and reliable magnetic confinement performance. Before manufacturing and assembling conductors, preliminary analysis of self-field induction is helpful for reducing the cost of varying-parameter experiments. Spatial helix shape of numerous strand elements and multi-level twist of the finalized cable, known as CICC type, make it unpractical to direct use finite-element methods and other numerical procedures for self-field calculation. An algorithm FDBS (fast direct Biot–Savart integration) is proposed to surmount this difficulty, which improves the traditional method (DBS, direct implementing Biot–Savart law for all strand sources) in terms of computational effort. As such the complexity reduces to O(N) from the original O(N 2 ) and speed enhancement is achieved in the parallel computation environment. FDBS calculates out a detailed self-field profile for the uncompressed ITER TF conductors carrying uniform current at each cabling level; the layered self-field distribution becomes more indistinct for higher level subcable
Field gradient calculation of HTS double-pancake coils considering the slanted turns and the splice
Energy Technology Data Exchange (ETDEWEB)
Baek, Geon Woo; Kim, Jin Sub; Song, Seung Hyun; Ko, Tae Kuk [Yonsei University, Seoul (Korea, Republic of); Lee, Woo Seung [JH ENGINEERING CO., LTD., Gunpo (Korea, Republic of); Lee, On You [Korea National University of Transportation, Chungju (Korea, Republic of)
2017-03-15
To obtain Nuclear Magnetic Resonance (NMR) measurement of membrane protein, an NMR magnet is required to generate high intensity, homogeneity, and stability of field. A High-Temperature Superconducting (HTS) magnet is a promising alternative to a conventional Low-Temperature Superconducting (LTS) NMR magnet for high field, current density, and stability margin. Conventionally, an HTS coil has been wound by several winding techniques such as Single-Pancake (SP), Double-Pancake (DP), and layer-wound. The DP winding technique has been frequently used for a large magnet because long HTS wire is generally difficult to manufacture, and maintenance of magnet is convenient. However, magnetic field generated by the slanted turns and the splice leads to field inhomogeneity in Diameter of Spherical Volume (DSV). The field inhomogeneity degrades performance of NMR spectrometer and thus effect of the slanted turns and the splice should be analyzed. In this paper, field gradient of HTS double-pancake coils considering the slanted turns and the splice was calculated using Biot-Savart law and numerical integration. The calculation results showed that magnetic field produced by the slanted turns and the splice caused significant inhomogeneity of field.
Vercamer, Vincent; Hunault, Myrtille O. J. Y.; Lelong, Gérald; Haverkort, Maurits W.; Calas, Georges; Arai, Yusuke; Hijiya, Hiroyuki; Paulatto, Lorenzo; Brouder, Christian; Arrio, Marie-Anne; Juhin, Amélie
2016-12-01
Advanced semiempirical calculations have been performed to compute simultaneously optical absorption and K pre-edge x-ray absorption spectra of Fe2 + in four distinct site symmetries found in minerals. The four symmetries, i.e., a distorted octahedron, a distorted tetrahedron, a square planar site, and a trigonal bipyramidal site, are representative of the Fe2 + sites found in crystals and glasses. A particular attention has been paid to the definition of the p -d hybridization Hamiltonian which occurs for noncentrosymmetric symmetries in order to account for electric dipole transitions. For the different sites under study, an excellent agreement between calculations and experiments was found for both optical and x-ray absorption spectra, in particular in terms of relative intensities and energy positions of electronic transitions. To our knowledge, these are the first calculations of optical absorption spectra on Fe2 + placed in such diverse site symmetries, including centrosymmetric sites. The proposed theoretical model should help to interpret the features of both the optical absorption and the K pre-edge absorption spectra of 3 d transition metal ions and to go beyond the usual fingerprint interpretation.
Directory of Open Access Journals (Sweden)
Beena Varghese
2017-01-01
Full Text Available A novel ethoxy derivative of an amino acid chemosensor, 3-naphthyl-1-phenyl-5-(2ʹ-fluoro-5ʹ-nitrophenyl-2-pyrazoline (NPFNP, has been synthesized and characterized by different spectroscopic methods. A single crystal of the ethoxy derivative, 3-naphthyl-1-phenyl-5-(2ʹ-ethoxy-5ʹ-nitrophenyl-2-pyrazoline NPENP, has been obtained and characterized. The structure holds interest as it carries biologically active pyrazoline as a central ring attaching to electron donating and withdrawing substituents. The major motivation for this work was to gain detailed insight into the structural parameters of this compound for investigating the influence of crystal packing and geometrical dimensions on optical properties. Time-dependent DFT calculations have been employed for comparing the XRD data with theoretical parameters. The results show that the DFT method at B3LYP/6-31G level can well reproduce the structure of the title compound.
Marchewka, M. K.; Drozd, M.; Janczak, J.
2011-08-01
The N-(4-nitrophenyl)-β-alanine in crystalline form directly by the addition of 4-nitroaniline to the acrylic acid in aqueous solution has been obtained. The title β-alanine derivative crystallizes in the P2 1/ c space group of monoclinic system with four molecules per unit cell. The X-ray geometry of β-alanine derivative molecule has been compared with those obtained by molecular orbital calculations corresponding to the gas phase. In the crystal the molecules related by an inversion center interact via symmetrically equivalent O-H⋯O hydrogen bonds with O⋯O distance of 2.656(2) Å forming a dimeric structure. The dimers of β-alanine derivative weakly interact via N-H⋯O hydrogen bonds between the H atom of β-amine groups and one of O atom of nitro groups. The room temperature powder vibrational (infrared and Raman) measurements are in accordance with the X-ray analysis. In aqueous solution of 4-nitroaniline and acrylic acid, the double C dbnd C bond of vinyl group of acrylic acid breaks as result of 4-nitroaniline addition.
The spin-3/2 Ising model AFM/AFM two-layer lattice with crystal field
International Nuclear Information System (INIS)
Yigit, A.; Albayrak, E.
2010-01-01
The spin-3/2 Ising model is investigated for the case of antiferromagnetic (AFM/AFM) interactions on the two-layer Bethe lattice by using the exact recursion relations in a pairwise approach for given coordination numbers q=3, 4 and 6 when the layers are under the influences of equal external magnetic and equal crystal fields. The ground state (GS) phase diagrams are obtained on the different planes in detail and then the temperature dependent phase diagrams of the system are calculated accordingly. It is observed that the system presents both second- and first-order phase transitions for all q, therefore, tricritical points. It was also found that the system exhibits double-critical end points and isolated points. The model also presents two Neel temperatures, TN, and the existence of which leads to the reentrant behavior.
Hu, Liang; Zhao, Nannan; Gao, Zhijian; Mao, Kai; Chen, Wenyu; Fu, Xin
2018-05-01
Determination of the distribution of a generated acoustic field is valuable for studying ultrasonic transducers, including providing the guidance for transducer design and the basis for analyzing their performance, etc. A method calculating the acoustic field based on laser-measured vibration velocities on the ultrasonic transducer surface is proposed in this paper. Without knowing the inner structure of the transducer, the acoustic field outside it can be calculated by solving the governing partial differential equation (PDE) of the field based on the specified boundary conditions (BCs). In our study, the BC on the transducer surface, i.e. the distribution of the vibration velocity on the surface, is accurately determined by laser scanning measurement of discrete points and follows a data fitting computation. In addition, to ensure the calculation accuracy for the whole field even in an inhomogeneous medium, a finite element method is used to solve the governing PDE based on the mixed BCs, including the discretely measured velocity data and other specified BCs. The method is firstly validated on numerical piezoelectric transducer models. The acoustic pressure distributions generated by a transducer operating in an homogeneous and inhomogeneous medium, respectively, are both calculated by the proposed method and compared with the results from other existing methods. Then, the method is further experimentally validated with two actual ultrasonic transducers used for flow measurement in our lab. The amplitude change of the output voltage signal from the receiver transducer due to changing the relative position of the two transducers is calculated by the proposed method and compared with the experimental data. This method can also provide the basis for complex multi-physical coupling computations where the effect of the acoustic field should be taken into account.
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.
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.
Ab-initio calculations of electric field gradient in Ru compounds and ...
Indian Academy of Sciences (India)
Home; Journals; Pramana – Journal of Physics; Volume 89; Issue 2. A b − i n i t i o calculations of electric field gradient in Ru compounds and their implication on the nuclear quadrupole moments of 99 Ru and 101 Ru. S N MISHRA. Research Article Volume 89 Issue 2 August 2017 Article ID 22 ...
Surface impedance of superconductors in wide frequency ranges for wake field calculations
International Nuclear Information System (INIS)
Davidovskii, V.G.
2006-01-01
The problem of the surface impedance of superconductors in wide frequency ranges for calculations of wake fields, generated by bunches of charged particles moving axially inside a metallic vacuum chambers, is solved. The case of specular electron reflection at the superconductor surface is considered. The expression for the surface impedance of superconductors suitable for numerical computation is derived [ru
A finite element method for calculating the 3-dimensional magnetic fields of cyclotron
International Nuclear Information System (INIS)
Zhao Xiaofeng
1986-01-01
A series of formula of the finite element method (scalar potential) for calculating the three-dimensional magnetic field of the main magnet of a sector focused cyclotron, and the realization method of the periodic boundary conditions in the code are given
Ab-initio calculations of electric field gradient in Ru compounds and ...
Indian Academy of Sciences (India)
S N Mishra
2017-07-11
Jul 11, 2017 ... with calculated electric field gradient (EFG) for a large number of Ru-based compounds. The ab-initio ... zz assumed to stem from geometric arrangement of ... tant nuclear probes for the measurements of quadrupole ... with the unit cell including the nucleus and no restriction is put on ..... The effect of on-site ...
Calculation of magnetic field and electromagnetic forces in MHD superconducting magnets
International Nuclear Information System (INIS)
Martinelli, G.; Morini, A.; Moisio, M.F.
1992-01-01
The realization of a superconducting prototype magnet for MHD energy conversion is under development in Italy. Electromechanical industries and University research groups are involved in the project. The paper deals with analytical methods developed at the Department of Electrical Engineering of Padova University for calculating magnetic field and electromagnetic forces in MHD superconducting magnets and utilized in the preliminary design of the prototype
Electric-field-induced flow-aligning state in a nematic liquid crystal.
Fatriansyah, Jaka Fajar; Orihara, Hiroshi
2015-04-01
The response of shear stress to a weak ac electric field as a probe is measured in a nematic liquid crystal under shear flow and dc electric fields. Two states with different responses are clearly observed when the dc electric field is changed at a constant shear rate: the flow aligning and non-flow aligning states. The director lies in the shear plane in the flow aligning state and out of the plane in the non-flow aligning state. Through application of dc electric field, the non-flow aligning state can be changed to the flow aligning state. In the transition from the flow aligning state to the non-flow aligning state, it is found that the response increases and the relaxation time becomes longer. Here, the experimental results in the flow aligning state are discussed on the basis of the Ericksen-Leslie theory.
International Nuclear Information System (INIS)
Dobberstein, M.P.; Krawczyk, F.; Schaefer-Jotter, M.
1990-11-01
The electrostatic field inside small drift cells shows in general edge effects which are not negligible. These are usually corrected by field shaping wires or strips. The operating voltages of the field shaping electrodes have to be adjusted to maximize the field homogeneity. We present the underlying ideas of such an optimization procedure for the cells of the ZEUS forward drift chambers. Using the finite difference code PROFI, the optimization can be performed automatically by a multiple solution of the Poisson equation. An experimental verification of the optimal voltages was carried out measuring the gas amplifications at the six sense wires. Modifications of the drift cell geometry were necessary for calibration measurements with a laser beam. This caused additional distortions of the electrostatic field. Their influence was calculated using the MAFIA code, which allows to include open boundary conditions. (orig.)
Theory and numerical calculation of the acoustic field exerted by eddy-current forces
Energy Technology Data Exchange (ETDEWEB)
Kawashima, K.
1976-01-01
The equations for calculating the acoustic field produced within a nonmagnetic metal by interaction of eddy currents with a static magnetic field were obtained on the assumptions (1) an ultrasonic wave is generated by the electromagentic force through classical and macroscopic phenomena; (2) the electric, magnetic, and elastic properties of the metal are linear, isotropic, and homogeneous throughout the metal, which occupies semi-infinite space; (3) the whole system is axially symmetric; and (4) eddy currents and elastic waves show a steady-state sinusoidal variation. The acoustic field produced by a specific electromagnetic ultrasonic transducer with axial symmetry was calculated numerically, and the results showed a well-defined ultrasonic wave beam, which was narrower than had been expected from the size of the transducer. (auth)
TE/TM alternating direction scheme for wake field calculation in 3D
Energy Technology Data Exchange (ETDEWEB)
Zagorodnov, Igor [Institut fuer Theorie Elektromagnetischer Felder (TEMF), Technische Universitaet Darmstadt, Schlossgartenstrasse 8, D-64289 Darmstadt (Germany)]. E-mail: zagor@temf.de; Weiland, Thomas [Institut fuer Theorie Elektromagnetischer Felder (TEMF), Technische Universitaet Darmstadt, Schlossgartenstrasse 8, D-64289 Darmstadt (Germany)
2006-03-01
In the future, accelerators with very short bunches will be used. It demands developing new numerical approaches for long-time calculation of electromagnetic fields in the vicinity of relativistic bunches. The conventional FDTD scheme, used in MAFIA, ABCI and other wake and PIC codes, suffers from numerical grid dispersion and staircase approximation problem. As an effective cure of the dispersion problem, a numerical scheme without dispersion in longitudinal direction can be used as it was shown by Novokhatski et al. [Transition dynamics of the wake fields of ultrashort bunches, TESLA Report 2000-03, DESY, 2000] and Zagorodnov et al. [J. Comput. Phys. 191 (2003) 525]. In this paper, a new economical conservative scheme for short-range wake field calculation in 3D is presented. As numerical examples show, the new scheme is much more accurate on long-time scale than the conventional FDTD approach.
Calculation of flux density distribution on irradiation field of electron accelerator
International Nuclear Information System (INIS)
Tanaka, Ryuichi
1977-03-01
The simple equation of flux density distribution in the irradiation field of an ordinary electron accelerator is a function of the physical parameters concerning electron irradiation. Calculation is based on the mean square scattering angle derived from a simple multiple scattering theory, with the correction factors of air scattering, beam scanning and number transmission coefficient. The flux density distribution was measured by charge absorption in a graphite target set in the air. For the calculated mean square scattering angles of 0.089-0.29, the values of calculation agree with those by experiment within about 10% except at large scattering angles. The method is applicable to dose evaluation of ordinary electron accelerators and design of various irradiators for radiation chemical reaction. Applicability of the simple multiple scattering theory in calculation of the scattered flux density and periodical variation of the flux density of scanning beam are also described. (auth.)
Crystal field excitations of YbMn{sub 2}Si{sub 2}
Energy Technology Data Exchange (ETDEWEB)
Mole, R.A. [Australian Nuclear Science and Technology Organisation, Lucas Heights, NSW 2234 (Australia); School of Physical, Environmental and Mathematical Sciences, The University of New South Wales at the Australian Defence Force Academy, Canberra, ACT 2600 (Australia); Hofmann, M. [School of Physical, Environmental and Mathematical Sciences, The University of New South Wales at the Australian Defence Force Academy, Canberra, ACT 2600 (Australia); Forschungsneutronenquelle Heinz Maier-Leibnitz (FRM II), Technische Universität München, 85747 Garching (Germany); Adroja, D.T. [ISIS Facility, Science and Technology Facilities Council, Rutherford Appleton Laboratory, Didcot, OX11 OQX (United Kingdom); Moze, O. [Dipartimento di Fisica, Università degli Studi di Modena e Reggio Emilia, Modena (Italy); Campbell, S.J., E-mail: stewart.campbell@adfa.edu.au [School of Physical, Environmental and Mathematical Sciences, The University of New South Wales at the Australian Defence Force Academy, Canberra, ACT 2600 (Australia)
2013-12-15
The crystal field excitations of the rare earth intermetallic compound YbMn{sub 2}Si{sub 2} have been measured by inelastic neutron scattering over the temperature range 2.5–50 K. The YbMn{sub 2}Si{sub 2} spectra exhibit three low energy excitations (∼3–7 meV) in the antiferromagnetic AFil region above the magnetic phase transition at T{sub N2} = 30(5) K. The crystal field parameters have been determined for YbMn{sub 2}Si{sub 2} in the antiferromagnetic AFil region. A further two inelastic excitations (∼9 meV, 17 meV) are observed below T{sub N2}=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 Yb{sup 3+} 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 T{sub N2} cannot be described fully in terms of molecular field models based on either a single Yb{sup 3+} site or two Yb{sup 3+} sites. This indicates that the magnetic behaviour of YbMn{sub 2}Si{sub 2} 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. - Highlights: • The inelastic neutron scattering from YbMn{sub 2}Si{sub 2} has been investigated over the temperature range 2.5–50 K. • The crystal field splitting has been monitored through the magnetic transition at 30(5) K. • We have determined the crystal field parameters for the antiferromagnetic AFil region. • The transition intensities are described well by Boltzmann occupancy models. • The spectra below the magnetic transition have been analysed by
Electromagnetic-field amplification in finite one-dimensional photonic crystals
International Nuclear Information System (INIS)
Gorelik, V. S.; Kapaev, V. V.
2016-01-01
The electromagnetic-field distribution in a finite one-dimensional photonic crystal is studied using the numerical solution of Maxwell’s equations by the transfer-matrix method. The dependence of the transmission coefficient T on the period d (or the wavelength λ) has the characteristic form with M–1 (M is the number of periods in the structure) maxima with T = 1 in the allowed band of an infinite crystal and zero values in the forbidden band. The field-modulus distribution E(x) in the structure for parameters that correspond to the transmission maxima closest to the boundaries of forbidden bands has maxima at the center of the structure; the value at the maximum considerably exceeds the incident-field strength. For the number of periods M ~ 50, more than an order of magnitude increase in the field amplification is observed. The numerical results are interpreted with an analytic theory constructed by representing the solution in the form of a linear combination of counterpropagating Floquet modes in a periodic structure.
Magnetic particle movement program to calculate particle paths in flow and magnetic fields
International Nuclear Information System (INIS)
Inaba, Toru; Sakazume, Taku; Yamashita, Yoshihiro; Matsuoka, Shinya
2014-01-01
We developed an analysis program for predicting the movement of magnetic particles in flow and magnetic fields. This magnetic particle movement simulation was applied to a capturing process in a flow cell and a magnetic separation process in a small vessel of an in-vitro diagnostic system. The distributions of captured magnetic particles on a wall were calculated and compared with experimentally obtained distributions. The calculations involved evaluating not only the drag, pressure gradient, gravity, and magnetic force in a flow field but also the friction force between the particle and the wall, and the calculated particle distributions were in good agreement with the experimental distributions. Friction force was simply modeled as static and kinetic friction forces. The coefficients of friction were determined by comparing the calculated and measured results. This simulation method for solving multiphysics problems is very effective at predicting the movements of magnetic particles and is an excellent tool for studying the design and application of devices. - Highlights: ●We developed magnetic particles movement program in flow and magnetic fields. ●Friction force on wall is simply modeled as static and kinetic friction force. ●This program was applied for capturing and separation of an in-vitro diagnostic system. ●Predicted particle distributions on wall were agreed with experimental ones. ●This method is very effective at predicting movements of magnetic particles
HEDO-2, Magnetic Field Calculation and Plot of Air Core Coils
International Nuclear Information System (INIS)
Preis, H.; Martin, P.
1979-01-01
1 - Nature of physical problem solved: HEDO-2 allows calculation of the magnetic field, magnetic volume forces, and the self and mutual inductance coefficients of arbitrary air-core coil systems. In addition, the program is suitable for the calculation and graphic representation of field and contour lines (lines B = const). 2 - Method of solution: Approximation of the spatially distributed currents by line currents, in which the number of closed line currents per coil can be freely chosen in accordance with the calculating accuracy required. All types of calculations possible with HEDO-2 are based on the field representation of line currents. 3 - Restrictions on the complexity of the problem: (a) The coils must have rectangular winding cross sections. (b) The contour of each coil must be symmetric to at least one coordinate axis. (c) The function describing the contour and the derivative of the function must be continuous. (d) Maximum number of coils n=200; (e) Maximum number of test points p=2000; (f) Test points ought not to be located on a line conductor
International Nuclear Information System (INIS)
Wang, Y.; Chen, W.; Chen, X.; Liu, H.Y.; Ding, Z.H.; Ma, Y.M.; Wang, X.D.; Cao, Q.P.; Jiang, J.Z.
2012-01-01
Highlights: ► Changes from NaCl-, WC- to anti-NiAs-type structures are for 4d and 5d metal monoborides. ► Vickers hardnesses of monoborides are relatively low. ► B-vacancies cause the difference in lattice parameters for IrB and PtB. ► Nonstoichiometric IrB and PtB phases synthesized. - Abstract: The crystal structures, stability, electronic and elastic properties of 4d and 5d transition metal monoborides have been studied by first principles calculations. It is found that NaCl-type ZrB, NbB, MoB, HfB, TaB and WB, WC-type TcB, RuB, ReB, OsB and IrB, and anti-NiAs-type RhB and PdB are thermodynamically stable at zero pressure. They all are metallic. The Vickers hardnesses of these monoborides are relatively low as compared with monocarbides and mononitrides. It is clarified that the presence of B-vacancies is the origin for the difference of lattice parameters between theoretical and experimental results for WC-type IrB and anti-NiAs-type PtB while IrB and PtB with stoichiometry from calculations are revealed to be mechanically unstable and dynamically unstable, respectively.
Monte-Carlo-calculations for the simulation of channelling-experiments with V3Si-single-crystals
International Nuclear Information System (INIS)
Kaufmann, R.
1978-05-01
The results of channelling-investigations on single-crystals of A15-type structure, like e.g. V 3 Si, are not directly comparable to analytical model-calculations. Therefore the channelling-process was simulated in a Monte-Carlo-program on the basis of the binary-collision-model. The calculated values for the minimum yield, Chisub(min), and the critical angle, Psisub(1/2), were in good agreement with the results of experiments with 2 MeV- 4 He + -particles. The lattice damage in the range of 2,000 Angstroem at the surface after an irradiation with a fluence of 6 x 10 16 - 4 He + /cm 2 at 300 KeV could be explained by normally distributed static displacements of the V-atoms with a mean value of 0.05 A. The transverse damage structure after an irradiation with a fluence of 1.5 x 10 16 - 4 He + /cm 2 at 50 KeV could be simulated by a step profile of 50% displacements of the V-atoms with a maximum value of 0.5 Angstroem at the depth of the projected range. (orig./HPOE) [de
Energy Technology Data Exchange (ETDEWEB)
Wang, Y.; Chen, W. [International Center for New-Structured Materials (ICNSM), Zhejiang University, and Laboratory of New-Structured Materials, State Key Laboratory of Silicon Materials, Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China); Chen, X.; Liu, H.Y. [State Key Laboratory of Superhard Materials, Jilin University, Changchun 130012 (China); Ding, Z.H.; Ma, Y.M. [State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, Jilin University, Changchun 130012 (China); Wang, X.D.; Cao, Q.P. [International Center for New-Structured Materials (ICNSM), Zhejiang University, and Laboratory of New-Structured Materials, State Key Laboratory of Silicon Materials, Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China); Jiang, J.Z., E-mail: jiangjz@zju.edu.cn [International Center for New-Structured Materials (ICNSM), Zhejiang University, and Laboratory of New-Structured Materials, State Key Laboratory of Silicon Materials, Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China)
2012-10-15
Highlights: Black-Right-Pointing-Pointer Changes from NaCl-, WC- to anti-NiAs-type structures are for 4d and 5d metal monoborides. Black-Right-Pointing-Pointer Vickers hardnesses of monoborides are relatively low. Black-Right-Pointing-Pointer B-vacancies cause the difference in lattice parameters for IrB and PtB. Black-Right-Pointing-Pointer Nonstoichiometric IrB and PtB phases synthesized. - Abstract: The crystal structures, stability, electronic and elastic properties of 4d and 5d transition metal monoborides have been studied by first principles calculations. It is found that NaCl-type ZrB, NbB, MoB, HfB, TaB and WB, WC-type TcB, RuB, ReB, OsB and IrB, and anti-NiAs-type RhB and PdB are thermodynamically stable at zero pressure. They all are metallic. The Vickers hardnesses of these monoborides are relatively low as compared with monocarbides and mononitrides. It is clarified that the presence of B-vacancies is the origin for the difference of lattice parameters between theoretical and experimental results for WC-type IrB and anti-NiAs-type PtB while IrB and PtB with stoichiometry from calculations are revealed to be mechanically unstable and dynamically unstable, respectively.
International Nuclear Information System (INIS)
Lamela, J.; Jaque, D.; Rodenas, A.; Jaque, F.; Torchia, G.A.; Vazquez, J.R.; Mendez, C.; Roso, L.
2008-01-01
Near-field-optical-microscopy has been used to study the micro-modifications caused by femtosecond laser pulses focused at the surface and in the volume of lithium niobate crystals. We have found experimental evidence of the existence, close to femtosecond ablation craters, of periodic modifications in the surface reflectivity. In addition, the potential application of near-field-optical microscopy for the spatial location of permanent modifications caused by femtosecond pulses focused inside lithium niobate crystals has been also demonstrated. (orig.)
Dissolved organic carbon--contaminant interaction descriptors found by 3D force field calculations.
Govers, H A J; Krop, H B; Parsons, J R; Tambach, T; Kubicki, J D
2002-03-01
Enthalpies of transfer at 300 K of various partitioning processes were calculated in order to study the suitability of 3D force fields for the calculation of partitioning constants. A 3D fulvic acid (FA) model of dissolved organic carbon (DOC) was built in a MM+ force field using AMI atomic charges and geometrical optimization (GO). 3,5-Dichlorobiphenyl (PCB14), 4,4'-dichlorobiphenyl (PCB15), 1,1,1-trichloro-2,2-bis-(4-chlorophenyl)-ethane (PPDDT) and 2-chloro-4-ethylamino-6-isopropylamino-s-triazine (Atrazine) were inserted into different sites and their interaction energies with FA were calculated. Energies of hydration were calculated and subtracted from FA-contaminant interactions of selected sites. The resulting values for the enthalpies of transfer from water to DOC were 2.8, -1.4, -6.4 and 0.0 kcal/mol for PCB 14, PCB15, PPDDT and Atrazine, respectively. The value of PPDDT compared favorably with the experimental value of -5.0 kcal/mol. Prior to this, the method was studied by the calculation of the enthalpies of vaporization and aqueous solution using various force fields. In the MM + force field GO predicted enthalpies of vaporization deviated by +0.7 (PCB14), +3.6 (PCB15) and -0.7 (PPDDT)kcal/mol from experimental data, whereas enthalpies of aqueous solution deviated by -3.6 (PCB14), +5.8 (PCB15) and +3.7 (PPDDT) kcal/mol. Only for PCB14 the wrong sign of this enthalpy value was predicted. Potential advantages and limitations of the approach were discussed.
International Nuclear Information System (INIS)
Kalin, J.; Petkovsek, B.; Montarnal, Ph.; Genty, A.; Deville, E.; Krivic, J.; Ratej, J.
2011-01-01
In the past years the Slovenian Performance Analysis/Safety Assessment team has performed many generic studies for the future Slovenian low and intermediate level waste repository, most recently a Special Safety Analysis for the Krsko site. The modelling approach was to split the problem into three parts: near-field (detailed model of the repository), far-field (i.e., geosphere) and biosphere. In the Special Safety Analysis the code used to perform the near-field calculations was Hydrus2D. Recently the team has begun a cooperation with the French Commisariat al'Energie Atomique/Saclay (CEA/Saclay) and, as a part of this cooperation, began investigations into using the Alliances numerical platform for near-field calculations in order to compare the overall approach and calculated results. The article presents the comparison between these two codes for a silo-type repository that was considered in the Special Safety Analysis. The physical layout and characteristics of the repository are presented and a hydraulic and transport model of the repository is developed and implemented in Alliances. Some analysis of sensitivity to mesh fineness and to simulation timestep has been preformed and is also presented. The compared quantity is the output flux of radionuclides on the boundary of the model. Finally the results from Hydrus2D and Alliances are compared and the differences and similarities are commented.
Energy Technology Data Exchange (ETDEWEB)
Kalin, J., E-mail: jan.kalin@zag.s [Slovenian National Building and Civil Engineering Institute, Dimiceva 12, SI-1000 Ljubljana (Slovenia); Petkovsek, B., E-mail: borut.petkovsek@zag.s [Slovenian National Building and Civil Engineering Institute, Dimiceva 12, SI-1000 Ljubljana (Slovenia); Montarnal, Ph., E-mail: philippe.montarnal@cea.f [CEA/Saclay, DM2S/SFME/LSET, Gif-sur-Yvette, 91191 cedex (France); Genty, A., E-mail: alain.genty@cea.f [CEA/Saclay, DM2S/SFME/LSET, Gif-sur-Yvette, 91191 cedex (France); Deville, E., E-mail: estelle.deville@cea.f [CEA/Saclay, DM2S/SFME/LSET, Gif-sur-Yvette, 91191 cedex (France); Krivic, J., E-mail: jure.krivic@geo-zs.s [Geological Survey of Slovenia, Dimiceva 14, SI-1000 Ljubljana (Slovenia); Ratej, J., E-mail: joze.ratej@geo-zs.s [Geological Survey of Slovenia, Dimiceva 14, SI-1000 Ljubljana (Slovenia)
2011-04-15
In the past years the Slovenian Performance Analysis/Safety Assessment team has performed many generic studies for the future Slovenian low and intermediate level waste repository, most recently a Special Safety Analysis for the Krsko site. The modelling approach was to split the problem into three parts: near-field (detailed model of the repository), far-field (i.e., geosphere) and biosphere. In the Special Safety Analysis the code used to perform the near-field calculations was Hydrus2D. Recently the team has begun a cooperation with the French Commisariat al'Energie Atomique/Saclay (CEA/Saclay) and, as a part of this cooperation, began investigations into using the Alliances numerical platform for near-field calculations in order to compare the overall approach and calculated results. The article presents the comparison between these two codes for a silo-type repository that was considered in the Special Safety Analysis. The physical layout and characteristics of the repository are presented and a hydraulic and transport model of the repository is developed and implemented in Alliances. Some analysis of sensitivity to mesh fineness and to simulation timestep has been preformed and is also presented. The compared quantity is the output flux of radionuclides on the boundary of the model. Finally the results from Hydrus2D and Alliances are compared and the differences and similarities are commented.
Effect of an external magnetic field on polytypism of CdI2 crystals grown from solutions
International Nuclear Information System (INIS)
Palosz, B.; Przedmojski, J.
1982-01-01
The effect of growth conditions on the polytypic structure of crystals of CdI 2 was analyzed for crystallization from solutions. Three solvents were used: H 2 O, 3 H 2 O + 1 C 2 H 5 OH and 1 H 2 O + 1 C 2 H 5 OH. Crystals were grown at two temperatures: 5 and 25 0 C with low and high growth rates; an external magnetic field of about 0.25 tesla was used. The effect of the above three parameters on the formation of the basic polytypes 2H and 4H and on the ordering of faults in disordered structures and in polytype cells was studied by X-ray analysis of crystal surfaces. Some distinct relations between the polytypic structure of crystals of CdI 2 and the magnetic field were found. (author)
Amm, O.; Fujii, R.; VanhamäKi, H.; Yoshikawa, A.; Ieda, A.
2013-05-01
We devise an approach to calculate the polarization electric field in the ionosphere, when the ionospheric conductances, the primary (modeled) or the total (measured) electric field, and the Cowling efficiency are given. In contrast to previous studies, our approach is a general solution which is not limited to specific geometrical setups, and all parameters may have any kind of spatial dependence. The solution technique is based on spherical elementary current (vector) systems (SECS). This way, we avoid the need to specify explicit boundary conditions for the searched polarization electric field of its potential which would be required if the problem was solved in a differential equation approach. Instead, we solve an algebraic matrix equation, and the implicit boundary condition that the divergence of the polarization electric field vanishes outside our analysis area is sufficient. In order to illustrate our theory, we then apply it to two simple models of auroral electrodynamic situations, the first being a mesoscale strong conductance enhancement in the early morning sector within a relatively weak southward primary electric field, and a morning sector auroral arc with only a weak conductance enhancement, but a large southward primary electric field at the poleward flank of the arc. While the significance of the polarization electric field for maximum Cowling efficiency is large for the first case, it is rather minor for the second one. Both models show that the polarization electric field effect may not only change the magnitude of the current systems but also their overall geometry. Furthermore, the polarization electric field may extend into regions where the primary electric field is small, thus even dominating the total electric field in these regions. For the first model case, the total Joule heating integrated over the analysis area decreases by a factor of about 4 for maximum Cowling efficiency as compared to the case of vanishing Cowling efficiency
Theoretical Crystal-Field Calculations for Rare-Earth Ions in III-V semiconductor Compounds
1991-10-01
22209 Director Director US Army Electronics Warfare Laboratory Defense Nuclear Agency Attn AMSEL-DD Attn Tech Library Attn AMSEL-DD, J. Charlton 6801...Washougal, WA 98671 Attn SLCHD-NW-TN, Chief Attn SLCHD-NW-TS, Chief Departmento Quimica Fundamental Attn SLCHD-PO, Chief Universidade Federal de
Phase-Field Modeling of Polycrystalline Solidification: From Needle Crystals to Spherulites—A Review
Gránásy, László; Rátkai, László; Szállás, Attila; Korbuly, Bálint; Tóth, Gyula I.; Környei, László; Pusztai, Tamás
2014-04-01
Advances in the orientation-field-based phase-field (PF) models made in the past are reviewed. The models applied incorporate homogeneous and heterogeneous nucleation of growth centers and several mechanisms to form new grains at the perimeter of growing crystals, a phenomenon termed growth front nucleation. Examples for PF modeling of such complex polycrystalline structures are shown as impinging symmetric dendrites, polycrystalline growth forms (ranging from disordered dendrites to spherulitic patterns), and various eutectic structures, including spiraling two-phase dendrites. Simulations exploring possible control of solidification patterns in thin films via external fields, confined geometry, particle additives, scratching/piercing the films, etc. are also displayed. Advantages, problems, and possible solutions associated with quantitative PF simulations are discussed briefly.
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.
Melt Motion Due to Peltier Marking During Bridgman Crystal Growth with an Axial Magnetic Field
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.
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.
40-Tesla pulsed-field cryomagnet for single crystal neutron diffraction
Duc, F.; Tonon, X.; Billette, J.; Rollet, B.; Knafo, W.; Bourdarot, F.; Béard, J.; Mantegazza, F.; Longuet, B.; Lorenzo, J. E.; Lelièvre-Berna, E.; Frings, P.; Regnault, L.-P.
2018-05-01
We present the first long-duration and high duty cycle 40-T pulsed-field cryomagnet addressed to single crystal neutron diffraction experiments at temperatures down to 2 K. The magnet produces a horizontal field in a bi-conical geometry, ±15° and ±30° upstream and downstream of the sample, respectively. Using a 1.15 MJ mobile generator, magnetic field pulses of 100 ms length are generated in the magnet, with a rise time of 23 ms and a repetition rate of 6-7 pulses per hour at 40 T. The setup was validated for neutron diffraction on the CEA-CRG three-axis spectrometer IN22 at the Institut Laue Langevin.
Numerical calculation of flashing from long pipes using a two-field model
International Nuclear Information System (INIS)
Rivard, W.C.; Torrey, M.D.
1976-05-01
A two-field model for two-phase flows, in which the vapor and liquid phases have different densities, velocities, and temperatures, has been used to calculate the flashing of water from long pipes. The IMF (Implicit Multifield) technique is used to numerically solve the transient equations that govern the dynamics of each phase. The flow physics is described with finite rate phase transitions, interfacial friction, heat transfer, pipe wall friction, and appropriate state equations. The results of the calculations are compared with measured histories of pressure, temperature, and void fraction. A parameter study indicates the relative sensitivity of the results to the various physical models that are used
Numerical calculation of flashing from long pipes using a two-field model
International Nuclear Information System (INIS)
Rivard, W.C.; Torrey, M.D.
1975-11-01
A two-field model for two-phase flows, in which the vapor and liquid phases have different densities, velocities, and temperatures, has been used to calculate the flashing of water from long pipes. The IMF (Implicit Multifield) technique is used to numerically solve the transient equations that govern the dynamics of each phase. The flow physics is described with finite rate phase transitions, interfacial friction, heat transfer, pipe wall friction, and appropriate state equations. The results of the calculations are compared with measured histories of pressure, temperature, and void fraction. A parameter study indicates the relative sensitivity of the results to the various physical models that are used
DEFF Research Database (Denmark)
Ruud, Kenneth; Helgaker, Trygve; Kobayashi, Rika
1994-01-01
to corresponding individual gauges for localized orbitals (IGLO) results. The London results show better basis set convergence than IGLO, especially for heavier atoms. It is shown that the choice of active space is crucial for determination of accurate nuclear shielding constants.......Nuclear shielding calculations are presented for multiconfigurational self-consistent field wave functions using London atomic orbitals (gauge invariant atomic orbitals). Calculations of nuclear shieldings for eight molecules (H2O, H2S, CH4, N2, CO, HF, F2, and SO2) are presented and compared...
The effect of magnetic field models on cosmic ray cutoff calculations
International Nuclear Information System (INIS)
Pfitzer, K.A.
1979-01-01
The inaccuracies in the 1974 Olson-Pfitzer model appeared to be the probable cause for discrepancies between the observed and calculated cosmic ray cutoff values. An improved version of the Olson-Pfitzer model is now available which includes the effects of the tilt of the earth's dipole axis and which has removed most of the problems encountered in the earlier model. The paper demonstrates that when this new accurate magnetic field model is used, the calculated and observed cutoff values agree with the experimental error without the need for invoking anomalous diffusion mechanisms. This tilt-dependent model also permits a study of cutoffs versus the tilt of the dipole axis
One-loop calculation in time-dependent non-equilibrium thermo field dynamics
International Nuclear Information System (INIS)
Umezawa, H.; Yamanaka, Y.
1989-01-01
This paper is a review on the structure of thermo field dynamics (TFD) in which the basic concepts such as the thermal doublets, the quasi-particles and the self-consistent renormalization are presented in detail. A strong emphasis is put on the computational scheme. A detailed structure of this scheme is illustrated by the one-loop calculation in a non-equilibrium time-dependent process. A detailed account of the one-loop calculation has never been reported anywhere. The role of the self-consistent renormalization is explained. The equilibrium TFD is obtained as the long-time limit of non-equilibrium TFD. (author)
The calculation of relative output factor and depth dose for irregular electron fields in water
International Nuclear Information System (INIS)
Dunscombe, Peter; McGhee, Peter; Chu, Terence
1996-01-01
Purpose: A technique, based on sector integration and interpolation, has been developed for the computation of both relative output factor and depth dose of irregular electron fields in water. The purpose of this study was to determine the minimum experimental data set required for the technique to yield results within accepted dosimetric tolerances. Materials and Methods: PC based software has been written to perform the calculations necessary to dosimetrically characterize irregular shaped electron fields. The field outline is entered via digitiser and the SSD and energy via the keyboard. The irregular field is segmented into sectors of specified angle (2 deg. was used for this study) and the radius of each sector computed. The central ray depth dose is reconstructed by summing the contributions from each sector deduced from calibration depth doses measured for circular fields. Relative output factors and depth doses at SSDs at which calibrations were not performed are found by interpolation. Calibration data were measured for circular fields from 2 to 9 cm diameter at 100, 105, 110, and 115 cm SSD. A clinical cut out can be characterized in less than 2 minutes including entry of the outline using this software. The performance of the technique was evaluated by comparing calculated relative output factors, surface dose and the locations of d 80 , d 50 and d 20 with experimental measurements on a variety of cut out shapes at 9 and 18 MeV. The calibration data set (derived from circular cut outs) was systematically reduced to identify the minimum required to yield an accuracy consistent with current recommendations. Results: The figure illustrates the ability of the technique to calculate the depth dose for an irregular field (shown in the insert). It was found that to achieve an accuracy of 2% in relative output factor and 2% or 2 mm (our criterion) in percentage depth dose, calibration data from five circular fields at the four SSDs spanning the range 100-115 cm
Giant crystal-electric-field effect and complex magnetic behavior in single-crystalline CeRh3Si2
Pikul, A. P.; Kaczorowski, D.; Gajek, Z.; Stȩpień-Damm, J.; Ślebarski, A.; Werwiński, M.; Szajek, A.
2010-05-01
Single-crystalline CeRh3Si2 was investigated by means of x-ray diffraction, magnetic susceptibility, magnetization, electrical resistivity, and specific-heat measurements carried out in wide temperature and magnetic field ranges. Moreover, the electronic structure of the compound was studied at room temperature by cerium core-level x-ray photoemission spectroscopy (XPS). The physical properties were analyzed in terms of crystalline electric field and compared with results of ab initio band-structure calculations performed within the density-functional theory approach. The compound was found to crystallize in the orthorhombic unit cell of the ErRh3Si2 type (space group Imma No.74, Pearson symbol: oI24 ) with the lattice parameters a=7.1330(14)Å , b=9.7340(19)Å , and c=5.6040(11)Å . Analysis of the magnetic and XPS data revealed the presence of well-localized magnetic moments of trivalent cerium ions. All the physical properties were found to be highly anisotropic over the whole temperature range studied and influenced by exceptionally strong crystalline electric field with the overall splitting of the 4f1 ground multiplet exceeding 5700 K. Antiferromagnetic order of the cerium magnetic moments at TN=4.70(1)K and their subsequent spin rearrangement at Tt=4.48(1)K manifest themselves as distinct anomalies in the temperature characteristic of all the physical properties investigated and exhibit complex evolution in an external magnetic field. A tentative magnetic B-T phase diagram, constructed for B parallel to the b axis being the easy magnetization direction, shows very complex magnetic behavior of CeRh3Si2 , similar to that recently reported for an isostructural compound CeIr3Si2 . The electronic band-structure calculations corroborated the antiferromagnetic ordering of the cerium magnetic moments and well-reproduced the experimental XPS valence-band spectrum.
Electrodisintegration of relativistic nuclei by a periodic crystal field in channeling
International Nuclear Information System (INIS)
Pivovarov, Yu.L.; Vorob'ev, S.A.
1981-01-01
Processes on channeled relativistic nuclei with transition into a continuous spectrum (electrodisintegration of nuclei with emission of neutron, proton, photon and etc.) are considered. A case of plane channeling is considered. The equivalent photon method is used for calculating the disintegration cross section. The beryllium disintegration cross section in the system of tungsten crystal (100) planes is calculated. At the γ=10 2 Lorentz factor the cross section value is 5.27 mb. The process considered is of interest from the viewpoint of production of monoenergy neutrons of high energies and γ quanta of excited nuclei. The channeling effect gives the possibility to study electromagnetic interactions of relativistic nuclei under suppre--ssion conditions of the nuclear interaction channel [ru
Energy Technology Data Exchange (ETDEWEB)
Mansy, Muhammad S., E-mail: mmansy88@asrt.sci.eg [Reactor Physics Department, Nuclear Research Centre, Atomic Energy Authority, Cairo (Egypt); Radioactive Waste Management Unit, Hot Labs Centre, Atomic Energy Authority, Cairo (Egypt); Adib, M.; Habib, N. [Reactor Physics Department, Nuclear Research Centre, Atomic Energy Authority, Cairo (Egypt); Bashter, I.I. [Physics Department, Faculty of Science, Zagazig University (Egypt); Morcos, H.N.; El-Mesiry, M.S. [Reactor Physics Department, Nuclear Research Centre, Atomic Energy Authority, Cairo (Egypt)
2016-10-01
Highlights: • Slow neutron cross-section calculation for poly- and mono-crystalline materials. • Monochromatic features of PbF{sub 2} and NaCl mono-crystals. • Characterization of poly- and mono-crystal filters used in neutron diffraction. • Computer code developed calculates neutron cross-section, transmission & reflection. - Abstract: A detailed study about the calculation of total neutron cross-section, transmission and reflection from crystalline materials was performed. The developed computer code is approved to be sufficient for the required calculations, also an excellent agreement has been shown when comparing the code results with the other calculated and measured values. The optimal monochromator and filter parameters were discussed in terms of crystal orientation, mosaic spread, and thickness. Calculations show that 30 cm thick of PbF{sub 2} poly-crystal is an excellent cold neutron filter producing neutron wavelengths longer than 0.66 nm needed for the investigation of magnetic structure experiments. While mono-crystal filter PbF{sub 2} cut along its (1 1 1), having mosaic spread (η = 0.5°) and thickness 10 cm can only transmit thermal neutrons of the desired wavelengths and suppress epithermal and γ-rays forming unwanted background, when it is cooled to liquid nitrogen temperature. NaCl (2 0 0) and PbF{sub 2} (1 1 1) monochromator crystals having mosaic spread (η = 0.5°) and thickness 10 mm shows high neutron reflectivity for neutron wavelengths (λ = 0.114 nm and λ = 0.43 nm) when they used as a thermal and cold neutron monochromators respectively with very low contamination from higher order reflections.
AC electric field assisted orientational photorefractive effect in C60-doped nematic liquid crystal
International Nuclear Information System (INIS)
Sun Xiudong; Pei Yanbo; Yao Fengfeng; Zhang Jianlong; Hou Chunfeng
2007-01-01
Photorefractive gratings were produced in a C 60 -doped nematic liquid crystal cell under the application of two coherent beams and a nonbiased sinusoidal ac electric field. The beam coupling and diffraction of the ac electric field assisted gratings were studied systematically. A stable asymmetric energy transference was obtained. Diffraction was observed when the angle (between the normal of the cell and the bisector of the writing beams) was 0 0 , and the dependence of diffraction efficiency on the peak-to-peak value of the ac voltage was similar to that at an incidence angle of 45 0 , suggesting that the role of the ac field was to facilitate the charge separation, and the space-charge field (SCF) originated predominantly from the diffusion of the ac electric field assisted photo-induced carriers under the application of nonuniform illumination and an applied ac field. The grating was produced by director reorientation induced by the cooperation of the SCF and the applied ac electric field. A self-erasing phenomenon was observed in this cell. An explanation in terms of the movement of two kinds of carriers with opposite signs was proposed
Energy Technology Data Exchange (ETDEWEB)
Taplin, D.J. [School of Physics and Astronomy, Monash University, Clayton, Victoria 3800 (Australia); Shibata, N. [Institute of Engineering Innovation, School of Engineering, University of Tokyo, Tokyo 113-8656 (Japan); Weyland, M. [Monash Centre for Electron Microscopy, Monash University, Clayton, Victoria 3800 (Australia); Department of Materials Science and Engineering, Monash University, Clayton, Victoria 3800 (Australia); Findlay, S.D., E-mail: scott.findlay@monash.edu [School of Physics and Astronomy, Monash University, Clayton, Victoria 3800 (Australia)
2016-10-15
To correlate atomistic structure with longer range electric field distribution within materials, it is necessary to use atomically fine electron probes and specimens in on-axis orientation. However, electric field mapping via low magnification differential phase contrast imaging under these conditions raises challenges: electron scattering tends to reduce the beam deflection due to the electric field strength from what simple models predict, and other effects, most notably crystal mistilt, can lead to asymmetric intensity redistribution in the diffraction pattern which is difficult to distinguish from that produced by long range electric fields. Using electron scattering simulations, we explore the effects of such factors on the reliable interpretation and measurement of electric field distributions. In addition to these limitations of principle, some limitations of practice when seeking to perform such measurements using segmented detector systems are also discussed. - Highlights: • Measuring electric fields by on-axis electron diffraction is explored by simulation. • Electron channelling reduces deflection predicted by the phase object approximation. • First moment measurements cannot distinguish electric fields from specimen mistilt. • Segmented detector estimates are fairly insensitive to camera length and orientation.
International Nuclear Information System (INIS)
Hauser, J.R.
1977-04-01
The results of three distinct studies are discussed. The first two chapters describe calculations of the geometric optical properties of crystals; the third chapter is concerned with the crystal structure analysis of two new double salts
Nestler, B.; Danilov, D.; Galenko, P.
2005-07-01
A phase-field model for non-isothermal solidification in multicomponent systems [SIAM J. Appl. Math. 64 (3) (2004) 775-799] consistent with the formalism of classic irreversible thermodynamics is used for numerical simulations of crystal growth in a pure material. The relation of this approach to the phase-field model by Bragard et al. [Interface Science 10 (2-3) (2002) 121-136] is discussed. 2D and 3D simulations of dendritic structures are compared with the analytical predictions of the Brener theory [Journal of Crystal Growth 99 (1990) 165-170] and with recent experimental measurements of solidification in pure nickel [Proceedings of the TMS Annual Meeting, March 14-18, 2004, pp. 277-288; European Physical Journal B, submitted for publication]. 3D morphology transitions are obtained for variations in surface energy and kinetic anisotropies at different undercoolings. In computations, we investigate the convergence behaviour of a standard phase-field model and of its thin interface extension at different undercoolings and at different ratios between the diffuse interface thickness and the atomistic capillary length. The influence of the grid anisotropy is accurately analyzed for a finite difference method and for an adaptive finite element method in comparison.
International Nuclear Information System (INIS)
Keskin, M.; Canko, O.; Temizer, U.
2007-01-01
Within a mean-field approach, the stationary states of the kinetic spin-1 Blume-Capel model in the presence of a time-dependent oscillating external magnetic field is studied. The Glauber-type stochastic dynamics is used to describe the time evolution of the system and obtain the mean-field dynamic equation of motion. The dynamic phase-transition points are calculated and phase diagrams are presented in the temperature and crystal-field interaction plane. According to the values of the magnetic field amplitude, three fundamental types of phase diagrams are found: One exhibits a dynamic tricritical point, while the other two exhibit a dynamic zero-temperature critical point
Energy Technology Data Exchange (ETDEWEB)
Brik, M.G. [Fukui Institute for Fundamental Chemistry, Kyoto University, 34-4 Takano Nishihiraki-cho, Sakyo-ku, Kyoto 606-8103 (Japan) and Department of Chemistry, School of Science and Technology, Kwansei Gakuin University, 2-1 Gakuen, Sanda, Hyogo 669-1337 (Japan)]. E-mail: brik@fukui.kyoto-u.ac.jp; Avram, N.M. [Department of Physics, West University of Timisoara, Bd. V. Parvan No. 4, 300223 Timisoara (Romania); Avram, C.N. [Department of Physics, West University of Timisoara, Bd. V. Parvan No. 4, 300223 Timisoara (Romania); Rudowicz, C. [Institute of Physics, Szczecin University of Technology, Al. Piastow 17, 70-310 Szczecin (Poland); Yeung, Y.Y. [Department of Mathematics, Science, Social Sciences and Technology, The Hong Kong Institute of Education, 10 Lo Ping Road, Tai Po, New Territories (Hong Kong); Gnutek, P. [Institute of Physics, Szczecin University of Technology, Al. Piastow 17, 70-310 Szczecin (Poland)
2007-04-25
The exchange charge model (ECM) of crystal field is utilized to provide the theoretical explanation of the ground state absorption and the excited state absorption observed for the octahedrally coordinated Ni{sup 2+} ions in the spinel MgAl{sub 2}O{sub 4}. The ECM enables modeling of the crystal field parameters (CFPs) for the impurity ions based on the crystal structure data of the host lattice. To ensure the reliability of the CFPs, the convergence of the CFP values with the increasing number of the coordination spheres taken into account in the ECM calculations is considered. The trigonal CFPs B{sub 2}{sup 0},B{sub 4}{sup 0}andB{sub 4}{sup -3} determined by the ECM, together with the appropriate Racah parameters B and C, serve as input to two crystal field analysis computer packages, which compute the energy level schemes within the whole 3d{sup 8} configuration. The cubic approximation utilizing only one CFP Dq is also discussed. Basic features of the ground and excited state absorption spectra observed for MgAl{sub 2}O{sub 4}:Ni{sup 2+} are satisfactorily explained by our crystal field analysis. In order to model the pressure dependence of the CFPs (and thus of the absorption spectra when relevant experimental data become available), the variation of the CFPs induced by possible distortions of the lattice due to, e.g. overall relaxation of the ions or accommodation of the impurity ions in the lattice, is studied. Analysis of the experimental absorption spectra enables us to evaluate also the Huang-Rhys parameter, the effective phonon energy, and the zero-phonon line position.
Chen, Jyh-Chen; Chiang, Pei-Yi; Nguyen, Thi Hoai Thu; Hu, Chieh; Chen, Chun-Hung; Liu, Chien-Cheng
2016-10-01
A three-dimensional simulation model is used to study the oxygen concentration distribution in silicon crystal during the Czochralski growth process under a transverse uniform magnetic field. The flow, temperature, and oxygen concentration distributions inside the furnace are calculated for different crystal lengths. There is significant variation in the flow structure in the melt with the growth length. The results show that in the initial stages, there is a decrease in the oxygen concentration at the crystal-melt interface as the length of the growing crystal increases. As the crystal lengthens further, a minimum value is reached after which the oxygen concentration increases continuously. This trend is consistent with that shown in the experimental results. The variation of the oxygen concentration with the growth length is strongly related to the depth of the melt in the crucible and the flow structure inside the melt. Better uniformity of the axial oxygen concentration can be achieved by proper adjustment of the crucible rotation rate during the growth process.
Guide to precision calculations in Dyson close-quote s hierarchical scalar field theory
International Nuclear Information System (INIS)
Godina, J.J.; Meurice, Y.; Oktay, M.B.; Niermann, S.
1998-01-01
The goal of this article is to provide a practical method to calculate, in a scalar theory, accurate numerical values of the renormalized quantities which could be used to test any kind of approximate calculation. We use finite truncations of the Fourier transform of the recursion formula for Dyson close-quote s hierarchical model in the symmetric phase to perform high-precision calculations of the unsubtracted Green close-quote s functions at zero momentum in dimension 3, 4, and 5. We use the well-known correspondence between statistical mechanics and field theory in which the large cutoff limit is obtained by letting β reach a critical value β c (with up to 16 significant digits in our actual calculations). We show that the round-off errors on the magnetic susceptibility grow like (β c -β) -1 near criticality. We show that the systematic errors (finite truncations and volume) can be controlled with an exponential precision and reduced to a level lower than the numerical errors. We justify the use of the truncation for calculations of the high-temperature expansion. We calculate the dimensionless renormalized coupling constant corresponding to the 4-point function and show that when β→β c , this quantity tends to a fixed value which can be determined accurately when D=3 (hyperscaling holds), and goes to zero like [Ln(β c -β)] -1 when D=4. copyright 1998 The American Physical Society
Study of wide band-gap crystal LiCaAlF6 by IR-reflection spectroscopy and ab initio calculations
International Nuclear Information System (INIS)
Novikova, N.N.; Klimin, S.A.; Mavrin, B.N.
2017-01-01
Polarized IR-reflection spectra and results of ab initio calculations of vibrational and electronic properties of LiCaAlF6 single crystal are presented. It is shown that the crystal band gap is direct. Experimental and theoretical parameters are obtained for dipole-active and all phonons, respectively, including silent modes. Experimental IR-reflection and Raman spectra are well described in the frame of results obtained by ab initio calculations. The peculiarities are discussed concerning the structure of electronic bands, the interatomic interactions, the character of lattice vibrations, and the phonon dispersion.
Estes, Robert D.
1989-01-01
A method is presented for calculating the electromagnetic wave field on the earth's surface associated with the operation of an electrodynamic tethered satellite system of constant or slowly varying current in the upper ionosphere. The wave field at the ionospheric boundary and on the earth's surface is obtained by numerical integration. The results suggest that the ionospheric waves do not propagate into the atmosphere and that the image of the Alfven wings from a steady-current tether should be greatly broadened on the earth's surface.
Evstigneeva, N.
2017-09-01
Numerical experiments have been carried out using a hydrodynamical model with nonlinear equations of motion and heat and salt advection to reconstruct the fields of hydrophysical parameters in the coastal regions of the Black Sea taking into account the real atmospheric forcing and river discharges for the winter and summer seasons of 2006. A higher spatial resolution allowed to get a detailed meso- and submesoscale structure of hydrophysical fields in the upper and deep layers of the Southern Coast of Crimea and the north-western shelf and to obtain quantitative and qualitative characteristics of the eddies and jets more accurately in comparison with previous calculations.
Calculation of longitudinal and transverse wake-field effects in dielectric structures
International Nuclear Information System (INIS)
Gai, W.
1989-01-01
The electro-magnetic radiation of a charged particle passing through a dielectric structure has many applications to accelerator physics. Recently a new acceleration scheme, called the dielectric wake field accelerator, has been proposed. It also can be used as a pick up system for a storage ring because of its slow wave characteristics. In order to study these effects in detail, in this paper we will calculate the wake field effects produced in a dielectric structure by a charged particle. 8 refs., 2 figs
MatchingTools: A Python library for symbolic effective field theory calculations
Criado, Juan C.
2018-06-01
MatchingTools is a Python library for doing symbolic calculations in effective field theory. It provides the tools to construct general models by defining their field content and their interaction Lagrangian. Once a model is given, the heavy particles can be integrated out at the tree level to obtain an effective Lagrangian in which only the light particles appear. After integration, some of the terms of the resulting Lagrangian might not be independent. MatchingTools contains functions for transforming these terms to rewrite them in terms of any chosen set of operators.
On-fiber 3D printing of photonic crystal fiber tapers for mode field diameter conversion
Bertoncini, Andrea; Rajamanickam, Vijayakumar Palanisamy; Liberale, Carlo
2017-01-01
The large mismatch between the Mode Field Diameter (MFD) of conventional single-mode fibers (SMFs) and the MFD of highly nonlinear Photonic Crystal Fibers (PCFs), that can be down to 1.5 μm, or Large Mode Area PCF, that can be up to 25 μm, would require a substantial fiber mode size rescaling in order to allow an efficient direct coupling between PCFs and SMFs. Over the years different solutions have been proposed, as fiber splicing of SMF to PCF. However these procedures are not straightforward, as they involve developing special splicing recipes, and can affect PCF optical properties at the splice interface [1].
Angular overlap model analysis of the D 2d crystal field effect in uranium (4+) compounds
Gajek, Z.; Hubert, S.; Krupa, J. C.
1988-12-01
Recent interpretations of the D 2d crystal field of U 4+ in β-ThCl 4, α, β-ThBr 4, ThSiO 4 and UCl 4 are discussed in terms of the simplified one-, two- and three-parameter versions of the Angular Overlap Model which are shown to be a handy tool in a trial interpretation of the effect. The variation of the CF parameters with a small D 2 distortion of the coordination is well reproduced by the model.
Crystal-field and clustering effects in the specific heat of Dy in Pd
International Nuclear Information System (INIS)
Devine, R.A.B.; Jacques, P.; Poirier, M.
1975-01-01
Recent results of specific-heat measurements on dilute alloys of Dy in Pd are reanalyzed. Assuming the ionic ground state found from paramagnetic-resonance measurements, the Schottky-anomaly and cluster contributions are segregated and the crystal-field splitting of the ground and first-excited states is found to be in reasonable agreement with theoretical predictions. The nature of the cluster contribution is discussed and an upper limit to the range of the Ruderman-Kittel-Kasuya-Yosida interaction deduced
On-fiber 3D printing of photonic crystal fiber tapers for mode field diameter conversion
Bertoncini, Andrea
2017-11-02
The large mismatch between the Mode Field Diameter (MFD) of conventional single-mode fibers (SMFs) and the MFD of highly nonlinear Photonic Crystal Fibers (PCFs), that can be down to 1.5 μm, or Large Mode Area PCF, that can be up to 25 μm, would require a substantial fiber mode size rescaling in order to allow an efficient direct coupling between PCFs and SMFs. Over the years different solutions have been proposed, as fiber splicing of SMF to PCF. However these procedures are not straightforward, as they involve developing special splicing recipes, and can affect PCF optical properties at the splice interface [1].
A contribution to the numerical calculation of static electromagnetic fields in unbounded domains
International Nuclear Information System (INIS)
Krawczyk, F.
1990-11-01
The numerical calculation of static electromagnetic fields for arbitrarily shaped three-dimensional structures, especially in unbounded domains, is very memory and cpu-time consuming. In this thesis several schemes that reduce memory and cpu-time consumption have been developed or introduced. The memory needed can be reduced by a special simulation of boundaries towards open space and by the use of a scalar potential for the field description. Known disadvantages of the use of such a potential are avoided by an improved formulation of the used algorithms. The cpu-time for the calculations can be reduced remarkably in many cases by using a multigrid solution scheme including a defect-correction. A computer code has been written that uses these algorithms. With the help of this program it has been demonstrated that using these algorithms, distinct improvements in terms of computer memory, cpu-time consumption and accuracy can be achieved. (orig.) [de
International Nuclear Information System (INIS)
Kazakov, E.K.; Chernukhina, G.M.
1974-01-01
Results of calculation of the temperature distribution in an annular fuel element at transient thermal conductivity and heat release values are given. The calculation has been carried out by the mesh technique with the third-order boundary conditions for the inner surface assumed and with heat fluxes and temperatures at the zone boundaries to be equal. Three variants of solving the problem of a stationary temperature field are considered for failed fuel elements with clad flaking or cracks. The results obtained show the nonuniformity of the fuel element temperature field to depend strongly on the perturbation parameter at transient thermal conductivity and heat release values. In case of can flaking at a short length, the core temperature rises quickly after flaking. While evaluating superheating, one should take into account the symmetry of can flaking [ru
International Nuclear Information System (INIS)
Kubo, H.; Harada, K.; Sakaeda, T.; Yamamoto, Y.
2013-01-01
On the basis of the Wilsonian renormalization group (WRG) analysis of nuclear effective field theory (NEFT) including pions, we propose a practical calculational scheme in which the short-distance part of one-pion exchange (S-OPE) is removed and represented as contact terms. The long-distance part of one-pion exchange (L-OPE) is treated as perturbation. The use of dimensional regularization (DR) for diagrams consisting only of contact interactions considerably simplifies the calculation of scattering amplitude and the renormalization group equations. NLO results for nucleon-nucleon elastic scattering in the S-waves are obtained and compared with experiments. A brief comment on NNLO calculations is given. (author)
International Nuclear Information System (INIS)
Muehlbauer, P.
1981-08-01
Experience is described gained with the application of computer code VELASCO in calculating the velocity field in fast reactor fuel assemblies taking into account configuration disturbances due to fuel pin displacement. Theoretical results are compared with the results of experiments conducted by UJV on aerodynamic models HEM-1 (model of the fuel assembly central part) and HEM-2 (model of the fuel assembly peripheral part). The results are reported of calculating the distribution of shear stress in wetted rod surfaces and in the assembly wall (model HEM-2) and the corresponding experimental results are shown. The shear stress distribution in wetted surfaces obtained using the VELASCO code allowed forming an opinion on the code capability of comprising local parameters of turbulent flow through a fuel rod bundle. The applicability was also tested of the code for calculating mean velocities in the individual zones, eg., in elementary cells. (B.S.)
A GPU-based calculation using the three-dimensional FDTD method for electromagnetic field analysis.
Nagaoka, Tomoaki; Watanabe, Soichi
2010-01-01
Numerical simulations with the numerical human model using the finite-difference time domain (FDTD) method have recently been performed frequently in a number of fields in biomedical engineering. However, the FDTD calculation runs too slowly. We focus, therefore, on general purpose programming on the graphics processing unit (GPGPU). The three-dimensional FDTD method was implemented on the GPU using Compute Unified Device Architecture (CUDA). In this study, we used the NVIDIA Tesla C1060 as a GPGPU board. The performance of the GPU is evaluated in comparison with the performance of a conventional CPU and a vector supercomputer. The results indicate that three-dimensional FDTD calculations using a GPU can significantly reduce run time in comparison with that using a conventional CPU, even a native GPU implementation of the three-dimensional FDTD method, while the GPU/CPU speed ratio varies with the calculation domain and thread block size.
On the calculation of finite-temperature effects in field theories
International Nuclear Information System (INIS)
Brandt, F.T.; Frenkel, J.; Taylor, J.C.
1991-03-01
We discuss an alternative method for computing finite-temperature effects in field theories, within the framework of the imaginary-time formalism. Our approach allows for a systematic calculation of the high temperature expansion in terms of Riemann Zeta functions. The imaginary-time result is analytically continued to the complex plane. We are able to obtain the real-time limit of the real and the imaginary parts of the Green functions. (author)
Fourier Bessel transform method for efficiently calculating the magnetic field of solenoids
International Nuclear Information System (INIS)
Nachamkin, J.; Maggiore, C.J.
1980-01-01
A numerical procedure for calculating the magnetic field of a selenoid is derived. Based on the properties of Bessel functions, the procedure is shown to be convergent everywhere, including within the windings of the solenoid. The most critical part of the procedure is detailed in the main text. A simple method is used to ensure numerical significance while allowing economical computational times. In the appendix the procedure is generalized to universal convergence by appropriate partitioning of the solenoid windings
Calculation of transitions in intense laser fields with the Magnus expansion
International Nuclear Information System (INIS)
Campos, D.; Krueger, H.
1975-01-01
For bound quantum systems in presence of strong long wavelength electromagnetic fields the time evolution operator is calculated by application of the Magnus expansion in the interaction picture. We find that the first two orders of the Magnus expansion of the interaction picture time evolution operator contain both the momentum-translation transform of H.R. Reiss and terms which give rise to a non-static Stark-effect. (orig.) [de
The calculation of the field of the three-electrode transaxial lens
Directory of Open Access Journals (Sweden)
Duseinova A.G.
2017-04-01
Full Text Available the article offered method of the calculation of the transaxial fields based on the partition of the potential into two terms. The main term is a harmonic function of two variables and satisfies the given boundary conditions. The harmonic component of the potential is found analytically using the methods of complex analysis. The second term is the solution of an inhomogeneous equation with zero Dirichlet boundary conditions and can be found numerically with the required accuracy.
Photon Splitting in a Strong Magnetic Field: Recalculation and Comparison with Previous Calculations
International Nuclear Information System (INIS)
Adler, S.L.; Schubert, C.
1996-01-01
We recalculate the amplitude for photon splitting in a strong magnetic field below the pair production threshold, using the world line path integral variant of the Bern-Kosower formalism. Numerical comparison (using programs that we have made available for public access on the Internet) shows that the results of the recalculation are identical to the earlier calculations of Adler and later of Stoneham, and to the recent recalculation by Baier, Milstein, and Shaisultanov. copyright 1996 The American Physical Society
Directory of Open Access Journals (Sweden)
William L. Montgomery
2015-09-01
Full Text Available Three cyano-1-(phenylsulfonylindole derivatives, 3-cyano-1-(phenylsulfonyl indole, (I, 2-cyano-1-(phenylsulfonylindole, (II, and 2,3-dicyano-1-(phenylsulfonyl indole, (III, and a key synthetic precursor 1-(phenylsulfonyl-1-(1,1-dimethylethyl indole-3-carboxamide, (IV, have been synthesized and their structures determined by single crystal X-ray crystallography. (I, C15H10N2O2S, is orthorhombic with space group P 212121 and cell constants: a = 4.9459(3 Å, b = 10.5401(7 Å, c = 25.0813(14 Å, V = 1307.50(14 Å3 and Z = 4. (II, C15H10N2O2S, is monoclinic with space group C 2/c and cell constants: a = 18.062(2 Å, b = 11.293(2 Å, c = 15.922(3 Å, α = 90°, β = 124.49(2°, g = 90°, V = 2676.7 Å3 and Z = 8. (III, C16H9N3O2S, is triclinic with space group P-1 and cell constants: a = 8.1986(8 Å, b = 9.6381(11 Å, c = 9.8113(5 Å, α = 95.053(6°, β = 101.441(6°, g = 108.071(9°, V = 713.02(11 Å3 and Z = 2. (IV, C19H20N2O3S, is orthorhombic with space group P ccn and cell constants: a = 13.7605(8 Å, b = 27.3177(14 Å, c = 9.7584(6 Å, α = 90°, β = 90°, g =90°, V = 3668.2(4 Å3 and Z = 8. All four compounds have the same indole nitrogen phenylsulfonyl substituent and (I, (II, and (III are nitrile derivatives. (IV is a tert-butylamide. In the crystals, the dihedral angle between the mean planes of the indole and phenylsulfonyl groups are 85.4(2° (I, 87.2(7° (II, 75.1(7° (III, and 88.6(2° (IV, respectively. Additionally, DFT geometry-optimized molecular orbital calculations were performed and frontier molecular orbitals of each compound are displayed. Correlation between the calculated molecular orbital energies (eV for the surfaces of the frontier molecular orbitals to the electronic excitation transitions from the absorption spectra of each compound has been proposed.
A procedure for temperature-stress fields calculation of WWER-1000 primary circuit in PTS event
Energy Technology Data Exchange (ETDEWEB)
Petkov, G [Technical Univ., Dept. Thermal and Nuclear Power Engineering, Sofia (Bulgaria); Groudev, P; Argirov, J [Bulgarian Academy of Science, Inst. for Nuclear Research and Nuclear Energy, Sofia (Bulgaria)
1997-09-01
The paper presents the procedure of an investigation of WWER-1000 primary circuit temperature-stress field by the use of thermohydraulic computation data for a pressurized thermal shock event ``Core overcooling``. The procedure is based on a model of the plane stress state with ideal contact between wall and medium for the calculation. The computation data are calculated on the base of WWER-1000 thermohydraulic model by the RELAP5/MOD3 codes. This model was developed jointly by the Bulgarian and BNL/USA staff to provide an analytical tool for performing safety analysis. As a result of calculations by codes the computation data for temperature field law (linear laws of a few distinguished parts) and pressure of coolant at points on inner surface of WWER-1000 primary circuit equipment are received. Such calculations can be used as a base for determination of all-important load-carrying sections of the primary circuit pipes and vessels, which need further consideration. (author). 7 refs, 2 figs, 2 tabs.
Auxiliary-field quantum Monte Carlo calculations of molecular systems with a Gaussian basis
International Nuclear Information System (INIS)
Al-Saidi, W.A.; Zhang Shiwei; Krakauer, Henry
2006-01-01
We extend the recently introduced phaseless auxiliary-field quantum Monte Carlo (QMC) approach to any single-particle basis and apply it to molecular systems with Gaussian basis sets. QMC methods in general scale favorably with the system size as a low power. A QMC approach with auxiliary fields, in principle, allows an exact solution of the Schroedinger equation in the chosen basis. However, the well-known sign/phase problem causes the statistical noise to increase exponentially. The phaseless method controls this problem by constraining the paths in the auxiliary-field path integrals with an approximate phase condition that depends on a trial wave function. In the present calculations, the trial wave function is a single Slater determinant from a Hartree-Fock calculation. The calculated all-electron total energies show typical systematic errors of no more than a few millihartrees compared to exact results. At equilibrium geometries in the molecules we studied, this accuracy is roughly comparable to that of coupled cluster with single and double excitations and with noniterative triples [CCSD(T)]. For stretched bonds in H 2 O, our method exhibits a better overall accuracy and a more uniform behavior than CCSD(T)
Hamed, A. E.; Kassem, M. E.; El-Wahidy, E. F.; El-Abshehy, M. A.
1995-03-01
The temperature dependence of specific heat at constant pressure, Cp(T), has been measured for lithium sodium sulphate, LiNaSo4 crystals, at different ?-radiation doses and external bias electric field (Eb), in the temperature range 300-900 K. A nonlinear dependence of transition temperature, T1 and a remarkable change in the thermodynamic parameters, were obtained as the effect of both electric field and ?-radiation. The effect of ?-radiation doses on the phase transition in LiNaSO4 crystals was explained as due to an internal bias field, Eb, originating from the interaction of polar defects with the order parameter of the host lattice. The internal bias field effect on the behaviour of Cp(T) in LiNaSO4 crystals was similar to that of the external electric field (E).
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.
Wang, Yeqing; Chen, Aixi; You, Zhenyu; Tu, Chaoyang
2015-12-01
A notable disorder crystal Yb:Ca3La2(BO3)4 crystal with Yb3+ ion doping concentration of 10 at.% was grown by the Czochralski method. The polarized absorption, polarized emission, and polarized gain cross sections were systematically calculated. The laser operations were investigated with Yb:Ca3La2(BO3)4 crystals cut along the a, b, and c crystallographic axes. The highest output power of 3.88 W was obtained by using the b-cut Yb:Ca3La2(BO3)4 crystal, with a slope efficiency of 62%. Additionally, it was confirmed that the output laser spectra were largely dependent on the output coupler.
International Nuclear Information System (INIS)
Wang, Yeqing; Chen, Aixi; You, Zhenyu; Tu, Chaoyang
2015-01-01
A notable disorder crystal Yb:Ca 3 La 2 (BO 3 ) 4 crystal with Yb 3+ ion doping concentration of 10 at.% was grown by the Czochralski method. The polarized absorption, polarized emission, and polarized gain cross sections were systematically calculated. The laser operations were investigated with Yb:Ca 3 La 2 (BO 3 ) 4 crystals cut along the a, b, and c crystallographic axes. The highest output power of 3.88 W was obtained by using the b-cut Yb:Ca 3 La 2 (BO 3 ) 4 crystal, with a slope efficiency of 62%. Additionally, it was confirmed that the output laser spectra were largely dependent on the output coupler. (paper)
Nagaoka, Tomoaki; Watanabe, Soichi
2012-01-01
Electromagnetic simulation with anatomically realistic computational human model using the finite-difference time domain (FDTD) method has recently been performed in a number of fields in biomedical engineering. To improve the method's calculation speed and realize large-scale computing with the computational human model, we adapt three-dimensional FDTD code to a multi-GPU cluster environment with Compute Unified Device Architecture and Message Passing Interface. Our multi-GPU cluster system consists of three nodes. The seven GPU boards (NVIDIA Tesla C2070) are mounted on each node. We examined the performance of the FDTD calculation on multi-GPU cluster environment. We confirmed that the FDTD calculation on the multi-GPU clusters is faster than that on a multi-GPU (a single workstation), and we also found that the GPU cluster system calculate faster than a vector supercomputer. In addition, our GPU cluster system allowed us to perform the large-scale FDTD calculation because were able to use GPU memory of over 100 GB.
arXiv Axion-photon conversion caused by dielectric interfaces: quantum field calculation
Ioannisian, Ara N.; Millar, Alexander J.; Raffelt, Georg G.
2017-09-05
Axion-photon conversion at dielectric interfaces, immersed in a near-homogeneous magnetic field, is the basis for the dielectric haloscope method to search for axion dark matter. In analogy to transition radiation, this process is possible because the photon wave function is modified by the dielectric layers ("Garibian wave function") and is no longer an eigenstate of momentum. A conventional first-order perturbative calculation of the transition probability between a quantized axion state and these distorted photon states provides the microwave production rate. It agrees with previous results based on solving the classical Maxwell equations for the combined system of axions and electromagnetic fields. We argue that in general the average photon production rate is given by our result, independently of the detailed quantum state of the axion field. Moreover, our result provides a new perspective on axion-photon conversion in dielectric haloscopes because the rate is based on an overlap integral between unpertu...
DEFF Research Database (Denmark)
Madsen, Kristoffer Hougaard; Ewald, Lars; Siebner, Hartwig R.
2015-01-01
Background: Field calculations for transcranial magnetic stimulation (TMS) are increasingly implemented online in neuronavigation systems and in more realistic offline approaches based on finite-element methods. They are often based on simplified and/or non-validated models of the magnetic vector...... potential of the TMS coils. Objective: To develop an approach to reconstruct the magnetic vector potential based on automated measurements. Methods: We implemented a setup that simultaneously measures the three components of the magnetic field with high spatial resolution. This is complemented by a novel...... approach to determine the magnetic vector potential via volume integration of the measured field. Results: The integration approach reproduces the vector potential with very good accuracy. The vector potential distribution of a standard figure-of-eight shaped coil determined with our setup corresponds well...
The calculation and visualization of the fluid field in the canned pump
International Nuclear Information System (INIS)
Cheng De; Xue Yabo; Shen Hong; Yao Zhenqiang; Lu Xiangping; Li Cangxue
2013-01-01
A kind of canned pump is composed of the motor and the pump section. The canned motor is lubricated and cooled by high pressure water. The rotor in the motor is big and the rotor's velocity is high. The water channel inside the motor is complicated. In this article, the software Fluent is used to calculate the fluid field of the key parts in the motor. Then post-processing software Ensight is used to visualize the result of the FEM analysis. The velocity and pressure of the fluid fields in the motor's key parts can be studied thoroughly. A video and pictures are created to illustrate the function of the middle impeller and the gratitude of the fluid fields. (authors)
Extensional flow of nematic liquid crystal with an applied electric field
CUMMINGS, L. J.; LOW, J.; MYERS, T. G.
2013-01-01
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.
Thermal field emission observation of single-crystal LaB6
International Nuclear Information System (INIS)
Nagata, H.; Harada, K.; Shimizu, R.
1990-01-01
TFE (thermal field emission) properties of LaB 6 left-angle 100 right-angle and left-angle 310 right-angle single crystals were investigated by emission pattern observation. It was found that field evaporation with the tip temperature held at ∼1500 degree C is very useful to get a clean pattern of fourfold symmetry. Each of four bright spots in the clean pattern was presumed to correspond to left-angle 310 right-angle emission. It is proposed, as the most appropriate operating condition, to use the left-angle 310 right-angle LaB 6 tip at a temperature ∼1000 degree C in vacuum of 10 -9 Torr region, promising a new TF emitter of high brightness and stability for practical use
Extensional flow of nematic liquid crystal with an applied electric field
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.
EPR studies of excited state exchange and crystal-field effects in rare earth compounds
International Nuclear Information System (INIS)
Huang, C.Y.; Sugawara, K.; Cooper, B.R.
1976-01-01
EPR in excited crystal-field states of Tm 3+ , Pr 3+ , and Tb 3+ in singlet-ground-state systems and in the excited state of Ce 3+ in CeP are reviewed. Because one is looking at a crystal-field excited state resonance, the exchange, even if isotropic, does not act as a secular perturbation. This means that one obtains different effects and has access to more information about the dynamic effects of exchange than in conventional paramagnetic resonance experiments. The Tm and Pr monopnictides studied are paramagnetic at all temperatures. The most striking feature of the behavior of the GAMMA 5 /sup (2)/ EPR in the Tm compounds is the presence of an anomalous maximum in the temperature dependence of the g-factor. The relationship of this effect to anisotropic exchange is discussed. The results of the EPR of the excited GAMMA 5 /sup (2)/ level of Tb 3 + (g-factor becomes very large at T/sub N/ in antiferromagnetic TbX (X = P, As, Sb) and that of the excited GAMMA 8 level of Ce 3+ in antiferromagnetic CeP will also be reported. For sufficient dilution of the Tb 3+ in the terbium monopnictides, the systems become paramagnetic (Van Vleck paramagnets) down to 0 0 K. The Tb 3+ excited state resonance EPR in Tb/sub 0.1/ La/sub 0.9/P was studied as an example of behavior in such systems. 10 fig
Large piezoelectricity in electric-field modified single crystals of SrTiO3
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.
International Nuclear Information System (INIS)
Li Fenglian; Wang Yuesheng; Zhang Chuanzeng
2011-01-01
A numerical method based on the Dirichlet-to-Neumann (DtN) map is presented to compute the bandgaps of two-dimensional phononic crystals, which are composed of square or triangular lattices of circular solid cylinders in a fluid matrix. The DtN map is constructed using the cylindrical wave expansion in a unit cell. A linear eigenvalue problem, which depends on the Bloch wave vector and involves relatively small matrices, is formulated. Numerical calculations are performed for typical systems with various acoustic impedance ratios of the solid inclusions and the fluid matrix. The results indicate that the DtN-map based method can provide accurate results for various systems efficiently. In particular it takes into account the fluid-solid interface conditions and the transverse wave mode in the solid component, which has been proven to be significant when the acoustic impedance of the solid inclusions is close to or smaller than that of the fluid matrix. For systems with an acoustic impedance of the inclusion much less than that of the matrix, physical flat bands appear in the band structures, which will be missed if the transverse wave mode in the solid inclusions is neglected.