Jahn-Teller effect in Rydberg series: A multi-state vibronic coupling problem

International Nuclear Information System (INIS)

Staib, A.; Domcke, W.; Sobolewski, A.L.

1990-01-01

Two simple limiting cases of Jahn-Teller (JT) coupling in Rydberg states of polyatomic molecules are considered, namely (i) JT coupling in Rydberg orbitals as well as in the ionization continuum (nondegenerate ion core, degenerate Rydberg series) and (ii) JT coupling in the ion core (degenerate ion core, nondegenerate Rydberg series). For both models simple and efficient algorithms for the computation of spectra (dynamical JT effect) are developed. The orbital JT effect is shown to represent a novel type of multi-state vibronic coupling, giving rise to interesting spectroscopic phenomena, among them resonant inter-Rydberg perturbations and JT induced autoionization. Particular attention is paid to the demonstration of the characteristic spectroscopic signatures of the two types of JT coupling in Rydberg states. (orig.)

Quantifying the effects of higher order coupling terms on fits using a second order Jahn-Teller Hamiltonian

Science.gov (United States)

Tran, Henry K.; Stanton, John F.; Miller, Terry A.

2018-01-01

The limitations associated with the common practice of fitting a quadratic Hamiltonian to vibronic levels of a Jahn-Teller system have been explored quantitatively. Satisfactory results for the prototypical X∼2E‧ state of Li3 are obtained from fits to both experimental spectral data and to an "artificial" spectrum calculated by a quartic Hamiltonian which accurately reproduces the adiabatic potential obtained from state-of-the-art quantum chemistry calculations. However the values of the Jahn-Teller parameters, stabilization energy, and pseudo-rotation barrier obtained from the quadratic fit differ markedly from those associated with the ab initio potential. Nonetheless the RMS deviations of the fits are not strikingly different. Guidelines are suggested for comparing parameters obtained from fits to experiment to those obtained by direct calculation, but a principal conclusion of this work is that such comparisons must be done with a high degree of caution.

Wave-Vector Dependence of the Jahn-Teller Interactions in TmVO4

DEFF Research Database (Denmark)

Kjems, Jørgen; Hayes, W.; Smith, S. H.

1975-01-01

The resonant Jahn-Teller coupling of the B2g acoustic phonon and the Zeeman-split ground doublet in TmVO4 has been studied by inelastic neutron scattering. Tuning of the magnetic field provides a means for investigating the wave-vector dependence of the interactions. We find that the coupling...

Jahn-Teller effect in vanadium, niobium and tantalum tetrafluoride molecules: ab initio study by the CASSCF method

International Nuclear Information System (INIS)

Solomonik, V.G.; Pogrebnaya, T.P.

2001-01-01

The basic and the first exciting electronic state of the VF 4 , NbF 4 and TaF 4 molecules were studied by the self-consistent field multifunctional method in the approximation of active orbitals full space. The symmetry of these states is defined as 2 E and 2 T 2 at tetrahedron configuration of the nuclei. The energies of electron excitation 2 E → 2 T 2 comprise 11610 (VF 4 ), 13450 (NbF 4 ) and 12560 cm -1 (TaF 4 ). In line to Jahn-Teller theorem the calculations evidenced instability of tetrahedron configuration of the molecules in the orbital-singular electronic states 2 E and 2 T 2 . The properties of the systems of the molecule potential energies were found, in keeping with deformation of tetrahedron configuration of the nuclei along the oscillation coordinates of the e symmetry, active in the Jahn-Teller effect. Equilibrium geometric configuration of the molecules with the lowest energy has a symmetry D 2d as in the basic ( 2 A 1 ), so in the first excited electronic state. The energy of the adiabatic electronic excitation 2 A 1 → 2 B 2 is equal to 8440 (VF 4 ), 9050 (NbF 4 ) and 11920 cm -1 (TaF 4 ). Deviations of molecules equilibrium geometry on the structure of the normal tetrahedron and the energy of Jahn-Teller stabilization E JT grow essentially in the series of the molecules VF 4 → NbF 4 → TaF 4 : E JT =E(T d , 2 E)Epy - E(D 2d , 2 A 1 )=412, 1856, 5970 cm -1 ; E JT =E(T d , 2 T 2 ) - E(D 2d , 2 B 2 )=3584, 6259, 6611 cm -1 . The quadratic force constants, the frequencies of normal oscillations and the intensities in the IR spectra of the VF 4 , NbF 4 and TaF 4 molecules in the basic state were calculated [ru

Jahn-Teller coupling at ND1 and GR1 centres in diamond

International Nuclear Information System (INIS)

Lowther, J.E.

1978-01-01

Stress parameters associated with the splitting of the GR1 and ND1 lines are examined in the light of the recent suggestion that ND1 arises from the negatively charged vacancy. The stress parameters are totally consistent with this interpretation; Jahn-Teller coupling in the excited states being similar for both centres. (author)

Experimental confirmation of the Jahn-Teller distortion of CH4+

International Nuclear Information System (INIS)

Gemmell, D.S.; Kanter, E.P.; Pietsch, W.J.

1979-01-01

Measured energy and angular distributions are reported for H + and C/sup n+/ (n = 2,3,4) fragments resulting from the collisional dissociation of 200-keV/amu CH/sub m/ + (m = 0 to 4) in thin carbon targets. From the systematic trends of these Coulomb explosion spectra, qualitative information can be obtained on the structures of these species. In particular, the series displays a narrowing of the carbon angular and energy widths as protons are symmetrically added around a central carbon atom and provide a focusing effect. Because of the Jahn-Teller distortion, the carbon width in CH 4 + is dramatically increased. 8 references

Influence of static Jahn-Teller distortion on the magnetic excitation spectrum of PrO2: A synchrotron x-ray and neutron inelastic scattering study

International Nuclear Information System (INIS)

Webster, C. H.; Helme, L. M.; Boothroyd, A. T.; McMorrow, D. F.; Wilkins, S. B.; Detlefs, C.; Detlefs, B.; Bewley, R. I.; McKelvy, M. J.

2007-01-01

A synchrotron x-ray diffraction study of the crystallographic structure of PrO 2 in the Jahn-Teller distorted phase is reported. The distortion of the oxygen sublattice, which was previously ambiguous, is shown to be a chiral structure in which neighboring oxygen chains have opposite chiralities. A temperature dependent study of the magnetic excitation spectrum, probed by neutron inelastic scattering, is also reported. Changes in the energies and relative intensities of the crystal field transitions provide an insight into the interplay between the static and dynamic Jahn-Teller effects

Jahn-Teller distortions, cation ordering and octahedral tilting in perovskites

International Nuclear Information System (INIS)

Lufaso, M.W.; Woodward, P.M.

2004-01-01

In transition metal oxides, preferential occupation of specific d orbitals on the transition metal ion can lead to the development of a long-range ordered pattern of occupied orbitals. This phenomenon, referred to as orbital ordering, is usually observed indirectly from the cooperative Jahn-Teller distortions (CJTDs) that result as a consequence of the orbital ordering. This paper examines the interplay between orbital ordering, octahedral tilting and cation ordering in perovskites. Both ternary AMX 3 perovskites containing an active Jahn-Teller (J-T) ion on the octahedral site and quaternary A 2 MM'X 6 perovskites containing a J-T ion on one-half of the octahedral sites have been examined. In AMX 3 perovskites, the tendency is for the occupied 3d 3x 2 -r 2 and 3d 3z 2 -r 2 orbitals to order in the ac plane, as exemplified by the crystal structures of LaMnO 3 and KCuF 3 . This arrangement maintains a favorable coordination environment for the anion sites. In AMX 3 perovskites, octahedral tilting tends to enhance the magnitude of the J-T distortions. In A 2 MM'X 6 perovskites, the tendency is for the occupied 3d 3z 2 -r 2 orbitals to align parallel to the c axis. This pattern maintains a favorable coordination environment about the symmetric M'-cation site. The orbital ordering found in rock-salt ordered A 2 MM'X 6 perovskites is compatible with octahedral rotations about the c axis (Glazer tilt system a 0 a 0 c - ) but appears to be incompatible with GdFeO 3 -type octahedral tilting (tilt system - b + a - ). (orig.)

The effect of band Jahn-Teller distortion on the magnetoresistivity of manganites: a model study

International Nuclear Information System (INIS)

Rout, G C; Panda, Saswati; Behera, S N

2011-01-01

We present a model study of magnetoresistance through the interplay of magnetisation, structural distortion and external magnetic field for the manganite systems. The manganite system is described by the Hamiltonian which consists of the s-d type double exchange interaction, Heisenberg spin-spin interaction among the core electrons, and the static and dynamic band Jahn-Teller (JT) interaction in the e g band. The relaxation time of the e g electron is found from the imaginary part of the Green's function using the total Hamiltonian consisting of the interactions due to the electron and phonon. The calculated resistivity exhibits a peak in the pure JT distorted insulating phase separating the low temperature metallic ferromagnetic phase and the high temperature paramagnetic phase. The resistivity is suppressed with the increase of the external magnetic field. The e g electron band splitting and its effect on magnetoresistivity is reported here. (paper)

The effect of band Jahn-Teller distortion on the magnetoresistivity of manganites: a model study

Energy Technology Data Exchange (ETDEWEB)

Rout, G C [Condensed Matter Physics Group, P G Department of Applied Physics and Ballistics, F M University, Balasore 756 019 (India); Panda, Saswati [Trident Academy of Technology, F2/A, Chandaka Industrial Estate, Bhubaneswar 751 024 (India); Behera, S N, E-mail: gcr@iopb.res.in, E-mail: saswatip7@gmail.com [National Institute of Science and Technology, Palur Hills, Berhampur 761 008 (India)

2011-10-05

We present a model study of magnetoresistance through the interplay of magnetisation, structural distortion and external magnetic field for the manganite systems. The manganite system is described by the Hamiltonian which consists of the s-d type double exchange interaction, Heisenberg spin-spin interaction among the core electrons, and the static and dynamic band Jahn-Teller (JT) interaction in the e{sub g} band. The relaxation time of the e{sub g} electron is found from the imaginary part of the Green's function using the total Hamiltonian consisting of the interactions due to the electron and phonon. The calculated resistivity exhibits a peak in the pure JT distorted insulating phase separating the low temperature metallic ferromagnetic phase and the high temperature paramagnetic phase. The resistivity is suppressed with the increase of the external magnetic field. The e{sub g} electron band splitting and its effect on magnetoresistivity is reported here. (paper)

The influence of band Jahn-Teller effect and magnetic order on the magneto-resistance in manganite systems

Energy Technology Data Exchange (ETDEWEB)

Rout, G.C., E-mail: gcr@iopb.res.i [Condensed Matter Physics Group, Department of Applied Physics and Ballistics, F.M. University, Balasore, Orissa 756019 (India); Parhi, Nilima [Department of Physics, M.P.C. (Autonomous) College, Baripada, Orissa 757001 (India); Behera, S.N. [Institute of Material Science, Bhubaneswar 751004 (India)

2009-08-01

A model calculation is presented in order to study the magneto-resistivity through the interplay between magnetic and structural transitions for the manganite systems. The model consists of an orbitally doubly degenerate conduction band and a periodic array of local moments of the t{sub 2g} electrons. The band electrons interact with the local t{sub 2g} electrons via the s-f hybridization. The phonons interact with the band electrons through static and dynamic band Jahn-Teller (J-T) interaction. The model Hamiltonian including the above terms is solved for the single particle Green's functions and the imaginary part of the self-energy gives the electron relaxation time. Thus the magneto-resistivity (MR) is calculated from the Drude formula. The MR effect is explained near the magnetic and structural transition temperatures.

Quantum friction of pseudorotation in Jahn-Teller system: Passage through conical intersection

Energy Technology Data Exchange (ETDEWEB)

Pae, Kaja, E-mail: kaja.pae@gmail.com; Hizhnyakov, Vladimir [Institute of Physics, University of Tartu, W. Ostwaldi 1, 50411 Tartu (Estonia)

2016-08-14

A theoretical study of the relaxation of an excited impurity center with strong E × e-type Jahn-Teller effect, caused by the emission of phonons to the bulk, is presented. The dependence of the passing the system through the conical intersection of the potential surface on the momentum of the pseudorotation is figured out. An analytical description of the quantum states of the conical intersection (Slonczewski resonances) is given. It is found that for realistic vibronic interactions with phonons, the characteristic time of the energy loss is several tenths of mean periods of phonons, i.e., it is in the picosecond range. It is also found that there is a finite probability of the speeding-up of the pseudorotation of the system at the intermediate stage of relaxation. In particular, this probability increases close to the Slonczewski resonances. During the relaxation, the system may change the direction of the pseudomoment; the probability of such a change also increases near the resonances.

Synthetic, structural, spectroscopic and theoretical study of a Mn(III)-Cu(II) dimer containing a Jahn-Teller compressed Mn ion

DEFF Research Database (Denmark)

Berg, Nelly; Hooper, Thomas N.; Liu, Junjie

2013-01-01

The heterobimetallic complex [Cu(II)Mn(III)(L)(2)(py)(4)](ClO(4))·EtOH (1) built using the pro-ligand 2,2'-biphenol (LH(2)), contains a rare example of a Jahn-Teller compressed Mn(III) centre. Dc magnetic susceptibility measurements on 1 reveal a strong antiferromagnetic exchange between the Cu...

Generalized Born-Oppenheimer treatment of Jahn-Teller systems in Hilbert spaces of arbitrary dimension: theory and application to a three-state model potential.

Science.gov (United States)

Varandas, A J C; Sarkar, B

2011-05-14

Generalized Born-Oppenheimer equations including the geometrical phase effect are derived for three- and four-fold electronic manifolds in Jahn-Teller systems near the degeneracy seam. The method is readily extendable to N-fold systems of arbitrary dimension. An application is reported for a model threefold system, and the results are compared with Born-Oppenheimer (geometrical phase ignored), extended Born-Oppenheimer, and coupled three-state calculations. The theory shows unprecedented simplicity while depicting all features of more elaborated ones.

Contribution of Jahn-Teller and charge transfer excitations to the photovoltaic effect of manganite/titanite heterojunctions

Science.gov (United States)

Ifland, Benedikt; Hoffmann, Joerg; Kressdorf, Birte; Roddatis, Vladimir; Seibt, Michael; Jooss, Christian

2017-06-01

The effect of correlation effects on photovoltaic energy conversion at manganite/titanite heterojunctions is investigated. As a model system we choose a heterostructure consisting of the small polaron absorber Pr0.66Ca0.34MnO3 (PCMO) epitaxially grown on single-crystalline Nb-doped SrTi0.998Nb0.002O3 (STNO) substrates. The high structural and chemical quality of the interfaces is proved by detailed characterization using high-resolution transmission electron microscopy (TEM) and electron energy loss spectroscopy (EELS) studies. Spectrally resolved and temperature-dependent photovoltaic measurements show pronounced contributions of both the Jahn-Teller (JT) excitations and the charge transfer (CT) transitions to the photovoltaic effect at different photon energies. A linear temperature dependence of the open-circuit voltage for an excitation in the PCMO manganite is only observed below the charge-ordering temperature, indicating that the diffusion length of the photocarrier exceeds the size of the space charge region. The photovoltaic response is compared to that of a heterojunction of lightly doped Pr0.05Ca0.95MnO3 (CMO)/STNO, where the JT transition is absent. Here, significant contributions of the CT transition to the photovoltaic effect set in below the Neel temperature. We conclude that polaronic correlations and ordering effects are essentials for photovoltaic energy conversion in manganites.

Jahn-Teller and Non-Jahn-Teller Systems Involving CuF64- Units: Role of the Internal Electric Field in Ba2ZnF6:Cu2+ and Other Insulating Systems

DEFF Research Database (Denmark)

Aramburu, J. A.; Garcia-Fernandez, P.; García Lastra, Juan Maria

2017-01-01

The applicability of the Jahn-Teller (JT) framework to 6-fold coordinated d9 ions whose local symmetry is not strictly octahedral is explored by means of first principle calculations. Our results contradict much of the existing literature where these systems are analyzed within the quasi-JT regime...... transitions for CuF64- units formed in Cu2+-doped the tetragonal Ba2ZnF6 host lattice. While the experimental d-d transitions cannot be reproduced through the isolated CuF64- unit at the equilibrium geometry, a reasonable agreement is reached adding in the calculation the internal electric field, ER...... state with the hole in the a1g(∼ 3z2-r2) level while it is always placed in the b1g(∼ x2-y2) level for MX6 complexes (M = Cu2+, Ag2+, NiΤ; X = F--, Cl-) in cubic lattices displaying a static JT effect. While the experimental results of CuF64- in Ba2ZnF6 cannot be understood within the JT framework...

Conduction band-edge d-states in high-k dielectrics due to Jahn-Teller term splittings

International Nuclear Information System (INIS)

Lucovsky, G.; Fulton, C.C.; Zhang, Y.; Luning, J.; Edge, L.; Whitten, J.L.; Nemanich, R.J.; Schlom, D.G.; Afanase'v, V.V.

2005-01-01

X-ray absorption spectroscopy (XAS) is used to study conduction band edge electronic structure of high-k transition metal (TM) and trivalent lanthanide series rare earth (RE) oxide dielectrics. Empty TM/RE d-states are studied by intra-atomic transitions originating in core level spin-orbit split p-states, and conduction band states are studied in inter-atomic transitions which originate in the oxygen atom 1s core level state. In non-crystalline Zr and Hf silicate alloys, the local bonding symmetry, or crystal field splits these d-states into doubly and triply degenerate features. In nano-crystalline oxides, there are additional d-state splittings due to contributions of more distant neighbors that completely remove d-state degeneracies via the Jahn-Teller effect mechanism. This gives rise to highly localized band edge states that are electronically active in photoconductivity, internal photoemission, and act as bulk traps in metal oxide semiconductor (MOS) devices

Reduction of the Jahn-Teller distortion at the insulator-to-metal transition in mixed valence manganites

International Nuclear Information System (INIS)

Garcia-Munoz, J.L.; Suaaidi, M.; Fontcuberta, J.; Rodriguez-Carvajal, J.

1997-01-01

The insulator-to-metal transition in the manganite La 0.52 Y 0.15 Ca 0.33 MnO 3 (T IM ∼115 K) has been studied by high-resolution neutron powder diffraction. The cell volume contraction at the Curie point is accompanied by a remarkable decrease of the Jahn-Teller distortion in MnO 6 octahedra. The change of the Mn-O bond lengths at T IM is anisotropic and brings about a drop out of the basal-plane collective distortion mode Q 2 , proposed to be the deformation responsible for the band split of e g↑ orbitals. This is consistent with the double-exchange picture, and precludes simple ferromagnetic exchange. copyright 1997 The American Physical Society

Modulation of Jahn-Teller effect on magnetization and spontaneous electric polarization of CuFeO2

Science.gov (United States)

Xiao, Guiling; Xia, Zhengcai; Wei, Meng; Huang, Sha; Shi, Liran; Zhang, Xiaoxing; Wu, Huan; Yang, Feng; Song, Yujie; Ouyang, Zhongwen

2018-03-01

CuFe0.99Mn0.01O2 and CuFe0.99Co0.01O2 single crystal samples are grown by a floating zone technique and their magnetization and spontaneous electric polarization have been investigated. Similarly with pure CuFeO2, an obviously anisotropic magnetization and spontaneous electric polarization were observed in the both doped samples, and their phase transition critical fields and temperatures are directly doping ion dependent. Considering the different d-shell configuration and ionic size between Mn3+, Co3+ and Fe3+ ions, in which the Mn3+ ion with Jahn-Teller (J-T) effect has different distortion on the geometry frustration from both of Fe3+ and Co3+ ion. Since for Mn3+ ion, the orbital splitting results from the low-symmetry J-T distortion in a crystal-field environment leads to a distorted MnO6 octahedron, which different from undistorted FeO6 and CoO6 octahedrons. The strain between distorted and undistorted octahedrons produces different effects on the spin reorientation transition and spontaneous electric polarization. Although the pure CuFeO2 has a very strong and robust frustration, the presence of the strain due to the random distribution of distorted MnO6 octahedron and undistorted CoO6 (FeO6) octahedrons leads to its spin reorientation transitions and spontaneous electric polarization different from CuFeO2.

Jahn-Teller coupling of Cr2+ ion with degenerate modes in ZnS, ZnSe, and ZnTe crystals: microscopic treatment

International Nuclear Information System (INIS)

Natadze, A.L.; Ryskin, A.I.

1980-01-01

The Jahn-Teller (JT) interaction energy is calculated for 5 T 2 and 5 E states of the Cr 2+ ion in ZnS, ZnSe, and ZnTe crystals. The calculations are made within the framework of a particular microscopic model of the crystal field in the distorted crystal (model of point-like exchange charges), the multimode interaction is taken into account. For the 5 T 2 term the energies of interaction with tetragonal and trigonal modes are of the same order of magnitude. This circumstance results in a small height of the barriers that separate various minima of the adiabatic potential and is responsible for the dynamic aspect of the static JT effect in these systems. (author)

Ab initio theory of spin-orbit coupling for quantum bits in diamond exhibiting dynamic Jahn-Teller effect

Science.gov (United States)

Gali, Adam; Thiering, Gergő

Dopants in solids are promising candidates for implementations of quantum bits for quantum computing. In particular, the high-spin negatively charged nitrogen-vacancy defect (NV) in diamond has become a leading contender in solid-state quantum information processing. The initialization and readout of the spin is based on the spin-selective decay of the photo-excited electron to the ground state which is mediated by spin-orbit coupling between excited states states and phonons. Generally, the spin-orbit coupling plays a crucial role in the optical spinpolarization and readout of NV quantum bit (qubit) and alike. Strong electron-phonon coupling in dynamic Jahn-Teller (DJT) systems can substantially influence the effective strength of spin-orbit coupling. Here we show by ab initio supercell density functional theory (DFT) calculations that the intrinsic spin-orbit coupling is strongly damped by DJT effect in the triplet excited state that has a consequence on the rate of non-radiative decay. This theory is applied to the ground state of silicon-vacancy (SiV) and germanium-vacancy (GeV) centers in their negatively charged state that can also act like qubits. We show that the intrinsic spin-orbit coupling in SiV and GeV centers is in the 100 GHz region, in contrast to the NV center of 10 GHz region. Our results provide deep insight in the nature of SiV and GeV qubits in diamond. EU FP7 DIADEMS project (Contract No. 611143).

An EPR investigation of the dynamic Jahn-Teller effect in SrCl2:y(2 plus) and SrCl2:Sc(2 plus)

Science.gov (United States)

Herrington, J. R.; Estle, T. L.; Boatner, L. A.

1972-01-01

EPR spectra have been observed for SrCl2:Y(2+) and SrCl2:Sc(2+) at liquid helium temperatures. At 1.2 K the spectra were dominated by anisotropic hyperfine patterns whose lineshapes and angular dependences were explained using second order solutions of the effective Hamiltonian for an isolated 2Eg state split by large random internal strains. Pronounced asymmetries in some of the strin produced lineshapes for Srcl2:Sc(2+) are shown to result from second order terms in the solution of the effective Hamiltonian. Coexisting with the anisotropic hyperfine patterns are weak nearly isotropic hyperfine patterns with typical lineshapes. Variations in the apparent intensity of lines in these weak hyperfine patterns as functions of the applied magnetic field direction and temperature imply that these lines result from averaging by vibronic relaxation of a portion of the anisotropic pattern. The effective Hamiltonian parameters for SrCl2:La(2+), SrCl2:y(2+), and SrCl2:SC(2+) are analyzed in terms of crystal field theory modified to include a dynamic Jahn-Teller effect.

A study of cooperative Jahn-Teller phase transitions in rare-earth vanadates by linear birefringence

International Nuclear Information System (INIS)

Gehring, G.A.; Harley, R.T.; Macfarlane, R.M.

1980-01-01

Changes in linear birefringence (Δn) associated with the cooperative Jahn-Teller phase transition of DyV04 near 14K as as a function of temperature and magnetic fields, B, between 0.024 and 0.095T have been measured. Theoretical arguments show that Δn is directly proportional to the order parameter of the transition and that B(2) is equivalent to the conjugate ordering field. By extrapolation to zero field the temperature dependence of the order parameter and the susceptibility were obtained. The data are compared with calculations based on a mean-field 'compressible' Ising model. For a reasonable choice of adjustable parameters this classical description gives a good fit to the data close to Tsub(D) consistent with general theoretical arguments and more detailed calculations, but it deviates progressively away from Tsub(D) presumably because of the known importance of short-range interactions in the system. (author)

Jahn-Teller distortion in the phosphorescent excited state of three-coordinate Au(I) phosphine complexes.

Science.gov (United States)

Barakat, Khaldoon A; Cundari, Thomas R; Omary, Mohammad A

2003-11-26

DFT calculations were used to optimize the phosphorescent excited state of three-coordinate [Au(PR3)3]+ complexes. The results indicate that the complexes rearrange from their singlet ground-state trigonal planar geometry to a T-shape in the lowest triplet luminescent excited state. The optimized structure of the exciton contradicts the structure predicted based on the AuP bonding properties of the ground-state HOMO and LUMO. The rearrangement to T-shape is a Jahn-Teller distortion because an electron is taken from the degenerate e' (5dxy, 5dx2-y2) orbital upon photoexcitation of the ground-state D3h complex. The calculated UV absorption and visible emission energies are consistent with the experimental data and explain the large Stokes' shifts while such correlations are not possible in optimized models that constrained the exciton to the ground-state trigonal geometry.

Cyclopropenyl Anions: Carbon Tunneling or Diradical Formation? A Contest between Jahn-Teller and Hund.

Science.gov (United States)

Kozuch, Sebastian

2015-07-14

The π bond shifting (automerization) by carbon tunneling of cyclopropenyl anions was computationally analyzed by the small curvature tunneling methodology. Similar to other antiaromatic cases, the process is hindered by substituents departing from planarity, since these groups must be realigned along with the π bond shifting. With hydrogens as substituents the tunneling is extremely fast, in a case of both heavy and light atom tunneling. But, with more massive substituents (such as Me and F), and especially with longer groups (such as CN), the tunneling probability is reduced or even virtually canceled. The automerization of triphenylcyclopropyl anion by tunneling was supposed to be impossible due to the high mass of the phenyl groups. However, it was found that the ground state of this species is actually a D3h aromatic triplet, a single-well system that cannot undergo automerization. For this and other systems with π acceptor groups, the superposition of states that generates the second-order Jahn-Teller distortion is diminished, and by Hund's rule, the triplet results in the ground state.

Jahn-Teller glass formation in beta-lithium ammonium sulfate monocrystals studied by means of the electron paramagnetic resonance of Mn sup 2 sup + and Cu sup 2 sup + ions

CERN Document Server

Waplak, S

2002-01-01

The EPR (electron paramagnetic resonance) spectra of non-Jahn-Teller (JT) Mn sup 2 sup + and JT Cu sup 2 sup + ions have been studied for alpha- or beta-LAS structure modification in the temperature range of 4.2-480 K. The experimental evidence for JT glass with frozen-in random strain fields due to the presence of the JT Cu sup 2 sup + ions is presented.

Bcc and Fcc transition metals and alloys: a central role for the Jahn-Teller effect in explaining their ideal and distorted structures.

Science.gov (United States)

Lee, Stephen; Hoffmann, Roald

2002-05-01

Transition metal elements, alloys, and intermetallic compounds often adopt the body centered cubic (bcc) and face centered cubic (fcc) structures. By comparing quantitative density functional with qualitative tight-binding calculations, we analyze the electronic factors which make the bcc and fcc structures energetically favorable. To do so, we develop a tight-binding function, DeltaE(star), a function that measures the energetic effects of transferring electrons within wave vector stars. This function allows one to connect distortions in solids to the Jahn-Teller effect in molecules and to provide an orbital perspective on structure determining deformations in alloys. We illustrate its use by considering first a two-dimensional square net. We then turn to three-dimensional fcc and bcc structures, and distortions of these. Using DeltaE(star), we rationalize the differences in energy of these structures. We are able to deduce which orbitals are responsible for instabilities in seven to nine valence electron per atom (e(-)/a) bcc systems and five and six e(-)/a fcc structures. Finally we demonstrate that these results account for the bcc and fcc type structures found in both the elements and binary intermetallic compounds of group 4 through 9 transition metal atoms. The outline of a theory of metal structure deformations based on loss of point group operation rather than translational symmetry is presented.

Synthesis under pressure and characterizations through optical spectroscopy of jahn-teller cations (LS Ni3+, is Co3+) as probes diluted in a perovskite matrix

Science.gov (United States)

Sanz-Ortiz, M. N.; Rodríguez, F.; Baranov, A.; Demazeau, G.

2008-07-01

The objective is to explore through optical spectroscopy and magnetic measurements the coordination and electronic structures of transition-metal ions introduced as impurities with unusual valence states in the oxide perovskite LaAlO3. The selected transition-metal ions Ni3+(3d7) and Co3+(3d6) are characterized by an electronic configuration likely leading to an orbital degenerate E state in Oh symmetry, and thus electron-lattice coupling due to the Jahn-Teller effect may induce low symmetry distortion around the impurity oxygen octahedron. We show that a sol-gel process followed by high oxygen pressure treatments yields stabilization of trivalent state in oxide perovskite. Information about the coordination, electronic structure and aggregation around the magnetic impurity was obtained from X-ray diffraction, FTIR and optical spectroscopy. Finally, evidence on the possible existence of intermediate spin state in Co3+ is under consideration.

Synthesis under pressure and characterizations through optical spectroscopy of jahn-teller cations (LS Ni3+, is Co3+) as probes diluted in a perovskite matrix

International Nuclear Information System (INIS)

Sanz-Ortiz, M N; RodrIguez, F; Baranov, A; Demazeau, G

2008-01-01

The objective is to explore through optical spectroscopy and magnetic measurements the coordination and electronic structures of transition-metal ions introduced as impurities with unusual valence states in the oxide perovskite LaAlO 3 . The selected transition-metal ions Ni 3+ (3d 7 ) and Co 3+ (3d 6 ) are characterized by an electronic configuration likely leading to an orbital degenerate E state in Oh symmetry, and thus electron-lattice coupling due to the Jahn-Teller effect may induce low symmetry distortion around the impurity oxygen octahedron. We show that a sol-gel process followed by high oxygen pressure treatments yields stabilization of trivalent state in oxide perovskite. Information about the coordination, electronic structure and aggregation around the magnetic impurity was obtained from X-ray diffraction, FTIR and optical spectroscopy. Finally, evidence on the possible existence of intermediate spin state in Co 3+ is under consideration

Jahn-teller domains and magnetic domains in Mn2FeO4

NARCIS (Netherlands)

Kub, J.; Brabers, V.A.M.; Novák, P.; Gemperle, R.; Simsova, J.

2000-01-01

Elastic (Jahn–Teller) domains and magnetic domains in the tetragonal spinel Mn2FeO4 were studied using X-ray double-crystal topography, X-ray diffractometry and the colloid-SEM method. The Jahn–Teller domains of the measured samples are tetragonal with the [0 0 1] c-axis alternating perpendicularly

Electronic Correlations, Jahn-Teller Distortions and Mott Transition to Superconductivity in Alkali-C60 Compounds

Directory of Open Access Journals (Sweden)

Alloul H.

2012-03-01

Full Text Available The discovery in 1991 of high temperature superconductivity (SC in A3C60 compounds, where A is an alkali ion, has been rapidly ascribed to a BCS mechanism, in which the pairing is mediated by on ball optical phonon modes. While this has lead to consider that electronic correlations were not important in these compounds, further studies of various AnC60 with n=1, 2, 4 allowed to evidence that their electronic properties cannot be explained by a simple progressive band filling of the C60 six-fold degenerate t1u molecular level. This could only be ascribed to the simultaneous influence of electron correlations and Jahn-Teller Distortions (JTD of the C60 ball, which energetically favour evenly charged C60 molecules. This is underlined by the recent discovery of two expanded fulleride Cs3C60 isomeric phases which are Mott insulators at ambient pressure. Both phases undergo a pressure induced first order Mott transition to SC with a (p, T phase diagram displaying a dome shaped SC, a common situation encountered nowadays in correlated electron systems. NMR experiments allowed us to study the magnetic properties of the Mott phases and to evidence clear deviations from BCS expectations near the Mott transition. So, although SC involves an electron-phonon mechanism, the incidence of electron correlations has an importance on the electronic properties, as had been anticipated from DMFT calculations.

Off-centre dynamic Jahn-Teller effect studied by electron spin relaxation of Cu2+ ions in SrF2 crystal

International Nuclear Information System (INIS)

Hoffmann, S.K.

2000-01-01

Temperature cw-EPR and pulsed EPR electron spin echo experiments were performed for a low concentration of Cu 2+ ions in cubic SrF 2 crystals. The well resolved EPR spectrum at low temperatures (below 30 K) with parameters g parallel = 2.493, g perpendicular = 2.083, A parallel = 121, A perpendicular = 8.7, A parallel ( 19 F) = 135, A parallel ( 19 F) = 33.0 (A-values in 10 -4 cm -1 ) is transformed continuously into a single broad line above 225 K on heating, due to the g-factor shift and EPR line broadening. These data along with the angular variation EPR data are described in terms of a pseudo-Jahn-Teller effect of (T 2g +A 2u )x(a 1g +e g +t 1u ) type producing six off-centre positions of the Cu 2+ ion in the fluorine cube. Above 30 K a two-step averaging g -factor process occurs and is governed by vibronic dynamics between potential wells of the off-centre positions. This dynamics governs the electron spin relaxation in the whole temperature range. The electron spin-lattice relaxation rate 1/T 1 grows rapidly by six orders of magnitude in the temperature range 30-100 K and is determined by the Orbach-type process with excitations to two excited vibronic levels of energy 83 and 174 cm -1 . For higher temperatures the relaxation is dominated by overbarrier jumps leading to the isotropic EPR spectrum above 225 K. The phase memory time T M has the rigid lattice value 3.5 μs determined by nuclear spectral diffusion and its temperature variation is governed by the vibronic dynamics indicating that the excitations between vibronic levels produce a dephasing of the electron spin precessional motion. (author)

Variation of the Jahn-Teller distortion with pressure in the layered perovskite Rb2CuCl4: local and crystal compressibilities

International Nuclear Information System (INIS)

Aguado, F; RodrIguez, F; Valiente, R; Hanfland, M; Itie, J P

2007-01-01

This work investigates the effect of pressure on the Jahn-Teller distortion (JTD) associated with the axially elongated CuCl 6 octahedra in the A 2 CuCl 4 perovskite layer (A: Rb, CH 3 NH 3 , C 2 H 5 NH 3 , C 3 H 7 NH 3 ). The aim is to elucidate whether pressure favours disappearance of the JTD in the antiferrodistortive (AFD) structure exhibited by Cu 2+ within the layers or whether it induces tilts of the CuCl 6 octahedra preserving the molecular distortion associated with the JT effect. We have carried out x-ray absorption (XAS) and x-ray diffraction (XRD) experiments under pressure along the compound series, whose interlayer distances at ambient pressure vary from 7.77 to 12.33 A. The use of both XAS and XRD techniques allows us a complete local- and crystal-structure characterization in Rb 2 CuCl 4 as a function of pressure in the 0-16 GPa range. We show that pressure reduces the axial (long) and equatorial (short) Cu-Cl distances, R ax and R eq , as well as the intralayer and interlayer Cu-Cu distances, d Cu-Cu and d inter . Interestingly, the variation of R ax is an order of magnitude bigger than that of the corresponding R eq , yielding a reduction of the JTD. However, no evidence of JTD suppression has been observed below 16 GPa. Pressure-induced CuCl 6 tilting preserves the JTD in a wide pressure range. Estimates based on structural data suggest that JT suppression would occur at about 40 GPa

Pseudo-Jahn-Teller Distortion in Two-Dimensional Phosphorus: Origin of Black and Blue Phases of Phosphorene and Band Gap Modulation by Molecular Charge Transfer.

Science.gov (United States)

Chowdhury, Chandra; Jahiruddin, Sheik; Datta, Ayan

2016-04-07

Phosphorene (Pn) is stabilized as a layered material like graphite, yet it possess a natural direct band gap (Eg = 2.0 eV). Interestingly, unlike graphene, Pn exhibits a much richer phase diagram which includes distorted forms like the stapler-clip (black Pn, α form) and chairlike (blue Pn, β form) structures. The existence of these phases is attributed to pseudo-Jahn-Teller (PJT) instability of planar hexagonal P6(6-) rings. In both cases, the condition for vibronic instability of the planar P6(6-) rings is satisfied. Doping with electron donors like tetrathiafulvalene and tetraamino-tetrathiafulvalene and electron acceptors like tetracyanoquinodimethane and tetracyanoethylene convert blue Pn into N-type and black Pn into efficient P-type semiconductors, respectively. Interestingly, pristine blue Pn, an indirect gap semiconductor, gets converted into a direct gap semiconductor on electron or hole doping. Because of comparatively smaller undulation in blue Pn (with respect to black Pn), the van der Waals interactions between the dopants and blue Pn is stronger. PJT distortions for two-dimensional phosphorus provides a unified understanding of structural features and chemical reactivity in its different phases.

THE SYMMETRY BREAKING PHENOMENON IN 1,2,3-TRIOXOLENE AND C2Y3Z2 (Z= O, S, Se, Te, Z= H, F COMPOUNDS: A PSEUDO JAHN-TELLER ORIGIN STUDY

Directory of Open Access Journals (Sweden)

Ali Reza Ilkhani

Full Text Available 1,2,3-Trioxolene (C2O3H2 is an intermediate in the acetylene ozonolysis reaction which is called primary ozonide intermediate. The symmetry breaking phenomenon were studied in C2O3H2 and six its derivatives then oxygen atoms of the molecule are substituted by sulphur, selenium, tellurium (C2Y3H2 and hydrogen ligands are replaced with fluorine atoms (C2Y3F2. Based on calculation results, all seven C2Y3Z2 considered in the series were puckered from unstable planar configuration with C2v symmetry to a Cs symmetry stable geometry. The vibronic coupling interaction between the 1A1 ground state and the first excited state 1B1 via the (1A1+1B1 ⊗b1 pseudo Jahn-Teller effect problem is the reason of the breaking symmetry phenomenon and un-planarity of the C2Y3 ring in the C2Y3Z2 series.

Aggregate frequency width, nuclear hyperfine coupling and Jahn-Teller effect of Cu2+ impurity ion ESR in SrLaAlO4 dielectric resonator at 20 millikelvin

Science.gov (United States)

Hosain, M. A.; Le Floch, J.-M.; Krupka, J.; Tobar, M. E.

2018-01-01

The impurity paramagnetic ion, Cu2+ substitutes Al in the SrLaAlO4 single crystal lattice, this results in a CuO6 elongated octahedron, and the resulting measured g-factors satisfy four-fold axes variation condition. The aggregate frequency width of the electron spin resonance with the required minimum level of impurity concentration has been evaluated in this single crystal SrLaAlO4 at 20 millikelvin. Measured parallel hyperfine constants, A\\Vert Cu , were determined to be -155.7×10-4~cm-1, ~ -163.0×10-4~cm-1, ~ -178.3×10-4~cm-1 and -211.1×10-4~cm-1 at 9.072~GHz~(WGH4, 1, 1) for the nuclear magnetic quantum number M_I=+\\frac{3}{2}, +\\frac{1}{2}, -\\frac{1}{2} , and -\\frac{3}{2} respectively. The anisotropy of the hyperfine structure reveals the characteristics of the static Jahn-Teller effect. The second-order-anisotropy term, ˜ (\\fracspin{-orbit~coupling}{10D_q}){\\hspace{0pt}}2 , is significant and cannot be disregarded, with the local strain dominating over the observed Zeeman-anisotropy-energy difference. The Bohr electron magneton, β=9.23× 10-24 JT-1 , (within -0.43% so-called experimental error) has been found using the measured spin-Hamiltonian parameters. Measured nuclear dipolar hyperfine structure parameter P\\Vert=12.3×10-4~cm-1 shows that the mean inverse third power of the electron distance from the nucleus is ≃ 5.23 a.u. for Cu2+ ion in the substituted Al3+ ion site assuming nuclear electric quadruple moment Q=-0.211 barn.

Variation of the Jahn-Teller distortion with pressure in the layered perovskite Rb{sub 2}CuCl{sub 4}: local and crystal compressibilities

Energy Technology Data Exchange (ETDEWEB)

Aguado, F [DCITIMAC, Facultad de Ciencias, Universidad de Cantabria, Santander 39005 (Spain); RodrIguez, F [DCITIMAC, Facultad de Ciencias, Universidad de Cantabria, Santander 39005 (Spain); Valiente, R [Departamento de Fisica Aplicada, Universidad de Cantabria, Santander 39005 (Spain); Hanfland, M [ESRF, BP220, 156 rue des Martires, 38043 Grenoble Cedex (France); Itie, J P [Universite Pierre et Marie Curie, B77 4 Place Jussieu 75252 Paris Cedex 05 (France)

2007-08-29

This work investigates the effect of pressure on the Jahn-Teller distortion (JTD) associated with the axially elongated CuCl{sub 6} octahedra in the A{sub 2}CuCl{sub 4} perovskite layer (A: Rb, CH{sub 3}NH{sub 3}, C{sub 2}H{sub 5}NH{sub 3}, C{sub 3}H{sub 7}NH{sub 3}). The aim is to elucidate whether pressure favours disappearance of the JTD in the antiferrodistortive (AFD) structure exhibited by Cu{sup 2+} within the layers or whether it induces tilts of the CuCl{sub 6} octahedra preserving the molecular distortion associated with the JT effect. We have carried out x-ray absorption (XAS) and x-ray diffraction (XRD) experiments under pressure along the compound series, whose interlayer distances at ambient pressure vary from 7.77 to 12.33 A. The use of both XAS and XRD techniques allows us a complete local- and crystal-structure characterization in Rb{sub 2}CuCl{sub 4} as a function of pressure in the 0-16 GPa range. We show that pressure reduces the axial (long) and equatorial (short) Cu-Cl distances, R{sub ax} and R{sub eq}, as well as the intralayer and interlayer Cu-Cu distances, d{sub Cu-Cu} and d{sub inter}. Interestingly, the variation of R{sub ax} is an order of magnitude bigger than that of the corresponding R{sub eq}, yielding a reduction of the JTD. However, no evidence of JTD suppression has been observed below 16 GPa. Pressure-induced CuCl{sub 6} tilting preserves the JTD in a wide pressure range. Estimates based on structural data suggest that JT suppression would occur at about 40 GPa.

Nodeless vibrational amplitudes and quantum nonadiabatic dynamics in the nested funnel for a pseudo Jahn-Teller molecule or homodimer

Science.gov (United States)

Peters, William K.; Tiwari, Vivek; Jonas, David M.

2017-11-01

The nonadiabatic states and dynamics are investigated for a linear vibronic coupling Hamiltonian with a static electronic splitting and weak off-diagonal Jahn-Teller coupling through a single vibration with a vibrational-electronic resonance. With a transformation of the electronic basis, this Hamiltonian is also applicable to the anti-correlated vibration in a symmetric homodimer with marginally strong constant off-diagonal coupling, where the non-adiabatic states and dynamics model electronic excitation energy transfer or self-exchange electron transfer. For parameters modeling a free-base naphthalocyanine, the nonadiabatic couplings are deeply quantum mechanical and depend on wavepacket width; scalar couplings are as important as the derivative couplings that are usually interpreted to depend on vibrational velocity in semiclassical curve crossing or surface hopping theories. A colored visualization scheme that fully characterizes the non-adiabatic states using the exact factorization is developed. The nonadiabatic states in this nested funnel have nodeless vibrational factors with strongly avoided zeroes in their vibrational probability densities. Vibronic dynamics are visualized through the vibrational coordinate dependent density of the time-dependent dipole moment in free induction decay. Vibrational motion is amplified by the nonadiabatic couplings, with asymmetric and anisotropic motions that depend upon the excitation polarization in the molecular frame and can be reversed by a change in polarization. This generates a vibrational quantum beat anisotropy in excess of 2/5. The amplitude of vibrational motion can be larger than that on the uncoupled potentials, and the electronic population transfer is maximized within one vibrational period. Most of these dynamics are missed by the adiabatic approximation, and some electronic and vibrational motions are completely suppressed by the Condon approximation of a coordinate-independent transition dipole between

Eu/RG absorption and excitation spectroscopy in the solid rare gases: state dependence of crystal field splitting and Jahn-Teller coupling.

Science.gov (United States)

Byrne, Owen; McCaffrey, John G

2011-03-28

Absorption spectroscopy recorded for annealed samples of matrix-isolated atomic europium reveals a pair of thermally stable sites in Ar and Kr while a single site exists in Xe. Plots of the matrix shifts of the visible s → p bands versus host polarizability, allowed the association of the single site in Xe and the blue sites in Ar and Kr. On the basis of the similar ground state bond lengths expected for the Eu-rare gas (RG) diatomics and the known Na-RG molecules, the blue sites are attributed to Eu occupancy in the smaller tetra-vacancy while the red sites are proposed to arise from hexa-vacancy sites. Both sites are of cubic symmetry, consistent with the pronounced Jahn-Teller structure present on the y(8)P ← a(8)S(7/2) transition for these bands in the three hosts studied. Site-selective excitation spectroscopy has been used to reanalyze complex absorption spectra previously published by Jakob et al. [Phys. Lett. A 57, 67 (1976)] for the near-UV f → d transitions. On the basis that a pair of thermally stable sites exist in solid argon, the occurrence of crystal field splitting has been identified to occur for the J ≥ 5/2 level of the (8)P state when isolated in these two sites with cubic symmetry. From a detailed lineshape analysis, the magnitude of the crystal field splittings on the J = 5/2 level in Ar is found to be 105 and 123 cm(-1) for the red and blue sites, respectively.

α-ScVSe2O8, β-ScVSe2O8, and ScVTe2O8: new quaternary mixed metal oxides composed of only second-order Jahn-Teller distortive cations.

Science.gov (United States)

Kim, Yeong Hun; Lee, Dong Woo; Ok, Kang Min

2013-10-07

Three new quaternary scandium vanadium selenium/tellurium oxides, α-ScVSe2O8, β-ScVSe2O8, and ScVTe2O8 have been synthesized through hydrothermal and standard solid-state reactions. Although all three reported materials are stoichiometrically similar, they exhibit different crystal structures: α-ScVSe2O8 has a three-dimensional framework structure consisting of ScO6, VO6, and SeO3 groups. β-ScVSe2O8 reveals another three-dimensional framework composed of ScO7, VO5, and SeO3 polyhedra. ScVTe2O8 shows a layered structure with ScO6, VO4, and TeO4 polyhedra. Interestingly, the constituent cations, that is, Sc(3+), V(5+), Se(4+), and Te(4+) are all in a distorted coordination environment attributable to second-order Jahn-Teller (SOJT) effects. Complete characterizations including infrared spectroscopy, elemental analyses, thermal analyses, dipole moment calculation, and the magnitudes of out-of-center distortions for the compounds are reported. Transformation reactions suggest that α-ScVSe2O8 may change to β-ScVSe2O8, and then to Sc2(SeO3)3·H2O under hydrothermal conditions.

Optical detection of magnetic resonance of the F-centre in CaO in its phosphorescent state

International Nuclear Information System (INIS)

Krap, C.J.

1980-01-01

The F-centre in CaO consists of two electrons trapped in an oxygen vacancy. The centre possesses bound excited states, of which the phosphorescent 3 Tsub(1u) state is a Jahn-Teller state. Jahn-Teller systems have been of interest in many investigations. However, detailed experimental studies about the relaxation paths for the Jahn-Teller states are relatively few. The author studies by means of optical detection of magnetic resonance (ODMR) and phosphorescence microwave double resonance (PMDR) techniques the relaxation between the components of the 3 Tsub(1u) state, the magnetic properties of the individual spin-vibronic Jahn-Teller states and the inhomogeneous line broadening in the ODMR and PMDR spectra. (Auth.)

Structural and thermal properties of LaMnO3 from neutron diffraction and first principles studies

International Nuclear Information System (INIS)

Wdowik, Urszula D; Ouladdiaf, Bachir; Chatterji, Tapan

2011-01-01

Neutron diffraction experiments have been performed on powder samples of LaMnO 3 below and above the Jahn-Teller transition temperature of 750 K. Experimental investigations are assisted by density functional theory calculations. Theoretical studies are carried out for the orbitally ordered state of LaMnO 3 which allows one to compare the behavior of the orbitally ordered and disordered structures as a function of temperature. The temperature dependences of the structural parameters characterizing the Jahn-Teller distortions are reported and discussed. A gradual departure of the experimental data from theoretical predictions is observed above 650 K. In this range of temperatures, anions surrounding the Jahn-Teller active cations perform more isotropic thermal motion. The onset of structural phase transition induces a reduction of the crystal volume by about 0.4% which follows from the structural transformations yielding more regular oxygen octahedra formed above the phase transformation. It is found that above the Jahn-Teller transition the distortions of the MnO 6 octahedra are not completely removed. The non-vanishing distortions are accompanied by the lifted degeneracy of the Mn e g states. Weak residual distortions can be assigned to the short-range orbital order that persists within a local scale but it seems quenched on average giving rise to a disappearance of the long-range order coherency of the Jahn-Teller effect.

The vibrational Jahn–Teller effect in E⊗e systems

Energy Technology Data Exchange (ETDEWEB)

Thapaliya, Bishnu P.; Dawadi, Mahesh B.; Ziegler, Christopher; Perry, David S., E-mail: dperry@uakron.edu

2015-10-16

Highlights: • The vibrational Jahn–Teller effect is documented for three E⊗e molecular systems. • The spontaneous vibrational Jahn–Teller distortion is very small. • Vibrational Jahn–Teller splittings are substantial (1–60 cm{sup −1}). • Vibrational conical intersections in CH{sub 3}OH are accessible at low energies. - Abstract: The Jahn–Teller theorem is applied in the vibrational context where degenerate high-frequency vibrational states (E) are considered as adiabatic functions of low-frequency vibrational coordinates (e). For CH{sub 3}CN and Cr(C{sub 6}H{sub 6})(CO){sub 3}, the global minimum of the non-degenerate electronic potential energy surface occurs at the C{sub 3v} geometry, but in CH{sub 3}OH, the equilibrium geometry is far from the C{sub 3v} reference geometry. In the former cases, the computed spontaneous Jahn–Teller distortion is exceptionally small. In methanol, the vibrational Jahn–Teller interaction results in the splitting of the degenerate E-type CH stretch into what have been traditionally assigned as the distinct ν{sub 2} and ν{sub 9} vibrational bands. The ab initio vibrational frequencies are fit precisely by a two-state high-order Jahn–Teller Hamiltonian (Viel and Eisfeld, 2004). The presence of vibrational conical intersections, including 7 for CH{sub 3}OH, has implications for spectroscopy, for geometric phase, and for ultrafast localized non-adiabatic energy transfer.

Effects of hydrostatic pressure and temperature on the electron paramagnetic resonance spectrum of off-centre Jahn-Teller [CuF sub 4 F sub 4] sup 6 sup - complexes in SrF sub 2 crystal

CERN Document Server

Ulanov, V A; Hoffmann, S K; Zaripov, M M

2003-01-01

Pressure and temperature variations of the spin-Hamiltonian parameters and electron paramagnetic resonance (EPR) linewidths of non-central Jahn-Teller [CuF sub 4 F sub 4] sup 6 sup - complexes in SrF sub 2 crystal were studied by continuous-wave EPR. It was found that the static spin-Hamiltonian parameters, found at T = 85 K and at normal pressure (g sub | sub | = 2.491, g sub p sub e sub r sub p sub e sub n sub d sub i sub c sub u sub l sub a sub r = 2.083, a sub p sub a sub r sub a sub l sub l sub e sub l = 360, a sub p sub e sub r sub p sub e sub n sub d sub i sub c sub u sub l sub a sub r = 26, A sub x sub ' sub ' = 96, A sub y sub ' sub ' = 99, A sub z sub ' sub ' = 403 and beta sub e sub x sub p = 17 diameter), are slightly changed with hydrostatic pressure and, at T = 85 K and P = 550 MPa, become equal to g sub | sub | = 2.489, g sub p sub e sub r sub p sub e sub n sub d sub i sub c sub u sub l sub a sub r = 2.083, a sub | sub | 348, a sub p sub e sub r sub p sub e sub n sub d sub i sub c sub u sub l s...

Effects of strong electron correlations in Ti8C12 Met-Car

International Nuclear Information System (INIS)

Varganov, Sergey A.; Gordon, Mark S.

2006-01-01

The results of multireference configuration interaction (MRCI) with single and double excitations and single reference coupled cluster (CCSD(T)) calculations on Ti 8 C 12 metallocarbohedryne (Met-Car) are reported. The distortions of the T d structure to D 2d and C 3v structures due to the Jahn-Teller effect are studied. It is shown that the Ti 8 C 12 wave function has significant multireference character. The choice of the active space for multireference self-consistent field (MCSCF) calculations is discussed. The failure of multireference perturbation theory with a small active space is attributed to multiple intruder states. A new, novel type of MCSCF calculation, ORMAS (occupation restricted multiple active spaces) with a large active space are carried out for several electronic states of Ti 8 C 12 . The Jahn-Teller distorted D 2d 1 A 1 (nearly T d ) structure is predicted to be the Ti 8 C 12 ground state. Predictions of the Ti 8 C 12 ionization potential with different ab initio methods are presented

The effect of automated teller machines on banks' services in Nigeria

African Journals Online (AJOL)

AFRICAN JOURNALS ONLINE (AJOL) · Journals · Advanced Search ... work is to find out the effects of Automated Teller Machines (ATM) on Bank's services. ... used by successful organizations for gaining competitive advantage over others.

Tensile Strain Effects on the Magneto-transport in Calcium Manganese Oxide Thin Films: Comparison with its Hole-doped Counterpart

Science.gov (United States)

Lawson, Bridget; Neubauer, Samuel; Chaudhry, Adeel; Hart, Cacie; Ferrone, Natalie; Houston, David; Yong, Grace; Kolagani, Rajeswari

Magnetoresistance properties of the epitaxial thin films of doped rare earth manganites are known to be influenced by the effect of bi-axial strain induced by lattice mismatch with the substrate. In hole-doped manganites, the effect of both compressive and tensile strain is qualitatively consistent with the expected changes in unit cell symmetry from cubic to tetragonal, leading to Jahn-Teller strain fields that affect the energy levels of Mn3 + energy levels. Recent work in our laboratory on CaMnO3 thin films has pointed out that tetragonal distortions introduced by tensile lattice mismatch strain may also have the effect of modulating the oxygen content of the films in agreement with theoretical models that propose such coupling between strain and oxygen content. Our research focuses on comparing the magneto-transport properties of hole-doped manganite LaCaMnO3 thin films with that of its electron doped counter parts, in an effort to delineate the effects of oxygen stoichiometry changes on magneto-transport from the effects of Jahn-Teller type strain. Towson University Office of Undergraduate Research, Fisher Endowment Grant and Undergraduate Research Grant from the Fisher College of Science and Mathematics, Seed Funding Grant from the School of Emerging technologies and the NSF Grant ECCS 112856.

Edward Teller Biographical Memoir

Energy Technology Data Exchange (ETDEWEB)

Libby, S B; Sessler, A M

2009-07-27

Edward Teller died on September 9, 2003 in Stanford, California at the age of 95. He was both one of the great theoretical physicists of the twentieth century and a leading figure in the development of nuclear weapons and broader defense advocacy. Teller's work in physics, spanning many decades of the twentieth century, includes some of the most fundamental insights in the quantum behaviors of molecules and their spectra, nuclei, surfaces, solid state and spin systems, and plasmas. In the defense arena, Teller is best known for his key insight that made thermonuclear weapons possible. Teller was both a great scientific collaborator and physics teacher at all levels, known for his openness, generosity, personal warmth, and powerful physical intuition. Many of his graduate students went on to illustrious careers.

High resolution photoelectron spectroscopy of clusters of Group V elements

International Nuclear Information System (INIS)

Wang, Lai-sheng; Niu, B.; Lee, Y.T.; Shirley, D.A.

1989-07-01

High resolution HeI (580 angstrom) photoelectron spectra of As 2 , As 4 , and P 4 were obtained with a newly-built high temperature molecular beam source. Vibrational structure was resolved in the photoelectron spectra of the three cluster species. The Jahn-Teller effect is discussed for the 2 E and 2 T 2 states of P 4 + and As 4 + . As a result of the Jahn-Teller effect, the 2 E state splits into two bands, and the 2 T 2 state splits into three bands, in combination with the spin-orbit effect. It was observed that the ν 2 normal vibrational mode was involved in the vibronic interaction of the 2 E state, while both the ν 2 and ν 3 modes were active in the 2 T 2 state. 26 refs., 5 figs., 3 tabs

The Close Relationships between the Crystal Structures of MO and MSO 4 (M = Group 10, 11, or 12 Metal), and the Predicted Structures of AuO and PtSO 4

KAUST Repository

Derzsi, Mariana; Hermann, Andreas; Hoffmann, Roald; Grochala, Wojciech

2013-01-01

The structural relations of (and between) late transition metal monoxides, MO, and monosulfates, MSO4, are analyzed. We show that all of these late transition metal oxides, as well as 4d and 5d metal sulfates, crystallize in distorted rock salt lattices and argue that the distortions are driven by collective first- and/or second order Jahn-Teller effects. The collective Jahn-Teller deformations lead either to tetragonal contraction or (seldom) elongation of the rock salt lattice. On the basis of the rock salt representation of the oxides and sulfates, we show that PdO, CuO, and AgO are metrically related and that the 4d and 5d metal sulfates are close to isostructural with their oxides. These observations guide us towards as yet unknown AuO and PtSO4, for which we predict crystal structures from electronic structure calculations. The structural relations of (and between) late transition metal monoxides, MO, and monosulfates, MSO4, are analyzed. We show that all of these late transition metal oxides, as well as 4d and 5d metal sulfates, crystallize in distorted rock salt lattices and argue that the distortions are driven by collective first- and/or second order Jahn-Teller effects, as quantified by the c′/a′ ratio. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The Close Relationships between the Crystal Structures of MO and MSO 4 (M = Group 10, 11, or 12 Metal), and the Predicted Structures of AuO and PtSO 4

KAUST Repository

Derzsi, Mariana

2013-08-21

The structural relations of (and between) late transition metal monoxides, MO, and monosulfates, MSO4, are analyzed. We show that all of these late transition metal oxides, as well as 4d and 5d metal sulfates, crystallize in distorted rock salt lattices and argue that the distortions are driven by collective first- and/or second order Jahn-Teller effects. The collective Jahn-Teller deformations lead either to tetragonal contraction or (seldom) elongation of the rock salt lattice. On the basis of the rock salt representation of the oxides and sulfates, we show that PdO, CuO, and AgO are metrically related and that the 4d and 5d metal sulfates are close to isostructural with their oxides. These observations guide us towards as yet unknown AuO and PtSO4, for which we predict crystal structures from electronic structure calculations. The structural relations of (and between) late transition metal monoxides, MO, and monosulfates, MSO4, are analyzed. We show that all of these late transition metal oxides, as well as 4d and 5d metal sulfates, crystallize in distorted rock salt lattices and argue that the distortions are driven by collective first- and/or second order Jahn-Teller effects, as quantified by the c′/a′ ratio. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Gamow-Teller Strength Distributions for Some Magic Nuclei

Directory of Open Access Journals (Sweden)

Necla ÇAKMAK

2014-12-01

Full Text Available The total Gamow-Teller strengths and their energy distributions for 96Zr, 96Sr, 54Ca, 28O, 24C and 14C have been obtained within the framework of Random Phase Approximation (RPA. The effective interaction potential has been described by considering the commutativity of the Gamow-Teller operator with the central part of the nuclear Hamiltonian.

Fine structure of V2+ energy levels in CsCaF3:V2+

International Nuclear Information System (INIS)

Avram, C.N.; Brik, M.G.

2004-01-01

Theoretical investigations of the fine structure of the lasing 4 T 2g level in a CsCaF 3 :V 2+ crystal were carried out. The spin-orbit splitting of the 4 T 2g term in the static low crystal field was obtained from the Eisenstein matrices and using parameters (Dq, B, C, ζ SO ) appropriate for the 4 T 2g - 4 A 2g zero-phonon line. The 4 T 2g spinor splitting has been modeled by the second-order spin-orbit Hamiltonian. The effect of the dynamical Jahn-Teller interaction on the spin-orbit splitting of the 4 T 2g term was taken into account; the Jahn-Teller stabilization energy, ZPL splitting and the Huang-Rhys parameter for the e g normal mode were all evaluated

Ultrasonic study of the charge mismatch effect in charge-ordered (Nd{sub 0.75}Na{sub 0.25}){sub x}(Nd{sub 0.5}Ca{sub 0.5}){sub 1-x}MnO{sub 3}

Energy Technology Data Exchange (ETDEWEB)

Jiang Liang; Su Jinrui; Kong Hui; Liu Yi; Zheng Shiyuan; Zhu Changfei [Laboratory of Advanced Functional Materials and Devices, Department of Materials Science and Engineering, University of Science and Technology of China, Hefei 230026 (China)

2006-09-20

The resistivity, magnetization and ultrasonic properties of charge-ordered polycrystalline (Nd{sub 0.75}Na{sub 0.25}){sub x}(Nd{sub 0.5}Ca{sub 0.5}){sub 1-x}MnO{sub 3} have been investigated from 50 to 300 K. A considerable velocity softening accompanied by an attenuation peak was observed around the charge-ordering transition temperature (T{sub CO}) upon cooling. The simultaneous occurrence of the charge ordering (CO) and the ultrasonic anomaly implies strong electron-phonon coupling, which originates from the cooperative Jahn-Teller effect. At very low temperature, another broad attenuation peak was observed, which is attributed to the phase separation (PS) and gives a direct evidence of spin-phonon coupling in the compound. With increasing x, T{sub CO} shifts to lower temperature, the magnetization of the system is strengthened and the PS is enhanced. The temperature dependence of the longitudinal modulus shows that the Jahn-Teller coupling energy E{sub JT} decreases with increasing Na content. The analysis suggests that the charge mismatch effect may be the main reason for the suppression of the CO and enhancement of the PS.

12 CFR 205.16 - Disclosures at automated teller machines.

Science.gov (United States)

2010-01-01

... 12 Banks and Banking 2 2010-01-01 2010-01-01 false Disclosures at automated teller machines. 205... SYSTEM ELECTRONIC FUND TRANSFERS (REGULATION E) § 205.16 Disclosures at automated teller machines. (a) Definition. Automated teller machine operator means any person that operates an automated teller machine at...

Colossal magnetoresistance manganites

Indian Academy of Sciences (India)

Keywords. Manganites; colossal magnetoresistance; strongly correlated electron systems; metal-insulator transitions and other electronic transitions; Jahn-Teller polarons and electron-phonon interaction.

96 THE EFFECT OF AUTOMATED TELLER MACHINES ON BANKS ...

African Journals Online (AJOL)

reduces the number of human deployment by banks thereby reducing cost of operations. ... United States (PLUS and CIRRUS) drooped their long standing opposition to allowing ..... Automated teller machine network pricing – A review of the.

Gamow-Teller matrix elements from 00 ( p,n) cross section

International Nuclear Information System (INIS)

Goodman, C.D.; Goulding, C.A.; Greenfield, M.B.; Rapaport, J.; Bainum, D.E.; Foster, C.C.; Love, W.G.; Petrovich, F.

1980-01-01

After simple corrections for distortion effects, 120-MeV, 0 0 (p,n) cross sections are found to be proportional to the squares of the corresponding Fermi and Gamow-Teller matrix elements extracted from β-decay measurements. It is suggested that this proportionality can be used to extract Gamow-Teller matrix elements for transitions inaccessible to β decay

Gamow-Teller strength function for 90Zr: Effects of spin and isospin exchange forces, and ground-state correlations

International Nuclear Information System (INIS)

Mathews, G.J.; Bloom, S.D.; Hausman, R.F. Jr.

1983-01-01

Shell-model calculations of the Gamow-Teller strength function for 90 Zr have been performed utilizing a realistic finite-range two-body interaction in a model space consisting of the 2p and 1g shells. The effects of admixtures of two-particle two-hole excitations in 90 Nb, mostly due to the spin and isospin exchange components of the nucleon-nucleon force, are discussed. Ground state correlations in 90 Zr are also added via seniority-zero two-proton excitations from the 2p shell into the 1g/sub 9/2/ shell. With the correlations the Gamow-Teller strength function is in good agreement with the experimental results and accounts for essentially all of the observed dispersion of strength. The inclusion of these correlations does not, however, produce either a displacement of Gamow-Teller strength to higher excitation energies, or a significant change in the total strength. Thus, they cannot account for the observed Gamow-Teller quenching. The quenching factor derived by a comparison of our calculated results with experiment is 0.52

Angle-resolved photoelectron spectroscopy of cyclopropane

Science.gov (United States)

Keller, P. R.; Taylor, J. W.; Carlson, Thomas A.; Whitley, T. A.; Grimm, F. A.

1985-10-01

The angular distribution parameter, β, determined for the valence orbitals (IP < 18 eV) of cyclopropane in the 10-30 eV photon energy range using dispersed polarized synchrotron radiation. The energy dependence of β for photoelectron energies between, 2 and 10 eV above threshold was found to be similar to those found previously for other σ orbitals. The effects of Jahn-Teller splitting on β for the 3e' orbital were found to be small but definitely present. The overall shape and magnitude of the β( hv) curve are, however, sufficiently for the different Jahn-Teller components that, for purposes of orbital assignments using β( hv) curves the shape and magnitude of the curves can be considered associated only with the initial state. Resonance photoionization features at a photon ener of ≈ 18 eV were observed in the 3e' and 3a' 1 orbitals and tentatively assigned to autoionization.

Interplay of structural transition and superconductivity in cuprates

International Nuclear Information System (INIS)

Ghosh, Haranath; Mitra, Manidipa; Behera, S.N.; Ghatak, S.K.

1997-01-01

The presence of lattice distortion is known to suppress the superconducting (SC) transition in the cuprates. It is now accepted that electron correlation plays a dominant role in shaping the properties of these undoped and doped systems. Furthermore, since the Fermi level in these systems lies in a degenerate band of Cu : d and O : p orbitals the structural transition can be modeled as a band Jahn-Teller effect. We study the coexistence of superconductivity and band Jahn-Teller (J-T) distortion, taking into account the electron correlation within the slave boson formalism. It is shown that with increasing dopant concentration (δ), the structural transition temperature (T s ) remains constant up to a certain value and then vanishes, while the SC transition temperature (T c ) increases to a maximum value. The highest value of T c corresponds to that value of δ where T s vanishes. Besides with increasing lattice distortion superconductivity is suppressed. These findings are in qualitative agreement with the experimental results. (author)

Anisotropy barrier reduction in fast-relaxing Mn12 single-molecule magnets

Science.gov (United States)

Hill, Stephen; Murugesu, Muralee; Christou, George

2009-11-01

An angle-swept high-frequency electron paramagnetic resonance (HFEPR) technique is described that facilitates efficient in situ alignment of single-crystal samples containing low-symmetry magnetic species such as single-molecule magnets (SMMs). This cavity-based technique involves recording HFEPR spectra at fixed frequency and field, while sweeping the applied field orientation. The method is applied to the study of a low-symmetry Jahn-Teller variant of the extensively studied spin S=10 Mn12 SMMs (e.g., Mn12 -acetate). The low-symmetry complex also exhibits SMM behavior, but with a significantly reduced effective barrier to magnetization reversal (Ueff≈43K) and, hence, faster relaxation at low temperature in comparison with the higher-symmetry species. Mn12 complexes that crystallize in lower symmetry structures exhibit a tendency for one or more of the Jahn-Teller axes associated with the MnIII atoms to be abnormally oriented, which is believed to be the cause of the faster relaxation. An extensive multi-high-frequency angle-swept and field-swept electron paramagnetic resonance study of [Mn12O12(O2CCH2But)16(H2O)4]ṡCH2Cl2ṡMeNO2 is presented in order to examine the influence of the abnormally oriented Jahn-Teller axis on the effective barrier to magnetization reversal. The reduction in the axial anisotropy, D , is found to be insufficient to account for the nearly 40% reduction in Ueff . However, the reduced symmetry of the Mn12 core gives rise to a very significant second-order transverse (rhombic) zero-field-splitting anisotropy, E≈D/6 . This, in turn, causes a significant mixing of spin projection states well below the top of the classical anisotropy barrier. Thus, magnetic quantum tunneling is the dominant factor contributing to the effective barrier reduction in fast relaxing Mn12 SMMs.

Crystallographic and magnetic properties of Ba/sub 2/(UCu)O/sub 6/

Energy Technology Data Exchange (ETDEWEB)

Padel, L; Poix, P [Paris-11 Univ., 91 - Orsay (France)

1975-07-07

Ba/sub 2/(UCu)O/sub 6/ structure can be described by a tetragonal unit cell whose parameters are a=5.777A and c=8.838A. Tetragonal distorsion is attributed to the Jahn-Teller effect of Cu/sup 2 +/; Copper octahedral sites are irregular. The compound presents antiferromagnetic properties with a Neel's temperature of 13K.

Hexagonal perovskites with cationic vacancies. 14. The rhombohedral 12 L-stacking polytypes Ba/sub 2/La/sub 2/Bsup(II)(W/sub 2/sup(VI)vacantO/sub 12/)

Energy Technology Data Exchange (ETDEWEB)

Kemmler-Sack, S [Tuebingen Univ. (Germany, F.R.). Lehrstuhl fuer Anorganische Chemie 2

1980-02-01

Rhombohedral 12 L-stacking polytypes with cationic vacancies of type Ba/sub 2/La/sub 2/Bsup(II)(W/sub 2/sup(VI)vacantO/sub 12/) are reported for Bsup(II) = Mg, Zn (white), Ni (light brown) and Co (brown). For Bsup(II) = Cu, as a consequence of the Jahn Teller effect, a triclinic distorted lattice is observed.

Theoretical evaluation of matrix effects on trapped atomic levels

Energy Technology Data Exchange (ETDEWEB)

Das, G.P.; Gruen, D.M.

1986-06-01

We suggest a theoretical model for calculating the matrix perturbation on the spectra of atoms trapped in rare gas systems. The model requires the ''potential curves'' of the diatomic system consisting of the trapped atom interacting with one from the matrix and relies on the approximation that the total matrix perturbation is a scalar sum of the pairwise interactions with each of the lattice sites. Calculations are presented for the prototype systems Na in Ar. Attempts are made to obtain ab initio estimates of the Jahn-Teller effects for excited states. Comparison is made with our recent Matrix-Isolation Spectroscopic (MIS) data. 10 refs., 3 tabs.

Theoretical evaluation of matrix effects on trapped atomic levels

International Nuclear Information System (INIS)

Das, G.P.; Gruen, D.M.

1986-06-01

We suggest a theoretical model for calculating the matrix perturbation on the spectra of atoms trapped in rare gas systems. The model requires the ''potential curves'' of the diatomic system consisting of the trapped atom interacting with one from the matrix and relies on the approximation that the total matrix perturbation is a scalar sum of the pairwise interactions with each of the lattice sites. Calculations are presented for the prototype systems Na in Ar. Attempts are made to obtain ab initio estimates of the Jahn-Teller effects for excited states. Comparison is made with our recent Matrix-Isolation Spectroscopic (MIS) data. 10 refs., 3 tabs

78 FR 18221 - Disclosures at Automated Teller Machines (Regulation E)

Science.gov (United States)

2013-03-26

... Disclosures at Automated Teller Machines (Regulation E) AGENCY: Bureau of Consumer Financial Protection... the EFTA to eliminate a requirement that a fee notice be posted on or at automated teller machines... legislation, though the Electronic Fund Transfer Act and Regulation E use the term ``automated teller machine...

Analogy Between Particle in a Box and Jahn–Teller Effect

Indian Academy of Sciences (India)

IAS Admin

Solving the SchrÄodinger equation, the allowed energy levels of the particle are given .... to slight distortion of the cube. Using (3), the new energy of ... ARTICLE. The Jahn–Teller theorem states that in a nonlinear molecule, if degenerate orbitals are asymmetrically occupied a distortion will occur to remove the degeneracy.

Task clarification, performance feedback, and social praise: Procedures for improving the customer service of bank tellers.

Science.gov (United States)

Crowell, C R; Anderson, D C; Abel, D M; Sergio, J P

1988-01-01

Customer service for bank tellers was defined in terms of 11 verbal behavior categories. An audio-recording system was used to track the occurrence of behaviors in these categories for six retail banking tellers. Three behavior management interventions (task clarification, performance feedback, and social praise), applied in sequence, were designed to improve overall teller performance with regard to the behavioral categories targeted. Clarification was accomplished by providing clear delineation of the various target categories, with specific examples of the behaviors in each. Feedback entailed presentation of ongoing verbal and visual information regarding teller performance. Praise consisted of verbal recognition of teller performance by branch managers. Results showed that clarification effects emerged quickly, producing an overall increase in desired behaviors of 12% over baseline. Feedback and praise effects occurred more gradually, resulting in overall increases of 6% and 7%, respectively. A suspension of all procedures led to a decline in overall performance, whereas reinstatement of feedback and praise was again accompanied by performance improvement. These findings extend the generality of behavior management applications and help to distinguish between possible antecedent and consequent effects of performance feedback.

Renner-Teller effects in the photoelectron spectra of CNC, CCN, and HCCN.

Science.gov (United States)

Coudert, Laurent H; Gans, Bérenger; Garcia, Gustavo A; Loison, Jean-Christophe

2018-02-07

The line intensity of photoelectron spectra when either the neutral or cationic species display a Renner-Teller coupling is derived and applied to the modeling of the photoelectron spectra of CNC, CCN, and HCCN. The rovibronic energy levels of these three radicals and of their cations are investigated starting from ab initio results. A model treating simultaneously the bending mode and the overall rotation is developed to deal with the quasilinearity problem in CNC + , CCN + , and HCCN and accounts for the large amplitude nature of their bending mode. This model is extended to treat the Renner-Teller coupling in CNC, CCN, and HCCN + . Based on the derived photoelectron line intensity, the photoelectron spectra of all three molecules are calculated and compared to the experimental ones.

The strength of electron electron correlation in Cs3C60

Science.gov (United States)

Baldassarre, L.; Perucchi, A.; Mitrano, M.; Nicoletti, D.; Marini, C.; Pontiroli, D.; Mazzani, M.; Aramini, M.; Riccó, M.; Giovannetti, G.; Capone, M.; Lupi, S.

2015-10-01

Cs3C60 is an antiferromagnetic insulator that under pressure (P) becomes metallic and superconducting below Tc = 38 K. The superconducting dome present in the T - P phase diagram close to a magnetic state reminds what found in superconducting cuprates and pnictides, strongly suggesting that superconductivity is not of the conventional Bardeen-Cooper-Schrieffer (BCS) type We investigate the insulator to metal transition induced by pressure in Cs3C60 by means of infrared spectroscopy supplemented by Dynamical Mean-Field Theory calculations. The insulating compound is driven towards a metallic-like behaviour, while strong correlations survive in the investigated pressure range. The metallization process is accompanied by an enhancement of the Jahn-Teller effect. This shows that electronic correlations are crucial in determining the insulating behaviour at ambient pressure and the bad metallic nature for increasing pressure. On the other hand, the relevance of the Jahn-Teller coupling in the metallic state confirms that phonon coupling survives in the presence of strong correlations.

An unusually strong resonant phonon scattering by 3-d impurities in II-VI semiconductors

Energy Technology Data Exchange (ETDEWEB)

Lonchakov, A.T.; Sokolov, V.I.; Gruzdev, N.B. [Institute of Metal Physics, Russian Academy of Sciences, Ural Branch, S. Kovalevskaya Str. 18, 620219 Ekaterinburg (Russian Federation)

2004-11-01

Low temperature phonon heat conductivity was measured for ZnSe and ZnS crystals, doped with 3-d impurities. A strong resonance-like phonon scattering by 3-d ions with orbitally degenerate ground state was observed. The Jahn-Teller effect is proposed as the reason of the strong resonance-like behaviour of heat conductivity. (copyright 2004 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Occupational Noise Exposure among Toll Tellers at Toll Plaza in Malaysia

Science.gov (United States)

Azmi, Sharifah Nadya Syed; Dawal, Siti Zawiah Md; Ya, Tuan Mohammad Yusoff Shah Tuan; Saidin, Hamidi

2010-10-01

Toll tellers working at toll plaza have potential of exposure to high noise from the vehicles especially for the peak level of sound emitted by the heavy vehicles. However, occupational exposures in this workplace have not been adequately characterized and identified. Occupational noise exposure among toll tellers at toll plaza was assessed using Sound Level Meter, Noise Dosimeter and through questionnaire survey. These data were combined to estimate the work shift exposure level and health impacts to the toll tellers by using statistical analysis. Noise Dosimeter microphone was located at the hearing zone of the toll teller which working inside the toll booth and full-period measurements were collected for each work shift. The measurements were taken at 20 toll booths from 6.00 am to 2.00 pm for 5 days. 71 respondents participated in the survey to identify the symptoms of noise induced hearing loss and other health related problems among toll tellers. Results of this study indicated that occupational noise exposure among toll tellers for Mean Continuous Equivalent Level, Leq was 79.2±1.4 dB(A), Mean Maximum Level, Lmax was 107.8±3.6 dB(A) and Mean Peak Level, Lpeak was 136.6±9.9 dB. The Peak Level reported statistically significantly at 140 dB, the level of TLV recommended by ACGIH. The research findings indicated that the primary risk exposure to toll tellers comes from noise that emitted from heavy vehicles. Most of the toll tellers show symptoms of noise induced hearing loss and annoyed by the sources of noise at the toll plaza.

After the Prestige: A Postmodern Analysis of Penn and Teller

Directory of Open Access Journals (Sweden)

Miller, Liz

2015-12-01

Full Text Available By mocking the magic community and revealing the secret behind some of their tricks, Penn and Teller perform a kind of parodic and post-modern “anti-magic.” Penn and Teller display an artful use of rhetoric; in exposing the secrets and shortcomings of conjuring, they are revolutionizing the way people think about both the art of magic and the magic community. Individuals such as Penn and Teller may use parody to subvert the hegemonic interpretations. However, we also know that it is difficult to bring down a system while operating within that system. Thus, this article explores the way Penn and Teller are challenging the metanarrative of the magic community, using several of the duo’s more popular illusions as examples for analysis. Ultimately, this paper should help us gain a better understanding of the way parody can be used to challenge hegemonic conceptions, and the limitations of this type of rhetorical approach.

Vibronic coupling in ionized organic molecules: structural distortions and chemical reactions

International Nuclear Information System (INIS)

Williams, Ffrancon

2003-01-01

Ionized organic molecules (radical cations) in radiation chemistry are liable to undergo vibronic coupling whenever there is a relatively small energy gap (∼0.5-1.5 eV) between their ground and excited states. As a result of this mixing, the force constant for the symmetry-allowed vibrational mode that couples these states is lowered in the ground state of the radical cation so that deformation can take place more easily along this specific mode. This pseudo-Jahn-Teller effect can then result in a permanent structural distortion of the radical cation relative to the symmetry of the parent neutral molecule. It can also bring about an energetically favored pathway for a facile chemical rearrangement along a reaction coordinate defined by the coupling mode. Examples taken from matrix-isolation studies are used to illustrate these dramatic consequences of vibronic coupling in radical cations. Thus, the bicyclo[2.2.2]oct-2-ene and tetramethylurea radical cations are found to have twisted structures departing from the C 2v symmetry of their parent molecules, while the oxirane and bicyclo[1.1.1]pentane radical cations undergo ring-opening rearrangements along reaction coordinates that correspond to the deformational modes predicted by the pseudo-Jahn-Teller effect

Specific heat of Cr-based semimagnetic semiconductors

NARCIS (Netherlands)

Twardowski, A.; Eggenkamp, P.J.T.; Mac, W.; Swagten, H.J.M.; Demianiuk, M.

1993-01-01

Specific heat of ZnCrSe and ZnCrS was measured for 1.5 Jahn-Teller distortion and spin-orbit interaction.

Gamow-Teller beta decay of proton-rich nuclei

International Nuclear Information System (INIS)

Klepper, O.; Rykaczewski, K.

1990-11-01

The beta decays of 48 Mn and of even-even nuclei near the double shell-closures at 100 Sn and 146 Gd are currently investigated at the GSI on-line mass separator. Their Gamow-Teller strength are surveyed in their present experimental status, together with related results from the ISOLDE (CERN) and ISOCELE (Orsay) separators, and are compared with predictions from different nuclear models. The strength of the 0 + → 1 + Gamow-Teller transitions is compiled in tables and graphs. (orig.)

Electrochemical Performance of LixMn2-yFeyO4-zClz Synthesized Through In-Situ Glycine Nitrate Combustion

Science.gov (United States)

2016-06-13

Electrochemical Performance of LixMn2-yFeyO4-zClz Synthesized Through In-Situ Glycine Nitrate Combustion Ashley L. Ruth, Paula C. Latorre, and...sites as well as the formation of Mn3+ ions via the Jahn- Teller effect. The use of the glycine nitrate combustion synthesis produces small particles at...advantage of submicron ceramic synthesis, namely the glycine nitrate combustion process (GNP), we propose the capability for in-situ B-site doping

Quantum fluctuations of D5d polarons on C60 molecules

International Nuclear Information System (INIS)

Wang Chui-Lin; Wang Wenzheng; Liu Yuliang; Su Zhaobin; Yu Lu.

1994-06-01

The dynamic Jahn-Teller splitting of the six equivalent D 5d polarons due to quantum fluctuations is studied in the framework of the Bogoliubov-de Gennes formalism. The tunneling induced level splittings are determined to be 2 T 1u + 2 T 2u and 1 A g + 1 H g for C 1- 60 and C -2 60 , respectively, which should give rise to observable effects in experiments. (author). 17 refs, 2 tabs

Benchmarking nuclear models for Gamow–Teller response

International Nuclear Information System (INIS)

Litvinova, E.; Brown, B.A.; Fang, D.-L.; Marketin, T.; Zegers, R.G.T.

2014-01-01

A comparative study of the nuclear Gamow–Teller response (GTR) within conceptually different state-of-the-art approaches is presented. Three nuclear microscopic models are considered: (i) the recently developed charge-exchange relativistic time blocking approximation (RTBA) based on the covariant density functional theory, (ii) the shell model (SM) with an extended “jj77” model space and (iii) the non-relativistic quasiparticle random-phase approximation (QRPA) with a Brueckner G-matrix effective interaction. We study the physics cases where two or all three of these models can be applied. The Gamow–Teller response functions are calculated for 208 Pb, 132 Sn and 78 Ni within both RTBA and QRPA. The strengths obtained for 208 Pb are compared to data that enable a firm model benchmarking. For the nucleus 132 Sn, also SM calculations are performed within the model space truncated at the level of a particle–hole (ph) coupled to vibration configurations. This allows a consistent comparison to the RTBA where ph⊗phonon coupling is responsible for the spreading width and considerable quenching of the GTR. Differences between the models and perspectives of their future developments are discussed.

Benchmarking nuclear models for Gamow–Teller response

Energy Technology Data Exchange (ETDEWEB)

Litvinova, E., E-mail: elena.litvinova@wmich.edu [Department of Physics, Western Michigan University, Kalamazoo, MI 49008-5252 (United States); National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, MI 48824-1321 (United States); Brown, B.A. [Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824-1321 (United States); National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, MI 48824-1321 (United States); Fang, D.-L. [National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, MI 48824-1321 (United States); Joint Institute for Nuclear Astrophysics, Michigan State University, East Lansing, MI 48824-1321 (United States); Marketin, T. [Physics Department, Faculty of Science, University of Zagreb (Croatia); Zegers, R.G.T. [Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824-1321 (United States); National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, MI 48824-1321 (United States); Joint Institute for Nuclear Astrophysics, Michigan State University, East Lansing, MI 48824-1321 (United States)

2014-03-07

A comparative study of the nuclear Gamow–Teller response (GTR) within conceptually different state-of-the-art approaches is presented. Three nuclear microscopic models are considered: (i) the recently developed charge-exchange relativistic time blocking approximation (RTBA) based on the covariant density functional theory, (ii) the shell model (SM) with an extended “jj77” model space and (iii) the non-relativistic quasiparticle random-phase approximation (QRPA) with a Brueckner G-matrix effective interaction. We study the physics cases where two or all three of these models can be applied. The Gamow–Teller response functions are calculated for {sup 208}Pb, {sup 132}Sn and {sup 78}Ni within both RTBA and QRPA. The strengths obtained for {sup 208}Pb are compared to data that enable a firm model benchmarking. For the nucleus {sup 132}Sn, also SM calculations are performed within the model space truncated at the level of a particle–hole (ph) coupled to vibration configurations. This allows a consistent comparison to the RTBA where ph⊗phonon coupling is responsible for the spreading width and considerable quenching of the GTR. Differences between the models and perspectives of their future developments are discussed.

TmCd quadrupolar ordering and magnetic interactions

International Nuclear Information System (INIS)

Aleonard, R.; Morin, P.

1979-01-01

The paramagnetic compound TmCd crystallizes with the CsCl-type structure. Its Jahn-Teller behavior was first observed by Luethi and coworkers. We analyze here various physical properties with a pure-harmonic-elasticity model. The structural transition between cubic and tetragonal phases is now fully described (first-order character and temperature of occurrence) as well as the magnetic susceptibility, magnetization process, specific-heat, elastic-constant, and strain data. The relevant Hamiltonian takes into account the second-order magnetoelastic coupling and the quadrupolar exchange in addition to the cubic crystal field and the Heisenberg bilinear interactions. TmCd appears to be closely related to isomorphous TmZn and completes the illustration of the competition between bilinear and quadrupolar interactions occurring in some rare-earth intermetallics. In these two compounds, the quadrupolar exchange is many times stronger than the magnetoelastic coupling and the quadrupolar ordering then drives the structural transition. This situation is opposite to that occurring in (actual) Jahn-Teller compounds

The analysis of strain of giant magnetoresistive Pr0.7Sr0.3MnO3/La0.5Ca0.5MnO3/Pr0.7Sr0.3MnO-3 trilayers

International Nuclear Information System (INIS)

Wang Haiou; Liu Hao; Dai Ping; Tan Weishi; Wu Xiaoshan; Jia Quanjie; Li Xiaolong

2012-01-01

Pr 0.7 Sr 0.3 MnO 3 /La 0.5 Ca 0.5 MnO 3 /Pr 0.7 Sr 0.3 MnO 3 (PSMO/LCMO/PSMO) trilayers were deposited on (001)-oriented single crystal MgO by pulsed laser deposition. The thickness of both PSMO layers was 36 nm while the thickness of LCMO layer was 6, 12, 18, 24, 30 and 36 nm, respectively. Out-of-plane and in-plane lattice parameters of trilayers were obtained by using symmetric scanning and asymmetric scanning mode of high resolution X-ray diffraction. Strain states of trilayers have been studied. The results showed that strain relaxation states of trilayers were decided by bulk strain and Jahn-Teller (JT) strain together: The mechanism for strain relaxation in trilayers is different from that for tetragonal distortion. The competition between bulk strain and Jahn-Teller (JT) strain played an important role in the magnetotransport and magnetic properties of trilayers. (authors)

Poschl-Teller potentials based solution to Hilbert's tenth problem Pöschl-Teller potentials based solution to Hilbert's tenth problem

Directory of Open Access Journals (Sweden)

Juan Ospina

2006-12-01

Full Text Available Hypercomputers compute functions or numbers, or more generally solve problems or carry out tasks, that cannot be computed or solved by a Turing machine. An adaptation of Tien D. Kieu¿s quantum hypercomputational algorithm is carried out for the dynamical algebra su(1, 1 of the Poschl-Teller potentials. The classically incomputable problem that is resolved with this hypercomputational algorithm is Hilbert¿s tenth problem. We indicated that an essential mathematical condition of these algorithms is the existence of infinitedimensional unitary irreducible representations of low dimensional dynamical algebras that allow the construction of coherent states of the Barut-Girardello type. In addition, we presented as a particular case of our hypercomputational algorithm on Poschl-Teller potentials, the hypercomputational algorithm on an infinite square well presented previously by the authors.Los hipercomputadores computan funciones o números, o en general solucionan problemas que no pueden ser computados o solucionados por una máquina de Turing. Se presenta una adaptación del algoritmo cuántico hipercomputacional propuesto por Tien D. Kieu, al álgebra dinámica su(1, 1 realizada en los potenciales Pöschl-Teller. El problema clásicamente incomputable que se resuelve con este algoritmo hipercomputacional es el d´ecimo problema de Hilbert. Se señala que una condición matemática fundamental para estos algoritmos es la existencia de una representación unitaria infinito dimensional irreducible de álgebras de baja dimensión que admitan la construcción de estados coherentes del tipo Barut-Girardello. Adicionalmente se presenta como caso límite del algoritmo propuesto sobre los potenciales Pöschl-Teller, el algoritmo hipercomputacional sobre la caja de potencial infinita construido previamente por los autores.

Symmetrical analysis of the defect level splitting in two-dimensional photonic crystals

International Nuclear Information System (INIS)

Malkova, N; Kim, S; Gopalan, V

2003-01-01

In this paper doubly degenerate defect states in the band gap of the two-dimensional photonic crystal are studied. These states can be split by a convenient distortion of the lattice. Through analogy with the Jahn-Teller effect in solids, we present a group theoretical analysis of the lifting of the degeneracy of doubly degenerate states in a square lattice by different vibronic modes. The effect is supported by the supercell plane-wave model and by the finite difference time domain technique. We suggest ways for using the effect in photonic switching devices and waveguides

The Hintermann-Merlini-Baxter-Wu and the infinite-coupling-limit Ashkin-Teller models

Energy Technology Data Exchange (ETDEWEB)

Huang Yuan, E-mail: huangy22@mail.ustc.edu.cn [Hefei National Laboratory for Physical Sciences at Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui 230026 (China); Deng Youjin, E-mail: yjdeng@ustc.edu.cn [Hefei National Laboratory for Physical Sciences at Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui 230026 (China); Jacobsen, Jesper Lykke, E-mail: jacobsen@lpt.ens.fr [Laboratoire de Physique Theorique, Ecole Normale Superieure, 24 rue Lhomond, 75231 Paris (France); Universite Pierre et Marie Curie, 4 place Jussieu, 75252 Paris (France); Salas, Jesus, E-mail: jsalas@math.uc3m.es [Grupo de Modelizacion, Simulacion Numerica y Matematica Industrial, Universidad Carlos III de Madrid, Avda. de la Universidad 30, 28911 Leganes (Spain); Grupo de Teorias de Campos y Fisica Estadistica, Instituto Gregorio Millan, Universidad Carlos III de Madrid, Unidad asociada al IEM-CSIC, Madrid (Spain)

2013-03-11

We show how the Hintermann-Merlini-Baxter-Wu model (which is a generalization of the well-known Baxter-Wu model to a general Eulerian triangulation) can be mapped onto a particular infinite-coupling-limit of the Ashkin-Teller model. We work out some mappings among these models, also including the standard and mixed Ashkin-Teller models. Finally, we compute the phase diagram of the infinite-coupling-limit Ashkin-Teller model on the square, triangular, hexagonal, and kagome lattices.

Role of the momentum transfer in the quenching of the Gamow-Teller strength

Energy Technology Data Exchange (ETDEWEB)

Marketin, Tomislav [Institut fuer Kernphysik, Technische Universitaet Darmstadt (Germany); Physics Department, Faculty of Science, University of Zagreb (Croatia); Martinez-Pinedo, Gabriel [Institut fuer Kernphysik, Technische Universitaet Darmstadt (Germany); Paar, Nils; Vretenar, Dario [Physics Department, Faculty of Science, University of Zagreb (Croatia)

2012-07-01

A fully consistent calculation of the Gamow-Teller strength is presented, based on a microscopic theoretical framework. Nuclear ground state is determined using the relativistic Hartree-Bogolyubov (RHB) model with density dependent meson-nucleon coupling constants, and transition rates are calculated via proton-neutron relativistic quasiparticle RPA using the same interaction as in the RHB equations. The (p,n) probe has a similar spin-isospin operator structure to the Gamow-Teller (GT) operator. However, they become comparable only if the GT cross section is measured at a very small momentum transfer q. At higher momentum transfer the isovector spin monopole (IVSM) mode occurs, with the r{sup 2}{sigma}{tau} transition operator. Unlike the Gamow-Teller operator which excites only the 0{Dirac_h}{omega} transitions, the isovector spin monopole operator can also excite 2{Dirac_h}{omega} transitions and can change the strength distribution at high excitation energies. We explore the strength beyond the resonance, examine the effect of momentum transfer on the total strength and compare the results with recent measurements.

Thermally assisted ordering in Mott insulators

Science.gov (United States)

Sims, Hunter; Pavarini, Eva; Koch, Erik

2017-08-01

Landau theory describes phase transitions as the competition between energy and entropy: The ordered phase has lower energy, while the disordered phase has larger entropy. When heating the system, ordering is reduced entropically until it vanishes at the critical temperature. This picture implicitly assumes that the energy difference between the ordered and disordered phases does not change with temperature. We show that for orbital ordering in the Mott insulator KCuF3, this assumption fails qualitatively: entropy plays a negligible role, while thermal expansion energetically stabilizes the orbitally ordered phase to such an extent that no phase transition is observed. To understand this strong dependence on the lattice constant, we need to take into account the Born-Mayer repulsion between the ions. It is the latter, and not the Jahn-Teller elastic energy, which determines the magnitude of the distortion. This effect will be seen in all materials where the distortion expected from the Jahn-Teller mechanism is so large that the ions would touch. Our mechanism explains not only the absence of a phase transition in KCuF3, but even suggests the possibility of an inverted transition in closed-shell systems, where the ordered phase emerges only at high temperatures.

Numerical study of the spin-1 Ashkin-Teller model

International Nuclear Information System (INIS)

Bekhechi, S.; Badehdah, M.; Benyoussef, A.; Ettaki, B.

1998-07-01

Two non perturbative methods by means of the Transfer-Matrix Finite-Size-Scaling (TMFSS) and Monte Carlo (MC) simulations are used to investigate the spin-1 Ashkin-Teller model (A.T.M.). We have obtained rich phase diagrams with first and second order phase transitions with several multicritical points of higher order. Also this model exhibits a new partially ordered phase PO2 which does not exist in the spin-1/2 Ashkin-Teller model (A.T.M.). Finally, the critical behaviour of this model is discussed. (author)

A variational study of the self-trapped magnetic polaron formation in double-exchange model

International Nuclear Information System (INIS)

Liu Tao; Feng Mang; Wang Kelin

2005-01-01

We study the formation of self-trapped magnetic polaron (STMP) in an antiferro/ferromagnetic double-exchange model semi-analytically by variational solutions. It is shown that the Jahn-Teller effect is not essential to the STMP formation and the STMP forms in the antiferromagnetic material within the region of the order of the lattice constant. We also confirm that no ground state STMP exists in the ferromagnetic background, but the ground state bound MP could appear due to the impurity potential

Even-Odd Differences and Shape Deformation of Metal Clusters

OpenAIRE

Hidetoshi, Nishioka; Yoshio, Takahashi; Department of Physics, Konan University; Faculty of General Education, Yamagata University

1994-01-01

The relation between even-odd difference of metal cluster and the deformation of equilibrium shape is studied in terms of two different models; (i) tri-axially deformed harmonic oscillator model, (ii) rectangular box model. Having assumed the matter density ρ kept constant for different shapes of a cluster, we can determine the equilibrium shape both for the two models. The enhancement of HOMO-LUMO gap is obtained and it is ascribed to Jahn-Teller effect. Good agreement of the calculated resu...

Gamow teller strength from n-nucleus scattering

International Nuclear Information System (INIS)

Haeusser, O.

1989-08-01

Detailed studies of the spin-isospin structure of nuclear excitations are possible at TRIUMF's medium resolution spectrometer using the (n,p), ( p → , p →/ and (p,n) reactions. We discuss here results on isospin symmetry of inelastic nucleon scattering reactions populating isospin triads in A=6 and A=12 nuclei. The empirical ratio of L=0 isovector spin flip cross sections at 200-450 MeV and B(GT) for strong Gamow-Teller transitions in p-shell nuclei is found to be larger than calculated in the DWIA using a free NN t-matrix. Based on empirical values of σ/B(GT) the β + Gamow Teller strength function from (n,p) reactions on (sd) and (fp) shell targets is substantially quenched compared to current nuclear structure models using the free-nucleon axial-vector coupling constant. (Author) 33 refs., 6 figs

Star wars and strategic defense initiatives: work activity and health symptoms of unionized bank tellers during work reorganization.

Science.gov (United States)

Seifert, A M; Messing, K; Dumais, L

1997-01-01

Work activity and health symptoms of bank tellers whose work was undergoing reorganization were examined during a university-union study of the health effects of work in women's traditional jobs. Data were gathered through collective and individual interviews, analysis of work activity, and a questionnaire administered to 305 tellers. Employees worked in a standing posture over 80 percent of the time. More than two-thirds frequently suffered pain in back, legs, and feet. The average teller had been involved in 3.7 robberies as a direct victim and six as a witness. Work required feats of memory and concentration. In order to meet job demands, tellers engaged in supportive activities and teamwork. The introduction of individualized objectives threatened the employees' ability to collaborate and induced distress. More than twice as many tellers as other female workers in Québec experience psychological distress (Ilfeld scale), related to: robbery during the past two years (odds ratio = 1.7; confidence interval = 1.0-2.9); difficult relations with superiors (O.R. = 2.6; C.I. = 1.3-5.3); and full-time work (O.R. = 2.3; C.I. = 1.3-3.9). Diverse methods enriched the analysis, and union participation allowed the proposal of concrete correction measures.

Dirac equation with spin symmetry for the modified Pöschl–Teller ...

Indian Academy of Sciences (India)

effective nuclear shell-model scheme [7–9]. Also, various potentials such as the Morse potential [10–12], Wood–Saxon potential [13], Coulomb and Hartmann potentials [14],. Eckart potential [15,16], Pöschl–Teller potential [17,18] and the harmonic potential [19,20] have been studied within the framework of the spin and ...

Direct probe of the bent and linear geometries of the core-excited Renner-Teller pair states by means of the triple-ion-coincidence momentum imaging technique

International Nuclear Information System (INIS)

Muramatsu, Y.; Ueda, K.; Chiba, H.; Saito, N.; Lavollee, M.; Czasch, A.; Weber, T.; Jagutzki, O.; Schmidt-Boecking, H.; Moshammer, R.; Becker, U.; Kubozuka, K.; Koyano, I.

2002-01-01

The doubly degenerate core-excited Π state of CO 2 splits into two due to static Renner-Teller effect. Using the triple-ion-coincidence momentum imaging technique and focusing on the dependence of the measured quantities on the polarization of the incident light, we have probed, directly and separately, the linear and bent geometries for the B 1 and A 1 Renner-Teller pair states, as a direct proof of the static Renner-Teller effect

APPLICATION OF QUEUING THEORY TO AUTOMATED TELLER MACHINE (ATM) FACILITIES USING MONTE CARLO SIMULATION

OpenAIRE

UDOANYA RAYMOND MANUEL; ANIEKAN OFFIONG

2014-01-01

This paper presents the importance of applying queuing theory to the Automated Teller Machine (ATM) using Monte Carlo Simulation in order to determine, control and manage the level of queuing congestion found within the Automated Teller Machine (ATM) centre in Nigeria and also it contains the empirical data analysis of the queuing systems obtained at the Automated Teller Machine (ATM) located within the Bank premises for a period of three (3) months. Monte Carlo Simulation is applied to th...

Optimal capacity of Ashkin-Teller neural networks

International Nuclear Information System (INIS)

Kozleowski, P.; Bolle, D.

2001-01-01

The maximal capacity per number of couplings is calculated for Ashkin-Teller type neural networks using a replica-symmetric Gardner approach. The results are compared with numerical simulations. The best value obtained at κ=0 is α c =2.26±0.01

Superconductivity and fast proton transport in nanoconfined water

Science.gov (United States)

Johnson, K. H.

2018-04-01

A real-space molecular-orbital density-wave description of Cooper pairing in conjunction with the dynamic Jahn-Teller mechanism for high-Tc superconductivity predicts that electron-doped water confined to the nanoscale environment of a carbon nanotube or biological macromolecule should superconduct below and exhibit fast proton transport above the transition temperature, Tc ≅ 230 K (-43 °C).

A SURVEY OF AUTOMATED TELLER MACHINE USAGE IN NORTH INDIA

OpenAIRE

Shweta Sankhwar*1 & Dhirendra Pandey2

2017-01-01

A machine that hand out cash or executes several banking services at a swipe of Automated Teller Machine (ATM) card in it. An ATM is a machine is use to withdraw cash using a debit card issued by a bank to the consumer(s). An ATM card is issued by a financial organization that permits user to access an Automated Teller Machine (ATM) such as to deposit amount, cash withdrawals, to check account information, etc. It is now preferred to cash by a large majority of the urban population in many ci...

A study of Gamow-Teller strength in A=37 nuclei

International Nuclear Information System (INIS)

Aufderheide, M.B.; Bloom, S.D.; Resler, D.A.; Goodman, C.D.

1992-01-01

An analysis is made of the recent β+ decay measurements of Garcia et al., in order to see whether the 1981 37 Cl(p,n) 37 Ar measurements of Rapaport et al. are consistent with them. Garcia et al., were not able to determine the amount of Gamow-Teller strength in the isobaric analog state (IAS) or the Coulomb mixing of Fermi strength to a state near the IAS, and were forced to determine the amount of Gamow-Teller strength in the daughter 1371 keV state by making the branching ratios sum to unity. These uncertainties leave a range of possible values open which we investigate. We find that the experiments are consistent within part of this range. We also examine the effect of this range of allowed values on solar and supernova neutrino cross sections of 37 Cl and find weak dependence on the uncertainties described here. We discuss how this range can be narrowed so that the consistency of the two experiments can be conclusively tested

customer-teller scheduling system for optimizing banks service

African Journals Online (AJOL)

els Bank Teller scheduling system for optimizing a Banks customer service. The model takes into account real time .... tinuous observation by management personnel and thus results in .... relationships in a mathematical model. A mathematical ...

Novel effect of spin dynamics with suppression of charge and orbital ordering in Nd0.5Ca0.5MnO3 under the influence of ac electric field

Science.gov (United States)

Sarwar, T.; Qamar, A.; Nadeem, M.

2017-07-01

Dynamics of spin ordering in the manganite Nd0.5Ca0.5MnO3 have been investigated in this paper. It was observed that the complex mixed magnetic ordering in pellets is comprised of antiferromagnetic ordering at 160 K (TN) and complete charge ordering at 250 K (TCO). Under ac field, appearance of unstable ferromagnetic correlations is observed above TCO, which is badly frustrated due to strong spin disorder induced by Jahn Teller distortions. Impedance measurements reveal the spin glass like scenario, suppressing the strong antiferromagnetic and charge ordering states below TN.

Judging Edward Teller: A Closer Look at One of the Most Influential Scientists of the Twentieth Century

Energy Technology Data Exchange (ETDEWEB)

Libby, S B

2010-12-29

Much has been written about Edward TEller, but little of it is objective. Given, on the one hand, his position as one of the most inventive theoretical physicists of the 20th century, and on the other, his central role in the development and advocacy of thermonuclear weapons, one might imagine it impossible at this point in history to write a scholarly, impartial account of Teller's life and his impact. Now, however, Istvan Hargittai, a prominent Hungarian physical chemist and historian of science, has written a balanced, thoughtful, and beautifully research biography that comes closest. Hargittai is uniquely qualified for this difficult task. Coming a generation and a half later from a similar Hungarian-Jewish background, Hargittai understands well the influences and terrible events that shaped Teller. The advent of virulent, political anti-Semitism, first in Hungary and then in Germany, made Teller twice a refugee. Both Teller and Hargittai lost close family in the Holocaust; Hargittai was himself liberated from a Nazi concentration camp as a child. While Teller was in the US by then, his and Hargittai's surviving family members in Hungary suffered mistreatment at the hands of the postwar Hungarian Communist dictatorship. Hargittai's informed Eastern European perspective also provides a fresh viewpoint to the cold war context of the second half of Teller's career. Furthermore, Hargittai's own scientific work in molecular structure clearly makes him appreciate of Teller's breakthroughs in that field in the 1930s.

Cu cluster shell structure at elevated temperatures

DEFF Research Database (Denmark)

Christensen, Ole Bøssing; Jacobsen, Karsten Wedel; Nørskov, Jens Kehlet

1991-01-01

Equilibrium structures of small (3–29)-atom Cu clusters are determined by simulated annealing, and finite-temperature ensembles are simulated by Monte Carlo techniques using the effective-medium theory for the energy calculation. Clusters with 8, 18, and 20 atoms are found to be particularly stable....... The equilibrium geometrical structures are determined and found to be determined by a Jahn-Teller distortion, which is found to affect the geometry also at high temperatures. The ‘‘magic’’ clusters retain their large stability even at elevated temperatures....

Studies of the fluorescent excited state of impurities in ionic crystals

International Nuclear Information System (INIS)

Romestain, Robert

1972-01-01

The author of this research thesis first presents experimental methods used in this research: principles (recall on the optical spectrum of an impurity in a solid, use of fluorescence polarization) and techniques (sample preparation, liquid helium cryostat, application of a disturbance, optical detection). Then, he reports the study of the Mn ++ ion in a tetrahedron crystalline field, the study of the Jahn Teller effect on the excited state of the F + centre in CaO, and the study by double resonance of a specific excited state of this same centre in CaO

Low temperature ultrasonic investigation of ZnSe crystals doped with Ni

Energy Technology Data Exchange (ETDEWEB)

Gudkov, Vladimir [Institute for Metal Physics, Ural Department of the Russian Academy of Sciences, 18, Kovalevskaya st., 620219 Ekaterinburg (Russian Federation); Russian State Vocational Pedagogical University, 11, Mashinostroitelei st., 620012 Ekaterinburg (Russian Federation); Lonchakov, Alexander; Sokolov, Victor; Zhevstovskikh, Irina; Gruzdev, Nikita [Institute for Metal Physics, Ural Department of the Russian Academy of Sciences, 18, Kovalevskaya st., 620219 Ekaterinburg (Russian Federation)

2005-03-01

The peak of ultrasonic absorption observed at {approx}13 K in ZnSe:Ni crystals with dopant concentration of 5.5 x 10{sup 19} cm{sup -3} was interpreted as due to the Jahn-Teller effect. The dynamic contribution to the effective elastic modulus was accounted for and the temperature dependences of relaxation time, relaxed and unrelaxed modulus C{sub 44} were obtained. The procedure of accounting for the dynamic contribution resulted in a more accurate determination of the temperature of phase transition. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Effect of Tensor Correlations on Gamow-Teller States in 90Zr and 208Pb

International Nuclear Information System (INIS)

Bai, C. L.; Zhang, H. Q.; Zhang, X. Z.

2009-01-01

The tensor terms of the Skyrme effective interaction are included in the self-consistent Hartree-Fock plus Random Phase Approximation (HF-RPA) model. The Gamow-Teller (GT) strength functions of 9 0Z r and 2 08P b is calculated with and without the tensor terms. The main peaks are moved downwards by about 2 MeV when including the tensor contribution. About 10% of the non-energy weighted sum rule is shifted to the excitation energy region above 30 MeV by the RPA tensor correlations. The contribution of the tensor terms to the energy weighted sum rule is given analytically, and compared to the outcome of RPA. A microscopic origin of the quenching of GT sum rule due to the tensor force is discussed.(author)

Lattice strain accompanying the colossal magnetoresistance effect in EuB6.

Science.gov (United States)

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

2014-08-08

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

Thermoelectric Power and Normal State of the High - Tc Copper Oxides

International Nuclear Information System (INIS)

Goodenough, J.B.; Zhou, J.S.; Besuker, G.I.

1995-01-01

The temperature dependence of the thermoelectric power and resistance for the system La 2-x Sr x CuO 4 , 0≤ x ≤0.30, are presented and interpreted. The following model emerges: (1) In the underdoped region 0 2 sheets by Sr substitution form non-adiabatic large polarons containing 6 ± 1 Cu atoms; a cooperative pseudo Jahn-Teller vibronic coupling increases the size of the polaron, but a contraction of the equilibrium Cu-O distance inside the polaron limits the size. Polaron motion occurs via a tunneling of one Cu - O bond at a time. A dynamic segregation into a hole-poor parent phase and a hole-rich superconductive phase occurs below 150K. (2) The range 0.10 2 sheet. In the polaron liquid, pairs of polarons form zig-zag polaron chains; these chains form an ordered array of alternating polaron and parent-phase stripes. Complete ordering of the stripes occurs below Tc. (4) In the overdoped region x>0.27, polaron overcrowding suppresses polaron formation; however, the vibronic coupling stabilized by the dynamic pseudo Jahn -Teller deformations persists to give unusual properties to the overdoped metallic phase. (author)

Electron spin transition causing structure transformations of earth's interiors under high pressure

Science.gov (United States)

Yamanaka, T.; Kyono, A.; Kharlamova, S.; Alp, E.; Bi, W.; Mao, H.

2012-12-01

To elucidate the correlation between structure transitions and spin state is one of the crucial problems for understanding the geophysical properties of earth interiors under high pressure. High-pressure studies of iron bearing spinels attract extensive attention in order to understand strong electronic correlation such as the charge transfer, electron hopping, electron high-low spin transition, Jahn-Teller distortion and charge disproponation in the lower mantle or subduction zone [1]. Experiment Structure transitions of Fe3-xSixO4, Fe3-xTixO4 Fe3-xCrxO4 spinel solid solution have been investigated at high pressure up to 60 GPa by single crystal and powder diffraction studies using synchrotron radiation with diamond anvil cell. X-ray emission experiment (XES) at high pressure proved the spin transition of Fe-Kβ from high spin (HS) to intermediate spin state (IS) or low spin state (LS). Mössbauer experiment and Raman spectra study have been also conducted for deformation analysis of Fe site and confirmation of the configuration change of Fe atoms. Jahn-Teller effect A cubic-to-tetragonal transition under pressure was induced by Jahn-Teller effect of IVFe2+ (3d6) in the tetrahedral site of Fe2TiO4 and FeCr2O4, providing the transformation from 43m (Td) to 42m (D2d). Tetragonal phase is formed by the degeneracy of e orbital of Fe2+ ion. Their c/a ratios are c/adisordered in the M2 site. At pressures above 53 GPa, Fe2TiO4 structure further transforms to Pmma. This structure change results in the order-disorder transition [2]. New structure of Fe2SiO4 The spin transition exerts an influence to Fe2SiO4 spinel structure and triggers two distinct curves of the lattice constant in the spinel phase. The reversible structure transition from cubic to pseudo-rhombohedral phase was observed at about 45 GPa. This transition is induced by the 20% shrinkage of ionic radius of VIFe2+at the low sin state. Laser heating experiment at 1500 K has confirmed the decomposition from the

Penentuan Jumlah Teller Optimum Dengan Menggunakan Teknik Simulasi ProModel di PT Bank Sumut Cabang Utama Medan

OpenAIRE

Handoko, Rio

2012-01-01

Sistem antrian yang diterapkan pada PT. Bank Sumut Cabang Utama Medan menerapkan sistem antrian FIFO / FCFS (First Come First Serve. Pada PT. Bank Sumut Cabang Utama Medan terdapat sepuluh teller atau server yang bertugas melayani pelanggan. Setiap pelanggan yang datang wajib mengambil nomor antrian kemudian menunggu untuk dipanggil oleh teller yang kosong dan kemudian melakukan transaksi. Teller yang telah selesai melayani satu pelanggan kemudian menekan tombol agar antrian berikutnya dapat ...

Band Jahn-Teller effect on the density of states of the magnetic high-Tc superconductors: A model study

International Nuclear Information System (INIS)

Pradhan, B.; Mohanta, K.L.; Rout, G.C.

2012-01-01

We report here a mean-field study of competing antiferromagnetism, superconductivity and lattice strain phases and their effect on the local density of states of the cuprate system. Our model Hamiltonian incorporating these interactions is reported earlier [G.C. Rout et al., Physica C, 2007]. The analytic expression for superconducting, antiferromagnetism and lattice strain order parameters are calculated and solved self-consistently. The interplay of these order parameters is investigated considering the calculated density of states (DOSs) of the conduction electrons. The DOS displays multiple gap structures with multiple peaks. It is suggested that the tunneling conductance data obtained from the scanning tunneling microscopy (STM) measurements could be interpreted by using the quasi-particle bands calculated from our model Hamiltonian. We have discussed the mechanism to calculate the order parameters from the conductance data.

Effect on Tensor Correlations on Gamow- Teller States in 90Zr and 208Pb

International Nuclear Information System (INIS)

Bai, C. L.; Sagawa, H.; Zhang, H. Q.

2009-01-01

The tensor terms of the Skyrme effective interaction are included in the self-consistent Hartree-Fock plus Random Phase Approximation (HF-RPA) model. The Gamow-Teller (GT) strength function of 9 0Z r and 2 08P b are calculated with and without the tensor terms. The main peaks are moved downwards by about 2 MeV when including the tensor contribution. About 10% of the non-energy weighted sum rule is shifted to the excitation energy region above 30 MeV by the RPA tensor correlations. The contribution of the tensor terms to the energy weighted sum rule is given analytically, and compared to the outcome of RPA. A microscopic origin of the quenching of GT sum rule is discussed in relation with the coupling to giant spin-quadrupole excitations by the tensor interactions.(author)

Lorentz-Lorenz quenching for the Gamow-Teller sum rule

International Nuclear Information System (INIS)

Delorme, J.; Ericson, M.; Figureau, A.

1984-03-01

We investigate the modification of the Gamow-Teller sum rule brought in by nucleonic excitations. The general trend of the data is well reproduced. The value of the force which mixes nucleonic and nuclear excitations is discussed

Science and Technology Review, July-August 1998: Celebrating Edward Teller at 90

Science.gov (United States)

Smart, J.

1998-07-01

On the occasion of Edward Teller's 90th birthday, Science and Technology Review (S&TR) has the pleasure of honoring Lawrence Livermore's co-founder and most influential scientist. Teller is known for his inventive work in physics, his concepts leading to thermonuclear explosions, and his strong stands on such issues as science education, the nation's strategic defense, the needs for science in the future, and sharing scientific information. The articles in this issue also show him, as always, tirelessly moving forward with his new and changing interests.

Semi-classical behavior of Poschl-Teller coherent states

Czech Academy of Sciences Publication Activity Database

Bergeron, H.; Gazeau, J.P.; Siegl, Petr; Youssef, A.

2010-01-01

Roč. 92, č. 6 (2010), s. 60003 ISSN 0295-5075 R&D Projects: GA MŠk LC06002 Institutional research plan: CEZ:AV0Z10480505 Institutional support: RVO:61389005 Keywords : coherent states * Pöschl-Teller potential * quantization Subject RIV: BE - Theoretical Physics Impact factor: 2.753, year: 2010

Superposition model analysis of nickel(II) ions in trigonal bipyramidal complexes exhibiting huge zero field splitting (aka ‘giant magnetic anisotropy’)

Energy Technology Data Exchange (ETDEWEB)

Rudowicz, Czesław, E-mail: crudowicz@zut.edu.pl [Faculty of Chemistry, A. Mickiewicz University, 61-614 Poznań (Poland); Institute of Physics, West Pomeranian University of Technology, Szczecin (Poland); Açıkgöz, Muhammed [Department of Chemistry, Rutgers University, Newark, New Jersey 07102 (United States); Gnutek, Paweł [Institute of Physics, West Pomeranian University of Technology, Szczecin (Poland)

2017-07-15

Graphical abstract: Using crystal structure data for [Ni(Me{sub 6}tren)Cl](ClO{sub 4}) and [Ni(Me{sub 6}tren)Br](Br) as well as taking into account the Jahn-Teller distortions of five-fold coordinated Ni-complexes revealed by DFT geometry optimization, the ZFSPs are predicted for several structural models and wide ranges of model parameters. - Highlights: • Semiempirical study of potential SMM [Ni(Me{sub 6}tren)Cl](ClO{sub 4}) and [Ni(Me{sub 6}tren)Br](Br). • Superposition model analysis of zero field splitting (ZFS) parameters carried out. • Jahn-Teller distortions revealed by DFT geometry optimization considered. • SPM predicts D(ZFS) of observed magnitudes with positive or negative signs. • Results corroborate giant ZFS, which shall not be equated with magnetic anisotropy. - Abstract: Potential single-ion magnet Ni{sup 2+} systems: [Ni(Me{sub 6}tren)Cl](ClO{sub 4}) and [Ni(Me{sub 6}tren)Br](Br) reveal unusually high zero field splitting (ZFS). The ZFS parameter (ZFSP) D{sub expt} = −120 to −180 cm{sup −1} was determined indirectly by high-magnetic field, high-frequency electron magnetic resonance (HMF-EMR). Modeling ZFSPs using the density functional theory (DFT) codes predicts D values: −100 to −200 cm{sup −1}. Such ZFSP values may seem controversial in view of the D values usually not exceeding several tens of cm{sup −1} for Ni{sup 2+} ions. To corroborate or otherwise these results and elucidate the origin of the huge ZFS (named inappropriately as ‘giant uniaxial magnetic anisotropy’) and respective wavefunctions, we have undertaken semiempirical modeling based on the crystal field (CF) and spin Hamiltonians (SH) theory. In this paper, a feasibility study is carried out to ascertain if superposition model (SPM) calculations may yield such huge D values for these Ni{sup 2+} systems. Using crystal structure data for [Ni(Me{sub 6}tren)Cl](ClO{sub 4}) and [Ni(Me{sub 6}tren)Br](Br) as well as taking into account the Jahn-Teller

Jahn-Teller effect and ferromagnetic ordering in La0.875Sr0.125MnO3: A reentrant behaviour

International Nuclear Information System (INIS)

Pinsard, L.; Revcolevschi, A.; Anane, A.; Dupas, C.

1997-01-01

The compound La 0.875 Sr 0.125 MnO 3 undergoes a series of structural phase transitions in which different physical effects are involved. The compound is rhombohedral above T RO ∝400 K. On cooling, a phase transition to an orthorhombic Pbnm O-phase takes place at T RO , no significant orbital ordering is observed. At T OO' ∝270 K a structural phase transition to another orthorhombic (O') form takes place, and an orbital ordering appears due to a cooperative JT effect. For this temperature range the compound is a paramagnetic semiconductor. Upon cooling it becomes ferromagnetic at T C ∝180 K and the orbital ordering is partially suppressed. Below a temperature T O'O '' ∝150 K at which the average Mn magnetic moment is about 2μ B the orbital ordering is completely suppressed by a first order structural transition to another orthorhombic phase (O '' ) similar to the O-phase. Between T C and T O'O '' the compound is metallic and becomes a ferromagnetic insulator below T O'O '' where a canting of the ferromagnetic order appears. (orig.)

One of My Favorite Assignments: Automated Teller Machine Simulation.

Science.gov (United States)

Oberman, Paul S.

2001-01-01

Describes an assignment for an introductory computer science class that requires the student to write a software program that simulates an automated teller machine. Highlights include an algorithm for the assignment; sample file contents; language features used; assignment variations; and discussion points. (LRW)

Phonon renormalization at small q values in the high-temperature phase of CsCuCl sub 3

CERN Document Server

Foerster, U; Schotte, U; Stuhr, U

1997-01-01

The hexagonal perovskite CsCuCl sub 3 exhibits a structural phase transition from a dynamically disordered high-temperature phase to an ordered low-temperature phase due to the cooperative Jahn-Teller effect. The lattice dynamics of the high-temperature phase has been studied by inelastic neutron scattering experiments. The investigations concentrated on small wave vectors q, where for the first time renormalized phonons at q=0.02-0.05 A sup - sup 1 could be observed. The measurements confirm the predictions of a theoretical approach based on the coupling between dynamic reorientation processes and acoustic lattice waves (pseudo-spin phonon coupling). (author)

Enhancing the Current Automated Teller Machine (ATM) in Nigerian ...

African Journals Online (AJOL)

This is going to be achieved by creating another input device that collects the money into the ATM system, reads its denomination and either saves it or transfers it the required customer ... Keywords: Automated Teller Machine (ATM), Interswitch, Local Area Network (LAN), Wide Area Network (WAN), Telecommunication.

Orbital symmetry fingerprints for magnetic adatoms in graphene

Science.gov (United States)

Uchoa, Bruno; Yang, Ling; Tsai, S.-W.; Peres, N. M. R.; Castro Neto, A. H.

2014-01-01

In this paper, we describe the formation of local resonances in graphene in the presence of magnetic adatoms containing localized orbitals of arbitrary symmetry, corresponding to any given angular momentum state. We show that quantum interference effects which are naturally inbuilt in the honeycomb lattice in combination with the specific orbital symmetry of the localized state lead to the formation of fingerprints in differential conductance curves. In the presence of Jahn-Teller distortion effects, which lift the orbital degeneracy of the adatoms, the orbital symmetries can lead to distinctive signatures in the local density of states. We show that those effects allow scanning tunneling probes to characterize adatoms and defects in graphene.

Comment on "Histories and Horoscopes: The Ethnographer as Fortune-Teller."

Science.gov (United States)

Luttrell, Wendy

1998-01-01

Explores the analogy of the researcher as fortune teller and the parallels between research histories and horoscopes and discusses the tension between what the subject is and what he or she is imagined to be by others. (SLD)

On the nature of the phase transition in uranium dioxide

Science.gov (United States)

Gofryk, K.; Mast, D.; Antonio, D.; Shrestha, K.; Andersson, D.; Stanek, C.; Jaime, M.

Uranium dioxide (UO2) is by far the most studied actinide material as it is a primary fuel used in light water nuclear reactors. Its thermal and magnetic properties remain, however, a puzzle resulting from strong couplings between magnetism and lattice vibrations. UO2 crystalizes in the face-centered-cubic fluorite structure and is a Mott-Hubbard insulator with well-localized uranium 5 f-electrons. In addition, below 30 K, a long range antiferromagnetic ordering of the electric-quadrupole of the uranium moments is observed, forming complex non-collinear 3-k magnetic structure. This transition is accompanied by Jahn-Teller distortion of oxygen atoms. It is believed that the first order nature of the transition results from the competition between the exchange interaction and the Jahn-Teller distortion. Here we present results of our extensive thermodynamic investigations on well-characterized and oriented single crystals of UO2+x (x = 0, 0.033, 0.04, and 0.11). By focusing on the transition region under applied magnetic field we are able to study the interplay between different competing interactions (structural, magnetic, and electrical), its dynamics, and relationship to the oxygen content. We will discuss implications of these results. Work supported by the Department of Energy, Office of Basic Energy Sciences, Materials Sciences, and Engineering Division.

Four-dimensional Ashkin-Teller gauge theory

International Nuclear Information System (INIS)

Alcaraz, F.C.; Jacobs, L.

1983-01-01

The authors construct and analyze a lattice field theory of two Z 2 gauge fields which interact in a minimal gauge-invariant fashion. Although the theory presented here, a generalization of the two-dimensional Ashkin-Teller spin system, has no formal continuum limit, it is found that it has an electrodynamicslike phase similar to that observed in general Z/sub N/ theories for N> or =4. This model is probably the simplest generalization of the conventional Z 2 pure gauge theory which has a massless phase separated from the strong- and weak-coupling regions by lines of second-order phase transitions

Frequency effects on charge ordering in Y0.5Ca0.5MnO3 by impedance spectroscopy

Science.gov (United States)

Sarwar, Tuba; Qamar, Afzaal; Nadeem, Muhammad

2015-02-01

In this work, structural and electrical properties of Y0.5Ca0.5MnO3 are investigated by employing X-ray diffraction and impedance spectroscopy, respectively. Applied ac electric field showed the charge ordering transition temperature around 265 K and below this temperature the heteromorphic behavior of the sample is discussed in the proximity of TCO. With frequency effects the volume of robust charge orbital ordering (COO) domains diminishes due to different competing phases along with Jahn Teller distortions. Comprehensive melting and collapse of charge orbital ordering occurs below TN(125 K), where a colossal drop in the value of impedance is observed. The change in profile of modulus plane plots determines the spreading of relaxation time of intermingled phases. Hopping mechanism is elaborated in terms of strong electron phonon coupling. Variable range hopping model and Arrhenius model are used to discuss the short and long range hopping between Mn3+ and Mn4+ channels assessing the activation energy Ea.

E x circle epsilon Jahn-Teller anharmonic coupling for an octahedral system

CERN Document Server

Avram, N M; Kibler, M R

2001-01-01

The coupling between doubly degenerate electronic states and doubly degenerate vibrations is analyzed for an octahedral system on the basis of the introduction of an anharmonic Morse potential for the vibronic part. The vibrations are described by anharmonic coherent states and their linear coupling with the electronic states is considered. The matrix elements of the vibronic interaction are built and the energy levels corresponding to the interaction Hamiltonian are derived.

First principle calculations of charge ordering in manganites

International Nuclear Information System (INIS)

Baldomir, D.; Pardo, V.; Castro, J.; Iglesias, M.; Arias, J.E.; Rivas, J.

2007-01-01

Electronic structure calculations were performed on the compound La 0.5 Ca 0.5 MnO 3 to study the relationship between the magnetic ordering, the charge ordering and the geometry of the compound. Charge ordering is intimately related to the magnetic ordering. An antiferromagnetic ordering induces charge disproportionation via a Jahn-Teller distortion. A full disproportionation in Mn 3+ /Mn 4+ occurs for the experimental geometry and allows to predict the experimentally found antiferromagnetic insulating state

Spontaneous symmetry breaking by double lithium adsorption in polyacenes

International Nuclear Information System (INIS)

Ortiz, Yenni. P.; Seligman, Thomas H.

2010-01-01

We show that adsorption of one lithium atom to polyacenes, i.e. chains of linearly fused benzene rings, will cause such chains to be slightly deformed. If we adsorb a second identical atom on the opposite side of the same ring, this deformation is dramatically enhanced despite the fact that a symmetric configuration seems possible. We argue, that this may be due to an instability of the Jahn-Teller type possibly indeed to a Peierls instability.

Classical motion and coherent states for Poeschl-Teller potentials

International Nuclear Information System (INIS)

Cruz y Cruz, S.; Kuru, S.; Negro, J.

2008-01-01

The trigonometric and hyperbolic Poeschl-Teller potentials are dealt with from the point of view of classical and quantum mechanics. We show that there is a natural correspondence between the algebraic structure of these two approaches for both kind of potentials. Then, the coherent states are constructed and the appropriate classical variables are compared with the expected values of their corresponding quantum operators

Chiral filter, axial charges and Gamow-Teller strengths

International Nuclear Information System (INIS)

Rho, M.

1983-09-01

The different ways that nuclear matter responds to the weak axial-vector current are interpreted in terms of modification of the ''vacuum'' in baryon-rich environments. The notion of ''chiral filter'' is introduced. Use of a ward identity is suggested. The Gamow-Teller quenching and the enhanced axial charge in O + O - transitions follow from this. I also discuss briefly possible relevance of the nucleon as a topological soliton configuration to the global property of nuclear axial response functions

Band Jahn-Teller effect on the density of states of the magnetic high-T{sub c} superconductors: A model study

Energy Technology Data Exchange (ETDEWEB)

Pradhan, B. [Department of Physics, Govt. Science College, Malkangiri 764 048 (India); Mohanta, K.L. [Department of Physics, ITER, Siksha ' O' Anusandhan University, Bhubaneswar 751 030 (India); Rout, G.C., E-mail: gcr@iopb.res.in [Condensed Matter Physics Group, Dept. of Applied Physics and Ballistics, F.M. University, Balasore 756 019 (India)

2012-05-15

We report here a mean-field study of competing antiferromagnetism, superconductivity and lattice strain phases and their effect on the local density of states of the cuprate system. Our model Hamiltonian incorporating these interactions is reported earlier [G.C. Rout et al., Physica C, 2007]. The analytic expression for superconducting, antiferromagnetism and lattice strain order parameters are calculated and solved self-consistently. The interplay of these order parameters is investigated considering the calculated density of states (DOSs) of the conduction electrons. The DOS displays multiple gap structures with multiple peaks. It is suggested that the tunneling conductance data obtained from the scanning tunneling microscopy (STM) measurements could be interpreted by using the quasi-particle bands calculated from our model Hamiltonian. We have discussed the mechanism to calculate the order parameters from the conductance data.

Ba ₃ (Cr _0.97(1) Te _0.03(1) ) ₂ TeO ₉ : in Search of Jahn–Teller Distorted Cr(II) Oxide

Energy Technology Data Exchange (ETDEWEB)

Li, Man-Rong; Deng, Zheng; Lapidus, Saul H.; Stephens, Peter W.; Segre, Carlo U.; Croft, Mark; Paria Sena, Robert; Hadermann, Joke; Walker, David; Greenblatt, Martha

2016-10-17

A novel 6H - type hexagonal perovskite Ba 3 (Cr 0.97(1) Te 0.03 (1 ) ) 2 TeO 9 was prepared at high pressure (6 GPa) and temperature ( 1 773 K). Both transmission electron microscopy and synchrotron powder x - ray diffraction data demonstrate that Ba 3 (Cr 0.97(1) Te 0.03(1) ) 2 TeO 9 crystallize s in P6 3 / mmc with face - shared (Cr 0.97(1) Te 0.03(1) )O 6 octahedral pairs interconnected with TeO 6 octahedra via corner - sharing. Structure analysis shows a mixed Cr 2+ /Cr 3+ valence state with ~ 10% Cr 2+ . The existence of Cr 2+ in Ba 3 (Cr 2+ 0.10(1) Cr 3+ 0.87(1) Te 6+ 0.03 ) 2 TeO 9 is further evidenced by x - ray absorption near edge spectr oscopy . Magnetic properties measurements show a paramagnetic response down to 4 K and a small glassy - state curvature at low temperature. In this work, the o ctahedral Cr 2+ O 6 component is stabilized in an oxide material for the first time ; the expected Jahn - Teller distortion of high - spin ( d 4 ) Cr 2+ is not found , which is attributed to the small proportion of Cr 2+ (~ 10%) and the face - sharing arrangement of CrO 6 octahedral pairs, that structu rally dis favor axial distortion.

1995 Edward teller lecture. Patience and optimism

International Nuclear Information System (INIS)

Miley, G.H.

1996-01-01

Remarks made in the author close-quote s acceptance lecture for the 1995 Edward Teller Medal are presented and expanded. Topics covered include research on nuclear-pumped lasers, the first direct e-beam-pumped laser, direct energy conversion and advanced fuel fusion, plus recent work on inertial electrostatic confinement. open-quote open-quote Patience close-quote close-quote and open-quote open-quote optimism close-quote close-quote are viewed as essential elements needed by scientists following the open-quote open-quote zig-zag close-quote close-quote path to fusion energy production. copyright 1996 American Institute of Physics

Gamow-Teller strength in the β-decay of 36Ca

International Nuclear Information System (INIS)

Trinder, W.; Adelberger, E.G.; Janas, Z.; Keller, H.; Krumbholz, K.; Pfuetzner, M.; Rykaczewski, K.

1994-11-01

The β-decay of 36 Ca has been studied at the projectile fragment separator at GSI Darmstadt. The Gamow-Teller strength function B(GT), deduced from the observed β-delayed proton- and γ-emission and from the measured half-life of 102(2) ms, is compared to results obtained from large-scale sd-shell model calculations. (orig.)

Gamow-Teller decay and nuclear deformation: implementing of a new total absorption spectrometer, study of isotopes N ≅ Z krypton and strontium

International Nuclear Information System (INIS)

Poirier, E.

2002-12-01

Nuclei with A ∼ 70 along the N=Z line are known to be the scene of phenomena closely related to the nuclear deformation and are of particular interest since theoretical mean field calculations predict that a large part of the Gamow-Teller resonance might be located below the ground state of the mother nucleus and then be accessible through β-decay studies. These results have shown the effect of the shape of the ground state on the intensity of the Gamow-Teller strength. Thus, the experimental determination, through δ-decay, of the Gamow-Teller strength distribution and the comparison to the theoretical predictions allow to pin down the quadrupolar deformation parameter of the ground state of the parent nucleus. In order to study the neutron deficient isotopes of krypton (A=72,73,74,75) and strontium (A=76,77,78) and to establish the β-strength on the full energy range, a new total absorption spectrometer (TAgS) has been built in the frame of an international collaboration and installed at the (SOLDE/CERN mass separator. For the data analysis, the response function R of the spectrometer has been calculated by means of Monte-Carlo simulations, based on the GEANT4 code, and of a statistical description of the level scheme in the daughter nucleus. The β-feeding distribution has been obtained from experimental spectra through a method based on Bayes theorem and then converted into Gamow-Teller strength. The results coming from the 74 Kr decay analysis allow to describe the ground state of such a nucleus as the coexistence of an oblate shape and of a prolate shape. In the case of 76 Sr, the experimental Gamow-Teller strength distribution strongly indicates a prolate deformation. (author)

Crystalline structure of the manganites solid solution RE(Me,MnO₃, (RE=Gd,Er; Me=Ni,Co

Directory of Open Access Journals (Sweden)

Peña, O.

2009-08-01

Full Text Available The structural properties of the manganites solid solution RE(Me,MnO₃, RE=Er,Gd, have been studied by X-ray diffraction and electric measurements. Powders were prepared by solid state reaction between the component oxides. Incorporation of Ni²⁺ or Co²⁺ on the lattice in the Mn sites leads to changes in the parameters and symmetry of the perovskite or hexagonal compounds GdMnO₃ and ErMnO₃ respectively. The phase transitions depend on the amount of substituted Jahn-Teller Mn³⁺ cations, and, therefore, of the cooperative Jahn-Teller interaction weakness. Solid solutions based on GdMnO₃ perovskite compound change from O’-type to O-type orthorhombic perovskite symmetry when the Mn³⁺ cation amount decreases, because of the progressive substitution for Ni, Co. This transition occurs for lower amount of Ni²⁺ than for Co²⁺ cation. The Er-based solid solutions showed a different behaviour. For Ni²⁺ and Co²⁺ incorporation there are changes from hexagonal ErMnO₃-type lattice to perovskite-type symmetry, for 20 at% and 30 at% respectively of substituting cations. The resultant perovskites crystallised directly in the O-type orthorhombic perovskite structure. The steric influence seems to play a secondary role, such as it can be deduced of the small variation of the Goldschmidt tolerance factor, t, for perovskite structure.

Las propiedades estructurales de las soluciones sólidas RE(Me,MnO₃, RE=Gd,Er, Me=Ni,Co, han sido estudiadas por difracción de rayos X, (DRX y medidas eléctricas. Las fases se sintetizaron por reacción en estado sólido entre los óxidos componentes. La incorporación de los cationes Ni²⁺ y Co^2+,3+ en la red en lugar de Mn lleva a cambios en los parámetros de red y en la simetría de la perovskita, GdMnO₃ o del compuesto hexagonal Er

Lattice Distortion Mediated Paramagnetic Relaxation in High-Spin High-Symmetry Molecular Magnets

Science.gov (United States)

Garg, Anupam

1998-08-01

Field-dependent maxima in the relaxation rate of the magnetic molecules Mn12-Ac and Fe8-tacn have commonly been ascribed to some resonant tunneling phenomena. We argue instead that the relaxation is purely due to phonons. The rate maxima arise because of a Jahn-Teller-like distortion caused by the coupling of phonons to degenerate Zeeman levels of the molecule at the top of the barrier. The binding energy of the distorted intermediate states lowers the barrier height and increases the relaxation rate. A nonperturbative calculation of this effect is carried out for a model system. An approximate result for the field variation near a maximum is found to agree reasonably with experiment.

Soft modes and structural phase transitions

Energy Technology Data Exchange (ETDEWEB)

Venkataraman, G [Reactor Research Centre, Kalpakkam (India)

1979-12-01

A survey of soft modes and their relationship to structural phase transitions is presented. After introducing the concept of a soft mode, the origin of softening is considered from a lattice-dynamical point. The Landau theory approach to structural transitions is then discussed, followed by a generalisation of the soft-mode concept through the use of the dynamic order-parameter susceptibility. The relationship of soft modes to broken symmetry is also examined. Experimental results for several classes of crystals are next presented, bringing out various features such as the co-operative Jahn-Teller effect. The survey concludes with a discussion of the central peak, touching upon both the experimental results and the theoretical speculations.

Displacement disorder and reconstruction of the (001) face of tungsten

International Nuclear Information System (INIS)

Egorushkin, V.E.; Kul'ment'ev, A.I.; Savushkin, E.V.

1992-01-01

The reconstruction of the (001) border of tungsten is examined taking into consideration random static displacements of surface atoms in the high-temperature (1 x 1) phase. A microscopic model is proposed, in which the creation of c(2 x 2) phase is described as a transition of the Jahn-Teller type and an ordering of static displacements. It is shown that displacement disorder induces instability of (001) tungsten with respect to reconstruction. The effect of a uniform electric field on a disordered reconstructing surface is examined. A possible reason is given for pronounced differences in the results of investigations of the structural conversion of the (001) face in tungsten when different experimental methods are used

Jahn-Teller and Non-Jahn-Teller Systems Involving CuF64- Units: Role of the Internal Electric Field in Ba2ZnF6:Cu2+ and Other Insulating Systems

DEFF Research Database (Denmark)

Aramburu, J. A.; Garcia-Fernandez, P.; García Lastra, Juan Maria

2017-01-01

transitions for CuF64- units formed in Cu2+-doped the tetragonal Ba2ZnF6 host lattice. While the experimental d-d transitions cannot be reproduced through the isolated CuF64- unit at the equilibrium geometry, a reasonable agreement is reached adding in the calculation the internal electric field, ER...... it is pointed out that a quasi-JT situation can however happen for a d9 ion in a cubic lattice under a strain of ∼10-3 in agreement with experimental data. The present results stress the key role played by the internal electric fields for a quantitative understanding of compounds with transition metal cations...

Ratio of Gamow-Teller to Fermi strength observed in /sup 13,14/C(p,n) at 492 and 590 MeV

International Nuclear Information System (INIS)

Ullmann, J.L.; Rapaport, J.; Lisowski, P.W.

1988-01-01

It has been recognized for a number of years that certain spin-isospin components of the nucleon-nucleus effective interaction can be inferred from (p,n) reactions to states of known nuclear structure. For L = 0, S = 0 and L = 0, S = 1 transitions, the 0-degree (p,n) cross section can be related respectively to Fermi and Gamow-Teller beta decay matrix elements. If these transitions occur in the same nucleus, the ratio of isovector spin-flip to non-spin-flip effective interactions can be measured without regard for absolute normalization. The best reaction to measure this is /sup 14/C(p,n) which goes by a pure Gamow-Teller transition to the 1/sup /plus// state at 3.95 MeV in /sup 14/N, and Fermi transition to the 2.31 MeV 0/sup /plus// state. This work extends the ratio measurements made at lower energies (ref. 1, 2, 3) to 492 and 590 MeV. We also report on the /sup 13/C(p,n) reaction which goes by a pure GT transition to the 3.51 MeV 3/2/sup /minus// state in /sup 13/N, but by a mixed Fermi plus Gamow-Teller transition to the 1/2/sup /minus// ground state. 11 refs., 4 figs., 2 tabs

Nonadiabatic Eigenfunctions Can Have Amplitude, Signed Conical Nodes, or Signed Higher Order Nodes at a Conical Intersection with Circular Symmetry (Open Access Publisher’s Version)

Science.gov (United States)

2017-09-26

marked by black rings on the potential energy surfaces. In some sense, only about half of the zero point energy is available to each of the two...wheel at the bottom. The conical intersection at q1 = q2 = 0 and E = 0 is submerged below the zero-point energy of Ezp = 181 cm −1 ( black curve). The...J. Chem. Phys. 123, 044102 (2005)]. J. Chem. Phys. 2008, 128, 109902. (49) Clinton, W. L.; Rice , B. Reformulation of the Jahn-Teller Theorem. J

Gamow-Teller decay and nuclear deformation: implementing of a new total absorption spectrometer, study of isotopes N {approx_equal} Z krypton and strontium; Decroissance Gamow-Teller et deformation nucleaire: mise en oeuvre d'un nouveau spectrometre a absorption totale, etude d'isotopes N {approx_equal} Z de krypton et strontium

Energy Technology Data Exchange (ETDEWEB)

Poirier, E

2002-12-01

Nuclei with A {approx} 70 along the N=Z line are known to be the scene of phenomena closely related to the nuclear deformation and are of particular interest since theoretical mean field calculations predict that a large part of the Gamow-Teller resonance might be located below the ground state of the mother nucleus and then be accessible through {beta}-decay studies. These results have shown the effect of the shape of the ground state on the intensity of the Gamow-Teller strength. Thus, the experimental determination, through {delta}-decay, of the Gamow-Teller strength distribution and the comparison to the theoretical predictions allow to pin down the quadrupolar deformation parameter of the ground state of the parent nucleus. In order to study the neutron deficient isotopes of krypton (A=72,73,74,75) and strontium (A=76,77,78) and to establish the {beta}-strength on the full energy range, a new total absorption spectrometer (TAgS) has been built in the frame of an international collaboration and installed at the (SOLDE/CERN mass separator. For the data analysis, the response function R of the spectrometer has been calculated by means of Monte-Carlo simulations, based on the GEANT4 code, and of a statistical description of the level scheme in the daughter nucleus. The {beta}-feeding distribution has been obtained from experimental spectra through a method based on Bayes theorem and then converted into Gamow-Teller strength. The results coming from the {sup 74}Kr decay analysis allow to describe the ground state of such a nucleus as the coexistence of an oblate shape and of a prolate shape. In the case of {sup 76}Sr, the experimental Gamow-Teller strength distribution strongly indicates a prolate deformation. (author)

Algebraic treatment of second Poeschl-Teller, Morse-Rosen and Eckart equations

International Nuclear Information System (INIS)

Barut, A.O.; Inomata, A.; Wilson, R.

1987-01-01

The method of algebraic treatment is applied to the non-compact case to solve a family of second Poeschl-Teller, Morse-Rosen and Eckart equations with quantized coupling constants. Both discrete and continuous spectra, bound state and scattering wave functions (transmission coefficients) are found from the matrix elements of group representations. (author). 24 refs, 1 tab

Binding energy and photoionization cross-section of hydrogen-like impurity in a Poschl-Teller quantum well

International Nuclear Information System (INIS)

Hakimifard, A.

2010-01-01

The effect of the donor impurity position and the form of confining potential on the binding energy and the photoionization cross-section if a semiconductor quantum well with Poschl-Teller potential is investigated. An analytical expression for the photoionization cross-section is obtained for the case when the polarization vector of light wave is directed along the direction of size quantization. It is shown that the photoionization cross-section has a threshold behavior

A2TiF5.nH2O (A=K, Rb, or Cs; n=0 or 1): Synthesis, structure, characterization, and calculations of three new uni-dimensional titanium fluorides

International Nuclear Information System (INIS)

Jo, Vinna; Woo Lee, Dong; Koo, Hyun-Joo; Ok, Kang Min

2011-01-01

Three new uni-dimensional alkali metal titanium fluoride materials, A 2 TiF 5 .nH 2 O (A=K, Rb, or Cs; n=0 or 1) have been synthesized by hydrothermal reactions. The structures of A 2 TiF 5 .nH 2 O have been determined by single-crystal X-ray diffraction. The Ti 4+ cations have been reduced to Ti 3+ during the synthesis reactions. All three A 2 TiF 5 .nH 2 O materials contain novel 1-D chain structures that are composed of the slightly distorted Ti 3+ F 6 corner-sharing octahedra attributable to the Jahn-Teller distortion. The coordination environment of the alkali metal cations plays an important role to determine the degree of turning in the chain structures. Complete structural analyses, Infrared and UV-vis diffuse reflectance spectra, and thermal analyses are presented, as are electronic structure calculations. -- Graphical abstract: Ball-and-stick and polyhedral representations for (a) β-K 2 TiF 5 and (b) Rb 2 TiF 5 .H 2 O or Cs 2 TiF 5 .H 2 O with the K + and Rb + (or Cs + ) coordination environment emphasized. Display Omitted Research highlights: → Synthesis, structure, characterization, and calculation of new titanium fluorides. → Study of reduction of starting Ti 4+ cations to Ti 3+ by DMF. → Novel 1-D chain structures with Jahn-Teller distorted TiF 6 octahedra.

Theoretical formulation of optical conductivity of La0.7Ca0.3MnO3 exhibiting paramagnetic insulator - ferromagnetic metal transition

Science.gov (United States)

Satiawati, L.; Majidi, M. A.

2017-07-01

A theory of high-energy optical conductivity of La0.7Ca0.3MnO3 has been proposed previously. The proposed theory works to explain the temperature-dependence of the optical conductivity for the photon energy region above ˜0.5 eV for up to ˜22 eV, but fails to capture the correct physics close to the dc limit in which metal-insulator transition occurs. The missing physics at the low energy has been acknowledged as mainly due to not incorporating phonon degree of freedom and electron-phonon interactions. In this study, we aim to complete the above theory by proposing a more complete Hamiltonian incorporating additional terms such as crystal field, two modes of Jahn-Teller vibrations, and coupling between electrons and the two Jahn-Teller vibrational modes. We solve the model by means of dynamical mean-field theory. At this stage, we aim to derive the analytical formulae involved in the calculation, and formulate the algorithmic implementation for the self-consistent calculation process. Our final goal is to compute the density of states and the optical conductivity for the complete photon energy range from 0 to 22 eV at various temperatures, and compare them with the experimental data. We expect that the improved model preserves the correct temperature-dependent physics at high photon energies, as already captured by the previous model, while it would also reveal ferromagnetic metal - paramagnetic insulator transition at the dc limit.

New SUSYQM coherent states for Poschl-Teller potentials: a detailed mathematical analysis

Czech Academy of Sciences Publication Activity Database

Bergeron, H.; Siegl, Petr; Youssef, A.

2012-01-01

Roč. 45, č. 24 (2012), 244028/1-244028/14 ISSN 1751-8113 R&D Projects: GA MŠk LC06002; GA ČR GAP203/11/0701 Institutional support: RVO:61389005 Keywords : supersymmetry * Poschi-Teller potential Subject RIV: BE - Theoretical Physics Impact factor: 1.766, year: 2012

Dynamics of the lattice and spins in the phase-separated manganite (Eu{sub 1−x}Gd{sub x}){sub 0.6}Sr{sub 0.4}MnO{sub 3}

Energy Technology Data Exchange (ETDEWEB)

Taniguchi, Haruka, E-mail: tanig@iwate-u.ac.jp [Department of Physical Science and Materials Engineering, Iwate University, Morioka 020-8551 (Japan); Kimura, Daichi; Matsukawa, Michiaki; Inomata, Tasuku; Kobayashi, Satoru [Department of Physical Science and Materials Engineering, Iwate University, Morioka 020-8551 (Japan); Nimori, Shigeki [National Institute for Materials Science, Tsukuba 305-0047 (Japan); Suryanarayanan, Ramanathaan [Laboratoire de Physico-Chimie de l’Etat Solide, CNRS, UMR8182, Université Paris-Sud, 91405 Orsay (France)

2017-06-15

We investigated slow relaxations of the magnetostriction and residual magnetostriction of the phase-separated system (Eu{sub 1−x}Gd{sub x}){sub 0.6}Sr{sub 0.4}MnO{sub 3}, in which the metamagnetic transition from a paramagnetic insulating state to a ferromagnetic metallic state is accompanied by a lattice shrinkage. The relaxations are well fitted by a stretched exponential function, suggesting the strong frustration between the double exchange interaction and Jahn-Teller effect. We have revealed that the Gd substitution suppresses the frozen phase-separated phase at low temperatures and stabilizes the paramagnetic insulating state in the dynamic phase-separated phase at intermediate temperatures. The former origin would be the randomness effect and the latter would be the suppression of the double exchange interaction.

A tight binding model study of tunneling conductance spectra of spin and orbitally ordered CMR manganites

Science.gov (United States)

Panda, Saswati; Sahoo, D. D.; Rout, G. C.

2018-04-01

We report here a tight binding model for colossal magnetoresistive (CMR) manganites to study the pseudo gap (PG) behavior near Fermi level. In the Kubo-Ohata type DE model, we consider first and second nearest neighbor interactions for transverse spin fluctuations in core band and hopping integrals in conduction band, in the presence of static band Jahn-Teller distortion. The model Hamiltonian is solved using Zubarev's Green's function technique. The electron density of states (DOS) is found out from the Green's functions. We observe clear PG near Fermi level in the electron DOS.

Formal verification of automated teller machine systems using SPIN

Science.gov (United States)

Iqbal, Ikhwan Mohammad; Adzkiya, Dieky; Mukhlash, Imam

2017-08-01

Formal verification is a technique for ensuring the correctness of systems. This work focuses on verifying a model of the Automated Teller Machine (ATM) system against some specifications. We construct the model as a state transition diagram that is suitable for verification. The specifications are expressed as Linear Temporal Logic (LTL) formulas. We use Simple Promela Interpreter (SPIN) model checker to check whether the model satisfies the formula. This model checker accepts models written in Process Meta Language (PROMELA), and its specifications are specified in LTL formulas.

Magnetic Dipole and Gamow-Teller Modes in Neutrino-Nucleus Reactions: Impact on Supernova Dynamics and Nucleosynthesis

International Nuclear Information System (INIS)

Neumann-Cosel, P. von; Byelikov, A.; Richter, A.; Shevchenko, A.; Adachi, T.; Fujita, Y.; Shimbara, Y.; Fujita, H.; Heger, A.; Kolbe, E.; Langanke, K.; Martinez-Pinedo, G.

2006-01-01

Some aspects of the importance of neutrino-induced reactions on nuclei within supernova physics are discussed. It is argued that important constraints on the experimentally unknown cross sections can be obtained from experimental studies of the nuclear response in selected cases. Examples are neutral-current induced reactions on fp-shell nuclei extracted from high-resolution inelastic electron scattering data providing the M1 strength distributions and the production of the exotic heavy, odd-odd nuclei 138La and 180Ta through charged-current reactions dominated by Gamow-Teller transitions. The Gamow-Teller strength can deduced from the (3He,t) charge-exchange reaction at zero degree

Impurity model for mixed-valent Mn3+/Mn4+ ions

International Nuclear Information System (INIS)

Schlottmann, P.; Lee, K.

1997-01-01

Intermediate valent tri- and tetravalent manganese ions play an important role in LaMnO 3 -based systems. We consider a Mn impurity with five orbitals in cubic symmetry which hybridize with conduction electrons. The exchange interaction in the d shell maximizes the impurity spin. We study the valence of the Mn impurity as a function of the splitting of the e g to t 2g orbitals in zero magnetic field and for the totally spin-polarized state. The lifting of the degeneracy of the e g levels due to a small quadrupolar field, related to the Mn-O bond length or a Jahn-Teller effect, is also investigated. Possible implications on the magnetoresistance are discussed. copyright 1997 The American Physical Society

ESR of Ag2+ ions in S2F2 crystal

International Nuclear Information System (INIS)

Zaripov, M.M.; Ulanov, V.A.; Falin, M.L.

1989-01-01

Experimental data on investigation of bivalent silver ions in S 2 F 2 crystals are presented. Due to the investigation of the grown crystals it is determined that centres of univalent silver ore formed in SrF 2 during crystal growth. X-ray irradiation at room temperature results in the transition of these centres in bivalent staes. Investigation of temperature dependence of ESR spectra type has allowed to make the conclusion about the presence of Jahn-Teller dynamic effect. Analysis of experimental data allows to develop a model of the investigated paramagnetic complex in S 2 F 2 crystal where Ag 2* ion has coordination polyhedron in the form of eight F - ion cube distorted by C 3 3 axis

Origin of Small Barriers in Jahn–Teller Systems

DEFF Research Database (Denmark)

Barriuso, M. T.; Ortiz-Sevilla, B.; Aramburu, J. A.

2013-01-01

. It is quantitatively proven that the elongated geometry observed for NaCl:Ni+ is due to the 3d–4s vibronic admixture, which is slightly larger than the anharmonicity in the eg JT mode that favors a compressed geometry. The existence of these two competing mechanisms explains the low value of B for the model system......Despite its relevance, the microscopic origin of the energy barrier, B, between the compressed and elongated geometries of Jahn–Teller (JT) systems is not well understood yet because of a lack of quantitative data about its various contributions. Seeking to clear up this matter, we have carried out...

New SUSYQM coherent states for Pöschl-Teller potentials: a detailed mathematical analysis

Science.gov (United States)

Bergeron, H.; Siegl, P.; Youssef, A.

2012-06-01

In a recent short note (Bergeron et al 2010 Europhys. Lett. 92 60003), we have presented the good properties of a new family of semi-classical states for Pöschl-Teller potentials. These states are built from a supersymmetric quantum mechanics (SUSYQM) approach and the parameters of these ‘coherent’ states are points in the classical phase space. In this paper, we develop all the mathematical aspects that have been left out of the previous paper (proof of the resolution of unity, detailed calculations of the quantized version of classical observables and mathematical study of the resulting operators: problems of domains, self-adjointness or self-adjoint extensions). Some additional questions such as asymptotic behavior are also studied. Moreover, the framework is extended to a larger class of Pöschl-Teller potentials. This article is part of a special issue of Journal of Physics A: Mathematical and Theoretical devoted to ‘Coherent states: mathematical and physical aspects’.

New SUSYQM coherent states for Pöschl–Teller potentials: a detailed mathematical analysis

International Nuclear Information System (INIS)

Bergeron, H; Siegl, P; Youssef, A

2012-01-01

In a recent short note (Bergeron et al 2010 Europhys. Lett. 92 60003), we have presented the good properties of a new family of semi-classical states for Pöschl–Teller potentials. These states are built from a supersymmetric quantum mechanics (SUSYQM) approach and the parameters of these ‘coherent’ states are points in the classical phase space. In this paper, we develop all the mathematical aspects that have been left out of the previous paper (proof of the resolution of unity, detailed calculations of the quantized version of classical observables and mathematical study of the resulting operators: problems of domains, self-adjointness or self-adjoint extensions). Some additional questions such as asymptotic behavior are also studied. Moreover, the framework is extended to a larger class of Pöschl–Teller potentials. This article is part of a special issue of Journal of Physics A: Mathematical and Theoretical devoted to ‘Coherent states: mathematical and physical aspects’. (paper)

Investigating the Human Computer Interaction Problems with Automated Teller Machine Navigation Menus

Science.gov (United States)

Curran, Kevin; King, David

2008-01-01

Purpose: The automated teller machine (ATM) has become an integral part of our society. However, using the ATM can often be a frustrating experience as people frequently reinsert cards to conduct multiple transactions. This has led to the research question of whether ATM menus are designed in an optimal manner. This paper aims to address the…

PERSAMAAN SCHRODINGER D-DIMENSI BAGIAN SUDUT POTENSIAL POSCHL-TELLER HIPERBOLIK TERDEFORMASI Q PLUS ROSEN-MORSE TRIGONOMETRI MENGGUNAKAN METODE NIKIFOROV-UVAROV

Directory of Open Access Journals (Sweden)

S. Suparmi

2016-11-01

Full Text Available Metode Nikivarof Uvarov merupakan metode penyelesaian persamaan diferensial orde dua dengan mengubah persamaan diferensial orde dua yang umum (persamaan Schrodinger menjadi persamaan diferensial tipe hipergeometrik melalui substitusi variabel yang sesuai untuk memperoleh eigen value dan fungsi gelombang bagian sudut. Penelitian ini merupakan studi literatur untuk menyelesaikan persamaan Schrodinger D-dimensi bagian sudut dengan potensial Poschl-Teller Hiperbolik Terdeformasi q plus Rosen Morse Trigonometri Terdeformasi q menggunakan metode Nikiforov-Uvarov (NU. Pada penelitian ini bertujuan untuk mengetahui bagaimana fungsi gelombang bagian sudut persamaan schrodinger D-dimensi  untuk potensial Poschl-Teller Hiperbolik Terdeformasi q plus Rosen Morse Trigonometri Terdeformasi q menggunakan metode Nikiforov-Uvarov (NU.Nikivarof Uvarov is a method to solve second order differential equations by changing general second order differential equation to hyper-geometric differential equation type through substituting relevant variable to obtain eigenvalues and the angle of wave function. This is a literature study to solve the D-dimensional Schrodinger equation with a corner section q Deformed Hyperbolic Poschl Teller plus q Deformed Trigonometric Rosen-Morse Potential using Nikiforov-Uvarov (NU. This study aims to determine the way the angle of wave function of D-dimensional Schrodinger equation for q-Deformed Hyperbolic Poschl Teller plus q Deformed  Trigonometric Rosen-Morse Potential using Nikiforov-Uvarov (NU. 

Gamow-teller transitions: progress and problems

International Nuclear Information System (INIS)

Walter, G.

1994-01-01

The determination of the Gamow-Teller (GT) matrix elements from beta-decay and charge exchange reactions has led to a series of discoveries concerning the structure of the nucleus and the properties of spin-isospin transitions in nuclei. The study of GT distribution and strength, either by charge exchange or weak decay, provides excellent tests for nuclear models as these parameters are extremely sensitive to the details of nuclear structure. Recent improvements of these models have reduced, for the most part, differences between experiment and theory, allowing in turn a more reliable estimate of weak decay rates in stellar matter. A better understanding of the 'missing strength' and of the failure of many experiments to detect the strength that is present have also been obtained. Recently, it appears also that weak decay studies in selected region (proton or neutron rich) of the N-Z plane give access to the GT giant resonance. (J.S.). 65 refs., 10 figs

The spin symmetry for deformed generalized Poeschl-Teller potential

International Nuclear Information System (INIS)

Wei Gaofeng; Dong Shihai

2009-01-01

In the case of spin symmetry we solve the Dirac equation with scalar and vector deformed generalized Poeschl-Teller (DGPT) potential and obtain exact energy equation and spinor wave functions for s-wave bound states. We find that there are only positive energy states for bound states in the case of spin symmetry based on the strong regularity restriction condition λ<-η for the wave functions. The energy eigenvalue approaches a constant when the potential parameter α goes to zero. Two special cases such as generalized PT potential and standard PT potential are also briefly discussed.

Anomalous multi-order Raman scattering in LaMnO.sub.3./sub. a signature of quantum lattice effects in a Jahn-Teller crystal

Czech Academy of Sciences Publication Activity Database

Kovaleva, Natalia; Kusmartseva, O.E.; Kugel, K.I.; Maksimov, A.A.; Nuzhnyy, Dmitry; Balbashov, A.M.; Demikhov, E.I.; Dejneka, Alexandr; Trepakov, Vladimír; Kusmartsev, F.V.; Stoneham, A.M.

2013-01-01

Roč. 25, č. 15 (2013), s. 1-8 ISSN 0953-8984 R&D Projects: GA TA ČR TA01010517 Institutional research plan: CEZ:AV0Z10100522 Keywords : quantum lattice effects * LaMnO 3 Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.223, year: 2013

Excitations and relaxation dynamics in multiferroic GeV4S8 studied by terahertz and dielectric spectroscopy

Science.gov (United States)

Reschke, S.; Wang, Zhe; Mayr, F.; Ruff, E.; Lunkenheimer, P.; Tsurkan, V.; Loidl, A.

2017-10-01

We report on THz time-domain spectroscopy on multiferroic GeV4S8 , which undergoes orbital ordering at a Jahn-Teller transition at 30.5 K and exhibits antiferromagnetic order below 14.6 K. The THz experiments are complemented by dielectric experiments at audio and radio frequencies. We identify a low-lying excitation close to 0.5 THz, which is only weakly temperature dependent and probably corresponds to a molecular excitation within the electronic level scheme of the V4 clusters. In addition, we detect complex temperature-dependent behavior of a low-lying phononic excitation, closely linked to the onset of orbitally driven ferroelectricity. In the high-temperature cubic phase, which is paramagnetic and orbitally disordered, this excitation is of relaxational character becomes an overdamped Lorentzian mode in the orbitally ordered phase below the Jahn-Teller transition, and finally appears as well-defined phonon excitation in the antiferromagnetic state. Abrupt changes in the real and imaginary parts of the complex dielectric permittivity show that orbital ordering appears via a structural phase transition with strong first-order character and that the onset of antiferromagnetic order is accompanied by significant structural changes, which are of first-order character, too. Dielectric spectroscopy documents that at low frequencies, significant dipolar relaxations are present in the orbitally ordered, paramagnetic phase only. In contrast to the closely related GaV4S8 , this relaxation dynamics that most likely mirrors coupled orbital and polar fluctuations does not seem to be related to the dynamic processes detected in the THz regime.

Structural analysis of LaVO3 thin films under epitaxial strain

Directory of Open Access Journals (Sweden)

H. Meley

2018-04-01

Full Text Available Rare earth vanadate perovskites exhibit a phase diagram in which two different types of structural distortions coexist: the strongest, the rotation of the oxygen octahedra, comes from the small tolerance factor of the perovskite cell (t = 0.88 for LaVO3 and the smaller one comes from inter-site d-orbital interactions manifesting as a cooperative Jahn-Teller effect. Epitaxial strain acts on octahedral rotations and crystal field symmetry to alter this complex lattice-orbit coupling. In this study, LaVO3 thin film structures have been investigated by X-ray diffraction and scanning transmission electron microscopy. The analysis shows two different orientations of octahedral tilt patterns, as well as two distinct temperature behaviors, for compressive and tensile film strain states. Ab initio calculations capture the strain effect on the tilt pattern orientation in agreement with experimental data.

Gamow-Teller decay of T = 1 nuclei to odd-odd N = Z nuclei

Energy Technology Data Exchange (ETDEWEB)

Lisetskiy, A F [National Superconducting Cyclotron Laboratory, MSU, East Lansing, MI 48824 (United States); Gelberg, A [Institute for Nuclear Physics, University of Cologne, 50937 Cologne (Germany); Institute of Physical and Chemical Reasearch (RIKEN), Wako, 351-0198 (Japan); Brentano, P von [Institute for Nuclear Physics, University of Cologne, 50937 Cologne (Germany)

2005-01-01

Transition strengths of Gamow-Teller decay of T{sub z} = {+-}1 nuclei to N = Z odd-odd nuclei have been calculated in a two-nucleon approximation for spherical and deformed nuclei. The results obtained for the latter are quite close to the values obtained by full-space shell-model calculations and to the experiment.

Electronic and geometric structures of Ge{sub n}{sup -} and Ge{sub n}{sup +} (n=5-10) clusters in comparison with corresponding Si{sub n} ions

Energy Technology Data Exchange (ETDEWEB)

Li Baoxing; Cao Peilin; Song Bin; Ye Zhezhen

2003-02-10

Using full-potential linear-muffin-tin-orbital molecular-dynamics (FP-LMTO-MD) method, we have studied the geometric and electronic structures of ionic Ge{sub 5-10} clusters. Our calculations show that the ground state structures of some Ge cluster ions are different from those of their corresponding neutral Ge clusters. Furthermore, the positive Ge ions have more severe structural distortion than the negative Ge ions due to Jahn-Teller distortion. In addition, there are differences between the ground state structures of Ge ions and Si ions, although most of the Ge ions have similar geometrical configurations to their corresponding Si ions.

Gamow Teller strength from charge exchange reactions at intermediate energies

International Nuclear Information System (INIS)

Haeusser, O.

1989-07-01

Detailed studies of the spin-isospin structure of nuclear excitations are possible at TRIUMF's medium resolution spectrometer using the (n,p), ( p → , p →/ ) and (p,n) reactions. We discuss here results on isospin symmetry of inelastic nucleon scattering reactions populating isospin triads in A=6 and A=12 nuclei. The β + Gamow Teller strength function from (n,p) reactions on (sd) and (fp) shell targets is found to be substantially quenched compared to current nuclear structure models using the free-nucleon axial-vector coupling constant. (Author) 22 refs., 3 figs

Cu2+ in layered compounds: origin of the compressed geometry in the model system K2ZnF4:Cu2+.

Science.gov (United States)

Aramburu, J A; García-Lastra, J M; García-Fernández, P; Barriuso, M T; Moreno, M

2013-06-17

Many relevant properties (including superconductivity and colossal magnetoresistance) of layered materials containing Cu(2+), Ag(2+), or Mn(3+) ions are commonly related to the Jahn-Teller instability. Along this line, the properties of the CuF6(4-) complex in the K2ZnF4 layered perovskite have recently been analyzed using a parametrized Jahn-Teller model with an imposed strain [Reinen, D. Inorg. Chem.2012, 51, 4458]. Here, we present results of ab initio periodic supercell and cluster calculations on K2ZnF4:Cu(2+), showing unequivocally that the actual origin of the unusual compressed geometry of the CuF6(4-) complex along the crystal c axis in that tetragonal lattice is due to the presence of an electric field due to the crystal surrounding the impurity. Our calculations closely reproduce the experimental optical spectrum. The calculated values of the equilibrium equatorial and axial Cu(2+)-F(-) distances are, respectively, R(ax) = 193 pm and R(eq) = 204 pm, and so the calculated distortion R(ax) - R(eq) = 11 pm is three times smaller than the estimated through the parametrized Jahn-Teller model. As a salient feature, we find that if the CuF6(4-) complex would assume a perfect octahedral geometry (R(ax) = R(eq) = 203 pm) the antibonding a(1g)*(∼3z(2) - r(2)) orbital is placed above b(1g)*(∼x(2) - y(2)) with a transition energy E((2)A(1g) → (2)B(1g)) = 0.34 eV. This surprising fact stresses that about half the experimental value E((2)A(1g) → (2)B(1g)) = 0.70 eV is not due to the small shortening of the axial Cu(2+)-F(-) distance, but it comes from the electric field, E(R)(r), created by the rest of the lattice ions on the CuF6(4-) complex. This internal field, displaying tetragonal symmetry, is thus responsible for the compressed geometry in K2ZnF4:Cu(2+) and the lack of symmetry breaking behind the ligand relaxation. Moreover, we show that the electronic energy gain in this process comes from bonding orbitals and not from antibonding ones. The present

Giant Optical Polarization Rotation Induced by Spin-Orbit Coupling in Polarons

Science.gov (United States)

Casals, Blai; Cichelero, Rafael; García Fernández, Pablo; Junquera, Javier; Pesquera, David; Campoy-Quiles, Mariano; Infante, Ingrid C.; Sánchez, Florencio; Fontcuberta, Josep; Herranz, Gervasi

2016-07-01

We have uncovered a giant gyrotropic magneto-optical response for doped ferromagnetic manganite La2 /3Ca1 /3MnO3 around the near room-temperature paramagnetic-to-ferromagnetic transition. At odds with current wisdom, where this response is usually assumed to be fundamentally fixed by the electronic band structure, we point to the presence of small polarons as the driving force for this unexpected phenomenon. We explain the observed properties by the intricate interplay of mobility, Jahn-Teller effect, and spin-orbit coupling of small polarons. As magnetic polarons are ubiquitously inherent to many strongly correlated systems, our results provide an original, general pathway towards the generation of magnetic-responsive gigantic gyrotropic responses that may open novel avenues for magnetoelectric coupling beyond the conventional modulation of magnetization.

Jahn-Teller effect in van der Waals complexes; Ar-C6H6 + and Ar-C6D6 +.

NARCIS (Netherlands)

Avoird, A. van der; Lotrich, VF

2004-01-01

The two asymptotically degenerate potential energy surfaces of argon interacting with the X (2)E(1g) ground state benzene(+) cation were calculated ab initio from the interaction energy of the neutral Ar-benzene complex given by Koch et al. [J. Chem. Phys. 111, 198 (1999)] and the difference of the

Automated Biometric Voice-Based Access Control in Automatic Teller Machine (ATM)

OpenAIRE

Yekini N.A.; Itegboje A.O.; Oyeyinka I.K.; Akinwole A.K.

2012-01-01

An automatic teller machine requires a user to pass an identity test before any transaction can be granted. The current method available for access control in ATM is based on smartcard. Efforts were made to conduct an interview with structured questions among the ATM users and the result proofed that a lot of problems was associated with ATM smartcard for access control. Among the problems are; it is very difficult to prevent another person from attaining and using a legitimate persons card, ...

Isospectral Trigonometric Pöschl-Teller Potentials with Position Dependent Mass Generated by Supersymmetry

International Nuclear Information System (INIS)

Santiago-Cruz, C

2016-01-01

In this work a position dependent mass Hamiltonian with the same spectrum of the trigonometric Pöschl-Teller one was constructed by means of the underlying potential algebra. The corresponding wave functions are determined by using the factorization method. A new family of isospectral potentials are constructed by applying a Darboux transformation. An example is presented in order to illustrate the formalism. (paper)

Description of the Gamov-Teller β+-decay of tin isotopes

International Nuclear Information System (INIS)

Kuz'min, V.A.; Solov'ev, V.G.

1988-01-01

The integrated log(ft) values of Gamow-Teller β + decays of the neutron-deficient tine isotopes are calculated in the random phase approximation with particle-hole and particle-particle residual interactions which parameters have been fixed earlier. For |g A /g V |=1 and |g A /g V |=1.263 a good correspondence with the experimental data is obtained for 104,106,108 Sn and a prediction is made for 102 Sn. It is shown that one cannot define from the rate of neutron-deficient nuclei β + decay the renormalization of the axial-vector weak interaction constant g A

AES Cardless Automatic Teller Machine (ATM) Biometric Security System Design Using FPGA Implementation

Science.gov (United States)

Ahmad, Nabihah; Rifen, A. Aminurdin M.; Helmy Abd Wahab, Mohd

2016-11-01

Automated Teller Machine (ATM) is an electronic banking outlet that allows bank customers to complete a banking transactions without the aid of any bank official or teller. Several problems are associated with the use of ATM card such card cloning, card damaging, card expiring, cast skimming, cost of issuance and maintenance and accessing customer account by third parties. The aim of this project is to give a freedom to the user by changing the card to biometric security system to access the bank account using Advanced Encryption Standard (AES) algorithm. The project is implemented using Field Programmable Gate Array (FPGA) DE2-115 board with Cyclone IV device, fingerprint scanner, and Multi-Touch Liquid Crystal Display (LCD) Second Edition (MTL2) using Very High Speed Integrated Circuit Hardware (VHSIC) Description Language (VHDL). This project used 128-bits AES for recommend the device with the throughput around 19.016Gbps and utilized around 520 slices. This design offers a secure banking transaction with a low rea and high performance and very suited for restricted space environments for small amounts of RAM or ROM where either encryption or decryption is performed.

High pressure effects on a trimetallic Mn(II/III) SMM.

Science.gov (United States)

Prescimone, Alessandro; Sanchez-Benitez, Javier; Kamenev, Konstantin V; Moggach, Stephen A; Lennie, Alistair R; Warren, John E; Murrie, Mark; Parsons, Simon; Brechin, Euan K

2009-09-28

A combined study of the high pressure crystallography and high pressure magnetism of the complex [Mn3(Hcht)2(bpy)4](ClO4)3.Et2O.2MeCN (1.Et2O.2MeCN) (H3cht is cis,cis-1,3,5-cyclohexanetriol) is presented in an attempt to observe and correlate pressure induced changes in its structural and physical properties. At 0.16 GPa the complex 1.Et2O.2MeCN loses all associated solvent in the crystal lattice, becoming 1. At higher pressures structural distortions occur changing the distances between the metal centres and the bridging oxygen atoms making the magnetic exchange between the manganese ions weaker. No significant variations are observed in the Jahn-Teller axis of the only Mn(III) present in the structure. High pressure dc chiMT plots display a gradual decrease in both the low temperature value and slope. Simulations show a decrease in J with increasing pressure although the ground state is preserved. Magnetisation data do not show any change in |D|.

Condensed matter optical spectroscopy an illustrated introduction

CERN Document Server

Ionita, Iulian

2014-01-01

Molecular Symmetry and the Symmetry GroupsSymmetry Elements and Symmetry OperationsPoint Groups and Molecular SymmetrySymmetry Classification of MoleculesMatrix Representation of Symmetry TransformationGroup RepresentationsProperties of Irreducible RepresentationsTables of CharactersSymmetry of Crystals and Space GroupsRotation Groups and OperatorsExamples of SymmetryStudy QuestionsReferencesCrystal Field TheoryStates and Energies of Free Atoms and IonsOptical Spectra of Ionic CrystalsImpurities in Crystal Lattice: Splitting of Levels and Terms in Lattice SymmetryWeak Crystalline Field of Octahedral SymmetryEffect of a Weak Crystalline Field of Lower SymmetriesSplitting of Multielectron dn Configurations in the Crystalline FieldJahn-Teller EffectConstruction of Energy-Level DiagramsTanabe-Sugano DiagramsExample of the Co IonLimitations of the Crystal Field TheoryStudy QuestionsReferencesSymmetry and Molecular Orbitals TheoryMolecular OrbitalsHybridization Scheme for σ OrbitalsHybridization Scheme for π Orbi...

Matrix elements of u and p for the modified Poeschl-Teller potential

International Nuclear Information System (INIS)

Gomez-Camacho, J; Lemus, R; Arias, J M

2004-01-01

Closed analytical expressions in terms of a single sum are obtained for the matrix elements of the momentum and the natural variable u tanh(αx) in the basis of the modified Poeschl-Teller (MPT) bound eigenstates. These matrix elements are first expressed in terms of Franck-Condon factors, which thereafter are substituted for analytic expressions. Expansions of the variables p and u in terms of creation and annihilation operators associated with the MPT bound eigenfunctions are also presented

Study of the giant Gamow-Teller resonance in nuclear beta-decay

International Nuclear Information System (INIS)

Dicklage, R.D. von; Hansen, P.G.

1984-01-01

A strong effort has been devoted to the development of new target-ion-source systems at ISOLDE which would give higher yields of proton-rich nuclei. The first break-trough has been obtained for the element argon where one recently was able to produce about three orders of magnitude higher yields than in the first experiments. This makes it possible to perform experiments, involving β-delayed protons and gamma-rays, which may give information about the giant Gamow-Teller resonance. This paper gives a report on the status of these experiments

Solution of Dirac equation for modified Poschl Teller plus trigonometric Scarf potential using Romanovsky polynomials method

International Nuclear Information System (INIS)

Prastyaningrum, I.; Cari, C.; Suparmi, A.

2016-01-01

The approximation analytical solution of Dirac equation for Modified Poschl Teller plus Trigonometric Scarf Potential are investigated numerically in terms of finite Romanovsky Polynomial. The combination of two potentials are substituted into Dirac Equation then the variables are separated into radial and angular parts. The Dirac equation is solved by using Romanovsky Polynomial Method. The equation that can reduce from the second order of differential equation into the differential equation of hypergeometry type by substituted variable method. The energy spectrum is numerically solved using Matlab 2011. Where the increase in the radial quantum number nr and variable of modified Poschl Teller Potential causes the energy to decrease. The radial and the angular part of the wave function also visualized with Matlab 2011. The results show, by the disturbance of a combination between this potential can change the wave function of the radial and angular part. (paper)

Solution Of Schrödinger Equation For Poschl-Teller Plus Scarf Non-Central Potential Using Supersymmetry Quantum Mechanics Aproach

Directory of Open Access Journals (Sweden)

Antomi Saregar

2015-04-01

Full Text Available In this paper, we show that the exact energy eigenvalues and eigenfunctions of the Schrödinger equation for charged particles moving in a certain class of noncentral potentials can be easily calculated analytically in a simple and elegant manner by using Supersymmetric method (SUSYQM. We discuss the Poschl-Teller plus Scarf non-central potential systems. Then, by operating the lowering operator we get the ground state wave function, and the excited state wave functions are obtained by operating raising operator repeatedly. The energy eigenvalue is expressed in the closed form obtained using the shape invariant properties. The results are in exact agreement with other methods. Keyword: supersymmetry, non-central potentials, poschl teller plus scarf.

Isotropic Kink and Quasiparticle Excitations in the Three-Dimensional Perovskite Manganite La_{0.6}Sr_{0.4}MnO_{3}.

Science.gov (United States)

Horiba, Koji; Kitamura, Miho; Yoshimatsu, Kohei; Minohara, Makoto; Sakai, Enju; Kobayashi, Masaki; Fujimori, Atsushi; Kumigashira, Hiroshi

2016-02-19

In order to reveal the many-body interactions in three-dimensional perovskite manganites that show colossal magnetoresistance, we performed an in situ angle-resolved photoemission spectroscopy on La_{0.6}Sr_{0.4}MnO_{3} and investigated the behavior of quasiparticles. We observed quasiparticle peaks near the Fermi momentum in both the electron and the hole bands, and clear kinks throughout the entire hole Fermi surface in the band dispersion. This isotropic behavior of quasiparticles and kinks suggests that polaronic quasiparticles produced by the coupling of electrons with Jahn-Teller phonons play an important role in the colossal magnetoresistance properties of the ferromagnetic metallic phase of three-dimensional manganites.

Manifestation of spin selection rules on the quantum tunneling of magnetization in a single-molecule magnet.

Science.gov (United States)

Henderson, J J; Koo, C; Feng, P L; del Barco, E; Hill, S; Tupitsyn, I S; Stamp, P C E; Hendrickson, D N

2009-07-03

We present low temperature magnetometry measurements on a new Mn3 single-molecule magnet in which the quantum tunneling of magnetization (QTM) displays clear evidence for quantum mechanical selection rules. A QTM resonance appearing only at high temperatures demonstrates tunneling between excited states with spin projections differing by a multiple of three. This is dictated by the C3 molecular symmetry, which forbids pure tunneling from the lowest metastable state. Transverse field resonances are understood by correctly orienting the Jahn-Teller axes of the individual manganese ions and including transverse dipolar fields. These factors are likely to be important for QTM in all single-molecule magnets.

Distribution of the ligand field at the Fe2+ ion in frozen aqueous solutions of Fe(ClO4)2

International Nuclear Information System (INIS)

Nagy, D.L.; Horvath, D.; Szuecs, I.S.; Spiering, H.

1981-01-01

Moessbauer spectra of eutectic frozen aqueous solutions of Fe(ClO 4 ) 2 have been measured at 4.2 K in applied longitudinal magnetic fields up to 5 T. The spectra are interpreted in terms of a model accounting for the random distribution of the ligand field at the Fe 2+ ion owing to the amorphity of the environment. The equilibrium state of the Fe(H 2 O) 6 2+ complex is determined by a static Jahn-Teller calculation. The main features of all spectra can be well reproduced by choosing Esub(JT)(tau)=140 cm -1 and ωsub(tau)=150 cm -1 . (author)

A quantum mechanical study of La-doped Pb(Zr,Ti)O{sub 3}

Energy Technology Data Exchange (ETDEWEB)

Stashans, Arvids [Grupo de Fisica de Cristales, Escuela de Electronica y Telecomunicaciones, Universidad Tecnica Particular de Loja, Apartado 11-01-608, Loja (Ecuador)]. E-mail: arvids@utpl.edu.ec; Maldonado, Frank [Grupo de Fisica de Cristales, Escuela de Electronica y Telecomunicaciones, Universidad Tecnica Particular de Loja, Apartado 11-01-608, Loja (Ecuador)

2007-04-15

Lanthanum-modified Pb(Zr,Ti)O{sub 3} (PZT) crystals have been investigated applying a quantum-mechanical approach based on the Hartree-Fock theory. A morphotropic phase boundary (MPB), PbZr{sub 0.53}Ti{sub 0.47}O{sub 3}, of the crystal was considered throughout the study. The obtained results show the outward atomic displacements with respect to the La impurity within the defective region and also the increase of covalent nature in the chemical bonding of the material. These outcomes are discussed and analyzed in light of the available experimental data. The occurrence of Jahn-Teller self-trapped electron polarons is predicted in the present report.

A quantum mechanical study of La-doped Pb(Zr,Ti)O3

International Nuclear Information System (INIS)

Stashans, Arvids; Maldonado, Frank

2007-01-01

Lanthanum-modified Pb(Zr,Ti)O 3 (PZT) crystals have been investigated applying a quantum-mechanical approach based on the Hartree-Fock theory. A morphotropic phase boundary (MPB), PbZr 0.53 Ti 0.47 O 3 , of the crystal was considered throughout the study. The obtained results show the outward atomic displacements with respect to the La impurity within the defective region and also the increase of covalent nature in the chemical bonding of the material. These outcomes are discussed and analyzed in light of the available experimental data. The occurrence of Jahn-Teller self-trapped electron polarons is predicted in the present report

A crossover in anisotropic nanomechanochemistry of van der Waals crystals

International Nuclear Information System (INIS)

Shimamura, Kohei; Misawa, Masaaki; Li, Ying; Kalia, Rajiv K.; Nakano, Aiichiro; Vashishta, Priya; Shimojo, Fuyuki

2015-01-01

In nanoscale mechanochemistry, mechanical forces selectively break covalent bonds to essentially control chemical reactions. An archetype is anisotropic detonation of layered energetic molecular crystals bonded by van der Waals (vdW) interactions. Here, quantum molecular dynamics simulations reveal a crossover of anisotropic nanomechanochemistry of vdW crystal. Within 10 −13 s from the passage of shock front, lateral collision produces NO 2 via twisting and bending of nitro-groups and the resulting inverse Jahn-Teller effect, which is mediated by strong intra-layer hydrogen bonds. Subsequently, as we transition from heterogeneous to homogeneous mechanochemical regimes around 10 −12 s, shock normal to multilayers becomes more reactive, producing H 2 O assisted by inter-layer N-N bond formation. These time-resolved results provide much needed atomistic understanding of nanomechanochemistry that underlies a wider range of technologies

Experimental elucidation: microscopic mechanism of resonant X-ray scattering in manganite films

CERN Document Server

Ohsumi, H; Kiyama, T

2003-01-01

Resonant X-ray scattering experiments have been performed on perovskite manganite La sub 0 sub . sub 5 Sr sub 0 sub . sub 5 MnO sub 3 thin films, which are grown on three distinct perovskite with a coherent epitaxial strain and have a forced ferro-type orbital ordering of Mn 3d orbitals. Using an interference technique, we have successfully observed the resonant X-ray scattering signal from the system having the ferro-type orbital ordering and also revealed the energy scheme of Mn 4p bands. For the forced ferro-type orbital ordering system, the present results evidence that the resonant X-ray scattering signal originates from the band structure effect due to the Jahn-Teller distortion of a MnO sub 6 octahedron, and not from the Coulomb interaction between 3d and 4p electrons. (author)

A crossover in anisotropic nanomechanochemistry of van der Waals crystals

Energy Technology Data Exchange (ETDEWEB)

Shimamura, Kohei [Department of Physics, Kumamoto University, Kumamoto 860-8555 (Japan); Collaboratory for Advanced Computing and Simulations, Department of Physics and Astronomy, Department of Computer Science, Department of Chemical Engineering and Materials Science, University of Southern California, Los Angeles, California 90089-0242 (United States); Graduate School of System Informatics, Kobe University, Kobe 657-8501 (Japan); Misawa, Masaaki [Department of Physics, Kumamoto University, Kumamoto 860-8555 (Japan); Collaboratory for Advanced Computing and Simulations, Department of Physics and Astronomy, Department of Computer Science, Department of Chemical Engineering and Materials Science, University of Southern California, Los Angeles, California 90089-0242 (United States); Li, Ying [Argonne Leadership Computing Facility, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Kalia, Rajiv K.; Nakano, Aiichiro; Vashishta, Priya [Collaboratory for Advanced Computing and Simulations, Department of Physics and Astronomy, Department of Computer Science, Department of Chemical Engineering and Materials Science, University of Southern California, Los Angeles, California 90089-0242 (United States); Shimojo, Fuyuki [Department of Physics, Kumamoto University, Kumamoto 860-8555 (Japan)

2015-12-07

In nanoscale mechanochemistry, mechanical forces selectively break covalent bonds to essentially control chemical reactions. An archetype is anisotropic detonation of layered energetic molecular crystals bonded by van der Waals (vdW) interactions. Here, quantum molecular dynamics simulations reveal a crossover of anisotropic nanomechanochemistry of vdW crystal. Within 10{sup −13} s from the passage of shock front, lateral collision produces NO{sub 2} via twisting and bending of nitro-groups and the resulting inverse Jahn-Teller effect, which is mediated by strong intra-layer hydrogen bonds. Subsequently, as we transition from heterogeneous to homogeneous mechanochemical regimes around 10{sup −12} s, shock normal to multilayers becomes more reactive, producing H{sub 2}O assisted by inter-layer N-N bond formation. These time-resolved results provide much needed atomistic understanding of nanomechanochemistry that underlies a wider range of technologies.

Ultrafast optically induced ferromagnetic/anti-ferromagnetic phase transition in GdTiO3 from first principles

Science.gov (United States)

Khalsa, Guru; Benedek, Nicole A.

2018-03-01

Epitaxial strain and chemical substitution have been the workhorses of functional materials design. These static techniques have shown immense success in controlling properties in complex oxides through the tuning of subtle structural distortions. Recently, an approach based on the excitation of an infrared active phonon with intense midinfrared light has created an opportunity for dynamical control of structure through special nonlinear coupling to Raman phonons. We use first-principles techniques to show that this approach can dynamically induce a magnetic phase transition from the ferromagnetic ground state to a hidden antiferromagnetic phase in the rare earth titanate GdTiO3 for realistic experimental parameters. We show that a combination of a Jahn-Teller distortion, Gd displacement, and infrared phonon motion dominate this phase transition with little effect from the octahedral rotations, contrary to conventional wisdom.

An Inventory-Routing Problem with Pickups and Deliveries Arising in the Replenishment of Automated Teller Machines

NARCIS (Netherlands)

van Anholt, Roel G.; Coelho, Leandro C.; Laporte, Gilbert; Vis, Iris F. A.

The purpose of this paper is to introduce, model, and solve a rich multiperiod inventory-routing problem with pickups and deliveries motivated by the replenishment of automated teller machines in the Netherlands. Commodities can be brought to and from the depot, as well as being exchanged among

An inventory-routing problem with pickups and deliveries arising in the replenishment of automated teller machines

NARCIS (Netherlands)

Van Anholt, Roel G.; Coelho, Leandro C.; Laporte, Gilbert; Vis, Iris F.A.

2016-01-01

The purpose of this paper is to introduce, model, and solve a rich multiperiod inventory-routing problem with pickups and deliveries motivated by the replenishment of automated teller machines in the Netherlands. Commodities can be brought to and from the depot, as well as being exchanged among

Characteristics of the Gamow-Teller Force in the β- Decay of 40Zr98

International Nuclear Information System (INIS)

Raden Oktova

2002-01-01

The characteristics of the β - decay force for the Gamow-Teller transition in the p-h and the p-p channels in the heavy neutron-rich nucleus 40 Zr 98 have been studied. The ground state single-particle levels in the parent nucleus were calculated self-consistently using the Fayans energy-density functional, and from them the quasi-particle basis was obtained using the BCS model. The residual charge-changing force responsible for the β - transition was taken as having a zero-range (a delta function); in the p-h channel the spin-isospin exchange → σ 1 . → σ 2 → τ 1 . → τ 2 term in the Migdal-Larkin force was used, and that in the p-p channel was a constant. The method employed was the proton-neutron QRPA (pnQRPA). The results show that the proton-neutron pairing p-p force in the Gamow-Teller decay is negligible for the nucleus considered. The value of the p-h force obtained is g ' = 0.735, slightly larger than the standard value of g ' = 0.7 commonly used for stable nuclei. (author)

Pseudo Jahn–Teller origin of ferroelectric instability in BaTiO{sub 3} type perovskites: The Green's function approach and beyond

Energy Technology Data Exchange (ETDEWEB)

Polinger, V., E-mail: polinv@uw.edu [Department of Physics, University of Washington, Seattle, WA 98195-1560 (United States); Garcia-Fernandez, P. [Ciencias de la Tierra y Física de la Materia Condensada, Universidad de Cantabria, Avenida de los Castros s/n, E-39005 Santander (Spain); Bersuker, I.B. [Department of Chemistry and Biochemistry, The University of Texas at Austin, Austin, TX 78712-0165 (United States)

2015-01-15

The local origin of dipolar distortions in ABO{sub 3} perovskite crystals is reexamined by means of a novel approach, the Green's function method augmented by DFT computations. The ferroelectric distortions are shown to be induced by the pseudo Jahn–Teller effect (PJTE). The latter involves vibronic hybridization (admixture) of the ground state to same-spin opposite-parity excited electronic bands. Similar to numerous molecular calculations, the PJT approach provides a deeper insight into the nature of chemical bonding in the octahedral cluster [BO{sub 6}] and, in particular, reveals the local origin of its polar instability. This allows predicting directly which transition ions can create ferroelectricity. In particular, the necessary conditions are established when an ABO{sub 3} perovskite crystal with an electronic d{sup n} configuration of the complex ion [BO{sub 6}] can possess both proper ferroelectric and magnetic properties. Distinguished from the variety of cluster approaches to local properties, the Green's function method includes the influence of the local vibronic-coupling perturbation on the whole crystal via the inter-cell interaction responsible for creation of electronic and vibrational bands. Calculated Green's functions combined with the corresponding numeric estimates for the nine electronic bands, their density of states, and the local adiabatic potential energy surface (APES) confirm the eight-minimum form of this surface and feasibility of the PJT origin of the polar instability in BaTiO{sub 3}. We show also that multicenter long-range dipole–dipole interactions critically depend on the PJTE largely determining the magnitude of the local dipoles. DFT calculations for the bulk crystal and its clusters confirm that the dipolar distortions are of local origin, but become possible only when their influence on (relaxation of) the whole lattice is taken into account. The results are shown to be in full qualitative and

Quenching of the Gamow-Teller matrix element in closed LS-shell-plus-one nuclei

International Nuclear Information System (INIS)

Towner, I.S.

1989-06-01

It is evident that nuclear Gamow-Teller matrix elements determined from β-decay and charge-exchange reactions are significantly quenched compared to simple shell-model estimates based on one-body operators and free-nucleon coupling constants. Here we discuss the theoretical origins of this quenching giving examples from light nuclei near LS-closed shells, such as 16 0 and 40 Ca. (Author) 12 refs., 2 tabs

The beta-decay of 48Mn: improved data on Gamow-Teller quenching

International Nuclear Information System (INIS)

Szerypo, J.; Bazin, D.; Brown, B.A.

1991-01-01

Beta-decay studies of very proton-rich nuclides allow to investigate the phenomenon of quenching of Gamow-Teller transitions. A presentation of the experimental techniques is followed by the discussion of preliminray results of the measurements in comparison to shell-model calculations. A corresponding reinvestigation is discussed. A mass-separated 48 Mn beam was used from 12 C( 40 Ca,p3n) reactions. The 48 Mn decay spectroscopy was performed simultaneously in two beam lines of the mass separator. (G.P.) 13 refs.; 2 figs

Atomic-scale understanding of non-stoichiometry effects on the electrochemical performance of Ni-rich cathode materials

Science.gov (United States)

Kong, Fantai; Liang, Chaoping; Longo, Roberto C.; Zheng, Yongping; Cho, Kyeongjae

2018-02-01

As the next-generation high energy capacity cathode materials for Li-ion batteries, Ni-rich oxides face the problem of obtaining near-stoichiometric phases due to excessive Ni occupying Li sites. These extra-Ni-defects drastically affect the electrochemical performance. Despite of its importance, the fundamental correlation between such defects and the key electrochemical properties is still poorly understood. In this work, using density-functional-theory, we report a comprehensive study on the effects of non-stoichiometric phases on properties of Ni-rich layered oxides. For instance, extra-Ni-defects trigger charge disproportionation reaction within the system, alleviating the Jahn-Teller distortion of Ni3+ ions, which constitutes an important reason for their low formation energies. Kinetic studies of these defects reveal their immobile nature, creating a "pillar effect" that increases the structural stability. Ab initio molecular dynamics revealed Li depletion regions surrounding extra-Ni-defects, which are ultimate responsible for the arduous Li diffusion and re-intercalation, resulting in poor rate performance and initial capacity loss. Finally, the method with combination of high valence cation doping and ion-exchange synthesis is regarded as the most promising way to obtain stoichiometric oxides. Overall, this work not only deepens our understanding of non-stoichiometric Ni-rich layered oxides, but also enables further optimizations of high energy density cathode materials.

Gamow-Teller strength in the continuum studied via the (p,n) reaction

International Nuclear Information System (INIS)

Wakasa, T.; Hatanaka, K.; Sakai, H.

2002-01-01

The double differential cross sections for θ lab between 0.0deg and 14.7deg and the polarization transfer coefficient D NN (0deg) for the 27 Al (p vector, n vector) reaction have been measured at a bombarding energy of 295 MeV. A multipole decomposition technique is applied for the cross section data to extract L=0, 1, 2, and 3 contributions. The Gamow-Teller (GT) strength B(GT) deduced from the L=0 contribution is compared with the B(GT) values calculated in a full sd shell-model space. The sum of B(GT) values up to 20 MeV excitation is S β- =4.0 ± 0.1 ± 0.1. A fairly large L=0 contribution is observed in the continuum region up to 50 MeV, which could be in part ascribed to the quenched GT strength. A limit on the effect that the Δ(1232)-isobar nucleon-hole admixture has upon the GT strength is estimated. (author)

Isospin symmetry of T-z=+/- 3/2 ->+/- 1/2 Gamow-Teller transitions in A=41 nuclei

NARCIS (Netherlands)

Fujita, Y; Shimbara, Y; Adachi, T; Berg, GPA; Fujita, H; Hatanaka, K; Kamiya, J; Nakanishi, K; Sakemi, Y; Sasaki, S; Shimizu, Y; Tameshige, Y; Uchida, M; Wakasa, T; Yosoi, M

2004-01-01

Under the assumption that isospin T is a good quantum number, isobaric analog states and various analogous transitions are expected in isobars with mass number A. The, strengths of T-z = +/-3/2 --> 1/2 analogous Gamow-Teller (GT) transitions and analogous M1 transitions within the A = 41 isobar

Isospin symmetry of T-z=+/- 3/2 ->+/- 1/2 Gamow-Teller transitions in A=41 nuclei

NARCIS (Netherlands)

Fujita, Y; Shimbara, Y; Adachi, T; Berg, GPA; Fujita, H; Hatanaka, K; Kamiya, J; Nakanishi, K; Sakemi, Y; Sasaki, S; Shimizu, Y; Tameshige, Y; Uchida, M; Wakasa, T; Yosoi, M

Under the assumption that isospin T is a good quantum number, isobaric analog states and various analogous transitions are expected in isobars with mass number A. The, strengths of T-z = +/-3/2 --> 1/2 analogous Gamow-Teller (GT) transitions and analogous M1 transitions within the A = 41 isobar

Frequency effects on charge ordering in Y{sub 0.5}Ca{sub 0.5}MnO{sub 3} by impedance spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Sarwar, Tuba, E-mail: sarwartuba@gmail.com [EMMG, Physics Division, PINSTECH, P. O. Nilore, Islamabad (Pakistan); DPAM, PIEAS, P. O. Nilore, Islamabad (Pakistan); Qamar, Afzaal [Queensland Micro-Nanotechnology Centre, Griffith University, Nathan, QLD 4111 (Australia); Nadeem, Muhammad [EMMG, Physics Division, PINSTECH, P. O. Nilore, Islamabad (Pakistan)

2015-02-01

In this work, structural and electrical properties of Y{sub 0.5}Ca{sub 0.5}MnO{sub 3} are investigated by employing X-ray diffraction and impedance spectroscopy, respectively. Applied ac electric field showed the charge ordering transition temperature around 265 K and below this temperature the heteromorphic behavior of the sample is discussed in the proximity of T{sub CO}. With frequency effects the volume of robust charge orbital ordering (COO) domains diminishes due to different competing phases along with Jahn Teller distortions. Comprehensive melting and collapse of charge orbital ordering occurs below T{sub N}(125 K), where a colossal drop in the value of impedance is observed. The change in profile of modulus plane plots determines the spreading of relaxation time of intermingled phases. Hopping mechanism is elaborated in terms of strong electron phonon coupling. Variable range hopping model and Arrhenius model are used to discuss the short and long range hopping between Mn{sup 3+} and Mn{sup 4+} channels assessing the activation energy E{sub a}. - Highlights: • Present study contains a detailed investigation over the electrical and structural properties of Y{sub 0.5}Ca{sub 0.5}MnO{sub 3} especially its behavior across the charge ordering transition. • Impedance measurements illustrate the comprehensive melting and collapse of robust charge orbital ordering with colossal drop in impedance. • In T{sub N}Teller distortions badly frustrating the spins of manganese. • Modulus plane plots determine the spreading of relaxation time of intermingled phases indicating the contribution of grain boundary and grain interior. • Variable range hopping model and Arrhenius model are used to discuss the short and long range hopping between Mn{sup 3+} and Mn{sup 4+} channels assessing the activation energy E{sub a}.

Influence of electric field, hydrostatic pressure and temperature on the electric state in a Poschl-Teller quantum well

International Nuclear Information System (INIS)

Hakimyfard, A.; Barseghyan, M.G.; Kirakosyan, A.A.; Duque, C.A.

2010-01-01

Influence of the electric field and hydrostatic pressure on the electronic states in a Poschl-Teller quantum well is studied. In the framework of variational method the dependences of the ground state energy on the electric field and hydrostatic pressure are calculated for different values of the potential parameters and the temperature. It is shown that the increase in the electric field leads to the increase in the ground state energy, while the increase in the well width leads to the strengthening of the electric field effect. The ground state energy decreases with increasing pressure and increases with increasing temperature

Study of the motion of electrons in non polar classical liquids. Measurement of Hall effect and f.i.r. search for low energy traps. Progress report

International Nuclear Information System (INIS)

1981-01-01

Progress is reported on experiments aimed at the measurement of the Hall mobility of injected electrons in classical non polar insulating liquids and the optical absorption associated with electrons captured by shallow traps in the liquefied rare gases. Theoretical work aimed at a better understanding of the trapping kinetics of electrons by SF 6 and O 2 dissolved in rare gas liquids was also carried out. Its conclusion is that the electric field dependence of the trapping probability can be explained, basically without adjustable parameters, by considering the Poole-Frenkel-Schotky ionization of the excited state of the traps. From the analysis of published data on the motion of electrons in liquid ethane it is tentatively concluded that at low temperatures the trapping of electrons in the liquid involves a Jahn-Teller like distortion of a single ethane molecule while at higher temperatures it is necessary to consider a small molecular cluster, possibly made up of 2 molecules

High resolution photoemission study of Nd1-xSrxMnO3

International Nuclear Information System (INIS)

Togashi, T.; Osawa, H.; Shin, S.; Tanaka, K.; Isozumi, Y.; Iwazumi, T.; Nozawa, S.

2004-01-01

Full text:Nd 1-x SrxMnO 3 shows the negative colossal magnetoresistance and various electronic phases. In order to reveal their states, we have performed a high- resolution Mn 2p-3d resonance photoemission (RPES) study of Nd 1-x SrxMnO 3 with an energy resolution of 100 meV at BL25SU in SPring-8. Figure 1 shows the Mn 2p-3d RPES spectra of Nd 1-x SrxMnO 3 . It is found that the spectral line shape in the ground-state phases (GS) at low temperatures is closely related to the shape of MnO 6 octahedra depending on x due to a static Jahn- Teller (JT) effect while the line shape in the paramagnetic insulator (PI) phase near room temperature is qualitatively similar to each other irrespective of x. These results strongly suggest that the dynamical and static JT effects are responsible for the 3d electronic states at high and low temperatures, respectively

On metal-insulator transition in cubic fullerides

Science.gov (United States)

Iwahara, Naoya; Chibotaru, Liviu

The interplay between degenerate orbital and electron correlation is a key to characterize the electronic phases in, for example, transition metal compounds and alkali-doped fullerides. Besides, the degenerate orbital couples to spin and lattice degrees of freedom ,giving rise to exotic phenomena. Here, we develop the self-consistent Gutzwiller approach for the simultaneous treatment of the Jahn-Teller effect and electron correlation, and apply the methodology to reveal the nature of the ground electronic state of fullerides. For small Coulomb repulsion on site U, the fulleride is quasi degenerate correlated metal. With increase of U, we found the quantum phase transition from the metallic phase to JT split phase. In the latter, the Mott transition (MT) mainly develops in the half-filled subband, whereas the empty and the completely filled subbands are almost uninvolved. Therefore, we can qualify the metal-insulator transition in fullerides as an orbital selective MT induced by JT effect.

Corrections to the free-nucleon values of the single-particle matrix elements of the M1 and Gamow-Teller operators, from a comparison of shell-model predictions with sd-shell data

International Nuclear Information System (INIS)

Brown, B.A.; Wildenthal, B.H.

1983-01-01

The magnetic dipole moments of states in mirror pairs of the sd-shell nuclei and the strengths of the Gamow-Teller beta decays which connect them are compared with predictions based on mixed-configuration shell-model wave functions. From this analysis we extract the average effective values of the single-particle matrix elements of the l, s, and [Y/sup( 2 )xs]/sup( 1 ) components of the M1 and Gamow-Teller operators acting on nucleons in the 0d/sub 5/2/, 1s/sub 1/2/, and 0d/sub 3/2/ orbits. These results are compared with the recent calculations by Towner and Khanna of the corrections to the free-nucleon values of these matrix elements which arise from the effects of isobar currents, mesonic-exchange currents, and mixing with configurations outside the sd shell

Gamow-Teller strength functions from N-nucleus scattering experiments at 200-400 MeV

International Nuclear Information System (INIS)

Haeusser, O.; British Columbia Univ., Vancouver; Vetterli, M.C.

1988-01-01

Recent measurements of (n,p), (p vector, p vector') and (p,n) reactions at TRIUMF have made possible a detailed examination of the spin-isospin structure of nuclear excitations up to 50 MeV. Cross sections for 54 Fe(n,p) 54 Mn and spin-flip cross sections for 54 Fe (p vector, p vector') near 300 MeV have been used to estimate the nuclear response for different multipoles L, spin transfers (ΔS = 0,1), and isospins of the residual nucleus (T f = 1,2). Qualitative features of the spin-flip probabilities in (p vector, p vector') are in good agreement with recent surface-RPA calculations. Between 200 and 400 MeV the ΔL=0 spin-flip isovector component is well described by the central part V στ of the Franey-Love interaction. The Gamow-Teller strength S + in 54 Fe, which is of significance in models of pre-collapse supernovae, is found to be smaller by a factor of two than the best available shell model calculations. In (sd)-shell nuclei ( 24,26 Mg, 28 Si) about (70±15)% of the Gamow-Teller strength predicted by untruncated shell-model calculations is found at low excitation. (orig.)

New perovskite-based manganite Pb2Mn2O5

International Nuclear Information System (INIS)

Hadermann, Joke; Abakumov, Artem M.; Perkisas, Tyche; D'Hondt, Hans; Tan Haiyan; Verbeeck, Johan; Filonenko, Vladimir P.; Antipov, Evgeny V.; Van Tendeloo, Gustaaf

2010-01-01

A new perovskite based compound Pb 2 Mn 2 O 5 has been synthesized using a high pressure high temperature technique. The structure model of Pb 2 Mn 2 O 5 is proposed based on electron diffraction, high angle annular dark field scanning transmission electron microscopy and high resolution transmission electron microscopy. The compound crystallizes in an orthorhombic unit cell with parameters a=5.736(1) A∼√2a p , b=3.800(1) A∼a p , c=21.562(6) A∼4√2a p (a p -the parameter of the perovskite subcell) and space group Pnma. The Pb 2 Mn 2 O 5 structure consists of quasi two-dimensional perovskite blocks separated by 1/2[110] p (101) p crystallographic shear planes. The blocks are connected to each other by chains of edge-sharing MnO 5 distorted tetragonal pyramids. The chains of MnO 5 pyramids and the MnO 6 octahedra of the perovskite blocks delimit six-sided tunnels accommodating double chains of Pb atoms. The tunnels and pyramidal chains adopt two mirror-related configurations ('left' L and 'right' R) and layers consisting of chains and tunnels of the same configuration alternate in the structure according to an -L-R-L-R-sequence. The sequence is sometimes locally violated by the appearance of -L-L- or -R-R-fragments. A scheme is proposed with a Jahn-Teller distortion of the MnO 6 octahedra with two long and two short bonds lying in the a-c plane, along two perpendicular orientations within this plane, forming a d-type pattern. - Graphical abstract: Order of the Jahn-Teller distorted MnO 6 octahedra in Pb 2 Mn 2 O 5 . Two long and two short bonds lie in the a-c plane, along two perpendicular orientations within this plane, forming a d-type pattern.

QRPA estimate for the Δ(1232) cotribution to the Gamow-Teller decay of heavy nuclei

International Nuclear Information System (INIS)

Suhonen, J.

1991-01-01

The contribution of the Δ(1232) isobars to the nuclear beta decay strength function is estimated in the framework of the charge-changing form of the QRPA. This procedure is applied to neutron-deficient tin isotopes. The results imply that the quenching of the low-energy Gamow-Teller decay strength cannot attributed to the presence of delta admixtures in the nuclear wave function. (orig.)

Magnetic phase transition in layered inorganic-organic hybrid (C12H25NH3)2CuCl4

Science.gov (United States)

Bochalya, Madhu; Kumar, Sunil; Kanaujia, Pawan K.; Prakash, G. Vijaya

2018-05-01

Inorganic-organic (IO) hybrids are material systems which have become an interesting theme of research for physicist and chemists recently due to the possibility of engineering specific magnetic, thermal or optoelectronic properties by playing around with the transition metal, halides and the organic components. Our experiments on (C12H25NH3)2CuCl4 show that the system exhibits a long range ferromagnetic order below ˜11 K. In such an inorganic-organic hybrid system, Jahn-Teller distortion of the copper ions results into a weak ferromagnetic order as compared to the antiferromagnetic spin-spin exchange in the pure inorganic CuCl2 compound. Moreover, this particular hybrid system also exhibits photoluminescence when excited below absorption maximum related to charge transfer peak though the effect is much weaker as compared to that in extensively studied other MX4-based (M = Sn, Pb; X = Cl, Br, I) counterparts.

Olivine-type cathodes. Achievements and problems

Science.gov (United States)

Yamada, Atsuo; Hosoya, Mamoru; Chung, Sai-Cheong; Kudo, Yoshihiro; Hinokuma, Koichiro; Liu, Kuang-Yu; Nishi, Yoshio

The recent progress at Sony in the design of practical olivine-type cathodes is reviewed briefly. First principle calculations revealed LiFePO 4 is a semiconductor with ca. 0.3 eV band gap and LiMnPO 4 is an insulator with ca. 2 eV band gap, which seems the major intrinsic obstacle to a smooth redox reaction at 4 V in the Mn-rich phase. Attention is also focused on the lattice frustration induced by the strong electron (Mn 3+: 3d 4-e gσ ∗)-lattice interaction (Jahn-Teller effect) in the charged state of Li(Mn yFe 1- y)PO 4 (0≤ y≤1). Dense nanocomposite formation with disordered conductive carbon as well as the choice of the appropriate synthetic precursors is highlighted as important engineering aspects, followed by some specific issues concerning tolerance to unusual conditions.

Vibronic interactions proceeding from combined analytical and numerical considerations: Covalent functionalization of graphene by benzene, distortions, electronic transitions

Energy Technology Data Exchange (ETDEWEB)

Krasnenko, V.; Boltrushko, V.; Hizhnyakov, V. [Institute of Physics, University of Tartu, W. Ostwaldi Str 1, 50411 Tartu (Estonia)

2016-04-07

Chemically bound states of benzene molecules with graphene are studied both analytically and numerically. The states are formed by switching off intrabonds of π-electrons in C{sub 6} rings to interbonds. A number of different undistorted and distorted structures are established both with aligned and with transversal mutual orientation of benzene and graphene. The vibronic interactions causing distortions of bound states are found, by using a combination of analytical and numerical considerations. This allows one to determine all electronic transitions of π-electrons without explicit numerical calculations of excited states, to find the conical intersections of potentials, and to show that the mechanism of distortions is the pseudo-Jahn-Teller effect. It is found that the aligned distorted benzene molecule placed between two graphene sheets makes a chemical bond with both of them, which may be used for fastening of graphene sheets together.

DFT calculations of the structures and vibrational spectra of the [Fe(bpy)3]2+ and [Ru(bpy)3]2+ complexes

International Nuclear Information System (INIS)

Alexander, Bruce D.; Dines, Trevor J.; Longhurst, Rayne W.

2008-01-01

Structures of the [M(bpy) 3 ] 2+ complexes (M = Fe and Ru) have been calculated at the B3-LYP/DZVP level. IR and Raman spectra were calculated using the optimised geometries, employing a scaled quantum chemical force field, and compared with an earlier normal coordinate analysis of [Ru(bpy) 3 ] 2+ which was based upon experimental data alone, and the use of a simplified model. The results of the calculations provide a highly satisfactory fit to the experimental data and the normal coordinate analyses, in terms of potential energy distributions, allow a detailed understanding of the vibrational spectra of both complexes. Evidence is presented for Jahn-Teller distortion in the 1 E MLCT excited state

DFT calculations of the structures and vibrational spectra of the [Fe(bpy) 3] 2+ and [Ru(bpy) 3] 2+ complexes

Science.gov (United States)

Alexander, Bruce D.; Dines, Trevor J.; Longhurst, Rayne W.

2008-09-01

Structures of the [M(bpy) 3] 2+ complexes (M = Fe and Ru) have been calculated at the B3-LYP/DZVP level. IR and Raman spectra were calculated using the optimised geometries, employing a scaled quantum chemical force field, and compared with an earlier normal coordinate analysis of [Ru(bpy) 3] 2+ which was based upon experimental data alone, and the use of a simplified model. The results of the calculations provide a highly satisfactory fit to the experimental data and the normal coordinate analyses, in terms of potential energy distributions, allow a detailed understanding of the vibrational spectra of both complexes. Evidence is presented for Jahn-Teller distortion in the 1E MLCT excited state.

Uniaxial pressure-induced half-metallic ferromagnetic phase transition in LaMnO3

Science.gov (United States)

Rivero, Pablo; Meunier, Vincent; Shelton, William

2016-03-01

We use first-principles theory to predict that the application of uniaxial compressive strain leads to a transition from an antiferromagnetic insulator to a ferromagnetic half-metal phase in LaMnO3. We identify the Q2 Jahn-Teller mode as the primary mechanism that drives the transition, indicating that this mode can be used to tune the lattice, charge, and spin coupling. Applying ≃6 GPa of uniaxial pressure along the [010] direction activates the transition to a half-metallic pseudocubic state. The half-metallicity opens the possibility of producing colossal magnetoresistance in the stoichiometric LaMnO3 compound at significantly lower pressure compared to recently observed investigations using hydrostatic pressure.

Conformal scalar field on the hyperelliptic curve and critical Ashkin-Teller multipoint correlation functions

International Nuclear Information System (INIS)

Zamolodchikov, A.B.

1987-01-01

A multipoint conformal block of Ramond states of the two-dimensional free scalar field is calculated. This function is related to the free energy of the scalar field on the hyperelliptic Riemann surface under a particular choice of boundary conditions. Being compactified on the circle this field leads to the crossing symmetric correlation functions with a discrete spectrum of scale dimensions. These functions are supposed to describe multipoint spin correlations of the critical Ashkin-Teller model. (orig.)

Pseudo Jahn–Teller effect in distortion and restoration of planar configurations of tetra-heterocyclic 1,2-diazetes C{sub 2}N{sub 2}E{sub 4}, E = H, F, Cl, Br

Energy Technology Data Exchange (ETDEWEB)

Ilkhani, Ali R. [Institute for Theoretical Chemistry, University of Texas at Austin, Austin, TX 78712 (United States); Department of Chemistry, Yazd Branch, Islamic Azad University, Yazd (Iran, Islamic Republic of); Gorinchoy, Natalia N. [Institute of Chemistry, Academy of Sciences of Moldova, Chisinau, Republic of Moldova (Moldova, Republic of); Bersuker, Isaac B., E-mail: bersuker@cm.utexas.edu [Institute for Theoretical Chemistry, University of Texas at Austin, Austin, TX 78712 (United States); Institute of Chemistry, Academy of Sciences of Moldova, Chisinau, Republic of Moldova (Moldova, Republic of)

2015-10-16

Highlights: • The pseudo Jahn–Teller mechanism of puckering of tetracyclic 1,2-diazetes is revealed. • Vibronic constants are extracted from ab initio calculations versus PJTE equations. • Methods of restoring the planar configuration by external perturbations are suggested. - Abstract: The pseudo Jahn–Teller effect (PJTE) is employed to explain the origin of the puckered structures of tetra-heterocyclic 1,2-diazetes, C{sub 2}N{sub 2}E{sub 4}, E = H, F, Cl, Br, and to reveal the conditions of restoration of their planar configuration. The high-symmetry C{sub 2v} planar configuration of all these compounds is unstable with respect to puckering, a{sub 2}-type distortions produced by the PJT coupling between their ground {sup 1}A{sub 1} and excited {sup 1}A{sub 2} electronic states. The PJTE coupling constants are estimated by fitting ab initio calculated energy profiles to the formulas of the vibronic coupling problem (A{sub 1} + A{sub 2}) ⊗ a{sub 2}. The conditions for the restoration of the planar configurations of the C{sub 2}N{sub 2}E{sub 4} cycles were revealed: the PJTE can be quenched by removing the outer two electrons, e.g. by producing a “triple-decker sandwich” structure with two electron acceptors on both sides of the neutral cycle.

Spin and Pseudospin Symmetries with Trigonometric Pöschl-Teller Potential including Tensor Coupling

Directory of Open Access Journals (Sweden)

M. Hamzavi

2013-01-01

Full Text Available We study approximate analytical solutions of the Dirac equation with the trigonometric Pöschl-Teller (tPT potential and a Coulomb-like tensor potential for arbitrary spin-orbit quantum number κ under the presence of exact spin and pseudospin ( p -spin symmetries. The bound state energy eigenvalues and the corresponding two-component wave functions of the Dirac particle are obtained using the parametric generalization of the Nikiforov-Uvarov (NU method. We show that tensor interaction removes degeneracies between spin and pseudospin doublets. The case of nonrelativistic limit is studied too.

Energy spectra of the hyperbolic and second Poeschl-Teller like potentials solved by new exact quantization rule

International Nuclear Information System (INIS)

Dong Shihai; Gonzalez-Cisneros, A.

2008-01-01

A new exact quantization rule simplifies the calculation of the energy levels for the exactly solvable quantum system. In this work we calculate the energy levels of the Schroedinger equation with the hyperbolic potential by this quantization rule. The corresponding eigenfunction is also derived for completeness. The second Poeschl-Teller like potential case is also carried out

Gamow-Teller transitions and neutron-proton-pair transfer reactions

Science.gov (United States)

Van Isacker, P.; Macchiavelli, A. O.

2018-05-01

We propose a schematic model of nucleons moving in spin-orbit partner levels, j = l ± 1/2, to explain Gamow-Teller and two-nucleon transfer data in N = Z nuclei above 40Ca. Use of the LS coupling scheme provides a more transparent approach to interpret the structure and reaction data. We apply the model to the analysis of charge-exchange, 42Ca(3He,t)42Sc, and np-transfer, 40Ca(3He,p)42Sc, reactions data to define the elementary modes of excitation in terms of both isovector and isoscalar pairs, whose properties can be determined by adjusting the parameters of the model (spin-orbit splitting, isovector pairing strength and quadrupole matrix element) to the available data. The overall agreement with experiment suggests that the approach captures the main physics ingredients and provides the basis for a boson approximation that can be extended to heavier nuclei. Our analysis also reveals that the SU(4)-symmetry limit is not realized in 42Sc.

Gamow-Teller Strengths from (3He,t) Charge-Exchange Reaction

International Nuclear Information System (INIS)

Fujita, Yoshitaka

2006-01-01

Gamow-Teller (GT) transition is the most popular nuclear weak process with the nature of spin-isospin excitation. GT transitions in pf-shell nuclei, including those starting from unstable nuclei, are of interest, due to their importance in astrophysical processes. Weak processes, however, gives us rather limited information on the GT response of nuclei. We introduce high-resolution ( 3 He, t) reaction at 0 0 and at an intermediate beam energy as a new spectroscopic tool for studying GT excitations. Owing to the high energy-resolution of the reaction (∼ 30 keV), individual transitions can be observed up to the region of GT giant resonance. Assuming isospin symmetry for the T z = ±1 → 0 isobaric analogous transitions in isobars with mass number A, we present a new method to deduce GT transition strengths starting from proton rich exotic nuclei

Effects of rare-earth size on the electronic structure of La1−xLuxVO3.

Science.gov (United States)

Chen, B; Laverock, J; Newby, D; McNulty, J F; Smith, K E; Glans, P-A; Guo, J-H; Qiao, R-M; Yang, W-L; Lees, M R; Tung, L D; Singh, R P; Balakrishnan, G

2015-03-18

The electronic structure of La(1-x)Lu(x)VO(3)(x = 0, 0.2, 0.6 and 1) single crystals has been investigated using soft x-ray absorption spectroscopy, soft x-ray emission spectroscopy, and resonant soft x-ray inelastic scattering to study the effects of rare-earth size. The x-ray absorption and emission spectra at the O K-edge present a progressive evolution with R-site cation, in agreement with local spin density approximation calculations. This evolution with R, together with the temperature dependence of the O K-edge spectra, is attributed to changes in the crystal structure of La(1-x)Lu(x)VO(3). The crystal-field dd. excitations probed by resonant inelastic x-ray scattering at the V L(3)-edge exhibit an increase in energy and enhanced intensity with the decrease of R-site ionic radius, which is mainly attributed to the increased tilting magnitude of the VO(6) octahedra. Upon cooling to ~95 K, the dd* excitations are prominently enhanced in relative Intensity, in agreement with the formation of the Jahn.Teller distortion int he orbital ordering phase. Additionally, the dd* transitions of the mixed compounds are noticeably suppressed with respect to those of the pure compounds, possibly owing to the formation of C-type orbital ordering induced by large R-site size variances.

Transition metal ions in silicate melts. I. Manganese in sodium silicate melts

Energy Technology Data Exchange (ETDEWEB)

Nelson, C; White, W B

1980-01-01

Optical absorption spectra obtained on glasses quenched from sodium silicate melts show Mn/sup 3 +/ to be the dominant species for melts heated in air and Mn/sup 2 +/ to be the dominant species for melts heated at P/sub O/sub 2// = 10/sup -17/ bar. The absorption spectrum of Mn/sup 3 +/ consists of an intense band at 20,000 cm/sup -1/ with a 15,000 cm/sup -1/ satellite possibly arising from the Jahn-Teller effect. The independence of the spectrum from melt composition and the high band intensity is offered as evidence for a distinct Mn/sup 3 +/ complex in the melt. The spectrum of Mn/sup 2 +/ is weak and many expected bands are not observed. A two-band luminescence spectrum from Mn/sup 2 +/ has been tentatively interpreted as due to Mn/sup 2 +/ in interstitial sites in the network and Mn/sup 2 +/ coordiated by non-bridging oxygens.

Theoretical Studies of the Spin Hamiltonian Parameters and Local Distortions for Cu2+ in Alkaline Earth Lead Zinc Phosphate Glasses

Science.gov (United States)

Wang, Bo-Kun; Wu, Shao-Yi; Yuan, Zi-Yi; Liu, Zi-Xuan; Jiang, Shi-Xin; Liu, Zheng; Yao, Zi-Jian; Teng, Bao-Hua; Wu, Ming-He

2016-08-01

The spin Hamiltonian parameters and local structures are theoretically studied for Cu2+-doped alkaline earth lead zinc phosphate (RPPZ, R=Mg, Ca, Sr, and Ba) glasses based on the high-order perturbation calculations for a tetragonally elongated octahedral 3d9 cluster. The relative elongation ratios are found to be ρ≈3.2%, 4.4%, 4.6%, and 3.3% for R=Mg, Ca, Sr, and Ba, respectively, because of the Jahn-Teller effect. The whole decreasing crystal-field strength Dq and orbital reduction factor k from Mg to Sr are ascribed to the weakening electrostatic coulombic interactions and the increasing probability of productivity of nonbridge oxygen (and hence increasing Cu2+-O2- electron cloud admixtures) under PbO addition, respectively, with increasing alkali earth ionic radius. The anomalies (the largest Dq and the next highest k among the systems) for R=Ba are attributed to the cross linkage of this large cation in the network. The overall increasing order (Mg≤Bacontaining copper dopants.

Polarization enhancement and ferroelectric switching enabled by interacting magnetic structures in DyMnO3 thin films

KAUST Repository

Lu, Chengliang

2013-12-02

The mutual controls of ferroelectricity and magnetism are stepping towards practical applications proposed for quite a few promising devices in which multiferroic thin films are involved. Although ferroelectricity stemming from specific spiral spin ordering has been reported in highly distorted bulk perovskite manganites, the existence of magnetically induced ferroelectricity in the corresponding thin films remains an unresolved issue, which unfortunately halts this step. In this work, we report magnetically induced electric polarization and its remarkable response to magnetic field (an enhancement of ?800% upon a field of 2 Tesla at 2 K) in DyMnO3 thin films grown on Nb-SrTiO3 substrates. Accompanying with the large polarization enhancement, the ferroelectric coercivity corresponding to the magnetic chirality switching field is significantly increased. A picture based on coupled multicomponent magnetic structures is proposed to understand these features. Moreover, different magnetic anisotropy related to strain-suppressed GdFeO 3-type distortion and Jahn-Teller effect is identified in the films.

The structure of the Gamow-Teller giant resonance and consequences for beta-delayed neutron spectra and element synthesis

International Nuclear Information System (INIS)

Klapdor, H.V.

1976-01-01

Recent results in β-delayed neutron emission are interpreted by structure of the Gamow-Teller giant resonance not included in the 'gross-theory' of β-decay. Inclusion of this structure of the β-decay function is important for calculations of β-decay production rates for heavy nuclides by astrophysical processes and thermonuclear explosions. (Auth.)

Enhanced way of securing automated teller machine to track the misusers using secure monitor tracking analysis

Science.gov (United States)

Sadhasivam, Jayakumar; Alamelu, M.; Radhika, R.; Ramya, S.; Dharani, K.; Jayavel, Senthil

2017-11-01

Now a days the people's attraction towards Automated Teller Machine(ATM) has been increasing even in rural areas. As of now the security provided by all the bank is ATM pin number. Hackers know the way to easily identify the pin number and withdraw money if they haven stolen the ATM card. Also, the Automated Teller Machine is broken and the money is stolen. To overcome these disadvantages, we propose an approach “Automated Secure Tracking System” to secure and tracking the changes in ATM. In this approach, while creating the bank account, the bank should scan the iris known (a part or movement of our eye) and fingerprint of the customer. The scanning can be done with the position of the eye movements and fingerprints identified with the shortest measurements. When the card is swiped then ATM should request the pin, scan the iris and recognize the fingerprint and then allow the customer to withdraw money. If somebody tries to break the ATM an alert message is given to the nearby police station and the ATM shutter is automatically closed. This helps in avoiding the hackers who withdraw money by stealing the ATM card and also helps the government in identifying the criminals easily.

Prediction of two-dimensional diluted magnetic semiconductors: Doped monolayer MoS2 systems

KAUST Repository

Cheng, Yingchun

2013-03-05

Using first-principles calculations, we propose a two-dimensional diluted magnetic semiconductor: monolayer MoS2 doped by transition metals. Doping of transition metal atoms from the IIIB to VIB groups results in nonmagnetic states, since the number of valence electrons is smaller or equal to that of Mo. Doping of atoms from the VIIB to IIB groups becomes energetically less and less favorable. Magnetism is observed for Mn, Fe, Co, Zn, Cd, and Hg doping, while for the other dopants from these groups it is suppressed by Jahn-Teller distortions. Analysis of the binding energies and magnetic properties indicates that (Mo,X)S2 (X=Mn, Fe, Co, and Zn) are promising systems to explore two-dimensional diluted magnetic semiconductors.

DFT calculations of the structures and vibrational spectra of the [Fe(bpy){sub 3}]{sup 2+} and [Ru(bpy){sub 3}]{sup 2+} complexes

Energy Technology Data Exchange (ETDEWEB)

Alexander, Bruce D. [School of Science, University of Greenwich at Medway, Central Avenue, Chatham Maritime, Kent ME4 4TB (United Kingdom); Dines, Trevor J. [Division of Electronic Engineering and Physics, University of Dundee, Dundee DD1 4HN (United Kingdom)], E-mail: t.j.dines@dundee.ac.uk; Longhurst, Rayne W. [Division of Electronic Engineering and Physics, University of Dundee, Dundee DD1 4HN (United Kingdom)

2008-09-03

Structures of the [M(bpy){sub 3}]{sup 2+} complexes (M = Fe and Ru) have been calculated at the B3-LYP/DZVP level. IR and Raman spectra were calculated using the optimised geometries, employing a scaled quantum chemical force field, and compared with an earlier normal coordinate analysis of [Ru(bpy){sub 3}]{sup 2+} which was based upon experimental data alone, and the use of a simplified model. The results of the calculations provide a highly satisfactory fit to the experimental data and the normal coordinate analyses, in terms of potential energy distributions, allow a detailed understanding of the vibrational spectra of both complexes. Evidence is presented for Jahn-Teller distortion in the {sup 1}E MLCT excited state.

Synchrotron radiation-based 61Ni Mössbauer spectroscopic study of Li(Ni1/3Mn1/3Co1/3)O2 cathode materials of lithium ion rechargeable battery

Science.gov (United States)

Segi, Takashi; Masuda, Ryo; Kobayashi, Yasuhiro; Tsubota, Takayuki; Yoda, Yoshitaka; Seto, Makoto

2016-12-01

Layered rocksalt type oxides, such as Li(Ni1/3Mn1/3Co1/3)O2, are widely used as the cathode active materials of lithium-ion rechargeable batteries. Because the nickel ions are associated with the role of the charge compensation at discharge and charge, the 61Ni Mössbauer measurements at 6 K using synchrotron radiation were performed to reveal the role of Ni. The Ni ions of the active materials play two roles for the redox process between the charge and discharge states of lithium-ion batteries. Half of the total Ni ions change to the low-spin Ni3+ with Jahn-Teller distortion from the Ni2+ ions of the discharge state. The remainder exhibit low-spin state divalent Ni ions.

New Layered Oxide-Fluoride Perovskites: KNaNbOF5 and KNaMO2F4 (M = Mo6+, W6+

Directory of Open Access Journals (Sweden)

Rachelle Ann F. Pinlac

2011-03-01

Full Text Available KNaNbOF5 and KNaMO2F4 (M = Mo6+, W6+, three new layered oxide-fluoride perovskites with the general formula ABB’X6, form from the combination of a second-order Jahn-Teller d0 transition metal and an alkali metal (Na+ on the B-site. Alternating layers of cation vacancies and K+ cations on the A-site complete the structure. The K+ cations are found in the A-site layer where the fluoride ions are located. The A-site is vacant in the adjacent A-site layer where the axial oxides are located. This unusual layered arrangement of unoccupied A-sites and under bonded oxygen has not been observed previously although many perovskite-related structures are known.

High-pressure phase of the cubic spinel NiMn2O4

DEFF Research Database (Denmark)

Åsbrink, S.; Waskowska, A.; Olsen, J. Staun

1998-01-01

experimental uncertainty, there is no volume change at the transition. The cia ratio of the tetragonal spinel is almost independent of pressure and equal to 0.91. The phase transition is attributed to the Jahn-Teller-type distortion and the ionic configurationcan be assumed as (Mn3+)(tetr)[Ni2+Mn3+](oct......It has been observed that the fee spinel NiMn2O4 transforms to a tetragonal structure at about 12 GPa. The tetragonal phase does not revert to the cubic phase upon decompression and its unit-cell constants at ambient pressure are a(0)=8.65(8) and c(0)=7.88(15) Angstrom (distorted fee). Within thr......). The bulk modulus of the cubic phase is 206(4) GPa....

Spontaneous electric polarization in the B-site magnetic spinel GeCu2O4

Science.gov (United States)

Yanda, Premakumar; Ghara, Somnath; Sundaresan, A.

2018-04-01

We report the observation of a spontaneous electric polarization at the antiferromagnetic ordering temperature (TN ∼ 33 K) of Cu2+ ions in the B-site magnetic spinel GeCu2O4, synthesized at high pressure and high temperature. This compound is known to crystallize in a tetragonal structure (space group I41/amd) due to Jahn-Teller distortion of Cu2+ ions and exhibit a collinear up-up-down-down (↑↑↓↓) antiferromagnetic spin configuration below TN. We found a clear dielectric anomaly at TN, where an electric polarization appears in the absence of applied magnetic field. The electric polarization is suppressed by applied magnetic fields, which demonstrates that the compound GeCu2O4 is a type-II multiferroic.

High pressure synthesis, crystal growth and magnetic properties of TiOF

Science.gov (United States)

Cumby, J.; Burchell, M. B.; Attfield, J. P.

2018-06-01

Polycrystalline samples of TiOF have been prepared at 1300 °C and 8 GPa, with small single crystals grown at the same conditions. The crystal structure remains tetragonal rutile-type down to at least 90 K (space group P42/mnm, a = 4.6533 (2) Å and c = 3.0143 (2) Å at 90 K) and the Ti(O,F)6 octahedra are slightly compressed, consistent with Jahn-Teller distortion of 3d1 Ti3+. Diffuse scattering reveals disordered structural correlations that may arise from local cis-order of oxide anions driven by covalency. TiOF is paramagnetic down to 5 K and observation of a small paramagnetic moment and a substantial Pauli term indicates that the d-electrons are partially delocalised.

What makes an automated teller machine usable by blind users?

Science.gov (United States)

Manzke, J M; Egan, D H; Felix, D; Krueger, H

1998-07-01

Fifteen blind and sighted subjects, who featured as a control group for acceptance, were asked for their requirements for automated teller machines (ATMs). Both groups also tested the usability of a partially operational ATM mock-up. This machine was based on an existing cash dispenser, providing natural speech output, different function menus and different key arrangements. Performance and subjective evaluation data of blind and sighted subjects were collected. All blind subjects were able to operate the ATM successfully. The implemented speech output was the main usability factor for them. The different interface designs did not significantly affect performance and subjective evaluation. Nevertheless, design recommendations can be derived from the requirement assessment. The sighted subjects were rather open for design modifications, especially the implementation of speech output. However, there was also a mismatch of the requirements of the two subject groups, mainly concerning the key arrangement.

Gamow-Teller resonances and a separable approximation for Skyrme tensor interactions

Directory of Open Access Journals (Sweden)

Severyukhin A. P.

2012-12-01

Full Text Available A finite rank separable approximation for the quasiparticle random phase approximation (QRPA with Skyrme interactions is applied to study properties of the Gamow-Teller (GT resonances in the neutron-rich Cd isotopes. This approximation enables one to reduce considerably the dimension of matrix that must be diagonalized to perform QRPA calculations in a very large configuration space. Our results from the SGII Skyrme interaction with the tensor interactions and the density-dependent zero-range pairing interaction show that the GT distribution is noticeably modified when the tensor correlations are taken into account. In particular, for 130Cd the dominant peak is moved 3.6 MeV downward and 10% of the GT distribution is shifted to the high excitation energy region near E=50MeV.

Optical spectroscopy of Al2O3:Ti3+ single crystal under hydrostatic pressure : The influence on the Jahn-Teller coupling

NARCIS (Netherlands)

García-Revilla, S.; Rodríguez, F.; Valiente, R.; Pollnau, Markus

2002-01-01

This work investigates the effect of hydrostatic pressure on the excitation and emission spectra, as well as on the lifetime, of Al2O3:Ti3+ at room temperature. The aim is to establish correlations between the pressure-induced band shifts and the corresponding local structural changes undergone by

Structural and magnetic properties of Nd0.67Ba0.33MnO3 manganites with partial replacement of Fe and Cu at Mn-site

Science.gov (United States)

Sudakshina, B.; Arun, B.; Chandrasekhar, K. Devi; Yang, H. D.; Vasundhara, M.

2018-06-01

We have investigated the structural and magnetic properties of Nd0.67Ba0.33MnO3 manganite and partial replacement of Mn with Fe and Cu compounds followed by X-ray diffraction (XRD), X-ray absorption spectroscopy (XAS) and vibrating sample magnetometer (VSM). The Rietveld refinement of XRD indicates orthorhombic crystal structure with I-mma space group for all the compounds and thus obtained lattice parameters confirm the presence of co-operative Jahn-Teller effect. XRD and XAS spectra results suggests the existence of Fe3+ in Fe-substituted compound where as a mixed state of Cu2+ and Cu3+ ions in the Cu-substituted compound. The ferromagnetic (FM) to paramagnetic (PM) transition and magnetic moment is found to decrease upon the substitution of Fe and Cu atoms because of the suppression of double exchange interaction. The theoretically obtained and experimentally determined values of effective PM moment and saturation magnetic moment confirms the presence of inhomogeneous magnetic states containing FM and antiferromagnetic clusters in all the studied compounds.

Two-Channel Kondo Physics due to As Vacancies in the Layered Compound ZrAs1.58Se0.39

Science.gov (United States)

Kirchner, Stefan; Cichorek, T.; Bochenek, L.; Schmidt, M.; Niewa, R.; Czuluccki, A.; Auffermann, G.; Steglich, F.; Kniep, R.

We address the origin of the magnetic-field independent - | A | T 1 / 2 term observed in the low-temperature resistivity of several As-based metallic systems of the PbFCl structure type. For the layered compound ZrAs1.58Se0.39, we show that vacancies in the square nets of As give rise to the low-temperature transport anomaly over a wide temperature regime of almost two decades in temperature. This low-temperature behavior is in line with the non-magnetic version of the two-channel Kondo effect, whose origin we ascribe to a dynamic Jahn-Teller effect operating at the vacancy-carrying As layer with a C4 symmetry. The pair-breaking nature of the dynamical defects in the square nets of As explains the low superconducting transition temperature Tc 0 . 14 K of ZrAs1.58Se0.39, as compared to the free-of-vacancies homologue ZrP1.54S0.46 (Tc 3 . 7 K). Our findings should be relevant to a wide class of metals with disordered pnictogen layers.

Lattice effects in La1-xCaxMnO3 (x=0→1): Relationships between distortions, charge distribution, and magnetism

International Nuclear Information System (INIS)

Booth, C.H.; Bridges, F.; Kwei, G.H.; Lawrence, J.M.; Cornelius, A.L.; Neumeier, J.J.

1998-01-01

X-ray-absorption fine-structure measurements from the Mn and La K edges of samples of La 1-x Ca x MnO 3 (x=0→1) are presented as a function of temperature. In the insulating state, distortions of the Mn-O environment are found to be linear with calcium concentration x. These distortions are consistent with a model where individual Mn 3+ sites have strong Jahn-Teller (JT) distortions while Mn 4+ sites do not, although intermediate distortions are also possible. Comparisons to simulations of various possible bond length distributions show that these distortions are best modeled as a JT distortion, as opposed to charge disproportionation or other models. In the metallic state, at least ∼70% of the distortion is removed. A similar effect is seen in the Mn-Mn bond length distribution. The La-O bond length distribution does not change significantly through the ferromagnetic transition, constraining possible changes in the Mn-O-Mn bond angle to less than 0.5 degree. The changes in the MnO 6 distortion that occur near T c are also present (to a lesser degree) in an insulating sample with x=0.12. The functional relation between the MnO 6 distortions and the magnetization is determined, and compared to transport measurements. copyright 1998 The American Physical Society

A classic case of Jahn–Teller effect theory revisited: Ab initio simulation of hyperfine coupling and pseudorotational tunneling in the 1"2E′ state of Na_3

International Nuclear Information System (INIS)

Hauser, Andreas W.; Pototschnig, Johann V.; Ernst, Wolfgang E.

2015-01-01

Highlights: • Multireference and Coupled Cluster methods are applied to Na_3. • The PES is characterized by an analytical function fitted to ab initio data. • An effective rovibrational Hamiltonian is set up, with all parameters derived ab initio. • The coupling of pseudorotational tunneling and hyperfine interactions is investigated. • The theoretical predictions are compared to microwave spectra. - Abstract: The predictive capabilities of current ab initio approaches are tested in a benchmark study on the well known case of the Na_3 ground state. This molecule is small enough to be treated with computationally demanding methods, but also shows an interesting interplay between Jahn–Teller-, spin-orbit-, rovibrational- and hyperfine-interactions. The necessary parameters for the effective Hamiltonian are derived from the potential energy surface of the 1"2E′ ground state and from spin density evaluations at selected geometries, without any fitting adjustments to experimental data. We compare our results to highly resolved microwave spectra, with the aim to improve previous assignment attempts, where some parameters had to be estimated from fits to measured spectra.

Novel effect of spin dynamics with suppression of charge and orbital ordering in Nd{sub 0.5}Ca{sub 0.5}MnO{sub 3} under the influence of ac electric field

Energy Technology Data Exchange (ETDEWEB)

Sarwar, T., E-mail: sarwartuba@gmail.com [EMMG, Physics Division, PINSTECH, P.O. Nilore, Islamabad (Pakistan); Qamar, A., E-mail: afzaal.qamar@griffithuni.edu.au [Queensland Micro-Nanotechnology Centre, Griffith University, Nathan, QLD 4111 (Australia); Nadeem, M. [EMMG, Physics Division, PINSTECH, P.O. Nilore, Islamabad (Pakistan)

2017-07-15

Highlights: • Electronic & magnetic behavior of Nd{sub 0.5}Ca{sub 0.5}MnO{sub 3} is explored using impedance spectroscopy. • Under ac field, possible signature of suppression of robust CO/OO antiferromagnetism is studied. • We propose the existence of spin glass state at low temperature. • A novel tactic is used to estimate the existence of weak ferromagnetism at high temperature. - Abstract: Dynamics of spin ordering in the manganite Nd{sub 0.5}Ca{sub 0.5}MnO{sub 3} have been investigated in this paper. It was observed that the complex mixed magnetic ordering in pellets is comprised of antiferromagnetic ordering at 160 K (T{sub N}) and complete charge ordering at 250 K (T{sub CO}). Under ac field, appearance of unstable ferromagnetic correlations is observed above T{sub CO}, which is badly frustrated due to strong spin disorder induced by Jahn Teller distortions. Impedance measurements reveal the spin glass like scenario, suppressing the strong antiferromagnetic and charge ordering states below T{sub N}.

Maximally localized Wannier functions in LaMnO3 within PBE + U, hybrid functionals and partially self-consistent GW: an efficient route to construct ab initio tight-binding parameters for eg perovskites.

Science.gov (United States)

Franchini, C; Kováčik, R; Marsman, M; Murthy, S Sathyanarayana; He, J; Ederer, C; Kresse, G

2012-06-13

Using the newly developed VASP2WANNIER90 interface we have constructed maximally localized Wannier functions (MLWFs) for the e(g) states of the prototypical Jahn-Teller magnetic perovskite LaMnO(3) at different levels of approximation for the exchange-correlation kernel. These include conventional density functional theory (DFT) with and without the additional on-site Hubbard U term, hybrid DFT and partially self-consistent GW. By suitably mapping the MLWFs onto an effective e(g) tight-binding (TB) Hamiltonian we have computed a complete set of TB parameters which should serve as guidance for more elaborate treatments of correlation effects in effective Hamiltonian-based approaches. The method-dependent changes of the calculated TB parameters and their interplay with the electron-electron (el-el) interaction term are discussed and interpreted. We discuss two alternative model parameterizations: one in which the effects of the el-el interaction are implicitly incorporated in the otherwise 'noninteracting' TB parameters and a second where we include an explicit mean-field el-el interaction term in the TB Hamiltonian. Both models yield a set of tabulated TB parameters which provide the band dispersion in excellent agreement with the underlying ab initio and MLWF bands.

An Anomaly in the Inglis-Teller Limits of the C VI Lyman and Balmer Series in Laser-Produced Plasmas

Science.gov (United States)

Elton, R.; Iglesias, E.; Griem, H.; Weaver, J.; Pien, G.; Mancini, R.

2002-11-01

Soft x-ray spectra from thin carbon layers heated by the OMEGA and NIKE lasers have been obtained with both spherical and planar targets, respectively, using a flat-field grazing incidence spectrograph equipped with a gated microchannel plate for temporal resolution. In both experiments, late-time (recombining) hydrogenic C VI spectra show an n-to-1 Lyman spectral series blending with the continuum at n=4, contrary to n=9 in the n-to-2 Balmer series. It appears unlikely that plasma inhomogeneities are the sole cause of this anomaly, given the difference in the experimental configurations. Other explanations for the line-to-continuum merging (other than the usual Stark-broadened Inglis-Teller effect) under consideration include non-thermal Doppler broadening, deviations from statistical sublevel population distributions, and opacity effects. Collisional-radiative and hydrodynamic modeling, including cascades, is employed to further understand this phenomenon.

Gamow-Teller strength distributions and electron capture rates for 55Co and 56Ni

International Nuclear Information System (INIS)

Nabi, Jameel-Un; Rahman, Muneeb-Ur

2005-01-01

The Gamow-Teller strength (GT) distributions and electron capture rates on 55 Co and 56 Ni have been calculated using the proton-neutron quasiparticle random phase approximation theory. We calculate these weak interaction mediated rates over a wide temperature (0.01x10 9 -30x10 9 K) and density (10-10 11 gcm -3 ) domain. Electron capture process is one of the essential ingredients involved in the complex dynamics of supernova explosion. Our calculations of electron capture rates show differences with the reported shell model diagonalization approach calculations and are comparatively enhanced at presupernova temperatures. We note that the GT strength is fragmented over many final states

Photophysics of trioxatriangulenium ion. Electrophilic reactivity in the ground state and excited singlet state

DEFF Research Database (Denmark)

Reynisson, J.; Wilbrandt, R.; Brinck, V.

2002-01-01

. The physical and chemical properties of the excited singlet state of the trioxatriangulenium (TOTA(+)) carbenium ion are investigated by experimental and Computational means. The degeneracy of the lowest excited states is counteracted by Jahn-Teller-type distortion, which leads to vibronic broadening...... of the long wavelength absorption band. A strong fluorescence is observed at 520 nm (tau(n) = 14.6 ns, phi(n) = 0.12 in deaerated acetonitrile). The fluorescence is quenched by 10 aromatic electron donors predominantly via a dynamic charge transfer mechanism, but ground state complexation is shown...... triphenylenes is studied separately. Phosphorescence spectra, triplet lifetimes, and triplet-triplet absorption spectra are provided. In the discussion, TOTA(+) is compared to the unsubstituted xanthenium ion and its 9-phenyl derivative with respect to the excited state properties....

Coupled Electronic and Magnetic Phase Transition in the Infinite-Layer Phase LaSrNiRuO4.

Science.gov (United States)

Patino, Midori Amano; Zeng, Dihao; Bower, Ryan; McGrady, John E; Hayward, Michael A

2016-09-06

Topochemical reduction of the ordered double perovskite LaSrNiRuO6 with CaH2 yields LaSrNiRuO4, an extended oxide phase containing infinite sheets of apex-linked, square-planar Ni(1+)O4 and Ru(2+)O4 units ordered in a checkerboard arrangement. At room temperature the localized Ni(1+) (d(9), S = (1)/2) and Ru(2+) (d(6), S = 1) centers behave paramagnetically. However, on cooling below 250 K the system undergoes a cooperative phase transition in which the nickel spins align ferromagnetically, while the ruthenium cations appear to undergo a change in spin configuration to a diamagnetic spin state. Features of the low-temperature crystal structure suggest a symmetry lowering Jahn-Teller distortion could be responsible for the observed diamagnetism of the ruthenium centers.

Synchrotron radiation-based {sup 61}Ni Mössbauer spectroscopic study of Li(Ni{sub 1/3}Mn{sub 1/3}Co{sub 1/3})O{sub 2} cathode materials of lithium ion rechargeable battery

Energy Technology Data Exchange (ETDEWEB)

Segi, Takashi, E-mail: segi.takashi@kki.kobelco.com [Kobelco Research Institute, Inc. (Japan); Masuda, Ryo; Kobayashi, Yasuhiro [Kyoto University, Research Reactor Institute (Japan); Tsubota, Takayuki [Kobelco Research Institute, Inc. (Japan); Yoda, Yoshitaka [Japan Synchrotron Radiation Research Institute, Research and Utilization Division (Japan); Seto, Makoto [Kyoto University, Research Reactor Institute (Japan)

2016-12-15

Layered rocksalt type oxides, such as Li(Ni{sub 1/3}Mn{sub 1/3}Co{sub 1/3})O{sub 2}, are widely used as the cathode active materials of lithium-ion rechargeable batteries. Because the nickel ions are associated with the role of the charge compensation at discharge and charge, the {sup 61}Ni Mössbauer measurements at 6 K using synchrotron radiation were performed to reveal the role of Ni. The Ni ions of the active materials play two roles for the redox process between the charge and discharge states of lithium-ion batteries. Half of the total Ni ions change to the low-spin Ni {sup 3+} with Jahn-Teller distortion from the Ni {sup 2+} ions of the discharge state. The remainder exhibit low-spin state divalent Ni ions.

Orbital physics in sulfur spinels: ordered, liquid and glassy ground states

International Nuclear Information System (INIS)

Buettgen, N; Hemberger, J; Fritsch, V; Krimmel, A; Muecksch, M; Nidda, H-A Krug von; Lunkenheimer, P; Fichtl, R; Tsurkan, V; Loidl, A

2004-01-01

Measurements of magnetization M(T, H), heat capacity C(T), NMR lineshift K(T) and linewidth Δ(T), neutron scattering S(Q, ω, T) and broadband dielectric spectroscopy ε(ω, T) provide experimental evidence of the different orbital ground states in the cubic sulfur spinels under investigation. In all compounds, the tetrahedrally coordinated Jahn-Teller ions Fe 2+ are characterized by a degeneracy of the orbital degrees of freedom. Particularly, we found a long-range orbital ordering in polycrystalline (PC) FeCr 2 S 4 , and a glassy freezing of the orbital degrees of freedom in FeCr 2 S 4 (single crystals) (SCs). In contrast, FeSc 2 S 4 belongs to the rare class of spin-orbital liquids, where quantum fluctuations accompanying the glassy freezing of the orbitals suppress long-range magnetic order

An Exploratory Study of the Critical Factors Affecting the Acceptability of Automated Teller Machine (ATM) in Nigeria

OpenAIRE

Olusegun Folorunso; Oluwafunmilayo Ayobami Ateji; Gabriel Oludare Awe

2010-01-01

This paper uses the Technology Acceptance Model (TAM) as a basis for studying critical factors that affects the acceptability of Automated Teller Machine (ATM) in Nigeria. Questionnaire approach was used with the respondents predominantly between 20-29 years old. Factor analysis was used to test which of the factors are the main factors affecting the adoption of the technology in Nigeria. It was discovered that the major factors affecting people’s intention to accept ATM are the security issu...

Gamow-Teller strength in deformed nuclei within self-consistent pnQRPA with the Gogny force

Directory of Open Access Journals (Sweden)

Martini M.

2014-03-01

Full Text Available In recent years fully consistent quasiparticle random-phase approximation (QRPA calculations using finite range Gogny force have been performed to study electromagnetic excitations of several axially-symmetric deformed nuclei up to the 238U. Here we present the extension of this approach to the charge-exchange nuclear excitations (pn-QRPA. In particular we focus on the Gamow-Teller (GT excitations. A comparison of the predicted GT strength distribution with existing experimental data is presented The role of nuclear deformation is shown. Special attention is paid to β-decay half-lives calculations for which experimental data exist.

A first-principles study of the dielectric properties of TiO{sub 2} polymorphs

Energy Technology Data Exchange (ETDEWEB)

Thilagam, A; Simpson, D J; Gerson, A R, E-mail: Thilagam.Lohe@unisa.edu.au, E-mail: Darren.Simpson@unisa.edu.au, E-mail: Andrea.Gerson@unisa.edu.au [Minerals and Materials Science and Technology, Mawson Institute, Division of IEEE, University of South Australia, Mawson Lakes Campus, South Australia 5095 (Australia)

2011-01-19

We present an analysis of the dielectric properties of the three polymorphs of TiO{sub 2} (rutile, anatase and brookite phases), using ab initio time-dependent density functional perturbation theory based on the Vignale-Kohn functional. We implement this functional, which incorporates many-body effects, using the periodic program BAND. The improved result for the density of states spectra for brookite is suggestive of increased titanium ion Jahn-Teller effects for this phase. The imaginary and real components of the frequency-dependent dielectric functions show notable dielectric anisotropies, with implications for excitonic interactions, for all three common phases of TiO{sub 2}. Comparison of the electron energy-loss spectrum for undoped and doped rutile and anatase reveals the critical role of collective charge excitations in photocatalytic mechanisms. The correlation between plasmon peaks present at lower energies and decreased photocatalytic activity due to substitutional aluminum doping in combination with oxygen vacancies in rutile and anatase is highlighted. Moreover, there is clear correlation between dielectric properties and the microstructure of the TiO{sub 2} polymorphs as suggested via the framework of the Born effective charge and Hirshfeld charge distribution schemes.

A first-principles study of the dielectric properties of TiO2 polymorphs

International Nuclear Information System (INIS)

Thilagam, A; Simpson, D J; Gerson, A R

2011-01-01

We present an analysis of the dielectric properties of the three polymorphs of TiO 2 (rutile, anatase and brookite phases), using ab initio time-dependent density functional perturbation theory based on the Vignale-Kohn functional. We implement this functional, which incorporates many-body effects, using the periodic program BAND. The improved result for the density of states spectra for brookite is suggestive of increased titanium ion Jahn-Teller effects for this phase. The imaginary and real components of the frequency-dependent dielectric functions show notable dielectric anisotropies, with implications for excitonic interactions, for all three common phases of TiO 2 . Comparison of the electron energy-loss spectrum for undoped and doped rutile and anatase reveals the critical role of collective charge excitations in photocatalytic mechanisms. The correlation between plasmon peaks present at lower energies and decreased photocatalytic activity due to substitutional aluminum doping in combination with oxygen vacancies in rutile and anatase is highlighted. Moreover, there is clear correlation between dielectric properties and the microstructure of the TiO 2 polymorphs as suggested via the framework of the Born effective charge and Hirshfeld charge distribution schemes.

Gamow-Teller strength distribution in the beta-decay of 100Ag from total-absorption gamma spectrometry

International Nuclear Information System (INIS)

Batist, L.; Bykov, A.; Moroz, F.; Wittmann, V.; Alkhazov, G.D.; Keller, H.; Kirchner, R.; Klepper, O.; Roeckl, E.; Huyse, M.; Duppen, P. van; Reusen, G.; Plochocki, A.; Pfuetzner, M.; Rykaczewski, K.; Szerypo, J.; Zylicz, J.; Brown, B.A.

1994-10-01

The EC/β + -decay of the odd-odd nucleus 100 Ag was studied by means of total absorption γ-ray spectrometry. Most of the Gamow-Teller strength was found to be concentrated at an excitation energy of 5.6 MeV in 100 Pd, the FWHM of this resonance being 1.5 MeV. The measured strength distribution which is interpreted within the BCS approximation as being due to the dominant population of four-quasiparticle excitations, resembles the distribution predicted by an advanced shell-model calculation for the 98 Ag→ 98 Cd decay. (orig.)

Analysis of the workload of bank tellers of a Brazilian public institution.

Science.gov (United States)

Serikawa, Simoni S; Albieri, Ana Carolina S; Bonugli, Gustavo P; Greghi, Marina F

2012-01-01

During the last decades there have been many changes in the banking sector organization. It has been also observed the mutual growing of musculoskeletal and mental disorders. This study investigated the workload of bank tellers at a Brazilian public institution. It was performed the Ergonomic Work Analysis (EWA). Three employees participated in this study. During the analysis process, three research instruments were applied: Inventory of Work and Risk of Illness, Yoshitake Fatigue Questionnaire and Nordic Musculoskeletal Questionnaire, beyond the realization of footage recordings and the self-confrontation. The results indicated the existence of an excess of workload on the evaluated workstations, mainly in relation to mental order constraints, that overlaps the physical aspects. Thereby it was found that the employees tend to adopt strategies trying to reduce the impacts of the excess of workload, in order to regulate it.

Role of momentum transfer in the quenching of the Gamow-Teller strength

International Nuclear Information System (INIS)

Marketin, T.; Martínez-Pinedo, G.; Paar, N.; Vretenar, D.

2012-01-01

A recent analysis of (p,n) and (n,p) reaction data from 90 Zr was performed recently, where a significant amount of Gamow-Teller strength was found above the resonance, an energy region previously unreachable by experimental setups. The extracted strengths in the β − and the β + channel indicate that approximately 10% of the total strength necessary to satisfy the model independent Ikeda sum rule is missing. One possible source of this discrepancy is the treatment of the isovector spin monopole (IVSM) mode of excitation which has been found to occurr at high excitation energies. Employing the relativistic Hartree-Bogoliubov (RHB) model and the protonneutron relativistic quasiparticle random phase approximation (pn-RQRPA) to calculate the nuclear response, we explore the contribution of the IVSM mode to the total L= 0 strength and apply our results to the available data.

Role of momentum transfer in the quenching of the Gamow-Teller strength

Energy Technology Data Exchange (ETDEWEB)

Marketin, T.; Martinez-Pinedo, G.; Paar, N.; Vretenar, D. [Institut fuer Kernphysik, Technische Universitaet Darmstadt, D-64289 Darmstadt, Germany and Physics Department, Faculty of Science, University of Zagreb, 10000 Zagreb (Croatia); Institut fuer Kernphysik, Technische Universitaet Darmstadt, D-64289 Darmstadt (Germany); Physics Department, Faculty of Science, University of Zagreb, 10000 Zagreb (Croatia)

2012-10-20

A recent analysis of (p,n) and (n,p) reaction data from {sup 90}Zr was performed recently, where a significant amount of Gamow-Teller strength was found above the resonance, an energy region previously unreachable by experimental setups. The extracted strengths in the {beta}{sub -} and the {beta}{sub +} channel indicate that approximately 10% of the total strength necessary to satisfy the model independent Ikeda sum rule is missing. One possible source of this discrepancy is the treatment of the isovector spin monopole (IVSM) mode of excitation which has been found to occurr at high excitation energies. Employing the relativistic Hartree-Bogoliubov (RHB) model and the protonneutron relativistic quasiparticle random phase approximation (pn-RQRPA) to calculate the nuclear response, we explore the contribution of the IVSM mode to the total L= 0 strength and apply our results to the available data.

An Exploratory Study of the Critical Factors Affecting the Acceptability of Automated Teller Machine (ATM in Nigeria

Directory of Open Access Journals (Sweden)

Olusegun Folorunso

2010-01-01

Full Text Available This paper uses the Technology Acceptance Model (TAM as a basis for studying critical factors that affects the acceptability of Automated Teller Machine (ATM in Nigeria. Questionnaire approach was used with the respondents predominantly between 20-29 years old. Factor analysis was used to test which of the factors are the main factors affecting the adoption of the technology in Nigeria. It was discovered that the major factors affecting people’s intention to accept ATM are the security issues and poor internet connectivity.

Quantum-classical dynamics of scattering processes in adiabatic and diabatic representations

International Nuclear Information System (INIS)

Puzari, Panchanan; Sarkar, Biplab; Adhikari, Satrajit

2004-01-01

We demonstrate the workability of a TDDVR based [J. Chem. Phys. 118, 5302 (2003)], novel quantum-classical approach, for simulating scattering processes on a quasi-Jahn-Teller model [J. Chem. Phys. 105, 9141 (1996)] surface. The formulation introduces a set of DVR grid points defined by the Hermite part of the basis set in each dimension and allows the movement of grid points around the central trajectory. With enough trajectories (grid points), the method converges to the exact quantum formulation whereas with only one grid point, we recover the conventional molecular dynamics approach. The time-dependent Schroedinger equation and classical equations of motion are solved self-consistently and electronic transitions are allowed anywhere in the configuration space among any number of coupled states. Quantum-classical calculations are performed on diabatic surfaces (two and three) to reveal the effects of symmetry on inelastic and reactive state-to-state transition probabilities, along with calculations on an adiabatic surface with ordinary Born-Oppenheimer approximation. Excellent agreement between TDDVR and DVR results is obtained in both the representations

Controllability of pure states for the Poeschl-Teller potential with a dynamical group SU(2)

International Nuclear Information System (INIS)

Dong, S.-H.; Tang Yu; Sun, G.-H.; Lara-Rosano, F.; Lozada-Cassou, M.

2005-01-01

The controllability of a quantum system for the modified Poeschl-Teller (MPT) potential with the discrete bound states is investigated. The creation and annihilation operators of this potential are constructed directly from the normalized wave function with the factorization method and associated to an su(2) algebra. It is shown that this quantum system with the nondegenerate discrete bound states can, in principle, be strongly completely controllable, i.e., the system eigenstates can be guided by the external field to approach arbitrarily close to a target state, which could be theoretically realized by the actions of the creation and annihilation operators on the ground state

IMPACT OF NEW GAMOW–TELLER STRENGTHS ON EXPLOSIVE TYPE IA SUPERNOVA NUCLEOSYNTHESIS

Energy Technology Data Exchange (ETDEWEB)

Mori, Kanji; Famiano, Michael A.; Kajino, Toshitaka; Suzuki, Toshio [National Astronomical Observatory of Japan 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan); Hidaka, Jun [Mechanical Engineering Department, Meisei University, 2-1-1 Hodokubo, Hino, Tokyo 191-8506 (Japan); Honma, Michio [Center for Mathematical Sciences, University of Aizu, Aizu-Wakamatsu, Fukushima 965-8580 (Japan); Iwamoto, Koichi [Department of Physics, College of Science and Technology, Nihon University, Tokyo 101-8308 (Japan); Nomoto, Ken’ichi [Kavli Institute for the Physics and Mathematics of the Universe (WPI), The University of Tokyo, Kashiwa, Chiba 277-8583 (Japan); Otsuka, Takaharu, E-mail: kanji.mori@nao.ac.jp, E-mail: kajino@nao.ac.jp, E-mail: michael.famiano@wmich.edu, E-mail: suzuki@phys.chs.nihon-u.ac.jp, E-mail: jun.hidaka@meisei-u.ac.jp, E-mail: m-honma@u-aizu.ac.jp, E-mail: iwamoto@phys.cst.nihon-u.ac.jp, E-mail: nomoto@astron.s.u-tokyo.ac.jp, E-mail: otsuka@phys.s.u-tokyo.ac.jp [Department of Physics, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan)

2016-12-20

Recent experimental results have confirmed a possible reduction in the Gamow–Teller (GT{sub +}) strengths of pf-shell nuclei. These proton-rich nuclei are of relevance in the deflagration and explosive burning phases of SNe Ia. While prior GT strengths result in nucleosynthesis predictions with a lower-than-expected electron fraction, a reduction in the GT{sub +} strength can result in a slightly increased electron fraction compared to previous shell model predictions, though the enhancement is not as large as previous enhancements in going from rates computed by Fuller, Fowler, and Newman based on an independent particle model. A shell model parametrization has been developed that more closely matches experimental GT strengths. The resultant electron-capture rates are used in nucleosynthesis calculations for carbon deflagration and explosion phases of SNe Ia, and the final mass fractions are compared to those obtained using more commonly used rates.

Electromagnetic dipole and Gamow-Teller responses of even and odd {sup 90-94}{sub 40}Zr isotopes in QRPA calculations with the D1M Gogny force

Energy Technology Data Exchange (ETDEWEB)

Deloncle, I. [CSNSM, CNRS et Universite Paris-Sud, Orsay (France); CEA, DAM, DIF, Arpajon (France); Peru, S. [CEA, DAM, DIF, Arpajon (France); Martini, M. [ESNT, CEA-Saclay, DSM, Irfu, Service de Physique Nucleaire, Gif-sur-Yvette (France)

2017-08-15

In this paper we present theoretical results on the dipole response in the proton spin-saturated {sup 90-94}Zr isotopes. The electric and magnetic dipole excitations are obtained in Hartree-Fock-Bogolyubov plus Quasi-particle Random Phase Approximation (QRPA) calculations performed with the D1M Gogny force. A pnQRPA charge exchange code is used to study the Gamow-Teller response. The results on the pygmy, the giant dipole resonances as well as those on the magnetic nuclear spin-flip excitation and the Gamow-Teller transitions are compared with available experimental or theoretical information. In our approach, the proton pairing plays a role in the phonon excitations, in particular in the M1 nuclear spin-flip resonance. (orig.)

Charge driven metal-insulator transitions in LaMnO3|SrTiO3 (111) superlattices

KAUST Repository

Cossu, Fabrizio; Tahini, Hassan Ali; Singh, Nirpendra; Schwingenschlö gl, Udo

2017-01-01

Interfaces of perovskite oxides, due to the strong interplay between the lattice, charge and spin degrees of freedom, can host various phase transitions, which is particularly interesting if these transitions can be tuned by external fields. Recently, ferromagnetism was found together with a seemingly insulating state in superlattices of manganites and titanates. We therefore study the (111) oriented $(\\text{LaMnO}_3)_{6-x}\\vert(\\text{SrTiO}_3)_{6+x}~(x = -0.5, 0, 0.5)$ superlattices by means of ab initio calculations, predicting a ferromagnetic ground state due to double exchange in all cases. We shed light on the ferromagnetic coupling in the LaMnO3 region and at the interfaces. The insulating states of specific superlattices can be understood on the basis of Jahn-Teller modes and electron/hole doping.

Direct and real time probe of photoinduced structure transition in colossal magnetoresistive material

Energy Technology Data Exchange (ETDEWEB)

Li, Junjie [Physics Department, Florida State University, Tallahassee, Florida 32310 (United States); National High Magnetic Field Laboratory, Tallahassee, Florida 32310 (United States); Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973 (United States); Wang, Xuan [Institute of physics, Chinese Academy of Sciences, P.O. Box 603, Beijing 100190 (China); Zhou, Haidong [National High Magnetic Field Laboratory, Tallahassee, Florida 32310 (United States); Zhou, Jun; Cao, Jianming, E-mail: jcao@magnet.fsu.edu [Physics Department, Florida State University, Tallahassee, Florida 32310 (United States); National High Magnetic Field Laboratory, Tallahassee, Florida 32310 (United States); Cheng, J. G. [Texas Materials Institute, University of Texas at Austin, Austin, Texas 78712 (United States)

2016-07-25

We report a direct and real time measurement of photoinduced structure phase transition in single crystal La{sub 0.84}Sr{sub 0.16}MnO{sub 3} using femtosecond electron diffraction. The melting of orthorhombic lattice ordering under femtosecond optical excitation is found involving two distinct processes with different time scales, an initial fast melting of orthorhombic phase in about 4 ps and a subsequent slower transformation in 90 ps and longer timescales. The fast process is designated as the initial melting of orthorhombic phase induced by the Mn-O bond change that is most likely driven by the quenching of the dynamic Jahn-Teller distortion following the photo-excitation. The slow process is attributed to the growing of newly formed structure domain from the photo-excited sites to the neighboring non-excited orthorhombic sites.

Charge driven metal-insulator transitions in LaMnO3|SrTiO3 (111) superlattices

KAUST Repository

Cossu, Fabrizio

2017-08-01

Interfaces of perovskite oxides, due to the strong interplay between the lattice, charge and spin degrees of freedom, can host various phase transitions, which is particularly interesting if these transitions can be tuned by external fields. Recently, ferromagnetism was found together with a seemingly insulating state in superlattices of manganites and titanates. We therefore study the (111) oriented $(\\\\text{LaMnO}_3)_{6-x}\\\\vert(\\\\text{SrTiO}_3)_{6+x}~(x = -0.5, 0, 0.5)$ superlattices by means of ab initio calculations, predicting a ferromagnetic ground state due to double exchange in all cases. We shed light on the ferromagnetic coupling in the LaMnO3 region and at the interfaces. The insulating states of specific superlattices can be understood on the basis of Jahn-Teller modes and electron/hole doping.

Lattice modes and the Jahn-Teller ferroelectric transition of GaV.sub.4./sub.S.sub.8./sub.

Czech Academy of Sciences Publication Activity Database

Hlinka, Jiří; Borodavka, Fedir; Rafalovskyi, Iegor; Dočekalová, Zuzana; Pokorný, Jan; Gregora, Ivan; Tsurkan, V.; Nakamura, H.; Mayr, F.; Kuntscher, C.A.; Loidl, A.; Bordács, S.; Szaller, D.; Lee, H.-J.; Lee, J.H.; Kézsmárki, I.

2016-01-01

Roč. 94, č. 6 (2016), 1-4, č. článku 060104. ISSN 2469-9950 R&D Projects: GA ČR GA13-15110S Institutional support: RVO:68378271 Keywords : augmented-wave method * crystals * phase Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.836, year: 2016

The position–momentum uncertainty relations for a Pöschl–Teller type potential and its squeezed phenomena

Energy Technology Data Exchange (ETDEWEB)

Chen, Chang-Yuan, E-mail: yctcccy@163.net [School of Physics and Electronics, Yancheng Teachers University, Yancheng 224051 (China); You, Yuan; Lu, Fa-Lin [School of Physics and Electronics, Yancheng Teachers University, Yancheng 224051 (China); Dong, Shi-Hai, E-mail: dongsh2@yahoo.com [Departamento de Física, Escuela Superior de Física y Matemáticas, Instituto Politécnico Nacional, Edificio 9, Unidad Profesional Adolfo López Mateos, Mexico D.F. 07738 (Mexico)

2013-06-17

We present the position–momentum uncertainties for the Pöschl–Teller potential. We observe that the Δx decreases with the potential depth λ but increases with quantum number n. Interestingly, we find that the Δp first increases and then decreases with the n. The ΔxΔp first decreases and then increases with the λ, but almost becomes a constant (n+1/2)ℏ for a larger λ. Particularly, there exists a squeezed phenomenon in position x for the lower states. The squeezing in x compensated for by an increase in momentum p, such that ΔxΔp⩾ℏ/2 is still satisfied.

The position–momentum uncertainty relations for a Pöschl–Teller type potential and its squeezed phenomena

International Nuclear Information System (INIS)

Chen, Chang-Yuan; You, Yuan; Lu, Fa-Lin; Dong, Shi-Hai

2013-01-01

We present the position–momentum uncertainties for the Pöschl–Teller potential. We observe that the Δx decreases with the potential depth λ but increases with quantum number n. Interestingly, we find that the Δp first increases and then decreases with the n. The ΔxΔp first decreases and then increases with the λ, but almost becomes a constant (n+1/2)ℏ for a larger λ. Particularly, there exists a squeezed phenomenon in position x for the lower states. The squeezing in x compensated for by an increase in momentum p, such that ΔxΔp⩾ℏ/2 is still satisfied.

Bethe, Oppenheimer, Teller and the Fermi Award: Norris Bradbury Speaks

Energy Technology Data Exchange (ETDEWEB)

Meade, Roger Allen [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

2017-04-28

In 1956 the Enrico Fermi Presidential Award was established to recognize scientists, engineers, and science policymakers who gave unstintingly over their careers to advance energy science and technology. The first recipient was John von Neumann. .1 Among those scientists who were thought eligible for the award were Hans Bethe, J. Robert Oppenheimer, and Edward Teller. In 1959 Norris Bradbury was asked to comment on the relative merits of each these three men, whom he knew well from their affiliation with Los Alamos. Below is a reproduction of the letter Bradbury sent to Dr. Warren C. Johnson of the AEC’s General Advisory Committee(GAC) containing his evaluation of each man. The letter might surprise those not accustomed to Bradbury’s modus operandi of providing very detailed and forthright answers to the AEC. The letter, itself, was found in cache of old microfilm. Whether because of the age of the microfilm or the quality of the filming process, portions of the letter are not legible. Where empty brackets appear, the word or words could not be read or deduced. Words appearing in brackets are guesses that appear, from the image, to be what was written. These guesses, of course, are just that – guesses.

Is talking to an automated teller machine natural and fun?

Science.gov (United States)

Chan, F Y; Khalid, H M

Usability and affective issues of using automatic speech recognition technology to interact with an automated teller machine (ATM) are investigated in two experiments. The first uncovered dialogue patterns of ATM users for the purpose of designing the user interface for a simulated speech ATM system. Applying the Wizard-of-Oz methodology, multiple mapping and word spotting techniques, the speech driven ATM accommodates bilingual users of Bahasa Melayu and English. The second experiment evaluates the usability of a hybrid speech ATM, comparing it with a simulated manual ATM. The aim is to investigate how natural and fun can talking to a speech ATM be for these first-time users. Subjects performed the withdrawal and balance enquiry tasks. The ANOVA was performed on the usability and affective data. The results showed significant differences between systems in the ability to complete the tasks as well as in transaction errors. Performance was measured on the time taken by subjects to complete the task and the number of speech recognition errors that occurred. On the basis of user emotions, it can be said that the hybrid speech system enabled pleasurable interaction. Despite the limitations of speech recognition technology, users are set to talk to the ATM when it becomes available for public use.

Observation of Fermi and Gamow-Teller strength in the 800 MeV(p,n) reaction

Energy Technology Data Exchange (ETDEWEB)

King, N S.P.; Lisowski, P W; Morgan, G L; Craig, P N; Jeppesen, R G; Lind, D A; Shepard, J R; Ullmann, J L; Zafiratos, C D; Goodman, C D

1986-08-07

Angular distributions have been measured for the (p,n) reaction on targets of /sup 6/Li, /sup 12/C, /sup 13/C, and /sup 15/N at 800 MeV with an energy resolution of 2.7 MeV allowing observation of discrete nuclear levels. As is the case at lower energies, this reaction is very selective, emphasizing Gamow-Teller (GT) and Fermi transitions. Absolute cross sections of pure GT transitions are reproduced by impulse approximation calculations. The ratio vertical strokeJsub(sigmatau)vertical stroke/sup 2//vertical strokeJsub(tau)vertical stroke/sup 2/ was extracted from /sup 13/C and /sup 15/N measurements at 800 MeV and from a /sup 13/C measurement at 318 MeV.

A Theoretical Investigation of the Structure and Reactivity of the Molecular Constituents of Oil Sand and Oil Shale

Energy Technology Data Exchange (ETDEWEB)

Parish, Carol A. [Univ. of Richmond, VA (United States)

2016-11-28

standing interest in polyoligomeric silsesquioxane (POSS) molecules.^1-2 These molecules have recently been used as advanced surface coatings for photovoltaic devices and have potential as molecular-based energy storage devices as well as magnetically controllable liquid marbles.^3-5 We have been investigating the small molecule encapsulation properties of POSS and discovered some interesting symmetry breaking processes that need to be better understood in order to use POSS in advanced materials. We have investigated this symmetry breaking mechanism in POSS monocations Si8O12(C(CH3)3)8+ and Si8O12Cl8+, using density functional theory (DFT) and group theory. Under Oh symmetry, these ions possess 2T2g and 2Eg electronic states, respectively, and undergo different symmetry breaking mechanisms. The ground states of Si₈O₁₂(C(CH₃)₃)₈⁺ and Si₈O₁₂Cl₈⁺ belong to the C_3v and D_4h point groups and are characterized by Jahn-Teller stabilization energies of 3959 and 1328 cm-1, respectively, at the B3LYP/def2-SVP level of theory. The symmetry distortion mechanism in Si₈O₁₂Cl₈⁺ is Jahn-Teller type, whereas in Si₈O₁₂(C(CH₃)₃)₈⁺ the distortion is a combination of both Jahn-Teller and pseudo-Jahn-Teller effects. The distortion force acting in Si₈O₁₂(C(CH₃)₃)₈⁺ is mainly localized on one Si-(tert-butyl) group while in Si₈O₁₂Cl₈⁺ it is distributed over the oxygen atoms. The main distortion forces acting on the Si8O12 core arise from the coupling between the electronic state and the vibrational modes; identified as 9t_2g+1e_g+3a_2u for the Si₈O₁₂(C(CH₃)₃

Enhanced vibronic interaction caused by local lattice symmetry lowering in the (Fe, Mg)As2 ternary system

Science.gov (United States)

Pishtshev, A.; Rubin, P.

2018-04-01

By means of periodic density functional theory (DFT) electronic structure calculations, we investigate iron-site doping effects in a structural model of bulk FeAs2. Simulations performed within the projector augmented-wave method-Perdew-Burke-Ernzerhof (PBE) generalized gradient approximation (GGA) functional scheme reveal that the impacts of the two stoichiometric substitutions Fe → Mg and Fe → Ni are radically different with respect to the structural and electronic behavior of the dopants. In particular, unlike the Ni dopant, the Mg dopant incorporated in FeAs2 occupies a noncentral equilibrium position characterized by an off-center displacement from the reference higher-symmetry position. Analysis of the respective electron and vibrational factors allows us to explain this result in terms of the local pseudo Jahn-Teller effect (pJTE). On the basis of DFT calculations, we deduce which electron orbitals and lattice vibrational modes are appropriate for promoting the local instability at the origin of the pJTE. Quantitative evaluations of the pJTE parameters performed within the polyatomic formalism of an effective tight-binding model show that it is just the enhanced vibronic interaction in the Mg-[FeAs6] cluster that is responsible for the local lattice symmetry breaking.

A study of the valence shell electronic states of s-triazine by photoabsorption spectroscopy and ab initio calculations

Energy Technology Data Exchange (ETDEWEB)

Holland, D.M.P., E-mail: david.holland@stfc.ac.uk [Daresbury Laboratory, Daresbury, Warrington, Cheshire WA4 4AD (United Kingdom); Shaw, D.A. [Daresbury Laboratory, Daresbury, Warrington, Cheshire WA4 4AD (United Kingdom); Stener, M.; Decleva, P. [Dipartimento di Scienze Chimiche e Farmaceutiche, Università degli Studi di Trieste, Via L. Giorgieri, I-34127 Trieste (Italy); Consorzio Interuniversitario Nazionale per la Scienze e Tecnologia dei Materiali, INSTM, Unità di Trieste (Italy); CNR-IOM, Trieste (Italy); Coriani, S. [Dipartimento di Scienze Chimiche e Farmaceutiche, Università degli Studi di Trieste, Via L. Giorgieri, I-34127 Trieste (Italy); Consorzio Interuniversitario Nazionale per la Scienze e Tecnologia dei Materiali, INSTM, Unità di Trieste (Italy); Aarhus Institute of Advanced Studies, Aarhus University, 8000 Aarhus C (Denmark)

2016-09-30

Highlights: • The valence shell photoabsorption spectrum of s-triazine has been measured. • Electronic structure calculated with TDDFT and coupled cluster approaches. • Assignments proposed for Rydberg and valence states. • Mixing between Rydberg and valence states important. - Abstract: The absolute photoabsorption cross section of s-triazine has been measured between 4 and 40 eV, and is dominated by bands associated with valence states. Structure due to Rydberg excitations is both weak and irregular. Jahn-Teller interactions affect the vibronic structure observed in the Rydberg absorption bands due to excitation from the 1e″ or 6e′ orbitals. The interpretation of the experimental spectrum has been guided by transition energies and oscillator strengths, for Rydberg and valence states, calculated with the time-dependent version of density functional theory and with the coupled cluster linear response approach. The theoretical studies indicate that Rydberg/Rydberg and Rydberg/valence mixing is important.

Local hydrated structure of an Fe2+/Fe3+ aqueous solution: an investigation using a combination of molecular dynamics and X-ray absorption fine structure methods

International Nuclear Information System (INIS)

Ye Qing; Zhou Jing; Zhao Haifeng; Chen Xing; Chu Wangsheng; Zheng Xusheng; Marcelli, Augusto; Wu Ziyu

2013-01-01

The hydrated shell of both Fe 2+ and Fe 3+ aqueous solutions are investigated by using the molecular dynamics (MD) and X-ray absorption structure (XAS) methods. The MD simulations show that the first hydrated shells of both Fe 2+ and Fe 3+ are characterized by a regular octahedron with an Fe-O distance of 2.08Å for Fe 2+ and 1.96Å for Fe 3+ , and rule out the occurrence of a Jahn-Teller distortion in the hydrated shell of an Fe 2+ aqueous solution. The corresponding X-ray absorption near edge fine structure (XANES) calculation successfully reproduces all features in the XANES spectra in Fe 2+ and Fe 3+ aqueous solution. A feature that is located at energy 1 eV higher than the white line (WL) in an Fe 3+ aqueous solution may be assigned to the contribution of the charge transfer. (authors)

Complex-forming capacity of some biologically active imidazoles

Energy Technology Data Exchange (ETDEWEB)

Lenarcik, B; Wisniewski, M

1983-01-01

By using the potentiometric and spectrophotometric methods, formation of Co(2), Cu(2), Zn(2), Ni(2) and Cd(2) complexes of (3S-cis)-3-ethyl-dihydro-4-((1-methyl-1H-imidazol-5-yl)-methyl)-2(3H)-furanone (pilocarpine, PLC), 4,5-dihydro-2-(phenylmethyl)-1H-imidazole (tolazoline, TLZ), 2-methyl-5-nitro-1H-imidazole-1-ethanol (metronidazole, MET) and 1H-imidazole-4-ethanamine (histamine, HIST) was investigated. The stability constants, ..beta../sub n/, of these complexes were determined. It was shown that the electron-donor strength of the ligands was controlled by the heterocyclic nitrogen atom, and that the formation of the Zn(2)-PLC complex was accompanied by the change in the structure of the coordination sphere of the metal. With Cu(2), the PLC and TLZ ligands were shown to enhance the Jahn-Teller deformation.

Structural features and electronic properties of group-III-, group-IV-, and group-V-doped Si nanocrystallites

International Nuclear Information System (INIS)

Ramos, L E; Degoli, Elena; Cantele, G; Ossicini, Stefano; Ninno, D; Furthmueller, J; Bechstedt, F

2007-01-01

We investigate the incorporation of group-III (B and Al), group-IV (C and Ge), and group-V (N and P) impurities in Si nanocrystallites. The structural features and electronic properties of doped Si nanocrystallites, which are faceted or spherical-like, are studied by means of an ab initio pseudopotential method including spin polarization. Jahn-Teller distortions occur in the neighborhood of the impurity sites and the bond lengths show a dependence on size and shape of the nanocrystallites. We find that the acceptor (group-III) and donor (group-V) levels become deep as the nanocrystallites become small. The energy difference between the spin-up and spin-down levels of group-III and group-V impurities decreases as the size of the Si nanocrystallite increases and tends to the value calculated for Si bulk. Doping with carbon introduces an impurity-related level in the energy gap of the Si nanocrystallites

Analysis of D Dimensional Dirac equation for q -deformed Posch-Teller combined with q -deformed trigonometric Manning Rosen Non-Central potential using Asymptotic Iteration Method (AIM)

International Nuclear Information System (INIS)

Alam, Y.; Suparmi; Cari; Anwar, F.

2016-01-01

In this study, we used asymptotic iteration method (AIM) to obtain the relativistic energy spectra and wavefunctions for D Dimensional Dirac equation. Solution of the D Dimensional Dirac equation using asymptotic iteration method was done by four steps. The first step, we substitutied q deformed Poschl-Teller potential plus q-deformed Manning Rosen Non-Central potential into D dimensional Dirac equation. And then, general term of D dimensioanl Dirac equation for q deformed Poschl-Teller potential plus q-deformed Manning Rosen Non-Central potential was reduced into one dimensioanal Dirac equation, consist of radial part and angular part. The second step, both of one dimensional part must be reduced to hypergeometric type differential equation by suitable parameter change. And then, hypergeometric type differential equation was transformed into AIM type differential equation. For the last step, AIM type differential equation can be solved to obtain the relativistic energy and wavefunctions of Dirac equation. Relativistic energy and wavefunctions were visualized by using Matlab software. (paper)

Double Gamow-Teller Transitions and its Relation to Neutrinoless β β Decay

Science.gov (United States)

Shimizu, Noritaka; Menéndez, Javier; Yako, Kentaro

2018-04-01

We study the double Gamow-Teller (DGT) strength distribution of 48Ca with state-of-the-art large-scale nuclear shell model calculations. Our analysis shows that the centroid energy of the DGT giant resonance depends mostly on the isovector pairing interaction, while the resonance width is more sensitive to isoscalar pairing. Pairing correlations are also key in neutrinoless β β (0 ν β β ) decay. We find a simple relation between the centroid energy of the 48Ca DGT giant resonance and the 0 ν β β decay nuclear matrix element. More generally, we observe a very good linear correlation between the DGT transition to the ground state of the final nucleus and the 0 ν β β decay matrix element. The correlation, which originates on the dominant short-range character of both transitions, extends to heavier systems including several β β emitters and also holds in energy-density functional results. Our findings suggest that DGT experiments can be a very valuable tool to obtain information on the value of 0 ν β β decay nuclear matrix elements.

Quantum information entropies of the eigenstates for the Pöschl—Teller-like potential

International Nuclear Information System (INIS)

Sun Guo-Hua; Aoki, M. Avila; Dong Shi-Hai

2013-01-01

Shannon entropy for lower position and momentum eigenstates of Pöschl—Teller-like potential is evaluated. Based on the entropy densities demonstrated graphically, we note that the wave through of the position information entropy density ρ(x) moves right when the potential parameter V 1 increases and its amplitude decreases. However, its wave through moves left with the increase in the potential parameter |V 2 |. Concerning the momentum information entropy density ρ(p), we observe that its amplitude increases with increasing potential parameter V 1 , but its amplitude decreases with increasing |V 2 |. The Bialynicki—Birula—Mycielski (BBM) inequality has also been tested for a number of states. Moreover, there exist eigenstates that exhibit squeezing in the momentum information entropy. Finally, we note that position information entropy increases with V 1 , but decreases with |V 2 |. However, the variation of momentum information entropy is contrary to that of the position information entropy. (general)

Gamow-Teller strength functions from (→p,→p') scattering experiments

International Nuclear Information System (INIS)

Hausser, O.

1987-01-01

We present here recent (→p, →'p) results from TRIUMF that are relevant to the determination of spin-flip isovector strength functions in nuclei. Distortion factors needed for the extraction of nuclear-structure information have been deduced from cross sections and analyzing powers in elastic scattering for several energies and targets. Nonrelativistic optical potentials obtained by folding effective nucleon (N)-nucleus interactions with nuclear densities are found to overpredict both elastic and reaction cross sections, whereas Dirac calculations that include Pauli blocking are in good agreement with the data. Spin observables (S nn and A y ) for the quasi-elastic region in 54 Fe(→p, →p) at 290 MeV provide some evidence for the reduction of the effective proton mass predicted in relativistic mean-field theories as a consequence of the attractive scalar field in the nuclear medium. The energy dependence of the effective N-nucleus interaction at small momentum transfers has been investigated using isoscalar and isovector 1 + states in 28 Si as probe states. We find that the cross sections for the isovector transitions are in good agreement with predictions for the dominant Vστ part of the Franey-Love interaction. Gamow-Teller (GT) strength functions have been obtained in 24 Mg and 54 Fe from measurements of both cross sections and spin-flip probabilities S nn . The spin-flip cross sections σS nn are particularly useful in heavier nuclei to discriminate against a continuous background of ΔS = 0 excitations. In the (s, d) shell where full shell-model wave functions are available, the GT quenching factors (g A eff / g A free ) 2 ≅ 0.7 are in good agreement with those from recent (p, n) and (n, p) experiments. We show that a state-by-state comparison of (p, p') and (e, e') results has the potential of identifying pionic current contributions in (e, e'). The GT quenching factors in 54 Fe are smaller than in the (s, d) shell probably because of severely

Probing electronic phase transitions with phonons via inelastic neutron scattering: superconductivity in borocarbides, charge and magnetic order in manganites

Energy Technology Data Exchange (ETDEWEB)

Weber, F.

2007-11-02

The present thesis concentrates on the signatures of strong electron-phonon coupling in phonon properties measured by inelastic neutron scattering. The inelastic neutron scattering experiments were performed on the triple-axis spectrometers 1T and DAS PUMA at the research reactors in Saclay (France) and Munich (Germany), respectively. The work is subdivided into two separate chapters: In the first part, we report measurements of the lattice dynamical properties, i.e. phonon frequency, linewidth and intensity, of the conventional, i.e. phonon-mediated, superconductor YNi{sub 2}B{sub 2}C of the rare-earth-borocarbide family. The detailed check of theoretical predictions for these properties, which were calculated in the theory group of our institute, was one major goal of this work. We measured phonons in the normal state, i.e. T>T{sub c}, for several high symmetry directions up to 70 meV. We were able to extract the full temperature dependence of the superconducting energy gap 2{delta}(T) from our phonon scans with such accuracy that even deviations from the weak coupling BCS behaviour could be clearly observed. By measuring phonons at different wave vectors we demonstrated that phonons are sensitive to the gap anisotropy under the precondition, that different phonons get their coupling strength from different parts of the Fermi surface. In the second part, we investigated the properties of Mn-O bond-stretching phonons in the bilayer manganite La{sub 2-2x}Sr{sub 1+2x}Mn{sub 2}O{sub 7}. At the doping level x=0.38 this compound has an ferromagnetic groundstate and exhibits the so-called colossal magnetoresistance effect in the vicinity of the Curie temperature T{sub C}. The atomic displacement patterns of the investigated phonons closely resemble possible Jahn-Teller distortions of the MnO{sub 6} octahedra, which are introduced in this compound by the Jahn-Teller active Mn{sup 3+} ions. We observed strong renormalizations of the phonon frequencies and clear peaks of

Probing electronic phase transitions with phonons via inelastic neutron scattering: superconductivity in borocarbides, charge and magnetic order in manganites

International Nuclear Information System (INIS)

Weber, F.

2007-01-01

The present thesis concentrates on the signatures of strong electron-phonon coupling in phonon properties measured by inelastic neutron scattering. The inelastic neutron scattering experiments were performed on the triple-axis spectrometers 1T and DAS PUMA at the research reactors in Saclay (France) and Munich (Germany), respectively. The work is subdivided into two separate chapters: In the first part, we report measurements of the lattice dynamical properties, i.e. phonon frequency, linewidth and intensity, of the conventional, i.e. phonon-mediated, superconductor YNi 2 B 2 C of the rare-earth-borocarbide family. The detailed check of theoretical predictions for these properties, which were calculated in the theory group of our institute, was one major goal of this work. We measured phonons in the normal state, i.e. T>T c , for several high symmetry directions up to 70 meV. We were able to extract the full temperature dependence of the superconducting energy gap 2Δ(T) from our phonon scans with such accuracy that even deviations from the weak coupling BCS behaviour could be clearly observed. By measuring phonons at different wave vectors we demonstrated that phonons are sensitive to the gap anisotropy under the precondition, that different phonons get their coupling strength from different parts of the Fermi surface. In the second part, we investigated the properties of Mn-O bond-stretching phonons in the bilayer manganite La 2-2x Sr 1+2x Mn 2 O 7 . At the doping level x=0.38 this compound has an ferromagnetic groundstate and exhibits the so-called colossal magnetoresistance effect in the vicinity of the Curie temperature T C . The atomic displacement patterns of the investigated phonons closely resemble possible Jahn-Teller distortions of the MnO 6 octahedra, which are introduced in this compound by the Jahn-Teller active Mn 3+ ions. We observed strong renormalizations of the phonon frequencies and clear peaks of the intrinsic phonon linewidth near the order

Minimum dipole moment required to bind an electron: molecular theorists rediscover phenomenon mentioned in Fermi-Teller paper twenty years earlier

International Nuclear Information System (INIS)

Turner, J.E.

1977-01-01

Work leading to the discovery of the minimum dipole moment for electron binding, D/sub min/=0.639 ea 0 (atomic units), by several groups in 1967--1968 is described. It was subsequently learned that this number had been published in 1947 by Fermi and Teller, who did not, however, indicate how they derived it. The author has found a numerical solution in Fermi's notebooks from 1946--1950 at the University of Chicago Library. Fermi's work is described and presented here with relevant material from his notebooks

Spectral intensities for stoichiometric elpasolites. I. Absorption and emission of Tm+3 in systems of the Cs2NaTmZ6 type

International Nuclear Information System (INIS)

Acevedo, R; Poblete, V; Pozo, J; Elgueta, R; Tanner, P.A

2000-01-01

Based upon new experimental data for systems such as, Cs 2 NaTmZ 6 , where Z - =Cl - , F - [1-4], we have carried out a thorough study of the mechanistic factors related with the spectral intensities for both the absorptions and the emissions of the Cs 2 NaTmZ 6 system. For the above purposes, we have generalized our previous calculation models, and in this article we show novel results for the emissions 3 H 4 (Γ i )→ 3 F 4 (Γ j ) and for the absorptions 3 H 6 (A 1 )→ 3 F 4 (Γ i ), 1 G 4 (Γ i ), 3 H 5 (Γ i ), with Γ-k(k=i,j)=A 1 ,E,T 1 ,T 2 and Γ 1 =T a 1 , T b 1 , E, T 2 . The effects due to dispersion (essentially, electrostatic in character), details of the short range vibrational force field and Jahn-Teller distortion are discussed in the text. The agreement among experiment and theory is satisfactory and a generalized model with a few number of adjustable parameters is introduced to account for the observed spectral intensities

Investigations on the Local Structures and the Spin Hamiltonian Parameters for Cu2+ in (90-x)TeO2-10GeO2-xWO3 Glasses

Science.gov (United States)

Feng, Chun-Rong; Jian, Jun; Chen, Xiao-Hong; Du, Quan; Wang, Ling

2017-12-01

The local structures and the spin Hamiltonian parameters (SHPs) for Cu2+ in (90-x)TeO2-10GeO2-xWO3 glasses are theoretically investigated at various WO3 concentrations (x=7.5, 15, 22.5 and 30 mol%). Subject to the Jahn-Teller effect, the [CuO6]10- groups are found to experience the small or moderate tetragonal elongation distortions (characterised by the relative tetragonal elongation ratios ρ≈0.35-3.09%) in C4 axis. With only three adjusted coefficients a, b and ω, the relevant model parameters (Dq, k and ρ) are described by the Fourier type and linear functions, respectively, and the measured concentration dependences of the d-d transition bands and SHPs are reproduced. The maximum of g∥ and the minimum of |A∥| at x=15 mol% are illustrated from the abrupt decrease of the copper-oxygen electron cloud admixtures or covalency and the obvious decline of the copper 3d-3s (4s) orbital admixtures due to the decreasing electron cloud density around oxygen ligands spontaneously bonding with Cu2+ and Te4+ (W6+), respectively.

Mitigating Voltage Decay of Li-Rich Cathode Material via Increasing Ni Content for Lithium-Ion Batteries.

Science.gov (United States)

Shi, Ji-Lei; Zhang, Jie-Nan; He, Min; Zhang, Xu-Dong; Yin, Ya-Xia; Li, Hong; Guo, Yu-Guo; Gu, Lin; Wan, Li-Jun

2016-08-10

Li-rich layered materials have been considered as the most promising cathode materials for future high-energy-density lithium-ion batteries. However, they suffer from severe voltage decay upon cycling, which hinders their further commercialization. Here, we report a Li-rich layered material 0.5Li2MnO3·0.5LiNi0.8Co0.1Mn0.1O2 with high nickel content, which exhibits much slower voltage decay during long-term cycling compared to conventional Li-rich materials. The voltage decay after 200 cycles is 201 mV. Combining in situ X-ray diffraction (XRD), ex situ XRD, ex situ X-ray photoelectron spectroscopy, and scanning transmission electron microscopy, we demonstrate that nickel ions act as stabilizing ions to inhibit the Jahn-Teller effect of active Mn(3+) ions, improving d-p hybridization and supporting the layered structure as a pillar. In addition, nickel ions can migrate between the transition-metal layer and the interlayer, thus avoiding the formation of spinel-like structures and consequently mitigating the voltage decay. Our results provide a simple and effective avenue for developing Li-rich layered materials with mitigated voltage decay and a long lifespan, thereby promoting their further application in lithium-ion batteries with high energy density.

Studies of the local distortions and the EPR parameters for Cu{sup 2+} in xLi{sub 2}O-(30-x)Na{sub 2}O-69.5B{sub 2}O glasses

Energy Technology Data Exchange (ETDEWEB)

Ding, Chang-Chun; Wu, Shao-Yi; Kuang, Min-Quan; Hu, Xian-Fen; Li, Guo-Liang [Univ. of Electronic Science and Technology of China, Chengdu (China). Dept. of Applied Physics

2016-07-01

The local distortions and electron paramagnetic resonance (EPR) parameters for Cu2+ in lithium sodium borate (LNB) glasses xLi{sub 2}O.(30-x).Na{sub 2}O.69.5B{sub 2}O{sub 3} (5 ≤ x ≤ 25 mol%) are theoretically studied at various concentrations x in a consistent way. Owing to the Jahn-Teller effect, the [CuO{sub 6}]{sup 10-} clusters are found to experience the significant tetragonal elongations of 16% along C{sub 4} axis. Despite the nearly unchanging observed g factors, measured d-d transition band (or cubic field parameter Dq) shows remarkable linear increases with concentration x, whose influences on g {sub parallel} and g {sub perpendicular} {sub to} are actually cancelled by the linearly increasing covalency factor N and relative elongation ratio η with x. The almost unvarying hyperfine structure constants are attributed to the fact that the influences of the linearly increasing N and the linearly decreasing core polarisation constant κ largely cancel one another. The microscopic mechanisms of the above concentration dependences for these quantities are illustrated from mixed alkali effect (modification of B{sub 2}O{sub 3} network by transforming some BO{sub 3} units into BO{sub 4} ones with variations in modifier Li{sub 2}O concentration).

A review of the low temperature properties of the rare earth vanadates

International Nuclear Information System (INIS)

Bowden, G.J.

1998-01-01

The rare earth vanadates have long been studied for their interesting magnetic properties and cooperative Jahn-Teller distortions. In the main, most of this work has been carried out at temperatures down to 1 K or so (e.g. Gehring and Gehring 1975). In this review NMRON (NMR on Oriented Nuclei), and other low temperature experiments in the mK regime, are presented and discussed. It will be argued that the low temperature properties of these compounds are just as interesting as their high temperature counterparts. In general, the nuclear and electronic wavefunctions become intermixed, leading to a variety of interesting physical effects, such as enhanced nuclear magnetism, quadrupolar induced intermediate state re-orientation etc. These effects have, in turn, spawned new methods for the investigation of magnetic structures, and thermometric detection of 166 Ho NMR both by internal and external thermometers. Several experiments are suggested, including magnetic refrigeration, Moessbauer, EPR in the ∼30 GHz range, in addition to thermometric NMR and NMRON. Nuclear Orientation (NO) studies of HoVO 4 , using in-situ radioactive 166 Ho, has led to the development of new techniques for the determination of complex spin structures and mixed domains, and can be used to rival or complement neutron scattering. Copyright (1998) Australian Journal of Physics

Quantum information entropies of the eigenstates for the P(o)schl-Teller-like potential

Institute of Scientific and Technical Information of China (English)

Guo-Hua Sun; M.Avila Aoki; Shi-Hai Dong

2013-01-01

Shannon entropy for lower position and momentum eigenstates of P(o)schl-Teller-like potential is evaluated.Based on the entropy densities demonstrated graphically,we note that the wave through of the position information entropy density ρ(x) moves right when the potential parameter V1 increases and its amplitude decreases.However,its wave through moves left with the increase in the potential parameter |V2|.Concerning the momentum information entropy density p(p),we observe that its amplitude increases with increasing potential parameter V1,but its amplitude decreases with increasing |V2|.The Bialynicki-Birula-Mycielski (BBM) inequality has also been tested for a number of states.Moreover,there exist eigenstates that exhibit squeezing in the momentum information entropy.Finally,we note that position information entropy increases with V1,but decreases with |V2|.However,the variation of momentum information entropy is contrary to that of the position information entropy.

Interplay between electron-phonon and electron-electron interactions

International Nuclear Information System (INIS)

Roesch, O.; Gunnarsson, O.; Han, J.E.; Crespi, V.H.

2005-01-01

We discuss the interplay between electron-electron and electron-phonon interactions for alkali-doped fullerides and high temperature superconductors. Due to the similarity of the electron and phonon energy scales, retardation effects are small for fullerides. This raises questions about the origin of superconductivity, since retardation effects are believed to be crucial for reducing effects of the Coulomb repulsion in conventional superconductors. We demonstrate that by treating the electron-electron and electron-phonon interactions on an equal footing, superconductivity can be understood in terms of a local pairing. The Jahn-Teller character of the important phonons in fullerides plays a crucial role for this result. To describe effects of phonons in cuprates, we derive a t-J model with phonons from the three-band model. Using exact diagonalization for small clusters, we find that the anomalous softening of the half-breathing phonon as well as its doping dependence can be explained. By comparing the solution of the t-J model with the Hartree-Fock approximation for the three-band model, we address results obtained in the local-density approximation for cuprates. We find that genuine many-body results, due to the interplay between the electron-electron and electron-phonon interactions, play an important role for the the results in the t-J model. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Optical investigations of La0.7Ca0.3-xKxMnO3 (x = 0.00, 0.05 and 0.10 probed by spectroscopic ellipsometry

Directory of Open Access Journals (Sweden)

N. Sdiri

2012-07-01

Full Text Available Using spectroscopic ellipsometry, we have studied the optical properties of doped manganites at the paramagnetic state in polycrystalline La0.7Ca0.3-xKxMnO3 samples for (x = 0.00, 0.05 and 0.10 in the energy range of 3.2-5.5 eV at room temperature. The surface morphology of the samples was obtained by using atomic force microscopy (AFM. Refractive indices, extinction coefficients, the transmission ellipsometric parameters Ψ and Δ are investigated at different wavelengths. The study of the optical conductivity σ reveals that optical behaviour and the activated transport in the paramagnetic state of these materials are consistent with Jahn-Teller small polaron. In addition, the spectrum of the complex dielectric constant ε reveals peaks for all samples, the results may be explained by the presence of space charges from the strongly dipole-allowed O(2p−Mn(3d transition.

Studies on strain relaxation of La{sub 0.5}Ba{sub 0.5}MnO{sub 3} film by normal and grazing incidence X-ray diffraction

Energy Technology Data Exchange (ETDEWEB)

Wang, Haiou [Hangzhou Dianzi University, Institute of Materials Physics, Hangzhou (China); Tan, Weishi [Hunan City University, College of Communication and Electronic Engineering, Yiyang (China); Nanjing University of Science and Technology, Key Laboratory of Soft Chemistry and Functional Materials, Department of Applied Physics, Ministry of Education, Nanjing (China); Liu, Hao [Suzhou Institute of Industrial Technology, Department of Electronic and Communication Engineering, Suzhou (China); Cao, Mengxiong; Wang, Xingyu; Ma, Chunlin [Nanjing University of Science and Technology, Key Laboratory of Soft Chemistry and Functional Materials, Department of Applied Physics, Ministry of Education, Nanjing (China); Jia, Quanjie [The Chinese Academy of Sciences, Institute of High Energy Physics, Beijing (China)

2017-03-15

Perovskite manganite La{sub 0.5}Ba{sub 0.5}MnO{sub 3} (LBMO) films were deposited on (001)-oriented single-crystal SrTiO{sub 3} (STO) substrates by pulsed laser deposition. High-resolution X-ray diffraction and grazing incidence X-ray diffraction techniques were applied to characterize the crystal structure and lattice strain of LBMO films. The in-plane and out-of-plane growth orientations of LBMO films with respect to substrate surface have been studied. The epitaxial orientation relationship LBMO (001) [100] //STO (001) [100] exists at the LBMO/STO interface. The lattice strain of LBMO film begins to relax with the thickness of LBMO film up to 12 nm. When the thickness is further increased up to 43 nm, the film is in fully strain-relaxed state. Jahn-Teller strain plays an important role in LBMO/STO system. The mechanism for strain relaxation is in accordance with that of tetragonal distortion. (orig.)

Prediction of Intrinsic Ferromagnetic Ferroelectricity in a Transition-Metal Halide Monolayer

Science.gov (United States)

Huang, Chengxi; Du, Yongping; Wu, Haiping; Xiang, Hongjun; Deng, Kaiming; Kan, Erjun

2018-04-01

The realization of multiferroics in nanostructures, combined with a large electric dipole and ferromagnetic ordering, could lead to new applications, such as high-density multistate data storage. Although multiferroics have been broadly studied for decades, ferromagnetic ferroelectricity is rarely explored, especially in two-dimensional (2D) systems. Here we report the discovery of 2D ferromagnetic ferroelectricity in layered transition-metal halide systems. On the basis of first-principles calculations, we reveal that a charged CrBr3 monolayer exhibits in-plane multiferroicity, which is ensured by the combination of orbital and charge ordering as realized by the asymmetric Jahn-Teller distortions of octahedral Cr - Br6 units. As an example, we further show that (CrBr3)2Li is a ferromagnetic ferroelectric multiferroic. The explored phenomena and mechanism of multiferroics in this 2D system not only are useful for fundamental research in multiferroics but also enable a wide range of applications in nanodevices.

Enhanced magnetic anisotropies of single transition-metal adatoms on a defective MoS2 monolayer.

Science.gov (United States)

Cong, W T; Tang, Z; Zhao, X G; Chu, J H

2015-03-23

Single magnetic atoms absorbed on an atomically thin layer represent the ultimate limit of bit miniaturization for data storage. To approach the limit, a critical step is to find an appropriate material system with high chemical stability and large magnetic anisotropic energy. Here, on the basis of first-principles calculations and the spin-orbit coupling theory, it is elucidated that the transition-metal Mn and Fe atoms absorbed on disulfur vacancies of MoS2 monolayers are very promising candidates. It is analysed that these absorption systems are of not only high chemical stabilities but also much enhanced magnetic anisotropies and particularly the easy magnetization axis is changed from the in-plane one for Mn to the out-of-plane one for Fe by a symmetry-lowering Jahn-Teller distortion. The results point out a promising direction to achieve the ultimate goal of single adatomic magnets with utilizing the defective atomically thin layers.

Dynamically fluctuating electric dipole moments in fullerene-based magnets.

Science.gov (United States)

Kambe, Takashi; Oshima, Kokichi

2014-09-19

We report here the direct evidence of the existence of a permanent electric dipole moment in both crystal phases of a fullerene-based magnet--the ferromagnetic α-phase and the antiferromagnetic α'-phase of tetra-kis-(dimethylamino)-ethylene-C60 (TDAE-C60)--as determined by dielectric measurements. We propose that the permanent electric dipole originates from the pairing of a TDAE molecule with surrounding C60 molecules. The two polymorphs exhibit clear differences in their dielectric responses at room temperature and during the freezing process with dynamically fluctuating electric dipole moments, although no difference in their room-temperature structures has been previously observed. This result implies that two polymorphs have different local environment around the molecules. In particular, the ferromagnetism of the α-phase is founded on the homogeneous molecule displacement and orientational ordering. The formation of the different phases with respect to the different rotational states in the Jahn-Teller distorted C60s is also discussed.

Study of Gamow-Teller giant resonance in /sup 90/Nb by the /sup 90/Zr(/sup 3/He,t)/sup 90/Nb reaction at 90 MeV

Energy Technology Data Exchange (ETDEWEB)

Fujiwara, M.; Fujita, Y.; Katayama, I.; Morinobu, S.; Yamazaki, T.; Itahashi, T.; Ikegami, H. [Osaka Univ., Suita (Japan). Research Center for Nuclear Physics; Hayakawa, S. I.; Ikegami, Hidetsugu; Muraoka, Mitsuo [eds.; Osaka Univ., Suita (Japan). Research Center for Nuclear Physics

1980-01-01

A Gamow-Teller giant resonance in /sup 90/Nb was excited by the /sup 90/Zr(/sup 3/He, t) reaction at 89.5 MeV. The strength of the resonance was localized in the energy region of Ex = 4.5 - 7.5 MeV. The transition was found to be dominated by the L = 2 transfer.

Breaking of the SU(4) limit for the Gamow-Teller strength in N{proportional_to}Z nuclei

Energy Technology Data Exchange (ETDEWEB)

Petermann, I. [Technische Universitaet Darmstadt, Institut fuer Kernphysik, Darmstadt (Germany); Gesellschaft fuer Schwerionenforschung Darmstadt, Darmstadt (Germany); Martinez-Pinedo, G. [Gesellschaft fuer Schwerionenforschung Darmstadt, Darmstadt (Germany); Langanke, K. [Gesellschaft fuer Schwerionenforschung Darmstadt, Darmstadt (Germany); Technische Universitaet Darmstadt, Institut fuer Kernphysik, Darmstadt (Germany); Caurier, E. [Universite Louis Pasteur, Institut de Recherches Subatomiques, Strasbourg (France)

2007-12-15

We have performed large-scale shell model calculations of the Gamow-Teller strength distributions in N{proportional_to}Z pf-shell nuclei. These calculations were motivated by the experimental attempts to measure the low-lying GT strength for the even-even N=Z+2 or N=Z-2 nuclei {sup 46}Ti, {sup 50}Cr, {sup 54}Fe and {sup 62}Ge, where a sizable low-energy GT strength could be interpreted as reminiscence of SU(4) symmetry; in the limit of exact SU(4) symmetry the GT{sub -} strength would be concentrated in a single transition to the lowest T=0, J=1{sup +} state in the daughter. We confirm that the SU(4) symmetry is strongly broken by the spin-orbit interaction and by increasing neutron excess. (orig.)

Hour-Glass Neural Network Based Daily Money Flow Estimation for Automatic Teller Machines

Science.gov (United States)

Karungaru, Stephen; Akashi, Takuya; Nakano, Miyoko; Fukumi, Minoru

Monetary transactions using Automated Teller Machines (ATMs) have become a normal part of our daily lives. At ATMs, one can withdraw, send or debit money and even update passbooks among many other possible functions. ATMs are turning the banking sector into a ubiquitous service. However, while the advantages for the ATM users (financial institution customers) are many, the financial institution side faces an uphill task in management and maintaining the cash flow in the ATMs. On one hand, too much money in a rarely used ATM is wasteful, while on the other, insufficient amounts would adversely affect the customers and may result in a lost business opportunity for the financial institution. Therefore, in this paper, we propose a daily cash flow estimation system using neural networks that enables better daily forecasting of the money required at the ATMs. The neural network used in this work is a five layered hour glass shaped structure that achieves fast learning, even for the time series data for which seasonality and trend feature extraction is difficult. Feature extraction is carried out using the Akamatsu Integral and Differential transforms. This work achieves an average estimation accuracy of 92.6%.

Minimum dipole moment required to bind an electron--molecular theorists rediscover phenomenon mentioned in Fermi--Teller paper on another subject twenty years earlier

International Nuclear Information System (INIS)

Turner, J.E.

1976-07-01

Work leading to the discovery of the minimum dipole moment for electron binding, D/sub min/ = 0.639 ea 0 (atomic units), by several groups in 1967-68 is described. It was subsequently learned that this number had been published in 1947 by Fermi and Teller, who did not, however, indicate how they derived it. The author has found a numerical solution in Fermi's notebooks from 1946-50 at the University of Chicago Library. Fermi's work is described and presented here with relevant material from his notebooks

Microbial Community Patterns Associated with Automated Teller Machine Keypads in New York City.

Science.gov (United States)

Bik, Holly M; Maritz, Julia M; Luong, Albert; Shin, Hakdong; Dominguez-Bello, Maria Gloria; Carlton, Jane M

2016-01-01

In densely populated urban environments, the distribution of microbes and the drivers of microbial community assemblages are not well understood. In sprawling metropolitan habitats, the "urban microbiome" may represent a mix of human-associated and environmental taxa. Here we carried out a baseline study of automated teller machine (ATM) keypads in New York City (NYC). Our goal was to describe the biodiversity and biogeography of both prokaryotic and eukaryotic microbes in an urban setting while assessing the potential source of microbial assemblages on ATM keypads. Microbial swab samples were collected from three boroughs (Manhattan, Queens, and Brooklyn) during June and July 2014, followed by generation of Illumina MiSeq datasets for bacterial (16S rRNA) and eukaryotic (18S rRNA) marker genes. Downstream analysis was carried out in the QIIME pipeline, in conjunction with neighborhood metadata (ethnicity, population, age groups) from the NYC Open Data portal. Neither the 16S nor 18S rRNA datasets showed any clustering patterns related to geography or neighborhood demographics. Bacterial assemblages on ATM keypads were dominated by taxonomic groups known to be associated with human skin communities ( Actinobacteria , Bacteroides , Firmicutes , and Proteobacteria ), although SourceTracker analysis was unable to identify the source habitat for the majority of taxa. Eukaryotic assemblages were dominated by fungal taxa as well as by a low-diversity protist community containing both free-living and potentially pathogenic taxa ( Toxoplasma , Trichomonas ). Our results suggest that ATM keypads amalgamate microbial assemblages from different sources, including the human microbiome, eukaryotic food species, and potentially novel extremophilic taxa adapted to air or surfaces in the built environment. DNA obtained from ATM keypads may thus provide a record of both human behavior and environmental sources of microbes. IMPORTANCE Automated teller machine (ATM) keypads represent

Measurement of effective analyzing powers for the NTOF polarimeter at LAMPF and DLL(0 degree) for Gamow-Teller transitions in p-shell nuclei

International Nuclear Information System (INIS)

Mercer, D.J.

1993-01-01

Measurements of neutron polarization from (rvec p,rvec n) reactions can provide valuable clues toward understanding the isovector nucleon-nucleus interaction. A neutron time-of-flight polarimeter has been constructed at the Los Alamos Meson Physics Facility to perform such measurements, but before the polarimeter can be used, its effective analyzing powers must be determined. This is accomplished by using the 14 C(rvec p,rvec n) 14 N reaction at a bombarding energy of 494 MeV to produce a beam of neutrons with known polarization, illuminating the detector with these neutrons, and measuring the azimuthal asymmetries after scattering from a hydrogenous analyzer fluid within the detector. Secondary measurements are made using the 2 H(rvec p,rvec n) 2 p reaction with bombarding energies of 318 and 494 MeV to produce a polarized neutron beam. The results from (rvec np) analyzing reactions within the detector agree with values anticipated from free nucleon-nucleon analyzing powers, but the results from (rvec np) analyzing reactions display a more than 33% reduction from the anticipated values. Additionally, measurements are made of the polarization transfer coefficient D LL (0 degree) for rvec p,rvec n Gamow-Teller reactions on 2 H, 7 Li 12 C, and 14 C targets. For a purely central interaction, one would expect that D LL (0 degree) ∼ -1/3 in the plane wave limit, but a simple average of the Jπ = 0 + → 1 + results at a bombardment energy of 494 MeV gives D LL (0 degree) = -0.689 ± 0.044. Thus, the measurements indicate that the nucleon-nucleus interaction -- which is largely central at 200 MeV -- has strong tensor contributions at higher energy

Possible origin of photoconductivity in La0.7Ca0.3MnO3

Science.gov (United States)

Sagdeo, P. R.; Choudhary, R. J.; Phase, D. M.

2010-01-01

The effect of photon energy on the density of states near Fermi level of pulsed laser deposited La0.7Ca0.3MnO3 thin film has been studied to investigate the possible origin of change in the conductivity of these manganites upon photon exposure. For this purpose the photoelectron spectroscopy measurements were carried out using CSR beamline (BL-2) on Indus-1 synchrotron radiation source. The valance band spectra were measured at room temperature with photon energy ranging from 40 to 60 eV. We could see huge change in the density of states near Fermi level and this change is observed to be highest at 56 eV which is due to the resonance between Mn 3p to Mn 3d level. Our results suggest that the probability of electron transfer from deep Mn 3p level to Mn 3d-eg level is higher than that of Mn 3d-t2g level. It appears that this transfer of electron from deep Mn level to Mn 3d-eg level not only modifies the density of state near Fermi level but also changes the mobility of electrons by modifying the electron lattice coupling due to presence of Mn+3 Jahn-Teller ion.

Investigations on the local structures and the spin Hamiltonian parameters for Cu{sup 2+} in (90-x)TeO{sub 2}-10GeO{sub 2}-xWO{sub 3} glasses

Energy Technology Data Exchange (ETDEWEB)

Feng, Chun-Rong [Xihua Univ., Chengdu (China). School of Science; Jian, Jun [Xihua Univ., Chengdu (China). Dept. of Applied Physics; Chen, Xiao-Hong; Du, Quan; Wang, Ling [Xihua Univ., Chengdu (China). School of Science and Research Center for Advanced Computation

2018-04-01

The local structures and the spin Hamiltonian parameters (SHPs) for Cu{sup 2+} in (90-x)TeO{sub 2}-10GeO{sub 2}-xWO{sub 3} glasses are theoretically investigated at various WO{sub 3} concentrations (x=7.5, 15, 22.5 and 30 mol%). Subject to the Jahn-Teller effect, the [CuO{sub 6}]{sup 10-} groups are found to experience the small or moderate tetragonal elongation distortions (characterised by the relative tetragonal elongation ratios ρ ∼ 0.35-3.09%) in C{sub 4} axis. With only three adjusted coefficients a, b and ω, the relevant model parameters (Dq, k and ρ) are described by the Fourier type and linear functions, respectively, and the measured concentration dependences of the d-d transition bands and SHPs are reproduced. The maximum of g {sub parallel} and the minimum of vertical stroke A {sub parallel} vertical stroke at x=15 mol% are illustrated from the abrupt decrease of the copper-oxygen electron cloud admixtures or covalency and the obvious decline of the copper 3d-3s (4s) orbital admixtures due to the decreasing electron cloud density around oxygen ligands spontaneously bonding with Cu{sup 2+} and Te{sup 4+} (W{sup 6+}), respectively.

Tunneling Splittings in Vibronic Structure of CH_3F^+ ( X^2E): Studied by High Resolution Photoelectron Spectra and AB Initio Theoretical Method

Science.gov (United States)

Mo, Yuxiang; Gao, Shuming; Dai, Zuyang; Li, Hua

2013-06-01

We report a combined experimental and theoretical study on the vibronic structure of CH_3F^+. The results show that the tunneling splittings of vibrational energy levels occur in CH_3F^+ due to the Jahn-Teller effect. Experimentally, we have measured a high resolution ZEKE spectrum of CH_3F up to 3500 cm^-^1 above the ground state. Theoretically, we performed an ab initio calculation based on the diabatic model. The adiabatic potential energy surfaces (APES) of CH_3F^+ have been calculated at the MRCI/CAS/avq(t)z level and expressed by Taylor expansions with normal coordinates as variables. The energy gradients for the lower and upper APES, the derivative couplings between them and also the energies of the APES have been used to determine the coefficients in the Taylor expansion. The spin-vibronic energy levels have been calculated by accounting all six vibrational modes and their couplings. The experimental ZEKE spectra were assigned based on the theoretical calculations. W. Domcke, D. R. Yarkony, and H. Köpple (Eds.), Conical Intersections: Eletronic Structure, Dynamics and Spectroscopy (World Scientific, Singapore, 2004). M. S. Schuurman, D. E. Weinberg, and D. R. Yarkony, J. Chem. Phys. 127, 104309 (2007).

Electron energy-loss spectroscopy on fullerenes and fullerene compounds

International Nuclear Information System (INIS)

Armbruster, J.

1996-03-01

A few years ago, a new form of pure carbon, the fullerenes, has been discovered, which shows many fascinating properties. Within this work the spatial and electronic structure of some selected fullerene compounds have been investigated by electron-energy-loss spectroscopy in transmission. Phase pure samples of alkali intercalated fullerides A x C 60 (A=Na, K, Cs) have been prepared using vacuum distillation. Measruements of K 3 C 60 show a dispersion of the charge carrier plasmon close to zero. This can be explained by calculations, which take into account both band structure and local-field (inhomogeneity) effects. The importance of the molecular structure can also be seen from the A 4 C 60 compounds, where the non-metallic properties are explained by a splitting of the t 1u and t 1g derived bands that is caused by electron-correlation and Jahn-Teller effects. First measurements of the electronic structure of Na x C 60 (x>6) are presented and reveal a complete transfer from the sodium atoms but an incomplete transfer onto the C 60 molecules. This behaviour can be explained by taking into account additional electronic states that are situated between the sodium atoms in the octahedral sites and are predicted by calculations using local density approximation. The crystal structure of the higher fullerenes C 76 and C 84 is found to be face-centered cubic

Investigation of the charge-orbital ordering mechanism in single-layered Pr0.5Ca1.5MnO4

Science.gov (United States)

Rangkuti, C. N.; Majidi, M. A.

2018-04-01

Motivated by the experimental study of half-doped single-layered Pr0.5Ca1.5MnO4 showing charge, orbital, and spin orderings [1], we propose a model to theoretically study the system to explain such ordering phenomena. The ground state electron configuration reveals that the charges form a checkerboard pattern with alternating Mn3+/Mn4+ sites, while the orbitals are aligned in zigzag chains [1, 2]. We calculate the ground state energy of this system to find the most preferable configuration by comparing three types of configurations (charge-unordered, charge-ordered, and charge-orbital-ordered states). The calculations are based on a tight-binding model representing effective electron hoppings among Mn ions in MnO2-plane. We take into account the horizontally- and vertically-oriented orbital and spin degrees of freedom at Mn sites. We assume that the hopping integral values depend on the relative orientation between the corresponding orbitals of adjacent Mn ions. The interaction terms we incorporate into our effective Hamiltonian include inter-orbital, intra-orbital Hubbard repulsions, and Jahn-Teller distortion [2]. We absorb the exchange interaction between spins into local self-energy that we calculate within dynamical mean field algorithm [2]. Within our model we show a circumstance in which the charge-orbital ordered configuration has the lowest energy, consistent with the ground state ordering revealed by the experimental data.

Spin states of reduced fullerenes (C60 and C120O) by CW and pulsed EPR

International Nuclear Information System (INIS)

Boas, J.F.; Drew, S.C.; Pilbrow, J.R.; Boyd, P.D.W.; Paul, P.; Reed, C.A.; Sun, D.

2003-01-01

Full text: The ESTN (Electron Spin Transient Nutation) EPR (Electron Paramagnetic Resonance) experiments reported at Wagga 2002 showed that the spin states of the reduced fullerenes C 120 O (2-), C 120 O (3-) and C 120 O (4-) were S = 1, S = 1/2 and S = 1 respectively. Further experiments using CW (Continuous Wave) EPR have confirmed the results of Paul et al. and have now shown that these states are the ground states of these anions. In the case of C 60 (3-), the recent CW and ESTN EPR experiments have shown that the electronic ground state of this anion is S = 1/2. The observation of ground states of low multiplicity for these anions is contrary to expectations based on MO calculations and the application of Hund's rules. A series of CW EPR experiments on C 60 (3-) have shown that some previous results may need to be re-interpreted. This arises from the delineation of the effects of microwave power, modulation amplitude and frequency, sample temperature and freezing rate on the EPR spectrum which is the combination of a broad line, attributed to C 60 (3-), and a 'spike' attributed to C 120 O impurities and other oxygen related species. Our results cast doubt on the existence of Jahn-Teller effects at low temperatures and of a low-lying spin quartet excited state

Magnetotransport properties of La0.67Ca0.33MnO3 with different grain sizes

International Nuclear Information System (INIS)

Ewe, L.S.; Hamadneh, I.; Salama, H.; Halim, S.A.; Hamid, N.A.; Abd-Shukor, R.

2009-01-01

The magnetotransport and magnetoresistive (MR) properties of manganese-based La 0.67 Ca 0.33 MnO 3 perovskite with different grain sizes are reported. The electrical resistivity was measured as a function of temperature in magnetic fields of 0.5 and 1 T. The insulator-metal transition temperature, T IM , shifted to a higher temperature with the application of the magnetic field. In zero field, T IM is almost constant (∝271 K) for all samples except for the sample with the largest grain size, where T IM =265 K. The temperature dependence of resistivity was fitted with several equations in the metallic (ferromagnetic) region and the insulating (paramagnetic) region. The density of states at the Fermi level, N(E F ), and the activation energy of electron hopping were estimated by fitting the resistivity versus temperature curves. The ρ-T 2 curves are nearly linear in the metallic regime, but the ρ-T 2.5 curves exhibit a deviation from linearity. The variable range hopping model and small polaron hopping model fit the data well in the high-temperature region, indicating the existence of the Jahn-Teller distortion that localizes the charge carriers. MR was found to increase with an increase in the magnetic field, an effect which is attributed to the intergrain spin tunneling effect. (orig.)

Studies of the g factors and the local structure of the orthorhombic Ni{sup +} center in KTaO{sub 3} crystal

Energy Technology Data Exchange (ETDEWEB)

Zhang Huaming, E-mail: huamingzhang66@gmail.com [Key Laboratory of Nondestructive Testing, Ministry of Education, Nanchang Hangkong University, Nanchang 330063 (China); Wan Xiong; Zhang Zhimin [Key Laboratory of Nondestructive Testing, Ministry of Education, Nanchang Hangkong University, Nanchang 330063 (China)

2012-06-15

The local structure and the g factor (g{sub x}, g{sub y}, and g{sub z}) of the Ni{sup +} center in KTaO{sub 3} are theoretically studied using the perturbation formulas of the g factors for a 3d{sup 9} ion in orthorhombically elongated octahedra. The orthorhombic field parameters are determined from the superposition model and the local geometry of the system. In view of the covalency, the contributions from the ligand orbital and spin-orbit coupling interactions are taken into account from the cluster approach. In the calculations, the orthorhombic center is attributed to Ni{sup +} occupying the host Ta{sup 5+} site, associated with the nearest-neighboring oxygen vacancy V{sub O} along the c-axis. Furthermore, the planar Ni{sup +}-O{sup 2-} bonds are found to experience the relative variation {Delta}R (Almost-Equal-To 0.076 A) along the a- and b-axis, respectively, due to the Jahn-Teller effect and the size mismatching substitution of Ta{sup 5+} by Ni{sup +}. Meanwhile, the effectively positive V{sub O} can make the central Ni{sup +} displace away from V{sub O} along the c-axis by about 0.20 A. The calculated g factors based on the above local distortions show good agreement with the experimental data.

Composition-dependent properties and phase stability of Fe-Pd ferromagnetic shape memory alloys: A first-principles study

Science.gov (United States)

Li, Chun-Mei; Hu, Yan-Fei

2017-12-01

The composition-dependent properties and their correlation with the phase stability of Fe75+xPd25-x (- 10.0 ≤x ≤10.0 ) alloys are systematically investigated by using first-principles exact muffin-tin orbitals (EMTO)-coherent potential approximation (CPA) calculations. It is shown that the martensitic transformation (MT) from L 12 to body-centered-tetragonal (bct) occurs in the ordered alloys with about -5.0 ≤x ≤10.0 . In both the L 12 and bct phases, the evaluated a and c/a agree well with the available experimental data; the average magnetic moment per atom increases whereas the local magnetic moments of Fe atoms, dependent on both their positions and the structure of the alloy, decrease with increasing x. The tetragonal shear elastic constant of the L 12 phase ( C ' ) decreases whereas that of the bct phase (Cs) increases with x. The tetragonality of the martensite ( |1 -c /a | ) increases whereas its energy relative to the austenite with a negative value decreases with Fe addition. All these effects account for the increase of MT temperature (TM) with x. The MT from L 12 to bct is finally confirmed originating from the splitting of Fe 3d Eg and T2 g bands upon tetragonal distortion due to the Jahn-Teller effect.

Unusual behavior of uranium dioxide at high magnetic fields. Part I

Science.gov (United States)

Gofryk, K.; Jaime, M.; Zapf, V.; Harrison, N.; Saul, A.; Radtke, G.; Lashley, J. C.; Salamon, M.; Andersson, A. D.; Stanek, C.; Durakiewicz, T.; Smith, J. L.

UO2 is a Mott-Hubbard insulator with well-localized 5 f-electrons and its crystal structure is the face-centered-cubic fluorite. It experiences a first-order antiferromagnetic phase transition at 30.8 K to a non-collinear antiferromagnetic structure that remains a topic of debate. It is believed that the first order nature of the transition results from the competition between the exchange interaction and the Jahn-Teller distortion of oxygen atoms. Despite extensive experimental and theoretical efforts the nature of the competing degrees of freedom and their couplings (such as spin-phonon coupling) are still unclear. Here we present results of our extensive thermodynamic investigations, on well-characterized and oriented single crystals of UO2, focusing on magnetization M(T,H) measurements in DC and pulsed magnetic fields to up 65 T at the NHMFL. Work supported by the Department of Energy, Office of Basic Energy Sciences, Materials Sciences, and Engineering Division. The NHMFL Pulsed Field Facility is supported by the NSF, the U.S. D.O.E., and the State of Florida through NSF cooperative Grant DMR.

Habit plane-driven P2-type manganese-based layered oxide as long cycling cathode for Na-ion batteries

Science.gov (United States)

Luo, Rui; Wu, Feng; Xie, Man; Ying, Yao; Zhou, Jiahui; Huang, Yongxin; Ye, Yusheng; Li, Li; Chen, RenJie

2018-04-01

Layered transition metal oxides are considered to be promising candidates as cathode materials for sodium-ion batteries. Herein, a facile solid-state reaction is developed to synthesize hexagons plate-like Na0.67Ni0.25Mn0.75O2+δ (denoted as P2-NNM) material with habit plane formed. The structure of this layered oxide is characterized by XRD, HR-TEM and SAED. The layered material delivers a high reversible capacity of 91.8 mAh g-1 at 0.2 C with a capacity retention of 94.4 % after 280 cycles, superior rate capability and long cycle life (84.2 % capacity retention after 1000 cycle). Ni2+ is an active ion and Ni doping alleviates the Jahn-Teller distortion, and Mn3+/Mn4+ coexist as Mn4+ is desired from the stability perspective. Particularly, CV and XPS results confirm these results. Moreover, the electrode exhibits a quasi-solid-solution reaction during the sodium extraction and insertion. This contribution demonstrates that P2-NNM is a promising cathode electrode for rechargeable long-life sodium-ion batteries.

Comparison of Magnetization Tunneling in the Giant-Spin and Multi-Spin Descriptions of Single-Molecule Magnets

Science.gov (United States)

Liu, Junjie; Del Barco, Enrique; Hill, Stephen

2010-03-01

We perform a mapping of the spectrum obtained for a triangular Mn3 single-molecule magnet (SMM) with idealized C3 symmetry via exact diagonalization of a multi-spin (MS) Hamiltonian onto that of a giant-spin (GS) model which assumes strong ferromagnetic coupling and a spin S = 6 ground state. Magnetic hysteresis measurements on this Mn3 SMM reveal clear evidence that the steps in magnetization due to magnetization tunneling obey the expected quantum mechanical selection rules [J. Henderson et al., Phys. Rev. Lett. 103, 017202 (2009)]. High-frequency EPR and magnetization data are first fit to the MS model. The tunnel splittings obtained via the two models are then compared in order to find a relationship between the sixth order transverse anisotropy term B6^6 in GS model and the exchange constant J coupling the Mn^III ions in the MS model. We also find that the fourth order transverse term B4^3 in the GS model is related to the orientation of JahnTeller axes of Mn^III ions, as well as J

Structure and reactivity of a mononuclear gold(II) complex

Science.gov (United States)

Preiß, Sebastian; Förster, Christoph; Otto, Sven; Bauer, Matthias; Müller, Patrick; Hinderberger, Dariush; Hashemi Haeri, Haleh; Carella, Luca; Heinze, Katja

2017-12-01

Mononuclear gold(II) complexes are very rare labile species. Transient gold(II) species have been suggested in homogeneous catalysis and in medical applications, but their geometric and electronic structures have remained essentially unexplored: even fundamental data, such as the ionic radius of gold(II), are unknown. Now, an unprecedentedly stable neutral gold(II) complex of a porphyrin derivative has been isolated, and its structural and spectroscopic features determined. The gold atom adopts a 2+2 coordination mode in between those of gold(III) (four-coordinate square planar) and gold(I) (two-coordinate linear), owing to a second-order Jahn-Teller distortion enabled by the relativistically lowered 6s orbital of gold. The reactivity of this gold(II) complex towards dioxygen, nitrosobenzene and acids is discussed. This study provides insight on the ionic radius of gold(II), and allows it to be placed within the homologous series of nd9 Cu/Ag/Au divalent ions and the 5d8/9/10 Pt/Au/Hg 'relativistic' triad in the periodic table.

Equilibrium Structure of Manganese Trifluoride (MnF3) Molecule

International Nuclear Information System (INIS)

Caliskan, M.

2004-01-01

The symmetry lowering in manganese trifluoride molecule due to Jahn-Teller distortion was demonstrated in both the experimental and computational results. The molecule does not have D 3 h (or C 3 v) symmetry, rather it has C 2 v symmetry it has been shown from electron-diffraction measurements, that even a molecule of D 3 h symmetry in its equilibrium geometry would appear as having C 3 v symmetry. The manganese trifluoride molecular structures is an example of concerted applications of electron diffraction experiment and computation. It was found two lower energy structures with C 2 v symmetry, one corresponding to the ground state and another corresponding to the transition state. In this work we have calculate the equilibrium structure of the MnF 3 in the C 2 v configuration using the Interionic Force Model. We have compared our results for equilibrium bond lengths and bond angles with measured values from electron diffraction and with the results of quantum chemical calculations. The agreement can be considered as very reasonable

Self-consistent EXAFS PDF Projection Method by Matched Correction of Fourier Filter Signal Distortion

International Nuclear Information System (INIS)

Lee, Jay Min; Yang, Dong-Seok

2007-01-01

Inverse problem solving computation was performed for solving PDF (pair distribution function) from simulated data EXAFS based on data FEFF. For a realistic comparison with experimental data, we chose a model of the first sub-shell Mn-0 pair showing the Jahn Teller distortion in crystalline LaMnO3. To restore the Fourier filtering signal distortion, involved in the first sub-shell information isolated from higher shell contents, relevant distortion matching function was computed initially from the proximity model, and iteratively from the prior-guess during consecutive regularization computation. Adaptive computation of EXAFS background correction is an issue of algorithm development, but our preliminary test was performed under the simulated background correction perfectly excluding the higher shell interference. In our numerical result, efficient convergence of iterative solution indicates a self-consistent tendency that a true PDF solution is convinced as a counterpart of genuine chi-data, provided that a background correction function is iteratively solved using an extended algorithm of MEPP (Matched EXAFS PDF Projection) under development

Quasi-Particle Relaxation and Quantum Femtosecond Magnetism in Non-Equilibrium Phases of Insulating Manganites

Science.gov (United States)

Perakis, Ilias; Kapetanakis, Myron; Lingos, Panagiotis; Barmparis, George; Patz, A.; Li, T.; Wang, Jigang

We study the role of spin quantum fluctuations driven by photoelectrons during 100fs photo-excitation of colossal magneto-resistive manganites in anti-ferromagnetic (AFM) charge-ordered insulating states with Jahn-Teller distortions. Our mean-field calculation of composite fermion excitations demonstrates that spin fluctuations reduce the energy gap by quasi-instantaneously deforming the AFM background, thus opening a conductive electronic pathway via FM correlation. We obtain two quasi-particle bands with distinct spin-charge dynamics and dependence on lattice distortions. To connect with fs-resolved spectroscopy experiments, we note the emergence of fs magnetization in the low-temperature magneto-optical signal, with threshold dependence on laser intensity characteristic of a photo-induced phase transition. Simultaneously, the differential reflectivity shows bi-exponential relaxation, with fs component, small at low intensity, exceeding ps component above threshold for fs AFM-to-FM switching. This suggests the emergence of a non-equilibrium metallic FM phase prior to establishment of a new lattice structure, linked with quantum magnetism via spin/charge/lattice couplings for weak magnetic fields.

Superconductivity, Mott-Hubbard states, and molecular orbital order in intercalated fullerides

CERN Document Server

Iwasa, Y

2003-01-01

This article reviews the current status of chemically doped fullerene superconductors and related compounds, with particular focus on Mott-Hubbard states and the role of molecular orbital degeneracy. Alkaline-earth metal fullerides produce superconductors of several kinds, all of which have states with higher valence than (C sub 6 sub 0) sup 6 sup - , where the second lowest unoccupied molecular orbital (the LUMO + 1 state) is filled. Alkali-metal-doped fullerides, on the other hand, afford superconductors only at the stoichiometry A sub 3 C sub 6 sub 0 (A denotes alkali metal) and in basically fcc structures. The metallicity and superconductivity of A sub 3 C sub 6 sub 0 compounds are destroyed either by reduction of the crystal symmetry or by change in the valence of C sub 6 sub 0. This difference is attributed to the narrower bandwidth in the A sub 3 C sub 6 sub 0 system, causing electronic instability in Jahn-Teller insulators and Mott-Hubbard insulators. The latter metal-insulator transition is driven by...

Structural study of CaMn_1_−_xMo_xO_3 (0.08 ≤ x ≤ 0.12) system by neutron powder diffraction

International Nuclear Information System (INIS)

Supelano, G.I.; Parra Vargas, C.A.; Barón-González, A.J.; Sarmiento Santos, A.; Frontera, C.

2016-01-01

Neutron powder diffraction experiments and magnetic measurements in polycrystalline CaMn_1_−_xMo_xO_3 (x = 0.08, 0.10, 0.12) point towards a possible charge and orbital order in this system. The analysis of structural and magnetic data show that the samples present structural phase transformation from Pnma to P2_1/m space group and the system has a C-type antiferromagnetic configuration at low temperature. A detailed analysis of the bond distances signals a small Jahn-Teller distortion of only one (x = 0.08) or of the two Mn ions (x = 0.10, 0.12). We identify the partially occupied e_g orbitals and this explains the C-type magnetic structure. - Highlights: • CaMn_1_−_xMo_xO_3 (x = 0.08, 0.10, 0.12) is investigated by neutron powder diffraction. • Analysis of individual Mn-O distances demonstrates the apparition of orbital order. • By symmetry analysis, we find that the low temperature magnetic structure is C-type. • Magnetic interactions foreseen by the orbital order explain the magnetic structure.

Studies in small angle scattering techniques

International Nuclear Information System (INIS)

Moellenbach, K.

1980-03-01

Small angle scattering of neutrons, X-rays and γ-rays are found among the spectroscopic methods developed in the recent years. Although these techniques differ from each other in many respects, e.g. radiation sources and technical equipment needed, their power to resolve physical phenomena and areas of application can be discussed in a general scheme. Selected examples are given illustrating the use of specific technical methods. Jahn-Teller driven structural phase transitions in Rare Earth zircons were studied with neutron scattering as well as small angle γ-ray diffraction. The study of neutron scattering from formations of magnetic domains in the Ising ferromagnet LiTbF 4 is a second example. Both these examples represent more than experimental test cases since the theoretical interpretations of the data obtained are discussed as well. As a last example the use of small angle scattering methods for the study of molecular biological samples is discussed. In particular the experimental procedures used in connection with scattering from aqueous solutions of proteins and protein complexes are given. (Auth.)

Evidence of a splitting of the Mn-O distance and of a large lattice disorder in the charge-ordered phase of LiMn2O4 obtained by EXAFS

International Nuclear Information System (INIS)

Paolone, A.; Castellano, C.; Cantelli, R.; Rousse, G.; Masquelier, C.

2003-01-01

We measured the extended x-ray-absorption fine-structure (EXAFS) spectrum of LiMn 2 O 4 below room temperature in the charge-ordered phase and for comparison at room temperature in the cubic phase. By means of a standard fit procedure we verified that, as reported by neutron-scattering experiments, also at the local level there are two different Mn-O distances below room temperature, which correspond to the surroundings of well-defined Mn 3+ and Mn 4+ ions. This result is different from the ones obtained from previous EXAFS measurements and confirms the physical picture of the phase transition caused by the ordering of charges in contrast to a cooperative Jahn-Teller phenomenon. Moreover a large lattice disorder in the charge-ordered state, which determines a significant static contribution to the EXAFS Debye-Waller factor, has been found. This last result can be considered as the EXAFS spectral mark of charge-order transitions, even in those materials in which there is no clear evidence of the splitting of bond lengths

Effect of large compressive strain on low field electrical transport in La0.88Sr0.12MnO3 thin films

International Nuclear Information System (INIS)

Prasad, Ravikant; Gaur, Anurag; Siwach, P K; Varma, G D; Kaur, A; Singh, H K

2007-01-01

We have investigated the effect of large in-plane compressive strain on the electrical transport in La 0.88 Sr 0.12 MnO 3 in thin films. For achieving large compressive strain, films have been deposited on single crystal LaAlO 3 (LAO, a = 3.798 A) substrate from a polycrystalline bulk target having average in-plane lattice parameter a av = (a b + b b )/2 = 3.925 A. The compressive strain was further relaxed by varying the film thickness in the range ∼6-75 nm. In the film having least thickness (∼6 nm) large increase (c = 3.929 A) in the out-of-plane lattice parameter is observed which gradually decreases towards the bulk value (c bulk = 3.87 A) for ∼75 nm thick film. This shows that the film having the least thickness is under large compressive strain, which partially relaxes with increasing film thickness. The T IM of the bulk target ∼145 K goes up to ∼235 K for the ∼6 nm thin film and even for partially strain relaxed ∼75 nm thick film T IM is as high as ∼200 K. This enhancement in T IM is explained in terms of suppression of Jahn-Teller distortion of the MnO 6 octahedra by the large in-plane compressive strain. We observe a large enhancement in the low field magnetoresistance (MR) just below T IM in the films having partial strain relaxation. Thick films of 6 and 20 nm have MR ∼14% at 3 kOe that almost doubles in 35 nm film to ∼27%. Similar enhancement is also obtained in the case of the temperature coefficient of resistivity. The near doubling of low field MR is explained in terms of delocalization of weakly localized carriers around T IM by small magnetic fields

Temperature dependent evolution of the electronic and local atomic structure in the cubic colossal magnetoresistive manganite La1-xSrxMnO3

International Nuclear Information System (INIS)

Arenholz, Elke; Mannella, N.; Booth, C.H.; Rosenhahn, A.; Sell, B.C.; Nambu, A.; Marchesini, S.; Mun, B. S.; Yang, S.-H.; Watanabe, M.; Ibrahim, K.; Arenholz, E.; Young, A.; Guo, J.; Tomioka, Y.; Fadley, C.S.

2007-01-01

We have studied the temperature-dependent evolution of the electronic and local atomic structure in the cubic colossal magnetoresistive manganite La 1-x Sr x MnO 3 (x= 0.3-0.4) with core and valence level photoemission (PE), x-ray absorption spectroscopy (XAS), x-ray emission spectroscopy (XES), resonant inelastic x-ray scattering (RIXS), extended x-ray absorption fine structure (EXAFS) spectroscopy and magnetometry. As the temperature is varied across the Curie temperature T c , our PE experiments reveal a dramatic change of the electronic structure involving an increase in the Mn spin moment from ∼ 3 (micro)B to ∼ 4 (micro)B, and a modification of the local chemical environment of the other constituent atoms indicative of electron localization on the Mn atom. These effects are reversible and exhibit a slow-timescale ∼200 K-wide hysteresis centered at T c . Based upon the probing depths accessed in our PE measurements, these effects seem to survive for at least 35-50 (angstrom) inward from the surface, while other consistent signatures for this modification of the electronic structure are revealed by more bulk sensitive spectroscopies like XAS and XES/RIXS. We interpret these effects as spectroscopic fingerprints for polaron formation, consistent with the presence of local Jahn-Teller distortions of the MnO 6 octahedra around the Mn atom, as revealed by the EXAFS data. Magnetic susceptibility measurements in addition show typical signatures of ferro-magnetic clusters formation well above the Curie temperature

Beta decay of 97Ag: evidence for the Gamow-Teller resonance near 100Sn

International Nuclear Information System (INIS)

Hu Zhiqiang

1999-03-01

In two complementary measurements, a cube like array of 6 Euroball-Cluster germanium detectors and a total-absorption γ-spectrometer were used to investigate the β decay of 97 Ag, a three proton-hole nucleus with respect to the 100 Sn core. The half-life and Q EC value of the decay of the 9/2 + ground-state of 97 Ag were determined to be 25.9(4) s and 6.98(11) MeV respectively. A total of 603 γ rays (578 new) was observed, and 151 levels (132 new) in 97 Pd have been identified. An interesting β-delayed γ cascade was observed, which comprises 6 γ-transitions with a de-excitation pattern involving an initial increase of the level spin. The Gamow-Teller (GT) β-decay strength distributions from the two measurements reveal a large GT resonance around 4 MeV with a width of about 1.8 MeV. The hindrance factor for the total GT strength summed from the ground-state up to 6 MeV excitation energy in 97 Pd, amounts to 4.3(6) with reference to a shell-model prediction. This factor is discussed in comparison with a core-polarization and a Monte-Carlo shell-model calculation. (orig.)

Antibiogram of bacteria isolated from automated teller machines in Hamadan, West Iran

Directory of Open Access Journals (Sweden)

Mahmoudi, Hassan

2017-02-01

Full Text Available Aim: Bacteria are ubiquitous in the environment. In keeping with the continued expansion of urbanization and the growing population, an increasing number of people use automated banking, i.e. automated teller machines (ATMs. The aim of this study was to investigate the bacterial contamination and its antibiotic sensitivity on computer keyboards located at ATMs in Hamadan province, Iran. Method: Out of 360 ATMs at four locations in Hamadan, 96 were randomly selected for this study. The antibiotic susceptibility pattern of all isolates was determined by the agar disk diffusion method using gentamicin (10 µg, vancomycin (30 µg, trimethoprim/sulfamethoxazole (25 µg, amikacin (30 µg, tobramycin (10 µg, cephalotin (30 µg, norfloxacin (5 µg, and ceftizoxim (30 µg disks. Results: Melli and Saderat Banks had the most frequently contaminated ATMS, with 18 (27.7% and 12 (18.5%, respectively. The most frequently isolated bacteria were in 12 (18.5% ATMs, in in 11 (16.9%, in 6 (9.2%, spp. in 8 (12.3%, spp. in 2 (3.1%, in 6 (9.2%, in 3 (4.6%, and spp. in 5 (7.69% cases. All isolated bacteria were susceptible to gentamicin, cephalotin, tobramycin, amikacin, norfloxacin, and vancomycin. The resistance rate to trimethoprim/sulfamole was 50%. Conclusion: All tested ATM keyboards were contaminated with at least one species of bacteria. Based on these findings, it is recommendable to disinfect the hands after entering one’s own apartment, work area or a hospital, in order to hinder the spread of critical pathogens in the personal environment or in the hospital.

Cu2+ Dual-Doped Layer-Tunnel Hybrid Na0.6Mn1- xCu xO2 as a Cathode of Sodium-Ion Battery with Enhanced Structure Stability, Electrochemical Property, and Air Stability.

Science.gov (United States)

Chen, Ting-Ru; Sheng, Tian; Wu, Zhen-Guo; Li, Jun-Tao; Wang, En-Hui; Wu, Chun-Jin; Li, Hong-Tai; Guo, Xiao-Dong; Zhong, Ben-He; Huang, Ling; Sun, Shi-Gang

2018-03-28

Sodium-ion batteries (SIBs) have been regarded as a promising candidate for large-scale renewable energy storage system. Layered manganese oxide cathode possesses the advantages of high energy density, low cost and natural abundance while suffering from limited cycling life and poor rate capacity. To overcome these weaknesses, layer-tunnel hybrid material was developed and served as the cathode of SIB, which integrated high capacity, superior cycle ability, and rate performance. In the current work, the doping of copper was adopted to suppress the Jahn-Teller effect of Mn 3+ and to affect relevant structural parameters. Multifunctions of the Cu 2+ doping were carefully investigated. It was found that the structure component ratio is varied with the Cu 2+ doping amount. Results demonstrated that Na + /vacancy rearrangement and phase transitions were suppressed during cycling without sacrificing the reversible capacity and enhanced electrochemical performances evidenced with 96 mA h g -1 retained after 250 cycles at 4 C and 85 mA h g -1 at 8 C. Furthermore, ex situ X-ray diffraction has demonstrated high reversibility of the Na 0.6 Mn 0.9 Cu 0.1 O 2 cathode during Na + extraction/insertion processes and superior air stability that results in better storage properties. This study reveals that the Cu 2+ doping could be an effective strategy to tune the properties and related performances of Mn-based layer-tunnel hybrid cathode.

Phase separation in strongly correlated electron systems with two types of charge carriers

International Nuclear Information System (INIS)

Kugel, K.I.; Rakhmanov, A.L.; Sboychakov, A.O.

2007-01-01

Full text: A competition between the localization of the charge carriers due to Jahn-Teller distortions and the energy gain due to their delocalization in doped manganite and related magnetic oxides is analyzed based on a Kondo-lattice type model. The resulting effective Hamiltonian is, in fact, a generalization of the Falicov-Kimball model. We find that the number of itinerant charge carriers can be significantly lower than that implied by the doping level x. The phase diagram of the model in the T plane is constructed. The system exhibits magnetic ordered (antiferromagnetic, ferromagnetic, or canted) states as well the paramagnetic states with zero and nonzero density of the itinerant electrons. It is shown that a phase-separation is favorable in energy for a wide doping range. The characteristic size of inhomogeneities in a phase-separated state is of the order of several lattice constants. We also analyzed the two-band Hubbard model in the limit of strong on-site Coulomb repulsion. It was shown that such a system has a tendency to phase separation into the regions with different charge densities even in the absence of magnetic or any other ordering, if the ratio of the bandwidths is large enough. The work was supported by the European project CoMePhS and by the Russian Foundation for Basic Research, project no. 05-02-17600. (authors)

Spectroscopic characterization of some Cu(II) complexes

International Nuclear Information System (INIS)

Singh, Puja; Sharma, S.

2014-01-01

3-hydroxy-4-methoxy benzaldehyde semicarbazone (HMBS) is a biologically active compound which has several potential donor sites. This compound has been used for complexation with Cu(II) ions to synthesize complexes of general formula [Cu(HMBS) 2 X 2 ] where X is Cl − , NO 3 − and CH 3 COO − . Cu(II) is a d 9 system for which 2 D term is generated. Under O h symmetry, this term splits into 2 E g and 2 T 2g . the ground term 2 Eg is doubly degenerate and hence suffers strong Jahn-Teller effect and accordingly the further splitting of terms occur to lower the symmetry from perfect O h . Here, the ligand occupies four planar positions while the two axial positions have been varied by using different ions like Cl − , NO 3 − and CH 3 COO − . These variations on the axial positions also add to the distortion in O h symmetry. Under strong distortion, the electronic spectral band splits into multiplets exhibiting tetragonal distortion in complexes. The extent of distortion has been derived by the derivation of the two radial parameters D s and D t from electronic spectral bands. The ESR spectra of complexes reveal the real position of the only unpaired electron of the d 9 system in complexes

Theoretical studies of the spin Hamiltonian parameters and local distortions for Cu{sup 2+} in alkaline earth lead zinc phosphate glasses

Energy Technology Data Exchange (ETDEWEB)

Wang, Bo-Kun; Yuan, Zi-Yi; Liu, Zi-Xuan; Jiang, Shi-Xin; Liu, Zheng; Yao, Zi-Jian [University of Electronic Science and Technology of China, Chengdu (China). School of Yingcai Honors; Wu, Shao-Yi; Teng, Bao-Hua; Wu, Ming-He [University of Electronic Science and Technology of China, Chengdu (China). Dept. of Applied Physics

2016-11-01

The spin Hamiltonian parameters and local structures are theoretically studied for Cu{sup 2+}-doped alkaline earth lead zinc phosphate (RPPZ, R=Mg, Ca, Sr, and Ba) glasses based on the high-order perturbation calculations for a tetragonally elongated octahedral 3d{sup 9} cluster. The relative elongation ratios are found to be ρ ∼ 3.2%, 4.4%, 4.6%, and 3.3% for R=Mg, Ca, Sr, and Ba, respectively, because of the Jahn-Teller effect. The whole decreasing crystal-field strength Dq and orbital reduction factor k from Mg to Sr are ascribed to the weakening electrostatic coulombic interactions and the increasing probability of productivity of nonbridge oxygen (and hence increasing Cu{sup 2+}-O{sup 2-} electron cloud admixtures) under PbO addition, respectively, with increasing alkali earth ionic radius. The anomalies (the largest Dq and the next highest k among the systems) for R=Ba are attributed to the cross linkage of this large cation in the network. The overall increasing order (Mg≤Ba

Electron density in non-ideal metal complexes. Pt. 1

International Nuclear Information System (INIS)

Varghese, J.N.; Maslen, E.N.

1985-01-01

The structure of copper sulphate pentahydrate was refined using an accurate set of X-ray data: Msub(r)=249.68, triclinic, Panti 1, a=6.1224(4), b=10.7223(4), c=5.9681(4) A, α=82.35(2), β=107.33(2), γ=102.60(4) 0 , V=364.02(3) A 3 , Z=2, Dsub(x)=2.278 Mg m -3 , Mo Kα, lambda=0.71069 A, μ=3.419 mm -1 , F(000)=254.0, T=298 K, R=0.039 for 7667 reflections. The structural parameters are compared with those obtained by neutron diffraction. The differences between X-ray and neutron positions are related to the hydrogen bonding in the structure. The dominant features in the residual density near the two crystallographically independent Cu atoms result from the redistribution of 3d electrons due to bonding. The density is anisotropic, as expected in view of the Jahn-Teller distortion in the structure. Marked differences in the d-electron distributions for the two Cu atoms correlate with small variations in molecular geometry. Second-nearest-neighbour effects, such as those arising from differently oriented ligating waters, are significant in this structure. Sharp features in the difference density close to the Cu nuclei are similar to those in other Cu 2+ complexes, indicating that the electron density in this region is more reliable than previously believed. (orig.)

Structure-property correlation in PrFe0.5Mn0.5O2.95

International Nuclear Information System (INIS)

Ganeshraj, C.; Santhosh, P.N.; Sharma, Neetika; Das, A.; Mahendiran, R.

2014-01-01

PrFe 0.5 Mn 0.5 O 2.95 (PFMO) prepared by the conventional ceramic route is analyzed using a variety of techniques to understand the structural, magnetic and electrical properties. From the Neutron diffraction data it is concluded that PFMO crystallizes in an orthorhombic structure (Pnma). The magnetic structure can be represented as Γ 2 : C x G y F z , in Bertaut's notation, which has a net ferromagnetic moment along z-direction, and the spin component along x-direction (C x ) is found to be negligibly small. The canted G-type antiferromagnet PrFe 0.5 Mn 0.5 O 2.95 shows an enhanced Jahn-Teller (JT) distortion below 150 K (T*). The resistivity of the grains can be described by variable range hopping (VRH) between the localized states and there is a dominant grain boundary contribution to dc resistivity, below T*. Above T*, the total dc resistivity follows small polaron hopping (SPH) conduction. By means of complex impedance analysis, it is found that the observed giant dielectric response can be ascribed to Maxwell-Wagner polarization at the grain/grain boundary interfaces. Despite the low concentration of JT active Mn 3+ ions, our result indicates an important role of JT effect on physical properties of PrFe 0.5 Mn 0.5 O 2.95 . (author)

Theory and experimental evidence of phonon domains and their roles in pre-martensitic phenomena

Science.gov (United States)

Jin, Yongmei M.; Wang, Yu U.; Ren, Yang

2015-12-01

Pre-martensitic phenomena, also called martensite precursor effects, have been known for decades while yet remain outstanding issues. This paper addresses pre-martensitic phenomena from new theoretical and experimental perspectives. A statistical mechanics-based Grüneisen-type phonon theory is developed. On the basis of deformation-dependent incompletely softened low-energy phonons, the theory predicts a lattice instability and pre-martensitic transition into elastic-phonon domains via 'phonon spinodal decomposition.' The phase transition lifts phonon degeneracy in cubic crystal and has a nature of phonon pseudo-Jahn-Teller lattice instability. The theory and notion of phonon domains consistently explain the ubiquitous pre-martensitic anomalies as natural consequences of incomplete phonon softening. The phonon domains are characterised by broken dynamic symmetry of lattice vibrations and deform through internal phonon relaxation in response to stress (a particular case of Le Chatelier's principle), leading to previously unexplored new domain phenomenon. Experimental evidence of phonon domains is obtained by in situ three-dimensional phonon diffuse scattering and Bragg reflection using high-energy synchrotron X-ray single-crystal diffraction, which observes exotic domain phenomenon fundamentally different from usual ferroelastic domain switching phenomenon. In light of the theory and experimental evidence of phonon domains and their roles in pre-martensitic phenomena, currently existing alternative opinions on martensitic precursor phenomena are revisited.

Spectroscopy of hexafluorides with an odd number of electrons; Spectroscopie des hexafluorures a nombre impair d'electrons

Energy Technology Data Exchange (ETDEWEB)

Boudon, V

1995-05-01

From a theoretical point of view, a tensorial formalism adapted to the study of molecules or octahedral ions with a half-integer angular momentum has been developed for the first time. We have used here the method of projective representations, more consistent than that of double groups. A complete set of coupling coefficients and formulas, as well as the corresponding computing programs have been elaborated. This has firstly allowed us to write a simple model describing the vibronic structure of colored hexafluorides. Then, some applications of this formalism to the study of ro-vibronic couplings of XY{sub 6} molecules in a fourfold degenerate electronic state have been considered, especially concerning operators associated to dynamic Jahn-Teller effect. From an experimental point of view, we have considered IrF{sub 6}, for which we have mastered the synthesis, purification and conservation processes. A first study at low resolution (absorption and Raman scattering) has been performed for this molecule. We have then set up two high resolution spectroscopic devices in the visible region (saturated absorption - tested with an iodine cell- and simple absorption with multiple pass). These especially use a dye laser. They should now allow the spectroscopy of the visible band of IrF{sub 6} in order to resolve for the first time its fine rotational structure. (author)

Mixed valence transition metal 2D-oxides: Comparison between delafossite and crednerite compounds

Science.gov (United States)

Martin, Christine; Poienar, Maria

2017-08-01

Transition metal oxides offer large opportunities to study relationships between structures and properties. Indeed these compounds crystallize in numerous frameworks corresponding to different dimensionalities and, accordingly, show a huge variety of properties (as high Tc superconductivity, colossal magnetoresistivity, multiferroicity..). The control of the oxidation state of the transition metal, via the monitoring of the oxygen content, is of prime importance to understand and optimize the properties, due to the strong coupling that exists between the lattice and the charges and spins of the transition metals. In this large playground for chemists, we reinvestigated several 2D-compounds derived from delafossite structure. Considering this paper as a very short review, we report here the results obtained on CuMO2 compounds (with M = Cr, Mn or Mn+Cu) by using a combination of techniques, as X-ray, neutrons and/or electrons diffraction on poly-crystals for structural characterisations that are correlated with electrical and/or magnetic properties. The complementarity of studies is also addressed by the synthesis and characterization of single crystals in addition to poly-crystals. Moreover the comparison of the structures of similar Cr and Mn based oxides highlights the crucial role of the Jahn-Teller effect of trivalent manganese to lift the degeneracy, which is responsible of the magnetic frustration in CuCrO2.

Spectroscopy of hexafluorides with an odd number of electrons

International Nuclear Information System (INIS)

Boudon, V.

1995-05-01

From a theoretical point of view, a tensorial formalism adapted to the study of molecules or octahedral ions with a half-integer angular momentum has been developed for the first time. We have used here the method of projective representations, more consistent than that of double groups. A complete set of coupling coefficients and formulas, as well as the corresponding computing programs have been elaborated. This has firstly allowed us to write a simple model describing the vibronic structure of colored hexafluorides. Then, some applications of this formalism to the study of ro-vibronic couplings of XY 6 molecules in a fourfold degenerate electronic state have been considered, especially concerning operators associated to dynamic Jahn-Teller effect. From an experimental point of view, we have considered IrF 6 , for which we have mastered the synthesis, purification and conservation processes. A first study at low resolution (absorption and Raman scattering) has been performed for this molecule. We have then set up two high resolution spectroscopic devices in the visible region (saturated absorption - tested with an iodine cell- and simple absorption with multiple pass). These especially use a dye laser. They should now allow the spectroscopy of the visible band of IrF 6 in order to resolve for the first time its fine rotational structure. (author)

Spectroscopy of hexafluorides with an odd number of electrons; Spectroscopie des hexafluorures a nombre impair d'electrons

Energy Technology Data Exchange (ETDEWEB)

Boudon, V

1995-05-01

From a theoretical point of view, a tensorial formalism adapted to the study of molecules or octahedral ions with a half-integer angular momentum has been developed for the first time. We have used here the method of projective representations, more consistent than that of double groups. A complete set of coupling coefficients and formulas, as well as the corresponding computing programs have been elaborated. This has firstly allowed us to write a simple model describing the vibronic structure of colored hexafluorides. Then, some applications of this formalism to the study of ro-vibronic couplings of XY{sub 6} molecules in a fourfold degenerate electronic state have been considered, especially concerning operators associated to dynamic Jahn-Teller effect. From an experimental point of view, we have considered IrF{sub 6}, for which we have mastered the synthesis, purification and conservation processes. A first study at low resolution (absorption and Raman scattering) has been performed for this molecule. We have then set up two high resolution spectroscopic devices in the visible region (saturated absorption - tested with an iodine cell- and simple absorption with multiple pass). These especially use a dye laser. They should now allow the spectroscopy of the visible band of IrF{sub 6} in order to resolve for the first time its fine rotational structure. (author)

A study of Gamow-Teller transitions for N = Z nuclei, {sup 24}Mg, {sup 28}Si, and {sup 32}S, by a deformed QRPA

Energy Technology Data Exchange (ETDEWEB)

Ha, Eunja; Cheoun, Myung-Ki [Soongsil University, Origin of Matter and Evolution of Galaxy Institute and Department of Physics, Seoul (Korea, Republic of)

2017-02-15

We investigated Gamow-Teller (GT) transitions and strength distributions of s-d shell N = Z nuclei, {sup 24}Mg, {sup 28}Si, and {sup 32}S, by a deformed quasi-particle random phase approximation (DQRPA). In the DQRPA, we included particle model space up to p-f shell and considered explicitly the deformation as well as the like- and unlike-pairing correlations. Shell evolution by deformation and attractive force by unlike-pairing correlations turned out to play vital roles to reproduce the experimental GT data. Correlations between the deformation and the pairing correlations are also discussed with the comparison to the experimental data shape. (orig.)

Effect of CuO addition on structure and electrical properties of low ...

Indian Academy of Sciences (India)

2016-08-26

Aug 26, 2016 ... Home; Journals; Bulletin of Materials Science; Volume 36; Issue 5. Effect of CuO addition on structure and electrical properties of low temperature sintered quaternary piezoelectric ceramics. Jianhua Li ... Keywords. Sintering; microstructure-final; piezoelectric properties; perovskites; Jahn–Teller effect.

Antibiogram of bacteria isolated from automated teller machines in Hamadan, West Iran

Science.gov (United States)

Mahmoudi, Hassan; Arabestani, Mohammad Reza; Alikhani, Mohammad Yousef; Sedighi, Iraj; Kohan, Hamed Farhadi; Molavi, Mohammad

2017-01-01

Aim: Bacteria are ubiquitous in the environment. In keeping with the continued expansion of urbanization and the growing population, an increasing number of people use automated banking, i.e. automated teller machines (ATMs). The aim of this study was to investigate the bacterial contamination and its antibiotic sensitivity on computer keyboards located at ATMs in Hamadan province, Iran. Method: Out of 360 ATMs at four locations in Hamadan, 96 were randomly selected for this study. The antibiotic susceptibility pattern of all isolates was determined by the agar disk diffusion method using gentamicin (10 µg), vancomycin (30 µg), trimethoprim/sulfamethoxazole (25 µg), amikacin (30 µg), tobramycin (10 µg), cephalotin (30 µg), norfloxacin (5 µg), and ceftizoxim (30 µg) disks. Results: Melli and Saderat Banks had the most frequently contaminated ATMS, with 18 (27.7%) and 12 (18.5%), respectively. The most frequently isolated bacteria were Staphylococcus epidermidis in 12 (18.5%) ATMs, Pseudomonas aeruginosa in 12 (18.5%), Bacillus subtilis in 11 (16.9%), Escherichia coli in 6 (9.2%), Klebsiella spp. in 8 (12.3%), Enterobacter spp. in 2 (3.1%), Bacillus cereus in 6 (9.2%), Staphylococcus aureus in 3 (4.6%), and Micrococcaceae spp. in 5 (7.69%) cases. All isolated bacteria were susceptible to gentamicin, cephalotin, tobramycin, amikacin, norfloxacin, and vancomycin. The S. aureus resistance rate to trimethoprim/sulfamethoxazole was 50%. Conclusion: All tested ATM keyboards were contaminated with at least one species of bacteria. Based on these findings, it is recommendable to disinfect the hands after entering one’s own apartment, work area or a hospital, in order to hinder the spread of critical pathogens in the personal environment or in the hospital. PMID:28197394

Measurement of Gamow-Teller and spin dipole strength in the 45Sc(n,p)45Ca reaction at 198 MeV

International Nuclear Information System (INIS)

Alford, W.P.; Celler, A.; Brown, B.A.; Long, S.; Raywood, K.

1990-11-01

The reaction 45 Sc(n,p) 45 Ca has been studied at an energy of 198 MeV with energy resolution of about 1 MeV. Measurements were carried out at nominal angles 0, 3, 6, 9, 12, 15, and 18 degrees and spectra obtained up to ∼40 MeV excitation energy in 45 Ca. Significant Gamow-Teller strength is observed at an excitation energy of about 7 MeV, somewhat higher than predicted by shell model calculations. The strength observed is in agreement with calculations using g A /g V ≅ 1. The spin dipole giant resonance is seen with centroid at about 15 MeV excitation and total cross section of 25 mb/sr at an angle of 6 degrees. (Author) (22 refs., 9 figs.)

Ashkin-Teller criticality and weak first-order behavior of the phase transition to a fourfold degenerate state in two-dimensional frustrated Ising antiferromagnets

Science.gov (United States)

Liu, R. M.; Zhuo, W. Z.; Chen, J.; Qin, M. H.; Zeng, M.; Lu, X. B.; Gao, X. S.; Liu, J.-M.

2017-07-01

We study the thermal phase transition of the fourfold degenerate phases (the plaquette and single-stripe states) in the two-dimensional frustrated Ising model on the Shastry-Sutherland lattice using Monte Carlo simulations. The critical Ashkin-Teller-like behavior is identified both in the plaquette phase region and the single-stripe phase region. The four-state Potts critical end points differentiating the continuous transitions from the first-order ones are estimated based on finite-size-scaling analyses. Furthermore, a similar behavior of the transition to the fourfold single-stripe phase is also observed in the anisotropic triangular Ising model. Thus, this work clearly demonstrates that the transitions to the fourfold degenerate states of two-dimensional Ising antiferromagnets exhibit similar transition behavior.

Electron localization, polarons and clustered states in manganites

International Nuclear Information System (INIS)

Mannella, N.

2004-01-01

Full text: A recent multi-spectroscopic study of prototypical colossal magnetoresistance (CMR) compounds La 1-x Sr x MnO 3 (LSMO, x = 0.3, 0.4) using photoemission (PE), x-ray absorption (XAS), x-ray emission (XES) and extended x-ray absorption e structure (EXAFS) has exposed a dramatic change in the electronic structure on crossing the ferromagnetic-to-paramagnetic transition temperature (T C ). In particular, this investigation revealed an increase of the Mn magnetic moment by ca. 1 Bohr magneton and charge transfer to the Mn atom on crossing T C concomitant with the presence of Jahn-Teller distortions, thus providing direct evidence of lattice polaron formation. These results thus challenge the belief of some authors that the LSMO compounds are canonical double-exchange (DE) systems in which polaron formation is unimportant, and thus help to unify the theoretical description of the CMR oxides. The relationship of these data to other recent work suggesting electron localization, polarons and phase separation, along with additional measurements of magnetic susceptibility indicating the formation of ferromagnetic clusters in the metallic paramagnetic state above T C will be discussed

Structural study of CaMn{sub 1−x}Mo{sub x}O{sub 3} (0.08 ≤ x ≤ 0.12) system by neutron powder diffraction

Energy Technology Data Exchange (ETDEWEB)

Supelano, G.I., E-mail: ivan.supelano@uptc.edu.co [Grupo Física de Materiales, Escuela de Física, Universidad Pedagógica y Tecnológica de Colombia, Tunja (Colombia); Parra Vargas, C.A.; Barón-González, A.J. [Grupo Física de Materiales, Escuela de Física, Universidad Pedagógica y Tecnológica de Colombia, Tunja (Colombia); Sarmiento Santos, A. [Grupo Superficies Electroquímica y Corrosión, Escuela de Física, Universidad Pedagógica y Tecnológica de Colombia, Tunja (Colombia); Frontera, C. [Institut de Ciència de Materials de Barcelona, CSIC, Campus Universitari de Bellaterra, E-08193, Bellaterra, Barcelona (Spain)

2016-08-15

Neutron powder diffraction experiments and magnetic measurements in polycrystalline CaMn{sub 1−x}Mo{sub x}O{sub 3} (x = 0.08, 0.10, 0.12) point towards a possible charge and orbital order in this system. The analysis of structural and magnetic data show that the samples present structural phase transformation from Pnma to P2{sub 1}/m space group and the system has a C-type antiferromagnetic configuration at low temperature. A detailed analysis of the bond distances signals a small Jahn-Teller distortion of only one (x = 0.08) or of the two Mn ions (x = 0.10, 0.12). We identify the partially occupied e{sub g} orbitals and this explains the C-type magnetic structure. - Highlights: • CaMn{sub 1−x}Mo{sub x}O{sub 3} (x = 0.08, 0.10, 0.12) is investigated by neutron powder diffraction. • Analysis of individual Mn-O distances demonstrates the apparition of orbital order. • By symmetry analysis, we find that the low temperature magnetic structure is C-type. • Magnetic interactions foreseen by the orbital order explain the magnetic structure.

Spin-state blockade in Te6+-substituted electron-doped LaCoO3

Science.gov (United States)

Tomiyasu, Keisuke; Koyama, Shun-Ichi; Watahiki, Masanori; Sato, Mika; Nishihara, Kazuki; Onodera, Mitsugi; Iwasa, Kazuaki; Nojima, Tsutomu; Yamasaki, Yuuichi; Nakao, Hironori; Murakami, Youichi

2015-03-01

Perovskite-type LaCoO3 (Co3+: d6) is a rare inorganic material with sensitive and characteristic responses among low, intermediate, and high spin states. For example, in insulating nonmagnetic low-spin states below about 20 K, light hole doping (Ni substitution) induces much larger magnetization than expected; over net 10μB/hole (5μB/Ni) for 1μB/hole (1μB/Ni), in which the nearly isolated dopants locally change the surrounding Co low-spin states to magnetic ones and form spin molecules with larger total spin. Further, the former is isotropic, whereas the latter exhibits characteristic anisotropy probably because of Jahn-Teller distortion. In contrast, for electron doping, relatively insensitive spin-state responses were reported, as in LaCo(Ti4+) O3, but are not clarified, and are somewhat controversial. Here, we present macroscopic measurement data of another electron-doped system LaCo(Te6+) O3 and discuss the spin-state responses. This study was financially supported by Grants-in-Aid for Young Scientists (B) (No. 22740209 and 26800174) from the MEXT of Japan.

Effect of single vacancy on the structural, electronic structure and magnetic properties of monolayer graphyne by first-principles

Energy Technology Data Exchange (ETDEWEB)

Yun, Jiangni, E-mail: niniyun@nwu.edu.cn; Zhang, Yanni; Xu, Manzhang; Wang, Keyun; Zhang, Zhiyong

2016-10-01

The effect of single vacancy on the structural, electronic and magnetic properties of monolayer graphyne is investigated by the first-principles calculations. The calculated results reveal that single vacancy can result in the spin polarization in monolayer graphyne and the spin polarization is sensitive to local geometric structure of the vacancy. In the case of monolayer graphyne with one single vacancy at the sp{sup 2} hybridized C site, the vacancy introduces rather weakly spin-polarized, flat bands in the band gap. Due to the localization nature of the defect-induced bands, the magnetic moment is mainly localized at the vacancy site. As for the monolayer graphyne with one single vacancy at the sp hybridized C site, one defect-induced state which is highly split appears in the band gap. The spin-up band of the defect-induced state is highly dispersive and shows considerable delocalization, suggesting that the magnetic moment is dispersed around the vacancy site. The above magnetization in monolayer graphyne with one single vacancy is possibly explained in terms of the valence-bond theory. - Graphical abstract: Calculated band structure of the monolayer graphyne without (a) and with one single vacancy at Vb site (b) and at Vr site(c), respectively. Blue and red lines represent the spin-up and spin-down bands, respectively. For the sake of clarity, the band structure near the Fermi energy is also presented on the right panel. The Fermi level is set to zero on the energy scale. - Highlights: • A Jahn-Teller distortion occurs in monolayer graphyne with single vacancy. • The spin polarization is sensitive to local geometric structure of the vacancy. • Vacancy lying at sp{sup 2} hybridized C site introduces weakly spin-polarized defect bands. • A strong spin splitting occurs when the vacancy lies at sp hybridized C site. • The magnetization is explained in terms of the valence-bond theory.

Vibronic coupling in molecular crystals: A Franck-Condon Herzberg-Teller model of H-aggregate fluorescence based on quantum chemical cluster calculations

Energy Technology Data Exchange (ETDEWEB)

Wykes, M., E-mail: mikewykes@gmail.com; Parambil, R.; Gierschner, J. [Madrid Institute for Advanced Studies, IMDEA Nanoscience, Calle Faraday 9, Campus Cantoblanco, 28049 Madrid (Spain); Beljonne, D. [Laboratory for Chemistry of Novel Materials, University of Mons, Place du Parc 20, 7000 Mons (Belgium)

2015-09-21

Here, we present a general approach to treating vibronic coupling in molecular crystals based on atomistic simulations of large clusters. Such clusters comprise model aggregates treated at the quantum chemical level embedded within a realistic environment treated at the molecular mechanics level. As we calculate ground and excited state equilibrium geometries and vibrational modes of model aggregates, our approach is able to capture effects arising from coupling to intermolecular degrees of freedom, absent from existing models relying on geometries and normal modes of single molecules. Using the geometries and vibrational modes of clusters, we are able to simulate the fluorescence spectra of aggregates for which the lowest excited state bears negligible oscillator strength (as is the case, e.g., ideal H-aggregates) by including both Franck-Condon (FC) and Herzberg-Teller (HT) vibronic transitions. The latter terms allow the adiabatic excited state of the cluster to couple with vibrations in a perturbative fashion via derivatives of the transition dipole moment along nuclear coordinates. While vibronic coupling simulations employing FC and HT terms are well established for single-molecules, to our knowledge this is the first time they are applied to molecular aggregates. Here, we apply this approach to the simulation of the low-temperature fluorescence spectrum of para-distyrylbenzene single-crystal H-aggregates and draw comparisons with coarse-grained Frenkel-Holstein approaches previously extensively applied to such systems.

Gamow-Teller transitions and proton-neutron pair correlation in N =Z odd-odd p -shell nuclei

Science.gov (United States)

Morita, Hiroyuki; Kanada-En'yo, Yoshiko

2017-10-01

We have studied the Gamow-Teller (GT) transitions from N =Z +2 neighbors to N =Z odd-odd nuclei in the p -shell region by using isospin-projected and β γ -constraint antisymmetrized molecular dynamics combined with the generator coordinate method. The calculated GT transition strengths from 0+1 states to 1+0 states such as 6He(01+1 ) →6Li(11+0 ) , 10Be(01+1 ) →10B(11+0 ) , and 14C(01+1 ) →14N(12+0 ) exhaust more than 50% of the sum rule. These N =Z +2 initial states and N =Z odd-odd final states are found to dominantly have S =0 ,T =1 n n pairs and S =1 ,T =0 p n pairs, respectively. Based on the two-nucleon (N N ) pair picture, we can understand the concentration of the GT strengths as the spin-isospin-flip transition n n (S =0 ,T =1 )→p n (S =1 ,T =0 ) in L S coupling. The GT transition can be a good probe to identify the spin-isospin partner states with n n pairs and p n pairs of N =Z +2 and N =Z odd-odd nuclei, respectively.

Beta decay of {sup 97}Ag: evidence for the Gamow-Teller resonance near {sup 100}Sn

Energy Technology Data Exchange (ETDEWEB)

Hu Zhiqiang

1999-03-01

In two complementary measurements, a cube like array of 6 Euroball-Cluster germanium detectors and a total-absorption {gamma}-spectrometer were used to investigate the {beta} decay of {sup 97}Ag, a three proton-hole nucleus with respect to the {sup 100}Sn core. The half-life and Q{sub EC} value of the decay of the 9/2{sup +} ground-state of {sup 97}Ag were determined to be 25.9(4) s and 6.98(11) MeV respectively. A total of 603 {gamma} rays (578 new) was observed, and 151 levels (132 new) in {sup 97}Pd have been identified. An interesting {beta}-delayed {gamma} cascade was observed, which comprises 6 {gamma}-transitions with a de-excitation pattern involving an initial increase of the level spin. The Gamow-Teller (GT) {beta}-decay strength distributions from the two measurements reveal a large GT resonance around 4 MeV with a width of about 1.8 MeV. The hindrance factor for the total GT strength summed from the ground-state up to 6 MeV excitation energy in {sup 97}Pd, amounts to 4.3(6) with reference to a shell-model prediction. This factor is discussed in comparison with a core-polarization and a Monte-Carlo shell-model calculation. (orig.)

Effective axial-vector strength and β-decay systematics

Science.gov (United States)

Delion, D. S.; Suhonen, J.

2014-09-01

We use the weak axial-vector coupling strength g_{\\text{A}} as a key parameter to reproduce simultaneously the available data for both the Gamow-Teller \\beta^- and \\beta^+/\\text{EC} decay rates in nine triplets of isobars with mass numbers A=70,78,100,104,106,110,116,128,130 . We use the proton-neutron quasiparticle random-phase approximation (pnQRPA) with schematic dipole interaction containing particle-particle and particle-hole parts with mass-dependent strengths. Our analysis points to a strongly quenched effective value g_{\\text{A}}\\approx 0.3 , with a relative error of 28%. We then perform a systematic computation of 218 experimentally known \\beta^- and \\beta^+/\\text{EC} decays with quite a remarkable success. The presently extracted value of g_{\\text{A}} should be taken as an effective one, specific for a given nuclear theory framework. Present studies suggest that the effective g_{\\text{A}} is suitable for the description of decay transitions to 1^+ states at moderate excitation, below the Gamow-Teller giant resonance region.

Storytelling as an age-dependent skill: oral recall of orally presented stories.

Science.gov (United States)

Mergler, N L; Faust, M; Goldstein, M D

During experiment 1, three taped prose passages read by college student, middle-aged, or old tellers were orally recalled by college students in an incidental memory paradigm. More story units were remembered as the age of the teller increased (r = +.642, p less than .05). Comparison of these results, with prior research using written, as opposed to oral, presentation and recall of these stories, showed no differences in specific story units remembered. Teller age predicted recall on the two "storied" passages. These passages elicited more favorable comments from listeners when read by older tellers. The third, descriptive passage was less favorably regarded by listeners hearing older tellers. During experiment 2, taped storied passages read by middle-aged tellers were falsely attributed to young, middle-aged, or old persons before the college students listened. Incidental recall did not show an age of teller effect in this case, but the listener's evaluation of the speaker exhibited age-dependent stereotypes. It was concluded that 1) physical qualities of older voices lead to more effective oral transmission; 2) that one expects to receive certain types of oral information from older persons; and 3) that a mismatch between physical vocal quality and age attribution effects evaluation of the speaker, not recall of the information.

Nuclear structure properties and stellar weak rates for 76Se: Unblocking of the Gamow Teller strength

Science.gov (United States)

Nabi, Jameel-Un; Ishfaq, Mavra; Böyükata, Mahmut; Riaz, Muhammad

2017-10-01

At finite temperatures (≥ 107K), 76Se is abundant in the core of massive stars and electron capture on 76Se has a consequential role to play in the dynamics of core-collapse. The present work may be classified into two main categories. In the first phase we study the nuclear structure properties of 76Se using the interacting boson model-1 (IBM-1). The IBM-1 investigations include the energy levels, B (E 2) values and the prediction of the geometry. We performed the extended consistent-Q formalism (ECQF) calculation and later the triaxial formalism calculation (constructed by adding the cubic term to the ECQF). The geometry of 76Se can be envisioned within the formalism of the potential energy surface based on the classical limit of IBM-1 model. In the second phase, we reconfirm the unblocking of the Gamow-Teller (GT) strength in 76Se (a test case for nuclei having N > 40 and Z fashion. Results are compared with experimental data and previous calculations. The calculated GT distribution fulfills the Ikeda sum rule. Rates for β-delayed neutrons and emission probabilities are also calculated. Our study suggests that at high stellar temperatures and low densities, the β+-decay on 76Se should not be neglected and needs to be taken into consideration along with electron capture rates for simulation of presupernova evolution of massive stars.

Trapping, self-trapping and the polaron family

International Nuclear Information System (INIS)

Stoneham, A M; Gavartin, J; Shluger, A L; Kimmel, A V; Ramo, D Munoz; Roennow, H M; Aeppli, G; Renner, C

2007-01-01

The earliest ideas of the polaron recognized that the coupling of an electron to ionic vibrations would affect its apparent mass and could effectively immobilize the carrier (self-trapping). We discuss how these basic ideas have been generalized to recognize new materials and new phenomena. First, there is an interplay between self-trapping and trapping associated with defects or with fluctuations in an amorphous solid. In high dielectric constant oxides, like HfO 2 , this leads to oxygen vacancies having as many as five charge states. In colossal magnetoresistance manganites, this interplay makes possible the scanning tunnelling microscopy (STM) observation of polarons. Second, excitons can self-trap and, by doing so, localize energy in ways that can modify the material properties. Third, new materials introduce new features, with polaron-related ideas emerging for uranium dioxide, gate dielectric oxides, Jahn-Teller systems, semiconducting polymers and biological systems. The phonon modes that initiate self-trapping can be quite different from the longitudinal optic modes usually assumed to dominate. Fourth, there are new phenomena, like possible magnetism in simple oxides, or with the evolution of short-lived polarons, like muons or excitons. The central idea remains that of a particle whose properties are modified by polarizing or deforming its host solid, sometimes profoundly. However, some of the simpler standard assumptions can give a limited, indeed misleading, description of real systems, with qualitative inconsistencies. We discuss representative cases for which theory and experiment can be compared in detail

Algebraic Topology Foundations of Supersymmetry and Symmetry Breaking in Quantum Field Theory and Quantum Gravity: A Review

Directory of Open Access Journals (Sweden)

Ion C. Baianu

2009-04-01

Full Text Available A novel algebraic topology approach to supersymmetry (SUSY and symmetry breaking in quantum field and quantum gravity theories is presented with a view to developing a wide range of physical applications. These include: controlled nuclear fusion and other nuclear reaction studies in quantum chromodynamics, nonlinear physics at high energy densities, dynamic Jahn-Teller effects, superfluidity, high temperature superconductors, multiple scattering by molecular systems, molecular or atomic paracrystal structures, nanomaterials, ferromagnetism in glassy materials, spin glasses, quantum phase transitions and supergravity. This approach requires a unified conceptual framework that utilizes extended symmetries and quantum groupoid, algebroid and functorial representations of non-Abelian higher dimensional structures pertinent to quantized spacetime topology and state space geometry of quantum operator algebras. Fourier transforms, generalized Fourier-Stieltjes transforms, and duality relations link, respectively, the quantum groups and quantum groupoids with their dual algebraic structures; quantum double constructions are also discussed in this context in relation to quasi-triangular, quasi-Hopf algebras, bialgebroids, Grassmann-Hopf algebras and higher dimensional algebra. On the one hand, this quantum algebraic approach is known to provide solutions to the quantum Yang-Baxter equation. On the other hand, our novel approach to extended quantum symmetries and their associated representations is shown to be relevant to locally covariant general relativity theories that are consistent with either nonlocal quantum field theories or local bosonic (spin models with the extended quantum symmetry of entangled, 'string-net condensed' (ground states.

Gamow-Teller strength and lepton captures rates on 66-71Ni in stellar matter

Science.gov (United States)

Nabi, Jameel-Un; Majid, Muhammad

Charge-changing transitions play a significant role in stellar weak-decay processes. The fate of the massive stars is decided by these weak-decay rates including lepton (positron and electron) captures rates, which play a consequential role in the dynamics of core collapse. As per previous simulation results, weak interaction rates on nickel (Ni) isotopes have significant influence on the stellar core vis-à-vis controlling the lepton content of stellar matter throughout the silicon shell burning phases of high mass stars up to the presupernova stages. In this paper, we perform a microscopic calculation of Gamow-Teller (GT) charge-changing transitions, in the β-decay and electron capture (EC) directions, for neutron-rich Ni isotopes (66-71Ni). We further compute the associated weak-decay rates for these selected Ni isotopes in stellar environment. The computations are accomplished by employing the deformed proton-neutron quasiparticle random phase approximation (pn-QRPA) model. A recent study showed that the deformed pn-QRPA theory is well suited for the estimation of GT transitions. The astral weak-decay rates are determined over densities in the range of 10-1011g/cm3 and temperatures in the range of 0.01 × 109-30 × 109K. The calculated lepton capture rates are compared with the previous calculation of Pruet and Fuller (PF). The overall comparison demonstrates that, at low stellar densities and high temperatures, our EC rates are bigger by as much as two orders of magnitude. Our results show that, at higher temperatures, the lepton capture rates are the dominant mode for the stellar weak rates and the corresponding lepton emission rates may be neglected.

Molecular properties of metal difluorides and their interactions with CO2 and H2O molecules: a DFT investigation.

Science.gov (United States)

Arokiyanathan, Agnes Lincy; Lakshmipathi, Senthilkumar

2017-11-18

A computational study of metal difluorides (MF 2 ; M = Ca to Zn) and their interactions with carbon dioxide and water molecules was performed. The structural parameter values obtained and the results of AIM analysis and energy decomposition analysis indicated that the Ca-F bond is weaker and less ionic than the bonds in the transition metal difluorides. A deformation density plot revealed the stablizing influence of the Jahn-Teller effect in nonlinear MF 2 molecules (e.g., where M= Sc, Ti, Cr). An anaysis of the metal K-edge peaks of the difluorides showed that shifts in the edge energy were due to the combined effects of the ionicity, effective nuclear charge, and the spin state of the metal. The interactions of CO 2 with ScF 2 (Scc3 geometry) and TiF 2 (Tic2 geometry) caused CO 2 to shift from its usual linear geometry to a bent geometry (η 2 (C=O) binding mode), while it retained its linear geometry (η 1 (O) binding mode) when it interacted with the other metal difluorides. Energy decomposition analysis showed that, among the various geometries considered, the Scc3 and Tic2 geometries possessed the highest interaction energies and orbital interaction energies. Heavier transition metal difluorides showed stronger affinities for H 2 O, whereas the lighter transition metal (Sc and Ti) difluorides preferred CO 2 . Overall, the results of this study suggest that fluorides of lighter transition metals with partially filled d orbitals (e.g., Sc and Ti) could be used for CO 2 capture under moist conditions. Graphical abstract Interaction of metal difluorides with carbon dioxide and water.

A framework for evaluating the performance of automated teller machine in banking industries: A queuing model-cum-TOPSIS approach

Directory of Open Access Journals (Sweden)

Christopher Osita Anyaeche

2018-04-01

Full Text Available The improvement in the provision of banking services to customers enhances bank’s performance (profitability and productivity and the amounts of dividend declared to shareholders as well as bank’s competitiveness. One means of fast tracking the service time for bank customers is through the use of self-servicing machines, such as automated teller machine (ATM. Total service cost, expected waiting time in queue, ATM utilization and percentage of customer loss are some of the performance indices that are used to evaluate the service rendered by a bank’s ATM. This study proposes a framework for evaluating the performance of ATM by integrating queuing model and Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS methodology. Applicability of the framework was tested using practical data obtained from four banks in Nigeria. It was observed that the average ATM usage in the study area was less than 50%. The TOPSIS results identified Bank A as the best ranked bank. In addition, the results obtained revealed that banks with two ATM were ranked higher than banks with more than two ATM

Are computers effective lie detectors? A meta-analysis of linguistic cues to deception.

Science.gov (United States)

Hauch, Valerie; Blandón-Gitlin, Iris; Masip, Jaume; Sporer, Siegfried L

2015-11-01

This meta-analysis investigates linguistic cues to deception and whether these cues can be detected with computer programs. We integrated operational definitions for 79 cues from 44 studies where software had been used to identify linguistic deception cues. These cues were allocated to six research questions. As expected, the meta-analyses demonstrated that, relative to truth-tellers, liars experienced greater cognitive load, expressed more negative emotions, distanced themselves more from events, expressed fewer sensory-perceptual words, and referred less often to cognitive processes. However, liars were not more uncertain than truth-tellers. These effects were moderated by event type, involvement, emotional valence, intensity of interaction, motivation, and other moderators. Although the overall effect size was small, theory-driven predictions for certain cues received support. These findings not only further our knowledge about the usefulness of linguistic cues to detect deception with computers in applied settings but also elucidate the relationship between language and deception. © 2014 by the Society for Personality and Social Psychology, Inc.

Thermodynamics properties study of diatomic molecules with q-deformed modified Poschl-Teller plus Manning Rosen non-central potential in D dimensions using SUSYQM approach

Science.gov (United States)

Suparmi, A.; Cari, C.; Pratiwi, B. N.

2016-04-01

D-dimensional Dirac equation of q-deformed modified Poschl-Teller plus Manning Rosen non-central potential was solved using supersymmetric quantum mechanics (SUSY QM). The relativistic energy spectra were analyzed by using SUSY QM and shape invariant properties from radial part of D dimensional Dirac equation and the angular quantum numbers were obtained from angular part of D dimensional Dirac equation. The SUSY operators was used to generate the D dimensional relativistic wave functions both for radial and angular parts. In the non-relativistic limit, the relativistic energy equation was reduced to the non-relativistic energy. In the classical limit, the partition function of vibrational, the specific heat of vibrational, and the mean energy of vibrational of some diatomic molecules were calculated from the equation of non-relativistic energy with the help of error function and Mat-lab 2011.

Modified automatic teller machine prototype for older adults: a case study of participative approach to inclusive design.

Science.gov (United States)

Chan, Chetwyn C H; Wong, Alex W K; Lee, Tatia M C; Chi, Iris

2009-03-01

The goal of this study was to enhance an existing automated teller machine (ATM) human-machine interface in order to accommodate the needs of older adults. Older adults were involved in the design and field test of the modified ATM prototype. The design of the user interface and functionality took the cognitive and physical abilities of older adults into account. The modified ATM system included only "cash withdrawal" and "transfer" functions based on the task demands and needs for services of older adults. One hundred and forty-one older adults (aged 60 or above) participated in the field test by operating modified or existing ATM systems. Those who operated the modified system were found to have significantly higher success rates than those who operated the existing system. The enhancement was most significant among older adults who had lower ATM-related abilities, a lower level of education, and no prior experience of using ATMs. This study demonstrates the usefulness of using a universal design and participatory approach to modify the existing ATM system for use by older adults. However, it also leads to a reduction in functionality of the enhanced system. Future studies should explore ways to develop a universal design ATM system which can satisfy the abilities and needs of all users in the entire population.

Photo-induced charge-transfer phase transition of rubidium manganese hexacyanoferrate in ferromagnetic and paramagnetic states

International Nuclear Information System (INIS)

Tokoro, Hiroko; Hashimoto, Kazuhito; Ohkoshi, Shin-ichi

2007-01-01

A charge transfer phase transition with thermal hysteresis loop is observed in a series of rubidium manganese hexacyanoferrates, RbMn[Fe(China) 6 ] (1), Rb 0.88 Mn[Fe(China) 6 ] 0.96 .0.6H 2 O (2), and Rb 0.97 Mn[Fe(China) 6 ] 0.99 .0.2H 2 O (3). This phase transition is accompanied by a structural change from cubic (F4-bar 3m) to tetragonal (I4-bar m2). Its high-temperature (HT) and low-temperature (LT) phases are composed of Mn II (S=2/5)NC-Fe III (S=1/2) and Mn III (S=2)-NC-Fe II (S=0), respectively. The phase transition is caused by a metal-to-metal charge transfer from Mn II to Fe III and a Jahn-Teller distortion of the produced Mn III ion. At the ferromagnetic state in LT phase of 2, the photo-induced phase transition is observed, i.e., magnetization is quenched by the irradiation with only one shot of laser pulse. This phenomenon is caused by a photo-induced phase transition from the LT phase to the HT phase. In 3, optical switching between LT and HT phases at room temperature in paramagnetic region is observed

Structural and electronic transformations in substituted La-Sr manganites depending on cations and oxygen content

Science.gov (United States)

Karpasyuk, Vladimir; Badelin, Alexey; Merkulov, Denis; Derzhavin, Igor; Estemirova, Svetlana

2018-05-01

In the present research experimental data are obtained for the Jahn-Teller O‧ phase formation, phase transformation "orthorhombic-rhombohedral structure" and the change of the conductance type in the systems of manganites La3+1-c+xSr2+c-xMn3+1-c-x-2γMn4+c+2γZn2+xO3+γ, La3+1-c-xSr2+c+xMn3+1-c-x-2γMn4+c+2γGe4+xO3+γ, La3+1-cSr2+cMn3+1-x-c-2γMn4+c+2γ(Zn2+0.5Ge4+0.5)xO3+γ, where Mn4+ ions concentration is independent of "x". Ceramic samples were sintered in air at 1473 K. As-sintered samples had an excess of oxygen content. In order to provide stoichiometric oxygen content, the samples were annealed at 1223 K and partial pressure of oxygen PO2 = 10-1 Pа. Structural characteristics of the O‧ phase were obtained. The position of the phase boundary "orthorhombic-rhombohedral structure" and the temperature of the conductance type change depending on the cation composition of manganites and oxygen content were determined. Possible approaches to the interpretation of experimental results were suggested.

Dynamics of ligand exchange mechanism at Cu(II) in water: an ab initio quantum mechanical charge field molecular dynamics study with extended quantum mechanical region.

Science.gov (United States)

Moin, Syed Tarique; Hofer, Thomas S; Weiss, Alexander K H; Rode, Bernd M

2013-07-07

Ab initio quantum mechanical charge field molecular dynamics (QMCF-MD) were successfully applied to Cu(II) embedded in water to elucidate structure and to understand dynamics of ligand exchange mechanism. From the simulation studies, it was found that using an extended large quantum mechanical region including two shells of hydration is required for a better description of the dynamics of exchanging water molecules. The structural features characterized by radial distribution function, angular distribution function and other analytical parameters were consistent with experimental data. The major outcome of this study was the dynamics of exchange mechanism and reactions in the first hydration shell that could not be studied so far. The dynamical data such as mean residence time of the first shell water molecules and other relevant data from the simulations are close to the results determined experimentally. Another major characteristic of hydrated Cu(II) is the Jahn-Teller distortion which was also successfully reproduced, leading to the final conclusion that the dominating aqua complex is a 6-coordinated species. The ab initio QMCF-MD formalism proved again its capabilities of unraveling even ambiguous properties of hydrated species that are far difficult to explore by any conventional quantum mechanics/molecular mechanics (QM/MM) approach or experiment.

Characterization of Carbon Composite LiMn1-xFexPO4 Cathodes

International Nuclear Information System (INIS)

Mishima, Y; Honda, S; Sadamura, H; Nakayama, N; Moriyoshi, C; Kuroiwa, Y

2011-01-01

The discharge capacities of 148 mAh/g (87 % theoretical value) at C/10 and 114mAh/g at 5C between 2.0 and 4.5 V at 25 deg. C were achieved for the carbon composite LiMn 0.8 Fe 0.2 PO 4 (C-LiMn 0.8 Fe 0.2 PO 4 ) cathode material of lithium-ion batteries (LIB), synthesized by a hydrothermal and annealing process. To improve the battery properties, we investigated the characteristics of C-LiMn 1-x Fe x PO 4 powders (x = 0.2 and 1) and the delithiated compound. While it was easier to form the homogeneous carbon layer on the surface of LiFePO 4 particles from the pyrolysis of sucrose, there was a tendency to form the particulate carbon on the LiMn 0.8 Fe 0.2 PO 4 particles. The lattice distortion of Mn 0.8 Fe 0.2 PO 4 was revealed by electron charge density study because of the Jahn-Teller active Mn 3+ ion associated with the phosphate ion. The surface and size of C- LiMn 0.8 Fe 0.2 PO 4 had to be modified because of these phenomena.

Dynamics of ligand exchange mechanism at Cu(II) in water: An ab initio quantum mechanical charge field molecular dynamics study with extended quantum mechanical region

International Nuclear Information System (INIS)

Moin, Syed Tarique; Hofer, Thomas S.; Weiss, Alexander K. H.; Rode, Bernd M.

2013-01-01

Ab initio quantum mechanical charge field molecular dynamics (QMCF-MD) were successfully applied to Cu(II) embedded in water to elucidate structure and to understand dynamics of ligand exchange mechanism. From the simulation studies, it was found that using an extended large quantum mechanical region including two shells of hydration is required for a better description of the dynamics of exchanging water molecules. The structural features characterized by radial distribution function, angular distribution function and other analytical parameters were consistent with experimental data. The major outcome of this study was the dynamics of exchange mechanism and reactions in the first hydration shell that could not be studied so far. The dynamical data such as mean residence time of the first shell water molecules and other relevant data from the simulations are close to the results determined experimentally. Another major characteristic of hydrated Cu(II) is the Jahn-Teller distortion which was also successfully reproduced, leading to the final conclusion that the dominating aqua complex is a 6-coordinated species. The ab initio QMCF-MD formalism proved again its capabilities of unraveling even ambiguous properties of hydrated species that are far difficult to explore by any conventional quantum mechanics/molecular mechanics (QM/MM) approach or experiment

Spin-state responses to light impurity substitution in low-spin perovskite LaCoO3

Science.gov (United States)

Tomiyasu, Keisuke; Kubota, Yuuki; Shimomura, Saya; Onodera, Mitsugi; Koyama, Syun-Ichi; Nojima, Tsutomu; Ishihara, Sumio; Nakao, Hironori; Murakami, Youichi

2013-06-01

We studied the spin-state responses to light impurity substitution in low-spin perovskite LaCoO3 (Co3+: d6) through magnetization, x-ray fluorescence, and electrical resistivity measurements of single-crystal LaCo0.99M0.01O3 (M = Cr, Mn, Fe, Ni). In the magnetization curves measured at 1.8 K, a change in the spin-state was not observed for Cr, Mn, or Fe substitution but was observed for Ni substitution. Strong magnetic anisotropy was also found in the Ni-substituted sample. The fluorescence measurements revealed that the valences were roughly estimated to be Cr3+, Mn(4-δ)+, Fe(3+δ')+, and Ni3+. From the observed chemical trends, we propose that the chemical potential is a key factor in inducing the change of the low-spin state. By expanding a model of the ferromagnetic spin-state heptamer generated by hole doping [Podlesnyak , Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.101.247603 101, 247603 (2008)], the emergence of highly anisotropic spin-state molecular ferromagnets induced by low-spin Ni3+ with Jahn-Teller activity is suggested. We also discuss applicability of the present results to other materials with Fe (d6).

Where do the doped holes go in La2-xSrxCuO4? A close look by XAFS

International Nuclear Information System (INIS)

Haskel, Daniel; Polinger, Victor; Stern, Edward A.

1999-01-01

Polarized x-ray absorption fine structure (XAFS) measurements at the La and Sr sites in La 2-x Sr x CuO 4 (0.075(less-or-similar sign)x(less-or-similar sign)0.35) indicate that doped holes introduced with Sr are not uniformly distributed in the CuO 2 planes but reside in impurity states with the majority of charge located on CuO 6 octahedra coupled to the Sr dopants by an apical oxygen (denoted as Sr octahedra). A model based on doped hole-induced Jahn Teller (JT) distortions of these Sr octahedra indicates the impurity states are overlapping singlet and triplet ones resulting from pairings of intrinsic and extrinsic holes. The more mobile singlet pairs reside in the CuO 2 planes, are bound by more than 0.1 eV and could Bose-condense into a superconducting state. The predominant appearance of (mostly) out-of plane triplet states at high x intimately related to the 2D-3D crossover in transport properties and could relate to the observed loss of high T c in the overdoped regime, as confinement of carriers to the CuO 2 planes is reduced. (c) 1999 American Institute of Physics

High-lying Gamow-Teller excited states in the deformed nuclei,76Ge,82Se and N = 20 nuclei in the island of inversion by the Deformed QRPA (DQRPA)

Science.gov (United States)

Cheoun, Myung-Ki; Ha, Eunja

2013-07-01

With the advent of high analysis technology in detecting the Gamow-Teller (GT) excited states beyond one nucleon emission threshold, the quenching of the GT strength to the Ikeda sum rule (ISR) seems to be recovered by the high-lying (HL) GT states. We address that these HL GT excited states result from the smearing of the Fermi surface by the increase of the chemical potential owing to the deformation within a framework of the deformed quasi-particle random phase approximation (DQRPA). Detailed mechanism leading to the smearing is discussed, and comparisons to the available experimental data on 76Ge,82Se and N = 20 nuclei are shown to explain the strong peaks on the HL GT excited states.

High-lying Gamow-Teller excited states in the deformed nuclei,76Ge,82Se and N = 20 nuclei in the island of inversion by the Deformed QRPA (DQRPA)

International Nuclear Information System (INIS)

Cheoun, Myung-Ki; Ha, Eunja

2013-01-01

With the advent of high analysis technology in detecting the Gamow-Teller (GT) excited states beyond one nucleon emission threshold, the quenching of the GT strength to the Ikeda sum rule (ISR) seems to be recovered by the high-lying (HL) GT states. We address that these HL GT excited states result from the smearing of the Fermi surface by the increase of the chemical potential owing to the deformation within a framework of the deformed quasi-particle random phase approximation (DQRPA). Detailed mechanism leading to the smearing is discussed, and comparisons to the available experimental data on 76 Ge, 82 Se and N = 20 nuclei are shown to explain the strong peaks on the HL GT excited states

Pseudo Jahn–Teller distortion for a tricyclic carbon sulfide (C{sub 6}S{sub 8}) and its suppression in S-oxygenated dithiine (C{sub 4}H{sub 4}(SO{sub 2}){sub 2})

Energy Technology Data Exchange (ETDEWEB)

Pratik, Saied Md.; Chowdhury, Chandra; Bhattacharjee, Rameswar; Jahiruddin, Sk.; Datta, Ayan, E-mail: spad@iacs.res.in

2015-10-16

Highlights: • DFT calculations show that sulfur rich cyclic molecules are generally distorted. • Such distortions are shown to arise from Pseudo Jahn–Teller (PJT) effects. • Low OMO–UMO gaps leads to strong vibronic instability for these systems. • Increasing the OMO–UMO gaps by substituting electronegative groups on the cyclic rings decreases PJT effects. • Suppressed PJT instability lead to planar sulfur rich cyclic molecules. - Abstract: The tricyclic carbon-sulfide, C{sub 6}S{sub 8} molecule containing two S-atoms in the 1,4-position of the central six-membered ring and one disulfide (S−S) and one thione (C=S) bond on the five membered rings on its either side (1) possesses a “butterfly flapping” type distorted ground state in the gas-phase and also in β-phase of the crystal. For the isolated molecule, better consideration of the S…S non-bonding interactions in the dithiine ring in the bent form at the M06-2X/6-31+G(d,p) level leads to a significant barrier for inversion of 2.4 kcal/mol which is 2–3 times more than that previously obtained by Weber and Dolg at the B3LYP/cc-pVTZ level due to underestimation of dispersion interactions at the B3LYP level. The origin of the distortion leading to lowering of symmetry for 1 (C{sub 2h} → C{sub 2}) is traced to vibronic mixing between the ground state (Ag) and the low lying excited states of A{sub u} symmetry through the a{sub u} normal mode, a (1A{sub g} + 1A{sub u} + 2A{sub u} + 3A{sub u}) × a{sub u} pseudo Jahn–Teller effect (PJTE) problem. Based on fitting of the ground state APES to the lowest root of the 4 × 4 secular determinant, we calculate the linear vibronic coupling constants (F{sub 0i}) between the relevant states. Similar in class to 1, the S-oxygenated derivative of dithiine, C{sub 4}H{sub 4}(SO{sub 2}){sub 2} (2) unlike most other dithiines, remains planar. The absence of the butterfly-type puckered structure in 2 is traced to the enhanced gap (Δ{sub 0}) and very small

Uranium hydrogeochemical and stream-sediment reconnaissance of the Teller NTMS Quadrangle, Alaska. National Uranium Resource Evaluation

International Nuclear Information System (INIS)

1982-06-01

This report presents results of a Hydrogeochemical and Stream Sediment Reconnaissance (HSSR) of the Teller NTMS quadrangle, Alaska. In addition to this abbreviated data release, more complete data are available to the public in machine-readable form. These machine-readable data, as well as quarterly or semiannual program progress reports containing further information on the HSSR program in general, or on the Los Alamos National Laboratory (LANL) portion of the program in particular, are available from DOE's Technical Library at its Grand Junction Area Office. Presented in this data release are location data, field analyses, and laboratory analyses of several different sample media. For the sake of brevity, many field site observations have not been included in this volume; these data are, however, available on the magnetic tape. Appendices A through D describe the sample media and summarize the analytical results for each medium. The data have been subdivided by one of the Los Alamos National Laboratory sorting programs of Zinkl and others (1981a) into groups of stream-sediment, lake-sediment, stream-water, lake-water, and ground-water samples. For each group which contains a sufficient number of observations, statistical tables, tables of raw data, and 1:1,000,000 scale maps of pertinent elements have been included in this report. Also included are maps showing results of multivariate statistical analyses. Information on the field and analytical procedures used by the Los Alamos National Laboratory during sample collection and analysis may be found in any HSSR data release prepared by the Laboratory and will not be included in this report

Ab Initio Ligand Field Molecular Mechanics and the Nature of Metal-Ligand π-Bonding in Fe(II) 2,6-di(pyrazol-1-yl)pyridine Spin Crossover Complexes.

Science.gov (United States)

Deeth, Robert J; Halcrow, Malcolm A; Kershaw Cook, Laurence J; Raithby, Paul R

2018-04-06

A ligand field molecular mechanics (LFMM) force field has been constructed for the spin states of [Fe(bpp) 2 ] 2+ (bpp=2,6-di(pyrazol-1-yl)pyridine) and related complexes. A new charge scheme is employed which interpolates between partial charges for neutral bpp and protonated [H 3 bpp] 3+ to achieve a target metal charge. The LFMM angular overlap model (AOM) parameters are fitted to fully ab initio d orbital energies. However, several AOM parameter sets are possible. The ambiguity is resolved by calculating the Jahn-Teller distortion mode for high spin, which indicates that in [Fe(bpp) 2 ] 2+ pyridine is a π-acceptor and pyrazole a weak π-donor. The alternative fit, assumed previously, where both ligands act as π-donors leads to an inconsistent distortion. LFMM optimisations in the presence of [BF 4 ] - or [PF 6 ] - anions are in good agreement with experiment and the model also correctly predicts the spin state energetics for 3-pyrazolyl substituents where the interactions are mainly steric. However, for 4-pyridyl or 4-pyrazolyl substituents, LFMM only treats the electrostatic contribution which, for the pyridyl substituents, generates a fair correlation with the spin crossover transition temperatures, T 1/2 , but in the reverse sense to the dominant electronic effect. Thus, LFMM generates its smallest spin state energy difference for the substituent with the highest T 1/2 . One parameter set for all substituted bpp ligands is insufficient and further LFMM development will be required. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Theoretical study of the local structures and the EPR parameters for RLNKB glasses with VO2+ and Cu2+ dopants

Science.gov (United States)

Ding, Chang-Chun; Wu, Shao-Yi; Wu, Li-Na; Zhang, Li-Juan; Peng, Li; Wu, Ming-He; Teng, Bao-Hua

2018-02-01

The electron paramagnetic resonance (EPR) parameters and local structures for impurities VO2+ and Cu2+ in RO-Li2O-Na2O-K2O-B2O3 (RLNKB; R = Zn, Mg, Sr and Ba) glasses are theoretically investigated by using the perturbation formulas of the EPR parameters for tetragonally compressed octahedral 3d1 and tetragonally elongated octahedral 3d9 clusters, respectively. The VO2+ and Cu2+ dopants are found to undergo the tetragonal compression (characterized by the negative relative distortion ratios ρ ≈ -3%, -0.98%, -1% and -0.8% for R = Zn, Mg, Sr and Ba) and elongation (characterized by the positive relative distortion ratios ρ ≈ 29%, 17%, 16% and 28%), respectively, due to the Jahn-Teller effect. Both dopants show similar overall decreasing trends of cubic field parameter Dq and covalency factor N with decreasing electronegativity of alkali earth cation R. The conventional optical basicities Λth and local optical basicities Λloc are calculated for both systems, and the local Λloc are higher for Cu2+ than for VO2+ in the same RLNKB glass, despite the opposite relationship for the conventional Λth. This point is supported by the weaker covalency or stronger ionicity for Cu2+ than VO2+ in the same RLNKB system, characterized by the larger N in the former. The above comparative analysis on the spectral and local structural properties would be helpful to understand structures and spectroscopic properties for the similar oxide glasses with transition-metal dopants of complementary electronic configurations.

Influence of the manganese and cobalt content on the electrochemical performance of P2-Na0.67MnxCo1-xO2 cathodes for sodium-ion batteries.

Science.gov (United States)

Hemalatha, K; Jayakumar, M; Prakash, A S

2018-01-23

The resurgence of sodium-ion batteries in recent years is due to their potential ability to form intercalation compounds possessing a high specific capacity and energy density comparable to existing lithium systems. To comprehend the role of cobalt substitution in the structure and electrochemical performance of Na 0.67 MnO 2 , the solid solutions of P2-Na 0.67 Mn x Co 1-x O 2 (x = 0.25, 0.5, 0.75) are synthesized and characterized. The XRD-Rietveld analysis revealed that the Co-substitution in Na 0.67 MnO 2 decreases lattice parameters 'a' and 'c' resulting in the contraction of MO 6 octahedra and the enlargement of inter-layer 'd' spacing. XPS indicates that the isovalent cobalt substitution in Na 0.67 MnO 2 results in the partial/complete replacement of Jahn-Teller active trivalent manganese to form low-spin complexes of better structural stability. The Na-ion diffusion coefficient, D Na + , derived from cyclic voltammetry and impedance spectroscopy, confirmed the enhanced mass transport in Co-rich phases compared to Mn-rich phases. Furthermore, higher diffusion coefficient values are observed for Co 3+ /Co 4+ than for their Mn 3+ /Mn 4+ redox processes. In addition, Co-rich phases exhibit a high structural stability and superior capacity retention, whereas Mn-rich phases discharge higher capacities.

The Rovibronic Spectra of the Cyclopentadienyl Radical

Science.gov (United States)

Sharma, Ketan; Miller, Terry A.; Stanton, John F.; Nesbitt, David

2017-06-01

Cyclopentadienyl (Cp) radical has been subject to numerous studies for the greater part of half a century. Experimental work has involved photo-electron spectroscopy, laser induced fluorescence excitation and emission, infrared absorption spectroscopy, and recently rotationally resolved spectra in the CH stretch region taken at JILA. Even more theoretical works appear in the literature, but substantial advances in computation have occurred since their completion. Cp's highly symmetric (D_{5h}) structure and doubly degenerate electronic ground (˜{X}^2E_1^{''}), which is subject to linear Jahn-Teller distortion, have been a great motivation for work on it. We have commenced new computational work to obtain a broad understanding of the electronic, vibrational, and rotational, i.e. rovibronic, structure of the Cp radical as revealed by its spectra, with particular emphasis on the new infrared spectra. The goal is to guide experiments and their analyses and reconcile results from spectroscopy and quantum chemistry calculations. T. Ichino, et al. J. Chem. Phys. 129, 084310 (2008) L. Yu, S. C. Foster, J. M. Williamson, M. C. Heaven and T. A. Miller J. Phys. Chem. 92, 4263 (1988) B. E. Applegate, A. J. Bezant and T. A. Miller J. Chem. Phys 114, 4869 (2001) D. Leicht, M. Kaufmann, G. Schwaab, and M. Havenith J. Chem. Phys. 145, 7 (2016), 074304.

Contribution of on-site Coulomb repulsion energy to structural, electronic and magnetic properties of SrCoO3 for different space groups: first-principles study

Directory of Open Access Journals (Sweden)

Muhammady Shibghatullah

2018-03-01

Full Text Available We report structural, electronic, and magnetic properties of SrCoO3 in Pm3̅m and P4/mbm space groups, which are calculated by using generalized gradient approximation corrected with on-site Coulomb repulsion U and exchange energies J. The cubic lattice parameter a and local magnetic moments of Co (μCo are optimized by varying U at Co 3d site. Employing ultrasoft pseudopotential, the values of U = 8 eV and J = 0.75 eV are the best choice for Pm3̅m space group. We found the value of μCo = 2.56 μB, which is consistent with the previous results. It was also found that Co 3d, hybridized with O 2p, is the main contributor to ferromagnetic metallic properties. Besides, norm-conserving pseudopotential promotes a, which is in good agreement with experimental result. However, it is not suitable for P4/mbm space group. By using ultrasoft pseudopotential, the value of U = 3 eV (J = 0.75 is the most suitable for P4/mbm group. Ferromagnetic metallic properties, Jahn-Teller distortion, and reasonable lattice parameters have been obtained. This study shows that U has significant contribution to the calculated properties and also points out that P4/mbm space group with US-PP is suitable to describe experimental results.

Structural and electrical properties of La{sub 0.5}Ca{sub 0.5}Mn{sub 0.95}Fe{sub 0.05}O{sub 3+{delta}} perovskite

Energy Technology Data Exchange (ETDEWEB)

Mohamed, E.A., E-mail: emanattamohammed@yahoo.com [Department of Physics, Faculty of Science (Girl' s Branch), Al Azhar University, Nasr City, Cairo (Egypt)

2012-12-05

Highlights: Black-Right-Pointing-Pointer La{sub 0.5}Ca{sub 0.5}Mn{sub 0.95}Fe{sub 0.05}O{sub 3+{delta}} synthesis has been achieved by co-precipitation process. Black-Right-Pointing-Pointer Moessbauer results show an evidence for the local distortion of Mn(Fe)O{sub 6} octahedron. Black-Right-Pointing-Pointer Metal-Semiconductor transition temperature (T{sub p}) is observed. - Abstract: La{sub 0.5}Ca{sub 0.5}Mn{sub 0.95}Fe{sub 0.05}O{sub 3+{delta}} was synthesized by co-precipitation method. The structure refinement by using the Rietveld method indicates that the sample was single phase with the presence of small impurities (Mn{sub 3}O{sub 4}) and crystallizes in an orthorhombic (Pbmn) structure. The room temperature (RT) Moessbauer spectrum shows clear evidence of the local structural distortion of the Mn(Fe)O{sub 6} octahedron on the basis of non-zero nuclear quadrupole interactions for high-spin Fe{sup 3+} ions. The Jahn-Teller coupling strength (E{sub JT}) was estimated from the Moessbauer results. Metal-Semiconductor transition temperature (T{sub p}) is observed at 80 K. At high temperature (T{sub P} < T < {theta}{sub D}/2) conductivity data satisfy the variable range hopping (VRH) model. For T > {theta}{sub D}/2 the small polaron hopping model is more appropriate than the VRH model.

Transverse acoustic phonon anomalies at intermediate wave vectors in MgV2O4

Science.gov (United States)

Weber, T.; Roessli, B.; Stock, C.; Keller, T.; Schmalzl, K.; Bourdarot, F.; Georgii, R.; Ewings, R. A.; Perry, R. S.; Böni, P.

2017-11-01

Magnetic spinels (with chemical formula A X2O4 , with X a 3 d transition metal ion) that also have an orbital degeneracy are Jahn-Teller active and hence possess a coupling between spin and lattice degrees of freedom. At high temperatures, MgV2O4 is a cubic spinel based on V3 + ions with a spin S =1 and a triply degenerate orbital ground state. A structural transition occurs at TOO=63 K to an orbitally ordered phase with a tetragonal unit cell followed by an antiferromagnetic transition of TN=42 K on cooling. We apply neutron spectroscopy in single crystals of MgV2O4 to show an anomaly for intermediate wave vectors at TOO associated with the acoustic phonon sensitive to the shear elastic modulus (C11-C12)/2 . On warming, the shear mode softens for momentum transfers near close to half the Brillouin zone boundary, but recovers near the zone center. High resolution spin-echo measurements further illustrate a temporal broadening with increased temperature over this intermediate range of wave vectors, indicative of a reduction in phonon lifetime. A subtle shift in phonon frequencies over the same range of momentum transfers is observed with magnetic fields. We discuss this acoustic anomaly in context of coupling to orbital and charge fluctuations.

Optical and electrical properties of vanadium-doped GaAs

International Nuclear Information System (INIS)

Ulrici, W.; Friedland, K.

1985-01-01

The results of optical absorption, luminescence, and temperature-dependent Hall-effect measurements on GaAs:V, p-type GaAs:V:Zn, and n-type GaAs:V:Si grown by LEC-technique are reported. It is found that the V/sub Ga//sup 3+/ ground state is located very close to or within the valence band and that the V/sub Ga//sup 2+/ acceptor level is at E/sub c/ - 0.14 eV. The near mid-gap level in GaAs:V responsible for its semi-insulating behaviour is proposed to be due to the complex (V/sub Ga//sup 2+/-X), where the correlation between the photoionization absorption connected with this centre and the EL2 concentration suggests that X is an arsenic vacancy. From this level scheme conditions for growing GaAs:V which is semi-insulating at room temperature are derived. The optical experiments on GaAs:V with different Fermi-level positions confirm the assignment of the triple-peaked absorption band at 1.1 eV to the 3 A 2 → 3 T 1 (F) transition of V/sub Ga//sup 3+/. The weak absorption due to the 3 A 2 → 3 T 2 (F) transition is found at 0.79 eV. The analysis of the temperature dependence of the line shape of the → 3 T 1 (F) absorption band as due to strong dynamical Txtau 2 Jahn-Teller effect provides the JT-parameters E/sub JT/ = 780 cm -1 , h/2ω/sub tau/ = 75 cm -1 , and c = 4.7 eV/nm. The temperature dependent asymmetry of the line shape is explained on the basis of earlier theoretical predictions of the simultaneous action of strong linear and quadratic JT-coupling. (author)

Density functional theory study on Herzberg-Teller contribution in Raman scattering from 4-aminothiophenol-metal complex and metal-4-aminothiophenol-metal junction

Science.gov (United States)

Liu, Shasha; Zhao, Xiuming; Li, Yuanzuo; Zhao, Xiaohong; Chen, Maodu

2009-06-01

Density functional theory (DFT) and time-dependent DFT calculations have been performed to investigate the Raman scattering spectra of metal-molecule complex and metal-molecule-metal junction architectures interconnected with 4-aminothiophenol (PATP) molecule. The simulated profiles of normal Raman scattering (NRS) spectra for the two complexes (Ag2-PATP and PATP-Au2) and the two junctions (Ag2-PATP-Au2 and Au2-PATP-Ag2) are similar to each other, but exhibit obviously different Raman intensities. Due to the lager static polarizabilities of the two junctions, which directly influence the ground state chemical enhancement in NRS spectra, the calculated normal Raman intensities of them are stronger than those of two complexes by the factor of 102. We calculate preresonance Raman scattering (RRS) spectra with incident light at 1064 nm, which is much lower than the S1 electronic transition energy of complexes and junctions. Ag2-PATP-Au2 and Au2-PATP-Ag2 junctions yield higher Raman intensities than those of Ag2-PATP and PATP-Au2 complexes, especially for b2 modes. This effect is mainly attributed to charge transfer (CT) between the metal gap and the PAPT molecule which results in the occurrence of CT resonance enhancement. The calculated pre-RRS spectra strongly depend on the electronic transition state produced by new structures. With excitation at 514.5 nm, the calculated pre-RRS spectra of two complexes and two junctions are stronger than those of with excitation at 1064 nm. A charge difference densities methodology has been used to visually describe chemical enhancement mechanism of RRS spectrum. This methodology aims at visualizing intermolecular CT which provides direct evidence of the Herzberg-Teller mechanism.

Safe-by-Design CuO Nanoparticles via Fe-Doping, Cu-O Bond Length Variation, and Biological Assessment in Cells and Zebrafish Embryos.

Science.gov (United States)

Naatz, Hendrik; Lin, Sijie; Li, Ruibin; Jiang, Wen; Ji, Zhaoxia; Chang, Chong Hyun; Köser, Jan; Thöming, Jorg; Xia, Tian; Nel, Andre E; Mädler, Lutz; Pokhrel, Suman

2017-01-24

The safe implementation of nanotechnology requires nanomaterial hazard assessment in accordance with the material physicochemical properties that trigger the injury response at the nano/bio interface. Since CuO nanoparticles (NPs) are widely used industrially and their dissolution properties play a major role in hazard potential, we hypothesized that tighter bonding of Cu to Fe by particle doping could constitute a safer-by-design approach through decreased dissolution. Accordingly, we designed a combinatorial library in which CuO was doped with 1-10% Fe in a flame spray pyrolysis reactor. The morphology and structural properties were determined by XRD, BET, Raman spectroscopy, HRTEM, EFTEM, and EELS, which demonstrated a significant reduction in the apical Cu-O bond length while simultaneously increasing the planar bond length (Jahn-Teller distortion). Hazard screening was performed in tissue culture cell lines and zebrafish embryos to discern the change in the hazardous effects of doped vs nondoped particles. This demonstrated that with increased levels of doping there was a progressive decrease in cytotoxicity in BEAS-2B and THP-1 cells, as well as an incremental decrease in the rate of hatching interference in zebrafish embryos. The dissolution profiles were determined and the surface reactions taking place in Holtfreter's solution were validated using cyclic voltammetry measurements to demonstrate that the Cu + /Cu 2+ and Fe 2+ /Fe 3+ redox species play a major role in the dissolution process of pure and Fe-doped CuO. Altogether, a safe-by-design strategy was implemented for the toxic CuO particles via Fe doping and has been demonstrated for their safe use in the environment.

An investigation of the sites occupied by atomic barium in solid xenon—A 2D-EE luminescence spectroscopy and molecular dynamics study

Science.gov (United States)

Davis, Barry M.; Gervais, Benoit; McCaffrey, John G.

2018-03-01

A detailed characterisation of the luminescence recorded for the 6p 1P1-6s 1S0 transition of atomic barium isolated in annealed solid xenon has been undertaken using two-dimensional excitation-emission (2D-EE) spectroscopy. In the excitation spectra extracted from the 2D-EE scans, two dominant thermally stable sites were identified, consisting of a classic, three-fold split Jahn-Teller band, labeled the blue site, and an unusual asymmetric 2 + 1 split band, the violet site. A much weaker band has also been identified, whose emission is strongly overlapped by the violet site. The temperature dependence of the luminescence for these sites was monitored revealing that the blue site has a non-radiative channel competing effectively with the fluorescence even at 9.8 K. By contrast, the fluorescence decay time of the violet site was recorded to be 4.3 ns and independent of temperature up to 24 K. The nature of the dominant thermally stable trapping sites was investigated theoretically with Diatomics-in-Molecule (DIM) molecular dynamics simulations. The DIM model was parameterized with ab initio multi-reference configuration interaction calculations for the lowest energy excited states of the BaṡXe pair. The simulated absorption spectra are compared with the experimental results obtained from site-resolved excitation spectroscopy. The simulations allow us to assign the experimental blue feature spectrum to a tetra-vacancy trapping site in the bulk xenon fcc crystal—a site often observed when trapping other metal atoms in rare gas matrices. By contrast, the violet site is assigned to a specific 5-atom vacancy trapping site located at a grain boundary.

Thermal properties of some cerium compounds, particularly CeB6

International Nuclear Information System (INIS)

Peysson, Y.

1986-09-01

Using measurements of specific heat between 0.3 to 250K in the absence of a magnetic field, and from 2 to 250K for magnetic fields between 0 and 8T, it is shown that the γ 8 quadruplet is the fundamental level of the Ce 3+ ion, the γ 8-7 separation energy being of the order of 500K. Detailed analysis suggests a lifting of degeneracy of the multiplet γ 8 in the paramagnetic phase, according to usual processes. Specific heat results obtained at very low temperatures reveal the importance of a significant gap in the spin wave energy spectra. Measurements under a strong magnetic field, around the two magnetic phase transitions of CeB6 show a spectacular reinforcement of the specific heat anomaly at a temperature of the order of T Q . Thermal conductivity of CEB6 is also studied in relation to the possible existence of a Jahn-Teller effect, likely to affect heat transfer by phonons. The problem of the different components of thermal transport prompts the analysis of the Weidemann-Franz law in the Kondo net, and also the study of the thermal conductivity of the compounds CeCu6, CeA12, the alloys Ce 0 . 7 5La 0 . 25 B 6 , Ce x La 1-x Cu 6 , and the fluctuating valence system SmB 6 . In all these bodies, an important contribution of phonons to electron transfer is shown. In the dense incoherent Kondo phase, it is not possible to envisage differences from the Weidemann-Franz law greater than those observed for highly diluted Kondo alloys [fr

Mechanisms of spin-flipping and metal-insulator transition in nano-Fe3O4

Science.gov (United States)

Dito Fauzi, Angga; Aziz Majidi, Muhammad; Rusydi, Andrivo

2017-04-01

Fe3O4 is a half-metallic ferrimagnet with {{T}\\text{C}}˜ 860 K exhibiting metal-insulator transition (MIT) at  ˜120 K. In bulk form, the saturation magnetization is 0.6 Tesla (˜471 emu cm-3). A recent experimental study has shown that the saturation magnetization of nano-Fe3O4 thin films can achieve up to  ˜760 emu cm-3, attributed to spin-flipping of Fe ions at tetrahedral sites assisted by oxygen vacancies (V O). Such a system has shown to have higher MIT temperature (˜150 K). The spin-flipping is a new phenomenon in Fe3O4, while the MIT is a long-standing one. Here, we propose a model and calculations to investigate the mechanisms of both phenomena. Our results show that, for the system without V O, the ferrimagnetic configuration is energetically favorable. Remakably, upon inclusion of V O, the ground-state configuration switches into ferromagnetic. As for the MIT, by proposing temperature dependences of some hopping integrals in the model, we demonstrate that the system without and with V O undergo the MIT in slightly different ways, leading to higher MIT temperature for the system with V O, in agreement with the experimental data. Our results also show that the MIT in both systems occur concomitantly with the redistribution of electrons among the three Fe ions in each Fe3O4 formula unit. As such temperature dependences of hopping integrals may arise due to dynamic Jahn-Teller effects, our phenomenological theory may provide a way to reconcile existing theories relating the MIT to the structural transition and the charge ordering.

Approximate analytical solution of the Dirac equation for pseudospin symmetry with modified Po schl-Teller potential and trigonometric Scarf II non-central potential using asymptotic iteration method

International Nuclear Information System (INIS)

Pratiwi, B N; Suparmi, A; Cari, C; Yunianto, M; Husein, A S

2016-01-01

We apllied asymptotic iteration method (AIM) to obtain the analytical solution of the Dirac equation in case exact pseudospin symmetry in the presence of modified Pcischl- Teller potential and trigonometric Scarf II non-central potential. The Dirac equation was solved by variables separation into one dimensional Dirac equation, the radial part and angular part equation. The radial and angular part equation can be reduced into hypergeometric type equation by variable substitution and wavefunction substitution and then transform it into AIM type equation to obtain relativistic energy eigenvalue and wavefunctions. Relativistic energy was calculated numerically by Matlab software. And then relativistic energy spectrum and wavefunctions were visualized by Matlab software. The results show that the increase in the radial quantum number n_r causes decrease in the relativistic energy spectrum. The negative value of energy is taken due to the pseudospin symmetry limit. Several quantum wavefunctions were presented in terms of the hypergeometric functions. (paper)

Walén test and de Hoffmann-Teller frame of interplanetary large-amplitude Alfvén waves

International Nuclear Information System (INIS)

Chao, J. K.; Hsieh, Wen-Chieh; Lee, L. C.; Yang, L.

2014-01-01

In this study, three methods of analysis are compared to test the Walén relation. Method 1 requires a good de Hoffmann-Teller (HT) frame. Method 2 uses three components separately to find the frame that is slightly modified from Method 1. This method is intended to improve the accuracy of the HT frame and able to demonstrate the anisotropic property of the fluctuations. The better the relation is, the closer the slope of a regression fitting the data of plasma versus Alfvén velocities is to 1. However, this criterion is based on an average HT frame, and the fitted slope does not always work for the Walén test because the HT frame can change so fast in the high-speed streams. We propose Method 3 to check the Walén relation using a sequence of data generated by taking the difference of two consecutive values of plasma and Alfvén velocities, respectively. The difference data are independent of the HT frame. We suggest that the ratio of the variances between plasma and Alfvén velocities is a better parameter to qualify the Walén relation. Four cases in two solar wind streams are studied using these three methods. Our results show that when the solar wind HT frame remains stable, all three methods can predict Alfvénic fluctuations well, but Method 3 can better predict the Walén relation when solar wind contains structures with several small streams. A simulated case also demonstrates that Method 3 is better and more robust than Methods 1 and 2. These results are important for a better understanding of Alfvénic fluctuations and turbulence in the solar wind.

High-resolution study of Gamow-Teller transitions in the 47Ti(3He,t)47V reaction

Science.gov (United States)

Ganioǧlu, E.; Fujita, H.; Fujita, Y.; Adachi, T.; Algora, A.; Csatlós, M.; Deaven, J. M.; Estevez-Aguado, E.; Guess, C. J.; Gulyás, J.; Hatanaka, K.; Hirota, K.; Honma, M.; Ishikawa, D.; Krasznahorkay, A.; Matsubara, H.; Meharchand, R.; Molina, F.; Okamura, H.; Ong, H. J.; Otsuka, T.; Perdikakis, G.; Rubio, B.; Scholl, C.; Shimbara, Y.; Susoy, G.; Suzuki, T.; Tamii, A.; Thies, J. H.; Zegers, R. G. T.; Zenihiro, J.

2013-01-01

Given the importance of Gamow-Teller (GT) transitions in nuclear structure and astrophysical nuclear processes, we have studied Tz=+3/2→+1/2, GT transitions starting from the 47Ti nucleus in the (3He,t) charge-exchange reaction at 0∘ and at an intermediate incident energy of 140 MeV/nucleon. The experiments were carried out at the Research Center for Nuclear Physics (RCNP), Osaka, using the high-resolution facility with a high-dispersion beam line and the Grand-Raiden spectrometer. With an energy resolution of 20 keV, individual GT transitions were observed and GT strength was derived for each state populated up to an excitation energy (Ex) of 12.5 MeV. The GT strength was widely distributed from low excitation energy up to 12.5 MeV, where we had to stop the analysis because of the high level density. The distribution of the GT strengths was compared with the results of shell model calculations using the GXPF1 interaction. The calculations could reproduce the experimental GT distributions well. The GT transitions from the ground state of 47Ti and the M1 transitions from the isobaric analog state in 47V to the same low-lying states in 47V are analogous. It was found that the ratios of GT transition strengths to the ground state, the 0.088-MeV state, and the 0.146-MeV state are similar to the ratios of the strengths of the analogous M1 transitions from the isobaric analog state (IAS) to these states. The measured distribution of the GT strengths was also compared with those starting from the Tz=+3/2 nucleus 41K to the Tz=+1/2 nucleus 41Ca.

High-resolution study of the Gamow-Teller strength distribution in the light nuclei 9B and 13N using the (3He,t) charge-exchange reaction at 420 MeV beam energy

International Nuclear Information System (INIS)

Scholl, Clemens

2010-01-01

Excited states in the light nuclei 9 B and 13 C were studied using the ( 3 He,t) charge-exchange reaction on 9 Be and 13 C targets. The measurements were performed at the research center for nuclear physics (RCNP) in Osaka, Japan, using the magnetic spectrometer Grand Raiden and the dispersive WS course. The 3 He beam with an energy of 420 MeV was accelerated by the RCNP Ring Cyclotron. The Grand Raiden spectrometer and the WS course allow to study the ( 3 He,t) charge-exchange reaction with an energy resolution of around 30 keV, which is one order of magnitude better than measurements with the (p,n) charge-exchange reaction. The high resolution allows to better separate individual states and to determine weak excitation strengths because of low background in the spectra. A total of 19 states in 13 N were studied, and a total of 20 states were observed in 9 B. Of these, 9 states in 13 C and 10 states in 9 B were identified as being excited by a Gamow-Teller transition. Charge-exchange reactions are related to beta-decay, and at zero momentum transfer a simple proportionality exists between the cross-section of the charge-exchange experiment and the Fermi (F) or Gamow-Teller (GT) beta-decay strength. While the Fermi strength B(F) is concentrated in the transition to the isobaric analog state, the Gamow-Teller strength B(GT) is scattered among the excited states. The main aim of the present study is to determine the B(GT) strengths in the nuclei 9 B and 13 N. The only charge-exchange study of 9 B was made 30 years ago with the (p,n) reaction and a resolution of around 300-400 keV. Many states, especially at high excitation energy, could not be resolved by that study. The present work was able to separate many weakly excited states with small decay width at high excitation energies (12-19 MeV) in 9 B and determine the B(GT) strength distribution by using recent high-precision beta-decay data. The results point to a strong difference in spatial structure between the

Raman scattering study of the structural phase transition in single crystal KDy(MoO4)2

Science.gov (United States)

Peschanskii, A. V.

2017-11-01

Raman scattering of light in single-crystal KDy(MoO4)2 is studied at frequencies of 3-1000 cm-1 for temperatures ranging from 2 to 300 K, including that of a structural phase transition of the cooperative Jahn-Teller type (TC ˜ 14.5 K). During the transition to the low-temperature phase, a series of additional phonon lines corresponding to the Ag, B1g, B2g, and B3g modes is observed which indicates a doubling of the unit cell during the phase transition. An analysis of the symmetry of the phonon modes shows that the low-temperature phase has a predominantly monoclinic symmetry with conservation of a second order axis along the crystallographic b direction, i.e., perpendicular to the layers. Excitations are discovered which correspond to low-energy electronic transitions between levels of the ground-state 6H15/2 multiplet of the Dy3+ ion, which is split in the crystal field with a C2 symmetry. In the vicinity of the first excited Kramers doublet of the Dy3+ ion in crystalline KDy(MoO4)2, the scattered spectrum contains four lines [16.5, 21.0, 24.9, and 29.1 cm-1 (2 K)] at low temperatures, instead of a single line [18.3 cm-1 (25 K)] above the phase transition temperature (14.5 K). This indicates the existence of four nonequivalent dysprosium ions in the low-temperature phase.

Synthesis and characterization of 6,6'-(2,4,6-triisopropylphenyl)-2,2'-bipyridine (tripbipy) and its complexes of the late first row transition metals.

Science.gov (United States)

Benson, Eric E; Rheingold, Arnold L; Kubiak, Clifford P

2010-02-15

The synthesis of tripbipy, a new substituted bipyridine ligand (6,6'-(2,4,6-triisopropylphenyl)-2,2'-bipyridine), and the syntheses, structures, and magnetic properties of the first coordination compounds based on this ligand are described. Tripbipy was synthesized by the Suzuki coupling of 2,4,6-triisopropylphenyl boronic acid and 6,6'-dibromo-2,2'-bipyridine. Reported here are the tripbipy complexes of five late first row transition metal chlorides (MCl(2); M = Fe, Co, Ni, Cu, Zn). Four of the complexes MCl(2)tripbipy (M = Fe, Co, Ni, Zn) crystallize in the space group P2(1)/c and are isomorphous with one solvent molecule of crystallization. The complex CuCl(2)tripbipy crystallizes in the space group P2(1)2(1)2(1) with two solvent molecules of crystallization. All MCl(2)tripbipy complexes are four coordinate and contain distorted tetrahedral metal centers. CuCl(2)tripbipy shows a pseudo Jahn-Teller distortion, and X-band electron paramagnetic resonance (EPR) in a toluene glass gives approximate g( perpendicular, parallel) values of 2.2 and 2.1. Magnetic measurements (M = Fe, Co, Ni, Cu) are consistent with high spin d(n) configurations (n = 6-9, S = 2, 3/2, 1, 1/2) tetrahedral complexes and give chi(M)T values at 300 K of 3.56, 2.10, 1.01, and 0.37 cm(3) M(-1) K, respectively.

Spectral intensities in cubic systems. II. The MoCl63- system in cubic elpasolite crystals

International Nuclear Information System (INIS)

Acevedo, R.; Meruane, T.; Poblete, V.

1998-01-01

The visible and near infrared luminescence spectra of MoCl 6 3- in Cs 2 NaMCl 6 (M=Sc, Y, In) and MoBr 6 3- in Cs 2 NaYBr 6 have been reported between 15000 cm -1 and 3000 cm -1 at liquid helium temperatures. It has been observed that each electronic transition shows an extensive and rich vibronic structure, which can be analysed to yield the vibrational frequencies of the MoX 6 3- ion in each electronic state. A through analysis of the spectra for these systems, show that the vibrational frequencies associated with each of the electronic transition is almost identical. This is an evidence of a weak or rather negligible Jahn-Teller distortions. The spectra though are strongly influenced by resonant interactions among the MoX 6 3- ion and the internal and lattice modes of the host lattices and there is also a noticeable variation of the relative vibronic distributions of parity forbidden transitions assisted by the odd parity normal modes of vibrations. This present work deals with the most likely intensity mechanisms and a strategy is put forward to carry out explicit calculations for both, the electronic and vibrational factors of transitions of the kind Γ 1 ↔ Γ 2 + v k for k=3, 4, and 6. Extension of this work to include the ion-phonon interaction is currently in progress in our laboratory. (Author)

The characterisation of VSe2: a study of the thermal expansion

International Nuclear Information System (INIS)

Wiegers, G.A.

1981-01-01

The thermal expansion of VSe 2 from 40-1175 K has been determined by x-ray diffraction. The lattice expansion is linear with temperature from 40 to about 300 K with αsub(a) = 18.6 x 10 -6 K -1 and αsub(c) = 9.8 x 10 -6 K -1 . The behaviour αsub(a) > αsub(c) is anomalous for a layer compound. From the relation between the thermal expansion and the elastic constants it follows that either the elastic constants of VSe 2 are anomalous for a layer compound or the elastic constants are normal but there is a large anisotropy in the Gruneisen functions γsub(a) and γsub(c) (γsub(a) > γsub(c)) together with a relatively large value of the cross compliance constant s 13 . The latter possibility is probably true. The physical origin lies in the electronic structure; the exceptionally high ratio c/a (1.823 at 40 K, 1.818 at 300 K) due to a band Jahn-Teller type distortion, decreases at increasing temperature. The expansion above about 300 K is no longer linear; with increasing temperature the expansion of the a axis increases while that of the c axis becomes almost zero. The non-linear behaviour is ascribed to the formation of Frenkel defects: intrasandwich vanadium is transferred to the interstitial sites in the Van der Waals gap. (author)

Role of 5f electrons in the structural stability of light actinide (Th-U) mononitrides under pressure.

Science.gov (United States)

Modak, P; Verma, Ashok K

2016-03-28

Pressure induced structural sequences and their mechanism for light actinide (Th-U) mononitrides were studied as a function of 5f-electron number using first-principles total energy and electronic structure calculations. Zero pressure lattice constants, bulk module and C11 elastic module vary systematically with 5f-electron number implying its direct role on crystal binding. There is a critical 5f-electron number below which the system makes B1-B2 and above it B1-R3̄m-B2 structural sequence under pressure. Also, the B1-B2 transition pressure increases with increasing 5f-electron number whereas an opposite trend is obtained for the B1-R3̄m transition pressure. The ascending of N p anti-bonding states through the Fermi level at high pressure is responsible for the structural instability of the system. Above the critical 5f-electron number in the system a narrow 5f-band occurs very close to the Fermi level which allows the system to lower its symmetry via band Jahn-Teller type lattice distortion and the system undergoes a B1-R3̄m phase transition. However, below the critical 5f-electron number this mechanism is not favorable due to a lack of sufficient 5f-state occupancy and thus the system undergoes a B1-B2 phase transition like other ionic solids.

New quaternary oxides with both families of second-order Jahn–Teller (SOJT) distortive cations: Solid-state synthesis, structure determination, and characterization of YNbTe{sub 2}O{sub 8} and YNbSe{sub 2}O{sub 8}

Energy Technology Data Exchange (ETDEWEB)

Kim, Yeong Hun [Department of Chemistry, Chung-Ang University, 84 Heukseok-ro, Dongjak-gu, Seoul 156-756 (Korea, Republic of); Jeon, Beom-Yong; You, Tae-Soo [Department of Chemistry, Chungbuk National University, Cheongju, Chungbuk 361-763 (Korea, Republic of); Ok, Kang Min, E-mail: kmok@cau.ac.kr [Department of Chemistry, Chung-Ang University, 84 Heukseok-ro, Dongjak-gu, Seoul 156-756 (Korea, Republic of)

2015-07-15

Graphical abstract: Ball-and-stick representation of YNbTe{sub 2}O{sub 8} composed of polyhedra of SOJT distortive cations, i.e., NbO{sub 6} and TeO{sub 3}, in the ac-plane. - Highlights: • Two novel tellurite and selenite (YNbQ{sub 2}O{sub 8}; Q = Te and Se) are synthesized. • YNbQ{sub 2}O{sub 8} possess both families of second-order Jahn–Teller distortive cations. • The distortive environments and bonding nature are supported by electronic structure calculations. - Abstract: Two novel quaternary mixed metal tellurite and selenite, YNbTe{sub 2}O{sub 8} and YNbSe{sub 2}O{sub 8}, respectively, have been synthesized through standard solid-state reactions using Y{sub 2}O{sub 3}, Nb{sub 2}O{sub 5}, TeO{sub 2} or SeO{sub 2} as reagents. Single crystal X-ray and powder neutron diffraction analyses have been utilized to determine the structures of the reported materials. YNbTe{sub 2}O{sub 8} and YNbSe{sub 2}O{sub 8} are isostructural to each other and crystallize in the monoclinic centrosymmetric space group, C2/m (No. 12). Due to the two families of constituent second-order Jahn–Teller (SOJT) distortive cations, i.e., Nb{sup 5+} and Te{sup 4+}/Se{sup 4+}, local asymmetric environments occur from the three-dimensional frameworks. Intra-octahedral distortions along the local C{sub 4} direction and asymmetric trigonal pyramidal coordination moieties generated by stereoactive lone pairs are observed from the NbO{sub 6} octahedra and TeO{sub 3} (or SeO{sub 3}) polyhedra, respectively. Thermogravimetric analysis, infrared and UV–vis diffuse reflectance spectroscopies, elemental analysis, out-of-center distortions, dipole moment calculations, and electronic structure calculations for the reported materials are presented.

Typicality and reasoning fallacies.

Science.gov (United States)

Shafir, E B; Smith, E E; Osherson, D N

1990-05-01

The work of Tversky and Kahneman on intuitive probability judgment leads to the following prediction: The judged probability that an instance belongs to a category is an increasing function of the typicality of the instance in the category. To test this prediction, subjects in Experiment 1 read a description of a person (e.g., "Linda is 31, bright, ... outspoken") followed by a category. Some subjects rated how typical the person was of the category, while others rated the probability that the person belonged to that category. For categories like bank teller and feminist bank teller: (1) subjects rated the person as more typical of the conjunctive category (a conjunction effect); (2) subjects rated it more probable that the person belonged to the conjunctive category (a conjunction fallacy); and (3) the magnitudes of the conjunction effect and fallacy were highly correlated. Experiment 2 documents an inclusion fallacy, wherein subjects judge, for example, "All bank tellers are conservative" to be more probable than "All feminist bank tellers are conservative." In Experiment 3, results parallel to those of Experiment 1 were obtained with respect to the inclusion fallacy.

Utilizing Co2+/Co3+ Redox Couple in P2-Layered Na0.66Co0.22Mn0.44Ti0.34O2 Cathode for Sodium-Ion Batteries.

Science.gov (United States)

Wang, Qin-Chao; Hu, Enyuan; Pan, Yang; Xiao, Na; Hong, Fan; Fu, Zheng-Wen; Wu, Xiao-Jing; Bak, Seong-Min; Yang, Xiao-Qing; Zhou, Yong-Ning

2017-11-01

Developing sodium-ion batteries for large-scale energy storage applications is facing big challenges of the lack of high-performance cathode materials. Here, a series of new cathode materials Na 0.66 Co x Mn 0.66- x Ti 0.34 O 2 for sodium-ion batteries are designed and synthesized aiming to reduce transition metal-ion ordering, charge ordering, as well as Na + and vacancy ordering. An interesting structure change of Na 0.66 Co x Mn 0.66- x Ti 0.34 O 2 from orthorhombic to hexagonal is revealed when Co content increases from x = 0 to 0.33. In particular, Na 0.66 Co 0.22 Mn 0.44 Ti 0.34 O 2 with a P2-type layered structure delivers a reversible capacity of 120 mAh g -1 at 0.1 C. When the current density increases to 10 C, a reversible capacity of 63.2 mAh g -1 can still be obtained, indicating a promising rate capability. The low valence Co 2+ substitution results in the formation of average Mn 3.7+ valence state in Na 0.66 Co 0.22 Mn 0.44 Ti 0.34 O 2 , effectively suppressing the Mn 3+ -induced Jahn-Teller distortion, and in turn stabilizing the layered structure. X-ray absorption spectroscopy results suggest that the charge compensation of Na 0.66 Co 0.22 Mn 0.44 Ti 0.34 O 2 during charge/discharge is contributed by Co 2.2+ /Co 3+ and Mn 3.3+ /Mn 4+ redox couples. This is the first time that the highly reversible Co 2+ /Co 3+ redox couple is observed in P2-layered cathodes for sodium-ion batteries. This finding may open new approaches to design advanced intercalation-type cathode materials.

The first 3D malonate bridged copper [Cu(O{sub 2}C-CH{sub 2}-CO{sub 2}H){sub 2}{center_dot}2H{sub 2}O]: Structure, properties and electronic structure

Energy Technology Data Exchange (ETDEWEB)

Seguatni, A., E-mail: seguatni@gmail.com [LBPC-INSERM U 698, Institut Galilee, Universite Paris XIII, 99, avenue J. B. Clement 93430, Villetaneuse (France); Fakhfakh, M. [Unite de recherche UR 12-30, Synthese et Structure de Materiaux Inorganiques, Faculte des Sciences de Bizerte, 7021 Zarzouna (Tunisia); Departement de Chimie, Universite du Quebec a Montreal, C.P. 8888, Succ. Centre-ville, Montreal, Que., H3C 3P8 (Canada); Smiri, L.S. [Unite de recherche UR 12-30, Synthese et Structure de Materiaux Inorganiques, Faculte des Sciences de Bizerte, 7021 Zarzouna (Tunisia); Gressier, P.; Boucher, F. [Institut des Materiaux Jean Rouxel, Universite de Nantes, CNRS, 2 rue de la Houssiniere, BP 32229, 44322 Nantes Cedex 3 (France); Jouini, N. [Departement de Chimie, Universite du Quebec a Montreal, C.P. 8888, Succ. Centre-ville, Montreal, Que., H3C 3P8 (Canada)

2012-03-15

A new inorganic-organic compound [Cu(O{sub 2}C-CH{sub 2}-CO{sub 2}H){sub 2}{center_dot}2H{sub 2}O] ([Cumal]) was hydrothermally synthesized and characterized by IR spectroscopy, thermal analysis and single crystal X-ray diffraction. [Cumal] is the first three-dimensional compound existing in the system Cu(II)-malonic acid-H{sub 2}O. Its framework is built up through carboxyl bridged copper where CuO{sub 6} octahedra are elongated with an almost D{sub 4h} symmetry (4+2) due to the Jahn-Teller effect. The magnetic properties were studied by measuring its magnetic susceptibility in the temperature range of 2-300 K indicating the existence of weak ferromagnetic interactions. The electronic structure of [Cumal] was calculated within the density functional theory (DFT) framework. Structural features are well reproduced using DFT structural optimizations and the optical spectra, calculated within the dielectric formalism, explain very well the light blue colour of the compound. It is shown that a GGA+U approach with a U{sub eff} value of about 6 eV is necessary for a better correlation with the experiment. - Graphical abstract: [Cu(O{sub 2}C-CH{sub 2}-CO{sub 2}H){sub 2}{center_dot}2H{sub 2}O]: the first 3D hybrid organic-inorganic compound built up carboxyl groups. The network presents a diamond-like structure achieved via carboxyl. Highlights: Black-Right-Pointing-Pointer A new organic-inorganic material with an unprecedented topology is synthesized. Black-Right-Pointing-Pointer Crystallographic structure is determined using single crystal X-ray diffraction. Black-Right-Pointing-Pointer Electronic structure is obtained from DFT, GGA+U calculation. Black-Right-Pointing-Pointer Framework can be described as formed from CuC{sub 4} tetrahedron sharing four corners. Black-Right-Pointing-Pointer This structure can be classified as an extended diamond structure.

Synthesis, structure, properties and immobilization on a gold surface of the monoribbed-functionalized tris-dioximate cobalt(II) clathrochelates and an electrocatalytic hydrogen production from H+ ions.

Science.gov (United States)

Voloshin, Y Z; Belov, A S; Vologzhanina, A V; Aleksandrov, G G; Dolganov, A V; Novikov, V V; Varzatskii, O A; Bubnov, Y N

2012-05-28

The cycloaddition of the mono- and dichloroglyoximes to the cobalt(II) bis-α-benzyldioximate afforded the cobalt(II) mono- and dichloroclathrochelates in moderate yields (40-60%). These complexes undergo nucleophilic substitution of their reactive chlorine atoms with aliphatic amines, alcohols and thiolate anions. In the case of ethylenediamine and 1,2-ethanedithiol, only the macrobicyclic products with α,α'-N(2)- and α,α'-S(2)-alicyclic six-numbered ribbed fragments were obtained. The cobalt(II) cage complexes with terminal mercapto groups were synthesized using aliphatic dithiols. The crystal and molecular structures of the six cobalt(II) clathrochelates were obtained by X-ray diffraction. Their CoN(6)-coordination polyhedra possess a geometry intermediate between a trigonal prism and a trigonal antiprism, and the encapsulated cobalt(II) ions are shifted from their centres due to the structural Jahn-Teller effect with the Co-N distances varying significantly (by 0.10-0.26 Å). The electrochemistry of the complexes obtained was studied by cyclic voltammetry (CV). The anodic waves correspond to the quasi-reversible Co(2+/3+) oxidations, whereas the cathodic ranges contain the quasi-reversibile waves assigned to the Co(2+/+) reductions; all the cobalt(i)-containing clathrochelate anions formed are stable in the CV time scale. The electrocatalytic properties of the cobalt complexes obtained were studied in the production of hydrogen from H(+) ions: the addition of HClO(4) resulted in the formation of the same catalytic cathodic reduction Co(2+/+) waves. The controlled-potential electrolysis with gas chromatography analysis confirmed the production of H(2) in high Faraday yields. The efficiency of this electrocatalytic process was enhanced by an immobilization of the complexes with terminal mercapto groups on a surface of the working gold electrode.

Microstructural, Magnetic, and Optical Properties of Pr-Doped Perovskite Manganite La0.67Ca0.33MnO3 Nanoparticles Synthesized via Sol-Gel Process

Science.gov (United States)

Xia, Weiren; Wu, Heng; Xue, Piaojie; Zhu, Xinhua

2018-05-01

We report on microstructural, magnetic, and optical properties of Pr-doped perovskite manganite (La1 - xPrx)0.67Ca0.33MnO3 (LPCMO, x = 0.0-0.5) nanoparticles synthesized via sol-gel process. Structural characterizations (X-ray and electron diffraction patterns, (high resolution) TEM images) provide information regarding the phase formation and the single-crystalline nature of the LPCMO systems. X-ray and electron diffraction patterns reveal that all the LPCMO samples crystallize in perovskite crystallography with an orthorhombic structure ( Pnma space group), where the MnO6 octahedron is elongated along the b axis due to the Jahn-Teller effect. That is confirmed by Raman spectra. Crystallite sizes and grain sizes were calculated from XRD and TEM respectively, and the lattice fringes resolved in the high-resolution TEM images of individual LPCMO nanoparticle confirmed its single-crystalline nature. FTIR spectra identify the characteristic Mn-O bond stretching vibration mode near 600 cm- 1, which shifts towards high wavenumbers with increasing post-annealing temperature or Pr-doping concentration, resulting in further distortion of the MnO6 octahedron. XPS revealed dual oxidation states of Mn3+ and Mn4+ in the LPCMO nanoparticles. UV-vis absorption spectra confirm the semiconducting nature of the LPCMO nanoparticles with optical bandgaps of 2.55-2.71 eV. Magnetic measurements as a function of temperature and magnetic field at field cooling and zero-field cooling modes, provided a Curie temperature around 230 K, saturation magnetization of about 81 emu/g, and coercive field of 390 Oe at 10 K. Such magnetic properties and the semiconducting nature of the LPCMO nanoparticles will make them as suitable candidate for magnetic semiconductor spintronics.

Optical studies of high quality synthetic diamond

International Nuclear Information System (INIS)

Sharp, S.J.

1999-01-01

This thesis is concerned with the study of fundamental and defect induced optical properties of synthetic diamond grown using high pressure, high temperature (HPHT) synthesis or chemical vapour deposition (CVD). The primary technique used for investigation is cathodoluminescence (including imaging and decay-time measurements) in addition to other forms of optical spectroscopy. This thesis is timely in that the crystallinity and purity of synthetic diamond has increased ten fold over the last few years. The diamond exciton emission, which is easily quenched by the presence of defects, is studied in high quality samples in detail. In addition the ability now exists to engineer the isotopic content of synthetic diamond to a high degree of accuracy. The experimental chapters are divided as follows: Chapter 2: High resolution, low temperature spectra reveal a splitting of the free-exciton phonon recombination emission peaks and the bound-exciton zero phonon line. Included are measurements of the variation in intensity and decay-time as a function of temperature. Chapter 3: The shift in energy of the phonon-assisted free-exciton phonon replicas with isotopic content has been measured. The shift is in agreement with the results of interatomic force model for phonon scattering due to isotope disorder. Chapter 4: A study of the shift in energy with isotopic content of the diamond of the GR1 band due to the neutral vacancy has allowed a verification of the theoretical predictions due to the Jahn Teller effect. Chapter 5: The spatial distribution of the free-exciton luminescence is studied in HPHT synthetic and CVD diamond. A variation in intensity with distance from the surface is interpreted as a significant non-radiative loss of excitons to the surface. Chapter 6: The decay-times of all known self-interstitial related centres have been measured in order to calculate the concentration of these centres present in electron irradiated diamond. (author)

12 CFR Appendix C to Part 229 - Model Availability Policy Disclosures, Clauses, and Notices; Model Substitute Check Policy...

Science.gov (United States)

2010-01-01

...-case holds) C-19Notice at automated teller machines C-20Notice at automated teller machines (delayed... would like a list of the routing numbers for these institutions. C-9—Automated Teller Machine Deposits (Extended Hold) Deposits at Automated Teller Machines Funds from any deposits (cash or checks) made at...

Crystalline behaviour and electrical properties of manganese perovskites substituted on A or B sites: ErMnO₃ modified by Ca and EuMnO₃ modified by Co

Directory of Open Access Journals (Sweden)

Tartaj, J.

2010-06-01

Full Text Available The structural and electrical features of the manganites solid solutions (Er,CaMnO₃ and Eu(Co,MnO₃, have been studied by X-ray diffraction and conductivity measurements. Powders were prepared by solid-state reaction between the component oxides and Calcium carbonate. Incorporation of Co²⁺ on the lattice in the B sites or the Ca²⁺ on the A sites leads to changes in the parameters and symmetry of the perovskite compound EuMnO₃ and hexagonal ErMnO₃ respectively. The phase transition depends on the amount of substituted Jahn-Teller Mn³⁺ cations. Solid solutions based on Eu(Mn,CoO₃ perovskite compound change from O’-type to O-type orthorhombic perovskite symmetry when the Mn³⁺ cation amount decreases, because of the progressive substitution by Co. This transition occurs for an amount of Co²⁺ as low as ~10 at% Co²⁺ cation. The (Er,CaMnO₃ based solid solutions showed a different behaviour. From x=0.25 there is a change in the symmetry of the solid solution from hexagonal to orthorhombic, O’-type perovskite. Steric influence seems to play a secondary role on the lattice distortion of manganites. Sintered samples of the perovskite solid solutions were measured for establishing their electrical properties. All the samples showed semiconducting behaviour.

Las características estructurales y eléctricas de las soluciones sólidas de manganitas (Er,CaMnO₃ y Eu(Co,MnO₃, han sido estudiadas por difracción de rayos X y medidas de la conductividad en continua. Los polvos fueron preparados por reacción en estado sólido entre los óxidos componentes y carbonato de calcio. La incorporación de Co²⁺ en la red en los sitios B o de Ca²⁺ en los sitios A conduce a cambios en los parámetros y la simetría de EuMnO₃ perovskita y ErMnO₃ hexagonal, respectivamente

Gamow-Teller strength distributions in 76Ge, 76,82Se, and 90,92Zr by the deformed proton-neutron QRPA

Science.gov (United States)

Ha, Eunja; Cheoun, Myung-Ki

2015-02-01

The deformed proton-neutron quasiparticle random phase approximation (QRPA) has been developed and applied to evaluate Gamow-Teller (GT) transition strength distributions, including high-lying excited states. The data of high-lying excited states are recently available beyond one or two nucleon threshold by charge exchange reactions using hundreds of MeV projectiles. Our calculations started with single-particle states calculated using a deformed, axially symmetric Woods-Saxon potential. The neutron-neutron and proton-proton pairing correlations are explicitly taken into account at the deformed Bardeen-Cooper-Schriffer theory. Additionally, the ground state correlations and two-particle and two-hole mixing states were included in the deformed QRPA. In this work, we used a realistic two-body interaction, given by the Brueckner G-matrix based on the CD Bonn potential to reduce the ambiguity on the nucleon-nucleon interactions inside nuclei. We applied our formalism to the GT transition strengths for 76Ge, 76,82Se, and 90,92Zr, and compared the results with the available experimental data. The GT strength distributions were sensitive to the deformation parameter as well as its sign, i.e., oblate or prolate. The Ikeda sum rule, which is usually thought to be satisfied under the one-body current approximation, regardless of nucleon models, was used to test our numerical calculations and shown to be satisfied without introducing the quenching factor, if high-lying GT excited states were properly taken into account. Most of the GT strength distributions of the nuclei considered in this work have the high-lying GT excited states beyond one-nucleon threshold, which are shown to be consistent with the available experimental data.

12 CFR 740.4 - Requirements for the official sign.

Science.gov (United States)

2010-01-01

... terms “branch,” “station,” “teller station,” and “window” do not include automated teller machines or... teller station or window where any nonfederally insured credit union also receives account funds. As exceptions to this prohibition: (1) A teller in a branch of a federally insured credit union may accept...

Effectively selling astronomy to the public -- fusing lessons learned from education, entertainment, advertising and public relations

Science.gov (United States)

Pallone, Arthur; Day, Jacque

2010-03-01

A great celestial story is only as effective as the teller of the tale. With passion and knowledge at the helm, we must search for ways to pass on enthusiasm to others while conveying sound science. Based on our experiences, we present an integrated approach -- one that borrows elements from education, entertainment, advertising, and public relations -- to choose an event, hook and keep the public's attention while making them want more, and provide some tips for increasing media presence.

Gamow-Teller response in the configuration space of a density-functional-theory-rooted no-core configuration-interaction model

Science.gov (United States)

Konieczka, M.; Kortelainen, M.; Satuła, W.

2018-03-01

Background: The atomic nucleus is a unique laboratory in which to study fundamental aspects of the electroweak interaction. This includes a question concerning in medium renormalization of the axial-vector current, which still lacks satisfactory explanation. Study of spin-isospin or Gamow-Teller (GT) response may provide valuable information on both the quenching of the axial-vector coupling constant as well as on nuclear structure and nuclear astrophysics. Purpose: We have performed a seminal calculation of the GT response by using the no-core configuration-interaction approach rooted in multireference density functional theory (DFT-NCCI). The model treats properly isospin and rotational symmetries and can be applied to calculate both the nuclear spectra and transition rates in atomic nuclei, irrespectively of their mass and particle-number parity. Methods: The DFT-NCCI calculation proceeds as follows: First, one builds a configuration space by computing relevant, for a given physical problem, (multi)particle-(multi)hole Slater determinants. Next, one applies the isospin and angular-momentum projections and performs the isospin and K mixing in order to construct a model space composed of linearly dependent states of good angular momentum. Eventually, one mixes the projected states by solving the Hill-Wheeler-Griffin equation. Results: The method is applied to compute the GT strength distribution in selected N ≈Z nuclei including the p -shell 8Li and 8Be nuclei and the s d -shell well-deformed nucleus 24Mg. In order to demonstrate a flexibility of the approach we present also a calculation of the superallowed GT β decay in doubly-magic spherical 100Sn and the low-spin spectrum in 100In. Conclusions: It is demonstrated that the DFT-NCCI model is capable of capturing the GT response satisfactorily well by using a relatively small configuration space, exhausting simultaneously the GT sum rule. The model, due to its flexibility and broad range of applicability, may

Diabatic models with transferrable parameters for generalized chemical reactions

International Nuclear Information System (INIS)

Reimers, Jeffrey R; McKemmish, Laura K; McKenzie, Ross H; Hush, Noel S

2017-01-01

Diabatic models applied to adiabatic electron-transfer theory yield many equations involving just a few parameters that connect ground-state geometries and vibration frequencies to excited-state transition energies and vibration frequencies to the rate constants for electron-transfer reactions, utilizing properties of the conical-intersection seam linking the ground and excited states through the Pseudo Jahn-Teller effect. We review how such simplicity in basic understanding can also be obtained for general chemical reactions. The key feature that must be recognized is that electron-transfer (or hole transfer) processes typically involve one electron (hole) moving between two orbitals, whereas general reactions typically involve two electrons or even four electrons for processes in aromatic molecules. Each additional moving electron leads to new high-energy but interrelated conical-intersection seams that distort the shape of the critical lowest-energy seam. Recognizing this feature shows how conical-intersection descriptors can be transferred between systems, and how general chemical reactions can be compared using the same set of simple parameters. Mathematical relationships are presented depicting how different conical-intersection seams relate to each other, showing that complex problems can be reduced into an effective interaction between the ground-state and a critical excited state to provide the first semi-quantitative implementation of Shaik’s “twin state” concept. Applications are made (i) demonstrating why the chemistry of the first-row elements is qualitatively so different to that of the second and later rows, (ii) deducing the bond-length alternation in hypothetical cyclohexatriene from the observed UV spectroscopy of benzene, (iii) demonstrating that commonly used procedures for modelling surface hopping based on inclusion of only the first-derivative correction to the Born-Oppenheimer approximation are valid in no region of the chemical

Neutron diffraction study of the inverse spinels Co2TiO4 and Co2SnO4

Science.gov (United States)

Thota, S.; Reehuis, M.; Maljuk, A.; Hoser, A.; Hoffmann, J.-U.; Weise, B.; Waske, A.; Krautz, M.; Joshi, D. C.; Nayak, S.; Ghosh, S.; Suresh, P.; Dasari, K.; Wurmehl, S.; Prokhnenko, O.; Büchner, B.

2017-10-01

We report a detailed single-crystal and powder neutron diffraction study of Co2TiO4 and Co2SnO4 between the temperature 1.6 and 80 K to probe the spin structure in the ground state. For both compounds the strongest magnetic intensity was observed for the (111)M reflection due to ferrimagnetic ordering, which sets in below TN=48.6 and 41 K for Co2TiO4 and Co2SnO4 , respectively. An additional low intensity magnetic reflection (200)M was noticed in Co2TiO4 due to the presence of an additional weak antiferromagnetic component. Interestingly, from both the powder and single-crystal neutron data of Co2TiO4 , we noticed a significant broadening of the magnetic (111)M reflection, which possibly results from the disordered character of the Ti and Co atoms on the B site. Practically, the same peak broadening was found for the neutron powder data of Co2SnO4 . On the other hand, from our single-crystal neutron diffraction data of Co2TiO4 , we found a spontaneous increase of particular nuclear Bragg reflections below the magnetic ordering temperature. Our data analysis showed that this unusual effect can be ascribed to the presence of anisotropic extinction, which is associated to a change of the mosaicity of the crystal. In this case, it can be expected that competing Jahn-Teller effects acting along different crystallographic axes can induce anisotropic local strain. In fact, for both ions Ti3 + and Co3 +, the 2 tg levels split into a lower dx y level yielding a higher twofold degenerate dx z/dy z level. As a consequence, one can expect a tetragonal distortion in Co2TiO4 with c /a <1 , which we could not significantly detect in the present work.

Synthesis and structural study of the transition metal doped rhodium perovskites

International Nuclear Information System (INIS)

Ting, J.; Kennedy, B.; Zhang, Z.

2009-01-01

Full text: One of the most common structures encountered in solid state chemistry is the perovskite structure. With a general formula of AB0 3, the A-type cations are 12-coordinate within a cubo-octahedral environment, while the B-type cations are 6-coordinate, forming an interconnecting three-dimensional octahedral network with neighbouring oxygen anions. While the ideal perovskite structure is cubic in Pm 3 m, many perovskites exhibit symmetry lowering tilting of the corner-sharing B0 6o ctahedral units as a result of A- and B-type cation size disparity. This is also evident in substituted perovskites, where two cations occupy the smaller octahedral site, AB 1- xB' x0 3' Electronic effects can also lower the symmetry. The two most commonly observed effects are the polarisation of the B-cation with a d 0 electronic configuration and Jahn-Teller distortion where the B-cation has a d 4 or d 9 electronic configuration, such as Mn 3+ or Cu 2+ respectively. Manganese containing perovskites have been shown in some compounds to exhibit long-range orbital ordering, giving rise to interesting properties. Heavier transition metals such as ruthenium and iridium have been previously incorporated into these perovskites as an avenue to regulate the properties of these materials. Two orthorhombic rhodium perovskite structures are presented, LaMn 0 . 5 Rh 0 . 5 O 3 and LaCu 05 Rh 0 . 5 O 3 ' A combination of synchrotron x-ray and neutron powder diffraction has been used to elucidate their structures, and have shown both B- and B'-type cations to be disordered across the same crystallographic site for both compounds. x-ray absorption spectroscopy measurements have been used to provide an insight into the valence states of the cations, which show a valency of +3.5 for rhodium due to an extensive charge delocalisation between copper and rhodium.

Electronic properties of rocksalt copper monoxide: a proxy structure for high temperature superconductivity

International Nuclear Information System (INIS)

Grant, Paul M

2008-01-01

Cubic rocksalt copper monoxide, in contrast to its lighter transition metal neighbours, does not exist in nature nor has it yet been successfully synthesized. Nonetheless, its numerical study as a structurally much simpler proxy for the layered cuprate perovskites may prove useful in probing the source of high temperature superconductivity in the latter family of compounds. Here we report such a study employing density functional theory (DFT) abetted by the local density approximation including cation on-site Hubbard interactions (LDA+U). Rather surprisingly, we find that unlike oxides of the light transition metals, cubic CuO remains metallic for all physically reasonable values of U and does not result in a Mott- Hubbard induced charge transfer insulator as might be expected, and, in fact, displays a Fermi surface with clearly nesting tendencies. Preliminary calculations of the net dimensionless electron-phonon coupling constant, λ, yield values in the range 0.6 - 0.7 similar to those found for the superconducting fullerenes and magnesium diboride. On the other hand, we do find as we gradually introduce a tetragonal distortion away from pure cubic symmetry that a charge- transfer insulator emerges for values of U ∼ 5 eV and c/a ∼ 1.3 in agreement with recent experimental data on forced-epitaxial growth of 2-4 ML thick films of tetragonal rocksalt CuO. We preliminarily conclude from these computational studies that high temperature superconductivity in the copper oxide compounds is at least initially mediated by Jahn-Teller driven electron-phonon coupling as originally suggested by Bednorz and Mueller.

Crystal and magnetic study of the disordered perovskites Ca(Mn0.5Sb0.5)O3 and Ca(Fe0.5Sb0.5)O3

International Nuclear Information System (INIS)

Retuerto, M.; Martinez-Lope, M.J.; Garcia-Hernandez, M.; Munoz, A.; Fernandez-Diaz, M.T.; Alonso, J.A.

2010-01-01

We have investigated the double perovskites Ca 2 MSbO 6 (M = Mn, Fe) that have been prepared by solid-state reaction (M = Fe) and wet chemistry procedures (M = Mn). The crystal and magnetic structures have been studied from X-ray (XRD) and neutron powder diffraction (NPD) data. Rietveld refinements show that the crystal structures are orthorhombic (space group Pbnm) with complete disorder of M and Sb cations, so the formula should be rewritten as Ca(M 0.5 Sb 0.5 )O 3 . Due to this disorder no evidences of Jahn-Teller distortion can be observed in the MnO 6 octahedra of Ca(Mn 0.5 Sb 0.5 )O 3 , in contrast with the ordered double perovskite Sr 2 MnSbO 6 . Ca(Fe 0.5 Sb 0.5 )O 3 behaves as an antiferromagnet with an ordered magnetic moment for Fe 3+ of 1.53(4)μ B and a propagation vector k = 0, as investigated by low-temperature NPD. The antiferromagnetic ordering is a result of the high degree of Fe/Sb anti-site disorder of the sample, which originates the spontaneous formation of Fe-rich islands, characterized by the presence of strong Fe-O-Fe antiferromagnetic couplings with enough long-range coherence to produce a magnetic contribution perceptible by NPD. By contrast, the magnetic structure of Ca(Mn 0.5 Sb 0.5 )O 3 cannot be observed by low-temperature NPD because the magnitude of the ordered magnetic moments is below the detection threshold for neutrons.

Neutron diffraction and ESR studies of pseudocubic Nd0.75Ba0.25MnO3 and its unusual critical behavior above TC

International Nuclear Information System (INIS)

Lazuta, A.V.; Ryzhov, V.A.; Smirnov, O.P.; Kiselev, I.A.; Chernenkov, Yu.P.; Borisov, S.A.; Troaynchuk, I.O.; Khalyavin, D.D.

2006-01-01

Results of structural neutron diffraction study and electron spin resonance (ESR) measurements are presented for insulating Nd 1-x Ba x MnO 3 (x=0.25) with the Curie temperature T C ∼129K. Its pseudocubic structure reveals the definite distortions to a lower symmetry. Detailed analysis of the data is performed in the frame of Pbnm space group in a temperature range 4.2-300K. The compound is found to exhibit the Jahn-Teller (JT) transition at T JT ∼250K. Character of the coherent JT distortions and their temperature evolution differ from those of the x=0.23 manganite. The ESR results correspond to behavior of a 3D isotropic ferromagnet above T*∼143K (τ*∼0.12= C )/T C ). It is shown that an anisotropic exchange coupling of the Mn and Nd magnetic moments may give a substantial contribution in ESR linewidth masking its critical enhancement. The different temperature treatments (slow/fast cooling/heating with/without external magnetic field) of the sample reveal a temperature hysteresis of the ESR spectra below T* indicating an anomalous response in the paramagnetic region. The study of the magnetic phase transition in the x=0.23 and 0.25 NdBa manganites suggests a change in its character from the second to first order at T*. The conventional free energy including the magnetization and magnetic field failed to describe this first-order transition. The unconventional critical behavior is attributed to an orbital liquid metallic phase that begins to coexist with the initial orbital-ordered phases below T*

Spectral intensities in cubic systems. II. The MoCl{sub 6} {sup 3-} system in cubic elpasolite crystals

Energy Technology Data Exchange (ETDEWEB)

Acevedo, R. [Department of Basic Chemistry, Faculty of Physical and Mathematical Sciences, University of Chile. Tupper 2069. Casilla 2777, Santiago, Chile (Chile); Meruane, T. [Department of Chemistry. Universidad Metropolitana de Ciencias de la Educacion. Av. J.P. Alessandri 774, Casilla 147, C. Santiago, Chile (Chile); Poblete, V. [Department of Nuclear Materials, Lo Aguirre, Comision Chilena de Energia Nuclear. Amunategui 95, Casilla 188-D, Santiago, Chile (Chile)

1998-12-01

The visible and near infrared luminescence spectra of MoCl{sub 6} {sup 3-} in Cs{sub 2}NaMCl{sub 6} (M=Sc, Y, In) and MoBr{sub 6} {sup 3-} in Cs{sub 2}NaYBr{sub 6} have been reported between 15000 cm {sup -1} and 3000 cm {sup -1} at liquid helium temperatures. It has been observed that each electronic transition shows an extensive and rich vibronic structure, which can be analysed to yield the vibrational frequencies of the MoX{sub 6} {sup 3-} ion in each electronic state. A through analysis of the spectra for these systems, show that the vibrational frequencies associated with each of the electronic transition is almost identical. This is an evidence of a weak or rather negligible Jahn-Teller distortions. The spectra though are strongly influenced by resonant interactions among the MoX{sub 6} {sup 3-} ion and the internal and lattice modes of the host lattices and there is also a noticeable variation of the relative vibronic distributions of parity forbidden transitions assisted by the odd parity normal modes of vibrations. This present work deals with the most likely intensity mechanisms and a strategy is put forward to carry out explicit calculations for both, the electronic and vibrational factors of transitions of the kind {Gamma}{sub 1}{r_reversible} {Gamma}{sub 2} + v{sub k} for k=3, 4, and 6. Extension of this work to include the ion-phonon interaction is currently in progress in our laboratory. (Author)

Local atomic structure of α-Pu

International Nuclear Information System (INIS)

Espinosa, F. J.; Villella, P.; Lashley, J. C.; Conradson, S. D.; Cox, L. E.; Martinez, R.; Martinez, B.; Morales, L.; Terry, J.; Pereyra, R. A.

2001-01-01

The local atomic structure of α-Pu was investigated using x-ray absorption fine structure (XAFS) spectroscopy. XAFS spectra were obtained for a zone-refined α-Pu and the results were compared to 32-year-old and Ce-doped (0.34 at.%) samples. X-ray diffraction (XRD) patterns were also measured for the zone-refined and 32-year-old materials. The extent of the Bragg peaks showed that amorphization of the 32-year-old sample had not occurred despite the prolonged exposure to self-radiation. Analogous to metastable δ-Pu alloys, the local atomic structure around Pu for the zone-refined material shows the possible presence of noncrystallographic Pu-Pu distances. Conversely, the Ce and the 32-year-old sample show no evidence for such noncrystallographic distances. Disorder in the Pu local environment was found to be impurity dependent. The Ce-doped sample presented a larger Pu-Pu nearest neighbor disorder than the aged sample, although the total amount of Am, U, and He impurities was actually higher in the aged sample. The local environment around U and Ce impurities is consistent with these elements being in substitutional lattice sites. In addition, U and Ce do not introduce significant lattice distortion to their nearest neighbors. This is consistent with disorder being more related to the perturbation of the coupling between the electronic and crystal structure, or the Peierls--Jahn-Teller distortion that generates the monoclinic α-Pu structure, and less to strain fields produced in the vicinity of the impurities

High-resolution study of the Gamow-Teller strength distribution in the light nuclei {sup 9}B and {sup 13}N using the ({sup 3}He,t) charge-exchange reaction at 420 MeV beam energy

Energy Technology Data Exchange (ETDEWEB)

Scholl, Clemens

2010-07-07

Excited states in the light nuclei {sup 9}B and {sup 13}C were studied using the ({sup 3}He,t) charge-exchange reaction on {sup 9}Be and {sup 13}C targets. The measurements were performed at the research center for nuclear physics (RCNP) in Osaka, Japan, using the magnetic spectrometer Grand Raiden and the dispersive WS course. The {sup 3}He beam with an energy of 420 MeV was accelerated by the RCNP Ring Cyclotron. The Grand Raiden spectrometer and the WS course allow to study the ({sup 3}He,t) charge-exchange reaction with an energy resolution of around 30 keV, which is one order of magnitude better than measurements with the (p,n) charge-exchange reaction. The high resolution allows to better separate individual states and to determine weak excitation strengths because of low background in the spectra. A total of 19 states in {sup 13}N were studied, and a total of 20 states were observed in {sup 9}B. Of these, 9 states in {sup 13}C and 10 states in {sup 9}B were identified as being excited by a Gamow-Teller transition. Charge-exchange reactions are related to beta-decay, and at zero momentum transfer a simple proportionality exists between the cross-section of the charge-exchange experiment and the Fermi (F) or Gamow-Teller (GT) beta-decay strength. While the Fermi strength B(F) is concentrated in the transition to the isobaric analog state, the Gamow-Teller strength B(GT) is scattered among the excited states. The main aim of the present study is to determine the B(GT) strengths in the nuclei {sup 9}B and {sup 13}N. The only charge-exchange study of {sup 9}B was made 30 years ago with the (p,n) reaction and a resolution of around 300-400 keV. Many states, especially at high excitation energy, could not be resolved by that study. The present work was able to separate many weakly excited states with small decay width at high excitation energies (12-19 MeV) in {sup 9}B and determine the B(GT) strength distribution by using recent high-precision beta-decay data. The

The benefits and risks of telling and listening to stories of difficulty over time: experimentally testing the expressive writing paradigm in the context of interpersonal communication between friends.

Science.gov (United States)

Koenig Kellas, Jody; Horstman, Haley Kranstuber; Willer, Erin K; Carr, Kristen

2015-01-01

The overarching goal of the current study was to determine the impact of talking interpersonally over time on emerging adults' individual and relational health. Using an expressive writing study design (see Frattaroli, 2006), we assessed the degree to which psychological health improved over time for college students who told and listened to stories about friends' current difficulties in comparison with tellers in control conditions. We also investigated the effects on tellers' and listeners' perceptions of each other's communication competence, communicated perspective-taking, and the degree to which each threatened the other's face during the interaction over time to better understand the interpersonal communication complexities associated with talking about difficulty over time. After completing prestudy questionnaires, 49 friend pairs engaged in three interpersonal interactions over the course of 1 week wherein one talked about and one listened to a story of difficulty (treatment) or daily events (control). All participants completed a poststudy questionnaire 3 weeks later. Tellers' negative affect decreased over time for participants exposed to the treatment group, although life satisfaction increased and positive affect decreased across time for participants regardless of condition. Perceptions of friends' communication abilities decreased significantly over time for tellers. The current study contributes to the literature on expressive writing and social support by shedding light on the interpersonal implications of talking about difficulty, the often-overlooked effects of disclosure on listeners, and the health effects of talking about problems on college students' health.

Effect of electrochemical oxidation of a viscose rayon based ...

African Journals Online (AJOL)

A viscose rayon based activated carbon cloth (ACC) was electrochemically oxidised to enhance its cation sorption capacity for comparison with as-received ACC. ACCs were characterised by sodium capacity measurement, pH titration, zeta potential measurement, elemental analysis, Brunauer-Emmet- Teller surface area ...

Synthesis and Characterization of Nanoporous Carbon Materials; The Effect of Surfactant Concentrations and Salts

Directory of Open Access Journals (Sweden)

Shokoofeh Geranmayeh

2011-01-01

Full Text Available Nanoporous carbon framework was synthesized using phenol and formaldehyde as carbon precursors and triblock copolymer (pluronic F127 as soft template via evaporation induced self-assembly. Hexagonal mesoporous carbon with specific surface area of 350 m2/g through optimizing the situation was obtained. The effects of different surfactant/phenol molar ratio and presence of salts on specific surface area, pore size and pore volume for all the prepared samples were studied by means of the Brunauer-Emmett-Teller (BET formalism, powder X-ray diffraction technique and FT-IR spectroscopy.

Limitations of a Short Demographic Questionnaire for Bedside Estimation of Patients’ Global Cognitive Functioning in Epilepsy Patients

Directory of Open Access Journals (Sweden)

Iris Gorny

2018-03-01

Full Text Available ObjectivesThe German socio-demographic estimation scale was developed by Jahn et al. (1 to quickly predict premorbid global cognitive functioning in patients. So far, it has been validated in healthy adults and has shown a good correlation with the full and verbal IQ of the Wechsler Adult Intelligence Scale (WAIS in this group. However, there are no data regarding its use as a bedside test in epilepsy patients.MethodsForty native German speaking adult patients with refractory epilepsy were included. They completed a neuropsychological assessment, including a nine scale short form of the German version of the WAIS-III and the German socio-demographic estimation scale by Jahn et al. (1 during their presurgical diagnostic stay in our center. We calculated means, correlations, and the rate of concordance (range ±5 and ±7.5 IQ score points between these two measures for the whole group, and a subsample of 19 patients with a global cognitive functioning level within 1 SD of the mean (IQ score range 85–115 and who had completed their formal education before epilepsy onset.ResultsThe German demographic estimation scale by Jahn et al. (1 showed a significant mean overestimation of the global cognitive functioning level of eight points in the epilepsy patient sample compared with the short form WAIS-III score. The accuracy within a range of ±5 or ±7.5 IQ score points for each patient was similar to that of the healthy controls reported by Jahn et al. (1 in our subsample, but not in our whole sample.ConclusionOur results show that the socio-demographic scale by Jahn et al. (1 is not sufficiently reliable as an estimation tool of global cognitive functioning in epilepsy patients. It can be used to estimate global cognitive functioning in a subset of patients with a normal global cognitive functioning level who have completed their formal education before epilepsy onset, but it does not reliably predict global cognitive functioning in epilepsy patients

Multi-State Vibronic Interactions in Fluorinated Benzene Radical Cations.

Science.gov (United States)

Faraji, S.; Köppel, H.

2009-06-01

Conical intersections of potential energy surfaces have emerged as paradigms for signalling strong nonadiabatic coupling effects. An important class of systems where some of these effects have been analyzed in the literature, are the benzene and benzenoid cations, where the electronic structure, spectroscopy, and dynamics have received great attention in the literature. In the present work a brief overview is given over our theoretical treatments of multi-mode and multi-state vibronic interactions in the benzene radical cation and some of its fluorinated derivatives. The fluorobenzene derivatives are of systematic interest for at least two different reasons. (1) The reduction of symmetry by incomplete fluorination leads to a disappearance of the Jahn-Teller effect present in the parent cation. (2) A specific, more chemical effect of fluorination consists in the energetic increase of the lowest σ-type electronic states of the radical cations. The multi-mode multi-state vibronic interactions between the five lowest electronic states of the fluorobenzene radical cations are investigated theoretically, based on ab initio electronic structure data, and employing the well-established linear vibronic coupling model, augmented by quadratic coupling terms for the totally symmetric vibrational modes. Low-energy conical intersections, and strong vibronic couplings are found to prevail within the set of tilde{X}-tilde{A} and tilde{B}-tilde{C}-tilde{D} cationic states, while the interactions between these two sets of states are found to be weaker and depend on the particular isomer. This is attributed to the different location of the minima of the various conical intersections occurring in these systems. Wave-packet dynamical simulations for these coupled potential energy surfaces, utilizing the powerful multi-configuration time-dependent Hartree method are performed. Ultrafast internal conversion processes and the analysis of the MATI and photo-electron spectra shed new light

Geochemical reanalysis of historical U.S. Geological Survey sediment samples from the Kougarok area, Bendeleben and Teller quadrangles, Seward Peninsula, Alaska

Science.gov (United States)

Werdon, Melanie B.; Granitto, Matthew; Azain, Jaime S.

2015-01-01

The State of Alaska’s Strategic and Critical Minerals (SCM) Assessment project, a State-funded Capital Improvement Project (CIP), is designed to evaluate Alaska’s statewide potential for SCM resources. The SCM Assessment is being implemented by the Alaska Division of Geological & Geophysical Surveys (DGGS), and involves obtaining new airborne-geophysical, geological, and geochemical data. As part of the SCM Assessment, thousands of historical geochemical samples from DGGS, U.S. Geological Survey (USGS), and U.S. Bureau of Mines archives are being reanalyzed by DGGS using modern, quantitative, geochemical-analytical methods. The objective is to update the statewide geochemical database to more clearly identify areas in Alaska with SCM potential. The USGS is also undertaking SCM-related geologic studies in Alaska through the federally funded Alaska Critical Minerals cooperative project. DGGS and USGS share the goal of evaluating Alaska’s strategic and critical minerals potential and together created a Letter of Agreement (signed December 2012) and a supplementary Technical Assistance Agreement (#14CMTAA143458) to facilitate the two agencies’ cooperative work. Under these agreements, DGGS contracted the USGS in Denver to reanalyze historical USGS sediment samples from Alaska. For this report, DGGS funded reanalysis of 302 historical USGS sediment samples from the statewide Alaska Geochemical Database Version 2.0 (AGDB2; Granitto and others, 2013). Samples were chosen from the Kougarok River drainage as well as smaller adjacent drainages in the Bendeleben and Teller quadrangles, Seward Peninsula, Alaska (fig. 1). The USGS was responsible for sample retrieval from the National Geochemical Sample Archive (NGSA) in Denver, Colorado through the final quality assurance/quality control (QA/QC) of the geochemical analyses obtained through the USGS contract lab. The new geochemical data are published in this report as a coauthored DGGS report, and will be incorporated

Penerapan Metode SERVQUAL pada Bank X

Directory of Open Access Journals (Sweden)

Nilda Tri Putri

2016-04-01

Full Text Available The banking sector had become industrial which keeps growing. Competition requires each bank competing to attract many customers in many ways both in terms of products, technologies, and services. Marketing Research Indonesia (MRI performs measurements of the services quality of the banking. X Bank occupies the fifth position in terms of service quality. X Bank need to do repair service constantly to improve customer loyalty. The method used was servqual consisting of five dimensions. Based on gap between perception and expectations known priority on X Bank. Repair service with the main priority is customer service quickly. A long customer service cause long queue at customer service and teller. Typically, most clients come at the beginning of the month. However, a large number of customer that are not anticipated by the number of teller and customer service. Customer satisfaction level of this attribute only 68,09%. That means the banks need to make improvements such as by adding the number of teller and customer service at a particular time and organizing shift work teller and customer service more effectively. Keywords : service quality, gap, Marketing Research Indonesia.

Nucleus as a chiral filter: the role of the Δ(1232)

International Nuclear Information System (INIS)

Rho, Mannque.

1982-03-01

We describe how two different modes of chiral symmetry can be seen in nuclei. In particular, it is shown that the nuclear axial charge or more precisely the O + O - , ΔT=1 transition at zero momentum transfer probe the nuclear configuration wherein the axial charge gsub(A) is effectively enhanced in nuclear medium due to soft pions, symptomatic of the Goldstone realization of chiral symmetry in the medium while the Gamow-Teller resonances probe the configuration wherein soft pions are no longer operative, suggesting an approach toward the Wigner realization of chiral symmetry. Using the celebrated Adler-Weisberger relation, it is argued that the observed approximately 50% quenching of the Gamow-Teller strength reflects the possibility that the Gamow-Teller operator sees the quarks inside the bag, blind to the Goldstone vacuum outside. Some implications on chiral phase transitions are also discussed

76 FR 16861 - Availability of Funds and Collection of Checks

Science.gov (United States)

2011-03-25

...)--Automated Teller Machine or ATM The Board proposes to clarify that an automated teller machine (ATM... ``other account transactions'' that may be performed at an automated teller machine (ATM); specifically... systems capable of automated processing of incoming electronic data files (e.g., X9.100-187 files...

International conference on defects in insulating crystals

International Nuclear Information System (INIS)

1977-01-01

Short summaries of conference papers are presented. Some of the conference topics included transport properties, defect levels, superionic conductors, radiation effects, John-Teller effect, electron-lattice interactions, and relaxed excited states

Usability of a virtual reality environment simulating an automated teller machine for assessing and training persons with acquired brain injury

Directory of Open Access Journals (Sweden)

Li Teresa HY

2010-04-01

Full Text Available Abstract Objective This study aimed to examine the usability of a newly designed virtual reality (VR environment simulating the operation of an automated teller machine (ATM for assessment and training. Design Part I involved evaluation of the sensitivity and specificity of a non-immersive VR program simulating an ATM (VR-ATM. Part II consisted of a clinical trial providing baseline and post-intervention outcome assessments. Setting A rehabilitation hospital and university-based teaching facilities were used as the setting. Participants A total of 24 persons in the community with acquired brain injury (ABI - 14 in Part I and 10 in Part II - made up the participants in the study. Interventions In Part I, participants were randomized to receive instruction in either an "early" or a "late" VR-ATM program and were assessed using both the VR program and a real ATM. In Part II, participants were assigned in matched pairs to either VR training or computer-assisted instruction (CAI teaching programs for six 1-hour sessions over a three-week period. Outcome Measures Two behavioral checklists based on activity analysis of cash withdrawals and money transfers using a real ATM were used to measure average reaction time, percentage of incorrect responses, level of cues required, and time spent as generated by the VR system; also used was the Neurobehavioral Cognitive Status Examination. Results The sensitivity of the VR-ATM was 100% for cash withdrawals and 83.3% for money transfers, and the specificity was 83% and 75%, respectively. For cash withdrawals, the average reaction time of the VR group was significantly shorter than that of the CAI group (p = 0.021. We found no significant differences in average reaction time or accuracy between groups for money transfers, although we did note positive improvement for the VR-ATM group. Conclusion We found the VR-ATM to be usable as a valid assessment and training tool for relearning the use of ATMs prior to real

Usability of a virtual reality environment simulating an automated teller machine for assessing and training persons with acquired brain injury.

Science.gov (United States)

Fong, Kenneth N K; Chow, Kathy Y Y; Chan, Bianca C H; Lam, Kino C K; Lee, Jeff C K; Li, Teresa H Y; Yan, Elaine W H; Wong, Asta T Y

2010-04-30

This study aimed to examine the usability of a newly designed virtual reality (VR) environment simulating the operation of an automated teller machine (ATM) for assessment and training. Part I involved evaluation of the sensitivity and specificity of a non-immersive VR program simulating an ATM (VR-ATM). Part II consisted of a clinical trial providing baseline and post-intervention outcome assessments. A rehabilitation hospital and university-based teaching facilities were used as the setting. A total of 24 persons in the community with acquired brain injury (ABI)--14 in Part I and 10 in Part II--made up the participants in the study. In Part I, participants were randomized to receive instruction in either an "early" or a "late" VR-ATM program and were assessed using both the VR program and a real ATM. In Part II, participants were assigned in matched pairs to either VR training or computer-assisted instruction (CAI) teaching programs for six 1-hour sessions over a three-week period. Two behavioral checklists based on activity analysis of cash withdrawals and money transfers using a real ATM were used to measure average reaction time, percentage of incorrect responses, level of cues required, and time spent as generated by the VR system; also used was the Neurobehavioral Cognitive Status Examination. The sensitivity of the VR-ATM was 100% for cash withdrawals and 83.3% for money transfers, and the specificity was 83% and 75%, respectively. For cash withdrawals, the average reaction time of the VR group was significantly shorter than that of the CAI group (p = 0.021). We found no significant differences in average reaction time or accuracy between groups for money transfers, although we did note positive improvement for the VR-ATM group. We found the VR-ATM to be usable as a valid assessment and training tool for relearning the use of ATMs prior to real-life practice in persons with ABI.

International conference on defects in insulating crystals

Energy Technology Data Exchange (ETDEWEB)

1977-01-01

Short summaries of conference papers are presented. Some of the conference topics included transport properties, defect levels, superionic conductors, radiation effects, John-Teller effect, electron-lattice interactions, and relaxed excited states. (SDF)

Saksa teadlane koostas Hitleri perekonna genealoogia / Urmas Kiil

Index Scriptorium Estoniae

Kiil, Urmas

2007-01-01

Saksa genealoog Ralf G. Jahn koostas detailse kroonika Hitleri perekonnast ning avaldas selle raamatuna "Hitlers Familiengeheimniss - Geschichte und Genealogie der Vorfahren und Verwandten von Adolf Hitler"

Letting down Rapunzel: Feminism's Effects on Fairy Tales

Science.gov (United States)

Smith, Angela

2015-01-01

The importance of stories written for young readers is undisputed, and in particular the central place of the fairy story in popular culture is clearly recognized. Whilst most of these stories are centuries old, they have been adapted by the cultures of the tellers to be more compatible with the ideological views of the audience. This article will…

Synthesis, structure, and physicochemical investigations of the new α Cu 0.50TiO(PO 4) oxyphosphate

Science.gov (United States)

Benmokhtar, S.; Belmal, H.; El Jazouli, A.; Chaminade, J. P.; Gravereau, P.; Pechev, S.; Grenier, J. C.; Villeneuve, G.; de Waal, D.

2007-02-01

The room-temperature crystal structure of a new Cu(II) oxyphosphate— α Cu 0.50IITiO(PO 4)—was determined from X-ray single crystals diffraction data, in the monoclinic system, space group P2 1/c. The refinement from 5561 independent reflections lead to the following parameters: a=7.5612(4)Å, b=7.0919(4)Å, c=7.4874(4)Å, β=122.25(1)°, Z=4, with the final R=0.0198, wR=0.0510. The structure of α Cu 0.50IITiO(PO 4) can be described as a TiOPO 4 framework constituted by chains of tilted corner-sharing [TiO 6] octahedra running parallel to the c-axis and cross linked by phosphate [PO 4] tetrahedra, where one-half of octahedral cavities created are occupied by Cu atoms. Ti atoms are displaced from the center of octahedra units in alternating long (2.308 Å) and short (1.722 Å) Ti-O(1) bonds along chains. Such O(1) atoms not linked to P atoms justify the oxyphosphate formulation α Cu 0.50TiO(PO 4). The divalent cations Cu 2+ occupy a Jahn-Teller distorted octahedron sharing two faces with two [TiO 6] octahedra. EPR and optical measurements are in good agreement with structural data. The X-ray diffraction results are supported by Raman and infrared spectroscopy studies that confirmed the existence of the infinite chains -Ti-O-Ti-O-Ti-. α Cu 0.50TiO(PO 4) shows a Curie-Weiss paramagnetic behavior in the temperature range 4-80 K.

C_6_0"3"- versus C_6_0"4"- /C_6_0"2"- - synthesis and characterization of five salts containing discrete fullerene anions

International Nuclear Information System (INIS)

Boeddinghaus, M. Bele; Klein, Wilhelm; Wahl, Bernhard; Faessler, Thomas F.; Jakes, Peter; Eichel, Ruediger A.

2014-01-01

Five new compounds, [Rb(18crown-6)]_3[C_6_0] (1), [Rb(18crown-6)]_6[C_6_0]_2(C_3H_7NO)_2(C_4H_8O)_2 (2), [Rb(benzo18crown-6)]_6[C_6_0]_2(C_2H_8N_2)_5 (3), [Cs(benzo18crown-6)]_3C_6_0(C_2H_8N_2)_2 (4), and [Cs_3(benzo18crown-6)_5]C_6_0(C_2H_8N_2)_(_4_._5_+_x_) (5) were synthesized and characterized by single-crystal X-ray structure determination. All compounds contain discrete C_6_0 anions, which are ordered in 1, 2, and 4, where direct cation-anion contacts occur. The unit cells of 1 and 2 contain two independent fullerides, which coordinate to the rubidium atoms either of two or of four [Rb(18crown-6)] units. Owing to the presence of differently coordinated fullerene units in compounds 1 and 2, a possible disproportionation of C_6_0"3"- into C_6_0"2"- and C_6_0"4"- anions is discussed. In 3 and 4 the C_6_0 anions are coordinated by three Rb and Cs atoms, respectively. In all compounds the average charge of the anion is -3. Magnetic data reveal a doublet spin state for 3. The EPR spectra are discussed for compounds 3 and 5. The role of a dynamic Jahn-Teller distortion is discussed, and we report the first IR spectroscopic data of fullerene trianions, which have been obtained in solution. (Copyright copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Intrinsic Local Distortions and charge carrier behavior in CMR manganites and cobaltites

Science.gov (United States)

Bridges, Frank

2010-03-01

We compare and contrast the local structure and electronic configurations in two oxide systems La1-xSrxCoO3 (LSCO) and La1-yCayMnO3 (LCMO). Although these oxides may appear quite similar they have rather different properties. At x=0, LaCoO3 (LCO) has unusual magnetic properties - diamagnetic at low T but developing a moment near 100K. The Sr doped LSCO materials show ferromagnetism for x > 0.2. For LCO, one of the possible spin state configurations called the intermediate spin (IS) state (S=1), should be Jahn-Teller (JT) active, while the low spin (S=0) and high spin (S=2) states have no JT distortion. Early local structure measurements suggested a JT distortion was present in LCO and therefore supported an IS spin model. However we find no evidence for any significant JT distortion (and hence no support for the IS model) for a range of bulk and nanoparticle cobaltites La1-xSrxCoO3, x = 0 - 0.35. In contrast there are large JT distortions in the manganites LCMO, 0.2 K-edge XANES data that shown no significant shift of the edge for the cobaltites as the Sr concentration increases from x =0 to 0.35 indicating essentially no change in the electronic configuration about Co; consequently, the holes introduced via Sr doping appear to go primarily into the O bands. In contrast there is a large shift of the Mn K-edge with Ca doping indicating a change in the average Mn valence, and a corresponding change in the Mn electronic configuration. We briefly discuss some possible models.

Crystal and magnetic study of the disordered perovskites Ca(Mn{sub 0.5}Sb{sub 0.5})O{sub 3} and Ca(Fe{sub 0.5}Sb{sub 0.5})O{sub 3}

Energy Technology Data Exchange (ETDEWEB)

Retuerto, M., E-mail: mretuerto@icmm.csic.es [Instituto de Ciencia de Materiales de Madrid, CSIC, Energia, Medio Ambiente y Tecnologias Sostenibles, Sor Juana Ines de la Cruz 3, Cantoblanco, E-28049 Madrid (Spain); Martinez-Lope, M.J.; Garcia-Hernandez, M. [Instituto de Ciencia de Materiales de Madrid, CSIC, Energia, Medio Ambiente y Tecnologias Sostenibles, Sor Juana Ines de la Cruz 3, Cantoblanco, E-28049 Madrid (Spain); Munoz, A. [Departamento de Fisica Aplicada, EPS, Universidad Carlos III, Avda. Universidad 30, E-28911 Leganes-Madrid (Spain); Fernandez-Diaz, M.T. [Institut Max Von Laue Paul Langevin, F-38042 Grenoble (France); Alonso, J.A. [Instituto de Ciencia de Materiales de Madrid, CSIC, Energia, Medio Ambiente y Tecnologias Sostenibles, Sor Juana Ines de la Cruz 3, Cantoblanco, E-28049 Madrid (Spain)

2010-10-15

We have investigated the double perovskites Ca{sub 2}MSbO{sub 6} (M = Mn, Fe) that have been prepared by solid-state reaction (M = Fe) and wet chemistry procedures (M = Mn). The crystal and magnetic structures have been studied from X-ray (XRD) and neutron powder diffraction (NPD) data. Rietveld refinements show that the crystal structures are orthorhombic (space group Pbnm) with complete disorder of M and Sb cations, so the formula should be rewritten as Ca(M{sub 0.5}Sb{sub 0.5})O{sub 3}. Due to this disorder no evidences of Jahn-Teller distortion can be observed in the MnO{sub 6} octahedra of Ca(Mn{sub 0.5}Sb{sub 0.5})O{sub 3}, in contrast with the ordered double perovskite Sr{sub 2}MnSbO{sub 6}. Ca(Fe{sub 0.5}Sb{sub 0.5})O{sub 3} behaves as an antiferromagnet with an ordered magnetic moment for Fe{sup 3+} of 1.53(4){mu}{sub B} and a propagation vector k = 0, as investigated by low-temperature NPD. The antiferromagnetic ordering is a result of the high degree of Fe/Sb anti-site disorder of the sample, which originates the spontaneous formation of Fe-rich islands, characterized by the presence of strong Fe-O-Fe antiferromagnetic couplings with enough long-range coherence to produce a magnetic contribution perceptible by NPD. By contrast, the magnetic structure of Ca(Mn{sub 0.5}Sb{sub 0.5})O{sub 3} cannot be observed by low-temperature NPD because the magnitude of the ordered magnetic moments is below the detection threshold for neutrons.

A Combined Variable-Temperature Neutron Diffraction and Thermogravimetric Analysis Study on a Promising Oxygen Electrode, SrCo0.9Nb0.1O3-δ, for Reversible Solid Oxide Fuel Cells.

Science.gov (United States)

Yang, Tianrang; Wang, Jie; Chen, Yan; An, Ke; Ma, Dong; Vogt, Thomas; Huang, Kevin

2017-10-11

The present study investigates the temperature-structure-stoichiometry relationship of a promising oxygen electrode SrCo 0.9 Nb 0.1 O 3-δ over a temperature (T) range from room temperature (RT) to 900 °C. The techniques employed are variable-temperature neutron diffraction (VTND) and thermogravimetric analysis (TGA). At T < 75 °C, VTND reveals a tetragonal (P4/mmm) structure with a G-type magnetic ordering. Above 75 °C, the nucleus structure remains the same, while the magnetic ordering disappears. A phase transition from tetragonal (P4/mmm) to cubic (Pm3̅m) is observed at 412 °C, where the two Co sites and three O sites in the P4/mmm phase converge to one equivalent site, respectively. The phase transition temperature coincides with the peak temperature of oxygen uptake obtained by TGA. It is also observed that the Nb dopant has no preferred Co site to occupy. The oxygen vacancies are mostly located at the O3 site surrounding the Co2 site in the P4/mmm structure. The intermediate-spin state of Co 3+ at the Co2 site is responsible for the observed distortions of CoO 6 octahedra, i.e., elongation of Co2O 6 octahedra and shortening of Co1O 6 octahedra along the c-axis, which is a phenomenon known as Jahn-Teller distortion. At high temperatures, large thermal displacement factor for O 2- is observed with high concentration of oxygen vacancies, providing a structural environment favorable to high O 2- conductivity in Nb-doped SrCoO 3 -based oxygen electrode materials.

La{sub 0.7}Sr{sub 0.3}MnO{sub 3} thin films deposited by pulsed laser ablation for spintronic applications

Energy Technology Data Exchange (ETDEWEB)

Martino, Maurizio; Cesaria, Maura; Caricato, Anna Paola [Physics Department, University of Salento, Via Arnesano, 73100 Lecce (Italy); Maruccio, Giuseppe [Physics Department, University of Salento, Via Arnesano, 73100 Lecce (Italy); NNL CNR-Istituto di Nanoscienze, Via Arnesano, 73100 Lecce (Italy); Cola, Adriano; Farella, Isabella [Institute for Microelectronics and Microsystems, IMM-CNR, 73100 Lecce (Italy)

2011-08-15

Among spintronic materials, mixed-valence manganite La{sub 0.7}Sr{sub 0.3}MnO{sub 3} (LSMO) is widely investigated due to its half-metal nature. LSMO thin films were grown by pulsed laser deposition (PLD) onto amorphous silica substrates heated at nearly 600 C. An ArF excimer laser was chosen to induce ablation due to its more energetic photons compared to the other quoted excimer laser sources. Different oxygen pressures were considered in order to study the influence of oxygen on the LSMO optical and electrical properties. In this respect, the visible transparency percentage of the deposited films is found good enough for spin-OLED applications. The absorption coefficient shows an absorption band tunable as a function of the oxygen content. Its energetic location and evolution with the oxygen content demonstrate it originates from radiative transitions between the spin-majority bands separated by the Jahn-Teller distortion. All of this lets relate the deposition oxygen pressure to the Mn{sup 3+} ion content in each film and interpret electrical data. The 200 and 100 nm thick samples exhibit weak metallic transport behavior at room temperature with a resistivity of 4.8 and 6.9 {omega} cm, respectively. Concerning the resistivity response versus temperature, the measured low metal-insulator transition temperature (150 K) is related to the sample structural features as involved by the depositions. Two different transport mechanisms describe the conductivity regime of the deposited samples, namely the small polaron variable range hopping (VRH) and the Arrhenius law. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Collective efficacy versus self-efficacy in coping responses to stressors and control: a cross-cultural study.

Science.gov (United States)

Schaubroeck, J; Lam, S S; Xie, J L

2000-08-01

This study examined how cultural differences and efficacy perceptions influence the role of job control in coping with job demands. Perceiving higher control mitigated the effects of demands on psychological health symptoms and turnover intentions only among American bank tellers reporting high job self-efficacy. Among American tellers reporting low job self-efficacy, perceived control exacerbated the effects of demands. However, in a matched Hong Kong sample, collective efficacy interacted in the same way with control and demands as job self-efficacy had in the American sample. These differences appear to be explained by the individual attributes of idiocentrism and allocentrism that are linked to the societal norms of individualism and collectivism, respectively.

Mixed-valence molecular four-dot unit for quantum cellular automata: Vibronic self-trapping and cell-cell response.

Science.gov (United States)

Tsukerblat, Boris; Palii, Andrew; Clemente-Juan, Juan Modesto; Coronado, Eugenio

2015-10-07

Our interest in this article is prompted by the vibronic problem of charge polarized states in the four-dot molecular quantum cellular automata (mQCA), a paradigm for nanoelectronics, in which binary information is encoded in charge configuration of the mQCA cell. Here, we report the evaluation of the electronic levels and adiabatic potentials of mixed-valence (MV) tetra-ruthenium (2Ru(ii) + 2Ru(iii)) derivatives (assembled as two coupled Creutz-Taube complexes) for which molecular implementations of quantum cellular automata (QCA) was proposed. The cell based on this molecule includes two holes shared among four spinless sites and correspondingly we employ the model which takes into account the two relevant electron transfer processes (through the side and through the diagonal of the square) as well as the difference in Coulomb energies for different instant positions of localization of the hole pair. The combined Jahn-Teller (JT) and pseudo JT vibronic coupling is treated within the conventional Piepho-Krauzs-Schatz model adapted to a bi-electronic MV species with the square-planar topology. The adiabatic potentials are evaluated for the low lying Coulomb levels in which the antipodal sites are occupied, the case just actual for utilization in mQCA. The conditions for the vibronic self-trapping in spin-singlet and spin-triplet states are revealed in terms of the two actual transfer pathways parameters and the strength of the vibronic coupling. Spin related effects in degrees of the localization which are found for spin-singlet and spin-triplet states are discussed. The polarization of the cell is evaluated and we demonstrate how the partial delocalization caused by the joint action of the vibronic coupling and electron transfer processes influences polarization of a four-dot cell. The results obtained within the adiabatic approach are compared with those based on the numerical solution of the dynamic vibronic problem. Finally, the Coulomb interaction between

Spectral intensities: The emission spectra for the Cs2NaScCl6: MoCl63- system in the Fm3m space group

International Nuclear Information System (INIS)

Acevedo, R.; Meruane, T.; Navarro, G.

2000-01-01

Taking advantage of the data reported by Flint and Paulusz, we have undertaken a theoretical investigation of the intensity mechanism for the various emissions; Γ 8 ( 2 T 2g ) → Γ 8 ( 4 A 2g ), Γ 8 ( 2 E g ), Γ 8 ( 2 T 1g ), Γ 6 ( 2 T 1g ) for the Cs 2 NaScCl 6 :MoCl 6 3- system in the Fm3m-space group. The experimental data reported by these authors, refer to the visible and near infrared luminescence spectra of MoCl 3- 6 complex ion in different host, such as Cs 2 NaMCl 6 (M = Sc, Y, In), measured between 15,000 cm -1 and 3,000 cm -1 at liquid helium temperatures. At least, five luminescence transitions have been identified and assigned and each of them show extensive vibronic structure, which was analyzed to yield the vibrational frequencies of the MoX 3- 6 (X -1 = Cl -1 Br -1 ) ion in each excitation. A careful analysis of the experimental data reported shows that for the various observed electronic transitions, the vibration frequencies do change only slightly, and therefore there is no indication that the system undergoes a Jahn-Teller distortion (along an active coordinate) of some importance to be taken into account in the current work. There is, though clear evidence that for the chloro-elpasolites, there is a strong resonance interaction between ν 3 (τ 1u : stretching) of the MoX 6 3- , complex ion and that of the host when M = In, Y. Thus for M = Sc, the slighter higher host ν 3 , wavenumber is likely to minimizes the effect of this coupling. This experimental evidence, will allow us for the Cs 2 NaScCl 6 3- system to neglect to first order approximation, the coupling among the internal and the external vibrations and to proceed using a both a molecular model and the independent system model (ISM)

DoD Cardholders Used Their Government Travel Cards for Personal Use at Casinos and Adult Entertainment Establishments

Science.gov (United States)

2015-05-19

GTCC: • transactions with no associated travel status in DTS; • automated teller machine (ATM) withdrawals that exceeded the overall Meal and...Defense Travel System or other DoD travel systems; 2. Automated teller machine withdrawals that exceed the overall meal and incidental expense...System or other DoD travel systems; • Automated teller machine withdrawals that exceed the overall meal and incidental expense amounts while in a travel

Viies "Postsovkhoz" : kultuuritehas / Maarin Ektermann

Index Scriptorium Estoniae

Ektermann, Maarin

2005-01-01

5.-15. VIII 2005 Moostes toimunud rahvusvahelistest mõtte- ja keskkonnakunsti talgutest "Postsovkhoz 5. Avalik/era" ja satelliitüritusena Tartus Y-galeriis toimunud lipunäitusest "Unfurled / Lahtirullitud" (kuraator Marisa Jahn)

Structural, Raman, and dielectric studies on multiferroic Mn-doped Bi 1-xLax FeO 3 ceramics

KAUST Repository

Xing, Zhibiao

2014-04-03

Multiferroic Bi1-xLaxFeO3 [BLFO (x)] ceramics with x = 0.10-0.50 and Mn-doped BLFO (x = 0.30) ceramics with different doping contents (0.1-1.0 mol%) were prepared by solid-state reaction method. They were crystallized in a perovskite phase with rhombohedral symmetry. In the BLFO (x) system, a composition (x)-driven structural transformation (R3c→C222) was observed at x = 0.30. The formation of Bi2Fe 4O9 impure phase was effectively suppressed with increasing the x value, and the rhombohedral distortion in the BLFO ceramics was decreased, leading to some Raman active modes disappeared. A significant red frequency shift (~13 cm-1) of the Raman mode of 232 cm-1 in the BLFO ceramics was observed, which strongly perceived a significant destabilization in the octahedral oxygen chains, and in turn affected the local FeO6 octahedral environment. In the Mn-doped BLFO (x = 0.30) ceramics, the intensity of the Raman mode near 628 cm-1 was increased with increasing the Mn-doping content, which was resulted from an enhanced local Jahn-Teller distortions of the (Mn,Fe)O6 octahedra. Electron microscopy images revealed some changes in the ceramic grain sizes and their morphologies in the Mn-doped samples at different contents. Wedge-shaped 71° ferroelectric domains with domain walls lying on the {110} planes were observed in the BLFO (x = 0.30) ceramics, whereas in the 1.0 mol% Mn-doped BLFO (x = 0.30) samples, 71° ferroelectric domains exhibited a parallel band-shaped morphology with average domain width of 95 nm. Dielectric studies revealed that high dielectric loss of the BLFO (x = 0.30) ceramics was drastically reduced from 0.8 to 0.01 (measured @ 104 Hz) via 1.0 mol% Mn-doping. The underlying mechanisms can be understood by a charge disproportion between the Mn4+ and Fe2+ in the Mn-doped samples, where a reaction of Mn4+ + Fe2+→Mn3+ + Fe3+ is taken place, resulting in the reduction in the oxygen vacancies and a suppression of the electron hopping from Fe3+ to Fe2+ ions

Vibration and Fluorescence Spectra of Porphyrin- CoredBis(methylol-propionic Acid Dendrimers

Directory of Open Access Journals (Sweden)

Boris Minaev

2009-03-01

Full Text Available Bis-MPA dendron-coated free-base tetraphenylporphyrin and zinc-tetraphenyl-porphyrin (TPPH2 and TPPZn were studied in comparison with simple porphyrins (H2P, ZnP by theoretical simulation of their infrared, Raman and electronic absorption spectra, as well as fluorescense emission. Infrared and fluorescence spectra of the dendrimers were measured and interpreted along with time-resolved measurements of the fluorescence. The 0-1 emission band of the dendron substituted TPPZn was found to experience a "heavy substitution"-effect. The 0-1 vibronic emission signal is associated with a longer decay time (approx. 7 - 8 ns than the 0-0 emission (approx. 1 - 1.5 ns. The former contributed with more relative emission yield for larger dendron substituents, in agreement with the appearance of steady-state emission spectra showing increased contribution from the 0-1 vibronic fluorescence band at 650 nm. No such substitution effect was observed in the electronic or vibrational spectra of the substituted free-base variant, TPPH2. Vibration spectra of the parent porphyrins (H2P, ZnP, TPPH2 and TPPZn were calculated by density functional theory (DFT using the B3LYP/6-31G** approximation and a detailed analysis of the most active vibration modes was made based on both literature and our own experimental data. Based on the results of theoretical calculations the wide vibronic bands in the visible region were assigned. The vibronic structure also gave a qualitative interpretation of bands in the electronic absorption spectra as well as in fluorescence emission depending on the size of dendrimer substitution. From the results of time-dependent DFT calculations it is suggested that the TPPZn-cored dendrimers indicate strong vibronic interaction and increased Jahn-Teller distortion of the prophyrin core for larger dendrimer generations. Specifically, this leads to the entirely different behaviour of the emission spectra upon substitution of the TPPH2 and TPPZn

Structural, Raman, and dielectric studies on multiferroic Mn-doped Bi 1-xLax FeO 3 ceramics

KAUST Repository

Xing, Zhibiao; Zhu, Xinhua; Zhu, Jianmin; Liu, Zhiguo; Al-Kassab, Talaat

2014-01-01

Multiferroic Bi1-xLaxFeO3 [BLFO (x)] ceramics with x = 0.10-0.50 and Mn-doped BLFO (x = 0.30) ceramics with different doping contents (0.1-1.0 mol%) were prepared by solid-state reaction method. They were crystallized in a perovskite phase with rhombohedral symmetry. In the BLFO (x) system, a composition (x)-driven structural transformation (R3c→C222) was observed at x = 0.30. The formation of Bi2Fe 4O9 impure phase was effectively suppressed with increasing the x value, and the rhombohedral distortion in the BLFO ceramics was decreased, leading to some Raman active modes disappeared. A significant red frequency shift (~13 cm-1) of the Raman mode of 232 cm-1 in the BLFO ceramics was observed, which strongly perceived a significant destabilization in the octahedral oxygen chains, and in turn affected the local FeO6 octahedral environment. In the Mn-doped BLFO (x = 0.30) ceramics, the intensity of the Raman mode near 628 cm-1 was increased with increasing the Mn-doping content, which was resulted from an enhanced local Jahn-Teller distortions of the (Mn,Fe)O6 octahedra. Electron microscopy images revealed some changes in the ceramic grain sizes and their morphologies in the Mn-doped samples at different contents. Wedge-shaped 71° ferroelectric domains with domain walls lying on the {110} planes were observed in the BLFO (x = 0.30) ceramics, whereas in the 1.0 mol% Mn-doped BLFO (x = 0.30) samples, 71° ferroelectric domains exhibited a parallel band-shaped morphology with average domain width of 95 nm. Dielectric studies revealed that high dielectric loss of the BLFO (x = 0.30) ceramics was drastically reduced from 0.8 to 0.01 (measured @ 104 Hz) via 1.0 mol% Mn-doping. The underlying mechanisms can be understood by a charge disproportion between the Mn4+ and Fe2+ in the Mn-doped samples, where a reaction of Mn4+ + Fe2+→Mn3+ + Fe3+ is taken place, resulting in the reduction in the oxygen vacancies and a suppression of the electron hopping from Fe3+ to Fe2+ ions

2. VIII avati Y-galerii hoovis ja ka mujal Tartus...

Index Scriptorium Estoniae

2005-01-01

"PostsovkhoZ 5" satelliitnäitus "Unfurled/Lahtirullitud : avalik lipunäitus". Kuraator Marisa Jahn (USA). Osalejad loetletud (Eestist Sirja Liisa Vahtra). E-saalis näidatakse Max Hattleri videot "Collision/Kokkupõrge"

Festival PostsovkhoZ kulmineerub täna / Siram

Index Scriptorium Estoniae

Siram, pseud., 1968-

2005-01-01

Kunstifestivalist "PostsovkhoZ 5/Avalik - era" Moostes, 13. VIII toimuvatest üritustest. Marisa Jahn USAst korraldab lastele seinamaali õpikoja ja kureerib festivali satelliitnäitust "Unfurled" Tartus Y-galeriis, kus koondub lipumotiiviga kunst

Isospin symmetry of Tz =±3/2→±1/2 Gamow-Teller transitions in A=41 nuclei

Science.gov (United States)

Fujita, Y.; Shimbara, Y.; Adachi, T.; Berg, G. P.; Brown, B. A.; Fujita, H.; Hatanaka, K.; Kamiya, J.; Nakanishi, K.; Sakemi, Y.; Sasaki, S.; Shimizu, Y.; Tameshige, Y.; Uchida, M.; Wakasa, T.; Yosoi, M.

2004-11-01

Under the assumption that isospin T is a good quantum number, isobaric analog states and various analogous transitions are expected in isobars with mass number A . The strengths of Tz =±3/2→±1/2 analogous Gamow-Teller (GT) transitions and analogous M1 transitions within the A=41 isobar quartet are compared in detail. The Tz =+3/2→+1/2 GT transitions from the Jπ = 3/2+ ground state of 41K leading to excited Jπ = 1/2+ , 3/2+ , and 5/2+ states in 41Ca were measured using the ( 3He ,t) charge-exchange reaction. With a high energy resolution of 35 keV , many fragmented states were observed, and the GT strength distribution was determined up to 10 MeV excitation energy ( Ex ) . The main part of the strength was concentrated in the Ex =4 6 MeV region. A shell-model calculation could reproduce the concentration, but not so well details of the strength distribution. The obtained distribution was further compared with two results of 41Ti β decay studying the analogous Tz =-3/2→-1/2 GT strengths. They reported contradicting distributions. One-to-one correspondences of analogous transitions and analog states were assigned up to Ex =6 MeV in the comparison with one of these 41Ti β -decay results. Combining the spectroscopic information of the analog states in 41Ca and 41Sc , the most probable Jπ values were deduced for each pair of analog states. It was found that 5/2+ states carry the main part of the observed GT strength, while much less GT strength was carried by 1/2+ and 3/2+ states. The gross features of the GT strength distributions for each J were similar for the isospin analogous Tz =±3/2→±1/2 transitions, but the details were somewhat different. From the difference of the distributions, isospin-asymmetry matrix elements of ≈8 keV were deduced. The Coulomb displacement energy, which is sensitive to the configuration of states, showed a sudden increase of about 50 keV at the excitation energy of 3.8 MeV . The strengths of several M1 transitions to the

75 FR 13483 - Notice of Intent To Request an Information Collection

Science.gov (United States)

2010-03-22

... System (CES) of the LGUs and their Federal partner, the Extension Service, now the National Institute of... Jahn, Acting Under Secretary, Research, Education, and Economics. [FR Doc. 2010-6140 Filed 3-19-10; 8...

32 CFR Appendix A to Part 231 - Sample Operating Agreement

Science.gov (United States)

2010-07-01

...) Electronic banking (i.e., automated teller machines, internet banking). b. Services for disbursing officers... nonaccountholders for use of automated teller machines shall be the customary service charges of the financial...

Demonstrating Recipiency: Knowledge Displays as a Resource for the Unaddressed Participant

OpenAIRE

Kidwell, Mardi

1997-01-01

This paper expands conversation analytic notions of recipiency by considering recipient proactivity. At issue are the methods by which an unaddressed participant of a story-in-progress makes claims on a teller's attention through a series of upgraded responses to the story. These claims range from gaze direction toward the teller, to displays of knowledge of particular story components. The recipient's displays of knowledge regarding the story provide a resource for her to elicit the teller's...

Memoirs a twentieth-century journey in science and politics

CERN Document Server

Teller, Edward

2001-01-01

The story of Edward Teller is the story of the twentieth century. Born in Hungary in 1908, Teller witnessed the rise of Nazism and anti-Semitism, two world wars, the McCarthy era, and the changing face of big science. A brilliant and controversial figure whose work on nuclear weapons was key to the American war effort, Teller has long believed in freedom through strong defense, a philosophy reflected in his stance on arms control and nuclear policy. These extraordinary recollections at last reveal the man behind the headlines-passionate and humorous, devoted and loyal. In clear and compelling prose, Teller tells of the people, events, and ideas that shaped him as a scientist, beginning with his early love of music and math, and continuing with his study of quantum physics with Werner Heisenberg. Present at many of the pivotal moments in modern science, Teller also describes his friendships with some of the century's greatest minds-Einstein, Bohr, Fermi, Szilard, von Neumann, Oppenheimer-and offers an honest a...

Exchange coupling transformations in Cu (II) heterospin complexes of “breathing crystals” under structural phase transitions

Energy Technology Data Exchange (ETDEWEB)

Morozov, Vitaly A.; Petrova, Marina V.; Lukzen, Nikita N., E-mail: luk@tomo.nsc.ru [International Tomography Center SB RUS, Institutskaya Str. 3a, Novosibirsk, 630090 (Russian Federation); Novosibirsk State University, Pirogova Str. 2, Novosibirsk 630090 (Russian Federation)

2015-08-15

Family of “breathing crystals” is the polymer-chain complexes of Cu(hfac){sub 2} with nitroxides. The polymer chains consist of one-, two- or three-spin clusters. The “breathing crystals” experience simultaneous magnetic and Jahn-Teller type structural phase transitions with change of total cluster spin and drastic change of bond lengths (ca. 10-12%). For the first time the intra-cluster magnetic couplings in ”breathing crystals” have been calculated both by band structure methods GGA + U and hybrid DFT (B3LYP and PBE0) for the isolated exchange clusters. The temperature dependence of the magnetic coupling constant was calculated for two polymer-chain compounds of the “breathing crystal” family - C{sub 21}H{sub 19}CuF{sub 12}N{sub 4}O{sub 6} with the chains containing two-spin clusters and C{sub 22}H{sub 21}CuF{sub 12}N{sub 4}O{sub 6} with the chains of alternating three-spin clusters and one-spin sites. It was found that adding a Hubbard-like parameter not only to the copper 3d electrons but also to the oxygen 2p electrons (GGA + U{sub d} + U{sub p} approach) results in an improved description of exchange coupling in the “breathing crystal” compounds. At the same time treatment of the isolated clusters by a large basis hybrid DFT with high computational cost provides a similar quality fit of the experimental magneto-chemical data as that for the GGA + U{sub d} + U{sub p} band structure calculation scheme. Our calculations also showed that in spite of the abrupt transformation of the magnetic coupling constant under the phase transition, the band gap in the “breathing crystals” remains about the same value with temperature decrease.

Preparation and properties of a monomeric Mn(IV)-oxo complex.

Science.gov (United States)

Parsell, Trenton H; Behan, Rachel K; Green, Michael T; Hendrich, Michael P; Borovik, A S

2006-07-12

Manganese-oxo complexes have long been investigated because of their proposed roles in biological and chemical catalysis. However, there are few examples of monomeric complexes with terminal oxo ligands, especially those with oxomanganese(IV) units. A oxomanganese(IV) complex has been prepared from [MnIIIH3buea(O)]2- ([H3buea]3-, tris[(N'-tert-butylureaylato)-N-ethylene]aminato), a monomeric MnIII-O complex in which the oxo ligand arises from cleavage of dioxygen. Treating [MnIIIH3buea(O)]2- with [Cp2Fe]BF4 in either DMF at -45 degrees C or DMSO at room temperature produces [MnIVH3buea(O)]-: lambdamax = 635 nm; nu(Mn-16O) = 737 cm-1; nu(Mn-18O) = 709 cm-1; g = 5.15, 2.44, 1.63, D = 3.0 cm-1, E/D = 0.26, aMn = 66 G (A = 190 MHz). These spectroscopic properties support the assignment of a mononuclear MnIV-oxo complex with an S = 3/2 ground state. Density functional theory supports this assignment and the Jahn-Teller distortion around the high-spin MnIV center that would alter the molecular structure of [MnIVH3buea(O)]- from trigonal symmetry (as indicated by the highly rhombic EPR signal). [MnIVH3buea(O)]- is relatively unstable in DMSO, converting to [MnIIIH3buea(OH)]- via a proposed X-H bond cleavage. [MnIVH3buea(O)]- reacts with 1,2-diphenylhydrazine to from azobenzene (95% yield) and [MnIIIH3buea(OH)]-. The MnIV-oxo does not react with triphenyl- or tricyclohexylphosphine. However, O-atom transfer is observed with methyldiphenylphosphine and dimethylphenylphosphine, producing the corresponding phosphine oxides. These results illustrate the diverse reactivity of the MnIV-oxo unit.

Far infrared spectroscopy of solids. I. Impurity states in Al2O3. II. Electron-hole droplets in Ge

International Nuclear Information System (INIS)

Aurbauch, R.L.

1975-01-01

Far infrared Fourier transform spectroscopy was used to study the low lying vibronic states of Mn 3+ in Al 2 O 3 and the plasma absorption of electron-hole droplets in Ge. The transmission of Mn-doped samples of Al 2 O 3 was measured in the frequency range from 3 to 30 cm -1 in applied magnetic fields up to 50 kG. Absorption lines were observed due to both ground and excited state transitions. Polarization measurements established that these absorption lines were due to electric dipole transitions. Temperature dependence measurements were used to derive a level diagram for the low lying states of Mn 3+ . A phenomenological model based on an electronic Hamiltonian was developed which successfully describes the data. The empirically determined trigonal field and spin-orbit quenching parameters of this model are 0.7 and 0.1 respectively. This quenching is attributed to the dynamic Jahn--Teller interaction. The plasma absorption of small (α) electron-hole drops in Ge was measured in the frequency range from 30 to 300 cm -1 . The observed absorption is in good agreement with measurements by Vavilov and other workers. A theoretical model which includes both intraband and interband contributions to the dielectric constant in the Rayleigh limit of Mie theory is used to describe the observed lineshape. Measurements of plasma absorption of large (γ) drops in inhomogeneously stressed Ge were made in magnetic fields up to 50 kG. The lineshape at zero applied field was calculated in the large sphere limit of Mie theory including intraband terms and a zero-strain interband term. Qualitative agreement with experiment was obtained. The peak absorption shifted quadratically with applied magnetic field and the total plasma absorption increased. No oscillatory structure was observed in the field-dependence of the total absorption

Structural and Chemical Evolution of Li- and Mn-rich Layered Cathode Material

Energy Technology Data Exchange (ETDEWEB)

Zheng, Jianming; Xu, Pinghong; Gu, Meng; Xiao, Jie; Browning, Nigel D.; Yan, Pengfei; Wang, Chong M.; Zhang, Jiguang

2015-02-24

Lithium (Li)- and manganese-rich (LMR) layered-structure materials are very promising cathodes for high energy density lithium-ion batteries. However, their voltage fading mechanism and its relationships with fundamental structural changes are far from being sufficiently understood. Here we report the detailed phase transformation pathway in the LMR cathode (Li[Li0.2Ni0.2Mn0.6]O2) during cycling for the samples prepared by hydro-thermal assistant method. It is found the transformation pathway of LMR cathode is closely correlated to its initial structure and preparation conditions. The results reveal that LMR cathode prepared by HA approach experiences a phase transformation from the layered structure to a LT-LiCoO2 type defect spinel-like structure (Fd-3m space group) and then to a disordered rock-salt structure (Fm-3m space group). The voltage fade can be well correlated with the Li ion insertion into octahedral sites, rather than tetrahedral sites, in both defect spinel-like structure and disordered rock-salt structure. The reversible Li insertion/removal into/from the disordered rock-salt structure is ascribed to the Li excess environment that can satisfy the Li percolating in the disordered rock-salt structure despite the increased kinetic barrier. Meanwhile, because of the presence of a great amount of oxygen vacancies, a significant decrease of Mn valence is detected in the cycled particle, which is below that anticipated for a potentially damaging Jahn-Teller distortion (+3.5). Clarification of the phase transformation pathway, cation redistribution, oxygen vacancy and Mn valence change undoubtedly provides insights into a profound understanding on the voltage fade, and capacity degradation of LMR cathode. The results also inspire us to further enhance the reversibility of LMR cathode via improving its surface structural stability.

Gaussian-3 theory using density functional geometries and zero-point energies

International Nuclear Information System (INIS)

Baboul, A.G.; Curtiss, L.A.; Redfern, P.C.; Raghavachari, K.

1999-01-01

A variation of Gaussian-3 (G3) theory is presented in which the geometries and zero-point energies are obtained from B3LYP density functional theory [B3LYP/6-31G(d)] instead of geometries from second-order perturbation theory [MP2(FU)/6-31G(d)] and zero-point energies from Hartree - Fock theory [HF/6-31G(d)]. This variation, referred to as G3//B3LYP, is assessed on 299 energies (enthalpies of formation, ionization potentials, electron affinities, proton affinities) from the G2/97 test set [J. Chem. Phys. 109, 42 (1998)]. The G3//B3LYP average absolute deviation from experiment for the 299 energies is 0.99 kcal/mol compared to 1.01 kcal/mol for G3 theory. Generally, the results from the two methods are similar, with some exceptions. G3//B3LYP theory gives significantly improved results for several cases for which MP2 theory is deficient for optimized geometries, such as CN and O 2 + . However, G3//B3LYP does poorly for ionization potentials that involve a Jahn - Teller distortion in the cation (CH 4 + , BF 3 + , BCl 3 + ) because of the B3LYP/6-31G(d) geometries. The G3(MP2) method is also modified to use B3LYP/6-31G(d) geometries and zero-point energies. This variation, referred to as G3(MP2)//B3LYP, has an average absolute deviation of 1.25 kcal/mol compared to 1.30 kcal/mol for G3(MP2) theory. Thus, use of density functional geometries and zero-point energies in G3 and G3(MP2) theories is a useful alternative to MP2 geometries and HF zero-point energies. copyright 1999 American Institute of Physics

C{sub 60}{sup 3-} versus C{sub 60}{sup 4-} /C{sub 60}{sup 2-} - synthesis and characterization of five salts containing discrete fullerene anions

Energy Technology Data Exchange (ETDEWEB)

Boeddinghaus, M. Bele; Klein, Wilhelm; Wahl, Bernhard; Faessler, Thomas F. [Department of Chemistry, Technische Universitaet Muenchen, Garching (Germany); Jakes, Peter; Eichel, Ruediger A. [Institut fuer Energie- und Klimaforschung (IEK-9), Forschungszentrum Juelich (Germany)

2014-04-15

Five new compounds, [Rb(18crown-6)]{sub 3}[C{sub 60}] (1), [Rb(18crown-6)]{sub 6}[C{sub 60}]{sub 2}(C{sub 3}H{sub 7}NO){sub 2}(C{sub 4}H{sub 8}O){sub 2} (2), [Rb(benzo18crown-6)]{sub 6}[C{sub 60}]{sub 2}(C{sub 2}H{sub 8}N{sub 2}){sub 5} (3), [Cs(benzo18crown-6)]{sub 3}C{sub 60}(C{sub 2}H{sub 8}N{sub 2}){sub 2} (4), and [Cs{sub 3}(benzo18crown-6){sub 5}]C{sub 60}(C{sub 2}H{sub 8}N{sub 2}){sub (4.5+x)} (5) were synthesized and characterized by single-crystal X-ray structure determination. All compounds contain discrete C{sub 60} anions, which are ordered in 1, 2, and 4, where direct cation-anion contacts occur. The unit cells of 1 and 2 contain two independent fullerides, which coordinate to the rubidium atoms either of two or of four [Rb(18crown-6)] units. Owing to the presence of differently coordinated fullerene units in compounds 1 and 2, a possible disproportionation of C{sub 60}{sup 3-} into C{sub 60}{sup 2-} and C{sub 60}{sup 4-} anions is discussed. In 3 and 4 the C{sub 60} anions are coordinated by three Rb and Cs atoms, respectively. In all compounds the average charge of the anion is -3. Magnetic data reveal a doublet spin state for 3. The EPR spectra are discussed for compounds 3 and 5. The role of a dynamic Jahn-Teller distortion is discussed, and we report the first IR spectroscopic data of fullerene trianions, which have been obtained in solution. (Copyright copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Structural characterization of terrestrial microbial Mn oxides from Pinal Creek, AZ

Science.gov (United States)

Bargar, J.R.; Fuller, C.C.; Marcus, M.A.; Brearley, A.J.; Perez De la Rosa, M.; Webb, S.M.; Caldwell, W.A.

2009-01-01

The microbial catalysis of Mn(II) oxidation is believed to be a dominant source of abundant sorption- and redox-active Mn oxides in marine, freshwater, and subsurface aquatic environments. In spite of their importance, environmental oxides of known biogenic origin have generally not been characterized in detail from a structural perspective. Hyporheic zone Mn oxide grain coatings at Pinal Creek, Arizona, a metals-contaminated stream, have been identified as being dominantly microbial in origin and are well studied from bulk chemistry and contaminant hydrology perspectives. This site thus presents an excellent opportunity to study the structures of terrestrial microbial Mn oxides in detail. XRD and EXAFS measurements performed in this study indicate that the hydrated Pinal Creek Mn oxide grain coatings are layer-type Mn oxides with dominantly hexagonal or pseudo-hexagonal layer symmetry. XRD and TEM measurements suggest the oxides to be nanoparticulate plates with average dimensions on the order of 11 nm thick ?? 35 nm diameter, but with individual particles exhibiting thickness as small as a single layer and sheets as wide as 500 nm. The hydrated oxides exhibit a 10-?? basal-plane spacing and turbostratic disorder. EXAFS analyses suggest the oxides contain layer Mn(IV) site vacancy defects, and layer Mn(III) is inferred to be present, as deduced from Jahn-Teller distortion of the local structure. The physical geometry and structural details of the coatings suggest formation within microbial biofilms. The biogenic Mn oxides are stable with respect to transformation into thermodynamically more stable phases over a time scale of at least 5 months. The nanoparticulate layered structural motif, also observed in pure culture laboratory studies, appears to be characteristic of biogenic Mn oxides and may explain the common occurrence of this mineral habit in soils and sediments. ?? 2008 Elsevier Ltd.

Electronic and vibronic properties of a discotic liquid-crystal and its charge transfer complex

Energy Technology Data Exchange (ETDEWEB)

Haverkate, Lucas A.; Mulder, Fokko M. [Reactor Institute Delft, Faculty of Applied Sciences, Delft University of Technology, Mekelweg 15, 2629JB Delft (Netherlands); Zbiri, Mohamed, E-mail: zbiri@ill.fr; Johnson, Mark R. [Institut Laue Langevin, 38042 Grenoble Cedex 9 (France); Carter, Elizabeth [Vibrational Spectroscopy Facility, School of Chemistry, The University of Sydney, NSW 2008 (Australia); Kotlewski, Arek; Picken, S. [ChemE-NSM, Faculty of Chemistry, Delft University of Technology, 2628BL/136 Delft (Netherlands); Kearley, Gordon J. [Bragg Institute, Australian Nuclear Science and Technology Organisation, Menai, NSW 2234 (Australia)

2014-01-07

Discotic liquid crystalline (DLC) charge transfer (CT) complexes combine visible light absorption and rapid charge transfer characteristics, being favorable properties for photovoltaic (PV) applications. We present a detailed study of the electronic and vibrational properties of the prototypic 1:1 mixture of discotic 2,3,6,7,10,11-hexakishexyloxytriphenylene (HAT6) and 2,4,7-trinitro-9-fluorenone (TNF). It is shown that intermolecular charge transfer occurs in the ground state of the complex: a charge delocalization of about 10{sup −2} electron from the HAT6 core to TNF is deduced from both Raman and our previous NMR measurements [L. A. Haverkate, M. Zbiri, M. R. Johnson, B. Deme, H. J. M. de Groot, F. Lefeber, A. Kotlewski, S. J. Picken, F. M. Mulder, and G. J. Kearley, J. Phys. Chem. B 116, 13098 (2012)], implying the presence of permanent dipoles at the donor-acceptor interface. A combined analysis of density functional theory calculations, resonant Raman and UV-VIS absorption measurements indicate that fast relaxation occurs in the UV region due to intramolecular vibronic coupling of HAT6 quinoidal modes with lower lying electronic states. Relatively slower relaxation in the visible region the excited CT-band of the complex is also indicated, which likely involves motions of the TNF nitro groups. The fast quinoidal relaxation process in the hot UV band of HAT6 relates to pseudo-Jahn-Teller interactions in a single benzene unit, suggesting that the underlying vibronic coupling mechanism can be generic for polyaromatic hydrocarbons. Both the presence of ground state CT dipoles and relatively slow relaxation processes in the excited CT band can be relevant concerning the design of DLC based organic PV systems.

LOW POWER UPCONVERSION FOR SOLAR FUELS PHOTOCHEMISTRY

Energy Technology Data Exchange (ETDEWEB)

Castellano, Felix N. [Bowling Green State University

2013-08-05

Earth abundant copper(I) diimine complexes represent a renewable and economically feasible alternative to commonly used heavy metal containing chromophores. In the metal-to-ligand charge transfer (MLCT) excited state, copper(I) diimine complexes typically undergo a significant structural rearrangement, leading to molecules with large Stokes shifts and very short excited state lifetimes, thereby limiting their usefulness as sensitizers in bimolecular electron and triplet energy transfer reactions. Strategically placed bulky substituents on the coordinating phenanthroline ligands have proven useful in restricting the transiently produced excited state Jahn-Teller distortion, leading to longer-lived excited states. By combining bulky sec-butyl groups in the 2- and 9- positions with methyl groups in the 3-,4-, 7-, and 8- positions, a remarkably long-lived (2.8 μs in DCM) copper(I) bis-phenanthroline complex, [Cu(dsbtmp)2]+, has been synthesized and characterized. Unlike other copper(I) diimine complexes, [Cu(dsbtmp)2]+ also retains a μs lifetime in coordinating solvents such as acetonitrile and water as a result of the cooperative sterics inherent in the molecular design. Preliminary results on the use of this complex in hydrogen-forming homogeneous photocatalysis is presented. Photon upconversion based on sensitized triplet-triplet annihilation (TTA) represents a photochemical means to generate high-energy photons (or high-energy chemical products) from low-energy excitation, having potential applications in solar energy conversion and solar fuels producing devices. For the first time, synthetically facile and earth abundant Cu(I) MLCT sensitizers have been successfully incorporated into two distinct photochemical upconversion schemes, affording both red-to-green and orange-to-blue wavelength conversions. Preliminary results on aqueous-based photochemical upconversion as well as intramolecular Sn(IV) porphyrins containing axially coordinated aromatic hydrocarbon

Geochemistry and geochronology of the mafic dikes in the Taipusi ...

Indian Academy of Sciences (India)

25

several large linear faults as dividing lines (Fig. 1b; Jahn ... activity between Bainaimiao city and Chifeng city (Stampfli and Borel, 2002). The formation ... In addition, previous studies in the area paid more attention to the geochemistry and.

Been there before? Examining "familiarity" as a moderator for discriminating between true and false intentions.

Science.gov (United States)

Knieps, Melanie; Granhag, Pär A; Vrij, Aldert

2014-01-01

Prospection is thinking about possible future states of the world. Commitment to perform a future action-commonly referred to as intention-is a specific type of prospection. This knowledge is relevant when trying to assess whether a stated intention is a lie or the truth. An important observation is that thinking of, and committing to, future actions often evoke vivid and detailed mental images. One factor that affects how specific a person experiences these simulations is location-familiarity. The purpose of this study was to examine to what extent location-familiarity moderates how liars and truth tellers describe a mental image in an investigative interview. Liars were instructed to plan a criminal act and truth tellers were instructed to plan a non-criminal act. Before they could carry out these acts, the participants were intercepted and interviewed about the mental images they may have had experienced in this planning phase. Truth tellers told the truth whereas liars used a cover story to mask their criminal intentions. As predicted, the results showed that the truth tellers reported a mental image significantly more often than the liars. If a mental image was reported, the content of the descriptions did not differ between liars and truth tellers. In a post interview questionnaire, the participants rated the vividness (i.e., content and clarity) of their mental images. The ratings revealed that the truth tellers had experienced their mental images more vividly during the planning phase than the liars. In conclusion, this study indicates that both prototypical and specific representations play a role in prospection. Although location-familiarity did not moderate how liars and truth tellers describe their mental images of the future, this study allows some interesting insights into human future thinking. How these findings can be helpful for distinguishing between true and false intentions will be discussed.

Been there before? Examining “familiarity” as a moderator for discriminating between true and false intentions

Science.gov (United States)

Knieps, Melanie; Granhag, Pär A.; Vrij, Aldert

2014-01-01

Prospection is thinking about possible future states of the world. Commitment to perform a future action—commonly referred to as intention—is a specific type of prospection. This knowledge is relevant when trying to assess whether a stated intention is a lie or the truth. An important observation is that thinking of, and committing to, future actions often evoke vivid and detailed mental images. One factor that affects how specific a person experiences these simulations is location-familiarity. The purpose of this study was to examine to what extent location-familiarity moderates how liars and truth tellers describe a mental image in an investigative interview. Liars were instructed to plan a criminal act and truth tellers were instructed to plan a non-criminal act. Before they could carry out these acts, the participants were intercepted and interviewed about the mental images they may have had experienced in this planning phase. Truth tellers told the truth whereas liars used a cover story to mask their criminal intentions. As predicted, the results showed that the truth tellers reported a mental image significantly more often than the liars. If a mental image was reported, the content of the descriptions did not differ between liars and truth tellers. In a post interview questionnaire, the participants rated the vividness (i.e., content and clarity) of their mental images. The ratings revealed that the truth tellers had experienced their mental images more vividly during the planning phase than the liars. In conclusion, this study indicates that both prototypical and specific representations play a role in prospection. Although location-familiarity did not moderate how liars and truth tellers describe their mental images of the future, this study allows some interesting insights into human future thinking. How these findings can be helpful for distinguishing between true and false intentions will be discussed. PMID:25071648

Investigations of the electronic, magnetic and crystalline structure of perovskite oxides and an oxide-oxide interface

International Nuclear Information System (INIS)

Raisch, Christoph Werner

2013-01-01

The mineral perovskite CaTiO 3 lends its name to the class of compounds with composition ABX 3 , which have the same type of crystal structure known as the perovskite structure. Here, A and B are cations while X is typically a halogen or oxygen anion. The bigger cation A and the X anions form a cubic close packing AX 3 with the smaller B cation occupying one quarter of the octahedral sites. The underlying work deals with three classes of perovskite oxides, the ''titanates'', the ''cuprates'' and the ''manganites'', where the central B cations are Ti, Cu and Mn respectively, each class with very characteristic properties. Strontium titanate, STO, like so many oxides is an insulator, yet paraelectric and diamagnetic. It gained special interest as a commercially available, high quality substrate for the growth of hightemperature superconductors and other oxide thin films. The huge class of perovskite cuprates is most famous for members like YBCO, the well-known high-temperature superconductor. Finally, the doped, mixed-valent perovskite manganites LXMO (here X = Sr, Ca, Ce) have to be mentioned. They appeared on the screen of experimental and theoretical physicists in the 1950s when ferromagnetism and magnetoresistance were discovered in these compounds, leading to the theory of double exchange. In the mid-1990s they further increased their importance, following the description of the Jahn-Teller polaron and the discovery of the colossal magnetoresistance phenomenom. They may be derived from an insulator, LaMnO 3 , but the doping allows the control of electric and magnetic properties over a wide range, i.e. from insulating behavior to metallic conductivity or from diamagnet to ferromagnet. Further notable effects are found when electric or magnetic fields are applied, including spin polarization and the related effect of colossal magnetoresistance. These substances may be approximated as consisting of

Untitled

Indian Academy of Sciences (India)

Metropolis N, Rosenblueth A, Rosenblueth M, Teller A and Teller E 1953 Equation of state calculations by fast computing machines; J. Chem. Phys, 21 1087-1092 ... its properties and use for automated interpretation; Geophysics 37 507-517 y.

Can News Draw Blood The Impact of Media Coverage on the Number and Severity of Terror Attacks

Science.gov (United States)

2016-05-01

groups devote to carrying out attacks, p are the costs of a single attack, and E measures the effectiveness of terrorist attacks, e.g. the average...8i) h A. h · A ( b) (r r ) A 2(a+b)JP , w ere IS t e expressiOn = a+ jP u3 + s- u1 . s A2 + 4bEw > 0, all three eigenvalues will be elements of the...May 2016 164 Jahn, Vera ; Steinhardt, Max Friedrich : Innovation and Immigration - Insights from a Placement Policy, February 2016 163 Beckmann

Uranium Hydrogeochemical and Stream Sediment Reconnaissance data from the area of the Teller, Bendeleben, Candle, and Kateel River Quadrangles, Seward Peninsula and vicinity, Alaska

International Nuclear Information System (INIS)

Sharp, R.R. Jr.; Hill, D.E.

1978-05-01

During July-August 1976, 2026 natural waters and 2085 bottom sediments were collected from 2209 sample locations (at a nominal density of one location each 23 km 2 ) on streams and small lakes throughout the Teller, Bendeleben, Candle, and western one-third of the Kateel River NTMS quadrangles, Alaska. Total uranium was measured in the waters by fluorometry and in the sediments and a few waters by delayed-neutron counting. The uranium content of the waters ranged from below the detection limit of 0.02 parts per billion (ppB) to a high of 14.50 ppB, averaging 0.44 ppB, and that of the sediments ranged from a low of 0.2 parts per million (ppM) to a high of 107.4 ppM, averaing 3.93 ppM. The uranium data for water and sediment are separately presented--as computer listings that include pertinent field measurements from each location, as graphically portrayed concentration overlays at 1:250,000 scale for each quadrangle, and as reduced figures showing contours drawn at various concentration levels for each quadrangle--and their areal distributions are compared and correlated with the known features and uranium showings. A test of increasingly detailed methods of data evaluation shows that the more extensive the evaluation, the more useful the reconnaissance uranium data are likely to be. The validity and potential usefulness of the HSSR uranium data are conclusively substantiated by the fact that evidence of all 23 of the reported uranium showings in the 50,000-km 2 study area can be discerned. Several new locations of interest for further field investigation are identified in each of the quadrangles, and most notably in the Bendeleben Mountains. However, the data presented would appear equally useful in guiding field investigation around the uranium occurrences already known, as noteworthy samples often come from close by but on tributary drainages adjacent, opposite, or above them

Isospin-symmetry-breaking effects in A∼70 nuclei within beyond-mean-field approach

Energy Technology Data Exchange (ETDEWEB)

Petrovici, A.; Andrei, O. [National Institute for Physics and Nuclear Engineering, R-077125 Bucharest (Romania)

2015-02-24

Particular isospin-symmetry-breaking probes including Coulomb energy differences (CED), mirror energy differences (MED), and triplet energy differences (TED) manifest anomalies in the A∼70 isovector triplets of nuclei. The structure of proton-rich nuclei in the A∼70 mass region suggests shape coexistence and competition between pairing correlations in different channels. Recent results concerning the interplay between isospin-mixing and shape-coexistence effects on exotic phenomena in A∼70 nuclei obtained within the beyond-mean-field complex Excited Vampir variational model with symmetry projection before variation using a realistic effective interaction in a relatively large model space are presented. Excited Vampir predictions concerning the Gamow-Teller β decay to the odd-odd N=Z {sup 66}As and {sup 70}Br nuclei correlated with the pair structure analysis in the T=1 and T=0 channel of the involved wave functions are discussed.

Many-Body Effects on the Thermodynamics of Fluids, Mixtures, and Nanoconfined Fluids.

Science.gov (United States)

Desgranges, Caroline; Delhommelle, Jerome

2015-11-10

Using expanded Wang-Landau simulations, we show that taking into account the many-body interactions results in sharp changes in the grand-canonical partition functions of single-component systems, binary mixtures, and nanoconfined fluids. The many-body contribution, modeled with a 3-body Axilrod-Teller-Muto term, results in shifts toward higher chemical potentials of the phase transitions from low-density phases to high-density phases and accounts for deviations of more than, e.g., 20% of the value of the partition function for a single-component liquid. Using the statistical mechanics formalism, we analyze how this contribution has a strong impact on some properties (e.g., pressure, coexisting densities, and enthalpy) and a moderate impact on others (e.g., Gibbs or Helmholtz free energies). We also characterize the effect of the 3-body terms on adsorption isotherms and adsorption thermodynamic properties, thereby providing a full picture of the effect of the 3-body contribution on the thermodynamics of nanoconfined fluids.

Science and Technology Review January/February 2008

International Nuclear Information System (INIS)

Chinn, D J

2007-01-01

This month's issue has the following articles: (1) The Edward Teller Centennial--Commentary by George H. Miller; (2) Edward Teller's Century: Celebrating the Man and His Vision--Colleagues at the Laboratory remember Edward Teller, cofounder of Lawrence Livermore, adviser to U.S. presidents, and physicist extraordinaire, on the 100th anniversary of his birth; (3) Quark Theory and Today's Supercomputers: It's a Match--Thanks to the power of BlueGene/L, Livermore has become an epicenter for theoretical advances in particle physics; and (4) The Role of Dentin in Tooth Fracture--Studies on tooth dentin show that its mechanical properties degrade with age

Soliton-soliton effective interaction

International Nuclear Information System (INIS)

Maki, J.N.

1986-01-01

A scheme of semi-phenomenological quantization is proposed for the collision process of two equal size envelopes-solitons provided by nonlinear Schroedinger equation. The time advance due to two envelopes-solitons collision was determined. Considering the solitons as puntual particles and using the description of classical mechanics, the effective envelope soliton-envelope soliton attractive potential, denominated modified Poschl-Teller potential. The obtainment of this potential was possible using the information in from of system memory, done by an analytical expression of time delay. Such system was quantized using this effective potential in Schroeding equation. The S col matrix of two punctual bodies was determined, and it is shown that, in the limit of 1 2 2 /mN 4 it reproduces the exact S 2N matrix obtained from soliton packet wich incurs on another soliton packet. Every ones have the same mass, interacts by contact force between two bodies. These packets have only one bound state, i e, do not have excited states. It was verified that, using the S col matrix, the binding energy of ground state of the system can be obtained, which is coincident with 2N particles in the 1/N approximation. In this scheme infinite spurious bound states are found (M.C.K.) [pt

Historiografie biologie a jejich grande dame Ilse Jahnová (1922-2010)

Czech Academy of Sciences Publication Activity Database

Hermann, Tomáš; Šimůnek, Michal V.

2010-01-01

Roč. 43, č. 4 (2010), s. 249-254 ISSN 0300-4414 R&D Projects: GA ČR GPP410/10/P550 Institutional research plan: CEZ:AV0Z80630520 Keywords : Ilse Jahn * historiography of biology * history of science Subject RIV: AB - History

Browse Title Index

African Journals Online (AJOL)

Items 151 - 200 of 235 ... Kalaivani Priyadarshini Sekaran, Aiya Subramani Parasuraman, Dinakaran Michael Rajamani. Vol 4, No 1 (2014), Molecular identification of nontuberculous mycobacteria ... Alison M. Lee, Naomi Guppy, John Bainbridge, Hanne Jahns. Vol 3, No 2 (2013), Non-invasive assessment of equine muscular ...

Nuclear structure information from nucleon-nucleus scattering experiments at TRIUMF

International Nuclear Information System (INIS)

Haeusser, O.

1989-02-01

We discuss a variety of forward-angle measurements of cross sections for (n,p), (p,p') and (p,n) reactions which were carried out using the medium-resolution spectrometer (MRS) at TRIUMF. The ratio of L=0 isovector spinflip cross section and Gamow-Teller strength has been investigated at 200-450 MeV for several strong transitions of known B(GT) in p-shell nuclei. Isospin symmetry in N-nucleus reactions has been tested for Gamow-Teller transitions to isospin triads in A=6 and A=12 nuclei. The prospects of identifying orbital and meson exchange current contributions in M1 transitions from a state-by-state comparison of M1 and Gamow-Teller strength in sd shell nuclei are discussed. Finally we describe a test of the Gamow-Teller sum rule in 54 Fe where both S - and S + strength are substantial and have been extracted from a multipole decomposition of (p,n) and (n,p) angular distributions

Microscopic insight into properties and electronic instabilities of impurities in cubic and lower symmetry insulators: the influence of pressure

International Nuclear Information System (INIS)

Moreno, M; Barriuso, M T; Aramburu, J A; GarcIa-Fernandez, P; GarcIa-Lastra, J M

2006-01-01

This article reviews the microscopic origin of properties due to transition-metal (TM) impurities, M, in insulator materials. Particular attention is paid to the influence of pressure upon impurity properties. Basic concepts such as the electronic localization in an MX N complex, the electrostatic potential, V R , arising from the rest of the lattice ions or the elastic coupling of the complex to the host lattice are initially exposed. The dependence of optical and magnetic parameters on the impurity-ligand distance, R, in cubic lattices is discussed in a first step. Emphasis is put on the actual origin of the R dependence of 10Dq. Examples revealing that laws for strict cubic symmetry cannot in general be transferred to lower symmetries are later given. This relevant fact is shown to come from allowed hybridizations like nd-(n+1)s as well as the influence of V R . As a salient feature the different colour in ruby and emerald is stressed to arise from distinct V R potentials in Al 2 O 3 and Be 3 Si 6 Al 2 O 18 . The last part of this review deals with electronic instabilities. The phenomena associated with the Jahn-Teller (JT) effect in cubic lattices, the origin of the energy barrier among equivalent minima and the existence of coherent tunnelling in systems like MgO:Cu 2+ are discussed. An increase of elastic coupling is pointed out to favour a transition from an elongated to a compressed equilibrium conformation. Interestingly the equilibrium geometry of JT ions in non-cubic lattices is shown to be controlled by mechanisms different to those in cubic systems, V R playing again a key role. The relevance of first principles calculations for clarifying the subtle mechanisms behind off-centre instabilities is also pointed out. Examples concern monovalent and divalent TM impurities in lattices with the CaF 2 structure. The instability due to the transition from the ground to an excited state is finally considered. For complexes with significant elastic coupling

TOPICAL REVIEW: Microscopic insight into properties and electronic instabilities of impurities in cubic and lower symmetry insulators: the influence of pressure

Science.gov (United States)

Moreno, M.; Barriuso, M. T.; Aramburu, J. A.; García-Fernández, P.; García-Lastra, J. M.

2006-05-01

This article reviews the microscopic origin of properties due to transition-metal (TM) impurities, M, in insulator materials. Particular attention is paid to the influence of pressure upon impurity properties. Basic concepts such as the electronic localization in an MXN complex, the electrostatic potential, VR, arising from the rest of the lattice ions or the elastic coupling of the complex to the host lattice are initially exposed. The dependence of optical and magnetic parameters on the impurity-ligand distance, R, in cubic lattices is discussed in a first step. Emphasis is put on the actual origin of the R dependence of 10Dq. Examples revealing that laws for strict cubic symmetry cannot in general be transferred to lower symmetries are later given. This relevant fact is shown to come from allowed hybridizations like nd-(n+1)s as well as the influence of VR. As a salient feature the different colour in ruby and emerald is stressed to arise from distinct VR potentials in Al2O3 and Be3Si6Al2O18. The last part of this review deals with electronic instabilities. The phenomena associated with the Jahn-Teller (JT) effect in cubic lattices, the origin of the energy barrier among equivalent minima and the existence of coherent tunnelling in systems like MgO:Cu2+ are discussed. An increase of elastic coupling is pointed out to favour a transition from an elongated to a compressed equilibrium conformation. Interestingly the equilibrium geometry of JT ions in non-cubic lattices is shown to be controlled by mechanisms different to those in cubic systems, VR playing again a key role. The relevance of first principles calculations for clarifying the subtle mechanisms behind off-centre instabilities is also pointed out. Examples concern monovalent and divalent TM impurities in lattices with the CaF2 structure. The instability due to the transition from the ground to an excited state is finally considered. For complexes with significant elastic coupling vibrational frequencies

Microscopic insight into properties and electronic instabilities of impurities in cubic and lower symmetry insulators: the influence of pressure.

Science.gov (United States)

Moreno, M; Barriuso, M T; Aramburu, J A; García-Fernández, P; García-Lastra, J M

2006-05-03

This article reviews the microscopic origin of properties due to transition-metal (TM) impurities, M, in insulator materials. Particular attention is paid to the influence of pressure upon impurity properties. Basic concepts such as the electronic localization in an MX(N) complex, the electrostatic potential, V(R), arising from the rest of the lattice ions or the elastic coupling of the complex to the host lattice are initially exposed. The dependence of optical and magnetic parameters on the impurity-ligand distance, R, in cubic lattices is discussed in a first step. Emphasis is put on the actual origin of the R dependence of 10Dq. Examples revealing that laws for strict cubic symmetry cannot in general be transferred to lower symmetries are later given. This relevant fact is shown to come from allowed hybridizations like nd-(n+1)s as well as the influence of V(R). As a salient feature the different colour in ruby and emerald is stressed to arise from distinct V(R) potentials in Al(2)O(3) and Be(3)Si(6)Al(2)O(18). The last part of this review deals with electronic instabilities. The phenomena associated with the Jahn-Teller (JT) effect in cubic lattices, the origin of the energy barrier among equivalent minima and the existence of coherent tunnelling in systems like MgO:Cu(2+) are discussed. An increase of elastic coupling is pointed out to favour a transition from an elongated to a compressed equilibrium conformation. Interestingly the equilibrium geometry of JT ions in non-cubic lattices is shown to be controlled by mechanisms different to those in cubic systems, V(R) playing again a key role. The relevance of first principles calculations for clarifying the subtle mechanisms behind off-centre instabilities is also pointed out. Examples concern monovalent and divalent TM impurities in lattices with the CaF(2) structure. The instability due to the transition from the ground to an excited state is finally considered. For complexes with significant elastic coupling

Evolution of the structural and multiferroic properties of PbFe{sub 2/3}W{sub 1/3}O{sub 3} ceramics upon Mn-doping

Energy Technology Data Exchange (ETDEWEB)

Ivanov, S.A. [Center of Materials Science, Karpov' Institute of Physical Chemistry, Vorontsovo Pole 10, Moscow, 105064 (Russian Federation); Department of Engineering Sciences, Uppsala University, Box 534, 751 21, Uppsala (Sweden); Bush, A.A. [Moscow State University of Information Technologies, RadioEngineering and Electronics, pr.Vernadskogo 78, Moscow, 119454 (Russian Federation); Ritter, C. [Institute Laue-Langevin, BP 156, F-38042, Grenoble (France); Behtin, M.A. [Moscow State University of Information Technologies, RadioEngineering and Electronics, pr.Vernadskogo 78, Moscow, 119454 (Russian Federation); Cherepanov, V.M. [National Research Centre Kurchatov Institute, pl. Kurchatova 1, Moscow, 123182 (Russian Federation); Autieri, C.; Kvashnin, Y.O.; Di Marco, I.; Sanyal, B.; Eriksson, O. [Department of Physics and Astronomy, Uppsala University, Box 516, 751 20, Uppsala (Sweden); Kumar, P. Anil; Nordblad, P. [Department of Engineering Sciences, Uppsala University, Box 534, 751 21, Uppsala (Sweden); Mathieu, R., E-mail: roland.mathieu@angstrom.uu.se [Department of Engineering Sciences, Uppsala University, Box 534, 751 21, Uppsala (Sweden)

2017-02-01

The perovskite system Pb(Fe{sub 1-x}Mn{sub x}){sub 2/3}W{sub 1/3}O{sub 3} (0 ≤ x ≤ 1, PFMWO) has been prepared by conventional solid-state reaction under different sintering conditions. Structures and phase composition as well as thermal, magnetic and dielectric properties of the compounds have been systematically investigated experimentally and by first-principles density functional calculations. A clean perovskite phase is established at room temperature for compositions 0 ≤ x ≤ 0.4. Rietveld refinements of X-ray and neutron powder diffraction patterns demonstrate that the compounds crystallize in space group Pm-3m (0 ≤ x ≤ 0.4). The degree of ordering of the Fe and W/Mn cations was found to depend on the concentration of Mn. First-principles calculations suggest that the structural properties of PFMWO are strongly influenced by the Jahn-Teller effect. The PFMWO compounds behave as relaxor ferroelectrics at weak Mn-doping with a dielectric constant that rapidly decreases with increasing Mn content. A low temperature antiferromagnetic G-type order with propagation vector k = (1/2,1/2,1/2) is derived from neutron powder diffraction data for the samples with x ≤ 0.4. However with increasing doping concentration, the magnetic order is perturbed. First-principles calculations show that the dominant exchange coupling is antiferromagnetic and occurs between nearest neighbor Fe atoms. When the system is doped with Mn, a relatively weak ferromagnetic (FM) interaction between Fe and Mn atoms emerges. However, due to the presence of this FM interaction, the correlation length of the magnetic order is greatly shortened already at rather low doping levels. - Highlights: • The perovskite system Pb(Fe{sub 1−x}Mn{sub x}){sub 2/3}W{sub 1/3}O{sub 3} (0 ≤ x ≤ 1, PFMWO) has been synthesized. • The structural, magnetic, and dielectric properties of PFMWO have been investigated. • The degree of ordering of the Fe and W/Mn cations was found to depend on x. �

BOOK REVIEW: Conversations on the Dark Secrets of Physics

Science.gov (United States)

Teller, Edward

2003-07-01

Over many years Edward Teller delivered a course of Physical Science Appreciation Lectures. This book is based on those lectures, which must have been very stimulating. In the preparation of the book, Edward Teller was assisted by his daughter, Wendy Teller, and also by Wilson Talley. On many pages there are footnotes in the form of conversations between 'ET', who explains, and 'WT', who asks intelligent questions. (It is never clear which 'WT' is which.) I mention these footnotes as they contribute enormously to the charm and humour of the book. The book contains numerous anecdotes, many of which were new to me. The verse in the New Yorker, by Harold Furth, recording the famous meeting between Dr Teller and Dr Anti-Teller, is included. Dr Teller's comment is `The remarkable fact is that Harold got paid for the poem'. Dr Anti-Teller's comment is anti-recorded. The topics in the book include simple mechanics, statistical mechanics, electromagnetism, quantum mechanics and 'uses of new knowledge'. Despite its origins, the book does not avoid mathematics ('I will use mathematics because physics without mathematics is meaningless' (p1)), but Teller does attempt to explain the mathematics he uses. In much of the book the mathematics is at school level, but in his treatment of quantum mechanics he uses differential equations. If one skips past the equations then his final chapters are less mathematically demanding. I have enjoyed reading this book. Teller's approach is refreshing, and his coverage comprehensive and generally authoritative. My only disquiet is over his coverage of electrons in solids, where it would be clearer to consider the one-dimensional case first, before treating the three-dimensional case. There is a substantial discussion on the correspondence principle, wave-particle duality and on the uncertainty principle. His disposal of Schrödinger's notorious cat is masterly. There are questions at the end of each chapter. One question is based on a possible

Conversations on the Dark Secrets of Physics

International Nuclear Information System (INIS)

Bocherdsd, P

2003-01-01

Over many years Edward Teller delivered a course of Physical Science Appreciation Lectures. This book is based on those lectures, which must have been very stimulating. In the preparation of the book, Edward Teller was assisted by his daughter, Wendy Teller, and also by Wilson Talley. On many pages there are footnotes in the form of conversations between 'ET', who explains, and 'WT', who asks intelligent questions. (It is never clear which 'WT' is which.) I mention these footnotes as they contribute enormously to the charm and humour of the book. The book contains numerous anecdotes, many of which were new to me. The verse in the New Yorker, by Harold Furth, recording the famous meeting between Dr Teller and Dr Anti-Teller, is included. Dr Teller's comment is 'The remarkable fact is that Harold got paid for the poem'. Dr Anti-Teller's comment is anti-recorded. The topics in the book include simple mechanics, statistical mechanics, electromagnetism, quantum mechanics and 'uses of new knowledge'. Despite its origins, the book does not avoid mathematics ('I will use mathematics because physics without mathematics is meaningless' (p1)), but Teller does attempt to explain the mathematics he uses. In much of the book the mathematics is at school level, but in his treatment of quantum mechanics he uses differential equations. If one skips past the equations then his final chapters are less mathematically demanding. I have enjoyed reading this book. Teller's approach is refreshing, and his coverage comprehensive and generally authoritative. My only disquiet is over his coverage of electrons in solids, where it would be clearer to consider the one-dimensional case first, before treating the three-dimensional case. There is a substantial discussion on the correspondence principle, wave-particle duality and on the uncertainty principle. His disposal of Schroedinger's notorious cat is masterly. There are questions at the end of each chapter. One question is based on a possible