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Sample records for monoclinic kywo42 single

  1. Anisotropy, phonon modes, and free charge carrier parameters in monoclinic β -gallium oxide single crystals

    NASA Astrophysics Data System (ADS)

    Schubert, M.; Korlacki, R.; Knight, S.; Hofmann, T.; Schöche, S.; Darakchieva, V.; Janzén, E.; Monemar, B.; Gogova, D.; Thieu, Q.-T.; Togashi, R.; Murakami, H.; Kumagai, Y.; Goto, K.; Kuramata, A.; Yamakoshi, S.; Higashiwaki, M.

    2016-03-01

    We derive a dielectric function tensor model approach to render the optical response of monoclinic and triclinic symmetry materials with multiple uncoupled infrared and far-infrared active modes. We apply our model approach to monoclinic β -Ga2O3 single-crystal samples. Surfaces cut under different angles from a bulk crystal, (010) and (2 ¯01 ), are investigated by generalized spectroscopic ellipsometry within infrared and far-infrared spectral regions. We determine the frequency dependence of 4 independent β -Ga2O3 Cartesian dielectric function tensor elements by matching large sets of experimental data using a point-by-point data inversion approach. From matching our monoclinic model to the obtained 4 dielectric function tensor components, we determine all infrared and far-infrared active transverse optic phonon modes with Au and Bu symmetry, and their eigenvectors within the monoclinic lattice. We find excellent agreement between our model results and results of density functional theory calculations. We derive and discuss the frequencies of longitudinal optical phonons in β -Ga2O3 . We derive and report density and anisotropic mobility parameters of the free charge carriers within the tin-doped crystals. We discuss the occurrence of longitudinal phonon plasmon coupled modes in β -Ga2O3 and provide their frequencies and eigenvectors. We also discuss and present monoclinic dielectric constants for static electric fields and frequencies above the reststrahlen range, and we provide a generalization of the Lyddane-Sachs-Teller relation for monoclinic lattices with infrared and far-infrared active modes. We find that the generalized Lyddane-Sachs-Teller relation is fulfilled excellently for β -Ga2O3 .

  2. Temperature-dependent index of refraction of monoclinic Ga2O3 single crystal.

    PubMed

    Bhaumik, Indranil; Bhatt, R; Ganesamoorthy, S; Saxena, A; Karnal, A K; Gupta, P K; Sinha, A K; Deb, S K

    2011-11-01

    We present temperature-dependent refractive index along crystallographic b[010] and a direction perpendicular to (100)-plane for monoclinic phase (β) Ga(2)O(3) single crystal grown by the optical floating zone technique. The experimental results are consistent with the theoretical result of Litimein et al.1. Also, the Sellmeier equation for wavelengths in the range of 0.4-1.55 μm is formulated at different temperatures in the range of 30-175 °C. The thermal coefficient of refractive index in the above specified range is ~10(-5)/°C. © 2011 Optical Society of America

  3. Spectroscopic refractive indices of monoclinic single crystal and ceramic Lutetium oxyorthosilicate (LSO) from 200 to 850 nm

    SciTech Connect

    Jellison Jr, Gerald Earle; Specht, Eliot D; Boatner, Lynn A; Singh, David J; Melcher, Charles L

    2012-01-01

    The four real values of the dielectric function tensor of the monoclinic crystal Lu2SiO5 or lutetium oxyorthosilicate (LSO) have been determined using generalized ellipsometry from 200 to 850 nm. The three principal values are fit to the Sellmeier model, and they indicate that the band gap of LSO is less than ~9 eV. The off-diagonal element 12 is non-zero over the entire spectrum, but it is very close to zero for wavelengths longer than ~400 nm, indicating that structurally monoclinic LSO is nearly optically orthorhombic in this wavelength region. The spectroscopic dielectric functions of three isotropic ceramic LSO samples are presented, which are consistent with the dielectric functions of single-crystal LSO when the effects of porosity are included. As a comparison, the dielectric functions are also determined using relativistic electronic structure and optical calculations based on the recently developed potential functional of Tran and Blaha (Phys. Rev. Lett. 102, 226401 (2009).)

  4. Photosensitive structures based on ZnP{sub 2} single crystals of monoclinic and tetragonal modifications: Fabrication and properties

    SciTech Connect

    Rud, V. Yu. Rud, Yu. V.; Vaipolin, A. A.; Bodnar, I. V.; Osipiva, M. A.; Ushakova, T. N.

    2009-07-15

    The method of gas-phase resublimation is used to grow the single-crystals of monoclinic and tetragonal modifications whose composition are identical and corresponds to the ZnP{sub 2} stoichiometry. The crystal-lattice parameters are determined and natural facets of the crystals of both modifications are identified. The obtained single crystals were used to fabricate for the first time the Schottky barriers and welded point structures; the latter exhibited rectification and the photovoltaic effect. On the basis of the first studies of photosensitivity of obtained structures subjected to the natural and linearly polarized radiation, the character of interband transitions is suggested, the values of the band gap are determined, and the influence of the position ordering of atoms on the structures' properties is observed. The phenomenon of natural photopleochroism observed in the structures based on oriented ZnP{sub 2} single crystals were studied. It is concluded that it is possible to use the zinc diphosphide in photoconversion of the intensity and polarization of optical radiation.

  5. Single crystalline monoclinic La0.7Sr0.3MnO3 nanowires with high temperature ferromagnetism

    SciTech Connect

    Carretero-Genevrier, Adrian; Gazquez Alabart, Jaume; Idrobo Tapia, Juan C; Oro, Judith; Arbiol, Jordi; Varela del Arco, Maria; Ferain, Etienne; Rodriguez-Carvajal, Juan; Puig, Teresa; Mestres, Narcis; Obradors, Xavier

    2011-01-01

    Porous mixed-valent manganese oxides are a group of multifunctional materials that can be used as molecular sieves, catalysts, battery materials, and gas sensors. However, material properties and thus activity can vary significantly with different synthesis methods or process conditions, such as temperature and time. Here, we report on a new synthesis route for MnO{sub 2} and LaSr-doped molecular sieve single crystalline nanowires based on a solution chemistry methodology combined with the use of nanoporous polymer templates supported on top of single crystalline substrates. Because of the confined nucleation in high aspect ratio nanopores and of the high temperatures attained, new structures with novel physical properties have been produced. During the calcination process, the nucleation and crystallization of {var_epsilon}-MnO{sub 2} nanoparticles with a new hexagonal structure is promoted. These nanoparticles generated up to 30 {mu}m long and flexible hexagonal nanowires at mild growth temperatures (T{sub g} = 700 C) as a consequence of the large crystallographic anisotropy of {var_epsilon}-MnO{sub 2}. The nanocrystallites of MnO{sub 2} formed at low temperatures serve as seeds for the growth of La{sub 0.7}Sr{sub 0.3}MnO{sub 3} nanowires at growth temperatures above 800 C, through the diffusion of La and Sr into the empty 1D-channels of {var_epsilon}-MnO{sub 2}. Our particular growth method has allowed the synthesis of single crystalline molecular sieve (LaSr-2 x 4) monoclinic nanowires with composition La{sub 0.7}Sr{sub 0.3}MnO{sub 3} and with ordered arrangement of La{sup 3+} and Sr{sup 2+} cations inside the 1D-channels. These nanowires exhibit ferromagnetic ordering with strongly enhanced Curie temperature (T{sub c} > 500 K) that probably results from the new crystallographic order and from the mixed valence of manganese.

  6. Growth, vibrational and luminescence analysis of monoclinic KGd(1-x)Prx(WO4)2 (x=0.005, 0.02, 0.05) single crystals

    NASA Astrophysics Data System (ADS)

    Thangaraju, D.; Moorthy Babu, S.; Durairajan, A.; Balaji, D.; Samuel, P.; Hayakawa, Y.

    2013-01-01

    Growth of pure KGW, 0.5, 2 and 5 wt% Pr3+ doped KGd(WO4)2 single crystals were carried out using top seeded solution growth (TSSG) method with K2WO4 as flux. Growth parameters that include the cooling rate and pulling rate were modified to achieve transparent doped crystals to that of pure crystals. Optically polished samples were used for optical and structural studies. Structure of grown crystals was confirmed and lattice parameter values were calculated using single crystal X-ray diffractometer. Both pure and doped crystals belong to the monoclinic phase with C2/c space group. When compared to pure matrix of KGW, some notable changes were observed in the lattice parameter values of doped crystals. It may be due to the ionic radii mismatch of replacing praseodymium ion in the place of gadolinium ion. Absorption and emission measurements were carried out for the 2 mm thick polished samples. The doped samples show a very good transparency with an intense absorption band around the blue region of the spectrum with additional absorption peaks in the IR region as well. Strong red emission was observed in the emission spectrum. The energy levels and their corresponding transitions were figured out in Pr3+ ions inside the matrix. Emission characteristics were compared for different dopant concentration. Raman spectra reveal the intense tungstate vibrational modes in the higher frequency region. Comparison of pure and doped samples reveal that there is no significant change in vibrational modes at higher doping concentration.

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

    NASA Astrophysics Data System (ADS)

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

    2016-12-01

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

  8. Two-photon excited fluorescence in the LYB:Eu monoclinic crystal: towards a new scheme of single-beam dual-voxel direct laser writing in crystals.

    PubMed

    Petit, Y; Royon, A; Marquestaut, N; Dussauze, M; Fargues, A; Veber, P; Jubera, V; Cardinal, T; Canioni, L

    2013-01-14

    We report on two-photon excited fluorescence in the oriented Eu(3+)doped LYB monoclinic crystal under femtosecond laser tight focusing. Due to spatial walk-off, the two polarization modes of the incident femtosecond beam simultaneously provide the independent excitation of two distinct focuses, leading to a single-beam dual-voxel nonlinear excitation of fluorescence below material modification threshold. These observations emphasize on the anisotropy of both two-photon absorption as well as fluorescence emission. They demonstrate the localized control of the nonlinear energy deposit, thanks to the adjustment of both the input power and polarization, by properly balancing the injected energy in each voxel. Such approach should be considered for future direct laser writing of waveguides in propagation directions out of the dielectric axes, so as to optimally cope with the highly probable anisotropy of laser-induced material modification thresholds in these crystals. These results open new ways for further potential developments in direct laser writing as the simultaneous inscription of double-line structures for original waveguides processes.

  9. Temperature dependence of the dielectric tensor of monoclinic Ga2O3 single crystals in the spectral range 1.0-8.5 eV

    NASA Astrophysics Data System (ADS)

    Sturm, C.; Schmidt-Grund, R.; Zviagin, V.; Grundmann, M.

    2017-08-01

    The full dielectric tensor of monoclinic Ga2O3 (β-phase) was determined by generalized spectroscopic ellipsometry in the spectral range from 1.0 eV up to 8.5 eV and temperatures in the range from 10 K up to 300 K. By using the oriented dipole approach, the energies and broadenings of the excitonic transitions are determined as a function of the temperature, and the exciton-phonon coupling properties are deduced.

  10. Evidence for monoclinic distortion in the ground state phase of underdoped La{sub 1.95}Sr{sub 0.05}CuO{sub 4}: A single crystal neutron diffraction study

    SciTech Connect

    Singh, Anar Schefer, Jürg; Frontzek, Matthias; Sura, Ravi; Conder, Kazimierz; Sibille, Romain F.; Ceretti, Monica; Paulus, Werner

    2016-03-28

    The existing controversy about the symmetry of the crystal structure of the ground state of the critical doped La{sub 1.95}Sr{sub 0.05}CuO{sub 4} has been resolved by analyzing the single crystal neutron diffraction data collected between 5 and 730 K. We observed small but significant intensities for “forbidden” reflections given by extinction rules of the orthorhombic Bmab space group at low temperatures. A careful investigation of neutron diffraction data reveals that the crystal structure of La{sub 1.95}Sr{sub 0.05}CuO{sub 4} at 5 K is monoclinic with B2/m (2/m 1 1) space group. The monoclinic structure emerges from the orthorhombic structure in a continuous way; however, the structure is stable below ∼120 K which agrees with other observed phenomena. Our results on symmetry changes are crucial for the interpretation of physical properties also in other high temperature superconductors with similar structures.

  11. Evidence for monoclinic distortion in the ground state phase of underdoped La1.95Sr0.05CuO4: A single crystal neutron diffraction study

    SciTech Connect

    Singh, Anar; Schefer, Jurg; Sura, Ravi; Conder, Kazimierz; Sibille, Romain F.; Ceretti, Monica; Frontzek, Matthias; Paulus, Werner

    2016-03-24

    The existing controversy about the symmetry of the crystal structure of the ground state of the critical doped La1.95Sr0.05CuO4 has been resolved by analyzing the single crystal neutron diffraction data collected between 5 and 730 K. We observed small but significant intensities for "forbidden" reflections given by extinction rules of the orthorhombic Bmab space group at low temperatures. A careful investigation of neutron diffraction data reveals that the crystal structure of La1.95Sr0.05CuO4 at 5 K is monoclinic with B2/m (2/m 1 1) space group. The monoclinic structure emerges from the orthorhombic structure in a continuous way; however, the structure is stable below similar to 120K which agrees with other observed phenomena. Lastly, our results on symmetry changes are crucial for the interpretation of physical properties also in other high temperature superconductors with similar structures.

  12. Evidence for monoclinic distortion in the ground state phase of underdoped La1.95Sr0.05CuO4: A single crystal neutron diffraction study

    DOE PAGES

    Singh, Anar; Schefer, Jurg; Sura, Ravi; ...

    2016-03-24

    The existing controversy about the symmetry of the crystal structure of the ground state of the critical doped La1.95Sr0.05CuO4 has been resolved by analyzing the single crystal neutron diffraction data collected between 5 and 730 K. We observed small but significant intensities for "forbidden" reflections given by extinction rules of the orthorhombic Bmab space group at low temperatures. A careful investigation of neutron diffraction data reveals that the crystal structure of La1.95Sr0.05CuO4 at 5 K is monoclinic with B2/m (2/m 1 1) space group. The monoclinic structure emerges from the orthorhombic structure in a continuous way; however, the structure ismore » stable below similar to 120K which agrees with other observed phenomena. Lastly, our results on symmetry changes are crucial for the interpretation of physical properties also in other high temperature superconductors with similar structures.« less

  13. First-principles calculations of high-pressure iron-bearing monoclinic dolomite and single-cation carbonates with internally consistent Hubbard U

    NASA Astrophysics Data System (ADS)

    Solomatova, Natalia V.; Asimow, Paul D.

    2017-08-01

    It has been proposed that iron has a significant effect on the relative stability of carbonate phases at high pressures, possibly even stabilizing double-cation carbonates (e.g., dolomite) with respect to single-cation carbonates (e.g., magnesite, aragonite and siderite). X-ray diffraction experiments have shown that dolomite transforms at 35 GPa to a high-pressure polymorph that is stable to decomposition; however, there has been disagreement on the structure of the high-pressure phase (Mao et al. in Geophys Res Lett 38, 2011. doi: 10.1029/2011GL049519; Merlini et al. in Proc Natl Acad Sci 109:13509-13514, 2012. doi: 10.1073/pnas.1201336109). Ab initio calculations interfaced with an evolutionary structure prediction algorithm demonstrated that a C2/c polymorph of pure CaMg(CO3)2 dolomite is more stable than previously reported structures (Solomatova and Asimow in Am Mineral 102:210-215, 2017, doi: 10.2138/am-2017-5830). In this study, we calculate the relative enthalpies up to 80 GPa for a set of carbonate phases including Fe-bearing solutions and endmembers, using the generalized gradient approximation and a Hubbard U parameter calculated through linear response theory to accurately characterize the electronic structure of Fe. When calculated with a constant U of 4 eV, the spin transition pressure of (Mg,Fe)CO3 agrees well with experiments, whereas an internally consistent U overestimates the spin transition pressure by 50 GPa. However, whether we use constant or internally consistent U values, a higher iron concentration increases the stability field of dolomite C2/c with respect to single-cation carbonate assemblages, but iron-free dolomite is not stable with respect to single-cation carbonates at any pressure. Thus, high-pressure polymorphs of Fe-bearing dolomite could in fact represent an important reservoir for carbon storage within oxidized sections of Earth's mantle.

  14. Polarized IR reflectance spectra of the monoclinic single crystal K2Ni(SO4)2.6H2O: dispersion analysis, dielectric and optical properties.

    PubMed

    Ivanovski, Vladimir; Mayerhöfer, Thomas G; Popp, Jürgen; Petrusevski, Vladimir M

    2008-02-01

    Polarized IR reflectance spectra of K2Ni(SO4)2.6H2O single crystal (belonging to the group of Tutton salts) were recorded at near-normal incidence. From the dispersion analysis performed on the spectra recorded from the ac crystal plane, mode parameters: transversal frequency, oscillator strength, attenuation constant and the orientation of the transition moment were determined. The polarized spectrum along the b crystallographic axis was also recorded and a dispersion analysis performed. Comparison between the spectroscopically obtained transition moment directions with those obtained from the structure data for various modes is discussed. All dielectric tensor component values were obtained for the whole mid-IR frequency range. Also, the real and the imaginary parts of the complex indexes of refraction for the waves with wave vector in the direction of the b crystallographic axis and in the ac plane (when the direction of the electric vector is oriented along the b axis) were found as functions of frequency.

  15. Superhard monoclinic polymorph of carbon.

    PubMed

    Li, Quan; Ma, Yanming; Oganov, Artem R; Wang, Hongbo; Wang, Hui; Xu, Ying; Cui, Tian; Mao, Ho-Kwang; Zou, Guangtian

    2009-05-01

    We report a novel phase of carbon possessing a monoclinic C2/m structure (8 atoms/cell) identified using an ab initio evolutionary structural search. This polymorph, which we call M-carbon, is related to the (2x1) reconstruction of the (111) surface of diamond and can also be viewed as a distorted (through sliding and buckling of the sheets) form of graphite. It is stable over cold-compressed graphite above 13.4 GPa. The simulated x-ray diffraction pattern and near K-edge spectroscopy are in satisfactory agreement with the experimental data [W. L. Mao, Science 302, 425 (2003)10.1126/science.1089713] on overcompressed graphite. The hardness and bulk modulus of this new carbon polymorph are calculated to be 83.1 and 431.2 GPa, respectively, which are comparable to those of diamond.

  16. Superhard Monoclinic Polymorph of Carbon

    SciTech Connect

    Li, Quan; Ma, Yanming; Oganov, Artem R.; Wang, Hongbo; Wang, Hui; Xu, Ying; Cui, Tian; Mao, Ho-Kwang; Zou, Guangtian; Jilin; SBU; CIW

    2009-05-08

    We report a novel phase of carbon possessing a monoclinic C2/m structure (8 atoms/cell) identified using an ab initio evolutionary structural search. This polymorph, which we call M-carbon, is related to the (2x1) reconstruction of the (111) surface of diamond and can also be viewed as a distorted (through sliding and buckling of the sheets) form of graphite. It is stable over cold-compressed graphite above 13.4 GPa. The simulated x-ray diffraction pattern and near K-edge spectroscopy are in satisfactory agreement with the experimental data [W.L. Mao et al., Science 302, 425 (2003)] on overcompressed graphite. The hardness and bulk modulus of this new carbon polymorph are calculated to be 83.1 and 431.2 GPa, respectively, which are comparable to those of diamond.

  17. Synthetic smythite and monoclinic Fe3S4

    NASA Astrophysics Data System (ADS)

    Fleet, Michael E.

    1982-11-01

    Smythite and monoclinic Fe3S4 have been identified by X-ray diffraction procedures in quenched ironsulfide compositions. Both phases appear to be metastable under the conditions of the experiments and their development is structurally induced. Smythite occurs as a coherent twinned intergrowth with hexagonal 3C pyrrhotite. Individual single crystals contain about 50% smythite. Reciprocal lattice rows with h-k ≠ 3n show continuous diffraction streaks. The available data suggest that smythite forms via a “polytypic” displacive transformation, by the introduction of stacking faults in the hexagonal close-packed layers of S atoms in high-temperature 1C pyrrhotite. This is analogous to the transformation of 2H wurtzite to intermediate ordered and disordered ZnS layer sequences. The ideal formula of smythite appears to be Fe13S16. Monoclinic Fe3S4 ( a=5.93, b=3.42, c=10.64 Å, β=91.9°) is present in amounts up to 25% of total sulfides. It has a derivative NiAs-type structure, and is isomorphous with monoclinic Cr3S4 and Fe3Se4. It occurs as small lenticular lamellae within grains of 3C pyrrhotite, and apparently corresponds to the unidentified lamellar phase of Arnold (1962). The lamellae have a rhombohedral morphology, with a habit plane close to {1011}. In single crystal grains of pyrrhotite, monoclinic Fe3S4 in twinned in a manner consistent with transformation from high-temperature 1C pyrrhotite. Although Fe3S4 lamellae have the general appearance of plate martensite, they do not represent a diffusionless transformation.

  18. Protonated Forms of Monoclinic Zirconia: A Theoretical Study

    SciTech Connect

    Mantz, Yves A.; Gemmen, Randall S.

    2010-05-06

    In various materials applications of zirconia, protonated forms of monoclinic zirconia may be formed, motivating their study within the framework of density-functional theory. Using the HCTH/120 exchange-correlation functional, the equations of state of yttria and of the three low-pressure zirconia polymorphs are computed, to verify our approach. Next, the favored charge state of a hydrogen atom in monoclinic zirconia is shown to be positive for all Fermilevel energies in the band gap, by the computation of defect formation energies.This result is consistent with a single previous theoretical prediction at midgap as well as muonium spectroscopy experiments. For the formally positively (+1e) charged system of a proton in monoclinic zirconia (with a homogeneous neutralizing background charge densityimplicitly included), modeled using up to a 3 x 3 x 3 arrangement of unit cells, different stable and metastable structures are identified. They are similar to those structures previously proposed for the neutral system of hydrogen-doedmonoclinic zirconia, at a similar level of theory. As predicted using the HCTH/120 functional, the lowest energy structure of the proton bonded to one of the two available oxygen atom types, O1, is favored by 0.39 eV compared to that of the proton bonded to O2. The rate of proton transfer between O1 ions is slower than that for hydrogen-dopedmonoclinic zirconia, whose transition-state structures may be lowered in energy by the extra electron.

  19. Phase field modeling of tetragonal to monoclinic phase transformation in zirconia

    NASA Astrophysics Data System (ADS)

    Mamivand, Mahmood

    Zirconia based ceramics are strong, hard, inert, and smooth, with low thermal conductivity and good biocompatibility. Such properties made zirconia ceramics an ideal material for different applications form thermal barrier coatings (TBCs) to biomedicine applications like femoral implants and dental bridges. However, this unusual versatility of excellent properties would be mediated by the metastable tetragonal (or cubic) transformation to the stable monoclinic phase after a certain exposure at service temperatures. This transformation from tetragonal to monoclinic, known as LTD (low temperature degradation) in biomedical application, proceeds by propagation of martensite, which corresponds to transformation twinning. As such, tetragonal to monoclinic transformation is highly sensitive to mechanical and chemomechanical stresses. It is known in fact that this transformation is the source of the fracture toughening in stabilized zirconia as it occurs at the stress concentration regions ahead of the crack tip. This dissertation is an attempt to provide a kinetic-based model for tetragonal to monoclinic transformation in zirconia. We used the phase field technique to capture the temporal and spatial evolution of monoclinic phase. In addition to morphological patterns, we were able to calculate the developed internal stresses during tetragonal to monoclinic transformation. The model was started form the two dimensional single crystal then was expanded to the two dimensional polycrystalline and finally to the three dimensional single crystal. The model is able to predict the most physical properties associated with tetragonal to monoclinic transformation in zirconia including: morphological patterns, transformation toughening, shape memory effect, pseudoelasticity, surface uplift, and variants impingement. The model was benched marked with several experimental works. The good agreements between simulation results and experimental data, make the model a reliable tool for

  20. Effective property of tooth enamel: monoclinic behavior.

    PubMed

    Lu, Cunyou; Nakamura, Toshio; Korach, Chad S

    2012-05-11

    Human tooth enamel possesses a unique morphology characterized by a repeated cell arrangement, which is composed of varying orientations of hydroxyapatite crystals. In the past, various investigators have reported diverse mechanical properties based on isotropic or orthotropic mechanical models in their experimental and numerical studies. However, these models are insufficient to capture the accurate microstructural effects on the enamel mechanical response. In this paper, a monoclinic anisotropic model, which offers correct descriptions of enamel deformation behaviors, is introduced. The model takes into account the 3D orientation changes of the hydroxyapatite crystals and their spatial elastic property variations. The proposed approach is based on a unit-cell and periodic boundary conditions, and it utilizes the collective deformation characteristics of many rods to determine 13 independent material constants required for the monoclinic model. These constants are necessary to utilize the effective property model to study various mechanical conditions such as abrasion, erosion, wear and fracture of whole tooth enamel.

  1. Monoclinal bending of strata over laccolithic intrusions

    USGS Publications Warehouse

    Koch, F.G.; Johnson, A.M.; Pollard, D.D.

    1981-01-01

    Sedimentary strata on top of some laccolithic intrusions are nearly horizontal and little deformed, but are bent into steeply dipping monoclinal flexures over the peripheries of these intrusions. This form of bending is not explained by previous theories of laccolithic intrusion, which predict either horizontal undeformed strata over the center and faulted strata around the periphery, or strata bent continuously into a dome. However, a slight generalization of these theories accomodates the observed form and contains the previous forms as special cases. A critical assumption is that the strength of contacts within a multilayered overburden is overcome locally by layer-parallel shear. If this strength is less than the strength of the layers themselves, then layers over the center remain bonded together and display negligible bending, whereas layers over the periphery slip over one another and are readily bent into a monoclinal flexure. ?? 1981.

  2. Post-patterning of an electronic homojunction in atomically thin monoclinic MoTe2

    NASA Astrophysics Data System (ADS)

    Kim, Sera; Kim, Jung Ho; Kim, Dohyun; Hwang, Geunwoo; Baik, Jaeyoon; Yang, Heejun; Cho, Suyeon

    2017-06-01

    Monoclinic group 6 transition metal dichalcogenides (TMDs) have been extensively studied for their intriguing 2D physics (e.g. spin Hall insulator) as well as for ohmic homojunction contacts in 2D device applications. A critical prerequisite for those applications is thickness control of the monoclinic 2D materials, which allows subtle engineering of the topological states or electronic bandgaps. Local thickness control enables the realization of clean homojunctions between different electronic states, and novel device operation in a single material. However, conventional fabrication processes, including chemical methods, typically produce non-homogeneous and relatively thick monoclinic TMDs, due to their distorted octahedral structures. Here, we report on a post-patterning technique using laser-irradiation to fabricate homojunctions between two different thickness areas in monoclinic MoTe2. A thickness-dependent electronic change from a metallic to semiconducting state, resulting in an electronic homojunction, was realized by the optical patterning of pristine MoTe2 flakes, and a pre-patterned device channel of monoclinic MoTe2 with a thickness-resolution of 5 nm. Our work provides insight on an optical post-process method for controlling thickness, as a promising approach for fabricating impurity-free 2D TMDs homojunction devices.

  3. First-principles study of structural and elastic properties of monoclinic and orthorhombic BiMnO3.

    PubMed

    Mei, Zhi-Gang; Shang, Shun-Li; Wang, Yi; Liu, Zi-Kui

    2010-07-28

    The structural and elastic properties of BiMnO(3) with monoclinic (C 2/c) and orthorhombic (Pnma) ferromagnetic (FM) structures have been studied by first-principles calculations within LDA + U and GGA + U approaches. The equilibrium volumes and bulk moduli of BiMnO(3) phases are evaluated by equation of state (EOS) fittings, and the bulk properties predicted by LDA + U calculations are in better agreement with experiment. The orthorhombic phase is found to be more stable than the monoclinic phase at ambient pressure. A monoclinic to monoclinic phase transition is predicted to occur at a pressure of about 10 GPa, which is ascribed to magnetism versus volume instability of monoclinic BiMnO(3). The single-crystal elastic stiffness constants c(ij)s of the monoclinic and orthorhombic phases are investigated using the stress-strain method. The c(46) of the monoclinic phase is predicted to be negative. In addition, the polycrystalline elastic properties including bulk modulus, shear modulus, Young's modulus, bulk modulus-shear modulus ratio, Poisson's ratio, and elastic anisotropy ratio are determined based on the calculated elastic constants. The presently predicted phase transition and elastic properties open new directions for investigation of the phase transitions in BiMnO(3), and provide helpful guidance for the future elastic constant measurements.

  4. Monoclinic zirconia distributions in plasma-sprayed thermal barrier coatings

    NASA Astrophysics Data System (ADS)

    Lance, M. J.; Haynes, J. A.; Ferber, M. K.; Cannon, W. R.

    2000-03-01

    Phase composition in an air plasma-sprayed Y2O3-stabilized ZrO2 (YSZ) top coating of a thermal barrier coating (TBC) system was characterized. Both the bulk phase content and localized pockets of monoclinic zirconia were measured with Raman spectroscopy. The starting powder consisted of ˜15 vol.% monoclinic zirconia, which decreased to ˜2 vol.% in the as-sprayed coating. Monoclinic zirconia was concentrated in porous pockets that were evenly distributed throughout the TBC. The pockets resulted from the presence of unmelted granules in the starting powder. The potential effect of the distributed monoclinic pockets on TBC performance is discussed.

  5. Local twin domains and tip-voltage-induced domain switching of monoclinic MC phase in Pb (M g1 /3N b2 /3) O3-0.34 PbTi O3 single crystal revealed by piezoresponse force microscopy

    NASA Astrophysics Data System (ADS)

    Wang, Ruixue; Yang, Bin; Luo, Zhenlin; Sun, Enwei; Sun, Yuan; Xu, Han; Zhao, Jiangtao; Zheng, Limei; Zhou, Hua; Gao, Chen; Cao, Wenwu

    2016-08-01

    The monoclinic (M) phases in high-performance relaxor-based ferroelectric single crystals have been recognized to be a vital structural factor for the outstanding piezoelectric property. However, due to the complexity of the structure in M phases, the understanding about it is still limited. In this paper, the local twin domains and tip-voltage-induced domain switching of the MC phase in Pb (M g1 /3N b2 /3) O3-0.34 PbTi O3 (PMN-0.34PT) single crystal have been intensively investigated by piezoresponse force microscopy (PFM). By theoretically analyzing the experimental patterns of domain walls on the (001) C face, the specific MC twin domains in the initial annealed state of a selected area have been clarified, and the polarization orientation of the MC phase in this sample is determined to be at an angle of 29∘ to the <001> C directions. In addition, based on the evolution of domains and the motion of domain walls under the step-increased PFM tip dc voltage (Vdc), the switching process and features of different types of MC domain variants are visually revealed.

  6. Local twin domains and tip-voltage-induced domain switching of monoclinic MC phase in Pb(Mg1/3Nb2/3)O3-0.34PbTiO3 single crystal revealed by piezoresponse force microscopy

    DOE PAGES

    Wang, Ruixue; Yang, Bin; Luo, Zhenlin; ...

    2016-08-29

    Here, the monoclinic (M) phases in high-performance relaxor-based ferroelectric single crystals have been recognized to be a vital structural factor for the outstanding piezoelectric property. However, due to the complexity of the structure in M phases, the understanding about it is still limited. In this paper, the local twin domains and tip-voltage-induced domain switching of the MC phase in Pb(Mg1/3Nb2/3)O3 - 0.34PbTiO3 (PMN-0.34PT) single crystal have been intensively investigated by piezoresponse force microscopy (PFM). By theoretically analyzing the experimental patterns of domain walls on the (001)C face, the specific MC twin domains in the initial annealed state of a selectedmore » area have been clarified, and the polarization orientation of the MC phase in this sample is determined to be at an angle of 29 degrees to the < 001 > C directions. In addition, based on the evolution of domains and the motion of domain walls under the step-increased PFM tip dc voltage (Vdc), the switching process and features of different types of MC domain variants are visually revealed« less

  7. Generalized dispersion analysis of arbitrarily cut monoclinic crystals.

    PubMed

    Höfer, Sonja; Ivanovski, Vladimir; Uecker, Reinhard; Kwasniewski, Albert; Popp, Jürgen; Mayerhöfer, Thomas G

    2017-10-05

    Dispersion analysis is applicable to arbitrarily cut monoclinic crystals of unknown orientation in order to find the symmetry axis. By this it is possible to differentiate between the transition moments oriented parallel and normal to the b-axis and to determine the dielectric tensor functions of those two principal directions. Dispersion analysis of arbitrarily cut monoclinic crystals is based on an extension of the evaluation scheme developed for arbitrarily cut orthorhombic crystals. We present dispersion analysis of monoclinic crystals exemplarily on spodumene (LiAl(SiO3)2) and yttrium orthosilicate (Y2SiO5). Copyright © 2017 Elsevier B.V. All rights reserved.

  8. Generalized dispersion analysis of arbitrarily cut monoclinic crystals

    NASA Astrophysics Data System (ADS)

    Höfer, Sonja; Ivanovski, Vladimir; Uecker, Reinhard; Kwasniewski, Albert; Popp, Jürgen; Mayerhöfer, Thomas G.

    2017-10-01

    Dispersion analysis is applicable to arbitrarily cut monoclinic crystals of unknown orientation in order to find the symmetry axis. By this it is possible to differentiate between the transition moments oriented parallel and normal to the b-axis and to determine the dielectric tensor functions of those two principal directions. Dispersion analysis of arbitrarily cut monoclinic crystals is based on an extension of the evaluation scheme developed for arbitrarily cut orthorhombic crystals. We present dispersion analysis of monoclinic crystals exemplarily on spodumene (LiAl(SiO3)2) and yttrium orthosilicate (Y2SiO5).

  9. Surface Monocline Development Along Normal Faults in Basalt, Southwest Iceland

    NASA Astrophysics Data System (ADS)

    Boersma, N. D.; Kattenhorn, S. A.

    2005-12-01

    The subaerial exposure of the Mid-Atlantic Ridge in southwest Iceland is characterized by a high angle of spreading obliquity (30°), resulting in a complex structural fabric along the ridge segment at the Reykjanes Peninsula (RP). Tension fractures, normal, oblique-slip, and strike-slip faults, eruptive fissures, and prominent hyaloclastite ridges demarcate a series of four closely-spaced fissure swarms across the length of the RP. Monoclines flank the hanging wall sides of numerous normal and oblique-slip faults in the fissure swarms. The formation of these surface flexures is likely the result of upward fault propagation from depth, facilitated by the growth of vertical fractures that nucleate at the upper fault tip and then rip through the highly fractured basalt lava pile. Subsurface slip along the buried fault causes a monocline to develop at the surface above the fault tip. As slip continues, the monocline grows in both height and width, accommodating throw at the surface purely by flexure. Bending stresses within the flexure induce tensile fracturing that breaches the upper hinge at the surface. Further movement along the underlying fault increases the dilation of this fracture resulting in a gaping chasm that may widen by collapse along the fracture walls. No throw occurs along this hinge fracture until the fault ultimately breaches the surface via the fracture. At this time, the monocline becomes a passive and detached hanging wall structure along a vertical fault scarp, thus preventing further growth of the flexure. Detailed field and aerial photo mapping from scanned then digitally orthorectified photos (0.125m/pixel) were used to analyze fracture style, surface monocline geometries, and to assess the spatial variability of monoclinal flexures across the RP and northwards into the Western Volcanic Zone (WVZ). To capture along-strike changes in monocline shape, elevation profiles were constructed at numerous locations along, and orthogonal to, fault

  10. What causes the Besnus transition in monoclinic pyrrhotite?

    NASA Astrophysics Data System (ADS)

    Gehring, A. U.; Koulialias, D.; Löffler, J. F.; Charilaou, M.

    2016-12-01

    Monoclinic 4C pyrrhotite (ideal formula Fe7S8) is a major magnetic remanence carrier in the Earth's crust and in extraterrestrial materials. Because of its low-temperature magnetic transition around 30 K also known as Besnus transition, this mineral phase is easily detectable in rock samples. An intrinsic origin of the Besnus transition due to a crystallographic change similar to that in the Verwey transition has generally been postulated (1). Although the physical properties of pyrrhotite have intensively been studied, the physics behind the pronounced change in magnetization at the low-temperature transition is still unresolved. To address this question we performed structural and magnetic analyses on a natural pyrrhotite single crystal (Fe6.6S8) from Auerbach, Germany (2,3). Chemical analysis, X-ray diffractometry and transmission electron microscopy show that this pyrrhotite consists of an intergrowth of 4C and an incommensurate 5C* superstructure that are polymorphs with different vacancy distributions. The occurrence of two superstructures is magnetically confirmed by symmetric inflection points in the hysteresis measurements above the transition at about 30 K. The disappearance of the inflection points and the associated change of the hysteresis parameters indicate that the two superstructures become embedded to form a unitary magnetic anisotropy system at the transition. This embedding of the 5C* into the 4C pyrrhotite at about 30 K is directly visible by the occurrence of additional 4-fold and 12-fold symmetry terms in magnetic anisotropy and anisotropic magnetic resistivity mesarurements, respectively. From this it follows that the Besnus transition in monoclinic pyrrhotite is an extrinsic magnetic phenomenon with respect to the 4C superstructure, i.e., a coupling effect, and therefore the physics behind it is in fact different from that of the well-known Verwey transition. (1) Rochette et al., The IRM Quarterly, 21, 1 (2011); (2) Charilaou et al., J

  11. Microstructural characterization and optical properties of green emitting hexagonal and monoclinic CePO4:Tb3+ nanocrystals

    NASA Astrophysics Data System (ADS)

    Sisira, S.; Alexander, Dinu; Thomas, Kukku; Vimal, G.; Mani, Kamal P.; Biju, P. R.; Unnikrishnan, N. V.; Joseph, Cyriac

    2017-02-01

    Green emitting CePO4:Tb3+ nanocrystals with hexagonal and monoclinic structures were successfully synthesized through microwave assisted sol gel method. The variation observed in the powder XRD pattern from that of bulk is explained using HRTEM analysis in relation with the preferential growth in distinct directions to form nanorods. The results obtained from the microstructural characterization of the hexagonal and monoclinic CePO4:Tb3+nanocrystals are successfully correlated with the single crystal data of CePO4 for the first time in accordance with the single crystal growth theory. FTIR spectrum of the CePO4 nanocrystals evidenced the splitting of fundamental vibrations of phosphate group in the nine fold coordination of lanthanide atoms and confirmed the low symmetry of monoclinic structure than the hexagonal system. The diminishing intensity of terbium emission in the hexagonal structure than the monoclinic structured CePO4:Tb3+ nanocrystals is explained in relation with the lattice symmetry. The high intensity green emission due to the strong 5D4-7F5 transition in monoclinic CePO4:Tb3+ nanocrystals make it as a potential candidate for optoelectronic applications.

  12. Near coincidence site lattice misorientations in monoclinic zirconia

    SciTech Connect

    Gertsman, V.Y. |; Zhilyaev, A.P. |; Szpunar, J.

    1996-12-01

    Zirconium dioxide, ZrO{sub 2}, exists in three crystalline phases: monoclinic, tetragonal, and cubic. Calculations of the coincidence site lattice (CSL) misorientations for the last two lattices and for hexagonal ones using the methods developed represent little difficulty. However, no procedure for the determination of the CSL misorientations in the monoclinic system has been reported so far. Monoclinic zirconia has the crystallographic space group P2{sub 1}/c and the following parameters of the unit cell (e.g., 5, 6): a = 5.1490 {angstrom}, b = 5.2133 {angstrom}, c = 5.3161 {angstrom}, and {beta} = 99.228{degree}. Before discussing possible CSL misorientations in zirconia, consider a simple example based on geometric considerations. In any monoclinic crystal (with any lattice parameters) the two symmetrical boundaries along the (001) and (100) planes must have highly ordered atomic structure. The misorientation of the first boundary is descried as a rotation of either 180{degree} around the [100] direction or 180{degree} around the normal to the (001) plane. The misorientation of the second boundary is 180{degree} [001] or 180{degree} around the normal to the (100) plane. It can be shown that three-dimensional CSLs will exist in both cases if (c/a)cos{beta} is a rational number. This example justifies the following approximation of the unit cell in the monoclinic zirconia: a = b = c and cos{beta} = {minus}1/6 (i.e., {beta} = 99.594{degree}). Consider the following prismatic cell in the monoclinic crystal structure: ([1 0 1], [{bar 1} 0 1], [0 1 0]). With the above approximation, this cell is orthogonal with the ratios of the squares of the edge lengths expressed as 5:7:3. Therefore, one can apply the algorithm for calculations of the CSL misorientations in orthorhombic lattices with rational ratios of squares of the lattice periods, which is based on the general vector-quaternion method of misorientation representation.

  13. Low temperature synthesis of high purity monoclinic celsian using topaz

    SciTech Connect

    Talmy, I.G.; Haught, D.A.

    1991-02-19

    This patent describes a process for preparing monoclinic BaO {center dot} Al{sub 2}O{sub 3} {center dot} 2SiO{sub 2}. It comprises: forming an intimate reaction mixture of powders of topaz and BaCO{sub 3} wherein the molar ratio of topaz to BaCO{sub 3} is from 2:1 to 4:1; and heating the reaction mixture to initiate a celsian formation reaction, in an atmosphere of gases generated by the celsian formation reaction, at a temperature in the range of from 900{degrees} C. to less than 1590{degrees} C. until the monoclinic celsian is produced.

  14. Low temperature magnetic properties of monoclinic pyrrhotite with particular relevance to the Besnus transition

    NASA Astrophysics Data System (ADS)

    Volk, M.; Gilder, S.; Feinberg, J. M.

    2016-12-01

    Monoclinic pyrrhotite (Fe7S8) is an important mineral on earth as well as in some meteorites. It owes its ferrimagnetism to an ordered array of Fe vacancies. Its magnetic properties change markedly around 30 K, in what is known as the Besnus transition. Plausible explanations for the Besnus transition are either due to changes in crystalline anisotropy from a transformation in crystal symmetry or from the establishment of a two-phase system with magnetic interaction between the two phases. To help resolve this discrepancy, we measured hysteresis loops every 5° and back field curves every 10° in the basal plane of an oriented single crystal of monoclinic pyrrhotite at 300 K and at 21 temperature steps from 50 K through the Besnus transition until 20 K. Between 50 and 30 K, hysteresis loops possess double inflections between crystallographic a-axes and only a single inflection parallel to the a-axes. The second inflection phenomenon and relative differences of the loops show a six-fold symmetry in this temperature range. The Besnus transition is best characterized by changes in magnetic remanence and coercivity over a 6° temperature span with a maximum rate of change at 30 K. A surprising yet puzzling finding is that the coercivity ratio becomes less than unity below the transition when four-fold symmetry arises. The saturation magnetization of natural pyrrhotite cycled from room temperature to successively lower temperatures through the Besnus transition decreases 2-4 times less than equivalent grain sizes of magnetite, with less than a 10% loss in remanence between 300 K and 150 K in pseudo-single domain pyrrhotite. As pseudo-single domain monoclinic pyrrhotite carries the magnetic remanence in some meteorites, it is likely that low temperature cycling in space to the Earth's surface will have only a minor influence on paleointensity values derived from those meteorites.

  15. The East Kaibab Monocline as a Lobate Scarp on Earth

    NASA Astrophysics Data System (ADS)

    Byrne, Paul; Klimczak, Christian

    2017-04-01

    The surfaces of Mercury, Mars, and the Moon show substantial evidence of crustal shortening. A principal manifestation of this tectonic deformation, usually in response to global contraction from interior cooling and/or volcanic loading, are cliff-like escarpments termed "lobate scarps". These landforms are highly asymmetric in transverse view, with steep slopes on one side and gentle backslopes on the other; in map view they typically show a broadly lobate outline. Analogues to another widespread class of extraterrestrial shortening structure, so-called "wrinkle ridges", have been reported at various locations across Earth, but so far no Terran counterparts to lobate scarps have been documented. We conducted a field survey and performed forward modeling to test the hypothesis that a major intraplate shortening landform in southern Utah—the East Kaibab monocline—is an eroded lobate scarp. Our field observations indicate that the fault-related folding that characterizes the monocline at the kilometer scale is accommodated by substantial brittle deformation at meter- to decameter scales, from distributed sets of small fractures to highly localized high-angle reverse faults. With the COULOMB elastic dislocation program we modeled topographic transects perpendicular to the strike of the monocline, using published parameters of the underlying Butte Fault, and restored the eroded portion of the monocline. When reconstructed, the monocline has a steep forward-facing escarpment and a gentle backslope, and bears a strong morphologically similarity to lobate scarps on Mercury, Mars, and the Moon. The attitudes of the deformed model rock volume at specific stratigraphic levels match our field measurements of dip angle for corresponding stratigraphic units in the monocline, verifying our model solutions. Our results strongly imply that the landforms historically termed "lobate scarps" on other planetary bodies are monoclines and asymmetric anticlines. The geometry

  16. Phonon anharmonicity of monoclinic zirconia and yttrium-stabilized zirconia

    DOE PAGES

    Li, Chen W.; Smith, Hillary L.; Lan, Tian; ...

    2015-04-13

    Inelastic neutron scattering measurements on monoclinic zirconia (ZrO2) and 8 mol% yttrium-stabilized zirconia were performed at temperatures from 300 to 1373 ωK. We reported temperature-dependent phonon densities of states (DOS) and Raman spectra obtained at elevated temperatures. First-principles lattice dynamics calculations with density functional theory gave total and partial phonon DOS curves and mode Grüneisen parameters. These mode Grüneisen parameters were used to predict the experimental temperature dependence of the phonon DOS with partial success. However, substantial anharmonicity was found at elevated temperatures, especially for phonon modes dominated by the motions of oxygen atoms. Yttrium-stabilized zirconia (YSZ) was somewhat moremore » anharmonic and had a broader phonon spectrum at low temperatures, owing in part to defects in its structure. YSZ also has a larger vibrational entropy than monoclinic zirconia.« less

  17. Alpha decay self-damage in cubic and monoclinic zirconolite

    SciTech Connect

    Clinard, F.W. Jr.; Land, C.C.; Peterson, D.E.; Rohr, D.L.; Roof, R.B.

    1981-01-01

    Samples of primarily-monoclinic /sup 238/Pu-doped zirconolite were stored at ambient temperature to allow accumulation of alpha decay self-damage to a dose of 1 x 10/sup 24/ ..cap alpha../m/sup 3/ (equivalent to a SYNROC age of approx. 10/sup 3/y). Bulk swelling reached 2.3 vol% with no tendency toward saturation, a damage response similar to that observed for cubic Pu-doped zirconolite. X-ray volumetric swelling at 4 x 10/sup 24/ ..cap alpha../m/sup 3/ was 1 vol%, considerably less than that for the cubic material. Changes in cell dimensions differed significantly from those reported by others for a monoclinic natural mineral. Extensive microcracking was observed, and is attributed at least partially to swelling differences between the matrix and minor phases.

  18. Phonon anharmonicity of monoclinic zirconia and yttrium-stabilized zirconia

    SciTech Connect

    Li, Chen W.; Smith, Hillary L.; Lan, Tian; Niedziela, Jennifer L.; Munoz, Jorge A.; Keith, J. Brian; Mauger, L.; Abernathy, Douglas L; Fultz, B.

    2015-04-13

    Inelastic neutron scattering measurements on monoclinic zirconia (ZrO2) and 8 mol% yttrium-stabilized zirconia were performed at temperatures from 300 to 1373 ωK. We reported temperature-dependent phonon densities of states (DOS) and Raman spectra obtained at elevated temperatures. First-principles lattice dynamics calculations with density functional theory gave total and partial phonon DOS curves and mode Grüneisen parameters. These mode Grüneisen parameters were used to predict the experimental temperature dependence of the phonon DOS with partial success. However, substantial anharmonicity was found at elevated temperatures, especially for phonon modes dominated by the motions of oxygen atoms. Yttrium-stabilized zirconia (YSZ) was somewhat more anharmonic and had a broader phonon spectrum at low temperatures, owing in part to defects in its structure. YSZ also has a larger vibrational entropy than monoclinic zirconia.

  19. Different structures of monoclinic martensitic phases in titanium nickelide

    NASA Astrophysics Data System (ADS)

    Voronin, V. I.; Naish, V. E.; Novoselova, T. V.; Pushin, V. G.; Sagaradze, I. V.

    2000-03-01

    The detailed theoretical and experimental analysis has been undertaken to bring to light the true structure of the monoclinic phase in titanium nickelide (NiTi). Theoretical models for such a phase have been proposed to describe the experimental data. In addition to the well-known B19‧ phase two more structures - new monoclinic M phase with Cm space group and triclinic phase with P1 space group - have been produced and analyzed in detail. Diffraction patterns have been obtained from different NiTi samples by using the neutron diffractometer IVV2 at different temperatures. From the refinement by DBWS-9411 program all these neutron patterns have been decoded successfully. The proposed new structures and stereotype B19‧ one agree with correspondent experimental data and the agreement is quite good.

  20. Solid State Synthesis and Properties of Monoclinic Celsian

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P.

    1996-01-01

    Monoclinic celsian of Ba(0.75)Sr(0.25)Al2Si2O8 (BSAS-1) and B(0.85)Sr(O.15)Al2Si2O8 (BSAS-2) compositions have been synthesized from metal carbonates and oxides by solid state reaction. A mixture of BaCO3, SrCO3, Al2O3, and SiO2 powders was precalcined at approx. 900-940 C to decompose the carbonates followed by hot pressing at approx. 1300 C. The hot pressed BSAS-1 material was almost fully dense and contained the monoclinic celsian phase, with complete absence of the undesirable hexacelsian as indicated by x-ray diffraction. In contrast, a small fraction of hexacelsian was still present in hot pressed BSAS-2. However, on further heat treatment at 1200 C for 24 h, the hexacelsian phase was completely eliminated. The average linear thermal expansion coefficients of BSAS-1 and BSAS-2 compositions, having the monoclinic celsian phase, were measured to be 5.28 x 10(exp -6)/deg C and 5.15 x 10(exp -6)/deg C, respectively from room temperature to 1200 C. The hot pressed BSAS-1 celsian showed room temperature flexural strength of 131 MPa, elastic modulus of 96 GPa and was stable in air up to temperatures as high as approx. 1500 C.

  1. Assignments of the Raman modes of monoclinic erbium oxide

    SciTech Connect

    Yan, D.; Wu, P. Zhang, S. P.; Liang, L.; Yang, F.; Pei, Y. L.; Chen, S.

    2013-11-21

    As a heavy rare earth oxide, erbium oxide (Er{sub 2}O{sub 3}) has many attractive properties. Monoclinic Er{sub 2}O{sub 3} has useful properties not found in stable cubic Er{sub 2}O{sub 3}, such as unique optical properties and high radiation damage tolerance. In this study, cubic Er{sub 2}O{sub 3} coating and Er{sub 2}O{sub 3} coating with mixed phases were prepared. The Raman scattering spectra of these coatings were investigated by using a confocal micro-Raman spectrometer equipped with 325, 473, 514, 532, 633, and 784 nm lasers. A total of 17 first-order Raman modes of monoclinic Er{sub 2}O{sub 3} were identified and assigned. The modes at 83, 112, 152, 170, 278, 290, 409, 446, 478, 521, 603, and 622 cm{sup −1} are of A{sub g} symmetry, whereas modes at 71, 98, 333, 409, 446, and 468 cm{sup −1} are of B{sub g} symmetry. This research provides basic data necessary for the characterization of monoclinic Er{sub 2}O{sub 3} by Raman spectroscopy.

  2. Zoledronic acid: monoclinic and triclinic polymorphs from powder diffraction data.

    PubMed

    Chernyshev, Vladimir V; Shkavrov, Sergey V; Paseshnichenko, Ksenia A; Puryaeva, Tamara P; Velikodny, Yurii A

    2013-03-01

    The crystal structures of the monoclinic and triclinic polymorphs of zoledronic acid, C5H10N2O7P2, have been established from laboratory powder X-ray diffraction data. The molecules in both polymorphs are described as zwitterions, namely 1-(2-hydroxy-2-phosphonato-2-phosphonoethyl)-1H-imidazol-3-ium. Strong intermolecular hydrogen bonds (with donor-acceptor distances of 2.60 Å or less) link the molecules into layers, parallel to the (100) plane in the monoclinic polymorph and to the (1-10) plane in the triclinic polymorph. The phosphonic acid groups form the inner side of each layer, while the imidazolium groups lie to the outside of the layer, protruding in opposite directions. In both polymorphs, layers related by translation along [100] interact through weak hydrogen bonds (with donor-acceptor distances greater than 2.70 Å), forming three-dimensional layered structures. In the monoclinic polymorph, there are hydrogen-bonded centrosymmetric dimers linked by four strong O-H...O hydrogen bonds, which are not present in the triclinic polymorph.

  3. Monoclinic pseudosymmetry in 2-phenoxybenzenesulfonamide, a triclinic structure having Z' = 4, and spontaneous resolution in monoclinic N-methyl-2-phenoxybenzenesulfonamide.

    PubMed

    Glidewell, Christopher; Low, John N; Skakle, Janet M S; Wardell, James L

    2004-05-01

    2-Phenoxybenzenesulfonamide, C(12)H(11)NO(3)S, (I), crystallizes in space group P-1 with Z' = 4, but the structure closely mimics the monoclinic space group P2(1)/b with Z' = 2. The molecules of (I) are linked by a combination of N-H...O and C-H...O hydrogen bonds into two independent chains of centrosymmetric edge-fused R(2)(2)(18) and R(6)(6)(34) rings. N-Methyl-2-phenoxybenzenesulfonamide, C(13)H(13)NO(3)S, (II), crystallizes in space group P2(1) with Z' = 1, and is an example of spontaneous resolution. The molecules are linked by N-H...O and C-H...O hydrogen bonds into chains of spiro-fused R(2)(2)(12) rings, and these chains are linked into sheets by a single C-H...pi(arene) hydrogen bond.

  4. Anisotropy, phonon modes, and lattice anharmonicity from dielectric function tensor analysis of monoclinic cadmium tungstate

    NASA Astrophysics Data System (ADS)

    Mock, A.; Korlacki, R.; Knight, S.; Schubert, M.

    2017-04-01

    We determine the frequency dependence of four independent Cartesian tensor elements of the dielectric function for CdWO4 using generalized spectroscopic ellipsometry within mid-infrared and far-infrared spectral regions. Different single crystal cuts, (010) and (001), are investigated. From the spectral dependencies of the dielectric function tensor and its inverse we determine all long-wavelength active transverse and longitudinal optic phonon modes with Au and Bu symmetry as well as their eigenvectors within the monoclinic lattice. We thereby demonstrate that such information can be obtained completely without physical model line-shape analysis in materials with monoclinic symmetry. We then augment the effect of lattice anharmonicity onto our recently described dielectric function tensor model approach for materials with monoclinic and triclinic crystal symmetries [M. Schubert et al., Phys. Rev. B 93, 125209 (2016), 10.1103/PhysRevB.93.125209], and we obtain an excellent match between all measured and modeled dielectric function tensor elements. All phonon mode frequency and broadening parameters are determined in our model approach. We also perform density functional theory phonon mode calculations, and we compare our results obtained from theory, from direct dielectric function tensor analysis, and from model line-shape analysis, and we find excellent agreement between all approaches. We also discuss and present static and above reststrahlen spectral range dielectric constants. Our data for CdWO4 are in excellent agreement with a recently proposed generalization of the Lyddane-Sachs-Teller relation for materials with low crystal symmetry [M. Schubert, Phys. Rev. Lett. 117, 215502 (2016), 10.1103/PhysRevLett.117.215502].

  5. Low-temperature anisotropy changes in monoclinic pyrrhotite

    NASA Astrophysics Data System (ADS)

    Koulialias, D.; Charilaou, M.; Löffler, J. F.; Gehring, A. U.

    2016-12-01

    Pyrrhotite refers to an iron monosulfide solid solution (Fe1-xS; 0 < x < 0.125) with a NiAs-type structure in common where iron occupies the interstitials in a hexagonal close-packed array of sulfur. Unoccupied octahedral sites form variable stacking sequences of vacancy and full sublattices that generate different superstructures. Torque measurements of monoclinic 4C pyrrhotite (ideal formula: Fe7S8) at 300 K generally show a 6-fold symmetry that stems from the hexagonal NiAs-type substructure (1). At 25 K, a 4-fold symmetry was reported and explained by a crystallographic change from monoclinic to triclinic associated with the Besnus transition (2). We investigated the anisotropy properties in the c-plane of the hexagonal substructure of a monoclinic pyrrhotite that consists of intergrown 4C and 5C* superstructures (3), between 200 and 10 K using a Physical Property Measurement System (PPMS: Quantum Design). In this temperature range, Fourier analysis of the torque shows a 6-fold and a 4-fold symmetry, whereby the intensity ratio I4/I6 down to 25 K is << 1. Upon further cooling, I4/I6 increases continuously from 1.1 at 20 K to 3.9 at 10 K. Such behavior is not expected for crystallographic changes. The 4-fold term, however, is explained by the interaction of the two epitaxial-intergrown superstructures with their hexagonal anisotropy systems displaced by 30°. This can be phenomenologically verified by extending the analytical solution to describe the anisotropy of 4C pyrrhotite (4). In this approach, the 4-fold term is the result of the different behavior of the anisotropy constants within the triaxial 5C* system and this in turn also leads to its striking increase below 25 K. The dominant presence of a 4-fold symmetry in pyrrhotite can further be shown by means of Monte Carlo simulations. Given the above, the occurrence of a 4-fold symmetry provides evidence of the heterogeneity in the superstructures of monoclinic pyrhotite. (1) Martín-Hernández et al

  6. Monoclinic Tungsten Oxide with {100} Facet Orientation and Tuned Electronic Band Structure for Enhanced Photocatalytic Oxidations.

    PubMed

    Zhang, Ning; Chen, Chen; Mei, Zongwei; Liu, Xiaohe; Qu, Xiaolei; Li, Yunxiang; Li, Siqi; Qi, Weihong; Zhang, Yuanjian; Ye, Jinhua; Roy, Vellaisamy A L; Ma, Renzhi

    2016-04-27

    Exploring surface-exposed highly active crystal facets for photocatalytic oxidations is promising in utilizing monoclinic WO3 semiconductor. However, the previously reported highly active facets for monoclinic WO3 were mainly toward enhancing photocatalytic reductions. Here we report that the WO3 with {100} facet orientation and tuned surface electronic band structure can effectively enhance photocatalytic oxidation properties. The {100} faceted WO3 single crystals are synthesized via a facile hydrothermal method. The UV-visible diffuse reflectance, X-ray photoelectron spectroscopy valence band spectra, and photoelectrochemical measurements suggest that the {100} faceted WO3 has a much higher energy level of valence band maximum compared with the normal WO3 crystals without preferred orientation of the crystal face. The density functional theory calculations reveal that the shift of O 2p and W 5d states in {100} face induce a unique band structure. In comparison with the normal WO3, the {100} faceted WO3 exhibits an O2 evolution rate about 5.1 times in water splitting, and also shows an acetone evolution rate of 4.2 times as well as CO2 evolution rate of 3.8 times in gaseous degradation of 2-propanol. This study demonstrates an efficient crystal face engineering route to tune the surface electronic band structure for enhanced photocatalytic oxidations.

  7. Conformal Domain Miniaturization and Adaptive Monoclinic (Pseudo-orthorhombic) Ferroelectric States

    NASA Astrophysics Data System (ADS)

    Jin, Y. M.; Wang, Yu; Khachaturyan, A. G.; Li, J. F.; Viehland, D.

    2003-08-01

    Ferroelectric and ferroelastic phases with very low domain wall energies have been shown to form miniaturized microdomain structures. A theory of an adaptive ferroelectric phase has been developed to predict the microdomain-averaged crystal lattice parameters of this structurally inhomogeneous state. The theory is an extension of conventional martensite theory, applied to ferroelectric systems with very low domain wall energies. The cases of ferroelectric microdomains of tetragonal (FEt) symmetry are considered. It is shown that a nano-scale coherent mixture of microdomains can be interpreted as an adaptive ferroelectric phase, whose microdomain-averaged crystal lattice is monoclinic. The crystal lattice parameters of this monoclinic phase are self-adjusting parameters, which minimize the transformation stress. Self-adjustment is achieved by application of the invariant plane strain (IPS) to the parent cubic lattice, and the value of the self-adjusted parameters constitutes a mixture of the lattice constants of the parent and product phases. Experimental investigations of Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) and Pb(Zn1/3Nb2/3)O3-PbTiO3 (PZN-PT) single crystals confirm many of the predictions of this theory.

  8. Low-temperature magnetic properties of monoclinic pyrrhotite with particular relevance to the Besnus transition

    NASA Astrophysics Data System (ADS)

    Volk, Michael W. R.; Gilder, Stuart A.; Feinberg, Joshua M.

    2016-12-01

    Monoclinic pyrrhotite (Fe7S8) owes its ferrimagnetism to an ordered array of Fe vacancies. Its magnetic properties change markedly around 30 K, in what is known as the Besnus transition. Plausible explanations for the Besnus transition are either due to changes in crystalline anisotropy from a transformation in crystal symmetry or from the establishment of a two-phase system with magnetic interaction between the two phases. To help resolve this discrepancy, we measured hysteresis loops every 5° and backfield curves every 10° in the basal plane of an oriented single crystal of monoclinic pyrrhotite at 300 K and every 2 K from 50 K through the Besnus transition until 20 K. Between 50 and 30 K, hysteresis loops possess double inflections between crystallographic a-axes and only a single inflection parallel to the a-axes. Magnetization energy calculations and relative differences of the loops show a sixfold symmetry in this temperature range. We propose that the inflections stem from magnetic axis switching, which is both field and temperature dependent, in a manner somewhat analogous to an isotropic point where magnetocrystalline constants change their sign. The Besnus transition is best characterized by changes in magnetic remanence and coercivity over a 6° temperature span (28-34 K) with a maximum rate of change at 30 K. A surprising yet puzzling finding is that the coercivity ratio becomes less than unity below the transition when fourfold symmetry arises. Because the changes in magnetic parameters are linked to the crystal structure, we conclude the Besnus transition owes its origin to a distortion of the crystallographic axes below 30 K rather than an apparition of a two-phase system. An isothermal magnetization of natural pyrrhotite cycled from room temperature to successively lower temperatures through the Besnus transition decreases 2-4 times less than equivalent grain sizes of magnetite, with less than a 10 per cent loss in remanence between 300 and 150 K

  9. Monoclinic crystal structure of α-RuCl3 and the zigzag antiferromagnetic ground state

    DOE PAGES

    Johnson, R. D.; Williams, S. C.; Haghighirad, A. A.; ...

    2015-12-10

    We have proposed the layered honeycomb magnet α - RuCl 3 as a candidate to realize a Kitaev spin model with strongly frustrated, bond-dependent, anisotropic interactions between spin-orbit entangled j eff = 1/2 Ru 3 + magnetic moments. We report a detailed study of the three-dimensional crystal structure using x-ray diffraction on untwinned crystals combined with structural relaxation calculations. We consider several models for the stacking of honeycomb layers and find evidence for a parent crystal structure with a monoclinic unit cell corresponding to a stacking of layers with a unidirectional in-plane offset, with occasional in-plane sliding stacking faults, inmore » contrast with the currently assumed trigonal three-layer stacking periodicity. We also report electronic band-structure calculations for the monoclinic structure, which find support for the applicability of the j eff = 1/2 picture once spin-orbit coupling and electron correlations are included. Of the three nearest-neighbor Ru-Ru bonds that comprise the honeycomb lattice, the monoclinic structure makes the bond parallel to the b axis nonequivalent to the other two, and we propose that the resulting differences in the magnitude of the anisotropic exchange along these bonds could provide a natural mechanism to explain the previously reported spin gap in powder inelastic neutron scattering measurements, in contrast to spin models based on the three-fold symmetric trigonal structure, which predict a gapless spectrum within linear spin wave theory. Our susceptibility measurements on both powders and stacked crystals, as well as magnetic neutron powder diffraction, show a single magnetic transition upon cooling below T N ≈ 13 K. Our analysis of our neutron powder diffraction data provides evidence for zigzag magnetic order in the honeycomb layers with an antiferromagnetic stacking between layers. Magnetization measurements on stacked single crystals in pulsed field up to 60 T show a single transition

  10. Unique Piezoelectric Properties of the Monoclinic Phase in Pb(Zr,Ti)O_{3} Ceramics: Large Lattice Strain and Negligible Domain Switching.

    PubMed

    Fan, Longlong; Chen, Jun; Ren, Yang; Pan, Zhao; Zhang, Linxing; Xing, Xianran

    2016-01-15

    The origin of the excellent piezoelectric properties at the morphotropic phase boundary is generally attributed to the existence of a monoclinic phase in various piezoelectric systems. However, there exist no experimental studies that reveal the role of the monoclinic phase in the piezoelectric behavior in phase-pure ceramics. In this work, a single monoclinic phase has been identified in Pb(Zr,Ti)O_{3} ceramics at room temperature by in situ high-energy synchrotron x-ray diffraction, and its response to electric field has been characterized for the first time. Unique piezoelectric properties of the monoclinic phase in terms of large intrinsic lattice strain and negligible domain switching have been observed. The extensional strain constant d_{33} and the transverse strain constant d_{31} are calculated to be 520 and -200  pm/V, respectively. These large piezoelectric coefficients are mainly due to the large intrinsic lattice strain, with very little extrinsic contribution from domain switching. The unique properties of the monoclinic phase provide new insights into the mechanisms responsible for the piezoelectric properties at the morphotropic phase boundary.

  11. Paired, facing monoclines in the Sanpete-Sevier Valley area, central Utah

    USGS Publications Warehouse

    Witkind, I.J.

    1992-01-01

    Several major monoclines that trend northward through the Sanpete-Sevier Valley area of central Utah are paired and face one another. This pairing of monoclines may have occurred when near-horizontal sedimentary and volcanic strata subsided into voids created as salt was removed from a salt diapir concealed beneath valley fill. Removal was mostly by dissolution or extrusion during Neogene time. The paired monoclines, thus, are viewed as collapse features rather than as normal synclinal folds. -from Author

  12. Hydroxyapatite: Vibrational spectra and monoclinic to hexagonal phase transition

    NASA Astrophysics Data System (ADS)

    Slepko, Alexander; Demkov, Alexander A.

    2015-02-01

    Fundamental studies of biomaterials are necessary to deepen our understanding of their degradation and to develop cure for related illnesses. Biomineral hydroxyapatite Ca10(PO4)6(OH)2 is the main mineral constituent of mammal bone, and its synthetic analogues are used in biomedical applications. The mineral can be found in either hexagonal or monoclinic form. The transformation between these two phases is poorly understood, but knowing its mechanism may be critical to reversing processes in bone related to aging. Using density functional theory, we investigate the mechanisms of the phase transformation and estimate the transition temperature to be 680 K in fair agreement with the experimental temperature of 470 K. We also report the heat capacity of hydroxyapatite and a peculiarity in its phonon dispersion that might allow for non-destructive measurements of the crystal composition with applications in preventive medical screening for bone mineral loss.

  13. Encapsulated monoclinic sulfur for stable cycling of li-s rechargeable batteries.

    PubMed

    Moon, San; Jung, Young Hwa; Jung, Wook Ki; Jung, Dae Soo; Choi, Jang Wook; Kim, Do Kyung

    2013-12-03

    Monoclinic S8 , an uncommon allotrope of sulfur at room temperature, can be formed when common orthorhombic S8 is heat-treated under enclosed environments in nanometer dimensions. Monoclinic S8 prevents the formation of soluble polysulfides during battery operation, resulting in unprecedented cycling performance over 1000 cycles under the highest sulfur content to date.

  14. Ceramic fiber-reinforced monoclinic celsian phase glass-ceramic matrix composite material

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P. (Inventor); Dicarlo, James A. (Inventor)

    1994-01-01

    A hyridopolysilazane-derived ceramic fiber reinforced monoclinic celsian phase barium aluminum silicate glass-ceramic matrix composite material is prepared by ball-milling an aqueous slurry of BAS glass powder and fine monoclinic celsian seeds. The fibers improve the mechanical strength and fracture toughness and with the matrix provide superior dielectric properties.

  15. Octahedral tilting, monoclinic phase and the phase diagram of PZT

    NASA Astrophysics Data System (ADS)

    Cordero, F.; Trequattrini, F.; Craciun, F.; Galassi, C.

    2011-10-01

    Anelastic and dielectric spectroscopy measurements on PbZr1-xTixO3 (PZT) close to the morphotropic (MPB) and antiferroelectric boundaries provide new insight into some controversial aspects of its phase diagram. No evidence is found of a border separating monoclinic (M) from rhombohedral (R) phases, in agreement with recent structural studies supporting a coexistence of the two phases over a broad composition range x < 0.5, with the fraction of M increasing toward the MPB. It is also discussed why the observed maximum of elastic compliance appears to be due to a rotational instability of the polarization linearly coupled to shear strain. Therefore it cannot be explained by extrinsic softening from finely twinned R phase alone, but indicates the presence also of M phase, not necessarily homogeneous. A new diffuse transition is found within the ferroelectric phase near x ˜ 0.1, at a temperature TIT higher than the well established boundary TT to the phase with tilted octahedra. It is proposed that around TIT the octahedra start rotating in a disordered manner and finally become ordered below TT. In this interpretation, the onset temperature for octahedral tilting monotonically increases up to the antiferroelectric transition of PbZrO3, and the depression of TT(x) below x = 0.18 would be a consequence of the partial relief of the mismatch between the average cation radii with the initial stage of tilting below TIT.

  16. Discovery of Fe7O9: a new iron oxide with a complex monoclinic structure

    NASA Astrophysics Data System (ADS)

    Sinmyo, Ryosuke; Bykova, Elena; Ovsyannikov, Sergey V.; McCammon, Catherine; Kupenko, Ilya; Ismailova, Leyla; Dubrovinsky, Leonid

    2016-09-01

    Iron oxides are fundamentally important compounds for basic and applied sciences as well as in numerous industrial applications. In this work we report the synthesis and investigation of a new binary iron oxide with the hitherto unknown stoichiometry of Fe7O9. This new oxide was synthesized at high-pressure high-temperature (HP-HT) conditions, and its black single crystals were successfully recovered at ambient conditions. By means of single crystal X-ray diffraction we determined that Fe7O9 adopts a monoclinic C2/m lattice with the most distorted crystal structure among the binary iron oxides known to date. The synthesis of Fe7O9 opens a new portal to exotic iron-rich (M,Fe)7O9 oxides with unusual stoichiometry and distorted crystal structures. Moreover, the crystal structure and phase relations of such new iron oxide groups may provide new insight into the cycling of volatiles in the Earth’s interior.

  17. Discovery of Fe7O9: a new iron oxide with a complex monoclinic structure

    PubMed Central

    Sinmyo, Ryosuke; Bykova, Elena; Ovsyannikov, Sergey V.; McCammon, Catherine; Kupenko, Ilya; Ismailova, Leyla; Dubrovinsky, Leonid

    2016-01-01

    Iron oxides are fundamentally important compounds for basic and applied sciences as well as in numerous industrial applications. In this work we report the synthesis and investigation of a new binary iron oxide with the hitherto unknown stoichiometry of Fe7O9. This new oxide was synthesized at high-pressure high-temperature (HP-HT) conditions, and its black single crystals were successfully recovered at ambient conditions. By means of single crystal X-ray diffraction we determined that Fe7O9 adopts a monoclinic C2/m lattice with the most distorted crystal structure among the binary iron oxides known to date. The synthesis of Fe7O9 opens a new portal to exotic iron-rich (M,Fe)7O9 oxides with unusual stoichiometry and distorted crystal structures. Moreover, the crystal structure and phase relations of such new iron oxide groups may provide new insight into the cycling of volatiles in the Earth’s interior. PMID:27605075

  18. Identification of monoclinic θ-phase dispersoids in a 6061 aluminium alloy

    NASA Astrophysics Data System (ADS)

    Buchanan, Karl; Ribis, Joël; Garnier, Jérôme; Colas, Kimberly

    2016-04-01

    Intermetallic dispersoids play an important role in controlling the 6xxx alloy series' grain distribution and increasing the alloy's toughness. The dispersoid distribution in a 6061 aluminium alloy (Al-Mg-Si) was analysed by transmission electron microscopy, selected area diffraction and energy-dispersive X-ray spectroscopy. The dispersoids had three unique crystal structures: simple cubic ?, body-centred cubic ? and monoclinic (C2/m). While the SC and BCC dispersoids have been well characterized in the literature, a detailed analysis of monoclinic dispersoids has not been presented. Therefore, the current work discusses the chemical composition, crystal structure and morphology of the monoclinic dispersoids.

  19. [Vibrational spectra of monoclinic diphosphates of formula AMP2O7].

    PubMed

    Serghini Idrissi, M; Rghioui, L; Nejjar, R; Benarafa, L; Saidi Idrissi, M; Lorriaux, A; Wallart, F

    2004-07-01

    The monoclinic pyrophosphates with AMP2O7 formula were synthesized. Their infrared and Raman spectra have been reported and analysed. The results of a force field calculation for CaCuP2O7 are presented.

  20. Vibrational Spectroscopy and Phonon-Related Properties of the L-Aspartic Acid Anhydrous Monoclinic Crystal.

    PubMed

    Silva, A M; Costa, S N; Sales, F A M; Freire, V N; Bezerra, E M; Santos, R P; Fulco, U L; Albuquerque, E L; Caetano, E W S

    2015-12-10

    The infrared absorption and Raman scattering spectra of the monoclinic P21 l-aspartic acid anhydrous crystal were recorded and interpreted with the help of density functional theory (DFT) calculations. The effect of dispersive forces was taken into account, and the optimized unit cells allowed us to obtain the vibrational normal modes. The computed data exhibits good agreement with the measurements for low wavenumbers, allowing for a very good assignment of the infrared and Raman spectral features. The vibrational spectra of the two lowest energy conformers of the l-aspartic molecule were also evaluated using the hybrid B3LYP functional for the sake of comparison, showing that the molecular calculations give a limited description of the measured IR and Raman spectra of the l-aspartic acid crystal for wavenumbers below 1000 cm(-1). The results obtained reinforce the need to use solid-state calculations to describe the vibrational properties of molecular crystals instead of calculations for a single isolated molecule picture even for wavenumbers beyond the range usually associated with lattice modes (200 cm(-1) < ω < 1000 cm(-1)).

  1. Polarized Raman scattering of epitaxial vanadium dioxide films with low-temperature monoclinic phase

    NASA Astrophysics Data System (ADS)

    Shibuya, Keisuke; Sawa, Akihito

    2017-07-01

    A polarized Raman scattering study was carried out on epitaxial VO2 thin films on MgF2(001) and (110) substrates to investigate the Raman symmetry and tensor elements of the phonon modes of the films in a low-temperature monoclinic phase. From the polarization angular dependence of the Raman intensity, we assigned the phonon modes at 137, 194, 310, 340, 499, 612, and 663 cm-1 to Ag symmetry and the phonon modes at 143, 262, 442, 480, 582, and 820 cm-1 to Bg symmetry. The angular-dependence measurements also revealed that two phonon modes with Ag and Bg symmetries are present at about 224 and 393 cm-1, although only a single peak was observed in the Raman spectra at around these wavenumbers. On the basis of the experimental results, we evaluated the Raman tensors of the identified phonon modes. From the Raman tensors, we found that the atomic displacements of the 194 and 340 cm-1 phonon modes are approximately perpendicular and parallel, respectively, to the V-V dimer direction. This is consistent with a previous theoretical prediction, i.e., these modes are attributable to the tilting motion and the stretching vibration of the V-V dimers, respectively.

  2. Compositional limits and analogs of monoclinic triple-chain silicates

    NASA Astrophysics Data System (ADS)

    Jenkins, David M.; Gilleaudeau, Geoffrey J.; Kawa, Cynthia; Dibiase, Jaclyn M.; Fokin, Maria

    2012-08-01

    Growing recognition of triple-chain silicates in nature has prompted experimental research into the conditions under which they can form and the extent of solid solution that is feasible for some key chemical substitutions. Experiments were done primarily in the range of 0.1-0.5 GPa and 200-850 °C for durations of 18-1,034 h. A wide range of bulk compositions were explored in this study that can be classified broadly into two groups: those that are Na free and involve various possible chemical substitutions into jimthompsonite (Mg10Si12O32(OH)4), and those that are Na bearing and involve chemical substitutions into the ideal end-member Na4Mg8Si12O32(OH)4. Numerous attempts to synthesize jimthompsonite or clinojimthompsonite were unsuccessful despite the type of starting material used (reagent oxides, magnesite + SiO2, talc + enstatite, or anthophyllite). Similarly, the chemical substitutions of F- for OH-, Mn2+, Ca2+, or Fe2+ for Mg2+, and 2Li+ for Mg2+ and a vacancy were unsuccessful at nucleating triple-chain silicates. Conversely, nearly pure yields of monoclinic triple-chain silicate could be made at temperatures of 440-630 °C and 0.2 GPa from the composition Na4Mg8Si12O32(OH)4, as found in previous studies, though its composition is most likely depleted in Na as evidenced by electron microprobe and FTIR analysis. Pure yields of triple-chain silicate were also obtained for the F-analog composition Na4Mg8Si12O32F4 at 550-750 °C and 0.2-0.5 GPa if a flux consisting of Na-halide salt and water in a 2:1 ratio by weight was used. In addition, limited chemical substitution could be documented for the substitutions of 2 Na+ for Na+ + H+ and of Mg2+ + vacancy for 2Na+. For the former, the Na content appears to be limited to 2.5 cations giving the ideal composition of Na2.5Mg8Si12O30.5(OH)5.5, while for the latter substitution the Na content may go as low as 1.1 cations giving the composition Na1.1Mg9.4Si12O31.9(OH)4.1 based on a fixed number of Si cations. Further

  3. Mechanics of monoclinal systems in the Colorado Plateau during the Laramide orogeny

    NASA Astrophysics Data System (ADS)

    Yin, An

    1994-11-01

    Monoclines developed in the Colorado Plateau region during the Laramide orogeny are divided into western and eastern groups by a broad NNW trending antiform through the central part of the plateau. In the western group the major monoclines verge to the east, whereas in the eastern group the major monoclines verge to the west. Paleogeographic reconstruction based on paleocurrent indicators and sedimentary facies distribution suggests that the broad antiform was developed during the Laramide orogeny and was coeval with the formation of the monoclines in the plateau. This relationship implies that the monoclines were drag folds verging towards the center of the plateau as a response to the antiformal warping of the plateau. To simulate the warping of the plateau region and the stress distribution that produced the variable trends of the monoclines, an elastic thin plate model considering in-plane stress was developed. This model assumes that (1) sedimentation in the Laramide basins provided vertical loading along the edge of the plateau region, (2) frictional sliding was operating along the Laramide faults on the northern and eastern boundaries, and (3) the greatest regional compressive stress was oriented in the N 60 deg E direction and was applied uniformly along the western and southwestern sides of the plateau. Buoyancy due to instantaneous isostatic adjustment of crustal thickening or magmatic addition was also considered. The result of the model suggests that the frictional strength of the Uinta thrust system on the northern side of the plateau is at least 2 times greater than that along the Park Range and Sangre de Cristo thrust systems on the eastern side of the plateau in order to explain the observed monoclinal trends and the warping pattern within the plateau during the Laramide orogeny.

  4. The High-Pressure Monoclinic Lawsonite Phase: The Primary Carrier of Water from Subducted Crust to the Deep Mantle

    NASA Astrophysics Data System (ADS)

    O'Bannon, E. F., III; Williams, Q.; Beavers, C.

    2016-12-01

    Lawsonite (CaAl2Si2O7(OH)2.H2O) is the primary subduction zone mineral that carries water within subducted oceanic crust to depths of greater than 80 km. The structure of lawsonite has been extensively studied under room temperature, high-pressure conditions using spectroscopic and X-ray diffraction techniques, as well as under room pressure and varying temperature conditions. Simultaneous high-pressure and temperature measurements on lawsonite to pressures and temperatures approaching its maximum stability are limited to a few multianvil synchrotron based powder diffraction studies. The initially orthorhombic lawsonite has been observed to undergo a phase transition near 9 GPa; however, the high-pressure monoclinic structure of lawsonite has only been reported from non-hydrostatic powder diffraction experiments. We conducted simultaneous high pressure and temperature single-crystal synchrotron based x-ray diffraction experiments on natural lawsonite under hydrostatic conditions. At room pressure and temperature, lawsonite crystallizes with Cmcm symmetry. We solved the structure of the high-pressure phase of lawsonite at 9.7 GPa as monoclinic with P21/m symmetry. The volume change from the low-pressure phase is negligible. Our simultaneous high-pressure and temperature measurements indicate that the orthorhombic to monoclinic transition occurs at nearly 1 GPa lower pressure when heated to temperatures of only 120 0C. There is no evidence of dehydration under these conditions, and the H2O molecule does not change its orientation across this transition. From our single-crystal data, the OH groups in lawsonite may become disordered across this high-pressure transition. The Si and Al sites do not become more distorted under compression or through the phase transition, but the Ca site shows a dramatic increase in its distortion across the high-pressure transition. Our results suggest that the bound water molecule in the high-pressure form of lawsonite is largely

  5. Measurement of elastic constants of monoclinic nickel-titanium and validation of first principles calculations

    SciTech Connect

    Stebner, A. P.; Brown, D. W.; Brinson, L. C.

    2013-05-27

    Polycrystalline, monoclinic nickel-titanium specimens were subjected to tensile and compressive deformations while neutron diffraction spectra were recorded in situ. Using these data, orientation-specific and macroscopic Young's moduli are determined from analysis of linear-elastic deformation exhibited by 13 unique orientations of monoclinic lattices and their relationships to each macroscopic stress and strain. Five of 13 elastic compliance constants are also identified: s{sub 11} = 1.15, s{sub 15} = -1.10, s{sub 22} = 1.34, s{sub 33} = 1.06, s{sub 35} = -1.54, all Multiplication-Sign 10{sup -2} GPa{sup -1}. Through these results, recent atomistic calculations of monoclinic nickel-titanium elastic constants are validated.

  6. A simple and low-cost combustion method to prepare monoclinic VO2 with superior thermochromic properties

    NASA Astrophysics Data System (ADS)

    Cao, Ziyi; Xiao, Xiudi; Lu, Xuanming; Zhan, Yongjun; Cheng, Haoliang; Xu, Gang

    2016-12-01

    In this approach, the VO2 nanoparticles have been successfully fabricated via combusting the low-cost precursor solution consisted of NH4VO3, C2H6O2 and C2H5OH. By the XRD, TEM and XPS analysis, it can be found that the synthetic monoclinic VO2 is single crystal and no impurity is defined. After dispersing the VO2 nanoparticles into the polymer, the solar modulation of VO2-based composite film is up to 12.5% with luminous transmission and haze around 62.2% and 0.5%, respectively. In other words, the composite films show high performance of thermochromic properties. This could open an efficient way to fabricate low-cost and large-scale VO2 (M) nanoparticles and thermochromic films.

  7. Growth rate induced monoclinic to tetragonal phase transition in epitaxial BiFeO{sub 3} (001) thin films

    SciTech Connect

    Liu Huajun; Yang Ping; Yao Kui; Wang, John

    2011-03-07

    Epitaxial BiFeO{sub 3} thin films were deposited on SrRuO{sub 3} buffered SrTiO{sub 3} (001) substrates at different growth rates by varying the radio frequency sputtering power. With increasing growth rate, the crystal structure of BiFeO{sub 3} films develops from monoclinic lattice to a mixture phase of tetragonal lattice T{sub 1} with c/a{approx}1.05 and giant tetragonal lattice T{sub 2} with c/a{approx}1.23, finally to a single tetragonal phase T{sub 2}, as shown by high resolution synchrotron x-ray diffraction reciprocal space mappings. The observed phase transitions, induced by film growth rate, offer an alternative strategy to manipulate crystalline phases in epitaxial ferroelectric thin films.

  8. A simple and low-cost combustion method to prepare monoclinic VO2 with superior thermochromic properties

    PubMed Central

    Cao, Ziyi; Xiao, Xiudi; Lu, Xuanming; Zhan, Yongjun; Cheng, Haoliang; Xu, Gang

    2016-01-01

    In this approach, the VO2 nanoparticles have been successfully fabricated via combusting the low-cost precursor solution consisted of NH4VO3, C2H6O2 and C2H5OH. By the XRD, TEM and XPS analysis, it can be found that the synthetic monoclinic VO2 is single crystal and no impurity is defined. After dispersing the VO2 nanoparticles into the polymer, the solar modulation of VO2-based composite film is up to 12.5% with luminous transmission and haze around 62.2% and 0.5%, respectively. In other words, the composite films show high performance of thermochromic properties. This could open an efficient way to fabricate low-cost and large-scale VO2 (M) nanoparticles and thermochromic films. PMID:27976748

  9. A simple and low-cost combustion method to prepare monoclinic VO2 with superior thermochromic properties.

    PubMed

    Cao, Ziyi; Xiao, Xiudi; Lu, Xuanming; Zhan, Yongjun; Cheng, Haoliang; Xu, Gang

    2016-12-15

    In this approach, the VO2 nanoparticles have been successfully fabricated via combusting the low-cost precursor solution consisted of NH4VO3, C2H6O2 and C2H5OH. By the XRD, TEM and XPS analysis, it can be found that the synthetic monoclinic VO2 is single crystal and no impurity is defined. After dispersing the VO2 nanoparticles into the polymer, the solar modulation of VO2-based composite film is up to 12.5% with luminous transmission and haze around 62.2% and 0.5%, respectively. In other words, the composite films show high performance of thermochromic properties. This could open an efficient way to fabricate low-cost and large-scale VO2 (M) nanoparticles and thermochromic films.

  10. Monoclinic nanodomains in morphotropic phase boundary Pb(Mg1/3Nb2/3)O3-PbTiO3

    NASA Astrophysics Data System (ADS)

    Sato, Y.; Hirayama, T.; Ikuhara, Y.

    2014-02-01

    Crystalline structure is a fundamental characteristic of many materials, and drastic changes in properties may accompany crystal phase transitions. A prominent example of this is the morphotropic phase boundary of (Pb(Mg1/3Nb2/3)O3-PbTiO3) single crystal, a region that exhibits a high piezoelectric effect. Although the highest piezoelectricity is often attributed to a monoclinic crystal phase, formation of ferroelectric nanodomains (NDs) complicates understanding of this crystal structure. In this Letter, we report dedicated transmission electron microscopy and electron diffraction analysis to understand the crystal structure at the ND level. Splitting of diffraction spots, caused by very small lattice distortion in the NDs, is important to understanding crystal structure and has been unambiguously observed. The results can be explained by monoclinic phase NDs. Combining these results with our previous findings on ND dynamics [Sato et al. Phys. Rev. Lett. 107, 187601 (2011)], monoclinic NDs can potentially make a considerable contribution to the piezoelectricity in these materials.

  11. On the relation between steep monoclinal flexure zones and steep hydraulic gradients.

    PubMed

    Yechieli, Y; Kafri, U; Wollman, S; Lyakhovsky, V; Weinberger, R

    2007-01-01

    Steep hydraulic gradients are found in association with steep monoclinal flexures. However, the physics of the reduction of the hydraulic conductivity, which is responsible for the steep gradients, has seldom been studied. We present results of hydrological and mechanical modeling aiming to study the effect of such steep hydraulic gradients demonstrated in the Judea Group Aquifer system, Israel. The hydrological configuration of steep dips and anisotropy between flows parallel and perpendicular to the bedding planes was simulated using the FEFLOW code. It exhibited a situation whereby part of the flow is oblique to the bedding planes and therefore some steepening of the hydraulic gradients occurred due to actual conductivity reduction. However, this reduction is not enough to account for the steeper gradients observed. The effect of a deep-seated reverse fault under the monocline on the permeability distribution within the structure was examined by numerical mechanical simulations. It exhibited a compressional stress distribution in the steep part of the monocline, which, due to shortening and closure of joints and voids, is presumably responsible for a significant pressure-induced permeability reduction. This process by itself in a layered structure, including interlayering of thin marl layers, could be responsible for the steep hydraulic gradients in the steep part of the monocline.

  12. Microstructure, bioactivity and osteoblast behavior of monoclinic zirconia coating with nanostructured surface.

    PubMed

    Wang, Guocheng; Meng, Fanhao; Ding, Chuanxian; Chu, Paul K; Liu, Xuanyong

    2010-03-01

    A monoclinic zirconia coating with a nanostructural surface was prepared on the Ti-6Al-4V substrate by an atmospheric plasma-spraying technique, and its microstructure and composition, as well as mechanical and biological properties, were investigated to explore potential application as a bioactive coating on bone implants. X-ray diffraction, transmission electron microscopy, scanning electron microscopy and Raman spectroscopy revealed that the zirconia coating was composed of monoclinic zirconia which was stable at low temperature, and its surface consists of nano-size grains 30-50 nm in size. The bond strength between the coating and the Ti-6Al-4V substrate was 48.4 + or - 6.1 MPa, which is higher than that of plasma-sprayed HA coatings. Hydrothermal experiments indicated that the coating was stable in a water environment and the phase composition and Vickers hardness were independent of the hydrothermal treatment time. Bone-like apatite is observed to precipitate on the surface of the coating after soaking in simulated body fluid for 6 days, indicating excellent bioactivity in vitro. The nanostructured surface composed of monoclinic zirconia is believed to be crucial to its bioactivity. Morphological observation and the cell proliferation test demonstrated that osteoblast-like MG63 cells could attach to, adhere to and proliferate well on the surface of the monoclinic zirconia coating, suggesting possible applications in hard tissue replacements.

  13. South Menderes Monocline: Low-temperature thermochronology constrains role of crustal extension in structural evolution of southwest Turkey

    NASA Astrophysics Data System (ADS)

    Ring, Uwe; Gessner, Klaus; Thomson, Stuart N.

    2017-08-01

    We report apatite and zircon fission-track data across the contact zones between the Menderes nappes, the Cycladic blueschist unit, and the Ören nappe, in the Anatolide belt of southwest Turkey. These data resolve previous debate on the deformation history of these Cretaceous to Eocene nappe contacts, including whether they were reactivated during late Oligocene to Miocene crustal extension. Apatite fission-track ages range from 18 to 28 Ma in the Menderes nappes, and 31 to 42 Ma in the Ören nappe. Zircon fission-track ages are 29 to 31 Ma in the Menderes nappes, 30 to 33 Ma in the Cycladic blueschist unit, and between 93 Ma and 129 Ma in the Ören nappe. The data reveal that the tectonic contacts within the Menderes nappes, and with the overlying Cycladic blueschist unit have been sealed since 35-30 Ma. In the Ören nappe, zircon fission-track ages are distinctly older (with mixed single grain ages between 300 and 75 Ma) reflecting partial to full resetting during late Cretaceous high-pressure metamorphism. The contact between the Cycladic blueschist unit and the Ören nappe shows no significant tectonic movement in the brittle crust after 70 Ma. These data reveal that the nappe boundaries in the southern Menderes Massif have undergone no significant differential offset relative to the Earth's surface since the Oligocene and therefore were not reactivated during late Oligocene to Miocene continental extension. We interpret the steeply dipping portion of the nappe pile in the southern Menderes Massif as a tilted crustal section, which we name the 'South Menderes Monocline'. We speculate this monocline formed by differential uplift in the Miocene, either at the hinge zone of a plateau, or by unloading of the Simav detachment footwall.

  14. Structural, microstructural and vibrational analyses of the monoclinic tungstate BiLuWO{sub 6}

    SciTech Connect

    Ait Ahsaine, H.; Taoufyq, A.; Patout, L.; Ezahri, M.; Benlhachemi, A.; Bakiz, B.; Villain, S.; Guinneton, F.; Gavarri, J.-R.

    2014-10-15

    The bismuth lutetium tungstate phase BiLuWO{sub 6} has been prepared using a solid state route with stoichiometric mixtures of oxide precursors. The obtained polycrystalline phase has been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Raman spectroscopy. In the first step, the crystal structure has been refined using Rietveld method: the crystal cell was resolved using monoclinic system (parameters a, b, c, β) with space group A2/m. SEM images showed the presence of large crystallites with a constant local nominal composition (BiLuW). TEM analyses showed that the actual local structure could be better represented by a superlattice (a, 2b, c, β) associated with space groups P2 or P2/m. The Raman spectroscopy showed the presence of vibrational bands similar to those observed in the compounds BiREWO{sub 6} with RE=Y, Gd, Nd. However, these vibrational bands were characterized by large full width at half maximum, probably resulting from the long range Bi/Lu disorder and local WO{sub 6} octahedron distortions in the structure. - Graphical abstract: The average structure of BiLuWO{sub 6} determined from X-ray diffraction data can be represented by A2/m space group. Experimental Electron Diffraction patterns along the [0vw] zone axes of the monoclinic structure and associated simulated patterns show the existence of a monoclinic superstructure with space group P2 or P2/m. - Highlights: • A new monoclinic BiLuWO{sub 6} phase has been elaborated from solid-state reaction. • The space group of the monoclinic disordered average structure should be A2/m. • Transmission electron microscopy leads to a superlattice with P2/m space group. • Raman spectroscopy suggests existence of local disorder.

  15. Structure and magnetism of low-doped monoclinic crystals of (Ga{sub 1-x}Mn{sub x}){sub 2}Se{sub 3}

    SciTech Connect

    Dubinin, S. F. Maksimov, V. I.; Parkhomenko, V. D.

    2011-12-15

    The influence that doping with Mn{sup 3+} ions has on the fine crystal structure of the monoclinic compound Ga{sub 2}Se{sub 3} was studied by single-crystal neutron diffraction and the measurements of magnetic properties. It was found that the structural state of the crystals changes even at relatively low doping levels (x = 0.04). Local Jahn-Teller distortions were shown to be responsible for the formation of the fine structure and magnetism in this type of compounds.

  16. Raman analysis of monoclinic Cu2SnS3 thin films

    NASA Astrophysics Data System (ADS)

    Berg, Dominik M.; Djemour, Rabie; Gütay, Levent; Siebentritt, Susanne; Dale, Phillip J.; Fontane, Xavier; Izquierdo-Roca, Victor; Pérez-Rodriguez, Alejandro

    2012-05-01

    Secondary phases like Cu2SnS3 are major obstacles for kesterite thin film solar cell applications. We prepare Cu2SnS3 using identical annealing conditions as used for the kesterite films. By x-ray diffraction, the crystal structure of Cu2SnS3 was identified as monoclinic. Polarization-dependent Raman investigations allowed the identification of the dominant peaks at 290 cm-1 and 352 cm-1 with the main A' symmetry vibrational modes from the monoclinic Cu2SnS3 phase. Furthermore, micro-resolved Raman investigations revealed local variations in the spectra that are attributed to a secondary phase (possibly Cu2Sn3S7). This exemplifies the abilities of micro-resolved Raman measurements in the detection of secondary phases.

  17. Fabrication and photoelectrocatalytic properties of nanocrystalline monoclinic BiVO4 thin-film electrode.

    PubMed

    Zhou, Bin; Qu, Jiuhui; Zhao, Xu; Liu, Huijuan

    2011-01-01

    Monoclinic bismuth vanadate (BiVO4) thin film was fabricated on indium-tin oxide glass from an amorphous heteronuclear complex via dip-coating. After annealation at 400, 500, and 600 degrees C, the thin films were characterized by X-ray diffraction, field emission scanning electron microscopy, X-ray photoelectron spectroscopy, and UV-Vis spectrophotometry. The BiVO4 particles on the ITO glass surface had a monoclinic structure. The UV-Visible diffuse reflection spectra showed the BiVO4 thin film had photoabsorption properties, with a band gap around 2.5 eV. In addition, the thin film showed high visible photocatalytic activities towards 2,4-dichlorophenol and Bisphenol A degradation under visible light irradiation (lambda > 420 nm). Over 90% of the two organic pollutants were removed in 5 hr. A possible degradation mechanism of 2,4-dichlorophenol were also studied.

  18. Evidence for photo-induced monoclinic metallic VO{sub 2} under high pressure

    SciTech Connect

    Hsieh, Wen-Pin Mao, Wendy L.; Trigo, Mariano; Reis, David A.; Andrea Artioli, Gianluca; Malavasi, Lorenzo

    2014-01-13

    We combine ultrafast pump-probe spectroscopy with a diamond-anvil cell to decouple the insulator-metal electronic transition from the lattice symmetry changing structural transition in the archetypal strongly correlated material vanadium dioxide. Coherent phonon spectroscopy enables tracking of the photo-excited phonon vibrational frequencies of the low temperature, monoclinic (M{sub 1})-insulating phase that transforms into the metallic, tetragonal rutile structured phase at high temperature or via non-thermal photo-excitations. We find that in contrast with ambient pressure experiments where strong photo-excitation promptly induces the electronic transition along with changes in the lattice symmetry, at high pressure, the coherent phonons of the monoclinic (M{sub 1}) phase are still clearly observed upon the photo-driven phase transition to a metallic state. These results demonstrate the possibility of synthesizing and studying transient phases under extreme conditions.

  19. Identification of monoclinic calcium pyrophosphate dihydrate and hydroxyapatite in human sclera using Raman microspectroscopy

    PubMed Central

    Chen, Ko-Hua; Li, Mei-Jane; Cheng, Wen-Ting; Balic-Zunic, Tonci; Lin, Shan-Yang

    2009-01-01

    Raman microspectroscopy was first used to determine the composition of a calcified plaque located at the pterygium-excision site of a 51-year-old female patient's left nasal sclera after surgery. It was unexpectedly found that the Raman spectrum of the calcified sample at 1149, 1108, 1049, 756, 517, 376 and 352/cm was similar to the Raman spectrum of monoclinic form of calcium pyrophosphate dihydrate (CPPD) crystal, but differed from the Raman spectrum of triclinic form of CPPD. An additional peak at 958/cm was also observed in the Raman spectrum of the calcified plaque, which was identical to the characteristic peak at 958/cm of hydroxyapatite (HA). This is the first study to report the spectral biodiagnosis of both monoclinic CPPD and HA co-deposited in the calcified plaque of a patient with sclera dystrophic calcification using Raman microspectroscopy. PMID:19200254

  20. Structural Discrimination via DFT: Monoclinic Mg2NiH4

    NASA Astrophysics Data System (ADS)

    Herbst, Jan; Hector, Louis, Jr.

    2009-03-01

    Mg2NiH4 is a semiconductor and forms an ordered low temperature monoclinic phase and a disordered high temperature cubic modification. Two distinct structures for the monoclinic phase from neutron diffraction studies of the deuterated analog, which we designate as LTI and LTII, are available in the published literature. We calculate the enthalpy of formation δH with density functional theory (DFT) for both using three different approximations for the exchange-correlation energy functional. Phonon spectra are calculated as well. DFT unequivocally identifies LTII as preferable since δH obtained for it is in better agreement with experiment and its phonon spectrum contains no anomalies. Structures approximating LTII derived from analyses of soft modes in LTI and in Mg-substituted CaMgNiH4 are also discussed.

  1. Changes in mobility of plastic crystal ethanol during its transformation into the monoclinic crystal state

    SciTech Connect

    Sanz, Alejandro Nogales, Aurora; Ezquerra, Tiberio A.; Puente-Orench, Inés; Jiménez-Ruiz, Mónica

    2014-02-07

    Transformation of deuterated ethanol from the plastic crystal phase into the monoclinic one is investigated by means of a singular setup combining simultaneously dielectric spectroscopy with neutron diffraction. We postulate that a dynamic transition from plastic crystal to supercooled liquid-like configuration through a deep reorganization of the hydrogen-bonding network must take place as a previous step of the crystallization process. Once these precursor regions are formed, subsequent crystalline nucleation and growth develop with time.

  2. Evaluation of physicochemical properties, and antimicrobial efficacy of monoclinic sulfur-nanocolloid

    NASA Astrophysics Data System (ADS)

    Roy Choudhury, Samrat; Mandal, Amrita; Chakravorty, Dipankar; Gopal, Madhuban; Goswami, Arunava

    2013-04-01

    Stable nanocolloids of monoclinic sulfur (β-SNPs) were prepared through `water-in-oil microemulsion technique' at room temperature after suitable modifications of the surface. The morphology (rod shaped; 50 nm in diameter) and allotropic nature (monoclinic) of the SNPs were investigated with Transmission Electron Microscopy and X-ray Diffraction technique. The surface modification, colloidal stability, and surface topology of β-SNPs were evaluated with Fourier Transform Infrared Spectroscopy, zeta potential analysis, and Atomic Force Microscopy. Thermal decomposition pattern of these nanosized particles was determined by Thermo Gravimetric Analysis (TGA). β-SNPs-colloids expressed excellent antimicrobial activities against a series of fungal and bacterial isolates with prominent deformities at their surface. In contrast, insignificant cytotoxicity was achieved against the human derived hepatoma (HepG2) cell line upon treatment with β-SNPs. A simultaneous study was performed to determine the stock concentration of β-SNP-colloids using a novel high phase liquid chromatographic method. Cumulative results of this study hence, elucidate the stabilization of nanosized monoclinic sulfur at room temperature and their potential antimicrobial efficacy over micron-sized sulfur.

  3. The creation of modulated monoclinic aperiodic composites in n-alkane/urea compounds

    DOE PAGES

    Mariette, Céline; Guérin, Laurent; Rabiller, Philippe; ...

    2014-09-12

    n-Dodecane/urea is a member of the prototype series of n-alkane/urea inclusion compounds. At room temperature, it presents a quasi-one dimensional liquid-like state for the confined guest molecules within the rigid, hexagonal framework of the urea host. At lower temperatures, we report the existence of two other phases. Below Tc=248 K there appears a phase with rank four superspace group P6122(00γ), the one typically observed at room temperature in n-alkane/urea compounds with longer guest molecules. A misfit parameter, defined by the ratio γ=ch/cg (chost/cguest), is found to be 0.632±0.005. Below Tc1=123 K, a monoclinic modulated phase is created with a constantmore » shift along c of the guest molecules in adjacent channels. The maximal monoclinic space group for this structure is P1211(α0γ). We discuss analogies and differences with n-heptane/urea, which also presents a monoclinic, modulated low-temperature phase.« less

  4. The creation of modulated monoclinic aperiodic composites in n-alkane/urea compounds

    SciTech Connect

    Mariette, Céline; Guérin, Laurent; Rabiller, Philippe; Chen, Yu-Sheng; Bosak, Alexei; Popov, Alexander; Hollingsworth, Mark D.; Toudic, Bertrand

    2014-09-12

    n-Dodecane/urea is a member of the prototype series of n-alkane/urea inclusion compounds. At room temperature, it presents a quasi-one dimensional liquid-like state for the confined guest molecules within the rigid, hexagonal framework of the urea host. At lower temperatures, we report the existence of two other phases. Below Tc=248 K there appears a phase with rank four superspace group P6122(00γ), the one typically observed at room temperature in n-alkane/urea compounds with longer guest molecules. A misfit parameter, defined by the ratio γ=ch/cg (chost/cguest), is found to be 0.632±0.005. Below Tc1=123 K, a monoclinic modulated phase is created with a constant shift along c of the guest molecules in adjacent channels. The maximal monoclinic space group for this structure is P1211(α0γ). We discuss analogies and differences with n-heptane/urea, which also presents a monoclinic, modulated low-temperature phase.

  5. Critical Role of Monoclinic Polarization Rotation in High-Performance Perovskite Piezoelectric Materials.

    PubMed

    Liu, Hui; Chen, Jun; Fan, Longlong; Ren, Yang; Pan, Zhao; Lalitha, K V; Rödel, Jürgen; Xing, Xianran

    2017-07-07

    High-performance piezoelectric materials constantly attract interest for both technological applications and fundamental research. The understanding of the origin of the high-performance piezoelectric property remains a challenge mainly due to the lack of direct experimental evidence. We perform in situ high-energy x-ray diffraction combined with 2D geometry scattering technology to reveal the underlying mechanism for the perovskite-type lead-based high-performance piezoelectric materials. The direct structural evidence reveals that the electric-field-driven continuous polarization rotation within the monoclinic plane plays a critical role to achieve the giant piezoelectric response. An intrinsic relationship between the crystal structure and piezoelectric performance in perovskite ferroelectrics has been established: A strong tendency of electric-field-driven polarization rotation generates peak piezoelectric performance and vice versa. Furthermore, the monoclinic M_{A} structure is the key feature to superior piezoelectric properties as compared to other structures such as monoclinic M_{B}, rhombohedral, and tetragonal. A high piezoelectric response originates from intrinsic lattice strain, but little from extrinsic domain switching. The present results will facilitate designing high-performance perovskite piezoelectric materials by enhancing the intrinsic lattice contribution with easy and continuous polarization rotation.

  6. Metastable monoclinic ZnMoO4: hydrothermal synthesis, optical properties and photocatalytic performance.

    PubMed

    Lv, Li; Tong, Wenming; Zhang, Yanbing; Su, Yiguo; Wang, Xiaojing

    2011-11-01

    Metastable monoclinic ZnMoO4 was successfully synthesized via a hydrothermal route with variation of reaction temperatures and time at pH value of 5.7. Systematic sample characterizations were carried out, including X-ray powder diffraction, scanning electron microscopy, Fourier transformed infrared spectra, UV-visible diffuse reflectance spectra, and photoluminescence spectra. The results show that all as-prepared ZnMoO4 samples were demonstrated to crystallize in a pure-phase of monoclinic wolframite structure. All samples were formed in plate-like morphology. Six IR active vibrational bands were observed in the wave number range of 400-900 cm(-1). The band gap of as-prepared ZnMoO4 was estimated to be 2.86 eV by Tauc equation. Photoluminescence measurement indicates that as-prepared ZnMoO4 exhibits a broad blue-green emission under excitation wavelength of 280 nm at room temperature. Photocatalytic activity of as-prepared ZnMoO4 was examined by monitoring the degradation of methyl orange dye in an aqueous solution under UV radiation of 365 nm. The as-prepared ZnMoO4 obtained at 180 degrees C for 40 h showed the best photocatalytic activity with completing degradation of MO in irradiation time of 120 min. Consequently, monoclinic ZnMoO4 proved to be an efficient near visible light photocatalyst.

  7. Critical Role of Monoclinic Polarization Rotation in High-Performance Perovskite Piezoelectric Materials

    NASA Astrophysics Data System (ADS)

    Liu, Hui; Chen, Jun; Fan, Longlong; Ren, Yang; Pan, Zhao; Lalitha, K. V.; Rödel, Jürgen; Xing, Xianran

    2017-07-01

    High-performance piezoelectric materials constantly attract interest for both technological applications and fundamental research. The understanding of the origin of the high-performance piezoelectric property remains a challenge mainly due to the lack of direct experimental evidence. We perform in situ high-energy x-ray diffraction combined with 2D geometry scattering technology to reveal the underlying mechanism for the perovskite-type lead-based high-performance piezoelectric materials. The direct structural evidence reveals that the electric-field-driven continuous polarization rotation within the monoclinic plane plays a critical role to achieve the giant piezoelectric response. An intrinsic relationship between the crystal structure and piezoelectric performance in perovskite ferroelectrics has been established: A strong tendency of electric-field-driven polarization rotation generates peak piezoelectric performance and vice versa. Furthermore, the monoclinic MA structure is the key feature to superior piezoelectric properties as compared to other structures such as monoclinic MB , rhombohedral, and tetragonal. A high piezoelectric response originates from intrinsic lattice strain, but little from extrinsic domain switching. The present results will facilitate designing high-performance perovskite piezoelectric materials by enhancing the intrinsic lattice contribution with easy and continuous polarization rotation.

  8. Remarkable features in lattice-parameter ratios of crystals. II. Monoclinic and triclinic crystals.

    PubMed

    de Gelder, R; Janner, A

    2005-06-01

    The frequency distributions of monoclinic crystals as a function of the lattice-parameter ratios resemble the corresponding ones of orthorhombic crystals: an exponential component, with more or less pronounced sharp peaks, with in general the most important peak at the ratio value 1. In addition, the distribution as a function of the monoclinic angle beta has a sharp peak at 90 degrees and decreases sensibly at larger angles. Similar behavior is observed for the three triclinic angular parameters alpha, beta and gamma, with characteristic differences between the organic and metal-organic, bio-macromolecular and inorganic crystals, respectively. The general behavior observed for the hexagonal, tetragonal, orthorhombic, monoclinic and triclinic crystals {in the first part of this series [de Gelder & Janner (2005). Acta Cryst. B61, 287-295] and in the present case} is summarized and commented. The data involved represent 366 800 crystals, with lattice parameters taken from the Cambridge Structural Database, CSD (294 400 entries), the Protein Data Bank, PDB (18 800 entries), and the Inorganic Crystal Structure Database, ICSD (53 600 entries). A new general structural principle is suggested.

  9. Testing Monoclines for Dextral Shear: Paleomagnetic Results From the Nacimiento Uplift, Northern New Mexico

    NASA Astrophysics Data System (ADS)

    Tetreault, J.; Jones, C. H.

    2001-12-01

    Dextral shear along the eastern margin of the Colorado Plateau has been inferred to have occurred in the Laramide orogeny by many workers. Some shear has been suggested to have occurred on exposed faults, but the limited strike extent of these faults presents a difficulty for advocates of large strike-slip Laramide motion. One possibility is that that shear is expressed as vertical-axis rotations along monoclinal folds that extend beyond the surface traces of the mapped faults. We examine one such monocline bounded to the west by the Nacimiento Fault in northern New Mexico. The Nacimiento Uplift is a north-south trending vertical structure along the eastern boundary of the San Juan Basin formed by Laramide reactivation of a Late Paleozoic uplift. Previous investigations have interpreted Laramide dextral slip along the Nacimiento Fault from minor fault data (Erslev, 2001), Proterozoic piercing lines (Cather, 1999), and related strike slip structures (Woodward, 1987). Paleomagnetic analysis was conducted to determine if the monocline accomodated strike-slip motion through vertical axis rotations. Preliminary results from the Late Cretaceous Mesaverde, Paleocene Nacimiento, and Paleocene Ojo Alamo formations north of the Nacimiento Fault establish an absence of vertical-axis rotation along the fold. The Mesaverde sandstone yields the most favorable results. Antipodal directions in the Mesaverde samples imply that a primary magnetization penecontemporaneous with deposition has been isolated. The tilt-corrected direction is D= 332+/- 11° , I = 53+/- 7° , α 95 = 8° , N = 24. The results are indistinguishable from the expected Late Cretaceous direction (D= 339+/- 8° , I = 63+/- 11° ) with a rotation of R = -7 +/- 14° . The Nacimiento and Ojo Alamo sandstones produced more scattered directions, yet still consistent with the virtual absence of rotation. Thus either (1) right-lateral shear does not occur along the Nacimiento monocline or (2) it does not produce

  10. Coordinate-Invariant Lyddane-Sachs-Teller Relationship for Polar Vibrations in Materials with Monoclinic and Triclinic Crystal Systems

    NASA Astrophysics Data System (ADS)

    Schubert, Mathias

    2016-11-01

    A coordinate-invariant generalization of the Lyddane-Sachs-Teller relation is presented for polar vibrations in materials with monoclinic and triclinic crystal systems. The generalization is derived from an eigendielectric displacement vector summation approach, which is equivalent to the microscopic Born-Huang description of polar lattice vibrations in the harmonic approximation. An expression for a general oscillator strength is also described for materials with monoclinic and triclinic crystal systems. A generalized factorized form of the dielectric response characteristic for monoclinic and triclinic materials is proposed. The generalized Lyddane-Sachs-Teller relation is found valid for monoclinic β -Ga2O3 , where accurate experimental data became available recently from a comprehensive generalized ellipsometry investigation [Phys. Rev. B 93, 125209 (2016)]. Data for triclinic crystal systems can be measured by generalized ellipsometry as well, and are anticipated to become available soon and results can be compared with the generalized relations presented here.

  11. Monoclinic and Tetragonal Plagioclase (An54) in Shock Veins from the Central Uplift of the Manicouagan Impact Structure

    NASA Astrophysics Data System (ADS)

    Spray, J. G.; Boonsue, S.

    2016-08-01

    This work documents the discovery of monoclinic- and tetragonal-structured plagioclase. Critically, the high-pressure polymorphs possess the same composition as the non-shocked triclinic phase (An54).

  12. Coordinate-Invariant Lyddane-Sachs-Teller Relationship for Polar Vibrations in Materials with Monoclinic and Triclinic Crystal Systems.

    PubMed

    Schubert, Mathias

    2016-11-18

    A coordinate-invariant generalization of the Lyddane-Sachs-Teller relation is presented for polar vibrations in materials with monoclinic and triclinic crystal systems. The generalization is derived from an eigendielectric displacement vector summation approach, which is equivalent to the microscopic Born-Huang description of polar lattice vibrations in the harmonic approximation. An expression for a general oscillator strength is also described for materials with monoclinic and triclinic crystal systems. A generalized factorized form of the dielectric response characteristic for monoclinic and triclinic materials is proposed. The generalized Lyddane-Sachs-Teller relation is found valid for monoclinic β-Ga_{2}O_{3}, where accurate experimental data became available recently from a comprehensive generalized ellipsometry investigation [Phys. Rev. B 93, 125209 (2016)]. Data for triclinic crystal systems can be measured by generalized ellipsometry as well, and are anticipated to become available soon and results can be compared with the generalized relations presented here.

  13. Dipole analysis of the dielectric function of color dispersive materials: Application to monoclinic Ga2O3

    NASA Astrophysics Data System (ADS)

    Sturm, C.; Schmidt-Grund, R.; Kranert, C.; Furthmüller, J.; Bechstedt, F.; Grundmann, M.

    2016-07-01

    We apply a generalized model for the determination and analysis of the dielectric function of optically anisotropic materials with color dispersion to phonon modes and show that it can also be generalized to excitonic polarizabilities and electronic band-band transitions. We take into account that the tensor components of the dielectric function within the Cartesian coordinate system are not independent of each other but are rather projections of the polarization of dipoles oscillating along directions defined by the, non-Cartesian, crystal symmetry and polarizability. The dielectric function is then composed of a series of oscillators pointing in different directions. The application of this model is exemplarily demonstrated for monoclinic (β -phase) Ga2O3 bulk single crystals. Using this model we are able to relate electronic transitions observed in the dielectric function to atomic bond directions and orbitals in the real space crystal structure. For a thin film revealing rotational domains we show that the optical biaxiality is reduced to uniaxial optical response.

  14. X-ray diffraction investigations and spectral analyses of monoclinic SmKFe(CN) 6 · 3H 2O

    NASA Astrophysics Data System (ADS)

    Mullica, D. F.; Sappenfield, E. L.; Perkins, H. O.

    1989-02-01

    Single-crystal and powder X-ray diffraction data, X-ray fluorescence and thermal gravimetric analyses, conoscopic results, and infrared spectral data are presented for SmKFe(CN) 6 · 3H 2O. The compound crystallizes in the monoclinic space group {P2 1}/{m} (No. 11), a = 7.329(2), b = 13.689(4), c = 7.324(3) Å, β = 119.97(3)°, Z = 2, Dm = 2.37(1) Mg m -3, and Dx = 2.376 Mg m -3. Final least-squares full-matrix refinement yielded R = 0.0574 and Rw = 0.0568 for 2138 unique reflections. The samarium ion is nine-coordinated forming a tricapped trigonal prism geometry. The octahedral FeC 6 groups are linked to the SmN 6(H 2O) 3 groups by cyanide bridging. The coordinated water molecules occupy general positions at two-thirds occupancy. The uncoordinated water molecule and the potassium ion (each at 0.5 occupancy) occupy holes in the structure. Important mean bond distances are: SmN = 2.478(5); SmO = 2.678(4); FeC = 1.899(5); and CN = 1.156(3) Å.

  15. Ultrasound assisted synthesis of monoclinic structured spindle BiVO4 particles with hollow structure and its photocatalytic property.

    PubMed

    Liu, Wei; Cao, Lixin; Su, Ge; Liu, Haisong; Wang, Xiangfei; Zhang, Lan

    2010-04-01

    Bismuth vanadate (BiVO(4)) spindle particles with monoclinic scheelite structure have been successfully synthesized via a facile sonochemical method. The as-prepared BiVO(4) photocatalyst exhibited a hollow interior structure constructed from the self-assembly of cone shape primary nanocrystals. A possible oriented attachment growth mechanism has been proposed based on the results of time-dependent experiments, which indicates the formation of spindle particles is mainly attributed to the phase transformation procedure induced by ultrasound irradiation. A series of morphology evolutions of BiVO(4) from compact microspheres, to hollow microspheres, and then to spindle particles have been arrested in the process of sonochemical treatment. Optical absorption experiments revealed the BiVO(4) spindle had strong absorption in the visible light region. A much higher photocatalytic activity of these spindle particles was found in comparison with the SSR-BiVO(4) material for degradation of rhodamine-B under visible light irradiation, which may be ascribed to its special single-crystalline nanostructure.

  16. Seismic transpressive basement faults and monocline development in a foreland basin (Eastern Guadalquivir, SE Spain)

    NASA Astrophysics Data System (ADS)

    Pedrera, A.; Ruiz-Constán, A.; Marín-Lechado, C.; Galindo-Zaldívar, J.; González, A.; Peláez, J. A.

    2013-12-01

    We examine the late Tortonian to present-day deformation of an active seismic sector of the eastern Iberian foreland basement of the Betic Cordillera, in southern Spain. Transpressive faults affecting Paleozoic basement offset up to Triassic rocks. Late Triassic clays and evaporites constitute a décollement level decoupling the basement rocks and a ~100 m thick cover of Jurassic carbonates. Monoclines trending NE-SW to ENE-WSW deform the Jurassic cover driven by the propagation of high-angle transpressive right-lateral basement faults. They favor the migration of clays and evaporites toward the propagated fault tip, i.e., the core of the anticline, resulting in fluid overpressure, fluid flow, and precipitation of fibrous gypsum parallel to a vertical σ3. The overall geometry of the studied monoclines, as well as the intense deformation within the clays and evaporites, reproduces three-layer discrete element models entailing a weak middle unit sandwiched between strong layers. Late Tortonian syn-folding sediments recorded the initial stages of the fault-propagation folding. Equivalent unexposed transpressive structures and associated monoclines reactivated under the present-day NW-SE convergence are recognized and analyzed in the Sabiote-Torreperogil region, using seismic reflection, gravity, and borehole data. A seismic series of more than 2100 low-magnitude earthquakes was recorded within a very limited area of the basement of this sector from October 2012 to May 2013. Seismic activity within a major NE-SW trending transpressive basement fault plane stimulated rupture along a subsidiary E-W (~N95°E) strike-slip relay fault. The biggest event (mbLg 3.9, MW 3.7) occurred at the junction between them in a transpressive relay sector.

  17. Structure of a monoclinic polymorph of human carbonic anhydrase II with a doubled a axis

    SciTech Connect

    Robbins, Arthur H.; Domsic, John F.; Agbandje-McKenna, Mavis; McKenna, Robert

    2010-05-01

    The crystal structure of human carbonic anhydrase II with a doubled a axis from that of the usually observed monoclinic cell has been determined and refined to 1.4 Å resolution. The two molecules comprising the asymmetric unit are related by a noncrystallographic translation of ½ along a, but one of the molecules has two alternate orientations related by a rotation of approximately 2°. The crystal structure of human carbonic anhydrase II with a doubled a axis from that of the usually observed monoclinic unit cell has been determined and refined to 1.4 Å resolution. The diffraction data with h = 2n + 1 were systematically weaker than those with h = 2n. Consequently, the scaling of the data, structure solution and refinement were challenging. The two molecules comprising the asymmetric unit are related by a noncrystallographic translation of ½ along a, but one of the molecules has two alternate positions related by a rotation of approximately 2°. This rotation axis is located near the edge of the central β-sheet, causing a maximum distance disparity of 1.7 Å between equivalent atoms on the diametrically opposite side of the molecule. The crystal-packing contacts are similar to two sequential combined unit cells along a of the previously determined monoclinic unit cell. Abnormally high final R{sub cryst} and R{sub free} values (20.2% and 23.7%, respectively) are not unusual for structures containing pseudo-translational symmetry and probably result from poor signal to noise in the weak h-odd data.

  18. A monoclinic form of dendocarbin A: a borderline case of one-dimensional isostructural polymorphism.

    PubMed

    Paz, Cristian; Burgos, Viviana; Suarez, Sebastián; Baggio, Ricardo

    2015-04-01

    The title compound, dendocarbin A [systematic name: (1R,5aS,9aS,9bR)-1-hydroxy-6,6,9a-trimethyldodecahydronaphtho[1,2-c]furan-3-one], C15H22O3, is a sesquiterpene lactone isolated from Drimys winteri var chilensis. The monoclinic phase described herein displays an identical molecular structure to the orthorhombic phase that we reported previously [Paz Robles et al. (2014). Acta Cryst. C70, 1007-1010], while varying significantly in chain pitch, and can thus be considered as a borderline case of one-dimensional isostructural polymorphism.

  19. Instantaneous band gap collapse in photoexcited monoclinic VO2 due to photocarrier doping.

    PubMed

    Wegkamp, Daniel; Herzog, Marc; Xian, Lede; Gatti, Matteo; Cudazzo, Pierluigi; McGahan, Christina L; Marvel, Robert E; Haglund, Richard F; Rubio, Angel; Wolf, Martin; Stähler, Julia

    2014-11-21

    Using femtosecond time-resolved photoelectron spectroscopy we demonstrate that photoexcitation transforms monoclinic VO2 quasi-instantaneously into a metal. Thereby, we exclude an 80 fs structural bottleneck for the photoinduced electronic phase transition of VO2. First-principles many-body perturbation theory calculations reveal a high sensitivity of the VO2 band gap to variations of the dynamically screened Coulomb interaction, supporting a fully electronically driven isostructural insulator-to-metal transition. We thus conclude that the ultrafast band structure renormalization is caused by photoexcitation of carriers from localized V 3d valence states, strongly changing the screening before significant hot-carrier relaxation or ionic motion has occurred.

  20. Thermal stress and end-bulging in monoclinic crystals: the case study of double tungstates.

    PubMed

    Yumashev, Konstantin; Loiko, Pavel

    2017-05-01

    An analytical description of the thermal stress and end-bulging component of thermal lensing is presented for monoclinic laser crystals, taking into account the anisotropy of their optical, thermal, and elastic properties for the first time, to the best of our knowledge. The geometry of longitudinal diode-pumping (plane stress approximation) is considered. The developed approach is applied to the monoclinic double tungstates (MDTs), Yb:KGW, Yb:KYW, and Yb:KLuW, yielding values of normal and shear stresses, tensile stress, and the end-bulging term. We show that for low-symmetry crystals, end-bulging is responsible for the astigmatism of the thermal lens. The geometry of this astigmatism is explained in terms of the principal meridional planes. We show that the crystal cut of the MDTs along the optical indicatrix axis Ng (propagation direction) provides low thermal stress and a purely positive and weakly astigmatic thermal lens, which is a key condition for power scaling and diffraction-limited laser output.

  1. Finite element analysis of the tetragonal to monoclinic phase transformation during oxidation of zirconium alloys

    NASA Astrophysics Data System (ADS)

    Platt, P.; Frankel, P.; Gass, M.; Howells, R.; Preuss, M.

    2014-11-01

    Corrosion is a key limiting factor in the degradation of zirconium alloys in light water reactors. Developing a mechanistic understanding of the corrosion process offers a route towards improving safety and efficiency as demand increases for higher burn-up of fuel. Oxides formed on zirconium alloys are composed of both monoclinic and meta-stable tetragonal phases, and are subject to a number of potential mechanical degradation mechanisms. The work presented investigates the link between the tetragonal to monoclinic oxide phase transformation and degradation of the protective character of the oxide layer. To achieve this, Abaqus finite element analysis of the oxide phase transformation has been carried out. Study of the change in transformation strain energy shows how relaxation of oxidation induced stress and fast fracture at the metal-oxide interface could destabilise the tetragonal phase. Central to this is the identification of the transformation variant most likely to form, and understanding why twinning of the transformed grain is likely to occur. Development of transformation strain tensors and analysis of the strain components allows some separation of dilatation and shear effects. Maximum principal stress is used as an indication of fracture in the surrounding oxide layer. Study of the stress distributions shows the way oxide fracture is likely to occur and the differing effects of dilatation and shape change. Comparison with literature provides qualitative validation of the finite element simulations.

  2. Variable defect structures cause the magnetic low-temperature transition in natural monoclinic pyrrhotite

    NASA Astrophysics Data System (ADS)

    Koulialias, D.; Kind, J.; Charilaou, M.; Weidler, P. G.; Löffler, J. F.; Gehring, A. U.

    2016-02-01

    Non-stoichiometric monoclinic 4C pyrrhotite (Fe7S8) is a major magnetic remanence carrier in the Earth's crust and in extraterrestrial materials. Because of its low-temperature magnetic transition around 30 K also known as Besnus transition, which is considered to be an intrinsic property, this mineral phase is easily detectable in natural samples. Although the physical properties of pyrrhotite have intensively been studied, the mechanism behind the pronounced change in magnetization at the low-temperature transition is still debated. Here we report magnetization experiments on a pyrrhotite crystal (Fe6.6S8) that consists of a 4C and an incommensurate 5C* superstructure that are different in their defect structure. The occurrence of two superstructures is magnetically confirmed by symmetric inflection points in hysteresis measurements above the transition at about 30 K. The disappearance of the inflection points and the associated change of the hysteresis parameters indicate that the two superstructures become strongly coupled to form a unitary magnetic anisotropy system at the transition. From this it follows that the Besnus transition in monoclinic pyrrhotite is an extrinsic magnetic phenomenon with respect to the 4C superstructure and therefore the physics behind it is in fact different from that of the well-known Verwey transition.

  3. Monoclinic tridymite in clast-rich impact melt rock from the Chesapeake Bay impact structure

    USGS Publications Warehouse

    Jackson, John C.; Horton, J. Wright; Chou, I-Ming; Belkin, Harvey E.

    2011-01-01

    X-ray diffraction and Raman spectroscopy confirm a rare terrestrial occurrence of monoclinic tridymite in clast-rich impact melt rock from the Eyreville B drill core in the Chesapeake Bay impact structure. The monoclinic tridymite occurs with quartz paramorphs after tridymite and K-feldspar in a microcrystalline groundmass of devitrified glass and Fe-rich smectite. Electron-microprobe analyses revealed that the tridymite and quartz paramorphs after tridymite contain different amounts of chemical impurities. Inspection by SEM showed that the tridymite crystal surfaces are smooth, whereas the quartz paramorphs contain irregular tabular voids. These voids may represent microporosity formed by volume decrease in the presence of fluid during transformation from tridymite to quartz, or skeletal growth in the original tridymite. Cristobalite locally rims spherulites within the same drill core interval. The occurrences of tridymite and cristobalite appear to be restricted to the thickest clast-rich impact melt body in the core at 1402.02–1407.49 m depth. Their formation and preservation in an alkali-rich, high-silica melt rock suggest initially high temperatures followed by rapid cooling.

  4. Magnetic structure driven by monoclinic distortions in the double perovskite Sr2YRuO6

    NASA Astrophysics Data System (ADS)

    Bernardo, P. L.; Ghivelder, L.; Amorim, H. S.; Neumeier, J. J.; García, S.

    2015-10-01

    The monoclinic double perovskite Sr2YRuO6 has recently gained a renewed interest in order to get a deeper insight into the exotic magnetic ground states associated with geometric frustration. Striking discrepancies between the spin order derived from the neutron diffraction refinements and the macroscopic magnetic and thermal responses is a major challenge that must be addressed. In this work, detailed neutron diffraction measurements as a function of temperature yield a completely different interpretation of the patterns. We show that at low temperatures a spin structure of the K2NiF4-type is an accessible configuration for the magnetic ground state. In the neighborhood of the magnetic transition, this configuration evolves into a canted superstructure. The deduced temperature dependence of the canting angle exhibits two closely spaced peaks, which are in excellent agreement with the double peaks in the magnetic contribution to the specific heat and in the thermal expansion coefficient. We explain these features in terms of reorientation of the net ferromagnetic moment of the noncollinear spin state, due to the local breaking of the inversion symmetry promoted by the monoclinic distortions, with structural changes acting as the driving force.

  5. Ab initio velocity-field curves in monoclinic β-Ga2O3

    NASA Astrophysics Data System (ADS)

    Ghosh, Krishnendu; Singisetti, Uttam

    2017-07-01

    We investigate the high-field transport in monoclinic β-Ga2O3 using a combination of ab initio calculations and full band Monte Carlo (FBMC) simulation. Scattering rate calculation and the final state selection in the FBMC simulation use complete wave-vector (both electron and phonon) and crystal direction dependent electron phonon interaction (EPI) elements. We propose and implement a semi-coarse version of the Wannier-Fourier interpolation method [Giustino et al., Phys. Rev. B 76, 165108 (2007)] for short-range non-polar optical phonon (EPI) elements in order to ease the computational requirement in FBMC simulation. During the interpolation of the EPI, the inverse Fourier sum over the real-space electronic grids is done on a coarse mesh while the unitary rotations are done on a fine mesh. This paper reports the high field transport in monoclinic β-Ga2O3 with deep insight into the contribution of electron-phonon interactions and velocity-field characteristics for electric fields ranging up to 450 kV/cm in different crystal directions. A peak velocity of 2 × 107 cm/s is estimated at an electric field of 200 kV/cm.

  6. Imaging metal-like monoclinic phase stabilized by surface coordination effect in vanadium dioxide nanobeam

    NASA Astrophysics Data System (ADS)

    Li, Zejun; Wu, Jiajing; Hu, Zhenpeng; Lin, Yue; Chen, Qi; Guo, Yuqiao; Liu, Yuhua; Zhao, Yingcheng; Peng, Jing; Chu, Wangsheng; Wu, Changzheng; Xie, Yi

    2017-06-01

    In correlated systems, intermediate states usually appear transiently across phase transitions even at the femtosecond scale. It therefore remains an open question how to determine these intermediate states--a critical issue for understanding the origin of their correlated behaviour. Here we report a surface coordination route to successfully stabilize and directly image an intermediate state in the metal-insulator transition of vanadium dioxide. As a prototype metal-insulator transition material, we capture an unusual metal-like monoclinic phase at room temperature that has long been predicted. Coordinate bonding of L-ascorbic acid molecules with vanadium dioxide nanobeams induces charge-carrier density reorganization and stabilizes metallic monoclinic vanadium dioxide, unravelling orbital-selective Mott correlation for gap opening of the vanadium dioxide metal-insulator transition. Our study contributes to completing phase-evolution pathways in the metal-insulator transition process, and we anticipate that coordination chemistry may be a powerful tool for engineering properties of low-dimensional correlated solids.

  7. Conduction band topology and optical properties of monoclinic ZrO_2

    NASA Astrophysics Data System (ADS)

    Freeman, A. J.; Medvedeva, J. E.; Geller, C. B.

    2004-03-01

    Zirconia is an attractive base material for a wide variety of optical applications, on account of its high refractive index, large band gap and low optical loss. We report highly precise density functional theory calculations on pure, monoclinic zirconia employing the self-consistent screened exchange local-density approximation(R. Asahi, W. Mannstadt, A. J. Freeman, Phys. Rev. B) 59, 7486 (1999) (sX-LDA) with the full-potential linearized augmented plane wave (FLAPW) method(E. Wimmer, H. Krakauer, M. Weinert, A.J. Freeman, Phys. Rev. B) 24, 864 (1981). The sX-LDA substantially reduces the overbinding error in the LDA resulting in a more accurate description of the band gap and excited states in semiconductors(C.B. Geller er al), Appl. Phys. Lett. 79, 368 (2001) and insulators (this work). The predicted sX-LDA indirect band gap of monoclinic ZrO2 is 5.7 eV, in agreement with experiment. The effects of carrier concentration on the effective masses and optical properties of zirconia are discussed.

  8. Lithostratigraphy and geochemistry of Upper Vendian‒Lower Cambrian deposits in the northeastern Baltic monocline

    NASA Astrophysics Data System (ADS)

    Podkovyrov, V. N.; Maslov, A. V.; Kuznetsov, A. B.; Ershova, V. B.

    2017-01-01

    The results of investigations of Upper Vendian‒Lower Cambrian deposits in the northeastern part of the Baltic monocline specify views on the evolution of depositional environments of sedimentary successions constituting the basal part of the sedimentary cover in inner areas of the northwestern East European Platform. It is shown that the Late Vendian and initial Cambrian were characterized by the consecutive influx of relatively mature terrigenous detrital material that originated from both the weathering crust of the Baltic Shield and new sources. Its deposition was interrupted by notable, although likely asynchronous, hiatuses, which are registered at the base of the Upper Vendian Vasileostrovskaya and Voronkovo formations and Lower Cambrian Lomonosov Formation. In the Late Vendian, sedimentary material was transported from the Baltic Shield, while beginning from the initial Early Cambrian the additional contribution to the formation of the sedimentary cover of the Baltic monocline was provided by coarse-grained sedimentary material from the Timan margin of the Baltica as follows from U‒Pb isotopic ages obtained for detrital zircons. At the same time, lithogeochemical parameters of fine-grained rocks experienced no substantial changes.

  9. Crystal structure of monoclinic calcium pyrophosphate dihydrate (m-CPPD) involved in inflammatory reactions and osteoarthritis.

    PubMed

    Gras, Pierre; Rey, Christian; André, Gilles; Charvillat, Cédric; Sarda, Stéphanie; Combes, Christèle

    2016-02-01

    Pure monoclinic calcium pyrophosphate dihydrate (m-CPPD) has been synthesized and characterized by synchrotron powder X-ray diffraction and neutron diffraction. Rietveld refinement of complementary diffraction data has, for the first time, allowed the crystal structure of m-CPPD to be solved. The monoclinic system P2(1)/n was confirmed and unit-cell parameters determined: a = 12.60842 (4), b = 9.24278 (4), c = 6.74885 (2) Å and β = 104.9916 (3)°. Neutron diffraction data especially have allowed the precise determination of the position of H atoms in the structure. The relationship between the m-CPPD crystal structure and that of the triclinic calcium pyrophosphate dihydrate (t-CPPD) phase as well as other pyrophosphate phases involving other divalent cations are discussed by considering the inflammatory potential of these phases and/or their involvement in different diseases. These original structural data represent a key step in the understanding of the mechanisms of crystal formation involved in different types of arthritis and to improve early detection of calcium pyrophosphate (CPP) phases in vivo.

  10. Monoclinic phase transformation and mechanical durability of zirconia ceramic after fatigue and autoclave aging.

    PubMed

    Mota, Yasmine A; Cotes, Caroline; Carvalho, Rodrigo F; Machado, João P B; Leite, Fabíola P P; Souza, Rodrigo O A; Özcan, Mutlu

    2017-10-01

    This study evaluated the influence of two aging procedures on the biaxial flexural strength of yttria-stabilized tetragonal zirconia ceramics. Disc-shaped zirconia specimens and (ZE: E.max ZirCAD, Ivoclar; ZT: Zirkon Translucent, Zirkonzahn) (N = 80) (∅:12 mm; thickness:1.2 mm, ISO 6872) were prepared and randomly divided into four groups (n = 10 per group) according to the aging procedures: C: Control, no aging; M: mechanical cycling (2 × 10(6) cycles/3.8 Hz/200 N); AUT: Aging in autoclave at 134°C, 2 bar for 24 h; AUT + M: Autoclave aging followed by mechanical cycling. After aging, the transformed monoclinic zirconia (%) were evaluated using X-ray diffraction and surface roughness was measured using atomic force microscopy. The average grain size was measured by scanning electron microscopy and the specimens were submitted to biaxial flexural strength testing (1 mm/min, 1000 kgf in water). Data (MPa) were statistically analyzed using 2-way analysis of variance and Tukey's test (α = 0.05). Aging procedures significantly affected (p = 0.000) the flexural strength data but the effect of zirconia type was not significant (p = 0.657). AUTZT (936.4 ± 120.9(b) ) and AUT + MZE (867.2 ± 49.3(b) ) groups presented significantly higher values (p < 0.05) of flexural strength than those of the control groups (CZT : 716.5 ± 185.7(a) ; CZE : 779.9 ± 114(a) ) (Tukey's test). The monoclinic phase percentage (%) was higher for AUTZE (71), AUTZT (66), AUT + MZE (71), and AUT + MZM (66) compared to the C groups (ZE:0; ZT:0). Surface roughness (µm) was higher for AUTZE (0.09), AUTZT (0.08), AUT + MZE (0.09 µm), and AUT + MZT (0.09 µm) than those of other groups. Regardless of the zirconia type, autoclave aging alone or with mechanical aging increased the flexure strength but also induced higher transformation from tetragonal to monoclinic phase in both zirconia materials tested. © 2016 Wiley Periodicals

  11. Monoclinic β-MoO(3) nanosheets produced by atmospheric microplasma: application to lithium-ion batteries.

    PubMed

    Mariotti, Davide; Lindström, Henrik; Bose, Arumugam Chandra; Ostrikov, Kostya Ken

    2008-12-10

    Porous high surface area thin films of nanosheet-shaped monoclinic MoO(3) were deposited onto platinized Si substrates using patch antenna-based atmospheric microplasma processing. The films were characterized by high resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM) and electrochemical analysis. The electrochemical analysis shows original redox peaks and high charge capacity, and also indicates a reversible electrochemical behaviour particularly beneficial for applications in Li-ion batteries. SEM shows that the films are highly porous and consist of nanosheets 50-100 nm thick with surface dimensions in the micrometre range. HRTEM reveals that the MoO(3) nanosheets consist of the monoclinic beta phase of MoO(3). These intricate nanoarchitectures made of monoclinic MoO(3) nanosheets have not been studied previously in the context of applications in Li-ion batteries and show superior structural and morphological features that enable effective insertion of Li ions.

  12. Monoclinic 122-Type BaIr₂Ge₂ with a Channel Framework: A Structural Connection between Clathrate and Layered Compounds.

    PubMed

    Gui, Xin; Chang, Tay-Rong; Kong, Tai; Pan, Max T; Cava, Robert J; Xie, Weiwei

    2017-07-18

    A new 122-type phase, monoclinic BaIr₂Ge₂ is successfully synthesized by arc melting; X-ray diffraction and scanning electron microscopy are used to purify the phase and determine its crystal structure. BaIr₂Ge₂ adopts a clathrate-like channel framework structure of the monoclinic BaRh₂Si₂-type, with space group P2₁/c. Structural comparisons of clathrate, ThCr₂Si₂, CaBe₂Ge₂, and BaRh₂Si2 structure types indicate that BaIr₂Ge₂ can be considered as an intermediate between clathrate and layered compounds. Magnetic measurements show it to be diamagnetic and non-superconducting down to 1.8 K. Different from many layered or clathrate compounds, monoclinic BaIr₂Ge₂ displays a metallic resistivity. Electronic structure calculations performed for BaIr₂Ge₂ support its observed structural stability and physical properties.

  13. Phase-controlled synthesis of polymorphic tungsten diphosphide with hybridization of monoclinic and orthorhombic phases as a novel electrocatalyst for efficient hydrogen evolution

    NASA Astrophysics Data System (ADS)

    Pi, Mingyu; Wu, Tianli; Guo, Weimeng; Wang, Xiaodeng; Zhang, Dingke; Wang, Shuxia; Chen, Shijian

    2017-05-01

    The design and development of high-efficiency and non-noble-metal hydrogen evolution reaction (HER) electrocatalysts for future clean and renewable energy system has excited significant research interests over the recent years. In this communication, the polymorphic tungsten diphosphide (p-WP2) nanoparticles with mixed monoclinic (α-) and orthorhombic (β-) phases are synthesized by phase-controlled phosphidation route via vacuum capsulation and explored as a novel efficient electrocatalyst towards HER. The p-WP2 catalyst delivers superior performance with excellent stability under both acidic and alkaline conditions over its single phases of α-WP2 and β-WP2. This finding demonstrates that a highly efficient hybrid electrocatalyst can be achieved via precise composition controlling and may open up exciting opportunities for their practical applications toward energy conversion.

  14. Calculation of thermodynamic, electronic, and optical properties of monoclinic Mg2NiH4

    SciTech Connect

    Myers, W.R.; Richardson, T.J.; Rubin, M.D.; Wang, L-W.

    2001-10-01

    Ab initio total-energy density functional theory is used to investigate the low temperature (LT) monoclinic form of Mg2NiH4. The calculated minimum energy geometry of LT Mg2NiH4 is close to that determined from neutron diffraction data, and the NiH4 complex is close to a regular tetrahedron. The enthalpies of the phase change to high temperature (HT) pseudo-cubic Mg2NiH4 and of hydrogen absorption by Mg2Ni are calculated and compared with experimental values. LT Mg2NiH4 is found to be a semiconductor with an indirect band gap of 1.4 eV. The optical dielectric function of LT Mg2NiH4 differs somewhat from that of the HT phase. A calculated thin film transmittance spectrum is consistent with an experimental spectrum.

  15. A second monoclinic polymorph of (E)-phen­yl(pyridin-2-yl)methanone oxime

    PubMed Central

    Rodríguez-Mora, Monserrath I.; Reyes-Martínez, Reyna; Flores-Alamo, Marcos; García, Juventino J.; Morales-Morales, David

    2013-01-01

    The title compound, C12H10N2O, a second monoclinic poly­morph of (E)-phen­yl(pyridin-2-yl)methanone oxime crystallizes in the space group P21/n (Z = 4). The previously reported polymorph [Taga et al. (1990 ▶). Acta Cryst. C46, 2241–2243] occurs in the space group C2/c (Z = 8). In the crystal, pairs of bifurcated O—H⋯(N,O) hydrogen bonds link the mol­ecules into inversion dimers. The dimers are linked by C—H⋯π inter­actions, forming a linear arrangement. The dihedral angle between the pyridine and phenyl rings is 67.70 (8)°. PMID:23424575

  16. A monoclinic post-stishovite polymorph of silica in the shergotty meteorite

    PubMed

    El Goresy A; Dubrovinsky; Sharp; Saxena; Chen

    2000-06-02

    A post-stishovite phase of silica was identified in the Shergotty meteorite by x-ray diffraction and field emission scanning electron microscopy. The diffraction pattern revealed a monoclinic lattice, similar to the baddeleyite-structured polymorph with the cell parameters a = 4.375(1) angstroms, b = 4.584(1) angstroms, c = 4. 708(1) angstroms, beta= 99.97(3), rho = 4.30(2) grams per cubic centimeter, where the numbers in parentheses are the maximum deviations. Transmission electron microscopy investigations indicate the presence of the alpha-lead dioxide-like polymorph, stishovite, and secondary cristobalite in the same silica grain. The mixture of high-density polymorphs suggests that several post-stishovite phases were formed during the shock event on the Shergotty parent body.

  17. THE MONOCLINIC PHASE IN PZT: NEW LIGHT ON MORPHOTROPIC PHASE BOUNDARIES

    SciTech Connect

    NOHEDA,B.; GONZALO,J.A.; GUO,R.; PARK,S.E.; CROSS,L.E.; COX,D.E.; SHIRANE,G.

    2000-03-09

    A summary of the work recently carried out on the morphotropic phase boundary (MPB) of PZT is presented. By means of x-ray powder diffraction on ceramic samples of excellent quality, the MPB has been successfully characterized by changing temperature in a series of closely spaced compositions. As a result, an unexpected monoclinic phase has been found to exist in between the well-known tetragonal and rhombohedral PZT phases. A detailed structural analysis, together with the investigation of the field effect in this region of compositions, have led to an important advance in understanding the mechanisms responsible for the physical properties of PZT as well as other piezoelectric materials with similar morphotropic phase boundaries.

  18. Electronic structure and optical properties of monoclinic clinobisvanite BiVO4.

    PubMed

    Zhao, Zongyan; Li, Zhaosheng; Zou, Zhigang

    2011-03-14

    Monoclinic clinobisvanite bismuth vanadate is an important material with wide applications. However, its electronic structure and optical properties are still not thoroughly understood. Density functional theory calculations were adopted in the present work, to comprehend the band structure, density of states, and projected wave function of BiVO(4). In particular, we put more emphasis upon the intrinsic relationship between its structure and properties. Based on the calculated results, its molecular-orbital bonding structure was proposed. And a significant phenomenon of optical anisotropy was observed in the visible-light region. Furthermore, it was found that its slightly distorted crystal structure enhances the lone-pair impact of Bi 6s states, leading to the special optical properties and excellent photocatalytic activities.

  19. Structural discrimination via density functional theory and lattice dynamics: Monoclinic Mg2NiH4

    NASA Astrophysics Data System (ADS)

    Herbst, J. F.; Hector, L. G., Jr.

    2009-04-01

    Two distinct crystal structures for the monoclinic, low-temperature phase of Mg2NiH4 , which we designate as LTI and LTII, are available in the published literature. We demonstrate that density functional theory and lattice dynamics can easily identify LTII as the preferable structure at two levels of inquiry. First, enthalpies of formation ΔH calculated using three different forms for the exchange-correlation energy functional are in better agreement with experiment for LTII. Second, the phonon spectrum calculated for LTII contains no anomalies while that for LTI exhibits a variety of soft modes. By analyzing the soft modes in LTI as well as those we find for the known CaMgNiH4 structure with Ca replaced by Mg we derive a crystal structure that closely approximates LTII.

  20. 1-Nitro-4-(4-nitro-phen-oxy)benzene: a second monoclinic polymorph.

    PubMed

    Naz, Mehwish; Akhter, Zareen; McKee, Vickie; Nadeem, Arif

    2013-11-06

    In the title compound, C12H8N2O5, the aromatic rings are inclined to one another by 56.14 (7)°. The nitro groups are inclined by to the benzene rings to which they are attached by 3.86 (17) and 9.65 (15)°. In the crystal, mol-ecules are linked by C-H⋯O hydrogen bonds, forming a three-dimensional structure. The title compound is a new monoclinic polymorph, crystallizing in space group P21/c. The first polymorph crystallized in space group C2/c and the mol-ecule possesses twofold rotation symmetry. Two low-temperature structures of this polymorph (150 K and 100 K, respectively) have been reported [Meciarova et al. (2004). Private Communication (refcode IXOGAD). CCDC, Cambridge, England, and Dey & Desiraju (2005). Chem. Commun. pp. 2486-2488].

  1. Giant Polarization and High Temperature Monoclinic Phase in a Lead-Free Perovskite of Bi(Zn0.5Ti0.5)O3-BiFeO3

    DOE PAGES

    Pan, Zhao; Chen, Jun; Yu, Runze; ...

    2016-09-15

    Lead-free piezoelectrics have attracted increasing attention due to the awareness of lead toxicity to the environment. Here, a new Bi-based lead-free perovskite of (1-x)Bi(Zn0.5Ti0.5)O3-xBiFeO3 has been synthesized via high-pressure and high-temperature method. It exhibits interest-ing properties of giant polarization, morphotropic phase boundary (MPB), and monoclinic phase. In particular, large tetragonality (c/a = 1.228) and giant spontaneous polariza-tion of 110 μC/cm2 has been obtained in 0.6Bi(Zn0.5Ti0.5)O3-0.4BiFeO3, which is much higher than most available lead-free materials and conventional Pb(Zr,Ti)O3. MPB is clearly identified to be constituted by tetragonal and monoclinic phases at x = 0.5. Notably, a single monoclinic phase has beenmore » observed at x = 0.6, which exhibits an intriguing high temperature property. In conclusion, the present results are helpful to explore new lead-free MPB systems in bismuth-based compounds.« less

  2. Giant Polarization and High Temperature Monoclinic Phase in a Lead-Free Perovskite of Bi(Zn0.5Ti0.5)O3-BiFeO3.

    PubMed

    Pan, Zhao; Chen, Jun; Yu, Runze; Yamamoto, Hajime; Rong, Yangchun; Hu, Lei; Li, Qiang; Lin, Kun; You, Li; Zhao, Kun; Fan, Longlong; Ren, Yang; Kato, Kenichi; Azuma, Masaki; Xing, Xianran

    2016-10-03

    Lead-free piezoelectrics have attracted increasing attention because of the awareness of lead toxicity to the environment. Here, a new bismuth-based lead-free perovskite, (1 - x)Bi(Zn0.5Ti0.5)O3-xBiFeO3, has been synthesized via a high-pressure and high-temperature method. It exhibits interesting properties of giant polarization, morphotropic phase boundary (MPB), and monoclinic phase. In particular, large tetragonality (c/a = 1.228) and giant spontaneous polarization of 110 μC/cm(2) has been obtained in 0.6 Bi(Zn0.5Ti0.5)O3-0.4BiFeO3, which is much higher than most available lead-free materials and conventional Pb(Zr,Ti)O3. MPB is clearly identified to be constituted of tetragonal and monoclinic phases at x = 0.5. Notably, a single monoclinic phase has been observed at x = 0.6, which exhibits an intriguing high-temperature property. The present results are helpful to explore new lead-free MPB systems in bismuth-based compounds.

  3. Investigation of the femtosecond optical limiting properties of monoclinic copper niobate

    NASA Astrophysics Data System (ADS)

    Priyadarshani, N.; Venugopal Rao, S.; Sabari Girisun, T. C.

    2016-10-01

    Investigation of the third-order nonlinear optical properties and optical limiting behaviour of microstructured monoclinic phase copper niobate (CuNb2O6) was performed by the Z-scan technique using femtosecond laser pulses (800 nm, 150 fs, 80 MHz). CuNb2O6 was synthesized by solid-state reaction at a sintering temperature of 700 °C maintained at different times of 3, 6, 9 and 12 h. Formation of rods at higher reaction time of 12 h was observed and is attributed to the mass transport and coalescence processes. From the absorption tail of UV-Vis spectrum, the optical band gap was estimated to be 3.5 eV. In the fluorescence spectra, blue emission was observed near 430 nm and was assigned to the charge transfer from oxygen to central niobium of Nb-O6 octahedra. Open-aperture Z-scan data demonstrated the presence of nonlinear absorption in copper niobate and are ascribed to two-photon absorption process. Closed-aperture data indicated a sign reversal in nonlinear refraction as the sintering time increased. Third-order nonlinear optical coefficients were estimated, and the largest coefficient was observed for the rod-structured CuNb2O6. Copper niobate exhibited optical limiting behaviour, and the limiting threshold was found to be lowest for microrod structures (~0.21 µJ/cm2). Due to the top-notch third-order nonlinear optical coefficients and excellent limiting behaviour, monoclinic copper niobate microrods can be used as a potential material for utilization as an optical limiter for femtosecond pulses.

  4. Structural evolution and electrochemistry of monoclinic NaNiO2 upon the first cycling process

    NASA Astrophysics Data System (ADS)

    Han, Man Huon; Gonzalo, Elena; Casas-Cabanas, Montse; Rojo, Teófilo

    2014-07-01

    Electrochemistry and structural evolution of monoclinic NaNiO2 as a cathode material for Na-ion battery is reported. The initial charge capacity reached 160 mA h g-1 and the following discharge capacity of 114.6 mA h g-1, within the voltage range of 4.0-1.5 V at C/10. The multiple phase transition leading to O‧3, P‧3, P″3, O″3, and O‴3 stacking types (NaNiO2, Na0.91NiO2, Na0.84NiO2, Na0.81NiO2 and Na0.79NiO2 transitions, respectively, according to a previous report) during the 1st charge/discharge process is analysed using ex situ and in situ XRD techniques, and the stoichiometry of each phase is herein revised. The charge/discharge profile shows a highly reversible nature of the cathode, except that fully sodiated phase could not be achieved at the subsequent discharge. Two new phases have been discovered: a monoclinic O3 structure (designated as O⁗3) at the beginning of the charge (and end of discharge) and a P3 structure (designated as P‴3) at 3.38 V that appeared only during the charge process. The composition of the new O⁗3-phase corresponds to Na0.83NiO2, which is the closest to the fully sodiated phase at room temperature achieved during the discharge process reported up to date, and the composition of the new P‴3-phase corresponds approximately to Na0.50NiO2.

  5. Crystal structure of 8-hy-droxy-quinoline: a new monoclinic polymorph.

    PubMed

    Castañeda, Raúl; Antal, Sofia A; Draguta, Sergiu; Timofeeva, Tatiana V; Khrustalev, Victor N

    2014-09-01

    In an attempt to grow 8-hy-droxy-quinoline-acetamino-phen co-crystals from equimolar amounts of conformers in a chloro-form-ethanol solvent mixture at room temperature, the title compound, C9H7NO, was obtained. The mol-ecule is planar, with the hy-droxy H atom forming an intra-molecular O-H⋯N hydrogen bond. In the crystal, mol-ecules form centrosymmetric dimers via two O-H⋯N hydrogen bonds. Thus, the hy-droxy H atoms are involved in bifurcated O-H⋯N hydrogen bonds, leading to the formation of a central planar four-membered N2H2 ring. The dimers are bound by inter-molecular π-π stacking [the shortest C⋯C distance is 3.2997 (17) Å] and C-H⋯π inter-actions into a three-dimensional framework. The crystal grown represents a new monoclinic polymorph in the space group P21/n. The mol-ecular structure of the present monoclinic polymorph is very similar to that of the ortho-rhom-bic polymorph (space group Fdd2) studied previously [Roychowdhury et al. (1978 ▶). Acta Cryst. B34, 1047-1048; Banerjee & Saha (1986 ▶). Acta Cryst. C42, 1408-1411]. The structures of the two polymorphs are distinguished by the different geometries of the hydrogen-bonded dimers, which in the crystal of the ortho-rhom-bic polymorph possess twofold axis symmetry, with the central N2H2 ring adopting a butterfly conformation.

  6. Paleomagnetic and structural evidence for oblique slip in a fault-related fold, Grayback monocline, Colorado

    USGS Publications Warehouse

    Tetreault, J.; Jones, C.H.; Erslev, E.; Larson, S.; Hudson, M.; Holdaway, S.

    2008-01-01

    Significant fold-axis-parallel slip is accommodated in the folded strata of the Grayback monocline, northeastern Front Range, Colorado, without visible large strike-slip displacement on the fold surface. In many cases, oblique-slip deformation is partitioned; fold-axis-normal slip is accommodated within folds, and fold-axis-parallel slip is resolved onto adjacent strike-slip faults. Unlike partitioning strike-parallel slip onto adjacent strike-slip faults, fold-axis-parallel slip has deformed the forelimb of the Grayback monocline. Mean compressive paleostress orientations in the forelimb are deflected 15??-37?? clockwise from the regional paleostress orientation of the northeastern Front Range. Paleomagnetic directions from the Permian Ingleside Formation in the forelimb are rotated 16??-42?? clockwise about a bedding-normal axis relative to the North American Permian reference direction. The paleostress and paleomagnetic rotations increase with the bedding dip angle and decrease along strike toward the fold tip. These measurements allow for 50-120 m of fold-axis-parallel slip within the forelimb, depending on the kinematics of strike-slip shear. This resolved horizontal slip is nearly equal in magnitude to the ???180 m vertical throw across the fold. For 200 m of oblique-slip displacement (120 m of strike slip and 180 m of reverse slip), the true shortening direction across the fold is N90??E, indistinguishable from the regionally inferred direction of N90??E and quite different from the S53??E fold-normal direction. Recognition of this deformational style means that significant amounts of strike slip can be accommodated within folds without axis-parallel surficial faulting. ?? 2008 Geological Society of America.

  7. Cadmium Stabilization Efficiency and Leachability by CdAl4O7 Monoclinic Structure.

    PubMed

    Su, Minhua; Liao, Changzhong; Chuang, Kui-Hao; Wey, Ming-Yen; Shih, Kaimin

    2015-12-15

    This study investigated the stabilization efficiencies of using an aluminum-rich precursor to incorporate simulated cadmium-bearing waste sludge and evaluated the leaching performance of the product phase. Cadmium oxide and γ-alumina mixtures with various Cd/Al molar ratios were fired at 800-1000 °C for 3 h. Cadmium could be crystallochemically incorporated by γ-alumina into CdAl4O7 monoclinic phase and the reaction was strongly controlled by the treatment temperature. The crystal structure details of CdAl4O7 were solved and refined with the Rietveld refinement method. According to the structural refinement results, the stabilization efficiencies were quantified and expressed as a transformation ratio (TR) with optimized processing parameters. The preferred treatment temperature was found to be 950 °C for mixtures with a Cd/Al molar ratio of 1/4, as its TR value indicated the cadmium incorporation was nearly completed after a 3 h treatment scheme. Constant-pH leaching tests (CPLT) were conducted by comparing the leachability of the CdO and CdAl4O7 phases in a pH 4.0 environment. A remarkable reduction in cadmium leachability could be achieved via monoclinic CdAl4O7 structure formation to effectively stabilize hazardous cadmium in the waste stream. The CPLT and X-ray photoelectron spectroscopy (XPS) results suggested incongruent dissolution behavior during the leaching of the CdAl4O7 phase.

  8. Influence of the monoclinic and tetragonal zirconia phases on the water gas shift reaction. A theoretical study.

    PubMed

    Cerón, María Luisa; Herrera, Barbara; Araya, Paulo; Gracia, Francisco; Toro-Labbé, Alejandro

    2013-07-01

    We present a theoretical study of the water gas shift reaction taking place on zirconia surfaces modeled by monoclinic and tetragonal clusters. In order to understand the charge transfer between the active species, in this work we analyze the influence of the geometry of monoclinic and tetragonal zirconia using reactivity descriptors such as electronic chemical potential (μ), charge transfer (ΔN) and molecular hardness (η). We have found that the most preferred surface is tetragonal zirconia (tZrO2) indicating also that low charge transfer systems will generate less stable intermediates, that will allow to facilitate desorption process.

  9. Local twin domains and tip-voltage-induced domain switching of monoclinic MC phase in Pb(Mg1/3Nb2/3)O3-0.34PbTiO3 single crystal revealed by piezoresponse force microscopy

    SciTech Connect

    Wang, Ruixue; Yang, Bin; Luo, Zhenlin; Sun, Enwei; Sun, Yuan; Xu, Han; Zhao, Jiangtao; Zheng, Limei; Zhou, Hua; Gao, Chen; Cao, Wenwu

    2016-08-29

    Here, the monoclinic (M) phases in high-performance relaxor-based ferroelectric single crystals have been recognized to be a vital structural factor for the outstanding piezoelectric property. However, due to the complexity of the structure in M phases, the understanding about it is still limited. In this paper, the local twin domains and tip-voltage-induced domain switching of the MC phase in Pb(Mg1/3Nb2/3)O3 - 0.34PbTiO3 (PMN-0.34PT) single crystal have been intensively investigated by piezoresponse force microscopy (PFM). By theoretically analyzing the experimental patterns of domain walls on the (001)C face, the specific MC twin domains in the initial annealed state of a selected area have been clarified, and the polarization orientation of the MC phase in this sample is determined to be at an angle of 29 degrees to the < 001 > C directions. In addition, based on the evolution of domains and the motion of domain walls under the step-increased PFM tip dc voltage (Vdc), the switching process and features of different types of MC domain variants are visually revealed

  10. Local twin domains and tip-voltage-induced domain switching of monoclinic MC phase in Pb(Mg1/3Nb2/3)O3-0.34PbTiO3 single crystal revealed by piezoresponse force microscopy

    SciTech Connect

    Wang, Ruixue; Yang, Bin; Luo, Zhenlin; Sun, Enwei; Sun, Yuan; Xu, Han; Zhao, Jiangtao; Zheng, Limei; Zhou, Hua; Gao, Chen; Cao, Wenwu

    2016-08-29

    Here, the monoclinic (M) phases in high-performance relaxor-based ferroelectric single crystals have been recognized to be a vital structural factor for the outstanding piezoelectric property. However, due to the complexity of the structure in M phases, the understanding about it is still limited. In this paper, the local twin domains and tip-voltage-induced domain switching of the MC phase in Pb(Mg1/3Nb2/3)O3 - 0.34PbTiO3 (PMN-0.34PT) single crystal have been intensively investigated by piezoresponse force microscopy (PFM). By theoretically analyzing the experimental patterns of domain walls on the (001)C face, the specific MC twin domains in the initial annealed state of a selected area have been clarified, and the polarization orientation of the MC phase in this sample is determined to be at an angle of 29 degrees to the < 001 > C directions. In addition, based on the evolution of domains and the motion of domain walls under the step-increased PFM tip dc voltage (Vdc), the switching process and features of different types of MC domain variants are visually revealed

  11. Ferroelectric Self-Poling, Switching, and Monoclinic Domain Configuration in BiFeO 3 Thin Films

    DOE PAGES

    Beekman, C.; Siemons, W.; Chi, M.; ...

    2016-05-23

    Self-poling of ferroelectric films, i.e., a preferred, uniform direction of the ferroelectric polarization in as-grown samples is often observed yet poorly understood despite its importance for device applications. The multiferroic perovskite BiFeO3, which crystallizes in two distinct structural polymorphs depending on applied epitaxial strain, is well known to exhibit self-poling. This study investigates the effect of self-poling on the monoclinic domain configuration and the switching properties of the two polymorphs of BiFeO3 (R' and T') in thin films grown on LaAlO3 substrates with slightly different La0.3Sr0.7MnO3 buffer layers. Our study shows that the polarization state formed during the growth actsmore » as “imprint” on the polarization and that switching the polarization away from this self-poled direction can only be done at the expense of the sample's monoclinic domain configuration. We observed reduction of the monoclinic domain size and found that it was largely reversible; hence, the domain size is restored when the polarization is switched back to its original orientation. This is a direct consequence of the growth taking place in the polar phase (below Tc). Finally, switching the polarization away from the preferred configuration, in which defects and domain patterns synergistically minimize the system's energy, leads to a domain state with smaller (and more highly strained and distorted) monoclinic domains.« less

  12. Triclinic-monoclinic-orthorhombic (T-M-O) structural transitions in phase diagram of FeVO4-CrVO4 solid solutions

    NASA Astrophysics Data System (ADS)

    Bera, Ganesh; Reddy, V. R.; Rambabu, P.; Mal, P.; Das, Pradip; Mohapatra, N.; Padmaja, G.; Turpu, G. R.

    2017-09-01

    Phase diagram of FeVO4-CrVO4 solid solutions pertinent with structural and magnetic phases is presented with unambiguous experimental evidences. Solid solutions Fe1-xCrxVO4 (0 ≤ x ≤ 1.0) were synthesized through the standard solid state route and studied by X-ray diffraction, scanning electron microscopy, energy dispersive spectra of X-rays, Raman spectroscopy, d.c. magnetization, and 57Fe Mössbauer spectroscopic studies. FeVO4 and CrVO4 were found to be in triclinic (P-1 space group) and orthorhombic structures (Cmcm space group), respectively. Cr incorporation into the FeVO4 lattice leads to the emergence of a new monoclinic phase dissimilar to the both end members of the solid solutions. In Fe1-xCrxVO4 up to x = 0.10, no discernible changes in the triclinic structure were found. A new structural monoclinic phase (C2/m space group) emerges within the triclinic phase at x = 0.125, and with the increase in Cr content, it gets stabilized with clear single phase signatures in the range of x = 0.175-0.25 as evidenced by the Rietveld analysis of the structures. Beyond x = 0.33, orthorhombic phase similar to CrVO4 (Cmcm space group) emerges and coexists with a monoclinic structure up to x = 0.85, which finally tends to stabilize in the range of x = 0.90-1.00. The Raman spectroscopic studies also confirm the structural transition. FeVO4 Raman spectra show the modes related to three nonequivalent V ions in the triclinic structure, where up to 42 Raman modes are observed in the present study. With the stabilization of structures having higher symmetry, the number of Raman modes decreases and the modes related to symmetry inequivalent sites collate into singular modes from the doublet structure. A systematic crossover from two magnetic transitions in FeVO4, at 21.5 K and 15.4 K to single magnetic transition in CrVO4, at 71 K (antiferromagnetic transition), is observed in magnetization studies. The intermediate solid solution with x = 0.15 shows two magnetic transitions

  13. Simultaneous photocatalytic reduction of Cr(VI) and oxidation of phenol over monoclinic BiVO4 under visible light irradiation.

    PubMed

    Xie, Baoping; Zhang, Hanxia; Cai, Peixiang; Qiu, Rongliang; Xiong, Ya

    2006-05-01

    BiVO4 powder with monoclinic structure was prepared and used as a visible-light catalyst simultaneously for the photooxidation of phenol and the photoreduction of Cr(VI). The photocatalytic efficiency was found to be rather low for either single phenol solution or single Cr(VI) solution. However, the photocatalytic reduction of Cr(VI) and photocatalytic oxidation of phenol proceed more rapidly for the coexistence system of phenol and Cr(VI) than for the single process, showing synergetic effect between the oxidation and reduction reactions. For the simultaneous photocatalytic reduction-oxidation process, the first-order kinetic constant of phenol degradation was 0.0314 min-1, being about six times higher than that for the photocatalytic process of single phenol. This result reveals the feasibility of using Cr(VI) as the electron scavenger of mBiVO4-mediated photocatalytic process of phenol degradation, and gives us an enlightenment to employ other semiconductor with a better visible light response but with a more positive band edge to efficiently degrade organic pollutants. This is the first report for simultaneous photocatalytic reduction of Cr(VI) and removal of phenol under visible light irradiation using photocatalyst mBiVO4.

  14. A phase transition caught in mid-course: independent and concomitant analyses of the monoclinic and triclinic structures of ((n)Bu4N)[Co(orotate)2(bipy)]·3H2O.

    PubMed

    Castro, Miguel; Falvello, Larry R; Forcén-Vázquez, Elena; Guerra, Pablo; Al-Kenany, Nuha A; Martínez, Gema; Tomás, Milagros

    2017-09-01

    The preparation and characterization of the (n)Bu4N(+) salts of two bis-orotate(2-) complexes of cobalt, namely bis(tetra-n-butylammonium) diaquabis(2,4-dioxo-1,2,3,4-tetrahydropyrimidin-1-ide-6-carboxylato-κ(2)N(1),O(6))cobalt(II) 1.8-hydrate, (C16H36N)2[Co(C5H2N2O4)2(H2O)2]·1.8H2O, (1), and tetra-n-butylammonium (2,2'-bipyridine-κ(2)N,N')bis(2,4-dioxo-1,2,3,4-tetrahydropyrimidin-1-ide-6-carboxylato-κ(2)N(1),O(6))cobalt(III) trihydrate, (C16H36N)[Co(C5H2N2O4)2(C10H8N2)]·3H2O, (2), are reported. The Co(III) complex, (2), which is monoclinic at room temperature, presents a conservative single-crystal-to-single-crystal phase transition below 200 K, producing a triclinic twin. The transition, which involves a conformational change in one of the (n)Bu groups of the cation, is reversible and can be cycled. Both end phases have been characterized structurally and the system was also characterized structurally in a two-phase intermediate state, using single-crystal diffraction techniques, with both the monoclinic and triclinic phases present. Thermal analysis allows a rough estimate of the small energy content, viz. 0.25 kJ mol(-1), for both the monoclinic-to-triclinic transformation and the reverse transition, in agreement with the nature of the structural changes involving only the (n)Bu4N(+) cation.

  15. Synthesis of monoclinic IrTe2 under high pressure and its physical properties

    DOE PAGES

    Li, X.; Yan, J. -Q.; Singh, D. J.; ...

    2015-10-12

    In a pressure-temperature (P-T) diagram for synthesizing IrTe2 compounds, the well-studied trigonal (H) phase with the CdI2-type structure is stable at low pressures. The superconducting cubic (C) phase can be synthesized under higher temperatures and pressures. A rhombohedral phase with the crystal structure similar to the C phase can be made at ambient pressure; but the phase contains a high concentration of Ir deficiency. Here, we report that a rarely studied monoclinic (M) phase can be stabilized in narrow ranges of pressure and temperature in this P-T diagram. Moreover, the peculiar crystal structure of the M-IrTe2 eliminates the tendency tomore » form Ir-Ir dimers found in the H phase. The M phase has been fully characterized by structural determination and measurements of electrical resistivity, thermoelectric power, DC magnetization, and specific heat. These physical properties have been compared with those in the H and C phases of Ir1-xTe2. Finally, we present magnetic and transport properties and specific heat of the M-IrTe2 can be fully justified by calculations with the density-functional theory.« less

  16. Luminescence properties of monoclinic Cu{sub 4}I{sub 4}(Piperidine){sub 4}

    SciTech Connect

    Jalilian, Ehsan; Liao, Rong-Zhen; Himo, Fahmi; Lidin, Sven

    2011-08-15

    Highlights: {yields} A new modification of Cu{sub 4}I{sub 4}Pip{sub 4} has been produced under hydrothermal conditions. {yields} This modification have fluorescence properties when it is exposed to UV light. {yields} The fluorescence properties was characterized with fluorescence spectrophotometer. {yields} Quantum mechanical calculations was also performed. -- Abstract: A new modification of Cu{sub 4}I{sub 4}Pip{sub 4} has been synthesized under hydrothermal conditions. X-ray crystallography revealed that this compound crystallized in the monoclinic system and consists of a tetrahedral core with composition Cu{sub 4}I{sub 4}, in which each Cu atom is coordinated by a piperidine molecule via the N atom. In contrast to a previously reported modification of Cu{sub 4}I{sub 4}Pip{sub 4}, the present modification shows luminescent properties when exposed to UV-light. In addition, we have used time-dependent density functional theory calculations to characterize both compounds in term of both absorption and emission.

  17. Ab initio prediction of superdense tetragonal and monoclinic polymorphs of carbon

    DOE PAGES

    Li, Zhen -Zhen; Wang, Jian -Tao; Xu, Li -Fang; ...

    2016-11-02

    The design and synthesis of three-dimensional denser carbons are one of the hot issues in condensed matter physics because of their fascinating properties. Here we identify by ab initio calculations several tetragonal and monoclinic polymorphs of carbon that adopt the t32, t32*, m32, and m32* structures in P4¯21c, P43212, P21/c, and C2 symmetry, respectively. These carbon polymorphs have large 32-atom unit cells in all-sp3 bonding networks comprising five- and six-membered rings that are dynamically stable, as verified by a phonon mode analysis. Electronic band structure calculations show that they are insulators with band gaps in the range of 5.19–5.41 eV,more » close to the calculated band gap of 5.34 eV for diamond. Remarkably, these carbon phases possess an extremely high atom number density exceeding that of diamond. Lastly, the present results establish different types of carbon phases and offer insights into their outstanding structural and electronic properties.« less

  18. Ab initio prediction of superdense tetragonal and monoclinic polymorphs of carbon

    SciTech Connect

    Li, Zhen -Zhen; Wang, Jian -Tao; Xu, Li -Fang; Chen, Changfeng

    2016-11-02

    The design and synthesis of three-dimensional denser carbons are one of the hot issues in condensed matter physics because of their fascinating properties. Here we identify by ab initio calculations several tetragonal and monoclinic polymorphs of carbon that adopt the t32, t32*, m32, and m32* structures in P4¯21c, P43212, P21/c, and C2 symmetry, respectively. These carbon polymorphs have large 32-atom unit cells in all-sp3 bonding networks comprising five- and six-membered rings that are dynamically stable, as verified by a phonon mode analysis. Electronic band structure calculations show that they are insulators with band gaps in the range of 5.19–5.41 eV, close to the calculated band gap of 5.34 eV for diamond. Remarkably, these carbon phases possess an extremely high atom number density exceeding that of diamond. Lastly, the present results establish different types of carbon phases and offer insights into their outstanding structural and electronic properties.

  19. New monoclinic phase at the composition Cu2SnSe3 and its thermoelectric properties.

    PubMed

    Fan, Jing; Carrillo-Cabrera, Wilder; Akselrud, Lev; Antonyshyn, Iryna; Chen, Lidong; Grin, Yuri

    2013-10-07

    A new monoclinic phase (m2) of ternary diamond-like compound Cu2SnSe3 was synthesized by reaction of the elements at 850 K. The crystal structure of m2-Cu2SnSe3 was determined through electron diffraction tomography and refined by full-profile techniques using synchrotron X-ray powder diffraction data (space group Cc, a = 6.9714(2) Å, b = 12.0787(5) Å, c = 13.3935(5) Å, β = 99.865(5)°, Z = 8). Thermal analysis and annealing experiments suggest that m2-Cu2SnSe3 is a low-temperature phase, while the high-temperature phase has a cubic crystal structure. According to quantum chemical calculations, m2-Cu2SnSe3 is a narrow-gap semiconductor. A study of the chemical bonding, applying the electron localizability approach, reveals covalent polar Cu-Se and Sn-Se interactions in the crystal structure. Thermoelectric properties were measured on a specimen consolidated using spark plasma sintering (SPS), confirming the semiconducting character. The thermoelectric figure of merit ZT reaches a maximum value of 0.33 at 650 K.

  20. Pressure induced tetragonal to monoclinic transition in RbN3 studied from first principles theory

    NASA Astrophysics Data System (ADS)

    Vaitheeswaran, G.; Babu, K. Ramesh

    2014-04-01

    Alkali metal azides are well known for their application as explosives and gas generators. They are used as precursors in synthesis of polymeric nitrogen, an ultimate green high energy density material. Among the alkali metal azides, rubidium azide RbN3 crystallizes in tetragonal structure with linear azide ions arranged in layers and binds through weak dispersive interactions. In this present work, we have studied the structural stability, electronic structure and optical properties of solid RbN3 by using van der Waals corrected density functional theory. We find that the ambient tetragonal structure undergoes a structural transition to monoclinic structure at 0.72 GPa, which is in good agreement with the experimental transition pressure of less than 1 GPa. The phonon frequencies at the gamma point are calculated and found that the lattice mode Eg softens under pressure which may supports the structural phase transition. The electronic band structure and optical properties are calculated by using Tran Blaha-modified Becke Johnson (TB-mBJ) functional and found that solid RbN3 is an insulator with a gap of 5.976 eV and the optical absorption starts with the UV light of wave length 207.5 nm.

  1. Amorphization of nanocrystalline monoclinic ZrO2 by swift heavy ion irradiation.

    PubMed

    Lu, Fengyuan; Wang, Jianwei; Lang, Maik; Toulemonde, Marcel; Namavar, Fereydoon; Trautmann, Christina; Zhang, Jiaming; Ewing, Rodney C; Lian, Jie

    2012-09-21

    Bulk ZrO(2) polymorphs generally have an extremely high amorphization tolerance upon low energy ion and swift heavy ion irradiation in which ballistic interaction and ionization radiation dominate the ion-solid interaction, respectively. However, under very high-energy irradiation by 1.33 GeV U-238, nanocrystalline (40-50 nm) monoclinic ZrO(2) can be amorphized. A computational simulation based on a thermal spike model reveals that the strong ionizing radiation from swift heavy ions with a very high electronic energy loss of 52.2 keV nm(-1) can induce transient zones with temperatures well above the ZrO(2) melting point. The extreme electronic energy loss, coupled with the high energy state of the nanostructured materials and a high thermal confinement due to the less effective heat transport within the transient hot zone, may eventually be responsible for the ionizing radiation-induced amorphization without transforming to the tetragonal polymorph. The amorphization of nanocrystalline zirconia was also confirmed by 1.69 GeV Au ion irradiation with the electronic energy loss of 40 keV nm(-1). These results suggest that highly radiation tolerant materials in bulk forms, such as ZrO(2), may be radiation sensitive with the reduced length scale down to the nano-metered regime upon irradiation above a threshold value of electronic energy loss.

  2. Microsphere morphology tuning and photo-luminescence properties of monoclinic Y2WO6

    NASA Astrophysics Data System (ADS)

    Gao, Hong; Bai, Yulong; Zhang, Junying; Tang, Zilong

    2015-04-01

    Effects of the solution pH value and reaction time on the precursor morphology and photoluminescence properties are investigated for hydrothermally prepared monoclinic Y2WO6 phosphors. In the near-neutral environment, sodium dodecyl benzene sulfonate (SDBS) surfactant forms small microspheres micelles as template to synthesize microspherical precursor. H+ ions concentration affects the arrangement of negative ionic surfactant SDBS. As a result, jujube-liked and popcorn-like loose microspheres formed at low pH value. When the pH value is 5.2 and the hydrothermal reaction time reaches 24 h, respectively, the strongest luminescent intensity can be obtained. Under this condition, the precursor presented regular microsphere with diameter of 4.0 μm. After high-temperature heat treatment, the obtained phosphor particles still exhibit microsphere-like shape. Therefore, we provide an effective method to tune the morphology of Y2WO6 phosphors and study the relationship between morphology and luminescent performance.

  3. Monoclinic high-pressure polymorph of AlOOH predicted from first principles

    NASA Astrophysics Data System (ADS)

    Zhong, Xin; Hermann, Andreas; Wang, Yanchao; Ma, Yanming

    2016-12-01

    Aluminum oxide hydroxide, AlOOH, is a prototypical hydrous mineral in the geonomy. The study of the high-pressure phase evolution of AlOOH is of fundamental importance in helping to understand the role of hydrous minerals in the water storage and transport in Earth, as in other planets. Here, we have systematically investigated the high-pressure phase diagram of AlOOH up to 550 GPa using the efficient crystal structure analysis by particle swarm optimization (CALYPSO) algorithm in conjunction with first principles calculations. We predict a peculiar monoclinic phase (space group P 21/c , 16 atoms/cell, Z =4 ) as the most stable phase for AlOOH above 340 GPa. The occurrence of this new phase results in the breakup of symmetric linear O-H-O hydrogen bonds into asymmetric, bent O-H-O linkages and in sevenfold coordinated metal cations. The new P 21/c phase turns out to be a universal high-pressure phase in group 13 oxide hydroxides, and stable for both compressed GaOOH and InOOH. The formation of the new phase in all compounds is favored by volume reduction due to denser packing.

  4. Synthesis of monoclinic structure gallium oxide film on sapphire substrate by magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Sun, Jian-xu; Mi, Wei; Zhang, De-shuang; Yang, Zheng-chun; Zhang, Kai-liang; Han, Ye-mei; Yuan, Yu-jie; Zhao, Jin-shi; Li, Bo

    2017-07-01

    Gallium oxide (Ga2O3) films were deposited on singlecrystalline sapphire (0001) substrate by radio frequency (RF) magnetron sputtering technique in the temperature range of 300—500 °C. The microstructure of the β-Ga2O3 films were investigated in detail using X-ray diffractometer (XRD) and scanning electron microscope (SEM). The results show that the film prepared at 500 °C exhibits the best crystallinity with a monoclinic structure ( β-Ga2O3). Structure analysis reveals a clear out-of-plane orientation of β-Ga2O3 (2̅01) ǁ Al2O3 (0001). The average transmittance of these films in the visible wavelength range exceeds 90%, and the optical band gap of the films varies from 4.68 eV to 4.94 eV which were measured by an ultraviolet-visible-near infrared (UV-vis-NIR) spectrophotometer. Therefore, it is hopeful that the β-Ga2O3 film can be used in the UV optoelectronic devices.

  5. Synthesis of monoclinic IrTe2 under high pressure and its physical properties

    SciTech Connect

    Li, X.; Yan, J. -Q.; Singh, D. J.; Goodenough, J. B.; Zhou, J. -S.

    2015-10-12

    In a pressure-temperature (P-T) diagram for synthesizing IrTe2 compounds, the well-studied trigonal (H) phase with the CdI2-type structure is stable at low pressures. The superconducting cubic (C) phase can be synthesized under higher temperatures and pressures. A rhombohedral phase with the crystal structure similar to the C phase can be made at ambient pressure; but the phase contains a high concentration of Ir deficiency. Here, we report that a rarely studied monoclinic (M) phase can be stabilized in narrow ranges of pressure and temperature in this P-T diagram. Moreover, the peculiar crystal structure of the M-IrTe2 eliminates the tendency to form Ir-Ir dimers found in the H phase. The M phase has been fully characterized by structural determination and measurements of electrical resistivity, thermoelectric power, DC magnetization, and specific heat. These physical properties have been compared with those in the H and C phases of Ir1-xTe2. Finally, we present magnetic and transport properties and specific heat of the M-IrTe2 can be fully justified by calculations with the density-functional theory.

  6. Phonon instability and pressure-induced isostructural semiconductor-semimetal transition of monoclinic V O2

    NASA Astrophysics Data System (ADS)

    He, Huabing; Gao, Heng; Wu, Wei; Cao, Shixun; Hong, Jiawang; Yu, Dehong; Deng, Guochu; Gao, Yanfeng; Zhang, Peihong; Luo, Hongjie; Ren, Wei

    2016-11-01

    Recent experiments have revealed an intriguing pressure-induced isostructural transition of the low temperature monoclinic V O2 and hinted to the existence of a new metallization mechanism in this system. The physics behind this isostructural phase transition and the metallization remains unresolved. In this work, we show that the isostructural transition is a result of pressure-induced instability of a phonon mode that relates to a CaC l2 -type of rotation of the oxygen octahedra, which alleviates, but does not completely remove, the dimerization and zigzagging arrangement of V atoms in the M1 phase. This phonon mode shows an increasing softening with pressure, ultimately leading to an isostructural phase transition characterized by the degree of the rotation of the oxygen octahedra. We also find that this phase transition is accompanied by an anisotropic compression, in excellent agreement with experiments. More interestingly, in addition to the experimentally identified M1' phase, we find a closely related M1 '' phase, which is nearly degenerate with the M1 ' phase. Unlike the M1 ' phase, which has a nearly pressure-independent electronic band gap, the gap of the M1 '' drops quickly at high pressures and vanishes at a theoretical pressure of about 40 GPa.

  7. 13C NMR chemical shifts of the triclinic and monoclinic crystal forms of valinomycin.

    PubMed

    Kameda, Tsunenori; McGeorge, Gary; Orendt, Anita M; Grant, David M

    2004-07-01

    Two different crystalline polymorphs of valinomycin, the triclinic and monoclinic forms, have been studied by high resolution, solid state (13)C CP-MAS NMR spectroscopy. Although the two polymorphs of the crystal are remarkably similar, there are distinct differences in the isotropic chemical shifts between the two spectra. For the triclinic form, the carbon chemical shift tensor components for the alpha carbons adjacent to oxygen in the lactic acid and hydroxyisovaleric acid residues and the ester carbonyls of the valine residue were obtained using the FIREMAT experiment. From the measured components, it was found that the behavior of the isotropic chemical shift, delta(iso), for valine residue ester carbonyl carbons is predominately influenced by the intermediate component, delta(22). Additionally it was found that the smallest shift component, delta(33), for the L -lactic acid ( L -Lac) and D -alpha-hydroxyisovaleric acid ( D -Hyi) C(alpha)-O carbon was significantly displaced depending upon the nature of individual amino acid residues, and it is the delta(33) component that governs the behavior of delta(iso) in these alpha carbons.

  8. Controlled synthesis and formation mechanism of monodispersive lanthanum vanadate nanowires with monoclinic structure

    SciTech Connect

    Tian, Li; Sun, Qiliang; Xu, Xijun; Li, Yaolin; Long, Yunfei; Zhu, Guangshan

    2013-04-15

    Monodisperse LaVO{sub 4} nanowires with relatively high aspect ratio larger than 50 have been prepared by a one-step solvothermal synthesis. This method provides a simple, inexpensive, controllable and reproducible process to produce LaVO{sub 4} nanowires with an average diameter of 15 nm and a high aspect ratio. The as-synthesized products have been characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and fast Fourier transform spectroscopy (FFT), indicative of a well-crystalline monoclinic structure and ascendant nanowire-morphology. The formation mechanism is suggested that oriented attachment plays a vital role in the growth of LaVO{sub 4} nanowires, which recommends a favorable route to fabricate similar morphological and structural nanometer materials. - Graphical abstract: The formation of LaVO{sub 4} nanowires is attributed to oriented attachment, a combination of nanocrystallites through their suitable surface planes, that is, with the same crystallographic orientations of [−120]. Highlights: ► Monodisperse LaVO{sub 4} nanowires with high aspect ratio have been prepared solvothermally without any templates. ► The morphology and structure of LaVO{sub 4} nanowires were characterized by XRD, SEM, TEM techniques. ► The formation mechanism of LaVO{sub 4} nanowires is suggested that oriented attachment plays a vital role.

  9. Monoclinic structured BiVO4 nanosheets: hydrothermal preparation, formation mechanism, and coloristic and photocatalytic properties.

    PubMed

    Zhang, Li; Chen, Dairong; Jiao, Xiuling

    2006-02-16

    Bismuth vanadate (BiVO(4)) nanosheets have been hydrothermally synthesized in the presence of sodium dodecyl benzene sulfonate (SDBS) as a morphology-directing template. The nanosheets were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) equipped with an X-ray energy dispersive spectrometer (EDS), X-ray photoelectron spectroscopy (XPS), IR spectroscopy, transmission electron microscopy (TEM), and high-resolution TEM (HR-TEM). The BiVO(4) nanosheets had a monoclinic structure, were ca. 10-40 nm thick, and showed a preferred (010) surface orientation. The formation mechanism and the effects of reaction temperature and time on the products were investigated. UV-visible diffuse reflection spectra indicated that the BiVO(4) nanosheets had outstanding spectral selectivity and improved color properties compared with the corresponding bulk materials. Furthermore, the nanosheets showed good visible photocatalytic activities as determined by degradation of N,N,N',N'-tetraethylated rhodamine (RB) under solar irradiation.

  10. Switch effect of the nonquantized intrinsic spin Hall conductivity in monolayered monoclinic transition metal dichalcogenides

    NASA Astrophysics Data System (ADS)

    Lin, Xianqing; Ni, Jun

    2017-07-01

    First-principles calculations have been performed to study the intrinsic spin Hall effect (SHE) and its behavior under vertical electric field in monoclinic transition metal dichalcogenide monolayers (1T‧-MX2 with M  =  Mo, W and X  =  S, Se, Te). We find that the pristine systems exhibit nonquantized intrinsic spin Hall conductivity (SHC) due to the unconserved spin around the direct band gaps though they have nontrivial band topology. The unconserved spin is attributed to the band crossings at Fermi levels for systems without spin-orbit coupling and the distinct composition of the band states around the crossings. Despite the nonquantization of SHC, calculations with the hybrid functional predict SHC approaching the quantized value in W based systems, especially 1T‧-WTe2, which has been realized in experiments. More interesting, a sharp drop of SHC to almost zero in semiconducting systems induced by vertical electric field is observed at the topological phase transition point, suggesting that such systems exhibit a strong switch effect of SHC. In contrast, the switch effect is weak in semi-metallic systems, where the SHC decreases almost continuously with increasing field strength for the chemical potential around the Fermi levels. Our findings suggest potential applications of the pristine 1T‧-MX2 and those under vertical electric field in spintronics devices by utilizing the intrinsic SHE of their bulk states.

  11. Monoclinic polymorph of poly[aqua(μ4-hydrogen tartrato)sodium

    PubMed Central

    Al-Dajani, Mohammad T. M.; Abdallah, Hassan H.; Mohamed, Nornisah; Quah, Ching Kheng; Fun, Hoong-Kun

    2010-01-01

    A monoclinic polymorph of the title compound, [Na(C4H5O6)(H2O)]n, is reported and complements an ortho­rhom­bic form [Kubozono, Hirano, Nagasawa, Maeda & Kashino (1993 ▶). Bull. Chem. Soc. Jpn, 66, 2166–2173]. The asymmetric unit contains a hydrogen tartrate anion, an Na+ cation and a water mol­ecule. The Na+ ion is surrounded by seven O atoms derived from one independent and three symmetry-related hydrogen tartrate anions, and a water mol­ecule, forming a distorted penta­gonal–bipyramidal geometry. Independent units are linked via a pair of inter­molecular bifurcated O—H⋯O acceptor bonds, generating an R 2 1(6) ring motif to form polymeric two-dimensional arrays parallel to the (100) plane. In the crystal packing, the arrays are linked by adjacent ring motifs, together with additional inter­molecular O—H⋯O inter­actions, into a three-dimensional network. PMID:21579620

  12. Monoclinic polymorph of poly[aqua(μ(4)-hydrogen tartrato)sodium].

    PubMed

    Al-Dajani, Mohammad T M; Abdallah, Hassan H; Mohamed, Nornisah; Quah, Ching Kheng; Fun, Hoong-Kun

    2010-01-09

    A monoclinic polymorph of the title compound, [Na(C(4)H(5)O(6))(H(2)O)](n), is reported and complements an ortho-rhom-bic form [Kubozono, Hirano, Nagasawa, Maeda & Kashino (1993 ▶). Bull. Chem. Soc. Jpn, 66, 2166-2173]. The asymmetric unit contains a hydrogen tartrate anion, an Na(+) cation and a water mol-ecule. The Na(+) ion is surrounded by seven O atoms derived from one independent and three symmetry-related hydrogen tartrate anions, and a water mol-ecule, forming a distorted penta-gonal-bipyramidal geometry. Independent units are linked via a pair of inter-molecular bifurcated O-H⋯O acceptor bonds, generating an R(2) (1)(6) ring motif to form polymeric two-dimensional arrays parallel to the (100) plane. In the crystal packing, the arrays are linked by adjacent ring motifs, together with additional inter-molecular O-H⋯O inter-actions, into a three-dimensional network.

  13. Ab initio prediction of superdense tetragonal and monoclinic polymorphs of carbon

    NASA Astrophysics Data System (ADS)

    Li, Zhen-Zhen; Wang, Jian-Tao; Xu, Li-Fang; Chen, Changfeng

    2016-11-01

    The design and synthesis of three-dimensional denser carbons are one of the hot issues in condensed matter physics because of their fascinating properties. Here we identify by ab initio calculations several tetragonal and monoclinic polymorphs of carbon that adopt the t 32 , t 32* , m 32 , and m 32* structures in P 4 ¯21c , P 43212 , P 21/c , and C 2 symmetry, respectively. These carbon polymorphs have large 32-atom unit cells in all-s p3 bonding networks comprising five- and six-membered rings that are dynamically stable, as verified by a phonon mode analysis. Electronic band structure calculations show that they are insulators with band gaps in the range of 5.19-5.41 eV, close to the calculated band gap of 5.34 eV for diamond. Remarkably, these carbon phases possess an extremely high atom number density exceeding that of diamond. The present results establish different types of carbon phases and offer insights into their outstanding structural and electronic properties.

  14. A new crystal phase of ammonium nitrate: a monoclinic distortion of AN-IV

    NASA Astrophysics Data System (ADS)

    Oleynik, Ivan; Steele, Brad

    2015-06-01

    Ammonium nitrate (AN) is a major component of the energetic material ANFO. It is important to understand the high-pressure crystal phases and corresponding phase transitions of AN as its structural polymorphism might affect the energetic performance, including crystal density, detonation velocity and shock initiation of chemical reactions. A new crystal phase of AN is found using first principles evolutionary crystal structure search. It is a monoclinic distortion of phase IV of AN (AN-IV) in the P21/m space group (AN-P21/m). The calculated Raman spectrum of this new phase is consistent with the recently reported experimental Raman spectrum that contains two peaks at high pressures associated with the phase transition. The new phase is calculated to have lower free energy than AN-IV above 11.2 GPa, a pressure close to the experimentally reported phase transition pressure of 17 GPa. The calculated Raman spectra of both AN-P21/m and AN-IV as a function of pressure display good agreement with experiment up to 40 GPa.

  15. New phase of ammonium nitrate: A monoclinic distortion of AN-IV

    NASA Astrophysics Data System (ADS)

    Steele, Brad A.; Oleynik, Ivan I.

    2015-12-01

    A new phase of ammonium nitrate (AN) is found using first principles evolutionary crystal structure search. It is this polymorph that is associated with the phase transition to previously unidentified phase, which was detected in experiment at 17 GPa upon appearance of the two extra peaks in Raman spectrum. The new phase has a monoclinic unit cell in the P21/m space group symmetry (AN-P21/m) and is similar to the known phase IV of AN (AN-IV) except the ammonium molecules are oriented differently relative to the nitrate molecules. The calculated free energy of AN-P21/m is found to be lower than AN-IV at pressures above 10.83 GPa. The equation of state of both AN-P21/m and AN-IV phases (volume vs hydrostatic pressure at room temperature) has been obtained within the quasi-harmonic approximation. The calculated Raman spectrum of both AN-P21/m and AN-IV as a function of pressure is in a good agreement with experiment. The energetic competitiveness of AN-IV and AN-P21/m at ambient conditions suggests a possibility of the phase transition in a small pressure-temperature range near ambient pressure and temperature.

  16. Bis[2-(hy-droxy-imino-meth-yl)phenolato]nickel(II): a second monoclinic polymorph.

    PubMed

    Rusanova, Julia A; Buvaylo, Elena A; Rusanov, Eduard B

    2011-01-15

    The title compound, [Ni(C(7)H(6)NO(2))(2)], (I), is a second monoclinic polymorph of the compound, (II), reported by Srivastava et al. [Acta Cryst. (1967), 22, 922] and Mereiter [Private communication (2002) CCDC refcode NISALO01]. The bond lengths and angles are similar in both structures. The mol-ecule in both structures lies on a crystallographic inversion center and both have an inter-nal hydrogen bond. The title compound crystallizes in the space group P2(1)/c (Z = 2), whereas compound (II) is in the space group P2(1)/n (Z = 2) with a similar cell volume but different cell parameters. In both polymorphs, mol-ecules are arranged in the layers but in contrast to the previously published compound (II) where the dihedral angle between the layers is 86.3°, in the title polymorph the same dihedral angle is 29.4°. The structure of (I) is stabilized by strong intra-molecular O-H⋯O hydrogen bonding between the O-H group and the phenolate O atom.

  17. Polarization-dependent angular distribution of the absorption behavior in Ytterbium-doped monoclinic LYB and LGB compounds

    NASA Astrophysics Data System (ADS)

    Gebremichael, W.; Petit, Y.; Rouzet, S.; Fargues, A.; Veber, P.; Velazquez, M.; Jubera, V.; Canioni, L.; Manek-Hönninger, I.

    2017-02-01

    In this contribution we detail the full characterization of the anisotropy of the absorption properties of two different Yb-doped monoclinic borate compounds under polarized light. The studied crystals are Li6(Gd)0.75Yb0.25(BO3)3 and Li6Y0.75Yb0.25(BO3)3, respectively, grown by the Czochralski method. We focused on the study of their absorption at the zero line transition as a function of the polarization direction of the incident light for two different crystal cuts of each compound. We discuss the different Eigen frames that must be considered in these materials due to their monoclinic character, as well as the optimal crystal orientation for the considered absorption and the potential influences when used as laser materials.

  18. Cooperative effect of monoclinic distortion and sinusoidal modulation in the martensitic structure of Ni 2FeGa

    NASA Astrophysics Data System (ADS)

    Lu, J. B.; Yang, H. X.; Tian, H. F.; Zeng, L. J.; Ma, C.; Feng, L.; Wu, G. H.; Li, J. Q.; Jansen, J.

    2010-02-01

    The structural features of the "5M" martensitic phase in Ni 2FeGa alloys have been determined by electron diffraction using the multi-slice least-squares (MSLS) method. The results demonstrate that the "5M" phase contains an evident cooperative effect of monoclinic distortion and sinusoidal modulation along the [110] c direction. Theoretical simulations based on our refined data suggest that the "5M" martensitic phase observed in Ni-Fe-Ga and Ni-Mn-Ga has visible common behaviors in both stacking sequence and local structural distortion. Considering the cooperative effect of monoclinic distortion and sinusoidal modulation, we demonstrate that the "7M" martensitic phase could adopt two equivalent structural phases corresponding with the stacking sequences of (43-)2 and (52-)2, respectively.

  19. Influence of downsizing of zeolite crystals on the orthorhombic ↔ monoclinic phase transition in pure silica MFI-type

    NASA Astrophysics Data System (ADS)

    Kabalan, Ihab; Michelin, Laure; Rigolet, Séverinne; Marichal, Claire; Daou, T. Jean; Lebeau, Bénédicte; Paillaud, Jean-Louis

    2016-08-01

    The impact of crystal size on the transition orthorhombic ↔ monoclinic phase in MFI-type purely silica zeolites is investigated between 293 and 473 K using 29Si MAS NMR and powder X-ray diffraction. Three silicalite-1 zeolites are synthesized: a material constituted of micron-sized crystals, pseudospherical nanometer-sized crystals and hierarchical porous zeolites with a mesoporous network created by the use of a gemini-type diquaternary ammonium surfactant giving nanosheet zeolites. Our results show for the first time that the orthorhombic ↔ monoclinic phase transition already known for micron-sized particles also occurs in nanometer-sized zeolite crystals whereas our data suggest that the extreme downsizing of the zeolite crystal to one unit cell in thickness leads to an extinction of the phase transition.

  20. Observation of reduced phase transition temperature in N-doped thermochromic film of monoclinic VO2

    NASA Astrophysics Data System (ADS)

    Wan, Meinan; Xiong, Mo; Li, Neng; Liu, Baoshun; Wang, Shuo; Ching, Wai-Yim; Zhao, Xiujian

    2017-07-01

    Research on monoclinic (M1) phase of VO2 has attracted a great of interest for smart coating applications due to its exceptional thermochromic property. Herein, we report the results using a novel approach to synthesize N-doped VO2(M1) thin films with high purity by heat treatment in NH3 atmosphere. The N dopant in the film can be regulated by varying NH3 concentration during the annealing process. We find that the N atoms are located at the interstitial sites or substitute oxygen atoms, and the V-N bonds in the VO2 thin films increase with NH3 concentration. The metal to insulator transition (MIT) temperature (τc,h) of the VO2 thin film is effectively reduced from 80.0 to 62.9 °C, while the solar modulation efficiency (ΔTsol) and the modulation efficiency at 2000 nm (ΔT2000nm) are 7.36% and 55.6% respectively. The band gap of N-doped VO2 thin films related to MIT (Eg1) is estimated to be as low as 0.18-0.25 eV whereas the band gap associated with the visible transparency (Eg2) is about 1.50-1.58 eV. Based on the highly accurate first-principles calculations, the Eg1 of VO2 (M1) is reduced after substituted or interstitial N-doping, while the Eg2 alters with the mode of N-doping, which is excellent agreement with experimental measurement.

  1. Batteries: encapsulated monoclinic sulfur for stable cycling of li-s rechargeable batteries (adv. Mater. 45/2013).

    PubMed

    Moon, San; Jung, Young Hwa; Jung, Wook Ki; Jung, Dae Soo; Choi, Jang Wook; Kim, Do Kyung

    2013-12-03

    On page 6547 Do Kyung Kim, Jang Wook Choi and co-workers describe a highly aligned and carbon-encapsulated sulfur cathode synthesized with an AAO template that exhibits a high and long cycle life, and the best rate capability based on the complete encapsulation of sulfur (physical) and implementation of the monoclinic sulfur phase (chemical). © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Analysis of tetragonal to monoclinic phase transformation caused by accelerated artificial aging and the effects of microstructure in stabilized zirconia

    NASA Astrophysics Data System (ADS)

    Lucas, Thomas J.

    This investigation addresses the issue that yttria stabilized zirconia is being used as a dental biomaterial without substantial evidence of its long-term viability. Furthermore, stabilized zirconia (SZ) undergoes low temperature degradation (LTD), which can lead to roughening of the surface. A rougher exterior can lead to increased wear of the antagonist in the oral environment. Despite the LTD concerns, SZ is now widely used in restorative dentistry, including full contour crowns. A comparison of aging methods to determine the role of artificial aging on inducing the transformation has not been extensively studied. Therefore, simulations of the transformation process were investigated by comparing different methods of accelerated aging. The rejected null hypothesis is that the temperature of aging treatment will not affect the time required to cause measurable monoclinic transformation of yttria stabilized zirconia. The transformation of SZ starts at the surface and progresses inward; however, it is unclear whether the progression is constant for different aging conditions. This investigation analyzed the depth of transformation as a function of aging conditions for stabilized zirconia in the top 5-6 mum from the surface. The rejected null hypothesis is that the transformation amount is constant throughout the first six micrometers from the surface. The effects of grain size on the amount of monoclinic transformation were also investigated. This study aimed to determine if the grain size of partially stabilized zirconia affects the amount of monoclinic transformation, surface roughness, and property degradation due to aging. The rejected null hypothesis is that the grain size will not affect the amount of monoclinic transformation, thus have no effect on surface roughening or property degradation. The final part of this study addresses the wear of enamel when opposing zirconia by observing how grain size and aging affected the wear rate of an enamel antagonist

  3. Ferroelectric Self-Poling, Switching, and Monoclinic Domain Configuration in BiFeO 3 Thin Films

    SciTech Connect

    Beekman, C.; Siemons, W.; Chi, M.; Balke, N.; Howe, J. Y.; Ward, T. Z.; Maksymovych, P.; Budai, J. D.; Tischler, J. Z.; Xu, R.; Liu, W.; Christen, H. M.

    2016-05-23

    Self-poling of ferroelectric films, i.e., a preferred, uniform direction of the ferroelectric polarization in as-grown samples is often observed yet poorly understood despite its importance for device applications. The multiferroic perovskite BiFeO3, which crystallizes in two distinct structural polymorphs depending on applied epitaxial strain, is well known to exhibit self-poling. This study investigates the effect of self-poling on the monoclinic domain configuration and the switching properties of the two polymorphs of BiFeO3 (R' and T') in thin films grown on LaAlO3 substrates with slightly different La0.3Sr0.7MnO3 buffer layers. Our study shows that the polarization state formed during the growth acts as “imprint” on the polarization and that switching the polarization away from this self-poled direction can only be done at the expense of the sample's monoclinic domain configuration. We observed reduction of the monoclinic domain size and found that it was largely reversible; hence, the domain size is restored when the polarization is switched back to its original orientation. This is a direct consequence of the growth taking place in the polar phase (below Tc). Finally, switching the polarization away from the preferred configuration, in which defects and domain patterns synergistically minimize the system's energy, leads to a domain state with smaller (and more highly strained and distorted) monoclinic domains.

  4. Ferroelectric Self-Poling, Switching, and Monoclinic Domain Configuration in BiFeO 3 Thin Films

    SciTech Connect

    Beekman, C.; Siemons, W.; Chi, M.; Balke, N.; Howe, J. Y.; Ward, T. Z.; Maksymovych, P.; Budai, J. D.; Tischler, J. Z.; Xu, R.; Liu, W.; Christen, H. M.

    2016-05-23

    Self-poling of ferroelectric films, i.e., a preferred, uniform direction of the ferroelectric polarization in as-grown samples is often observed yet poorly understood despite its importance for device applications. The multiferroic perovskite BiFeO3, which crystallizes in two distinct structural polymorphs depending on applied epitaxial strain, is well known to exhibit self-poling. This study investigates the effect of self-poling on the monoclinic domain configuration and the switching properties of the two polymorphs of BiFeO3 (R' and T') in thin films grown on LaAlO3 substrates with slightly different La0.3Sr0.7MnO3 buffer layers. Our study shows that the polarization state formed during the growth acts as “imprint” on the polarization and that switching the polarization away from this self-poled direction can only be done at the expense of the sample's monoclinic domain configuration. We observed reduction of the monoclinic domain size and found that it was largely reversible; hence, the domain size is restored when the polarization is switched back to its original orientation. This is a direct consequence of the growth taking place in the polar phase (below Tc). Finally, switching the polarization away from the preferred configuration, in which defects and domain patterns synergistically minimize the system's energy, leads to a domain state with smaller (and more highly strained and distorted) monoclinic domains.

  5. Petrology of Karoo volcanic rocks in the southern Lebombo monocline, Mozambique

    NASA Astrophysics Data System (ADS)

    Melluso, Leone; Cucciniello, Ciro; Petrone, Chiara M.; Lustrino, Michele; Morra, Vincenzo; Tiepolo, Massimo; Vasconcelos, Lopo

    2008-11-01

    The Karoo volcanic sequence in the southern Lebombo monocline in Mozambique contains different silicic units in the form of pyroclastic rocks, and two different basalt types. The silicic units in the lower part of the Lebombo sequence are formed by a lower unit of dacites and rhyolites (67-80 wt.% SiO 2) with high Ba (990-2500 ppm), Zr (800-1100 ppm) and Y (130-240 ppm), which are part of the Jozini-Mbuluzi Formation, followed by a second unit, interlayered with the Movene basalts, of high-SiO 2 rhyolites (76-78 wt.%; the Sica Beds Formation), with low Sr (19-54 ppm), Zr (340-480 ppm) and Ba (330-850 ppm) plus rare quartz-trachytes (64-66 wt.% SiO 2), with high Nb and Rb contents (240-250 and 370-381 ppm, respectively), and relatively low Zr (450-460 ppm). The mafic rocks found at the top of the sequence are basalts and ferrobasalts belonging to the Movene Formation. The basalts have roughly flat mantle-normalized incompatible element patterns, with abundances of the most incompatible elements not higher than 25 times primitive mantle. The ferrobasalt has TiO 2 ˜ 4.7 wt.%, Fe 2O 3t = 16 wt.%, and high Y (100 ppm), Zr (420 ppm) and Ba (1000 ppm). The Movene basalts have initial (at 180 Ma) 87Sr/ 86Sr = 0.7052-0.7054 and 143Nd/ 144Nd = 0.51232, and the Movene ferrobasalt has even lower 87Sr/ 86Sr (0.70377) and higher 143Nd/ 144Nd (0.51259). The silicic rocks show a modest range of initial Sr-( 87Sr/ 86Sr = 0.70470-0.70648) and Nd-( 143Nd/ 144Nd = 0.51223-0.51243) isotope ratios. The less evolved dacites could have been formed after crystal fractionation of oxide-rich gabbroic cumulates from mafic parental magmas, whereas the most silica-rich rhyolites could have been formed after fractional crystallization of feldspars, pyroxenes, oxides, zircon and apatite from a parental dacite magma. The composition of the Movene basalts imply different feeding systems from those of the underlying Sabie River basalts.

  6. Photocatalytic and photoelectrochemical water oxidation over metal-doped monoclinic BiVO(4) photoanodes.

    PubMed

    Parmar, Kanak Pal Singh; Kang, Hyun Joon; Bist, Amita; Dua, Piyush; Jang, Jum Suk; Lee, Jae Sung

    2012-10-01

    The visible-light-induced water oxidation ability of metal-ion-doped BiVO(4) was investigated and of 12 metal ion dopants tested, only W and Mo dramatically enhanced the water photo-oxidation activity of bare BiVO(4); Mo had the highest improvement by a factor of about six. Thus, BiVO(4) and W- or Mo-doped (2 atom %) BiVO(4) photoanodes about 1 μm thick were fabricated onto transparent conducting substrate by a metal-organic decomposition/spin-coating method. Under simulated one sun (air mass 1.5G, 100 mW cm(-2)) and at 1.23 V versus a reversible hydrogen electrode, the highest photocurrent density (J(PH)) of about 2.38 mA cm(-2) was achieved for Mo doping followed by W doping (J(PH) ≈ 1.98 mA cm(-2)), whereas undoped BiVO(4) gave a J(PH) value of about 0.42 mA cm(-2). The photoelectrochemical water oxidation activity of W- and Mo-doped BiVO(4) photoanodes corresponded to the incident photon to current conversion efficiency of about 35 and 40 % respectively. Electrochemical impedance spectroscopy and Mott-Schottky analysis indicated a positive flat band shift of about 30 mV, a carrier concentration 1.6-2 times higher, and a charge-transfer resistance reduced by 3-4-fold for W- or Mo-doped BiVO(4) relative to undoped BiVO(4). Electronic structure calculations revealed that both W and Mo were shallow donors and Mo doping generated superior conductivity to W doping. The photo-oxidation activity of water on BiVO(4) photoanodes (undopedmonoclinic BiVO(4) by drastically reducing its charge-transfer resistance and thereby minimizing photoexcited electron-hole pair recombination. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Method of forming high density oxide pellets by hot pressing at 50$sup 0$ to 100$sup 0$C above the cubic to monoclinic phase transformation temperature

    DOEpatents

    Pasto, A.E.

    1975-08-01

    A process for low temperature sintering of rare earth and actinide oxides which have a cubic to monoclinic transformation is described. The process involves hot pressing a powder compact at a temperature just above the transformation temperature. (auth)

  8. Template-Engaged In Situ Synthesis of Carbon-Doped Monoclinic Mesoporous BiVO4: Photocatalytic Treatment of Rhodamine B

    NASA Astrophysics Data System (ADS)

    Yao, Mingming; Gan, Lihua; Liu, Mingxian; Tripathi, Pranav K.; Liu, Yafei; Hu, Zhonghua

    2015-06-01

    In this paper, carbon-doped monoclinic scheelite mesoporous bismuth vanadate was synthesized through template-engaged in situ method. The bismuth nitrate pentahydrate and ammonia metavanadate were used as bismuth and vanadium precursors, respectively, glucose as carbon source, and mesoporous SiO2 aerogel as a hard template. Carbon-doped monoclinic mesoporous BiVO4 were obtained by heat treatment of BiVO4/glucose/template to carbonize glucose and form monoclinic crystal, followed by etching with NaOH solution to remove the SiO2 template. The samples were characterized by x-ray diffraction, N2 adsorption and desorption, UV-visible spectroscopy, Energy dispersive spectrometry, Raman spectroscopy, and Transmission electron microscopy. It was found that the sample with a carbon content of 0.5 wt.% possesses a specific surface area of 10.2 m2/g and has mesoporous structure with the most probable pore size of 13.9 nm. The band gap of carbon-doped monoclinic mesoporous BiVO4 was estimated to be 2.33 eV, indicating the superior photocatalytic activity under visible light. The photocatalytic efficiency of carbon-doped monoclinic mesoporous BiVO4 for the degradation of Rhodamine B under visible light (λ > 400 nm) in 120 min reaches 98.7%, Besides, the carbon-doped monoclinic mesoporous BiVO4 photocatalyst still showed high stability: 85% for Rhodamine B degradation after ten recycles.

  9. Monoclinic β-Li2TiO3 nanocrystalline particles employing novel urea assisted solid state route: Synthesis, characterization and sintering behavior

    NASA Astrophysics Data System (ADS)

    Tripathi, Biranchi M.; Mohanty, Trupti; Prakash, Deep; Tyagi, A. K.; Sinha, P. K.

    2017-07-01

    Pure phase monoclinic nano-crystalline Li2TiO3 powder was synthesized by a novel urea assisted solid state synthesis method using readily available and economical precursors. A single phase and well crystalline Li2TiO3 powder has been obtained at slightly lower temperature (600-700 °C) and shorter duration (2 h) as compared to the conventional solid state method. The proposed method has significant advantages in comparison to other viable methods mainly in terms of phase purity, powder properties and sinterability. Analysis of chemical composition using inductively coupled plasma atomic emission spectroscopy (ICP-AES) shows no loss of lithium from Li2TiO3 in the proposed method. The emergence of monoclinic Li2TiO3 phase was confirmed by X-ray diffraction (XRD) pattern of as-synthesized powder. The crystallite size of Li2TiO3 powder was calculated to be in the range of 15-80 nm, which varied as a function of urea composition and temperature. The morphology of as-prepared Li2TiO3 powders was examined by scanning electron microscope (SEM). The effect of urea composition on phase and morphology was investigated so as to delineate the role of urea. Upon sintering at < 1000 °C temperature, the Li2TiO3 powder compact attained about 98% of the theoretical density with fine grained (grain size: 2-3 μm) microstructure. It indicates excellent sinter-ability of Li2TiO3 powder synthesized by the proposed method. The fine grained structure is desirable for better tritium breeding performance of Li2TiO3. Electrochemical impedance spectroscopy at variable temperature showed good electrical properties of Li2TiO3. The proposed method is simple, anticipated to be cost effective and convenient to realise for large scale production of phase pure nanocrystalline and having significantly enhanced sinter-ability Li2TiO3 powder.

  10. Neutron diffraction study of monoclinic brannerite-type CoV{sub 2}O{sub 6}

    SciTech Connect

    Markkula, Mikael; Arevalo-Lopez, Angel M.; Paul Attfield, J.

    2012-08-15

    A variable-temperature powder neutron diffraction study of the monoclinic brannerite-type CoV{sub 2}O{sub 6} (space group C2/m, a=9.2531(2), b=3.5040(1), c=6.6201(1) A and {beta}=111.617(1) Degree-Sign at 300 K) is reported. No structural transition is observed down to 4 K, but a magnetostriction accompanying antiferromagnetic order at T{sub N}=15 K is discovered. Antiferromagnetic order observed below T{sub N} has an a Multiplication-Sign b Multiplication-Sign 2c supercell in which Co{sup 2+} moments of magnitude 4.77(4) {mu}{sub B} at 4 K lie in the ac plane and are ferromagnetically coupled within chains of edge-sharing CoO{sub 6} octahedra parallel to b. Ferromagnetic chains are coupled antiferromagnetically to neighbouring chains in the a and c directions, and a model for the interchain order in the reported 1/3 magnetization plateau region is proposed. - Graphical abstract: Antiferromagnetic order of Co{sup 2+} moments in monoclinic brannerite type CoV2O6 results in a magnetostriction at the 15 K Neel transition. An alternative coupling between ferromagnetic chains is proposed to account for a 1/3 magnetization plateau in this material. Highlights: Black-Right-Pointing-Pointer Variable-temperature powder neutron diffraction study of the monoclinic brannerite-type CoV{sub 2}O{sub 6} is reported. Black-Right-Pointing-Pointer Magnetostriction accompanying antiferromagnetic order at T{sub N}=15 K in monoclinic CoV{sub 2}O{sub 6} is discovered. Black-Right-Pointing-Pointer Antiferromagnetic order in a Multiplication-Sign b Multiplication-Sign 2c supercell of CoV{sub 2}O{sub 6} is determined. Black-Right-Pointing-Pointer Model for spin order in the reported 1/3 magnetization plateau of CoV{sub 2}O{sub 6} is proposed.

  11. Half analytical method with application to the high order Laue zone effects in monoclinic and triclinic crystals.

    PubMed

    Cai, Can Ying; Zeng, Song Jun; Liu, Hong Rong; Yang, Qi Bin

    2008-10-01

    The simulation of the high order Laue zone (HOLZ) diffractions of monoclinic and triclinic crystals is a very complicated problem. The conventional multislice (MS) method suffers from the problem of infinity of the phase grating size. To avoid the difficulty of the infinity, Chen et al. arranged the phase grating plane along the ab plane of the crystal lattice. In this paper we introduce a new method which allows the incident and exit wavefunction planes perpendicular to the zone axis without the difficulty of infinity. We name the method half analytical method. The results calculated by half analytical method are in good agreement with those calculated by the conventional MS method.

  12. Characterization of dislocations in monoclinic hen egg-white lysozyme crystals by synchrotron monochromatic-beam X-ray topography

    NASA Astrophysics Data System (ADS)

    Sawaura, Takuya; Fujii, Daiki; Shen, Mengyuan; Yamamoto, Yu; Wako, Kei; Kojima, Kenichi; Tachibana, Masaru

    2011-03-01

    Dislocations in monoclinic hen egg-white lysozyme crystals were investigated by means of synchrotron monochromatic-beam X-ray topography. The loop and curved dislocations were observed to be predominant in the crystals. Almost all the dislocations lay in (1 0 1¯) crystallographic plane, which corresponds to that with smallest slicing energy estimated by macrobond approach. One of the Burgers vectors of the dislocations was determined to be [0 1 0], which corresponds to the smallest lattice translational vector on the (1 0 1¯) plane. It is suggested that the loop and curved dislocations are slip ones introduced by a stress concentration during or after the growth.

  13. Deep-seated landslides affecting monoclinal flysch morphostructure: Evaluation of LiDAR-derived topography of the highest range of the Czech Carpathians

    NASA Astrophysics Data System (ADS)

    Břežný, Michal; Pánek, Tomáš

    2017-05-01

    The recent launch of national-scale LiDAR-derived topographic data provides an opportunity for (re)evaluating the geomorphic imprint of landslides in forested mountains. A LiDAR-based inventory of deep-seated landslides (DSLs) in the highest part of Czech Outer Western Carpathians (Moravskoslezské Beskydy Mts.) reveals that nearly 20% of the territory is affected by ancient DSLs. Rather than the topography itself, we show that the geological characteristics of flysch rocks control the density, scaling relationships and morphometry of DSLs. They reveal a strong tendency to clustering in areas with favourable structural conditions, such as cataclinal slopes of individual monoclinal ridges formed by thick-bedded sandstones. In comparison with high-mountain areas and regions dominated by weaker lithology (e.g., claystone-dominated flysch), sandstone-dominated monoclinal structure of the Moravskoslezské Beskydy Mts. features predominantly short-travelled DSLs that are arrested on slopes and thus reveal a higher slope gradient than non-landslide terrain. Finally, we propose a conceptual model for the evolution of DSLs on monoclinal flysch morphostructures, particularly where coherent sandstone caps overlie weak claystone/siltstone-dominated flysch. In these conditions, we distinguish between ;low; and ;high; monoclinal ridges, where the former is capped by relatively thin sandstones overlying claystone formations and sandstones predominate in the structure of the latter. We show that the density of DSLs on the cataclinal/dip slopes is similar on both types of monoclinal ridges, but that major differences exist in the evolution of anaclinal/escarpment slopes. Here, low monoclinal ridges are highly affected by DSLs, but escarpments of high monoclinal ridges are nearly devoid of any DSLs.

  14. Determination of Stress Coefficient Terms in Cracked Solids for Monoclinic Materials with Plane Symmetry at x3 = 0

    NASA Technical Reports Server (NTRS)

    Yuan, F. G.

    1998-01-01

    Determination of all the coefficients in the crack tip field expansion for monoclinic materials under two-dimensional deformation is presented in this report. For monoclinic materials with a plane of material symmetry at x(sub 3) = 0, the in-plane deformation is decoupled from the anti-plane deformation. In the case of in-plane deformation, utilizing conservation laws of elasticity and Betti's reciprocal theorem, together with selected auxiliary fields, T-stress and third-order stress coefficients near the crack tip are evaluated first from path-independent line integrals. To determine the T-stress terms using the J-integral and Betti's reciprocal work theorem, auxiliary fields under a concentrated force and moment acting at the crack tip are used respectively. Through the use of Stroh formalism in anisotropic elasticity, analytical expressions for all the coefficients including the stress intensity factors are derived in a compact form that has surprisingly simple structure in terms of the Barnett-Lothe tensors, L. The solution forms for degenerated materials, orthotropic, and isotropic materials are presented.

  15. Ab initio calculation of electron-phonon coupling in monoclinic β-Ga2O3 crystal

    NASA Astrophysics Data System (ADS)

    Ghosh, Krishnendu; Singisetti, Uttam

    2016-08-01

    The interaction between electrons and vibrational modes in monoclinic β-Ga2O3 is theoretically investigated using ab-initio calculations. The large primitive cell of β-Ga2O3 gives rise to 30 phonon modes all of which are taken into account in transport calculation. The electron-phonon interaction is calculated under density functional perturbation theory and then interpolated using Wannier-Fourier interpolation. The long-range interaction elements between electrons and polar optical phonon (POP) modes are calculated separately using the Born effective charge tensor. The direction dependence of the long-range POP coupling in a monoclinic crystal is explored and is included in the transport calculations. Scattering rate calculations are done using the Fermi golden rule followed by solving the Boltzmann transport equation using the Rode's method to estimate low field mobility. A room temperature mobility of 115 cm2/V s is observed. Comparison with recent experimentally reported mobility is done for a wide range of temperatures (30 K-650 K). It is also found that the POP interaction dominates the electron mobility under low electric field conditions. The relative contribution of the different POP modes is analyzed and the mode 21 meV POP is found to have the highest impact on low field electron mobility at room temperature.

  16. Effect of annealing on down-conversion properties of monoclinic Gd2O3:Er3+ nanophosphors.

    PubMed

    Tamrakar, Raunak Kumar; Bisen, D P; Upadhyay, Kanchan

    2015-09-01

    Erbium-doped nano-sized Gd2O3 phosphor was prepared by a solution combustion method in the presence of urea as a fuel. The phosphor was characterized by X-ray diffractometry (XRD), Fourier transform infra-red spectroscopy, energy dispersive X-ray analysis (EDX) and transmission electron microscopy (TEM). The results of the XRD shows that the phosphor has a monoclinic phase, which was further confirmed by the TEM results. Particle size was calculated by the Debye-Scherrer formula. The erbium-doped Gd2O3 nanophosphor was revealed to have good down-conversion (DC) properties and the intensity of phosphor could be modified by annealing. The effects of annealing at 900°C on the particle size and luminescence properties were studied and compared with freshly prepared Gd2O3:Er(3+) nanoparticles. The average particle sizes were calculated as 8 and 20 nm for the freshly prepared samples and samples annealed at 900°C for 1 h, respectively. The results show that both freshly prepared and annealed Gd2O3:Er(3+) have monoclinic structure. Copyright © 2014 John Wiley & Sons, Ltd.

  17. Ab initio calculation of electron–phonon coupling in monoclinic β-Ga{sub 2}O{sub 3} crystal

    SciTech Connect

    Ghosh, Krishnendu Singisetti, Uttam

    2016-08-15

    The interaction between electrons and vibrational modes in monoclinic β-Ga{sub 2}O{sub 3} is theoretically investigated using ab-initio calculations. The large primitive cell of β-Ga{sub 2}O{sub 3} gives rise to 30 phonon modes all of which are taken into account in transport calculation. The electron-phonon interaction is calculated under density functional perturbation theory and then interpolated using Wannier–Fourier interpolation. The long-range interaction elements between electrons and polar optical phonon (POP) modes are calculated separately using the Born effective charge tensor. The direction dependence of the long-range POP coupling in a monoclinic crystal is explored and is included in the transport calculations. Scattering rate calculations are done using the Fermi golden rule followed by solving the Boltzmann transport equation using the Rode's method to estimate low field mobility. A room temperature mobility of 115 cm{sup 2}/V s is observed. Comparison with recent experimentally reported mobility is done for a wide range of temperatures (30 K–650 K). It is also found that the POP interaction dominates the electron mobility under low electric field conditions. The relative contribution of the different POP modes is analyzed and the mode 21 meV POP is found to have the highest impact on low field electron mobility at room temperature.

  18. Magnetic structure and orbital ordering in tetragonal and monoclinic KCrF(3) from first-principles calculations.

    PubMed

    Xu, Yuanhui; Hao, Xianfeng; Lv, Minfeng; Wu, Zhijian; Zhou, Defeng; Meng, Jian

    2008-04-28

    KCrF(3) has been systematically investigated by using the full-potential linearized augmented plane wave plus local orbital method within the generalized gradient approximation and the local spin density approximation plus the on-site Coulomb repulsion approach. The total energies for ferromagnetic and three different antiferromagnetic configurations are calculated in the high-temperature tetragonal and low-temperature monoclinic phases, respectively. It reveals that the ground state is the A-type antiferromagnetic in both phases. Furthermore, the ground states of the two phases are found to be Mott-Hubbard insulators with the G-type orbital ordering pattern. In addition, our calculations show the staggered orbital ordering of the 3d(x(2) ) and 3d(y(2) ) orbitals for the tetragonal phase and the 3d(z(2) ) and 3d(x(2) ) orbitals for the monoclinic phase, which is in agreement with the available data. More importantly, the relationship between magnetic structure and orbital ordering as well as the origin of the orbital ordering are analyzed in detail.

  19. Nanoscale monoclinic domains in epitaxial SrRuO{sub 3} thin films deposited by pulsed laser deposition

    SciTech Connect

    Ghica, C. Negrea, R. F.; Nistor, L. C.; Chirila, C. F.; Pintilie, L.

    2014-07-14

    In this paper, we analyze the structural distortions observed by transmission electron microscopy in thin epitaxial SrRuO{sub 3} layers used as bottom electrodes in multiferroic coatings onto SrTiO{sub 3} substrates for future multiferroic devices. Regardless of the nature and architecture of the multilayer oxides deposited on the top of the SrRuO{sub 3} thin films, selected area electron diffraction patterns systematically revealed the presence of faint diffraction spots appearing in forbidden positions for the SrRuO{sub 3} orthorhombic structure. High-resolution transmission electron microscopy (HRTEM) combined with Geometric Phase Analysis (GPA) evidenced the origin of these forbidden diffraction spots in the presence of structurally disordered nanometric domains in the SrRuO{sub 3} bottom layers, resulting from a strain-driven phase transformation. The local high compressive strain (−4% ÷ −5%) measured by GPA in the HRTEM images induces a local orthorhombic to monoclinic phase transition by a cooperative rotation of the RuO{sub 6} octahedra. A further confirmation of the origin of the forbidden diffraction spots comes from the simulated diffraction patterns obtained from a monoclinic disordered SrRuO{sub 3} structure.

  20. A phase transition caught in mid-course: independent and concomitant analyses of the monoclinic and triclinic structures of (nBu4N)[Co(orotate)2(bipy)]·3H2O

    PubMed Central

    Castro, Miguel; Falvello, Larry R.; Forcén-Vázquez, Elena; Al-Kenany, Nuha A.; Martínez, Gema

    2017-01-01

    The preparation and characterization of the nBu4N+ salts of two bis-orotate(2−) complexes of cobalt, namely bis­(tetra-n-butyl­ammonium) di­aqua­bis­(2,4-dioxo-1,2,3,4-tetra­hydro­pyrimidin-1-ide-6-carboxyl­ato-κ2 N 1,O 6)cobalt(II) 1.8-hydrate, (C16H36N)2[Co(C5H2N2O4)2(H2O)2]·1.8H2O, (1), and tetra-n-butyl­ammonium (2,2′-bi­pyridine-κ2 N,N′)bis­(2,4-dioxo-1,2,3,4-tetra­hydro­pyrimidin-1-ide-6-carbox­yl­ato-κ2 N 1,O 6)cobalt(III) trihydrate, (C16H36N)[Co(C5H2N2O4)2(C10H8N2)]·3H2O, (2), are reported. The CoIII complex, (2), which is monoclinic at room tem­perature, presents a conservative single-crystal-to-single-crystal phase transition below 200 K, producing a triclinic twin. The transition, which involves a conformational change in one of the nBu groups of the cation, is reversible and can be cycled. Both end phases have been characterized structurally and the system was also characterized structurally in a two-phase inter­mediate state, using single-crystal diffraction techniques, with both the monoclinic and triclinic phases present. Thermal analysis allows a rough estimate of the small energy content, viz. 0.25 kJ mol−1, for both the monoclinic-to-triclinic transformation and the reverse transition, in agreement with the nature of the structural changes involving only the nBu4N+ cation. PMID:28872072

  1. Monoclinic crystal structure of α-RuCl3 and the zigzag antiferromagnetic ground state

    SciTech Connect

    Johnson, R. D.; Williams, S. C.; Haghighirad, A. A.; Singleton, J.; Zapf, V.; Manuel, P.; Mazin, I. I.; Li, Y.; Jeschke, H. O.; Valentí, R.; Coldea, R.

    2015-12-10

    We have proposed the layered honeycomb magnet α - RuCl 3 as a candidate to realize a Kitaev spin model with strongly frustrated, bond-dependent, anisotropic interactions between spin-orbit entangled j eff = 1/2 Ru 3 + magnetic moments. We report a detailed study of the three-dimensional crystal structure using x-ray diffraction on untwinned crystals combined with structural relaxation calculations. We consider several models for the stacking of honeycomb layers and find evidence for a parent crystal structure with a monoclinic unit cell corresponding to a stacking of layers with a unidirectional in-plane offset, with occasional in-plane sliding stacking faults, in contrast with the currently assumed trigonal three-layer stacking periodicity. We also report electronic band-structure calculations for the monoclinic structure, which find support for the applicability of the j eff = 1/2 picture once spin-orbit coupling and electron correlations are included. Of the three nearest-neighbor Ru-Ru bonds that comprise the honeycomb lattice, the monoclinic structure makes the bond parallel to the b axis nonequivalent to the other two, and we propose that the resulting differences in the magnitude of the anisotropic exchange along these bonds could provide a natural mechanism to explain the previously reported spin gap in powder inelastic neutron scattering measurements, in contrast to spin models based on the three-fold symmetric trigonal structure, which predict a gapless spectrum within linear spin wave theory. Our susceptibility measurements on both powders and stacked crystals, as well as magnetic neutron powder diffraction, show a single magnetic transition upon cooling below T N ≈ 13 K. Our analysis of our neutron powder diffraction data provides evidence for zigzag magnetic order in the honeycomb layers with an antiferromagnetic stacking between layers. Magnetization measurements on stacked single crystals in

  2. Monoclinic phase of the misfit-layered cobalt oxide (Ca 0.85OH) 1.16CoO 2

    NASA Astrophysics Data System (ADS)

    Shizuya, Mitsuyuki; Isobe, Masaaki; Baba, Yuji; Nagai, Takuro; Matsui, Yoshio; Takayama-Muromachi, Eiji

    2006-12-01

    A monoclinic phase of the misfit-layered cobalt oxide (Ca 0.85OH) 1.16CoO 2 was successfully synthesized and characterized. It was found that this new material is a poly-type phase of the orthorhombic form of (CaOH) 1.14CoO 2, recently discovered by the present authors. Both the compounds consist of two interpenetrating subsystems: CdI 2-type CoO 2 layers and rock-salt-type double-atomic-layer CaOH blocks. However, these two phases exhibit a different stacking structure. By powder X-ray and electron diffraction (ED) studies, it was found that the two subsystems of (Ca 0.85OH) 1.16CoO 2 have c-centered monoclinic Bravais lattices with common a=4.898 Å, c=8.810 Å and β=95.8° lattice parameters, and different b parameters: b1=2.820 Å and b2=4.870 Å. Chemical analyses revealed that the monoclinic phase has a cobalt valence of +3.1-3.2. Resistivity of the monoclinic phase is approximately 10 1-10 5 times lower than that of the orthorhombic phase. This suggests that the monoclinic phase is a hole-doped phase of the insulating orthorhombic phase. Furthermore, large positive Seebeck coefficients (˜100 μV/K) were observed near room temperature.

  3. Evidence of a minority monoclinic LaNiO2.5 phase in lanthanum nickelate thin films.

    PubMed

    López-Conesa, L; Rebled, J M; Pesquera, D; Dix, N; Sánchez, F; Herranz, G; Fontcuberta, J; Magén, C; Casanove, M J; Estradé, S; Peiró, F

    2017-03-29

    LaNiO3 (LNO) thin films of 14 nm and 35 nm thicknesses grown epitaxially on LaAlO3 (LAO) and (LaAlO3)0.3(Sr2TaAlO6)0.7 (LSAT) substrates are studied using High Resolution Transmission Electron Microscopy (HRTEM) and High Angle Annular Dark Field (HAADF) imaging. The strain state of the films is studied using Geometric Phase Analysis (GPA). Results show the successful in-plane adaptation of the films to the substrates, both in the compressive (LAO) and tensile (LSAT) cases. Through the systematic analysis of HRTEM superstructure contrast modulation along different crystal orientations, localized regions of the monoclinic LaNiO2.5 phase are detected in the 35 nm films.

  4. Tunable ferroelectric domain wall alignment in strained monoclinic KxNa1-xNbO3 epitaxial films

    NASA Astrophysics Data System (ADS)

    Braun, D.; Schmidbauer, M.; Hanke, M.; Kwasniewski, A.; Schwarzkopf, J.

    2017-06-01

    Epitaxial growth of ferroelectric KxNa1-xNbO3 thin films on (110) NdScO3 substrates results in the formation of domain walls which significantly differ in their arrangement from commonly observed 45° or 90° inclinations. The deviation is attributed to the monoclinic symmetry of the evolving a1a2/MC herringbone pattern and can be controlled by the epitaxial strain. In this work, tuning of the in-plane domain angle is systematically performed by the variation of the potassium content in KxNa1-xNbO3. The experimental data are in full agreement with a theoretical model. The observed behavior yields a promising pathway for domain engineering and patterning of periodic structures.

  5. Monoclinic β-Li2TiO3: Neutron diffraction study and estimation of Li diffusion pathways

    NASA Astrophysics Data System (ADS)

    Monchak, M.; Dolotko, O.; Mühlbauer, M. J.; Baran, V.; Senyshyn, A.; Ehrenberg, H.

    2016-11-01

    A neutron powder diffraction study on lithium titanate Li2TiO3 was performed at low temperatures. The monoclinic β-phase has been found to be stable over the whole investigated range of temperatures (4 K-300 K). A smooth and nonlinear increase of the lattice parameters has been observed upon heating and correlated to the behavior of interatomic distances. Lithium diffusion pathways in Li2TiO3 were estimated theoretically on the basis of the obtained structural data using bond-valence modeling. Experimentally diffusion pathways were evaluated by analysis of the negative nuclear scattering densities at 1073 K, which were reconstructed using a maximum entropy method. Although the bond-valence mismatch map indicated a possible Li diffusion either in ab plane or along c direction, analysis of the experimental data revealed that Li migration is thermodynamically less feasible in latter case.

  6. Electron Distributions in Hexagonal Selenium and Tellurium and Monoclinic Selenium with Dilute Impurities and Associated Nuclear Quadrupole Interactions*.

    NASA Astrophysics Data System (ADS)

    Maharjan, N. B.; Paudyal, D. D.; Mishra, D. R.; Byahut, S.; Aryal, M. M.; Cho, Hwa-Suck; Scheicher, R. H.; Chow, Lee; Jeong, Junho; Das, T. P.

    2006-03-01

    The electron structures of Selenium chains and rings with Te impurities in hexagonal and monoclinic structures respectively and Se impurities in Te chains in hexagonal lattice have been studied using Hartree-Fock cluster model including many-body effects, including lattice relaxation effects. The calculated electronic wave-functions are utilized to obtain ^77Se and ^125Te nuclear quadrupole coupling constants e^2qQ and asymmetry parameters η and compared with available experimental data from Mossbauer and perturbed angular correlation measurements. From our results, the expected nature of nuclear quadrupole interactions associated with Sb impurities will be discussed. *Supported by NSF US-Nepal Program and UGC Nepal **Also at UCF, Orlando

  7. Donor-acceptor pair recombination luminescence from monoclinic Cu{sub 2}SnS{sub 3} thin film

    SciTech Connect

    Aihara, Naoya; Tanaka, Kunihiko Uchiki, Hisao; Kanai, Ayaka; Araki, Hideaki

    2015-07-20

    The defect levels in Cu{sub 2}SnS{sub 3} (CTS) were investigated using photoluminescence (PL) spectroscopy. A CTS thin film was prepared on a soda-lime glass/molybdenum substrate by thermal co-evaporation and sulfurization. The crystal structure was determined to be monoclinic, and the compositional ratios of Cu/Sn and S/Metal were determined to be 1.8 and 1.2, respectively. The photon energy of the PL spectra observed from the CTS thin film was lower than that previously reported. All fitted PL peaks were associated with defect related luminescence. The PL peaks observed at 0.843 and 0.867 eV were assigned to donor-acceptor pair recombination luminescence, the thermal activation energies of which were determined to be 22.9 and 24.8 meV, respectively.

  8. Gold derivatives of eight rare-earth-metal-rich tellurides: monoclinic R7Au2Te2 and orthorhombic R6AuTe2 types.

    PubMed

    Chai, Ping; Corbett, John D

    2012-03-19

    Two series of rare-earth-metal (R) compounds, R(7)Au(2)Te(2) (R = Tb, Dy, Ho) and R(6)AuTe(2) (R = Sc, Y, Dy, Ho, Lu), have been synthesized by high-temperature techniques and characterized by X-ray diffraction analyses as monoclinic Er(7)Au(2)Te(2)-type and orthorhombic Sc(6)PdTe(2)-type structures, respectively. Single-crystal diffraction results are reported for Ho(7)Au(2)Te(2), Lu(6)AuTe(2), Sc(6)Au(0.856(2))Te(2), and Sc(6)Au(0.892(3))Te(2). The structure of Ho(7)Au(2)Te(2) consists of columns of Au-centered tricapped trigonal prisms (TCTPs) of Ho condensed into 2D zigzag sheets that are interbridged by Te and additional Ho to form the 3D network. The structure of Lu(6)AuTe(2) is built of pairs of Au-centered Lu TCTP chains condensed with double Lu octahedra in chains into 2D zigzag sheets that are separated by Te atoms. Tight binding-linear muffin-tin orbital-atomic sphere approximation electronic structure calculations on Lu(6)AuTe(2) indicate a metallic property. The principal polar Lu-Au and Lu-Te interactions constitute 75% of the total Hamilton populations, in contrast to the small values for Lu-Lu bonding even though these comprise the majority of the atoms. A comparison of the theoretical results for Lu(6)AuTe(2) with those for isotypic Lu(6)AgTe(2) and Lu(6)CuTe(2) provides clear evidence of the greater relativistic effects in the bonding of Au. The parallels and noteworthy contrasts between Ho(7)Au(2)Te(2) (35 valence electrons) and the isotypic but much electron-richer Nb(7)P(4) (55 valence electrons) are analyzed and discussed. © 2012 American Chemical Society

  9. Giant Polarization and High Temperature Monoclinic Phase in a Lead-Free Perovskite of Bi(Zn0.5Ti0.5)O3-BiFeO3

    SciTech Connect

    Pan, Zhao; Chen, Jun; Yu, Runze; Yamamoto, Hajime; Rong, Yangchun; Hu, Lei; Li, Qiang; Lin, Kun; You, Li; Zhao, Kun; Fan, Longlong; Ren, Yang; Kato, Kenichi; Azuma, Masaki; Xing, Xianran

    2016-09-15

    Lead-free piezoelectrics have attracted increasing attention due to the awareness of lead toxicity to the environment. Here, a new Bi-based lead-free perovskite of (1-x)Bi(Zn0.5Ti0.5)O3-xBiFeO3 has been synthesized via high-pressure and high-temperature method. It exhibits interest-ing properties of giant polarization, morphotropic phase boundary (MPB), and monoclinic phase. In particular, large tetragonality (c/a = 1.228) and giant spontaneous polariza-tion of 110 μC/cm2 has been obtained in 0.6Bi(Zn0.5Ti0.5)O3-0.4BiFeO3, which is much higher than most available lead-free materials and conventional Pb(Zr,Ti)O3. MPB is clearly identified to be constituted by tetragonal and monoclinic phases at x = 0.5. Notably, a single monoclinic phase has been observed at x = 0.6, which exhibits an intriguing high temperature property. In conclusion, the present results are helpful to explore new lead-free MPB systems in bismuth-based compounds.

  10. Effect of grain size on the monoclinic transformation, hardness, roughness, and modulus of aged partially stabilized zirconia.

    PubMed

    Lucas, Thomas J; Lawson, Nathaniel C; Janowski, Gregg M; Burgess, John O

    2015-12-01

    Low-temperature-degradation (LTD) has been reported to cause property changes in yttria-tetragonal zirconia polycrystals (Y-TZP). The current study measured monoclinic phase transformation of Y-TZP with different grain sizes and corresponding property changes due to artificial aging. the grain size of aged Y-TZP will not influence its transformation, roughness, hardness or modulus of elasticity. Four groups of Y-TZP were examined with differing grain sizes (n=5). The line intercept technique was used to determine grain sizes on SEM images (100,000×). Artificial aging was accomplished by autoclaving at 2 bar pressure for 5 h. X-ray diffraction (30 mA, 40 kV) was used to measure tetragonal to monoclinic transformation (t→m). Surface roughness analysis was performed using a non-contact surface-profilometer. Nano-hardness and modulus of elasticity were measured using nano-indentation. SEM analyses showed different grain sizes for each sample group (0.350 μm, 0.372 μm, 0.428 μm, and 0.574 μm). The fraction of t→m transformation increased as grain size increased; furthermore, aging of zirconia caused increased roughness. Modulus and hardness after aging displayed no significant correlation or interaction with grain size. Smaller grains caused less transformation, and aging caused increased roughness, but grain size did not influence the amount of increased surface roughness. Future studies are needed to determine the effects of grain size on the wear and fracture properties of dental zirconia. Copyright © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  11. Crustal-scale thrusting and origin of the Montreal River monocline-A 35-km-thick cross section of the midcontinent rift in northern Michigan and Wisconsin

    USGS Publications Warehouse

    Cannon, W.F.; Peterman, Z.E.; Sims, P.K.

    1993-01-01

    A structurally simple, 35-km-thick, north facing stratigraphic succession of Late Archean to Middle Proterozoic rocks is exposed near the Montreal River, which forms the border between northern Wisconsin and Michigan. This structure, the Montreal River monocline, is composed of steeply dipping to vertical sedimentary rocks and flood basalts of the Keweenawan Supergroup (Middle Proterozoic) along the south limb of the Midcontinent rift, and disconformably underlying sedimentary rocks of the Marquette Range Supergroup (Early Proterozoic). These rocks lie on an Archean granite-greenstone complex, about 10 km of which is included in the monocline. This remarkable thickness of rocks appears to be essentially structurally intact and lacks evidence of tectonic thickening or repetition.Tilting to form the monocline resulted from southward thrusting on listric faults of crustal dimension. The faults responsible for the monocline are newly recognized components of a well-known regional fault system that partly closed and inverted the Midcontinent rift system. Resetting of biotite ages on the upper plate of the faults indicates that faulting and uplift occurred at about 1060 +/−20 Ma and followed very shortly after extension that formed the Midcontinent rift system.

  12. Electronic structure of ferromagnetic semiconductor material on the monoclinic and rhombohedral ordered double perovskites La{sub 2}FeCoO{sub 6}

    SciTech Connect

    Fuh, Huei-Ru; Chang, Ching-Ray; Weng, Ke-Chuan; Wang, Yin-Kuo

    2015-05-07

    Double perovskite La{sub 2}FeCoO{sub 6} with monoclinic structure and rhombohedra structure show as ferromagnetic semiconductor based on density functional theory calculation. The ferromagnetic semiconductor state can be well explained by the superexchange interaction. Moreover, the ferromagnetic semiconductor state remains under the generalized gradient approximation (GGA) and GGA plus onsite Coulomb interaction calculation.

  13. Investigation of antimicrobial physiology of orthorhombic and monoclinic nanoallotropes of sulfur at the interface of transcriptome and metabolome.

    PubMed

    Roy Choudhury, Samrat; Mandal, Amrita; Ghosh, Mahua; Basu, Sulagna; Chakravorty, Dipankar; Goswami, Arunava

    2013-07-01

    Nanosized elemental sulfur (ES) is already reported to exert superior antimicrobial efficacy than micron-sized ES, which encourages their use in drugs and therapeutics. The aim of the present study is to explore the possible route and mode of antimicrobial action of orthorhombic (α-SNPs) and monoclinic (β-SNPs) allotropes of sulfur, respectively, at their nano-dimensions. The antimicrobial efficacy of α- and β-SNPs was determined against both the conventionally ES-resistant and ES-susceptible fungi and bacteria. Both the SNPs inhibited the microbial growth, irrespective of their resistance profile to ES and caused significant deformities on the microbial cell surfaces. However, the extent of antimicrobial efficacy was found to be optimum for α-SNPs, which can be attributed to their size, shape, and surface modification. Subsequent transcript profiling, metabolite profiling, and enzymatic analyses revealed that α- and β-SNPs impaired a cluster of mitochondrial enzymes involved in cellular respiration and oxidative phosphorylation. ES and SNPs stress were found to elicit the NADPH-dependent glutathione reductase mediated ES-detoxification response in fungi and caused them to undertake the glyoxylate shunt in favor of energy conservation. A simultaneous study was also undertaken to assess the biocompatible or bio-adverse properties of SNPs in terms of their cytotoxic and genotoxic effects against the human derived lung fibroblast cell line (MRC-5). The present study hence explores the antimicrobial physiology of two novel functional materials and demonstrates their compatibility as a future putative antimicrobial drug.

  14. In situ disordering of monoclinic titanium monoxide Ti5O5 studied by transmission electron microscope TEM.

    PubMed

    Rempel, А А; Van Renterghem, W; Valeeva, А А; Verwerft, M; Van den Berghe, S

    2017-09-07

    The superlattice and domain structures exhibited by ordered titanium monoxide Ti5O5 are disrupted by low energy electron beam irradiation. The effect is attributed to the disordering of the oxygen and titanium sublattices. This disordering is caused by the displacement of both oxygen and titanium atoms by the incident electrons and results in a phase transformation of the monoclinic phase Ti5O5 into cubic B1 titanium monoxide. In order to determine the energies required for the displacement of titanium or oxygen atoms, i.e. threshold displacement energies, a systematic study of the disappearance of superstructure reflections with increasing electron energy and electron bombardment dose has been performed in situ in a transmission electron microscope (TEM). An incident electron energy threshold between 120 and 140 keV has been observed. This threshold can be ascribed to the displacements of titanium atoms with 4 as well as with 5 oxygen atoms as nearest neighbors. The displacement threshold energy of titanium atoms in Ti5O5 corresponding with the observed incident electron threshold energy lies between 6.0 and 7.5 eV. This surprisingly low value can be explained by the presence of either one or two vacant oxygen lattice sites in the nearest neighbors of all titanium atoms.

  15. O K-energy loss near-edge structure change induced by tantalum impurity in monoclinic hafnium oxide

    SciTech Connect

    Yang, Mino; Baik, Hionsuck; Ivanovskaya, Viktoria; Colliex, Christian; Benayad, Anass

    2011-03-01

    The present paper reports the energy loss near-edge structure (ELNES) study of monoclinic HfO{sub 2} (m-HfO{sub 2}) and tantalum doped m-HfO{sub 2} (Ta{sub 0.1}Hf{sub 0.9}O{sub 2}) thin films prepared by radio frequency magnetron co-sputtering method. A change in the O K-ELNES spectra was observed as the amount of dopant increases. In order to precise the common features and the differences as a function of Ta defect nature (substitutional or interstitial) in HfO{sub 2}, the O K-ELNES were commented with respect to density functional theory calculations implemented in Vienna ab initio simulation package code. The calculated Ta doped HfO{sub 2} band structure showed that substitutional tantalum is the dominant defect and the spectral differences between doped and non-doped HfO{sub 2} are mainly originated from the change in the local cation distribution around the oxygen atoms.

  16. Pressure induced tetragonal to monoclinic transition in RbN{sub 3} studied from first principles theory

    SciTech Connect

    Vaitheeswaran, G. Babu, K. Ramesh

    2014-04-24

    Alkali metal azides are well known for their application as explosives and gas generators. They are used as precursors in synthesis of polymeric nitrogen, an ultimate green high energy density material. Among the alkali metal azides, rubidium azide RbN{sub 3} crystallizes in tetragonal structure with linear azide ions arranged in layers and binds through weak dispersive interactions. In this present work, we have studied the structural stability, electronic structure and optical properties of solid RbN{sub 3} by using van der Waals corrected density functional theory. We find that the ambient tetragonal structure undergoes a structural transition to monoclinic structure at 0.72 GPa, which is in good agreement with the experimental transition pressure of less than 1 GPa. The phonon frequencies at the gamma point are calculated and found that the lattice mode Eg softens under pressure which may supports the structural phase transition. The electronic band structure and optical properties are calculated by using Tran Blaha-modified Becke Johnson (TB-mBJ) functional and found that solid RbN{sub 3} is an insulator with a gap of 5.976 eV and the optical absorption starts with the UV light of wave length 207.5 nm.

  17. Structural, Optical, and Electrical Characterization of Monoclinic β-Ga2O3 Grown by MOVPE on Sapphire Substrates

    NASA Astrophysics Data System (ADS)

    Tadjer, Marko J.; Mastro, Michael A.; Mahadik, Nadeemullah A.; Currie, Marc; Wheeler, Virginia D.; Freitas, Jaime A.; Greenlee, Jordan D.; Hite, Jennifer K.; Hobart, Karl D.; Eddy, Charles R.; Kub, Fritz J.

    2016-04-01

    Epitaxial growth of monoclinic β-Ga2O3 on a-plane and c-plane sapphire substrates by metalorganic vapor-phase epitaxy (MOVPE) is reported. Crystalline phase, growth rate (˜150 nm/h), and energy gap (˜4.7 eV) were determined by x-ray diffraction and optical reflectance measurements. Film density of ˜5.6 g/cm3 measured by x-ray reflectivity suggests the presence of vacancies, and the O-rich growth regime implies the presence of Ga vacancies in the films. O/Ga ratio of 1.13, as measured by XPS for Ga2O3 grown on c-plane Al2O3, suggests that, near the surface, the film is O-deficient. Atomic force microscopy revealed smoother, smaller grain size when films were grown on c-plane Al2O3. Raman spectroscopy suggested inclusions of α-Ga2O3, likely present at the sapphire interface due to growth on nonnative substrate. Samples of β-Ga2O3 were selectively implanted with Si in the source/drain regions and subsequently annealed at 1000°C for 10 min. Normally-off transistors (V T ≅ 4.7 V) with 20-nm-thick Al2O3 gate oxide were fabricated, and a maximum drain-source current of 4.8 nA was measured.

  18. Photocatalytic degradation and removal mechanism of ibuprofen via monoclinic BiVO4 under simulated solar light.

    PubMed

    Li, Fuhua; Kang, Yapu; Chen, Min; Liu, Guoguang; Lv, Wenying; Yao, Kun; Chen, Ping; Huang, Haoping

    2016-05-01

    Characterized as by X-ray diffraction, scanning electron microscopy and UV-vis diffuse reflectance spectra techniques, BiVO4 photocatalyst was hydrothermally synthesized. The photocatalytic degradation mechanisms of ibuprofen (IBP) were evaluated in aqueous media via BiVO4. Results demonstrated that the prepared photocatalyst corresponded to phase-pure monoclinic scheelite BiVO4. The synthesized BiVO4 showed superior photocatalytic properties under the irradiation of visible-light. The photocatalytic degradation rate of IBP decreased with an increase in the initial IBP concentration. The degradation process followed first-order kinetics model. At an IBP concentration of 10 mg L(-1), while a BiVO4 concentration of 5.0 g L(-1) with pH value of 4.5, the rate of IBP degradation was obtained as 90% after 25 min. The photocatalytic degradation of IBP was primarily accomplished via the generation of superoxide radical (O2(•-)) and hydroxyl radicals ((•)OH). During the process of degradation, part of the (•)OH was converted from the O2(•-). The direct oxidation of holes (h(+)) made a minimal contribution to the degradation of IBP. Copyright © 2016 Elsevier Ltd. All rights reserved.

  19. Surface, optical characteristics and photocatalytic ability of Scheelite-type monoclinic Bi3FeMo2O12 nanoparticles

    NASA Astrophysics Data System (ADS)

    Nie, Xinming; Wulayin, Wumitijiang; Song, Tingting; Wu, Minxiao; Qiao, Xuebin

    2016-11-01

    Bi3FeMo2O12 nanoparticles with the Scheelite-type monoclinic structure were prepared by the Pechini synthesis. The Bi3FeMo2O12 nanoparticle has a size of about 50 nm. The phase formation and structural characteristic were studied by X-ray diffraction (XRD) patterns and Rietveld refinements. The Scheelite framework is characterized by a superstructure constructed by the ordered arrangement of Fe/Mo tetrahedral on the B sites. The surface characteristics of Bi3FeMo2O12 nanoparticles were studied by the measurements such as the scanning electron microscope (SEM), the transmission electron microscopy (TEM), and the N2-adsorption-desorption isotherm. Bi3FeMo2O12 nanoparticles present an efficient optical absorption in a wide wavelength region from UV to 540 nm. The band gap energy was decided to be 2.3 eV and characterized by a direct allowed electronic optical transition. The photocatalytic activity of Bi3FeMo2O12 nanoparticles was confirmed by the photodegradation of the rhodamine B (RhB) dye solution. The experiments indicate that the Scheelite-type molybdate could be a potential candidate of a visible-light-driven photocatalyst.

  20. A monoclinic modification of propane-1,3-diyl bis­(pyridine-3-carboxyl­ate)

    PubMed Central

    Brito, Iván; Vallejos, Javier; Cárdenas, Alejandro; López-Rodríguez, Matías; Bolte, Michael

    2011-01-01

    In the title compound, C15H14N2O4, (I), the mol­ecule lies on a twofold rotation axis which passes through the central C atom of the aliphatic chain, giving one half-mol­ecule per asymmetric unit. The structure is a monoclinic polymorph of the triclinic structure previously reported [Brito, Vallejos, Bolte & López-Rodríguez (2010). Acta Cryst. E66, o792], (II). The most obvious difference between them is the O/C/C/C—O/C/C/C torsion angle [58.2 (7)° in (I) and 173.4 (3)/70.2 (3)° in (II) for GG and TG conformations, respectively]. Another important difference is observed in the dihedral angle between the planes of the aromatic rings [86.49 (7)° for (I) and 76.4 (3)° for (II)]. The crystal structure features a weak π–π inter­action [centroid–centroid distance = 4.1397 (10)Å]; this latter kind of inter­action is not evident in the triclinic polymorph. PMID:21522970

  1. Synthesis of monoclinic structured BiVO4 spindly microtubes in deep eutectic solvent and their application for dye degradation.

    PubMed

    Liu, Wei; Yu, Yaqin; Cao, Lixin; Su, Ge; Liu, Xiaoyun; Zhang, Lan; Wang, Yonggang

    2010-09-15

    Monoclinic structured spindly bismuth vanadate microtubes were fabricated on a large scale by a simple ionothermal treatment in the environment-friendly green solvent of urea/choline chloride. The as-prepared samples were characterized by XRD, SEM, TEM, IR and their photocatalytic activity was evaluated by photocatalytic decolorization of rhodamine B aqueous solution under visible-light irradiation. As-obtained BiVO(4) microtubes exhibit the spindly shape with a side length of ca. 800 nm and a wall thickness of ca. 100 nm. The opening of these microtubes presents a saw-toothed structure, which is seldom in other tube-shaped materials. The formation mechanism of the spindly microtubes is ascribed to the complex cooperation of the reaction-crystallization process controlled by BiOCl and the nucleation-growth process of nanosheets induced by solvent molecules attached on the surface of microtubes. Such spindly microtubes exhibit much higher visible-light photocatalytic activity than that of bulk BiVO(4) prepared by solid-state reaction, possibly resulting from their large surface area and improved crystallinity. Copyright 2010 Elsevier B.V. All rights reserved.

  2. Monoclinic Hydroxyapatite Nanoplates Hybrid Composite with Improved Compressive Strength, and Porosity for Bone Defect Repair: Biomimetic Synthesis and Characterization.

    PubMed

    Xue, Bo; Farghaly, Ahmed A; Guo, Zhenzhao; Zhao, Pengg; Li, Hong; Zhou, Changren; Li, Lihua

    2016-03-01

    Calcium phosphate cement (CPC) has been used for bone restoration despite its intrinsic fragile property. In order to enhance the CPC mechanical properties, biopolymers were introduced as filler to prepare CPC based cements. Chitosan/tetracalcium phosphate (TTCP)/dicalcium phosphate anhydrous (DCPA) based cement for bone repair has been prepared in the study. Solidification of the prepared cement was carried out in a simulate body fluid at 37 degrees C. The introduction of chitosan improved the mechanical performance of the as-prepared CPC hybrid nanocomposite. FTIR, SEM, TEM, HRTEM, XRD, and SAED were used to characterize the CPC nanocomposite. Data simulations have been performed to assist in determining the crystalline phase/s in the CPC hybrid nanocomposite. Based on the SAED, HRTEM measurements and data simulations, a monoclinic phase of hydroxyapatite (HAP) with a plate-like structure was obtained in the CPC system, which is believed to be responsible for the observed enhancement in CPC mechanical properties. The obtained composite has a biocompatibility comparable to that of commercial sample.

  3. The formation of conjugate normal fault systems in folded sandstone by sequential jointing and shearing, Waterpocket monocline, Utah

    NASA Astrophysics Data System (ADS)

    Davatzes, Nicholas C.; Aydin, Atilla

    2003-10-01

    We report conjugate normal fault development by the formation and subsequent shearing of joints during flexure and associated extension of the Jurassic Wingate and Navajo Sandstones at the core of the Waterpocket monocline, Utah. Geometry and structural components across fault zones were quantified from an incipient stage to a relatively well-developed stage where the zone is 120 m wide and accommodates more than 3.5 m of slip. Shearing of joints leads to the formation of splay fractures near the joints' tip. Subsequently, these splay fractures are sheared and a new generation of splay fractures forms. Multiple generations of splay fractures cause the width of the fault damage zone to expand into the surrounding host rock, producing unusually wide fault damage zones with respect to fault offset. These extensive fault damage zones are stratigraphically confined and develop with low strains at small bed dips during folding. The faults formed by this sequential process develop a characteristic fault architecture distinguished by the type of component structures, their geometric relationships, and their distribution. We conclude that cyclic joint formation, shearing accompanied by splay fracture formation, and repeated shearing produce a geometric pattern similar to a classical conjugate fault system. However, the mechanism identified here has different implications for fault intersection angles, stress inversion, and fault architecture.

  4. Synthesis and characterization of monoclinic BiVO 4 nanorods and nanoplates via microemulsion-mediated hydrothermal method

    NASA Astrophysics Data System (ADS)

    Li, Haibin; Liu, Guocong; Chen, Shuguang; Liu, Qicheng; Lu, Weiming

    2011-05-01

    Monoclinic BiVO 4 nanorods and nanoplates were synthesized via the CTAB/water/n-butanol/n-octane microemulsion-mediated hydrothermal process. The physical and photophysical properties of the as-prepared samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Raman spectroscopy, and UV-vis diffuse reflectance spectroscopy (UV-vis). It was found that the ratio of H 2O to CTAB in microemulsion played a key role in the morphology evolution of the products. The possible formation mechanism of BiVO 4 nanostructure with various morphologies was briefly discussed. The Raman results indicated that the symmetry distortions in the local structure of the synthesized BiVO 4 were affected by the morphology of the products. The bandgaps ( Eg) of BiVO 4 nanorods and nanoplates are 2.45 and 2.38 eV, respectively. The synthesized BiVO 4 nanoplates showed superior photocatalytic activity compared with BiVO 4 nanorods due to their higher degree of structural distortion, larger surface area, and thinness.

  5. Efficient Sunlight-Induced Methylene Blue Removal over One-Dimensional Mesoporous Monoclinic BiVO4 Nanorods

    PubMed Central

    Hou, Linrui; Yang, Long; Li, Jiaoyang; Tan, Jie; Yuan, Changzhou

    2012-01-01

    Sunlight-driven mesoporous BiVO4 nanorods with monoclinic structure have been successfully synthesized via a simple hydrothermal method. The as-prepared one-dimensional BiVO4 nanorods exhibited high specific surface area due to their unique mesoporous structure. The mesoporous BiVO4 nanorods possessed strong photoabsorption properties in the visible light region as well as the ultravisible region, and the band gap was estimated to be ca. 2.18 eV. The photocatalytic activities were evaluated by decolorization of methylene blue under sunlight irradiation. Photocatalytic tests demonstrated that the decolorization rate of as-prepared mesoporous BiVO4 nanorods was even up to 98.8% in 180 min, much better than that prepared by solid-state reaction (23.1%) and the commercial TiO2 (Degussa P25) (14.2%) under the same conditions, due to their higher specific surface area and appropriate band gap. Moreover, the unique BiVO4 nanorods exhibit high stability after five photocatalytic degradation recycles. PMID:22567556

  6. Monoclinic Sr(1-x)Na(x)SiO(3-0.5x): new superior oxide ion electrolytes.

    PubMed

    Singh, Preetam; Goodenough, John B

    2013-07-10

    Oxide ion electrolytes determine the temperature of operation of solid oxide fuel cells, oxygen separation membranes, and oxygen sensors. There is a strong incentive to lower their operating temperatures, in a solid oxide fuel cell, for example, from Top > 800 °C to Top ≈ 500 °C. The use of low-cost Na(+) rather than K(+) as the dopant in monoclinic SrSiO3 (C12/C1) is shown to provide a larger solid solution range (0 < x ≤ 0.45) in Sr1-xNaxSiO3-0.5x and to achieve an oxide ion conductivity σo ≥ 10(-2) S·cm(-1) by 525 °C as a result of lowering the temperature of a smooth transition to full disorder of the mobile oxide ions. The Sr1-xNaxSiO3-0.5x electrolytes are much less hygroscopic than Sr1-xKxSiO3-0.5x and are stable with a nickel composite anode in 5% H2/Ar as well as with cathodes such as La1-xSrxMnO3-δ and Sr0.7Y0.3CoO3-δ in air, which makes them candidate electrolytes for intermediate-temperature solid oxide fuel cells or for other applications of oxide ion electrolytes.

  7. Template-Free Synthesis of Monoclinic BiVO4 with Porous Structure and Its High Photocatalytic Activity

    PubMed Central

    Dong, Pengyu; Xi, Xinguo; Zhang, Xinjiang; Hou, Guihua; Guan, Rongfeng

    2016-01-01

    Monoclinic BiVO4 photocatalysts with porous structures were synthesized by a two-step approach without assistance of any templates. The as-prepared samples were characterized by X-ray diffraction pattern (XRD), scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET), ultraviolet–visible (UV–vis) diffuse reflectance spectroscopy (DRS), photocurrent responses, and electrochemical impedance spectra (EIS). It is found that the as-prepared BiVO4 samples had a porous structure with aperture diameter of 50–300 nm. Moreover, the BET specific surface area of the porous BiVO4-200 °C sample reaches up to 5.69 m2/g, which is much higher than that of the sample of BiVO4 particles without porous structure. Furthermore, a possible formation mechanism of BiVO4 with porous structure was proposed. With methylene blue (MB) as a model compound, the photocatalytic oxidation of organic contaminants in aqueous solution was investigated under visible light irradiation. It is found that the porous BiVO4-200 °C sample exhibits the best photocatalytic activity, and the photocatalytic rate constant is about three times of that of the sample of BiVO4 particles without porous structure. In addition, the photocurrent responses and electrochemical impedance spectra strongly support this conclusion. PMID:28773809

  8. First-principles electronic structure study of the monoclinic crystal bismuth triborate BiB3O6.

    PubMed

    Yang, Jun; Dolg, Michael

    2006-10-05

    Monoclinic BiB(3)O(6) is an excellent nonlinear optical material with many advantages compared to other borate crystals. The origins of the optical effects and the chemical stability of BiB(3)O(6) are studied with gradient-corrected hybrid B3PW density functional theory within the Gaussian-orbital-based CO-LCAO scheme. Including spin-orbit coupling, the B3PW hybrid functional provides an estimate of the indirect band gap of 4.29-4.99 eV closer to the experimental value of 4.3 eV than HF, LDA, or GGA. The crystal orbital overlap population to give a detailed first-principles analysis of chemical bonding and the density of optical absorptions by convoluting the occupied density of states and the virtual density of states have been calculated. Obvious Bi-O covalent bonds have been found with different energy ranges for 6s-2p and 6p-2p interactions. The reason that [BiO(4)](5-) units are mainly responsible for the optics of BiB(3)O(6) in the long-wavelength region is due to the electronic transfer from occupied O 2p to empty Bi 6p orbitals favored by the Bi-O covalent bonds. The relativistic and correlation effects lead to fundamental differences of the band structure, chemical bonds, and optical effects for BiB(3)O(6) compared with nonrelativistic and uncorrelated calculations.

  9. Tuning oxygen vacancy photoluminescence in monoclinic Y2WO6 by selectively occupying yttrium sites using lanthanum

    PubMed Central

    Ding, Bangfu; Han, Chao; Zheng, Lirong; Zhang, Junying; Wang, Rongming; Tang, Zilong

    2015-01-01

    The effect of isovalent lanthanum (La) doping on the monoclinic Y2WO6 photoluminescence was studied. Introducing the non-activated La3+ into Y2WO6 brings new excitation bands from violet to visible regions and strong near-infrared emission, while the bands position and intensity depend on the doping concentration. It is interesting to find that doping La3+ into Y2WO6 promotes the oxygen vacancy formation according to the first-principle calculation, Raman spectrum, and synchrotron radiation analysis. Through the Rietveld refinement and X-ray photoelectron spectroscopy results, La3+ is found to mainly occupy the Y2 (2f) site in low-concentration doped samples. With increasing doping concentration, the La3+ occupation number at the Y3 (4g) site increases faster than those at the Y1 (2e) and Y2 (2f) sites. When La3+ occupies different Y sites, the localized energy states caused by the oxygen vacancy pair change their position in the forbidden band, inducing the variation of the excitation and emission bands. This research proposes a feasible method to tune the oxygen vacancy emission, eliminating the challenge of precisely controlling the calcination atmosphere. PMID:25821078

  10. Structural and microstructural changes in monoclinic ZrO{sub 2} during the ball-milling with stainless steel assembly

    SciTech Connect

    Stefanic, G. . E-mail: stefanic@irb.hr; Music, S.; Gajovic, A.

    2006-04-13

    High-energy ball-milling of monoclinic ZrO{sub 2} was performed in air using the planetary ball mill with a stainless steel milling assembly. Structural and microstructural changes during the ball-milling were monitored using X-ray powder diffraction, Raman spectroscopy, Moessbauer spectroscopy, field emission scanning electron microscopy and energy dispersive X-ray spectrometry. The results of line broadening analysis indicated a decrease in the crystallite size and an increase in the microstrains with the ball-milling time increased up to {approx}150 min. The results of quantitative phase analysis indicated the presence of a very small amount of tetragonal ZrO{sub 2} phase in this early stage of ball-milling. The onset of m-ZrO{sub 2} {sup {yields}} t-ZrO{sub 2} transition occurred between 10 and 15 h of ball-milling, which resulted in a complete transition after 20 h of ball-milling. Further ball-milling caused a decrease of the t-ZrO{sub 2} lattice parameters followed by a probable transition into c-ZrO{sub 2}. It was concluded that the stabilization of t- and c-ZrO{sub 2} polymorphs at RT can be attributed to the incorporation of aliovalent cations (Fe{sup 2+}, Fe{sup 3+} and Cr{sup 3+}) introduced into the sample due to the wear and oxidation of the milling media.

  11. On the kinetics and impact of tetragonal to monoclinic transformation in an alumina/zirconia composite for arthroplasty applications.

    PubMed

    Chevalier, Jérôme; Grandjean, Sylvie; Kuntz, Meinhard; Pezzotti, Giuseppe

    2009-10-01

    Latest trends in load-bearing materials for arthroplastic applications involve the development of highly fracture resistant alumina/zirconia composites, as an alternative choice to alumina and zirconia monolithic ceramics. Composite materials are designed from both chemical and microstructural viewpoints in order to prevent environmental degradation and fracture events in vivo, whose shadow yet hampers the full exploitation of ceramic materials in the field of arthroplasty. The aim of this paper is to evaluate the resistance to environmental degradation in an alumina/zirconia composite (Biolox Delta), which represents a primary candidate for hip and knee joint applications. Our approach consists first in the experimental determination of an activation energy value for environmentally driven tetragonal to monoclinic (t-m, henceforth) polymorphic transformation in the zirconia phase of the material; then, based on such an experimental value, a prediction is given for the long-term in vivo environmental resistance of prostheses made of the composite material. The present evaluation clarifies the in vivo performance of this new composite for orthopedic applications.

  12. Pure monoclinic La(1-x)Eu(x)PO₄ micro-/nano-structures: fast synthesis, shape evolution and optical properties.

    PubMed

    Chen, Huanhuan; Ni, Yonghong; Ma, Xiang; Hong, Jianming

    2014-08-15

    Rare-earth-doped LaPO4 crystals have been attracting considerable interest. In this work, we reported the fast syntheses of LaPO4 and Eu-doped LaPO4 crystals via a simple oil-bath route, employing La(NO3)3 and KH2PO4 as the original reactants, Eu2O3 as the dopant. The reaction was carried out in ethylene glycol system at 120°C for 30 min without any assistance of surfactants or templates. X-ray powder diffraction analyses showed that pure monoclinic LaPO4 form was obtained in the system without Eu(3+) ions, and the above phase was not changed after integrating Eu(3+) ions into LaPO4 matrix. However, electron microscopy observations discovered that the integration of Eu(3+) ions into LaPO4 matrix obviously changed the morphology and size of the final La(1-x)Eu(x)PO4 crystals. With the increase in Eu(3+) amount from 0 to 0.35, the shape of the final product varied from homogeneous egg-like nanospheroids, to irregular grains with microscales, and to homogeneous microspheroids. Also, the Eu(3+) ion content in La(1-x)Eu(x)PO4 markedly affected the photoluminescence properties of the final product. When x=0.2, the product exhibited the strongest PL emission.

  13. Tuning oxygen vacancy photoluminescence in monoclinic Y2WO6 by selectively occupying yttrium sites using lanthanum

    NASA Astrophysics Data System (ADS)

    Ding, Bangfu; Han, Chao; Zheng, Lirong; Zhang, Junying; Wang, Rongming; Tang, Zilong

    2015-03-01

    The effect of isovalent lanthanum (La) doping on the monoclinic Y2WO6 photoluminescence was studied. Introducing the non-activated La3+ into Y2WO6 brings new excitation bands from violet to visible regions and strong near-infrared emission, while the bands position and intensity depend on the doping concentration. It is interesting to find that doping La3+ into Y2WO6 promotes the oxygen vacancy formation according to the first-principle calculation, Raman spectrum, and synchrotron radiation analysis. Through the Rietveld refinement and X-ray photoelectron spectroscopy results, La3+ is found to mainly occupy the Y2 (2f) site in low-concentration doped samples. With increasing doping concentration, the La3+ occupation number at the Y3 (4g) site increases faster than those at the Y1 (2e) and Y2 (2f) sites. When La3+ occupies different Y sites, the localized energy states caused by the oxygen vacancy pair change their position in the forbidden band, inducing the variation of the excitation and emission bands. This research proposes a feasible method to tune the oxygen vacancy emission, eliminating the challenge of precisely controlling the calcination atmosphere.

  14. Efficient Sunlight-Induced Methylene Blue Removal over One-Dimensional Mesoporous Monoclinic BiVO(4) Nanorods.

    PubMed

    Hou, Linrui; Yang, Long; Li, Jiaoyang; Tan, Jie; Yuan, Changzhou

    2012-01-01

    Sunlight-driven mesoporous BiVO(4) nanorods with monoclinic structure have been successfully synthesized via a simple hydrothermal method. The as-prepared one-dimensional BiVO(4) nanorods exhibited high specific surface area due to their unique mesoporous structure. The mesoporous BiVO(4) nanorods possessed strong photoabsorption properties in the visible light region as well as the ultravisible region, and the band gap was estimated to be ca. 2.18 eV. The photocatalytic activities were evaluated by decolorization of methylene blue under sunlight irradiation. Photocatalytic tests demonstrated that the decolorization rate of as-prepared mesoporous BiVO(4) nanorods was even up to 98.8% in 180 min, much better than that prepared by solid-state reaction (23.1%) and the commercial TiO(2) (Degussa P25) (14.2%) under the same conditions, due to their higher specific surface area and appropriate band gap. Moreover, the unique BiVO(4) nanorods exhibit high stability after five photocatalytic degradation recycles.

  15. Monoclinic phase of the misfit-layered cobalt oxide (Ca{sub 0.85}OH){sub 1.16}CoO{sub 2}

    SciTech Connect

    Shizuya, Mitsuyuki; Isobe, Masaaki . E-mail: ISOBE.Masaaki@nims.go.jp; Baba, Yuji; Nagai, Takuro; Matsui, Yoshio; Takayama-Muromachi, Eiji

    2006-12-15

    A monoclinic phase of the misfit-layered cobalt oxide (Ca{sub 0.85}OH){sub 1.16}CoO{sub 2} was successfully synthesized and characterized. It was found that this new material is a poly-type phase of the orthorhombic form of (CaOH){sub 1.14}CoO{sub 2}, recently discovered by the present authors. Both the compounds consist of two interpenetrating subsystems: CdI{sub 2}-type CoO{sub 2} layers and rock-salt-type double-atomic-layer CaOH blocks. However, these two phases exhibit a different stacking structure. By powder X-ray and electron diffraction (ED) studies, it was found that the two subsystems of (Ca{sub 0.85}OH){sub 1.16}CoO{sub 2} have c-centered monoclinic Bravais lattices with common a=4.898 A, c=8.810 A and {beta}=95.8{sup o} lattice parameters, and different b parameters: b {sub 1}=2.820 A and b {sub 2}=4.870 A. Chemical analyses revealed that the monoclinic phase has a cobalt valence of +3.1-3.2. Resistivity of the monoclinic phase is approximately 10{sup 1}-10{sup 5} times lower than that of the orthorhombic phase. This suggests that the monoclinic phase is a hole-doped phase of the insulating orthorhombic phase. Furthermore, large positive Seebeck coefficients ({approx}100 {mu}V/K) were observed near room temperature. - Graphical abstract: Crystal structure of two kinds of poly-type phases of the misfit-layered cobalt oxides (Ca{sub 1-} {sub {delta}} OH) {sub x} CoO{sub 2}: (a) projection along the a-axis of the orthorhombic structure; (b) projection along the b-axis of the monoclinic structure; and (c) projection along the [-1 0 0] direction of the clinic structure. In each case, the rectangle is the unit cell.

  16. About lamination upper and convexification lower bounds on the free energy of monoclinic shape memory alloys in the context of T 3-configurations and R-phase formation

    NASA Astrophysics Data System (ADS)

    Fechte-Heinen, R.; Schlömerkemper, A.

    2016-11-01

    This work is concerned with different estimates of the quasiconvexification of multi-well energy landscapes of NiTi shape memory alloys, which models the overall behavior of the material. Within the setting of the geometrically linear theory of elasticity, we consider a formula of the quasiconvexification which involves the so-called energy of mixing.We are interested in lower and upper bounds on the energy of mixing in order to get a better understanding of the quasiconvexification. The lower bound on the energy of mixing is obtained by convexification; it is also called Sachs or Reuß lower bound. The upper bound on the energy of mixing is based on second-order lamination. In particular, we are interested in the difference between the lower and upper bounds. Our numerical simulations show that the difference is in fact of the order of 1% and less in martensitic NiTi, even though both bounds on the energy of mixing were rather expected to differ more significantly. Hence, in various circumstances it may be justified to simply work with the convexification of the multi-well energy, which is relatively easy to deal with, or with the lamination upper bound, which always corresponds to a physically realistic microstructure, as an estimate of the quasiconvexification. In order to obtain a potentially large difference between upper and lower bound, we consider the bounds along paths in strain space which involve incompatible strains. In monoclinic shape memory alloys, three-tuples of pairwise incompatible strains play a special role since they form so-called T 3-configurations, originally discussed in a stress-free setting. In this work, we therefore consider in particular numerical simulations along paths in strain space which are related to these T 3-configurations. Interestingly, we observe that the second-order lamination upper bound along such paths is related to the geometry of the T 3-configurations. In addition to the purely martensitic regime, we also consider

  17. Bicollinear antiferromagnetic order, monoclinic distortion, and reversed resistivity anisotropy in FeTe as a result of spin-lattice coupling

    SciTech Connect

    Bishop, Christopher B.; Moreo, Adriana; Dagotto, Elbio

    2016-09-08

    The bicollinear antiferromagnetic order experimentally observed in FeTe is shown to be stabilized by the coupling g~12 between monoclinic lattice distortions and the spin-nematic order parameter with B2g symmetry, within a three-orbital spin-fermion model studied with Monte Carlo techniques. A finite but small value of g~12 is required, with a concomitant lattice distortion compatible with experiments, and a tetragonal-monoclinic transition strongly first order. Remarkably, the bicollinear state found here displays a planar resistivity with the reversed puzzling anisotropy discovered in transport experiments. Orthorhombic distortions are also incorporated, and phase diagrams interpolating between pnictides and chalcogenides are presented. Here, we conclude that the spin-lattice coupling we introduce is sufficient to explain the challenging properties of FeTe.

  18. Bicollinear antiferromagnetic order, monoclinic distortion, and reversed resistivity anisotropy in FeTe as a result of spin-lattice coupling

    SciTech Connect

    Bishop, Christopher B.; Moreo, Adriana; Dagotto, Elbio

    2016-09-08

    The bicollinear antiferromagnetic order experimentally observed in FeTe is shown to be stabilized by the coupling g~12 between monoclinic lattice distortions and the spin-nematic order parameter with B2g symmetry, within a three-orbital spin-fermion model studied with Monte Carlo techniques. A finite but small value of g~12 is required, with a concomitant lattice distortion compatible with experiments, and a tetragonal-monoclinic transition strongly first order. Remarkably, the bicollinear state found here displays a planar resistivity with the reversed puzzling anisotropy discovered in transport experiments. Orthorhombic distortions are also incorporated, and phase diagrams interpolating between pnictides and chalcogenides are presented. Here, we conclude that the spin-lattice coupling we introduce is sufficient to explain the challenging properties of FeTe.

  19. Room-temperature monoclinic and low-temperature triclinic phase-transition structures of meso-octamethylcalix[4]pyrrole-dimethyl sulfoxide (1/1).

    PubMed

    Lynch, V M; Gale, P A; Sessler, J L; Madeiros, D

    2001-12-01

    Crystals of the title complex, C28H36N4*C2H6OS, undergo a phase transition between room temperature and 198 K, as determined by X-ray diffraction techniques. A monoclinic form is observed at room temperature, while a triclinic modification is found at 198 K, with Z' changing from 1 to 2. Differential scanning calorimetry (DSC) of the calixpyrrole-dimethyl sulfoxide complex revealed a series of phase changes between 273 and 243 K. The transition from the room-temperature monoclinic form to the low-temperature triclinic form is reversible, as determined by changes in the cell dimensions from remeasuring selected reflections at room temperature and at temperatures below 223 K. The uncomplexed calix[4]pyrrole molecule shows no phase changes occurring between room temperature and 233 K, the low-temperature limit of the DSC.

  20. Bicollinear antiferromagnetic order, monoclinic distortion, and reversed resistivity anisotropy in FeTe as a result of spin-lattice coupling

    DOE PAGES

    Bishop, Christopher B.; Moreo, Adriana; Dagotto, Elbio

    2016-09-08

    The bicollinear antiferromagnetic order experimentally observed in FeTe is shown to be stabilized by the coupling g~12 between monoclinic lattice distortions and the spin-nematic order parameter with B2g symmetry, within a three-orbital spin-fermion model studied with Monte Carlo techniques. A finite but small value of g~12 is required, with a concomitant lattice distortion compatible with experiments, and a tetragonal-monoclinic transition strongly first order. Remarkably, the bicollinear state found here displays a planar resistivity with the reversed puzzling anisotropy discovered in transport experiments. Orthorhombic distortions are also incorporated, and phase diagrams interpolating between pnictides and chalcogenides are presented. Here, we concludemore » that the spin-lattice coupling we introduce is sufficient to explain the challenging properties of FeTe.« less

  1. Diffraction theory of nanotwin superlattices with low symmetry phase: Application to rhombohedral nanotwins and monoclinic M{sub A} and M{sub B} phases

    SciTech Connect

    Wang, Yu U.

    2007-07-01

    The Brillouin zone-dependent conditions for coherent and adaptive diffractions are formulated. Adaptive diffraction phenomenon of nanotwins is analyzed. Extraordinary Bragg reflection peaks appear and adaptively shift along the conventional twin peak splitting vectors, whose positions are determined by lever rule according to twin variant volume fractions. Analysis of rhombohedral nanotwins shows that the nanotwin superlattices of rhombohedral phase with {l_brace}001{r_brace} and {l_brace}110{r_brace} twin planes diffract incident waves just like monoclinic M{sub A} and M{sub B} phases, respectively, whose lattice parameters are intrinsically related to that of rhombohedral phase. Crystallographic analysis of rhombohedral nanotwins by nanodomain averaging gives the same monoclinic M{sub A} and M{sub B} phases.

  2. Nonstoichiometric La(2 - x)GeO(5 - delta) monoclinic oxide as a new fast oxide ion conductor.

    PubMed

    Ishihara, T; Arikawa, H; Akbay, T; Nishiguchi, H; Takita, Y

    2001-01-17

    Oxide ion conductivity in La(2)GeO(5)-based oxide was investigated and it was found that La-deficient La(2)GeO(5) exhibits oxide ion conductivity over a wide range of oxygen partial pressure. The crystal structure of La(2)GeO(5) was estimated to be monoclinic with P2(1)/c space group. Conductivity increased with increasing the amount of La deficiency and the maximum value was attained at x = 0.39 in La(2 - x)GeO(5 - delta). The oxide ion transport number in La(2)GeO(5)-based oxide was estimated to be unity by the electromotive force measurement in H(2)-O(2) and N(2)-O(2) gas concentration cells. At a temperature higher than 1000 K, the oxide ion conductivity of La(1.61)GeO(5 - delta) was almost the same as that of La(0.9)Sr(0.1)Ga(0.8)Mg(0.2)O(3 - delta) or Ce(0.85)Gd(0.15)O(2 - delta), which are well-known fast oxide ion conductors. On the other hand, a change in the activation energy for oxide ion conductivity was observed at 973 K, and at intermediate temperature, the oxide ion conductivity of La(1.61)GeO(5 - delta) became much smaller than that of these well-known fast oxide ion conductors. The change in the activation energy of the oxide ion conductivity seems to be caused by a change in the local oxygen vacancy structure. However, doping a small amount of Sr for La in La(2)GeO(5) was effective to stabilize the high-temperature crystal structure to low temperature. Consequently, doping a small amount of Sr increases the oxide ion conductivity of La(2)GeO(5)-based oxide at low temperature.

  3. Thermal properties of monoclinic KLu(WO4)2 as a promising solid state laser host.

    PubMed

    Silvestre, Oscar; Grau, Joan; Pujol, Maria Cinta; Massons, Jaume; Aguiló, Magdalena; Díaz, Francesc; Borowiec, Mieczyslaw T; Szewczyk, Andrzej; Gutowska, Maria U; Massot, Marta; Salazar, Agustín; Petrov, Valentin

    2008-03-31

    Thermal analysis of the monoclinic solid state laser host KLu(WO4)2 is presented. The specific heat was measured by the relaxation method in the temperature range from 1.9 to 385 K: its value at room temperature is 0.324 J/gK. The Debye temperature and the sound velocity amount to 303+/-3 K and 3734 m/s. The linear thermal expansion tensor was measured by X-ray powder diffraction from room temperature up to 773 K. The eigenvalues of this tensor are alpha'(11)=8.98 x 10(-6) K(-1), alpha'(22)=3.35 x 10(-6) K(-1), and alpha'(33)=16.72 x 10(-6) K(-1), with the maximum value in the a-b crystallographic plane, at 31.94 degrees from the N(g) principal optical axis. The thermal diffusivity and its anisotropy in the temperature range between 300 and 500 K were measured by the pyroelectric method to determine the thermal conductivity tensor. The eigenvalues of the thermal conductivity are kappa'(11)=2.95 Wm(-1)K(-1), kappa'(22)=2.36 Wm-1K-1, and kappa'(33)=4.06 Wm(-1)K(-1), with the maximum value along a direction again in the a-b crystallographic plane, at 40.75 degrees from the N(g) principal optical axis. Simulation of the temperature distribution in a bulk sample of KLu(WO4)2 with dimensions 3 x 3 x 3 mm(3) shows that pump and laser beam directions along the N(p) principal optical axis in terms of thermal effects are preferable because the propagation is along a quasi-isothermal path.

  4. Crystal structure, phase relations and electrochemical properties of monoclinic Li{sub 2}MnSiO{sub 4}

    SciTech Connect

    Politaev, V.V.; Petrenko, A.A. Nalbandyan, V.B.; Medvedev, B.S.; Shvetsova, E.S.

    2007-03-15

    Phase relations in the MnO-SiO{sub 2}-Li{sub 4}SiO{sub 4} subsystem have been investigated by X-ray diffraction after solid-state reactions in hydrogen at 950-1150 deg. C. Both cation-deficient and cation-excess solid solutions Li{sub 2+2} {sub x} Mn{sub 1-} {sub x} SiO{sub 4} (-0.2{<=}x{<=}0.2) based on Li{sub 2}MnSiO{sub 4} have been found. According to Rietveld analysis, Li{sub 2}MnSiO{sub 4} (monoclinic, P2{sub 1}/n, a=6.3368(1), b=10.9146(2), c=5.0730(1) A, {beta}=90.987(1){sup o}) is isostructural with {gamma} {sub II}-Li{sub 2}ZnSiO{sub 4} and low-temperature Li{sub 2}MgSiO{sub 4}. All components are in tetrahedral environment, (MnSiO{sub 4}){sup 2-} framework is built of four-, six- and eight-member rings of tetrahedra. Testing Li{sub 2}MnSiO{sub 4} in an electrochemical cell showed that only 4% Li could be extracted between 3.5 and 5 V against Li metal. These results are discussed in comparison with those for recently reported orthorhombic layered Li{sub 2}MnSiO{sub 4} and other tetrahedral Li{sub 2} MXO{sub 4} phases. - Graphical abstract: Arrangement of Mn (large white balls) and Si (small grey balls) atoms in Li{sub 2}MnSiO{sub 4} structure. Bold lines connect atoms linked via common oxygen (not shown)

  5. Facile synthesis and photocatalytic activity of monoclinic BiVO{sub 4} micro/nanostructures with controllable morphologies

    SciTech Connect

    Wang, Xinkun; Li, Guicun; Ding, Jie; Peng, Hongrui; Chen, Kezheng

    2012-11-15

    Graphical abstract: Display Omitted Highlights: ► BiVO{sub 4} micro/nanostructures have been synthesized by a facile solvothermal method. ► The shapes of BiVO{sub 4} micro/nanostructures can be controlled by tuning the synthetic parameters. ► BiVO{sub 4} nanorods with rectangular cross sections exhibit improved photocatalytic activities. -- Abstract: Monoclinic BiVO{sub 4} (m-BiVO{sub 4}) micro/nanostructures, such as nanorods, nanofibers, bundle-like nanostructures, and porous submicrometer-sized rods, have been successfully synthesized by a facile solvothermal method in an ethylene glycol–water–sodium oleate system. The morphologies and sizes of m-BiVO{sub 4} micro/nanostructures can be controlled by adjusting the synthetic parameters, such as the concentrations of sodium oleate and reaction time. Among them, the synthesized m-BiVO{sub 4} nanorods have rectangular cross sections, and can grow along the [0 0 1] direction, and are enclosed by well-defined facets, such as (0 0 2), (2 4 0), and (2{sup ¯}10), which are distinct from that with circular cross sections. A crystallization-cleavage-disassembly process has been proposed for the formation of m-BiVO{sub 4} nanorods with rectangular cross sections. The photocatalytic activity of m-BiVO{sub 4} nanostructures is affected greatly by the sizes and shapes of m-BiVO{sub 4} nanostructures. Photocatalytic measurements show that the m-BiVO{sub 4} nanorods with rectangular cross sections exhibit higher photocatalytic activities of Rhodamine B in comparison with m-BiVO{sub 4} nanofibers with circular cross-sections and porous submicrometer-sized rods.

  6. A Green Route to Hexagonal and Monoclinic BiPO4:Ln3+ (Ln = Sm, Eu, Tb, Dy) Nanocrystallites for Tailoring Luminescent Performance.

    PubMed

    Yang, Errui; Li, Guangshe; Zheng, Yunlong; Li, Liping

    2016-04-01

    Selective synthesis of specific phased nanomaterials via a green route is a promising yet challeng- ing task. In the present work, the hexagonal and monoclinic phases of BiPO4:Ln3+ (Ln = Sm, Eu, Tb, Dy) were prepared via room temperature co-precipitation method. For adjusting the phase of the products, the prepared mediums selected were the most common solvents, i.e., water and ethanol. It was very important that the prepared mediums could be easily recycled and reused by evapo- rating the filtrate. The formation mechanisms of hexagonal in water and monoclinic in ethanol were investigated. Interestingly, the growth behaviors of these phases were quite distinct and thus gave rise to distinct morphology and particle size. The hexagonal phase possesses a rod-like morphol- ogy with diameters of 50-160 nm and lengths of 65-400 nm while the monoclinic phase consists of almost entirely irregular nanoparticles. Also, it was found that the bending and stretching vibrations of O-H and PO4 tetrahedra were quite different for the products prepared in water and ethanol. Moreover, it was found that the luminescence properties, including emission intensity, lifetime, quan- tum efficiency, and color, could be readily tailored through controlling the phase structures and microstructures. The results showed that the monoclinic phase exhibited superior luminescent per- formance to the hexagonal phase. The methodologies reported in this work were fundamentally important, which could be easily extended to large-scale synthesis of other phased nanomaterials for potential applications as electroluminescent devices, optical integrated circuits, or biomarkers.

  7. Neutron diffraction study of the monoclinic to tetragonal structural transition in LaNbO{sub 4} and its relation to proton mobility

    SciTech Connect

    Huse, M.; Skilbred, A.W.B.; Karlsson, M.; Eriksson, S.G.; Norby, T.; Haugsrud, R.; Knee, C.S.

    2012-03-15

    The fergusonite-scheelite structural transition of LaNbO{sub 4} was characterized by high-intensity variable temperature neutron powder diffraction in an effort to link structural changes to proton transport in the low temperature monoclinic and high temperature tetragonal polymorphs. The pronounced decrease in enthalpy of proton mobility with increasing temperature in monoclinic LaNbO{sub 4}, identified by Fjeld et al. , was found to coincide with the decrease in a key inter-tetrahedral oxygen separation. At temperatures above the transition, this oxygen to oxygen distance remains constant, behavior that is consistent with the invariant nature of the calculated enthalpy of mobility for the tetragonal phase. This oxygen separation is therefore proposed as the key structural parameter determining the success rate of proton transfer and ultimately the proton diffusion in LaNbO{sub 4}. Infrared measurements performed on acceptor-doped LaNbO{sub 4} show an absorption in the region 2500 to 3700 cm{sup -1} attributed to the O-H stretching motion influenced by hydrogen bonding. - Graphical Abstract: The structural phase transition from monoclinic fergusonite to tetragonal scheelite crystal structure clearly influences the proton conductivity of acceptor-doped LaNbO{sub 4} (see Figure). The present article attempts to explain why. Highlights: Black-Right-Pointing-Pointer Transition from monoclinic to tetragonal structure studied using neutron diffraction. Black-Right-Pointing-Pointer Change in proton mobility linked to contraction of a key oxygen separation. Black-Right-Pointing-Pointer Infra-red spectra reveal intermediate strength hydrogen bonding.

  8. Strain engineering of monoclinic domains in K x Na1-x NbO3 epitaxial layers: a pathway to enhanced piezoelectric properties

    NASA Astrophysics Data System (ADS)

    Schmidbauer, Martin; Braun, Dorothee; Markurt, Toni; Hanke, Michael; Schwarzkopf, Jutta

    2017-06-01

    A novel concept to obtain a ferroelectric material with enhanced piezoelectric properties is proposed. This approach is based on the combination of two pathways: (i) the evolution of a ferroelectric monoclinic phase and, (ii) the coexistence of different types of ferroelectric domains leading to polarization discontinuities at the domain walls. Each of these pathways enables polarization rotation in the material which is responsible for giant piezoelectricity. Targeted incorporation of anisotropic epitaxial lattice strain is used to implement this approach. The feasibility of our concept is demonstrated for K0.9Na0.1NbO3 epitaxial layers grown on NdScO3 substrates where the coexistence of (100)pc and (001)pc pseudocubic oriented monoclinic domains is experimentally verified. This coexistence results in a complex periodic domain pattern with alternating emergence of ferroelectric in-plane a 1 a 2 and inclined M C monoclinic phases, which differ in the direction of the electrical polarization vector. Our approach opens the possibility to exploit ferroelectric properties in both vertical and lateral directions and to achieve enhanced piezoelectric properties in lead-free material caused by singularities at the domains walls.

  9. Mechanical and Transport Properties of Poly(propylene-co-1-heptene) Copolymers and Their Dependence on Monoclinic and/or Mesomorphic Polymorphs.

    PubMed

    García-Peñas, Alberto; Gómez-Elvira, José M; Lorenzo, Vicente; Pérez, Ernesto; Cerrada, María L

    2016-02-25

    Poly(propylene-co-1-heptene) copolymers have been evaluated in a wide 1-heptene content range. Two different polymorphs can be observed in this interval under the processing conditions imposed: monoclinic crystallites and mesomorphic entities. The unique presence of one or the other lattice at specific content or the coexistence of both of them at the intermediate composition interval is a key factor affecting some of the exhibited properties. The influence is observed in characteristics mainly dependent on either crystalline structure, like rigidity, or the amorphous regions, as location and intensity of glass transition. To get a deeper understanding, the transition from mesophase to monoclinic crystallites has also been studied by DSC and by WAXS and SAXS experiments using synchrotron radiation. It is observed that this transformation is only partial and just involves one-third of the initial ordered mesomorphic entities. Permeability to different gases is mainly dependent on amorphous content and hindrance that monoclinic or mesomorphic entities impose on those disordered regions.

  10. Soft modes and elastic strain at the tetragonal-to-monoclinic phase transition in antifluorite and related structure types

    NASA Astrophysics Data System (ADS)

    Ihringer, J.; Abrahams, S. C.

    1984-12-01

    Group-theoretical normal-mode analysis of the antifluorite A2BX6 structure in space group P4mnc (D64h) identifies two effective modes with Eg symmetry. Either mode may condense independently of the other at the phase transition to space group P21n (C52h). One mode produces a displacement of the A+ ions, the other a rotation of the BX62- octahedra. Lattice distortion thereby results from the coupling between order parameter (Q) and elastic strain (e). Linear and quadratic symmetry invariant coupling in terms of free energy results in e13~Q and, independently, e22-e11 ~Q2. The linear coupling produces a discontinuous change in soft-mode frequency at Tc, whereas the change in specific heat is caused primarily by the quadratic coupling. Measurements on K2TeBr6 reveal that one Eg mode condenses at the second-order phase transition to P21n at 400 K and follows a Landau critical power law with e13 ~(400K-T)12, leaving e22-e11=0 for 359monoclinic transition as further octahedral rotation becomes blocked. Evidence for the two Eg-mode displacement fields is found in the literature for all elpasolite A2B'B''X6 and cryolite A3BX6 structures determined in space group P21n. Formation of an additional phase by the antifluorites K2SeBr6 and K2SnCl6 in space group C 2c (C62h) on cooling from P4mnc to P21n results from two octahedral rotations due to the Eg-mode basis vectors having order parameters of equal magnitude. The orthorhombic pseudosymmetry in C 2c is caused only by the e12 strain component. The coupling found in K2TeBr6 is shown to apply generally to related structure types.

  11. Physical properties of V 1-xTixO₂ (0 < x < 0.187) single crystals

    DOE PAGES

    Kong, Tai; Masters, Morgan W.; Bud’ko, Sergey L.; ...

    2015-02-13

    Free standing, low strain, single crystals of pure and titanium doped VO₂ were grown out of an excess of V ₂O₅ using high temperature solution growth techniques. At TMI ~ 340 K, pure VO₂ exhibits a clear first-order phase transition from a high-temperature paramagnetic tetragonal phase (R) to a low-temperature non-magnetic monoclinic phase (M1). With Ti doping, another monoclinic phase (M2) emerges between the R and M1 phases. The phase transition temperature between R and M2 increases with increasing Ti doping while the transition temperature between M2 and M1 decreases.

  12. Pressure dependence of the monoclinic phase in (1–x)Pb(Mg1/3Nb2/3)O3-xPbTiO₃ solid solutions

    SciTech Connect

    Ahart, Muhtar; Sinogeikin, Stanislav; Shebanova, Olga; Ikuta, Daijo; Ye, Zuo-Guang; Mao, Ho-kwang; Cohen, R. E.; Hemley, Russell J.

    2012-12-26

    We combine high-pressure x-ray diffraction, high-pressure Raman scattering, and optical microscopy to investigate a series of (1–x)Pb(Mg1/3Nb2/3)O3-xPbTiO₃ (PMN-xPT) solid solutions (x=0.2, 0.3, 0.33, 0.35, 0.37, 0.4) in diamond anvil cells up to 20 GPa at 300 K. The Raman spectra show a peak centered at 380 cm⁻¹ starting above 6 GPa for all samples, in agreement with previous observations. X-ray diffraction measurements are consistent with this spectral change indicating a structural phase transition; we find that the triplet at the pseudocubic (220) Bragg peak merges into a doublet above 6 GPa. Our results indicate that the morphotropic phase boundary region (x=0.33–0.37) with the presence of monoclinic symmetry persists up to 7 GPa. The pressure dependence of ferroelectric domains in PMN-0.32PT single crystals was observed using a polarizing optical microscope. The domain wall density decreases with pressure and the domains disappear at a modest pressure of 3 GPa. We propose a pressure-composition phase diagram for PMN-xPT solid solutions.

  13. Pressure dependence of the monoclinic phase in (1–x)Pb(Mg1/3Nb2/3)O3-xPbTiO₃ solid solutions

    DOE PAGES

    Ahart, Muhtar; Sinogeikin, Stanislav; Shebanova, Olga; ...

    2012-12-26

    We combine high-pressure x-ray diffraction, high-pressure Raman scattering, and optical microscopy to investigate a series of (1–x)Pb(Mg1/3Nb2/3)O3-xPbTiO₃ (PMN-xPT) solid solutions (x=0.2, 0.3, 0.33, 0.35, 0.37, 0.4) in diamond anvil cells up to 20 GPa at 300 K. The Raman spectra show a peak centered at 380 cm⁻¹ starting above 6 GPa for all samples, in agreement with previous observations. X-ray diffraction measurements are consistent with this spectral change indicating a structural phase transition; we find that the triplet at the pseudocubic (220) Bragg peak merges into a doublet above 6 GPa. Our results indicate that the morphotropic phase boundary regionmore » (x=0.33–0.37) with the presence of monoclinic symmetry persists up to 7 GPa. The pressure dependence of ferroelectric domains in PMN-0.32PT single crystals was observed using a polarizing optical microscope. The domain wall density decreases with pressure and the domains disappear at a modest pressure of 3 GPa. We propose a pressure-composition phase diagram for PMN-xPT solid solutions.« less

  14. Monoclinic Tm3+:MgWO4: a promising crystal for continuous-wave and passively Q-switched lasers at ∼2  μm.

    PubMed

    Loiko, Pavel; Serres, Josep Maria; Mateos, Xavier; Aguiló, Magdalena; Díaz, Francesc; Zhang, Lizhen; Lin, Zhoubin; Lin, Haifeng; Zhang, Ge; Yumashev, Konstantin; Petrov, Valentin; Griebner, Uwe; Wang, Yicheng; Choi, Sun Yung; Rotermund, Fabian; Chen, Weidong

    2017-03-15

    Monoclinic thulium-doped magnesium monotungstate, Tm3+:MgWO4, is promising for efficient power-scalable continuous-wave (CW) and passively Q-switched lasers at >2  μm. Under diode pumping at 802 nm, a compact CW laser based on Z-cut Tm:MgWO4 generated 3.09 W at 2022-2034 nm with a slope efficiency of 50% which represents the highest output power ever achieved with this type of laser host. Stable passive Q-switching of the Tm:MgWO4 laser is demonstrated for the first time, to the best of our knowledge, using single-walled carbon nanotubes, graphene, and Cr2+:ZnS saturable absorbers. Using the latter, the best performance is achieved with 16.1 μJ/13.6 ns pulses at 2017.8 nm with a maximum average output power of 0.87 W and a peak power of 1.18 kW.

  15. Pressure dependence of the monoclinic phase in (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 solid solutions

    NASA Astrophysics Data System (ADS)

    Ahart, Muhtar; Sinogeikin, Stanislav; Shebanova, Olga; Ikuta, Daijo; Ye, Zuo-Guang; Mao, Ho-kwang; Cohen, R. E.; Hemley, Russell J.

    2012-12-01

    We combine high-pressure x-ray diffraction, high-pressure Raman scattering, and optical microscopy to investigate a series of (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-xPT) solid solutions (x=0.2, 0.3, 0.33, 0.35, 0.37, 0.4) in diamond anvil cells up to 20 GPa at 300 K. The Raman spectra show a peak centered at 380 cm-1 starting above 6 GPa for all samples, in agreement with previous observations. X-ray diffraction measurements are consistent with this spectral change indicating a structural phase transition; we find that the triplet at the pseudocubic (220) Bragg peak merges into a doublet above 6 GPa. Our results indicate that the morphotropic phase boundary region (x=0.33-0.37) with the presence of monoclinic symmetry persists up to 7 GPa. The pressure dependence of ferroelectric domains in PMN-0.32PT single crystals was observed using a polarizing optical microscope. The domain wall density decreases with pressure and the domains disappear at a modest pressure of 3 GPa. We propose a pressure-composition phase diagram for PMN-xPT solid solutions.

  16. Monoclinic distortion and magnetic coupling in the double perovskite Sr{sub 2−x}Ca{sub x}YRuO{sub 6}

    SciTech Connect

    Bernardo, P.L.; Ghivelder, L.; Eslava, G.G.; Amorim, H.S.; Felner, I.; Garcia, S.

    2014-12-15

    Abstracts: This work investigates in the insulating double perovskites Sr{sub 2−x}Ca{sub x}YRuO{sub 6}. We address the angular dependence of the strength of the magnetic coupling due to the deviation from planarity of the basal layers of the monoclinic structure, characterized by the in-plane angle α<180°, in order to probe the impact of the structural distortions in the magnetic properties of the compounds. High resolution x-ray powder diffraction, susceptibility, and specific heat measurements were performed. The deviation from planarity significantly increases (α=144° for x=1) while the bond distances vary in a complex way as a consequence of the strong monoclinic distortion. We found that the magnetic transition temperature, T{sub M}, shows a linear dependence on cos [(π−α)/2]. This result is discussed in terms of t{sub 2g}(π)–e{sub g}(σ) mixing of the magnetic orbitals of the Ru{sup 5+} ions and unbalanced competitive super-exchange interactions. The deleterious effect of Ca doping for the magnetic coupling is confirmed by the reduction in the short-range antiferromagnetic correlations characteristic of the parent compound at T>>T{sub M} and the enhancement of magnetic frustration for Tmonoclinic distortions. - Highlights: • Neel temperatures in SrCaYRuO were correlated quantitatively with lattice distortions. • Bending of Ru–O–Y planes plays a major role in the magnetic properties of SrCaYRuO. • The structural–magnetic correlation is due to π–σ mixing of the magnetic orbitals.

  17. Electron paramagnetic resonance characterization of defects in monoclinic HfO{sub 2} and ZrO{sub 2} powders

    SciTech Connect

    Wright, Sandra; Barklie, R. C.

    2009-11-15

    Electron paramagnetic resonance (EPR) measurements have been made at X-band and room temperature on monoclinic HfO{sub 2} and ZrO{sub 2} powders from several suppliers. They reveal the presence of eight main paramagnetic centers H1, H2, H3, H4, and Z1, Z2, Z3, and Z4. H1 and Z1 are analogous as H4 and Z4 and H2 and Z2 are similar as H3 and Z3. H1 and Z1 have axial symmetry with g{sub ||}=300 deg. C. Their concentration reaches a maximum of order 10{sup 17} cm{sup -3} or 10{sup 12} cm{sup -2} in the range of 550-750 deg. C. They are also most likely to be mainly at and/or near the surface and to involve an electron trapped in an oxygen vacancy cluster. The EPR spectra of H2 and Z2 are consistent with those of S=1/2 centers of orthorhombic symmetry with principal g values about equal to or just less than g{sub e} suggesting that they are trapped electron centers. The electrons produced by gamma-irradiation are trapped at precursors to H2 but are easily detrapped. Z2 centers also appear to be shallow electron traps. Their identity is uncertain

  18. Monoclinic structure of hydroxylpyromorphite Pb10(PO4)6(OH)2 - hydroxylmimetite Pb10(AsO4)6(OH)2 solid solution series

    NASA Astrophysics Data System (ADS)

    Giera, Alicja; Manecki, Maciej; Borkiewicz, Olaf; Zelek, Sylwia; Rakovan, John; Bajda, Tomasz; Marchlewski, Tomasz

    2016-04-01

    Seven samples of hydroxyl analogues of pyromorphite-mimetite solid solutions series were synthesized from aqueous solutions at 80° C in a computer-controlled chemistate: 200 mL aqueous solutions of 0.05M Pb(NO3)2 and 0.03M KH2AsO4 and/or KH2PO4 were dosed with a 0.25 mL/min rate to a glass beaker, which initially contained 100 mL of distilled water. Constant pH of 8 was maintained using 2M KOH. The syntheses yielded homogeneous fine-grained white precipitates composition of which was close to theoretical Pb10[(PO4)6-x(AsO4)x](OH)2, where x = 0, 1, 2, 3, 4, 5, 6. High-resolution powder X-ray diffraction data were obtained in transmission geometry at the beamline 11-BM at the Advanced Photon Source (Argonne National Laboratory in Illinois, USA). The structure Rietveld refinements based on starting parameters of either hexagonal hydroxylpyromorphite or monoclinic mimetite-M were performed using GSAS+EXPGUI software. Apatite usually crystallizes in the hexagonal crystal system with the space group P63/m. For the first time, however, the lowering of the hexagonal to monoclinic crystal symmetry was observed in the hydroxyl variety of pyromorphite-mimetite solid solution series. This is indicated by better fitting of the modeled monoclinic structure to the experimental data. The same is not the case for analogous calcium hydroxylapatite series Ca5(PO4)3OH - Ca5(AsO4)3OH (Lee et al. 2009). Systematical linear increase of unit cell parameters is observed with As substitution from a=9.88, b=19.75, and c=7.43 for Pb10(PO4)6(OH)2 to a=10.23, b=20.32, and c=7.51 for Pb10(AsO4)6(OH)2. A strong pseudohexagonal character (γ ≈ 120° and b ≈ 2a) of the analyzed monoclinic phases was established. This work is partially funded by AGH research grant no 11.11.140.319 and partially by Polish NCN grant No 2011/01/M/ST10/06999. Lee Y.J., Stephens P.W., Tang Y., Li W., Philips B.L., Parise J.B., Reeder R.J., 2009. Arsenate substitution in hydroxylapatite: Structural characterization

  19. A very promising piezoelectric property of Ta{sub 2}O{sub 5} thin films. I: Monoclinic-trigonal phase transition

    SciTech Connect

    Audier, M.; Chenevier, B.; Roussel, H.; Vincent, L.; Pena, A.

    2011-08-15

    Ceramic thin films of tantalum oxide of a new trigonal structure (a=12.713(7) A, {alpha}=28.201(0){sup o}, space-group R3) were produced by thermal treatments of amorphous deposits on (001)Si wafers, either by electrostatic spray deposition or by injection metal-organic chemical vapor decomposition. This trigonal phase comes from the transformation of a monoclinic phase 11L- or 25L-Ta{sub 2}O{sub 5}. The transformation is reversible under oxygen atmosphere and, from results of TEM investigations, occurs mainly via atomic motions along the z unique axis of the monoclinic structure parallel to the polar three-fold axis of the trigonal structure. The non-centrosymmetry and direction of polar axis of the trigonal phase, identified by high resolution TEM imaging, indicate a possibility of very high electric dipole moments linked to a strong piezoelectricity. From results of XPS analyses of both monoclinic and trigonal structures, the binding energies remain similar to those of Ta{sub 2}O{sub 5}. As the formation of the trigonal structure gives rise to an important volume expansion, stresses induced in ceramic thin films are likely influencing both properties of birefringence and piezoelectricity which are presented in a separated article (part II). It is mentioned that the formation of trigonal phase does not occur in bulk Ta{sub 2}O{sub 5} samples, for which an incommensurate phase transition has been observed in a previous work. - Graphical abstract: (a) {theta}/2{theta} X-ray pattern of the tantalum oxide layer prepared by i-MOCVD, cooled down at 5 deg. C min{sup -1} after a thermal treatment at 850 deg. C under N{sub 2} for 1 h. (b) Rhombohedral cell of the Ta{sub 2}O{sub 5} trigonal structure of R3 space-group decorated with its 10 Ta sites. Highlights: > We examine crystallographic properties of a new Ta{sub 2}O{sub 5} trigonal phase. > Its formation occurs only in thin films. > It comes from a reversible transition with a monoclinic phase. > A possibility of

  20. Monoclinic to two-dimensional hexagonal transformation in hexacatenar molecules with a 1,2,3-triazole-based conjugated rod: morphology-dependent thermochromic behavior.

    PubMed

    Han, Kyuwon; Cho, Byoung-Ki

    2014-10-14

    Novel hexacatenar molecules based on a 1,2,3-triazole-extended aromatic rod self-assemble into crystalline monoclinic and liquid crystalline hexagonal columnar structures depending on temperature. The phase transition may involve a conformational change from an anisotropic transoid to a half-disk cisoid conformer upon melting. In a hexacatenar molecule with sixfold octyl chains, the crystal-to-LC transition accompanies a photoluminescence color change from sky blue to dark blue, which is attributed to the formation of higher-order aggregates in the crystalline state.

  1. Monoclinically distorted perovskites, A{sub 2}ZnTiO{sub 6} (A=Pr, Gd): Rietveld refinement, and dielectric studies

    SciTech Connect

    Das, Nibedita; Nath, Masood A.; Thakur, Gohil S.; Thirumal, M.; Ganguli, Ashok K.

    2015-09-15

    Double perovskite related oxide A{sub 2}ZnTiO{sub 6}A=Pr, Gd were synthesized by the solid state reaction method at 1523 K. The structure and microstructure of the compounds were studied by X-ray, SAED and FESEM. Rietveld refinement of the powder X-ray analysis shows that the compounds crystallizes in monoclinic space group P2{sub 1}/n (a{sup +}b{sup −}b{sup −}) with unit cell parameter √2a{sub p}×√2a{sub p}×2a{sub p} (a=5.5026(1) Å, b=5.6305(1) Å, c=7.8149(1) Å, β=90.02(1)° for Pr{sub 2}ZnTiO{sub 6} and a=5.3621(1) Å, b=5.6565(2) Å, c=7.6779(2) Å and β=90.264(2)° for Gd{sub 2}ZnTiO{sub 6}. Electron diffraction study confirms P2{sub 1}/n symmetry of the oxides. The monoclinic distortion is larger in Gd{sub 2}ZnTiO{sub 6} than Pr{sub 2}ZnTiO{sub 6} which is associated with the tolerance factor and the tilting angle of ZnO{sub 6} and TiO{sub 6} octahedra (ϕ=13.64° for Pr{sub 2}ZnTiO{sub 6} and 16.51° for Gd{sub 2}ZnTiO{sub 6}). The compounds are highly ordered. The charge and size difference between B site cations are the driving force for the ordering of the B′O{sub 6} and B″O{sub 6} octahedra. Pr{sub 2}ZnTiO{sub 6} shows a dielectric constant of 27 and dielectric loss of 0.003 while Gd{sub 2}ZnTiO{sub 6} has a dielectric constant of 17 and dielectric loss of 0.005 measured at 1 MHz. - Graphical abstract: Synthesis of new double perovskite dielectric material with very low dielectric loss. - Highlights: • Synthesis of new monoclinically distorted double perovskite (Pr{sub 2}ZnTiO{sub 6}). • Synthesis of monoclinically distorted double perovskite (Gd{sub 2}ZnTiO{sub 6}). • Selected area electron diffraction study of A{sub 2}ZnTiO{sub 6} (A=Pr, Gd). • Study of dielectric properties of A{sub 2}ZnTiO{sub 6} (A=Pr, Gd)

  2. Exchange-correlation effects in the monoclinic to tetragonal phase stabilization of yttrium-doped ZrO2: A first-principles approach

    NASA Astrophysics Data System (ADS)

    Sangalli, Davide; Debernardi, Alberto

    2011-12-01

    We describe, within an ab initio approach, the stabilization of the tetragonal phase versus the monoclinic one in yttrium-doped zirconia. The process is believed to be influenced from different mechanisms. Indeed, we show that there is a delicate balance between the change in electrostatic and kinetic energy and exchange-correlation effects. In the tetragonal phase, the perturbation induced by doping is better screened at the price of sacrificing correlation energy. Our work opens the opportunity to use the same approach to predict the tetragonal phase stabilization of materials such as zirconia or hafnia, with different and less characterized dopants.

  3. Grain size dependent phase stabilities and presence of a monoclinic (Pm) phase in the morphotropic phase boundary region of (1−x)Bi(Mg{sub 1/2}Ti{sub 1/2})O{sub 3}-xPbTiO{sub 3} piezoceramics

    SciTech Connect

    Upadhyay, Ashutosh; Singh, Akhilesh Kumar E-mail: aksingh.mst@itbhu.ac.in

    2015-04-14

    Results of the room temperature structural studies on (1−x)Bi(Mg{sub 1/2}Ti{sub 1/2})O{sub 3}-xPbTiO{sub 3} ceramics using Rietveld analysis of the powder x-ray diffraction data in the composition range 0.28 ≤ x ≤ 0.45 are presented. The morphotropic phase boundary region exhibits coexistence of monoclinic (space group Pm) and tetragonal (space group P4 mm) phases in the composition range 0.33 ≤ x ≤ 0.40. The structure is nearly single phase monoclinic (space group Pm) in the composition range 0.28 ≤ x ≤ 0.32. The structure for the compositions with x ≥ 0.45 is found to be predominantly tetragonal with space group P4 mm. Rietveld refinement of the structure rules out the coexistence of rhombohedral and tetragonal phases in the morphotropic phase boundary region reported by earlier authors. The Rietveld structure analysis for the sample x = .35 calcined at various temperatures reveals that phase fraction of the coexisting phases in the morphotropic phase boundary region varies with grain size. The structural parameters of the two coexisting phases also change slightly with changing grain size.

  4. Isotopically enriched polymorphs of dysprosium single molecule magnets.

    PubMed

    Kishi, Y; Pointillart, F; Lefeuvre, B; Riobé, F; Le Guennic, B; Golhen, S; Cador, O; Maury, O; Fujiwara, H; Ouahab, L

    2017-03-23

    A triclinic polymorph Dy(t) and a monoclinic polymorph Dy(m) of [Dy(tta)3(L)] with L = 4-[6-(1,3-benzothiazol-2-yl)pyridin-3-yl]-4',5'-bis(methylthio)tetrathiafulvene behave as Single-Molecule Magnets with hysteresis loops opened at zero field. Magnetic properties were enhanced through magnetic dilution and (164)Dy isotopic enrichment which definitively support the importance of isotopes for the control of quantum magnets.

  5. Anisotropic magnetic behaviors of monoclinic Li{sub 3}Fe{sub 2}(PO{sub 4}){sub 3}

    SciTech Connect

    He, Zhangzhen; Guo, Wenbin; Cheng, Wendan; Itoh, Mitsuru

    2014-07-01

    Large sized α-Li{sub 3}Fe{sub 2}(PO{sub 4}){sub 3} single crystals with high quality are successfully grown by a flux method. Magnetic behaviors of the grown crystals are investigated by means of magnetic susceptibility, magnetization, and heat capacity measurements along different directions. The results confirm that α-Li{sub 3}Fe{sub 2}(PO{sub 4}){sub 3} exhibits weak ferrimagnetic behaviors at low temperature, which are in good agreement with those reported previously. However magnetic anisotropy is confirmed for the first time, suggesting that the c-axis is the likely magnetic easy axis and the a-axis is the magnetic hard one. Two anomalies are clearly observed in magnetic susceptibility along the a-axis and heat capacity data at zero field, suggesting the appearance of two successive magnetic transitions at ∼26 and ∼22 K in the system. - Graphical abstract: Magnetic anisotropy is confirmed for the first time using a single crystal sample of α-Li{sub 3}Fe{sub 2}(PO{sub 4}){sub 3} obtained by the flux method. - Highlights: • Large-sized single crystals of α-Li{sub 3}Fe{sub 2}(PO{sub 4}){sub 3} are grown by the flux method. • Magnetic anisotropy is confirmed for the first time in the system. • Two successive magnetic transitions are observed along the a-axis.

  6. Difference in the luminescence properties of orthorhombic and monoclinic forms of Y{sub 2}GeO{sub 5}:Ln (Ln = Tb{sup 3+} and Dy{sup 3+})

    SciTech Connect

    Tyagi, Adish; Shah, Alpa; Sudarsan, V. Vatsa, R.K.; Jain, V.K.

    2015-04-15

    Highlights: • Improved emission colour purity with orthorhombic form of Y{sub 2}GeO{sub 5}. • Non-stationary quenching exists in orthorhombic and monoclinic forms of Y{sub 2}GeO{sub 5}:Tb. • Ion pair formation and cross relaxation quenching operating for Y{sub 2}GeO{sub 5}:Dy samples. - Abstract: The luminescence properties of Tb{sup 3+} and Dy{sup 3+} doped orthorhombic and monoclinic forms of Y{sub 2}GeO{sub 5} are significantly different. Orthorhombic Y{sub 2}GeO{sub 5} doped with Tb{sup 3+} and Dy{sup 3+} ions gives bright green and blue emission upon UV light excitation with CIE coordinates (0.25, 0.46) and (0.25, 0.24), respectively. The monoclinic Y{sub 2}GeO{sub 5} doped with these ions exhibits light green and yellowish white emissions, respectively. This has been attributed to the differences in crystallographic environments around Y{sup 3+} ions in orthorhombic and monoclinic forms of Y{sub 2}GeO{sub 5}. Quantum yield of emission for orthorhombic Y{sub 2}GeO{sub 5}:Tb (∼29%) is significantly higher than that of the monoclinic Y{sub 2}GeO{sub 5}:Tb (∼14%). Lifetime values corresponding to {sup 4}F{sub 9/2} level of Dy{sup 3+} ions in both monoclinic and orthorhombic forms of Y{sub 2}GeO{sub 5} follow an opposite trend with respect to {sup 5}D{sub 4} level of Tb{sup 3+} ions. This is attributed to difference in the concentration quenching mechanism operating for Tb{sup 3+} and Dy{sup 3+} ions.

  7. Crystal structure, electronic and physical properties of monoclinic RECuTe2 in contrast to RECuSe2 (RE = Pr, Sm, Gd, Dy and Er)

    NASA Astrophysics Data System (ADS)

    Esmaeili, Mehdi; Forbes, Scott; Tseng, Yu-Chih; Mozharivskyj, Yurij

    2014-10-01

    The ternary tellurides RECuTe2 (RE = Gd, Dy and Er) have been synthesized, their crystal structure and charge transport properties have been investigated. The tellurides adopt a monoclinicly distorted variant (C2/m, z = 2) of the trigonal structure (P 3 bar m1, Z = 1) observed for RECuSe2 with RE = Dy, Er. The charge transport properties of RECuSe2 with RE = Pr and Sm have been also explored. While RECuTe2 display a metallic type resistivity, RECuSe2 show semiconducting properties. The room-temperature resistivities are between 0.22 and 10.5 Ω cm, with larger values observed for the selenides. Electronic structure calculations support metallic and semiconducting conductivities for the tellurides and selenides, respectively. The Seebeck coefficient indicates that the dominant charge carries are holes for all phases.

  8. Stress-induced VO{sub 2} films with M2 monoclinic phase stable at room temperature grown by inductively coupled plasma-assisted reactive sputtering

    SciTech Connect

    Okimura, Kunio; Watanabe, Tomo; Sakai, Joe

    2012-04-01

    We report on growth of VO{sub 2} films with M2 monoclinic phase stable at room temperature under atmospheric pressure. The films were grown on quartz glass and Si substrates by using an inductively coupled plasma-assisted reactive sputtering method. XRD-sin{sup 2}{Psi} measurements revealed that the films with M2 phase are under compressive stress in contrast to tensile stress of films with M1 phase. Scanning electron microscopy observations revealed characteristic crystal grain aspects with formation of periodical twin structure of M2 phase. Structural phase transition from M2 to tetragonal phases, accompanied by a resistance change, was confirmed to occur as the temperature rises. Growth of VO{sub 2} films composed of M2 phase crystalline is of strong interest for clarifying nature of Mott transition of strongly correlated materials.

  9. Growth, spectroscopy and lasing of the Yb-doped monoclinic Gd2SiO5 in the prospect of hydrogen laser cooling with Lyman-α radiation

    NASA Astrophysics Data System (ADS)

    Cabaret, L.; Robert, J.; Lebbou, K.; Brenier, A.; Cabane, H.

    2016-12-01

    We have grown good optical quality 10% Yb-doped Gd2SiO5 monocrystal by the Czochralski technique. The Yb segregation coefficient was measured to be 0.747. In agreement with the monoclinic symmetry of the host, the Yb fluorescence extrema were found to deviate from the Nm and Ng principal axes and a fourth spectroscopic parameter representing the rotation of the fluorescence distribution was introduced for a full description. Diode pumped laser operation at Brewster incidence was demonstrated to be significantly more efficient if the lasing propagation corresponds to the maximum fluorescence inside the crystal. We obtained a laser emission tunable between 1079 and 1100 nm, showing that our crystal is the best choice for the application to the production of QCW Lyman-α radiation by resonant four-wave-mixing in mercury vapor.

  10. Second monoclinic form of (E)-3-(4-fluoro­phen­yl)-1-phenyl­prop-2-en-1-one

    PubMed Central

    Arias-Ruiz, Saira N.; Romero, Nancy; Lobato-García, Carlos E.; Gómez-Rivera, Abraham; Mendoza, Angel

    2013-01-01

    The unit-cell dimensions and space group of the second monoclinic polymorph of the title compound, C15H11FO, differ from those of the previously reported form [Jing (2009 ▶). Acta Cryst. E65, o2515]. The title compound shows an E conformation of the C=C bond with the 4-fluoro­phenyl group opposite to the benzoyl group. The torsion angle of between the planes of the 4-fluoro­phenyl and benzoyl groups is 10.53 (6)°. In the crystal, weak C—H⋯O and C—H⋯F inter­actions form a cross-linked packing motif, building sheets parallel to (-102). PMID:24454121

  11. The effect of nanocrystallite size in monoclinic HfO{sub 2} films on lattice expansion and near-edge optical absorption

    SciTech Connect

    Cisneros-Morales, M. C.; Aita, C. R.

    2010-05-10

    Nanocrystalline monoclinic HfO{sub 2} films were sputter deposited on fused silica substrates, air annealed at 573 to 1273 K to affect crystallite growth, and analyzed by x-ray diffraction and spectrophotometry. Lattice expansion occurs with diminishing crystallite size. O 2p->Hf 5d interband absorption dominates the optical edge at energy E>=6.24 eV, with an optical band gap, E{sub o}=5.48+-0.023, which is independent of crystallite size. However, the strength of a localized resonant band, with onset at 5.65 eV and maximum at 5.94 eV, is affected by crystallite size. Its polaronic origin in a perfect HfO{sub 2} lattice is discussed.

  12. Crystal structure of (E)-2-(4-chloro-benzyl-idene)-3,4-di-hydro-naphthalen-1(2H)-one: a second monoclinic polymorph.

    PubMed

    Haroon, Muhammad; Akhtar, Tashfeen; Tahir, Muhammad Nawaz

    2015-10-01

    The title compound, C17H13ClO, is the second monoclinic polymorph to crystallize in the space group P21/c. The first polymorph crystallized with two independent mol-ecules in the asymmetric unit [Bolognesi et al. (1975 ▸). Acta Cryst. A31, S119; Z' = 2; no atomic coordinates available], whereas the title compound has Z' = 1. In the title polymorph, the dihedral angle between the plane of the benzene ring of the tetra-lone moiety and that of the 4-chloro-benzyl ring is 52.21 (11)°. The cyclo-hex-2-en-1-one ring of the tetra-lone moiety has a screw-boat conformation. In the crystal, mol-ecules are liked by pairs of C-H⋯π inter-actions forming inversion dimers. There are no other significant inter-molecular inter-actions present.

  13. Comment on ``Monoclinic phase of PbZr0.52Ti0.48O3 ceramics: Raman and phenomenological thermodynamic studies''

    NASA Astrophysics Data System (ADS)

    Frantti, J.; Lappalainen, J.; Lantto, V.; Nishio, S.; Kakihana, M.

    2001-05-01

    Recently, Souza Filho et al. [A. G. Souza Filho, K. C. V. Lima, A. P. Ayala, I. Guedes, P. T. C. Freire, J. Mendes Filho, E. B. Araujo, and J. A. Eiras, Phys. Rev. B 61, 14 283 (2000)] reported a phase transition between monoclinic and tetragonal phases as a function of temperature in a PbZr0.52Ti0.48O3 ceramic sample, observed by Raman spectroscopy. We show that their observation has no relation to the phase transition and the anomaly they interpreted as an indication of a phase transition was due to the erroneous curve fit procedure, which predicts a clearly observable phase transition for all tetragonal lead-zirconate-titanate ceramics, including lead titanate. A more appropriate way to study this phase transition phenomena by Raman spectroscopy is discussed.

  14. Crystal structure of the monoclinic phase (phase IV) of bis­(tetra­methyl­ammonium) tetra­chlorido­cuprate(II)

    PubMed Central

    Seck, Gorgui Awa; Diop, Libasse; Oliver, Allen G.

    2017-01-01

    The crystal structure of the low-temperature monoclinic phase of the title compound, [(CH3)4N]2[CuCl4], was determined at 120 K. The structure of the room-temperature phase has been determined in the ortho­rhom­bic space group Pmcm [Morosin & Lingafelter (1961 ▸). J. Phys. Chem. 50–51; Clay et al. (1975 ▸). Acta Cryst. B31 289–290]. The asymmetric unit consists of one discrete tetra­chlorido­cuprate anion with a distorted tetra­hedral geometry and two tetra­methyl­ammonium cations. In the crystal, the cations and the anions are linked via weak C—H⋯Cl hydrogen bonds. PMID:28316808

  15. Monoclinic crystal structure of polycrystalline Na{sub 0.5}Bi{sub 0.5}TiO{sub 3}.

    SciTech Connect

    Aksel, E.; Forrester, J. S.; Jones, J. L.; Thomas, P. A.; Page, K.; Suchomel, M. R.

    2011-01-01

    Bismuth-based ferroelectric ceramics are currently under intense investigation for their potential as Pb-free alternatives to lead zirconate titanate-based piezoelectrics. Na{sub 0.5}Bi{sub 0.5}TiO{sub 3} (NBT), one of the widely studied compositions, has been assumed thus far to exhibit the rhombohedral space group R3c at room temperature. High-resolution powder x-ray diffraction patterns, however, reveal peak splitting in the room temperature phase that evidence the true structure as monoclinic with space group Cc. This peak splitting and Cc space group is only revealed in sintered powders; calcined powders are equally fit to an R3c model because microstructural contributions to peak broadening obscure the peak splitting.

  16. Monoclinic crystal structure of polycrystalline Na{sub 0.5}Bi{sub 0.5}TiO{sub 3}

    SciTech Connect

    Aksel, Elena; Forrester, Jennifer S.; Jones, Jacob L.; Thomas, Pam A.; Page, Katharine; Suchomel, Matthew R.

    2011-04-11

    Bismuth-based ferroelectric ceramics are currently under intense investigation for their potential as Pb-free alternatives to lead zirconate titanate-based piezoelectrics. Na{sub 0.5}Bi{sub 0.5}TiO{sub 3} (NBT), one of the widely studied compositions, has been assumed thus far to exhibit the rhombohedral space group R3c at room temperature. High-resolution powder x-ray diffraction patterns, however, reveal peak splitting in the room temperature phase that evidence the true structure as monoclinic with space group Cc. This peak splitting and Cc space group is only revealed in sintered powders; calcined powders are equally fit to an R3c model because microstructural contributions to peak broadening obscure the peak splitting.

  17. Structural, electronic and optical properties of monoclinic Na2Ti3O7 from density functional theory calculations: A comparison with XRD and optical absorption measurements

    NASA Astrophysics Data System (ADS)

    Araújo-Filho, Adailton A.; Silva, Fábio L. R.; Righi, Ariete; da Silva, Mauricélio B.; Silva, Bruno P.; Caetano, Ewerton W. S.; Freire, Valder N.

    2017-06-01

    Powder samples of bulk monoclinic sodium trititanate Na2Ti3O7 were prepared carefully by solid state reaction, and its monoclinic P21/m crystal structure and morphology were characterized by X-ray powder diffraction (XRD) and scanning electron microscopy (SEM), respectively. Moreover, the sodium trititanate main energy band gap was estimated as Eg=3.51±0.01 eV employing UV-Vis spectroscopy, which is smaller than the measured 3.70 eV energy gap published previously by other authors. Aiming to achieve a better understanding of the experimental data, density functional theory (DFT) computations were performed within the local density and generalized gradient approximations (LDA and GGA, respectively) taking into account dispersion effects through the scheme of Tkatchenko and Scheffler (GGA+TS). Optimal lattice parameters, with deviations relative to measurements Δa=-0.06 Å, Δb=0.02 Å, and Δc=-0.09 Å, were obtained at the GGA level, which was then used to simulate the sodium trititanate electronic and optical properties. Indirect band transitions have led to a theoretical gap energy value of about 3.25 eV. Our results, however, differ from pioneer DFT results with respect to the specific Brillouin zone vectors for which the indirect transition with smallest energy value occurs. Effective masses for electrons and holes were also estimated along a set of directions in reciprocal space. Lastly, our calculations revealed a relatively large degree of optical isotropy for the Na2Ti3O7 optical absorption and complex dielectric function.

  18. Off-resonance effects in (14)N NQR signals from the pulsed spin-locking (PSL) and three-pulse echo sequence; a study for monoclinic TNT.

    PubMed

    Smith, John A S; Rowe, Michael D; Althoefer, Kaspar; Peirson, Neil F; Barras, Jamie

    2015-10-01

    In NQR detection applications signal averaging by the summation of rapidly regenerated signals from multiple pulse sequences of the pulsed spin-locking (PSL) type is often used to improve sensitivity. It is important to characterise and if possible minimise PSL sequence off-resonance effects since they can make it difficult to optimise detection performance. We illustrate this with measurements of the variation of the decay time T2e and the amplitude of PSL signal trains with pulse spacing and excitation offset frequency for the 870 kHz ν+(14)N NQR line of monoclinic TNT under carefully stabilised temperature conditions. We have also carried out a similar study of signals from monoclinic TNT and 1H-1,2,3-triazole generated by a three-pulse echo sequence and the results are shown to agree well with a theoretical treatment appropriate to polycrystalline NQR samples such as TNT for which spin I=1, asymmetry parameter η≠0 and T1≫T2. Based on this theory we derive simple models for calculating TNT PSL signal trains and hence the pulse spacing and off-resonance dependence of signal amplitude and T2e which we compare to our experimental data. We discuss the influence of PSL echo summation on off-resonance effects in detected signal intensity and show how a phase-alternated multiple pulse sequence can be used in combination with the PSL sequence to eliminate variation in detection performance due to off-resonance effects. Copyright © 2015 Elsevier Inc. All rights reserved.

  19. Monoclinic polymorph of 4-[(1H-benz-imidazol-1-yl)meth-yl]benzoic acid.

    PubMed

    Kuai, Hai-Wei; Cheng, Xiao-Chun

    2011-10-01

    Three polymorphs of the title compound, C(15)H(12)N(2)O(2), were obtained accidentally as single crystals in the hydro-thermal reaction of the title compound with manganese bromide in the presence of N,N'-dimethyl-formamide at 373 K. Here we report the structure of the first polymorph. The benzimidazole ring is almost planar, the maximum deviation from the mean plane being 0.016 (1) Å. The benzimidazole and benzene rings are approximately perpendicular, making a dihedral angle 85.56 (7)°, which is a reflection of the axial rotation of the flexible benzimidazolyl arm. In the crystal, adjacent mol-ecules are connected through O-H⋯N hydrogen bonds into a chain along [100], and neighboring chains are further linked by via weak C-H⋯O hydrogen-bonding inter-actions, forming a two-dimensional network.

  20. Impact of the oxygen defects and the hydrogen concentration on the surface of tetragonal and monoclinic ZrO2 on the reduction rates of stearic acid on Ni/ZrO2

    SciTech Connect

    Foraita, Sebastian D.; Fulton, John L.; Chase, Zizwe A.; Vjunov, Aleksei; Xu, Pinghong; Barath, Eszter; Camaioni, Donald M.; Zhao, Chen; Lercher, Johannes A.

    2015-02-02

    The effect of the physicochemical properties of ZrO2 phases on the activity of Ni/ZrO2 catalysts for hydrodeoxygenation of stearic acid are described. A synergistic interaction between Ni and ZrO2 support was found. The effect is greatest for the monoclinic phase of ZrO2.

  1. A Process for Modelling Diffuse Scattering from Disordered Molecular Crystals, Illustrated by Application to Monoclinic 9-Chloro-10-methylanthracene

    DOE PAGES

    Goossens, D. J.

    2015-01-01

    Diffuse scattering from a crystal contains valuable information about the two-body correlations (related to the nanoscale order) in the material. Despite years of development, the detailed analysis of single crystal diffuse scattering (SCDS) has yet to become part of the everyday toolbox of the structural scientist. Recent decades have seen the pair distribution function approach to diffuse scattering (in fact, total scattering) from powders become a relatively routine tool. However, analysing the detailed, complex, and often highly anisotropic three-dimensional distribution of SCDS remains valuable yet rare because there is no routine method for undertaking the analysis. At present, analysis requiresmore » significant investment of time to develop specialist expertise, which means that the analysis of diffuse scattering, which has much to offer, is not incorporated thorough studies of many compounds even though it has the potential to be a very useful adjunct to existing techniques. This article endeavours to outline in some detail how the diffuse scattering from a molecular crystal can be modelled relatively quickly and largely using existing software tools. It is hoped this will provide a template for other studies. To enable this, the entire simulation is included as deposited material.« less

  2. A Process for Modelling Diffuse Scattering from Disordered Molecular Crystals, Illustrated by Application to Monoclinic 9-Chloro-10-methylanthracene

    SciTech Connect

    Goossens, D. J.

    2015-01-01

    Diffuse scattering from a crystal contains valuable information about the two-body correlations (related to the nanoscale order) in the material. Despite years of development, the detailed analysis of single crystal diffuse scattering (SCDS) has yet to become part of the everyday toolbox of the structural scientist. Recent decades have seen the pair distribution function approach to diffuse scattering (in fact, total scattering) from powders become a relatively routine tool. However, analysing the detailed, complex, and often highly anisotropic three-dimensional distribution of SCDS remains valuable yet rare because there is no routine method for undertaking the analysis. At present, analysis requires significant investment of time to develop specialist expertise, which means that the analysis of diffuse scattering, which has much to offer, is not incorporated thorough studies of many compounds even though it has the potential to be a very useful adjunct to existing techniques. This article endeavours to outline in some detail how the diffuse scattering from a molecular crystal can be modelled relatively quickly and largely using existing software tools. It is hoped this will provide a template for other studies. To enable this, the entire simulation is included as deposited material.

  3. Temperature and Field Induced Strain Measurements in Single Crystal Gd5Si2Ge2

    NASA Astrophysics Data System (ADS)

    McCall, S. K.; Nersessian, N.; Carman, G. P.; Pecharsky, V. K.; Schlagel, D. L.; Radousky, H. B.

    2016-06-01

    The first-order magneto-structural transformation that occurs in Gd5Si2Ge2 near room temperature makes it a strong candidate for many energy harvesting applications. Understanding the single crystal properties is crucial for allowing simulations of device performance. In this study, magnetically and thermally induced transformation strains were measured in a single crystal of Gd5Si2.05Ge1.95 as it transforms from a high-temperature monoclinic paramagnet to a lower-temperature orthorhombic ferromagnet. Thermally induced transformation strains of -8500 ppm, +960 ppm and +1800 ppm, and magnetically induced transformation strains of -8500 ppm, +900 ppm and +2300 ppm were measured along the a, b and c axes, respectively. Using experimental data coupled with general thermodynamic considerations, a universal phase diagram was constructed showing the transition from the monoclinic to the orthorhombic phase as a function of temperature and magnetic field.

  4. First-principles prediction of the thermodynamic stability of xenon in monoclinic, tetragonal, and yttrium-stabilized cubic ZrO{sub 2}

    SciTech Connect

    Jiang Chao; Liu Xiangyang; Sickafus, Kurt E.

    2011-02-01

    Fission product incorporation in ceramic fuels has long been an active area of research. In this work, we consider a special case of xenon incorporation in ZrO{sub 2} in the framework of closed systems under extreme radiation conditions where thermal defects are less important than cascade driven defects. The energetics of a variety of defect configurations associated with xenon incorporation are considered. We use first-principles density-functional theory (DFT) calculations to predict the thermodynamic stability of xenon in different ZrO{sub 2} structural forms, including monoclinic, tetragonal, and yttrium-stabilized cubic ZrO{sub 2}. Two defect configurations are found to dominate the fission gas incorporation process: xenon interstitial and oxygen substitutional configurations. In yttrium-stabilized cubic ZrO{sub 2}, the pre-existing structural oxygen vacancies provide ideal sites for Xe incorporation since no oxygen Frenkel pairs need to be formed. The charge-transfer issue in oxides modeling is important in defects calculations. This issue has also been addressed through our supercell benchmark calculations.

  5. Bioweathering of Kupferschiefer black shale (Fore-Sudetic Monocline, SW Poland) by indigenous bacteria: implication for dissolution and precipitation of minerals in deep underground mine.

    PubMed

    Matlakowska, Renata; Skłodowska, Aleksandra; Nejbert, Krzysztof

    2012-07-01

    The Upper Permian polymetallic, organic-rich Kupferschiefer black shale in the Fore-Sudetic Monocline is acknowledged to be one of the largest Cu-Ag deposits in the world. Here we report the results of the first study of bioweathering of this sedimentary rock by indigenous heterotrophic bacteria. Experiments were performed under laboratory conditions, employing both petrological and microbiological methods, which permitted the monitoring and visualization of geomicrobiological processes. The results demonstrate that bacteria play a prominent role in the weathering of black shale and in the biogeochemical cycles of elements occurring in this rock. It was shown that bacteria directly interact with black shale organic matter to produce a widespread biofilm on the Kupferschiefer shale surface. As a result of bacterial activity, the formation of pits, bioweathering of ore and rock-forming minerals, the mobilization of elements and secondary mineral precipitation were observed. The chemistry of the secondary minerals unequivocally demonstrates the mobilization of elements from minerals comprising Kupferschiefer. The redistribution of P, Al, Si, Ca, Mg, K, Fe, S, Cu and Pb was confirmed. The presence of bacterial outer membrane vesicles on the surface of black shale was observed for the first time. Biomineralization reactions occurred in both the membrane vesicles and the bacterial cells.

  6. Dynamic heterogeneity in the glass-like monoclinic phases of CBr(n)Cl(4-n), n = 0,1,2.

    PubMed

    Zuriaga, M J; Perez, S C; Pardo, L C; Tamarit, J Ll

    2012-08-07

    Glassy dynamics of rigid molecules is still a matter of controversy: the physics behind the relaxation process at time scales faster than that ruled by the viscosity, the so called Johari-Goldstein process, is not known. In this work we unravel the mechanism of such a process by using a simple molecular model in which the centers of mass of the molecules are forming an ordered lattice, and molecular reorientation is performed by jumps between equilibrium orientations. We have studied the dynamics of simple quasi-tetrahedral molecules CBr(n)Cl(4-n), n = 0, 1, 2, in their monoclinic phases by means of dielectric spectroscopy and nuclear quadrupole resonance: the first technique allows to measure in a broad time scale but it is insensitive to molecular particularities, while the second has a restricted time window but senses the movement of each chlorine atom separately. The dynamic picture emerging from these techniques is that the secondary relaxation process is related to the different molecular surroundings around each nonequivalent atom of the molecule. Dynamical heterogeneities thus seem to be the cause of the secondary relaxation in this simple model of glass.

  7. CTAB-assisted synthesis of monoclinic BiVO4 photocatalyst and its highly efficient degradation of organic dye under visible-light irradiation.

    PubMed

    Yin, Wenzong; Wang, Wenzhong; Zhou, Lin; Sun, Songmei; Zhang, Ling

    2010-01-15

    A highly efficient monoclinic BiVO(4) photocatalyst (C-BVO) was synthesized by an aqueous method with the assistance of cetyltrimethylammonium bromide (CTAB). The structure, morphology and photophysical properties of the C-BVO were characterized by XRD, FE-SEM and diffuse reflectance spectroscopy, respectively. The photocatalytic efficiencies were evaluated by the degradation of rhodamine B (RhB) under visible-light irradiation, revealing that the degradation rate over the C-BVO was much higher than that over the reference BiVO(4) prepared by aqueous method and over the one prepared by solid-state reaction. The efficiency of de-ethylation and that of the cleavage of conjugated chromophore structure were investigated, respectively. The chemical oxygen demand (COD) values of the RhB were measured after the photocatalytic degradation over the C-BVO and demonstrated a 53% decrease in COD. The effects of CTAB on the synthesis of C-BVO were investigated, which revealed that CTAB not only changed the reaction process via the formation of BiOBr as an intermediate, but also facilitated the transition from BiOBr to BiVO(4). Comparison experiments were carried out and showed that the existence of impurity level makes significant contribution to the high photocatalytic efficiency of the C-BVO.

  8. Density functional theory insights into the structural stability and Li diffusion properties of monoclinic and orthorhombic Li2FeSiO4 cathodes

    NASA Astrophysics Data System (ADS)

    Lu, Xia; Chiu, Hsien-Chieh; Bevan, Kirk H.; Jiang, De-Tong; Zaghib, Karim; Demopoulos, George P.

    2016-06-01

    Lithium iron orthosilicate (Li2FeSiO4) is an important alternative cathode for next generation Li-ion batteries due to its high theoretical capacity (330 mA h/g). However, its development has faced great challenges arising from significant structural complexity, including the disordered arrangement/orientation of Fe/Si tetrahedra, polytypes and its poorly understood Li storage and transport properties. In this context, ab-initio calculations are employed to investigate the phase stability and Li diffusion profiles of both monoclinic (P21) and orthorhombic (Pmn21) Li2FeSiO4 orthosilicates. The calculations demonstrate that formation of Lisbnd Fe antisites can induce a metastability competition between both phases, with neither dominating across nearly the entire discharging profile from Li2FeSiO4 through to LiFeSiO4. Furthermore, structural instability is shown to be a serious concern at discharge concentrations below LiFeSiO4 (1 Li extraction) due to the shared occupation of Li donated electrons with oxygen 2p orbitals - rather than the hypothesized transition to a tetravalent Fe4+ state. This finding is further supported by diffusion calculations that have determined a high activation energy barrier towards fast charging and rapid phase transitions. In summary, these theoretical results provide critical and timely insight into the structural dynamics of lithium iron orthosilicate, in pursuit of high energy density cathodes.

  9. Surfactant-free synthesis of hyperbranched monoclinic bismuth vanadate and its applications in photocatalysis, gas sensing, and lithium-ion batteries.

    PubMed

    Zhao, Yu; Xie, Yi; Zhu, Xi; Yan, Si; Wang, Sunxi

    2008-01-01

    Hyperbranched monoclinic BiVO(4) (h-BiVO(4)) has been synthesized on a large scale and with good uniformity by a surfactant-free hydrothermal route. h-BiVO(4) consists of four trunks with branches distributed on opposite sides. From observation of the intermediates at an early stage of the reaction process, it can be seen that during formation h-BiVO(4) has different growth rates along the a, b, and c axes. Based on crystal structure analysis and experimental results, h-BiVO(4) shows preferential growth along the [100] direction, and subsequently, along the [010] and [001] directions. As-synthesized h-BiVO(4) exhibits excellent photocatalytic ability in the photodegradation reaction of an aqueous solution of RB under visible light. Electrochemical measurements predict that h-BiVO(4) possesses high sensitivity to formaldehyde and ethanol gases, favorable discharge capacity, and capacity retention, which indicate potential applications in the fields of sensing devices and lithium-ion batteries.

  10. First-principles investigation of the structural stability and electronic properties of Pd doped monoclinic Cu6Sn5 intermetallic compounds

    NASA Astrophysics Data System (ADS)

    Shao, Wei-Quan; Lu, Wen-Cai; Chen, Sha-Ou

    2014-12-01

    Tri-layer Au/Pd/Ni(P) films have been widely used as surface finish over the Cu pads in high-end packaging applications. It was found that a thin (Cu,Pd)6Sn5 IMC layer was beneficial in effective reducing inter-diffusion between a Cu substrate and a solder, and therefore the growth of the IMC layer and the EM (electromigration) processes. In this study, the structural properties and phase stability of monoclinic Cu6Sn5-based structures with Pd substitutions were studied by using the first-principles method. The (Cu,Pd)6Sn5 structure with the 4e site substituted by Pd has the lowest heat of formation and is the most stable among (Cu,Pd)6Sn5 structures. Hybridization of Pd-d and Sn-p states is a dominant factor for stability improvement. Moreover, Pd atoms concentration corresponding to the most stable structure of (Cu,Pd)6Sn5 was found to be 1.69 %, which is consistent with the experimental results.

  11. Monoclinic and triclinic concomitant polymorphs of di-mu-pyridazine-1kappa(2)N:2kappa(2)N'-bis[(saccharinato)silver(I)].

    PubMed

    Hamamci, Sevim; Yilmaz, Veysel T; Büyükgüngör, Orhan

    2006-01-01

    Crystallization of the title compound, di-mu-pyridazine-1kappa(2)N:2kappa(2)N'-bis[(2,3-dihydro-3-oxobenzisosulfonazolato-kappaN)silver(I)], [Ag2(C7H4NO3S)2(C4H4N2)2], from acetonitrile yields both monoclinic, (I), and triclinic, (II), polymorphs. In both forms, the silver(I) ions have a slightly distorted trigonal AgN(3) coordination geometry and are doubly bridged by two neutral pyridazine (pydz) ligands, generating a centrosymmetric dimeric structure. The saccharinate (sac) ligands are N-coordinated. The dihedral angles between the sac and pydz rings are 8.43 (7) and 7.94 (8) degrees in (I) and (II), respectively, suggesting that the dimeric molecule is nearly flat. The bond geometry is similar in both polymorphs. In (I), the dimers interact with each other via aromatic pi(sac)-pi(pydz) stacking interactions, forming two-dimensional layers, which are further crosslinked by weak C-H...O interactions. Compound (II) exhibits similar C-H...O and pi-pi interactions, but additional C-H...pi and pi...Ag interactions help to stabilize the packing of the dimers.

  12. Magnetic properties of monoclinic lanthanide metaborates, Ln(BO2)3, Ln  =  Pr, Nd, Gd, Tb

    NASA Astrophysics Data System (ADS)

    Mukherjee, P.; Suard, E.; Dutton, S. E.

    2017-10-01

    The bulk magnetic properties of the lanthanide metaborates, Ln(BO2)3, Ln  =  Pr, Nd, Gd, Tb are studied using magnetic susceptibility, heat capacity and isothermal magnetisation measurements. They are found to crystallise in a monoclinic structure containing chains of magnetic Ln 3+ and could therefore exhibit features of low-dimensional magnetism and frustration. Pr(BO2)3 is found to have a non-magnetic singlet ground state. No magnetic ordering is observed down to 0.4 K for Nd(BO2)3. Gd(BO2)3 exhibits a sharp magnetic transition at 1.1 K, corresponding to 3D magnetic ordering. Tb(BO2)3 shows two magnetic ordering features at 1.05 K and 1.95 K. A magnetisation plateau at a third of the saturation magnetisation is seen at 2 K for both Nd(BO2)3 and Tb(BO2)3, which persists in an applied field of 14 T. This is proposed to be a signature of quasi 1D behaviour in Nd(BO2)3 and Tb(BO2)3.

  13. Temperature-induced reversible first-order single crystal to single crystal phase transition in Boc-γ(4)(R)Val-Val-OH: interplay of enthalpy and entropy.

    PubMed

    Pal, Rumpa; Reddy, M B Madhusudana; Dinesh, Bhimareddy; Balaram, Padmanabhan; Guru Row, Tayur N

    2014-10-09

    Crystals of Boc-γ(4)(R)Val-Val-OH undergo a reversible first-order single crystal to single crystal phase transition at Tc ≈ 205 K from the orthorhombic space group P22121 (Z' = 1) to the monoclinic space group P21 (Z' = 2) with a hysteresis of ∼2.1 K. The low-temperature monoclinic form is best described as a nonmerohedral twin with ∼50% contributions from its two components. The thermal behavior of the dipeptide crystals was characterized by differential scanning calorimetry experiments. Visual changes in birefringence of the sample during heating and cooling cycles on a hot-stage microscope with polarized light supported the phase transition. Variable-temperature unit cell check measurements from 300 to 100 K showed discontinuity in the volume and cell parameters near the transition temperature, supporting the first-order behavior. A detailed comparison of the room-temperature orthorhombic form with the low-temperature (100 K) monoclinic form revealed that the strong hydrogen-bonding motif is retained in both crystal systems, whereas the non-covalent interactions involving side chains of the dipeptide differ significantly, leading to a small change in molecular conformation in the monoclinic form as well as a small reorientation of the molecules along the ac plane. A rigid-body thermal motion analysis (translation, libration, screw; correlation of translation and libration) was performed to study the crystal entropy. The reversible nature of the phase transition is probably the result of an interplay between enthalpy and entropy: the low-temperature monoclinic form is enthalpically favored, whereas the room-temperature orthorhombic form is entropically favored.

  14. Vapor-liquid-solid (VLS) synthesis of alpha-monoclinic selenium and antimony selenide nanowires and sonication synthesis of blue photoluminescent zero-dimensional nanoparticles

    NASA Astrophysics Data System (ADS)

    Farfan Mendoza, Willinton

    Semiconducting nanostructures such as nanowires and 0-D nanoparticles have received great interest due to their improved properties in comparison with macroscopic materials. Therefore, these nanostructures have attracted considerable attention for optoelectronics and biological applications, among others. In this way, this thesis reports the synthesis of alpha-monoclinic selenium and antimony selenide (Sb2Se3) semiconducting nanowires using a physical vapor-liquid-solid (VLS) process for the first time. In addition, synthesis of naturally dispersed Sb2Se 3 0-D nanoparticles using a sonication process is also reported here for the first time. Crystalline alpha-monoclinic selenium nanowires with diameters in the range between 20 nm and 1im and lengths up to 30 mum were synthesized. The majority of these VLS synthesized nanowires have a diameter of ~50 nm. As-obtained nanowires grew perpendicular to the (053) plane and exhibit an energy band-gap of 2.20 +/- 0.05 eV, showing a blue shift of 0.18 eV relative to the bulk than is attributed to quantum confinement from the most abundant produced nanowires (~50 nm). Crystalline Sb2Se3 nanowires with diameters in the range between 20 nm and 2mum and lengths up to 30 mum were synthesized. The diameter of the most abundant produced nanowires is ~800 nm. Our nanowires are oriented along the [010] crystallographic direction. Growth along this orientation is being reported for the first time. Due to the anisotropy of the lattice, [010] oriented nanowires have properties different to the ones produced by the other methods that are [001] oriented. This thesis also analyses the controversial band gap energy results reported in the literature and conclude that is due to incorrect interpretation of experimental measurements. Photoluminescence (PL) measurements of powdered crystalline bulk Sb2Se3 at room temperature and under UV excitation are reported here for the first time. The PL spectra show that Sb2Se3 crystalline exhibits high

  15. Comparison and validation of Logistic Regression and Analytic Hierarchy Process models of landslide susceptibility in monoclinic regions. A case study in Moldavian Plateau, N-E Romania

    NASA Astrophysics Data System (ADS)

    Ciprian Margarint, Mihai; Niculita, Mihai

    2014-05-01

    The regions with monoclinic geological structure are large portions of earth surface where the repetition of similar landform patterns is very distinguished, the scarps of cuestas being characterized by similar values of morphometrical variables. Landslides are associated with these scarps of cuestas and consequently, a very high value of landslide susceptibility can be reported on its surface. In these regions, landslide susceptibility mapping can be realized for the entire region, or for test areas, with accurate, reliable, and available datasets, concerning multi-temporal inventories and landslide predictors. Because of the similar geomorphologic and landslide distribution we think that if any relevance of using test areas for extrapolating susceptibility models is present, these areas should be targeted first. This study case try to establish the level of usability of landslide predictors influence, obtained for a 90 km2 sample located in the northern part of the Moldavian Plateau (N-E Romania), in other areas of the same physio-geographic region. In a first phase, landslide susceptibility assessment was carried out and validated using logistic regression (LR) approach, using a multiple landslide inventory. This inventory was created using ortorectified aerial images from 1978 and 2005, for each period being considered both old and active landslides. The modeling strategy was based on a distinctly inventory of depletion areas of all landslide, for 1978 phase, and on a number of 30 covariates extracted from topographical and aerial images (both from 1978 and 2005 periods). The geomorphometric variables were computed from a Digital Elevation Model (DEM) obtained by interpolation from 1:5000 contour data (2.5 m equidistance), at 10x10 m resolution. Distance from river network, distance from roads and land use were extracted from topographic maps and aerial images. By applying Akaike Information Criterion (AIC) the covariates with significance under 0.001 level

  16. Monoclinic polymorph of 2,5-dide­oxy-2,5-epithio-1,3:4,6-bis-O-[(R)-phenyl­methyl­ene]-l-iditol1

    PubMed Central

    Gibson, Jerrell G.; Cho, Jung Young; Fronczek, Frank R.; Watkins, Steven F.

    2012-01-01

    The title compound C20H20O4S, is polymorphic. In the tetra­gonal form, the mol­ecule lies on a crystallographic twofold axis, while the monoclinic form has only approximate C 2 mol­ecular symmetry. The greatest excursion from C 2 symmetry is in the orientation of the two phenyl rings; at 100 K, one of the rings is rotated −37.2 (3)° and the other by 46.9 (3)° from their symmetric (tetra­gonal) positions. There are only minor differences in the three-ring nucleus; the best mol­ecular fit of the tetra­gonal and monoclinic forms, both at 100 K and excluding phenyl rings and H atoms, shows an r.m.s. deviation of 0.066 Å. Both forms have the same absolute configuration. PMID:22969563

  17. Electrochemical characterization of monoclinic and orthorhombic Li3CrF6 as positive electrodes in lithium-ion batteries synthesized by a sol-gel process with environmentally benign chemicals

    NASA Astrophysics Data System (ADS)

    Lieser, Georg; Winkler, Volker; Geßwein, Holger; de Biasi, Lea; Glatthaar, Sven; Hoffmann, M. J.; Ehrenberg, Helmut; Binder, Joachim R.

    2015-10-01

    Lithium transition metal fluorides (Li3MF6; M = Fe, V) with cryolite structure are investigated as positive electrode materials for lithium-ion batteries. A novel sol-gel process with trifluoroacetic acid as fluorine source was used to synthesize monoclinic and orthorhombic Li3CrF6. A ball milling process with Li3CrF6, binder, and conductive agent was applied to form a Li3CrF6 composite, which was electrochemically characterized against lithium metal for the first time. The electrochemical properties of two different modifications are quite similar, with a reversible specific capacity of 111 mAhg-1 for monoclinic Li3CrF6 and 106 mAhg-1 for orthorhombic Li3CrF6 (1 eq. Li ≙ 143 mAhg-1). The electrochemically active redox couple CrIII/CrII was confirmed by X-ray photoelectron spectroscopy.

  18. Ag3PO4 nanocrystals deposited on monoclinic olive-like BiVO4 with efficient photodegradation of organic dyes under visible light irradiation

    NASA Astrophysics Data System (ADS)

    Chen, Jingshuai; Jiang, Liang-Liang; Liu, Xing-Pei; Mao, Chang-Jie; Song, Ji-Ming; Niu, Helin; Zhang, Shengyi

    2017-05-01

    Olive-like BiVO4 microstructures with lengths of 600-1000 nm and widths of 300-600 nm have been synthesized via a facile and additive-free solvothermal method. Studies find that the type of solvent plays an important role in the morphology of the final products. Furthermore, Ag3PO4 nanocrystals are successfully deposited on monoclinic olive-like BiVO4 via in situ precipitation method. The as-synthesized samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), photoluminescence (PL) spectra, and UV-vis diffuse reflectance spectra (DRS). The photocatalytic activities of the catalysts are evaluated by degradation of rhodamine B (RhB) and methylene blue (MB) under visible light (≥420 nm) irradiation. The experimental results suggest that catalytic activity of the composite photocatalysts is greatly influenced by the loading level of Ag3PO4. The molar ratio of 0.8:1.0 Ag3PO4-loaded BiVO4 exhibits higher photocatalytic activity in both the decolorization of RhB and MB than that of individual BiVO4 and P25. The observed improvement in photocatalytic activity is associated with the extended absorption in the visible light region resulting from the Ag3PO4 nanoparticles, and the effective separation of photogenerated carriers at the Ag3PO4/BiVO4 interfaces through the formation of heterojunction structure. The study provides a general and effective method in the fabrication of composite with sound heterojunctions that may show a variety of applications.

  19. Crystal structures of N-(pyridin-2-ylmeth-yl)pyrazine-2-carboxamide (monoclinic polymorph) and N-(pyridin-4-ylmeth-yl)pyrazine-2-carboxamide.

    PubMed

    Cati, Dilovan S; Stoeckli-Evans, Helen

    2014-07-01

    The title compounds, C11H10N4O (HL1) and C11H10N4O (HL2), are pyridine 2-ylmethyl and 4-ylmethyl derivatives, respectively, of pyrazine-2-carboxamide. HL1 was measured at 153 K and crystallized in the monoclinic space group P21/c with Z = 4. There has been a report of the same structure measured at room temperature but assumed to crystallize in the triclinic space group P-1 with Z = 4 [Sasan et al. (2008 ▶). Monatsh. Chem. 139, 773-780]. In HL1, the pyridine ring is inclined to the pyrazine ring by 61.34 (6)°, while in HL2 this dihedral angle is 84.33 (12)°. In both mol-ecules, there is a short N-H⋯N inter-action involving the pyrazine carboxamide unit. In the crystal of HL1, mol-ecules are linked by N-H⋯N hydrogen bonds, forming inversion dimers with an R 2 (2)(10) ring motif. The dimers are linked via bifurcated-acceptor C-H⋯O hydrogen bonds, forming sheets lying parallel to (102). The sheets are linked via C-H⋯N hydrogen bonds, forming a three-dimensional structure. In the crystal of HL2, mol-ecules are linked by N-H⋯N and C-H⋯N hydrogen bonds to form chains propagating along [010]. The chains are linked via C-H⋯O hydrogen bonds, forming sheets lying parallel to (100). Within the sheets there are π-π inter-actions involving neighbouring pyrazine rings [inter-centroid distance = 3.711 (15) Å]. Adjacent sheets are linked via parallel slipped π-π inter-actions involving inversion-related pyridine rings [inter-centroid distance = 3.6395 (17) Å], forming a three-dimensional structure.

  20. EPR studies of gamma-irradiated taurine single crystals

    NASA Astrophysics Data System (ADS)

    Bulut, A.; Karabulut, B.; Tapramaz, R.; Köksal, F.

    2000-04-01

    An EPR study of gamma-irradiated taurine [C 2H 7NO 3S] single crystal was carried out at room temperature. The EPR spectra were recorded in the three at mutually perpendicular planes. There are two magnetically distinct sites in monoclinic lattice. The principle values of g and hyperfine constants for both sites were calculated. The results have indicated the presence of 32ṠO -2 and 33ṠO -2 radicals. The hyperfine values of 33ṠO -2 radical were used to obtain O-S-O bond angle for both sites.

  1. The high-pressure phase of lawsonite: A single crystal study of a key mantle hydrous phase

    NASA Astrophysics Data System (ADS)

    O'Bannon, Earl; Beavers, Christine M.; Kunz, Martin; Williams, Quentin

    2017-08-01

    Lawsonite CaAl2Si2O7(OH)2·H2O is an important water carrier in subducting oceanic crusts and the primary hydrous phase in basalt at depths greater than 80 km. We have conducted high-pressure synchrotron single-crystal X-ray diffraction experiments on natural lawsonite at room temperature up to 10.0 GPa to study its high-pressure polymorphism. We find that lawsonite remains orthorhombic with Cmcm symmetry up to 9.3 GPa and shows nearly isotropic compression. Above 9.3 GPa, lawsonite becomes monoclinic with P21/m symmetry. Across the phase transition, the Ca polyhedron becomes markedly distorted, and the average positions of the H2O molecules and hydroxyls change. The changes observed in the H-atom positions under compression are different than the low-temperature changes in this material. We resolve for the first time the H-bonding configuration of the high-pressure monoclinic phase of lawsonite. A bond valence approach is deployed to determine that the phase transition from orthorhombic to monoclinic is primarily driven by the Si2O7 groups, and in particular their bridging oxygen atoms (O1). The changes in the structure strongly indicate that entropy increases across the symmetry-lowering transition and hence that the slope of the phase transition is negative. Monoclinic lawsonite is thus stable under the pressure and temperature conditions that exist in the Earth and is likely to be a major water carrier in colder, deep subducted slabs. Monoclinic lawsonite also likely has enhanced electrical conductivity along its c axis due to its dynamically disordered hydrogen atoms.

  2. High pressure phase transitions in lawsonite at simultaneous high pressure and temperature: A single crystal study

    NASA Astrophysics Data System (ADS)

    O'Bannon, E. F., III; Vennari, C.; Beavers, C. C. G.; Williams, Q. C.

    2015-12-01

    Lawsonite (CaAl2Si2O7(OH)2.H2O) is a hydrous mineral with a high overall water content of ~11.5 wt.%. It is a significant carrier of water in subduction zones to depths greater than ~150 km. The structure of lawsonite has been extensively studied under room temperature, high-pressure conditions. However, simultaneous high-pressure and high-temperature experiments are scarce. We have conducted synchrotron-based simultaneous high-pressure and temperature single crystal experiments on lawsonite up to a maximum pressure of 8.4 GPa at ambient and high temperatures. We used a natural sample of lawsonite from Valley Ford, California (Sonoma County). At room pressure and temperature lawsonite crystallizes in the orthorhombic system with Cmcm symmetry. Room temperature compression indicates that lawsonite remains in the orthorhombic Cmcm space group up to ~9.0 GPa. Our 5.0 GPa crystal structure is similar to the room pressure structure, and shows almost isotropic compression of the crystallographic axes. Unit cell parameters at 5.0 GPa are a- 5.7835(10), b- 8.694(2), and c- 13.009(3). Single-crystal measurements at simultaneous high-pressure and temperature (e.g., >8.0 GPa and ~100 oC) can be indexed to a monoclinic P-centered unit cell. Interestingly, a modest temperature increase of ~100 oC appears to initiate the orthorhombic to monoclinic phase transition at ~0.6-2.4 GPa lower than room temperature compression studies have shown. There is no evidence of dehydration or H atom disorder under these conditions. This suggests that the orthorhombic to monoclinic transition could be kinetically impeded at 298 K, and that monoclinic lawsonite could be the dominant water carrier through much of the depth range of upper mantle subduction processes.

  3. Growth and Characterization of Single Crystal Ga2O3 Nanowires and Nano-Ribbons for Sensing Applications

    DTIC Science & Technology

    2005-01-01

    Growth and characterization of single crystal Ga2O3 nanowires and nano-ribbons for sensing applications. S.M. Prokes, W.E. Carlos and O.J...Glembocki US Naval Research Laboratory 4555 Overlook Ave. SW Washington DC 20375 Keywords: Ga2O3 nanowires, nano-ribbons, VLS growth, Raman...spectroscopy, electron spin resonance, sensing. ABSTRACT The growth of monoclinic Ga2O3 nanowires, nano-ribbons and nano-sheets has been

  4. The topotactic dehydration of monoclinic {[Co(pht)(bpy)(H2O)2]·2H2O}n into orthorhombic [Co(pht)(bpy)(H2O)2]n (pht is phthalate and bpy is 4,4'-bipyridine).

    PubMed

    Harvey, Miguel Angel; Suarez, Sebastián; Cukiernik, Fabio D; Baggio, Ricardo

    2014-10-01

    Controlled heating of single crystals of the previously reported [Köferstein & Robl (2007). Z. Anorg. Allg. Chem. 633, 1127-1130] dihydrate {[Co(pht)(bpy)(H2O)2]·2H2O}n, (II) [where pht is phthalate (C8H4O4) and bpy is 4,4'-bipyridine (C10H8N2)], produced a topotactic transformation into an unreported diaqua anhydrate, namely poly[diaqua(μ2-benzene-1,2-dicarboxylato-κ(2)O(1):O(2))(μ2-4,4'-bipyridine-κ(2)N:N')cobalt(II)], [Co(C8H4O4)(C10H8N2)(H2O)2]n, (IIa). The structural change consists of the loss of the two solvent water molecules linking the original two-dimensional covalent substructures which are the `main frame' of the monoclinic P2/n hydrate (strictly preserved during the transformation), with further reaccommodation of the latter. The anhydrate organizes itself in the orthorhombic system (space group Pmn2(1)) in a disordered fashion, where the space-group-symmetry restrictions are achieved only in a statistical sense, with mirror-related two-dimensional planar substructures, mirrored in a plane perpendicular to [100]. Thus, the asymmetric unit in the refined model is composed of two superimposed mirror-related `ghosts' of half-occupancy each. Similarities and differences with the parent dihydrate and some other related structures in the literature are discussed.

  5. Monoclinic-to-orthorhombic phase transition of the hexamethylenetetramine-2-methylbenzoic acid (1/2) cocrystal with temperature-dependent dynamic molecular disorder.

    PubMed

    Chia, Tze Shyang; Quah, Ching Kheng

    2016-12-01

    As a function of temperature, the hexamethylenetetramine-2-methylbenzoic acid (1/2) cocrystal, C6H12N4·2C8H8O2, undergoes a reversible structural phase transition. The orthorhombic high-temperature phase in the space group Pccn has been studied in the temperature range between 165 and 300 K. At 164 K, a t2 phase transition to the monoclinic subgroup P21/c space group occurs; the resulting twinned low-temperature phase was investigated in the temperature range between 164 and 100 K. The domains in the pseudomerohedral twin are related by a twofold rotation corresponding to the matrix (100/0-10/00-1. Systematic absence violations represent a sensitive criterium for the decision about the correct space-group assignment at each temperature. The fractional volume contributions of the minor twin domain in the low-temperature phase increases in the order 0.259 (2) → 0.318 (2) → 0.336 (2) → 0.341 (3) as the temperature increases in the order 150 → 160 → 163 → 164 K. The transformation occurs between the nonpolar point group mmm and the nonpolar point group 2/m, and corresponds to a ferroelastic transition or to a t2 structural phase transition. The asymmetric unit of the low-temperature phase consists of two hexamethylenetetramine molecules and four molecules of 2-methylbenzoic acid; it is smaller by a factor of 2 in the high-temperature phase and contains two half molecules of hexamethylenetetramine, which sit across twofold axes, and two molecules of the organic acid. In both phases, the hexamethylenetetramine residue and two benzoic acid molecules form a three-molecule aggregate; the low-temperature phase contains two of these aggregates in general positions, whereas they are situated on a crystallographic twofold axis in the high-temperature phase. In both phases, one of these three-molecule aggregates is disordered. For this disordered unit, the ratio between the major and minor conformer increases upon cooling from

  6. Crystal structure and microstructure of Nd1.8Sr0.2NiO3.72: A K2NiF4-type nickelate with monoclinic symmetry and ordered oxygen vacancies

    NASA Astrophysics Data System (ADS)

    Medarde, M.; Rodríguez-Carvajal, J.; Vallet-Regí, M.; González-Calbet, J. M.; Alonso, J.

    1994-04-01

    The crystallographic structure of the Ni1+/Ni2+ mixed valence Nd1.8Sr0.2NiO3.72 compound has been investigated over a wide temperature range (from 16 K to room temperature) by using neutron-powder diffraction. In contrast with stoichiometric Nd2NiO4.00, the symmetry of this new oxygen-defective phase is monoclinic, and it can be described by the B112/n(C2/c) space group in the whole range of temperatures. Between 200 and 16 K, a smooth decrease of the monoclinic strain s=2(b sinγ-a)/(a+b sinγ) has been observed, which presents the same characteristics as the Bmab-->P42/ncm first-order structural phase transition reported for Nd2NiO4.00 at Tc1~=130 K. The oxygen vacancies are concentrated in the basal plane of the NiO6 octahedra along the [110] crystallographic direction and, in consequence, some of the Ni atoms are expected to be in square planar coordination. On the other hand, the strong additional broadening observed in the (hhl) reflections indicates the existence of microstrains, whose origin lies in the local fluctuations of the oxygen content along the ordering direction of the vacancies.

  7. Symmetry of piezoelectric (1–x)Pb(Mg1/3Nb2/3)O₃-xPbTiO₃ (x=0.31) single crystal at different length scales in the morphotropic phase boundary region

    DOE PAGES

    Kim, Kyou-Hyun; Payne, David A.; Zuo, Jian-Min

    2012-11-29

    We use probes of three different length scales to examine symmetry of (1–x)Pb(Mg1/3Nb2/3)O₃-xPbTiO₃ (PMN-xPT) single crystals in the morphotropic phase boundary (MPB) region at composition x = 0.31 (PMN-31% PT). On the macroscopic scale, x-ray diffraction (XRD) shows a mixture of strong and weak diffraction peaks of different widths. The closest match to XRD peak data is made with monoclinic Pm (MC) symmetry. On the local scale of a few nanometers, convergent beam electron diffraction (CBED) studies, with a 1.6-nm electron probe, reveal no obvious symmetry. These CBED experimental patterns can be approximately matched with simulations based on monoclinic symmetry,more » which suggests locally distorted monoclinic structure. A monoclinic Cm (MA or MB)-like symmetry could also be obtained from certain regions of the crystal by using a larger electron probe size of several tens of nanometers in diameter. Thus the monoclinic symmetry of single crystal PMN-31%PT is developed only in parts of the crystal by averaging over locally distorted structure on the scale of few tens of nanometers. The macroscopic symmetry observed by XRD is a result of averaging from the local structure in PMN-31%PT single crystal. The lack of local symmetry at a few nanometers scale suggests that the polarization switching results from a change in local displacements, which are not restricted to specific symmetry planes or directions.« less

  8. Hydrogen diffusion and stabilization in single-crystal VO2 micro/nanobeams by direct atomic hydrogenation.

    PubMed

    Lin, Jian; Ji, Heng; Swift, Michael W; Hardy, Will J; Peng, Zhiwei; Fan, Xiujun; Nevidomskyy, Andriy H; Tour, James M; Natelson, Douglas

    2014-09-10

    We report measurements of the diffusion of atomic hydrogen in single crystalline VO2 micro/nanobeams by direct exposure to atomic hydrogen, without catalyst. The atomic hydrogen is generated by a hot filament, and the doping process takes place at moderate temperature (373 K). Undoped VO2 has a metal-to-insulator phase transition at ∼340 K between a high-temperature, rutile, metallic phase and a low-temperature, monoclinic, insulating phase with a resistance exhibiting a semiconductor-like temperature dependence. Atomic hydrogenation results in stabilization of the metallic phase of VO2 micro/nanobeams down to 2 K, the lowest point we could reach in our measurement setup. Optical characterization shows that hydrogen atoms prefer to diffuse along the c axis of rutile (a axis of monoclinic) VO2, along the oxygen "channels". Based on observing the movement of the hydrogen diffusion front in single crystalline VO2 beams, we estimate the diffusion constant for hydrogen along the c axis of the rutile phase to be 6.7 × 10(-10) cm(2)/s at approximately 373 K, exceeding the value in isostructural TiO2 by ∼38×. Moreover, we find that the diffusion constant along the c axis of the rutile phase exceeds that along the equivalent a axis of the monoclinic phase by at least 3 orders of magnitude. This remarkable change in kinetics must originate from the distortion of the "channels" when the unit cell doubles along this direction upon cooling into the monoclinic structure. Ab initio calculation results are in good agreement with the experimental trends in the relative kinetics of the two phases. This raises the possibility of a switchable membrane for hydrogen transport.

  9. Polarized infrared and raman spectra of monoclinic CsH 2PO 4 single crystal and its deuterated homologue CsD 2PO 4. Part 1. Hydrogen bond study

    NASA Astrophysics Data System (ADS)

    Videnova-Adrabińska, V.; Baran, J.

    1987-01-01

    The object of clearly distinguishing the streching modes originating from the short ( v2) and the long ( v1) hydrogen bond in CsH 2PO 4 has been achieved by recording polarized IR spectra on the (010) plane using different orientations of the electric vector component. Band parameters of the v1 stretching mode are taken as a function of the temperature. Calculations of the orientation of the transition dipole moments for the six proton vibrations ( v1, δ 1, γ 1 and v2, δ 2, γ 2) are performed and correlated with the experimental results.

  10. A monoclinic, pseudo-orthorhombic Au-Hg mineral of potential economic significance in Pleistocene Snake River alluvial deposits of southeastern Idaho

    USGS Publications Warehouse

    Desborough, G.A.; Foord, E.E.

    1992-01-01

    A mineral with the approximate composition of Au94Hg6 - Au88Hg12 (atomic %) has been identified in Pleistocene Snake River alluvial deposits. The gold-mercury mineral occurs as very small grains or as polycrystalline masses composed of subhedral to nearly euhedral attached crystals. Vibratory cold-polishing techniques with 0.05-??m alumina abrasive for polished sections revealed a porous internal texture for most subhedral crystals after 48-72 hours of treatment. Thus, optical character (isotropic or anisotropic) could not be determined by reflected-light microscopy, and pore-free areas were too small for measurement of reflectance. X-ray-diffraction lines rather than individual reflections (spots), on powder camera X-ray films of unrotated spindles of single grains that morphologically appear to be single crystals, indicate that individual subhedral or euhedral crystals are composed of domains in random orientation. Thus, no material was found suitable for single-crystal X-ray diffraction studies. -from Authors

  11. A second monoclinic polymorph of 2-(3,5-dimethyl-1H-pyrazol-1-yl)-2-hy­droxy­imino-N′-[1-(pyridin-2-yl)ethyl­idene]acetohydrazide

    PubMed Central

    Plutenko, Maxym O.; Lampeka, Rostislav D.; Haukka, Matti; Nordlander, Ebbe

    2013-01-01

    The title compound, C14H16N6O2, is a second monoclinic polymorph of 2-[1-(3,5-dimeth­yl)pyrazol­yl]-2-hy­droxy­imino-N′-[1-(2-pyrid­yl)ethyl­idene] acetohydrazide, with two crystallographically independent mol­ecules per asymmetric unit. The non-planar mol­ecules are chemically equal having similar geometric parameters. The previously reported polymorph [Plutenko et al. (2012 ▶). Acta Cryst. E68, o3281] was described in space group Cc (Z = 4). The oxime group and the O atom of the amide group are anti with respect to the C—C bond. In the crystal, mol­ecules are connected by N—H⋯N hydrogen bonds into zigzag chains extending along the b axis. PMID:23723911

  12. Evidence for anisotropic dielectric properties of monoclinic hafnia using valence electron energy-loss spectroscopy in high-resolution transmission electron microscopy and ab initio time-dependent density-functional theory

    NASA Astrophysics Data System (ADS)

    Guedj, C.; Hung, L.; Zobelli, A.; Blaise, P.; Sottile, F.; Olevano, V.

    2014-12-01

    The effect of nanocrystal orientation on the energy loss spectra of monoclinic hafnia (m-HfO2) is measured by high resolution transmission electron microscopy (HRTEM) and valence energy loss spectroscopy (VEELS) on high quality samples. For the same momentum-transfer directions, the dielectric properties are also calculated ab initio by time-dependent density-functional theory (TDDFT). Experiments and simulations evidence anisotropy in the dielectric properties of m-HfO2, most notably with the direction-dependent oscillator strength of the main bulk plasmon. The anisotropic nature of m-HfO2 may contribute to the differences among VEELS spectra reported in literature. The good agreement between the complex dielectric permittivity extracted from VEELS with nanometer spatial resolution, TDDFT modeling, and past literature demonstrates that the present HRTEM-VEELS device-oriented methodology is a possible solution to the difficult nanocharacterization challenges given in the International Technology Roadmap for Semiconductors.

  13. Evidence for anisotropic dielectric properties of monoclinic hafnia using valence electron energy-loss spectroscopy in high-resolution transmission electron microscopy and ab initio time-dependent density-functional theory

    SciTech Connect

    Guedj, C.; Hung, L.; Sottile, F.; Zobelli, A.; Blaise, P.; Olevano, V.

    2014-12-01

    The effect of nanocrystal orientation on the energy loss spectra of monoclinic hafnia (m-HfO{sub 2}) is measured by high resolution transmission electron microscopy (HRTEM) and valence energy loss spectroscopy (VEELS) on high quality samples. For the same momentum-transfer directions, the dielectric properties are also calculated ab initio by time-dependent density-functional theory (TDDFT). Experiments and simulations evidence anisotropy in the dielectric properties of m-HfO{sub 2}, most notably with the direction-dependent oscillator strength of the main bulk plasmon. The anisotropic nature of m-HfO{sub 2} may contribute to the differences among VEELS spectra reported in literature. The good agreement between the complex dielectric permittivity extracted from VEELS with nanometer spatial resolution, TDDFT modeling, and past literature demonstrates that the present HRTEM-VEELS device-oriented methodology is a possible solution to the difficult nanocharacterization challenges given in the International Technology Roadmap for Semiconductors.

  14. Plastic Deformation by Twinning in CsHSO4 Single Crystal

    NASA Astrophysics Data System (ADS)

    Ozaki, Toru; Itoh, Kazuyuki; Nakamura, Eiji

    1982-01-01

    Plastic deformation by mechanical twinning with (001) twin plane has been observed in the b-plate of CsHSO4 single crystals at room temperature. A parallelogram-shaped hysteresis loop is found between the external shear stress and the deformation angle of the crystal plate. The maximum deformation angle is found to be 24° which is very close to 2(β-90°), where β{=}101.51° is the monoclinic angle of the crystal lattice. A microscopic model based on the crystal structure for the twin structure is proposed.

  15. Effects of specimen size and yttria concentration on mechanical properties of single crystalline yttria-stabilized tetragonal zirconia nanopillars

    NASA Astrophysics Data System (ADS)

    Zhang, Ning; Asle Zaeem, Mohsen

    2017-07-01

    The nanoscale plastic deformation of yttria-stabilized tetragonal zirconia (YSTZ) is highly dependent on the crystallographic orientations, i.e., dislocation is induced when the loading direction is 45° tilted to {111} and {101} slip planes, while tetragonal to monoclinic phase transformation dominates the plastic deformation when loading direction is perpendicular to the slip planes. This study investigates the effects of specimen size and yttria concentration on the mechanical response of single crystalline YSTZ nanopillars. Through uniaxial compression test, the smaller-is-stronger phenomenon is revealed in nanopillars deformed through a dislocation motion mechanism. Serrated stacking faults are observed in the smallest nanopillar, while neat primary slip plane forms in the largest nanopillar. In contrast, the larger-is-stronger relation is observed in nanopillars in which deformation is mediated by tetragonal to monoclinic phase transformation. It is noted that the ratio of transformed monoclinic phase to the remaining tetragonal phase is the highest in the smallest nanopillar. The strength of nanopillars is identified to decrease by increasing the amount of yttria due to the creation of more oxygen vacancies that act as weak points to facilitate dislocation motion and accelerate phase transformation.

  16. CsAl(H(2)AsO(4))(2)(HAsO(4)): a new monoclinic protonated arsenate with decorated kröhnkite-like chains.

    PubMed

    Schwendtner, Karolina; Kolitsch, Uwe

    2007-03-01

    The crystal structure of hydrothermally synthesized caesium aluminium bis[dihydrogen arsenate(V)] hydrogen arsenate(V), CsAl(H(2)AsO(4))(2)(HAsO(4)), was determined from single-crystal X-ray diffraction data collected at room temperature. The compound represents a new structure type that is characterized by decorated kröhnkite-like [100] chains of corner-sharing AlO(6) octahedra and AsO(4) tetrahedra. Ten-coordinated Cs atoms are situated between the chains, which are interconnected by five different hydrogen bonds [O...O = 2.569 (4)-2.978 (4) A]. All atoms are in general positions. CsAl(H(2)AsO(4))(2)(HAsO(4)) is very closely related to CsGa(H(1.5)AsO(4))(2)(H(2)AsO(4)) and isotypic CsCr(H(1.5)AsO(4))(2)(H(2)AsO(4)).

  17. Temperature and field induced strain measurements in single crystal Gd5Si2Ge2

    DOE PAGES

    McCall, S. K.; Nersessian, N.; Carman, G. P.; ...

    2016-03-29

    The first-order magneto-structural transformation that occurs in Gd5Si2Ge2 near room temperature makes it a strong candidate for many energy harvesting applications. Understanding the single crystal properties is crucial for allowing simulations of device performance. In this study, magnetically and thermally induced transformation strains were measured in a single crystal of Gd5Si2.05Ge1.95 as it transforms from a high-temperature monoclinic paramagnet to a lower-temperature orthorhombic ferromagnet. Thermally induced transformation strains of –8500 ppm, +960 ppm and +1800 ppm, and magnetically induced transformation strains of –8500 ppm, +900 ppm and +2300 ppm were measured along the a, b and c axes, respectively. Furthermore,more » using experimental data coupled with general thermodynamic considerations, a universal phase diagram was constructed showing the transition from the monoclinic to the orthorhombic phase as a function of temperature and magnetic field.« less

  18. Single-domain-like behavior in a 3-mm natural single crystal of magnetite

    NASA Astrophysics Data System (ADS)

    Özdemir, Özden; Dunlop, David J.

    1998-02-01

    We have observed single-domain (SD) like behavior in a 3-mm natural single crystal of magnetite following low-temperature demagnetization (LTD), which consists of zero-field cycling through the Verwey transition to erase remanence carried by pinned domain walls. We compared stepwise alternating field (AF) and thermal demagnetization curves of 1-mT total thermoremanent magnetization (TRM), 1-mT partial TRM (pTRM) acquired between the Curie point (TC = 575°C) and 565°C, and saturation isothermal remanent magnetization (SIRM) measured with and without prior LTD. AF demagnetization curves of untreated TRM and SIRM decreased exponentially with increasing AF. SIRM was more resistant to demagnetization than was TRM, a multidomain (MD) result of the Lowrie-Fuller test. After LTD the TRM and SIRM memories had AF demagnetization curves with sigmoid shapes and initial plateaus below 8 mT in which little or no demagnetization occurred. Both features are reminiscent of SD behavior. During thermal demagnetization, untreated TRM and SIRM decreased almost linearly with increasing temperature up to ≈500°C. Such distributed unblocking temperatures TUB are expected for pinned walls in MD grains. The remaining 60% of TRM and 40% of SIRM were lost over a narrow temperature interval concentrated between 560°C and TC. The TRM memory after LTD was very stable against thermal demagnetization. There was no decrease in remanence below 550°C and very little change until 565°C, only 10°C below TC. This very high TUB fraction of TRM seems to have SD-like character. SIRM has similar behavior. In the case of pTRM, both the untreated remanence and the memory after LTD have almost entirely high TUBs, identical to the range of pTRM blocking temperatures TB, 565°C-TC. TUB = TB is a basic property of SD partial TRM. The pTRM memory fraction is also larger than that of total TRM or SIRM. These observations suggest that pTRM(TC, 565°C) isolates an SD-like fraction of remanence similar to that

  19. Dicarboxylate assisted synthesis of the monoclinic heterometallic tetrathiocyanato bridged copper(II) and mercury(II) coordination polymer {Cu[Hg(SCN) 4]} n: Synthesis, structural, vibration, luminescence, EPR studies and DFT calculations

    NASA Astrophysics Data System (ADS)

    Khandar, Ali Akbar; Klein, Axel; Bakhtiari, Akbar; Mahjoub, Ali Reza; Pohl, Roland W. H.

    2011-02-01

    The synthesis of the monoclinic polymorph of {Cu[Hg(SCN) 4]} n is reported. The compound, as determined by X-ray diffraction of a twinned crystal, consists of mercury and copper atoms linked by μ1,3-SCN bridges. The crystal packing shows a highly porous infinite 3D structure. Diagnostic resonances for the SCN - ligand and metal-ligand bonds in the IR, far-IR and Raman spectra are assigned and discussed. The electronic band structure along with density of states (DOS) calculated by the DFT method indicates that the compound is an indirect band gap semiconductor. The DFT calculations show that the observed luminescence of the compound arises mainly from an excited LLCT state with small MLCT contributions (from the copper to unoccupied π* orbital of the thiocyanate groups). The X-band EPR spectrum of the powdered sample at room temperature reveals an axial signal with anisotropic g factors consistent with the unpaired electron of Cu(II) ion in the dx2- y2 orbital.

  20. Presence of a monoclinic (Pm) phase in the morphotropic phase boundary region of multiferroic (1 - x)Bi(Ni1/2Ti1/2)O3-xPbTiO3 solid solution: A Rietveld study

    NASA Astrophysics Data System (ADS)

    Pandey, Rishikesh; Singh, Akhilesh Kumar

    2014-07-01

    We present here the results of structural studies on multiferroic (1 - x)Bi(Ni1/2Ti1/2)O3-xPbTiO3 solid solution using Rietveld analysis on powder x-ray diffraction data in the composition range 0.35 ≤ x ≤ 0.55. The stability region of various crystallographic phases at room temperature for (1 - x)Bi(Ni1/2Ti1/2)O3-xPbTiO3 is determined precisely. Structural transformation from pseudo-cubic (x ≤ 0.40) to tetragonal (x ≥ 0.50) phase is observed via phase coexistence region demarcating the morphotropic phase boundary. The morphotropic phase boundary region consists of coexisting tetragonal and monoclinic structures with space group P4mm and Pm, respectively, stable in composition range 0.41 ≤ x ≤ 0.49 as confirmed by Rietveld analysis. The results of Rietveld analysis completely rule out the coexistence of rhombohedral and tetragonal phases in the morphotropic phase boundary region reported by earlier workers. A comparison between the bond lengths for "B-site cations-oxygen anions" obtained after Rietveld refinement, with the bond length calculated using Shannon-Prewitt ionic radii, reveals the ionic nature of B-O (Ni/Ti-O) bonds for the cubic phase and partial covalent character for the other crystallographic phases.

  1. A monoclinic polymorph of [(Z)-N-(3-chloro­phen­yl)-O-methyl­thio­carbamato-κS](tri­phenyl­phosphane-κP)gold(I): crystal structure and Hirshfeld surface analysis

    PubMed Central

    Yeo, Chien Ing; Tan, Sang Loon; Tiekink, Edward R. T.

    2016-01-01

    The title compound, [Au(C8H7ClNOS)(C18H15P)], is a monoclinic (P21/n, Z′ = 1; form β) polymorph of the previously reported triclinic form (P-1, Z′ = 1; form α) [Tadbuppa & Tiekink (2010 ▸). Acta Cryst. E66, m664]. The mol­ecular structures of both forms feature an almost linear gold(I) coordination geometry [P—Au—S = 175.62 (5)° in the title polymorph], being coordinated by thiol­ate S and phosphane P atoms, a Z conformation about the C=N bond and an intra­molecular Au⋯O contact. The major conformational difference relates to the relative orientations of the residues about the Au—S bond: the P—Au—S—C torsion angles are −8.4 (7) and 106.2 (7)° in forms α and β, respectively. The mol­ecular packing of form β features centrosymmetric aggregates sustained by aryl-C—H⋯O inter­actions, which are connected into a three-dimensional network by aryl-C—H⋯π contacts. The Hirshfeld analysis of forms α and β shows many similarities with the notable exception of the influence of C—H⋯O inter­actions in form β. PMID:27536384

  2. Triclinic and monoclinic polymorphs of meso-(E,E)-1,1'-[1,2-bis(4-chlorophenyl)ethane-1,2-diyl]bis(phenyldiazene): the high-yield synthesis of an unexpected product, concomitant polymorphism and configurational disorder.

    PubMed

    Mohamed, Shaaban K; Younes, Sabry H H; Abdel-Raheem, Eman M M; Horton, Peter N; Akkurt, Mehmet; Glidewell, Christopher

    2016-01-01

    Pyrazolidine-3,5-diones and their derivatives exhibit a wide range of biological activities. Seeking to explore the effect of combining a hydrocarbyl ring substituent, as present in sulfinpyrazone (used to treat gout), with a chlorinated aryl ring, as present in muzolimine (a diuretic), we explored the reaction between 1-phenylpyrazolidine-3,5-dione and 4-chlorobenzaldehyde under mildly basic conditions in the expectation of producing the simple condensation product 4-(4-chlorobenzylidene)-1-phenylpyrazolidine-3,5-dione. However, the reaction product proved to be meso-(E,E)-1,1'-[1,2-bis(4-chlorophenyl)ethane-1,2-diyl]bis(phenyldiazene), C26H20Cl2N4, and a tentative mechanism is proposed. Crystallization from ethanol produces two concomitant polymorphs, i.e. a triclinic form, (I), in the space group P-1, and a monoclinic form, (II), in the space group C2/c. In both polymorphs, the molecules lie across centres of inversion, but in (II), the molecules are subject to whole-molecule disorder equivalent to configurational disorder with occupancies of 0.6021 (19) and 0.3979 (19). There are no hydrogen bonds in the crystal structure of polymorph (I), but the molecules of polymorph (II) are linked by C-H...π(arene) hydrogen bonds into complex chains, which are further linked into sheets by C-H...N interactions.

  3. A second monoclinic polymorph of 2-[2-(4-meth­oxy­phen­yl)hydrazinyl­idene]-1,3-diphenyl­propane-1,3-dione

    PubMed Central

    Bustos, Carlos; Alvarez-Thon, Luis; Barría, Daniela; Cárcamo, Juan-Guillermo; Garland, Maria Teresa

    2011-01-01

    The title compound, C22H18N2O3 is the second monoclinic polymorph (P21/c) of the compound, the first being reported in space group P21 [Bertolasi et al. (1993 ▶). J. Chem. Soc. Perkin Trans. 2, pp. 2223–2228]. In the mol­ecular structure of the title compound, the inter­planar angle between the benzoyl units is 80.04 (5)°, while the corresponding angles between the phenyl­hydrazinyl­idene and benzoyl groups are 36.11 (5) and 55.77 (2)°. A strong resonance-assisted intra­molecular N—H⋯O hydrogen bond is found. In the crystal, the entire supra­molecular structure is constructed by weak inter­molecular C—H⋯O inter­actions and an inter-ring π–π inter­action [centroid–centroid distance = 3.6088 (8) Å]. PMID:21837198

  4. Unique three-phase states in (1-x)Pb(Zn1/3Nb2/3)O3- xPbTiO3 single crystals

    NASA Astrophysics Data System (ADS)

    Topolov, V. Yu

    2004-04-01

    This paper reports results on the crystallographic study of heterophase structures in relaxor-ferroelectric (1- x)Pb (Zn1/3Nb2/3)O3-xPbTiO3 single crystals with 0.06monoclinic' and 'monoclinic-tetragonal', can be elastically matched along so-called zero-net-strain planes, parallel to the (100) or (010) domain (twin) walls in the intermediate monoclinic phase, where the Miller indices (hkl) are written in terms of the perovskite axes of the cubic unit cell. Calculated volume fractions of the three phases coexisting at 0.06

  5. Prediction of a novel monoclinic carbon allotrope

    NASA Astrophysics Data System (ADS)

    Amsler, Maximilian; Flores-Livas, José A.; Marques, Miguel A. L.; Botti, Silvana; Goedecker, Stefan

    2013-09-01

    A novel allotrope of carbon with P2/ m symmetry was identified during an ab initio minima-hopping structural search which we call M10-carbon. This structure is predicted to be more stable than graphite at pressures above 14.4 GPa and consists purely of s p 3 bonds. It has a high bulk modulus and is almost as hard as diamond. A comparison of the simulated X-ray diffraction pattern shows a good agreement with experimental results from cold compressed graphite.

  6. Template-free synthesis of BiVO4 nanostructures: II. Relationship between various microstructures for monoclinic BiVO4 and their photocatalytic activity for the degradation of rhodamine B under visible light.

    PubMed

    Ren, Lu; Ma, Lili; Jin, Lei; Wang, Jian-Bo; Qiu, Mingqiang; Yu, Ying

    2009-10-07

    The shape-controlled synthesis of nanostructured materials has opened up new possibilities to improve their physical and chemical properties. In this work, new types of monoclinic structured BiVO4 with complex morphologies, namely flowerlike, disclike, tubelike and platelike shapes, have been synthesized in a binary green solvent (water and ethanol) through controlling reaction conditions such as solvent, pH value, concentration of precursors and reaction temperature. The morphology of BiVO4 can transform from three-dimensional (3D) flowerlike superstructures and hexagonal-prismatic nanotubes to two-dimensional (2D) platelike and disclike structures. UV-vis absorption spectra show that all of the prepared nano- and microstructures can respond to visible light and the optical properties of BiVO4 samples are relevant to their structures. More importantly, the photocatalytic activities of various BiVO4 samples are strongly dependent on their morphology for the degradation of rhodamine B (RhB) under visible-light irradiation. The 2D (disclike and platelike) BiVO4 demonstrates better photocatalytic activity than 3D and bulk BiVO4. Among the nano- and microstructures, the nanoplate BiVO4 exhibit the highest photocatalytic activity for degradation of organic pollutants. Additionally, it is found that the different microstructure of BiVO4 leads to the different degradation route for organic compounds of RhB. The reasons for the differences in the photocatalytic behavior for these BiVO4 nanostructures are further discussed. The relationship between the microstructure and the photocatalytic activity for BiVO4 may give clues for the preparation of photocatalysts with high activity based on material morphology design. Moreover, the prepared 2D BiVO4 can be a good photocatalyst used in environmental pollution control.

  7. Template-free synthesis of BiVO4 nanostructures: II. Relationship between various microstructures for monoclinic BiVO4 and their photocatalytic activity for the degradation of rhodamine B under visible light

    NASA Astrophysics Data System (ADS)

    Ren, Lu; Ma, Lili; Jin, Lei; Wang, Jian-Bo; Qiu, Mingqiang; Yu, Ying

    2009-10-01

    The shape-controlled synthesis of nanostructured materials has opened up new possibilities to improve their physical and chemical properties. In this work, new types of monoclinic structured BiVO4 with complex morphologies, namely flowerlike, disclike, tubelike and platelike shapes, have been synthesized in a binary green solvent (water and ethanol) through controlling reaction conditions such as solvent, pH value, concentration of precursors and reaction temperature. The morphology of BiVO4 can transform from three-dimensional (3D) flowerlike superstructures and hexagonal-prismatic nanotubes to two-dimensional (2D) platelike and disclike structures. UV-vis absorption spectra show that all of the prepared nano- and microstructures can respond to visible light and the optical properties of BiVO4 samples are relevant to their structures. More importantly, the photocatalytic activities of various BiVO4 samples are strongly dependent on their morphology for the degradation of rhodamine B (RhB) under visible-light irradiation. The 2D (disclike and platelike) BiVO4 demonstrates better photocatalytic activity than 3D and bulk BiVO4. Among the nano- and microstructures, the nanoplate BiVO4 exhibit the highest photocatalytic activity for degradation of organic pollutants. Additionally, it is found that the different microstructure of BiVO4 leads to the different degradation route for organic compounds of RhB. The reasons for the differences in the photocatalytic behavior for these BiVO4 nanostructures are further discussed. The relationship between the microstructure and the photocatalytic activity for BiVO4 may give clues for the preparation of photocatalysts with high activity based on material morphology design. Moreover, the prepared 2D BiVO4 can be a good photocatalyst used in environmental pollution control.

  8. EPR and optical absorption studies on Gd 3+ ions in ammonium hydrogen malonate single crystals

    NASA Astrophysics Data System (ADS)

    Kripal, Ram; Mishra, Indrajeet

    2010-01-01

    X-Band electron paramagnetic resonance (EPR) studies of Gd 3+ ions in ammonium hydrogen malonate single crystals have been done at room temperature. Detailed EPR analysis indicates the presence of four physically equivalent but magnetically inequivalent sites. The zero-field splitting parameters and g factor are determined. The Gd 3+ ion is in 8S state; its levels are split by the action of the crystalline electric field of monoclinic symmetry. The optical absorption spectra of Gd 3+ ions in single crystals of ammonium hydrogen malonate are also recorded at room temperature. The energy levels of the 4f 7 configuration are calculated and compared with those observed experimentally. The values of E1=5854±11, E2=31±0.36, E3=592±3.3 and ζ 4f=1595±25 cm -1 are found to give the best over-all agreement between experimentally observed and calculated levels.

  9. Single crystal growth and magnetic excitations of transistion metal oxide CoV2 O6

    NASA Astrophysics Data System (ADS)

    Stockdale, Christopher; Wallington, F.; Taylor, J. W.; Garcia-Sakai, V.; Arevalo-Lopez, A. M.; Attfield, P.; Stock, C.

    2015-03-01

    Low-dimensional magnetic materials are an area of interest due to their unusual properties such as metamagnetism and magnetization plateaus. Solid state synthesis has produced polycrystalline CoV2O6 which exists in two polymorphs: one with a monoclinic structure, and the other with a triclinic structure. Single crystals have been grown from polycrystalline CoV2O6 using the flux method under vacuum and are large enough to aid in single crystal neutron diffraction. Magnetic excitations have been measured using powder neutron diffraction in the low temperatures regime with variable energy. The magnetic excitations have been compared between the two phases. The energy of the system has been modelled in terms of the spin-orbit coupling, structural distortions, and the crystal field and compared to neutron data.

  10. Polymorphism and structure of Nd2MoO6 single crystals

    NASA Astrophysics Data System (ADS)

    Antipin, A. M.; Sorokina, N. I.; Alekseeva, O. A.; Dudka, A. P.; Chernyshev, D. Yu.; Voronkova, V. I.

    2017-07-01

    The tetragonal and monoclinic modifications of Nd2MoO6 single crystals have been investigated by X-ray diffraction. The analysis has been on laboratory sources (2D CCD diffractometers: Xcalibur S (Shared Research Center, Institute of Crystallography, Russian Academy of Sciences) and BRUKER Smart APEX 2 (Shared Research Center, Institute of General and Inorganic Chemistry, Russian Academy of Sciences)) and on a synchrotron radiation source (ESRF, Grenoble, PILATUS@SNBL diffractometer). Local displacements of all atoms in the oxymolybdate structure have been revealed for the first time using electron density difference maps. Possible violation of the translational periodicity in the distribution of Mo and Nd atoms over types is indirectly confirmed, and statistical disorder of oxygen atoms is revealed. The results of the study confirm the previous suggestion that polymorphic transformations occur in oxymolybdates at a very low rate and, apparently, continuously in a wide temperature range. With an increase in temperature, layers undergo ordering according to the cation type as a result of the phase transition from the monoclinic to the tetragonal phase.

  11. Single-Crystal Elasticity of Earth Materials: An Appraisal

    NASA Astrophysics Data System (ADS)

    Duffy, T. S.

    2015-12-01

    The elastic properties of minerals are of central importance for interpreting seismic data for the Earth's crust, mantle, and core. Mineral elasticity data also have more general applications towards understanding equations of state, phase equilibria, interatomic forces, material strength, and phase transitions. The singe-crystal elastic properties are the most generally useful as they provide complete information on the anisotropy of elastic moduli (e.g. Poisson's ratio, Young's modulus), sound velocities, and compressibility. Measurement of the full set of single-crystal elastic properties remains challenging especially for lower symmetry crystals. In this talk, I present an overview of our current understanding of single-crystal elasticity based on a newly constructed database of single-crystal elastic properties. At ambient conditions the full elastic tensor of about 150 minerals have now been measured, along with about another 60 related compounds that are not formally minerals. About two-thirds of the measured minerals are oxides or silicates. A limitation of the existing database is that only about 10% of the measurements are on crystals of monoclinic or triclinic symmetry, while these two systems account for about 40% of known minerals. Additionally, only a smaller subset of minerals have been examined at high pressure or temperature conditions. Several applications of the database will be presented emphasizing trends in elastic anisotropy. The pyroxenes will be used as an illustrative example.

  12. Polarized Raman spectra of the oriented NaY(WO 4) 2 and KY(WO 4) 2 single crystals

    NASA Astrophysics Data System (ADS)

    Macalik, L.; Hanuza, J.; Kaminskii, A. A.

    2000-11-01

    Polarized Raman scattering spectra of the NaY(WO 4) 2 (NYW) single crystal have been measured. Its structure is described in the tetragonal space group isomorphic to CaWO 4 scheelite. The A g, B g and E g spectra were made and discussed in terms of factor group analysis. These spectra are compared to those of monoclinic KY(WO 4) 2 (KYW) single crystals whose structure differs from the other crystal. The NYW unit cell comprises of the isolated WO 4 tetrahedra whereas the KYW structure is built from the WO 6 octahedra joined by WO 2W double bonds and WOW single bridges. The vibrational characteristics of the bridge bond systems are proposed. On this basis, the role of the vibronic transitions for the KYW crystal doped with Eu 3+ ions is discussed.

  13. Characteristics of electric-field-induced polarization rotation in <001>-poled Pb(Mg1/3Nb2/3)O3-PbTiO3 single crystals close to the morphotropic phase boundary

    NASA Astrophysics Data System (ADS)

    Peräntie, J.; Hagberg, J.; Uusimäki, A.; Tian, J.; Han, P.

    2012-08-01

    The special characteristics of polarization rotation and accompanying electric-field-induced ferroelectric-ferroelectric phase transitions in <001>-poled Pb(Mg1/3Nb2/3)1-xTixO3 (x = 27.4, 28.8, and 30.7 mol. %) single crystals close to the morphotropic phase boundary region were studied by means of dielectric and thermal measurements as a function of a unipolar electric field at various temperatures. Discontinuous first-order-type phase transition behavior was evidenced by distinct and sharp changes in polarization and thermal responses with accompanying hysteresis as a function of the electric field. All compositions of crystals showed either one or two reversible discontinuities along the polarization rotation paths, which can be understood by electric-field-induced phase transition sequences to the tetragonal phase through different monoclinic phases previously observed along the polarization rotation path. Together with increasing polarization, a field-induced reversible decrease in temperature was observed with increasing electric field, indicating increased dipolar entropy during the electric-field-induced phase transitions. Constructed electric field-temperature phase diagrams based on the polarization and thermal data suggest that the complex polarization rotation path extends to a wider composition range than previously observed. The measured thermal response showed that a transition from the monoclinic to the tetragonal phase produced a greater thermal change in comparison with a transition within two monoclinic phases.

  14. Growth and characterization of morpholinium dihydrogenphosphate single crystal

    NASA Astrophysics Data System (ADS)

    Babu, D. Rajan; Arul, H.; Vizhi, R. Ezhil

    2016-10-01

    Morpholinium dihydrogenphosphate (MDP) single crystals were synthesized, and were subsequently grown by controlled evaporation technique at room temperature for nonlinear optical applications. The grown crystal, which belongs to the monoclinic system with the space group P21, was subjected to single crystal X-ray diffraction to confirm the structure. UV-vis-NIR spectroscopy was done on the grown crystal and it showed good optical transparency in the entire visible region with a minimum cut-off wavelength of 289 nm. The optical band gap was computed as a function of photon energy using Tauc's plot. The refractive index of the grown crystal was determined using a Metricon Prism Coupler. The thermogravimetric (TG) and differential thermal analysis (DTA) traces disclosed the thermal stability of the compound. The mechanical strength of the crystal was investigated by a Vickers microhardness tester. Dielectric constant and dielectric loss were calculated and plotted as a function of frequency at different temperatures. The second harmonic conversion efficiency was determined using the Kurtz-Perry powder technique, and the efficiency was found to be 1.2 times greater than that of standard KDP.

  15. Crystalline transformations in nylon-6/single-walled carbon nanotube nanocomposites.

    PubMed

    Naffakh, M; Marco, C; Gómez, M A; Ellis, G; Maser, W K; Benito, A; Martínez, M T

    2009-10-01

    Nylon-6/single-walled carbon nanotube (SWNT) nanocomposites with different SWNTs loadings were prepared by melt-blending. An efficient dispersion of SWNTs into the nylon-6 matrix was confirmed by scanning electron microscopy. DSC and time-resolved synchrotron X-ray diffraction were used to provide detailed information on the effect of SWNTs on the crystalline phase transition of nylon-6 in the nanocomposites. The incorporation of SWNTs accelerated the crystallization rate of nylon-6 due to a nucleating effect. The variable-temperature WAXS experiments, in both neat nylon-6 and nylon-6 nanocomposites, showed that the crystallization from the melt occured through the formation of the pseudo-hexagonal crystal form (gamma) and its transformation to the monoclinic form (alpha) on cooling. Additionally, this crystalline transition was reversible as observed upon heating. The alpha-gamma crystalline transformation temperature of nylon-6 was dependent on heating rate and, more importantly, on the SWNT content.

  16. Investigation on nucleation kinetics, growth and characterization of urea oxalic acid-ferroelectric single crystal

    NASA Astrophysics Data System (ADS)

    Dhivya, R.; Ezhil Vizhi, R.; Rajan Babu, D.

    2017-06-01

    Nucleation and growth kinetics renders the information about the crystal growth process, which can be adopted to grow large size crystals. Urea oxalic acid was synthesized by slow evaporation method. Solubility was analyzed gravimetrically and it was observed that it exhibits positive temperature coefficient of solubility which is suitable for bulk growth. Metastable zonewidth was observed by adopting polythermal method. Induction period was measured by isothermal method for the saturation temperature by varying the degrees of supersaturation. Based on the classical theory of nucleation, the other nucleation parameters such as interfacial energy, Gibbs critical free energy and radius of critical nuclei were calculated. Urea oxalic acid (UOA) was synthesized and subsequently grown by a slow cooling technique. Single crystal X-ray diffraction study confirms that the crystal belongs to a monoclinic system. Dielectric analysis affirms the ferroelectric property of the material and the results were further discussed in detail.

  17. Creep of Oxide Single Crystals

    DTIC Science & Technology

    1990-08-01

    Perovskite (orthorhombic) 5.48 BaZrO3 2650 Perovskite (cubic) 6.26 LaCrO3 2510 Perovskite (orthorhombic) 6.69 CaZrO 3 2345 Perovskite (monoclinic) 4.76...LaA1O 3 2100 Perovskite (rhombohedral) Cr203 2270 Corundum (hexagonal) 5.21 A12 0 3 2040 Corundum (hexagonal) 3.96 MgCr2O4 2400 Spinel (cubic) 4.39...material quality prevented creep measurements on Sc 20 3. The perovskite -like oxides appear quite attractive based on melting points, but they suffer from

  18. Study of GaN nanowires converted from β-Ga2O3 and photoconduction in a single nanowire

    NASA Astrophysics Data System (ADS)

    Kumar, Mukesh; Kumar, Sudheer; Chauhan, Neha; Sakthi Kumar, D.; Kumar, Vikram; Singh, R.

    2017-08-01

    The formation of GaN nanowires from β-Ga2O3 nanowires and photoconduction in a fabricated single GaN nanowire device has been studied. Wurtzite phase GaN were formed from monoclinic β-Ga2O3 nanowires with or without catalyst particles at their tips. The formation of faceted nanostructures from catalyst droplets presented on a nanowire tip has been discussed. The nucleation of GaN phases in β-Ga2O3 nanowires and their subsequent growth due to interfacial strain energy has been examined using a high resolution transmission electron microscope. The high quality of the converted GaN nanowire is confirmed by fabricating single nanowire photoconducting devices which showed ultra high responsivity under ultra-violet illumination.

  19. Structural and vibrational properties of single crystals of Scandia, Sc{sub 2}O{sub 3} under high pressure

    SciTech Connect

    Ovsyannikov, Sergey V. E-mail: sergey2503@gmail.com; Wenz, Michelle D.; Pakhomova, Anna S.; Dubrovinsky, Leonid; Bykova, Elena; Bykov, Maxim; Glazyrin, Konstantin; Liermann, Hanns-Peter

    2015-10-28

    We report the results of single-crystal X-ray diffraction and Raman spectroscopy studies of scandium oxide, Sc{sub 2}O{sub 3}, at ambient temperature under high pressure up to 55 and 28 GPa, respectively. Both X-ray diffraction and Raman studies indicated a phase transition from the cubic bixbyite phase (so-called C-Res phase) to a monoclinic C2/m phase (so-called B-Res phase) at pressures around 25–28 GPa. The transition was accompanied by a significant volumetric drop by ∼6.7%. In addition, the Raman spectroscopy detected a minor crossover around 10–12 GPa, which manifested in the appearance of new and disappearance of some Raman modes, as well as in softening of one Raman mode. We found the bulk modulus values of the both C-Res and B-Res phases as B{sub 0} = 198.2(3) and 171.2(1) GPa (for fixed B′ = 4), respectively. Thus, the denser high-pressure lattice of Sc{sub 2}O{sub 3} is much softer than the original lattice. We discuss possible mechanisms that might be responsible for the pronounced elastic softening in the monoclinic high-pressure phase in this “simple” oxide with an ultra-wide band gap.

  20. Stresses of Single Parenting

    MedlinePlus

    ... ways to avoid the stress of being a single parent? Single parenthood can bring added pressure and stress ... share day-to-day responsibilities or decision-making, single parents must provide greater support for their children while ...

  1. Wheel-shaped [Mn12] single-molecule magnets.

    PubMed

    Rumberger, Evan M; Shah, Sonali J; Beedle, Christopher C; Zakharov, Lev N; Rheingold, Arnold L; Hendrickson, David N

    2005-04-18

    The reaction of [Mn(12)O(12)(O(2)CCH(3))(16)(H(2)O)(4)].4H(2)O.2CH(3)COOH with n-methyldiethanol amine (H(2)mdea), n-ethyldiethanol amine (H(2)edea), or n-butyldiethanol amine (H(2)bdea) leads to the formation of wheel-shaped Mn(III)(6)Mn(II)(6) complexes with the general formula [Mn(12)(R)(O(2)CCH(3))(14)] (1, R = mdea; 2, R = edea; and 3, R = bdea). Complex 1 crystallizes in the triclinic space group P1, whereas complex 3 crystallizes in the monoclinic space group C(2/c). Complex 1a has the same molecular structure as complex 1 but crystallizes in the monoclinic space group P2(1/n). Complex 3a has the same molecular structure as complex 3 but crystallizes in the triclinic space group P1. Variable-temperature magnetic susceptibility data collected for complexes 1, 2, and 3 indicate that antiferromagnetic exchange interactions are present. The spin ground states of complexes 1, 2, and 3 were determined by fitting variable-field magnetization data collected in the 2-5 K temperature range. Fitting of these data yielded the spin ground-state parameters of S = 8, g = 2.0, and D = -0.47 cm(-1) for complex 1; S = 8, g = 2.0, and D = -0.49 cm(-1) for complex 2; and S = 8, g = 2, and D = -0.37 cm(-1) for complex 3. The ac magnetic susceptibility data were measured for complexes 1, 2, and 3 at temperatures between 1.8 and 10 K with a 3 G ac field oscillating in the range 50-1000 Hz. Slow kinetics of magnetization reversal relative to the frequency of the oscillating ac field were observed as frequency-dependent out-of-phase peaks for complexes 1, 2, and 3, and it can be concluded that these three complexes are single-molecule magnets.

  2. Temperature and field induced strain measurements in single crystal Gd5Si2Ge2

    SciTech Connect

    McCall, S. K.; Nersessian, N.; Carman, G. P.; Pecharsky, V. K.; Schlagel, D. L.; Radousky, H. B.

    2016-03-29

    The first-order magneto-structural transformation that occurs in Gd5Si2Ge2 near room temperature makes it a strong candidate for many energy harvesting applications. Understanding the single crystal properties is crucial for allowing simulations of device performance. In this study, magnetically and thermally induced transformation strains were measured in a single crystal of Gd5Si2.05Ge1.95 as it transforms from a high-temperature monoclinic paramagnet to a lower-temperature orthorhombic ferromagnet. Thermally induced transformation strains of –8500 ppm, +960 ppm and +1800 ppm, and magnetically induced transformation strains of –8500 ppm, +900 ppm and +2300 ppm were measured along the a, b and c axes, respectively. Furthermore, using experimental data coupled with general thermodynamic considerations, a universal phase diagram was constructed showing the transition from the monoclinic to the orthorhombic phase as a function of temperature and magnetic field.

  3. Single grain analysis on a nanoscale in ZrO2:Al2O3 nano-composites by means of high-resolution scanning transmission electron Microscopy

    NASA Astrophysics Data System (ADS)

    Brossmann, Ulrich; Albu, Mihaela; Hofer, Ferdinand; Würschum, Roland

    2016-12-01

    Nano-particulate powders of Al2O3:ZrO2 composites and the pure constituents were prepared by microwave plasma process synthesis and studied by high resolution scanning transmission electron microscopy. The ZrO2:Al2O3 nanocomposite samples showed a structure of randomly arranged, crystalline grains of both ZrO2 and Al2O3 with a size in the range of 3-5 nm. For each constituent, both cubic and monoclinic grains were observed. Similarly prepared, single phase Al2O3 nanoparticles were found to be completely amorphous. In the case of ZrO2, the crystallite size and the fraction of the monoclinic ZrO2 phase is noticeably reduced in the ZrO2:Al2O3 nanocomposite in comparison to single phase samples. The observation of ultra-small crystalline Al2O3 in the composite samples, is tentatively ascribed to a modification of the interface energy by the contact of Al2O3 and ZrO2 as well as a possible uptake of ZrO2 into the Al2O3 grains from the gas phase during synthesis.

  4. Synthesis, growth and spectral, optical and thermal characterization studies on L-Tryptophan p-nitrophenol (LTPN) single crystals for NLO applications.

    PubMed

    Suresh, P; Janarthanan, S; Sugaraj Samuel, R; Jestin Lenus, A; Shanthi, C

    2015-01-25

    The novel nonlinear optical single crystal of L-Tryptophan p-nitrophenol (LTPN) has been successfully synthesized by taking the appropriate amount of L-Tryptophan and p-nitrophenol. The single crystals have been grown by slow evaporation solution growth technique. The single crystal XRD studies confirmed that the grown crystal belongs to the monoclinic system. The various functional groups presented in the crystal were confirmed by FT-IR and (1)H NMR spectroscopic studies. The absorptions of the grown crystals were analyzed using UV-Vis-NIR spectral studies. The thermal analysis was performed to study the thermal stability of the grown crystals. The second harmonic generation behavior of L-Tryptophan p-nitrophenol crystal was tested by Kurtz-Perry powder technique.

  5. High Pressure Single Crystal Diffraction at PX^2

    PubMed Central

    Zhang, Dongzhou; Dera, Przemyslaw K.; Eng, Peter J.; Stubbs, Joanne E.; Zhang, Jin S.; Prakapenka, Vitali B.; Rivers, Mark L.

    2017-01-01

    In this report we describe detailed procedures for carrying out single crystal X-ray diffraction experiments with a diamond anvil cell (DAC) at the GSECARS 13-BM-C beamline at the Advanced Photon Source. The DAC program at 13-BM-C is part of the Partnership for Extreme Xtallography (PX^2) project. BX-90 type DACs with conical-type diamond anvils and backing plates are recommended for these experiments. The sample chamber should be loaded with noble gas to maintain a hydrostatic pressure environment. The sample is aligned to the rotation center of the diffraction goniometer. The MARCCD area detector is calibrated with a powder diffraction pattern from LaB6. The sample diffraction peaks are analyzed with the ATREX software program, and are then indexed with the RSV software program. RSV is used to refine the UB matrix of the single crystal, and with this information and the peak prediction function, more diffraction peaks can be located. Representative single crystal diffraction data from an omphacite (Ca0.51Na0.48)(Mg0.44Al0.44Fe2+0.14Fe3+0.02)Si2O6 sample were collected. Analysis of the data gave a monoclinic lattice with P2/n space group at 0.35 GPa, and the lattice parameters were found to be: a = 9.496 ±0.006 Å, b = 8.761 ±0.004 Å, c = 5.248 ±0.001 Å, β = 105.06 ±0.03º, α = γ = 90º. PMID:28117811

  6. High Pressure Single Crystal Diffraction at PX^2.

    PubMed

    Zhang, Dongzhou; Dera, Przemyslaw K; Eng, Peter J; Stubbs, Joanne E; Zhang, Jin S; Prakapenka, Vitali B; Rivers, Mark L

    2017-01-16

    In this report we describe detailed procedures for carrying out single crystal X-ray diffraction experiments with a diamond anvil cell (DAC) at the GSECARS 13-BM-C beamline at the Advanced Photon Source. The DAC program at 13-BM-C is part of the Partnership for Extreme Xtallography (PX^2) project. BX-90 type DACs with conical-type diamond anvils and backing plates are recommended for these experiments. The sample chamber should be loaded with noble gas to maintain a hydrostatic pressure environment. The sample is aligned to the rotation center of the diffraction goniometer. The MARCCD area detector is calibrated with a powder diffraction pattern from LaB6. The sample diffraction peaks are analyzed with the ATREX software program, and are then indexed with the RSV software program. RSV is used to refine the UB matrix of the single crystal, and with this information and the peak prediction function, more diffraction peaks can be located. Representative single crystal diffraction data from an omphacite (Ca0.51Na0.48)(Mg0.44Al0.44Fe(2+)0.14Fe(3+)0.02)Si2O6 sample were collected. Analysis of the data gave a monoclinic lattice with P2/n space group at 0.35 GPa, and the lattice parameters were found to be: a = 9.496 ±0.006 Å, b = 8.761 ±0.004 Å, c = 5.248 ±0.001 Å, β = 105.06 ±0.03º, α = γ = 90º.

  7. Raman spectroscopy of single-domain multiferroic BiFeO3

    NASA Astrophysics Data System (ADS)

    Palai, R.; Schmid, H.; Scott, J. F.; Katiyar, R. S.

    2010-02-01

    We report the investigation of polarized Raman spectroscopy of multiferroic bismuth ferrite (BiFeO3) from 81-273 K, using a ferroelectric/ferroelastic single-domain crystal with an as-grown pseudocubic (pc) (100)pc -oriented surface, compared with (001)pc thin film, grown by pulsed laser deposition. The polarized Raman spectra of the single crystal taken at different crystallographic orientations agree with the rhombohedral crystal structure with C3v point group, whereas the (001)pc thin film shows monoclinic structure, contrary to the bulklike rhombohedral and tetragonal structures reported earlier, but consistent with the recent synchrotron radiation studies. Earlier Raman scattering measurements on single crystals violated theoretical predictions. This may be due to mechanical polishing, which allows forbidden E (LO) scattering [J. F. Scott, J. Chem. Phys. 48, 874 (1968); J. F. Scott, J. Chem. Phys.49, 98 (1968)]. All of the different phonon vibrations ( A1 and E modes) in the single crystal have unambiguously been assigned.

  8. Growth morphology of single-crystal grains obtained by directional crystallisation of an Al-Cu-Fe alloy

    NASA Astrophysics Data System (ADS)

    Surowiec, Marian; Bogdanowicz, Wlodzimierz; Krawczyk, Jacek; Formanek, Bolesław; Sozanska, Maria

    2011-07-01

    Quasicrystalline as well as crystalline faceted single grains of four phases were obtained during directional crystallisation of an Al-Cu-Fe alloy by the Bridgman technique. The monoclinic λ phase, Al13(Cu, Fe)4, dominating at high temperatures formed single-crystal lamellae 0.5 mm to 1 mm thick. A second type of attractive morphological form exhibiting flux dissolution terraces was observed on spherical single crystals of β phase Al(Fe, Cu). Rectangular, hexagonal and octagonal shaped dissolution terraces were revealed at the positions of two-, three- and four-fold symmetry axes, respectively. A single quasicrystalline ψ phase, Al6Cu2Fe, exhibited icosahedral symmetry with growth forms of a dodecahedron with pentagonal facets. The flux dissolution of the β phase apparently plays an essential role in a peritectic reaction leading to quasicrystalline ψ phase formation. Polygonal single grains of ω phase Al7Cu2Fe exhibiting tetragonal symmetry formed the fourth type of thermodynamically stable growth forms. Single grains of the ω phase crystallised in the form of pellets with an octagonal cross-section. The growth morphology of the stable phases was investigated by scanning electron microscopy. The chemical composition of the growth forms described was confirmed by X-ray microanalysis using a scanning electron microscope, whereas the phase composition was determined using electron selected area diffraction and X-ray powder diffraction.

  9. The temperature-dependent single-crystal Raman spectroscopy of a model dipeptide: L-Alanyl-L-alanine

    NASA Astrophysics Data System (ADS)

    Silva, J. G.; Arruda, L. M.; Pinheiro, G. S.; Lima, C. L.; Melo, F. E. A.; Ayala, A. P.; Filho, J. Mendes; Freire, P. T. C.

    2015-09-01

    A single-crystal of peptide L-alanyl-L-alanine (C6H12N2O3) was studied by Raman spectroscopy at low-temperature, and a tentative assignment of the normal modes was given. Evidence of a second order structural phase transition was found through Raman spectroscopy between the temperatures of 80 K and 60 K. Group theory considerations suggest that the transition leads the sample from the tetragonal to a monoclinic structure. Additionally, our study suggests that the mechanism for the structural phase transition is governed by the occupation of non-equivalent C1 local symmetry sites by the CH3 molecular groups. Analysis based on group theory suggests L-alanyl-L-alanine presents C2 symmetry at low temperatures.

  10. The temperature-dependent single-crystal Raman spectroscopy of a model dipeptide: L-Alanyl-L-alanine.

    PubMed

    Silva, J G; Arruda, L M; Pinheiro, G S; Lima, C L; Melo, F E A; Ayala, A P; Filho, J Mendes; Freire, P T C

    2015-09-05

    A single-crystal of peptide L-alanyl-L-alanine (C6H12N2O3) was studied by Raman spectroscopy at low-temperature, and a tentative assignment of the normal modes was given. Evidence of a second order structural phase transition was found through Raman spectroscopy between the temperatures of 80K and 60K. Group theory considerations suggest that the transition leads the sample from the tetragonal to a monoclinic structure. Additionally, our study suggests that the mechanism for the structural phase transition is governed by the occupation of non-equivalent C1 local symmetry sites by the CH3 molecular groups. Analysis based on group theory suggests L-alanyl-L-alanine presents C2 symmetry at low temperatures.

  11. Single Custodial Fathers.

    ERIC Educational Resources Information Center

    Hanson, Shirley May Harmon

    This paper reviews literature from the past 10 years about single fathers. Statistics are presented to show the number of single fathers, their race, socioeconomic status, religion, age, and employment. Other issues discussed include an analysis of single fathers' parenting and homemaking skills, their motivation for custody, and visiting and…

  12. Single-Sex Classrooms

    ERIC Educational Resources Information Center

    Protheroe, Nancy

    2009-01-01

    Although single-sex education was once the norm in the U.S., the practice has largely been confined to private schools for more than a century. However, with the introduction of the final version of the U.S. Department of Education's so-called single-sex regulations in 2006, public schools were allowed greater flexibility to offer single-sex…

  13. Spectroscopy and kinetics of the population of monoclinic KYb{sub 0.5}Y{sub 0.43}Tm{sub 0.07}(WO{sub 4}){sub 2} crystals pumped by a pulsed Nd:YAG laser

    SciTech Connect

    Vatnik, S M; Maiorov, A P; Plakushchev, D V; Pavlyuk, A A

    2001-01-31

    The kinetics of pump radiation absorption and luminescence of monoclinic crystals of potassium-yttrium-ytterbium tungstate doped with thulium are studied. It is shown theoretically and experimentally that due to the 'excitation multiplication' caused by absorption of pump radiation from metastable states of thulium ions accompanied by cross-relaxation, above 50 % of a total number of thulium ions can occupy the {sup 3}F{sub 4} level. The cross sections of stimulated transitions in the spectral region from 1600 to 2100 nm are calculated from luminescence spectra, and the gain in the crystal is estimated. The prospects of practical applications of the results obtained in the paper are discussed. (active media)

  14. Electric field induced monoclinic phase stability in Ca doped Na0.5Bi0.5TiO3: Case of 0.93Na0.5Bi0.5 TiO3 - 0.07CaTiO3 ferroelectric ceramics

    NASA Astrophysics Data System (ADS)

    Roukos, Roy; Geoffroy, Nicolas; Chaumont, Denis

    2017-01-01

    The ferroelectric perovskite complex 0.93Na0.5Bi0.5TiO3 - 0.07CaTiO3 (NBT -0.07CT) ceramics were studied by a simple X-ray diffraction upon application of an increasing electric field. It is shown that the field induced rhombohedral (R3c) to monoclinic (Cc) phase transition at room temperature. This induced phase is stable after removal the electric field. Our results has been interpreted by intrinsic polarization rotation theory, in comparison with Pb-base system such as PMT-PT, PZN-PT, …near the morphotropic phase boundary (MPB) region. Apparently, the NBT - 0.07CT pretends to have a ferroelectric and structural instability around room temperature.

  15. Studies on 2-amino-5-nitropyridinium nitrate (2A5NPN): A semi-organic third order nonlinear optical single crystal

    SciTech Connect

    Sivasubramani, V.; Pandian, Muthu Senthil Ramasamy, P.

    2016-05-23

    2-amino-5-nitropyridinium nitrate (2A5NPN) is a semi-organic nonlinear optical crystal and optically good quality 2A5NPN single crystals were successfully grown by slow evaporation solution growth technique (SEST) at ambient temperature. The crystallographic structure of the grown crystal was determined by single crystal X-Ray diffraction analysis and it belongs to Monoclinic crystal system with centro symmetric crystalline nature. The crystallinity of the grown crystal was confirmed by powder X-ray diffraction analysis. The other physical properties of grown crystals are also characterized using TG-DTA, UV-Visible NIR, chemical etching, photoconductivity and Z-scan measurements. The Z-scan method reveals that the 2A5NPN crystal possesses multi photon absorption behaviour and the significantly higher third order susceptibility and it is a promising potential NLO material.

  16. Bulk Crystallization in a SiO2/Al2O3/Y2O3/AlF3/B2O3/Na2O Glass: Fivefold Pseudo Symmetry due to Monoclinic Growth in a Glassy Matrix Containing Growth Barriers

    PubMed Central

    Wisniewski, Wolfgang; Seyring, Martin; Patzig, Christian; Höche, Thomas; Keshavarzi, Ashkan; Rüssel, Christian

    2016-01-01

    A glass with the mol% composition 17 Y2O3·33 Al2O3·40 SiO2·2 AlF3·3 Na2O·2 CeF3·3 B2O3 is heat treated at 1000 °C for 6–24 h. This results in the surface nucleation and growth of YAG. Nucleation and growth of star-shaped alumina and later of monoclinic β-Y2Si2O7 and orthorhombic δ-Y2Si2O7 are additionally observed in the bulk. Phase identification and localization are performed by electron backscatter diffraction (EBSD) as well as TEM analysis. The monoclinic β-Y2Si2O7 observed in the bulk occurs in the form of large, crystal agglomerates which range from 50 to 120 μm in size. The individual crystals are aligned along the c-axis which is the fastest growing axis. Ten probability maxima are observed in the pole-figures illustrating the rotation of orientations around the c-axes indicating a fivefold symmetry. This symmetry is caused by multiple twinning which results in a high probability of specific orientation relationships with rotation angles of ~36°, ~108° (also referred to as the pentagon angle) and ~144° around the c-axis. All these rotation angles are close to the multiples of 36° which are required for an ideal fivefold symmetry. This is the first report of a fivefold symmetry triggered by the presence of barriers hindering crystal growth. PMID:26813152

  17. Fergusonite-type CeNbO4+δ: Single crystal growth, symmetry revision and conductivity

    NASA Astrophysics Data System (ADS)

    Bayliss, Ryan D.; Pramana, Stevin S.; An, Tao; Wei, Fengxia; Kloc, Christian L.; White, Andrew J. P.; Skinner, Stephen J.; White, Timothy J.; Baikie, Tom

    2013-08-01

    Large fergusonite-type (ABO4, A=Ce, B=Nb) oxide crystals, a prototype electrolyte composition for solid oxide fuel cells (SOFC), were prepared for the first time in a floating zone mirror furnace under air or argon atmospheres. While CeNbO4 grown in air contained CeNbO4.08 as a minor impurity that compromised structural analysis, the argon atmosphere yielded a single phase crystal of monoclinic CeNbO4, as confirmed by selected area electron diffraction, powder and single crystal X-ray diffraction. The structure was determined in the standard space group setting C12/c1 (No. 15), rather than the commonly adopted I12/a1. AC impedance spectroscopy conducted under argon found that stoichiometric CeNbO4 single crystals showed lower conductivity compared to CeNbO4+δ confirming interstitial oxygen can penetrate through fergusonite and is responsible for the higher conductivity associated with these oxides.

  18. Antimony oxofluorides - a synthesis concept that yields phase pure samples and single crystals.

    PubMed

    Ali, Sk Imran; Johnsson, Mats

    2016-07-26

    The single crystals of the new isostructural compounds Sb3O4F and Y0.5Sb2.5O4F and the two previously known compounds M-SbOF and α-Sb3O2F5 were successfully grown by a hydrothermal technique at 230 °C. The new compound Sb3O4F crystallizes in the monoclinic space group P21/c; a = 5.6107(5) Å, b = 4.6847(5) Å, c = 20.2256(18) Å, β = 94.145(8)°, z = 4. The replacing part of Sb with Y means a slight increase in the unit cell dimensions. The compounds M-SbOF and α-Sb3O2F5 have not been grown as single crystals before and it can be concluded that hydrothermal synthesis has proved to be a suitable technique for growing single crystals of antimony oxofluorides because of the relatively low solubility of such compounds compared to other antimony oxohalides that most often have been synthesised at high temperatures by solid state reactions or gas-solid reactions.

  19. SINGLE: single photon sensitive cryogenic light detectors

    NASA Astrophysics Data System (ADS)

    Biassoni, Matteo; SINGLE Collaboration

    2017-09-01

    Thermal detectors operated at few mK as calorimeters are a powerful tool for the study of rare particle physics processes. In order to implement particle identification, light detection can be effectively performed by means of other thermal detectors operated as light sensors. This configuration can be used also in large scale, thousand-channels setups, but the light sensors must be sensitive enough to detect few, possibly a single, photons. The SINGLE project described here aims at producing silicon based, large area devices that can be operated as thermal detectors with single-photon sensitivity, and demonstrate the reliability of the performance, scalability of the production process and integrability with present and next generation cryogenic experiments for the search for rare events.

  20. Living with a Single Parent

    MedlinePlus

    ... Video: Getting an X-ray Living With a Single Parent KidsHealth > For Kids > Living With a Single Parent ... single parents can be a great idea, too. Single Parents and Work Single parents are often working parents ...

  1. Living with a Single Parent

    MedlinePlus

    ... Happens in the Operating Room? Living With a Single Parent KidsHealth > For Kids > Living With a Single Parent ... single parents can be a great idea, too. Single Parents and Work Single parents are often working parents ...

  2. Single molecule and single cell epigenomics.

    PubMed

    Hyun, Byung-Ryool; McElwee, John L; Soloway, Paul D

    2015-01-15

    Dynamically regulated changes in chromatin states are vital for normal development and can produce disease when they go awry. Accordingly, much effort has been devoted to characterizing these states under normal and pathological conditions. Chromatin immunoprecipitation followed by sequencing (ChIP-seq) is the most widely used method to characterize where in the genome transcription factors, modified histones, modified nucleotides and chromatin binding proteins are found; bisulfite sequencing (BS-seq) and its variants are commonly used to characterize the locations of DNA modifications. Though very powerful, these methods are not without limitations. Notably, they are best at characterizing one chromatin feature at a time, yet chromatin features arise and function in combination. Investigators commonly superimpose separate ChIP-seq or BS-seq datasets, and then infer where chromatin features are found together. While these inferences might be correct, they can be misleading when the chromatin source has distinct cell types, or when a given cell type exhibits any cell to cell variation in chromatin state. These ambiguities can be eliminated by robust methods that directly characterize the existence and genomic locations of combinations of chromatin features in very small inputs of cells or ideally, single cells. Here we review single molecule epigenomic methods under development to overcome these limitations, the technical challenges associated with single molecule methods and their potential application to single cells. Copyright © 2014 Elsevier Inc. All rights reserved.

  3. Single Molecule and Single Cell Epigenomics

    PubMed Central

    Hyun, Byung-Ryool; McElwee, John L.; Soloway, Paul D.

    2014-01-01

    Dynamically regulated changes in chromatin states are vital for normal development and can produce disease when they go awry. Accordingly, much effort has been devoted to characterizing these states under normal and pathological conditions. Chromatin immunoprecipitation followed by sequencing (ChIP-seq) is the most widely used method to characterize where in the genome transcription factors, modified histones, modified nucleotides and chromatin binding proteins are found; bisulfite sequencing (BS-seq) and its variants are commonly used to characterize the locations of DNA modifications. Though very powerful, these methods are not without limitations. Notably, they are best at characterizing one chromatin feature at a time, yet chromatin features arise and function in combination. Investigators commonly superimpose separate ChIP-seq or BS-seq datasets, and then infer where chromatin features are found together. While these inferences might be correct, they can be misleading when the chromatin source has distinct cell types, or when a given cell type exhibits any cell to cell variation in chromatin state. These ambiguities can be eliminated by robust methods that directly characterize the existence and genomic locations of combinations of chromatin features in very small inputs of cells or ideally, single cells. Here we review single molecule epigenomic methods under development to overcome these limitations, the technical challenges associated with single molecule methods and their potential application to single cells. PMID:25204781

  4. Single photon quantum cryptography.

    PubMed

    Beveratos, Alexios; Brouri, Rosa; Gacoin, Thierry; Villing, André; Poizat, Jean-Philippe; Grangier, Philippe

    2002-10-28

    We report the full implementation of a quantum cryptography protocol using a stream of single photon pulses generated by a stable and efficient source operating at room temperature. The single photon pulses are emitted on demand by a single nitrogen-vacancy color center in a diamond nanocrystal. The quantum bit error rate is less that 4.6% and the secure bit rate is 7700 bits/s. The overall performances of our system reaches a domain where single photons have a measurable advantage over an equivalent system based on attenuated light pulses.

  5. Single ventricle cardiac defect.

    PubMed

    Eren, Bulent; Turkmen, Nursel; Turkmen, Nurset; Fedakar, Recep; Senel, Berna; Cetin, Volkan; Cetin, Volkn

    2010-05-01

    Single ventricle heart is defined as a rare cardiac abnormality with a single ventricle chamber involving diverse functional and physiological defects. Our case is of a ten month-old baby boy who died shortly after admission to the hospital due to vomiting and diarrhoea. Autopsy findings revealed cyanosis of finger nails and ears. Internal examination revealed; large heart, weighing 60 grams, single ventricle, without a septum and upper membranous part. Single ventricle is a rare pathology, hence, this paper aims to discuss this case from a medico-legal point of view.

  6. Single Umbilical Artery

    PubMed Central

    Cairns, J. David; McKee, James

    1964-01-01

    A prospective study of 2000 obstetrical deliveries was undertaken to establish the incidence of single umbilical artery in the newborn and the frequency of congenital malformations reported to be associated with this disorder. Twenty cases of single umbilical artery were discovered; two proved to have an associated congenital malformation. In neither of these cases was medical management affected by the discovery of a single artery. In addition, the vascular arrangement in the cords of 31 concurrently occurring congenitally malformed babies was examined, and in no instance was a single umbilical artery found. PMID:14214230

  7. Understanding Single Adulthood.

    ERIC Educational Resources Information Center

    Stein, Peter J.

    The life styles and life chances of the unmarried include elements of choices. Singles may be grouped and characterized according to whether their status may be considered stable or temporary. A life cycle, or continuum model of singlehood is reviewed, including its different factors, or phases. A new model for singles is proposed--a life spiral…

  8. Single Mothers "Do" Family

    ERIC Educational Resources Information Center

    Nelson, Margaret K.

    2006-01-01

    This paper explores how single mothers both incorporate others into family life (e.g., when they ask others to care for their children) and simultaneously "do families" in a manner that holds out a vision of a "traditional" family structure. Drawing on research with White, rural single mothers, the author explores the manner in which these women…

  9. Moving Single Atoms

    NASA Astrophysics Data System (ADS)

    Stuart, Dustin

    2016-05-01

    Single neutral atoms are promising candidates for qubits, the fundamental unit of quantum information. We have built a set of optical tweezers for trapping and moving single Rubidium atoms. The tweezers are based on a far off-resonant dipole trapping laser focussed to a 1 μm spot with a single aspheric lens. We use a digital micromirror device (DMD) to generate dynamic holograms of the desired arrangement of traps. The DMD has a frame rate of 20 kHz which, when combined with fast algorithms, allows for rapid reconfiguration of the traps. We demonstrate trapping of up to 20 atoms in arbitrary arrangements, and the transport of a single-atom over a distance of 14 μm with continuous laser cooling, and 5 μm without. In the meantime, we are developing high-finesse fibre-tip cavities, which we plan to use to couple pairs of single atoms to form a quantum network.

  10. Single Nanoparticle Plasmonic Sensors

    PubMed Central

    Sriram, Manish; Zong, Kelly; Vivekchand, S. R. C.; Gooding, J. Justin

    2015-01-01

    The adoption of plasmonic nanomaterials in optical sensors, coupled with the advances in detection techniques, has opened the way for biosensing with single plasmonic particles. Single nanoparticle sensors offer the potential to analyse biochemical interactions at a single-molecule level, thereby allowing us to capture even more information than ensemble measurements. We introduce the concepts behind single nanoparticle sensing and how the localised surface plasmon resonances of these nanoparticles are dependent upon their materials, shape and size. Then we outline the different synthetic approaches, like citrate reduction, seed-mediated and seedless growth, that enable the synthesis of gold and silver nanospheres, nanorods, nanostars, nanoprisms and other nanostructures with tunable sizes. Further, we go into the aspects related to purification and functionalisation of nanoparticles, prior to the fabrication of sensing surfaces. Finally, the recent developments in single nanoparticle detection, spectroscopy and sensing applications are discussed. PMID:26473866

  11. Crystal growth, structural, thermal and mechanical behavior of L-arginine 4-nitrophenolate 4-nitrophenol dihydrate (LAPP) single crystals

    NASA Astrophysics Data System (ADS)

    Mahadevan, M.; Ramachandran, K.; Anandan, P.; Arivanandhan, M.; Bhagavannarayana, G.; Hayakawa, Y.

    2014-12-01

    Single crystals of L-arginine 4-nitrophenolate 4-nitrophenol dihydrate (LAPP) have been grown successfully from the solution of L-arginine and 4-nitrophenol. Slow evaporation of solvent technique was adopted to grow the bulk single crystals. Single crystal X-ray diffraction analysis confirms the grown crystal has monoclinic crystal system with space group of P21. Powder X-ray diffraction analysis shows the good crystalline nature. The crystalline perfection of the grown single crystals was analyzed by HRXRD by employing a multicrystal X-ray diffractometer. The functional groups were identified from proton NMR spectroscopic analysis. Linear and nonlinear optical properties were determined by UV-Vis spectrophotometer and Kurtz powder technique respectively. It is found that the grown crystal has no absorption in the green wavelength region and the SHG efficiency was found to be 2.66 times that of the standard KDP. The Thermal stability of the crystal was found by obtaining TG/DTA curve. The mechanical behavior of the grown crystal has been studied by Vicker's microhardness method.

  12. Growth, structural and characterization of a novel third order nonlinear optical Benzimidazolium Maleate single crystal

    NASA Astrophysics Data System (ADS)

    Amudha, M.; Muthu, S.; Gunasekaran, B.; Praveen Kumar, P.

    2017-10-01

    Good optical quality single crystals of Benzimidazolium Maleate (BML), a new organic charge transfer molecular complex salt, were grown successfully by the slow evaporation solution growth technique using deionised water as solvent at room temperature. The grown crystals of BML were characterised by single crystal X-ray diffraction (XRD) and powder XRD which confirm that the crystal belongs to monoclinic system with the centrosymmetric space group P21/n. The presence of functional groups in the grown crystal was confirmed by Fourier transform infrared spectral analysis. The BML crystal is thermally stable up to 147.7 °C and it is found by TG-DTA analysis. The transparency of the crystal was identified using UV-Vis spectrophotometer. Vickers microhardness analysis shows the mechanical stability of the grown crystal. The dependence of dielectric properties with frequency and temperature were also studied. Nonlinear optical absorption coefficient determined from open aperture Z-scan analysis revealed that the BML crystal can serve as a promising candidate for optical limiting applications.

  13. Synthesis, growth, optical and mechanical studies of ferroelectric urea-oxalic acid single crystals

    NASA Astrophysics Data System (ADS)

    Vizhi, R. Ezhil; Dhivya, R.; Babu, D. Rajan

    2016-10-01

    A single crystal of urea oxalic acid was grown by slow evaporation method. The lattice parameters are a=5.13 Å, b=12.48 Å, c=7.07 Å, β=98.13° with V=448.5 Å3 which belongs to monoclinic system with space group P21/c obtained from single crystal X-ray diffraction analysis. UV-visible spectrum was recorded from the wavelength region of 200-800 nm and its cutoff wavelength was found to be 270 nm. Optical energy band gap of 4.57 eV was determined using Tau's plot relation. Fourier transform infrared vibrational spectrum confirmed the presence of N-H asymmetric stretching which occurs at 3444 cm-1 and 1853 cm-1 arising due to the amide C=O symmetric stretching. The emission was observed at 364 nm from the photoluminescence spectrum. The mechanical stability of the grown crystal was estimated by Vickers microhardness studies and it is evident that the grown crystal belongs to soft material category. Hardness related parameters such as elastic stiffness constant, fracture mechanics, brittleness index and yield strength were also evaluated. The dielectric constant and dielectric loss of the grown crystal were carried out as a function of frequency for different temperatures.

  14. Single mode communication link

    NASA Astrophysics Data System (ADS)

    Cole, Stephen R.; Reid, D. C.; Carpenter, R.

    1990-02-01

    Optical fiber transmission has many features which make it very attractive for military applications. Furthermore, single mode fiber is superior to multimode fiber in terms of bandwidth, attenuation, radiation resistance and cost. The benefits of single mode optical fiber transmission can be further enhanced with the use of wavelength division multiplexing (WDM) technology in which multiple, independent optical signals may be simultaneously transmitted over a single fiber. This permits single fiber transmission of mixed signal traffic (e.g., digital data, voice, video, analog, etc.) as well as parallel digital traffic characteristic of computer data transfer. In addition, this technology creates new system design options and architectural flexibility for local area networks (LANs). This technical report describes the design and development of the critical element for implementing such a communications link - a 16 channel single mode WDM. Specifically, it describes the development and performance of a grating-based single mode WDM system suitable for use with single longitudinal lasers (e.g., distributed feedback lasers (DFB's)). The 16 channel WDM features channels with 3 dB bandwidths of 2.4 nM and separation of 7.2 nM. Any particular channel can be set to a precise wavelength due to the mechanical design features. End-to-End system channel insertion losses of 12.5 dB have been achieved with adjacent channel crosstalk of better than -25 dB.

  15. Single Electron Tunneling

    SciTech Connect

    Ruggiero, Steven T.

    2005-07-25

    Financial support for this project has led to advances in the science of single-electron phenomena. Our group reported the first observation of the so-called ''Coulomb Staircase'', which was produced by tunneling into ultra-small metal particles. This work showed well-defined tunneling voltage steps of width e/C and height e/RC, demonstrating tunneling quantized on the single-electron level. This work was published in a now well-cited Physical Review Letter. Single-electron physics is now a major sub-field of condensed-matter physics, and fundamental work in the area continues to be conducted by tunneling in ultra-small metal particles. In addition, there are now single-electron transistors that add a controlling gate to modulate the charge on ultra-small photolithographically defined capacitive elements. Single-electron transistors are now at the heart of at least one experimental quantum-computer element, and single-electron transistor pumps may soon be used to define fundamental quantities such as the farad (capacitance) and the ampere (current). Novel computer technology based on single-electron quantum dots is also being developed. In related work, our group played the leading role in the explanation of experimental results observed during the initial phases of tunneling experiments with the high-temperature superconductors. When so-called ''multiple-gap'' tunneling was reported, the phenomenon was correctly identified by our group as single-electron tunneling in small grains in the material. The main focus throughout this project has been to explore single electron phenomena both in traditional tunneling formats of the type metal/insulator/particles/insulator/metal and using scanning tunneling microscopy to probe few-particle systems. This has been done under varying conditions of temperature, applied magnetic field, and with different materials systems. These have included metals, semi-metals, and superconductors. Amongst a number of results, we have

  16. [Single-patient rooms].

    PubMed

    Jensen, Elisabeth Brøgger

    2009-05-18

    The Danish government has allocated funding to achieve the goal of replacing 50% of all existing hospital buildings by new facilities. Facing such a building boom, the debate for and against single-patient rooms is in progress. A review of the literature shows that single-patient rooms have a direct impact on patient safety. Patient Safety Leadership Walkrounds and failure modes and effects analysis can be used for identifying risks before designing single rooms in future hospitals. The acuity adaptability model needs to be revised.

  17. Single Beam Holography.

    ERIC Educational Resources Information Center

    Chen, Hsuan; Ruterbusch, Paul H.

    1979-01-01

    Discusses how holography can be used as part of undergraduate physics laboratories. The authors propose a single beam technique of holography, which will reduce the recording scheme as well as relax the isolation requirements. (HM)

  18. Single-cell nanosurgery.

    PubMed

    Zeigler, Maxwell B; Chiu, Daniel T

    2013-01-01

    This chapter explains the steps necessary to perform laser surgery upon single adherent mammalian cells, where individual organelles are extracted from the cells by optical tweezers and the cells are monitored post-surgery to check their viability. Single-cell laser nanosurgery is used in an increasing range of methodologies because it offers great flexibility. Its main advantages are (a) there is not any physical contact with the cells so they remain in a sterile environment, (b) high spatial selectivity so that single organelles can be extracted from specific areas of individual cells, (c) the method can be conducted in the cell's native media, and (d) in comparison to other techniques that target single cells, such as micromanipulators, laser nanosurgery has a comparatively high throughput.

  19. Single molecule electronic devices.

    PubMed

    Song, Hyunwook; Reed, Mark A; Lee, Takhee

    2011-04-12

    Single molecule electronic devices in which individual molecules are utilized as active electronic components constitute a promising approach for the ultimate miniaturization and integration of electronic devices in nanotechnology through the bottom-up strategy. Thus, the ability to understand, control, and exploit charge transport at the level of single molecules has become a long-standing desire of scientists and engineers from different disciplines for various potential device applications. Indeed, a study on charge transport through single molecules attached to metallic electrodes is a very challenging task, but rapid advances have been made in recent years. This review article focuses on experimental aspects of electronic devices made with single molecules, with a primary focus on the characterization and manipulation of charge transport in this regime. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Single-photon sources

    NASA Astrophysics Data System (ADS)

    Lounis, Brahim; Orrit, Michel

    2005-05-01

    The concept of the photon, central to Einstein's explanation of the photoelectric effect, is exactly 100 years old. Yet, while photons have been detected individually for more than 50 years, devices producing individual photons on demand have only appeared in the last few years. New concepts for single-photon sources, or 'photon guns', have originated from recent progress in the optical detection, characterization and manipulation of single quantum objects. Single emitters usually deliver photons one at a time. This so-called antibunching of emitted photons can arise from various mechanisms, but ensures that the probability of obtaining two or more photons at the same time remains negligible. We briefly recall basic concepts in quantum optics and discuss potential applications of single-photon states to optical processing of quantum information: cryptography, computing and communication. A photon gun's properties are significantly improved by coupling it to a resonant cavity mode, either in the Purcell or strong-coupling regimes. We briefly recall early production of single photons with atomic beams, and the operation principles of macroscopic parametric sources, which are used in an overwhelming majority of quantum-optical experiments. We then review the photophysical and spectroscopic properties and compare the advantages and weaknesses of various single nanometre-scale objects used as single-photon sources: atoms or ions in the gas phase and, in condensed matter, organic molecules, defect centres, semiconductor nanocrystals and heterostructures. As new generations of sources are developed, coupling to cavities and nano-fabrication techniques lead to improved characteristics, delivery rates and spectral ranges. Judging from the brisk pace of recent progress, we expect single photons to soon proceed from demonstrations to applications and to bring with them the first practical uses of quantum information.

  1. Crystal Structures of Ca-Free Pb 2Sr 2RCu 3O 8 ( R = La, Pr, Nd, Eu, Tb, and Dy) Single Crystals

    NASA Astrophysics Data System (ADS)

    Xue, J. S.; Greedan, J. E.; Maric, M.

    1993-02-01

    Structures of Pb2Sr2RCu3O8 have been determined by single crystal X-ray diffraction. A monoclinic symmetry (C2/m, Z = 2) was found for those crystals with R = Pr, Nd, and Tb, orthorhombic (Cmmm, Z = 2) for R = La, and tetragonal (P4/mmm, Z = 1) for R = Eu and Dy. The relationship among different crystal symmetries can be understood in terms of different oxygen orderings in the PbO layers driven by the Ph2+ lone pair orientation. There is evidence for a ∼ 9% deficiency in electron density at the R = Eu and Dy sites (and ∼ 4.5% for R = Tb) which has been confirmed by mass spectroscopy as being due to cation vacancies at these sites. Bond valence sum calculations have been performed to evaluate the strains existing in the crystal structures of Pb2Sr2RCu3O8.

  2. Synthesis, spectral, thermal, X-ray single crystal of new RuCl₂(dppb)diamine complexes and their application in hydrogenation of Cinnamic aldehyde.

    PubMed

    Warad, Ismail; Al-Hussain, Hanan; Al-Far, Rawhi; Mahfouz, Refaat; Hammouti, Belkheir; Hadda, Taibi Ben

    2012-09-01

    The preparation of new three trans-[RuCl(2)(dppb)(N-N)] with mixed diamine (N-N) and 1,4-bis-(diphenylphosphino)butane (dppb) ligands, starting from RuCl(2)(PPh(3))(3) as precursor is presented. The complexes are characterized on the basis of elemental analysis, IR, (1)H, (13)C and (31)P{(1)H}NMR, FAB-MS, TG/DTA and single crystal X-ray diffraction studies. Complex (2L(1)) crystallizes in the monoclinic unit cells with the space group P2(1). The catalysts are evaluated for their Cinnamic aldehyde hydrogenation. The catalysts show excellent activity and selectivity for the unsaturated carbonyl compound under mild conditions. Copyright © 2012 Elsevier B.V. All rights reserved.

  3. Synthesis, spectral, thermal, X-ray single crystal of new RuCl2(dppb)diamine complexes and their application in hydrogenation of Cinnamic aldehyde

    NASA Astrophysics Data System (ADS)

    Warad, Ismail; Al-Hussain, Hanan; Al-Far, Rawhi; Mahfouz, Refaat; Hammouti, Belkheir; Hadda, Taibi Ben

    The preparation of new three trans-[RuCl2(dppb)(N-N)] with mixed diamine (N-N) and 1,4-bis-(diphenylphosphino)butane (dppb) ligands, starting from RuCl2(PPh3)3 as precursor is presented. The complexes are characterized on the basis of elemental analysis, IR, 1H, 13C and 31P{1H}NMR, FAB-MS, TG/DTA and single crystal X-ray diffraction studies. Complex (2L1) crystallizes in the monoclinic unit cells with the space group P21. The catalysts are evaluated for their Cinnamic aldehyde hydrogenation. The catalysts show excellent activity and selectivity for the unsaturated carbonyl compound under mild conditions.

  4. Temperature-dependent thermal conductivity and diffusivity of a Mg-doped insulating β-Ga2O3 single crystal along [100], [010] and [001

    NASA Astrophysics Data System (ADS)

    Handwerg, M.; Mitdank, R.; Galazka, Z.; Fischer, S. F.

    2016-12-01

    The monoclinic crystal structure of β-{{Ga}}2{{{O}}}3 leads to significant anisotropy of the thermal properties. The 2ω-method is used to measure the thermal diffusivity D in [010] and [001] direction respectively and to determine the thermal conductivity values λ of the [100], [010] and [001] direction from the same insulating Mg-doped β-{{Ga}}2{{{O}}}3 single crystal. We detect a temperature independent anisotropy factor of both the thermal diffusivity and conductivity values of {D}[010]/{D}[001]={λ }[010]/{λ }[001]=1.4+/- 0.1. The temperature dependence is in accord with phonon-phonon-Umklapp-scattering processes from 300 K down to 150 K. Below 150 K point-defect-scattering lowers the estimated phonon-phonon-Umklapp-scattering values.

  5. Bismuth(III) dialkyldithiophosphates: Facile single source precursors for the preparation of bismuth sulfide nanorods and bismuth phosphate thin films

    SciTech Connect

    Biswal, Jasmine B.; Garje, Shivram S.; Nuwad, Jitendra; Pillai, C.G.S.

    2013-08-15

    Two different phase pure materials (Bi{sub 2}S{sub 3} and Bi{sub 2}P{sub 4}O{sub 13}) have been prepared under different conditions using the same single source precursors. Solvothermal decomposition of the complexes, Bi(S{sub 2}P(OR){sub 2}){sub 3} [where, R=Methyl (Me) (1), Ethyl (Et) (2), n-Propyl (Pr{sup n}) (3) and iso-Propyl (Pr{sup i}) (4)] in ethylene glycol gave orthorhombic bismuth sulfide nanorods, whereas aerosol assisted chemical vapor deposition (AACVD) of the same precursors deposited monoclinic bismuth tetraphosphate (Bi{sub 2}P{sub 4}O{sub 13}) thin films on glass substrates. Surface study of the thin films using SEM illustrated the formation of variety of nanoscale morphologies (spherical-, wire-, pendent-, doughnut- and flower-like) at different temperatures. AFM studies were carried out to evaluate quality of the films in terms of uniformity and roughness. Thin films of average roughness as low as 1.4 nm were deposited using these precursors. Photoluminescence studies of Bi{sub 2}P{sub 4}O{sub 13} thin films were also carried out. - Graphical abstract: Solvothermal decomposition of bismuth(III) dialkyldithiophosphates in ethylene glycol gave Bi{sub 2}S{sub 3} nanoparticles, whereas aerosol assisted chemical vapor deposition of these single source precursors deposited Bi{sub 2}P{sub 4}O{sub 13} thin films. Display Omitted - Highlights: • Preparation of phase pure orthorhombic Bi{sub 2}S{sub 3} nanorods and monoclinic Bi{sub 2}P{sub 4}O{sub 13} thin films. • Use of single source precursors for deposition of bismuth phosphate thin films. • Use of solvothermal decomposition and AACVD methods. • Morphology controlled synthesis of Bi{sub 2}P{sub 4}O{sub 13} thin films. • Bi{sub 2}S{sub 3} nanorods and Bi{sub 2}P{sub 4}O{sub 13} thin films using same single source precursors.

  6. Single spin magnetic resonance

    NASA Astrophysics Data System (ADS)

    Wrachtrup, Jörg; Finkler, Amit

    2016-08-01

    Different approaches have improved the sensitivity of either electron or nuclear magnetic resonance to the single spin level. For optical detection it has essentially become routine to observe a single electron spin or nuclear spin. Typically, the systems in use are carefully designed to allow for single spin detection and manipulation, and of those systems, diamond spin defects rank very high, being so robust that they can be addressed, read out and coherently controlled even under ambient conditions and in a versatile set of nanostructures. This renders them as a new type of sensor, which has been shown to detect single electron and nuclear spins among other quantities like force, pressure and temperature. Adapting pulse sequences from classic NMR and EPR, and combined with high resolution optical microscopy, proximity to the target sample and nanoscale size, the diamond sensors have the potential to constitute a new class of magnetic resonance detectors with single spin sensitivity. As diamond sensors can be operated under ambient conditions, they offer potential application across a multitude of disciplines. Here we review the different existing techniques for magnetic resonance, with a focus on diamond defect spin sensors, showing their potential as versatile sensors for ultra-sensitive magnetic resonance with nanoscale spatial resolution.

  7. Single spin magnetic resonance.

    PubMed

    Wrachtrup, Jörg; Finkler, Amit

    2016-08-01

    Different approaches have improved the sensitivity of either electron or nuclear magnetic resonance to the single spin level. For optical detection it has essentially become routine to observe a single electron spin or nuclear spin. Typically, the systems in use are carefully designed to allow for single spin detection and manipulation, and of those systems, diamond spin defects rank very high, being so robust that they can be addressed, read out and coherently controlled even under ambient conditions and in a versatile set of nanostructures. This renders them as a new type of sensor, which has been shown to detect single electron and nuclear spins among other quantities like force, pressure and temperature. Adapting pulse sequences from classic NMR and EPR, and combined with high resolution optical microscopy, proximity to the target sample and nanoscale size, the diamond sensors have the potential to constitute a new class of magnetic resonance detectors with single spin sensitivity. As diamond sensors can be operated under ambient conditions, they offer potential application across a multitude of disciplines. Here we review the different existing techniques for magnetic resonance, with a focus on diamond defect spin sensors, showing their potential as versatile sensors for ultra-sensitive magnetic resonance with nanoscale spatial resolution. Copyright © 2016 Elsevier Inc. All rights reserved.

  8. Single-Mode VCSELs

    NASA Astrophysics Data System (ADS)

    Larsson, Anders; Gustavsson, Johan S.

    The only active transverse mode in a truly single-mode VCSEL is the fundamental mode with a near Gaussian field distribution. A single-mode VCSEL produces a light beam of higher spectral purity, higher degree of coherence and lower divergence than a multimode VCSEL and the beam can be more precisely shaped and focused to a smaller spot. Such beam properties are required in many applications. In this chapter, after discussing applications of single-mode VCSELs, we introduce the basics of fields and modes in VCSELs and review designs implemented for single-mode emission from VCSELs in different materials and at different wavelengths. This includes VCSELs that are inherently single-mode as well as inherently multimode VCSELs where higher-order modes are suppressed by mode selective gain or loss. In each case we present the current state-of-the-art and discuss pros and cons. At the end, a specific example with experimental results is provided and, as a summary, the most promising designs based on current technologies are identified.

  9. Domain structure analysis of Pb(Zn1/3Nb2/3)O3-9%PbTiO3 single crystals using optical second harmonic generation microscopy

    NASA Astrophysics Data System (ADS)

    Kaneshiro, Junichi; Uesu, Yoshiaki

    2010-11-01

    The domain structures of relaxor-ferroelectric Pb(Zn1/3Nb2/3)O3-9%PbTiO3 (PZN-9PT) single crystals with a morphotropic phase boundary (MPB) composition are observed with a scanning second harmonic generation (SHG) microscope. Three-dimensional domain structures are obtained from sectional SH images along the axial direction. The domain structures are explained well by the strain compatibility theory that is based on the ferroelectric/ferroelastic phase transition of m3¯mFm(p) with the monoclinic space group Pm . The SHG images are divided into several parts, and the light-polarization dependence (PolD) at each site is calculated by minimizing the least-squares errors of the nonlinear susceptibilities. The PolDs are fitted well by theoretical formulas of the SH intensities for the Pm symmetry, and the two-dimensional map of the PolD coincides well with the corresponding SHG image of the domain structures. The monoclinic Pm symmetry at the MPB of PZN-9PT is determined at the optical diffraction limit of 460 nm.

  10. Growth of NBT-BT single crystals by flux method and their structural, morphological and electrical characterizations

    NASA Astrophysics Data System (ADS)

    Kanuru, Sreenadha Rao; Baskar, K.; Dhanasekaran, R.; Kumar, Binay

    2016-05-01

    In this paper, one of the important, eco-friendly polycrystalline material, (1-x)(Na0.5Bi0.5)TiO3 (NBT) - xBaTiO3 (BT) of different compositions (x=0.07, 0.06 and 0.05 wt%) around the morphotropic phase boundary (MPB) were synthesized by solid state reaction technique. And the single crystals with 13×7×7 mm3, 12×12×7 mm3 and 10×7×4 mm3 dimensions were grown by self flux method. The morphology, crystal structure and unit-cell parameters have been studied and the monoclinic phase has been identified for 0.07 wt% of BT. Higher BT concentration changes the crystal habit and the mechanism has been studied clearly. Raman spectroscopy at room-temperature confirms the presence of functional groups. The quality of the as grown single crystals was examined by high resolution x-ray diffraction analysis. The dielectric properties of the as grown crystals were investigated in the frequency range of 20 Hz-2 MHz from room temperature to 450 °C. The broad dielectric peak and frequency dispersion demonstrates the relaxor behavior of grown crystals. The dielectric constant (εr), transition temperature (Tm), and depolarization temperature (Td) of the grown crystals are found to be comparatively good. The diffusive factor (γ) from Curie-Weiss law confirms the as grown NBT-BT single crystals are relaxor in nature.

  11. Synthesis, growth, structure, mechanical and optical properties of a new semi-organic 2-methyl imidazolium dihydrogen phosphate single crystal

    SciTech Connect

    Nagapandiselvi, P.; Baby, C.; Gopalakrishnan, R.

    2016-09-15

    Highlights: • 2MIDP crystals were grown by slow evaporation solution growth technique. • Single crystal XRD revealed self-assembled supramolecular framework. • Z scan technique is employed for third order nonlinear optical susceptibility. • Structure-property correlation is established. - Abstract: A new semi-organic compound, 2-methyl imidazolium dihydrogen phosphate (2MIDP), was prepared and good quality single crystals of 2MIDP were grown by slow evaporation solution growth technique. Crystal structure elucidated using Single crystal XRD showed that 2MIDP crystallizes in monoclinic system with P2{sub 1}/c space group. FT-IR, UV-Vis-NIR, Fluorescence and FT-NMR spectra confirm the molecular structure of 2MIDP. The UV-Vis-NIR spectra established the suitability of the compound for NLO applications. TG-DSC showed that 2MIDP is thermally stable up to 200 °C. Mechanical characteristics like hardness number (H{sub v}), stiffness constant (C{sub 11}), yield strength (σ{sub v}), fracture toughness (K{sub c}) and brittleness index (B{sub i}) were assessed using Vicker’s microhardness tester. Third order nonlinear optical properties determined from Z-scan measurement using femto and picosecond lasers showed two photon reverse saturable absorption. The enhancement of nonlinear optical properties in femto second laser, revealed the suitability of 2MIDP for optical limiting applications.

  12. Single Bubble Sonoluminescence

    NASA Astrophysics Data System (ADS)

    Farley, Jennifer; Hough, Shane

    2003-05-01

    Single Bubble Sonoluminescence is the emission of light from a single bubble suspended in a liquid caused by a continuum of repeated implosions due to pressure waves generated from a maintained ultrasonic sinusoidal wave source. H. Frenzel and H. Schultz first studied it in 1934 at the University of Cologne. It was not until 1988 with D.F. Gaitan that actual research began with single bubble sonoluminescence. Currently many theories exist attempting to explain the observed bubble phenomenon. Many of these theories require spherical behavior of the bubble. Observation of the bubble has shown that the bubble does not behave spherically in most cases. One explanation for this is known as jet theory. A spectrum of the bubble will give us the mean physical properties of the bubble such as temperature and pressure inside the bubble. Eventually, with the aide of fluorocene dye a full spectrum of the bubble will be obtained.

  13. Single-plasmon interferences

    PubMed Central

    Dheur, Marie-Christine; Devaux, Eloïse; Ebbesen, Thomas W.; Baron, Alexandre; Rodier, Jean-Claude; Hugonin, Jean-Paul; Lalanne, Philippe; Greffet, Jean-Jacques; Messin, Gaétan; Marquier, François

    2016-01-01

    Surface plasmon polaritons are electromagnetic waves coupled to collective electron oscillations propagating along metal-dielectric interfaces, exhibiting a bosonic character. Recent experiments involving surface plasmons guided by wires or stripes allowed the reproduction of quantum optics effects, such as antibunching with a single surface plasmon state, coalescence with a two-plasmon state, conservation of squeezing, or entanglement through plasmonic channels. We report the first direct demonstration of the wave-particle duality for a single surface plasmon freely propagating along a planar metal-air interface. We develop a platform that enables two complementary experiments, one revealing the particle behavior of the single-plasmon state through antibunching, and the other one where the interferences prove its wave nature. This result opens up new ways to exploit quantum conversion effects between different bosonic species as shown here with photons and polaritons. PMID:26998521

  14. Single event mass spectrometry

    DOEpatents

    Conzemius, Robert J.

    1990-01-16

    A means and method for single event time of flight mass spectrometry for analysis of specimen materials. The method of the invention includes pulsing an ion source imposing at least one pulsed ion onto the specimen to produce a corresponding emission of at least one electrically charged particle. The emitted particle is then dissociated into a charged ion component and an uncharged neutral component. The ion and neutral components are then detected. The time of flight of the components are recorded and can be used to analyze the predecessor of the components, and therefore the specimen material. When more than one ion particle is emitted from the specimen per single ion impact, the single event time of flight mass spectrometer described here furnis This invention was made with Government support under Contract No. W-7405-ENG82 awarded by the Department of Energy. The Government has certain rights in the invention.

  15. Single-Cell Metabolomics.

    PubMed

    Emara, Samy; Amer, Sara; Ali, Ahmed; Abouleila, Yasmine; Oga, April; Masujima, Tsutomu

    2017-01-01

    The dynamics of a cell is always changing. Cells move, divide, communicate, adapt, and are always reacting to their surroundings non-synchronously. Currently, single-cell metabolomics has become the leading field in understanding the phenotypical variations between them, but sample volumes, low analyte concentrations, and validating gentle sample techniques have proven great barriers toward achieving accurate and complete metabolomics profiling. Certainly, advanced technologies such as nanodevices and microfluidic arrays are making great progress, and analytical techniques, such as matrix-assisted laser desorption ionization (MALDI), are gaining popularity with high-throughput methodology. Nevertheless, live single-cell mass spectrometry (LCSMS) values the sample quality and precision, turning once theoretical speculation into present-day applications in a variety of fields, including those of medicine, pharmaceutical, and agricultural industries. While there is still room for much improvement, it is clear that the metabolomics field is progressing toward analysis and discoveries at the single-cell level.

  16. Single-Molecule Bioelectronics

    PubMed Central

    Rosenstein, Jacob K.; Lemay, Serge G.; Shepard, Kenneth L.

    2014-01-01

    Experimental techniques which interface single biomolecules directly with microelectronic systems are increasingly being used in a wide range of powerful applications, from fundamental studies of biomolecules to ultra-sensitive assays. Here we review several technologies which can perform electronic measurements of single molecules in solution: ion channels, nanopore sensors, carbon nanotube field-effect transistors, electron tunneling gaps, and redox cycling. We discuss the shared features among these techniques that enable them to resolve individual molecules, and discuss their limitations. Recordings from each of these methods all rely on similar electronic instrumentation, and we discuss the relevant circuit implementations and potential for scaling these single-molecule bioelectronic interfaces to high-throughput arrayed sensing platforms. PMID:25529538

  17. Single-plasmon interferences.

    PubMed

    Dheur, Marie-Christine; Devaux, Eloïse; Ebbesen, Thomas W; Baron, Alexandre; Rodier, Jean-Claude; Hugonin, Jean-Paul; Lalanne, Philippe; Greffet, Jean-Jacques; Messin, Gaétan; Marquier, François

    2016-03-01

    Surface plasmon polaritons are electromagnetic waves coupled to collective electron oscillations propagating along metal-dielectric interfaces, exhibiting a bosonic character. Recent experiments involving surface plasmons guided by wires or stripes allowed the reproduction of quantum optics effects, such as antibunching with a single surface plasmon state, coalescence with a two-plasmon state, conservation of squeezing, or entanglement through plasmonic channels. We report the first direct demonstration of the wave-particle duality for a single surface plasmon freely propagating along a planar metal-air interface. We develop a platform that enables two complementary experiments, one revealing the particle behavior of the single-plasmon state through antibunching, and the other one where the interferences prove its wave nature. This result opens up new ways to exploit quantum conversion effects between different bosonic species as shown here with photons and polaritons.

  18. Single-molecule electrometry

    NASA Astrophysics Data System (ADS)

    Ruggeri, Francesca; Zosel, Franziska; Mutter, Natalie; Różycka, Mirosława; Wojtas, Magdalena; Ożyhar, Andrzej; Schuler, Benjamin; Krishnan, Madhavi

    2017-05-01

    Mass and electrical charge are fundamental properties of biological macromolecules. Although molecular mass has long been determined with atomic precision, a direct and precise determination of molecular charge remains an outstanding challenge. Here we report high-precision (<1e) measurements of the electrical charge of molecules such as nucleic acids, and globular and disordered proteins in solution. The measurement is based on parallel external field-free trapping of single macromolecules, permits the estimation of a dielectric coefficient of the molecular interior and can be performed in real time. Further, we demonstrate the direct detection of single amino acid substitution and chemical modifications in proteins. As the electrical charge of a macromolecule strongly depends on its three-dimensional conformation, this kind of high-precision electrometry offers an approach to probe the structure, fluctuations and interactions of a single molecule in solution.

  19. Single Cell Oncogenesis

    NASA Astrophysics Data System (ADS)

    Lu, Xin

    It is believed that cancer originates from a single cell that has gone through generations of evolution of genetic and epigenetic changes that associate with the hallmarks of cancer. In some cancers such as various types of leukemia, cancer is clonal. Yet in other cancers like glioblastoma (GBM), there is tremendous tumor heterogeneity that is likely to be caused by simultaneous evolution of multiple subclones within the same tissue. It is obvious that understanding how a single cell develops into a clonal tumor upon genetic alterations, at molecular and cellular levels, holds the key to the real appreciation of tumor etiology and ultimate solution for therapeutics. Surprisingly very little is known about the process of spontaneous tumorigenesis from single cells in human or vertebrate animal models. The main reason is the lack of technology to track the natural process of single cell changes from a homeostatic state to a progressively cancerous state. Recently, we developed a patented compound, photoactivatable (''caged'') tamoxifen analogue 4-OHC and associated technique called optochemogenetic switch (OCG switch), which we believe opens the opportunity to address this urgent biological as well as clinical question about cancer. We propose to combine OCG switch with genetically engineered mouse models of head and neck squamous cell carcinoma and high grade astrocytoma (including GBM) to study how single cells, when transformed through acute loss of tumor suppressor genes PTEN and TP53 and gain of oncogenic KRAS, can develop into tumor colonies with cellular and molecular heterogeneity in these tissues. The abstract is for my invited talk in session ``Beyond Darwin: Evolution in Single Cells'' 3/18/2016 11:15 AM.

  20. SINGLE CRYSTAL NEUTRON DIFFRACTION.

    SciTech Connect

    KOETZLE,T.F.

    2001-03-13

    Single-crystal neutron diffraction measures the elastic Bragg reflection intensities from crystals of a material, the structure of which is the subject of investigation. A single crystal is placed in a beam of neutrons produced at a nuclear reactor or at a proton accelerator-based spallation source. Single-crystal diffraction measurements are commonly made at thermal neutron beam energies, which correspond to neutron wavelengths in the neighborhood of 1 Angstrom. For high-resolution studies requiring shorter wavelengths (ca. 0.3-0.8 Angstroms), a pulsed spallation source or a high-temperature moderator (a ''hot source'') at a reactor may be used. When complex structures with large unit-cell repeats are under investigation, as is the case in structural biology, a cryogenic-temperature moderator (a ''cold source'') may be employed to obtain longer neutron wavelengths (ca. 4-10 Angstroms). A single-crystal neutron diffraction analysis will determine the crystal structure of the material, typically including its unit cell and space group, the positions of the atomic nuclei and their mean-square displacements, and relevant site occupancies. Because the neutron possesses a magnetic moment, the magnetic structure of the material can be determined as well, from the magnetic contribution to the Bragg intensities. This latter aspect falls beyond the scope of the present unit; for information on magnetic scattering of neutrons see Unit 14.3. Instruments for single-crystal diffraction (single-crystal diffractometers or SCDs) are generally available at the major neutron scattering center facilities. Beam time on many of these instruments is available through a proposal mechanism. A listing of neutron SCD instruments and their corresponding facility contacts is included in an appendix accompanying this unit.

  1. SINGLE CRYSTAL NEUTRON DIFFRACTION.

    SciTech Connect

    KOETZLE,T.F.

    2001-03-13

    Single-crystal neutron diffraction measures the elastic Bragg reflection intensities from crystals of a material, the structure of which is the subject of investigation. A single crystal is placed in a beam of neutrons produced at a nuclear reactor or at a proton accelerator-based spallation source. Single-crystal diffraction measurements are commonly made at thermal neutron beam energies, which correspond to neutron wavelengths in the neighborhood of 1 Angstrom. For high-resolution studies requiring shorter wavelengths (ca. 0.3-0.8 Angstroms), a pulsed spallation source or a high-temperature moderator (a ''hot source'') at a reactor may be used. When complex structures with large unit-cell repeats are under investigation, as is the case in structural biology, a cryogenic-temperature moderator (a ''cold source'') may be employed to obtain longer neutron wavelengths (ca. 4-10 Angstroms). A single-crystal neutron diffraction analysis will determine the crystal structure of the material, typically including its unit cell and space group, the positions of the atomic nuclei and their mean-square displacements, and relevant site occupancies. Because the neutron possesses a magnetic moment, the magnetic structure of the material can be determined as well, from the magnetic contribution to the Bragg intensities. This latter aspect falls beyond the scope of the present unit; for information on magnetic scattering of neutrons see Unit 14.3. Instruments for single-crystal diffraction (single-crystal diffractometers or SCDs) are generally available at the major neutron scattering center facilities. Beam time on many of these instruments is available through a proposal mechanism. A listing of neutron SCD instruments and their corresponding facility contacts is included in an appendix accompanying this unit.

  2. Arrays vs. single telescopes

    NASA Astrophysics Data System (ADS)

    Johnson, H. L.

    The question of the relative efficiencies of telescope arrays versus an equivalent mirror-area very large telescope is re-examined and summarized. Four separate investigations by Bowen, Johnson and Richards, Code, and Disney all came to the same conclusion: that an array of telescopes is superior, both scientifically and economically, to a single very large telescope. The costs of recently completed telescopes are compared. The costs of arrays of telescopes are shown to be significantly lower than that of a single, very large telescope, with the further advantage that because existing, proven, designs can be used, no engineering 'break-throughs' are needed.

  3. From single molecule to single tubules

    NASA Astrophysics Data System (ADS)

    Guo, Chin-Lin

    2012-02-01

    Biological systems often make decisions upon conformational changes and assembly of single molecules. In vivo, epithelial cells (such as the mammary gland cells) can respond to extracellular matrix (ECM) molecules, type I collagen (COL), and switch their morphology from a lobular lumen (100-200 micron) to a tubular lumen (1mm-1cm). However, how cells make such a morphogenetic decision through interactions with each other and with COL is unclear. Using a temporal control of cell-ECM interaction, we find that epithelial cells, in response to a fine-tuned percentage of type I collagen (COL) in ECM, develop various linear patterns. Remarkably, these patterns allow cells to self-assemble into a tubule of length ˜ 1cm and diameter ˜ 400 micron in the liquid phase (i.e., scaffold-free conditions). In contrast with conventional thought, the linear patterns arise through bi-directional transmission of traction force, but not through diffusible biochemical factors secreted by cells. In turn, the transmission of force evokes a long-range (˜ 600 micron) intercellular mechanical interaction. A feedback effect is encountered when the mechanical interaction modifies cell positioning and COL alignment. Micro-patterning experiments further reveal that such a feedback is a novel cell-number-dependent, rich-get-richer process, which allows cells to integrate mechanical interactions into long-range (> 1mm) linear coordination. Our results suggest a mechanism cells can use to form and coordinate long-range tubular patterns, independent of those controlled by diffusible biochemical factors, and provide a new strategy to engineer/regenerate epithelial organs using scaffold-free self-assembly methods.

  4. Beyond the Single Story

    ERIC Educational Resources Information Center

    McKenney, Yekaterina

    2016-01-01

    Teachers of world literature have the opportunity to help students explore the more complex reality behind the stereotypes that they often see in the media. If we don't encourage students to challenge one-dimensional "single stories" that characterize an entire people--whether Muslims, Russians, Mexicans, African Americans, Chinese,…

  5. Single molecules: Thermodynamic limits

    NASA Astrophysics Data System (ADS)

    Liphardt, Jan

    2012-09-01

    Technologies aimed at single-molecule resolution of non-equilibrium systems increasingly require sophisticated new ways of thinking about thermodynamics. An elegant extension to standard fluctuation theory grants access to the kinetic intermediate states of these systems -- as DNA-pulling experiments now demonstrate.

  6. Single Parent Families.

    ERIC Educational Resources Information Center

    Ryan, Patricia

    This booklet attempts to reassure single parents that they can raise healthy, happy children and provides some suggestions for parents' specific questions and concerns. The first section discusses the emotional stages children pass through when they lose a parent, ways to explain to children the loss of a parent, and ways to handle children's…

  7. Contemporary Single Mothers.

    ERIC Educational Resources Information Center

    Eiduson, Bernice T.

    Fifty Caucasian, never-married single mothers aged 18-30, who had opted to keep their babies, were studied longitudinally from the last trimester of pregnancy through the first three years of their children's lives in order to learn the extent to which they had reinterpreted traditional roles and responsibilities and had restructured their lives.…

  8. Contemporary Single Mothers.

    ERIC Educational Resources Information Center

    Eiduson, Bernice T.

    Fifty Caucasian, never-married single mothers aged 18-30, who had opted to keep their babies, were studied longitudinally from the last trimester of pregnancy through the first three years of their children's lives in order to learn the extent to which they had reinterpreted traditional roles and responsibilities and had restructured their lives.…

  9. Beyond the Single Story

    ERIC Educational Resources Information Center

    McKenney, Yekaterina

    2016-01-01

    Teachers of world literature have the opportunity to help students explore the more complex reality behind the stereotypes that they often see in the media. If we don't encourage students to challenge one-dimensional "single stories" that characterize an entire people--whether Muslims, Russians, Mexicans, African Americans, Chinese,…

  10. Single Mother's Resource Handbook.

    ERIC Educational Resources Information Center

    Ferando, Annette; Newbert, David

    Funded under the Women's Educational Equity Act, the Assertiveness Training Program for Single Mothers was offered to mothers with children enrolled in the Omaha Head Start and Parent-Child Center Programs. The 16-week long program, providing a total of 40 hours of training, covered a wide range of topics in addition to the initial workshops on…

  11. TRANSVERSITY SINGLE SPIN ASYMMETRIES.

    SciTech Connect

    BOER,D.

    2001-04-27

    The theoretical aspects of two leading twist transversity single spin asymmetries, one arising from the Collins effect and one from the interference fragmentation functions, are reviewed. Issues of factorization, evolution and Sudakov factors for the relevant observables are discussed. These theoretical considerations pinpoint the most realistic scenarios towards measurements of transversity.

  12. Flame Synthesized Single Crystal Nanocolumn-Structured WO3 Thin Films for Photoelectrochemical Water Splitting.

    PubMed

    Ding, Jin-Rui; Kim, Kyo-Seon

    2016-02-01

    Tungsten oxide thin films have been found as an active visible light driven photoanode material for photoelectrochemical water splitting due to its good stability in aqueous solution and energetically favorable valence band position for water oxidation. Morphology control, which determines the performance of WO3 photoanode, is one of most focuses of recent research interests. In this work, we successfully prepared monoclinic WO3 thin films on ITO glass at low range of substrate temperature with a fabrication rate around 100 nm per minute by using aerosol flame deposition process. Single crystal nanocolumns with both triangular pyramid-like and triangular prism-like structure were obtained at certain process conditions. Photoelectrochemical properties of photoelectrodes assembled with both structured WO3 thin films were investigated. The prism-like nanocolumn-structured thin film generated the current density of 1.58 mAcm(-2) at potential of 1.0 V versus Ag/AgCl in 0.5 M H2SO4 solution under illumination of AM 1.5 simulated solar light (100 mVcm(-2)). It presented superior photoelectrochemical performance to pyramid-like nanocolumn-structured WO3 thin film.

  13. Anisotropic small-polaron hopping in W:BiVO4 single crystals

    NASA Astrophysics Data System (ADS)

    Rettie, Alexander J. E.; Chemelewski, William D.; Lindemuth, Jeffrey; McCloy, John S.; Marshall, Luke G.; Zhou, Jianshi; Emin, David; Mullins, C. Buddie

    2015-01-01

    DC electrical conductivity, Seebeck and Hall coefficients are measured between 300 and 450 K on single crystals of monoclinic bismuth vanadate that are doped n-type with 0.3% tungsten donors (W:BiVO4). Strongly activated small-polaron hopping is implied by the activation energies of the Arrhenius conductivities (about 300 meV) greatly exceeding the energies characterizing the falls of the Seebeck coefficients' magnitudes with increasing temperature (about 50 meV). Small-polaron hopping is further evidenced by the measured Hall mobility in the ab-plane (10-1 cm2 V-1 s-1 at 300 K) being larger and much less strongly activated than the deduced drift mobility (about 5 × 10-5 cm2 V-1 s-1 at 300 K). The conductivity and n-type Seebeck coefficient is found to be anisotropic with the conductivity larger and the Seebeck coefficient's magnitude smaller and less temperature dependent for motion within the ab-plane than that in the c-direction. These anisotropies are addressed by considering highly anisotropic next-nearest-neighbor (≈5 Å) transfers in addition to the somewhat shorter (≈4 Å), nearly isotropic nearest-neighbor transfers.

  14. Anisotropic small-polaron hopping in W:BiVO{sub 4} single crystals

    SciTech Connect

    Rettie, Alexander J. E.; Chemelewski, William D.; Zhou, Jianshi; Lindemuth, Jeffrey; McCloy, John S.; Marshall, Luke G.; Emin, David; Mullins, C. Buddie

    2015-01-12

    DC electrical conductivity, Seebeck and Hall coefficients are measured between 300 and 450 K on single crystals of monoclinic bismuth vanadate that are doped n-type with 0.3% tungsten donors (W:BiVO{sub 4}). Strongly activated small-polaron hopping is implied by the activation energies of the Arrhenius conductivities (about 300 meV) greatly exceeding the energies characterizing the falls of the Seebeck coefficients' magnitudes with increasing temperature (about 50 meV). Small-polaron hopping is further evidenced by the measured Hall mobility in the ab-plane (10{sup −1 }cm{sup 2 }V{sup −1 }s{sup −1} at 300 K) being larger and much less strongly activated than the deduced drift mobility (about 5 × 10{sup −5 }cm{sup 2 }V{sup −1 }s{sup −1} at 300 K). The conductivity and n-type Seebeck coefficient is found to be anisotropic with the conductivity larger and the Seebeck coefficient's magnitude smaller and less temperature dependent for motion within the ab-plane than that in the c-direction. These anisotropies are addressed by considering highly anisotropic next-nearest-neighbor (≈5 Å) transfers in addition to the somewhat shorter (≈4 Å), nearly isotropic nearest-neighbor transfers.

  15. Structural, thermal and dielectric properties of cobaltous malonate single crystals grown in limited diffusion media

    NASA Astrophysics Data System (ADS)

    Lincy, A.; Mahalakshmi, V.; Tinto, A. J.; Thomas, J.; Saban, K. V.

    2010-11-01

    Well-faceted crystals of cobaltous malonate (C 6 H 12 Co 2 O 12) have been grown by the controlled diffusion of ionic species in hydrosilica gel. Single crystal X-ray diffraction studies show that the crystal belongs to the monoclinic system with space group C2/m. The unit cell dimensions are a=12.6301(9) Å, b=7.3857(9) Å, c=7.2945(7) Å, α= γ=90°, β=120.193(9)°. The functional groups, elucidated from the FT-IR spectrum, are in conformity with the information derived from the X-ray diffraction studies. The thermal behaviour of the material has been investigated using TG-DTA in the temperature range 30-1050 °C. The optical band gap of the sample is estimated using diffuse reflectance spectroscopy (DRS). The dielectric constant and dielectric loss of the crystal have been studied over wide temperature and frequency ranges. AC conductivity measurements reveal a thermally activated process and the mechanism behind the conduction process has been discussed.

  16. Switching VO₂ Single Crystals and Related Phenomena: Sliding Domains and Crack Formation.

    PubMed

    Fisher, Bertina; Patlagan, Larisa

    2017-05-19

    VO₂ is the prototype material for insulator-metal transition (IMT). Its transition at TIMT = 340 K is fast and consists of a large resistance jump (up to approximately five orders of magnitude), a large change in its optical properties in the visible range, and symmetry change from monoclinic to tetragonal (expansion by 1% along the tetragonal c-axis and 0.5% contraction in the perpendicular direction). It is a candidate for potential applications such as smart windows, fast optoelectronic switches, and field-effect transistors. The change in optical properties at the IMT allows distinguishing between the insulating and the metallic phases in the mixed state. Static or dynamic domain patterns in the mixed-state of self-heated single crystals during electric-field induced switching are in strong contrast with the percolative nature of the mixed state in switching VO₂ films. The most impressive effect-so far unique to VO₂-is the sliding of narrow semiconducting domains within a metallic background in the positive sense of the electric current. Here we show images from videos obtained using optical microscopy for sliding domains along VO₂ needles and confirm a relation suggested in the past for their velocity. We also show images for the disturbing damage induced by the structural changes in switching VO₂ crystals obtained for only a few current-voltage cycles.

  17. 75 FR 9247 - Single Family Mortgage Insurance Premium, Single Family

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-03-01

    ... URBAN DEVELOPMENT Single Family Mortgage Insurance Premium, Single Family AGENCY: Office of the Chief... the Single Family Premium Collection Subsystem-Upfront (SFPCS-U) to remit the upfront premium to... manage and process upfront single family mortgage insurance premium collections and corrections to...

  18. Energy levels and crystal field parameters for Nd3+ ions in BaY2F8, LiKYF5, and K2YF5 single crystals.

    PubMed

    Karbowiak, M; Gnutek, P; Rudowicz, C

    2012-02-15

    The available experimental energy levels of Nd(3+) ions doped into single crystals of BaY(2)F(8), LiKYF(5), and K(2)YF(5), which exhibit low site symmetry, are reanalyzed. A combined approach based on the ascent/descent in symmetry (ADS) method, the superposition model (SPM) analysis, and the pseudosymmetry axes method (PAM) is utilized to extract the crystal field (CF) parameters, B(kq), from experimental spectra. Corresponding sets of the free-ion parameters are also fitted. The crystallographic data are used to establish the axis systems most appropriate for approximation of the actual monoclinic C(2) site symmetry to higher orthorhombic D(2) and tetragonal D(4) symmetry used in CF calculations for BaY(2)F(8). Similarly, for triclinic C(1) site symmetry in LiKYF(5) and K(2)YF(5) approximation to monoclinic C(2) and orthorhombic D(2) symmetry for LiKYF(5), whereas the monoclinic C(s) symmetry for K(2)YF(5), are considered. It is shown that the C(2v) approximation used previously for K(2)YF(5):Nd(3+) is not suitable. SPM enables to calculate for the unapproximated and idealized polyhedrons YF(8) in a given ion-host system of the combined coordination factors Sg(k,q) expressed in the modified crystallographic axis system CAS* and approximated symmetry adapted axis systems, respectively. The quantities Sg(k,q) serve as input for PAM calculations for independent determination of the axis system appropriate for higher symmetry approximations. The pseudosymmetry axes represent the axis system that reflects most closely the approximated higher symmetry of the nearest ligands in a paramagnetic complex embodied in the 4th-rank CF parameters. The combined ADS/SPM/PAM approach provides sets of starting CF parameters (CFPs) in well-defined axis systems. Multiple fittings starting from different points in the CF parameter space yield converging solutions, thus increasing the reliability of the final optimized solutions, which may be then considered as the global minima. The

  19. Single electron spintronics.

    PubMed

    Dempsey, Kari J; Ciudad, David; Marrows, Christopher H

    2011-08-13

    Single electron electronics is now well developed, and allows the manipulation of electrons one-by-one as they tunnel on and off a nanoscale conducting island. In the past decade or so, there have been concerted efforts in several laboratories to construct single electron devices incorporating ferromagnetic components in order to introduce spin functionality. The use of ferromagnetic electrodes with a non-magnetic island can lead to spin accumulation on the island. On the other hand, making the dot also ferromagnetic introduces new physics such as tunnelling magnetoresistance enhancement in the cotunnelling regime and manifestations of the Kondo effect. Such nanoscale islands are also found to have long spin lifetimes. Conventional spintronics makes use of the average spin-polarization of a large ensemble of electrons: this new approach offers the prospect of accessing the quantum properties of the electron, and is a candidate approach to the construction of solid-state spin-based qubits.

  20. Single Crystal Membranes

    NASA Technical Reports Server (NTRS)

    Stormont, R. W.; Morrison, A.

    1974-01-01

    Single crystal a- and c-axis tubes and ribbons of sodium beta-alumina and sodium magnesium beta-alumina were grown from sodium oxide rich melts. Additional experiments grew ribbon crystals containing sodium magnesium beta, beta double prime, beta triple prime, and beta quadruple prime. A high pressure crystal growth chamber, sodium oxide rich melts, and iridium for all surfaces in contact with the melt were combined with the edge-defined, film-fed growth technique to grow the single crystal beta-alumina tubes and ribbons. The crystals were characterized using metallographic and X-ray diffraction techniques, and wet chemical analysis was used to determine the sodium, magnesium, and aluminum content of the grown crystals.

  1. Single frequency multitransmitter telemetry

    NASA Technical Reports Server (NTRS)

    Carreno, Victor A. (Inventor)

    1986-01-01

    The invention relates to a single frequency multitransmitter telemetry system that will deliver a substantial amount of data at low cost. The invention consists essentially of a plurality of sensor transmitter units at different locations, with individual signal conditioning and logic, which send sampled data signals to a single receiver. The transmitters operate independently on the same frequency in a frequency shift keying modulation system and are not synchronized to the receiver. The problem of reception of data from more than one transmitter simultaneously is solved by discarding the data - when there is overlap of data from two or more transmitters, the data is discarded and when there is no overlap the data is retained. The invention utilizes a unique overlap detection technique to determine if data should be retained or discarded. When data is received from a transmitter, it goes into a shift register.

  2. A monoclinic polymorph of KY(PO(3))(4).

    PubMed

    Horchani-Naifer, Karima; Jouini, Anis; Férid, Mokhtar

    2008-05-17

    The title compound, potassium yttrium polyphosphate, KY(PO(3))(4), was synthesized using the flux method. The atomic arrangement consists of an infinite long-chain polyphosphate organization. Chains, with a period of four PO(4) tetra-hedra, run along the a-axis direction. Two other polymorphs of this phosphate are known, in space groups P21/n and C2/c.

  3. A monoclinic polymorph of KY(PO3)4

    PubMed Central

    Horchani-Naifer, Karima; Jouini, Anis; Férid, Mokhtar

    2008-01-01

    The title compound, potassium yttrium polyphosphate, KY(PO3)4, was synthesized using the flux method. The atomic arrangement consists of an infinite long-chain polyphosphate organization. Chains, with a period of four PO4 tetra­hedra, run along the a-axis direction. Two other polymorphs of this phosphate are known, in space groups P21/n and C2/c. PMID:21202436

  4. A new monoclinic polymorph of trans-dichloridodipyridine-palladium(II).

    PubMed

    Lee, Hon Man; Liao, Chuang-Yi

    2008-10-22

    In the structure of the title compound, [PdCl(2)(C(5)H(5)N)(2)], the Pd(II) atom is located on an inversion centre and the pyridine rings are coplanar. There is inter-molecular π-π stacking between the pyridyl rings, with a centroid-to-centroid separation of 3.916 (1) Å. The structure is a new polymorph of two previously determined structures [Viossat, Dung & Robert (1993 ▶). Acta Cryst. C49, 84-85; Liao & Lee (2006 ▶). Acta Cryst. E62, m680-m681].

  5. Watching single molecules dance

    NASA Astrophysics Data System (ADS)

    Mehta, Amit Dinesh

    Molecular motors convert chemical energy, from ATP hydrolysis or ion flow, into mechanical motion. A variety of increasingly precise mechanical probes have been developed to monitor and perturb these motors at the single molecule level. Several outstanding questions can be best approached at the single molecule level. These include: how far does a motor progress per energy quanta consumed? how does its reaction cycle respond to load? how many productive catalytic cycles can it undergo per diffusional encounter with its track? and what is the mechanical stiffness of a single molecule connection? A dual beam optical trap, in conjunction with in vitro ensemble motility assays, has been used to characterize two members of the myosin superfamily: muscle myosin II and chick brain myosin V. Both move the helical polymer actin, but myosin II acts in large ensembles to drive muscle contraction or cytokinesis, while myosin V acts in small numbers to transport vesicles. An optical trapping apparatus was rendered sufficiently precise to identify a myosin working stroke with 1nm or so, barring systematic errors such as those perhaps due to random protein orientations. This and other light microscopic motility assays were used to characterize myosin V: unlike myosin II this vesicle transport protein moves through many increments of travel while remaining strongly bound to a single actin filament. The step size, stall force, and travel distance of myosin V reveal a remarkably efficient motor capable of moving along a helical track for over a micrometer without significantly spiraling around it. Such properties are fully consistent with the putative role of an organelle transport motor, present in small numbers to maintain movement over long ranges relative to cellular size scales. The contrast between myosin II and myosin V resembles that between a human running on the moon and one walking on earth, where the former allows for faster motion when in larger ensembles but for less

  6. Single rotor turbine engine

    DOEpatents

    Platts, David A.

    2002-01-01

    There has been invented a turbine engine with a single rotor which cools the engine, functions as a radial compressor, pushes air through the engine to the ignition point, and acts as an axial turbine for powering the compressor. The invention engine is designed to use a simple scheme of conventional passage shapes to provide both a radial and axial flow pattern through the single rotor, thereby allowing the radial intake air flow to cool the turbine blades and turbine exhaust gases in an axial flow to be used for energy transfer. In an alternative embodiment, an electric generator is incorporated in the engine to specifically adapt the invention for power generation. Magnets are embedded in the exhaust face of the single rotor proximate to a ring of stationary magnetic cores with windings to provide for the generation of electricity. In this alternative embodiment, the turbine is a radial inflow turbine rather than an axial turbine as used in the first embodiment. Radial inflow passages of conventional design are interleaved with radial compressor passages to allow the intake air to cool the turbine blades.

  7. Single-fiber electromyography.

    PubMed

    Tanhehco, Justina L

    2003-05-01

    Single-fiber EMG is a technique introduced in 1963 by Stålberg and Ekstedt for recording single muscle fiber action potentials by means of a specially constructed needle with a 25-microm recording surface. The needle is positioned in the muscle to record from two or more time-locked potentials belonging to the same motor unit. Jitter is the variability in the arrival time of action potentials to the recording electrode between consecutive discharges. This variability reflects end-plate conduction and is measured along with fiber density, which is the average number of fibers belonging to the same motor unit that is in the recording area. An abnormal test is one in which more than 10%, or the mean, of 20 fiber pairs has increased jitter when compared with normal reference values. Increased fiber density is seen with reinnervation. Single-fiber EMG is more sensitive than conventional EMG and is the most sensitive, but not specific, test for myasthenia gravis. Lambert-Eaton myasthenic syndrome, and other neuromusculasr junction pathology. It has been useful in the evaluation of some neuropathies and myopathies and has provided valuable information on the motor unit spatial arrangement, territory, microphysiology, and pathophysiology.

  8. Ageing single file motion

    NASA Astrophysics Data System (ADS)

    Metzler, R.; Sanders, L.; Lomholt, M. A.; Lizana, L.; Fogelmark, K.; Ambjörnsson, Tobias

    2014-12-01

    The mean squared displacement of a tracer particle in a single file of identical particles with excluded volume interactions shows the famed Harris scaling ≃ K1/2t1/2 as function of time. Here we study what happens to this law when each particle of the single file interacts with the environment such that it is transiently immobilised for times τ with a power-law distribution ψ(τ) ≃ (τ★)α, and different ranges of the exponent α are considered. We find a dramatic slow-down of the motion of a tracer particle from Harris' law to an ultraslow, logarithmic time evolution ≃ K0 log 1/2(t) when 0 < α < 1. In the intermediate case 1 < α < 2, we observe a power-law form for the mean squared displacement, with a modified scaling exponent as compared to Harris' law. Once α is larger than two, the Brownian single file behaviour and thus Harris' law are restored. We also point out that this process is weakly non-ergodic in the sense that the time and ensemble averaged mean squared displacements are disparate.

  9. Single wall penetration equations

    NASA Technical Reports Server (NTRS)

    Hayashida, K. B.; Robinson, J. H.

    1991-01-01

    Five single plate penetration equations are compared for accuracy and effectiveness. These five equations are two well-known equations (Fish-Summers and Schmidt-Holsapple), two equations developed by the Apollo project (Rockwell and Johnson Space Center (JSC), and one recently revised from JSC (Cour-Palais). They were derived from test results, with velocities ranging up to 8 km/s. Microsoft Excel software was used to construct a spreadsheet to calculate the diameters and masses of projectiles for various velocities, varying the material properties of both projectile and target for the five single plate penetration equations. The results were plotted on diameter versus velocity graphs for ballistic and spallation limits using Cricket Graph software, for velocities ranging from 2 to 15 km/s defined for the orbital debris. First, these equations were compared to each other, then each equation was compared with various aluminum projectile densities. Finally, these equations were compared with test results performed at JSC for the Marshall Space Flight Center. These equations predict a wide variety of projectile diameters at a given velocity. Thus, it is very difficult to choose the 'right' prediction equation. The thickness of a single plate could have a large variation by choosing a different penetration equation. Even though all five equations are empirically developed with various materials, especially for aluminum alloys, one cannot be confident in the shield design with the predictions obtained by the penetration equations without verifying by tests.

  10. Single-Atom Electrocatalysts.

    PubMed

    Zhu, Chengzhou; Fu, Shaofang; Shi, Qiurong; Du, Dan; Lin, Yuehe

    2017-05-23

    Recent years have witnessed the increasing production of the sustainable and renewable energy. The limitations of electrochemical performances are closely associated with the search for highly efficient electrocatalysts with more rational control of size, shape, composition and structure. Specifically, the rapidly emerging studies on single-atom catalysts (SACs) have sparked new interests in electrocatalysis because of the unique properties such as high catalytic activity, selectivity and 100% atom utilization. In this review, we introduce the innovative synthesis and advanced characterizations of SACs and primarily focus on their electrochemical applications in oxygen reduction/evolution reaction, hydrogen evolution reaction, hydrocarbon conversion reactions for fuel cells (methanol, ethanol and formic acid electrooxidation) and other related fields. Significantly, this unique single atom-depended electrocatalytic performance together with the underlying mechanism will also be discussed. Furthermore, future research directions and challenges are proposed to further realize the ultimate goal of tailoring single-atoms for electrochemical applications. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Single Echo MRI

    PubMed Central

    Galiana, Gigi; Constable, R. Todd

    2014-01-01

    Purpose Previous nonlinear gradient research has focused on trajectories that reconstruct images with a minimum number of echoes. Here we describe sequences where the nonlinear gradients vary in time to acquire the image in a single readout. The readout is designed to be very smooth so that it can be compressed to minimal time without violating peripheral nerve stimulation limits, yielding an image from a single 4 ms echo. Theory and Methods This sequence was inspired by considering the code of each voxel, i.e. the phase accumulation that a voxel follows through the readout, an approach connected to traditional encoding theory. We present simulations for the initial sequence, a low slew rate analog, and higher resolution reconstructions. Results Extremely fast acquisitions are achievable, though as one would expect, SNR is reduced relative to the slower Cartesian sampling schemes because of the high gradient strengths. Conclusions The prospect that nonlinear gradients can acquire images in a single <10 ms echo makes this a novel and interesting approach to image encoding. PMID:24465837

  12. Presence of a monoclinic (Pm) phase in the morphotropic phase boundary region of multiferroic (1 − x)Bi(Ni{sub 1/2}Ti{sub 1/2})O{sub 3}-xPbTiO{sub 3} solid solution: A Rietveld study

    SciTech Connect

    Pandey, Rishikesh E-mail: aksingh.mst@itbhu.ac.in; Singh, Akhilesh Kumar E-mail: aksingh.mst@itbhu.ac.in

    2014-07-28

    We present here the results of structural studies on multiferroic (1 − x)Bi(Ni{sub 1/2}Ti{sub 1/2})O{sub 3}-xPbTiO{sub 3} solid solution using Rietveld analysis on powder x-ray diffraction data in the composition range 0.35 ≤ x ≤ 0.55. The stability region of various crystallographic phases at room temperature for (1 − x)Bi(Ni{sub 1/2}Ti{sub 1/2})O{sub 3}-xPbTiO{sub 3} is determined precisely. Structural transformation from pseudo-cubic (x ≤ 0.40) to tetragonal (x ≥ 0.50) phase is observed via phase coexistence region demarcating the morphotropic phase boundary. The morphotropic phase boundary region consists of coexisting tetragonal and monoclinic structures with space group P4mm and Pm, respectively, stable in composition range 0.41 ≤ x ≤ 0.49 as confirmed by Rietveld analysis. The results of Rietveld analysis completely rule out the coexistence of rhombohedral and tetragonal phases in the morphotropic phase boundary region reported by earlier workers. A comparison between the bond lengths for “B-site cations-oxygen anions” obtained after Rietveld refinement, with the bond length calculated using Shannon-Prewitt ionic radii, reveals the ionic nature of B-O (Ni/Ti-O) bonds for the cubic phase and partial covalent character for the other crystallographic phases.

  13. Growth, spectral, optical, thermal, and mechanical behaviour of an organic single crystal: Quinolinium 2-carboxy 6-nitrophthalate monohydrate

    NASA Astrophysics Data System (ADS)

    Mohana, J.; Ahila, G.; Bharathi, M. Divya; Anbalagan, G.

    2016-09-01

    Organic single crystals of quinolinium 2-carboxy 6-nitrophthalate monohydrate (QN) were grown by slow evaporation solution growth technique using ethanol and water as a mixed solvent. X-ray powder diffraction analysis revealed that the crystal belongs to the monoclinic crystal system with space group of P21/c. The functional groups present in the crystallized material confirmed its molecular structure. The optical transparency range and the lower cutoff wavelength were identified from the UV-vis spectrum. The optical constants were determined by UV-visible transmission spectrum at normal incidence, measured over the 200-700 nm spectral range. The dispersion of the refractive index was discussed in terms of the single-oscillator Wemple and DiDomenico model. The calculated HOMO and LUMO energies show that the charge transfer occur within the molecule. Electronic excitation properties were discussed within the framework of two level model on the basis of an orbital analysis. The nonlinear optical absorption coefficient (β) and nonlinear refraction (n2) of QN was measured by Z-scan technique and reported here. Thermal stability of QN was determined using TGA/DSC curves. Vicker's microhardness studies were carried out on the (1 1 ̅0) plane to understand the mechanical properties of the grown crystal. The microhardness measurements showed a Vickers hardness value as 18.4 kg/mm2 which is comparable to well-known organic crystal, urea.

  14. Hexameric RSF1010 helicase RepA: the structural and functional importance of single amino acid residues

    PubMed Central

    Ziegelin, Günter; Niedenzu, Timo; Lurz, Rudi; Saenger, Wolfram; Lanka, Erich

    2003-01-01

    In the known monoclinic crystals the 3-dimensional structure of the hexameric, replicative helicase RepA encoded by plasmid RSF1010 shows 6-fold rotational symmetry. In contrast, in the cubic crystal form at 2.55 Å resolution described here RepA has 3-fold symmetry and consists of a trimer of dimers. To study structure–function relationships, a series of repA deletion mutants and mutations yielding single amino acid exchanges were constructed and the respective gene products were analyzed in vivo and in vitro. Hexamerization of RepA occurs via the N-terminus and is required for NTP hydrolysis. The C-terminus is essential both for the interaction with the replication machinery and for the helicase activity. Functional analyses of RepA variants with single amino acid exchanges confirmed most of the predictions that were based on the published 3-dimensional structure. Of the five motifs conserved in family 4 helicases, all residues conserved in RepA and T7 gp4 helicases participate in DNA unwinding. Residues K42, E76, D77, D139 and H178, proposed to play key roles in catalyzing the hydrolysis of NTPs, are essential for RepA activity. Residue H178 of motif H3 couples nucleotide consumption to DNA strand separation. PMID:14530440

  15. Synthesis, growth, structural, optical, thermal and mechanical properties of an organic Urea maleic acid single crystals for nonlinear optical applications

    NASA Astrophysics Data System (ADS)

    Vinothkumar, P.; Kumar, R. Mohan; Jayavel, R.; Bhaskaran, A.

    2016-07-01

    A potential organic urea maleic acid (UMA) was synthesized and single crystals were grown at room temperature by slow evaporation and seed rotation methods. The grown crystal has been subjected to single crystal XRD analysis and found to have been crystallized in a noncentrosymmetric monoclinic crystal system with Cc as space group. The High resolution X-ray diffraction analysis revealed that the specimen is free from structural grain boundaries. The transparency of the grown crystal was confirmed by optical absorption and transmittance spectra with lower cut-off wavelength of 285 nm. The microhardness test was carried out on different planes to study the load dependent hardness values. The dislocation density of the UMA crystal was estimated from the etching studies. The dielectric permittivity and dielectric loss of the grown crystal was carried out as a function of frequency for different temperatures along three crystallographic axes. Thermal properties of UMA crystals were studied by TG-DTA analysis and it is stable upto 112 °C. The laser induced surface damage threshold of the grown crystal was measured using Nd: YAG laser. The birefringence of the crystal measured in the visible region was found to vary with the wavelength. The particle size dependent SHG of the sample was measured with different input energies by Kurtz's powder method using Nd:YAG laser.

  16. Synthesis, Crystal Growth and Characterization of bis Dl-Valine Picrate Single Crystal for Second-Order Nonlinear Optical Applications

    NASA Astrophysics Data System (ADS)

    Silambarasan, A.; Krishna Kumar, M.; Sudhahar, S.; Thirunavukkarasu, A.; Mohan Kumar, R.; Umarani, P. R.

    2013-08-01

    An organic compound Bis DL-Valine picrate (BDLVP) was synthesized successfully and single crystal was grown by slow evaporation solution growth method. The presence of functional groups in the compound was identified by FTIR spectral analysis. Single crystal X-ray diffraction study revealed that the grown crystal belongs to P21/n space group of monoclinic crystal system. Powder X-ray diffraction pattern was recorded to know the crystalline perfection of the grown crystal. The reaction mechanism, thermal decomposition stages and thermal stability of the grown crystal were studied by using TG/DTA analysis. From the UV-visible spectral study, the electronic band gap energy (Eg) of the grown crystal was found to be 2.43 eV. The second harmonic generation (SHG) efficiency of grown crystal was found to be 1.3 times higher than KDP crystal by using Kurtz powder SHG technique. The microhardness property of the grown crystal was examined by Vicker's microhardness test.

  17. Single port transvesical prostatectomy.

    PubMed

    Vicentini, Fabio C; Hisano, Marcelo; Agresta, Tulio S; Murta, Claudio B; Claro, Joaquim F A

    2012-01-01

    To describe a case of a transvesical prostatectomy performed by a single port technique. JLS, 64y, diabetic and hypertense, under treatment of LUTS for 8 years with 4mg doxazosin and 5mg finasteride. The IPSS score was 26. The digital rectal exam showed a more than 60g benign prostate. The Body Mass Index was 28.9. The total PSA was 5.4ng/mL and the free/total PSA was 22%. A 12-fragments prostate biopsy showed BPH. The sonography revealed a 106g prostate and the maximum urinary flow was 12 mL/s. The patient was under general anesthesia and was positioned in dorsal decubitus with Trendelemburg. The bladder was filled until that a bexigoma was visible. A 2 cm longitudinal infra-umbelical incision was done. The Gel Point Single Port System (Applied, Ca, USA) was placed inside the bladder and the pneumovesicum was done until 10mmHg. A peri-bladder neck incision was done and the adenoma dissection was performed until its remotion. The hemostasia was done under vision. A 3-way 24-Fr Foley catheter and an 8-Fr plastic catheter were placed inside the bladder. The adenoma was removed and the bladder and the abdominal wall were closed. The procedure took 55 minutes and the blood loss was 180 ml. The patient evolved uneventfully, the bladder irrigation stayed for 24 h, the hemoglobin drop was 2.4g/dL and the patient was discharge after 36 hours. The urethral catheters stayed for 5 days. The postoperative IPSS was 6 and the maximum flow was 26 ml/s. The surgery was safe and effective, showing that the single port transvesical prostatectomy can be an option in the surgical treatment of large prostates.

  18. Single molecule diffraction.

    PubMed

    Spence, J C H; Doak, R B

    2004-05-14

    For solving the atomic structure of organic molecules such as small proteins which are difficult to crystallize, the use of a jet of doped liquid helium droplets traversing a continuous high energy electron beam is proposed as a means of obtaining electron diffraction patterns (serial crystallography). Organic molecules (such as small proteins) within the droplet (and within a vitreous ice jacket) may be aligned by use of a polarized laser beam. Iterative methods for solving the phase problem are indicated. Comparisons with a related plan for pulsed x-ray diffraction from single proteins in a molecular beam are provided.

  19. The single antenna interferometer

    SciTech Connect

    Fitch, J.P.

    1990-01-15

    Air and space borne platforms using synthetic aperture radars (SAR) have made interferometric measurements by using either two physical antennas mounted on one air-frame or two passes of one antenna over a scene. In this paper, a new interferometric technique using one pass of a single-antenna SAR system is proposed and demonstrated on data collected by the NASA-JPL AirSAR. Remotely sensed L-band microwave data are used to show the sensitivity of this technique to ocean surface features as well as a baseline for comparison with work by others using two-antenna systems. 7 refs., 3 figs.

  20. Single nanowire extinction spectroscopy.

    PubMed

    Giblin, Jay; Vietmeyer, Felix; McDonald, Matthew P; Kuno, Masaru

    2011-08-10

    Here we show the first direct extinction spectra of single one-dimensional (1D) semiconductor nanostructures obtained at room temperature utilizing a spatial modulation approach. (1) For these materials, ensemble averaging in conventional extinction spectroscopy has limited our understanding of the interplay between carrier confinement and their electrostatic interactions. (2-4) By probing individual CdSe nanowires (NWs), we have identified and assigned size-dependent exciton transitions occurring across the visible. In turn, we have revealed the existence of room temperature 1D excitons in the narrowest NWs.

  1. Single Axis Piezoceramic Gimbal

    NASA Technical Reports Server (NTRS)

    Horner, Garnett C.; Taleghani, Barmac K.

    1999-01-01

    This paper describes the fabrication, testing, and analysis of a single axis piezoceramic gimbal. The fabrication process consist of pre-stressing a piezoceramic wafer using a high-temperature thermoplastic polyimide and a metal foil. The differential thermal expansion between the ceramic and metal induces a curvature. The pre-stressed, curved piezoceramic is mounted on a support mechanism and a mirror is attached to the piezoceramic. A plot of gimbal angle versus applied voltage to the piezoceramic is presented. A finite element analysis of the piezoceramic gimbal is described. The predicted gimbal angle versus applied voltage is compared to experimental results.

  2. Single crystals of chitosan.

    PubMed

    Cartier, N; Domard, A; Chanzy, H

    1990-10-01

    Lamellar single crystals of chitosan were prepared at 125 degrees C by adding ammonia to a low DP fraction of chitosan dissolved in water. The crystals gave sharp electron diffraction diagrams which could be indexed in an orthorhombic P2(1)2(1)2(1) unit cell with a = 8.07 A, b = 8.44 A, c = 10.34 A. The unit cell contained two anti-parallel chitosan chains and no water molecules. It was found that cellulose microfibrils from Valonia ventricosa could act as nuclei for inducing the crystallization of chitosan on cellulose. This produced a shish-kebab morphology.

  3. Single implant tooth replacement.

    PubMed

    Briley, T F

    1998-01-01

    It has been shown that direct bone anchorage of dental implants will provide long-term predictability for single tooth implants and multi-unit implants. The function of implant-supported restoration is now routinely achieved. The real challenge facing the restorative dentist and laboratory technician is to achieve optimal aesthetics. The learning objective of this article is to review the prosthodontic procedures essential to maximizing natural aesthetics in implant supported restorations. It will provide a review of master impression techniques, prepable titanium abutments and designing the cement on restoration. Particular emphasis is directed to the soft tissue model from which a series of sequenced techniques can be followed to achieve optimal aesthetics. Analysis of the implant alignment with regard to the neighboring teeth will result in having to make a choice of which prepable abutment will maximize the aesthetic result. The following case outlines how to replace a single missing tooth using an externally hexed implant system and a prefabricated titanium abutment on a 26-year-old male patient.

  4. Single-spin entanglement

    NASA Astrophysics Data System (ADS)

    Furman, G. B.; Meerovich, V. M.; Sokolovsky, V. L.

    2017-09-01

    We show that the operators and the quadrupole and Zeeman Hamiltonians for a spin 3/2 can be represented in terms for a system of two coupling fictitious spins 1/2 using the Kronecker product of Pauli matrices. Particularly, the quadrupole Hamiltonian which describes the interaction of the nuclear quadrupole moment with an electric field gradient is represented as the Hamiltonian of the Ising model in a transverse selective magnetic field. The Zeeman Hamiltonian, which describes interaction of the nuclear spin with the external magnetic field, can be considered as the Hamiltonian of the Heisenberg model in a selective magnetic field. The total Hamiltonian can be interpreted as the Hamiltonian of 3 D Heisenberg model in an inhomogeneous magnetic field applied along the x-axis. The representation of a single spin 3/2 as two-spin 1/2 system allows us to study entanglement in the spin system. One of the features of the fictitious spin system is that, in both the pure and the mixed states, the concurrence tends to 0.5 with increase of an applied magnetic field. The representation of a spin 3/2 as a system of two coupling fictitious spins 1/2 and possibility of formation of the entangled states in this system open a way to the application of a single spin 3/2 in quantum computation.

  5. Single cell wound repair

    PubMed Central

    Abreu-Blanco, Maria Teresa; Verboon, Jeffrey M

    2011-01-01

    Cell wounding is a common event in the life of many cell types, and the capacity of the cell to repair day-to-day wear-and-tear injuries, as well as traumatic ones, is fundamental for maintaining tissue integrity. Cell wounding is most frequent in tissues exposed to high levels of stress. Survival of such plasma membrane disruptions requires rapid resealing to prevent the loss of cytosolic components, to block Ca2+ influx and to avoid cell death. In addition to patching the torn membrane, plasma membrane and cortical cytoskeleton remodeling are required to restore cell function. Although a general understanding of the cell wound repair process is in place, the underlying mechanisms of each step of this response are not yet known. We have developed a model to study single cell wound repair using the early Drosophila embryo. Our system combines genetics and live imaging tools, allowing us to dissect in vivo the dynamics of the single cell wound response. We have shown that cell wound repair in Drosophila requires the coordinated activities of plasma membrane and cytoskeleton components. Furthermore, we identified an unexpected role for E-cadherin as a link between the contractile actomyosin ring and the newly formed plasma membrane plug. PMID:21922041

  6. Single compartment drug delivery

    PubMed Central

    Cima, Michael J.; Lee, Heejin; Daniel, Karen; Tanenbaum, Laura M.; Mantzavinou, Aikaterini; Spencer, Kevin C.; Ong, Qunya; Sy, Jay C.; Santini, John; Schoellhammer, Carl M.; Blankschtein, Daniel; Langer, Robert S.

    2014-01-01

    Drug design is built on the concept that key molecular targets of disease are isolated in the diseased tissue. Systemic drug administration would be sufficient for targeting in such a case. It is, however, common for enzymes or receptors that are integral to disease to be structurally similar or identical to those that play important biological roles in normal tissues of the body. Additionally, systemic administration may not lead to local drug concentrations high enough to yield disease modification because of rapid systemic metabolism or lack of sufficient partitioning into the diseased tissue compartment. This review focuses on drug delivery methods that physically target drugs to individual compartments of the body. Compartments such as the bladder, peritoneum, brain, eye and skin are often sites of disease and can sometimes be viewed as “privileged,” since they intrinsically hinder partitioning of systemically administered agents. These compartments have become the focus of a wide array of procedures and devices for direct administration of drugs. We discuss the rationale behind single compartment drug delivery for each of these compartments, and give an overview of examples at different development stages, from the lab bench to phase III clinical trials to clinical practice. We approach single compartment drug delivery from both a translational and a technological perspective. PMID:24798478

  7. Single-Mode VISAR

    SciTech Connect

    Krauter, Kerry

    2007-11-28

    High energy-density physics (HEDP) experiments examine the properties of materials under extreme conditions. These experiments rely on the measurement of one or two velocities. These velocities are used to obtain Hugoniot relationships and thermodynamic equations of state. This methodology is referred to as 'velocimetry' and an instrument used to measure the shock wave is called a 'velocimeter' or a '(velocity) diagnostic'. The two most-widely used existing velocity diagnostics are; photonic Doppler velocimetry (PDV) and velocity interferometer system for any reflector (VISAR). PDV's advantages are a fast rise-time and ease of implementation but PDV has an upper velocity limit. Traditional implementations of VISAR have a rise time 10 times slower than PDV and are not easily implemented but are capable of measuring any velocity produced during HEDP experiments. This thesis describes a novel method of combining the positive attributes of PDV and VISAR into a more cost effective diagnostic called a Single-Mode VISAR (SMV). The new diagnostic will consist of PDV parts in a VISAR configuration. This configuration will enable the measurement of any velocity produced during shock physics experiments while the components used to build the diagnostic will give the diagnostic a fast rise time and make it easy to use. This thesis describes the process of building and testing the first single-mode VISAR. The tests include verifying the performance of the components and the diagnostic as a whole.

  8. Single ion heat engine

    NASA Astrophysics Data System (ADS)

    Singer, Kilian

    2015-03-01

    An experimental realization of a heat engine with a single ion is presented, which will allow for work extraction even with non-classical thermal reservoirs. To this goal a custom designed linear Paul trap with a single ion performing an Otto cycle is presented. The radial state of the ion is used as the working gas analogous to the gas in a conventional heat engine. The conventional piston is realized by the axial degrees of freedom and the axial motional excitation stores the generated work, just like a conventional fly-wheel. The heat baths can be realized by tailored laser radiation. Alternatively electrical noise can be used to control the state of the ion. The presented system possesses advantageous properties, as the working parameters can be tuned over a broad range and the motional degrees of freedom of the ion can be accurately determined. Dark resonances allow for fast stroboscopic thermometry during the entire working cycle. Monte Carlo simulations are performed to predict the efficiency and the gained work of the working cycle. We have also shown how the equations for the Carnot limit have to be modified if a squeezed thermal reservoir is employed. Furthermore structural phase transitions with laser cooled linear ion crystals are induced verifying the Kibble-Zurek mechanism.

  9. Compression of Single-Crystal Orthopyroxene to 60GPa

    NASA Astrophysics Data System (ADS)

    Finkelstein, G. J.; Dera, P. K.; Holl, C. M.; Dorfman, S. M.; Duffy, T. S.

    2010-12-01

    Orthopyroxene ((Mg,Fe)SiO3) is one of the dominant phases in Earth’s upper mantle - it makes up ~20% of the upper mantle by volume. At high pressures and temperatures, this phase undergoes several well-characterized phase transitions. However, when compressed at low temperature and high-pressure, orthopyroxene is predicted to exhibit metastable behavior(1). Previous researchers have found orthoenstatite (Mg endmember of orthopyroxene) persists up to ~10 GPa, and diffraction(2-3), Raman(4), and elasticity(5) experiments suggest a phase transition above this pressure to an as-yet unidentified structure. While earlier diffraction data has surprisingly only been evaluated for structural information to ~9 GPa(2), changes in high-pressure Raman spectra to ~70 GPa indicate that several more high-pressure phase transitions in orthopyroxene are likely, including at least one change in Si-coordination(6). We have recently conducted exploratory experiments to further elucidate the high-pressure behavior of orthopyroxene. Compressing a single crystal of Fe-rich orthopyroxene (Fe0.66Mg0.24Ca0.05SiO3) using a diamond anvil cell, we observe phase transitions at ~10, 14, and 30 GPa, with the new phases having monoclinic, orthorhombic, and orthorhombic symmetries, respectively. While the first two transitions do not show a significant change in volume, the phase transition at ~30 GPa shows a large decrease in volume, which is consistent with a change in Si coordination number to mixed 4- and 6-fold coordination. References: [1] S. Jahn, American Mineralogist 93, 528-532 (2008). [2] R. J. Angel, J. M. Jackson, American Mineralogist 87, 558-561 (2002). [3] R. J. Angel, D. A. Hugh-Jones, Journal of Geophysical Research-Solid Earth 99, 19,777-19,783 (1994). [4] G. Serghiou, Journal of Raman Spectroscopy 34, 587-590 (2003). [5] J. Kung et al., Physics of the Earth and Planetary Interiors 147, 27-44 (2004). [6] G. Serghiou, A. Chopelas, R. Boehler, Journal of Physics: Condensed

  10. Study of temperature-dependent Raman spectroscopy and electrical properties in [001]-oriented 0.35Pb(In1/2Nb1/2)O3-0.35Pb(Mg1/3Nb2/3)O3-0.30PbTiO3-Mn single crystals

    NASA Astrophysics Data System (ADS)

    Liu, Xing; Fang, Bijun; Deng, Ji; Yan, Hong; Deng, Hao; Yue, Qingwen; Ding, Jianning; Zhao, Xiangyong; Luo, Haosu

    2016-01-01

    In this work, the temperature-dependent Raman spectra and electrical properties of the [001]-oriented 0.5 mol. % Mn-doped 0.35Pb(In1/2Nb1/2)O3-0.35Pb(Mg1/3Nb2/3)O3-0.30PbTiO3-Mn (PIMNT-Mn) single crystals were investigated. All the unpoled and poled PIMNT-Mn single crystals experience a ferroelectric tetragonal phase to paraelectric cubic phase transition (FET-PC) around 183 °C (TC), which exhibits a second-order transition behavior. Whereas, the poled PIMNT-Mn single crystals exhibit another two dielectric anomalies around 130 °C (TRM) and 148 °C (TMT), in which the ferroelectric rhombohedral phase to ferroelectric monoclinic phase (FER-FEM) and the ferroelectric monoclinic phase to ferroelectric tetragonal phase (FEM-FET) transitions take place, respectively. Both the two ferroelectric phase transitions exhibit a first-order transition behavior. The discontinuous change of the phase degree (θ) and frequencies (fr and fa) around TRM suggest the occurrence of the FER-FEM phase transition in the poled PIMNT-Mn single crystals. The narrowing of the 510 cm-1 and 582 cm-1 Raman modes around the TRM, TMT, and TC temperatures shown in the temperature-dependent Raman spectra suggests their increased ordering of the local structure. The intensity ratio of I272 cm-1/I801 cm-1 increases obviously around the phase transition temperatures (TRM, TMT, and TC), indicating the reduction of the long-range order. The anomalous broadening of the 272 cm-1 Raman mode around the TRM, TMT, and TC temperatures indicates the occurrence of the successive ferroelectric phase transitions (FER-FEM, FEM-FET, and FET-PC) with increasing temperature in the poled PIMNT-Mn single crystals.

  11. Mandibular First Molar with a Single Root and Single Canal

    PubMed Central

    Sooriaprakas, Chandrasekaran; Ballal, Suma; Velmurugan, Natanasabapathy

    2014-01-01

    Successful endodontic management of mandibular first molar with a single root and single canal is diagnosed with the aid of dental operating microscope and multiple angled radiographs. In addition all the mandibular molars and premolars were single rooted on either side. PMID:24715990

  12. Single crystalline magnetite nanotubes.

    PubMed

    Liu, Zuqin; Zhang, Daihua; Han, Song; Li, Chao; Lei, Bo; Lu, Weigang; Fang, Jiye; Zhou, Chongwu

    2005-01-12

    We descried a method to synthesize single crystalline Fe3O4 nanotubes by wet-etching the MgO inner cores of MgO/Fe3O4 core-shell nanowires. Homogeneous Fe3O4 nanotubes with controllable length, diameter, and wall thickness have been obtained. Resistivity of the Fe3O4 nanotubes was estimated to be approximately 4 x 10-2 Omega cm at room temperature. Magnetoresistance of approximately 1% was observed at T = 77 K when a magnetic field of B = 0.7 T was applied. The synthetic strategy presented here may be extended to a variety of materials such as YBCO, PZT, and LCMO which should provide ideal candidates for fundamental studies of superconductivity, piezoelectricity, and ferromagnetism in nanoscale structures.

  13. Single-Axis Accelerometer

    NASA Technical Reports Server (NTRS)

    Tucker, Dennis Stephen (Inventor); Capo-Lugo, Pedro A. (Inventor)

    2016-01-01

    A single-axis accelerometer includes a housing defining a sleeve. An object/mass is disposed in the sleeve for sliding movement therein in a direction aligned with the sleeve's longitudinal axis. A first piezoelectric strip, attached to a first side of the object and to the housing, is longitudinally aligned with the sleeve's longitudinal axis. The first piezoelectric strip includes a first strip of a piezoelectric material with carbon nanotubes substantially aligned along a length thereof. A second piezoelectric strip, attached to a second side of the object and to the housing, is longitudinally aligned with the sleeve's longitudinal axis. The second piezoelectric strip includes a second strip of the piezoelectric material with carbon nanotubes substantially aligned along a length thereof. A voltage sensor is electrically coupled to at least one of the first and second piezoelectric strips.

  14. Single Cell Physiology

    NASA Astrophysics Data System (ADS)

    Neveu, Pierre; Sinha, Deepak Kumar; Kettunen, Petronella; Vriz, Sophie; Jullien, Ludovic; Bensimon, David

    The possibility to control at specific times and specific places the activity of biomolecules (enzymes, transcription factors, RNA, hormones, etc.) is opening up new opportunities in the study of physiological processes at the single cell level in a live organism. Most existing gene expression systems allow for tissue specific induction upon feeding the organism with exogenous inducers (e.g., tetracycline). Local genetic control has earlier been achieved by micro-injection of the relevant inducer/repressor molecule, but this is an invasive and possibly traumatic technique. In this chapter, we present the requirements for a noninvasive optical control of the activity of biomolecules and review the recent advances in this new field of research.

  15. Photochemically Initiated Single Polymer Immobilization

    PubMed Central

    2015-01-01

    This Concept article surveys methods for attaching single polymer molecules on solid substrates. A general approach to single polymer immobilization based on the photochemistry of perfluorophenylazides is elaborated. PMID:17444538

  16. Study on dielectric and piezoelectric properties of 0.7 Pb(Mg1/3Nb2/3)O3-0.3 PbTiO3 single crystal with nano-patterned composite electrode

    NASA Astrophysics Data System (ADS)

    Chang, Wei-Yi; Huang, Wenbin; Bagal, Abhijeet; Chang, Chih-Hao; Tian, Jian; Han, Pengdi; Jiang, Xiaoning

    2013-09-01

    Effect of nano-patterned composite electrode and backswitching poling technique on dielectric and piezoelectric properties of 0.7 Pb(Mg1/3Nb2/3)O3-0.3 PbTiO3 was studied in this paper. Composite electrode consists of Mn nano-patterns with pitch size of 200 nm, and a blanket layer of Ti/Au was fabricated using a nanolithography based lift-off process, heat treatment, and metal film sputtering. Composite electrode and backswitching poling resulted in 27% increase of d33 and 25% increase of dielectric constant, and we believe that this is attributed to regularly defined nano-domains and irreversible rhombohedral to monoclinic phase transition in crystal. The results indicate that nano-patterned composite electrode and backswitching poling has a great potential in domain engineering of relaxor single crystals for advanced devices.

  17. Non-covalent interactions in 2-methylimidazolium copper(II) complex (MeImH)2[Cu(pfbz)4]: Synthesis, characterization, single crystal X-ray structure and packing analysis

    NASA Astrophysics Data System (ADS)

    Sharma, Raj Pal; Saini, Anju; Kumar, Santosh; Kumar, Jitendra; Sathishkumar, Ranganathan; Venugopalan, Paloth

    2017-01-01

    A new anionic copper(II) complex, (MeImH)2 [Cu(pfbz)4] (1) where, MeImH = 2-methylimidazolium and pfbz = pentafluorobenzoate has been isolated by reacting copper(II) sulfate pentahydrate, pentafluorobenzoic acid and 2-methylimidazole in ethanol: water mixture in 1:2:2 molar ratio. This complex 1 has been characterized by elemental analysis, thermogravimetric analysis, spectroscopic techniques (UV-Vis, FT-IR) and conductance measurements. The complex salt crystallizes in monoclinic crystal system with space group C2/c. Single crystal X-ray structure determination revealed the presence of discrete ions: [Cu(pfbz)4]2- anion and two 2-methylimidazolium cation (C4H7N2)+. The crystal lattice is stabilized by strong hydrogen bonding and F⋯F interactions between cationic-anionic and the anionic-anionic moieties respectively, besides π-π interactions.

  18. Structure of Wallach's compound. Single-crystal x-ray structure determination of trans-2,5-bis(trichloromethyl)-N-(1'-hydroxy-2',2',2'-trichloroethyl)-4-imino-1,3-dioxolane

    SciTech Connect

    Irving, A.; Irving, H.M.N.H.; Koch, K.R.

    1987-04-01

    The structure of Wallach's compound, C/sub 7/H/sub 4/O/sub 3/NCl/sub 9/, prepared in 1874 from concentrated aqueous solutions of potassium cyanide and chloral hydrate, has long been undecided. By single crystal X-ray crystallography it has now been established as trans-2,5-bis(trichloromethyl)-N-(1'-hydroxy-2',2',2'-trichloroethyl)-4-imino-1,3-dioxolane, confirming the tentative assignment by /sup 1/H and /sup 13/C NMR spectrography. The title compound is monoclinic, P2/sub 1//c; a = 8.445 (1), b = 10.948(1), c = 17.923(4) A; ..beta.. = 94.36(1)/sup 0/; Z = 4. The structure was solved by direct methods, from data collected at room temperature on an Enraf-Nonius CAD4 diffractometer, and refined by least squares to a final R value of 0.041 using 2101 reflections.

  19. Study on dielectric and piezoelectric properties of 0.7 Pb(Mg1/3Nb2/3)O3-0.3 PbTiO3 single crystal with nano-patterned composite electrode

    PubMed Central

    Chang, Wei-Yi; Huang, Wenbin; Bagal, Abhijeet; Chang, Chih-Hao; Tian, Jian; Han, Pengdi; Jiang, Xiaoning

    2013-01-01

    Effect of nano-patterned composite electrode and backswitching poling technique on dielectric and piezoelectric properties of 0.7 Pb(Mg1/3Nb2/3)O3-0.3 PbTiO3 was studied in this paper. Composite electrode consists of Mn nano-patterns with pitch size of 200 nm, and a blanket layer of Ti/Au was fabricated using a nanolithography based lift-off process, heat treatment, and metal film sputtering. Composite electrode and backswitching poling resulted in 27% increase of d33 and 25% increase of dielectric constant, and we believe that this is attributed to regularly defined nano-domains and irreversible rhombohedral to monoclinic phase transition in crystal. The results indicate that nano-patterned composite electrode and backswitching poling has a great potential in domain engineering of relaxor single crystals for advanced devices. PMID:24170960

  20. Synthesis, Single Crystal Structure, and Magnetic Properties of 3-D Cu(NITpPy)2[Cu(CN)3].2CH3OH.2H2O Complexes

    NASA Astrophysics Data System (ADS)

    Dasna, I. W.; Golhen, S.; Ouahab, L.; Subakti

    2017-05-01

    A new Cu(II) complexes containing nitroxide radicals Cu(NITpPy)2[Cu(CN)3]. 2CH3OH.2H2O has been successfully synthesized. The single crystal X-ray analysis revealed that the compound belongs to monoclinic crystal system (C2/c (#15)). The existence of the C≡N radical and water molecules are observed by using infra-red within the range of 4000-500 cm-1 and 3500-3000 cm-1, respectively. The Cu(NITpPy)2 2+ units are connected through N(CN)2- bridging ligands in 2 coordination developing, respectively, into one-dimensional and two-dimensional polymeric networks. Paramagnetic interactions in the compound appear in the vicinity of room temperature. As the temperature decreased, low dimensional antiferromagnetic interactions established and Cu(II)-radicals antiferromagnetic interactions dominates down to 2 K with μeff = 0.8129 μB

  1. Study on dielectric and piezoelectric properties of 0.7 Pb(Mg1/3Nb2/3)O3-0.3 PbTiO3 single crystal with nano-patterned composite electrode.

    PubMed

    Chang, Wei-Yi; Huang, Wenbin; Bagal, Abhijeet; Chang, Chih-Hao; Tian, Jian; Han, Pengdi; Jiang, Xiaoning

    2013-09-21

    Effect of nano-patterned composite electrode and backswitching poling technique on dielectric and piezoelectric properties of 0.7 Pb(Mg1/3Nb2/3)O3-0.3 PbTiO3 was studied in this paper. Composite electrode consists of Mn nano-patterns with pitch size of 200 nm, and a blanket layer of Ti/Au was fabricated using a nanolithography based lift-off process, heat treatment, and metal film sputtering. Composite electrode and backswitching poling resulted in 27% increase of d33 and 25% increase of dielectric constant, and we believe that this is attributed to regularly defined nano-domains and irreversible rhombohedral to monoclinic phase transition in crystal. The results indicate that nano-patterned composite electrode and backswitching poling has a great potential in domain engineering of relaxor single crystals for advanced devices.

  2. Single Sex Education. WEEA Digest.

    ERIC Educational Resources Information Center

    Pollard, Diane S.

    Title IX of the Educational Amendments of 1972 prohibits discrimination on the basis of sex in educational institutions that receive federal financial assistance. This digest focuses on the theme of single-sex education. Articles featured in this issue include: (1) "Single-Sex Education" (Diane S. Pollard); (2) "A Legal Framework for Single-Sex…

  3. Single Parenting of the Adolescent.

    PubMed

    Carroll

    1991-06-01

    This article discusses issues that are of interest and concern to all parents of adolescents, but that may be particularly difficult for single parents to manage. It also provides a framework for examining the areas of similarity as well as difference between the adolescent and the single parent. Attention is paid to the potential advantages of single-parent status.

  4. Investigation of thermal diffusivity dependence on temperature in a group of optical single crystals doped with rare earth ions

    NASA Astrophysics Data System (ADS)

    Trefon-Radziejewska, D.; Bodzenta, J.

    2015-07-01

    The group of YAG, YVO4 and GdCOB single crystals was examined to determine the thermal diffusivity as a function of temperature in range from 30 °C to 300 °C. Further investigations concerned on analysis of the influence of dopants on these dependencies. The experimental setup based on thermal wave method with mirage detection was used. The samples represented different crystallographic systems such as cubic (YAG) tetragonal (YVO4) and monoclinic (GdCOB). The anisotropy of thermal conductivity of investigated samples was taken into account in the investigations. The crystals were doped with calcium ions, rare earth ions such as ytterbium, neodymium, and thulium, and also with transition metal vanadium. The results confirmed that influence of doping on the thermal diffusivity of investigated materials strongly depends on temperature. In general the thermal diffusivity decreases with increasing of sample temperature from 30 °C to 300 °C, however the drop in thermal diffusivity is the highest for pure single crystals. Doping is another factor reducing the heat transport in single crystals. Introduction of dopant ions into a crystal lattice leads to a significant decrease in the thermal diffusivity at lower temperatures in comparison with pure crystals. However, the influence of dopants becomes less pronounced with increasing temperature, and in case of weakly doped crystals it becomes negligible at higher temperatures. The interpretation of thermal diffusivity dependence on temperature for single crystals was based on the Debye model of lattice thermal conductivity of solids. The results allowed to conclude that the decrease of thermal diffusivity with temperature and increasing concentration of impurities is caused by shortening of the phonons mean free path due to phonon-phonon and phonon-point defect scatterings.

  5. The crystal structure of {pi}-ErBO{sub 3}: New single-crystal data for an old problem

    SciTech Connect

    Pitscheider, Almut; Kaindl, Reinhard; Oeckler, Oliver; Huppertz, Hubert

    2011-01-15

    Single crystals of the orthoborate {pi}-ErBO{sub 3} were synthesized from Er{sub 2}O{sub 3} and B{sub 2}O{sub 3} under high-pressure/high-temperature conditions of 2 GPa and 800 {sup o}C in a Walker-type multianvil apparatus. The crystal structure was determined on the basis of single-crystal X-ray diffraction data, collected at room temperature. The title compound crystallizes in the monoclinic pseudowollastonite-type structure, space group C2/c, with the lattice parameters a=1128.4(2) pm, b=652.6(2) pm, c=954.0(2) pm, and {beta}=112.8(1){sup o} (R{sub 1}=0.0124 and wR{sub 2}=0.0404 for all data). -- graphical abstract: The first satisfying single-crystal structure determination of {pi}-ErBO{sub 3} sheds light on the extensively discussed structure of {pi}-orthoborates. The application of light pressure during the solid state synthesis yielded in high-quality crystals, due to pressure-induced crystallization. Research highlights: {yields} High-quality single crystals of {pi}-ErBO{sub 3} were prepared via high-pressure-induced crystallization. {yields} At least five different space groups for the rare-earth {pi}-orthoborates are reported. {yields} {pi}-ErBO{sub 3} is isotypic to the pseudowollastonite-type CaSiO{sub 3}. {yields} Remaining ambiguities regarding the structure of the rare-earth {pi}-orthoborates are resolved.

  6. A single particle energies

    SciTech Connect

    Bodmer, A.R. |; Usmani, Q.N.; Sami, M.

    1993-09-01

    We consider the binding energies of {Lambda} hypernuclei (HN), in particular the single-particle (s.p.) energy data, which have been obtained for a wide range of HN with mass numbers A {le} 89 and for orbital angular momenta {ell}{sub {Lambda}} {le} 4. We briefly review some of the relevant properties of A hypernuclei. These are nuclei {sub {Lambda}}{sup A}Z with baryon number A in which a single {Lambda} hyperon (baryon number = 1) is bound to an ordinary nucleus {sup A}Z consisting of A - 1 nucleons = Z protons + N neutrons. The {Lambda} hyperon is neutral, has spin 1/2, strangeness S = {minus}1, isospin I = O and a mass M{sub {Lambda}} = 1116 MeV/c{sup 2}. Although the {Lambda} interacts with a nucleon, its interaction is only about half as strong as that between two nucleons, and thus very roughly V{sub {Lambda}N} {approx} 0.5 V{sub NN}. As a result, the two-body {Lambda}N system is unbound, and the lightest bound HN is the three-body hypertriton {sub {Lambda}}{sup 3}H in which the {Lambda} is bound to a deuteron with the {Lambda}-d separation energy being only {approx} 0.1 MeV corresponding to an exponential tail of radius {approx} 15 fm! In strong interactions the strangeness S is of course conserved, and the {Lambda} is distinct from the nucleons. In a HN strangeness changes only in the weak decays of the {Lambda} which can decay either via ``free`` pionic decay {Lambda} {yields} N + {pi} or via induced decay {Lambda} + N {yields} N + N which is only possible in the presence of nucleons. Because of the small energy release the pionic decay is strongly suppressed in all but the lightest HN and the induced decay dominates. However, the weak decay lifetime {approx} 10{sup {minus}10}s is in fact close to the lifetime of a free {Lambda}. Since this is much longer than the strong interaction time {approx} 10{sup {minus}22}s we can ignore the weak interactions when considering the binding of HN, just as for ordinary nuclei.

  7. Synthesis, growth, structural, spectral, thermal, chemical etching, linear and nonlinear optical and mechanical studies of an organic single crystal 4-chloro 4-nitrostilbene (CONS): a potential NLO material.

    PubMed

    Dinakaran, Paul M; Kalainathan, S

    2013-07-01

    4-Chloro 4-nitrostilbene (CONS) a new organic nonlinear optical material has been synthesized. Employing slow evaporation method, good optical quality single crystals (dimensions up to 6×2×3 mm(3)) have been grown using ethyl methyl ketone (EMK) as a solvent. The grown crystals have been subjected to various characterizations such as single crystal X-ray diffraction, powder XRD, Fourier Transform Infrared spectroscopy (FTIR), proton NMR, solid UV absorption, SHG studies. Single crystal X-ray diffraction reveals that the crystal system belongs to monoclinic with noncentrosymmetric space group P21. The UV-Vis absorption spectrum has been recorded and found that the cut off wavelength is 380 nm. Functional groups and the structure of the title compound have been confirmed by FTIR and (1)H NMR spectroscopic analyses respectively. Molecular mass of the CONS confirmed by the high resolution mass spectral analysis .The thermal behavior of the grown crystal has been studied by TG/DTA analysis and it shows the melting point is at 188.66 °C. Dislocations and growth pattern present in the grown crystal revealed by the etching study. The mechanical strength of the CONS crystal has been studied by Vicker's hardness measurement. The SHG efficiency of the grown crystal has been determined by Kurtz and Perry powder test which revealed that the CONS crystal (327 mV) has 15 times greater efficiency than that of KDP (21.7 mV).

  8. Synthesis, growth, structural, spectral, thermal, chemical etching, linear and nonlinear optical and mechanical studies of an organic single crystal 4-chloro 4-nitrostilbene (CONS): A potential NLO material

    NASA Astrophysics Data System (ADS)

    Dinakaran, Paul M.; Kalainathan, S.

    2013-07-01

    4-Chloro 4-nitrostilbene (CONS) a new organic nonlinear optical material has been synthesized. Employing slow evaporation method, good optical quality single crystals (dimensions up to 6 × 2 × 3 mm3) have been grown using ethyl methyl ketone (EMK) as a solvent. The grown crystals have been subjected to various characterizations such as single crystal X-ray diffraction, powder XRD, Fourier Transform Infrared spectroscopy (FTIR), proton NMR, solid UV absorption, SHG studies. Single crystal X-ray diffraction reveals that the crystal system belongs to monoclinic with noncentrosymmetric space group P21. The UV-Vis absorption spectrum has been recorded and found that the cut off wavelength is 380 nm. Functional groups and the structure of the title compound have been confirmed by FTIR and 1H NMR spectroscopic analyses respectively. Molecular mass of the CONS confirmed by the high resolution mass spectral analysis .The thermal behavior of the grown crystal has been studied by TG/DTA analysis and it shows the melting point is at 188.66 °C. Dislocations and growth pattern present in the grown crystal revealed by the etching study. The mechanical strength of the CONS crystal has been studied by Vicker's hardness measurement. The SHG efficiency of the grown crystal has been determined by Kurtz and Perry powder test which revealed that the CONS crystal (327 mV) has 15 times greater efficiency than that of KDP (21.7 mV).

  9. Single Molecule Mechanochemistry

    NASA Astrophysics Data System (ADS)

    Li, Shaowei; Zhang, Yanxing; Ho, Wilson; Wu, Ruqian; Ruqian Wu, Yanxing Zhang Team; Wilson Ho, Shaowei Li Team

    Mechanical forces can be used to trigger chemical reactions through bending and stretching of chemical bonds. Using the reciprocating movement of the tip of a scanning tunneling microscope (STM), mechanical energy can be provided to a single molecule sandwiched between the tip and substrate. When the mechanical pulse center was moved to the outer ring feature of a CO molecule, the reaction rate was significantly increased compared with bare Cu surface and over Au atoms. First, DFT calculations show that the presence of CO makes the Cu cavity more attractive toward H2 Second, H2 prefers the horizontal adsorption geometry in the Cu-Cu and Au-Cu cavities and no hybridization occurs between the antibonding states of H2 and states of Cu atoms. While H2 loses electrons from its bonding state in all three cavities, the filling of its anti-bonding state only occurs in the CO-Cu cavity. Both make the CO-Cu cavity much more effectively to chop the H2 molecule. Work was supported by the National Science Foundation Center for Chemical Innovation on Chemistry at the Space-Time Limit (CaSTL) under Grant No. CHE-1414466.

  10. Single slip dynamics

    NASA Astrophysics Data System (ADS)

    Bizzarri, Andrea; Petri, Alberto

    2016-12-01

    In the present paper we consider a 1-D, single spring-slider analog model of fault and we solve the equation of motion within the coseismic time window. We incorporate in the dynamic problem different rheologic behavior, starting from the Coulomb friction (which postulates a constant value of the dynamic resistance), then the viscous rheology (where the friction resistance linearly depends on the sliding speed), and finally a version of the more refined rate-and state-dependent friction law. We present analytical solutions of the equation of motion for the different cases and we are able to find the common features of the solutions, in terms of the most important physical observables characterizing the solutions of a 1-D dynamic fault problem; the peak slip velocity, the time at which it is attained (or, in other words, the so-called rise time), the total cumulative slip developed at the end of the process (assumed to occur when the sliding speed vanishes or become comparable to its initial value). We also extract some useful dependences of these quantities on the parameters of the models. Finally, we compare the spectral behavior of the resulting sliding velocity and its fall-off at high frequencies.

  11. Single-nucleon experiments

    SciTech Connect

    Deur, Alexandre

    2009-12-01

    We discuss the Jefferson Lab low momentum transfer data on moments of the nucleon spin structure functions $g_1$ and $g_2$ and on single charged pion electroproduction off polarized proton and polarized neutron. A wealth of data is now available, while more is being analyzed or expected to be taken in the upcoming years. Given the low momentum transfer selected by the experiments, these data can be compared to calculations from Chiral Perturbation theory, the effective theory of strong force that should describe it at low momentum transfer. The data on various moments and the respective calculations do not consistently agree. In particular, experimental data for higher moments disagree with the calculations.The absence of contribution from the $\\Delta$ resonance in the various observables was expected to facilitate the calculations and hence make the theory predictions either more robust or valid over a larger $Q^2$ range. Such expectation is verified only for the Bjorken sum, but not for other observables in which the $\\Delta$ is suppressed. Preliminary results on pion electroproduction off polarized nucleons are also presented and compared to phenomenological models for which contributions from different resonances are varied. Chiral Perturbation calculations of these observables, while not yet available, would be valuable and, together with these data, would provide an extensive test of the effective theory.

  12. Towards single molecule DNA sequencing

    NASA Astrophysics Data System (ADS)

    Liu, Hao

    Single molecule DNA Sequencing technology has been a hot research topic in the recent decades because it holds the promise to sequence a human genome in a fast and affordable way, which will eventually make personalized medicine possible. Single molecule differentiation and DNA translocation control are the two main challenges in all single molecule DNA sequencing methods. In this thesis, I will first introduce DNA sequencing technology development and its application, and then explain the performance and limitation of prior art in detail. Following that, I will show a single molecule DNA base differentiation result obtained in recognition tunneling experiments. Furthermore, I will explain the assembly of a nanofluidic platform for single strand DNA translocation, which holds the promised to be integrated into a single molecule DNA sequencing instrument for DNA translocation control. Taken together, my dissertation research demonstrated the potential of using recognition tunneling techniques to serve as a general readout system for single molecule DNA sequencing application.

  13. Unfolding single- and multilayers

    NASA Astrophysics Data System (ADS)

    Llorens, Maria-Gema; Bons, Paul D.; Griera, Albert; Gomez-Rivas, Enrique

    2014-05-01

    When planar structures (e.g. sedimentary layers, veins, dykes, cleavages, etc.) are subjected to deformation, they have about equal chances to be shortened or stretched. The most common shortening and stretching structures are folds and boudinage, respectively. However, boudinage requires additional deformation mechanisms apart from viscous flow, like formation of fractures or strain localization. When folded layers are subjected to extension, they could potentially unfold back to straight layers. Although probably not uncommon, this would be difficult to recognize. Open questions are whether folded layers can unfold, what determines their mechanical behaviour and how we can recognize them in the field. In order to approach these questions, we present a series of numerical experiments that simulate stretching of previously folded single- and multi-layers in simple shear, using the two dimensional numerical modelling platform ELLE, including the finite element module BASIL that calculates viscous deformation. We investigate the parameters that affect a fold train once it rotates into the extensional field. The results show that the unfolding process strongly depends on the viscosity contrast between the layer and matrix (Llorens et al., 2013). Layers do not completely unfold when they experience softening before or during the stretching process or when other neighbouring competent layers prevent them from unfolding. The foliation refraction patterns are the main indicators of unfolded folds. Additionally, intrafolial folds and cusp-like folds adjacent to straight layers, as well as variations in fold amplitudes and limb lengths of irregular folds can also be used as indicators of stretching of a layer after shortening and folding. References: Llorens, M-.G., Bons, P.D., Griera, A. and Gomez-Rivas, E. 2013. When do folds unfold during progressive shear?. Geology, 41, 563-566.

  14. Single Molecule Detection and Imaging in Single Living Cells

    NASA Astrophysics Data System (ADS)

    Nie, Shuming

    2002-03-01

    Direct observation of single molecules and single molecular events inside living cells could dramatically improve our understanding of basic cellular processes (e.g., signal transduction and gene transcription) as well as improving our knowledge on the intracellular transport and fate of therapeutic agents (e.g., antisense RNA and gene therapy vectors). This talk will focus on using single-molecule fluorescence and luminescent quantum dots to examine the dynamics and spatial distribution of RNA and proteins inside living cells and on the surface membrane surface. These single-molecule studies yield a detailed description of molecular events and cellular structures under physiological conditions.

  15. {Lambda} single particle energies

    SciTech Connect

    Usmani, Q.N.; Bodmer, A.R. |

    1999-11-01

    The {Lambda} single-particle energies B{sub {Lambda}} of hypernuclei (HN) are calculated microscopically using the Fermi hypernetted chain method to obtain for our {Lambda}N and {Lambda}NN potentials the {Lambda} binding D({rho}) to nuclear matter, and the effective mass m{sub {Lambda}}{sup {asterisk}}({rho}) at densities {rho}{le}{rho}{sub 0} ({rho}{sub 0} is normal nuclear density), and also the corresponding effective {Lambda}N and {Lambda}NN potentials. The {Lambda} core-nucleus potential U{sub {Lambda}}(r) is obtained by suitably folding these into the core density. The Schr{umlt o}dinger equation for U{sub {Lambda}} and m{sub {Lambda}}{sup {asterisk}} is solved for B{sub {Lambda}}. The fringing field (FF) due to the finite range of the effective potentials is theoretically required. We use a dispersive {Lambda}NN potential but also include a phenomenological {rho} dependence allowing for less repulsion for {rho}{lt}{rho}{sub 0}, i.e., in the surface. The best fits to the data with a FF give a large {rho} dependence, equivalent to an {ital A} dependent strength consistent with variational calculations of {sub {Lambda}}{sup 5}He, indicating an effective {Lambda}NN dispersive potential increasingly repulsive with {ital A} whose likely interpretation is in terms of dispersive plus two-pion-exchange {Lambda}NN potentials. The well depth is 29{plus_minus}1&hthinsp;MeV. The {Lambda}N space-exchange fraction corresponds to m{sub {Lambda}}{sup {asterisk}}({rho}){approx}0.75{endash}0.80 and a ratio of {ital p}- to {ital s}-state potentials of {approx}0.5{plus_minus}0.1. Charge symmetry breaking (CSB) is significant for heavy HN with a large neutron excess; with a FF the strength agrees with that obtained from the A=4&hthinsp;HN. The fits without FF are excellent but inconsistent with the requirement for a FF, with {sub {Lambda}}{sup 5}He, and also with the CSB sign for A=4. {copyright} {ital 1999} {ital The American Physical Society}

  16. Self-Phase-Matched Second-Harmonic and White-Light Generation in a Biaxial Zinc Tungstate Single Crystal

    PubMed Central

    Osewski, Pawel; Belardini, Alessandro; Petronijevic, Emilija; Centini, Marco; Leahu, Grigore; Diduszko, Ryszard; Pawlak, Dorota A.; Sibilia, Concita

    2017-01-01

    Second-order nonlinear optical materials are used to generate new frequencies by exploiting second-harmonic generation (SHG), a phenomenon where a nonlinear material generates light at double the optical frequency of the input beam. Maximum SHG is achieved when the pump and the generated waves are in phase, for example through birefringence in uniaxial crystals. However, applying these materials usually requires a complicated cutting procedure to yield a crystal with a particular orientation. Here we demonstrate the first example of phase matching under the normal incidence of SHG in a biaxial monoclinic single crystal of zinc tungstate. The crystal was grown by the micro-pulling-down method with the (102) plane perpendicular to the growth direction. Additionally, at the same time white light was generated as a result of stimulated Raman scattering and multiphoton luminescence induced by higher-order effects such as three-photon luminescence enhanced by cascaded third-harmonic generation. The annealed crystal offers SHG intensities approximately four times larger than the as grown one; optimized growth and annealing conditions may lead to much higher SHG intensities. PMID:28338074

  17. Growth and characterization of a single crystal of Urea Adipic acid (UAA) - A third order nonlinear optical material

    NASA Astrophysics Data System (ADS)

    Shanthi, A.; Krishnan, C.; Selvarajan, P.

    2014-03-01

    An organic single crystal of Urea Adipic acid (UAA) was successfully grown in methanol solvent by slow solvent evaporation technique at room temperature (30 °C). The structure of grown crystal was elucidated from the X-ray diffraction study and it belongs to monoclinic system with centrosymmetric space group P21/c. The optical transmission spectrum of UAA has been recorded and its theoretical calculations were carried out to determine the linear optical constants such as linear absorption coefficient, extinction coefficient, refractive index and reflectance etc. The third-order nonlinearities of UAA crystal have been investigated by Z-scan method. The values of nonlinear refractive index (n2), the absorption coefficient (β) and third-order nonlinear susceptibility (χ(3)) are found to be the order of 0.96 × 10-10 cm2/W, 1.248 × 10-4 cm/W and 6.44 × 10-8 esu respectively. Fourier Transform Infra Red and Raman spectroscopy studies reveal the intermolecular interactions present in the UAA sample. The dielectric and mechanical measurements of the title compound are also reported.

  18. Bismuth(III) dialkyldithiophosphates: Facile single source precursors for the preparation of bismuth sulfide nanorods and bismuth phosphate thin films

    NASA Astrophysics Data System (ADS)

    Biswal, Jasmine B.; Garje, Shivram S.; Nuwad, Jitendra; Pillai, C. G. S.

    2013-08-01

    Two different phase pure materials (Bi2S3 and Bi2P4O13) have been prepared under different conditions using the same single source precursors. Solvothermal decomposition of the complexes, Bi{S2P(OR)2}3 [where, R=Methyl (Me) (1), Ethyl (Et) (2), n-Propyl (Prn) (3) and iso-Propyl (Pri) (4)] in ethylene glycol gave orthorhombic bismuth sulfide nanorods, whereas aerosol assisted chemical vapor deposition (AACVD) of the same precursors deposited monoclinic bismuth tetraphosphate (Bi2P4O13) thin films on glass substrates. Surface study of the thin films using SEM illustrated the formation of variety of nanoscale morphologies (spherical-, wire-, pendent-, doughnut- and flower-like) at different temperatures. AFM studies were carried out to evaluate quality of the films in terms of uniformity and roughness. Thin films of average roughness as low as 1.4 nm were deposited using these precursors. Photoluminescence studies of Bi2P4O13 thin films were also carried out.

  19. Growth and characterization of Bis(L-threonine) copper (II) monohydrate single crystals: A semiorganic second order nonlinear optical material

    NASA Astrophysics Data System (ADS)

    Subhashini, R.; Sathya, D.; Sivashankar, V.; Latha Mageshwari, P. S.; Arjunan, S.

    2016-12-01

    Highly transparent solitary nonlinear semiorganic optical material Bis(L-threonine) copper (II) monohydrate [BLTCM], was synthesized by a conventional slow evaporation solution growth technique. The grown crystals were subjected to structural, optical, electrical, thermal, mechanical, SHG and Laser damage threshold studies. Single crystal XRD shows that the material crystallizes in monoclinic system with noncentrosymmetric space group P21. FT-IR and FT-RAMAN analyses confirm the various functional groups present in the grown crystal. The transparency range of BLTCM was determined by UV-vis-NIR studies and various optical constants such as extinction coefficient (K), refractive index, optical conductivity and electric susceptibility with real and imaginary parts of dielectric constant were calculated using the transmittance data which have applications in optoelectronic devices. Dielectric studies of the crystal were carried out at different frequencies and temperatures to analyze the electrical properties. TGA and DSC analyses were performed to study the thermal behaviour of the sample. The hardness stability of the grown specimen was investigated by Vickers microhardness test. The output intensity of second harmonic generation was confirmed using the Kurtz and Perry powder method. The laser induced surface damage threshold of the crystal was measured using Nd:YAG laser.

  20. Crystal growth and optical properties of Gd admixed Ce-doepd Lu2Si2O7 single crystals

    NASA Astrophysics Data System (ADS)

    Horiai, Takahiko; Kurosawa, Shunsuke; Murakami, Rikito; Yamaji, Akihiro; Shoji, Yasuhiro; Ohashi, Yuji; Pejchal, Jan; Kamada, Kei; Yokota, Yuui; Yoshikawa, Akira

    2017-06-01

    Ce-doped Lu2Si2O7 scintillator contains radioactive isotope 176Lu which causes an unwanted intrinsic background signal. The development of scintillators with reduced Lu concentration were required in some applications. In this study, we developed the Gd admixed lutetium pyrosilicate, where the average ion radius at the rare earth site was similar to the Tm3+ ion radius, for which the RE2Si2O7 (RE=Tm, Yb, Lu) crystal structure is stable from room temperature to melting point. We have grown (Cex Lu1-x-y Gdy)2Si2O7 (x=0.01, y=0.00, 0.05, 0.10) single crystals. Their crystal systems were monoclinic with a space group C2/m. The absorption spectra revealed the energy transitions in Ce and Gd ions might be occurred. The light output was degraded and decay time was accelerated comparing the Gd 5% admixed sample with the Gd 10% one.

  1. Self-Phase-Matched Second-Harmonic and White-Light Generation in a Biaxial Zinc Tungstate Single Crystal

    NASA Astrophysics Data System (ADS)

    Osewski, Pawel; Belardini, Alessandro; Petronijevic, Emilija; Centini, Marco; Leahu, Grigore; Diduszko, Ryszard; Pawlak, Dorota A.; Sibilia, Concita

    2017-03-01

    Second-order nonlinear optical materials are used to generate new frequencies by exploiting second-harmonic generation (SHG), a phenomenon where a nonlinear material generates light at double the optical frequency of the input beam. Maximum SHG is achieved when the pump and the generated waves are in phase, for example through birefringence in uniaxial crystals. However, applying these materials usually requires a complicated cutting procedure to yield a crystal with a particular orientation. Here we demonstrate the first example of phase matching under the normal incidence of SHG in a biaxial monoclinic single crystal of zinc tungstate. The crystal was grown by the micro-pulling-down method with the (102) plane perpendicular to the growth direction. Additionally, at the same time white light was generated as a result of stimulated Raman scattering and multiphoton luminescence induced by higher-order effects such as three-photon luminescence enhanced by cascaded third-harmonic generation. The annealed crystal offers SHG intensities approximately four times larger than the as grown one; optimized growth and annealing conditions may lead to much higher SHG intensities.

  2. Self-Phase-Matched Second-Harmonic and White-Light Generation in a Biaxial Zinc Tungstate Single Crystal.

    PubMed

    Osewski, Pawel; Belardini, Alessandro; Petronijevic, Emilija; Centini, Marco; Leahu, Grigore; Diduszko, Ryszard; Pawlak, Dorota A; Sibilia, Concita

    2017-03-24

    Second-order nonlinear optical materials are used to generate new frequencies by exploiting second-harmonic generation (SHG), a phenomenon where a nonlinear material generates light at double the optical frequency of the input beam. Maximum SHG is achieved when the pump and the generated waves are in phase, for example through birefringence in uniaxial crystals. However, applying these materials usually requires a complicated cutting procedure to yield a crystal with a particular orientation. Here we demonstrate the first example of phase matching under the normal incidence of SHG in a biaxial monoclinic single crystal of zinc tungstate. The crystal was grown by the micro-pulling-down method with the (102) plane perpendicular to the growth direction. Additionally, at the same time white light was generated as a result of stimulated Raman scattering and multiphoton luminescence induced by higher-order effects such as three-photon luminescence enhanced by cascaded third-harmonic generation. The annealed crystal offers SHG intensities approximately four times larger than the as grown one; optimized growth and annealing conditions may lead to much higher SHG intensities.

  3. Growth and characterization of a single crystal of Urea Adipic acid (UAA)--a third order nonlinear optical material.

    PubMed

    Shanthi, A; Krishnan, C; Selvarajan, P

    2014-03-25

    An organic single crystal of Urea Adipic acid (UAA) was successfully grown in methanol solvent by slow solvent evaporation technique at room temperature (30 °C). The structure of grown crystal was elucidated from the X-ray diffraction study and it belongs to monoclinic system with centrosymmetric space group P21/c. The optical transmission spectrum of UAA has been recorded and its theoretical calculations were carried out to determine the linear optical constants such as linear absorption coefficient, extinction coefficient, refractive index and reflectance etc. The third-order nonlinearities of UAA crystal have been investigated by Z-scan method. The values of nonlinear refractive index (n2), the absorption coefficient (β) and third-order nonlinear susceptibility (χ((3))) are found to be the order of 0.96×10(-10) cm(2)/W, 1.248×10(-4) cm/W and 6.44×10(-8) esu respectively. Fourier Transform Infra Red and Raman spectroscopy studies reveal the intermolecular interactions present in the UAA sample. The dielectric and mechanical measurements of the title compound are also reported.

  4. Composition and temperature-dependent phase transition in miscible Mo1−xWxTe2 single crystals

    PubMed Central

    Lv, Yang-Yang; Cao, Lin; Li, Xiao; Zhang, Bin-Bin; Wang, Kang; Bin Pang, B P; Ma, Ligang; Lin, Dajun; Yao, Shu-Hua; Zhou, Jian; Chen, Y. B.; Dong, Song-Tao; Liu, Wenchao; Lu, Ming-Hui; Chen, Yulin; Chen, Yan-Feng

    2017-01-01

    Transition metal dichalcogenides (TMDs) WTe2 and MoTe2 with orthorhombic Td phase, being potential candidates as type-II Weyl semimetals, are attracted much attention recently. Here we synthesized a series of miscible Mo1−xWxTe2 single crystals by bromine vapor transport method. Composition-dependent X-ray diffraction and Raman spectroscopy, as well as composition and temperature-dependent resistivity prove that the tunable crystal structure (from hexagonal (2H), monoclinic (β) to orthorhombic (Td) phase) can be realized by increasing W content in Mo1−xWxTe2. Simultaneously the electrical property gradually evolves from semiconductor to semimetal behavior. Temperature-dependent Raman spectroscopy proves that temperature also can induce the structural phase transition from β to Td phase in Mo1−xWxTe2 crystals. Based on aforementioned characterizations, we map out the temperature and composition dependent phase diagram of Mo1−xWxTe2 system. In addition, a series of electrical parameters, such as carrier type, carrier concentration and mobility, have also been presented. This work offers a scheme to accurately control structural phase in Mo1−xWxTe2 system, which can be used to explore type-II Weyl semimetal, as well as temperature/composition controlled topological phase transition therein. PMID:28294191

  5. Synthesis, growth, optical and anisotropic mechanical behaviour of organic nonlinear optical imidazolium 2-chloro-4-nitrobenzoate single crystals

    NASA Astrophysics Data System (ADS)

    Krishnakumar, Varadharajan; Jayaprakash, Jeyaram; Boobas, Singaram; Komathi, Muniraj

    2016-10-01

    The title compound, imidazolium 2-chloro-4-nitrobenzoate (I2C4NB), has been synthesized and optical quality single crystals were grown with a dimension of 4 × 2 × 1 mm3 using an ethanol and acetone (1:1) mixed solvent by slow evaporation solution growth technique. The powder XRD analysis confirmed the crystal structure and found that it is crystallized in the non-centrosymmetric space group P21 with the monoclinic system. The symmetries of molecular vibrations were confirmed by FT-IR spectrum. The CHN(S) analysis confirmed the stoichiometric composition of the grown crystal. It also exhibits a good transparency in the entire visible region (300-800nm) and it was thermally stable up to 131.1 °C. The microhardness measurement shows the anisotropic nature of I2C4NB and also that it belongs to a soft material category. Photoconductivity studies reveal a linear increase of the photocurrent with respect to the applied electric field. HOMO LUMO studies were carried out for the crystal. The second harmonic generation test by the Kurtz powder method shows that the crystal exhibits phase matching and a conversion efficiency which is 2 times that of KDP.

  6. Composition and temperature-dependent phase transition in miscible Mo1‑xWxTe2 single crystals

    NASA Astrophysics Data System (ADS)

    Lv, Yang-Yang; Cao, Lin; Li, Xiao; Zhang, Bin-Bin; Wang, Kang; Bin Pang; Ma, Ligang; Lin, Dajun; Yao, Shu-Hua; Zhou, Jian; Chen, Y. B.; Dong, Song-Tao; Liu, Wenchao; Lu, Ming-Hui; Chen, Yulin; Chen, Yan-Feng

    2017-03-01

    Transition metal dichalcogenides (TMDs) WTe2 and MoTe2 with orthorhombic Td phase, being potential candidates as type-II Weyl semimetals, are attracted much attention recently. Here we synthesized a series of miscible Mo1‑xWxTe2 single crystals by bromine vapor transport method. Composition-dependent X-ray diffraction and Raman spectroscopy, as well as composition and temperature-dependent resistivity prove that the tunable crystal structure (from hexagonal (2H), monoclinic (β) to orthorhombic (Td) phase) can be realized by increasing W content in Mo1‑xWxTe2. Simultaneously the electrical property gradually evolves from semiconductor to semimetal behavior. Temperature-dependent Raman spectroscopy proves that temperature also can induce the structural phase transition from β to Td phase in Mo1‑xWxTe2 crystals. Based on aforementioned characterizations, we map out the temperature and composition dependent phase diagram of Mo1‑xWxTe2 system. In addition, a series of electrical parameters, such as carrier type, carrier concentration and mobility, have also been presented. This work offers a scheme to accurately control structural phase in Mo1‑xWxTe2 system, which can be used to explore type-II Weyl semimetal, as well as temperature/composition controlled topological phase transition therein.

  7. Single well electric oil stimulation

    SciTech Connect

    Perkins, Th. K.

    1985-06-11

    A single well method and apparatus for electrically applying heat and stimulating is comprised of a relatively lower surface area formation electrode and relatively high surface area overburden electrode extending downward into the borehole past low resistivity water zones. This long overburden electrode may be formed of nonmagnetic metal to reduce hysteresis losses in the electrode. This improved single well system causes most of power to be dissipated in the oil pay zone and thereby renders single well production economical.

  8. Quantitative biology of single neurons

    PubMed Central

    Eberwine, James; Lovatt, Ditte; Buckley, Peter; Dueck, Hannah; Francis, Chantal; Kim, Tae Kyung; Lee, Jaehee; Lee, Miler; Miyashiro, Kevin; Morris, Jacqueline; Peritz, Tiina; Schochet, Terri; Spaethling, Jennifer; Sul, Jai-Yoon; Kim, Junhyong

    2012-01-01

    The building blocks of complex biological systems are single cells. Fundamental insights gained from single-cell analysis promise to provide the framework for understanding normal biological systems development as well as the limits on systems/cellular ability to respond to disease. The interplay of cells to create functional systems is not well understood. Until recently, the study of single cells has concentrated primarily on morphological and physiological characterization. With the application of new highly sensitive molecular and genomic technologies, the quantitative biochemistry of single cells is now accessible. PMID:22915636

  9. Single-incision laparoscopic myomectomy

    PubMed Central

    Jackson, Tiffany R; Einarsson, Jon I

    2011-01-01

    Laparoscopic myomectomy is a minimally invasive surgical option for the treatment of uterine leiomyomas. Single-incision laparoscopy is a relatively new concept that has potential in gynaecological surgery although the technical challenges of single-incision access have limited the widespread use of the technique. The use of intracorporeal suturing is a significant component of the learning curve for laparoscopic myomectomy and presents an even greater challenge with single-incision laparoscopic myomectomy. This article describes a surgeon’s approach to single-incision laparoscopic myomectomy. PMID:21197249

  10. Single-Atom Single-Photon Quantum Interface

    NASA Astrophysics Data System (ADS)

    Moehring, David; Bochmann, Joerg; Muecke, Martin; Specht, Holger; Weber, Bernhard; Wilk, Tatjana; Rempe, Gerhard

    2008-05-01

    By combining atom trapping techniques and cavity cooling schemes we are able to trap a single neutral atom inside a high-finesse cavity for several tens of seconds. We show that our coupled atom-cavity system can be used to generate single photons in a controlled way. With our long trapping times and high single-photon production efficiency, the non-classical properties of the emitted light can be shown in the photon correlations of a single atom. In a similar atom-cavity setup, we investigate the interface between atoms and photons by entangling a single atom with a single photon emitted into the cavity and by further mapping the quantum state of the atom onto a second single photon. These schemes are intrinsically deterministic and establish the basic element required to realize a distributed quantum network with individual atoms at rest as quantum memories and single flying photons as quantum messengers. This work was supported by the Deutsche Forschungsgemeinschaft, and the European Union SCALA and CONQUEST programs. D. L. M. acknowledges support from the Alexander von Humboldt Foundation.

  11. Single wheel testers, single track testers, and instrumented tractors

    USDA-ARS?s Scientific Manuscript database

    Single wheel testers and single track testers are used for determining tractive performance characteristics of tires and tracks. Instrumented tractors are useful in determining the tractive performance of tractors. These machines are also used for determining soil-tire and soil-track interactions,...

  12. Assessing Dimensions of Single Parenting: The Single Parenting Questionnaire.

    ERIC Educational Resources Information Center

    Stolberg, Arnold L.; Ullman, Ann J.

    1984-01-01

    Developed and validated an instrument that assesses five dimensions of single parenting: problem solving skills, parental warmth, discipline procedures, parent rules, enthusiasm for parenting and parent support systems. Results gave statistical support for the Single Parenting Questionnaire, suggesting it may be useful in both clinical and…

  13. Single photon sources with single semiconductor quantum dots

    NASA Astrophysics Data System (ADS)

    Shan, Guang-Cun; Yin, Zhang-Qi; Shek, Chan Hung; Huang, Wei

    2014-04-01

    In this contribution, we briefly recall the basic concepts of quantum optics and properties of semiconductor quantum dot (QD) which are necessary to the understanding of the physics of single-photon generation with single QDs. Firstly, we address the theory of quantum emitter-cavity system, the fluorescence and optical properties of semiconductor QDs, and the photon statistics as well as optical properties of the QDs. We then review the localization of single semiconductor QDs in quantum confined optical microcavity systems to achieve their overall optical properties and performances in terms of strong coupling regime, efficiency, directionality, and polarization control. Furthermore, we will discuss the recent progress on the fabrication of single photon sources, and various approaches for embedding single QDs into microcavities or photonic crystal nanocavities and show how to extend the wavelength range. We focus in particular on new generations of electrically driven QD single photon source leading to high repetition rates, strong coupling regime, and high collection efficiencies at elevated temperature operation. Besides, new developments of room temperature single photon emission in the strong coupling regime are reviewed. The generation of indistinguishable photons and remaining challenges for practical single-photon sources are also discussed.

  14. Formation of a dinuclear copper(II) complex through the cleavage of CN bond of 1-benzoyl-3-(pyridin-2-yl)-1H-pyrazole

    SciTech Connect

    Shardin, Rosidah; Pui, Law Kung; Yamin, Bohari M.; Kassim, Mohammad B.

    2014-09-03

    A simple mononuclear octahedral copper(II) complex was attempted from the reaction of three moles of 1-benzoyl-3-(pyridin-2-yl)-1H-pyrazole and one mole of copper(II) perchlorate hexahydrate in methanol. However, the product of the reaction was confirmed to be a dinuclear copper(II) complex with μ-(3-(pyridin-2-yl)-pyrazolato) and 3-(pyridin-2-yl)-1H-pyrazole ligands attached to each of the Cu(II) centre atom. The copper(II) ion assisted the cleavage of the C{sub benzoyl}N bond afforded a 3-(pyridin-2-yl)-1H-pyrazole molecule. Deprotonation of the 3-(pyridin-2-yl)-1H-pyrazole gave a 3-(pyridin-2-yl)-pyrazolato, which subsequently reacted with the Cu(II) ion to give the (3-(pyridin-2-yl)-pyrazolato)(3-(pyridin-2-yl)-1H-pyrazole)Cu(II) product moiety. The structure of the dinuclear complex was confirmed by x-ray crystallography. The complex crystallized in a monoclinic crystal system with P2(1)/n space group and cell dimensions of a = 12.2029(8) Å, b = 11.4010(7) Å, c = 14.4052(9) Å and β = 102.414(2)°. The compound was further characterized by mass spectrometry, CHN elemental analysis, infrared and UV-visible spectroscopy and the results concurred with the x-ray structure. The presence of d-d transition at 671 nm (ε = 116 dm{sup 3} mol{sup −1} cm{sup −1}) supports the presence of Cu(II) centres.

  15. Formation of a dinuclear copper(II) complex through the cleavage of CN bond of 1-benzoyl-3-(pyridin-2-yl)-1H-pyrazole

    NASA Astrophysics Data System (ADS)

    Shardin, Rosidah; Pui, Law Kung; Yamin, Bohari M.; Kassim, Mohammad B.

    2014-09-01

    A simple mononuclear octahedral copper(II) complex was attempted from the reaction of three moles of 1-benzoyl-3-(pyridin-2-yl)-1H-pyrazole and one mole of copper(II) perchlorate hexahydrate in methanol. However, the product of the reaction was confirmed to be a dinuclear copper(II) complex with μ-{3-(pyridin-2-yl)-pyrazolato} and 3-(pyridin-2-yl)-1H-pyrazole ligands attached to each of the Cu(II) centre atom. The copper(II) ion assisted the cleavage of the CbenzoylN bond afforded a 3-(pyridin-2-yl)-1H-pyrazole molecule. Deprotonation of the 3-(pyridin-2-yl)-1H-pyrazole gave a 3-(pyridin-2-yl)-pyrazolato, which subsequently reacted with the Cu(II) ion to give the {3-(pyridin-2-yl)-pyrazolato}{3-(pyridin-2-yl)-1H-pyrazole}Cu(II) product moiety. The structure of the dinuclear complex was confirmed by x-ray crystallography. The complex crystallized in a monoclinic crystal system with P2(1)/n space group and cell dimensions of a = 12.2029(8) Å, b = 11.4010(7) Å, c = 14.4052(9) Å and β = 102.414(2)°. The compound was further characterized by mass spectrometry, CHN elemental analysis, infrared and UV-visible spectroscopy and the results concurred with the x-ray structure. The presence of d-d transition at 671 nm (ɛ = 116 dm3 mol-1 cm-1) supports the presence of Cu(II) centres.

  16. Single-cavity SLED device

    SciTech Connect

    Lippmann, B.A.

    1984-09-01

    The conventional SLED device used at SLAC requires two cavities. However, the same effect can be obtained with a single cavity; the theory and operation of the device is the same, only the hardware is changed. The single-cavity device is described here.

  17. Single-Gender Schools Scrutinized

    ERIC Educational Resources Information Center

    Zubrzycki, Jaclyn

    2012-01-01

    This article reports on a study on publicly run schools in the Republic of Trinidad and Tobago which has found that, while single-sex schools may benefit female students who prefer a single-sex environment, they are not inherently beneficial for boys or most girls. While the findings are based on data from one Caribbean nation, experts say they…

  18. Single-photon quadratic optomechanics

    PubMed Central

    Liao, Jie-Qiao; Nori, Franco

    2014-01-01

    We present exact analytical solutions to study the coherent interaction between a single photon and the mechanical motion of a membrane in quadratic optomechanics. We consider single-photon emission and scattering when the photon is initially inside the cavity and in the fields outside the cavity, respectively. Using our solutions, we calculate the single-photon emission and scattering spectra, and find relations between the spectral features and the system's inherent parameters, such as: the optomechanical coupling strength, the mechanical frequency, and the cavity-field decay rate. In particular, we clarify the conditions for the phonon sidebands to be visible. We also study the photon-phonon entanglement for the long-time emission and scattering states. The linear entropy is employed to characterize this entanglement by treating it as a bipartite one between a single mode of phonons and a single photon. PMID:25200128

  19. Single-wall-carbon-nanotube/single-carbon-chain molecular junctions

    NASA Astrophysics Data System (ADS)

    Börrnert, Felix; Börrnert, Carina; Gorantla, Sandeep; Liu, Xianjie; Bachmatiuk, Alicja; Joswig, Jan-Ole; Wagner, Frank R.; Schäffel, Franziska; Warner, Jamie H.; Schönfelder, Ronny; Rellinghaus, Bernd; Gemming, Thomas; Thomas, Jürgen; Knupfer, Martin; Büchner, Bernd; Rümmeli, Mark H.

    2010-02-01

    Stable junctions between a single carbon chain and two single-wall carbon nanotubes were produced via coalescence of functionalized fullerenes filled into a single-wall carbon nanotube and directly imaged by in situ transmission electron microscopy. First principles quantum chemical calculations support the observed stability of such molecular junctions. They also show that short carbon chains bound to other carbon structures are cumulenes and stable semiconductors due to Peierls-like distortion. Junctions like this can be regarded as archetypical building blocks for all-carbon molecular electronics.

  20. Synthesis, spectral characterization, and single crystal structure studies of (2-nitro-ethene-1,1-diyl)-bis-((4-isopropyl-benzyl)sulfane)

    SciTech Connect

    Sakthikumar, L.; Mahalakshmy, R.; Bhargavi, G.; Srinivasan, N.

    2015-12-15

    The title compound (2-nitro-ethene-1,1-diyl)-bis-(4-isopropylbenzyl)sulfane) (5), was synthesised using a two step process. The structure of the product (5) was established by UV, FT-IR, {sup 1}H NMR, {sup 13}C NMR, C,H,N analysis, LC-MS and single crystal X-ray diffraction analysis. The single crystal of the title compound (5) was crystallized in Monoclinic with the space group of P21/c. The crystal exhibit the following unit cell parameters a = 12.8165(18), b = 6.1878(6), c = 27.082(4) Å, β = 90.705(17)°, V = 2147.6(5) A{sup 3}, Z = 4, D{sub x} = 1.242 Mg/m{sup 3} and the molecular formula of C{sub 22}H{sub 27}N{sub 1}O{sub 2}S{sub 2} was found. The final R value was 0.0776. The crystal structure is stabilized by an interesting intramolecular push and pull five membered electrocyclic interaction between the O1–N1–C2–C1–S1- and via the intermolecular H-bonding interaction between C2–H2···O2.

  1. Single phase synthesis and room temperature neutron diffraction studies on multiferroic PbFe{sub 0.5}Nb{sub 0.5}O{sub 3}

    SciTech Connect

    Matteppanavar, Shidaling; Angadi, Basavaraj; Rayaprol, Sudhindra

    2013-02-05

    The lead-iron-niobate, (PbFe{sub 0.5}Nb{sub 0.5}O{sub 3} or PFN) was synthesized by low temperature sintering Single Step / Solid State Reaction Method. The 700 Degree-Sign C/2 hrs. calcined powder was sintered at 1050 Degree-Sign C/1 hr. The sintered pellets were characterized through X-Ray Diffraction and Neutron Diffraction at room temperature. It is found from the XRD pattern that the materials is in single phase with no traces of pyrochlore phase. It was also confirmed from the neutron diffraction pattern, the structure of PFN to be monoclinic, space group Cm. Structural studies has been carried out by refining the obtained neutron diffraction data by Rietveld refinement method using Fullprof program. The neutron diffraction pattern at 300 K (room temperature) was selected to refine the structure. The lattice parameters obtained are; a = 5.6709 A, b = 5.6732 A, c = 4.0136 A, and {alpha}= 90, {beta}= 89.881, {gamma}= 90. The P-E measurements showed hysteretic behavior with high remnant polarization.

  2. Preparation of single-crystal spherical γ-Mo2N by temperature-programmed reaction between β-MoO3 and NH3

    NASA Astrophysics Data System (ADS)

    Wang, Lu; Zhang, Guo-Hua; Chou, Kuo-Chih

    2017-10-01

    In the present wok, single-crystalline spherical γ-Mo2N powders was successfully prepared by the temperature-programmed reaction of single-crystal spherical β-MoO3 with NH3 in the temperature ranges of 1013-1073 K. Herein, the Mo source used was monoclinic system, β-MoO3, a metastable phase of MoO3. It is found that the characterizations of the as-prepared γ-Mo2N powders are strongly depended on the selection of the MoO3 precursor. In other words, the as-prepared γ-Mo2N powders inherited the shape, size and structure of the used β-MoO3 precursors upon reaction with NH3. In order to make a comparison, β-MoO3 was also reduced by the mixed gases of N2 and H2 with the flow rate ratio of 1:3 at the identical conditions. It was found that pure β-Mo2N polycrystalline can be obtained when the temperature was 1013 K; while further increasing the reaction temperature, metal Mo powder will be turned up.

  3. Structural confirmation, single X-ray crystallographic behavior, molecular docking and other physico-chemical properties of gerberinol, a natural dimethyl dicoumarol from Gerbera lanuginosa Benth. (Compositae)

    NASA Astrophysics Data System (ADS)

    Brahmachari, Goutam; Das, Saktipada; Kumar, Abhishek; Misra, Neeraj; Sharma, Sakshi; Gupta, Vivek K.

    2017-05-01

    The proposed structure of gerberinol (1), a naturally occurring dimethyl dicoumarol, has been conclusively established on the basis of its detailed spectral and single crystal X-ray analyses. The compound, C21H16O6, crystallizes in the monoclinic space group P21/c with the following unit-cell parameters: a = 14.0884(14), b = 15.1746(15), c = 7.6392(8)Å, α = 90.00°, β = 98.949(4)°, γ = 90.00° and Z = 4. The crystal structure was solved by direct methods using single-crystal X-ray diffraction data collected at room temperature and refined by full-matrix least-squares procedures to a final R-value of 11.43 for 2377 observed reflections. Exhaustive theoretical studies on the molecular structure, vibrational spectra, HOMO, LUMO, MESP surfaces, and molecular docking of this plant-derived natural molecule have also been performed. The equilibrium geometry of the title compound has been obtained and analyzed using DFT-B3LYP/6-311 + G(d,p) method. Molecular docking study of the molecule for predicting its possible biological activities revealed that the compound might be a potent antimicrobial, neurodegenerative and anticancer agent as evidenced from its excellent FF (full fitness) score for 1FUJ and 1ZX1 enzymes.

  4. Synthesis, 1H NMR, single crystal X-ray determined and ab-initio molecular structural analyses on 1-(isopropylideneaminomethyl)pyrene

    NASA Astrophysics Data System (ADS)

    Brown, R. E.; Chateauneuf, G. M.; Klassen, P. R.; Luck, R. L.; Mendenhall, G. D.

    2001-04-01

    A previously unobserved crystalline precipitate in an extract of crude 1-(aminomethyl) pyrene was shown to be 1-(isopropylideneaminomethyl)pyrene. The identity of this compound was established by a single crystal X-ray determination that revealed an overall planar arrangement for the non-hydrogen atoms. The molecule crystallized in the monoclinic space group P2 1/ c, with the following unit cell dimensions: a=11.6650(10) Å, b=8.2850(9) Å, c=16.0220(9) Å, β=108.297(6)°, V=1470(2) Å3, and Z=4. The structure was refined to R=0.059 ( Rw=0.150) for 2576 data points with Fo2>2 σ( Fo2). The results of ab-initio-calculations at the STO-3G level suggest that the difference in rotational conformer energy for rotation about the C-N single bond varied by less than 1 kcal/mol between the maximum (-30°) and minimum (90°) values. Packing forces in the solid state arrangement are believed to be responsible for the difference between this result and experiment, since an AM1 calculation with 1 constrained between two molecules of 1 at the experimental distances led to the planar structure as the one with lowest energy.

  5. Composition Dependence of Electrocaloric Effect in (1 - x)Pb(Mg1/3Nb2/3)O3 -xPbTiO3 Single Crystals

    NASA Astrophysics Data System (ADS)

    Qiu, Jian-Hua; Wang, Xiu-Qin; Yuan, Ning-Yi; Ding, Jian-Ning

    2015-07-01

    Composition dependence of electrocaloric effect is investigated in (1 - x)Pb(Mg1/3Nb2/3)O3 - xPbTiO3 single crystals by using an eighth-order Landau-Devonshire theory. The applied electric field along [001] direction reduces the ferroelectric-ferroelectric phase transition temperatures, but increases the Curie temperatures. The electrocaloric coefficients of tetragonal phase are much larger than that of rhombohedral and monoclinic phase. A negative electrocaloric effect is observed near the MC-T phase transition in 0.69Pb(Mg1/3Nb2/3)O3-0.31PbTiO3 single crystal. The application of a strong enough electric field results in a high adiabatic temperature change over a broad range of temperature. Therefore, it would be useful to construct a solid state cooling cycle over a broad temperature range for practical applications. Supported by the State Key Program of National Natural Science of China under Grant No. 51335002, Changzhou Science and Technology Project under Grant No. CJ20130022, and the Priority Academic Program Development of Jiangsu Higher Education Institutions on Renewable Energy Material Science and Engineering

  6. Self-assembled supramolecular structure of 1-methyl piperazinium 4-nitrophenolate 4-nitrophenol monohydrate single crystal: Synthesis, growth, thermal and photo physical properties

    NASA Astrophysics Data System (ADS)

    Nagapandiselvi, P.; Baby, C.; Gopalakrishnan, R.

    2015-08-01

    A new photoactive organic crystal, 1-methyl piperazinium 4-nitrophenolate-4-nitrophenol monohydrate (MP4NPM) has been synthesised at 35 °C. Good quality single crystals of MP4NPM have successfully been grown by slow evaporation solution growth technique. Single crystal X-ray diffraction analysis shows that MP4NPM belongs to monoclinic crystal system with space group P21/n. The molecular structure was further confirmed by modern spectroscopic techniques like FT-NMR (both 1D and 2D), FT-IR, UV-Vis-NIR and fluorescence. The UV-Vis-NIR spectrum was performed to understand the range of optical transparency and the results showed its suitability for nonlinear optical applications. Fluorescence emission revealed that MP4NPM can serve as a photo active material. Thermal properties of MP4NPM were investigated using simultaneous TG-DSC analysis. Frequency and temperature dependent dielectric properties were studied in the frequency range 500 Hz-5 MHz and 40-50 °C, respectively. Vicker's microhardness measurements revealed that MP4NPM belongs to the category of soft material. Kurtz and Perry powder technique shows that MP4NPM has SHG efficiency 0.89 times that of potassium dihydrogen phosphate (KDP).

  7. Self-assembled supramolecular structure of 1-methyl piperazinium 4-nitrophenolate 4-nitrophenol monohydrate single crystal: Synthesis, growth, thermal and photo physical properties.

    PubMed

    Nagapandiselvi, P; Baby, C; Gopalakrishnan, R

    2015-08-05

    A new photoactive organic crystal, 1-methyl piperazinium 4-nitrophenolate-4-nitrophenol monohydrate (MP4NPM) has been synthesised at 35 °C. Good quality single crystals of MP4NPM have successfully been grown by slow evaporation solution growth technique. Single crystal X-ray diffraction analysis shows that MP4NPM belongs to monoclinic crystal system with space group P2₁/n. The molecular structure was further confirmed by modern spectroscopic techniques like FT-NMR (both 1D and 2D), FT-IR, UV-Vis-NIR and fluorescence. The UV-Vis-NIR spectrum was performed to understand the range of optical transparency and the results showed its suitability for nonlinear optical applications. Fluorescence emission revealed that MP4NPM can serve as a photo active material. Thermal properties of MP4NPM were investigated using simultaneous TG-DSC analysis. Frequency and temperature dependent dielectric properties were studied in the frequency range 500 Hz-5 MHz and 40-50 °C, respectively. Vicker's microhardness measurements revealed that MP4NPM belongs to the category of soft material. Kurtz and Perry powder technique shows that MP4NPM has SHG efficiency 0.89 times that of potassium dihydrogen phosphate (KDP).

  8. Growth, optical, thermal, mechanical and dielectric studies of sodium succinate hexahydrate (β phase) single crystal: A promising third order NLO material

    NASA Astrophysics Data System (ADS)

    Mageshwari, P. S. Latha; Priya, R.; Krishnan, S.; Joseph, V.; Das, S. Jerome

    2016-11-01

    A third order nonlinear optical (NLO)single crystals of sodium succinate hexahydrate (SSH) (β phase) has been grown by a slow evaporation growth technique using aqueous solution at ambient temperature. The lattice parameters and morphology of SSH were determined by single crystal X-ray diffraction analysis. SSH crystallizes in centrosymmetric monoclinic system with space group P 21 / c and the crystalline purity was analyzed by powder X-ray diffraction analysis. The UV-vis-NIR spectrum reveals that the crystal is transparent in the entire visible region. The recorded FT-IR spectrum verified the presence of various functional groups in the material. NMR analysis of the grown crystal confirms the structural elucidation and detects the major and minor functional groups present in the title compound. ICP-OES analysis proved the presence of sodium in SSH. TG-DTA/DSCanalysis was used to investigate the thermal stability of the material. The dielectric permittivity and dielectric loss of SSH were carried out as a function of frequency for different temperatures and the results were discussed. The mechanical stability was evaluated from Vicker's microhardness test. The third order nonlinear optical properties of SSH has been investigated employing Z-scan technique with He-Ne laser operating at 632.8 nm wavelength.

  9. Growth, spectral, thermal, laser damage threshold, microhardness, dielectric, linear and nonlinear optical properties of an organic single crystal: L-phenylalanine DL-mandelic acid

    NASA Astrophysics Data System (ADS)

    Jayaprakash, P.; Peer Mohamed, M.; Krishnan, P.; Nageshwari, M.; Mani, G.; Lydia Caroline, M.

    2016-12-01

    Single crystals of L-phenylalanine dl-mandelic acid [C9H11NO2. C8H8O3], have been grown by the slow evaporation technique at room temperature using aqueous solution. The single crystal XRD study confirms monoclinic system for the grown crystal. The functional groups present in the grown crystal have been identified by FTIR and FT-Raman analyses. The optical absorption studies show that the crystal is transparent in the visible region with a lower cut-off wavelength of 257 nm and the optical band gap energy Eg is determined to be 4.62 eV. The Kurtz powder second harmonic generation was confirmed using Nd:YAG laser with fundamental wavelength of 1064 nm. Further, the thermal studies confirmed no weight loss up to 150°C for the as-grown crystal. The photoluminescence spectrum exhibited three peaks (414 nm, 519 nm, 568 nm) due to the donation of protons from carboxylic acid to amino group. Laser damage threshold value was found to be 4.98 GW/cm2. The Vickers microhardness test was carried out on the grown crystals and there by Vickers hardness number (Hv), work hardening coefficient (n), yield strength (σy), stiffness constant C11 were evaluated. The dielectric behavior of the crystal has been determined in the frequency range 50 Hz-5 MHz at various temperatures.

  10. Single crystal growth of spin-ladder compound La8Cu7O19 by the travelling-solvent floating zone method

    NASA Astrophysics Data System (ADS)

    Mohan, A.; Singh, S.; Partzsch, S.; Zwiebler, M.; Geck, J.; Wurmehl, S.; Büchner, B.; Hess, C.

    2016-08-01

    Large single crystals of La8Cu7O19 have been grown using the travelling-solvent floating zone method. A rather high oxygen pressure of 9 bar in the growth chamber and a slow growth speed of 0.5 mm/h were among the most important parameters in stabilizing the growth of this incongruently melting compound. Interestingly, a novel growth scenario has been witnessed. The crystal structure of the grown La8Cu7O19 crystal has been analyzed using single crystal diffractometry to extract important structural parameters of this compound. We find that La8Cu7O19 crystallizes in a monoclinic structure with space group C 2 / c and has the lattice parameters a ≈ 13.83 Å, b ≈ 3.75 Å, c ≈ 34.59 Å, and β ≈ 99.33 °, in good agreement with the data obtained on polycrystalline samples in the literature. The magnetization shows a highly anisotropic behavior, and an anomaly at T ≈103 K.

  11. Synthesis, spectral characterization, and single crystal structure studies of (2-nitro-ethene-1,1-diyl)-bis-((4-isopropyl-benzyl)sulfane)

    NASA Astrophysics Data System (ADS)

    Sakthikumar, L.; Mahalakshmy, R.; Bhargavi, G.; Srinivasan, N.

    2015-12-01

    The title compound (2-nitro-ethene-1,1-diyl)-bis-(4-isopropylbenzyl)sulfane) (5), was synthesised using a two step process. The structure of the product (5) was established by UV, FT-IR, 1H NMR, 13C NMR, C,H,N analysis, LC-MS and single crystal X-ray diffraction analysis. The single crystal of the title compound (5) was crystallized in Monoclinic with the space group of P21/ c. The crystal exhibit the following unit cell parameters a = 12.8165(18), b = 6.1878(6), c = 27.082(4) Å, β = 90.705(17)°, V = 2147.6(5) A3, Z = 4, D x = 1.242 Mg/m3 and the molecular formula of C22H27N1O2S2 was found. The final R value was 0.0776. The crystal structure is stabilized by an interesting intramolecular push and pull five membered electrocyclic interaction between the O1-N1-C2-C1-S1- and via the intermolecular H-bonding interaction between C2-H2···O2.

  12. Synthesis, crystal growth and characterization of bioactive material: 2-amino-1H-benzo[d]imidazol-3-ium salicylate single crystal-a proton transfer molecular complex

    NASA Astrophysics Data System (ADS)

    Fathima, K. Saiadali; Anitha, K.

    2017-05-01

    The 1:1 molecular adducts 2-aminobenzimidazolium salicylate (ABIS) single crystal was synthesized and grown from 2-aminobenzimidazole (ABI) as a donor and salicylic acid (SA) as an acceptor. The cell parameter was determined using single crystal X-Ray diffraction method and the complex ABIS belongs to monoclinic system. The spectroscopic studies showed that ABIS crystal was an ion pair complex. The FTIR and Raman spectra showed that the presence of O-H, C=N, C=O vibration which confirms the proton transfer from SA to ABI. The UV-Vis spectrum exhibited a visible band at 359nm for ABIS due to the salicylate anion of the molecule. Further the antimicrobial activity of ABIS complex against Staphylococcus aureus, klebsiella pneumonia, Pseudomonas eruginos and E.coli pathogens was investigated. So the complex molecule inhibits both Gram positive and Gram negative bacterial. It is found that benzimidazole with aminogroup at position 2 increases the general antimicrobial activities of ABIS crystal.

  13. Room-temperature magnetoelectric coupling in single-phase BaTiO{sub 3}-BiFeO{sub 3} system

    SciTech Connect

    Yang, Su-Chul; Kumar, Ashok; Priya, Shashank; Petkov, Valeri

    2013-04-14

    In this paper, single-phase multiferroic ceramics of (1 - x) BaTiO{sub 3}-x BiFeO{sub 3} (BT - x BFO) were synthesized by solid-solution method in the wide range of material composition (x = 0.025 - 1.0). The changes in crystal structure were confirmed via X-ray diffractions (XRD) and atomic pair distribution functions (PDFs). The room-temperature ME coupling was found to exhibit significant magnitude in the narrow composition window (x = 0.71 - 0.8) where the average crystal structure was found to be rhombohedral. Especially, the BT - 0.725 BFO ceramics containing local monoclinic distortions within rhombohedral phase were found to exhibit high room-temperature ME coefficient ({alpha}{sub ME}) of 0.87 mV/cm{center_dot}Oe with high piezoelectric properties (g{sub 33} = 18.5 Multiplication-Sign 10 mV m N{sup -1} and d{sub 33} = 124 pC N{sup -1}). We believe that the high room-temperature ME coupling in single-phase lead-free BT-BFO ceramics provides a possibility of developing electrically or magnetically tunable thin-film devices.

  14. Single element magnetic suspension actuator

    NASA Technical Reports Server (NTRS)

    Groom, Nelson J. (Inventor)

    1991-01-01

    The invention, a single element magnetic suspension actuator with bidirectional force capability along a single axis, includes an electromagnet and a nonmagnetic suspended element. A permanent magnet mounted on the suspended element interacts with a magnetic field established by the electromagnet to produce bidirectional forces in response to a variable force command voltage V (sub FC) applied to the electromagnet. A sensor measures the position of the suspended element on the single axis which is a function of force command voltage V (sub FC).

  15. Single-interface Casimir torque

    NASA Astrophysics Data System (ADS)

    Morgado, Tiago A.; Silveirinha, Mário G.

    2016-10-01

    A different type of Casimir-type interaction is theoretically predicted: a single-interface torque at a junction of an anisotropic material and a vacuum or another material system. The torque acts to reorient the polarizable microscopic units of the involved materials near the interface, and thus to change the internal structure of the materials. The single-interface torque depends on the zero-point energy of the interface localized and extended modes. Our theory demonstrates that the single-interface torque is essential to understand the Casimir physics of material systems with anisotropic elements and may influence the orientation of the director of nematic liquid crystals.

  16. Single Cell Electrical Characterization Techniques

    PubMed Central

    Mansor, Muhammad Asraf; Ahmad, Mohd Ridzuan

    2015-01-01

    Electrical properties of living cells have been proven to play significant roles in understanding of various biological activities including disease progression both at the cellular and molecular levels. Since two decades ago, many researchers have developed tools to analyze the cell’s electrical states especially in single cell analysis (SCA). In depth analysis and more fully described activities of cell differentiation and cancer can only be accomplished with single cell analysis. This growing interest was supported by the emergence of various microfluidic techniques to fulfill high precisions screening, reduced equipment cost and low analysis time for characterization of the single cell’s electrical properties, as compared to classical bulky technique. This paper presents a historical review of single cell electrical properties analysis development from classical techniques to recent advances in microfluidic techniques. Technical details of the different microfluidic techniques are highlighted, and the advantages and limitations of various microfluidic devices are discussed. PMID:26053399

  17. Single Cell Electrical Characterization Techniques.

    PubMed

    Mansor, Muhammad Asraf; Ahmad, Mohd Ridzuan

    2015-06-04

    Electrical properties of living cells have been proven to play significant roles in understanding of various biological activities including disease progression both at the cellular and molecular levels. Since two decades ago, many researchers have developed tools to analyze the cell's electrical states especially in single cell analysis (SCA). In depth analysis and more fully described activities of cell differentiation and cancer can only be accomplished with single cell analysis. This growing interest was supported by the emergence of various microfluidic techniques to fulfill high precisions screening, reduced equipment cost and low analysis time for characterization of the single cell's electrical properties, as compared to classical bulky technique. This paper presents a historical review of single cell electrical properties analysis development from classical techniques to recent advances in microfluidic techniques. Technical details of the different microfluidic techniques are highlighted, and the advantages and limitations of various microfluidic devices are discussed.

  18. Fluorescence Microscopy of Single Molecules

    ERIC Educational Resources Information Center

    Zimmermann, Jan; van Dorp, Arthur; Renn, Alois

    2004-01-01

    The investigation of photochemistry and photophysics of individual quantum systems is described with the help of a wide-field fluorescence microscopy approach. The fluorescence single molecules are observed in real time.

  19. Fluorescence Microscopy of Single Molecules

    ERIC Educational Resources Information Center

    Zimmermann, Jan; van Dorp, Arthur; Renn, Alois

    2004-01-01

    The investigation of photochemistry and photophysics of individual quantum systems is described with the help of a wide-field fluorescence microscopy approach. The fluorescence single molecules are observed in real time.

  20. Systems and the Single School

    ERIC Educational Resources Information Center

    Chase, William W.

    1970-01-01

    Reports that the modular, or systems construction technique, through greater preplanning, is providing improved school facilities while holding the line on construction costs. Examples of the successful use of this systems approach in single school buildings are provided. (JF)