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Sample records for polarised neutron diffraction

  1. Polarised neutron scattering from dynamic polarised targets in biology

    NASA Astrophysics Data System (ADS)

    Knop, W.; Hirai, M.; Olah, G.; Meerwinck, W.; Schink, H.-J.; Stuhrman, H. B.; Wagner, R.; Wenkow-EsSouni, M.; Zhao, J.; Schärpf, O.; Crichton, R. R.; Krumpolc, M.; Nierhaus, K. H.; Niinikoski, T. O.; Rijllart, A.

    1991-10-01

    The contrast giving rise to neutron small-angle scattering can be enhanced considerably by polarisation of the hydrogen nuclei [J. des Coizeaux and G. Jannink, Les Polymères en Solution, Les Editions de Physique, F-91944 Les Ulis, France (1987)]. Using polarised neutrons the scattering from protonated labels in a deuterated matrix will increase by an order of magnitude. This is the basis of nuclear spin contrast variation, a method which is of particular interest for the in situ structure determination of macromolecular components. A new polarised target for neutron scattering has been designed by CERN and tested successfully at FRG-1 of the GKSS research centre. For the purpose of thermal-neutron scattering the frozen solutions of biomolecules are immersed in liquid helium 4, which is thermally coupled to the cooling mixture of helium 3/helium 4 of the dilution refrigerator. The nuclear spins are aligned with respect to the external magnetic field-parallel or antiparallel-by dynamic nuclear polarisation (DNP). The gain in neutron scattering compared to earlier experiments using direct cooling of the sample by helium 3 is a factor of 30. Another factor of 30 arises from the installation of the cold source and the beryllium reflector in FRG-1 [W. Knop et al., J. Appl. Cryst. 22 (1989) 352]. Pure nuclear spin targets are produced from dynamic polarised targets by selective depolarisation. In biological material only the hydrogen isotopes contribute significantly to polarised neutron scattering. Thus, saturation of the proton NMR yields a deuteron target, provided the target material has been enriched by the latter isotope. A proton target is obtained from the dynamic polarised target by saturation of deuteron NMR. This leads to six additional scattering functions reflecting the proton and deuteron spin densities and the correlations between the polarised isotopes. Polarised neutron scattering from nuclear spin targets of apoferritin and various derivatives of the

  2. Contributions of the electronic spin and orbital current to the CoCl{sub 4}{sup 2-} magnetic field probed in polarised neutron diffraction experiments

    SciTech Connect

    Cassam-Chenaie, Patrick; Jayatilaka, Dylan

    2012-08-14

    Polarised neutron diffraction experiments conducted at 4.2 K on Cs{sub 3}CoCl{sub 5} crystals have been analysed by using a four-dimensional model Hilbert space made of ab initio n-electron wave functions of the CoCl{sub 4}{sup 2-} molecular ion. Two spin-orbit mixing coefficients and several configuration interaction coefficients have been optimized by fitting calculated magnetic structure factors to experimental ones, to obtain the best ensemble density operator that is representable in the model space. A goodness of fit, {chi}{sup 2}, less then 1 has been obtained for the first time for the two experimental data sets available. In the present article, the optimized density operators are used to calculate the magnetic field densities that are the genuine observables probed in neutron diffraction experiments. Density maps of such observables are presented for the first time and numerical details are provided. The respective contributions of spin density and orbital current to the magnetic field density are analyzed.

  3. Polarised nuclei for neutron science: recent applications and perspectives

    NASA Astrophysics Data System (ADS)

    Glättli, Hans

    2004-08-01

    Neutron scattering on nuclei is spin dependent, particularly strongly for 1H. The means to achieve large nuclear polarisations and its use for structure analysis or as spin-handling device are reviewed. High resolution (diffraction) as well as low resolution (SANS) measurements can benefit from polarised nuclei by changing selectively the form factors of Bragg reflections or the contrasts (the scattering length density profiles) in SANS. The internal structure of ribosomes and the conformation of polymers in solution have been investigated by this method. A numerical simulation is presented to show the influence of steady-state polarisation of protons on the scattering from a protein-ARN model complex. In addition, a more recent technique, time-resolved SANS is described. It makes use of spatial polarisation gradients created around paramagnetic centres at the onset of nuclear polarisation. Such polarisation domains can enhance considerably the scattering amplitude of free radicals and thus contribute to determine their positions inside a complex protein. Examples of possible future experiments are proposed which combine simultaneously the selectivity of solid-state NMR techniques and neutron scattering.

  4. The strange history of polarised neutrons in Australia

    NASA Astrophysics Data System (ADS)

    Hicks, T. J.

    2016-04-01

    The history of polarised neutrons in Australia is unusual firstly because of the particular access that individuals in universities had to the facilities at the reactor site and because this resulted in the experiments being done almost all being with polarisation analysis. Two instruments were initially available. One was a conventional instrument albeit with a tilting counter. The other was a primitive polarisation analysis instrument purpose built for diffuse scattering. This latter instrument evolved over more than thirty years and produced results ranging from the separation of magnetic and nuclear diffuse scattering, for which it was conceived, to the isolation of magnetic features in inelastic spectra.

  5. Spin echo small angle neutron scattering using a continuously pumped {sup 3}He neutron polarisation analyser

    SciTech Connect

    Parnell, S. R.; Li, K.; Yan, H.; Stonaha, P.; Li, F.; Wang, T.; Baxter, D. V.; Snow, W. M.; Washington, A. L.; Walsh, A.; Chen, W. C.; Parnell, A. J.; Fairclough, J. P. A.; Pynn, R.

    2015-02-15

    We present a new instrument for spin echo small angle neutron scattering (SESANS) developed at the Low Energy Neutron Source at Indiana University. A description of the various instrument components is given along with the performance of these components. At the heart of the instrument are a series of resistive coils to encode the neutron trajectory into the neutron polarisation. These are shown to work well over a broad range of neutron wavelengths. Neutron polarisation analysis is accomplished using a continuously operating neutron spin filter polarised by Rb spin-exchange optical pumping of {sup 3}He. We describe the performance of the analyser along with a study of the {sup 3}He polarisation stability and its implications for SESANS measurements. Scattering from silica Stöber particles is investigated and agrees with samples run on similar instruments.

  6. Neutron diffraction on pulsed sources

    NASA Astrophysics Data System (ADS)

    Aksenov, V. L.; Balagurov, A. M.

    2016-03-01

    The current capabilities of and major scientific problems solved by time-of-flight neutron diffraction are reviewed. The reasons for the rapid development of the method over the last two decades have been mainly the emergence of third-generation pulsed sources with a megawatt time-averaged power and advances in neutron optical devices and detector systems. The paper discusses some historical aspects of time-of-flight neutron diffraction and examines the contribution to this method from F L Shapiro, the centennial of whose birth was celebrated in 2015. The state of the art with respect to neutron sources for studies on extracted beams is reviewed in a special section.

  7. Industrial applications of neutron diffraction

    SciTech Connect

    Felcher, G.P.

    1989-01-01

    Neutron diffraction (or, to be more general, neutron scattering) is a most versatile and universal tool, which has been widely employed to probe the structure, the dynamics and the magnetism of condensed matter. Traditionally used for fundamental research in solid state physics, this technique more recently has been applied to problems of immediate industrial interest, as illustrated in examples covering the main fields of endeavour. 14 refs., 14 figs.

  8. High-pressure neutron diffraction

    SciTech Connect

    Xu, Hongwu

    2011-01-10

    This lecture will cover progress and prospect of applications of high-pressure neutron diffraction techniques to Earth and materials sciences. I will first introduce general high-pressure research topics and available in-situ high-pressure techniques. Then I'll talk about high-pressure neutron diffraction techniques using two types of pressure cells: fluid-driven and anvil-type cells. Lastly, I will give several case studies using these techniques, particularly, those on hydrogen-bearing materials and magnetic transitions.

  9. Polarisation Analysis Neutron Spectrometer, POLANO, at J-PARC - Concept and Magnetic Field Optimisation

    NASA Astrophysics Data System (ADS)

    Ohoyama, K.; Yokoo, T.; Itoh, S.; Nanbu, M.; Iwasa, K.; Ohkawara, M.; Kaneko, N.; Ino, T.; Hayashida, H.; Oku, T.; Kira, H.; Tasaki, S.; Takeda, M.; Kimura, H.; Sato, T. J.

    2016-04-01

    The status of the polarised neutron spectrometer constructed at the Japan Proton Accelerator Research Complex through a collaboration between Tohoku University and KEK will be reported. In particular, the optimisation of magnetic fields to minimise neutron- beam depolarisation using the finite element method will be discussed on the basis of several simulations using the finite element method.

  10. Structure of hydrogenous liquids: separation of coherent and incoherent cross sections using polarised neutrons

    NASA Astrophysics Data System (ADS)

    Stunault, A.; Vial, S.; Pusztai, L.; Cuello, G. J.; Temleitner, L.

    2016-04-01

    The determination of the coherent structure factor of hydrogenous liquids is very difficult: while X-rays are barely sensitive to hydrogen, neutrons results still lack accuracy due to the contamination of the scattering intensities by a huge spin-incoherent signal from the 1H atoms. Using polarised neutrons with polarisation analysis, one can experimentally separate the coherent and incoherent contributions to the scattered intensity. We present the upgrade of the D3 polarised hot neutron diffractometer at ILL to study hydrogenated liquids. We show first data obtained from a test sample of water and detail the data reduction leading to an unprecedented accuracy in the extraction of the coherent signal, representative of the structure.

  11. Optimizing Crystal Volume for Neutron Diffraction

    NASA Technical Reports Server (NTRS)

    Snell, Edward H.; vanderWoerd, Mark; Damon, Michael; Judge, Russell, A.; Myles, Dean; Meilleur, F.

    2006-01-01

    Neutron diffraction is uniquely sensitive to hydrogen positions and protonation state. In that context structural information from neutron data is complementary to that provided through X-ray diffraction. However, there are practical obstacles to overcome in fully exploiting the potential of neutron diffraction, Le. low flux and weak scattering. Several approaches are available to overcome these obstacles and we have investigated the simplest: increasing the diffracting volume of the crystals. Volume is a quantifiable metric that is well suited for experiment design and optimization techniques. By using response surface methods we have optimized xylose isomerase crystal volume, enabling neutron diffraction while we determined the crystallization parameters with the minimum of experiments. Our results suggest a systematic means of enabling neutron diffraction studies for a larger number of samples that require information on hydrogen position and/or protonation state.

  12. High-Accuracy Analysis of Compton Scattering in Chiral EFT: Proton and Neutron Polarisabilities

    NASA Astrophysics Data System (ADS)

    Griesshammer, Harald W.; Phillips, Daniel R.; McGovern, Judith A.

    2013-10-01

    Compton scattering from protons and neutrons provides important insight into the structure of the nucleon. A new extraction of the static electric and magnetic dipole polarisabilities αE 1 and βM 1 of the proton and neutron from all published elastic data below 300 MeV in Chiral Effective Field Theory shows that within the statistics-dominated errors, the proton and neutron polarisabilities are identical, i.e. no iso-spin breaking effects of the pion cloud are seen. Particular attention is paid to the precision and accuracy of each data set, and to an estimate of residual theoretical uncertainties. ChiEFT is ideal for that purpose since it provides a model-independent estimate of higher-order corrections and encodes the correct low-energy dynamics of QCD, including, for few-nucleon systems used to extract neutron polarisabilities, consistent nuclear currents, rescattering effects and wave functions. It therefore automatically respects the low-energy theorems for photon-nucleus scattering. The Δ (1232) as active degree of freedom is essential to realise the full power of the world's Compton data.Its parameters are constrained in the resonance region. A brief outlook is provided on what kind of future experiments can improve the database. Supported in part by UK STFC, DOE, NSF, and the Sino-German CRC 110.

  13. X-ray Polarisation in highly-magnetized neutron stars

    NASA Astrophysics Data System (ADS)

    Turolla, Roberto

    2016-07-01

    Radiation emitted in the vicinity of an isolated neutron star is expected to be intrinsically polarized because the high magnetic field (B˜10^{12}-10^{15} G) strongly affects the plasma opacity. The polarization fraction and polarization angle measured by an instrument, however, do not necessary coincide with the intrinsic ones, due to the effects of both quantum electrodynamics in the highly magnetized vacuum around the star (the vacuum polarization) and rotation of the Stokes parameters in the plane perpendicular to the line of sight induced by the non-uniform magnetic field. I'll review theoretical estimates for the polarization observables in the case of thermal surface emission from neutron stars and of the (soft) X-ray emission from magnetars, where magnetospheric reprocessing of radiation by resonant cyclotron scattering is important. The potentials of X-ray polarimetry to probe the physical conditions in neutron star sources and to test, for the first time, vacuum polarization are discussed in connection with the recently proposed polarimetric missions, like XIPE.

  14. A New High-Accuracy Analysis of Compton Scattering in Chiral EFT: Neutron Polarisabilities

    NASA Astrophysics Data System (ADS)

    Griesshammer, Harald W.; McGovern, Judith A.; Phillips, Daniel R.

    2015-04-01

    Low-energy Compton scattering tests the symmetries and interaction strengths of a target's internal degrees of freedom in the electric and magnetic fields of a real, external photon. In the single-nucleon sector, information is often compressed into the static scalar dipole polarisabilities which are experimentally not directly accessible but encode information on the pion cloud and the Δ(1232) excitation. The interaction of the photon with the charged pion-exchange also provides a conceptually clean probe of few-nucleon binding. After demonstrating the statistical consistency of the world's γd dataset including the new data from the MAX-IV collaboration described in the preceding talk, we present a new extraction of the neutron polarisabilities in Chiral Effective Field Theory: αn = [ 11 . 55 +/- 1 . 25(stat) +/- 0 . 2(BSR) +/- 0 . 8(th) ] and βn = [ 3 . 65 -/+ 1 . 25(stat) +/- 0 . 2(BSR) -/+ 0 . 8(th) ] , in 10-4 fm3, with χ2 = 45 . 2 for 44 degrees of freedom. The new data reduced the statistical uncertainties by 30%. We discuss data accuracy and consistency, the role of the Δ(1232) , and an estimate of residual theoretical uncertainties. Within statistical and systematic errors, proton and neutron polarisabilities remain identical. Supported in part by UK STFC and US DOE.

  15. Pulsed neutron diffraction in special sample environments

    SciTech Connect

    Jorgensen, J.D.

    1987-05-01

    Neutron diffraction is a powerful tool for structural studies of samples in special sample environments because of the high penetrating power of neutrons compared to x rays. The neutrons readily penetrate special sample containers, heat shields, pressure vessels, etc., making it unnecessary in most cases to compromise the effectiveness of the sample environment system by providing windows for the incident and scattered neutrons. Pulsed neutrons obtained from an accelerator-based pulsed neutron source offer the additional advantage that many diffraction experiments can be done at a single, fixed scattering angle by the time-of-flight technique. In the fixed-angle scattering geometry, shielding and collimation can be optimized in order to access the largest possible sample volume with neutrons while completely avoiding scattering from the surrounding sample vessel. Thus, the data are free from unwanted background scattering. In this paper, the basic principles of neutron diffraction in special sample environments are discussed and examples of apparatus used for neutron diffraction measurements at low temperature, high temperature, and high pressure are presented. 36 refs., 15 figs., 3 tabs.

  16. Oxygen as a site specific structural probe in neutron diffraction

    SciTech Connect

    Neuefeind, Joerg C; Simonson, J Michael {Mike}; Salmon, Phil; Zeidler, Anita; Fischer, Henry E; Rauch, Helmut; Markland, Thomas; Lemmel, Hartmut

    2011-01-01

    Oxygen is a ubiquitous element, playing an essential role in most scientific and technological disciplines, and is often incorporated within a structurally disordered material where examples include molten silicates in planetary science, glasses used for lasers and optical communication, and water in biological processes. Establishing the structure of a liquid or glassy oxide and thereby its relation to the functional properties of a material is not, however, a trivial task owing to the complexity associated with atomic disorder. Here we approach this challenge by measuring the bound coherent neutron scattering lengths of the oxygen isotopes with the sensitive technique of neutron interferometry. We find that there is a small but finite contrast of 0.204(6) fm between the scattering lengths of the isotope 18O and oxygen of natural isotopic abundance natO, contrary to tables of recommended values. This has enabled us to investigate the structure of both light and heavy water by exploiting, for the first time, the method of oxygen isotope substitution in neutron diffraction, thus circumventing many of the significant problems associated with more traditional methods in which hydrogen is substituted by deuterium. We find a difference of ~0.5% between the O-H and O-D intra-molecular bond distances which is much smaller than recent estimates based on diffraction data and is found to be in excellent agreement with path integral molecular dynamics simulations made with a flexible polarisable water model. Our results demonstrate the potential for using oxygen isotope substitution as a powerful and effective site specific probe in a plethora of materials, of pertinence as instrumentation at next generation neutron sources comes online

  17. Optimizing Crystal Volume for Neutron Diffraction Studies

    NASA Technical Reports Server (NTRS)

    Snell, E. H.

    2003-01-01

    For structural studies with neutron diffraction more intense neutron sources, improved sensitivity detector and larger volume crystals are all means by which the science is being advanced to enable studies on a wider range of samples. We have chosen a simplistic approach using a well understood crystallization method, with minimal amounts of sample and using design of experiment techniques to maximize the crystal volume all for minimum effort. Examples of the application are given.

  18. SPECIAL ISSUE DEVOTED TO THE 80TH ANNIVERSARY OF ACADEMICIAN N G BASOV'S BIRTH: An optically polarised dense 3He target as a spin filter for slow-neutron beams

    NASA Astrophysics Data System (ADS)

    Kolachevsky, Nikolai N.; Prokof'ichev, Yu V.; Skoi, V. R.; Sobel'man, Igor I.; Sorokin, Vadim N.

    2003-01-01

    The possibility of polarising 3He and preserving the polarisation in an external magnetic field of 0.05 Oe is demonstrated experimentally. A neutron filter with an extremely weak guiding field is fabricated for obtaining polarised neutron beams. The degree of polarisation equal to 25% was obtained for 0.025-eV neutrons. Some fields of application of other polarised noble gases are considered. The cross section for cross-relaxation of nuclear polarisation in the 129Xe — 131Xe mixture is estimated.

  19. Spectroscopy of ultracold neutrons diffracted by a moving grating

    NASA Astrophysics Data System (ADS)

    Kulin, G. V.; Frank, A. I.; Goryunov, S. V.; Geltenbort, P.; Jentschel, M.; Bushuev, V. A.; Lauss, B.; Schmidt-Wellenburg, P.; Panzarella, A.; Fuchs, Y.

    2016-03-01

    Spectra of ultracold neutrons that appeared in experiments on neutron diffraction by a moving grating were measured using the time-of-flight Fourier spectrometer. Diffraction lines of five orders were observed simultaneously. The obtained data are in good agreement with the theoretical predictions based on the multiwave dynamical theory of neutron diffraction by a moving grating.

  20. A neutron diffraction study of amorphous boron

    NASA Astrophysics Data System (ADS)

    Delaplane, R. G.; Lundström, T.; Dahlborg, U.; Howells, W. S.

    1991-07-01

    The structure of amorphous boron has been studied with pulsed neutron diffraction techniques using the ISIS facilities at the Rutherford Appleton Laboratory. The experimental static structure factor S(Q) and radial distribution function support a structural model based on units of B12 icosahedra resembling those found in crystalline β-rhombohedral boron, but with a certain degree of disorder occurring in the linking between these subunits.

  1. DNA hydration studied by neutron fiber diffraction

    SciTech Connect

    Fuller, W.; Forsyth, V.T.; Mahendrasingam, A.; Langan, P.; Pigram, W.J.

    1994-12-31

    The development of neutron high angle fiber diffraction to investigate the location of water around the deoxyribonucleic acid (DNA) double-helix is described. The power of the technique is illustrated by its application to the D and A conformations of DNA using the single crystal diffractometer, D19, at the Institute Laue-Langevin, Grenoble and the time of flight diffractometer, SXD, at the Rutherford Appleton ISIS Spallation Neutron Source. These studies show the existence of bound water closely associated with the DNA. The patterns of hydration in these two DNA conformations are quite distinct and are compared to those observed in X-ray single crystal studies of two-stranded oligodeoxynucleotides. Information on the location of water around the DNA double-helix from the neutron fiber diffraction studies is combined with that on the location of alkali metal cations from complementary X-ray high angle fiber diffraction studies at the Daresbury Laboratory SRS using synchrotron radiation. These analyses emphasize the importance of viewing DNA, water and ions as a single system with specific interactions between the three components and provide a basis for understanding the effect of changes in the concentration of water and ions in inducing conformations] transitions in the DNA double-helix.

  2. Unraveling protein catalysis through neutron diffraction

    NASA Astrophysics Data System (ADS)

    Myles, Dean

    Neutron scattering and diffraction are exquisitely sensitive to the location, concentration and dynamics of hydrogen atoms in materials and provide a powerful tool for the characterization of structure-function and interfacial relationships in biological systems. Modern neutron scattering facilities offer access to a sophisticated, non-destructive suite of instruments for biophysical characterization that provide spatial and dynamic information spanning from Angstroms to microns and from picoseconds to microseconds, respectively. Applications range from atomic-resolution analysis of individual hydrogen atoms in enzymes, through to multi-scale analysis of hierarchical structures and assemblies in biological complexes, membranes and in living cells. Here we describe how the precise location of protein and water hydrogen atoms using neutron diffraction provides a more complete description of the atomic and electronic structures of proteins, enabling key questions concerning enzyme reaction mechanisms, molecular recognition and binding and protein-water interactions to be addressed. Current work is focused on understanding how molecular structure and dynamics control function in photosynthetic, cell signaling and DNA repair proteins. We will highlight recent studies that provide detailed understanding of the physiochemical mechanisms through which proteins recognize ligands and catalyze reactions, and help to define and understand the key principles involved.

  3. Neutron Laue diffraction in macromolecular crystallography

    NASA Astrophysics Data System (ADS)

    Myles, D. A. A.; Bon, C.; Langan, P.; Cipriani, F.; Castagna, J. C.; Lehmann, M. S.; Wilkinson, C.

    The time scales required for conventional neutron diffraction analysis of biological single crystals at, or near, atomic resolution are prohibitive - such studies are rarely performed. Laue (white beam) diffraction can provide a more rapid and efficient survey of reciprocal space, maximising the flux at the sample and stimulating large numbers of reflections simultaneously. A LAue DIffractometer (LADI), designed specifically for macromolecular crystallography, has been installed on a cold neutron guide at ILL. The detector comprises a large Gd 2O 3-doped neutron-sensitive image plate (400 × 800 mm) mounted on a cylindrical camera (318 mm diameter) that is read in phonographic mode after exposure. Detector response has been evaluated and performance indicators are given. Narrow (Quasi-Laue) band-passes (d/ gl/ λ = 8-20%) are often required for large unit-cell biological crystals in order to reduce reflection overlap and incoherent background. Laue and Quasi-Laue data have now been collected for a number of proteins and other biological crystals. Recent results are presented and future prospects reviewed.

  4. Status of the Neutron Imaging and Diffraction Instrument IMAT

    NASA Astrophysics Data System (ADS)

    Kockelmann, Winfried; Burca, Genoveva; Kelleher, Joe F.; Kabra, Saurabh; Zhang, Shu-Yan; Rhodes, Nigel J.; Schooneveld, Erik M.; Sykora, Jeff; Pooley, Daniel E.; Nightingale, Jim B.; Aliotta, Francesco; Ponterio, Rosa C.; Salvato, Gabriele; Tresoldi, Dario; Vasi, Cirino; McPhate, Jason B.; Tremsin, Anton S.

    A cold neutron imaging and diffraction instrument, IMAT, is currently being constructed at the ISIS second target station. IMAT will capitalize on time-of-flight transmission and diffraction techniques available at a pulsed neutron source. Analytical techniques will include neutron radiography, neutron tomography, energy-selective neutron imaging, and spatially resolved diffraction scans for residual strain and texture determination. Commissioning of the instrument will start in 2015, with time-resolving imaging detectors and two diffraction detector prototype modules. IMAT will be operated as a user facility for material science applications and will be open for developments of time-of-flight imaging methods.

  5. Growing Larger Crystals for Neutron Diffraction

    NASA Technical Reports Server (NTRS)

    Pusey, Marc

    2003-01-01

    Obtaining crystals of suitable size and high quality has been a major bottleneck in macromolecular crystallography. With the advent of advanced X-ray sources and methods the question of size has rapidly dwindled, almost to the point where if one can see the crystal then it was big enough. Quality is another issue, and major national and commercial efforts were established to take advantage of the microgravity environment in an effort to obtain higher quality crystals. Studies of the macromolecule crystallization process were carried out in many labs in an effort to understand what affected the resultant crystal quality on Earth, and how microgravity improved the process. While technological improvements are resulting in a diminishing of the minimum crystal size required, neutron diffraction structural studies still require considerably larger crystals, by several orders of magnitude, than X-ray studies. From a crystal growth physics perspective there is no reason why these 'large' crystals cannot be obtained: the question is generally more one of supply than limitations mechanism. This talk will discuss our laboratory s current model for macromolecule crystal growth, with highlights pertaining to the growth of crystals suitable for neutron diffraction studies.

  6. Neutron diffraction studies of natural glasses

    SciTech Connect

    Wright, A.C.; Erwin Desa, J.A.; Weeks, R.A.; Sinclair, R.N.; Bailey, D.K.

    1983-08-01

    A neutron diffraction investigation has been carried out of the structures of several naturally occurring glasses, viz. Libyan Desert glass, a Fulgurite, Wabar glass, Lechatelierite from Canon Diablo, a Tektite, Obsidian (3 samples), and Macusani glass. Libyan Desert sand has also been examined, together with crystalline ..cap alpha..-quartz and ..cap alpha..-cristobalite. A comparison of data for the natural glasses and synthetic vitreous silica (Spectrosil B) in both reciprocal and real space allows a categorisation into Silicas, which closely resemble synthetic vitreous silica, and Silicates, for which the resemblance to silica is consistently less striking. The data support the view that Libyan Desert glass and sand have a common origin, while the Tektite has a structure similar to that of volcanic glasses.

  7. Pulsed Neutron Powder Diffraction for Materials Science

    SciTech Connect

    Kamiyama, T.

    2008-03-17

    The accelerator-based neutron diffraction began in the end of 60's at Tohoku University which was succeeded by the four spallation neutron facilities with proton accelerators at the High Energy Accelerator Research Organization (Japan), Argonne National Laboratory and Los Alamos Laboratory (USA), and Rutherford Appleton Laboratory (UK). Since then, the next generation source has been pursued for 20 years, and 1MW-class spallation neutron sources will be appeared in about three years at the three parts of the world: Japan, UK and USA. The joint proton accelerator project (J-PARC), a collaborative project between KEK and JAEA, is one of them. The aim of the talk is to describe about J-PARC and the neutron diffractometers being installed at the materials and life science facility of J-PARC. The materials and life science facility of J-PARC has 23 neutron beam ports and will start delivering the first neutron beam of 25 Hz from 2008 May. Until now, more than 20 proposals have been reviewed by the review committee, and accepted proposal groups have started to get fund. Those proposals include five polycrystalline diffractometers: a super high resolution powder diffractometer (SHRPD), a 0.2%-resolution powder diffractometer of Ibaraki prefecture (IPD), an engineering diffractometers (Takumi), a high intensity S(Q) diffractometer (VSD), and a high-pressure dedicated diffractometer. SHRPD, Takumi and IPD are being designed and constructed by the joint team of KEK, JAEA and Ibaraki University, whose member are originally from the KEK powder group. These three instruments are expected to start in 2008. VSD is a super high intensity diffractometer with the highest resolution of {delta}d/d = 0.3%. VSD can measure rapid time-dependent phenomena of crystalline materials as well as glass, liquid and amorphous materials. The pair distribution function will be routinely obtained by the Fourier transiformation of S(Q) data. Q range of VSD will be as wide as 0.01 A{sup -1}

  8. Pulsed Neutron Powder Diffraction for Materials Science

    NASA Astrophysics Data System (ADS)

    Kamiyama, T.

    2008-03-01

    The accelerator-based neutron diffraction began in the end of 60's at Tohoku University which was succeeded by the four spallation neutron facilities with proton accelerators at the High Energy Accelerator Research Organization (Japan), Argonne National Laboratory and Los Alamos Laboratory (USA), and Rutherford Appleton Laboratory (UK). Since then, the next generation source has been pursued for 20 years, and 1MW-class spallation neutron sources will be appeared in about three years at the three parts of the world: Japan, UK and USA. The joint proton accelerator project (J-PARC), a collaborative project between KEK and JAEA, is one of them. The aim of the talk is to describe about J-PARC and the neutron diffractometers being installed at the materials and life science facility of J-PARC. The materials and life science facility of J-PARC has 23 neutron beam ports and will start delivering the first neutron beam of 25 Hz from 2008 May. Until now, more than 20 proposals have been reviewed by the review committee, and accepted proposal groups have started to get fund. Those proposals include five polycrystalline diffractometers: a super high resolution powder diffractometer (SHRPD), a 0.2%-resolution powder diffractometer of Ibaraki prefecture (IPD), an engineering diffractometers (Takumi), a high intensity S(Q) diffractometer (VSD), and a high-pressure dedicated diffractometer. SHRPD, Takumi and IPD are being designed and constructed by the joint team of KEK, JAEA and Ibaraki University, whose member are originally from the KEK powder group. These three instruments are expected to start in 2008. VSD is a super high intensity diffractometer with the highest resolution of Δd/d = 0.3%. VSD can measure rapid time-dependent phenomena of crystalline materials as well as glass, liquid and amorphous materials. The pair distribution function will be routinely obtained by the Fourier transiformation of S(Q) data. Q range of VSD will be as wide as 0.01 Å-1

  9. Neutron diffraction studies of viral fusion peptides

    NASA Astrophysics Data System (ADS)

    Bradshaw, Jeremy P.; J. M. Darkes, Malcolm; Katsaras, John; Epand, Richard M.

    2000-03-01

    Membrane fusion plays a vital role in a large and diverse number of essential biological processes. Despite this fact, the precise molecular events that occur during fusion are still not known. We are currently engaged on a study of membrane fusion as mediated by viral fusion peptides. These peptides are the N-terminal regions of certain viral envelope proteins that mediate the process of fusion between the viral envelope and the membranes of the host cell during the infection process. As part of this study, we have carried out neutron diffraction measurements at the ILL, BeNSC and Chalk River, on a range of viral fusion peptides. The peptides, from simian immunodeficiency virus (SIV), influenza A and feline leukaemia virus (FeLV), were incorporated into stacked phospholipid bilayers. Some of the peptides had been specifically deuterated at key amino acids. Lamellar diffraction data were collected and analysed to yield information on the peptide conformation, location and orientation relative to the bilayer.

  10. Neutron Diffraction Studies of Carbonate Apatite

    NASA Astrophysics Data System (ADS)

    Moghaddam, Hadi Y.; Leventouri, Theodora; Chakoumakos, Bryan C.

    1998-11-01

    Moghaddam H.Y., Leventouri Th.* (Dept. of Physics & Alloy Research Center, Florida Atlantic Univ.) Chakoumakos B.C. (Solid State Division, Oak Ridge National Lab.**,kou@ornl.gov) We report Rietveld structural refinements of neutron diffraction data of a highly crystalline, single-phase natural carbonate apatite,(francolite of Epirus, Greece), in order to elucidate the details of carbonate substitution in the apatites. The composition is Ca9.56Na0.38Mg0.08(PO4)4.82(CO3)0.946(SO4)0.2F2.34, as determined by electron microprobe analysis. We report refinements of data for the native francolite as a function of temperature between 296K and 10K after the material had been heated at 750 °C to drive off adsorbed water and CO2. The neutron diffractioii@data were collected using a wavelength 1.0912 A on the HB4 high resolution powder diffractometer at the High Flux Isotope Reactor at Oak Ridge National Laboratory. Analysis of the temperature dependence of the anisotropic displacement parameters can reveal the contribution from the temperature independent static positional disorder. Difference displacement parameters evaluated along various bonding directions are being used to describe the mechanics and dynamics of the carbonate for phosphate substitution.*Supported by a SURA-ORNL Summer Cooperative Research Program 1998.**Supported by the Division of Materials Sciences,U.S. D.O.E. (contract DE-AC05-96OR22464 with Lockheed Martin Energy Research Corporation).

  11. Structure of yttrium cobaltate from neutron diffraction

    SciTech Connect

    Mehta, A.; Berliner, R.; Smith, R.W.

    1997-05-01

    The crystal structure of YCoO{sub 3} has been determined from Rietveld analysis of the powder neutron diffraction data at 17, 100, and 300 K. At each temperature, the structure is a distorted perovskite with orthorhombic symmetry, space group Pbnm (Z = 4). The lattice parameters, at 300 K, are 5.1388 (5) x 5.4191(5) x 7.3658(7) {angstrom}. Structural analysis indicates that the formal valence of cobalt in YCoO{sub 3} is +3. Analysis of the Co-O distances and the absence of magnetic structure indicates that the majority of the Co{sup 3+} ions in YCoO{sub 3} are in the low-spin (i.e. t{sub 2g}{sup 6}e{sub g}{sup 0}) state. The data also show that perhaps 10% of the CO{sup 3+} ions at 300 K (but insignificant fractions at 100 and 17 K) are in the high-spin state.

  12. Future directions in high-pressure neutron diffraction

    NASA Astrophysics Data System (ADS)

    Guthrie, M.

    2015-04-01

    The ability to manipulate structure and properties using pressure has been well known for many centuries. Diffraction provides the unique ability to observe these structural changes in fine detail on lengthscales spanning atomic to nanometre dimensions. Amongst the broad suite of diffraction tools available today, neutrons provide unique capabilities of fundamental importance. However, to date, the growth of neutron diffraction under extremes of pressure has been limited by the weakness of available sources. In recent years, substantial government investments have led to the construction of a new generation of neutron sources while existing facilities have been revitalized by upgrades. The timely convergence of these bright facilities with new pressure-cell technologies suggests that the field of high-pressure (HP) neutron science is on the cusp of substantial growth. Here, the history of HP neutron research is examined with the hope of gleaning an accurate prediction of where some of these revolutionary capabilities will lead in the near future. In particular, a dramatic expansion of current pressure-temperature range is likely, with corresponding increased scope for extreme-conditions science with neutron diffraction. This increase in coverage will be matched with improvements in data quality. Furthermore, we can also expect broad new capabilities beyond diffraction, including in neutron imaging, small angle scattering and inelastic spectroscopy.

  13. Future directions in high-pressure neutron diffraction.

    PubMed

    Guthrie, M

    2015-04-22

    The ability to manipulate structure and properties using pressure has been well known for many centuries. Diffraction provides the unique ability to observe these structural changes in fine detail on lengthscales spanning atomic to nanometre dimensions. Amongst the broad suite of diffraction tools available today, neutrons provide unique capabilities of fundamental importance. However, to date, the growth of neutron diffraction under extremes of pressure has been limited by the weakness of available sources. In recent years, substantial government investments have led to the construction of a new generation of neutron sources while existing facilities have been revitalized by upgrades. The timely convergence of these bright facilities with new pressure-cell technologies suggests that the field of high-pressure (HP) neutron science is on the cusp of substantial growth. Here, the history of HP neutron research is examined with the hope of gleaning an accurate prediction of where some of these revolutionary capabilities will lead in the near future. In particular, a dramatic expansion of current pressure-temperature range is likely, with corresponding increased scope for extreme-conditions science with neutron diffraction. This increase in coverage will be matched with improvements in data quality. Furthermore, we can also expect broad new capabilities beyond diffraction, including in neutron imaging, small angle scattering and inelastic spectroscopy. PMID:25789450

  14. Cold neutron diffraction contrast tomography of polycrystalline material.

    PubMed

    Peetermans, S; King, A; Ludwig, W; Reischig, P; Lehmann, E H

    2014-11-21

    Traditional neutron imaging is based on the attenuation of a neutron beam through scattering and absorption upon traversing a sample of interest. It offers insight into the sample's material distribution at high spatial resolution in a non-destructive way. In this work, it is expanded to include the diffracted neutrons that were ignored so far and obtain a crystallographic distribution (grain mapping). Samples are rotated in a cold neutron beam of limited wavelength band. Projections of the crystallites formed by the neutrons they diffract are captured on a two dimensional imaging detector. Their positions on the detector reveal their orientation whereas the projections themselves are used to reconstruct the shape of the grains. Indebted to established synchrotron diffraction contrast tomography, this 'cold neutron diffraction contrast tomography' is performed on recrystallized aluminium for experimental comparison between both. Differences between set-up and method are discussed, followed by the application range in terms of sample properties (crystallite size and number, mosaicity and typical materials). Neutron diffraction contrast tomography allows to study large grains in bulky metallic structures. PMID:25274183

  15. A low temperature X-ray single-crystal diffraction and polarised infra-red study of epidote

    NASA Astrophysics Data System (ADS)

    Gatta, G. Diego; Alvaro, Matteo; Bromiley, Geoffrey

    2012-01-01

    The effects of low-temperature on the crystal structure of a natural epidote [Ca1.925Fe0.745Al2.265Ti0.004Si3.037O12(OH), a = 8.8924(7), b = 5.6214(3), c = 10.1547(6)Å and β = 115.396(8)° at room conditions, Sp. Gr. P21 /m] have been investigated with a series of structure refinements down to 100 K on the basis of X-ray single-crystal diffraction data. The reflection conditions confirm that the space group is maintained within the T-range investigated. Structural refinements at all temperatures show the presence of Fe3+ at the octahedral M(3) site only [%Fe(M3) = 70.6(4)% at 295 K]. Only one independent proton site was located and two possible H-bonds occur, with O(10) as donor and O(4) and O(2) as acceptors. The H-bonding scheme is maintained down to 100 K and is supported by single crystal room- T polarised FTIR data. FTIR Spectra over the region 4,000-2,500 cm-1 are dominated by the presence of a strongly pleochroic absorption feature which can be assigned to protonation of O(10)-O(4). Previously unobserved splitting of this absorption features is consistent with a NNN influence due to the presence of Al and Fe3+ on the nearby M(3) site. An additional relatively minor absorption feature in FTIR spectra can be tentatively assigned to protonation of O(10)-O(2). Low- T does not affect significantly the tetrahedral and octahedral bond distances and angles, even when distances are corrected for "rigid body motions". A more significant effect is observed for the bond distances of the distorted Ca(1)- and Ca(2)-polyhedra, especially when corrected for "non-correlated motion". The main low- T effect is observed on the vibrational regime of the atomic sites, and in particular for the two Ca-sites. A significant reduction of the magnitude of the thermal displacement ellipsoids, with a variation of U eq (defined as one-third of the trace of the orthogonalised U ij tensor) by ~40% is observed for the Ca-sites between 295 and 100 K. Within the same T-range, the U eq of

  16. Macromolecular structure phasing by neutron anomalous diffraction.

    PubMed

    Cuypers, Maxime G; Mason, Sax A; Mossou, Estelle; Haertlein, Michael; Forsyth, V Trevor; Mitchell, Edward P

    2016-01-01

    In this report we show for the first time that neutron anomalous dispersion can be used in a practical manner to determine experimental phases of a protein crystal structure, providing a new tool for structural biologists. The approach is demonstrated through the use of a state-of-the-art monochromatic neutron diffractometer at the Institut Laue-Langevin (ILL) in combination with crystals of perdeuterated protein that minimise the level of hydrogen incoherent scattering and enhance the visibility of the anomalous signal. The protein used was rubredoxin in which cadmium replaced the iron at the iron-sulphur site. While this study was carried out using a steady-state neutron beam source, the results will be of major interest for capabilities at existing and emerging spallation neutron sources where time-of-flight instruments provide inherent energy discrimination. In particular this capability may be expected to offer unique opportunities to a rapidly developing structural biology community where there is increasing interest in the identification of protonation states, protein/water interactions and protein-ligand interactions - all of which are of central importance to a wide range of fundamental and applied areas in the biosciences. PMID:27511806

  17. Macromolecular structure phasing by neutron anomalous diffraction

    PubMed Central

    Cuypers, Maxime G.; Mason, Sax A.; Mossou, Estelle; Haertlein, Michael; Forsyth, V. Trevor; Mitchell, Edward P.

    2016-01-01

    In this report we show for the first time that neutron anomalous dispersion can be used in a practical manner to determine experimental phases of a protein crystal structure, providing a new tool for structural biologists. The approach is demonstrated through the use of a state-of-the-art monochromatic neutron diffractometer at the Institut Laue-Langevin (ILL) in combination with crystals of perdeuterated protein that minimise the level of hydrogen incoherent scattering and enhance the visibility of the anomalous signal. The protein used was rubredoxin in which cadmium replaced the iron at the iron-sulphur site. While this study was carried out using a steady-state neutron beam source, the results will be of major interest for capabilities at existing and emerging spallation neutron sources where time-of-flight instruments provide inherent energy discrimination. In particular this capability may be expected to offer unique opportunities to a rapidly developing structural biology community where there is increasing interest in the identification of protonation states, protein/water interactions and protein-ligand interactions – all of which are of central importance to a wide range of fundamental and applied areas in the biosciences. PMID:27511806

  18. Maximizing Macromolecule Crystal Size for Neutron Diffraction Experiments

    NASA Technical Reports Server (NTRS)

    Judge, R. A.; Kephart, R.; Leardi, R.; Myles, D. A.; Snell, E. H.; vanderWoerd, M.; Curreri, Peter A. (Technical Monitor)

    2002-01-01

    A challenge in neutron diffraction experiments is growing large (greater than 1 cu mm) macromolecule crystals. In taking up this challenge we have used statistical experiment design techniques to quickly identify crystallization conditions under which the largest crystals grow. These techniques provide the maximum information for minimal experimental effort, allowing optimal screening of crystallization variables in a simple experimental matrix, using the minimum amount of sample. Analysis of the results quickly tells the investigator what conditions are the most important for the crystallization. These can then be used to maximize the crystallization results in terms of reducing crystal numbers and providing large crystals of suitable habit. We have used these techniques to grow large crystals of Glucose isomerase. Glucose isomerase is an industrial enzyme used extensively in the food industry for the conversion of glucose to fructose. The aim of this study is the elucidation of the enzymatic mechanism at the molecular level. The accurate determination of hydrogen positions, which is critical for this, is a requirement that neutron diffraction is uniquely suited for. Preliminary neutron diffraction experiments with these crystals conducted at the Institute Laue-Langevin (Grenoble, France) reveal diffraction to beyond 2.5 angstrom. Macromolecular crystal growth is a process involving many parameters, and statistical experimental design is naturally suited to this field. These techniques are sample independent and provide an experimental strategy to maximize crystal volume and habit for neutron diffraction studies.

  19. Magnetic structures of actinide materials by pulsed neutron diffraction

    SciTech Connect

    Lawson, A.C.; Goldstone, J.A.; Huber, J.G.; Giorgi, A.L.; Conant, J.W.; Severing, A.; Cort, B.; Robinson, R.A.

    1990-01-01

    We describe some attempts to observe magnetic structure in various actinide (5f-electron) materials. Our experimental technique is neutron powder diffraction as practiced at a spallation (pulsed) neutron source. We will discuss our investigations of {alpha}-Pu, {delta}-Pu, {alpha}-UD{sub 3} and {beta}-UD{sub 3}. {beta}-UD{sub 3} is a simple ferromagnet: surprisingly, the moments on the two non-equivalent uranium atoms are the same within experimental error. {alpha}-UD{sub 3}, {alpha}-Pu and {delta}-Pu are non-magnetic, within the limits of our observations. Our work with pulsed neutron diffraction shows that it is a useful technique for research on magnetic materials.

  20. Grazing incidence neutron diffraction from large scale 2D structures

    SciTech Connect

    Toperverg, B. P.; Felcher, G. P.; Metlushko, V. V.; Leiner, V.; Siebrecht, R.; Nikonov, O.

    2000-01-13

    The distorted wave Born approximation (DWBA) is applied to evaluate the diffraction pattern of neutrons (or X-rays) from a 2D array of dots deposited onto a dissimilar substrate. With the radiation impinging on the surface at a grazing incidence angle {alpha}, the intensities diffracted both in and out the plane of specular reflection are calculated as a function of the periodicity of the array, height and diameter of the dots. The results are presented in the form of diffracted intensity contours in a plane with coordinates {alpha} and {alpha}{prime}, the latter being the glancing angle of scattering. The optimization of the experimental conditions for polarized neutron experiments on submicron dots is discussed. The feasibility of such measurements is confirmed by a test experiment.

  1. Feasibility studies for high pressure neutron powder diffraction experiments

    SciTech Connect

    Von Dreele, R.B. ); Parise, J. )

    1990-01-01

    We recently performed two neutron powder diffraction experiments on very small samples on the High Intensity Powder Diffractometer (HIPD). These were done to determine the feasibility of performing in situ high pressure/high temperature neutron diffraction experiments on HIPD at pressures which would exceed the previous limit of {approximately}50 kbar achievable in a neutron diffraction experiment. The first experiment consisted of examining the product from a high pressure preparation done at Stony Brook. The sample, which had been prepared at 65 kbar and 1000{degree}C, consisted of a small platinum capsule filled with CaGeO{sub 3} perovskite. The weights of the capsule included 225 mg of platinum and 49 mg of the germanate. A diffraction experiment taking {approximately}8.6 hrs at a LANSCE proton beam current of {approximately}53 {mu}A gave peaks of good intensity from both Pt and CaGeO{sub 3}; we could begin to see them after only 20 min of beam time. The second experiment was to test the possibility of diffraction from a high pressure apparatus. We placed in the HIPD sample position the central assembly from a 100 kbar octahedral press. Four tungsten carbide anvils and a copper block previously pressed to 65 kbar were held in an aluminum frame. The sample consisted of a small bit of nickel foil (175 mg) placed in a 3 mm hole in the copper block. The active sample volume is defined by the gap between the anvils and the length of the sample. A small portion of the copper block is also seen in this arrangement. This is viewed at 90{degree} 2{Theta} through a similar gap between the anvils by 4 1/2 in. {times} 12 in. {sup 3}He counter tubes. This arrangement simulates the operating conditions of a high pressure run at 100 kbar and takes advantage of the fixed instrument geometry possible in time-of-flight neutron diffraction experiments.

  2. Neutron Laue diffraction studies of coenzyme cob(II)alamin.

    PubMed

    Langan, P; Lehmann, M; Wilkinson, C; Jogl, G; Kratky, C

    1999-01-01

    Using a recently designed neutron single-crystal diffractometer utilizing a narrow-band Laue concept (LADI), diffraction data were collected from a crystal of the coenzyme cob(II)alamin (B12r), crystallized from a mixture of D2O and perdeuterated acetone. The instrument was placed at the end of a cold neutron guide at the Institute Laue Langevin (ILL, Grenoble, France), and data collection with neutrons of 1.8-8.0 A wavelength to a crystallographic resolution of 1.43 A was complete after about 36 h. This compares favourably with a previous experiment utilizing the same crystal specimen, where more than four weeks were required to collect monochromatic diffraction data to about 1 A resolution. Using the Laue data, the structure was solved by molecular replacement with the known X-ray crystal structure. Difference density maps revealed the atomic positions (including deuterium atoms) of seven ordered solvent water molecules and two (partially disordered) acetone molecules. These density maps were compared with corresponding maps computed with monochromatic neutron-diffraction data collected to 1. 0 A resolution using the same crystal specimen, as well as to maps derived from high-resolution (0.90 A) synchrotron X-ray data. In spite of the better definition of atomic positions in the two high-resolution maps, the 1.43 A LADI maps show considerable power for the determination of the location of hydrogen and deuterium positions. PMID:10089394

  3. The structure of liquid fluorosulfuric acid investigated by neutron diffraction

    NASA Astrophysics Data System (ADS)

    McLain, S. E.; Benmore, C. J.; Turner, J. F. C.

    2002-08-01

    The results of an investigation into the liquid structure of fluorosulfuric acid measured using neutron diffraction with isotopic substitution are reported. The first-order neutron difference function is extracted from data recorded at 300 and 193 K from isotopically labeled FSO3H and FSO3D. Analysis of the derived radial distribution functions shows that unique, multisite hydrogen bonding is present in the liquid. These results suggest hydrogen bonding between the hydrogen and fluorine as well as oxygen occurs in the liquid. The fraction of molecules that is hydrogen bound in each way varies with temperature, with the 193 K data showing a more tightly bound system.

  4. Investigation of Acrylic Acid at High Pressure Using Neutron Diffraction

    PubMed Central

    2014-01-01

    This article details the exploration of perdeuterated acrylic acid at high pressure using neutron diffraction. The structural changes that occur in acrylic acid-d4 are followed via diffraction and rationalized using the Pixel method. Acrylic acid undergoes a reconstructive phase transition to a new phase at ∼0.8 GPa and remains molecular to 7.2 GPa before polymerizing on decompression to ambient pressure. The resulting product is analyzed via Raman and FT-IR spectroscopy and differential scanning calorimetry and found to possess a different molecular structure compared with polymers produced via traditional routes. PMID:24650085

  5. Neutron diffraction study of the deuterides of Ti Mo alloys

    NASA Astrophysics Data System (ADS)

    Sun, Kai; Yuan, Xuezhong; Wu, Erdong; Chen, Dongfeng; Gou, Cheng

    2006-11-01

    The structures of the deuterides of seven Ti-Mo alloys with different Mo contents ranging from 5 to 40 at% are studied by neutron diffraction. After deuterization at ∼150 kPa, the saturated deuterides containing ∼1.8-1.9 deuterium per alloy atom with a δ-phase titanium hydride type of structure have formed. The lattice constants of the deuterides decrease consistently with the increase of Mo content. The analysis of the line broadening of the diffraction patterns has revealed the relationship between lattice deformation and the contents of the alloying Mo in the deuterides.

  6. Structural molecular biology: Recent results from neutron diffraction

    NASA Astrophysics Data System (ADS)

    Timmins, Peter A.

    1995-02-01

    Neutron diffraction is of importance in structural biology at several different levels of resolution. In most cases the unique possibility arising from deuterium labelling or contrast variation is of fundamental importance in providing information complementary to that which can be obtained from X-ray diffraction. At high resolution, neutron crystallography of proteins allows the location of hydrogen atoms in the molecule or of the hydration water, both of which may be central to biological activity. A major difficulty in this field has been the poor signal-to-noise ratio of the data arising not only from relatively low beam intensities and small crystals but, most importantly from the incoherent background due to hydrogen atoms in the sample. Modern methods of molecular biology now offer ways of producing fully deuterated proteins by cloning in bacteria grown on fully deuterated media. At a slightly lower resolution, there are a number of systems which may be ordered in one or two dimensions. This is the case in the purple membrane where neutron diffraction with deuterium labelling has complemented high resolution electron diffraction. Finally there is a class of very large macromolecular systems which can be crystallised and have been studied by X-ray diffraction but in which part of the structure is locally disordered and usually has insufficient contrast to be seen with X-rays. In this case the use of H 2O/D 2O contrast variation allows these components to be located. Examples of this are the nucleic acid in virus structures and detergent bound to membrane proteins.

  7. Diffraction measurements with a boron-based GEM neutron detector

    NASA Astrophysics Data System (ADS)

    Croci, Gabriele; Albani, Giorgia; Cazzaniga, Carlo; Perelli Cippo, Enrico; Schooneveld, Erik; Claps, Gerardo; Cremona, Anna; Grosso, Giovanni; Muraro, Andrea; Murtas, Fabrizio; Rebai, Marica; Scherillo, Antonella; Tardocchi, Marco; Gorini, Giuseppe

    2014-07-01

    The research of reliable substitutes of 3He detectors is an important task for the affordability of new neutron scattering instrumentation for future spallation sources like the European Spallation Source. GEM (Gas Electron Multiplier)-based detectors represent a valid alternative since they can combine high-rate capability, coverage of up to 1\\ \\text{m}^{2} area and good intrinsic spatial resolution (for this detector class it can be better than 0.5 mm). The first neutron diffraction measurements performed using a borated GEM detector are reported. The detector has an active area of 10 \\times 5\\ \\text{cm}^{2} and is equipped with a borated cathode. The GEM detector was read out using the standard ISIS Data Acquisition System. The comparison with measurements performed with standard 3He detectors shows that the broadening of the peaks measured on the diffractogram obtained with the GEM is 20-30% wider than the one obtained by 3He tubes but the active area of the GEM is twice that of 3He tubes. The GEM resolution is improved if half of its active area is considered. The signal-to-background ratio of the GEM is about 1.5 to 2 times lower than that of 3He. This measurement proves that GEM detectors can be used for neutron diffraction measurements and paves the way for their use at future neutron spallation sources.

  8. Engineering related neutron diffraction measurements probing strains, texture and microstructure

    SciTech Connect

    Clausen, Bjorn; Brown, Donald W; Tome, Carlos N; Balogh, Levente; Vogel, Sven C

    2010-01-01

    Neutron diffraction has been used for engineering applications for nearly three decades. The basis of the technique is powder diffraction following Bragg's Law. From the measured diffraction patterns information about internal, or residual, strain can be deduced from the peak positions, texture information can be extracted from the peak intensities, and finally the peak widths can provide information about the microstructure, e.g. dislocation densities and grain sizes. The strains are measured directly from changes in lattice parameters, however, in many cases it is non-trivial to determine macroscopic values of stress or strain from the measured data. The effects of intergranular strains must be considered, and combining the neutron diffraction measurements with polycrystal deformation modeling has proven invaluable in determining the overall stress and strain values of interest in designing and dimensioning engineering components. Furthelmore, the combined use of measurements and modeling has provided a tool for elucidating basic material properties, such as critical resolved shear stresses for the active deformation modes and their evolution as a function of applied deformation.

  9. Polarisation of Light

    NASA Astrophysics Data System (ADS)

    Spottiswoode, William

    2015-01-01

    Preface; 1. Methods of polarisation; 2. Double refraction: polariscopes; 3. Chromatic polarisation: the wave theory; 4. Circular polarisation; 5. Circular polarisation by reflexion; 6. Phenomena produced by mechanical means: unannealed glass; 7. Atmospheric and other polarisation: the polar clock; 8. Rings and brushes produced by crystal plates; 9. Composition of colours by polarised light; Index.

  10. Neutron Diffraction Studies of Intercritically Austempered Ductile Irons

    SciTech Connect

    Druschitz, Alan; Aristizabal, Ricardo; Druschitz, Edward; Hubbard, Camden R; Watkins, Thomas R

    2011-01-01

    Neutron diffraction is a powerful tool that can be used to identify the phases present and to measure the spacing of the atomic planes in a material. Thus, the residual stresses can be determined within a component and/or the phases present. New intercritically austempered irons rely on the unique properties of the austenite phase present in their microstructures. If these materials are to see widespread use, methods to verify the quality (behavior consistency) of these materials and to provide guidance for further optimization will be needed. Neutron diffraction studies were performed at the second generation neutron residual stress facility (NRSF2) at the High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory on a variety of intercritically austempered irons. For similar materials, such as TRIP steels, the strengthening mechanism involves the transformation of metastable austenite to martensite during deformation. For the intercritically austempered ductile irons two different deformation/strengthening mechanisms, phase transformation and slip, dependent upon the iron chemistry, were observed. Lattice strain and phase fraction data as a function of applied stress are presented.

  11. Carbonation profiles in cement paste analyzed by neutron diffraction

    NASA Astrophysics Data System (ADS)

    Galan, I.; Sanchez, J.; Andrade, C.; Evans, A.

    2012-02-01

    The present work deals with the carbonation process in cement based materials such as concrete. In order to clarify the evolution of the two main phases involved in the process, portlandite and calcium carbonate as a function of depth, spatially resolved neutron diffraction experiments have been performed at SALSA diffractometer at ILL in carbonated cement paste samples. Specimens submitted to different carbonation processes, both natural and accelerated, have been analyzed with this non destructive technique. The evolution of the main diffraction peaks of portlandite and calcite has been followed by means of neutron diffraction patterns measured at different depths. The results indicate that, in specimens subjected to CO2 atmospheres for 24 and 48 hours, the amount of calcite increases from the centre of the specimen to the surface. In both type of specimens calcite is formed at all depths analyzed, with higher quantities for the ones submitted to the longest carbonation period. Regarding the evolution of portlandite in these specimens, it almost completely disappeared, with only a low amount of the phase constant throughout the sample. In specimens subjected to air in a closed chamber for 21 months, higher amounts of portlandite were observed throughout the sample and little increase of calcite in the outer part, pointing out a much less severe reaction. The absorption effects are characterized by measuring in perpendicular directions and an absorption coefficient is calculated for portlandite.

  12. Neutron diffraction facilities at the high flux reactor, Petten

    NASA Astrophysics Data System (ADS)

    Ohms, C.; Youtsos, A. G.; Bontenbal, A.; Mulder, F. M.

    2000-03-01

    The High Flux Reactor in Petten is equipped with twelve beam tubes for the extraction of thermal neutrons for applications in materials and medical science. Beam tubes HB4 and HB5 are equipped with diffractometers for residual stress and powder investigations. Recently at HB4 the Large Component Neutron Diffraction Facility has been installed. It is a unique facility with respect to its capability of handling heavy components up to 1000 kg in residual stress testing. Its basic features are described and the first applications on thick piping welds are shown. The diffractometer at HB5 can be set up for powder and stress measurements. Recent applications include temperature dependent measurements on phase transitions in intermetallic compounds and on Li ion energy storage materials.

  13. Structural studies of magnesium nitride fluorides by powder neutron diffraction

    SciTech Connect

    Brogan, Michael A.; Hughes, Robert W.; Smith, Ronald I.; Gregory, Duncan H.

    2012-01-15

    Samples of ternary nitride fluorides, Mg{sub 3}NF{sub 3} and Mg{sub 2}NF have been prepared by solid state reaction of Mg{sub 3}N{sub 2} and MgF{sub 2} at 1323-1423 K and investigated by powder X-ray and powder neutron diffraction techniques. Mg{sub 3}NF{sub 3} is cubic (space group: Pm3m) and has a structure related to rock-salt MgO, but with one cation site vacant. Mg{sub 2}NF is tetragonal (space group: I4{sub 1}/amd) and has an anti-LiFeO{sub 2} related structure. Both compounds are essentially ionic and form structures in which nitride and fluoride anions are crystallographically ordered. The nitride fluorides show temperature independent paramagnetic behaviour between 5 and 300 K. - Graphical abstract: Definitive structures of the ternary magnesium nitride fluorides Mg{sub 3}NF{sub 3} and the lower temperature polymorph of Mg{sub 2}NF have been determined from powder neutron diffraction data. The nitride halides are essentially ionic and exhibit weak temperature independent paramagnetic behaviour. Highlights: Black-Right-Pointing-Pointer Definitive structures of Mg{sub 3}NF{sub 3} and Mg{sub 2}NF were determined by neutron diffraction. Black-Right-Pointing-Pointer Nitride and fluoride anions are crystallographically ordered in both structures. Black-Right-Pointing-Pointer Both compounds exhibit weak, temperature independent paramagnetic behaviour. Black-Right-Pointing-Pointer The compounds are essentially ionic with ionicity increasing with F{sup -} content.

  14. Investigation of Methacrylic Acid at High Pressure Using Neutron Diffraction.

    PubMed

    Marshall, William G; Urquhart, Andrew J; Oswald, Iain D H

    2015-09-10

    This article shows that pressure can be a low-intensity route to the synthesis of polymethacrylic acid. The exploration of perdeuterated methacrylic acid at high pressure using neutron diffraction reveals that methacrylic acid exhibits two polymorphic phase transformations at relatively low pressures. The first is observed at 0.39 GPa, where both phases were observed simultaneously and confirm our previous observations. This transition is followed by a second transition at 1.2 GPa to a new polymorph that is characterized for the first time. On increasing pressure, the diffraction pattern of phase III deteriorates significantly. On decompression phase III persists to 0.54 GPa before transformation to the ambient pressure phase. There is significant loss of signal after decompression, signifying that there has been a loss of material through polymerization. The orientation of the molecules in phase III provides insight into the possible polymerization reaction. PMID:26289930

  15. Non invasive measurement of strain and temperature by neutron diffraction

    NASA Astrophysics Data System (ADS)

    Holden, T. M.; Root, J. H.; Tennant, D. C.; Kroeze, D. E.; Leggett, D.

    1990-06-01

    Two methods have been developed to determine temperature noninvasively within engineering components by neutron diffraction. The integrated intensity of a diffraction line depends on temperature through the Debye-Waller factor. The angular position of the line, in the absence of an applied load, depends on temperature through the thermal expansion coefficient. Temperature may thus be determined by accurate relative intensity measurements with respect to a reference temperature and, alternatively, by accurate measurement of the interplanar spacings. It was also shown to be feasible to measure the strain response to an applied load at elevated temperatures. Measurements were made on Waspalloy and the Ti alloy AMS 4928. For Waspalloy, the thermal expansion at zero stress gave the average temperature with a precision of +/- 4 K and agreed with thermocouple measurements to within 5 K on average. The intensity data suggest that temperature can be measured with a precision of +/- 10 K in a loaded component.

  16. Bayesian Library for the Analysis of Neutron Diffraction Data

    NASA Astrophysics Data System (ADS)

    Ratcliff, William; Lesniewski, Joseph; Quintana, Dylan

    During this talk, I will introduce the Bayesian Library for the Analysis of Neutron Diffraction Data. In this library we use of the DREAM algorithm to effectively sample parameter space. This offers several advantages over traditional least squares fitting approaches. It gives us more robust estimates of the fitting parameters, their errors, and their correlations. It also is more stable than least squares methods and provides more confidence in finding a global minimum. I will discuss the algorithm and its application to several materials. I will show applications to both structural and magnetic diffraction patterns. I will present examples of fitting both powder and single crystal data. We would like to acknowledge support from the Department of Commerce and the NSF.

  17. Crystal structure of human tooth enamel studied by neutron diffraction

    NASA Astrophysics Data System (ADS)

    Ouladdiaf, Bachir; Rodriguez-Carvajal, Juan; Goutaudier, Christelle; Ouladdiaf, Selma; Grosgogeat, Brigitte; Pradelle, Nelly; Colon, Pierre

    2015-02-01

    Crystal structure of human tooth enamel was investigated using high-resolution neutron powder diffraction. Excellent agreement between observed and refined patterns is obtained, using the hexagonal hydroxyapatite model for the tooth enamel, where a large hydroxyl deficiency ˜70% is found in the 4e site. Rietveld refinements method combined with the difference Fourier maps have revealed, however, that the hydroxyl ions are not only disordered along the c-axis but also within the basal plane. Additional H ions located at the 6h site and forming HPO42- anions were found.

  18. Neutron diffraction studies of welds of aerospace aluminum alloys

    SciTech Connect

    Martukanitz, R.P.; Howell, P.R.; Payzant, E.A.; Spooner, S.; Hubbard, C.R.

    1996-10-01

    Neutron diffraction and electron microscopy were done on residual stress in various regions comprising variable polarity plasma arc welds of alloys 2219 (Al-6.3Cu) and 2195 (Al-4.0Cu-1.0Li-0.5Mg-0.5Ag). Results indicate that lattice parameter changes in the various weld regions may be attributed to residual stresses generated during welding, as well as local changes in microstructure. Distribution of longitudinal and transverse stress of welded panels shows peaks of tension and compression, respectively, within the HAZ and corroborate earlier theoretical results. Position of these peaks are related to position of minimum strength within the HAZ, and the magnitude of these peaks are a fraction of the local yield strength in this region. Weldments of alloy 2195-T8 exhibited higher peak residual stress than alloy 2219-T87. Comparison of neutron diffraction and microstructural analysis indicate decreased lattice parameters associated with the solid solution of the near HAZ; this results in decreased apparent tensile residual stress within this region and may significantly alter interpretation of residual stress measurements of these alloys. Considerable relaxation of residual stress occurs during removal of specimens from welded panels and was used to aid in differentiating changes in lattice parameters attributed to residual stress from welding and modifications in microstructure.

  19. Structural Study of PMN-xPT by Neutron Diffraction

    NASA Astrophysics Data System (ADS)

    Phelan, D.; Gehring, P. M.; Huang, Q.; Ye, Z.-G.; Stock, C.; Xu, G.; Wen, J.

    2009-03-01

    Stark differences between x-ray and neutron measurements of the structures of ferroelectric-relaxors PMN-xPT ((1-x)Pb(Mg1/3Nb2/3)O3+xPbTiO3) and PZN-xPT (Z=Zn) have been reported [1]. One explanation for these differences is that these crystals have strained surface layers on the order of several tens of μm thick, the crystal structure of which differs from that of the crystal bulk. This phenomenon has been coined the ``anomalous skin effect'' but has been recently challenged [2] and thus remains controversial. We reinvestigated the skin effect in PMN-xPT by considering the possibility that the oxygen stoichiometry might play a role. Two sets of powders (x=0.1, 0.2, 0.3, and 0.4) were grown, one with and one without oxygen annealing, and high resolution neutron powder diffraction measurements were carried out for both sets. For a given x, both sets of powders have the same structural phase, suggesting that the effects of oxygen annealing are minimal. For x=0.1 and x=0.2 both sets of powders are rhombohedral, which contrasts with the single crystal neutron diffraction measurements. This supports a skin effect in that the grain size of the powders is small enough that the Bragg peaks are dominated by the strained surface layer. References [1] G. Xu et al., Phase Transitions 79, 135 (2006) [2] E. H. Kisi and J.S. Forrester, J. Phys.:Condens. Matter 17, L381 (2005)

  20. Neutron diffraction characterization of Japanese artworks of Tokugawa age.

    PubMed

    Grazzi, F; Bartoli, L; Civita, F; Zoppi, M

    2009-12-01

    Neutron time-of-flight diffraction technique has been used to characterize some Japanese historical artifacts. With this method, metal samples can be analyzed in their bulk properties without need of sampling. Results shown here were obtained at the Italian Neutron Experimental Station (INES@ISIS) located at the pulsed neutron source ISIS (UK). The parallel use of a scanning electron microscope equipped with an energy-dispersive X-ray fluorescence device (SEM-EDX) permitted a full quantitative characterization of the investigated samples, namely four hand-guards (Tsubas) of Japanese swords attributed to the Tokugawa age. In particular, we were able to obtain, in a totally non-invasive non-destructive way, a full quantitative phase characterization of the samples, a detailed Bragg peak broadening analysis, and a quantitative texture determination. These results, complemented with those obtained via the traditional analysis method of SEM-EDX, allowed a full characterization of both the bulk and the surface of the artifacts. PMID:19711059

  1. Rotation of the compound nucleus 236U ∗ in the fission reaction 235U( n,f) induced by cold polarised neutrons

    NASA Astrophysics Data System (ADS)

    Goennenwein, F.; Mutterer, M.; Gagarski, A.; Guseva, I.; Petrov, G.; Sokolov, V.; Zavarukhina, T.; Gusev, Yu.; von Kalben, J.; Nesvizhevski, V.; Soldner, T.

    2007-08-01

    Surprisingly, for one of the best investigated nuclear reactions a new phenomenon was discovered. In an experiment performed at the High Flux Reactor of the Institut Laue Langevin in Grenoble, France, the reaction 235U(n , f) was studied. Fission was induced by cold polarised neutrons. Besides the two main fragments also ternary light charged particles were measured. The centres or the detector assemblies for fragments and light particles were positioned at right angles relative to each other in a plane perpendicular to the neutron beam. It is well known that the majority of ternary particles are emitted closely perpendicular to the fission axis. With the neutron spin pointing parallel or anti-parallel to the neutron beam it was observed that, upon flipping periodically the neutron spin, the distributions of angles between fragments and light particles are wobbling back and forth. The phenomenon is traced to the rotation of the scissioning nucleus while the light particles are ejected. This interpretation is corroborated by trajectory calculations for ternary α-particles being accelerated in a rotating Coulomb field provided by the two main fragments. The angle through which the fission axis and the trajectories of α-particles rotate is very small and barely exceeds 0.2°. This so far unreported feature of nuclear fission has been called the “ROT-effect”.

  2. Single crystal neutron diffraction for the inorganic chemist - a practical guide.

    SciTech Connect

    Piccoli, P.; Koetzle, T. F.; Schultz, A. J.; Intense Pulsed Neutron Source

    2007-01-01

    Advances and upgrades in neutron sources and instrumentation are poised to make neutron diffraction more accessible to inorganic chemists than ever before. These improvements will pave the way for single crystal investigations that currently may be difficult, for example due to small crystal size or large unit cell volume. This article aims to highlight what can presently be achieved in neutron diffraction and looks forward toward future applications of neutron scattering in inorganic chemistry.

  3. Neutron diffraction studies of amphipathic helices in phospholipid bilayers

    SciTech Connect

    Bradshaw, J.P.; Gilchrist, P.J.; Duff, K.C.; Saxena, A.M.

    1994-12-31

    The structural feature which is thought to facilitate the interaction of many peptides with phospholipid bilayers is the ability to fold into an amphipathic helix. In most cases the exact location and orientation of this helix with respect to the membrane is not known, and may vary with factors such as pH and phospholipid content of the bilayer. The growing interest in this area is stimulated by indications that similar interactions can contribute to the binding of certain hormones to their cell-surface receptors. We have been using the techniques of neutron diffraction from stacked phospholipid bilayers in an attempt to investigate this phenomenon with a number of membrane-active peptides. Here we report some of our findings with three of these: the bee venom melittin; the hormone calcitonin; and a synthetic peptide representing the ion channel fragment of influenza A M2 protein.

  4. Powder neutron diffraction studies of a carbonate fluorapatite

    SciTech Connect

    Leventouri, Th.; Chakoumakos, B. C.; Moghaddam, H. Y.; Perdikatsis, V.

    2000-02-01

    Atomic positional disorder of a single-phase natural carbonate fluorapatite (francolite) is revealed from analysis of the atomic displacement parameters (ADPs) refined from neutron powder diffraction data as a function of temperature and carbonate content. The ADPs of the francolite show a strong disturbance at the P, O3, and F sites. When it is heat treated to partially or completely remove the carbonate, the ADPs as well as the other structural parameters resemble those of a fluorapatite (Harding pegmatite) that was measured under the same conditions. The various structural changes are consistent with a substitution mechanism whereby the planar carbonate group replaces a phosphate group and lies on the mirror plane of the apatite structure. (c) 2000 Materials Research Society.

  5. Neutron diffraction studies of liquid iso-propanol

    NASA Astrophysics Data System (ADS)

    Zetterström, P.; Dahlborg, U.; Delaplane, R. G.; Howells, W. S.

    1991-07-01

    The structure of deuterated liquid iso-propanol has been studied with neutron diffraction at the LAD diffractometer at the ISIS spallation source. Measurements were performed at temperatures 190, 220, 250 and 275 K. To correct for inelastic effects a model for the dynamic structure factor which obeys detailed balance and included recoil effects was used. The static molecular structure factor SM(Q) exhibits a pre-peak at about 0.75 Å-1. The origin of the pre-peak, which increases in amplitude with temperature, is presently unknown. The structure of the iso-propanol molecule was obtained from the total pair distribution function and from a fit of the intramolecular form factor f1(Q) to the measured SM(Q) at large Q. The obtained values of the bond length and Debye-Waller factors are in good agreement to those obtained from lower alcohols.

  6. Neutron diffraction studies on rubredoxin from Pyrococcus furiosus.

    PubMed

    Bau, Robert

    2004-01-01

    Single-crystal neutron diffraction data up to a resolution of 1.5 A have been collected at room temperature on two forms of rubredoxin using the BIX-3 diffractometer at the JRR-3 reactor of the Japan Atomic Energy Research Institute (JAERI). Rubredoxin is a small iron-sulfur redox protein with 53 amino acid residues, and the source of this particular protein is the hyperthermophile Pyrococcus furiosus, a microorganism that normally lives at temperatures near that of boiling water. Data were collected on crystals of the wild-type protein and on a mutant in which three of the residues have been replaced. In this paper we will be describing several sets of results arising from these high-resolution neutron structure determinations: (a) the H/D exchange pattern of the N-H bonds of the main backbone, which give information about which regions of the molecule are more exposed to solvent; (b) the orientations of some of the O-D bonds in the protein, information which is often not obtainable from X-ray results; (c) the structure and appearance of water molecules in the protein crystals; and (d) some structural features which may help rationalize the remarkable thermal stability of the wild-type protein from this intriguing microorganism PMID:14646139

  7. Ultra high resolution neutron scattering: Neutron Resonance Spin-Echo and Larmor Diffraction

    NASA Astrophysics Data System (ADS)

    Walters, Andrew; Keller, Thomas; Keimer, Bernhard

    2012-02-01

    The TRISP spectrometer at the FRM II neutron source near Munich, Germany, is a unique world-leading neutron scattering instrument which employs the Neutron Resonance Spin-Echo technique (NRSE). Linewidths of dispersive excitations with energy transfers up to 50 meV can be measured with an energy resolution in the μeV range without the restrictive flux limitations that normally apply to high resolution neutron triple-axis spectrometers. Pioneering studies on the electron-phonon interaction in elemental superconductorsootnotetextP. Aynajian et al., Science 319 1509 (2008) and the lifetimes of magnetic excitations in archetypal magnetic systems will be reviewed.ootnotetextS. Bayrakci et al., Science 312 1928 (2006) The instrument can also be used as a Larmor diffractometer, enabling d-spacings to be measured with a resolution of δdd ˜10-6, i.e. more than one order of magnitude more sensitive than conventional diffraction techniques.ootnotetextC. Pfleiderer et al., Science 316 1871 (2007) Ongoing and future NRSE and Larmor diffraction projects will be outlined, especially in regard to prospective studies which will take full advantage of the new low temperature and high pressure sample environment capabilities now available at TRISP.

  8. The early development of neutron diffraction: science in the wings of the Manhattan Project.

    PubMed

    Mason, T E; Gawne, T J; Nagler, S E; Nestor, M B; Carpenter, J M

    2013-01-01

    Although neutron diffraction was first observed using radioactive decay sources shortly after the discovery of the neutron, it was only with the availability of higher intensity neutron beams from the first nuclear reactors, constructed as part of the Manhattan Project, that systematic investigation of Bragg scattering became possible. Remarkably, at a time when the war effort was singularly focused on the development of the atomic bomb, groups working at Oak Ridge and Chicago carried out key measurements and recognized the future utility of neutron diffraction quite independent of its contributions to the measurement of nuclear cross sections. Ernest O. Wollan, Lyle B. Borst and Walter H. Zinn were all able to observe neutron diffraction in 1944 using the X-10 graphite reactor and the CP-3 heavy water reactor. Subsequent work by Wollan and Clifford G. Shull, who joined Wollan's group at Oak Ridge in 1946, laid the foundations for widespread application of neutron diffraction as an important research tool. PMID:23250059

  9. Powder diffraction in materials science using the KENS cold-neutron source

    SciTech Connect

    Kamiyama, T.; Oikawa, K.; Akiba, E.

    1997-12-01

    Since superconductivity fever spread around the world, neutron powder diffraction has become very popular and been widely used by crystallographers, physicists, chemists, mineralogists, and materials scientists. The purpose of present paper is to show, firstly, important characteristics of time-of-flight TOF powder diffraction using cold-neutron source in the study of materials science, and, secondly, recent studies on the structure and function of batteries at the Neutron Science Laboratory (KENS) in the High Energy Accelerator Research Organization (KEK).

  10. Three-port beam splitter for slow neutrons using holographic nanoparticle-polymer composite diffraction gratings

    SciTech Connect

    Klepp, J.; Fally, M.; Tomita, Y.; Pruner, C.; Kohlbrecher, J.

    2012-10-08

    Diffraction of slow neutrons by nanoparticle-polymer composite gratings has been observed. By carefully choosing grating parameters such as grating thickness and spacing, a three-port beam splitter operation for slow neutrons - splitting the incident neutron intensity equally into the {+-}1st and the 0th diffraction orders - has been realized. As a possible application, a Zernike three-path interferometer is briefly discussed.

  11. Powder Neutron Diffraction Study of HoCoGa5

    SciTech Connect

    Kabayashi, Riki; Kaneko, Koji; Wakimoto, Shuichi; Chi, Songxue; Sanada, Naoyuki; Watanuki, Ryuta; Suzuki, Kazuya

    2013-01-01

    We have studied successive magnetic transitions of HoCoGa5 at TN1 = 9.6 K and TN2 = 7.5 K by using powder neutron diffraction. Apparent superlattice peaks were observed at temperatures below TN1. With further decreases temperature, the patterns exhibit a substantial change at temperatures below TN2. The observed magnetic peaks at 8 K (AntiFerromagnetic InCommensurate (AFIC) phase : TN2 < T < TN1) can be represented by the propagation vector qL = (1/2 0 ) with = 0.35(2). In contrast, the magnetic structure becomes commensurate with qC = (1/2 0 1/2) at 4 K (AntiFerromagnetic Commensurate (AFC) phase : T < TN2). The temperature dependence of magnetic intensity shows an apparent temperature hysteresis at TN2, indicates a first-order transition at TN2. Analysis of the integrated intensity at 4 K reveals that the Ho moment with a size of 8.6(2) B, oriented parallel to the c-axis in the AFC phase. While the successive transitions of HoCoGa5 are different from those of TbCoGa5, the magnetic structure in the AFC phase of HoCoGa5 is the same as the AFTb I of TbCoGa5, and may indicate an additional transition at a lower temperature in HoCoGa5.

  12. Neutron diffraction studies for realtime leaching of catalytic Ni.

    PubMed

    Iles, Gail N; Devred, François; Henry, Paul F; Reinhart, Guillaume; Hansen, Thomas C

    2014-07-21

    The leaching of Al from intermetallic samples of Nickel Aluminium alloys to form Raney-type nickel catalysts is widely used in the hydrogenation industry, however, little is known of the leaching process itself. In this study, the leaching of Al was measured in realtime, in situ, using the high-flux powder neutron diffractometer, D20, at the Institut Laue-Langevin. Despite the liberation of hydrogen and effervescent nature of the reaction the transformation of the dry powder phases into Raney-type Ni was determined. Samples produced by gas-atomisation were found to leach faster than those produced using the cast and crushed technique. Regardless of processing route of the precursor powder, the formation of spongy-Ni occurs almost immediately, while Ni2Al3 and NiAl3 continue to transform over longer periods of time. Small-angle scattering and broadening of the diffraction peaks is an evidence for the formation of the smaller Ni particles. Understanding the kinetics of the leaching process will allow industry to refine production of catalysts for optimum manufacturing time while knowledge of leaching dynamics of powders produced by different manufacturing techniques will allow further tailoring of catalytic materials. PMID:25053313

  13. Neutron diffraction studies for realtime leaching of catalytic Ni

    SciTech Connect

    Iles, Gail N. Reinhart, Guillaume; Devred, François; Henry, Paul F. Hansen, Thomas C.

    2014-07-21

    The leaching of Al from intermetallic samples of Nickel Aluminium alloys to form Raney-type nickel catalysts is widely used in the hydrogenation industry, however, little is known of the leaching process itself. In this study, the leaching of Al was measured in realtime, in situ, using the high-flux powder neutron diffractometer, D20, at the Institut Laue-Langevin. Despite the liberation of hydrogen and effervescent nature of the reaction the transformation of the dry powder phases into Raney-type Ni was determined. Samples produced by gas-atomisation were found to leach faster than those produced using the cast and crushed technique. Regardless of processing route of the precursor powder, the formation of spongy-Ni occurs almost immediately, while Ni{sub 2}Al{sub 3} and NiAl{sub 3} continue to transform over longer periods of time. Small-angle scattering and broadening of the diffraction peaks is an evidence for the formation of the smaller Ni particles. Understanding the kinetics of the leaching process will allow industry to refine production of catalysts for optimum manufacturing time while knowledge of leaching dynamics of powders produced by different manufacturing techniques will allow further tailoring of catalytic materials.

  14. Neutron diffraction studies for realtime leaching of catalytic Ni

    NASA Astrophysics Data System (ADS)

    Iles, Gail N.; Devred, François; Henry, Paul F.; Reinhart, Guillaume; Hansen, Thomas C.

    2014-07-01

    The leaching of Al from intermetallic samples of Nickel Aluminium alloys to form Raney-type nickel catalysts is widely used in the hydrogenation industry, however, little is known of the leaching process itself. In this study, the leaching of Al was measured in realtime, in situ, using the high-flux powder neutron diffractometer, D20, at the Institut Laue-Langevin. Despite the liberation of hydrogen and effervescent nature of the reaction the transformation of the dry powder phases into Raney-type Ni was determined. Samples produced by gas-atomisation were found to leach faster than those produced using the cast and crushed technique. Regardless of processing route of the precursor powder, the formation of spongy-Ni occurs almost immediately, while Ni2Al3 and NiAl3 continue to transform over longer periods of time. Small-angle scattering and broadening of the diffraction peaks is an evidence for the formation of the smaller Ni particles. Understanding the kinetics of the leaching process will allow industry to refine production of catalysts for optimum manufacturing time while knowledge of leaching dynamics of powders produced by different manufacturing techniques will allow further tailoring of catalytic materials.

  15. Exploring the magnetic phase diagram of dysprosium with neutron diffraction

    NASA Astrophysics Data System (ADS)

    Yu, J.; LeClair, P. R.; Mankey, G. J.; Robertson, J. L.; Crow, M. L.; Tian, W.

    2015-01-01

    With one of the highest intrinsic magnetic moments (10.6 μB/atom ) among the heavy rare-earth elements, dysprosium exhibits a rich magnetic phase diagram, including several modulated magnetic phases. Aided by the Ruderman-Kittel-Kasuya-Yosida interaction, the magnetic modulations propagate coherently over a long range. Neutron diffraction experiments were performed to determine the microscopic magnetic origin of the field induced phases in bulk Dy as a function of temperature, covering regions of the well-known ferromagnetic, helical antiferromagnetic, fan phases, and several possible new phases suggested by previous studies. A short-range ordered fan phase was identified as the intermediate state between ferromagnetism and long-range ordered fan. In a field of 1 T applied along the a axis, the temperature range of a coexisting helix/fan phase was determined. The magnetic phase diagram of Dy was thus refined to include the detailed magnetic origin and the associated phase boundaries. Based on the period of the magnetic modulation and the average magnetization, the evolution of the spin arrangement upon heating was derived quantitatively for the modulated magnetic phases.

  16. Neutron diffraction observations of interstitial protons in dense ice

    PubMed Central

    Guthrie, Malcolm; Boehler, Reinhard; Tulk, Christopher A.; Molaison, Jamie J.; dos Santos, António M.; Li, Kuo; Hemley, Russell J.

    2013-01-01

    The motif of distinct H2O molecules in H-bonded networks is believed to persist up to the densest molecular phase of ice. At even higher pressures, where the molecule dissociates, it is generally assumed that the proton remains localized within these same networks. We report neutron-diffraction measurements on D2O that reveal the location of the D atoms directly up to 52 GPa, a pressure regime not previously accessible to this technique. The data show the onset of a structural change at ∼13 GPa and cannot be described by the conventional network structure of ice VII above ∼26 GPa. Our measurements are consistent with substantial deuteron density in the octahedral, interstitial voids of the oxygen lattice. The observation of this “interstitial” ice VII form provides a framework for understanding the evolution of hydrogen bonding in ice that contrasts with the conventional picture. It may also be a precursor for the superionic phase reported at even higher pressure with important consequences for our understanding of dense matter and planetary interiors. PMID:23757495

  17. Neutron-diffraction study of liquid hydrogen iodide

    NASA Astrophysics Data System (ADS)

    Andreani, C.; Nardone, M.; Ricci, F. P.; Soper, A. K.

    1992-10-01

    Neutron-diffraction experiments on liquid DI, HI, and on an equimolar mixture of HI and DI are presented. All these three samples were in the same thermodynamic state corresponding to the orthobaric liquid at T=253 K. The three partial structure factors SII(Q), SHI(Q), SHH(Q) are derived exploiting the standard isotopic substitution procedure. The corresponding pair correlation functions gII(r), gHI(r), and gHH(r) are evaluated and compared with those given by a model that neglects all orientational correlations. Our data indicate that gII(r) (which is essentially the center-center correlation function) is well reproduced by the pair distribution function of a monatomic Lennard-Jones fluid and that gHI(r) (which should be sensitive to the correlations between molecular and intermolecular axes) is very similar to the one derived neglecting orientational correlations. On the contrary, orientational correlations between the molecular axes are clearly present in the gHH(r), which deviates significantly from the uncorrelated model results. These facts are consistent with the idea that H bonding is not present in liquid HI and indicate also that the only relevant terms of the anisotropic intermolecular potential are those due to the electric multipolar interactions.

  18. Time-of-flight diffraction at pulsed neutron sources: An introduction to the symposium

    SciTech Connect

    Jorgensen, J.D.

    1994-05-01

    In the 25 years since the first low-power demonstration experiments, pulsed neutron sources have become as productive as reactor sources for many types of diffraction experiments. The pulsed neutron sources presently operating in the United States, England, and Japan offer state of the art instruments for powder and single crystal diffraction, small angle scattering, and such specialized techniques as grazing-incidence neutron reflection, as well as quasielastic and inelastic scattering. In this symposium, speakers review the latest advances in diffraction instrumentation for pulsed neutron sources and give examples of some of the important science presently being done. In this introduction to the symposium, I briefly define the basic principles of pulsed neutron sources, review their development, comment in general terms on the development of time-of-flight diffraction instrumentation for these sources, and project how this field will develop in the next ten years.

  19. Single crystal neutron diffraction refinement of bullvalene at 110 K

    SciTech Connect

    Luger, P.; Buschmann, J.; McMullan, R.K.; Ruble, J.R.; Matias, P.; Jeffrey, G.A.

    1986-11-26

    A low-temperature neutron diffraction refinement of the crystal structure of bullvalene, C/sub 10/H/sub 10/, tricyclo(3.3.2.0/sup 2.8/)deca-2,5,8-triene, shows that the molecule is distorted only very slightly from the C/sub 3 upsilon/ symmetry expected for the isolated molecule, although the crystal structure symmetry is monoclinic. There is a small but significant difference between the shortest and longest of the C-C bonds in the cyclopropane ring, which are 1.536 (1), 1.533 (1), and 1.530 (1) A. The three ethylenic wings of the molecule are virtually identical, except for small differences in planarity and C-C-H angles. One wing is exactly planar within 0.002 (3) A. In the other two, one of the hydrogen atoms in each is significantly displaced from the plane by 0.027 (3) and 0.023 (3) A. The mean bond lengths in the ethylenic wings are C/sub ring/-C, 1.4727 (7) A; C=C, 1.3423 (7) A; =C-C, 1.5163 (7) A. The C-H bond lengths range from 1.086 (2) to 1.092 (2) A. The thermal motion analysis gives an unusually good fit to the rigid-body model. Corrections for harmonic thermal motion lengthened all C-C and C=C bonds uniformly by 0.003 A. For the C-H bonds, the harmonic riding motion and anharmonicity corrections almost cancel, so that the thermally corrected bond lengths differ from those measured by +/- 0.001 A.

  20. X-ray structure of perdeuterated diisopropyl fluorophosphatase (DFPase): perdeuteration of proteins for neutron diffraction

    PubMed Central

    Blum, Marc-Michael; Tomanicek, Stephen J.; John, Harald; Hanson, B. Leif; Rüterjans, Heinz; Schoenborn, Benno P.; Langan, Paul; Chen, Julian C.-H.

    2010-01-01

    The signal-to-noise ratio is one of the limiting factors in neutron macromolecular crystallography. Protein perdeuteration, which replaces all H atoms with deuterium, is a method of improving the signal-to-noise ratio of neutron crystallography experiments by reducing the incoherent scattering of the hydrogen isotope. Detailed analyses of perdeuterated and hydrogenated structures are necessary in order to evaluate the utility of perdeuterated crystals for neutron diffraction studies. The room-temperature X-ray structure of perdeuterated diisopropyl fluorophosphatase (DFPase) is reported at 2.1 Å resolution. Comparison with an independently refined hydrogenated room-temperature structure of DFPase revealed no major systematic differences, although the crystals of perdeuterated DFPase did not diffract neutrons. The lack of diffraction is examined with respect to data-collection and crystallo­graphic parameters. The diffraction characteristics of successful neutron structure determinations are presented as a guideline for future neutron diffraction studies of macromolecules. X-ray diffraction to beyond 2.0 Å resolution appears to be a strong predictor of successful neutron structures. PMID:20383004

  1. In-situ neutron diffraction study of cathode/electrolyte interactions under electrical load and elevated temperature

    NASA Astrophysics Data System (ADS)

    Tonus, F.; Skinner, S. J.

    2016-05-01

    Fuel cells are proposed as a future energy conversion technology that will reduce greenhouse gas emissions at the point of operation due to their ability to produce electrical energy from non-hydrocarbon fuel sources. The Solid Oxide Fuel Cell (SOFC) is amongst the most efficient fuel cell types, however, due to the high cell operating temperature cation diffusion occurs between the different components of the cell, resulting in rapid degradation of the power output. In this paper we investigate cation migration between the promising intermediate temperature-SOFC cathode La1-xSrxCo1-yFeyO3-δ (LSCF) and a fluorite type electrolyte Ce1-xPrxO2-δ (CPO). The crystallographic structure evolution and degradation of the materials were studied by neutron diffraction in-situ under pseudo-operating conditions, i.e. at 600 °C under air and under electrical polarisation. The lattice parameter and cation occupancy evolution were analysed by Rietveld refinement as a function of time and applied potential. The materials were found to be stable, as no impurity formation, lattice parameter or site occupancy evolution was observed during the experiment. However La migration prior to the experiment from LSCF to CPO was observed as well as B-site vacancies in LSCF.

  2. Cottingham formula and nucleon polarisabilities

    NASA Astrophysics Data System (ADS)

    Gasser, J.; Hoferichter, M.; Leutwyler, H.; Rusetsky, A.

    2015-08-01

    The difference between the electromagnetic self-energies of proton and neutron can be calculated with the Cottingham formula, which expresses the self-energies as an integral over the electroproduction cross sections - provided the nucleon matrix elements of the current commutator do not contain a fixed pole. We show that, under the same proviso, the subtraction function occurring in the dispersive representation of the virtual Compton forward scattering amplitude is determined by the cross sections. The representation in particular leads to a parameter-free sum rule for the nucleon polarisabilities. We evaluate the sum rule for the difference between the electric polarisabilities of proton and neutron by means of the available parameterisations of the data and compare the result with experiment.

  3. Neutron scattering and diffraction instrument for structural study on biology in Japan

    SciTech Connect

    Niimura, Nobuo

    1994-12-31

    Neutron scattering and diffraction instruments in Japan which can be used for structural studies in biology are briefly introduced. Main specifications and general layouts of the instruments are shown.

  4. The early development of neutron diffraction: Science in the wings of the Manhattan Project

    SciTech Connect

    Mason, Thom; Gawne, Timothy J; Nagler, Stephen E; Nestor, Margaret Boone {Bonnie}; Carpenter, John M

    2012-01-01

    Although neutron diffraction was first observed using radioactive decay sources shortly after the discovery of the neutron, it was only with the availability of higher intensity neutron beams from the first nuclear reactors, constructed as part of the Manhattan project, that systematic investigation of Bragg scattering became possible. Remarkably, at a time when the war effort was singularly focused on the development of the atomic bomb, groups working at Oak Ridge and Chicago carried out key measurements and recognized the future utility of neutron diffraction quite independent of its contributions to the measurements of nuclear cross sections. Ernest O. Wollan, Lyle B. Borst, and Walter H. Zinn were all able to observe neutron diffraction in 1944 using the X-10 graphite reactor and the CP-3 heavy water reactor.

  5. Neutron diffraction studies of Gd 2Zr 2O 7 pyrochlore

    NASA Astrophysics Data System (ADS)

    Kennedy, Brendan J.; Zhou, Qingdi; Avdeev, Maxim

    2011-07-01

    The structure of Gd 2Zr 2O 7 pyrochlore over the temperature range 4-300 K has been refined from powder neutron diffraction data. The sample was enriched in 160Gd to avoid the high neutron absorption of naturally occurring Gd. The diffraction pattern showed well resolved superlattice reflections indicative of the pyrochlore structure and no evidence is found for anion-disorder from the structural refinements.

  6. The early development of neutron diffraction: science in the wings of the Manhattan Project

    SciTech Connect

    Mason, T. E. Gawne, T. J.; Nagler, S. E.; Nestor, M. B.; Carpenter, J. M.

    2013-01-01

    Early neutron diffraction experiments performed in 1944 using the first nuclear reactors are described. Although neutron diffraction was first observed using radioactive decay sources shortly after the discovery of the neutron, it was only with the availability of higher intensity neutron beams from the first nuclear reactors, constructed as part of the Manhattan Project, that systematic investigation of Bragg scattering became possible. Remarkably, at a time when the war effort was singularly focused on the development of the atomic bomb, groups working at Oak Ridge and Chicago carried out key measurements and recognized the future utility of neutron diffraction quite independent of its contributions to the measurement of nuclear cross sections. Ernest O. Wollan, Lyle B. Borst and Walter H. Zinn were all able to observe neutron diffraction in 1944 using the X-10 graphite reactor and the CP-3 heavy water reactor. Subsequent work by Wollan and Clifford G. Shull, who joined Wollan’s group at Oak Ridge in 1946, laid the foundations for widespread application of neutron diffraction as an important research tool.

  7. Scientific Advancements and Technological Developments of High P-T Neutron Diffraction at LANSCE, Los Alamos

    NASA Astrophysics Data System (ADS)

    Zhao, Y.; Daemen, L. L.; Zhang, J.

    2003-12-01

    In-situ high P-T neutron diffraction experiments provide unique opportunities to study the crystal structure, hydrogen bonding, magnetism, and thermal parameters of light elements (eg. H, Li, B) and heavy elements (eg. Ta, U, Pu,), that are virtually impossible to determine with x-ray diffraction techniques. For example, thermoelasticity and Debye-Waller factor as function of pressure and temperature can be derived using in-situ high P-T neutron diffraction techniques. These applications can also be extended to a much broader spectrum of scientific problems. For instance, puzzles in Earth science such as the carbon cycle and the role of hydrous minerals for water exchange between lithosphere and biosphere can be directly addressed. Moreover, by introducing in-situ shear, texture of metals and minerals accompanied with phase transitions at high P-T conditions can also be studied by high P-T neutron diffraction. We have successfully conducted high P-T neutron diffraction experiments at LANSCE and achieved simultaneous high pressures and temperatures of 10 GPa and 1500 K. With an average 3-6 hours of data collection, the diffraction data are of sufficiently high quality for the determination of structural parameters and thermal vibrations. We have studied hydrous mineral (MgOD), perovskite (K.15,Na.85)MgF3, clathrate hydrates (CH4-, CO2-, and H2-), metals (Mo, Al, Zr), and amorphous materials (carbon black, BMG). The aim of our research is to accurately map bond lengths, bond angles, neighboring atomic environments, and phase stability in P-T-X space. Studies based on high-pressure neutron diffraction are important for multi-disciplinary science and we welcome researchers from all fields to use this advanced technique. We have developed a 500-ton toroidal press, TAP-98, to conduct simultaneous high P-T neutron diffraction experiments inside of HIPPO (High-Pressure and Preferred-Orientation diffractometer). We have also developed a large gem-crystal anvil cell, ZAP-01

  8. Incident spectrum determination for time-of-flight neutron powder diffraction data analysis.

    SciTech Connect

    Hodges, J. P.

    1998-08-27

    Accurate characterization of the incident neutron spectrum is an important requirement for precise Rietveld analysis of time-of-flight powder neutron diffraction data. Without an accurate incident spectrum the calculated model for the measured relative intensities of individual Bragg reflections will possess systematic errors. We describe a method for obtaining an accurate numerical incident spectrum using data from a transmitted beam monitor.

  9. Proceedings of the 1986 workshop on advanced time-of-flight neutron powder diffraction

    SciTech Connect

    Lawson, A.C.; Smith, K.

    1986-09-01

    This report contains abstracts of talks and summaries of discussions from a small workshop held to discuss the future of time-of-flight neutron powder diffraction and its implementation at the Los Alamos Neutron Scattering Center. 47 refs., 3 figs.

  10. Neutron irradiated uranium silicides studied by neutron diffraction and Rietveld analysis

    SciTech Connect

    Birtcher, R.C.; Mueller, M.H.; Richardson, J.W. Jr.

    1990-11-01

    The irradiation behavior of high-density uranium silicides has been a matter of interest to the nuclear industry for use in high power or low enrichment applications. Transmission electron microscopy studies have found that heavy ion bombardment renders U{sub 3}Si and U{sub 3}Si{sub 2} amorphous at temperatures below about 250 C and that U{sub 3}Si becomes mechanically unstable suffering rapid growth by plastic flow. In this present work, crystallographic changes preceding amorphization by fission fragment damage have been studied by high-resolution neutron diffraction as a function of damage produced by uranium fission at room temperature. Initially, both silicides had tetragonal crystal structures. Crystallographic and amorphous phases were studied simultaneously by combining conventional Rietveld refinement of the crystallographic phases with Fourier-filtering analysis of the non-crystalline scattering component. 13 refs., 5 figs.

  11. Non-invasive temperature measurements by neutron diffraction in aero-engine components

    SciTech Connect

    Holden, T.M.; Root, J.H.; Tennant, D.C.; Leggett, D.

    1995-12-31

    A requirement exists in the aeronautical industry for measuring temperature non-invasively in critical components, such as the turbine disc in an operating engine. Neutron diffraction, unique among nuclear techniques, offers the possibility of measuring both temperature and strain within an operating engine by virtue of the high penetration of neutrons through industrial materials. Static diffraction experiments on Waspaloy and Ti6Al4V showed, by comparison with thermocouples, that both the diffraction peak position and the peak intensity can measure the temperature to within {+-}6 K at 800 K.

  12. Neutron diffraction measurements of residual stresses in friction stir welding: a review

    SciTech Connect

    Woo, Wan Chuck; Feng, Zhili; Wang, Xun-Li; David, Stan A

    2011-01-01

    Significant amounts of residual stresses are often generated during welding and result in critical degradation of the structural integrity and performance of components. Neutron diffraction has become a well established technique for the determination of residual stresses in welds because of the unique deep penetration, three-dimensional mapping capability, and volume averaged bulk measurements characteristic of the scattering neutron beam. Friction stir welding has gained prominence in recent years. The authors reviewed a number of neutron diffraction measurements of residual stresses in friction stir welds and highlighted examples addressing how the microstructures and residual stresses are correlated with each other. An example of in situ neutron diffraction measurement result shows the evolution of the residual stresses during welding.

  13. The early development of neutron diffraction: science in the wings of the Manhattan Project

    PubMed Central

    Mason, T. E.; Gawne, T. J.; Nagler, S. E.; Nestor, M. B.; Carpenter, J. M.

    2013-01-01

    Although neutron diffraction was first observed using radioactive decay sources shortly after the discovery of the neutron, it was only with the availability of higher intensity neutron beams from the first nuclear reactors, constructed as part of the Manhattan Project, that systematic investigation of Bragg scattering became possible. Remarkably, at a time when the war effort was singularly focused on the development of the atomic bomb, groups working at Oak Ridge and Chicago carried out key measurements and recognized the future utility of neutron diffraction quite independent of its contributions to the measurement of nuclear cross sections. Ernest O. Wollan, Lyle B. Borst and Walter H. Zinn were all able to observe neutron diffraction in 1944 using the X-10 graphite reactor and the CP-3 heavy water reactor. Subsequent work by Wollan and Clifford G. Shull, who joined Wollan’s group at Oak Ridge in 1946, laid the foundations for widespread application of neutron diffraction as an important research tool. PMID:23250059

  14. A preliminary neutron diffraction study of rasburicase, a recombinant urate oxidase enzyme, complexed with 8-azaxanthin

    SciTech Connect

    Budayova-Spano, Monika; Bonneté, Françoise; Ferté, Natalie; El Hajji, Mohamed; Meilleur, Flora; Blakeley, Matthew Paul; Castro, Bertrand

    2006-03-01

    Neutron diffraction data of hydrogenated recombinant urate oxidase enzyme (Rasburicase), complexed with a purine-type inhibitor 8-azaxanthin, was collected to 2.1 Å resolution from a crystal grown in D{sub 2}O by careful control and optimization of crystallization conditions via knowledge of the phase diagram. Deuterium atoms were clearly seen in the neutron-scattering density map. Crystallization and preliminary neutron diffraction measurements of rasburicase, a recombinant urate oxidase enzyme expressed by a genetically modified Saccharomyces cerevisiae strain, complexed with a purine-type inhibitor (8-azaxanthin) are reported. Neutron Laue diffraction data were collected to 2.1 Å resolution using the LADI instrument from a crystal (grown in D{sub 2}O) with volume 1.8 mm{sup 3}. The aim of this neutron diffraction study is to determine the protonation states of the inhibitor and residues within the active site. This will lead to improved comprehension of the enzymatic mechanism of this important enzyme, which is used as a protein drug to reduce toxic uric acid accumulation during chemotherapy. This paper illustrates the high quality of the neutron diffraction data collected, which are suitable for high-resolution structural analysis. In comparison with other neutron protein crystallography studies to date in which a hydrogenated protein has been used, the volume of the crystal was relatively small and yet the data still extend to high resolution. Furthermore, urate oxidase has one of the largest primitive unit-cell volumes (space group I222, unit-cell parameters a = 80, b = 96, c = 106 Å) and molecular weights (135 kDa for the homotetramer) so far successfully studied with neutrons.

  15. Area detectors in single-crystal neutron diffraction

    NASA Astrophysics Data System (ADS)

    McIntyre, Garry J.

    2015-12-01

    The introduction of area detectors has brought about a gentle revolution in the routine application of single-crystal neutron diffractometry. Implemented first for macromolecular crystallography, electronic detectors subsequently gradually spread to chemical and physics-oriented crystallography at steady-state sources. The volumetric surveying of reciprocal space implicit in the Laue technique has required area detectors right from the start, whether using film and more recently image plates and CCD-based detectors at reactors, or scintillation detectors at spallation sources. Wide-angle volumetric data collection has extended application of neutron single-crystal diffractometry to chemical structures, sample volumes, and physical phenomena previously deemed impossible. More than 30 of the dedicated single-crystal neutron diffractometers at steady-state reactor and neutron spallation sources worldwide and accessible via peer-review proposal mechanisms are currently equipped with area detectors. Here we review the historical development of the various types of area detectors used for single crystals, discuss experimental aspects peculiar to experiments with such detectors, highlight the scientific fields where the use of area detectors has had a special impact, and forecast future developments in hardware, implementation, and software.

  16. Neutron Diffraction Study of LaSr3Fe3O10 in the Temperature Range 25 - 650 deg. C

    SciTech Connect

    Neov, S.; Prokhnenko, O.; Velinov, N.; Kozhukharov, V.; Neov, D.; Dabrowski, L.

    2007-04-23

    The effect of high temperature on the structure of LaSr3Fe3O10 has been studied by neutron diffraction. Neutron data have been correlated with Moessbauer spectroscopy results and electrical conductivity measurements.

  17. Investigation on Deformation Behavior of Nickel Aluminum Bronze by Neutron Diffraction and Transmission Electron Microscopy

    NASA Astrophysics Data System (ADS)

    Xu, Xiaoyan; Wang, Hong; Lv, Yuting; Lu, Weijie; Sun, Guangai

    2016-05-01

    The deformation behavior, deformation microstructures, and generated inter-phase stresses of nickel aluminum bronze were investigated by in situ neutron diffraction instrument and transmission electron microscopy in this paper. Lattice strains calculated by both peak shifting and broadening by Gaussian fitting of α and κ phase neutron diffraction peak profiles at both holding stress conditions and unloaded stress conditions were compared. Twining and stacking faults in α matrix were observed after deformed by different tensile stresses. Compressive internal/residual stress in α matrix and tensile internal stress in κ phase in elasto-plastic region were calculated based on neutron diffraction analysis. The piled-up dislocations around hard κ phases increase with increasing the deformation degree, which raise the stress concentration near α/ κ interface and increase the internal stresses.

  18. in-situ chemistry mapping of hydrogen storage materials by neutron diffraction

    SciTech Connect

    Payzant, E Andrew; Bowman Jr, Robert C; Johnson, Terry A; Jorgensen, Scott W

    2013-01-01

    Neutron diffraction was used to nondestructively study the microstructures for two hydrogen storage media systems. In the first case, sodium alanate based hydrogen storage is a vehicle-scale candidate system developed by Sandia/GM. Neutron scattering was used to determine the distribution of phases in the storage media at different hydrogen loading levels, to help understand the absorption/desorption of hydrogen in large-scale systems. This study also included a 3D neutron tomographic study of the microstructure. In the second case, tin-doped lanthanum nickel alloys have been studied at JPL for space-based applications, for which the gradual degradation of the material due to segregation and disproportionation of phases is a known problem. A regenerative process developed to restore the storage properties of these alloys was studied, using in-situ neutron diffraction to relate the microstructure to the thermodynamic simulations.

  19. Adaptation of a neutron diffraction detector to coded aperture imaging

    SciTech Connect

    Vanier, P.E.; Forman, L.

    1997-02-01

    A coded aperture neutron imaging system developed at Brookhaven National Laboratory (BNL) has demonstrated that it is possible to record not only a flux of thermal neutrons at some position, but also the directions from whence they came. This realization of an idea which defied the conventional wisdom has provided a device which has never before been available to the nuclear physics community. A number of potential applications have been explored, including (1) counting warheads on a bus or in a storage area, (2) investigating inhomogeneities in drums of Pu-containing waste to facilitate non-destructive assays, (3) monitoring of vaults containing accountable materials, (4) detection of buried land mines, and (5) locating solid deposits of nuclear material held up in gaseous diffusion plants.

  20. The use of pulsed neutron diffraction to measure strain in composites

    SciTech Connect

    Bourke, M.A.M.; Goldstone, J.A.; Shi, N.; Gray, G.T. III; James, M.R.; Todd, R.I.

    1994-03-01

    Neutron diffraction is a technique for measuring strain in crystalline materials. It is non destructive, phase discriminatory and more penetrating than X rays. Pulsed neutron sources (in contrast with steady state reactor sources) are particularly appropriate for examining heterogeneous materials or for recording the polycrystalline response of all lattice reflections. Several different aspects of composite behavior can be characterized and examples are given of residual strain measurements, strain relaxation during heating, applied loading, and determination of the strain distribution function.

  1. High-Pressure Neutron Diffraction Studies for Materials Sciences and Energy Sciences

    NASA Astrophysics Data System (ADS)

    Zhao, Y.; Los Alamos High Pressure Materials Research Team

    2013-05-01

    The development of neutron diffraction under extreme pressure (P) and temperature (T) conditions is highly valuable to condensed matter physics, crystal chemistry, materials sciences, as well as earth and planetary sciences. We have incorporated a 500-ton press TAP-98 into the HiPPO diffractometer at LANSCE to conduct in situ high P-T neutron diffraction experiments. We have worked out a large gem-crystal anvil cell, ZAP, to conduct neutron diffraction experiments at high-P and low-T. The ZAP cell can be used to integrate multiple experimental techniques such as neutron diffraction, laser spectroscopy, and ultrasonic interferometery. Recently, we have developed high-P low-T gas/fluid cells in conjunction with neutron diffraction and inelastic neutron scattering instruments. These techniques enable in-situ and real-time examination of gas uptake/release processes and allow high-resolution time-dependent determination of changes in crystal structure and related reaction kinetics. We have successfully used these techniques to study the equation of state, structural phase transition, and thermo-mechanical properties of metals, ceramics, and minerals. We have conducted researches on the formation of methane and hydrogen clathrates, and hydrogen adsorption of the inclusion compounds such as the recently discovered metal-organic frameworks (MOFs). The aim of our research is to accurately map phase diagram, lattice parameters, thermal parameters, bond lengths, bond angles, neighboring atomic environments, and phase stability in P-T-X space. We are currently developing further high P-T technology with a new "true" triaxial loading press, TAP_6x, to compress cubic sample package to achieve pressures up to 20 GPa and temperatures up to 2000 K in routine experiments. The implementation of TAP_6x300 with high-pressure neutron beamlines is underway for simultaneous high P-T neutron diffraction, ultrasonic, calorimetry, radiography, and tomography studies. Studies based on high

  2. Fatigue investigations of autofrettaged steel cylinders based on neutron-diffraction measurements

    NASA Astrophysics Data System (ADS)

    de Swardt, R. R.; Venter, A. M.; van der Watt, M. W.

    A series of cyclic internal pressurization fatigue experiments was conducted on partially autofrettaged cylinders with multiple internal radial elliptic shaped cracks covering a wide range of possible configurations. A theoretical model was developed to predict the theoretical fatigue life using as input data the actual measured position of the plastic boundary from neutron-diffraction measurements on the failed specimens, as well as a position calculated analytically from the autofrettage pressure. The theoretical fatigue-life predictions based on the neutron-diffraction results were found to give the best correlation with experimental fatigue results.

  3. Total neutron diffraction: the correct way to determine the true structure of crystalline materials?

    NASA Astrophysics Data System (ADS)

    Hibble, S. J.; Hannon, A. C.; Fawcett, I. D.

    1999-11-01

    Crystallography, using conventional Bragg diffraction, and the study of atomic correlation functions, using total diffraction, have historically been carried out separately. There exist two different scientific communities, which in the case of neutron diffraction normally use different instruments. However, modern time-of-flight neutron diffractometers allow data to be collected to high maximum momentum transfer, Qmax, and with good reciprocal-space resolution, icons/Journals/Common/Delta" ALT="Delta" ALIGN="TOP"/> d/d. The high Qmax yields correlation functions with good real-space resolution, whilst the good reciprocal-space resolution yields data well suited to conventional crystallographic analysis. We show how the Liquids and Amorphous Diffractometer, LAD, at the ISIS spallation neutron source at the Rutherford Appleton Laboratory has been used to obtain new information on a number of disordered crystalline molybdates, Li2MoO3, LiMoO2 and D2MoO3. The average crystal structures are determined using Rietveld refinement of the Bragg diffraction data, whilst the local structures are determined by modelling the correlation functions, T(r), obtained from total neutron diffraction data. Reconciling the information from the two techniques provides a deeper understanding of structures than is possible using either technique in isolation. Finally, we discuss how the next generation of instruments will allow the development of this technique with specific reference to the new General Materials Diffractometer, GEM, at ISIS.

  4. Determination of toluene hydrogenation kinetics with neutron diffraction.

    PubMed

    Falkowska, Marta; Chansai, Sarayute; Manyar, Haresh G; Gladden, Lynn F; Bowron, Daniel T; Youngs, Tristan G A; Hardacre, Christopher

    2016-06-29

    Total neutron scattering has been used to follow the hydrogenation of toluene-d8 to methylcyclohexane-d14 over 3 wt% platinum supported on highly ordered mesoporous silica (MCM-41) at 298 K and under 150 mbar D2 pressure. The detailed kinetic information so revealed indicates that liquid reorganisation inside pores is the slowest step of the whole process. Additionally, the results were compared with the reaction performed under 250 mbar D2 pressure as well as with toluene-h8 hydrogenation using D2 at 150 mbar. PMID:27052196

  5. Recent advances in the study of H environments and behavior in minerals using neutron powder diffraction

    NASA Astrophysics Data System (ADS)

    Welch, M. D.

    2002-12-01

    It is now possible to probe the structural environments and behavior of H atoms directly in complex minerals such as amphiboles, micas, chlorites and humites using neutron powder diffraction, in some cases as a function of pressure and/or temperature. A combination of high neutron flux and increased detector sensitivity and size offers the chance to see details of H behaviour. In the last year or so the advent of new gasket designs for the Paris-Edinburgh pressure cell allow the use of ethanol/methanol (EtOD/MeOD) as a pressure medium, removing peak broadening arising from deviatoric stress that occurs above 3 GPa for the standard fluorinert pressure medium. Essentially hydrostatic conditions obtain with EtOD/MeOD to 8 GPa at 298 K. A further recent development has been the design of a high P-T module for use with the Paris-Edinburgh cell. These technological improvements in pressure-cell design now allow us to make meaningful correlations between OH vibrational spectra collected at high P and/or T and detailed structural information on H behaviour obtained from neutron diffraction under similar conditions. In this talk I shall discuss recent neutron diffraction experiments on the effect of pressure upon hydrogen bonding in deuterated chlorite to 5 GPa (298 K), and a high P-T study of hydrogen bonding in deuterated brucite to 7 GPa, 1100 K. These two studies illustrate how far high-pressure neutron diffraction has come in the last 5 years. Finally, I shall describe a neutron powder diffraction study (ambient conditions) of leucophoenicite, Mn7Si3O12(OH)2, a close structural analogue of Phase-B and Superhydrous-B: the structure of leucophoenicite is topologically identical to the hydrous sheet of Phase-B and similar to that of Superhydrous-B. For various reasons it was not possible to deuterate the sample. Nonetheless, the two distinct H atoms were approximately located in difference-Fourier maps and then refined isotropically. The H positions in Phase-B were only

  6. Single-crystal neutron diffraction studies of hydrogen-bonded systems: Two recent examples from IPNS

    NASA Astrophysics Data System (ADS)

    Koetzle, Thomas F.; Piccoli, Paula M. B.; Schultz, Arthur J.

    2009-02-01

    Beginning with work in the 1950s at the first generation of research reactors, studies of hydrogen-bonded systems have been a prime application for single-crystal neutron diffraction. The range of systems studied was extended in the 1960s and 1970s, with the advent of high flux reactor sources, and beginning around 1980 studies at pulsed neutron sources have made increasingly important contributions. Recently at the Argonne Intense Pulsed Neutron Source (IPNS), working with collaborators, we completed two studies of hydrogen-bonded systems that will serve to illustrate topics of current interest. In the first study, on andrographolide, an active diterpenoid natural product, our neutron diffraction results definitively characterize the hydrogen-bonding interactions. The second IPNS study is on tetraacetylethane (TAE), a β-diketone enol system with a very short, strong intramolecular O-H⋯O hydrogen bond. At IPNS, we have determined the neutron crystal structure of TAE at five temperatures between 20 and 298 K to investigate changes in the structure with temperature and to probe for disorder. Despite the successes illustrated by the two examples presented here and by many other studies, at present applications of single-crystal neutron diffraction continue to be extremely flux limited and constrained by the requirement for mm-size crystals for many problems. These limitations are being addressed through the realization of powerful instruments at a new generation of pulsed neutron sources, including in the USA the TOPAZ and MaNDi single-crystal diffractometers that are under development at the Spallation Neutron Source (SNS).

  7. Neutron diffraction residual stress studies for aero-engine component applications

    NASA Astrophysics Data System (ADS)

    Clay, K.; Small, C.

    1991-12-01

    Computer graphics for a presentation describing how Rolls-Royce is refining the method of residual stress measurement by neutron diffraction to suit the characteristic stress fields of components are presented. Results to date are given. An outline of how this residual stress data is to be used in developing stress models for critical rotating components is given.

  8. Combined X-ray and neutron fibre diffraction studies of biological and synthetic polymers.

    SciTech Connect

    Parrot, I. M.; Urban, Volker S; Gardner, K. H.; Forsyth, V. T.

    2005-04-01

    The fibrous state is a natural one for polymer molecules which tend to assume regular helical conformations rather than the globular structures characteristic of many proteins. Fibre diffraction therefore has broad application to the study of a wide range of biological and synthetic polymers. The purpose of this paper is to illustrate the general scope of the method and in particular to demonstrate the impact of a combined approach involving both X-ray and neutron diffraction methods. While the flux of modern X-ray synchrotron radiation sources allows high quality datasets to be recorded with good resolution within a very short space of time, neutron studies can provide unique information through the ability to locate hydrogen or deuterium atoms that are often difficult or impossible to locate using X-ray methods. Furthermore, neutron fibre diffraction methods can, through the ability to selectively label specific parts of a structure, be used to highlight novel aspects of polymer structure that can not be studied using X-rays. Two examples are given. The first describes X-ray and neutron diffraction studies of conformational transitions in DNA. The second describes structural studies of the synthetic high-performance polymer poly(p-phenylene terephthalamide) (PPTA), known commercially as Kevlar{reg_sign} or Twaron{reg_sign}.

  9. Atom Pair Distribution Functions of Liquid Water at 25circC from Neutron Diffraction

    NASA Astrophysics Data System (ADS)

    Narten, A. H.; Thiessen, W. E.; Blum, L.

    1982-09-01

    The structure of liquid water is described by three atom pair distribution functions gOO(r), gOH(r), and gHH(r). These functions have now been derived from neutron diffraction data on four mixtures of light and heavy water. They will provide a crucial and sensitive test for proposed models of liquid water.

  10. Observation of an intermediate phase in dysprosium near the Neel point by neutron diffraction

    SciTech Connect

    Bessergenev, V.G.; Gogava, V.V.; Kovalevskaya, Y.A.; Mandzhavidze, A.G.; Fedorov, V.M.; Shilo, S.I.

    1985-11-25

    The magnetic structure of dysprosium near the point of magnetic disordering has been studied as a function of the thermal history of the sample by neutron diffraction. An intermediate vortex phase appears during cooling from the paramagnetic phase and then converts into a helicoidal phase.

  11. Processing of Neutron Diffraction Data for Strain Measurement in Geological Materials

    SciTech Connect

    Polsky, Yarom; An, Ke; Anovitz, Lawrence {Larry} M; Bingham, Philip R; Carmichael, Justin R; Dessieux Jr, Luc Lucius

    2014-01-01

    : Conventional rock mechanics testing techniques typically involve the loading of samples and measurement of displacements or strains on the outer boundary of the specimen surface. Neutron diffraction based strain measurement techniques represent a unique and powerful tool for measuring the strain within geological materials under load. The structural variability and non-uniform crystallinity of geological materials, however, create many complexities in the intensity patterns that must be analyzed to quantify strains within the material. The attenuating and scattering properties of the pressure cell housing the sample further add difficulties to the data analysis. This paper describes the methods and processes used to process neutron scattering data for strain measurement in geological materials. It is intended to provide a primer for those in the rock mechanics community that are interested in utilizing this technique along with additional discussion of neutron diffraction experimental factors that may affect data quality.

  12. Rietveld refinement with time-of-flight powder diffraction data from pulsed neutron sources

    SciTech Connect

    David, W.I.F. ); Jorgensen, J.D. )

    1990-10-01

    The recent development of accelerator-based pulsed neutron sources has led to the widespread use of the time-of-flight technique for neutron powder diffraction. The properties of the pulsed source make possible unusually high resolution over a wide range of d spacings, high count rates, and the ability to collect complete data at fixed scattering angles. The peak shape and other instrument characteristics can be accurately modelled, which make Rietveld refinement possible for complex structures. In this paper we briefly review the development of the Rietveld method for time-of-flight diffraction data from pulsed neutron sources and discuss the latest developments in high resolution instrumentation and advanced Rietveld analysis methods. 50 refs., 12 figs., 14 tabs.

  13. FAST TRACK COMMUNICATION Determination of atomic site susceptibility tensors from neutron diffraction data on polycrystalline samples

    NASA Astrophysics Data System (ADS)

    Gukasov, A.; Brown, P. J.

    2010-12-01

    Polarized neutron diffraction can provide information about the atomic site susceptibility tensor χij characterizing the magnetic response of individual atoms to an external magnetic field (Gukasov and Brown 2002 J. Phys.: Condens. Mater. 14 8831). The six independent atomic susceptibility parameters (ASPs) can be determined from polarized neutron flipping ratio measurements on single crystals and visualized as magnetic ellipsoids which are analogous to the thermal ellipsoids obtained from atomic displacement parameters (ADPs). We demonstrate now that the information about local magnetic susceptibility at different magnetic sites in a crystal can also be obtained from polarized and unpolarized neutron diffraction measurements on magnetized powder samples. The validity of the method is illustrated by the results of such measurements on a polycrystalline sample of Tb2Sn2O7.

  14. Neutron diffraction investigation of an in-plane biaxial fatigued stainless steel sample of cruciform geometry

    NASA Astrophysics Data System (ADS)

    Taran, Yu V.; Balagurov, A. M.; Sheverev, S. G.; Schreiber, J.; Korsunsky, A. M.; Vorster, W. J. J.; Bomas, H.; Stoeberl, C.

    2008-03-01

    Fatigue and fracture under multiaxial stresses are among the most important current research topics aimed at ensuring improved reliability of industrial components. An ex situ in-plane biaxial low cycle fatigued sample of cruciform geometry from austenitic stainless steel AISI 321 H was investigated on the FSD stress-diffractometer at the IBR-2 pulsed nuclear reactor by using the neutron strain scanner and the uniaxial stress rig. The phase composition of fatigued material was determined and the residual macrostresses and phase microstresses were measured. To the best of our knowledge, no neutron diffraction investigations of materials subjected to biaxial loading have been previously carried out. The first results of the neutron diffraction experiment are presented and discussed.

  15. In-situ neutron diffraction measurements of temperature and stresses during friction stir welding of 6061-T6 aluminum alloy

    SciTech Connect

    Feng, Zhili; Wang, Xun-Li; David, Stan A; Choo, Hahn; Hubbard, Camden R; Woo, Wan Chuck; Brown, D. W.; Clausen, B; An, Ke

    2007-01-01

    The evolution of temperature and thermal stresses during friction stir welding of Al6061-T6 was investigated by means of in situ, time resolved neutron diffraction technique. A method was developed to deconvolute the temperature and stress from the lattice spacing changes measured by neutron diffraction. The deep penetration capability of neutrons made it possible for the first time to obtain the temperature and thermal stresses inside a friction stir weld.

  16. In-situ neutron diffraction measurements of temperature and stresses during friction stir welding of 6061-T6 aluminum alloy

    SciTech Connect

    Woo, Wan Chuck; Feng, Zhili; Wang, Xun-Li; Brown, D. W.; Clausen, B; An, Ke; Choo, Hahn; Hubbard, Camden R; David, Stan A

    2007-01-01

    The evolution of temperature and thermal stresses during friction stir welding of Al6061-T6 was investigated by means of in-situ, time-resolved neutron diffraction technique. A method is developed to deconvolute the temperature and stress from the lattice spacing changes measured by neutron diffraction. The deep penetration capability of neutrons made it possible for the first time to obtain the temperature and thermal stresses inside a friction stir weld.

  17. Preliminary time-of-flight neutron diffraction study on diisopropyl fluorophosphatase (DFPase) from Loligo vulgaris

    SciTech Connect

    Blum, Marc-Michael; Koglin, Alexander; Rüterjans, Heinz; Schoenborn, Benno; Langan, Paul; Chen, Julian C.-H.

    2007-01-01

    Diisopropyl fluorophosphatase (DFPase) effectively hydrolyzes a number of organophosphorus nerve agents, including sarin, cyclohexylsarin, soman and tabun. Neutron diffraction data have been collected from DFPase crystals to 2.2 Å resolution in an effort to gain further insight into the mechanism of this enzyme. The enzyme diisopropyl fluorophosphatase (DFPase) from Loligo vulgaris is capable of decontaminating a wide variety of toxic organophosphorus nerve agents. DFPase is structurally related to a number of enzymes, such as the medically important paraoxonase (PON). In order to investigate the reaction mechanism of this phosphotriesterase and to elucidate the protonation state of the active-site residues, large-sized crystals of DFPase have been prepared for neutron diffraction studies. Available H atoms have been exchanged through vapour diffusion against D{sub 2}O-containing mother liquor in the capillary. A neutron data set has been collected to 2.2 Å resolution on a relatively small (0.43 mm{sup 3}) crystal at the spallation source in Los Alamos. The sample size and asymmetric unit requirements for the feasibility of neutron diffraction studies are summarized.

  18. Polarisation properties of pulsars at optical wavelengths

    NASA Astrophysics Data System (ADS)

    Mignani, Roberto; Marelli, Martino; Shearer, Andrew; Slowikowska, Agnieszka

    2016-07-01

    Polarisation measurements of pulsars offer unique insights into their highly-magnetised relativistic environments and represent a primary test for neutron star magnetosphere models and radiation emission mechanisms. Besides the radio band, optical observations have been, so far, best suited to these goals, with polarisation measurements in the X-rays becoming possible in the near future thanks to missions, such as XIPE and IXPE. In this talk, we review the status of the optical polarisation measurements of pulsars and we foresee possible synergies between X-ray polarimetry observations of selected pulsars with, e.g XIPE and IXPE, and optical observations with the next generation of extremely large telescope, such as the E-ELT.

  19. Crystallization of porcine pancreatic elastase and a preliminary neutron diffraction experiment

    SciTech Connect

    Kinoshita, Takayoshi; Tamada, Taro; Imai, Keisuke; Kurihara, Kazuo; Ohhara, Takashi; Tada, Toshiji; Kuroki, Ryota

    2007-04-01

    To investigate the structural characteristics of a covalent inhibitor bound to porcine pancreatic elastase (PPE), including H atoms and hydration by water, a crystal of porcine pancreatic elastase with its inhibitor was grown to a size of 1.6 mm{sup 3} for neutron diffraction study. The crystal diffracted to 2.3 Å resolution with sufficient quality for further structure determination owing to the similar atomic scattering properties of deuterium and carbon. Porcine pancreatic elastase (PPE) resembles the attractive drug target leukocyte elastase, which has been implicated in a number of inflammatory disorders. In order to investigate the structural characteristics of a covalent inhibitor bound to PPE, including H atoms and the hydration by water, a single crystal of PPE for neutron diffraction study was grown in D{sub 2}O containing 0.2 M sodium sulfate (pD 5.0) using the sitting-drop vapour-diffusion method. The crystal was grown to a size of 1.6 mm{sup 3} by repeated macroseeding. Neutron diffraction data were collected at room temperature using a BIX-3 diffractometer at the JRR-3 research reactor of the Japan Atomic Energy Agency (JAEA). The data set was integrated and scaled to 2.3 Å resolution in space group P2{sub 1}2{sub 1}2{sub 1}, with unit-cell parameters a = 51.2, b = 57.8, c = 75.6 Å.

  20. Preliminary time-of-flight neutron diffraction study of human deoxyhemoglobin

    SciTech Connect

    Kovalevsky, A. Y.; Chatake, T.; Shibayama, N.; Park, S.-Y.; Ishikawa, T.; Mustyakimov, M.; Fisher, S. Z.; Langan, P.; Morimoto, Y.

    2008-04-01

    In order to investigate the role of the protonation states of protein residues in O{sub 2} binding, large crystals of deoxy HbA (∼20 mm{sup 3}) were grown in D{sub 2}O under anaerobic conditions for neutron diffraction studies. Human hemoglobin (HbA) is an intricate system that has evolved to efficiently transport oxygen molecules (O{sub 2}) from lung to tissue. Its quaternary structure can fluctuate between two conformations, T (tense or deoxy) and R (relaxed or oxy), which have low and high affinity for O{sub 2}, respectively. The binding of O{sub 2} to the heme sites of HbA is regulated by protons and by inorganic anions. In order to investigate the role of the protonation states of protein residues in O{sub 2} binding, large crystals of deoxy HbA (∼20 mm{sup 3}) were grown in D{sub 2}O under anaerobic conditions for neutron diffraction studies. A time-of-flight neutron data set was collected to 1.8 Å resolution on the Protein Crystallography Station (PCS) at the spallation source run by Los Alamos Neutron Science Center (LANSCE). The HbA tetramer (64.6 kDa; 574 residues excluding the four heme groups) occupies the largest asymmetric unit (space group P2{sub 1}) from which a high-resolution neutron data set has been collected to date.

  1. Microscopic structure factor of liquid hydrogen by neutron-diffraction measurements

    NASA Astrophysics Data System (ADS)

    Celli, M.; Bafile, U.; Cuello, G. J.; Formisano, F.; Guarini, E.; Magli, R.; Neumann, M.; Zoppi, M.

    2005-01-01

    The center-of-mass structure factor of liquid para hydrogen has been measured, using neutron diffraction, in four thermodynamic states close to the triple point. Path integral Monte Carlo simulations have been carried out at the same temperatures and densities. The present experimental data are in reasonable quantitative agreement with the simulations and closer to these results than previous neutron determinations available in the literature. The thermodynamic derivatives of the structure factor, from both experiment and simulation, have been compared to previous measurements obtaining a quantitative consistency.

  2. MnO spin-wave dispersion curves from neutron powder diffraction

    SciTech Connect

    Goodwin, Andrew L.; Dove, Martin T.; Tucker, Matthew G.; Keen, David A.

    2007-02-15

    We describe a model-independent approach for the extraction of spin-wave dispersion curves from powder neutron total scattering data. Our approach is based on a statistical analysis of real-space spin configurations to calculate spin-dynamical quantities. The RMCPROFILE implementation of the reverse Monte Carlo refinement process is used to generate a large ensemble of supercell spin configurations from MnO powder diffraction data collected at 100 K. Our analysis of these configurations gives spin-wave dispersion curves for MnO that agree well with those determined independently using neutron triple-axis spectroscopic techniques.

  3. A rotator for single-crystal neutron diffraction at high pressure.

    PubMed

    Fang, J; Bull, C L; Hamidov, H; Loveday, J S; Gutmann, M J; Nelmes, R J; Kamenev, K V

    2010-11-01

    We present a modified Paris-Edinburgh press which allows rotation of the anvils and the sample under applied load. The device is designed to overcome the problem of having large segments of reciprocal space obscured by the tie rods of the press during single-crystal neutron-scattering experiments. The modified press features custom designed hydraulic bearings and provides controls for precision rotation and positioning. The advantages of using the device for increasing the number of measurable reflections are illustrated with the results of neutron-diffraction experiments on a single crystal of germanium rotated under a load of 70 tonnes. PMID:21133480

  4. Heterogeneous Catalysis under pressure - In-situ neutron diffraction under industrial conditions

    NASA Astrophysics Data System (ADS)

    Kandemir, Timur; Girgsdies, Frank; Kasatkin, Igor; Kunkes, Edward; Liss, Klaus-Dieter; Peterson, Vanessa K.; Schlögl, Robert; Behrens, Malte

    2012-02-01

    The present work describes the application of a tubular reactor that allows in-situ neutron diffraction on working catalysts at high pressures. The designed reactor enables the application to a sample of industrially-relevant reaction conditions, i.e., in a temperature range up to 330° C and 60 bar pressure, coupled with online gas-analysis. Application of the cell is demonstrated by ammonia synthesis over a commercial catalyst with diffraction data obtained from the high-resolution powder diffractometer, Echidna, at the Australian Nuclear Science and Technology Organisation, ANSTO.

  5. Electrostatic levitation facility optimized for neutron diffraction studies of high temperature liquids at a spallation neutron source

    DOE PAGESBeta

    Mauro, N. A.; Vogt, A. J.; Derendorf, K. S.; Johnson, M. L.; Rustan, G. E.; Quirinale, D. G.; Kreyssig, A.; Lokshin, K. A.; Neuefeind, J. C.; An, Ke; et al

    2016-01-01

    Neutron diffraction studies of metallic liquids provide valuable information about inherent topological and chemical ordering on multiple length scales as well as insight into dynamical processes at the level of a few atoms. But, there exist very few facilities in the world that allow such studies to be made of reactive metallic liquids in a containerless environment, and these are designed for use at reactor-based neutron sources. We present an electrostatic levitation facility, NESL (for Neutron ElectroStatic Levitator), which takes advantage of the enhanced capabilities and increased neutron flux available at spallation neutron sources (SNSs). NESL enables high quality elasticmore » and inelastic neutron scattering experiments to be made of reactive metallic and other liquids in the equilibrium and supercooled temperature regime. The apparatus is comprised of a high vacuum chamber, external and internal neutron collimation optics, and a sample exchange mechanism that allows up to 30 samples to be processed between chamber openings. Two heating lasers allow excellent sample temperature homogeneity, even for samples approaching 500 mg, and an automated temperature control system allows isothermal measurements to be conducted for times approaching 2 h in the liquid state, with variations in the average sample temperature of less than 0.5%. Furthermore, to demonstrate the capabilities of the facility for elastic scattering studies of liquids, a high quality total structure factor for Zr64Ni36 measured slightly above the liquidus temperature is presented from experiments conducted on the nanoscale-ordered materials diffractometer (NOMAD) beam line at the SNS after only 30 min of acquisition time for a small sample ( 100 mg).« less

  6. Electrostatic levitation facility optimized for neutron diffraction studies of high temperature liquids at a spallation neutron source

    SciTech Connect

    Mauro, N. A.; Vogt, A. J.; Derendorf, K. S.; Johnson, M. L.; Rustan, G. E.; Quirinale, D. G.; Kreyssig, A.; Lokshin, K. A.; Neuefeind, J. C.; An, Ke; Wang, Xun-Li; Goldman, A. I.; Egami, T.; Kelton, K. F.

    2016-01-01

    Neutron diffraction studies of metallic liquids provide valuable information about inherent topological and chemical ordering on multiple length scales as well as insight into dynamical processes at the level of a few atoms. But, there exist very few facilities in the world that allow such studies to be made of reactive metallic liquids in a containerless environment, and these are designed for use at reactor-based neutron sources. We present an electrostatic levitation facility, NESL (for Neutron ElectroStatic Levitator), which takes advantage of the enhanced capabilities and increased neutron flux available at spallation neutron sources (SNSs). NESL enables high quality elastic and inelastic neutron scattering experiments to be made of reactive metallic and other liquids in the equilibrium and supercooled temperature regime. The apparatus is comprised of a high vacuum chamber, external and internal neutron collimation optics, and a sample exchange mechanism that allows up to 30 samples to be processed between chamber openings. Two heating lasers allow excellent sample temperature homogeneity, even for samples approaching 500 mg, and an automated temperature control system allows isothermal measurements to be conducted for times approaching 2 h in the liquid state, with variations in the average sample temperature of less than 0.5%. Furthermore, to demonstrate the capabilities of the facility for elastic scattering studies of liquids, a high quality total structure factor for Zr64Ni36 measured slightly above the liquidus temperature is presented from experiments conducted on the nanoscale-ordered materials diffractometer (NOMAD) beam line at the SNS after only 30 min of acquisition time for a small sample ( 100 mg).

  7. Electrostatic levitation facility optimized for neutron diffraction studies of high temperature liquids at a spallation neutron source

    NASA Astrophysics Data System (ADS)

    Mauro, N. A.; Vogt, A. J.; Derendorf, K. S.; Johnson, M. L.; Rustan, G. E.; Quirinale, D. G.; Kreyssig, A.; Lokshin, K. A.; Neuefeind, J. C.; An, Ke; Wang, Xun-Li; Goldman, A. I.; Egami, T.; Kelton, K. F.

    2016-01-01

    Neutron diffraction studies of metallic liquids provide valuable information about inherent topological and chemical ordering on multiple length scales as well as insight into dynamical processes at the level of a few atoms. However, there exist very few facilities in the world that allow such studies to be made of reactive metallic liquids in a containerless environment, and these are designed for use at reactor-based neutron sources. We present an electrostatic levitation facility, NESL (for Neutron ElectroStatic Levitator), which takes advantage of the enhanced capabilities and increased neutron flux available at spallation neutron sources (SNSs). NESL enables high quality elastic and inelastic neutron scattering experiments to be made of reactive metallic and other liquids in the equilibrium and supercooled temperature regime. The apparatus is comprised of a high vacuum chamber, external and internal neutron collimation optics, and a sample exchange mechanism that allows up to 30 samples to be processed between chamber openings. Two heating lasers allow excellent sample temperature homogeneity, even for samples approaching 500 mg, and an automated temperature control system allows isothermal measurements to be conducted for times approaching 2 h in the liquid state, with variations in the average sample temperature of less than 0.5%. To demonstrate the capabilities of the facility for elastic scattering studies of liquids, a high quality total structure factor for Zr64Ni36 measured slightly above the liquidus temperature is presented from experiments conducted on the nanoscale-ordered materials diffractometer (NOMAD) beam line at the SNS after only 30 min of acquisition time for a small sample (˜100 mg).

  8. Electrostatic levitation facility optimized for neutron diffraction studies of high temperature liquids at a spallation neutron source.

    PubMed

    Mauro, N A; Vogt, A J; Derendorf, K S; Johnson, M L; Rustan, G E; Quirinale, D G; Kreyssig, A; Lokshin, K A; Neuefeind, J C; An, Ke; Wang, Xun-Li; Goldman, A I; Egami, T; Kelton, K F

    2016-01-01

    Neutron diffraction studies of metallic liquids provide valuable information about inherent topological and chemical ordering on multiple length scales as well as insight into dynamical processes at the level of a few atoms. However, there exist very few facilities in the world that allow such studies to be made of reactive metallic liquids in a containerless environment, and these are designed for use at reactor-based neutron sources. We present an electrostatic levitation facility, NESL (for Neutron ElectroStatic Levitator), which takes advantage of the enhanced capabilities and increased neutron flux available at spallation neutron sources (SNSs). NESL enables high quality elastic and inelastic neutron scattering experiments to be made of reactive metallic and other liquids in the equilibrium and supercooled temperature regime. The apparatus is comprised of a high vacuum chamber, external and internal neutron collimation optics, and a sample exchange mechanism that allows up to 30 samples to be processed between chamber openings. Two heating lasers allow excellent sample temperature homogeneity, even for samples approaching 500 mg, and an automated temperature control system allows isothermal measurements to be conducted for times approaching 2 h in the liquid state, with variations in the average sample temperature of less than 0.5%. To demonstrate the capabilities of the facility for elastic scattering studies of liquids, a high quality total structure factor for Zr64Ni36 measured slightly above the liquidus temperature is presented from experiments conducted on the nanoscale-ordered materials diffractometer (NOMAD) beam line at the SNS after only 30 min of acquisition time for a small sample (∼100 mg). PMID:26827330

  9. Bauschinger Effect in an Austenitic Steel: Neutron Diffraction and a Multiscale Approach

    NASA Astrophysics Data System (ADS)

    Fajoui, Jamal; Gloaguen, David; Legrand, Vincent; Oum, Guy; Kelleher, Joe; Kockelmann, Winfried

    2016-05-01

    The generation of internal stresses/strains arising from mechanical deformations in single-phase engineering materials was studied. Neutron diffraction measurements were performed to study the evolution of intergranular strains in austenitic steel during sequential loadings. Intergranular strains expand due to incompatibilities between grains and also resulting from single-crystal elastic and plastic anisotropy. A two-level homogenization approach was adopted in order to predict the mechanical state of deformed polycrystals in relation to the microstructure during Bauschinger tests. A mechanical description of the grain was developed through a micro-meso transition based on the Kröner model. The meso-macro transition using a self-consistent approach was applied to deduce the global behavior. Mechanical tests and neutron diffraction measurements were used to validate and assess the model.

  10. Neutron diffraction measurements and modeling of residual strains in metal matrix composites

    NASA Technical Reports Server (NTRS)

    Saigal, A.; Leisk, G. G.; Hubbard, C. R.; Misture, S. T.; Wang, X. L.

    1996-01-01

    Neutron diffraction measurements at room temperature are used to characterize the residual strains in tungsten fiber-reinforced copper matrix, tungsten fiber-reinforced Kanthal matrix, and diamond particulate-reinforced copper matrix composites. Results of finite element modeling are compared with the neutron diffraction data. In tungsten/Kanthal composites, the fibers are in compression, the matrix is in tension, and the thermal residual strains are a strong function of the volume fraction of fibers. In copper matrix composites, the matrix is in tension and the stresses are independent of the volume fraction of tungsten fibers or diamond particles and the assumed stress free temperature because of the low yield strength of the matrix phase.

  11. Structural analysis of a completely amorphous {sup 238}Pu-doped zircon by neutron diffraction.

    SciTech Connect

    Fortner, J. A.; Badyal, Y.; Price, D. C.; Hanchar, J. M.; Weber, W. J.; Materials Science Division; PNNL

    1999-01-01

    The structure of a completely amorphous zircon was determined by time-of-flight neutron diffraction at Argonne's Intense Pulsed Neutron Source (IPNS). The sample of metamict zircon (ZrSiO{sub 4}), initially doped to 8.85 weight percent {sup 238}Pu, had been completely amorphized by alpha-recoil damage since its synthesis in 1981 at the Pacific Northwest National Laboratory (PNNL). The measured diffraction structure factor, S(Q), indicated a completely amorphous sample, with no signs of residual zircon microcrystallinity. The pair distribution function obtained indicated that the structure was that of an oxide glass, retaining the Si-0, Zr-0, and O-O bond lengths of crystalline zircon.

  12. Structural analysis of a completely amorphous {sup 238}Pu-doped zircon by neutron diffraction.

    SciTech Connect

    Fortner, J. A.

    1998-12-16

    The structure of a completely amorphous zircon was determined by time-of-flight neutron diffraction at Argonne's Intense Pulsed Neutron Source (IPNS). The sample of metamict zircon (ZrSiO{sub 4}),initially doped to 8.85 weight percent {sup 238}Pi, had been completely amorphized by alpha-recoil damage since its synthesis in 1981 at the Pacific Northwest National Laboratory (PNNL). The measured diffraction structure factor, S(Q), indicated a completely amorphous sample, with no signs of residual zircon microcrystallinity. The pair distribution function obtained indicated that the structure was that of an oxide glass, retaining the Si-0, Zr-0, and O-O bond lengths of crystalline zircon.

  13. X-ray and neutron diffraction study of nanocrystalline Ti-Ru-Fe-O compounds

    SciTech Connect

    Blouin, M.; Guay, D.; Huot, J.; Schulz, R.; Swainson, I.P.

    1998-11-01

    The effect of adding oxygen on the structure of nanocrystalline Ti-Ru-Fe compounds obtained by high-energy ball-milling has been studied by X-ray and neutron diffraction using a Rietveld refinement analysis. It is shown that oxygen atoms readily oxidize Ti to form various types of titanium oxides depending on the oxygen content. In each case, a simple cubic structure (cP2-CsCl) is also formed during milling but with a concentration higher than expected on the basis of various reaction schemes. Through a detailed analysis of the neutron and X-ray diffraction peaks, it is shown that the 1a site of the CsCl-type unit cell is depleted from Ti atoms by preferential substitution with Fe. At high oxygen concentration, the alloy is a multiphase material containing Ti{sub 2{minus}x}Ru{sub 1+y}Fe{sub 1+z}, Ti oxides, Ru, and Fe.

  14. α-Phase transformation kinetics of U - 8 wt% Mo established by in situ neutron diffraction

    NASA Astrophysics Data System (ADS)

    Steiner, M. A.; Calhoun, C. A.; Klein, R. W.; An, K.; Garlea, E.; Agnew, S. R.

    2016-08-01

    The α-phase transformation kinetics of as-cast U - 8 wt% Mo below the eutectoid temperature have been established by in situ neutron diffraction. α-phase weight fraction data acquired through Rietveld refinement at five different isothermal hold temperatures can be modeled accurately utilizing a simple Johnson-Mehl-Avrami-Kolmogorov impingement-based theory, and the results are validated by a corresponding evolution in the γ-phase lattice parameter during transformation that follows Vegard's law. Neutron diffraction data is used to produce a detailed Time-Temperature-Transformation diagram that improves upon inconsistencies in the current literature, exhibiting a minimum transformation start time of 40 min at temperatures between 500 °C and 510 °C. The transformation kinetics of U - 8 wt% Mo can vary significantly from as-cast conditions after extensive heat treatments, due to homogenization of the typical dendritic microstructure which possesses non-negligible solute segregation.

  15. In-Situ Studies of Intercritically Austempered Ductile Iron Using Neutron Diffraction

    SciTech Connect

    Druschitz, Alan; Aristizabal, Ricardo; Druschitz, Edward; Hubbard, Camden R; Watkins, Thomas R; Walker, Larry R; Ostrander, M

    2012-01-01

    Intercritically austempered ductile irons hold promise for applications requiring fatigue durability, excellent castability, low production energy requirements, reduced greenhouse gas emissions and excellent machinability. In the present study, four different ductile iron alloys, containing manganese and nickel as the primary austenite-stabilizing elements, were heat treated to obtain different quantities of austenite in the final microstructure. This paper reports the microstructures and phases present in these alloys. Further, lattice strains and diffraction elastic constants in various crystallographic directions and the transformation characteristics of the austenite as a function of applied stress were determined using in-situ loading with neutron diffraction at the second generation Neutron Residual Stress Facility (NRSF2) at the High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory (ORNL).

  16. Neutron diffraction measurements and modeling of residual strains in metal matrix composites

    SciTech Connect

    Saigal, A.; Leisk, G.G.; Hubbard, C.R.; Misture, S.T.; Wang, X.L.

    1996-04-01

    Neutron diffraction measurements at room temperature are used to characterize the residual strains in tungsten fiber-reinforced copper matrix, tungsten fiber-reinforced Kanthal matrix, and diamond particulate-reinforced copper matrix composites. Results of finite element modeling are compared with the neutron diffraction data. In tungsten/Kanthal composites, the fibers are in compression, the matrix is in tension, and the thermal residual strains are a strong function of the volume fraction of fibers. In copper matrix composites, the matrix is in tension and the stresses are independent of the volume fraction of tungsten fibers or diamond particles and the assumed stress free temperature because of the low yield strength of the matrix phase.

  17. Texture analysis of bulk YBa sub 2 Cu sub 3 O sub x by neutron diffraction

    SciTech Connect

    Kallend, J.S. ); Biondo, A.C.; Schultz, A.J.; Goretta, K.C. )

    1990-09-01

    Neutron diffraction has been used to generate Orientation Distribution Functions for two sinter-forged YBa{sub 2}Cu{sub 3}O{sub x} specimens. Sinter forging imparted a strong texture, with c axes of crystals preferentially aligned parallel to the forging direction. The distribution of a and b axes was not uniform, which may have implications to critical current density. 14 refs., 6 figs.

  18. Revealing cyclic hardening mechanism of a TRIP steel by real-time in situ neutron diffraction

    SciTech Connect

    Yu, Dunji; An, Ke; Chen, Yan; Chen, Xu

    2014-01-01

    Real-time in situ neutron diffraction was performed on a transformation-induced plasticity (TRIP) steel under cyclic loading at room temperature. By Rietveld refinement and single peak analysis, the volume fraction and average stress estimates as well as dislocation density of individual phases (austenite and martensite phase) were derived. The results reveal that the volume fraction of martensite phase, instead of individual phase strengthening, should be accounted for the remarkable secondary cyclic hardening.

  19. Monte-Carlo sorption and neutron diffraction study of the filling isotherm in clathrate hydrates

    SciTech Connect

    Klapproth, Alice; Kuhs, Werner F.; Chazallon, Bertrand

    1999-06-15

    We are interested in the thermodynamics of the gas filling of clathrate hydrates. In order to determine the pressure-dependent filling of the cages, neutron powder diffraction experiments on N{sub 2} and CO{sub 2} clathrates were performed. Interaction potentials were refined by comparing the experimentally determined fillings with those generated by MC-sorption calculations. Unsatisfactory agreement between experiment and simulation is observed when using the widely employed SPC water-water interaction potential.

  20. Neutron and X-ray powder diffraction study of skutterudite thermoelectrics

    DOE PAGESBeta

    Wang, H.; Kirkham, M. J.; Watkins, T. R.; Payzant, E. A.; Salvador, J. R.; Thompson, A. J.; Sharp, J.; Brown, D.; Miller, D.

    2016-02-17

    N- and p-type filled-skutterudite materials prepared for thermoelectric power generation modules were analyzed by neutron diffraction at the POWGEN beam line of the Spallation Neutron Source (SNS) and X-ray diffraction (XRD). The skutterudite powders were processed by melt spinning, followed by ball milling and annealing. The n-type material consists of Ba–Yb–Co–Sb and the p-type material consists of Di–Fe–Ni–Sb or Di–Fe–Co–Sb (Di = didymium, an alloy of Pr and Nd). Powders for prototype module fabrication from General Motors and Marlow Industries were analyzed in this study. XRD and neutron diffraction studies confirm that both the n- and p-type materials have cubicmore » symmetry. Structural Rietveld refinements determined the lattice parameters and atomic parameters of the framework and filler atoms. The cage filling fraction was found to depend linearly on the lattice parameter, which in turn depends on the average framework atom size. Ultimately, this knowledge may allow the filling fraction of these skutterudite materials to be purposefully adjusted, thereby tuning the thermoelectric properties.« less

  1. Neutron diffraction and the electronic properties of BaFe2Se3

    NASA Astrophysics Data System (ADS)

    Lovesey, S. W.; Khalyavin, D. D.; van der Laan, G.

    2016-01-01

    It is argued on the basis of previously published experimental data that, the magnetic space-group Cac (#9.41) is the correct description of magnetically ordered BaFe2Se3. The corresponding crystal class m1‧ allows axial and polar dipoles and forbids bulk ferromagnetism. Magneto-electric multipoles that are both time-odd and parity-odd are allowed, e.g., a magnetic charge (monopole) and an anapole (magnetic toroidal dipole). The experimental observation of magneto-electric multipoles must shed light on valence electrons involved in bonding, including charge transfer using 3d(Fe) and p-states of ligand ions. We provide the appropriate structure factors for the Bragg diffraction neutrons, together with estimates of atomic form factors. Structure factors for resonant x-ray Bragg diffraction are also considered, because the analysis of successful experiments will yield complementary information about electronic properties. Magneto-electric multipoles, over and above those that contribute to magnetic neutron diffraction, include the magnetic monopole. A time-odd, parity-even monopole created from the magnetic dipole and an electric toroidal dipole, which is a manifestation of a structural rotation, is allowed in BaFe2Se3 but it is not visible in diffraction, nor is the corresponding dipole.

  2. Analysis of neutron diffraction peak broadening caused by internal stresses in composite materials

    SciTech Connect

    Todd, R.I.; Borsa, C.; Derby, B.; Bourke, M.A.M.

    1994-07-01

    Neutron diffraction is an essential tool in the study of internal stresses in composite materials. In most work only the peak shifts caused by the related elastic strains are considered, but other valuable information exists in the form of peak shape changes. The conditions under which the pure diffraction profile of the composite (i.e. the profile when all sources of broadening not caused by the residual stresses are removed) represents the probability distribution of the peak shifts corresponding to the strains are examined. It is shown that in these conditions, the pure diffraction profile has no attributes of particle size broadening (and vice versa), thereby providing a test for the validity of results interpreted in this way. The experimental derivation of measured strain distributions in Al{sub 2}O{sub 3}/SiCp composites using neutron diffraction is described. No apparent particle size broadening was detected, demonstrating the validity of the results, which also satisfied other tests for consistency.

  3. In situ neutron diffraction under high pressure—Providing an insight into working catalysts

    NASA Astrophysics Data System (ADS)

    Kandemir, Timur; Wallacher, Dirk; Hansen, Thomas; Liss, Klaus-Dieter; Naumann d'Alnoncourt, Raoul; Schlögl, Robert; Behrens, Malte

    2012-05-01

    In the present work the construction and application of a continuous flow cell is presented, from which neutron diffraction data could be obtained during catalytic reactions at high pressure. By coupling an online gas detection system, parallel structure and activity investigations of working catalysts under industrial relevant conditions are possible. The flow cell can be operated with different feed gases in a wide range from room temperature to 603 K. Pressures from ambient up to 6 MPa are applicable. An exchangeable sample positioning system makes the flow cell suitable for several different goniomter types on a variety of instrument beam lines. Complementary operational test measurements were carried out monitoring reduction of and methanol synthesis over a Cu/ZnO/Al2O3 catalyst at the high-flux powder diffraction beamline D1B at ILL and high-resolution diffraction beamline Echidna at ANSTO.

  4. Investigation of the structure of multilayer lipid membranes by real-time neutron diffraction

    NASA Astrophysics Data System (ADS)

    Ryabova, N. Yu.; Kiselev, M. A.; Beskrovnyĭ, A. I.; Balagurov, A. M.

    2010-05-01

    This paper reports on the results of neutron diffraction experiments on the study of structural changes in multilayer lipid membranes as a function of the degree of hydration. The experiments have been performed on a time-of-flight diffractometer at the IBR-2 pulsed reactor (Joint Institute for Nuclear Research, Dubna, Russia) with a dipalmitoylphosphatidylcholine (DPPC) multilayer membrane oriented on a quartz plate. The structural parameters have been determined from the simultaneously measured several (up to five) diffraction orders of reflection, which has made it possible to calculate the profile of the DPPC bilayer structure. A high rate of the measurement of diffraction patterns has allowed one to trace the evolution the lamellar structure of the lipid bilayer in the course of its hydration and dehydration. The minimum time of accumulation of the necessary statistics is 3 min, which has made it possible to determine the characteristic times of transition processes in the membrane with a high accuracy.

  5. Magnetic symmetries in neutron and resonant x-ray Bragg diffraction patterns of four iridium oxides

    NASA Astrophysics Data System (ADS)

    Lovesey, S. W.; Khalyavin, D. D.; Manuel, P.; Chapon, L. C.; Cao, G.; Qi, T. F.

    2012-12-01

    The magnetic properties of Sr2IrO4, Na2IrO3, Sr3Ir2O7 and CaIrO3 are discussed, principally in the light of experimental data in recent literature for Bragg intensities measured in x-ray diffraction with enhancement at iridium L-absorption edges. The electronic structure factors we report, which incorporate parity-even and acentric entities, serve the immediate purpose of making full use of crystal and magnetic symmetry to refine our knowledge of the magnetic properties of the four iridates from resonant x-ray diffraction data. They also offer a platform on which to interpret future investigations, using dichroic signals, resonant x-ray diffraction and neutron diffraction, for example, as well as ab initio calculations of electronic structure. Unit-cell structure factors, suitable for x-ray Bragg diffraction enhanced by an electric dipole-electric dipole (E1-E1) event, reveal exactly which iridium multipoles are visible, e.g., a magnetic dipole parallel to the crystal c-axis (z-axis) and an electric quadrupole with yz-like symmetry in the specific case of CaIrO3. Magnetic space-groups are assigned to Sr2IrO4, Sr3Ir2O7 and CaIrO3, namely, PIcca, PAban and Cm‧cm‧, respectively, in the Belov-Neronova-Smirnova notation. The assignment for Sr2IrO4 is possible because of our new high-resolution neutron diffraction data, gathered on a powder sample. In addition, the new data are used to show that the ordered magnetic moment of an Ir4+ ion in Sr2IrO4 does not exceed 0.29(4) μB. Na2IrO3 has two candidate magnetic space-groups that are not resolved with currently available resonant x-ray data.

  6. The ferroelectric phase of CdTiO{sub 3}: A powder neutron diffraction study

    SciTech Connect

    Kennedy, Brendan J.; Zhou Qingdi; Avdeev, Maxim

    2011-11-15

    The synthesis of bulk samples of polycrystalline CdTiO{sub 3} in both the rhombohedral ilmenite and orthorhombic perovskite forms is described and the structures of these have been refined using powder neutron diffraction data. This involved the preparation of samples enriched in {sup 114}Cd. Cooling perovskite-type CdTiO{sub 3} to 4 K induces a ferroelectric phase transition, with the neutron data suggesting the low temperature structure is in Pna2{sub 1}. Mode analysis shows the polar mode to be dominant at low temperatures. The ilmenite-structure of CdTiO{sub 3} is compared with that of ZnTiO{sub 3}. The refined scattering length of the {sup 114}Cd is estimated to be 5.56 fm. Attempts to dope CdTiO{sub 3} with Ca and Sr are described. - Graphical abstract: The structure of three phases of CdTiO{sub 3} have been refined using high resolution powder neutron diffraction data. This involved the preparation of samples enriched in {sup 114}Cd. Cooling perovskite-type CdTiO{sub 3} to 4 K results in a ferroelectric phase in Pna2{sub 1}. Highlights: > Both the ilmenite and perovskite forms of CdTiO{sub 3} have been prepared using {sup 114}Cd. > Cooling the perovskite form results in a ferroelectric phase. > The structures of these are refined from powder neutron diffraction data. > Attempts to dope CdTiO{sub 3} are described.

  7. Neutron diffraction study of hydrogen-bond symmetrization in δ-AlOOD

    NASA Astrophysics Data System (ADS)

    Sano-Furukawa, A.; Hattori, T.; Kuribayashi, T.

    2013-12-01

    δ-AlOOH, a high-pressure polymorph of diaspore, is an important hydrous mineral in the deep earth that has the ability to transport hydrogen into the lower mantle. Theoretical studies have pointed out that hydrogen would locate at the center between two oxygen atoms at high pressure, which is so called hydrogen-bond symmetrization [1]. It was also suggested that the symmetrization would trigger the increase of bulk modulus, which is one of the important parameters of minerals at high pressure. The transition of δ-AlOOH(D) at high pressure has been suggested by X-ray and neutron diffraction [2, 3]. X-ray diffraction study found that the axes a and b where the hydrogen bond is oriented become less compressible above 12 GPa in δ-AlOOD. Neutron diffraction study on δ-AlOOD up to 9.2 GPa showed the increase of O-D bond distance, that is considered as a precousor phenomena of the symmetrization. However, the pressure was insufficient to observe the symmetrization. To investigate the symmetrization of hydrogen bond directly, we conducted neutron diffraction experiments to 16.7 GPa at PLANET, MLF in J-PARC. Powder sample of δ-AlOOD was loaded in Paris-Edinburgh press with double-toroid sintered diamond anvils with methanol-ethanol mixture of pressure medium. In the experiments, the disappearance of 120 refrection was observed at 12.1 GPa, indicating the transition from P21nm to Pnnm, which can be attributed to the disorder of hydrogen bond or the symmtrization. Results of Rietveld refienment will be shown in the presentation. [1] Tsuchiya et al., Geophys. Res. Lett., 29, 1909, 2002. [2] Sano-Furukawa et al., Am. Mineral., 93, 1558-1567, 2008. [3] Sano-Furukawa et al., Am. Mineral., 94, 1255-1261, 2009.

  8. Polarised light sheet tomography.

    PubMed

    Reidt, Sascha L; O'Brien, Daniel J; Wood, Kenneth; MacDonald, Michael P

    2016-05-16

    The various benefits of light sheet microscopy have made it a widely used modality for capturing three-dimensional images. It is mostly used for fluorescence imaging, but recently another technique called light sheet tomography solely relying on scattering was presented. The method was successfully applied to imaging of plant roots in transparent soil, but is limited when it comes to more turbid samples. This study presents a polarised light sheet tomography system and its advantages when imaging in highly scattering turbid media. The experimental configuration is guided by Monte Carlo radiation transfer methods, which model the propagation of a polarised light sheet in the sample. Images of both reflecting and absorbing phantoms in a complex collagenous matrix were acquired, and the results for different polarisation configurations are compared. Focus scanning methods were then used to reduce noise and produce three-dimensional reconstructions of absorbing targets. PMID:27409945

  9. Time-of-flight neutron diffraction study of bovine [gamma]-chymotrypsin at the Protein Crystallography Station

    SciTech Connect

    Lazar, Louis M.; Fisher, S. Zoe; Moulin, Aaron G.; Kovalevsky, Andrey; Novak, Walter R.P.; Langan, Paul; Petsko, Gregory A.; Ringe, Dagmar

    2012-02-06

    The overarching goal of this research project is to determine, for a subset of proteins, exact hydrogen positions using neutron diffraction, thereby improving H-atom placement in proteins so that they may be better used in various computational methods that are critically dependent upon said placement. In order to be considered applicable for neutron diffraction studies, the protein of choice must be amenable to ultrahigh-resolution X-ray crystallography, be able to form large crystals (1 mm{sup 3} or greater) and have a modestly sized unit cell (no dimension longer than 100 {angstrom}). As such, {gamma}-chymotrypsin is a perfect candidate for neutron diffraction. To understand and probe the role of specific active-site residues and hydrogen-bonding patterns in {gamma}-chymotrypsin, neutron diffraction studies were initiated at the Protein Crystallography Station (PCS) at Los Alamos Neutron Science Center (LANSCE). A large single crystal was subjected to H/D exchange prior to data collection. Time-of-flight neutron diffraction data were collected to 2.0 {angstrom} resolution at the PCS with 85% completeness. Here, the first time-of-flight neutron data collection from {gamma}-chymotrypsin is reported.

  10. Tau polarisation at LEP

    NASA Astrophysics Data System (ADS)

    Alemany, Ricard

    1999-04-01

    The measurements of the tau polarisation at LEP I are reviewed. Special emphasis is given to the new preliminary results presented at this conference. The ALEPH collaboration has studied the polarisation as a function of the polar angle using a new method based on the tau direction reconstruction and fully exploiting the angular correlations. A second traditional approach, based on the single tau decays has been also developed. The DELPHI collaboration has also studied the full data sample using an individual tau decay method and an inclusive hadronic selection. The results from the four experiments are presented with discussion of the compatibility among the methods and experiments.

  11. Crystallization and preliminary neutron diffraction experiment of human farnesyl pyrophosphate synthase complexed with risedronate

    PubMed Central

    Yokoyama, Takeshi; Ostermann, Andreas; Mizuguchi, Mineyuki; Niimura, Nobuo; Schrader, Tobias E.; Tanaka, Ichiro

    2014-01-01

    Nitrogen-containing bisphosphonates (N-BPs), such as risedronate and zoledronate, are currently used as a clinical drug for bone-resorption diseases and are potent inhibitors of farnesyl pyrophosphate synthase (FPPS). X-ray crystallographic analyses of FPPS with N-BPs have revealed that N-BPs bind to FPPS with three magnesium ions and several water molecules. To understand the structural characteristics of N-BPs bound to FPPS, including H atoms and hydration by water, neutron diffraction studies were initiated using BIODIFF at the Heinz Maier-Leibnitz Zentrum (MLZ). FPPS–risedronate complex crystals of approximate dimensions 2.8 × 2.5 × 1.5 mm (∼3.5 mm3) were obtained by repeated macro-seeding. Monochromatic neutron diffraction data were collected to 2.4 Å resolution with 98.4% overall completeness. Here, the first successful neutron data collection from FPPS in complex with N-BPs is reported. PMID:24699741

  12. Structure of molten Al and eutectic Al-Si alloy studied by neutron diffraction

    SciTech Connect

    Dahlborg, U.; Kramer, Matthew J.; Besser, M.; Morris, J. R.; Calvo-Dahlborg, M.

    2012-11-24

    The structure of molten eutectic Al87.8Si12.2 alloy has been studied by neutron diffraction during a temperature cycle. For comparison measurements were performed on pure molten Al. The measurements show that the alloy after heating above the liquidus contains particles of two kinds, aluminum-rich and silicon-rich. The silicon-rich particles are partly dissolved after a further heating. Earlier published data obtained by the γ-ray absorption technique of the density of the molten eutectic Al–Si alloy had demonstrated the existence of two temperatures above the liquidus temperature: A dissolution temperature Td, at which the microstructure of the melt inherited from the ingot starts to dissolve and a branching temperature, Tb, at which the melt reaches a fully mixed state. The highest temperature that was possible to reach during the neutron experiments lies between Td and Tb. The obtained results support these conclusions that molten alloys after melting are inhomogeneous up to a temperature well above the liquidus. Moreover, the difference in shape between the static structure factors measured by neutron and X-ray diffraction on molten aluminum is observed and is found to be more accentuated and to extend to larger wavevectors than in earlier works.

  13. Preliminary neutron diffraction studies of Escherichia coli dihydrofolate reductase bound to the anticancer drug methotrexate

    SciTech Connect

    Bennett, Brad C.; Meilleur, Flora; Myles, Dean A A; Howell, Elizabeth E.; Dealwis, Chris G.

    2005-01-01

    The contribution of H atoms in noncovalent interactions and enzymatic reactions underlies virtually all aspects of biology at the molecular level, yet their 'visualization' is quite difficult. To better understand the catalytic mechanism of Escherichia coli dihydrofolate reductase (ecDHFR), a neutron diffraction study is under way to directly determine the accurate positions of H atoms within its active site. Despite exhaustive investigation of the catalytic mechanism of DHFR, controversy persists over the exact pathway associated with proton donation in reduction of the substrate, dihydrofolate. As the initial step in a proof-of-principle experiment which will identify ligand and residue protonation states as well as precise solvent structures, a neutron diffraction data set has been collected on a 0.3 mm{sup 3} D{sub 2}O-soaked crystal of ecDHFR bound to the anticancer drug methotrexate (MTX) using the LADI instrument at ILL. The completeness in individual resolution shells dropped to below 50% between 3.11 and 3.48 {angstrom} and the I/{sigma}(I) in individual shells dropped to below 2 at around 2.46 {angstrom}. However, reflections with I/{sigma}(I) greater than 2 were observed beyond these limits (as far out as 2.2 {angstrom}). To our knowledge, these crystals possess one of the largest primitive unit cells (P6{sub 1}, a = b = 92, c = 73 {angstrom}) and one of the smallest crystal volumes so far tested successfully with neutrons.

  14. Design of a new lithium ion battery test cell for in-situ neutron diffraction measurements

    NASA Astrophysics Data System (ADS)

    Roberts, Matthew; Biendicho, Jordi Jacas; Hull, Stephen; Beran, Premysl; Gustafsson, Torbjörn; Svensson, Gunnar; Edström, Kristina

    2013-03-01

    This paper introduces a new cell design for the construction of lithium ion batteries with conventional electrochemical performance whilst allowing in situ neutron diffraction measurement. A cell comprising of a wound cathode, electrolyte and anode stack has been prepared. The conventional hydrogen-containing components of the cell have been replaced by hydrogen-free equivalents. The electrodes are fabricated using a PTFE binder, the electrolyte consists of deuterated solvents which are supported in a quartz glass fibre separator. Typical battery performance is reported using the hydrogen-free components with a specific capacity of 140 mA h g-1 being observed for LiFePO4 at a rate of 0.2 C. Neutron diffraction patterns of full cells were recorded with phase change reactions monitored. When aluminium packaging was used a better signal to noise ratio was obtained. The obtained atomic positions and lattice parameters for all cells investigated were found to be consistent with parameters refined from the diffraction pattern of a powder of the pure electrode material. This paper highlights the pertinent points in designing cells for these measurements and addresses some of the problems.

  15. Characterisation of Residual Stresses Generated by Laser Shock Peening by Neutron and Synchrotron Diffraction

    NASA Astrophysics Data System (ADS)

    Evans, Alexander Dominic; King, Andrew; Pirling, Thilo; Peyre, Patrice; Withers, Phillip John

    The fatigue behaviour of engineering alloys can be significantly improved through the application of mechanical surface treatments. These processes generate significant compressive residual stresses near surface by inhomogeneous plastic deformation. In the case of mechanical surface treatments such as laser shock peening, certain burnishing and rolling techniques and ultrasonic impact treatment (UIT), the compressive residual stress layer can extend to a depth of the order of millimeters, with balancing tensile stresses located deeper. Techniques to characterise the residual stresses generated by such mechanical surface treatments non-destructively are mainly limited to diffraction methods using penetrating neutron and synchrotron X-ray radiations. The application of these radiation sources is illustrated here by the characterisation of residual strain distributions in a two types of specimens treated with laser shock peening (LSP). Analyses of diffraction peak broadening provide qualitative information concerning the depth to which the plastic deformation of the treatments extends. Two case studies of laser shock peening of titanium and aluminium alloys is presented to demonstrate the capabilities of neutron and synchrotron diffraction techniques in the field of residual stress characterisation of surface engineered material non-destructively.

  16. Neutron diffraction analysis of residual strain/stress distribution in the vicinity of high strength welds

    NASA Astrophysics Data System (ADS)

    Mráz, L.; Karlsson, L.; Hamák, I.; Vrána, M.; Mikula, P.

    2010-06-01

    Residual stresses resulting from non homogeneous heat distribution during welding process belong to most significant factor influencing behavior of welded structures. These stresses are responsible for defect occurrence during welding and they are also responsible for crack initiation and propagation at the either static or dynamic load. The significant effect of weld metal chemical composition as well as the effect of fatigue load and local plastic deformation on residual stress distribution and fatigue life have been recognized for high strength steels welds. The changes in residual stress distribution have then positive effect on cold cracking behavior and also on fatigue properties of the welds [1-3]. Several experimental methods, both destructive and non-destructive, such as hole drilling method, X-ray diffraction, neutron diffraction and others, have been used to examine residual stress distribution in all three significant orientations in the vicinity of the welds. The present contribution summarizes the results of neutron diffraction measurements of residual stress distribution in the vicinity of single-pass high-strength-steel welds having different chemical composition as well as the influence of fatigue load and local plastic deformation. It has been observed that the chemical composition of the weld metal has a significant influence on the stress distribution around the weld. Similarly, by aplying both cyclic load or pre-stress load on the specimens, stress relaxation was observed even in the region of approximately 40 mm far from the weld toe.

  17. Neutron and X-ray diffraction of plasma-sprayed zirconia-yttria thermal barrier coatings

    NASA Technical Reports Server (NTRS)

    Shankar, N. R.; Herman, H.; Singhal, S. P.; Berndt, C. C.

    1984-01-01

    ZrO2-7.8mol. pct. YO1.5, a fused powder, and ZrO2-8.7mol. pct. YO1.5, a prereacted powder, were plasma-sprayed onto steel substrates. Neutron diffraction and X-ray diffraction of the as-received powder, the powder plasma sprayed into water, as-sprayed coatings, and coatings heat-treated for 10 and 100 h were carried out to study phase transformations and ordering of the oxygen ions on the oxygen sublattice. The as-received fused powder has a much lower monoclinic percentage than does the pre-reacted powder, this resulting in a much lower monoclinic percentage in the coating. Heat treatment increases the percentages of the cubic and monoclinic phases, while decreasing the tetragonal content. An ordered tetragonal phase is detected by the presence of extra neutron diffraction peaks. These phase transformations and ordering will result in volume changes. The implications of these transformations on the performance of partially stabilized zirconia thermal barrier coatings is discussed.

  18. Structure of deuterated liquid n-butanol by neutron diffraction and molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Cristiglio, Viviana; Gonzalez, Miguel Angel; Cuello, Gabriel Julio; Cabrillo, Carlos; Pardo, Luis Carlos; Silva-Santisteban, Alvaro

    Aliphatic alcohols are the simpler molecular liquids possessing a polar hydroxylic group and a nonpolar alkyl tail. While the structure of the smallest alcohols has been relatively well studied, no much attention has been paid to the temperature dependence of the pre-peak observed before the main diffraction peak. The role of H-bonding in causing this feature and the direct relation between the number of C atoms and their distance were discovered very early, suggesting a liquid picture constituted of straight chains joined by H-bonds with the formation of mesoscopic size clusters. X-rays and neutron diffraction measurements showed that the height of the pre-peak associated with the formation of H-bonds increases with temperature. To explain this counterintuitive effect, a complete diffraction study using two neutron diffractometers D4 and D16 (ILL, Grenoble, France) allowing to cover the range 0.01-23 Å t1 and exploring a temperature range from 100 K (glassy butanol) to 400 K (moderately supercritical conditions) has been conducted. Molecular Dynamics simulations using the OPLS-AA potential were also carried out as a function of temperature and compared to experiment. Experimental and numerical results of liquid n-butanol and its glassy transition will be presented.

  19. Similar quartz crystallographic textures in rocks of continental earth's crust (by neutron diffraction data): I. Quartz textures in monomineral rocks

    NASA Astrophysics Data System (ADS)

    Nikitin, A. N.; Ivankina, T. I.; Ullemeyer, K.; Vasin, R. N.

    2008-09-01

    Quartz crystallographic textures in different rocks have been investigated by neutron diffraction. Various types of crystallographic textures of quartz-bearing mineral associations in monomineral and multiphase rocks from a representative collection of samples have been revealed and classified. Experimental investigations have been performed on special neutron texture diffractometers designed at the Frank Laboratory of Neutron Physics and mounted in the seventh channel of the IBR-2 reactor at the Joint Institute for Nuclear Research (Dubna).

  20. Similar quartz crystallographic textures in rocks of continental earth's crust (by neutron diffraction data): I. Quartz textures in monomineral rocks

    SciTech Connect

    Nikitin, A. N. Ivankina, T. I.; Ullemeyer, K.; Vasin, R. N.

    2008-09-15

    Quartz crystallographic textures in different rocks have been investigated by neutron diffraction. Various types of crystallographic textures of quartz-bearing mineral associations in monomineral and multiphase rocks from a representative collection of samples have been revealed and classified. Experimental investigations have been performed on special neutron texture diffractometers designed at the Frank Laboratory of Neutron Physics and mounted in the seventh channel of the IBR-2 reactor at the Joint Institute for Nuclear Research (Dubna).

  1. Hydrogen site analysis of hydrous ringwoodite in mantle transition zone by pulsed neutron diffraction

    NASA Astrophysics Data System (ADS)

    Purevjav, Narangoo; Okuchi, Takuo; Tomioka, Naotaka; Abe, Jun; Harjo, Stefanus

    2014-10-01

    Hydrogen site positions and occupancies in the crystal structure of synthetic hydrous ringwoodite have been determined for the first time by high-resolution neutron powder diffraction conducted at the pulsed neutron source at Japan Proton Accelerator Research Complex (J-PARC). It is demonstrated that hydrogen exchanges not only with Mg or Fe but also with Si cations to form hydroxyl and hydrogen bonding, both within the relevant octahedra or tetrahedra created by their surrounding oxygen anions. The hydrated octahedra shrink, whereas the hydrated tetrahedra expand. The occurrence of simultaneous hydration of octahedra and tetraheda is thus unambiguously confirmed, whereby the latter plays an especially unique role in reducing seismic velocity and for enhancing the electrical conductivity of ringwoodite at high pressures and temperatures. These results provide distinctive implications for discussing the physical properties of hydrous ringwoodite occurring in the mantle transition zone and evaluating the actual water content in the zone.

  2. Neutron diffraction study of a nitrogen martensitic steel 0Kh16N4AB under load

    NASA Astrophysics Data System (ADS)

    Sumin, V. V.; Papushkin, I. V.; Bannykh, O. A.; Blinov, V. M.; Lukáš, P.

    2008-01-01

    An austenitic-martensitic nitrogen steel 0Kh16N4AB has been studied under load using high-resolution neutron diffraction analysis on an FSD neutron diffractometer at an IBR-2 reactor (Dubna) and on a diffractometer with a focusing monochromator on a reactor of the Nuclear Physics Institute (Czech Republic). Young's moduli calculated from different reflections of the martensite and austenite phases have been obtained. It has been found that the yield strength σ0.2 corresponding to the slip plane (111) of the austenite phase is anomalously low and that with increasing degree of uniaxial tension the width of lines (111)γ strongly grows. In the steel under consideration the plane (111) of the austenite phase appears to be an easy-slip plane that ensures the enhanced properties of the steel, i.e., the combination of a high ultimate strength (1600 MPa) with a high plasticity (δ = 16%).

  3. Determination of the residual stress tensor in textured zirconium alloy by neutron diffraction

    NASA Astrophysics Data System (ADS)

    Sumin, V. V.; Papushkin, I. V.; Vasin, R. N.; Venter, А. M.; Balagurov, А. М.

    2012-02-01

    Results of neutron diffraction studies of crystallographic texture and residual stress tensor components in cold-worked and annealed cylindrical components made from E-110 zirconium alloy are presented. Those components are used as plugs in the fuel elements of the VVER-type reactors; the resident residual stresses influence the durability and safety of the fuel elements. The experiments were carried out on the neutron diffractometers at Dubna (the IBR-2 pulsed reactor) and Berlin Helmholtz-Zentrum (the BER II research reactor). It is shown that the samples have fiber texture that is changed considerably with annealing. The type I residual stress tensors for both samples were calculated by the BulkPathGEO model. The cold worked component has 136-166 MPa tensile residual stress in the radial direction and zero stress along the axial direction. Residual stress values in the annealed component are close to zero.

  4. Intergranular Strain Evolution in Titanium During Tensile Loading: Neutron Diffraction and Polycrystalline Model

    NASA Astrophysics Data System (ADS)

    Gloaguen, David; Oum, Guy; Legrand, Vincent; Fajoui, Jamal; Moya, Marie-José; Pirling, Thilo; Kockelmann, Winfried

    2015-11-01

    Intergranular strains due to tensile plastic deformation were investigated in a commercially pure Ti. Neutron diffraction has been used to characterize the evolution of residual elastic strain in grains with different crystallographic orientations. Experimental data have been obtained for the macroscopic stress-strain curve and the intergranular strain evolution in the longitudinal and transverse direction relative to the uniaxial loading axis. The elasto-plastic self-consistent (EPSC) approach was used to model the deformation behavior of the studied material. Comparison between the neutron measurements and the model predictions shows that in most cases the EPSC approach can predict the lattice strain evolution and capture the plastic anisotropy observed in the experiments.

  5. The Existence of Ferroelectric Ice on Icy Bodies in Space: a Neutron Diffraction Study

    NASA Astrophysics Data System (ADS)

    Fukazawa, Hiroshi

    The complex behavior of water and the unusual properties of ferroelectric ice XI continue to attract much interest. Whether ice in the space exists as ice XI, is an important question, because long range electrostatic forces caused by the ferroelectricity might be an important factor for planet formation. From neutron diffraction experiments, we found the temperature and pressure conditions for the transformation of the largest fraction of ice into ferroelectric ice. It suggests that myriad big icy-bodies, which exist as dwarf planets and Kuiper Belt Object, consist of thick ferroelectric-ice surface. Furthermore, we report spectral and vibrational properties of ferroelectric ice investigated by inelastic neutron scattering and infrared absorption measurements. Because the spectral properties of ferroelectric ice are clearly different from those of ordinary ice, the distinct ferroelectric ice in the universe is detectable using infrared telescopes and planetary exploration.

  6. The magnetic structure of Co(NCNH)₂ as determined by (spin-polarized) neutron diffraction

    SciTech Connect

    Jacobs, Philipp; Houben, Andreas; Senyshyn, Anatoliy; Müller, Paul; Dronskowski, Richard

    2013-06-01

    The magnetic structure of Co(NCNH)₂ has been studied by neutron diffraction data below 10 K using the SPODI and DNS instruments at FRM II, Munich. There is an intensity change in the (1 1 0) and (0 2 0) reflections around 4 K, to be attributed to the onset of a magnetic ordering of the Co²⁺ spins. Four different spin orientations have been evaluated on the basis of Rietveld refinements, comprising antiferromagnetic as well as ferromagnetic ordering along all three crystallographic axes. Both residual values and supplementary susceptibility measurements evidence that only a ferromagnetic ordering with all Co²⁺ spins parallel to the c axis is a suitable description of the low-temperature magnetic ground state of Co(NCNH)₂. The deviation of the magnetic moment derived by the Rietveld refinement from the expectancy value may be explained either by an incomplete saturation of the moment at temperatures slightly below the Curie temperature or by a small Jahn–Teller distortion. - Graphical abstract: The magnetic ground state of Co(NCNH)₂ has been clarified by (spin-polarized) neutron diffraction data at low temperatures. Intensity changes below 4 K arise due to the onset of ferromagnetic ordering of the Co²⁺ spins parallel to the c axis, corroborated by various (magnetic) Rietveld refinements. Highlights: • Powderous Co(NCNH)₂ has been subjected to (spin-polarized) neutron diffraction. • Magnetic susceptibility data of Co(NCNH)₂ have been collected. • Below 4 K, the magnetic moments align ferromagnetically with all Co²⁺ spins parallel to the c axis. • The magnetic susceptibility data yield an effective magnetic moment of 4.68 and a Weiss constant of -13(2) K. • The ferromagnetic Rietveld refinement leads to a magnetic moment of 2.6 which is close to the expectancy value of 3.

  7. Assessment of Shape Memory Alloys - From Atoms To Actuators - Via In Situ Neutron Diffraction

    NASA Technical Reports Server (NTRS)

    Benafan, Othmane

    2014-01-01

    As shape memory alloys (SMAs) become an established actuator technology, it is important to identify the fundamental mechanisms responsible for their performance by understanding microstructure performance relationships from processing to final form. Yet, microstructural examination of SMAs at stress and temperature is often a challenge since structural changes occur with stress and temperature and microstructures cannot be preserved through quenching or after stress removal, as would be the case for conventional materials. One solution to this dilemma is in situ neutron diffraction, which has been applied to the investigation of SMAs and has offered a unique approach to reveal the fundamental micromechanics and microstructural aspects of bulk SMAs in a non-destructive setting. Through this technique, it is possible to directly correlate the micromechanical responses (e.g., internal residual stresses, lattice strains), microstructural evolutions (e.g., texture, defects) and phase transformation properties (e.g., phase fractions, kinetics) to the macroscopic actuator behavior. In this work, in situ neutron diffraction was systematically employed to evaluate the deformation and transformation behavior of SMAs under typical actuator conditions. Austenite and martensite phases, yield behavior, variant selection and transformation temperatures were characterized for a polycrystalline NiTi (49.9 at. Ni). As the alloy transforms under thermomechanical loading, the measured textures and lattice plane-level variations were directly related to the cyclic actuation-strain characteristics and the dimensional instability (strain ratcheting) commonly observed in this alloy. The effect of training on the shape memory characteristics of the alloy and the development of two-way shape memory effect (TWSME) were also assessed. The final conversion from a material to a useful actuator, typically termed shape setting, was also investigated in situ during constrained heatingcooling and

  8. Neutron diffraction of hydrogenous materials: Measuring incoherent and coherent intensities separately

    NASA Astrophysics Data System (ADS)

    Temleitner, László; Stunault, Anne; Cuello, Gabriel J.; Pusztai, László

    2015-07-01

    Accurate determination of the coherent static structure factor of any disordered material containing substantial amounts of proton nuclei has proven to be rather problematic by neutron diffraction, due to the large incoherent cross section of 1H. This problem has continued to set severe obstacles to the reliable determination of liquid structures of hydrogenous materials up to this day, by introducing large uncertainties whenever a sample with a 1H content larger than about 20% had to be investigated by neutron diffraction. Huge theoretical efforts over the past 40 years which were aimed at estimating the incoherent background of such data did not result in any practical solution to the problem. Here, we present data for the coherent and incoherent contributions to the total static structure of mixtures of light and heavy water. The measurements were done using the polarized neutron diffraction technique, which uniquely allows determination of the two contributions separately. The data covers a wide range of momentum transfer (0.8-21 Å-1) and the entire composition range, i.e., light water contents between 0 and 100% at five different values. We show that the measured incoherent scattering can be approximated by a Gaussian function. The separately measured coherent intensities exhibit signs of small inelastic contributions. Out of several possible approaches, we have chosen to subtract a cubic background using the reverse Monte Carlo algorithm. This algorithm has the advantage of requiring an actual physical model with thousands of realistic water molecules at the correct density describing the corrected data. Finally, coherent static structure factors for five different compositions of liquid H2O and D2O mixtures are presented for which the huge incoherent background could actually be measured and separated, instead of being approximated as it has been done so far. These experimental results provide a strong hope that determining the structure of hydrogenous

  9. Insights into Analogue Perovskite Solid Solutions from High-Resolution Neutron Powder Diffraction

    NASA Astrophysics Data System (ADS)

    Redfern, S. A.; Chaddock, E. H.; Becerro, A. I.

    2002-12-01

    Neutron powder diffraction provides a powerful tool for the study of phase transitions as a function of pressure, temperature, or chemical composition. The structural information obtainable from powders using diffractometers such as HRPD (ISIS, UK) or D2B (ILL, France) rivals, and in some respects exceeds what may be possible using conventional crystallographic techniques reliant on single crystals. We have used both instruments to explore the subtle phase transitions observed in the (CaxSr1-x)TiO3 and (SrxBa1-x)SnO3 solid solutions. We have also used low resolution high flux instruments to explore the thermal dependence of the superlattice behavior below the cubic to tetragonal phase transition in (CaxSr1-x)TiO3. In each case a sequence of phase transitions from Pm-3m through I4/mcm to Pbnm is seen as a function of composition, and is driven by the change in average radius of the B-cation. This sequence of transitions is the same as expected for a magnesium silicate perovskite structure on increasing temperature. It is now recognised that lower mantle perovskite is likely aluminous, with solid solution towards either a stoichiometric or oxygen-defect end-member. The analogue systems we have characterised have been doped with trivalent cations on the B site to explore the effect of such substitution on the sequence of phase transitions. High-temperature neutron diffraction shows that oxygen defects stabilize the higher symmetry structures, lowering Tc for the transition to cubic. New developments in high-T high-P neutron diffraction techniques will allow the extension of these ambient pressure studies to the investigation of the influence of pressure as a variable, and hence the extension of such analogue studies to the whole range of variables experienced in the lower mantle. These will be briefly outlined.

  10. Localization of glycolipids in membranes by in vivo labeling and neutron diffraction.

    PubMed

    Weik, M; Patzelt, H; Zaccai, G; Oesterhelt, D

    1998-02-01

    Evidence is accumulating for the lateral organization of cell membrane lipids and proteins in the context of sorting or intracellular signaling. So far, however, information has been lacking on the details of protein-lipid interactions in such aggregates. Purple membranes are patches made up of lipids and the protein bacteriorhodopsin in the plasma membrane of certain Archaea. Naturally crystalline, they provide a unique opportunity to study the structure of a natural membrane at submolecular resolution by diffraction methods. We present a direct structural determination of the glycolipids with respect to bacteriorhodopsin in these membranes. Deuterium labels incorporated in vivo into the sugar moieties of the major glycolipid were localized by neutron diffraction. The data suggest a role for specific aromatic residue-carbohydrate stacking interactions in the formation of the purple membrane crystalline patches. PMID:9660925

  11. Real-time observations of lithium battery reactions-operando neutron diffraction analysis during practical operation.

    PubMed

    Taminato, Sou; Yonemura, Masao; Shiotani, Shinya; Kamiyama, Takashi; Torii, Shuki; Nagao, Miki; Ishikawa, Yoshihisa; Mori, Kazuhiro; Fukunaga, Toshiharu; Onodera, Yohei; Naka, Takahiro; Morishima, Makoto; Ukyo, Yoshio; Adipranoto, Dyah Sulistyanintyas; Arai, Hajime; Uchimoto, Yoshiharu; Ogumi, Zempachi; Suzuki, Kota; Hirayama, Masaaki; Kanno, Ryoji

    2016-01-01

    Among the energy storage devices for applications in electric vehicles and stationary uses, lithium batteries typically deliver high performance. However, there is still a missing link between the engineering developments for large-scale batteries and the fundamental science of each battery component. Elucidating reaction mechanisms under practical operation is crucial for future battery technology. Here, we report an operando diffraction technique that uses high-intensity neutrons to detect reactions in non-equilibrium states driven by high-current operation in commercial 18650 cells. The experimental system comprising a time-of-flight diffractometer with automated Rietveld analysis was developed to collect and analyse diffraction data produced by sequential charge and discharge processes. Furthermore, observations under high current drain revealed inhomogeneous reactions, a structural relaxation after discharge, and a shift in the lithium concentration ranges with cycling in the electrode matrix. The technique provides valuable information required for the development of advanced batteries. PMID:27357605

  12. Real-time observations of lithium battery reactions—operando neutron diffraction analysis during practical operation

    PubMed Central

    Taminato, Sou; Yonemura, Masao; Shiotani, Shinya; Kamiyama, Takashi; Torii, Shuki; Nagao, Miki; Ishikawa, Yoshihisa; Mori, Kazuhiro; Fukunaga, Toshiharu; Onodera, Yohei; Naka, Takahiro; Morishima, Makoto; Ukyo, Yoshio; Adipranoto, Dyah Sulistyanintyas; Arai, Hajime; Uchimoto, Yoshiharu; Ogumi, Zempachi; Suzuki, Kota; Hirayama, Masaaki; Kanno, Ryoji

    2016-01-01

    Among the energy storage devices for applications in electric vehicles and stationary uses, lithium batteries typically deliver high performance. However, there is still a missing link between the engineering developments for large-scale batteries and the fundamental science of each battery component. Elucidating reaction mechanisms under practical operation is crucial for future battery technology. Here, we report an operando diffraction technique that uses high-intensity neutrons to detect reactions in non-equilibrium states driven by high-current operation in commercial 18650 cells. The experimental system comprising a time-of-flight diffractometer with automated Rietveld analysis was developed to collect and analyse diffraction data produced by sequential charge and discharge processes. Furthermore, observations under high current drain revealed inhomogeneous reactions, a structural relaxation after discharge, and a shift in the lithium concentration ranges with cycling in the electrode matrix. The technique provides valuable information required for the development of advanced batteries. PMID:27357605

  13. Pulsed neutron powder diffraction at high pressure by a capacity-increased sapphire anvil cell

    NASA Astrophysics Data System (ADS)

    Okuchi, Takuo; Yoshida, Masashi; Ohno, Yoshiki; Tomioka, Naotaka; Purevjav, Narangoo; Osakabe, Toyotaka; Harjo, Stefanus; Abe, Jun; Aizawa, Kazuya; Sasaki, Shigeo

    2013-12-01

    A new design of opposed anvil cell for time-of-flight neutron powder diffraction was prepared for use at advanced pulsed sources. A couple of single-crystal sapphire sphere anvils and a gasket of fully hardened Ti-Zr null alloy were combined to compress 35 mm3 of sample volume to 1 GPa and 11 mm3 to 2 GPa of pressures, respectively. A very high-quality powder diffraction pattern was obtained at Japan Proton Accelerator Research Complex for a controversial high pressure phase of methane hydrate. The counting statistics, resolution, absolute accuracy and d-value range of the pattern were all improved to be best suitable for precise structure refinement. The sample is optically accessible to be measured by Raman and fluorescence spectroscopy during and after compression. The current cell will be an alternative choice to study hydrogenous materials of complex structures that are stable at the described pressure regime.

  14. REVIEW ARTICLE: Determination of residual stresses in materials and industrial components by neutron diffraction

    NASA Astrophysics Data System (ADS)

    Albertini, Gianni; Bruno, Giovanni; Carradò, Adele; Fiori, Fabrizio; Rogante, Massimo; Rustichelli, Franco

    1999-03-01

    We present a review of the determination of residual stresses in materials and components of industrial interest by using the non-destructive technique of neutron diffraction. The fundamental aspects are discussed, together with a brief description of the experimental facilities. Several experimental results are then reported, particularly concerning applications to materials and components for power plants (CrMo steel, AISI304 stainless steel and 2.25Cr1Mo ferritic steel), aerospace and automotive technology (Al alloys, metal matrix composites, nickel superalloy gas-turbine components) and fusion-reactor technology (AISI316L for the first wall). A few thermomechanical treatments are considered, such as welding, cold-expanded holes, thermoelastic coupling and thermal and mechanical fatigue. Moreover, a few applications to general industrial problems are shown, namely brazed ceramic-steel components, coatings and fatigue-cracked samples. In some cases, experimental results are compared with numerical models or results from x-ray diffraction measurements.

  15. Neutron diffraction study of NiTi during compressive deformation and after shape-memory recovery

    SciTech Connect

    Dunand, D.C.; Mari, D.; Bourke, M.A.M.; Goldstone, J.A.

    1995-09-01

    Neutron diffraction measurements of internal elastic strains and texture were performed during compressive deformation of martensitic NiTi deforming by twinning. Rietveld refinement of the diffraction spectrum was performed in order to obtain lattice parameter variations and preferred orientation of martensitic variants. The elastic internal strains, are proportional to the externally applied stress but strongly dependent on crystallographic orientation. Plastic deformation by matrix twinning is consistent with type I (1-1-1) twinning, whereby (100) and (011) planes tend to align perpendicular and parallel to the stress axis, respectively. The preferred orientation ratio r according to the model by March and Dollase is proportional to the macroscopic plastic strain for (100) and (011) planes for loading, unloading and shape-memory recovery. To the best of our knowledge, this is the first in situ bulk measurement of reversible twinning in NiTi. Finally, shape-memory recovery results in a marked change of NiTi cell parameters.

  16. Structure of liquid equiatomic potassium--lead alloy: A neutron diffraction experiment

    SciTech Connect

    Saboungi, M.; Blomquist, R.; Volin, K.J.; Price, D.L.

    1987-08-15

    Neutron diffraction measurements have been performed on liquid equiatomic potassium--lead alloy at T = 870, 900, and 930 K to determine the influence of temperature on the structure. A well-defined first sharp diffraction peak (FSDP) at Q = 0.96 A/sup -1/, similar to that found in glassy materials, was obtained in the total structure factors S(Q) at the three temperatures. While the position of the peak remained unaffected by temperature changes, its magnitude decreased with increasing temperature. The other features of S(Q) were almost unaltered by temperature, as expected. The FSDP can be related to the presence of chemical bonds or clusters whose stability decreases with increasing temperature. A molecular model based on the random packing of K/sub 4/Pb/sub 4/ structural units is shown to give a remarkable correspondence with the measured structure factors.

  17. Residual stress measurements in a zircaloy-4 weld by neutron diffraction

    SciTech Connect

    Carr, D.G.; Ripley, M.I.; Holden, T.M.; Brown, D.W.; Vogel, S.C

    2004-08-16

    The macroscopic stress distribution across a Zircaloy-4 gas tungsten arc weld was measured by time-of-flight neutron diffraction at the SMARTS diffractometer at Los Alamos National Laboratory. The method enabled the measurement of strain for all the available reflections permitted by the rolling texture of the plate and the modified texture in the weld-metal and heat affected zone. A maximum longitudinal stress of 220 {+-} 40 MPa was observed in the weld compared with the 0.2% yield stress of 390 MPa of the plate. A maximum transverse stress of 60 {+-} 40 MPa was observed in the weld. Textures were measured at the HIPPO diffractometer.

  18. In situ observation of ErD2 formation during D-2 loading via neutron diffraction

    SciTech Connect

    Browning, Jim; Snow, Clark; Wixom, Ryan R; Llobet, Anna; Rodriguez, Mark

    2011-01-01

    In an effort to better understand the structural changes occurring during hydrogen loading of erbium target materials, we have performed in situ D{sub 2} loading of erbium metal (powder) at temperature (450 C) with simultaneous neutron diffraction analysis. This experiment tracked the conversion of Er metal to the {alpha} erbium deuteride (solid-solution) phase and then into the {beta} (fluorite) phase. Complete conversion to ErD{sub 2.0} was accomplished at 10 Torr D{sub 2} pressure with deuterium fully occupying the tetrahedral sites in the fluorite lattice.

  19. Anomalous structural feature of LiNbO{sub 3} observed using neutron diffraction

    SciTech Connect

    Fernandez-Ruiz, R.; Bermudez, V.; Martin y Marero, D.

    2005-11-01

    An anomalous structural effect has been observed and analyzed on LiNbO{sub 3} at low temperature by neutron-diffraction experiments. Two minima in the unit-cell volume at 55 and 100 K related with maxima and minima in the volume vibrational isotropic factors of Li and Nb atoms, respectively, and a change in the curve slope of the spontaneous stress at 55 K have been identified. This fact, together with the shortening in distance of the Li and O layers at 55 K, has been related with variations in the Ps factor through the secondary pyroelectric effect.

  20. Structural Study of Liquid Se-Te Alloys by Neutron Diffraction

    NASA Astrophysics Data System (ADS)

    Takeda, Shin'ichi; Tamaki, Shigeru; Waseda, Yoshio

    1986-12-01

    The neutron diffraction study of liquid Se-Te system has been carried out to reveal the origin of characteristic temperature dependence of various properties related to the structural order in atomic scale. The temperature dependence of measured structural functions of liquid SexTe1-x system could be explained by a gradual transition from two-fold coordinated component (non-metallic) to the three-fold coordinated one (metallic). The partial structure factors of these two-fold and three-fold coordinations are separated with the help of the thermodynamic data. A configurational model satisfying these situations is also presented.

  1. Neutron powder diffraction studies as a function of temperature of structure II hydrate formed from propane

    USGS Publications Warehouse

    Rawn, C.J.; Rondinone, A.J.; Chakoumakos, B.C.; Circone, S.; Stern, L.A.; Kirby, S.H.; Ishii, Y.

    2003-01-01

    Neutron powder diffraction data confirm that hydrate samples synthesized with propane crystallize as structure type II hydrate. The structure has been modeled using rigid-body constraints to describe C3H8 molecules located in the eight larger polyhedral cavities of a deuterated host lattice. Data were collected at 12, 40, 100, 130, 160, 190, 220, and 250 K and used to calculate the thermal expansivity from the temperature dependence of the lattice parameters. The data collected allowed for full structural refinement of atomic coordinates and the atomic-displacement parameters.

  2. The Crystal Structure of Thorium and Zirconium Dihydrides by X-ray and Neutron Diffraction

    DOE R&D Accomplishments Database

    Rundle, R.E.; Shull, C.G.; Wollan, E.O.

    1951-04-20

    Thorium forms a tetragonal lower hydride of composition ThH{sub 2}. The hydrides ThH{sub 2}, ThD{sub 2}, and ZrD{sub 2} have been studied by neutron diffraction in order that hydrogen positions could be determined. The hydrides are isomorphous, and have a deformed fluorite structure. Metal-hydrogen distances in thorium hydride are unusually large, as in UH{sub 3}. Thorium and zirconium scattering amplitudes and a revised scattering amplitude for deuterium are reported.

  3. Structure and dynamics of hydrogen molecules in the novel clathrate hydrate by high pressure neutron diffraction.

    PubMed

    Lokshin, Konstantin A; Zhao, Yusheng; He, Duanwei; Mao, Wendy L; Mao, Ho-Kwang; Hemley, Russell J; Lobanov, Maxim V; Greenblatt, Martha

    2004-09-17

    The D2 clathrate hydrate crystal structure was determined as a function of temperature and pressure by neutron diffraction for the first time. The hydrogen occupancy in the (32+X)H2.136H(2)O, x=0-16 clathrate can be reversibly varied by changing the large (hexakaidecahedral) cage occupancy between two and four molecules, while remaining single occupancy of the small (dodecahedral) cage. Above 130-160 K, the guest D2 molecules were found in the delocalized state, rotating around the centers of the cages. Decrease of temperature results in rotation freezing followed by a complete localization below 50 K. PMID:15447276

  4. Neutron diffraction method for stored energy measurement in interstitial free steel

    SciTech Connect

    Rajmohan, N.; Hayakawa, Y.; Szpunar, J.A.; Root, J.H.

    1997-06-01

    Part of the energy acquired by polycrystalline metals during plastic deformation is stored in the form of dislocations and other crystal defects. A method is described for the measurement of the orientation dependence of the stored energy of cold work, using neutron diffraction line broadening. To illustrate the method, the measured stored energy values for 80% cold rolled interstitial free (IF) steel are compared with the stored energy in a stress relieved specimen. The correlation between the Taylor factor and the stored energy for an 80% cold rolled specimen is discussed.

  5. Molecular-dynamics modelling and neutron diffraction study of the site disorder in air clathrate hydrates

    SciTech Connect

    Chazallon, Bertrand; Klapproth, Alice; Kuhs, Werner F.

    1999-06-15

    We present the results of MD-simulation runs with subsequent quenches for clathrate hydrates using SPC water in order to model properly the crystallographic site disorder of the guest molecules in the water cages. A procedure is described to transform the results of the quench (symmetry P1) into the proper space-time averaged space group (Fd3-bar m) of the clathrate hydrate. The resulting disorder models are compared with the outcome of crystallographic structure refinements (R-factors, Fourier maps) from our neutron powder diffraction data. A correct description of the disorder is important for a reliable determination of the pressure-dependent cage filling.

  6. Non-contact measurement of the stress within granular materials via neutron diffraction

    NASA Astrophysics Data System (ADS)

    Wensrich, C. M.; Kisi, E. H.; Luzin, V.; Kirstein, O.

    2013-06-01

    For some time neutron diffraction approaches have provided the ability to look within solid materials in order to make accurate measurements of stress and strain. More recently this technique has been applied to granular materials with some very promising results. Measurements of this type provide detailed information on the distribution of the full triaxial stress state at all points within a sample; something that is not yet achievable using any other method. In this paper we outline the basic principles behind the method and provide an example of the type of data that it can provide.

  7. The chemical reactivity and structure of collagen studied by neutron diffraction

    SciTech Connect

    Wess, T.J.; Wess, L.; Miller, A.

    1994-12-31

    The chemical reactivity of collagen can be studied using neutron diffraction (a non-destructive technique), for certain reaction types. Collagen contains a number of lysine and hydroxylysine side chains that can react with aldehydes and ketones, or these side chains can themselves be converted to aldehydes by lysyl oxidase. The reactivity of these groups not only has an important role in the maintenance of mechanical strength in collagen fibrils, but can also manifest pathologically in the cases of aging, diabetes (reactivity with a variety of sugars) and alcoholism (reactivity with acetaldehyde). The reactivity of reducing groups with collagen can be studied by neutron diffraction, since the crosslink formed in the adduction process is initially of a Schiff base or keto-imine nature. The nature of this crosslink allows it to be deuterated, and the position of this relatively heavy scattering atom can be used in a process of phase determination by multiple isomorphous replacement. This process was used to study the following: the position of natural crosslinks in collagen; the position of adducts in tendon from diabetic rats in vivo and the in vitro position of acetaidehyde adducts in tendon.

  8. Existence of ferroelectric ice on planets—A neutron diffraction study

    NASA Astrophysics Data System (ADS)

    Fukazawa, Hiroshi; Hoshikawa, Akinori; Chakoumakos, Bryan C.; Fernandez-Baca, Jaime A.

    2009-02-01

    From neutron powder-diffraction experiments, we have studied the growth process of ferroelectric ice XI (eleven) with deuteron-ordered arrangements. We measured time-resolved neutron diffraction of 0.001-M KOD-doped D2O ice. We observed the growth of ice XI at 72-74 K. The mass fraction f (the ratio of mass of ice XI to that of the doped ice) linearly increased with time for about 2 days. The de-transformed ice Ih, obtained after warming above the transition temperature of 76 K, retransformed to ice XI at 66 K. The observed increase of f with time is in good agreement with the nucleation process of the ordering and the constant growth of the ordered domain. A large fraction of ice Ih sample doped with sodium hydroxide changed to ice XI at 68 K. The results suggest that large quantities of ice on cold icy bodies in our solar system are able to transform to ice XI, which may be detectable by space telescope and planetary exploration.

  9. Unraveling cyclic deformation mechanisms of a rolled magnesium alloy using in situ neutron diffraction

    SciTech Connect

    Wu, Wei; An, Ke; Liaw, Peter K.

    2014-12-23

    In the current study, the deformation mechanisms of a rolled magnesium alloy were investigated under cyclic loading using real-time in situ neutron diffraction under a continuous-loading condition. The relationship between the macroscopic cyclic deformation behavior and the microscopic response at the grain level was established. The neutron diffraction results indicate that more and more grains are involved in the twinning and detwinning deformation process with the increase of fatigue cycles. The residual twins appear in the early fatigue life, which is responsible for the cyclic hardening behavior. The asymmetric shape of the hysteresis loop is attributed to the early exhaustion of the detwinning process during compression, which leads to the activation of dislocation slips and rapid strain-hardening. The critical resolved shear stress for the activation of tensile twinning closely depends on the residual strain developed during cyclic loading. In the cycle before the sample fractured, the dislocation slips became active in tension, although the sample was not fully twinned. The increased dislocation density leads to the rise of the stress concentration at weak spots, which is believed to be the main reason for the fatigue failure. Furthermore, the deformation history greatly influences the deformation mechanisms of hexagonal-close-packed-structured magnesium alloy during cyclic loading.

  10. Cage occupancies in the high pressure structure H methane hydrate: A neutron diffraction study

    SciTech Connect

    Tulk, Christopher A; Klug, Dennis D; Moreira Dos Santos, Antonio F; Karotsis, Georgios; Guthrie, Malcolm; Molaison, Jamie J; Pradhan, Neelam

    2012-01-01

    A neutron diffraction study was performed on the CD{sub 4}: D{sub 2}O structure H clathrate hydrate to refine its CD{sub 4} fractional cage occupancies. Samples of ice VII and hexagonal (sH) methane hydrate were produced in a Paris-Edinburgh press and in situ neutron diffraction data collected. The data were analyzed with the Rietveld method and yielded average cage occupancies of 3.1 CD{sub 4} molecules in the large 20-hedron (5{sup 12}6{sup 8}) cages of the hydrate unit cell. Each of the pentagonal dodecahedron (5{sup 12}) and 12-hedron (4{sup 3}5{sup 6}6{sup 3}) cages in the sH unit cell are occupied with on average 0.89 and 0.90 CD{sub 4} molecules, respectively. This experiment avoided the co-formation of Ice VI and sH hydrate, this mixture is more difficult to analyze due to the proclivity of ice VI to form highly textured crystals, and overlapping Bragg peaks of the two phases. These results provide essential information for the refinement of intermolecular potential parameters for the water methane hydrophobic interaction in clathrate hydrates and related dense structures.

  11. Pressure dependence of the magnetic order in CrAs: a neutron diffraction investigation

    DOE PAGESBeta

    Keller, L.; White, J. S.; Babkevich, P.; Susner, Michael A.; Sims, Zachary C; Safa-Sefat, Athena; Ronnow, H. M.; Ruegg, Ch.

    2015-01-29

    The suppression of magnetic order with pressure concomitant with the appearance of pressure-induced superconductivity was recently discovered in CrAs. Here we present a neutron diffraction study of the pressure evolution of the helimagnetic ground-state towards and in the vicinity of the superconducting phase. Neutron diffraction on polycrystalline CrAs was employed from zero pressure to 0.65 GPa and at various temperatures. The helimagnetic long-range order is sustained under pressure and the magnetic propagation vector does not show any considerable change. The average ordered magnetic moment is reduced from 1.73(2) μB at ambient pressure to 0.4(1) μB close to the critical pressuremore » Pc ≈ 0.7 GPa, at which magnetic order is completely suppressed. The width of the magnetic Bragg peaks strongly depends on temperature and pressure, showing a maximum in the region of the onset of superconductivity. In conclusion, we interpret this as associated with competing ground-states in the vicinity of the superconducting phase.« less

  12. In situ synthesis and characterization of uranium carbide using high temperature neutron diffraction

    NASA Astrophysics Data System (ADS)

    Reiche, H. Matthias; Vogel, Sven C.; Tang, Ming

    2016-04-01

    We investigated the formation of UCx from UO2+x and graphite in situ using neutron diffraction at high temperatures with particular focus on resolving the conflicting reports on the crystal structure of non-quenchable cubic UC2. The agents were UO2 nanopowder, which closely imitates nano grains observed in spent reactor fuels, and graphite powder. In situ neutron diffraction revealed the onset of the UO2 + 2C → UC + CO2 reaction at 1440 °C, with its completion at 1500 °C. Upon further heating, carbon diffuses into the uranium carbide forming C2 groups at the octahedral sites. This resulting high temperature cubic UC2 phase is similar to the NaCl-type structure as proposed by Bowman et al. Our novel experimental data provide insights into the mechanism and kinetics of formation of UC as well as characteristics of the high temperature cubic UC2 phase which agree with proposed rotational rehybridization found from simulations by Wen et al.

  13. The hydration structure of a Z-DNA hexameric duplex determined by a neutron diffraction technique.

    PubMed

    Chatake, Toshiyuki; Tanaka, Ichiro; Umino, Hisao; Arai, Shigeki; Niimura, Nobuo

    2005-08-01

    In order to reveal the hydration structure of Z-DNA, a neutron diffraction study has been carried out at 1.8 A resolution on a Z-DNA hexamer d(CGCGCG). Neutron diffraction data were collected with the BIX-3 single-crystal diffractometer at the JRR-3 reactor in the Japan Atomic Energy Research Institute (JAERI) using a large crystal (1.6 mm3) obtained from D2O solution. It has been found that almost all the guanine bases have participated in H/D exchange at the C8-H8 group, consistent with the acidic nature of this bond. 44 water molecules were found in the nuclear density maps, of which 29 showed the entire contour of all three atoms (D-O-D). The remaining 15 water molecules had a simple spherical shape, indicating that they were rotationally disordered. An interesting relationship was found between the orientational disorder of the water molecules and their locations. Almost all water molecules in the minor groove were well ordered in the crystal, while 40% of the water molecules in the major groove were rotationally disordered. The hydrogen-bonding networks in the hydration shells have two structural aspects: flexibility and regularity. PMID:16041074

  14. Magnetic Structure of Goethite α-FeOOH: A Neutron Diffraction Study

    NASA Astrophysics Data System (ADS)

    Zepeda-Alarcon, E.; Nakotte, H.; Vogel, S. C.; Wenk, H.

    2013-12-01

    Goethite (α-FeOOH) is found in diverse natural ecosystems, it is by far the most common oxyhydroxide in terrestrial soils, sediments and clays and an important mineral in the biogeochemical cycle of iron at the Earth's surface. Neutron diffraction studies have found that the iron magnetic moments are collinear in a two sublattice antiferromagnetic structure, aligned parallel to the c axis in space group Pbnm (Forsyth et. al. 1968). However, goethite shows superparamagnetic behavior and also a weak ferromagnetic component that has been attributed to the presence of lattice distortions. It is thought that these changes in magnetic ordering could be due to a 13° canting of the magnetic moment with respect to the c-axis, which enables the flipping of the spins due to small perturbations in the lattice (Coey et. al. 1995). In this study we used neutron diffraction at HIPPO and NPDF beamlines at LANSCE of Los Alamos National Laboratory on a powder of natural goethite provided by A. Gualtieri. The nuclear and magnetic structures were determined by means of a Rietveld refinement with GSAS and it was found that the spins of the iron atoms are aligned parallel to the c-axis, with no evidence of spin canting. The net magnetic moment is lower than what has previously been found. These results provide further insight into the magnetic ordering of this mineral and can be important in understanding the physical processes responsible for goethite's intriguing magnetic behavior.

  15. Unraveling cyclic deformation mechanisms of a rolled magnesium alloy using in situ neutron diffraction

    DOE PAGESBeta

    Wu, Wei; An, Ke; Liaw, Peter K.

    2014-12-23

    In the current study, the deformation mechanisms of a rolled magnesium alloy were investigated under cyclic loading using real-time in situ neutron diffraction under a continuous-loading condition. The relationship between the macroscopic cyclic deformation behavior and the microscopic response at the grain level was established. The neutron diffraction results indicate that more and more grains are involved in the twinning and detwinning deformation process with the increase of fatigue cycles. The residual twins appear in the early fatigue life, which is responsible for the cyclic hardening behavior. The asymmetric shape of the hysteresis loop is attributed to the early exhaustionmore » of the detwinning process during compression, which leads to the activation of dislocation slips and rapid strain-hardening. The critical resolved shear stress for the activation of tensile twinning closely depends on the residual strain developed during cyclic loading. In the cycle before the sample fractured, the dislocation slips became active in tension, although the sample was not fully twinned. The increased dislocation density leads to the rise of the stress concentration at weak spots, which is believed to be the main reason for the fatigue failure. Furthermore, the deformation history greatly influences the deformation mechanisms of hexagonal-close-packed-structured magnesium alloy during cyclic loading.« less

  16. Pressure dependence of the magnetic order in CrAs: a neutron diffraction investigation

    SciTech Connect

    Keller, L.; White, J. S.; Babkevich, P.; Susner, Michael A.; Sims, Zachary C; Safa-Sefat, Athena; Ronnow, H. M.; Ruegg, Ch.

    2015-01-29

    The suppression of magnetic order with pressure concomitant with the appearance of pressure-induced superconductivity was recently discovered in CrAs. Here we present a neutron diffraction study of the pressure evolution of the helimagnetic ground-state towards and in the vicinity of the superconducting phase. Neutron diffraction on polycrystalline CrAs was employed from zero pressure to 0.65 GPa and at various temperatures. The helimagnetic long-range order is sustained under pressure and the magnetic propagation vector does not show any considerable change. The average ordered magnetic moment is reduced from 1.73(2) μB at ambient pressure to 0.4(1) μB close to the critical pressure Pc ≈ 0.7 GPa, at which magnetic order is completely suppressed. The width of the magnetic Bragg peaks strongly depends on temperature and pressure, showing a maximum in the region of the onset of superconductivity. In conclusion, we interpret this as associated with competing ground-states in the vicinity of the superconducting phase.

  17. Malayaite ceramic pigments: A combined optical spectroscopy and neutron/X-ray diffraction study

    SciTech Connect

    Cruciani, Giuseppe; Dondi, Michele; Ardit, Matteo; Lyubenova, Teodora Stoyanova; Carda, Juan B.; Matteucci, Francesco; Costa, Anna L.

    2009-08-05

    Ceramic pigments based on the Cr-doped malayaite structure were synthesized by solid state reaction and characterized by optical spectroscopy and combined X-ray and neutron powder diffraction in order to elucidate the still unclear chromium substitution mechanisms. The results show that coloration is actually due to simultaneous occurrence of Cr{sup 4+} and Cr{sup 3+} ions in the crystal lattice. Spectroscopy data confirm that Cr{sup 4+} is replacing Sn{sup 4+} in the octahedral site and, in minor amount, Si{sup 4+} in the tetrahedral site. In addition, neutron powder diffraction data suggest that Cr{sup 3+} substitution for octahedral Sn{sup 4+} is charge balanced by the formation of oxygen vacancies with no preference over the different oxygen sites. Upon incorporation of Cr ion, the SnO{sub 6} octahedra exhibit an off-centre displacement of central cation which in turn induces a rearrangement of both the octahedral and tetrahedral coordination shells.

  18. Preparation and neutron diffraction study of polycrystalline Cu-Zn-Fe materials

    NASA Astrophysics Data System (ADS)

    Darul, J.; Nowicki, W.

    2009-10-01

    Polycrystalline oxides Cu1-xZnxFe2O4 (0.0≤x≤0.05) have been successfully prepared by a simple combustion method using citrate-nitrate precursors. The nature of structural transition in inverse spinels and ferrimagnetic behavior of the materials have been investigated by the neutron diffraction technique. At room temperature neutron diffraction study confirms the presence of a single-phase structure, where tetragonal unit cell with c/a>1 is observed. In these distorted spinel ferrites it is found that tetragonal → cubic transformation is attributed to the decrease of the concentration of Jahn-Teller ions Cu2+ (d9) in the host structure at the octahedral sites as a result of zinc substitution. The introduction of non-magnetic ion in place of Cu2+ in the spinel unit cell results in the reduction of intersublattice contributions, this in turn decreases temperature of the magnetic ordering (Curie point) in these diluted ferrimagnets.

  19. Neutron diffraction study of water freezing on aircraft engine combustor soot.

    PubMed

    Tishkova, V; Demirdjian, B; Ferry, D; Johnson, M

    2011-12-14

    The study of the formation of condensation trails and cirrus clouds on aircraft emitted soot particles is important because of its possible effects on climate. In the present work we studied the freezing of water on aircraft engine combustor (AEC) soot particles under conditions of pressure and temperature similar to the upper troposphere. The microstructure of the AEC soot was found to be heterogeneous containing both primary particles of soot and metallic impurities (Fe, Cu, and Al). We also observed various surface functional groups such as oxygen-containing groups, including sulfate ions, that can act as active sites for water adsorption. Here we studied the formation of ice on the AEC soot particles by using neutron diffraction. We found that for low amount of adsorbed water, cooling even up to 215 K did not lead to the formation of hexagonal ice. Whereas, larger amount of adsorbed water led to the coexistence of liquid water (or amorphous ice) and hexagonal ice (I(h)); 60% of the adsorbed water was in the form of ice I(h) at 255 K. Annealing of the system led to the improvement of the crystal quality of hexagonal ice crystals as demonstrated from neutron diffraction. PMID:21996755

  20. Dynamical Theory of Neutron Diffraction for Perfect Crystals with and Without Strain Gradients

    NASA Astrophysics Data System (ADS)

    Maheswaran, Saravanamuthu

    The dynamical theory of neutron diffraction is studied for perfect crystals and crystals with strain gradients. In the case of parallel-sided slab crystals, it is customary to distinguish the Bragg case where the beam enters and exits on the same side of the slab and the Laue case where the beam enters on one side and exits on the other. The symmetric Bragg case has the angle of incidence equal to the angle of diffraction with respect to the surface, that is the scattering vector is perpendicular to the surface. In the symmetric Laue case the scattering vector is parallel to the surface. In extreme cases either the incoming or exiting beam is close to being parallel to the surface. Schrodinger's equation for the perfect slab crystal with a periodic potential is solved by two methods which can give similar results. In the first method, which is known as the eikonal approach, a quartic dispersion relation is obtained and solved for all possible internal wave vectors. A given incident plane wave generates four pairs of internal waves. Each pair is coupled together by the periodic potential. Four waves, in addition to the incident wave, appear outside the crystal as a result of the interaction with the crystal slab. All the unknown internal and external amplitudes are found from the boundary conditions. In non-extreme cases, two pairs of internal waves suffice to describe the propagation of neutrons in the crystal. In the second approach, commonly referred to as the Takagi-Taupin method, one assumes that the wave amplitudes are position dependent solutions of coupled differential equations. We have measured the dependence of the diffracted beam intensity as a function of thickness of Si wafers and found good agreement with the theory. The theory has applications in the design of elements for neutron optics, particularly monochromating and analyzing crystals. In the extreme cases, all four pairs of internal waves are considered. It is shown that three pairs are

  1. Probing the Hydrogen Sublattice of FeHx with High-Pressure Neutron Diffraction

    NASA Astrophysics Data System (ADS)

    Murphy, C. A.; Guthrie, M.; Boehler, R.; Somayazulu, M.; Fei, Y.; Molaison, J.; dos Santos, A. M.

    2013-12-01

    The combination of seismic, cosmochemical, and mineral physics observations have revealed that Earth's iron-rich core must contain some light elements, such as hydrogen, carbon, oxygen, silicon, and/or sulfur. Therefore, understanding the influence of these light elements on the structural, thermoelastic, and electronic properties of iron is important for constraining the composition of this remote layer of the Earth and, in turn, providing constraints on planetary differentiation and core formation models. The high-pressure structural and magnetic properties of iron hydride (FeHx) have previously been studied using synchrotron x-ray diffraction and Mössbauer spectroscopy. Such experiments revealed that the double hexagonal close-packed (dhcp) structure of FeHx is stable above a pressure of ~5 GPa and up to at least 80 GPa at 300 K [1]. In addition, dhcp-FeHx is ferromagnetic at low-pressures, but undergoes a magnetic collapse around 22 GPa [2]. X-ray experiments provide valuable insight into the properties of FeHx, but such techniques are largely sensitive to the iron component because it is difficult to detect the hydrogen sublattice with x-rays. Therefore, neutron diffraction has been used to investigate metastable FeHx, which is formed by quenching the high-pressure phase to liquid nitrogen temperatures and probing the sample at ambient pressure [3]. However, such neutron experiments have been limited to formation pressures below 10 GPa, and cannot be performed at ambient temperature. Here we present the first in-situ investigation of FeHx at 300 K using high-pressure neutron diffraction experiments performed at the Spallation Neutrons and Pressure Diffractometer (SNAP) instrument at the Spallation Neutron Source, Oak Ridge National Laboratory. In order to achieve pressures of ~50 GPa, we loaded iron samples with a hydrogen gas pressure medium into newly designed large-volume panoramic diamond-anvil cells (DACs) for neutron diffraction experiments [4; 5]. We

  2. A revised structure and hydrogen bonding system in cellulose II from a neutron fiber diffraction analysis

    SciTech Connect

    Langan, P.; Nishiyama, Y.; Chanzy, H.

    1999-11-03

    The crystal and molecular structure and hydrogen bonding system in cellulose II have been revised using new neutron diffraction data extending to 1.2 {angstrom} resolution collected from two highly crystalline fiber samples of mercerized flax. Mercerization was achieved in NaOH/H{sub 2}O for one sample and in NaOD/D{sub 2}O for the other, corresponding to the labile hydroxymethyl moieties being hydrogenated and deuterated, respectively. Fourier difference maps were calculated in which neutron difference amplitudes were combined with phases calculated from two revised X-ray models of cellulose II. The revised phasing models were determined by refinement against the X-ray data set of Kolpak and Blackwell, using the LALS methodology. Both models have two antiparallel chains organized in a P2{sub 1} space group and unit cell parameters: a = 8.01 {angstrom}, b = 9.04 {angstrom}, c = 10.36 {angstrom}, and {gamma} = 117.1{degree}. One has equivalent backbone conformations for both chains but different conformations for the hydroxymethyl moieties: gt for the origin chain and tg for the center chain. The second model based on the recent crystal structures of cellotetraose, has different conformations for the two chains but nearly equivalent conformations for the hydroxymethyl moieties. On the basis of the X-ray data alone, the models could not be differentiated. From the neutron Fourier difference maps, possible labile hydrogen atom positions were identified for each model and refined using LALS. The second model is significantly different from previous proposals based on the crystal structures of cellotetraose, MD simulations of cellulose II, and any potential hydrogen-bonding network in the structure of cellulose II determined in earlier X-ray fiber diffraction studies. The exact localization of the labile hydrogen atoms involved in this bonding, together with their donor and acceptor characteristics, is presented and discussed. This study provides, for the first time

  3. Texture and anisotropy analysis of a laminated lower crust: a neutron diffraction study of felsic granulites

    NASA Astrophysics Data System (ADS)

    Benitez Perez, J.; Gomez Barreiro, J.; Martinez-Catalan, J. R.; Castiñeiras Garcia, P.; Vogel, S. C.; Wenk, H.; Alvarez Valero, A.

    2013-12-01

    Quantitative fabric analyses of high-P and high-T tectonites were done with HIPPO, a Time-Of-Flight (TOF) neutron diffractometer at Los Alamos National Lab. Samples were collected in the Sobrado unit (NW Spain), a tectonic stack of highly deformed slices of metabasites, paragneisses and ultramafic rocks. Metamorphism ranges from granulites on top, to eclogites at the bottom of the unit. The ensemble represents and excellent example of laminated lower crust. The alternation of mechanically contrasted lithologies and/or the development of crystal preferred orientation might result into anisotropy. We explore the contribution of crystallographic preferred orientation or texture to the seismic anisotropy of the lower crust. Since strain partitioning occurred between mechanically strong and weak lithologies, a higher crystal preferred orientation is expected along the weak levels: the metasediments. TOF neutron diffraction experiments were conducted in HIPPO (LANSCE) with high-P and high-T mylonitic felsic paragneisses. Quantitative texture analysis of neutron data was accomplished by using the Rietveld method, with E-WIMW algorithm, implemented in the program package MAUD (Material Analysis Using Diffraction; Lutterotti, 1999). The orientation distribution function (ODF) for each mineral was calculated in MAUD and then processed in BEARTEX (Wenk et al. 1998). Selected pole figures were plotted for major components, quartz, plagioclase and biotite (first setting in monoclinic crystals). Texture patterns are compatible with non-coaxial progressive deformation and discussed accordingly in terms of dislocation activity. Besides, seismic waves velocities were computed from the texture data in BEARTEX. Calculated velocities and anisotropy were based on ODF, volume fraction of each mineral and their single-crystal elastic constant. Kinematic and mechanical implications are discussed in terms of the regional geology. The correlation of texture, mineral composition and seismic

  4. Neutron diffraction studies of a four-coordinated hydride in near square-planar geometry.

    PubMed

    Liao, Jian-Hong; Dhayal, Rajendra Singh; Wang, Xiaoping; Kahlal, Samia; Saillard, Jean-Yves; Liu, C W

    2014-10-20

    The structure of a nanospheric polyhydrido copper cluster, [Cu20(H)11{S2P(O(i)Pr)2}9], was determined by single-crystal neutron diffraction. The Cu20 cluster consists of an elongated triangular orthobicupola constructed from 18 Cu atoms that encapsulate a [Cu2H5](3-) ion with an exceptionally short Cu-Cu distance. The 11 hydrides in the cluster display three different coordination modes to the Cu atoms: six μ3-hydrides in a pyramidal geometry, two μ4-hydrides in a tetrahedral cavity, and three μ4-hydrides in an unprecedented near square-planar geometry. The neutron data set was collected for 7 days on a small crystal with dimensions of 0.20 mm × 0.50 mm × 0.65 mm using the Spallation Neutron Source TOPAZ single-crystal time-of-flight Laue diffractometer at Oak Ridge National Laboratory. The final R-factor was 8.63% for 16,014 reflections. PMID:25290745

  5. Neutron diffraction studies of a four-coordinated hydride in near square-planar geometry

    DOE PAGESBeta

    Liao, Jian -Hong; Dhayal, Rajendra Singh; Wang, Xiaoping; Kahlal, Samia; Saillard, Jean -Yves; Liu, C. W.

    2014-10-07

    The structure of a nanospheric polyhydrido copper cluster, [Cu20(H)11{S2P(OiPr)2}9], was determined by single-crystal neutron diffraction. Cu20 cluster consists of an elongated triangular orthobicupola constructed from 18 Cu atoms that encapsulate a [Cu2H5}3- ion in the center with an exceptionally short Cu-Cu distance. The eleven hydrides in the cluster display three different coordination modes to the Cu atoms: Six μ3-hydrides in pyramidal geometry, two μ4-hydrides in tetrahedral cavity, and three μ4-hydrides in an unprecedented near square-planar geometry. The neutron data set was collected on a small crystal of the size 0.20 mm x 0.50 mm x 0.65 mm for seven daysmore » using the Spallation Neutron Source TOPAZ single-crystal time-of-flight Laue diffractometer at the Oak Ridge National Laboratory. Furthermore, the final R-factor is 8.64% for 16014 reflections.« less

  6. Neutron diffraction studies of a four-coordinated hydride in near square-planar geometry

    SciTech Connect

    Liao, Jian -Hong; Dhayal, Rajendra Singh; Wang, Xiaoping; Kahlal, Samia; Saillard, Jean -Yves; Liu, C. W.

    2014-10-07

    The structure of a nanospheric polyhydrido copper cluster, [Cu20(H)11{S2P(OiPr)2}9], was determined by single-crystal neutron diffraction. Cu20 cluster consists of an elongated triangular orthobicupola constructed from 18 Cu atoms that encapsulate a [Cu2H5}3- ion in the center with an exceptionally short Cu-Cu distance. The eleven hydrides in the cluster display three different coordination modes to the Cu atoms: Six μ3-hydrides in pyramidal geometry, two μ4-hydrides in tetrahedral cavity, and three μ4-hydrides in an unprecedented near square-planar geometry. The neutron data set was collected on a small crystal of the size 0.20 mm x 0.50 mm x 0.65 mm for seven days using the Spallation Neutron Source TOPAZ single-crystal time-of-flight Laue diffractometer at the Oak Ridge National Laboratory. Furthermore, the final R-factor is 8.64% for 16014 reflections.

  7. A Rietveld refinement method for angular- and wavelength-dispersive neutron time-of-flight powder diffraction data

    PubMed Central

    Jacobs, Philipp; Houben, Andreas; Schweika, Werner; Tchougréeff, Andrei L.; Dronskowski, Richard

    2015-01-01

    This paper introduces a two-dimensional extension of the well established Rietveld refinement method for modeling neutron time-of-flight powder diffraction data. The novel approach takes into account the variation of two parameters, diffraction angle 2θ and wavelength λ, to optimally adapt to the varying resolution function in diffraction experiments. By doing so, the refinement against angular- and wavelength-dispersive data gets rid of common data-reduction steps and also avoids the loss of high-resolution information typically introduced by integration. In a case study using a numerically simulated diffraction pattern of Rh0.81Fe3.19N taking into account the layout of the future POWTEX instrument, the profile function as parameterized in 2θ and λ is extracted. As a proof-of-concept, the resulting instrument parameterization is then utilized to perform a typical refinement of the angular- and wavelength-dispersive diffraction pattern of CuNCN, yielding excellent residuals within feasible computational efforts. Another proof-of-concept is carried out by applying the same approach to a real neutron diffraction data set of CuNCN obtained from the POWGEN instrument at the Spallation Neutron Source in Oak Ridge. The paper highlights the general importance of the novel approach for data analysis at neutron time-of-flight diffractometers and its possible inclusion within existing Rietveld software packages. PMID:26664340

  8. Neutron powder-diffraction studies of lithium, sodium, and potassium metal

    SciTech Connect

    Berliner, R.; Fajen, O. ); Smith, H.G. ); Hitterman, R.L. )

    1989-12-15

    Neutron powder-diffraction measurements have been performed on polycrystalline lithium and sodium specimens at 80 and 20 K and on potassium metal at 80 and 10 K. Lithium is bcc (body-centered cubic) at room temperature and undergoes a martensitic structural phase transformation to a 9{ital R} (samarium-type) form at low temperature. This experiment presents evidence that the 9{ital R} phase is present in sodium as well as lithium. No evidence of a transformation was observed in potassium at 10 K. The diffraction lines for both lithium and sodium after the phase transformation exhibit position shifts and broadening characteristic of stacking-fault defects. The line shifts, line broadening, and transformed fraction for the low-temperature phase of lithium and sodium metal are reported. The diffraction peak position shifts are, however, different from those predicted for deformation-type stacking faults alone. Qualitative agreement of the experimental results with stacking-fault-model calculations was obtained for a double-twin'' type of layer defect.

  9. Measuring strain and stress distributions along rebar embedded in concrete using time-of-flight neutron diffraction

    NASA Astrophysics Data System (ADS)

    Suzuki, H.; Kusunoki, K.; Hatanaka, Y.; Mukai, T.; Tasai, A.; Kanematsu, M.; Kabayama, K.; Harjo, S.

    2014-02-01

    In modern society, architectural and civil engineering structures such as reinforced concrete buildings require high seismic performance to minimize the ‘megarisk’ exposed from urban earthquake hazards. In the reinforced concrete structures, the bond resistance between rebar and concrete is one important parameter for discussing its performance and it has been typically evaluated by measuring the strain distribution along the embedded rebar. Here, we present in-situ strain and stress measurements for the rebar in reinforced concrete using time-of-flight neutron diffraction as a novel alternative technique to typical strain gauges. It was demonstrated in this study that the three-dimensional deformation behavior of the embedded rebar in normal-strength concrete, cured in air, can be accurately measured under pull-out loading using time-of-flight neutron diffraction. Wider applications of neutron diffraction in the structural engineering field are expected for advanced understanding of actual phenomena on reinforced concrete structures.

  10. Neutron diffraction studies of molecular liquids using the new detector system of the PSD diffractometer at the Budapest Research Reactor

    NASA Astrophysics Data System (ADS)

    Temleitner, László; Mészáros, György; Pusztai, László; Sváb, Erzsébet

    2004-07-01

    Neutron diffraction experiments on several molecular liquids have been performed using the PSD neutron diffractometer (Budapest Research Reactor) which has recently been equipped with a new detector system. Raw data are presented for liquid carbon-tetrachloride which served as a `calibration standard' for molecular liquids. Detailed comparison with data taken on the previous detector system, for several stages of the correction/evaluation process, validates results obtained by using the new detectors.

  11. Thermal neutron diffraction determination of the magnetic structure of EuCu{sub 2}Ge{sub 2}

    SciTech Connect

    Rowan-Weetaluktuk, W. N.; Ryan, D. H.; Lemoine, P.; Cadogan, J. M.

    2014-05-07

    The magnetic structure of EuCu{sub 2}Ge{sub 2} has been determined by flat-plate neutron powder diffraction. Two magnetic phases are present in the neutron diffraction pattern at 3.5 K. They have the same moment, within error, and a common transition temperature. Both {sup 151}Eu and {sup 153}Eu Mössbauer spectroscopy show that the two magnetic phases belong to the same crystallographic phase. Both phases can be modelled by planar helimagnetic structures: one with a propagation vector of [0.654(1), 0, 0], the other with a propagation vector of [0.410(1), 0.225(1), 0].

  12. Analysis of the Tensile Behavior of 12 pct Mn Multi-phase ( α + γ) TWIP + TRIP Steel by Neutron Diffraction

    NASA Astrophysics Data System (ADS)

    Lee, Sangwon; Woo, Wanchuck; de Cooman, Bruno C.

    2016-05-01

    The tensile behavior of intercritically annealed Fe-12 pctMn-0.3 pctC-2 pctAl and Fe-12 pctMn-0.3 pctC-3 pctAl steel was studied by means of in situ neutron diffraction and microstructural analysis. The in situ neutron diffraction measurements showed that the ferrite had a much higher yield strength and lower work hardening rate as compared to the austenite. The strain hardening of the austenite was controlled by deformation twinning and strain-induced transformation, occurring in succession. This TWIP + TRIP effect acted as an effective plasticity-enhancing mechanism which increased the work hardening rate.

  13. Uranium Hydridoborates: Synthesis, Magnetism, and X-ray/Neutron Diffraction Structures.

    PubMed

    Braunschweig, H; Gackstatter, A; Kupfer, T; Radacki, K; Franke, S; Meyer, K; Fucke, K; Lemée-Cailleau, M-H

    2015-08-17

    While uranium hydridoborate complexes containing the [BH4](-) moiety have been well-known in the literature for many years, species with functionalized borate centers remained considerably rare. We were now able to prepare several uranium hydridoborates (1-4) with amino-substituted borate moieties with high selectivity by smooth reaction of [Cp*2UMe2] (Cp* = C5Me5) and [Cp'2UMe2] (Cp' = 1,2,4-tBu3C5H2) with the aminoborane H2BN(SiMe3)2. A combination of nuclear magnetic resonance spectroscopy, deuteration experiments, magnetic SQUID measurements, and X-ray/neutron diffraction studies was used to verify the anticipated molecular structures and oxidation states of 1-4 and helped to establish a linear tridentate coordination mode of the borate anions. PMID:26247295

  14. Accelerated carbonation of cement pastes in situ monitored by neutron diffraction

    SciTech Connect

    Castellote, M. Andrade, C.; Turrillas, X.; Campo, J.; Cuello, G.J.

    2008-12-15

    In-situ monitoring of the changes that take place in the phase composition of cement pastes during accelerated carbonation (100% CO{sub 2}) for different binders, has been carried out, by taking Neutron Diffraction patterns in parallel with the carbonation experiments. The variation of the intensity of chosen reflections for each phase along the experiment has been used to monitor concentration changes and has supplied data, in real time, for fractional conversion of different phases (Portlandite, Ettringite and CSH gel) of the hydrated cement pastes. Fitting of these results has allowed to make a qualitative approach to the kinetics of the carbonation of the different phases and extracting conclusions on the microstructural changes that takes place during the carbonation of cement pastes.

  15. In-situ monitoring the realkalisation process by neutron diffraction: Electroosmotic flux and portlandite formation

    SciTech Connect

    Castellote, Marta . E-mail: martaca@ietcc.csic.es; Llorente, Irene; Andrade, Carmen; Turrillas, Xavier; Alonso, Cruz; Campo, Javier

    2006-05-15

    Even though the electroosmotic flux through hardened cementitious materials during laboratory realkalisation trials had been previously noticed, it has never been in-situ monitored, analysing at the same time the establishment of the electroosmotic flux and the microstructure changes in the surroundings of the rebar. In this paper, two series of cement pastes, cast with CEM I and CEM I substituted in a 35% by fly ash, previously carbonated at 100% CO{sub 2}, were submitted to realkalisation treatments followed on line by simultaneous acquisition of neutron diffraction data. As a result, it has been possible to confirm the electroosmosis as the driving force of carbonates towards the rebar and to determine the range of pH in the anolyte in which most of the relevant electroosmotic phenomena takes place. On the other hand, the behaviour of the main crystalline phases involved in the process has been monitored during the treatment, with the precipitation of portlandite as main result.

  16. Development of MnBi permanent magnet: Neutron diffraction of MnBi powder

    SciTech Connect

    Cui, J. Choi, J. P.; Li, G.; Polikarpov, E.; Darsell, J.; Kramer, M. J.; Zarkevich, N. A.; Wang, L. L.; Johnson, D. D.; Marinescu, M.; Huang, Q. Z.; Wu, H.; Vuong, N. V.; Liu, J. P.

    2014-05-07

    MnBi attracts great attention in recent years for its great potential as permanent magnet materials. MnBi phase is difficult to obtain because of the rather drastic peritectic reaction between Mn and Bi. In this paper, we report our effort on synthesizing high purity MnBi compound using conventional powder metallurgical approaches. Neutron diffraction was carried out to investigate the crystal and nuclear structure of the obtained powder. The result shows that the purity of the obtained powder is about 91 wt. % at 300 K, and the magnetic moment of the Mn atom in MnBi lattice is 4.424 and 4.013 μ{sub B} at 50 K and 300 K, respectively.

  17. Development of MnBi permanent magnet: Neutron diffraction of MnBi powder

    SciTech Connect

    Cui, J.; Choi, J. P.; Li, G.; Polikarpov, E.; Darsell, J.; Kramer, M. J.; Zarkevich, N. A.; Wang, L. L.; Johnson, D. D.; Marinescu, M.; Huang, Q. Z.; Wu, H.; Vuong, N. V.; Liu, J. P.

    2014-05-07

    MnBi attracts great attention in recent years for its great potential as permanent magnet materials. MnBi phase is difficult to obtain because of the rather drastic peritectic reaction between Mn and Bi. In this paper, we report our effort on synthesizing high purity MnBi compound using conventional powder metallurgical approaches. Neutron diffraction was carried out to investigate the crystal and nuclear structure of the obtained powder. The result shows that the purity of the obtained powder is about 91 wt. % at 300 K, and the magnetic moment of the Mn atom in MnBi lattice is 4.424 and 4.013 μB at 50 K and 300 K, respectively.

  18. Applications of pulsed neutron powder diffraction to actinide elements. [Pu-Al

    SciTech Connect

    Lawson, A.C.; Richardson, J.W.; Mueller, M.H.; Lander, G.H.; Goldstone, J.A.; Williams, A.; Kwei, G.H.; Von Dreele, R.B.; Faber, J. Jr.; Hitterman, R.L.

    1987-11-01

    We have been using the technique of pulsed neutron powder diffraction to study several problems in the physics and chemistry of the actinide elements. In these elements one often encounters very complex structures resulting from polymorphic transformations presumably induced by the presence of 5f-electrons. For example, at least five distinct structures of plutonium metal are found between room temperature and its melting point of 640/sup 0/C, and two of the structures are monoclinc. The determination of the crystal structure of beta-uranium (tetragonal, 30 atoms per unit cell) which has finnaly been shown to be centrosymmetric, after decades of uncertainty is discussed. Some preliminary results on the structure of alpha-plutonium (which confirm Zachariasen's original determination of the monoclinic structure) are presented. Pu-Al alloys were also studied. 12 refs., 18 figs.

  19. A neutron diffraction study of local stress concentrations surrounding defects in pipeline steel

    NASA Astrophysics Data System (ADS)

    Clapham, L.; Sabet-Sharghi, R.; Holden, T.; Atherton, D. L.

    Magnetic flux leakage (MFL) is the most commonly used technique for the in-service inspection of both gas and oil pipelines. However, MFL is sensitive to the stress state of the pipe wall and the area surrounding defects. MFL tools are often calibrated using pipe sections with defects artificially introduced into the pipe wall prior to the pipe being pressurized. Naturally occurring defects, however, occur while the pipe wall is under stress due to line pressure. In this study, neutron diffraction is used to map the strain surrounding the two defects that have been introduced into plates of pipeline grade steel, one into a plate prior to uniaxial loading, the second into a plate held at a constant background load high enough to ensure that stress at the edge of the defect exceeds the elastic limit of the material.

  20. SURFING: A Program for Precise Determination of Sample Position in Stress Measurements Via Neutron Diffraction

    SciTech Connect

    Wang, D.-Q.

    2000-08-08

    Precise determination of the specimen position relative to the sampling volume for texture and stress measurements by neutron diffraction is difficult or sometimes impossible using only optical devices due to large or irregular sample dimensions and/or complicated shape of the sampling volume. The knowledge of the shape and size of the sampling volume allows development of a general mathematical model for the intensity variation with a parallelogram-shape sampling volume moving from outside to inside the specimen for both transmission and reflection geometric set-ups. Both fixed slits and radial collimators are options in defining the geometrical setup. The attenuation by the sample also has been taken into account in this model. Experimental results agree well with the model calculations. The program SURFING is based on the model calculation and was written in Labwindows/CVI{copyright}.

  1. Magnetostructural transition in Fe5SiB2 observed with neutron diffraction

    NASA Astrophysics Data System (ADS)

    Cedervall, Johan; Kontos, Sofia; Hansen, Thomas C.; Balmes, Olivier; Martinez-Casado, Francisco Javier; Matej, Zdenek; Beran, Premysl; Svedlindh, Peter; Gunnarsson, Klas; Sahlberg, Martin

    2016-03-01

    The crystal and magnetic structure of Fe5SiB2 has been studied by a combination of X-ray and neutron diffraction. Also, the magnetocrystalline anisotropy energy constant has been estimated from magnetisation measurements. High quality samples have been prepared using high temperature synthesis and subsequent heat treatment protocols. The crystal structure is tetragonal within the space group I4/mcm and the compound behaves ferromagnetically with a Curie temperature of 760 K. At 172 K a spin reorientation occurs in the compound and the magnetic moments go from aligning along the c-axis (high T) down to the ab-plane (low T). The magnetocrystalline anisotropy energy constant has been estimated to 0.3 MJ/m3 at 300 K.

  2. Neutron diffraction determination of the residual stress redistribution in cracked autofrettaged tubing

    SciTech Connect

    Bourke, M.A. ); McGillivray, H.J.; Webster, G.A. . Dept. of Mechanical Engineering); Webster, P.J. . Dept. of Civil Engineering)

    1991-01-01

    Neutron diffraction has been used to measure the residual stress distributions in uncracked and fatigue cracked rings taken from a high strength, low alloy steel autofrettage tube with a bore diameter of 60mm and a wall thickness of 32mm. Stresses were determined to a precision of {plus minus} 10MPa. Three crack sixes were examines. No appreciable stress redistribution was observed until the crack was grown into a region which originally contained tensile residual hoop stress. When this occurred an increase in residual hoop tension was observed ahead of the crick tip. Qualitative agreement was achieved between the measured hoop stress distribution and values predicted using a boundary element method. 9 refs., 12 figs.

  3. Neutron Diffraction Characterization of Residual Strain in Welded Inconel 718 for NASA Space Shuttle Flow Liners

    SciTech Connect

    Rathod, C.R.; Vaidyanathan, R.; Livescu, V.; Clausen, B.; Bourke, M. A. M.; Notardonato, W.U.; Femminineo, M.

    2004-06-28

    This work quantitatively assesses residual strains and stresses associated with the weld repair process used to repair cracks on NASA's space shuttle flow liners. The coupons used in this investigation were made of the same INCONEL 718 alloy used for the flow liners. They were subjected to identical welding and certification procedures that were carried out on the space shuttle. Neutron diffraction measurements at Los Alamos National Laboratory determined residual strains at selected locations in a welded coupon at 293 K and 135 K. The weld repair process introduced Mises effective residual stresses of up to 555 MPa. On comparing the measurements at 293 K and 135 K, no significant change to the residual strain profile was noted at the low temperature. This indicated minimal mismatch in the coefficients of thermal expansion between the base metal and the weld.

  4. Degradation analysis of 18650-type lithium-ion cells by operando neutron diffraction

    NASA Astrophysics Data System (ADS)

    Shiotani, Shinya; Naka, Takahiro; Morishima, Makoto; Yonemura, Masao; Kamiyama, Takashi; Ishikawa, Yoshihisa; Ukyo, Yoshio; Uchimoto, Yoshiharu; Ogumi, Zempachi

    2016-09-01

    In-situ and operando neutron diffraction are used to analyze the degradation of 18650-type Li-ion cells. Structural characterization of the electrode materials is performed by applying the Rietveld refinement technique to the in-situ data. The structural refinement of both electrodes in the degraded cells indicates that the amount of active Li-ions is reduced by 14.4% and 13.7% in the cathode and anode, respectively. This reduction is good in agreement with the capacity loss determined electrochemically. The results suggest that capacity loss might be mainly caused by loss of active Li-ions due to side reactions such as solid electrolyte interface (SEI) growth. Furthermore, operando measurements are performed to examine the deterioration of the electrode and active materials. Because the structural evolution depending on capacity is increased in the cathode of degraded cells, it is presumed that the cathode active material has deteriorated due to phase transitions.

  5. Tensile behavior of TRIP-aided multi-phase steels studied by in situ neutron diffraction

    SciTech Connect

    Tomota, Y. . E-mail: tomota@mx.ibaraki.ac.jp; Tokuda, H.; Adachi, Y.; Wakita, M.; Minakawa, N.; Moriai, A.; Morii, Y.

    2004-12-01

    TRIP-aided multi-phase steels were made by thermo-mechanically controlled process, where the ferrite grain size and the amount of the retained austenite were changed by controlling process conditions. The tensile behavior of four steels was studied by in situ neutron diffraction. It is found that the retained austenite bearing about 1.0 wt% C is plastically harder than the ferrite matrix. The steel with a ferrite grain size of {approx}2.0 {mu}m showed tensile strength of 1.1 GPa and a uniform elongation of 18.4%, in which stress-induced martensitic transformation occurs during plastic deformation but a considerable amount of austenite remains even after the onset of necking. It is concluded that the enhancement of uniform elongation is caused mainly by the work-hardening due to the hard austenite and martensite, where the contribution of the transformation strain is negligible.

  6. Experimental determination of residual stress by neutron diffraction in a boiling water reactor core shroud

    SciTech Connect

    Payzant, A.; Spooner, S.; Zhu, Xiaojing; Hubbard, C.R.

    1996-06-01

    Residual strains in a 51 mm (2-inch) thick 304L stainless steel plate have been measured by neutron diffraction and interpreted in terms of residual stress. The plate, measuring (300 mm) in area, was removed from a 6m (20-ft.) diameter unirradiated boiling water reactor core shroud, and included a multiple-pass horizontal weld which joined two of the cylindrical shells which comprise the core shroud. Residual stress mapping was undertaken in the heat affected zone, concentrating on the outside half of the plate thickness. Variations in residual stresses with location appeared consistent with trends expected from finite element calculations, considering that a large fraction of the residual hoop stress was released upon removal of the plate from the core shroud cylinder.

  7. Development of MnBi permanent magnet: Neutron diffraction of MnBi powder

    NASA Astrophysics Data System (ADS)

    Cui, J.; Choi, J. P.; Li, G.; Polikarpov, E.; Darsell, J.; Kramer, M. J.; Zarkevich, N. A.; Wang, L. L.; Johnson, D. D.; Marinescu, M.; Huang, Q. Z.; Wu, H.; Vuong, N. V.; Liu, J. P.

    2014-05-01

    MnBi attracts great attention in recent years for its great potential as permanent magnet materials. MnBi phase is difficult to obtain because of the rather drastic peritectic reaction between Mn and Bi. In this paper, we report our effort on synthesizing high purity MnBi compound using conventional powder metallurgical approaches. Neutron diffraction was carried out to investigate the crystal and nuclear structure of the obtained powder. The result shows that the purity of the obtained powder is about 91 wt. % at 300 K, and the magnetic moment of the Mn atom in MnBi lattice is 4.424 and 4.013 μB at 50 K and 300 K, respectively.

  8. Experimental setup for simultaneous measurements of neutron diffraction and dielectric spectroscopy during crystallization of liquids

    NASA Astrophysics Data System (ADS)

    Jiménez-Ruiz, M.; Sanz, A.; Nogales, A.; Ezquerra, T. A.

    2005-04-01

    Here we present an experimental setup to obtain information on structural and dynamical changes in liquids during crystallization. This setup consists in a sample cell that allows performing simultaneous measurements of neutron diffraction and dielectric spectroscopy experiments. The capabilities of the technique have been probed by following in real time the crystallization process of a model liquid: the isopropanol. By performing the simultaneous experiment information can be obtained from both phases, amorphous and crystalline, and therefore it can provide a complete description of the changes occurring during a crystallization process. The use of this setup allowed us to demonstrate that a breakage of the hydrogen-bond network is a precursor step for the crystallization of isopropanol.

  9. Neutron diffraction measurement of internal strain in the first Japanese ITER CS conductor sample

    NASA Astrophysics Data System (ADS)

    Hemmi, T.; Harjo, S.; Nunoya, Y.; Kajitani, H.; Koizumi, N.; Aizawa, K.; Machiya, S.; Osamura, K.

    2013-08-01

    Several conductor samples were fabricated and tested in the SULTAN facility at CRPP for ITER Central Solenoid (CS) conductor qualification. From the result of the cyclic testing on the first and second conductor samples named CSJA01 and CSJA02, continuous linear degradation of the current sharing temperature (Tcs) was found. From the result of the visual inspection, a large deflection on the lower loading side (LLS) in the high field zone (HFZ) was observed. The bending strain of the strands cannot be evaluated from only the deflection obtained visually. To evaluate the strain of strands in CSJA01 quantitatively, a neutron diffraction measurement of the CSJA01 left leg was performed using the engineering materials diffractometer ‘Takumi’ in J-PARC. From the result, the large bending strain at the LLS in the HFZ was found. Therefore, the Tcs degraded position in the conductor sample due to the cyclic testing can be determined.

  10. Complex magnetic ordering in CeFe1.76 studied by neutron diffraction

    SciTech Connect

    Jayasekara, Wageesha T; Tian, W; Hodovanets, Halyna; Canfield, Paul C; Bud'ko, Serguei L; Kreyssig, Andreas; Goldman, Alan I

    2014-10-01

    Neutron diffraction measurements on a single crystal of CeGe1.76 reveal a complex series of magnetic transitions at low temperature. At TN≈7 K, there is a transition from a paramagnetic state at higher temperature to an incommensurate magnetic structure characterized by a magnetic propagation vector (0 0 τ) with τ≈1/4 and the magnetic moment along the a axis of the orthorhombic unit cell. Below TLI≈5 K, the magnetic structure locks in to a commensurate structure with τ=1/4 and the magnetic moment remains along the a axis. Below T≈4 K, we find additional half-integer and integer indexed magnetic Bragg peaks consistent with a second commensurately ordered antiferromagnetic state.

  11. Development of MnBi permanent magnet: Neutron diffraction of MnBi powder

    SciTech Connect

    Cui, J; Choi, JP; Li, G; Polikarpov, E; Darsell, J; Kramer, MJ; Zarkevich, NA; Wang, LL; Johnson, DD; Marinescu, M; Huang, QZ; Wu, H; Vuong, NV; Liu, JP

    2014-05-07

    MnBi attracts great attention in recent years for its great potential as permanent magnet materials. MnBi phase is difficult to obtain because of the rather drastic peritectic reaction between Mn and Bi. In this paper, we report our effort on synthesizing high purity MnBi compound using conventional powder metallurgical approaches. Neutron diffraction was carried out to investigate the crystal and nuclear structure of the obtained powder. The result shows that the purity of the obtained powder is about 91 wt. % at 300 K, and the magnetic moment of the Mn atom in MnBi lattice is 4.424 and 4.013 mu(B) at 50 K and 300 K, respectively. (C) 2014 AIP Publishing LLC.

  12. Development of MnBi permanent magnet: neutron diffraction of MnBi powder

    SciTech Connect

    Cui, Jun; Choi, Jung-Pyung; Li, Guosheng; Polikarpov, Evgueni; Darsell, Jens T.; Kramer, Matthew J.; Zarkevich, Nikolai; Wang, L. L.; Johnson, D. D.; Marinescu, Melania; Huang, Qingzhen; Wu, Hui; Vuong, Nguyen V.; Liu, J.Ping

    2014-03-05

    MnBi attracts great attention in recent years for its great potential as permanent magnet materials. MnBi phase is difficult to obtain because of the rather drastic peritectic reaction between Mn and Bi. In this paper, we report our effort on synthesizing high purity MnBi compound using conventional powder metallurgical approaches. Neutron diffraction was carried out to investigate the crystal and nuclear structure of the obtained power. The result shows that the purity of the obtained powder is about 91wt.% at 300K, and the magnetic moment of the Mn atom in MnBi lattice is 4.424 and 4.013 μB at 50 K and 300 K respectively.

  13. Neutron-diffraction study of Ho/sub 2/C at 4--296 K

    SciTech Connect

    Atoji, M.

    1981-02-01

    By neutron powder diffraction, trigonal Ho/sub 2/C has been shown to become ferromagnetic below 100 K. The paramagnetic scattering indicates the free Ho/sup 3 +/-ion moment, while the saturation moment in the ferromagnetic phase is 7.16 Bohr magnetons (72% of the free-ion moment), showing a sizeable crystal-field effect. The preferential crystallite orientation induced by the applied magnetic field has shown that the ordered moments are aligned parallel to the (104) axis which corresponds to the (100) axis of the high-temperature cubic modification. The previously proposed HoN-type magnetic ordering is not compatible with our results. The residual, disordered moments exhibit a ferromagnetic short-range order superposing on the ferromagnetic long-range order. Crystallographic-structure data at 296 and 4 K are also presented.

  14. A neutron diffraction and computer modeling study of the interatomic structure of phosphoric acid

    NASA Astrophysics Data System (ADS)

    Tromp, R. Hans; Spieser, Stephane H.; Neilson, George W.

    1999-01-01

    Wide angle neutron diffraction in combination with H/D substitution was used to determine the inter- and intramolecular structure of 100% phosphoric acid (H3PO4, PA). From radial distribution functions gHH(r), gHX(r), and gXX(r) (where X is either O or P) the hydrogen bonds were found to be characterized by a very short O…H distance (1.54 Å). Within a molecule, the orientation of an OH group was found to be preferably in one of the three O-P-O planes. In the interpretation of the radial distribution functions, use was made of preliminary results of molecular dynamics simulations. Temperature effects on the structure of PA were only found in the hydrogen bond structure, which becomes somewhat less well defined when heating up from room temperature to 60 °C. Polyphosphates could not be detected, probably due to the small degree of polymerization.

  15. Structure of aqueous ammonium calcium nitrate glass former studied by neutron diffraction

    NASA Astrophysics Data System (ADS)

    Ansell, S.; Neilson, G. W.

    1999-09-01

    A neutron diffraction experiment was carried out on the glass-forming aqueous system of ammonium calcium nitrate tetrahydrate, ACN (NH4NO3.Ca(NO3)2.4H2O). The method of isotopic substitution was used to determine the local structure round the NO-3 ion, the hydrogen-hydrogen (gHH(r)), the hydrogen-oxygen (gOH(r)), and the nitrogen-hydrogen (gN2H(r)) radial pair distribution functions, in both the glassy (153 K) and liquid (303 K) states. The results show that significant changes occur on glassification. In particular, the nitrate ion exhibits an increase in the number of close hydrogen contacts and enhancement of its local structure. A microstructural model is proposed to explain the strong glass-forming ability of ACN.

  16. Study of tempering behavior of lath martensite using in situ neutron diffraction

    SciTech Connect

    Shi, Z.M.; Gong, W.; Tomota, Y.; Harjo, S.; Li, J.; Chi, B.; Pu, J.

    2015-09-15

    To elucidate changes in the density and substructure of dislocations during tempering of lath martensite steel, a convolutional multiple whole-profile fitting method was applied to in situ neutron diffraction profiles. With increasing tempering temperature, the dislocation density scarcely changed in the beginning and then decreased at temperatures above 473 K, whereas the dislocation arrangement drastically changed at temperatures above 673 K. The strength of the steel is speculated to depend on the density and arrangement of dislocations. - Highlights: • A convolutional multiple whole-profile fitting method was applied. • Dislocation density and dislocation arrangement changing with tempering were discussed. • Dislocation density scarcely changed in the beginning. • And then dislocation density decreased at temperatures above 473 K. • The dislocation arrangement drastically changed at temperatures above 673 K.

  17. Texture Evolution and Phase Transformation in Titanium Investigated by In-Situ Neutron Diffraction

    SciTech Connect

    Ma, Dong; Stoica, Alexandru Dan; An, Ke; Yang, Ling; Bei, Hongbin; Mills, Rebecca A; Skorpenske, Harley David; Wang, Xun-Li

    2011-01-01

    We report in-situ neutron diffraction studies of texture evolution and the (hcp) (bcc) phase transformation in commercially pure cold-drawn titanium upon continuous heating and cooling, complemented by differential scanning calorimetry (DSC) measurements. We show that the recrystallization of the phase at elevated temperature enhanced the preexisting fiber texture, which eventually facilitated the nucleation and growth of the phase favored by the Burgers orientation relationship, i.e., {0001} //{110} . More strikingly, upon completion of the transformation, the {110} texture (or preferred orientation) in was eliminated immediately by the rapid grain growth of intergranular allotriomorphs. This resulted in the loss of the original -texture when Ti was transformed back to from to upon subsequent cooling, distinct from the known texture memory effect for rolling textures in titanium. Our present work provides useful experimental results for understanding the mechanisms of texture evolution and phase transformation in titanium and its alloys and, by and large, low-symmetry alloys such as zirconium.

  18. Determination of the residual stress in a centrifuge bowl by neutron diffraction

    NASA Astrophysics Data System (ADS)

    Albertini, G.; Giuliani, A.; Lin Peng, R.; Manescu, A.; Ponzetti, A.

    An experimental study of the stress field in centrifuges for food processing and for agricultural applications was undertaken. The model, the dimensions and the material of the sample are those of the most recent line of production of the Nuova M.A.I.P. company. The rotor is also one of the largest rotors produced by that firm. The residual strains and stresses were determined by using neutron-diffraction techniques before centrifugation and after centrifugation, to evaluate the evolution of stress induced by centrifuging. The upper part of the rotating bowl is investigated, where the highest stress field during centrifugation is theoretically forecast to occur. A data elaboration aiming at avoiding systematic errors leads to the conclusion that no appreciable residual stress is induced by centrifugation.

  19. A study of internal damage of metal matrix composites by neutron diffraction

    SciTech Connect

    Shi, N.; Bourke, M.A.M.; Goldstone, J.A.

    1994-12-31

    Using neutron diffraction, we have measured the elastic phase strains of Al/TiC and Al/SiC composites under uniaxial tensile loading. The phase strains were used to reconstruct the global elastic strain. It has been found that, above macroscopic yield, the global elastic strain response is not linear. A theoretical model shows that the nonlinearity is dictated by changes in the ratio of longitudinal phase stresses. Furthermore, the changes in this ratio resulting from matrix plasticity and reinforcement fracture are different which leads to distinct slope changes in the global elastic strain response that can be used to distinguish the onset of these two processes on the global elastic strain loading curve.

  20. Spin distribution in the diphenylpicrylhydrazyl (DPPH) radical measured by neutron diffraction

    NASA Astrophysics Data System (ADS)

    Boucherle, J. X.; Gillon, B.; Maruani, J.; Schweizer, J.

    A complete experimental determination of the spin density has been performed on a DPPH : C6H6 single crystal using the polarized neutron diffraction technique. A parametric description of the spin density has been used, this being necessary for non-centrosymmetrical crystals. A large amount of the spin density (61 per cent) remains localized on the central hydrazyl group, in accordance with magnetic resonance data, with a slight excess of Nβ over Nα. The remaining part of the spin density (39 per cent) is delocalized on the three aromatic rings of DPPH, the amount of spin transferred on to a ring depending on the twist angle of the ring with respect to the hydrazyl backbone. On every ring the spin density changes its sign from carbon to carbon atom, in accordance with magnetic resonance and quantum theory. The spin populations measured for the carbons of the rings compare well with the hyperfine coupling constants of the adjacent protons, which permits a direct experimental verification of McConnell's first relation. These neutron diffraction results are compared with two quantum-mechanical calculations performed for the isolated DPPH radical, using the experimental geometry measured in the crystal. Both calculations reproduce fairly well the details of the spin density observed on the rings. The experimental spin distribution on the central nitrogen atoms is better reproduced by the local spin density (LSD) method than by the unrestricted Hartree-Fock (UHF) method, which overlocalizes the spin density on atom Nβ. None of these calculations predicts accurately the amount of delocalization on the rings.

  1. Temperature effects on the structure of liquid D-methanol through neutron diffraction

    NASA Astrophysics Data System (ADS)

    Sahoo, A.; Sarkar, S.; Krishna, P. S. R.; Joarder, R. N.

    2004-08-01

    The study of changes in the structure (H-bonded) of liquid alcohols at elevated temperatures is rare probably due to low flash points of these liquids. An indigenously devised special quartz cell is now used to carry out the structural studies of these liquids at elevated temperatures through neutron diffraction. Here, the liquid consists of deuterated methanol and neutron data was collected on the high-Q diffractometer at Dhruva, BARC. The corrected data at elevated temperatures (BP (boiling point) and double the BP) show that there is a large change in the H-bonded structure of this liquid. The pre-peak or hump, known to be signature of H-bonded clusters appears to be present at all the three temperatures studied. In the low-Q (scattering vector) data Ornstein--Zernike (OZ) behaviour is also observed. It is, however, seen that the intramolecular structure does not change very much at higher temperatures. A detailed model analysis is in progress and would be reported later.

  2. The magnetic and crystal structures of Sr2IrO4: A neutron diffraction study

    SciTech Connect

    Ye, Feng; Chi, Songxue; Chakoumakos, Bryan C; Fernandez-Baca, Jaime A; Qi, Tongfei; Cao, Gang

    2013-01-01

    We report a single-crystal neutron diffraction study of the layered Sr2IrO4. This work unambigu- ously determines the magnetic and crystal structures, and reveals that the spin orientation rigidly tracks the staggered rotation of the IrO6 octahedra in Sr2IrO4. The long-range antiferromagnetic order has a canted spin configuration with an ordered moment of 0.208(3) B/Ir site within the basal plane; a detailed examination of the spin canting yields 0.202(3) and 0.049(2) B/site for the a-axis and the b-axis, respectively. It is intriguing that forbidden nuclear reflections of space group I41/acd are also observed in a wide temperature range from 4 K to 600 K, which suggests a reduced crystal structure symmetry. This neutron scattering work provides a direct, well-refined experimen- tal characterization of the magnetic and crystal structures that are crucial to the understanding of the unconventional magnetism existent in this unusual magnetic insulator.

  3. Neutron-diffraction study up to 1600 °C of 3:2 mullite

    NASA Astrophysics Data System (ADS)

    Brunauer, G.; Frey, F.; Boysen, H.; Schneider, H.; Fischer, P.; Hansen, Th.; Többens, D.; Ehrenberg, H.

    Neutron-diffraction studies were carried out on pure and Cr-doped 3:2 (`sinter') mullite. To learn about structure-property relationships of this refractory material, thermal expansion coefficients and structural parameters were determined by in situ high-temperature investigations. Neutron experiments were performed at the powder diffractometers D2B/ILL, E9/HMI, and HRPT/PSI. All data gave a rather uniform picture of the thermal expansion coefficients: a linear behaviour below 1000 °C and significantly increased (mean) expansion between 1000 and 1600 °C. There is a marked anisotropy of the highest values along the b-axis of the orthorhombic mullite structure. Concerning the structural parameters and the derived bond lengths, there is an expansion of the Al1O6 octahedra, whereas the cross-linking Al2SiO4 tetrahedra stay more or less rigid, but may slightly rotate. Thus a major expansion along the b direction may be qualitatively understood. A structural discussion, however, is affected by the presence of disorder in mullite, in particular in Cr-doped mullite, as it is also reflected by the presence of a modulated diffuse background in the powder patterns.

  4. Neutron diffraction measurement of residual stresses in Al-clad U-10Mo fuel plates

    NASA Astrophysics Data System (ADS)

    Brown, D. W.; Okuniewski, M. A.; Clausen, B.; Moore, G. A.; Sisneros, T. A.

    2016-06-01

    Neutron diffraction was used to determine residual stress in monolithic two Al-clad U 10 weight percent Mo mini-fuel plates and a full sized fuel plate. One mini-plate was cooled following hot isostatic pressing at a rate of 6.75 °C/min, the second at 0.675 °C/min. A non-traditional method of calibrating the neutron diffractometer at each measurement point was necessitated by the thin nature of the sample. The in-plane stresses in the U-10Mo foils are relatively large, -250 MPa in the U-10Mo foil of the fast cooled mini-plate,-150 MPa in the slow cooled mini-plate and -275 MPa in the full-sized plate. Likewise, the in-plane stresses in the Al-cladding of the fast-cooled mini-plate and full-sized plate were determined to reach ∼50 MPa, while in the slow-cooled sample the stresses in the Al cladding were on the level of the measurement uncertainty. The in-plane stresses in the Zr diffusion barrier were estimated to be as large as -300 MPa.

  5. Polymorphism in Photoluminescent KNdW2O8: Synthesis, Neutron Diffraction, and Raman Study

    SciTech Connect

    S. M. Bhat, Swetha; Swain, Diptikanta; Feygenson, Mikhail; Neuefeind, Joerg C; Sundaram, Nalini

    2014-01-01

    Polymorphs of KNdW2O8 ( -KNdW2O8 and -KNdW2O8) phosphors were synthesized by an efficient solution combustion technique for the first time. The crystal structure of the polymorphs analyzed from Rietveld refinement of neutron diffraction data confirms that -KNdW2O8 crystallizes in the tetragonal system (space group I4 ), and -KNdW2O8 crystallizes in the monoclinic system (space group C2/m). The local structure of both polymorphs was elucidated using combined neutron pair distribution function (PDF) and Raman scattering techniques. Photoluminescence measurements of the polymorphs showed broadened emission line width and increased intensity for -KNdW2O8 in the visible region compared to -KNdW2O8. This phenomenon is attributed to the increased distortion in the coordination environment of the luminescing Nd3+ ion. Combined PDF, Rietveld, and Raman measurements reveal distortions of the WO6 octahedra and NdO8 polyhedra in -KNdW2O8. This crystal structure photoluminescence study suggests that this class of tungstates can be exploited for visible light emitting devices by tuning the crystal symmetry.

  6. Residual stresses in a shape welded steel tube by neutron diffraction

    NASA Astrophysics Data System (ADS)

    Taran, Yu V.; Balagurov, A. M.; Schreiber, J.; Stuhr, U.

    2008-03-01

    Measurements of the triaxial residual strains in a composite tube from an austenitic stainless steel as a parent material and a shape welded ferritic steel were carried out by the time-of-flight neutron diffraction method on the POLDI instrument at the PSI SINQ neutron pulsed facility. The shape weld is used to build compressive stresses and, as a result, to suppress stress corrosion. Investigations of the residual stresses in such composite tubes are important for developing optimal welding techniques. Calculation of the residual stresses was performed using measurement results with a comb-sample, machined from the tube by the electro-discharge method, as the stress free reference sample. The results of the POLDI measurements of the stress state in the composite tube are presented and compared to the results of the destructive turning out method and theoretical predictions of calculations by the finite element method. Semiquantitative agreement between all the used methods was only observed for the tangential component of the stress tensor. In this case, the ferrite cladding produced a tangential compressive stress of about 800 MPa on the austenitic tube.

  7. Rearrangement of twin variants in ferromagnetic shape memory alloy polyurethane composites studied by stroboscopic neutron diffraction

    NASA Astrophysics Data System (ADS)

    Feuchtwanger, J.; Lázpita, P.; Vidal, N.; Barandiaran, J. M.; Gutiérrez, J.; Hansen, T.; Peel, M.; Mondelli, C.; O'Handley, R. C.; Allen, S. M.

    2008-03-01

    The use of ferromagnetic shape memory alloy (FSMA) particles as fillers in polymeric matrix composites has been proposed for vibration damping. The large pseudo-plastic recoverable deformation of the FSMA particles due to the rearrangement of twin variants can dissipate a large amount of energy, both under compression and tension. The composites studied are made by mixing particles of NiMnGa with a polyurethane matrix. A magnetic field is applied to the composite while the matrix sets, to achieve a strong [112] texture in the field direction. In situ strobed neutron diffraction measurements were carried out while the composites were subjected to a cyclic deformation. They show that the intensity of certain peaks varies during the deformation cycle. All the peaks that show this behavior can be grouped into pairs that stem from a single austenitic peak. The (020) and (112) martensite peaks correspond to the splitting of the (220) austenite peak, and the intensity of one increases as that of the other decreases. The neutron measurements show directly that there is a change in the texture of the composite during the stress cycle applied to the composite and confirm that the large mechanical loss observed in the stress-strain cycles is in good part due to the rearrangement of twin variants in the FSMA filler used in the composites.

  8. Diffraction limit of the theory of multiple small-angle neutron scattering by a dense system of scatterers

    NASA Astrophysics Data System (ADS)

    Dzheparov, F. S.; Lvov, D. V.

    2016-02-01

    Multiple small-angle neutron scattering by a high-density system of inhomogeneities has been considered. A combined approach to the analysis of multiple small-angle neutron scattering has been proposed on the basis of the synthesis of the Zernike-Prince and Moliére formulas. This approach has been compared to the existing multiple small-angle neutron scattering theory based on the eikonal approximation. This comparison has shown that the results in the diffraction limit coincide, whereas differences exist in the refraction limit because the latter theory includes correlations between successive scattering events. It has been shown analytically that the existence of correlations in the spatial position of scatterers results in an increase in the number of unscattered neutrons. Thus, the narrowing of spectra of multiple small-angle neutron scattering observed experimentally and in numerical simulation has been explained.

  9. Lamellar spacing of photosystem II membrane fragments upon dehydration studied by neutron membrane diffraction

    NASA Astrophysics Data System (ADS)

    Pieper, Jörg; Rusevich, Leonid; Hauß, Thomas; Renger, Gernot

    2016-02-01

    The effect of dehydration on the lamellar spacing of photosystem II (PS II) membrane fragments from spinach has been investigated using neutron membrane diffraction at room temperature. The diffraction data reveal a major peak at a scattering vector Q of 0.049 Å-1 at a relative humidity (r.h.) of 90% corresponding to a repeat distance D of about 129 Å. Upon dehydration to 44% r.h., this peak shifts to about 0.060 Å-1 corresponding to a distance of 104.7±2.5 Å. Within experimental error, the latter repeat distance remains almost the same at hydration levels below 44% r.h. indicating that most of the hydration water is removed. This result is consistent with the earlier finding that hydration-induced conformational protein motions in PS II membrane fragments are observed above 44% r.h. and correlated with the onset electron transfer in PS II (Pieper et al. 2008, Eur. Biophys. J. 37: 657-663).

  10. Lamellar spacing of photosystem II membrane fragments upon dehydration studied by neutron membrane diffraction

    NASA Astrophysics Data System (ADS)

    Pieper, Jörg; Rusevich, Leonid; Hauß, Thomas; Renger, Gernot

    2015-12-01

    The effect of dehydration on the lamellar spacing of photosystem II (PS II) membrane fragments from spinach has been investigated using neutron membrane diffraction at room temperature. The diffraction data reveal a major peak at a scattering vector Q of 0.049 Å-1 at a relative humidity (r.h.) of 90% corresponding to a repeat distance D of about 129 Å. Upon dehydration to 44% r.h., this peak shifts to about 0.060 Å-1 corresponding to a distance of 104.7±2.5 Å. Within experimental error, the latter repeat distance remains almost the same at hydration levels below 44% r.h. indicating that most of the hydration water is removed. This result is consistent with the earlier finding that hydration-induced conformational protein motions in PS II membrane fragments are observed above 44% r.h. and correlated with the onset electron transfer in PS II (Pieper et al. 2008, Eur. Biophys. J. 37: 657-663).