Observation of dynamical oscillations for neutron scattering by Ge crystals using the inclination method

Соменков, В. А.; Shilstein, S.Sh.; Belova, N. E.; Utemisov, K.

doi:10.1016/0038-1098(78)91497-7

Cited by 31 publications

(31 citation statements)

References 3 publications

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“…In vanadium, for concentrations above 50% hydrogen, both the T-and the O-sites are found to be occupied with 90% T-sites and 10% O-sites. 5 This mix of site occupation in the vanadium hydride -phase state has been attributed to both the high electronegativity of vanadium 6 and the geometric effects resulting from a large distortion of the vanadium hydride lattice. 7 In this work, there is evidence that hydrogen is more stable in the O-site of vanadium compared with niobium and tantalum because of a lower charge transfer between the vanadium and the hydrogen atoms at the O-site, which results in a lower hydrogen-hydrogen repulsion energy.…”

Section: Introductionmentioning

confidence: 99%

“…A comprehensive study of all of the possible ordered and disordered configurations of the hydrogen T-site occupation (and O-site occupation in the case of vanadium) is beyond the scope of this work, and only a finite number of structures are examined in order to understand and identify trends in the hydrogen absorption process. For niobium and tantalum, an additional hydrogen configuration at c ) 0.5 is simulated, which is based on the tantalum hydride neutron diffraction measurements of Somenkov et al 5 At increased values of hydrogen content, the metal hydride lattice constant changes compared to the lattice constant of the pure metal, as shown in Table 3. At the maximum concentration investigated in this work (c ) 0.5), the lattice constant changes by approximately 2% in the case of niobium and tantalum and approximately 3% for vanadium.…”

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confidence: 99%

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A Density Functional Theory Study of the Charge State of Hydrogen in Metal Hydrides

Aboud

Wilcox

2010

J. Phys. Chem. C

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Density functional theory and Bader charge analyses were used to investigate the charge state of hydrogen in vanadium, niobium, tantalum, palladium, and niobium-palladium alloys. Over a range of concentrations and hydrogen-site configurations, it is found that hydrogen consistently acquires a net charge of between approximately -0.51e and -0.64e in the pure group 5 metals compared with a significantly smaller value of 0.3e in palladium. Although there is indirect evidence that the electronic charge plays a role in the solubility and diffusivity of hydrogen in the group 5 metals, this is the first work to quantify the value of the charge. Hydrogen tends to migrate to regions of the metal lattice that minimize its overall charge density, which generally corresponds to the T-site in the bcc metals. It is found that the charge of hydrogen at the O-site of vanadium can be slightly lower due to lattice deformation and may explain the occupation of both T-and O-sites in vanadium hydrides.

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Section: Introductionmentioning

confidence: 99%

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confidence: 99%

A Density Functional Theory Study of the Charge State of Hydrogen in Metal Hydrides

Aboud

Wilcox

2010

J. Phys. Chem. C

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“…This behaviour, which describes the coherent transfer of the flux of energy back and forth between the transmitted and the reflected beam directions, is analogous to the oscillations of energy from one to the other of two equal coupled pendulums, and was called by Ewald, in 1916, "Pendellosung" [l] . Pendellosung fringes have been investigated in many neutron diffraction experiments in nearly perfect non magnetic crystals [2,3,4,5,6,7].Although theoretically predicted by different authors [8,9,10,11,12,13} no observation of their magnetic counterpart has been reported, in spite of several attempts. This is not very surprising, since perfect enough magnetic crystal are not available.…”

Section: Introductionmentioning

confidence: 99%

Observation of pendellösung effect in polarized neutron scattering from a magnetic crystal

Baruchel

Guigay²,

Mazuré-Espejo

et al. 1983

Physica B+C

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Résumé. -Nous avons obtenu ce que nous croyons être la première mise en évidence expérimentale de l'effet de Pendellosung en diffraction des neutrons par un cristal magnétique. L'échantillon, un monocristal de YIG, a été sélectionné et taillé de façon que les défauts qu'il présente -des bandes de croissance, pour l'essentieln'aient pas d'influence sur la diffraction dans la géométrie que nous avons choisie.Nous avons mesuré le rapport de retournement R ainsi que les pouvoirs réflecteurs p+ et p_ correspondant au deux polarisations du faisceau de neutrons, en fonction de la longueur d'onde. R(X) et p + (A) présentent bien les oscillations prévues dans le cas d'un cristal parfait, mais avec une amplitude plus faible dont on peut rendre compte, par exemple, en utilisant la théorie statistique de la diffraction développée par Kato.Abstract. -We have obtained what we believe to be the first experimental evidence, in neutron diffraction from a magnetic crystal, of the Pendellosung effect predicted by dynamical theory. We measured the flipping ratio, R, and the reflecting powers for both polarizations, p+ and pas a function of wavelength, from a carefully selected YIG single crystal, cut in a such a way that its main defects -growth bandsare inoperative in the chosen scattering geometry. Both R(x"> and p+CA"* present characteristic oscillating behaviours, related to those calculated for a perfect crystal. It is possible to account for the discrepancy between the experimental and calculated amplitudes of the oscillations using e.g. Kato's statistical theory of diffraction.

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“…an oscillating dependence of the scattered intensity in Laue geometry on the ratio of the crystal thickness to the extinction length. The dynamical oscillations were studied in detail in X-ray scattering (Kato & Lang, 1959;Utemisov, Somenkova, Somenkov & Shilstein, 1980) and in nuclear neutron scattering (Sippel, Kleinstiick & Schulze, 1965;Shull, 1968;Somenkov, Shilstein, Belova & Utemisov, 1978). The theoretical aspects of neutron scattering by perfect magnetically ordered crystals were treated in a number of papers (Stassis & Oberteuffer, 1974;Sivardi~re, 1975;Gukasov & 0108 -7673 / 92/040423 -08506.00 Ruban, 1975;Schmidt & Deimel, 1976;Belyakov & Bokun, 1975, 1976Mendiratta & Blume, 1976;Baryshevskii, 1976;Guigay & Schlenker, 1978), However, Pendell6sung oscillations were observed in the magnetic neutron scattering case only recently (Baruchel, Guigay, Mazure-Espejo, Schlenker & Schweizer, 1982;Kvardakov, Somenkov & Shilstein, 1988;Zelepukhin, Kvardakov, Somenkov & Shilstein, 1989) owing to the small number of perfect magnetically ordered crystals.…”

Section: Introductionmentioning

confidence: 99%

“…Kvardakov, Somenkov & Shilstein (1988) and Zelepukhin, Kvardakov, Somenkov & Shilstein (1989) reported on the Pendell6sung-effect observation in pure magnetic neutron scattering by using the inclination method. The method was proposed earlier by Somenkov et al (1978) for the case of nuclear neutron scattering and later it was used for Pendel16sung-effect investigation in X-ray (Utemisov et al, 1980) and synchrotron-radiation (Belova & Kabannik, 1985) scattering, for precise determination of structure factors (Saka & Kato, 1986) and for the study of extinction parameters connected with microdefects (Voronkov, Piskunov, Chukhovskii & Maksimov, 1987).…”

Section: Introductionmentioning

confidence: 99%

Magnetic Pendellösung effects in neutron scattering by perfect magnetic crystals

Kvardakov¹,

Соменков²

1992

Acta Cryst Sect A

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Pendell6sung effects in magnetic neutron scattering by thin (thickness of the order of the extinction length) crystals of weak ferromagnets FeBO3 and a-Fe203 were investigated. Dynamical oscillations in the scattering intensity dependences on the crystal's effective thickness, temperature and magnetic field orientation have been found. The influence of irregularities in the magnetic structure related to domains, a magnetic phase transition and magnetoelastic oscillations on the Pendell6sung oscillation amplitude has been established. The oscillation amplitude and the scattering intensity dependence on the structure-factor magnitude have been used to obtain information on small deformations from perfection of the crystalline and magnetic structures, which are difficult to detect by other methods.

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Observation of dynamical oscillations for neutron scattering by Ge crystals using the inclination method

Cited by 31 publications

References 3 publications

A Density Functional Theory Study of the Charge State of Hydrogen in Metal Hydrides

A Density Functional Theory Study of the Charge State of Hydrogen in Metal Hydrides

Observation of pendellösung effect in polarized neutron scattering from a magnetic crystal

Magnetic Pendellösung effects in neutron scattering by perfect magnetic crystals

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