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Forker, M.; Hütten, U.; Lieder, Michael

doi:10.1103/physrevb.49.8556

Cited by 12 publications

(4 citation statements)

References 13 publications

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“…Wolf and Herzig [13,14] extended this EFG analysis to include P6 3 symmetry and concluded that agreement was still better for P6 3 cm, although the results were found to be quite sensitive to the small crystallographic differences between the experimentally reported structures and total-energy optimized structures. Additional comparison [13] of calculated yttrium EFG's with data from 181 Tadoped YH 3 in perturbed angular correlation measurements [42] indicated better agreement for both P6 3 cm and P6 3 structures than for the P 3 3c1 structure.…”

Section: Introductionmentioning

confidence: 90%

The nature of deuterium arrangements in YD₃ and other rare-earth trideuterides

Udovic¹,

Huang²,

Santoro³

et al. 2008

Zeitschrift Für Kristallographie

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The efficacy of different structural models for describing the observed neutron-powder-diffraction (NPD) measurements of bulk polycrystalline YD 3 as well as other hexagonal rare-earth (i.e., Nd, Tb, Dy, Ho, Er, and Tm) trideuteride powders has been investigated via Rietveld refinement. Between the two possible structural configurations, centrosymmetric P 3 3c1 and noncentrosymmetric P6 3 cm, the latter can be excluded due to very high correlations found between the positions of the D sites. Hence, the true "diffraction-average" structure for YD 3 and all other rare-earth deuterides studied is centrosymmetric (P 3 3c1). This seems to contrast with the prior evidence from first-principles calculations and various spectroscopic probes suggesting that the true local symmetry is not P 3 3c1, but rather, noncentrosymmetric. A possible way to reconcile the apparently conflicting conclusions from NPD and spectroscopic measurements is by assuming that the real structure is a twinned arrangement of nanosized, noncentrosymmetric configurations. For example, we demonstrate that the diffraction-average centrosymmetric P 3 3c1 structure can result from a superposition of individual, noncentrosymmetric P3c1 twins. A comparison of neutron vibrational spectra for YH 3 and YD 3 confirms that both compounds share similar structural arrangements.

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Section: Introductionmentioning

confidence: 90%

The nature of deuterium arrangements in YD₃ and other rare-earth trideuterides

Udovic¹,

Huang²,

Santoro³

et al. 2008

Zeitschrift Für Kristallographie

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“…Importantly, the temperature region in which the deuterium Pake patterns sharpen and become most evident is also the region in which measurements of the EFG at the yttrium site 15 gave evidence of a phase transition from a disordered structure to a more symmetric one. We suggest that the yttrium-site EFG data do not indicate a phase transition, but a gradual change with temperature due to motional averaging, just as for the present deuterium spectra.…”

Section: B Spectral Changes With Temperaturementioning

confidence: 95%

Nuclear magnetic resonance evidence of disorder and motion in yttrium trideuteride

et al. 1998

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Three samples of YD x , with x ranging from 2.9 to nearly 3.0, were studied with deuterium nuclear magnetic resonance to gain insight into the locations of the D atoms in the lattice and their motions. Line shapes at low temperatures ͑200-330 K͒ show substantial disorder at some of the deuterium sites. Near 355 K, the spectrum sharpens to yield three uniaxial Pake patterns, reflecting a motional averaging process. However, the three measured intensities do not match the ratios expected from the neutron-determined, HoD 3 -like structure. This is strong evidence that the structure and space group of YD 3 are different than reported, or that the current model needs adjustment. At still higher temperatures near 400 K, the Pake doublet features broaden, and a single sharp resonance develops, signalling a diffusive motion that carries all D atoms over all sites. The temperature at which line shape changes occur depends on the number of deuterium vacancies, 3Ϫx. The changes occur at lower temperatures in the most defective sample, indicating the role of D-atom vacancies in the motional processes. The longitudinal relaxation rate T 1 Ϫ1 displays two regimes, being nearly temperature independent below 300 K and strongly thermally activated above. The relaxation rate depends on the number of deuterium vacancies, 3Ϫx, varying an order of magnitude over the range of stoichiometries studied and suggesting that D-atom diffusion is involved. Also, the activation energy describing T 1 Ϫ1 (Ӎk B ϫ5500 K) approximately matches that for diffusion. An unusual 0 Ϫ0.7 frequency dependence of T 1 Ϫ1 is observed. A relaxation mechanism is proposed in which diffusion is the rate-determining step and in which frequency dependence arises from a field-dependent radius of the relaxation zones.

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“…Measurements of nuclear electric quadrupole interactions (QI) by NQR [1], Mössbauer spectroscopy [2] and perturbed angular correlations (PACs) [3][4][5] are an important tool for the investigation of metal-hydrogen systems. The interaction between the quadrupole moment of a nuclear state and the tensor of electric-field gradient (EFG) reflects the charge distribution at the nuclear site and therefore carries information on structure and electronic properties of these systems.…”

Section: Introductionmentioning

confidence: 99%

¹⁸¹Ta perturbed-angular-correlation study of electric quadrupole interactions in yttrium metal and yttrium-hydrogen solid solutions

Forker

Hütten

Müller

2000

J. Phys.: Condens. Matter

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The perturbed-angular-correlation (PAC) technique has been used to study the electric quadrupole interaction (QI) of the nuclear probe 181Ta in yttrium metal and yttrium-hydrogen solid solutions α-YHx with 0⩽x⩽0.2. The temperature dependence of the quadrupole frequency νq of 181Ta in yttrium metal, measured in the range 290 K⩽T⩽1700 K, follows the linear relation νq(T) = νq(0)(1-AT) with νq(0) = 423(3) MHz and A = 4.74(4)×10-4 K-1. The absorption of hydrogen enhances the temperature dependence of the QI: the parameters νq(0) and A of the linear temperature variation of the 181Ta QI in α-YHx measured between 25 K and 1000 K for 0⩽x⩽0.2 both increase with increasing concentration x. These trends are consistent with the anionic model of the electronic state of hydrogen in rare earth metals. At T⩾500 K a dynamic QI caused by diffusing hydrogen has been observed. The activation energy for hydrogen jumps in α-YH0.10 deduced from the temperature dependence of the quadrupole relaxation rate is Ea = 0.49(15) eV.

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Investigation of the electric-field gradient at the Y site inYH3

Cited by 12 publications

References 13 publications

The nature of deuterium arrangements in YD₃ and other rare-earth trideuterides

The nature of deuterium arrangements in YD₃ and other rare-earth trideuterides

Nuclear magnetic resonance evidence of disorder and motion in yttrium trideuteride

¹⁸¹Ta perturbed-angular-correlation study of electric quadrupole interactions in yttrium metal and yttrium-hydrogen solid solutions

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Investigation of the electric-field gradient at the Y site inYH3

Cited by 12 publications

References 13 publications

The nature of deuterium arrangements in YD3 and other rare-earth trideuterides

The nature of deuterium arrangements in YD3 and other rare-earth trideuterides

Nuclear magnetic resonance evidence of disorder and motion in yttrium trideuteride

181Ta perturbed-angular-correlation study of electric quadrupole interactions in yttrium metal and yttrium-hydrogen solid solutions

Contact Info

Product

Resources

About

The nature of deuterium arrangements in YD₃ and other rare-earth trideuterides

The nature of deuterium arrangements in YD₃ and other rare-earth trideuterides

¹⁸¹Ta perturbed-angular-correlation study of electric quadrupole interactions in yttrium metal and yttrium-hydrogen solid solutions