NMR study of hydrogen motion in hydrogen-stabilized C15-type compounds ZrTi2Hx

Skripov, A. V.; Rychkova, S V; Belyaev, M. Yu.; Stepanov, A. P.

doi:10.1016/0038-1098(89)90722-9

Cited by 33 publications

(19 citation statements)

References 12 publications

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“…17,18 However, such a model should also lead to changes in the frequency dependence of R 1 which becomes weaker than ω -2 in the limit slow motion. [17][18][19] Since in our case the frequency dependence of R 1 at the low-temperature slope of the R 1 peak is well described by ω -2 , we can reject the model with a continuous distribution of the jump rates. Furthermore, the data presented in Figure 1 exhibit the inflection point near 180 K; this suggests that the observed temperature dependence of R 1 can be described as a superposition of two peaks with different slopes.…”

Section: Experimental Methodsmentioning

confidence: 99%

Nuclear Magnetic Resonance Study of the Rotational Motion and the Phase Transition in LiBH₄

et al. 2008

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To study the rotational motion of BH 4 tetrahedra in LiBH 4 , we have measured the 1 H and 11 B nuclear magnetic resonance spectra and spin-lattice relaxation rates in this compound over wide ranges of temperature (92-424 K) and resonance frequency (14-90 MHz for 1 H and 14-28 MHz for 11 B). In the low-temperature (orthorhombic) phase of LiBH 4 , our spin-lattice relaxation results are consistent with a coexistence of two types of the rotational motion of BH 4 tetrahedra with the activation energies of 0.182 ( 0.003 eV and 0.251 ( 0.004 eV. For both types of motions, the jump rates of the reorientations reach the values of the order of 10 11 s -1 near the upper limit of the temperature range of the orthorhombic phase stability (T 0 ≈ 381 K). In the high-temperature (hexagonal) phase, both the 1 H and 11 B spin-lattice relaxation rates are governed by an additional low-frequency fluctuation process (with the characteristic rate of the order of 10 7 s -1 just above T 0 ) due to the translational diffusion of Li ions.

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Section: Experimental Methodsmentioning

confidence: 99%

Nuclear Magnetic Resonance Study of the Rotational Motion and the Phase Transition in LiBH₄

et al. 2008

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“…Such an approach has been found to give a good description of the proton spin relaxation data for C15-type ZrTi 2 H x in a very wide frequency range. 21 At each temperature the motional contribution to the relaxation rate is calculated as…”

Section: B Proton Spin-lattice Relaxation Measurementsmentioning

confidence: 99%

Hydrogen motion inC15-typeZrMo2Hx
Skripov
¹
,
Cook
²
,
Karmonik
³

et al. 1999
Phys. Rev. B
19
7
22
0
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In order to determine the parameters of H motion in the cubic (C15-type͒ Laves phase ZrMo 2 , we have performed quasielastic neutron scattering measurements and nuclear-magnetic-resonance measurements of the proton spin-lattice relaxation rate on ZrMo 2 H x (0.3рxр1.0) in the temperature range 10-430 K. The diffusive motion of hydrogen in this system can be described in terms of two jump processes: the fast localized H motion within the hexagons formed by interstitial g (Zr 2 Mo 2 ) sites and the slower hopping from one hexagon to the other. The hopping rate l Ϫ1 of the faster process is found to be of the order of 10 10 s Ϫ1 at 300 K. The characteristic frequency d Ϫ1 of the slower process at the same temperature is about 6ϫ10 7 s Ϫ1

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“…Such an approach can be used to search for a distribution of atomic jump rates 19 or a coexistence of several types of jump motion with different rates. 20 Our R 1 measurements have been performed over a wide range of the resonance frequencies (14-90 MHz). The temperature range of our R 1 measurements is also substantially wider than in the previous NMR experiments; this is expected to result in the higher precision of the activation energies obtained from the data.…”

Section: Introductionmentioning

confidence: 99%

“…However, to characterize complex atomic motions, it is often important to investigate the frequency dependence of R 1 . Such an approach can be used to search for a distribution of atomic jump rates or a coexistence of several types of jump motion with different rates . Our R 1 measurements have been performed over a wide range of the resonance frequencies (14−90 MHz).…”

Section: Introductionmentioning

confidence: 99%

Structural and Dynamical Properties of NaBH₄ and KBH₄: NMR and Synchrotron X-ray Diffraction Studies

et al. 2010

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The temperature dependence of the structural parameters of NaBH 4 has been investigated by synchrotron X-ray diffraction over the range of 80-500 K. On the basis of the diffraction data, we revise the structure of the low-temperature (tetragonal) phase of NaBH 4 and discuss the changes in the lattice parameters and the patterns of H • • • H contacts in the low-T and high-T phases. To study the atomic motion in NaBH 4 and KBH 4 , we have performed nuclear magnetic resonance (NMR) measurements of the 1 H and 11 B spin-lattice relaxation rates in these compounds over wide ranges of temperature (82-424 K) and resonance frequency (14-90 MHz). For both compounds, the NMR results are governed by the thermally activated reorientational motion of the BH 4 groups, and the changes in the jump rates of reorientations are traced over the range of 8 orders of magnitude. The activation energies of the reorientational motion are found to be equal to 0.151 ( 0.002 eV (low-T phase of NaBH 4 ), 0.126 ( 0.003 eV (high-T phase of NaBH 4 ), and 0.161 ( 0.002 eV (high-T phase of KBH 4 ). Structural changes in the series of alkali metal borohydrides are analyzed in connection with the changes in the phase-transition temperature, the compressibility, and the barrier of the reorientational BH 4 motion. On the basis of this analysis, we discuss the role of different interatomic interactions in determining the physical properties of alkali metal borohydrides.

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NMR study of hydrogen motion in hydrogen-stabilized C15-type compounds ZrTi2Hx

Cited by 33 publications

References 12 publications

Nuclear Magnetic Resonance Study of the Rotational Motion and the Phase Transition in LiBH₄

Nuclear Magnetic Resonance Study of the Rotational Motion and the Phase Transition in LiBH₄

Hydrogen motion inC15-typeZrMo2Hx
Skripov
¹
,
Cook
²
,
Karmonik
³

et al. 1999
Phys. Rev. B
19
7
22
0
View full text Add to dashboard Cite

Structural and Dynamical Properties of NaBH₄ and KBH₄: NMR and Synchrotron X-ray Diffraction Studies

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NMR study of hydrogen motion in hydrogen-stabilized C15-type compounds ZrTi2Hx

Cited by 33 publications

References 12 publications

Nuclear Magnetic Resonance Study of the Rotational Motion and the Phase Transition in LiBH4

Nuclear Magnetic Resonance Study of the Rotational Motion and the Phase Transition in LiBH4

Hydrogen motion inC15-typeZrMo2HxSkripov1, Cook2, Karmonik3 et al. 1999Phys. Rev. B197220View full textAdd to dashboardCite

Structural and Dynamical Properties of NaBH4 and KBH4: NMR and Synchrotron X-ray Diffraction Studies

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Nuclear Magnetic Resonance Study of the Rotational Motion and the Phase Transition in LiBH₄

Nuclear Magnetic Resonance Study of the Rotational Motion and the Phase Transition in LiBH₄

Hydrogen motion inC15-typeZrMo2Hx
Skripov
¹
,
Cook
²
,
Karmonik
³

et al. 1999
Phys. Rev. B
19
7
22
0
View full text Add to dashboard Cite

Structural and Dynamical Properties of NaBH₄ and KBH₄: NMR and Synchrotron X-ray Diffraction Studies