Dynamics of hydrogen in Pr2Fe17H4 and Pr2Fe17H5 studied by quasielastic neutron scattering

Evolution of the Reorientational Motions of the Tetrahydroborate Anions in Hexagonal LiBH4–LiI Solid Solution by High-Q Quasielastic Neutron Scattering

“…A general formalism for such motion can be found elsewhere. 39 In this case, the incoherent scattering functions in eq 2 are written: 40,41…”

Hydrogen dynamics in Ce2Fe17H5: inelastic and quasielastic neutron scattering studies

“…The presence of such correlations does not affect the validity of equation 2, since in our case the observed neutron scattering is dominated by the incoherent contribution, and the EISF is determined by the set of sites visited by an individual H atom [22,23]. In the case of Pr 2 Fe 17 H x , it was found [10] that the values of p for compounds with x = 5 and 4 are nearly the same. Thus, removing one-half of the hydrogen atoms from the 18g sites does not lead to any significant increase in the fraction of mobile H atoms.…”

“…The existence of fast hydrogen jump motion in Pr 2 Fe 17 H x was first revealed by Mössbauer spectroscopy [8]. Subsequent quasielastic neutron scattering (QENS) experiments [9,10] gave direct evidence that this fast jump process corresponds to localized H motion over the 18g-site hexagons, whereas H atoms at the 9e sites in Pr 2 Fe 17 H x remain static on the time scale of the QENS measurements. Such a microscopic picture of hydrogen motion in Pr 2 Fe 17 H x is consistent with the structure of the H sublattice in Th 2 Zn 17 -type hydrides [1,3], since the 18g-site hexagons appear to be well separated from each other and from the 9e sites.…”

“…While the structural aspects of Th 2 Zn 17 -type hydrides R 2 Fe 17 H x are well understood, little is known about the hydrogen dynamics in these compounds. The only Th 2 Zn 17 -type system for which the H dynamics has been investigated in detail is Pr 2 Fe 17 H x [8][9][10][11]. The existence of fast hydrogen jump motion in Pr 2 Fe 17 H x was first revealed by Mössbauer spectroscopy [8].…”

Neutron vibrational spectroscopy of the Pr2Fe17-based hydrides

“…The t sites form arrays of isolated, partially hydrogen-occupied hexagons in the basal plane of the Pr 2 Fe 17 structure. The t-site hydrogen (H t ) atoms jump readily among adjacent vertices of each hexagon, as evidenced initially by Mössbauer spectroscopy [4] and subsequently in greater detail by quasielastic neutron scattering measurements [5,6]. This interesting H t dynamical behavior is dictated by the details of the hydrogen binding potentials.…”