Neutron diffraction investigation of the dhcp and hcp iron hydrides and deuterides

Neutron vibrational spectroscopy of the Pr2Fe17-based hydrides

“…This is consistent with the value of 105 meV found for the largely degenerate vibrational mode energy of octahedrally coordinated hydrogen in dhcp Fe hydride [9]. These o sites possess a local cubic symmetry with similar Fe H o bond distances of ≈1.894Å [10]. Since the c-oriented Fe H o Fe axis possesses a 0.1Å longer Fe H o bond distance of ≈1.99Å [2] than that along the basal-plane direction, the H o vibration along this direction should be noticeably lower.…”

High‐Pressure Geophysical Properties of Fcc Phase FeHX

“…Hydrogen content of FeH X can be estimated using the formula: in which V FeHX and V Fe are unit cell volumes of iron hydride and pure iron metal, respectively, and Δ V H is a predetermined volume expansion due to a single formula unit of interstitial hydrogen. The value of Δ V H is not precisely known for iron hydrides, and previous studies have utilized fixed values ranging from 1.8 to 2.6 Å 3 (Antonov et al, ; Badding et al, ; Fukai, ; Narygina et al, ). The basis for these approximations is the interstitial volumes associated with other 3d ‐transition metal hydrides or deuterides (e.g., CoH; Fukai, ) at ambient pressure.…”

Hydrogenation of iron in the early stage of Earth’s evolution

“…So far, however, neutron beam fluxes have remained very low, and there has been no in situ observation of iron hydride or deuteride under pressure. Although high-pressure phases of iron hydride and its deuteride that form by the reaction of iron and hydrogen or deuterium have previously been examined by powder neutron diffraction25, the observations were made at ambient pressure in a metastable condition after quenching by rapid freezing. A new beamline dedicated to high- P – T in situ neutron studies was recently constructed at the pulsed spallation neutron source at the Japan Proton Accelerator Research Complex (J-PARC), Tokai, Japan.…”