Neutronenbeugung an “hexagonalem Chrom”

Crystal structure and lattice dynamics of chromium hydrides

“…[9]. The NiAs-type crystal structure of -CrH agrees with earlier neutron diffraction data [5]. The octahedral hydrogen coordination established for both -CrH and ␥-CrH is characteristic of all hydrides with close-packed metal lattices that are formed by transition metals of groups VI-VIII (see review [10] and recent paper on ␥-CoH [11]).…”

“…Depending on the synthesis conditions, the hydrides can have a hcp () or fcc (␥) metal lattice [2,4]. A room-temperature neutron diffraction investigation of the -CrH produced electrolytically showed that hydrogen atoms occupy octahedral interstitial positions in the hcp chromium lattice and that the hydride is not magnetically ordered [5]. The vibrational spectrum of hydrogen in a high-pressure -CrH sample was studied by inelastic neutron scattering (INS) at 15 K in the range of energy transfers 40-500 meV [6].…”

Magnetic properties of Cr–CrH and YFe2–YFe2H4

“…chromium (with lattice parameter a = 2.895Å) leads to a structural transition. In the present work we considered only the most experimentally investigated hexagonal anti-NiAs structure ␤-CrH phase with space group P6 3 mc [14] and lattice parameters a = 2.72 and c = 4.42Å [5], although other cubic polymorphic phases have been reported [5]. While Cr has an antiferromagnetic behavior with a Néel temperature T N = 311 K [15], it has been shown that the hydride CrH x becomes paramagnetic for values of x larger than x ≈ 0.8 with a strong Pauli susceptibility close to 5 × 10 −6 emu/g [16].…”

Phase Diagram and Superabundant Vacancy Formation in Cr-H Alloys

“…1-3).) Both these hydrides were originally formed by cathodic electrodeposition of Cr, 4) but one of them (hcp) was later synthesized by direct reaction with high pressure H 2 gas as well, 5) and the bcc-hcp boundary was determined in the range of H 2 pressure up to p(H 2 ) = 1.6 GPa and temperature up to T 700 K. 6,7) The structure of the hcp hydride was determined by neutron diffraction to be of NiAs type with Cr atoms occupying the As sites, 8) and its composition was close to x = [H]/[Cr] = 1.0. The hydrogen concentration of the fcc hydride appeared to be higher (x ≥ 1.0), and was initially identified with dihydride of CaF 2 type by analogy with other metal-hydrogen systems, 9) but in fact rather variable depending on the condition of sample preparation.…”