Determination of the position and occupancy of deuterium in CaNi5 deuterides by neutron diffraction

Structural and hydrogen sorption properties of SmNi5−xAlx system – An experimental and theoretical study

“…In the previous DFT study on the SmNi 5 H x compounds [16] and some other DFT studies on isostructural ANi 5 H x compounds [65e68] it was found that H atoms prefer octahedral(-like) (off)-centered ((O)C) 3f(12n) positions 2 . These results are in agreement with the experimental findings obtained from the neutron diffraction experiments in the case of LaNi 5 D x [70,71] and CaNi 5 D x [72,73] compounds with lower (x < 1.0) deuterium content. Therefore, in this segment of the computational part of the present study it was assumed that H atoms occupy (O)C positions which could be coordinated with 0À2 Al atoms.…”

Phase transformation in La(CoxNi5−x)–H systems (x=2, 3, 5) studied by in situ X-ray diffraction

“…However, hydrogen occupation in ␥-LaCo 5 D 4.5 should be different from that in ␤ II -PrCo 5 D 2.9 because there is an apparent difference in the hydrogen content between them. Based on the hydrogen content, ␤-CaNi 5 D 4.8 with Im2m symmetry [24] possibly has a hydrogen occupation similar to ␥-LaCo 5 D 4.5 . The hydrogen occupation in ␥-LaCo 5 D y attracts much interest because the c-axis significantly contracts during the phase transformation from the ␤ phase to the ␥ phase even though the hydrogen content increases, which is quite unusual.…”

An in-situ neutron diffraction study of the ageing of CaNi5Dx at 80°C and 9bar

“…Previous experimental studies of the so named 'disproportionation' process in AB 5 [4]. However, while the evidence for B (in metallic form) continues to increase, the evidence of any intermetallic A x B y H z or AH x phases remains weak and inconclusive.…”

“…Neutron diffraction measurements [5] have identified the dilute concentration hexagonal ␣ phase (CaNi 5 D 0.3 ) in P6/mmm, the two intermediate concentration orthorhombic phases ␣ (CaNi 5 D 0.9 ) and ␤ (CaNi 5 D 4.8 ), both in Im2m, and the concentrated trigonal ␥ phase (CaNi 5 D 6.1 ) in P31m. In terms of increasing pressure, the three plateau regions correspond to two-phase mixtures of the ␣/␣ , ␣ /␤, and ␤/␥ phases, respectively.…”

“…Recent in-situ diffraction data has demonstrated for the LaNi 5 system that the intermediate concentration ␥ phase plays a fundamental role in the long-term extrinsic segregation of fcc Ni [10] during capacity decay. CaNi 5 also takes the CaCu 5 type structure, and as such, its intermediate concentration orthorhombic hydride phases [5] should be regarded as a structural test bed for the positional origins of Ni.…”