ISSN:
1600-5767
Source:
Crystallography Journals Online : IUCR Backfile Archive 1948-2001
Topics:
Geosciences
,
Physics
Notes:
X-ray and neutron-diffraction techniques have been used to ascertain the structures of vanadium deuterides with compositions between V2D and V4D3 over a temperature range 5–425 °K. The β phase, V2D, has a monoclinic crystal structure at room temperature with a∼c = 4.46; b = 3.00 Å, β = 95.5°. The deuterium atoms prefer octahedral interstitial sites. Near 425 °K this phase transforms to a b.c.c. phase, and the deuterium atoms prefer tetrahedral sites. The b.c.c. phase of V4D3 has been designated α′ and transforms to α′′ at about 220 °K. This transition is an ordering of deuterium as shown by additional neutron-diffraction peaks. This α′′ structure can be indexed with a∼c∼4.46; b∼3.00 Å; β = 90°. Below 160 °K an additional neutron peak appears at 2&thgr; = 12° which indicates a doubling of the b lattice parameter. This transformation to α′′′ phase involves further ordering. The metal sublattice in α′ and α′′′ is very near b.c.c. Therefore, the neutron patterns do not allow a determination of octahedral or tetrahedral site occupancy. The exact crystal structure cannot be determined. The V–D system is not completely analogous to the V–H system and some of the differences are discussed.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1107/S0021889873008496
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