Boron-induced hydrogen localization in the novel metal hydride LaNi 3BHx (x = 2.5-3.0)
(2005) Inorganic Chemistry — Vol. 44, n° 12, p. 4398-4406 (2005)
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- Abstract
- The crystal structure and hydrogenation properties of the intermetallic boride LaNi3B were investigated. The hydrogen-free compound has a novel structure with orthorhombic symmetry, space group Imma, a = 4.9698(8) Å, b = 7.1337(8) Å, c = 8.3001(9) Å, and V = 294.26(7) Å3. Thermal gravimetrical analysis reveals a hydride phase that forms near ambient conditions within the compositional range LaNi 3BH2.5-3.0. Single-crystal X-ray diffraction on both the alloy and the hydride, using the same crystal, shows an expansion in the a-c plane (by up to ∼8%) and a contraction along b (by ∼3%), while the symmetry changes from Imma to Bmmb (Cmcm) and the unit cell doubles along a and b. The cell parameters for the composition of LaNi3BD 2.73(4) are a = 10.7709(7) Å, b = 16.0852(10) Å, c = 7.6365(5) Å, V = 1323.03(15) Å3, and space group Cmcm. Four nearly fully occupied interstitial hydrogen sites were located by neutron powder diffraction on deutendes and found to have tetrahedral, La 2Ni2 (D1,D2), trigonal-prismatic, La3Ni 3 (D3), and trigonal-bipyramidal, La2Ni3 (D4), metal environments. The structure can also be described in terms of alternating quasi two-dimensional [NiD]- slabs (Ni-D = 1.62-1.97 Å) and La-B sheets for which bond-valence sums suggest the limiting formula La 3+B0[Ni3D3]3-. The La-B planes do not accommodate deuterium; the B-D and D-D interactions appear to be repulsive. The shortest B-D and D-D contacts are 2.52(2) and 2.33(2) Å, respectively. © 2005 American Chemical Society.
- Affiliations
University of Geneva (Switzerland) Crystallography
Citations
Filinchuk, Y., & Yvon, K. (2005). Boron-induced hydrogen localization in the novel metal hydride LaNi 3BHx (x = 2.5-3.0). Inorganic Chemistry, 44(12), 4398-4406. https://doi.org/10.1021/ic050416j (Original work published 2005)