Crystal chemistry and thermodynamic properties of anisotropic Ce2Ni7H4.7 hydride
2007 (English)In: Journal of Solid State Chemistry, ISSN 0022-4596, E-ISSN 1095-726X, Vol. 180, no 9, 2566-2576 p.Article in journal (Refereed) Published
A new intermetallic deuteride Ce2Ni7D4.7 with an anomalous volume expansion has been studied. Its structure was solved on the basis of in situ neutron diffraction data. Expansion proceeds along the c-axis and within the CeNi2 slabs only. All D atoms are located inside these slabs and on the border between CeNi2 and CeNi5. Ordering of D atoms in the bulk of CeNi2 is accompanied by substantial deformation of these slabs thus lowering the hexagonal symmetry to orthorhombic [space group Pmcn (No. 62); a = 4.9251(3) angstrom b = 8.4933(4) angstrom, c = 29.773(1) angstrom]. Inside the CeNi2 layer the hydrogen sublattice is completely ordered; all D-D distances exceed 2.0 angstrom Local coordination of Ni by D inside the CeNi, blocks is of "open", saddle-like type. Hydrogen ordering is mainly determined by Ce-H and H-H interactions. The press ure-composition-temperature measurements yielded the following thermodynamic parameters of the formation of the hydride: Delta H = -22.4 kJ/MOl(H), Delta S = -59.9 J/(K mol(H)).
Place, publisher, year, edition, pages
2007. Vol. 180, no 9, 2566-2576 p.
metal hydrides, crystal structure and symmetry, neutron diffraction, pressure-composition-temperature relationships
Natural Sciences Engineering and Technology
IdentifiersURN: urn:nbn:se:uu:diva-143405DOI: 10.1016/j.jssc.2007.07.002ISI: 000249591300021OAI: oai:DiVA.org:uu-143405DiVA: diva2:390045