B. Bertheville et al., Structure data for K2MgH4 and Rb2CaH4 and comparison with hydride and fluoride analogues, J ALLOY COM, 325(1-2), 2001, pp. L13-L16
Neutron powder diffraction data on the deuterides of the title compounds co
nfirm their tetragonal K2NiF4 type structures (space group I4/mmm; K2MgD4:
a=4.0361(1) Angstrom, c=13.5921(5) Angstrom, c/a=3.37; Rb2CaD4: a=4.4976(2)
Angstrom, c=14.8294(7) Angstrom, c/a=3.30; T=293 K). The alkaline earth ce
ntred deuterium octahedra in the magnesium compound are compressed along th
e tetragonal axis (Mg-D=2.00 Angstrom axial, 2.02 Angstrom basal), whereas
those in the calcium compound are elongated (Ca-D=2.30 Angstrom axial, 2.25
Angstrom basal). A survey of isostructuraI hydride and fluoride analogues
shows that big alkali cations tend to flatten the anion octahedra and to in
crease the cell parameter ratios c/a, whereas big alkaline earth cations te
nd to elongate the anion octahedra and to decrease c/a. (C) 2001 Elsevier S
cience B.V. All rights reserved.