S. Boudin et al., CATIONIC DISTRIBUTION IN 2 NEW TRIVALENT TRANSITION-METAL DIPHOSPHATES CD(5)M(2)(III) (P2O7)(4) (M=V, FE), Journal of solid state chemistry, 121(2), 1996, pp. 291-300
Two new diphosphates, Cd(5)M(2)(III) (P2O7)(4) with M = V, Fe, isotypi
c with (Fe5Fe2III)-Fe-II(P2O7)(4), have been synthesized. They crystal
lize in the space group C222(1) with a similar to 8.8 Angstrom, b simi
lar to 9.9 Angstrom, and c similar to 24.1 Angstrom. The single crysta
l structure determination of the V phase and the Mossbauer spectroscop
y study of the Fe phase, show that the cationic distribution is differ
ent from that observed in (Fe5Fe2III)-Fe-II(P2O7)(4), i.e., V(III) or
Fe(III) is located in two kinds of sites instead of one kind of site.
A detailed analysis of this structure shows that its octahedral layers
consist of rock salt type ribbons, themselves built up from infinite
chains of edge-sharing octahedra, interconnected through trioctahedral
units of edge-sharing octahedra. On the basis of this description, th
e different cationic distribution compared to the pure Fe phase is the
n explained by the mismatch between infinite octahedral chains and tri
octahedral units, due to the larger size of Cd(II) compared to Fe(II).
(C) 1996 Academic Press, Inc.