title: Synthesis and crystal and electronic structures of the Na2(Sc4Nb2)(Nb6O12)3 octahedral niobium cluster oxide. Structural correlations between AnBM6L12(Z) series and Chevrel Phases.
abstract: We report here the synthesis and crystal and electronic structures of the Na(2)(Sc(4)Nb(2))(Nb(6)O(12))(3) niobium oxide whose structure is related to that of Ti(2)Nb(6)O(12). It constitutes a new member of the larger A(n)()BM(6)L(12)(Z) families (A = monovalent cation located in tetrahedral cavities of units, B = monovalent or trivalent cations located in octahedral cavities of units, M = rare earth, Zr, or Nb, Z = interstitial except for M = Nb). The structural relationships between the A(n)BM(6)L(12)(Z) series (M(6)L(i)(12)L(a)(6) unit-based compounds with a M(6)L(i)(6)L(i-a)(6/2)L(a-i)(6/2) cluster framework) and Chevrel Phases (M(6)L(i)(8)L(a)(6) unit-based compounds with a M(6)L(i)(2)L(i-a)(6/2)L(a-i)(6/2) cluster framework) are shown in terms of M(6)L(18) and M(6)L(14) unit packing. Despite a topology similar to that encountered in Chevrel Phases, intercalation properties are not expected in the Nb(6)O(i)(6)O(i-a)(6/2)O(a-i)(6/2) cluster framework-based compounds. Finally, it is shown, from theoretical LMTO calculations, that a semiconducting behavior is expected for a maximum VEC of 14 in the Nb(6)O(i)(6)O(i-a)(6/2)O(a-i)(6/2) cluster framework.
authors.affiliation: Laboratoire de Chimie du Solide et Inorganique Moléculaire, UMR 6511 CNRS-Université de Rennes 1, ENSC Rennes, Institut de Chimie de Rennes, Avenue du Général Leclerc, F-35042 Rennes Cedex, France. stephane.cordier@univ-rennes1.fr
authors.forename: Stéphane
authors.initials: S
authors.lastname: Cordier
authors.forename: Kaplan
authors.initials: K
authors.lastname: Kirakci
authors.forename: Bruno
authors.initials: B
authors.lastname: Fontaine
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Halet
authors.forename: Régis
authors.initials: R
authors.lastname: Gautier
authors.forename: Christiane
authors.initials: C
authors.lastname: Perrin