Site-specific vanadates Co4Fe3.33(VO4)6 and Mn3Fe4(VO4)6.
Single crystals of Co4Fe3.33(VO4)6 and Mn3Fe4(VO4)6 were grown from equivalent CoO/Fe2O3/V2O5 and MnO/Fe2O3/V2O5 melts, respectively. The former crystallizes in the orthorhombic space group Pnma with parameters a = 4.965(1) A, b = 10.211(1) A, c = 17.188(3) A, and Z = 2 and is a homeotype of such catalysts as Mg2.5VMoO8. The latter crystallizes in the triclinic space group P1 with parameters a = 6.703(2) A, b = 8.137(1) A, c = 9.801(2) A, alpha = 105.56(1) degrees, beta = 105.58(2) degrees, gamma = 102.35(1) degrees, and Z = 1 and is a homeotype of beta-Cu3Fe4(VO4)6, the low-pressure form of alpha-Cu3Fe4(VO4)6. The cobalt analogue deviates in stoichiometry from the reactant melt to form the more dense alpha-Cu3Fe4(VO4)6 structure type comprised of partially occupied face-sharing octahedral and trigonal prismatic coordination sites.
Department of Chemistry, Northwestern University, Evanston, Illinois 60208-3113, USA.
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Wang
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Vander Griend
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Stern
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Poeppelmeier