Fei Wang - EuAgxAl11-x with the BaCd11-Type Structure: Phase Width, Coloring, and Electronic Structure

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      Publication Details (including relevant citation   information):

      Wang, F.; Pearson, K. N.; Miller, G. J.; Chem. Mater. 2009, 21,   230.

      Abstract:

      The EuAgxAl11−x (loading   composition, x ≈ 3−8) ternary system was experimentally   and theoretically investigated. According to powder X-ray   diffraction, phases adopting the BaCd11-type structure   (space group I41/amd, Z =   4) were obtained for a narrow composition range, i.e., x  ≈ 5−6. Single-crystal X-ray crystallography showed that Ag and Al   atoms share 4b, 8d, and 32i sites and that 4b site distinctly   prefers Ag to Al. Eu is divalent in these phases, which was   supported by both magnetometry and unit-cell dimensional   analysis. Comparison with other isostructural RE (rare   earth)−Ag−Al compounds showed that the BaCd11-type   structure is stable specifically at the valence electron   concentrations (vec) of 2.1−2.3 e per atom. A   Mulliken population analysis was performed with Extended Hückel   calculations, the result of which explained the observed site   preferences of the Ag and Al atoms. TB-LMTO-ASA calculations were   used to study the relative energies of various models established   according to crystallography and the coloring problem was   included by maximizing the number of Ag−Al contacts. The   calculated density of states (DOS) and crystal orbital   Hamiltonian population (COHP) curves explain the stability of the   BaCd11-type structure at specifically vec ≈ 2.1−2.3   e per atom in RE−Ag−Al ternary compounds.

      Address (URL): http://pubs.acs.org/doi/abs/10.1021/cm803021u