(Ca/Sr)Au{sub x}Cd{sub 1-x}: Stacking variants of the CrB-FeB series

Journal Article · Thu Jan 14 23:00:00 EST 2010 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1016/j.jssc.2009.10.027· OSTI ID:21372462

Harms, Wiebke; Duerr, Ines; Daub, Michael ^[1]; Roehr, Caroline ^[1]

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1. Institut fuer Anorganische und Analytische Chemie, University of Freiburg, Albertstr. 21, D-79104 Freiburg (Germany)

The structural chemistry of binary 1:1 alkaline earth metallides A{sup II}M (M=p-block or late transition element) is dominated by planar M zig-zag chains, which are stacked in different orientations (CrB (c) to FeB (h) type) and with variable stacking distances (types I and II). As a case study of the electronic influences, the substitution of Au against Cd in the respective Ca and Sr aurides was examined by means of experimental, crystallographic and computational methods. Starting from CaAu, up to 11% of Au can be substituted by Cd without a change in the CrB structure type (orthorhombic, space group Cmcm, a=398.2(1), b=1122.6(6), c=460.9(2)pm, Z=4, R1=0.0303). Starting from SrAu (stacking sequence (hc){sub 2}(h{sub 2}c){sub 2}), depending on the proportion of the Cd substitution a successive change to structures with increased hexagonality is observed: In SrAu{sub 0.93}Cd{sub 0.07} (monoclinic, space group P2{sub 1}/m, a=621.3(4), b=472.4(2), c=1216.1(9)pm, beta=96.97(5){sup 0}, Z=6, R1=0.0467) the stacking sequence is h{sub 2c}, i.e. the hexagonality is 66.67%. A slightly more increased Cd content in SrAu{sub 0.78}Cd{sub 0.22} (orthorhombic, space group Pnma, a=3243.3(8), b=474.17(8), c=626.20(9)pm, Z=16, R1=0.0682) drives the hexagonality to 75%, with a (h{sub 3}c){sub 2} stacking sequence known from several rare earth nickel compounds. Further Cd substitution is not possible. However, in the Cd-rich section of the two series, where the CsCl/beta-brass structure type occurs for both alkaline earth elements, a small Au substitution, as determined from powder data by Rietveld refinements, is possible. The substitution limit and the stability ranges of the CsCl and the CrB type can be rationalized from the calculated band structures. Geometrical and electronic criteria are used to compare and discuss the stability ranges in a structural map. - SrAu{sub 0.93}Cd{sub 0.97}, one of the stacking sequences of the CrB/FeB structure type series found in the quasibinary section SrAu-SrCd.

• OSTI ID: 21372462
• Journal Information: Journal of Solid State Chemistry, Journal Name: Journal of Solid State Chemistry Journal Issue: 1 Vol. 183; ISSN 0022-4596; ISSN JSSCBI
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
ALLOYS
BORIDES
BORON COMPOUNDS
CADMIUM ALLOYS
CALCIUM ALLOYS
CHROMIUM BORIDES
CHROMIUM COMPOUNDS
CRYSTAL LATTICES
CRYSTAL STRUCTURE
CRYSTALLOGRAPHY
GOLD ALLOYS
IRON BORIDES
IRON COMPOUNDS
MONOCLINIC LATTICES
NICKEL COMPOUNDS
ORIENTATION
ORTHORHOMBIC LATTICES
RARE EARTH COMPOUNDS
SPACE GROUPS
STRONTIUM ALLOYS
SYMMETRY GROUPS
TRANSITION ELEMENT ALLOYS
TRANSITION ELEMENT COMPOUNDS