Structure‐Composition Subtleties in NaZn13‐type Derivatives of Sr/Ca(AuxAl1–x)12–13

In the ternary (Sr/Ca)‐Au‐Al phase space for 5–8 at % Sr/Ca and nearly equimolar mixture of Au and Al, five new NaZn13‐derivatives Sr/Ca(AuxAl1–x)12–13 were discovered and their atomic site preferences and electronic structures were studied: (1) at higher Au content, cubic SrAuxAl13–x [7.24(2) ≥ x ≥...

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Published in:Zeitschrift für anorganische und allgemeine Chemie (1950) 2021-02, Vol.647 (2-3), p.41-52
Main Authors: Pham, Joyce, Palasyuk, Andriy, Miller, Gordon J.
Format: Article
Language:English
Subjects:
Aluminum
Atomic properties
Atomic site preference
Chemical pressure
Coloring problem
Derivatives
Electropositivity
Gold
Icosahedrons
NaZn13
Polar intermetallics
Single crystals
Site preference (crystals)
Strontium
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Summary:In the ternary (Sr/Ca)‐Au‐Al phase space for 5–8 at % Sr/Ca and nearly equimolar mixture of Au and Al, five new NaZn13‐derivatives Sr/Ca(AuxAl1–x)12–13 were discovered and their atomic site preferences and electronic structures were studied: (1) at higher Au content, cubic SrAuxAl13–x [7.24(2) ≥ x ≥ 6.68(2)] shows no obvious atomic site preferences; (2) at lower Au content, tetragonal SrAuxAl13–x [6.59(1) ≥ x ≥ 6.35(3)] shows icosahedra exclusively centered by Al and preferential atomic arrangements to maximize the number of Au–Al (or Al‐rich) shortest distances; (3) a monoclinic SrAu6.10(3)Al6.40 compound was uncovered from studies of a single crystal specimen with problematic refinement issues but more detailed powder X‐ray diffraction analysis which suggest even more pronounced geometric distortion from the NaZn13‐type structure as well as preferential arrangements for Au–Al nearest contacts; (4) tetragonal SrAu5.75(2)Al6.25 with all empty icosahedra; and (5) orthorhombic CaAu6.09(2)Al6.01(1) with icosahedra that are half empty and half partially occupied by Al. Electronic DOS and COHP curves were used to rationalize the structural depiction of Sr/Ca(AuxAl1–x)12–13 as icosahedra packing of (AuxAl1–x)12–13 with voids filled by the electropositive Sr/Ca.
ISSN:0044-2313
1521-3749
DOI:10.1002/zaac.202000329