Structure-Composition Subtleties in NaZn13-type Derivatives of Sr/Ca(AuxAl1-x)(12-13)
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Ames National Laboratory is a government-owned, contractor-operated national laboratory of the U.S. Department of Energy (DOE), operated by and located on the campus of Iowa State University in Ames, Iowa.
For more than 70 years, the Ames National Laboratory has successfully partnered with Iowa State University, and is unique among the 17 DOE laboratories in that it is physically located on the campus of a major research university. Many of the scientists and administrators at the Laboratory also hold faculty positions at the University and the Laboratory has access to both undergraduate and graduate student talent.
The Department of Chemistry seeks to provide students with a foundation in the fundamentals and application of chemical theories and processes of the lab. Thus prepared they me pursue careers as teachers, industry supervisors, or research chemists in a variety of domains (governmental, academic, etc).
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The Department of Chemistry was founded in 1880.
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1880-present
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- College of Liberal Arts and Sciences (parent college)
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Abstract
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.