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Wendorff M, Röhr C. Alkaline-earth tri-mercurides A
IIHg3 (A
II=Ca, Sr, Ba): binary intermetallic compounds with a common and a new structure type. Z KRIST-CRYST MATER 2018. [DOI: 10.1515/zkri-2018-2054] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Abstract
The alkaline-earth tri-mercurides AHg3 (A=Ca, Sr, Ba) were yielded from stoichiometric melts of the elements in pure phase (in the case of Sr with Sr11Hg54 as a by-product) and their structures were determined by means of single crystal X-ray data. As reported long ago from powder data, CaHg3 and SrHg3 crystallize in the Ni3Sn-type (P63/mmc, a=662.26(2)/689.39(3), c=501.64(2)/510.38(3) pm, Z=2, R1=0.0233/0.0306 for A=Ca/Sr). The structure consists of a hexagonal close packing of ordered layers AHg3 or a dense packing of anti-cuboctahedra [AHg12] (as cation coordination polyhedra, CCP) and [Hg6] octahedra fused via opposite faces to form columns along c. BaHg3 crystallizes in a unique structure type (P4/ncc, a=1193.04(3), c=958.02(5) pm, Z=12, R1=0.0461). It contains three crystallographically different Hg atoms, which form layers of distorted flat square pyramids. In contrast to the layers of the BaAl4-type,
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of the pyramids are missing. Due to the 45 degree rotation of adjacent layers, the connection between the layers is not a ‘apical-to-apical’ one like in BaAl4, but is established by ‘apical-to-basal’ bonds. Compared to the Ca and Sr compound, the CCPs of the two different Ba atoms, which are embedded between the pyramid layers, are increased to 12+4 and 14+2 (for Hg+Ba). For all title compounds and the Li phase LiHg3, which is isotypic to CaHg3, the electronic band structures were calculated within the framework of the FP-LAPW DFT method. Even though the compounds are metals and exhibit only very slight minima of the tDOS at the Fermi level, the electron transfer from the alkali/alkaline-earth element towards mercury is almost complete. Thus, Coulomb interactions and the optimized size and arrangement of the A CCPs, besides the flexible Hg–Hg bonding within the polyanion, determine the structure formation.
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Affiliation(s)
- Marco Wendorff
- Institut für Anorganische und Analytische Chemie , Universität, Freiburg , Albertstr. 21 , D-79104 Freiburg , Germany
| | - Caroline Röhr
- Institut für Anorganische und Analytische Chemie , Universität, Freiburg , Albertstr. 21 , D-79104 Freiburg , Germany
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Hilpert K. Study of the Vaporization of Amalgams with a New Knudsen Cell Mass Spectrometer System Part I: The Compounds MgHg and MgHg2. ACTA ACUST UNITED AC 2010. [DOI: 10.1002/bbpc.19800840513] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Inglesfield JE. Perturbation theory and alloying behaviour II. The mercury-magnesium system. ACTA ACUST UNITED AC 2002. [DOI: 10.1088/0022-3719/2/7/321] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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