Ge Pairs and Sb Ribbons in Rare‐Earth Germanium Antimonides RE12Ge7−xSb21 (RE=La–Pr) |
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Authors: | Haiying Bie Arthur Mar Prof. |
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Affiliation: | Department of Chemistry, University of Alberta, Edmonton, AB T6G 2G2 (Canada), Fax: (+1)?780‐492‐8231 |
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Abstract: | The ternary rare‐earth germanium antimonides RE12Ge7?xSb21 (RE=La–Pr; x=0.4–0.5) are synthesized by direct reactions of the elements. Single‐crystal X‐ray diffraction studies indicate that they adopt a new structure type (space group Immm, Z=2, a=4.3165(4)–4.2578(2) Å, b=15.2050(12)–14.9777(7) Å, c=34.443(3)–33.9376(16) Å in the progression from RE=La to Pr), integrating complex features found in RE6Ge5?xSb11+x and RE12Ga4Sb23. A three‐dimensional polyanionic framework, consisting of Ge pairs and Sb ribbons, outlines large channels occupied by columns of face‐sharing RE6 trigonal prisms. These trigonal prisms are centered by additional Ge and Sb atoms to form GeSb3 trigonal‐planar units. A bonding analysis attempted through a Zintl–Klemm approach suggests that full electron transfer from the RE atoms to the anionic substructure cannot be assumed. This is confirmed by band‐structure calculations, which also reveal the importance of Ge? Sb and Sb? Sb bonding. Magnetic measurements on Ce12Ge6.5Sb21 indicate antiferromagnetic coupling but no long‐range ordering down to 2 K. |
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Keywords: | antimony germanium intermetallic phases polyanions rare earths |
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