Preparation and Crystal Structure of the Intermetallics La4Mo7Al51and La4W7Al51

✍ Scribed by Verena M.T Thiede; Wolfgang Jeitschko

• Publisher: Elsevier Science
• Year: 1999
• Tongue: English
• Weight: 147 KB
• Volume: 143
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.1999.8076

✦ Synopsis

The title compounds have been prepared by reaction of the elemental components in alumina crucibles. Their crystal structure was determined from single-crystal X-ray data of La 4 Mo 7 Al 51 : P3 m1, a ‫؍‬ 1042.4(3) pm, c ‫؍‬ 1174.3(3) pm, Z ‫؍‬ 1, R ‫؍‬ 0.023 for 892 structure factors and 62 variables. The lattice constants of the isotypic compound La 4 W 7 Al 51 are a ‫؍‬ 1041.3(4) pm, c ‫؍‬ 1173.3(4) pm. The structure is closely related to that reported for Ca 4 Cr 7 Al 48 . The atoms occupy 12 atomic positions, of which four show significant deviations from the full occupancy, resulting in the formula La 3.662(4) Mo 7 Al 50.26(8) . All atoms have high coordination numbers. The two different lanthanum atoms are coordinated by 1 lanthanum and 15 aluminum atoms, the two molydenum sites by 12 and 11 aluminum atoms, respectively, in the form of bi-and monocapped pentagonal antiprisms. The eight different aluminum atoms have between 11 and 14 neighbors with between 2 and 4 lanthanum and/or molybdenum atoms. All coordination polyhedra of the aluminum atoms have at least some rectangular or nearly rectangular faces.