Erschienen in:Zeitschrift für anorganische und allgemeine Chemie
Sprache:
Englisch
DOI:
10.1002/zaac.200600113
ISSN:
0044-2313;
1521-3749
Entstehung:
Anmerkungen:
Beschreibung:
<jats:title>Abstract</jats:title><jats:p>The new magnesium based intermetallic compounds Nd<jats:sub>4</jats:sub>Co<jats:sub>2</jats:sub>Mg<jats:sub>3</jats:sub> and Sm<jats:sub>4</jats:sub>Co<jats:sub>2</jats:sub>Mg<jats:sub>3</jats:sub> were synthesized by induction melting of the elements in sealed tantalum tubes in a water‐cooled sample chamber. The compounds were studied by X‐ray powder and single crystal diffractometer data: <jats:italic>P</jats:italic>2/<jats:italic>m</jats:italic>, <jats:italic>a</jats:italic> = 765.42(14), <jats:italic>b</jats:italic> = 380.53(5), <jats:italic>c</jats:italic> = 832.47(16) pm, β = 109.79(1)°, wR2 = 0.0489, 1026 F<jats:sup>2</jats:sup> values for Nd<jats:sub>4</jats:sub>Co<jats:sub>2</jats:sub>Mg<jats:sub>3</jats:sub>, <jats:italic>a</jats:italic> = 760.12(15), <jats:italic>b</jats:italic> = 377.11(6), <jats:italic>c</jats:italic> = 826.84(16) pm, β = 109.68(1)°, wR2 = 0.0518, 731 F<jats:sup>2</jats:sup> values for Sm<jats:sub>4</jats:sub>Co<jats:sub>2</jats:sub>Mg<jats:sub>3</jats:sub> with 30 variable parameters for each refinement. These ternary magnesium compounds crystallize with a new structure type. They are simple 1:3 intergrowth variants of distorted AlB<jats:sub>2</jats:sub> and CsCl related slabs of compositions <jats:italic>RE</jats:italic>Co<jats:sub>2</jats:sub> and <jats:italic>RE</jats:italic>Mg. The Co–Co distance within the AlB<jats:sub>2</jats:sub> related slab is 237 pm in Nd<jats:sub>4</jats:sub>Co<jats:sub>2</jats:sub>Mg<jats:sub>3</jats:sub> and 235 pm in Sm<jats:sub>4</jats:sub>Co<jats:sub>2</jats:sub>Mg<jats:sub>3</jats:sub>. The crystal chemistry of this new structure type is discussed in line with the related structures of Mn<jats:sub>2</jats:sub>AlB<jats:sub>2</jats:sub> and Mo<jats:sub>2</jats:sub>FeB<jats:sub>2</jats:sub> which are 1:1 intergrowth variants of the two slabs.</jats:p>