Magnesium and Cadmium in Covalently‐Bonded Lonsdaleite Networks: Synthesis, Structure, and Bonding of AETMg2 and SrTCd2 (AE = Ca, Sr; T = Pd, Ag, Pt, Au). Issue 5 (5th March 2013)

• Record Type: Journal Article
• Authors: Kersting, Marcel; Johnscher, Michael; Matar, Samir F.; Pöttgen, Rainer
• Is Part Of: Zeitschrift für anorganische und allgemeine Chemie. Volume 639:Issue 5(2013)
• Page Start: 707
• Page End: 713
• Publication Date: 2013-03-05
• Subjects: Chemistry, Inorganic -- Periodicals; Chemistry -- Periodicals; 540
• DOI: 10.1002/zaac.201200538
• Languages: English
• ISSNs: 0044-2313

Abstract

<abstract abstract-type="main" xml:lang="en"> <title>Abstract</title> <p>The alkaline earth metal compounds <italic>AET</italic>Mg<sub>2</sub> and <italic>AET</italic>Cd<sub>2</sub> (<italic>AE</italic> = Ca, Sr; <italic>T</italic> = Pd, Ag, Pt, Au) were synthesized by induction‐melting (or in muffle furnaces) of the elements in sealed niobium ampoules. The new phases were characterized by powder X‐ray diffraction. The structures of SrPdMg<sub>2</sub> and SrPdCd<sub>2</sub> were investigated by X‐ray diffraction on single crystals: MgCuAl<sub>2</sub> type, <italic>Cmcm</italic>, <italic>a</italic> = 436.42(4), <italic>b</italic> = 1130.1(1), <italic>c</italic> = 820.54(7) pm, <italic>wR</italic><sub>2</sub> = 0.0115, 511 <italic>F</italic><sup>2</sup> values for SrPdMg<sub>2</sub> and <italic>a</italic> = 443.5(2), <italic>b</italic> = 1063.0(2), <italic>c</italic> = 810.2(2) pm, <italic>wR</italic><sub>2</sub> = 0.0296, 386 <italic>F</italic><sup>2</sup> values for SrPdCd<sub>2</sub> with 16 variables for each refinement. The magnesium and cadmium atoms build up [<italic>T</italic>Mg<sub>2</sub>] and [<italic>T</italic>Cd<sub>2</sub>] polyanionic networks, which leave cavities for the calcium and strontium atoms. The bonding variations within the polyanions, which are mainly influenced by the length of the <italic>b</italic> axis are discussed. Ab initio calculations of electronic structure, charge densities, and chemical bonding, characterize SrPdMg<sub>2</sub> with a larger cohesive energy than SrPdCd<sub>2</sub>. This is illustrated by larger bonding Pd–Mg interactions, opposite to compensating Pd–Cd between bonding and antibonding states.</p> </abstract>