Syntheses and crystal structures of EuZnIn, EuPtIn and EuZnSn: three different site occupancies of the transition metal and indium (tin) atoms on the copper position of the CeCu2 type

Abstract

Abstract The title compounds were prepared from the elements in sealed tantalum tubes at 1320 K and subsequent annealing at 970 K. EuZnIn adopts the CeCu2 structure (space group Imma) with a random distribution of the Zn and In atoms on the Cu position. EuPtIn and EuZnSn crystallize with the ordered CeCu2 structure (space group Pnma). The three structures were refined from single crystal X-ray diffractometer data: a = 482.3(1) pm, b = 780.7(2) pm, c = 827.6(2) pm, wR2 = 0.0773, 367 F 2 values and 13 variables for EuZnIn, a = 746.94(8) pm, b = 447.27(6) pm, c = 843.46(9) pm, wR2 = 0.0689, 381 F 2 values and 20 variables for EuPtIn, and a = 789.4(1) pm, b = 476.7(1) pm, c = 807.9(1) pm, wR2 = 0.0955, 474 F 2 values and 20 variables for EuZnSn. The site occupancies for the transition metal and indium (tin) atoms are different in EuPtIn and EuZnSn. The more electronegative atoms, Pt and Sn, occupy the energetically favored positions with the maximum Pt – Pt and Sn – Sn separation in the rhombus of the [PtIn] and [ZnSn] polyanions. The crystal chemistry and chemical bonding of EuZnIn, EuZnSn, and EuPtIn is discussed in comparison with other intermetallic europium compounds, all of which crystallize with structures related to CeCu2 and TiNiSi.