CRYSTAL STRUCTURE OF THE COMPOUND Y1-xYbxFe2Si2 x=0.24: SINGLE CRYSTAL INVESTIGATION

For the first time, the complete single-crystal structure study of the compound Y1-xYbxFe2Si2 x=0.24 was performed. It belongs to the CeGa2Al2 structure type, Pearson’s symbol tI10,139, space group I4/mmm, lattice parameters a = 3.911(1), c = 9.929(4) Å, Z = 2. The compound was prepared by arc-melting of the initial elements with а purity of not less than 99.9 % under argon followed by annealing in silica tubes at 870 K for 1400 h. Single crystals for structural examination were selected under a microscope from the broken alloys obtained. X-ray diffraction data of one of the irregularly faceted single crystals was obtained at a temperature of 300(2) K using a single crystal X-ray diffractometer Bruker D8 Venture with monochromatized MoKα-radiation. The structure is refined using the program SHELXL, version 2018/3 (full-matrix least-squares refinement with anisotropic atomic parameters), R1 = 0.015, wR2 = 0.036 for 107 unique reflections with Io > 2σ(Io) and 10 refined parameters. Coordinates of atoms are the following: 2R at 2а 0 0 0; 4Fe at 4d 0 1/2 1/4; 4Si at 4e 0 0 z, z=0.3760(1), R = 0.767(5)Y + 0.233(5)Yb. The coordination numbers of R, Fe, and Si atoms are 20, 12, and 10, respectively. The interatomic distances, except Fe–Si, are longer than the sum of the metallic radii of the corresponding atoms. Fe–Si distances (2.322(1) Å) are smaller than the sum of the radii of these atoms (2.43 Å) and indicate a significant interaction between Fe and Si in the structure. Currently known RFe2Si2 (R=Y, Yb) are members of complete series of compounds RFe2Si2 (R=rare earths) isotypic with CeGa2Al2. A partial substitution Y by Yb does not change the crystal structure as well a cell volume of Y1-xYbxFe2Si2 x=0.24.