Ternary arsenides based on platinum–indium and palladium–indium fragments of the Cu₃Au-type: Crystal structures and chemical bonding

Highlights: • Three metal-rich platinum–indium and palladium–indium arsenides were synthesized. • Their crystal structures were determined from powder XRD. • Electronic structures and bonding were studied using DFT/FP-LAPW calculations. • Multi-centered Pt–In or Pd–In bonding was revealed using ELF and ELI-D analysis. • Extra pairwise Pt–Pt interactions are observed only for Pt-based compounds. - Abstract: Three metal-rich palladium–indium and platinum–indium arsenides, Pd₅InAs, Pt₅InAs, and Pt₈In₂As, were synthesized using a high-temperature ampoule technique. Their crystal structures were determined from Rietveld analysis of powder diffraction data. All the compounds crystallize in tetragonal system with P4/mmm space group (Pd₅InAs: a = 3.9874(1) Å, c = 6.9848(2) Å, Z = 1, R_p = 0.053; R_b = 0.013; Pt₅InAs: a = 3.9981(2) Å, c = 7.0597(4) Å, Z = 1, R_p = 0.058, R_b = 0.016; Pt₈In₂As: a = 3.9872(3) Å, c = 11.1129(7) Å, Z = 1, R_p = 0.047; R_b = 0.014). The first two compounds belong to the Pd₅TlAs structure type, while the third one is isotypic with the recently discovered Pd₈In₂Se. Main structural units in all arsenides are indium-centered [TM₁₂In] cuboctahedra (TM = Pd, Pt) of the Cu₃Au type, single- and double-stacked along the c axis in TM₅InAs and Pt₈In₂As, respectively, alternating with [TM₈As] rectangular prisms. DFT electronic structure calculations predict all three compounds to be 3D metallic conductors and Pauli-like paramagnets. According to the bonding analysis based on the electron localization function and electron localizability indicator topologies, all compounds feature multi-centered interactions between transition metal and indium in their heterometallic fragments. Additionally, pairwise interactions between platinum atoms are also observed, indicating a somewhat more localized bonding in the case of platinum-based compounds