New ternary phosphides RE5Pd9P7 (RE=Tm, Lu): synthesis, crystal and electronic structure

The crystal structure of the new ternary phosphideTm5Pd9P7 was determined from powder X‐ray diffraction data: space group P6‾ , a=9.9971(2), c=3.94371(8) Å, RI=0.0518, Rp=0.0667, Rp=0.0667, wRp=0.1065. The crystal structure of the phosphide Tm5Pd9P7 is closely related with the Zr2Fe12P7‐type, and is formed by combination of two types of structural units with the compositions [TmPd6P3] and [TmTm3Pd3P3] mutually displaced by 1/2 along the c axis. Connection of the last units forms the trigonal prisms [Tm6] around P3 atoms in the crystallographic position 1a (0 0 0). The isotypic ternary phosphide Lu5Pd9P7 was synthesized (a=9.9934(7), c=3.9207(4) Å). The electronic and bonding properties of Tm5Pd9P7 are obtained from tight binding linear muffin‐tin orbital (TB‐LMTO) calculations and a crystal orbital Hamiltonian population (COHP) bonding analysis. These analyses show strong covalent bonding within (Pd9P7)15− nanotubes which are ionically bound via the Tm atoms to three dimensional network.