Crystal and electronic structure of the new ternary phosphide Ho5Pd19P12

The title compound was prepared from the pure elements by sintering. The crystal structure was investigated by means of powder X-ray diffraction data. Ho5Pd19P12 exhibits the hexagonal Ho5Ni19P12-type structure with space group P 6 ‾ 2 m $P‾{6}2m$ , a = 13.1342(2), c = 3.9839(1) Å, R I = 0.060, R p = 0.080. The crystal structure can be described as a combination of two types of the structural units, [HoPd6P3] and [Ho3Pd10P6], respectively, mutually displaced by 1/2 along the crystallographic c axis. Quantum chemical calculations have been performed to analyze the electronic structure and provide deeper insight into the structure-property relationships. The results of the quantum chemical calculations indicate that the material features metallic bonding between Ho and Pd and covalent bonding between Pd and P.

Synthesis, crystal and electronic structure of CaNi2Al8

Single crystals of CaNi2Al8 were obtained during attempts to synthesize CaNi2Al9 from the elements in Nb or Al2O3 crucibles in an induction furnace. The orthorhombic structure of CaNi2Al8 was refined based on single-crystal X-ray diffraction data (Pbam, a = 1252.30(6), b = 1443.73(7), c = 395.78(2) pm, wR2 = 0.0423, 2225 F 2 values, 63 variables) and full atomic ordering was observed. The compositions of the samples were checked by powder X-ray diffraction experiments; no phase pure samples could be obtained. To analyze the bonding situation of the title compound in detail, quantum-chemical calculations were conducted. According to Density Functional Theory, CaNi2Al8 is a intermetallic compound with a polar covalently bonded [Ni2Al8] network showing strong Ni–Al and Al–Al bonding.

Mechanism of Defect Formation in Zr1 – xVxNiSn Thermoelectric Material

Crystal and electronic structure, transport and energy state characteristics of the Zr1−xVx NiSn (0.01 ≤ x ≤ 0.1) thermoelectric material are investigated in the 80–400 K temperature interval. A mechanism of simultaneous generation of structural defects of the acceptor and donor nature, which determines the electric conductivity of the material, is established. It is shown that energetically expedient is a simultaneous occupation of the 4c position of Ni (3d84s2) atoms by V (3d34s2) atoms, which generates structural defects of the acceptor nature and the impurity acceptor band Ꜫ1A, as well as the 4a position of Zr (4d25s2) atoms, generating structural defects of the donor nature and the impurity donor band Ꜫ2D.