ISSN:
0947-6539
Keywords:
conducting materials
;
electronic structure
;
magnetic properties
;
phase transitions
;
sulfur
;
Chemistry
;
General Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
Ba6Ni25S27, synthesized by solid-state reaction of BaS, NiS, and Ni at 675°C, is cubic (Pm3m, a = 10.057(1) Å). The structure was refined by using powder X-ray diffraction and Rietveld methods with Rp = 6.28%, Rwp = 8.13%, χ2 = 3.120. The structure, isotypic with Ba6Co25S27, consists of an extended network of Ni8S14 pseudo-cube clusters, NiS6 octahedra, and Ba6S octahedra. Extended Hückel calculations of this compound indicate the band structure near the Fermi level to be composed mostly of d-character orbitals of tetrahedral Ni, and reveal a peak in the density of states slightly below the Fermi level. The temperature dependence of the electrical resistivity exhibits a local maximum with thermal hysteresis at around 230 K. Above and below this transition, the slope of the resistivity is positive, with a room-temperature resistivity (ρ = 0.23 mωcm) in the range for that of a poor metal conductor. Magnetic susceptibility measurements from 4 to 900 K indicate a sharp change in slope at around 225 K, with a steadily increasing susceptibility up to 900 K. The susceptibility below 225 K suggests Pauli paramagnetic behavior. Low-temperature powder X-ray diffraction and subsequent structure refinement shows that the lattice parameter, a, undergoes a slight change in slope at temperatures of around 235 K.
Additional Material:
9 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/chem.19970031121
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