A new polymorph of NiSb2 was obtained under high-pressure/temperature condi
tion of 6 GPa and 550-650 degreesC. The crystal structure is orthorhombic w
ith the space group Phca (No. 61). isostructural with the low-temperature f
orm of NiAs2 (pararammelsbergite). The crystallographic parameters were ref
ined by the Rietveld analysis of the powder X-ray diffraction data (a = 0.6
2866(2) nm, b-0.63643(2) nm, c = 1.23670(3) nm, Z = 8). The structure can b
e regarded as an intermediate structure between the marcasite-type and the
pyrite-type. The pararammelsbergite-type NiSb2 is a high-pressure form of N
iSb2 and the density is slightly higher than that of ambient pressure form
with the marcasite-type structure. (C) 2000 Elsevier Science Ltd. All right
s reserved.