High-pressure crystal chemistry of nickel sulphides

Monochromatic synchrotron x-ray diffraction data collected at CHESS and ESRF at varying temperatures and pressures were used to investigate the crystal structures of phases with the composition Ni3S2. At low pressures Ni3S2 has the rhombohedral heazlewoodite structure (Ni3S2 I), but transforms to two new structures at higher pressures and temperatures. Ni3S2 III is orthorhombic (space group Cmcm, a = 3.118 A, b = 10.862 A, c 6.730 A) and contains Ni coordinated by five S atoms in a square pyramid. The structure of Ni3S2 III is described in this report along with an analysis of electronic structures of nickel sulphides