Abstract
Using argon as the pressure medium, the structural and elastic properties of NiO have been investigated up to 67 GPa by the in situ synchrotron x-ray diffraction in a diamond anvil cell. Up to 67 GPa, NiO remains in the rhombohedral distorted rocksalt structure without phase transition. The lattice parameters of a and c, indexed in the hexagonal lattice, were found to decrease monotonically with increasing pressure, while the c/a ratio remains almost constant. The elastic properties of NiO were studied by analyzing the linewidth of various diffraction perks, which indicates that the factor S = (S-11-S-12-S-44/2) is negative although the single-crystal elastic compliances S11 is positive, respectively, in the investigated pressure range. (c) 2008 American Institute of Physics. [DOI: 10.1063/1.3031697]