The crystallographic structure of hexagonal NiS has been determined at temperatures above and below the metal-semiconducting transition. The powder x-ray diffraction peak intensities were used to determine the atom positions in both phases. The symmetry of the unit cell is found to change from $\frac{P{6}_3}{mmc\left(D_{6h}^{{}^4}\right)}$ in the metallic phase to $P{6}_{3}mc\left(C_{6v}^4\right)$ in the semiconducting phase.

• Received 2 June 1970

DOI:https://doi.org/10.1103/PhysRevB.2.2859