Structural deformations in metastable cubic compounds Ni$_{(1-x)}$Zn$_x$O (0.6 $\le x\le$ 0.99)

X-ray diffraction has been used for studying the fine crystal structure of metastable cubic oxide compounds Ni$_{(1-x)}$Zn$_x$O (0.6 $\le x\le$ 0.99) obtained from the initial hexagonal phase by quenching of the samples at a high temperature and under external hydrostatic pressure. It has been found that the diffraction patterns of these compounds include a system of diffuse superstructure maxima, whose number and intensity essentially depend on the composition. The origin of this superstructure has been discussed.