Second-Order Phase Transition in the VS One-Phase Region

Abstract

The lattice parameters and the densities of vanadium monosulfide samples have been determined by Guinier x‐ray powder diffraction and pycnometry, respectively. The samples spanned the homogeneity range of vanadium monosulfide. The data obtained are consistent with sulfur vacancies in samples for which $\text{S\hspace{0.17em}/\hspace{0.17em}V\hspace{0.17em}<\hspace{0.17em}1}$ , and vandium vacancies for samples with S / V > 1. The lattice parameters were found to vary continuously through the transition from the NiAs structure type to the MnP structure type, indicating that the transition is second order.