Interatomic potentials for the simulation of the zinc-blende and wurtzite forms of $\mathrm{ZnS}$ and $\mathrm{CdS}$: Bulk structure, properties, and phase stability

We present new interatomic potentials with which to model the structures and stabilities of the zinc-blende $\left(\mathrm{ZB}\right)$ and wurtzite $\left(\mathrm{W}\right)$ polytypes of $\mathrm{ZnS}$ and $\mathrm{CdS}$. The potentials are able to reproduce many of the properties of all four minerals to within a few percent of the experimental values. In contrast to the majority of previous forcefields, the calculated relative stabilities of the cubic and hexagonal phases are found to be in the correct order for both $\mathrm{ZnS}$ and $\mathrm{CdS}$, with the key being the inclusion of a four-body contribution to the energy. For $\mathrm{ZnS}$, the cubic polytype is predicted to be the most favorable while for $\mathrm{CdS}$, the hexagonal phase is the more stable. In solid solutions of ${\mathrm{Zn}}_x{\mathrm{Cd}}_{1-x}\mathrm{S}$ we find that the transition from hexagonal to cubic occurs for a composition of $x=0.6$.

Figure 1

Energy of the cubic (squares) and hexagonal (diamonds) polymorphs as a function of cation site composition $x$ for the solid solution ${\mathrm{Zn}}_x{\mathrm{Cd}}_{1-x}\mathrm{S}$, calculated within the mean-field model.