Ferroelectricity in perovskitelikeNaCaF3predictedab initio

The ability of zero-stress simulations, using Gordon-Kim pair potentials, to describe the structures and transformations of known fluoride-based perovskites is demonstrated for the case of ${\mathrm{KCaF}}_3$. When ${\mathrm{K}}^{+}$ is replaced by ${\mathrm{Na}}^{+}$ a new ferroelectric crystal isomorphous with ${\mathrm{LiNbO}}_3$ is predicted. The equivalent relationships of the ferroelectric lithium niobate structure with the perovskite and antiperovskite structures are examined. A polarization of 21 μC/${\mathrm{cm}}^2$ at room temperature and a transition temperature of 550 K are predicted for ${\mathrm{NaCaF}}_3$. Surface effects are examined in simulations of a 1080-ion cluster.