Orthorhombic $ABC$ Semiconductors as Antiferroelectrics

We use a first-principles rational-design approach to identify a previously unrecognized class of antiferroelectric materials in the $Pnma$ MgSrSi structure type. The MgSrSi structure type can be described in terms of antipolar distortions of the nonpolar $P{6}_3/mmc$ ZrBeSi structure type, and we find many members of this structure type are close in energy to the related polar $P{6}_{3}mc$ LiGaGe structure type, which includes many members we predict to be ferroelectric. We highlight known $ABC$ combinations in which this energy difference is comparable to the antiferroelectric-ferroelectric switching barrier of ${\mathrm{PbZrO}}_3$. We calculate structural parameters and relative energies for all three structure types, both for reported and as-yet hypothetical representatives of this class. Our results provide guidance for the experimental realization and further investigation of high-performance materials suitable for practical applications.

Figure 1

Left panel: planar buckling distortions of the polar $P{6}_{3}mc$ LiGaGe structure relative to the $P{6}_3/mmc$ high-symmetry ZrBeSi structure type (center), as described in Ref. 5. Right panel: antipolar distortions of the $Pnma$ MgSrSi structure type relative to the high-symmetry ZrBeSi structure type (center), showing antipolar buckling of the planes formed by atoms $BC$ (smaller spheres, connected by solid black lines) at Wyckoff positions $2b$ (dark blue) and $2b^{\prime }$ (gold) and antipolar displacements of the stuffing atoms $A$ (larger spheres, connected by dashed gray lines) at $2a$ (green).

Figure 2

Minimum-energy path for switching between the nonpolar $Pnma$ and polar $P{6}_{3}mc$ phases of NaCdAs, as calculated by the NEB method. (a)–(c): isosurfaces of an interplanar bonding state (MLWF), which reverses orientation during the switching process. Lower panel: graph of energy vs reaction coordinate, showing that our proposed reaction pathway from $Pnma$ to $P{6}_{3}mc$ has a barrier of 0.11 eV. This is in comparison to a path that would have the high-symmetry $P{6}_3/mmc$ structure as our intermediate, which would be 0.19 eV.