Stability, Electronic Structure and Ferroelectric Switching of Wurtzite KMgSb

We report the crystal structure, elasticity, phonon spectrum, electronic structure and ferroelectricity of KMgSb in the wurtzite LiGaGe‐type phase. The simulation is performed by means of total‐energy calculations within density‐functional theory (DFT). The mechanical and dynamical stability of the material studied are verified via the elastic constants and phonon frequencies. The electronic structure is described in terms of the band structure and density of states. In order to overcome the inherent shortcoming of DFT in reproducing bandgaps, the local‐density approximation is used in combination with the modified Becke–Johnson functional. It is shown that wurtzite KMgSb exhibits an indirect bandgap of 1.54 eV and low effective masses around ±0.5. We also employ the Berry‐phase theory to provide the spontaneous polarization and Born effective charges associated with the polar wurtzite structure of KMgSb. The spontaneous polarization is found to be equal to 0.37 C/m 2 , and the effective charges are close to their nominal values. Furthermore, we demonstrate the ferroelectric behaviour by computing the double potential well that characterizes polarization switching. The low values of the switching energy barrier (0.093 eV/f.u.) and coercive electric field (7.31 MV/cm) suggest that the polarization can be reversed quite easily, making wurtzite KMgSb suitable for ferroelectric applications.