Atomistic study of finite temperature properties in ferroelectric BiAlO$_3$

The lead-free perovskite ferroelectrics captivate researchers with their unique functional properties leading to important technological applications. In the search for a new lead-free perovskite of technological importance, we develop a first-principles based atomistic model to accurately predict the properties of BiAlO$_3$ in experimentally relevant conditions. Consistent with the experimental observations, our simulations predict a rhombohedral ferroelectric ($R3c$) ground state for BiAlO$_3$ facilitated by a structural phase transition from paraelectric (cubic, $Pm\Bar{3}m$) phase. The room-temperature spontaneous polarization and Curie temperature are obtained to be 81 $\mu$C/cm$^2$ (along [111] direction) and 1160 K, respectively. Our simulations reveal strong coupling between ferroelectric and antiferrodistortive modes for a broad spectrum of temperature and electric field. We find that hydrostatic pressure suppresses both spontaneous polarization and Curie temperature, while both uniaxial and biaxial stresses induce multiple phase transitions in BiAlO$_3$.