Comparative density functional studies of BiMO3 polymorphs (M = Al, Ga, In) based on LDA, GGA, and meta-GGA functionals

Abstract

We report the relative stabilities, structural properties and ferroelectric properties of different polymorphs of BiMO₃ (M = Al, Ga, In) in the framework of density functional theory (DFT). We compared several exchange–correlation functionals at different levels of DFT. This includes a local density approximation (LDA), different forms of a generalized gradient approximation (GGA) and a meta-generalized gradient approximation (meta-GGA), as well as hybrid functionals. First, we calculated the structural, electronic, and ferroelectric properties of the ground state phases of BiMO₃. We compared our results with the experimental data. We found that AM05, MS0, and SCAN functionals improved the values of structural parameters at a same level of accuracy as the hybrid HSE functional. Next, we analyzed the relative stabilities of 16 BiMO₃ polymorphs. We found that only two meta-GGA functionals, MS2 and SCAN, described correctly the crystallographic ground states of BiMO₃. As a result, these functionals are most suitable to study polymorphism in BiMO₃ compounds. We also found that most of the low-energy phases of BiAlO₃ and BiGaO₃ were polar structures with large values of ferroelectric polarization. This suggests that these materials could be an alternative to the widely used toxic Pb-based ferroelectrics.