Variation in the electronic, mechanical, and structural properties among the polymorphs of bismuth ferrite: a first-principles approach

Bismuth ferrite has been under intense research for many years as it can exhibit first- and second-order transitions where all the phases have distinct properties encapsulating various exciting phenomena. This work reports a computational study of bismuth ferrite and its varied phases using density functional theory with the implementation of Hubbard correction for increased accuracy. The proposed method is validated through Linear Response Theory using Quantum ESPRESSO. The phase transition and the mechanical properties are explored by calculating elastic tensors for different polymorphs. A negative Poisson's ratio for the tetragonal phase supporting its growth in compressive environments is predicted. The electronic properties of different phases of bismuth ferrite are explored, which helps in understanding properties such as charge transfer excitation, metal-insulator transition, ferroelectric nature based on lone pair charges and orbital hybridization. The phonon modes of different phases are also investigated.