Complex antipolar root 2 x 4 x 2 root 2 structure with Pnma symmetry in BiFeO3 and BiFe1/2Sc1/2O3: First-principles calculations

Abstract

First principles calculations are done for a root 2 x 4 x 2 root 2 Pnma structure, which has been recently discussed in several attempts to describe experiments in complex magnetoelectric perovskites and which experimentally was shown to compete with several ferroelectric phases. This makes these materials extremely attracting as switchers, starters, field-stimulated capacitors, high-voltage converters, transmitters, etc. The relative energies of the root 2 x 4 x 2 root 2 Pnma structure have been calculated from first principles and analyzed as a function of pressure in BiFeO3. The stability of two polymorphs of the root 2 x 4 x 2 root 2 Pnma structure has been studied for solid solution BiFe1/2Sc1/2O3. The main distortions and relative energies of these two polymorphs in BiFe1/2Sc1/2O3, in terms of Pm (3) over barm parent symmetry, have been calculated from first principles as well.