Fig. 3: Structure and ferroelectricity of bulk AgBr.
a Schematic structure of AgBr during the L1-H-L2 phase transition. The L1,2 phase belongs to F-43m and the H phase belongs to Fm-3m. The process can be considered as Br moving along the path \(\left(\frac{1}{4},\frac{1}{4},\frac{1}{4}\right)\to \left(\frac{1}{2},\frac{1}{2},\frac{1}{2}\right)\to \left(\frac{3}{4},\frac{3}{4},\frac{3}{4}\right)\). b The energy barrier calculated by NEB and the evolution of the polarization in the primitive cell along the path in (a), where the primitive cells of L1, H, L2 are depicted. Here the polarizations of L1 and L2 are \({{{{{\bf{P}}}}}}_{1}=\frac{1}{4}{{{{\bf{Q}}}}}\) and \({{{{{\bf{P}}}}}}_{2}=-\frac{1}{4}{{{{\bf{Q}}}}}\), respectively. Q is the polarization quantum along the [111] direction. The polarization difference is \({{{{\boldsymbol{\triangle }}}}}{{{{\bf{P}}}}}=\frac{1}{2}{{{{\bf{Q}}}}}\).
