Origin of the Bloch-type polarization components at the 180° domain walls in ferroelectric PbTiO3

Abstract

Determination of atomic and electronic structures of ferroelectric domain walls is crucial to understand and explore their unusual properties. Using first-principles calculations based on the density functional theory, we explored the atomic and electronic structures of 180° domain walls in PbTiO3, in order to understand the origin of Bloch-type polarization components. It is found that Bloch-type polarization components originate from the large displacements of Pb atoms and the Pb-O hybridization at the domain walls. The development of Bloch-type polarization components significantly reduce the domain wall energies and change the Peierls barriers of domain wall motion in different orientations.

Converse flexoelectricity around ferroelectric domain walls

“…Two types of exchange-correlation (EC) functionals (local density approximation (LDA) and generalized gradient approximation for solids (PBE-sol)) were adopted in the calculations and other technical details can be found in the method section, Supplementary Fig. 4, and Supplementary Note 3 [16][17][18] . The Pb sublattice shows an offset of about 0.61 Å across the DW (Fig.…”

Chiral phase transition at 180° domain walls in ferroelectric PbTiO3 driven by epitaxial compressive strains

“…The [100]-oriented 180 DW was considered and a 12 Â 1 Â 1 supercell was chosen, since our previous studies showed that this size would be large enough to reflect the polarization state of 180 DWs. 16 The Ising, Bloch and normal components are the polarization components along the z, y and x directions, as shown in Fig. 1.…”

“…As reported in our previous studies, Ising-type polarization components are the main feature of 180 DWs in PTO and the emergence of Bloch-type and normal components will only cause about 10% reduction of the DW energy. 16 We applied compressive epitaxial strains to a and b axes of DW-I models and allowed the c axis to relax in order to obtain the optimized DW-I models. Using these models as references, we did constrained relaxations to determine the optimized Bloch and normal components at different strains.…”

“…6,7 However, recent theoretical studies indicate that polarization vectors actually rotate around DWs, and other polarization components may exist around DWs, including those normal and parallel to DWs. [8][9][10][11][12][13][14][15][16] The components parallel to DWs are termed as Bloch-type and there exist two chiral variants according to the rotation manner of polarization vectors, while the normal components are termed as N eel-type, and this type of DWs is not chiral as there exists a mirror symmetry. 17 180 DWs in PbTiO 3 (PTO) were predicted to undergo a ferroelectric transition to develop large Bloch-type polarization components with the decrease of temperature.…”

Atomic-scale measurement of polar entropy

“…energy cost associated with them 10,11 . However, recent research have pointed out that fluctuations away from the Ising polarization direction do exist in ferroelectrics, with Bloch and Néel components arising at domain walls, which were predicted and also experimentally detected [12][13][14][15] .…”