The behaviour of 180° polarization switching in BaTiO3 from first principles calculations

In this paper, the behaviour of 180° polarization switching in tetragonal BaTiO3 single crystal was investigated by first principles density functional theory calculations to understand the atomic scale mechanisms of 180° switching in this ferroelectric material. The calculation results indicate that the switching energy barrier per unit cell for direct 180° switching (5.11 × 10−3 eV) is over 4.5 times higher than the barrier for two-step 90° switching (1.10 × 10−3 eV). Consequently, there are two critical electric fields for 180° switching in tetragonal BaTiO3 single crystal and which can be evaluated as E 90 ° c = 744 V / mm for two-step 90° switching and E 180 ° c = 2445 V / mm for direct 180° switching in an ideal condition, respectively. In other words, if the applied antiparallel field E a ≤ E 90 ° c , the switching cannot happen. If E 90 ° c ≤ E a ≤ E 180 ° c , the 180° switching occurs by two 90°-switching steps. If E a ≥ E 180 ° c , the direct 180° switching can occur. These calculation results can explain the 180° switching behaviours experimentally observed under various electric field intensities.