应变对四方相BaTiO3缺陷及极化的影响

Effects of Strain on Defects and Polarization in Tetragonal BaTiO_3

采用第一性原理方法,模拟了应变对四方相BaTiO3(BTO)空位形成能的影响,并计算了应变和双空位共同作用下BaTiO3体系的极化.计算结果表明,应变改变了空位形成能,且在–3%到3%的应变范围内,氧空位的形成能逐渐减小,亦即压应变抑制了氧空位的形成,这与Ti–O键的变化有关.此外压应变在改变双空位形成能的同时,增大了体系的极化和极化偏移,对于1A和2A组合的双空位即使在–3%的应变下其极化偏移也只有1μC/cm2和0.3μC/cm2,而极化偏移是印记效应的表现,因此应变对印记效应的影响很小,可以忽略.

The first-principle methods are used to calculate the effects of in-plane strain on the formation energies of neutral vacancies. It is shown that the formation energies of neutral O vacancy increase with compressive strain, while decrease for tensile strain. In other words, the O vacancy can be suppressed by compressive strain, which is contributed to the variation of the Ti-O bond. The formation energies of Ba-O divacancies and polarization of the tetragonal BaTiO3 are studied under different strain conditions. The strain changes the formation energies of Ba-O divacancies and the polarization of the systems containing Ba-O divacancies. More over, the results show that the polarization offset increases gradually when the strain changes from tensile to compressive strain. In other words the polarization imprint of BaTiO3 increase under compressive strain, but the changes are slight and negligible.