Effects of Strain on Defects and Polarization in Tetragonal BaTiO_3

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.