Using Ab Initio Simulations to Examine the Flexoelectric Effect in Perovskites

Flexoelectricity is a property that dielectric materials exhibit where they produce polarization when subject to an inhomogeneous deformation. In the past, this effect has been largely ignored, as its effect in bulk materials has been much less significant than the related effect of piezoelectricity, the polarization of material due to uniform deformation. Interest in flexoelectricity has been increasing in recent years due to the development of nanotechnologies. Flexoelectricity is proportional to the strain gradient a material is subjected to making the flexoelectric effect immense on the nanoscale. Additionally, the flexoelectric effect scales with the dielectric constant making it have a significant effect in newly developed high permittivity materials such as ferroelectrics and relaxors. Applications being looked into for this phenomenon include improving the electro-mechanical response of piezoelectric materials as well as the creating of electro-mechanical sensors and actuators out of non-ferroelectric insulators. Research in this project includes using DFT simulations to determine the longitudinal flexoelectric coefficient, which is difficult to determine experimentally. This calculation was performed for several high permittivity perovskite compounds. Additionally, calculations of the flexoelectric coefficient using local density approximation functionals and generalized gradient approximation functionals are compared.