Atomistic modeling of flexoelectricity in periclase

Flexoelectricity is evolution of a macroscopic polarization due to a strain gradient. We present a molecular dynamics study of flexoelectricity in the cubic ionic MgO periclase phase. Using an effective interaction force field with polarizable oxygen atoms and applying it to an inhomogeneously strained periclase sample, we detect a collective flexoelectric response of the oxygen dipole moments in visualizations. This induced polarization depends linearly on the strength of the strain gradient as well as the primary polarization, which is caused by the displacement of the ion charges. By three different inhomogeneous deformation modes all three flexoelectric coefficients of periclase are determined.