First-principles study of the photorefractive material KNbO$_{3}$

The perovskite based material KNbO$_{3}$ has been studied extensively for its photorefractive properties, where the electro-optic effect combined with photoconductivity changes the local refractive index of the material in response to the incident intensities. The presence of a transition metal impurity like Fe is required for efficient photorefractive performance of this material. Recent experiments suggest that Ag co-doping enhances the photorefractive properties significantly. To shed light on the physical mechanism of this behavior, we perform first-principles calculations within the density functional theory framework. In this poster, we present the structural relaxation results for the different crystal forms that the pure host KNbO$_{3}$ can exist in at room temperature and higher. Preliminary calculations about the role of Fe on the geometric and electronic structures of KNbO$_{3}$ will also be presented.