Ab initio study of metastable layered perovskites R2Ti2O7 (R = Sm and Gd)

The structural, electronic, and ferroelectric properties of metastable R2Ti2O7(R = Sm and Gd) layered perovskites materials are investigated by first-principles density functional theory calculations. The computed structural parameters are found to be in good agreement with experimental findings. The calculated spontaneous polarizations of the studied titanates are found to be larger than the spontaneous polarization of the usual R2Ti2O7 layered perovskites materials. GGA + U electronic structures predict a good photocatalytic activity for the studied compounds, in particular for Gd2Ti2O7, which lacks electron-carriers trapping in the conduction band. From the results of the total energy and the polarization as functions of structure we estimate the responses of the materials to external electrostatic fields.