New highly polar semiconductor ferroelectrics through d 8 cation-O vacancy substitution into PbTiO3: A theoretical study

We use first-principles density functional theory (DFT) calculations to investigate the ground-state structures of PbTiO3 solid solutions containing Ni, Pd, and Pt. Anomalous effective charges are reported, including the first report of negative Born effective charges for nominal +2 cations. We predict that these proposed materials will display a decreased band gap when compared to PbTiO3 while maintaining or enhancing polarization. They are promising candidates for use as semiconducting ferroelectric substrates for solar conversion devices.