New highly polar semiconductor ferroelectrics through d8 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 PbTiO(3) 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 PbTiO(3) while maintaining or enhancing polarization. They are promising candidates for use as semiconducting ferroelectric substrates for solar conversion devices.