Giant Static Dielectric Constant of Strained PbTiO₃

First-principles density functional perturbation calculations are employed to study the dielectric and piezoelectric properties of strained tetragonal PbTiO₃. Lattice distortion, static dielectric constant, Born effective charge, zone-centre phonons, and piezoelectric constant are obtained. For the strained tetragonal PbTiO₃, we obtain a giant static dielectric constant (3600) under a strain 0.77%. Moreover, the calculated piezoelectric constant e₁₅ of strained PbTiO₃ reaches about 203C/m² which is about 20 times of that of unstrained system. The giant static dielectric constant is mainly due to the softening of the lowest-frequency phonon mode and the reduce of Ti-O bond length. This work demonstrates a route to a giant static dielectrics for electrically microwave and other devices.