Abstract: The mechanical property, electronic structure, and optical properties of tetragonal perovskite PbTiO₃ and Ni, Cu, Zn-doped PbTiO₃ were studied by first principles. The mechanical property calculations show that Ni-doped PbTiO₃ exhibits the highest values for volume modulus, shear modulus, and elastic modulus among the three doping systems. Notably, the Ni-doped system also has the highest Debye temperature. The G/B ratio represents the material's brittleness and toughness, which is highest for Zn-doped PbTiO₃, indicating the highest degree of chemical bond orientation. The G/B range for Ni and Zn-doped systems is 0.56<G/B<1.75, indicating brittle materials, while the intrinsic PbTiO₃ and Cu-doped systems have G/B values less than 0.56, indicating ductile materials. The electronic structure reveals that the doped systems have narrower band gaps and reduced transition energies compared to the intrinsic system. The introduction of Ni introduces impurity levels at the Fermi energy level in PbTiO₃, while Cu and Zn doping shifts the valence band maximum upwards, causing the Fermi level to enter the valence band and resulting in p-type conductivity for Cu and Zn-doped PbTiO₃. The doping of Ni, Cu and Zn expands the absorption range of PbTiO₃ to the infrared region and enhances the absorption intensity in the visible light range. Among the intrinsic PbTiO₃ and three single-doped PbTiO₃ materials, Cu-doped PbTiO₃ exhibits the best photocatalytic properties.

Key words: first principle, PbTiO₃, doping, mechanical property, electronic structure, optical property