Perovskite distortion models of supercell (2×2×2) were set up for BaTiO₃, PbTiO₃, PbZrO₃, and three selected alloys of PbZrO₃-PbTiO₃, and (2×2×3) for PbMg_1/3Nb_2/3O₃. Ab initio molecular dynamics simulations were performed for understanding their polarization and piezoelectricity. Spontaneous polarization P^* of alloys was determined by the atom B and its distortion away from the center of oxygen cage: .

Key words: polarization, piezoelectricity, ab initio molecular dynamics, ferroelectric material