First-principles study of piezoelectricity in tetragonal PbTiO3 and PbZr1/2Ti1/2O3

The local orbital extension of the linearized augmented plane wave (LAPW+LO ) method within the general gradient approximation was used to determine st ructural and ferroelectric properties of tetragonal PbTiO3 (PT), and two ch emically ordered PbZr1/2Ti1/2O3 (PZT 50/50) phases, with B-site cations ord ered along [001], and [111] directions. Stable ferroelectric ground states were found in all structures. Bulk spontaneous polarization, dynamical char ges (Z*), and piezoelectric stress tensor elements were determined from gro und-state Berry's phase calculations. Ordering along the polar [001] direct ion was found to enhance the e(33) piezoelectric stress modulus in PZT 50/5 0. While theoretical piezoelectric stress moduli of PT, e(15)=3.15 C/m(2), e(31)= -0.93 C/m(2), and e(33)=3.23 C/m(2), agree well with single-crystal experimental data, computed proper moduli of bulk crystalline PZT, e(33)(P4 mm)=4.81 C/m(2) and e(33)(I4mm)=3.60 C/m(2), differ significantly from low- temperature experimental moduli of polycrystalline samples. [S0163-1829(99) 03319-6].