Dipole moment of a Pb-O vacancy pair in PbTiO3 -: art. no. 144116

The polarization of a nearest-neighbor (nn) Pb-O vacancy pair [(V-Pb-V-O)(nn)] in PbTiO3 is calculated, using the modern theory of polarization, implemented in the density-functional-theory ultrasoft pseudopotential formalism. The dipole moment per divacancy, (mu) over right arrow ((VPb)-V-O)(nn), is about 2.28e (r) over right arrow (nn), where (r) over right arrow (nn) is the vector from the V-Pb site to the V-O site. This value is slightly larger than the value of 2e (r) over right arrow (nn) for a purely ionic model of PbTiO3. The dipole moment is about twice as large as typical polarizations per cell in Pb-based ferroelectrics, which indicates that V-Pb compensated by V-O can be an important source of local polarization and electric fields in Pb-containing perovskites.