Ab initio study of dipolar defects and 180° domain walls in PbTiO3

We have calculated the electronic and ionic structures for oxygen-vacancy-impurity-metal complexes and 180 degrees domain walls in PbTiO3 using a first-principles total energy method. The binding energy of an oxygen vacancy to a Pt impurity in PbTiO3 is calculated to be similar to 3.0 eV. The complex is strongly polar, stabilized by electron capture, and pins the polarization of the surrounding lattice. Domain walls are found to be Pb-centered and extremely narrow with a width of only about two lattice constants. The energy density of a domain wall is calculated to be similar to 150 erg/cm(2.) (C) 1999 Elsevier Science Ltd. All rights reserved.