Microscopic study of structural properties of hydrogen impurity in ferroelectric PbTiO3

We investigate the structural properties of hydrogen impurities in the ferr oelectric perovskite phase of PbTiO3 on ferroelectricity through first-prin ciples pseudopotential total-energy calculations. We find that H-O bond sig nificantly weakens nearby O-Ti bondings. The H impurity can induce a cohere nt ferroelectric-like pattern of large-scale atomic displacements, that giv e rise to a macroscopic ionic polarization. The hydrogen contamination can affect the bulk polarization in tetragonal ferroelectric phase either adver sely or not, depending on its location. When the O-H axis lies on the ab-pl ane in the tetragonal ferroelectrics, the bulk polarization is reduced.