title: Evidence for Pb-O covalency in tetragonal PbTiO3.
abstract: Accurate charge-density distributions of cubic and tetragonal PbTiO3 and BaTiO3 have been obtained by the MEM(maximum entropy method)/Rietveld analysis using synchrotron-radiation powder data. The Pb-O bonds in tetragonal PbTiO3 show rather strong covalency, while those in cubic PbTiO3 are ionic. This is the clear evidence of the Pb-O hybridization in tetragonal PbTiO3, which has been theoretically predicted as a key factor of much larger ferroelectricity of this substance than that of BaTiO3. Tetragonal PbTiO3 forms a layered structure of a two-dimensional covalent-bonding network consisting of the Ti-O5 pyramid.
authors.affiliation: Department of Physics, Okayama University, Okayama 700-8530, Japan. kuroiwa@science.okayama-u.ac.jp
authors.forename: Y
authors.initials: Y
authors.lastname: Kuroiwa
authors.forename: S
authors.initials: S
authors.lastname: Aoyagi
authors.forename: A
authors.initials: A
authors.lastname: Sawada
authors.forename: J
authors.initials: J
authors.lastname: Harada
authors.forename: E
authors.initials: E
authors.lastname: Nishibori
authors.forename: M
authors.initials: M
authors.lastname: Takata
authors.forename: M
authors.initials: M
authors.lastname: Sakata