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Disorder in the Cubic Phase of PbHfO3 by High Energy Synchrotron Radiation Diffraction
Yoshihiro Kuroiwa,Akikatsu Sawada,Hiroshi Fujiwara,Hitoshi Kawaji,Tooru Atake 한국물리학회 2005 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.46 No.1
The electron charge density distributions of PbHfO3 in the cubic phase have been investigated in association with the antiferroelectric phase transition, by analyzing high-energy synchrotronradiation powder diraction data by the maximum entropy method (MEM)/Rietveld method. The Pb atom is found to be ionic and disordered in the h100i direction. Clear covalency is observed on the Hf-O bonding. The charge density distributions around the O atom are extremely anisotropic, and are extended in the directions perpendicular to the Hf-O covalent bond. These structural characteristics are observed both at 500 K near Tc (= 476 K) and at 700 K far above Tc.
Atomic Replacement Effect on Electron Charge Density of Perovskite Oxides
Yoshihiro Kuroiwa,Akikatsu Sawada,Eiji Nishibori,Hiroshi Tanaka,Jimpei Harada,Makoto Sakata,Masaki Takata,Shinobu Aoyagi 한국물리학회 2003 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.42 No.IV
Charge density distributions of cubic SrTiO3 have been investigated related to the atomic replacement eect on the phase transition, by analyzing the synchrotron-radiation X-ray powder-diraction data by the MEM(Maximum Entropy Method)/Rietveld method. The chemical bonding natures between constituent atoms in cubic SrTiO3 are compared with those in cubic BaTiO3 that we investigated previously at the same temperature. The Characteristic charge density distribution around the O atom, which may present a clue what kind of phase transition occurs in the cubic perovskite oxide, is found in SrTiO3.
Charge Density Study of Negative-Thermal-Expansion Material ZrW2O8
Ayumi Kojima,Yoshihiro Kuroiwa,Akikatsu Sawada,Noriyuki Nakajima,Shinobu Aoyagi,Toshihide Tsuji,Yasuhisa Yamamura 한국물리학회 2003 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.42 No.IV
The covalent bonding nature of the negative thermal expansion material, ZrW2O8, has been revealed in the accurate charge-density distribution at 300 K, by analyzing the synchrotron-radiation high-energy powder-diraction data by the MEM/Rietveld method. It is found that two WO4 tetrahedra are bonded covalently by the bridging O atom along the body diagonal directions in the cubic structure. The bonding electron density between the W atom and the terminal O atom, which has a key to the mechanism of the order-disorder phase transition, is highest among the W-O covalent bonds.
Atomic Replacement Eect on Electron Charge Density of Perovskite Oxides
Yoshihiro Kuroiwa,Shinobu Aoyagiy,Akikatsu Sawada,Eiji Nishibori,Masaki Takata,Makoto Sakata,Hiroshi Tanaka,Jimpei Harada 한국물리학회 2003 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.42 No.IV
Charge density distributions of cubic SrTiO3 have been investigated related to the atomic replacement eect on the phase transition, by analyzing the synchrotron-radiation X-ray powder-diraction data by the MEM(Maximum Entropy Method)/Rietveld method. The chemical bonding natures between constituent atoms in cubic SrTiO3 are compared with those in cubic BaTiO3 that we investigated previously at the same temperature. The Characteristic charge density distribution around the O atom, which may present a clue what kind of phase transition occurs in the cubic perovskite oxide, is found in SrTiO3.