| Project/Area Number |
63540282
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
物性一般（含極低温･固体物性に対する理論）
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| Research Institution | Okayama University of Science |
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Principal Investigator |
MATSUBARA Takeo Okayama University of Science, Department of Applied Physics Professor, 理学部, 教授 (60025202)
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| Project Period (FY) |
1988 – 1990
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| Project Status |
Completed (Fiscal Year 1990)
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| Budget Amount *help |
¥2,000,000 (Direct Cost: ¥2,000,000)
Fiscal Year 1990: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 1989: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 1988: ¥700,000 (Direct Cost: ¥700,000)
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| Keywords | Perovskite type oxides / Ferroelectricity / Structural change / Layered structure oxides / High T_c superconductors / Band theory / 構造相転移 / 強誘電性 / ペロブスカイト |
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| Research Abstract |
1. The sigma - and pi-bands of perovskite type oxides are constructed from the hybrid of d- and p- orbitals, and band parameters are determined for different compounds.
2. Low temperature behaviors of quantum paraelectrics are explained using self-consistent phonon theory and importance of mode-mode coupling is pointed out in order to have quantitative agreement with observation.
3. Induced ferroelectric phase transition in quantum paraelectrics under uniaxial stress or arroying is discussed on the basis of the change in energy bands. In particular the ferroelectricity in Na_<1-x>K_xTaO_3 is interpreted theoretically based on band theory.
4. Pressure effects on the soft phonons in perovskite oxides are discussed from the expected variations in energy bands under pressure.
5. A unified statistical mechanical approach is proposed to the high temperature superconductivity in layered structure oxides.
6. Theoretical method to determine the band parameters for different materials is checked by applying the same techniques to more simple structure insulators with available experimental data.
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