2001 Fiscal Year Final Research Report Summary
Origin of Incommensurate Phase Transition and the New Viewpoint on the Phase Fluctuation
| Project/Area Number |
11640311
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
固体物性Ⅰ(光物性・半導体・誘電体)
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| Research Institution | The University of Electro-Communications |
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Principal Investigator |
SHIGENARI Takeshi The University of Electro-Communications, Faculty of Electro-Communications, Department of Applied Physics and Chemistry, Professor, 電気通信学部, 教授 (90017335)
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| Co-Investigator(Kenkyū-buntansha) |
DMITRIEV Sergey v. The University of Electro-Communications, Faculty of Electro-Communications, Department of Applied Physics and Chemistry, Associated Professor, 電気通信学部, 助教授 (00334574)
ABE Kohji The University of Electro-Communications, Faculty of Electro-Communications, Department of Applied Physics and Chemistry, Associated Professor, 電気通信学部, 助教授 (20183139)
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| Project Period (FY) |
1999 – 2001
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| Keywords | PHASE TRANSITION / INCOMMENSURATE PHASE / PHASE FLUCTUATION / RAMAN SCATTERING / MOLECULAR DYNAMICS / QUARTZ / Debye-Waller FACTOR / SiO2 |
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| Research Abstract |
The aim of this project is to show that the effect of phase fluctuation plays the crucial role in appearance of incommensurate structure in crystals. We propose a new model to explain the origin of the incommensurate phase transition in quartz. In this model, the intensity of the satellite intensity observed in diffraction experiments is strongly attenuated due to the decrease of Debye-Waller factor, which is attributed to the phase fluctuation. In this research we have proved this model from the following method.
(1) From the detailed investigation of low frequency Raman spectrum in the high symmetry beta phase, the temperature dependence of the integrated intensity was found not to exactly follow the Curie-Weiss law ,but deviates from 30K above the incommensurate phase transition temperature. This is consistent with our model.
(2) The MD calculation was performed using Tsuneyuki potential. The result shows that the short period modulation is more likely to appear than long wave modulation in contrast to the currently accepted model.
(3) The characteristics of incommensurate structure in' dielectric crystals are explained by the rotational degree of freedom of certain group of atoms. The elastically hinged molecule (EHM) model was proposed. The dynamics of the transition is investigated by the computer simulation using the EHM model. The negative poison ratio and several non-linear soliton-like behavior of lattice were also investigated by this and similar models.
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