1994 Fiscal Year Final Research Report Summary
Orientational Correlations in Plastic Crystals by X-ray Scattering and Neutron Spin Echo Method
| Project/Area Number |
04452044
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
固体物性
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| Research Institution | KYUSHU UNIVERSITY |
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Principal Investigator |
ACHIWA Norio KYUSHU UNIV.PHYSICS Professor, 理学部, 教授 (60027456)
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| Co-Investigator(Kenkyū-buntansha) |
SHIONO Masaaki KYUSHU UNIV.PHYSICS Research Associate, 理学部, 助手 (80235499)
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| Project Period (FY) |
1992 – 1994
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| Keywords | plastic crystal / orientational glass / orientational correlation / time resolved X-ray / progressive correlation / neutron inelastic scattering / molecular rotation / relaxation process in glass |
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| Research Abstract |
Three big subjects for plastic crystal of adamantane derivatives in order to study molecular orientational correlations and dynamics of the plastic and orientational glass phases.
(1) The crystal structures of all the three different (III-order, II-semi-order, I-plastic) phases of 1-bromoadamantane C_<10>H_<15>Br have been determined by means of X-ray diffraction technique. Observed structure factors in the I phase were compared with calculated ones which were derived by the simplified model : a spherically oriented adamantane plus oriented Br atoms along six equivalent cubic <100> axs. The relations between phase transitions and orientations of the molecular axis are discussed in three phases. The sequence of the phases I,II and III is characterized as the step by step ordering of disordered molecular orientations along the equivalent six cubic <100> axs. In the I-plastic phase X-ray diffuse scattering due to nearly free molecular rotation was observed both for powdered and single crys
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tals.
(2) Inter-molecular orientational correlations have been studied in a plastic phase and a orientationally glassy phase of 1-cyanoadamantane by observing patterns of diffuse scattering on a single crystal. The obtained patterns of the diffuse scattering are compared with simulations based on Monte Carlo method supposing that orientations of the molecular axis are randomly distributed six equivalent <100> directions of the fcclattice.
(3) Progressive molecular orientational ordering on single crystal of 1-cyanoadamantane just below the glass transition temperature have been studied by a time resolved X-ray scattering technique. Time evolution of profiles of Bragg reflections and that of diffuse scattering in various reciprocal lattice points of the fcc structure were measured. The results demonstrate the evolution process of local ordering of molecular orientations in the mother glassy phase. After aging 3 days, we found new diffusive scattering around (2,1<plus-minus>delta, 0) (delta-1/2). Through every processes the cubic symmetry of the single crystal was preserve Less
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