| Budget Amount *help |
¥3,300,000 (Direct Cost: ¥3,300,000)
Fiscal Year 1998: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1997: ¥2,800,000 (Direct Cost: ¥2,800,000)
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| Research Abstract |
1. In order to clarify the impurity effect on structural phase transition ranging from displacive type to order-disorder type thermodynamically, heat capacity calorimetry of high precision was planned. The experiments on the displacive and order-disorder systems had been completed before this project started. Since the sample remained was commercially unavailable, the ac calorimetry applicable to very small samples was chosen as the experimental technic. The chopped-light ac calorimeter with high thermal stability was developed.
2. By quenching liquid solution of 4,4"-difluoro-p-terphenyl (DFTP) and 3,6-diphenyl-1,2,4,5-tetrazine (DPTZ), thin uniform sample of the solid solution was prepared and used for the ac calorimetry. Strong suppression of thermal anomaly of DFTP upon increasing DPTZ contents showed an intermediate phase transition was much more sensitive to the impurity than order-disorder transition in p-terphenyl and similarity to the displacive transition in biphenyl. It is highly desired to establish a unified understanding the impurity effect on structural phase transitions theoretically.
3. Molecular dynamics simulations were made on a simple model showing a displacive phase transition. A discussion concerning the mechanism of the strong impurity effect in displacive systems was confirmed in part. That is, the strong effect has a close connection to localization of lattice vibration, I.e., the soft-mode.
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