权益分类	功能权益	普通用户	{{item.name}}会员
{{category.name}}	{{benefitItem.name}}

Impurity Effect on a Structural Phase Transition Intermediate between the Order-Disorder and Displacive Types.

杂质对有序无序型和位移型中间结构相变的影响。

基本信息

批准号：
09640689
负责人：
SAITO Kazuya
金额：
$ 2.11万
依托单位：
Osaka University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1997
资助国家：
日本
起止时间：
1997 至 1998
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-09640689/
关键词：
structural phase transition Impurity Effect polyphenyl ac calorinetry 熱容量シミュレーション

项目摘要

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.

1.为了从热力学上阐明杂质对从位移型到有序无序型结构相变的影响，设计了高精度的热容量热法。在本项目开始之前，已经完成了对位移和有序无序系统的实验。由于剩余样品无法在商业上获得，因此选择了适用于极小样品的交流量热法作为实验技术。研制了具有较高热稳定性的斩波式交流量能器。通过对4，4“-二氟对三联苯(DFTP)和3，6-二苯基-1，2，4，5-四嗪(DPTZ)的溶液淬火，制备了薄而均匀的固溶体样品，并用于交流热分析。随着DPTZ含量的增加，DFTP热反常受到强烈的抑制，表明中间相变比对三联苯的有序-无序相变更敏感，与联苯的位移相变相似。从理论上对杂质对结构相变的影响建立统一的认识是迫切需要的。在一个简单的模型上进行了分子动力学模拟，显示了一个位移相变。部分证实了关于置换体系中强杂质效应的机制的讨论。也就是说，强效应与晶格振动的局域化，即软模密切相关。