Heat Capacity at Constant Volume and Molecular Motion of Crystal, Orientationally Disordered Crystal and Liquid

晶体、无序晶体和液体的定体积热容和分子运动

基本信息

批准号：
02453008
负责人：
OGUNI Masaharu
金额：
$ 4.61万
依托单位：
Tokyo Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1990
资助国家：
日本
起止时间：
1990 至 1991
项目状态：
已结题

项目摘要

The present research aimed at making progress in the thermodynamic understanding on the coupling effects between orientational degrees of freedom and between them and the other degrees of freedom in orientationally disordered crystals.1) Effort was made to construct an automatic high-pressure calorimeter which measures simultaneously both heat capacity and volume at constant pressure to allow one to derive heat capacity at constant volume later from. The calorimeter is workable in the temperature range of 13 K to 500 K and enables high-precision thermometry of 10^<-5> K and heat capacity measurement with inaccuracy around 1 % at high pressures. We have so far succeeded in maintaining high pressure up to 200 MPa with its imprecision of 1 kPa within the high-pressure system. The remaining problem to be solved is in preparation of a thin sample-ampoule of indium which separates the sample and high pressure medium within the calorimeter cell.2) Orientationally disordered crystals, 2-haloge … More nothiophenes and pyridinium salts, were studied through heat capacity measurements under atmosphere. In the former crystals, glass transitions of one step and of two steps were observed in 2-bromothiophene and 2-chlorothiophene, respectively, and their properties changed continuously with a variation of composition between the two substances. These indicate that two reorientational processes couple with each other in both the dynamic and thermodynamic properties. In the latter cystals, pyridium iodide exhibited one phase transition while the chloride two phase transitions leading to the same high-temperature states in their orientational degrees of freedom. In pyridinium hexafluorophosphate, orientational disorderings of the cation and anion proceeded under strong coupling with each other showing only one phase transition as in the iodide. These suggest that the coupling effects stated above play quite important role in the evolution of orientational disordering both in the static and dynamic aspects. Less

本研究旨在从热力学角度理解无序晶体中取向自由度之间以及取向自由度与其他自由度之间的耦合效应。 1) 构建了一种同时测量的自动高压量热仪。热量计可在 13 K 至 500 K 的温度范围内工作，并可实现高精度测温。 10^<-5> K 和高压下热容测量的误差约为 1% 迄今为止，我们已成功地在高压系统内保持了高达 200 MPa 的高压，其误差为 1 kPa。需要解决的问题是制备一个薄的铟样品安瓿，它将样品和热量计单元内的高压介质分开。2) 定向无序晶体，2-卤素……通过大气下热容测量研究了更多的噻吩和吡啶鎓盐。在前一种晶体中，2-溴噻吩和2-氯噻吩分别观察到一级和两级玻璃化转变，并且它们的性质随着变化而连续变化。这表明，在后一种晶体中，两种重新取向过程在动力学和热力学性质上相互耦合，而碘化吡啶表现出一个相变。在六氟磷酸吡啶鎓中，氯化物的两个相变导致其取向自由度相同的高温状态，阳离子和阴离子的取向无序在彼此强耦合下进行，仅显示出与碘化物中的一个相变。上述耦合效应在静态和动态方向无序的演化中都起着相当重要的作用。