STRUCTURAL PHASE-CHANGE IN S-TRIAZINE - RECONCILIATION OF X-RAY-DIFFRACTION AND NQR MEASUREMENTS

被引:19
作者
RAE, AIM
机构
[1] Department of Physics, University of Birmingham, Birmingham B15 2TT
关键词
D O I
10.1063/1.437543
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
Previous x-ray diffraction studies of the low-temperature phase of s-triazine identified the order parameter with a shear strain of the unit cell and interpreted the data in terms of a weakly first-order transition. Independent measurements of the nuclear quadrupole resonance spectrum showed that the 14N lines split in the low temperature phase; this splitting was taken to be proportional to the order parameter and its variation with temperature was described in terms of that associated with a second-order phase change, with a fluctuation contribution in the region of the transition. The present work shows that the first order nature of the transition is a necessary consequence of the symmetry of the system and the temperature dependence of the NQR frequencies can be explained if they are expressed as a sum of a term proportional to the order parameter together with a relatively large quadratic term whose magnitude can be qualitatively understood by a consideration of the environment of the nitrogen atoms. © 1979 American Institute of Physics.
引用
收藏
页码:639 / 642
页数:4
相关论文
共 11 条