Modulated Structures Induced by Phase Transformations
作者:
Gervais Chapuis,
期刊:
Crystallography Reviews
(Taylor Available online 1996)
卷期:
Volume 5,
issue 2
页码: 109-128
ISSN:0889-311X
年代: 1996
DOI:10.1080/08893119608035389
出版商: Taylor & Francis Group
关键词: Modulated structures;incommensurate structures;phase transitions;diffraction of modulated phases;molecular dynamics
数据来源: Taylor
摘要:
Modulated structures can be found in organic, inorganic and even quasicrystalline structures. They are generally detected by diffraction from the presence of satellites surrounding the Bragg reflections. Their positions may vary continuously with temperature or pressure so that the phase can be considered as incommensurately modulated. Incommensurate phases usually transform to a periodic high symmetry phase by increasing temperature and to a commensurate lock-in phase by lowering the temperature. Their domain of stability varies with temperature, pressure and with the type of compound. Examples have been identified where the interval of equilibrium vary from a few tenths to a few hundreds of degrees. Recent progress in the field of incommensurate structure analysis has been greatly favoured by the superspace group approach which is now almost exclusively applied. In many cases, the resolution of the modulated phases by diffraction methods has contributed towards the understanding of the phase changes. In addition, microscopic models for the transition mechanisms have been developed to understand small organic systems. The methods of molecular dynamics have been able to explain the formation of various sequences of commensurate and incommensurate phases observed experimentally.
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