On the Sequence of Phase Transitions in Tridymite

被引：0

作者：

A. K. A. Pryde

M. T. Dove

机构：

[1] Department of Earth Sciences,

[2] University of Cambridge,undefined

[3] Downing Street,undefined

[4] Cambridge,undefined

[5] UK,undefined

[6] CB2 3EQ Fax: +44 1223 333450,undefined

[7] e-mail: martin@esc.cam.ac.uk,undefined

来源：

Physics and Chemistry of Minerals | 1998年 / 26卷

关键词：

Key words Tridymite; Rigid unit modes; Phase transitions;

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摘要：

We consider the phase transitions in tridymite from the perspective of the rigid unit mode model. The rigid unit modes are the low-frequency phonons of a crystal structure that consists of an infinite framework of tetrahedra linked at corners, that can propagate without the tetrahedra distorting. Because they give distortions of the structure with a low energy cost they are the natural soft modes for displacive phase transitions. We consider the normal phase transition sequence in tridymite on cooling, HP LHP ..., as a successive condensation of rigid unit modes acting as soft modes. Some of the low-temperature phases (e.g. MX-1) arise as rigid unit mode distortions of the high-temperature structure and do not follow the sequence of phases found at higher temperatures. We are able to account for all the commensurate phases and some of the modulated phase within the framework of the rigid unit mode model.

引用

页码：171 / 179

页数：8