Superspace approach to high pressure superstructures

作者：Bykov Maxim; Bykova Elena; Hanfland Michael; Liermann Hanns Peter; van Smaalen Sander^*

来源：High Pressure Research, 2013, 33(3): 501-510.

DOI：10.1080/08957959.2013.822076

• phase transitions
• high pressure single-crystal X-ray diffraction
• superspace approach

Single-crystal X-ray diffraction in a diamond anvil cell has proven to be a powerful tool for studying matter at extreme conditions. Displacive zone-boundary phase transitions between a high-symmetry low pressure structure and a low-symmetry high pressure superstructure represent a significant part of pressure-induced processes. However, the analysis of such superstructures is usually complicated by low angular resolution and limited reciprocal space coverage. This leads to unfavorable data/parameter ratio during the structure solution and refinement. The superspace approach is an established method to describe commensurately modulated structures, however it is not often applied to high pressure phase transitions. Here, we discuss the advantages of the superspace approach for the description and crystal-chemical analysis of high pressure superstructures. The main ideas of this approach are illustrated by the examples of isostructural FeOCl and CrOCl, forming different superstructures above 15 GPa.

• 出版日期2013-8-20