Crystal structure of simple metals at high pressures

Abstract

The effects of pressure on the crystal structure of simple (or sp-) elements are analysed in terms of changes in coordination number, packing density, and interatomic distances, and general rules are established. In the polyvalent elements from groups 14–17, the covalently bonded structures tend to transform to metallic phases with a gradual increase in coordination number and packing density, a behaviour normally expected under pressure. Group 1 and 2 metallic elements, however, show a reverse trend towards structures with low packing density due to intricate changes in their electronic structure. Complex crystal structures such as host–guest and incommensurately modulated structures found in these elements are given special attention in this review in an attempt to determine their role in the observed phase-transition sequences.

Keywords:

• simple metals
• incommensurate crystal structure
• phase stability
• interatomic distances
• coordination number
• high pressure

Acknowledgements

The support from the Royal Society is greatly acknowledged. The author would like to thank Valentina Degtyareva for fruitful discussions and critical reading of this manuscript.