Abstract
In situ x-ray-diffraction measurements under high pressure (P up to 20 GPa) have been used to study structural changes in the rhombohedral and the tetragonal phases of at room temperature. Lattice parameters of the tetragonal phase regularly change with increasing pressure while the rhombohedral phase undergoes two structural phase transitions: A trigonal structure is observed for and a new -like phase appears for These observations lead to ascribe the appearance of superconductivity to the trigonal phase while the highest can be related to the transition towards the -like phase that differs from the low-pressure phases by the almost planar bonds of silicon.
- Received 31 March 2000
DOI:https://doi.org/10.1103/PhysRevB.62.11392
©2000 American Physical Society