Abstract
Under pressure, is found to undergo an isostructural transition, as observed by Raman spectroscopy, extended x-ray-absorption fine structure, and x-ray diffraction. Rietveld analysis of the x-ray diffraction data shows a homothetic contraction of the host lattice after the structural transition at . Using the Rietveld and maximum-entropy methods, we have performed an analysis of high resolution x-ray diffraction patterns collected from ambient to obtained in a diamond anvil cell using He as a quasihydrostatic pressure transmitting medium. The results indicate unambiguously that the homothetic phase transition at about is due to an extensive rehybridization of the Si atoms leading to a transfer of valence electrons from the bonding to the interstitial region. Consequently, the Si–Si bonds are weakened substantially at high density, leading to an abrupt collapse of the unit cell volume without a change in crystalline structure. The transition pressure and the change in the chemical bonding are remarkably similar to that observed in elemental Si–V.
- Received 22 January 2007
DOI:https://doi.org/10.1103/PhysRevB.76.174109
©2007 American Physical Society