Abstract
The microscopic origin of the intermediate phase in two prototypical covalently bonded network glass forming systems, where or Si, , and , was investigated by combining neutron diffraction with first-principles molecular-dynamics methods. Specifically, the structure of glassy and was examined, and the calculated total structure factor and total pair-correlation function for both materials are in good agreement with experiment. The structure of both glasses differs markedly from a simple model comprising undefective corner-sharing tetrahedra in which all atoms are linked by dimers. Instead, edge-sharing tetrahedra occur and the twofold coordinated Se atoms form three distinct structural motifs, namely, , Se-SeGe (or Se-SeSi), and (or ). This identifies several of the conformations that are responsible for the structural variability in and glasses, a quantity that is linked to the finite width of the intermediate phase window.
- Received 8 September 2008
DOI:https://doi.org/10.1103/PhysRevB.79.174201
©2009 American Physical Society