The microscopic origin of the intermediate phase in two prototypical covalently bonded Ax B1-x network glass forming systems, where A=Ge or Si, B=Se, and 0≤x≤1, was investigated by combining neutron diffraction with first-principles molecular-dynamics methods. Specifically, the structure of glassy GeSe4 and SiSe4 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 A B4 corner-sharing tetrahedra in which all A atoms are linked by B2 dimers. Instead, edge-sharing tetrahedra occur and the twofold coordinated Se atoms form three distinct structural motifs, namely, Se-Se2, Se-SeGe (or Se-SeSi), and Se-Ge2 (or Se-Si2). This identifies several of the conformations that are responsible for the structural variability in Gex Se1-x and Six Se1-x glasses, a quantity that is linked to the finite width of the intermediate phase window. © 2009 The American Physical Society.
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|Publication status||Published - 1 May 2009|
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics
Massobrio, C., Celino, M., Salmon, P. S., Martin, R. A., Micoulaut, M., & Pasquarello, A. (2009). Atomic structure of the two intermediate phase glasses SiSe4 and GeSe4. Physical Review B - Condensed Matter and Materials Physics, 79(17), -. . https://doi.org/10.1103/PhysRevB.79.174201