Atomic structure of the two intermediate phase glasses SiSe4 and GeSe4
The microscopic origin of the intermediate phase in two prototypical covalently bonded A(x)B(1-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 AB(4) corner-sharing tetrahedra in which all A atoms are linked by B-2 dimers. Instead, edge-sharing tetrahedra occur and the twofold coordinated Se atoms form three distinct structural motifs, namely, Se-Se-2, Se-SeGe (or Se-SeSi), and Se-Ge-2 (or Se-Si-2). This identifies several of the conformations that are responsible for the structural variability in GexSe1-x and SixSe1-x glasses, a quantity that is linked to the finite width of the intermediate phase window.
Keywords: bonds (chemical) ; germanium alloys ; glass ; glass structure ; molecular dynamics method ; neutron diffraction ; selenium alloys ; silicon alloys ; Stiffness Threshold Composition ; Short-Range Order ; Gexse1-X Glasses ; Rigidity Transitions ; Network Glasses ; Liquid Gese2 ; Chalcogenide Glasses ; Molecular-Dynamics ; Solids ; Organization
Record created on 2009-10-08, modified on 2016-08-08