Short and medium range structures of binary GeO2-SiO2 glasses from molecular dynamic simulations

N Marchin and JC Du, JOURNAL OF NON-CRYSTALLINE SOLIDS, 640, 123110 (2024).

DOI: 10.1016/j.jnoncrysol.2024.123110

This study explores the structural properties of mixed silica-germania glasses, which find wide applications in microelectronics and optoelectronics, by using molecular dynamics (MD) simulations. After validating the germanium related potential parameters, the short and medium-range structural features across the binary glass range were investigated. The results show that Ge-O bond distance is 1.71 & Aring; and germanium maintains four-fold coordination in all the glasses. The GeO4 tetrahedrons are slightly more distorted as compared to silica while the intertetrahedral angle distributions become narrower with increasing GeO2. GeO2-rich glasses exhibit broader ring size distributions. SiO4 and GeO4 tetrahedrons are randomly mixed forming a continuous random network. Comparison of the simulated glass structures with results from experiments such as neutron diffraction, solid state NMR and Raman spectroscopy showed good agreements, validating the structural model from MD simulations. This paves the way for future studies of composition dependence of properties of these mixed former glasses.

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