Understanding Local Structures in Amorphous Oxides Through Raman Spectroscopy

We present a reformulated algorithm that enables ab initio calculations of Raman spectra for large-size systems, utilizing an external electric field and the Born effective charge to reduce the number of calculations. Using this approach, we compute the Raman spectra of amorphous GeO₂ and Ti-doped GeO₂ and demonstrate that our theoretical predictions closely align with experimentally observed features. Local structure and vibrational modes are captured. In addition, molecular dynamics simulations allow us to investigate structure features at 10² nm scale. Results from combined Raman spectroscopy and simulated annealing provide in-depth insight into short- and medium-range order. Structural characteristics of these amorphous oxides are discussed.