Ab-Initio modeling of vibrational spectra of silicate glasses and decomposition into principal structural components.

Dimitrios Kilymis (1) , Bernard Hehlen (1) , S. Peuget , Jean-Marc Delaye (2) , Simona Ispas (1)

1 L2C - Laboratoire Charles Coulomb
2 SECM - Service d'Etudes du Comportement des Matériaux de Conditionnement

Density functional theory is used to calculate the vibrational properties of pure silica and sodo-silicate glasses with 20, 25, and 33 mol% of Na2O. The infrared and Raman spectra are calculated and the full responses are decomposed into principal structural components (PSC). Those are for example the SiO4 n--tetrahedra with n nonbrigding oxygens defining the Qn-species at the origin of the structured feature at high frequency, and the Si-O-Si bridges leading the broad Raman R-band at intermediate frequencies. Our results confirm that Si-O-Si bending in bridges with large angle vibrate preferentially at lower frequencies than those with low angle. In addition, the spectral response of the Q2-species is bimodal and overlaps with that of the Q3, while the Q4 response covers almost all of the spectral range of the Qn-band. The ab-initio individual spectral responses of the PSC are used to reconstruct the experimental Raman responses. Contrary to the commonly used multi-Gaussian decomposition, this approach provides unambiguous band-assignments and hence a more accurate way to probe the structural and chemical properties of glasses from their spectroscopic signature.

Domaines: Systèmes désordonnés et réseaux de neurones [cond-mat.dis-nn]

Dimitrios Kilymis, Bernard Hehlen, S. Peuget, Jean-Marc Delaye, Simona Ispas. Ab-Initio modeling of vibrational spectra of silicate glasses and decomposition into principal structural components.. Glass & Optical Material Division, Annual Meeting 2017 (GOMD), May 2017, Waikoloa - Hawaï, United States. ⟨hal-01937865⟩