Polarized Raman spectroscopy of v-SiO2 under rare gas compression Auteur(s): Weigel C., Foret M.
Conference: 54th European High Pressure Research Group Meeting (EHPRG 2016) (Bayreuth, DE, 2016-09-05) Ref HAL: hal-01909031_v1 Exporter : BibTex | endNote Résumé: High-pressure polarized Raman spectra of vitreous silica are measured up to 8 GPa in a diamond-anvil cell at room temperature. The combined use of either a nonpenetrating pressurizing medium—argon—or a penetrating one—helium, allows one to separate density from stress effects on the Raman frequencies. In the framework of a simple central force model, the results emphasize the distinct role played by the shrinkage of the intertetrahedral angle Si-O-Si and the force-constant stiffening during the compression. The polarization analysis further reveals the existence of an additional isotropic component in the high-frequency wing of the boson peak. The pressure dependence of the genuine boson peak frequency is found to be much weaker than previously reported and even goes through a minimum around 2 GPa in remarkable coincidence with the anomalous compressibility maximum of silica. |