Résumé:

We present a study of structural and dynamical properties of a liquid and glassy sodium borosilicate of composition 3Na2O-B2O3-6SiO2, study carried out using first principles molecular dynamics simulations. This glass composition is thus similar to the glass wool that is used in our daily life. The simulations were carried out within the DFT framework as implemented in the VASP code. The samples contained 320 atoms, which is rather demanding for ab initio calculations, but it has allowed to study the intermediate order in glasses. In particular, we have investigated how boron atoms integrate and modify the silica network. Furthermore we have determined the vibrational properties and identified the contributions of the different species to the density of states. We found that 3- and 4-fold coordinated boron atoms give rise to specific features in the density of states. The infrared spectra of our glassy models is also presented and directly compared to experimental data.