The vibrational properties of silica glass have been intensively studied experimentally and theoretically during the last four decades. However there are few theoretical studies of the evolution of the vibrational properties for more complex silicate glasses (binary, ternary etc...). In the first part of this talk, we will present the structural and vibrational properties a sodium silicate glass of composition 4Na 2 O-6SiO 2 (NS1.5). The study has been carried out using first principles calculations within the density functional theory framework as implemented in the VASP code. We have studied the structural and vibrational properties of this glass, and we have identified the contributions of the various species to the vibrational density of states (VDOS) as well as to the IR spectra. In particular we will discuss how the presences of the sodium atoms affect the relevant vibrational parameters: positions, shapes and intensities of the main peaks of the VDOS and IR spectra. In the second part, we will discuss the properties of several complex borosilicate glasses. Computing physical properties of complex glass compositions via numerical simulations often suffers of inaccurate predictions when using classical potentials, or it is excessively time consuming simulations when glass structures are obtained using ab-initio methods. The study has been carried out by combining classical and ab initio molecular dynamics (MD) methods and by varying the concentrations of SiO 2 , B 2 O 3 , Na 2 O, CaO, Al 2 O 3 and MgO. The classical MD included liquid equilibration, quenching and preliminary relaxation, while ab initio method was used to further relax the samples. Two sets of effective potentials have been used for the classical simulations. This strategy allows of course a significant CPU time saving. We have compared the structural properties of the simulated samples and have found that classical MD simulations cannot provide reliable glass models for complex borosilicates (at least with the potentials we have chosed), especially for the peculiar aspect of Boron coordination. The ab initio simulations have corrected the unreliable classical simulated structures and provided results in good agreement with previous studies of borosilicate glasses. We have also noticed that the presence of Al and Mg has influenced the fraction of 3-fold coordinated Boron, as expected from experimental data. The vibrational properties have been equally studied within the ab initio approach, and the contributions of the various species have been identified. We have found that 3- and 4-fold coordinated borons give rise to distinguished spectral features.