Our results show that a proper assessment of the dispersion model against computationally very expensive ab initio methods, such as the random phase approximation, is in principal necessary. The choice of the dispersion model is expected to have a major impact on the low-frequency modes (< 100 cm -1 ) because they are dominated by layerlayer interactions. However, we focus in this study on high-frequency modes, which are governed by intralayer interactions. In the latter case, the stability of the AIMD simulation is a sufficient criterion as demonstrated in Sections 6.2 to 6.5.