The phonon dispersion relations of 2D materials can provide valuable insights into their stability. On the top row of Figure we present the phonon dispersion curves for graphene, silicene, h-BN, h-AlN, and h-GaN obtained with four different methods: the reference DFT method, the GAP method, the DFT-HIPHIVE method, and GAP-HIPHIVE method. As shown in the figure, the GAP and DFT-HIPHIVE methods are indistinguishable from the DFT results, despite having significantly lower computational costs. Notably, the GAP-HIPHIVE method, which is based on GAP calculations and therefore has the lowest computational cost, reproduces the phonon dispersion relations closely as well. The middle and bottom rows of Figure present plots of Grüneisen parameters versus frequency for DFT and GAP, respectively, for all the 2D materials. The Grüneisen parameters reflect the derivative of phonon frequencies with respect to crystal volume (or area in the case of 2D systems).