This approach has been championed, in particular, by the Van Speybroeck group in Gent. In 2019, Rogge et al. performed mesoscale MD simulations of several flexible MOFs: MIL-53(Al), DMOF-1(Zn), MIL-53(Al)-F, and CoBDP. In order to achieve this scale-up in size, they needed a speed-up in the calculation of interatomic interactions, and ab initio MD methods (relying on calculation of forces at the DFT level) were not feasible at this scale. Therefore, they parameterized classical force fields for these flexible MOFs, based on first-principles data, through the QuickFF approach. This allowed them to run MD simulations of very large systems, such as an 8×2×8 supercell of DMOF-1(Zn), to elucidate the mechanism of structural transition beyond the unit cell. In later work, this group leveraged the massive parallelism of state-of-the-art GPUs using the OpenMM software package to study the "breathing" transitions in MIL-53(Al) in a 37 × 10 × 37 supercell containing 1,040,440 atoms. Through constant-temperature constantstress simulations, the authors could show that two different mechanisms for the transition were possible, depending on the range of external pressure applied -as depicted on Figure .