Two types of geometry optimisation were performed on the conventional unit cells of the zeolite frameworks considered in this study. In one case, starting from the literature geometries (IZA Structure Commission, Database of Zeolite Structures: ), we obtained four distinct distorted cells from each structure, in which the cell parameters varied by -3%, -1.5%, 0% and +1.5%. In the other cases, full optimization of the system was achieved by performing an iterative optimisation cycle, alternating between the optimization of internal coordinates and the optimization of cell parameters, until both converged. We found this approach more robust in finding the lowest energy structure compared to the simultaneous optimization of both lattice and internal coordinates.