The sharp peaks centred around 0.063Å in Figure , show that typical organic bonds are very well replicated. Metal containing bonds are also well replicated, though to a lesser extent, with 76.63% of M-M bonds being within 0.250Å of the reference crystal structure value. The cases where optimized M-M bonds are outside this threshold involve a change of atomic connectivity during the optimization, (b) (a) typically caused by the removal of structural ligands. For example, the structure AGARUW 61 is a La 3+ containing MOF, where 1D chains of La 3+ ions are deca-coordinated by a mixture of coordinating and chelating carbonato ligands and water. In the cleaned structure in the CoRE database (refcode AGARUW_clean ), the water ligands are removed, resulting in a significant rearrangement of the coordination environment of each La 3+ ion and a consequent reduction in one of the La-La distances from 4.923Å to 2.874Å. Most force fields developed specially for MOFs have placed special attention on ensuring the correct geometries of common sets of inorganic building units. We checked the metal clusters used in popular MOFs such as M2O paddlewheels found in HKUST-1, trimeric oxo-centered M3O in MIL-100 series, M4O octahedron in MOF-5, and finally the 12-connected M6O cuboctahedron in UiO-66. Very good results are shown for all metal nodes, the deviation of optimized structure is presented in Figure . The two key distances in building blocks that affect the lattice parameters of the optimized structure are the M-O and MM bond lengths, which in a layer-pillar MOF, affect the a, b and the c lattice dimensions respectively. Cu-based paddlewheel is highly conserved, with Cu-Cu bond length deviating only -0.030Å from the experimental value. Other M2O paddlewheels, Ni2O and Zn2O exhibit a higher deviation, contracting 0.3Å and 0.15Å in bond length between the two metals. For all paddlewheels, the M-O bonds are very well conserved with all deviations less than ±0.1Å. Structures for Ni2O and Zn2O paddlewheels are supplied in the supporting information.