The zirconium oxide building block, from the well-known UiO-66 MOF (e.g. refcode RUBTAK03 ) is similarly well-conserved. GFN-xTB has corrected the inner oxygen positions from being symmetric, to having two types of oxygen atoms -one capped with hydrogen and another one without hydrogen. The distinct zirconium-oxygen bonds optimized to a longer bond for Zr-OH (refer to O2 in figure ) and a shorter bond for Zr-O (refer to O1 in figure ). This correction is justified as the crystal structure represents an average of oxygen positions, where 50% of the oxygen atoms bear a hydrogen atom, but which oxygen atoms (i.e. the orientation of the building block) is not pre-defined.