Potential interaction energy scans of the dimer systems were performed as a function of the Fe-O distance, radially along the Fe-O direction spanned from the relaxed geometry. At least 32 points were evaluated to plot smooth potential energy curves in the range of 3.6 to 15.0 Å. To allow identifying the depth of the curve, many points at an incremental of 0.1 Å were evaluated in the vicinity of the minimum. The generated geometries were not further optimized.