Quantitative determination of molecular adsorption structures: STM and DFT are not enough

There is now a range of well-established experimental methods for quantitative determination of the structure of crystalline surfaces with sub-angstrom precision, but increasingly in recent years structure 'determinations' are being based only on a combination of scanning tunnelling microscopy (STM) images and density functional theory (DFT) calculations. The dangers and limitations of this approach are described using a few specific examples that illustrate the complementarity, rather than competitive use, of these two different approaches.