Detail:
Abstract: The study of molecule/metal interfaces is important for fundamental and applied surface science, and the electronic properties of these interfaces can be tuned by controlling their geometries. In this regard, a particular challenge for electronic structure theory is to reliably model the structure and stability of such hybrid interfaces. Here, we demonstrate that our DFT+vdWsurf method, which accurately and efficiently includes van der Waals (vdW) forces in the framework of density-functional theory (DFT), is able to describe 25 model adsorption systems with an accuracy of 0.1 Å in adsorption heights and 0.1 eV in binding energies wrt. reliable experimental data. In addition, the DFT+vdWsurf calculations lead to a few peculiar findings: (1) The vdW energy can contribute significantly to both strongly and weakly bound systems, which is even more to the binding of covalently bonded systems than it does in physisorbed interfaces; (2) the physically bound (precursor) state for aromatics on metal surfaces can be prominently stabilized and long-lived, making it potentially useful in molecular switches; (3) efficient enantiomeric separation of small chiral molecules could be achieved with bimetallic stepped surfaces for which strain, both in the surface and the molecule, increases significantly upon deposition; and (4) we uncover a general mechanism – termed as inner orbital broadening mechanism – that goes beyond the celebrated frontier molecular orbital theory, rationalizing the C=C bond activation in multi-unsaturated hydrocarbons as a result of significant surface-induced broadening of high-energy inner molecular orbital.
