A Computational Study of the Adsorption and Reactive Dynamics of Diglycine on Cu(110)

Adsorption of diglycine on the Cu(110) interface in the gas phase at medium coverage is investigated by means of classical all-atom reactive molecular dynamics simulations (ReaxFF) with a focus on preferential binding arrangements and peptide dynamics. Differently from earlier studies, where the slab model was frozen during all calculations, the constraints on the substrate have, in this investigation, been removed, and the atoms can readjust their location in response to the local environment and to the characteristics of the chosen copper face. Relaxation and reconstruction are indeed observed. The results are compared with the data sampled for the perfect slab where the position of every atom of the interface is kept fixed at the bulk geometry. In line with previous studies, the most stably adsorbed molecules are connected to the copper layer through all their oxygen atoms and the terminus nitrogen, adopting an on-top position at an average distance of about 2 A from the interface. In the case of surface reconstruction other strong binding modes are identified together with favorable arrangements which are reinforced by the tight packing ability of the peptides and by their positioning at the step edge of a terrace. There, at the terrace, backbone atoms are found in direct contact with the substrate. On the perfect slab chiral footprints and typical self-assembling arrangements (parallel and antiparallel beta-sheet structures) are recognized, but they disappear on the reconstructed model.