Adsorption and bonding mechanism of a N,N-'-di(n-butyl)quinacridone monolayer studied by density functional theory including semiempirical dispersion corrections

Franke JH, Caciuc V, Chi LF, Fuchs H

Abstract

The adsorption of a monolayer of N,N-'-di(n-butyl)quinacridone on Ag(110) is studied by density functional theory including semiempirical dispersion corrections. The bonding mechanism is governed by the formation of an oxygen-Ag bond involving first-layer Ag atoms and the butyl chains are found to be folded away from the substrate in the most stable geometry. A small charge donation from the substrate to the lowest unoccupied molecular orbital is observed. Work-function changes are calculated for different adsorption energies, indicating a lowering of the work function by up to 0.85 eV. The semiempirical dispersion corrections give a large energy gain upon adsorption that is almost site unspecific. Accordingly the molecule-surface distance is reduced especially for weakly bound configurations. The induced change to the electronic structure in these cases also alters the calculated work function change significantly.