1205.6065 (Haiping Lan et al.)

Role of the dispersion correction in the modeling of molecule-metal
interfaces: Thiophene adsorbed on Cu(100), Cu(110) and Cu(111)    [PDF]

Haiping Lan, Wei Ji

Density functional theory calculations were carried out to investigate the role of the dispersion correction on the geometry, adsorption energy, electronic density of states and bonding picture of thiophene adsorbed on Copper surfaces. The inclusion of the dispersion correction, implemented using the DFT-D2 method, showed a substantial effect on the molecular geometry of thiophene/Cu(111), while it only affected the molecular titling angle of thiophene on Cu(100) and Cu(110) surfaces. In comparison with experiments where the molecular geometry was measured by x-rays, it was found that the consideration of electron-corehole interaction and its induced screening charges, rather than the inclusion of the dispersion correction, is crucial to theoretically reproduce the measured structure of thiophene/Cu(111). It was demonstrated being consistent with the experiments fairly well that the theoretical results of adsorption energy calculated using a specially chosen functional (RPBE) in together with the dispersion correction. Partial density of states revealed that the dispersion correction does not notably modify the electronic structures of occupied states, but slightly perturbs the unoccupied states. An explicit covalent bonding between thiophene and Cu surfaces was identified by inspecting differential charge densities of two interfaces and charge densities of two particular states. Our results suggest that the dispersion correction shall be included in theoretical studies of adsorption energy and related properties in thiophene/Cu and similar molecule-metal interfaces. However, the results of other properties, especially electronic properties, substantially share the same physics with or without the dispersion correction applied.

View original: http://arxiv.org/abs/1205.6065