Toward Accurate Modeling of Aperiodic Surfaces: Cluster-Based DFT Analysis of Pentacene on Cu(111) Surface

With the aim of applying it to molecular adsorption on quasicrystalline surfaces, we investigated the applicability of the cluster model in density functional theory calculations by comparing it with the slab model. The adsorption structure and stability of pentacene on the Cu(111) surface were evaluated using two van der Waals (vdW) functionals (vdW-DF and rev-vdW-DF2). The rev-vdW-DF2 functional, which yields a larger adsorption energy than the vdW-DF functional, is clearly superior to the vdW-DF functional for the adsorption height. The potential energy surfaces (PES) obtained using cluster models exhibited an artificial jagged structure around the PES maximum when using a smaller cluster, but otherwise agreed well with those from slab models, validating the cluster approach for predicting stable adsorption structures. These findings provide a foundation for the accurate modeling of adsorption on quasicrystalline surfaces.