Our goal in this first-principle study is two folded: Firstly we study the adsorption of poly-para-phenylene polymer on the graphene and secondly we investigated the bulk and narrow MnSe nanowires. In the first part many-body perturbation theory at the G 0 W 0 level was employed to study the electronic properties of physisorbed poly-para-phenylene () on graphene. Analysis of charge density and electrostatic potential shows that the polymer-surface interaction gives rise to formation of weak surface dipoles with no charge transfer between the polymer and the surface. Within the local-density approximation (LDA) of density functional theory, the band structure of combined system appears as a superposition of the band structures of isolated constituents. Consequently the LDA band gap of remains unchanged upon adsorption on the graphene layer. G 0 W 0 calculations, however renormalize the electronic levels of the weakly physisorbed polymer. Thereby, its band gap is considerably reduced compared to isolated chain. This effect can be understood in terms of image charges induced in the graphene layer, which allows us to explain the quasi-particle gap of versus polymer-graphene distance by applying a Keywords : Ab initio, G 0 W 0 many-body perturbation theory, Energy gap, Pseudo particle, Poly-para-phenylene, Polymer, Nanowire, Dangling bond, Formation energy, Phenomenological model.
