DFT optimized adsorption configurations of PA on Cu (111). (a) schematic representation of PA, and two carbon atoms in the acetylenic bond are denoted as C1 and C2. (b) Initial adsorption positions considered in DFT calculations. The black balls indicate the C1 positions in phenylvinylidene form, and black dumbbells refer to the C1–C2 bond positions in styrene derivative form. All of the initial adsorption configurations are optimized into two final configurations as shown in panels (c) and (d). (c) and (d) DFT optimized phenylvinylidene model and styrene derivative model, respectively.