First-principles investigation on the bonding mechanism between graphyne and the (111) surface of Cu, Ag and Au

A series of adsorption configurations with less than 2% lattice mismatch of graphyne adsorbed at different sites on the (111) surface of Cu, Ag and Au are obtained by a systematic rotation of the graphyne sheet. Besides, all the non-equivalent adsorption configurations of graphyne on metal surfaces are obtained by a structure screening method based on the translation of graphyne sheet and the calculation of the atomic overlapping area at the interface. The most stable adsorption configuration of graphyne on each metal surface is obtained by optimizing these non-equivalent adsorption configurations with a small computational cost. Then the adsorption energy, differential charge density, and partial density of states are calculated using a first-principles method in order to investigate the bonding mechanism between graphyne and the (111) surface of these three metals. The results show that the adsorption types of graphyne on the (111) surface of Cu, Ag and Au are chemisorption, chemical and physical mixed adsorption and pure physisorption, respectively. In detail, when a metal (Cu or Ag) atom is below a C atom, the C-p_z orbital will interact with the s and d orbitals of the metal atom and then form a covalent bond with the metal atom. In particular, when a Cu atom lies below two carbon atoms joined by an acetylene bond, the s and d orbitals of the Cu atom hybridize with each other to form two identical sd orbitals and then form two covalent bonds with two C-p_z orbitals. Our results not only provide a structure screening method for obtaining the most stable configuration with a very small lattice mismatch but also reveal the interface bonding mechanism between graphyne and metals, which will provide help for the preparation of graphyne and its application in composite materials. (paper)