▎ 摘　　要

Doping metallic element(s) serves as an effective approach in enhancing favorable electronic properties of graphene. Derived by a wide array of applications in electronic devices, addressing graphene-metal interactions have been in the center of mounting research over the last few years. Nevertheless, pertinent literature has overlooked the effect of geometrical, orientation and positional aspects of such doping systems on estimated electronic properties. In this contribution, we deployed DFT periodic slab calculations to investigate effect of orientational dependence of Al- and Si-adsorbed graphene systems. We utilized 2 x 2 and 2 x root 3 graphene supercells with 1:8 (Al, Si: C) atomic ratio. We observed that the relative orientation of adsorbent atoms exerts profound influence on electronic structures in conjunction with a matching effect caused by the distinct adsorption sites (i.e. bridge, hollow or top). The orientation effects of Si-adsorbed graphene on electronic structure are greater than their Al analogous structures. We anticipate our finding herein, of low adatom concentration on graphene, to prompt re-examination of metal-graphene systems to account for the previously unnoticed but significant orientational effect that adds an additional degree of freedom to elemental adsorption on graphene. (C) 2015 Elsevier Ltd. All rights reserved.