DFT Study of the Structural Properties of Various Stacked Bilayer Graphdiyne and HCN Adsorption

HCN, as one of the cyanide species, is an extremely powerful and colorless poison. It isusually produced on an industrial scale and is a highly valuable precursor to many chemicalcompounds. Exposure of organism to HCN is highly toxic because it inhibits the consumption ofoxygen by body cells[1]. Graphdiyne is a recently-synthesized carbon allotrope with a frameworkof sp and sp2 hybridized carbon atoms with high degrees of π-conjugation that features uniformlydistributed pores. The hypothetical architecture was first designed by inserting four sphybridizedcarbon atoms into the sp2-sp2 bonds of graphene forming linear -C≡C-C≡Clinkages[2, 3] .In this work, all computations were performed using the spin polarized first-principlemethod as implemented in the Dmol3 code. The generalized gradient approximation (GGA) withthe Perdew-Burke-Ernzerh of (PBE) exchange-correlation functional was used, in combinationwith the double numerical plus polarization (DNP). The empirically-corrected density functionaltheory (DFT+D) method within in Grimme scheme was employed in all the calculation toconsider the Van der Waals forces [4]. We used a 7×7×1 Gamma-centered Monkhorst–Pack kgridfor integration of Brillouin-zone and cut off 4.7 Å. We optimized four bilayer stackedconfigurations that nominated as AA, AB, AC, and AD. Results show that distance betweenlayers is 3.482, 3.271, 3.126, and 3.168 Å, respectively. Also, the most stable bilayerconfiguration is the AC stacking and then AA, AB and AD stacking, respectively. In thefollowing, we checked out the interaction tendency of AC stacking graphdiyne with HCN gasand its adsorption on the pristine bilayer graphdiyne was considered. In this regard, adsorptionenergy and band gap for all interacting systems are evaluated. Various directions for HCNnamely perpendicular from N-head and H-head as well as horizontal direction were selected forapproaching to graphdiyne plane. Also, center of 18-membered and hexagonal rings and top ofacetylenic linkage were examined. The results showed that for center of 18-membered andhexagonal rings, horizontal direction is the best and has more adsorption energy than others andfor acetylenic linkage perpendicular direction from H-head is the most stable configuration.After HCN adsorption, the band gap values and layer distances increased for all configurations.

کلیدواژه ها:

Stacking ، DFT-D ، Graphdiyne ، 2-D Carbon Structure ، Adsorption Energy