First-principle prediction of the existence of C64-graphyne and (BN)64

By using of the first-principles calculations based on density functional theory, a novel monolayer planar structure named C-64-graphyne is predicted. Tetratomic and hexatomic rings, as well as C-C triple bonds exist in this new stable structure with the lattice parameter of 9.291 angstrom. The carbon hexatomic ring in C-64-graphyne contains two quite distinct C-C bonds, which is known as cyclohexatriene. Its electronic band structures show a semiconductor nature with a narrow direct band gap of 0.35 eV. Interestingly, by substituting a carbon atom with one nitrogen atom either in the hexatomic ring or in the chain of C-64-graphyne, two stable planar structures are obtained. Such doping with nitrogen atom induced metallic properties in this monolayer structure. Further investigation shows that the alternating substitution of boron and nitrogen atoms for all carbon atoms in C-64-graphyne also induced a new stable structure, the (BN)(64) structure. The electronic studies proved its insulator property with the band gap of 4.08 eV.