▎ 摘　　要

The structural and electronic properties of XC7 (X = B, Al, N, P, Ge) sheets were investigated through first-principles calculations. Two types of graphene-like sheets named g- and beta-XC7 with honeycomb lattice structures were considered. Their cohesive energies indicate that these sheets are energetically favorable. Both g- and beta-XC7 sheets were found to have good stabilities. The results indicate that g-GeC7 and beta-GeC7 sheets, as well as g-SiC7 and beta-SiC7 sheets, are semiconductors. Their band gaps are dependent on the arrangement of Ge and C atoms. For X = B, Al, N, and P, the g- and beta-XC7 sheets are predicted to have metallic properties. Our results show that graphene-like XC7 sheets with proper electronic properties may be good candidates for applications in modern and future nanoelectronic devices.