▎ 摘　　要

The epitaxial growth of graphene on GaN(0 0 0 1) surfaces is studied by first principles total energy calculations. The idea is to understand how defect-free graphene can be grown on substrates. It is found that the most stable structures were a 4 x 4(0 0 0 1) GaN/3 root 3 x 3 root 3 graphene and a 2 root 3 x 2 root 3(0 0 0 1) GaN Northrup bilayer/root 21 x root 21 graphene, grown under N- and Ga-rich conditions, respectively. In these structures, graphene maintains its hexagonal honeycomb structure with the C C bonds intact. Preservation of the pi-network for the graphene layers was demonstrated by the presence of Dirac cones. The band structures for both the N- and Ga-rich configurations show metallic characteristics and the Garich configuration is slightly magnetic. This demonstrates that GaN(0 0 0 1) is an excellent substrate for supporting graphene layers. (C) 2014 Elsevier B.V. All rights reserved.