▎ 摘　　要

To aid the analysis of interlayer interactions in double-layer carbon nanotubes, the interactions between two graphene sheets have been analytically examined within the framework of the Huckel approximation. Although there is a limitation to apply the present results to the actual double-layer nanotubes, it has been suggested that a certain interlayer interaction mode affects the metallic state of a nanotube with the direct zero-energy gap changing into the indirect one and, moreover, that other mode even changes into non-metallic state. Copyright (C) 1997 Elsevier Science Ltd.