Structural and electronic properties of a-, ß-, ?-, and 6,6,18-graphdiyne sheets and nanotubes

Abstract

a-, ß-, ?- and 6,6,18-graphdiyne (GDYs) sheets, as well as the corresponding nanotubes (GDYNTs) are investigated systematically by using the self-consistent-field crystal orbital method. The calculations show that the GDYs and GDYNTs with different structures have different electronic properties. The a-GDY sheet is a conductor, while 2D ß-, ?- and 6,6,18-GDYs are semiconductors. The carrier mobilities of ß- and ?-GDY sheets in different directions are almost the same, indicating the isotropic transport characteristics. In addition, the electron mobility is in the order of 106cm2V-1s-1and it is two orders of magnitude larger than the hole mobility of 2D ?-GDY. However, a- and 6,6,18-GDY sheets have anisotropic mobilities, which are different along different directions. For the 1D tubes, the order of stability is ?-GDYNTs > 6,6,18-GDYNTs > ß-GDYNTs > a-GDYNTs and is independent of the tube chirality and size. ß- and ?-GDYNTs as well as zigzag a- and 6,6,18-GDYNTs are semiconductors with direct bandgaps, while armchair a-GDYNTs are metals, and armchair 6,6,18-GDYNTs change from semiconductors to metals with increasing tube size. The armchair ß- and ?-GDYNTs are more favourable to transport holes, while the corresponding zigzag tubes prefer to transport electrons.