Systematic theoretical study of carbon nanotubes rolled from a two-dimensional tetrahex-carbon nanosheet

Abstract

A recently proposed two-dimensional (2D) carbon allotrope, tetrahex-carbon composed of tetragonal and hexagonal rings in a buckled plane, draws scientific research interests due to its remarkable mechanical and electronic properties, including ultrahigh strength, negative Poisson's ratio, finite direct band gap, and high carrier mobility. In this work, a series of carbon nanotubes rolled from this new 2D tetrahex-C nanosheet with various size and chirality are studied through first-principles density-functional theory calculations. The tube diameter is in the range of 4.5--18 \AA{}. It is found that the smallest thermodynamically stable nanotubes have the diameter of 4.5 \AA{} for zigzag tetrahex-C nanotubes (z-TH-CNTs) and 6.0 \AA{} for armchair tetrahex-C nanotubes (a-TH-CNTs). The z-TH-CNTs are energetically more favorable than the a-TH-CNTs given similar size. The single-wall nanotubes have a particular wall thickness which shrinks with the decrease of tube size. It is also found that all explored nanotubes show semiconducting behavior and HSE predicted band gaps can be effectively tuned in the range of 1.84--2.69 eV with size and chirality. Large curvature in small z-TH-CNTs alters the band structures, resulting in a significantly reduced effective mass of electron thus indicating potentially enhanced carrier mobility. Work function of the tubes can be manipulated within the range of 5.25--5.43 eV dependent on the tube size and chirality. These remarkable structural and electronic properties in the tetrahex-C nanotubes may have potential applications in nanoelectronics.