Atomic structure, comparative stability and electronic properties of hydroxylated Ti2C and Ti3C2 nanotubes

Recently, hydroxylated and fluorinated graphene-like titanium carbide Tic(x) layers have been solvothermally fabricated in large amounts from so-called MAX phase Ti3AlC2. We assume, that a wide family of novel planar and tubular forms of titanium carbides may exist and design the atomic models for mono-layers and nanotubes with nominal stoichiometry Ti2C, Ti3C2 and for their hydroxylated forms Ti2C(OH)(2), Ti3C2(OH)(2). The stability and electronic properties of these nanostructures are examined by means of density-functional theory tight-binding method depending on the composition and the type of OH arrangement. We reveal that the type of OH termination plays a minor role in the variation of nanotubes strain energies, but causes a difference in the relative stability of their parent planar phases. The electronic structure for all nanotubes studied has metallic-like character, while their precursors (planar layers) demonstrate either metallic-like or semiconducting behavior depending on the arrangement of the surface OH groups. (C) 2012 Elsevier B.V. All rights reserved.