Computational studies on structural and electronic properties of functionalized MXene monolayers and nanotubes

Abstract

MXenes, two-dimensional (2D) layered early transition metal carbide, nitride and carbonitride materials, have been prepared by exfoliating MAX phases. In addition to 2D planar MXene, one-dimensional tubular forms are also expected to form. Herein, we design atomic models for Sc₂C monolayers and nanotubes as well as their functionalized counterparts, and investigate their stability and electronic properties through the density functional theory tight-binding method. Dramatic distortion of Sc₂C and Sc₂CO₂ tubular structures occurs, while Sc₂CH₂ and Sc₂C(OH)₂ nanotubes preserve their tubular morphology upon structural relaxation. Moreover, we reveal that the radii of nanotubes play an important role in the relative stability and band gaps of tubular forms. Sc₂CH₂ and Sc₂C(OH)₂ nanotubes are direct-band-gap semiconductors, while the electronic structure of their corresponding planar forms depends on the arrangement of the functional groups.