Please replace the description with this corrected version:
CNTbands can simulate electronic band structure and density of states for carbon nanotubes (CNT), as well as graphene nanoribbons (GNR). It also computes some basic parameters, such as nanotube diameter, number of hexagons in the unit cell, and band gap. Users may select the GNR structure to be simulated by selecting a starting point and components for a chiral vector. CNTs are simulated either with a simple Pz orbital model or Extended Huckel theory. The Extended Huckel model can deliver more accurate simulation results, especially for small-diameter CNTs.