Effective masses of charge carriers in selected symmorphic and nonsymmorphic carbon nanotubes

We performed ab initio, self-consistent calculations for the electronic structure of selected semiconducting carbon nanotubes in the symmorphic and nonsymmorphic groups. We employed a real space approach in the linear combination of atomic orbital formalism. We utilized a nonlocal density-functional potential in the generalized gradient approximation. We present the electronic structure and effective masses of charge carriers in symmorphic nanotubes that include (10,0), (13,0), (17,0), and (22,0), and the nonsymmorphic tubes (8,4) and (10,5). For nonsymmorphic carbon nanotubes (8,4) and (10,5), the top of the highest occupied valence band and the bottom of the lowest unoccupied conduction band are not at the Gamma point, but at about +/-0.1(1,0,0)pi/L, where the tubule axis is defined as the (1,0,0) direction. The band gaps in the nonsymmorphic (8,4) and (10,5) can be direct for transitions at +0.1(1,0,0)pi/L or -0.1(1,0,0)pi/L, and can also be indirect for transitions from +0.1(1,0,0)pi/L to -0.1(1,0,0)pi/L, or vice versa.