Solution LAB3 CNT

• Back to the previous page: Electronic properties of 2D and 1D systems#Exercise 3: A small Carbon nanotube (CNT)

In order to build the cell we can use a CNT generator, several options available:

Step 1

• go to CNT generator http://turin.nss.udel.edu/research/tubegenonline.html
• For simplicity set the crystal cell as cubic
• Choose a format with PBC (e.g. PDB with PBC). Note that the units are in Angstrom.
• In building the input file: Note the tube axis is along z.

Suggestions: (Use ibrav=8, set an arbitrary amount of vacuum, and set cilldm(3)=c/a)

• Visualize the structure using xcrysden

Step 2

• You can use cell_dofree='z' to relax the cell parameter along the tube axis
• Set a value of k-points (along z) not tool large (12 should be enough)
• Set forc_conv_thr = 1.0d-2/1de-3 otherwise the relaxation process it too long (celldm(1)=20 ~15 min)
• Visualize the relaxation output in xcrysden (curvature effects wrt ideal graphene structure)