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)