Carbon nano tube

[farzaneh]

Dear friends

I want to simulate carbon nano tube. To this end, I should insert vacuum layers in the direction perpendicular to the carbon nano tube axis. I have a question about the method of Brillouin zone sampling.

I have already set the Gamma point sampling of 1*1*21, but the accuracy of the stress results is not favorable. Is it necessary to have 2*2*x sampling or not?

[alex]

Unlikely, since you have no 3D periodicity in these directions. Try to increase the cutoff energy (Pulay stress) if you are optimising the lattice parameter along the nanotube. You might also cut back on your k-points depending on the size of the lattice parameter in this direction.

Hth

alex

[farzaneh]

I have set cutoff energy as 500 eV, and I have relaxed the structure to obtain the optimized lattice parameter. I have applied the axial strain along the longitudinal direction. However, the accuracy of the stress is low.