[DFTB-Plus-User] Kpoint of CNTs

[jsxz]

Dear all,
Good time,

I'm trying to optimum the structure of carbon nanotube with the length of 42 A.

How to determine KPointsAndWeights?

Which is right?

(1)
KPointsAndWeights = SupercellFolding{
  1   0   0
  0   1   0
  0   0   5
  0.0 0.0 0.0
  }
or
(2)
 KPointsAndWeights[relative] = KLines{
  1 0.0 0.0 0.0
  4 0.0 0.0 0.5
  }

In addition, in the KPointsAndWeights section of the DFTB+ manual, the sentence
"It is important to note that DFTB+ does not take the symmetry of your system explicitly into
account. For small high symmetric systems with a low number of k-points in the sampling this
could eventually lead to unphysical results. (Components of tensor properties–e.g. forces–could be
finite, even if they must vanish due to symmetry reasons.) For those cases, you should explicitly
specify k-points with the correct symmetry."

For the CNTs, should I explicitly specify k-points with the correct symmetry?


Could you advice me, Please?

Thanks in advance.
Bests Regards.

Xiaobao Zhang

 
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