# [Pw_forum] Slow calculation of (5, 5) CNT transmission and complex bands.

chengyu yang chengyu.young at gmail.com
Tue Aug 9 17:37:16 CEST 2011

```Dr. Sclaizero and all,
points, I still have some problem.
(1) I heard that to calculate bandstructure, one need to use more than
20 k points to get a reliable result, that's why I was looking for more k
points. I did only use the three high symmetry k points in the nscf
calculation, but the final result seems to be too simple to be true. I
attached them for you to have a look.
(2) In the conductance example for Al, I see they used 50 k points to
get a bandstructure, and I was wondering how did they get them? I can only
find at most 10 high symmetry points for Al. Do we need the same
amount/scale of K point ? If so, how?

k points in the al.nscf.in:

K_POINTS
50
0.00   0.00       0.00000000      0.00000000
0.00   0.00       0.00721538      0.00721538
0.00   0.00       0.01443075      0.01443075
0.00   0.00       0.02164613      0.02164613
0.00   0.00       0.02886150      0.02886150
0.00   0.00       0.03607688      0.03607688
0.00   0.00       0.04329225      0.04329225
0.00   0.00       0.05050763      0.05050763
0.00   0.00       0.05772300      0.05772300
0.00   0.00       0.06493838      0.06493838
0.00   0.00       0.07215375      0.07215375
0.00   0.00       0.07936913      0.07936913
0.00   0.00       0.08658450      0.08658450
0.00   0.00       0.09379988      0.09379988
0.00   0.00       0.10101525      0.10101525
0.00   0.00       0.10823063      0.10823063
0.00   0.00       0.11544601      0.11544601
0.00   0.00       0.12266138      0.12266138
0.00   0.00       0.12987676      0.12987676
0.00   0.00       0.13709213      0.13709213
0.00   0.00       0.14430751      0.14430751
0.00   0.00       0.15152288      0.15152288
0.00   0.00       0.15873826      0.15873826
0.00   0.00       0.16595363      0.16595363
0.00   0.00       0.17316901      0.17316901
0.00   0.00       0.18038438      0.18038438
0.00   0.00       0.18759976      0.18759976
0.00   0.00       0.19481513      0.19481513
0.00   0.00       0.20203051      0.20203051
0.00   0.00       0.20924588      0.20924588
0.00   0.00       0.21646126      0.21646126
0.00   0.00       0.22367663      0.22367663
0.00   0.00       0.23089201      0.23089201
0.00   0.00       0.23810739      0.23810739
0.00   0.00       0.24532276      0.24532276
0.00   0.00       0.25253814      0.25253814
0.00   0.00       0.25975351      0.25975351
0.00   0.00       0.26696889      0.26696889
0.00   0.00       0.27418426      0.27418426
0.00   0.00       0.28139964      0.28139964
0.00   0.00       0.28861501      0.28861501
0.00   0.00       0.29583039      0.29583039
0.00   0.00       0.30304576      0.30304576
0.00   0.00       0.31026114      0.31026114
0.00   0.00       0.31747651      0.31747651
0.00   0.00       0.32469189      0.32469189
0.00   0.00       0.33190726      0.33190726
0.00   0.00       0.33912264      0.33912264
0.00   0.00       0.34633802      0.34633802
0.00   0.00       0.35355339      0.35355339

Best regards.

Chengyu Yang
MMAE,University of Central Florida

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