# [Pw_forum] Problem of bands data

lan haiping lanhaiping at gmail.com
Tue Jan 29 17:52:58 CET 2008

```Dear All,

I have performed a bands calculation on a carbon nanotube system (7,0).
SCF and NSCF calculations are well converged,  but the bands data obtained
from bands.x is very strange.
I then checked the bands data between the output of nscf calculation and the
data from bands.x calculation, and found some obvious
differences , for example , at kpoint (0.00 0.000 0.8803) , output of nscf
calculation gave data below :
k = 0.0000 0.0000 0.8803     band energies (ev):
-23.2631 -22.8169 -22.8148 -21.5536 -21.5517 -19.6376 -19.6331 -19.2573
-18.8505 -18.8483 -17.7098 -17.7079 -17.3344 -17.3317 -15.8326 -15.7203
-15.7153 -15.5144 -15.5128 -15.0403 -15.0395 -13.5446 -13.5400 -13.5214
-13.5210 -12.6873 -12.6836 -11.6226 -11.3921 -11.3913 -11.0763 -11.0745
-11.0744 -11.0738 -10.9811 -10.9786 -10.0482  -9.7632  -9.7609  -8.5038
-8.5037  -8.3616  -8.3610  -7.6188  -7.6184  -7.3844  -6.9549  -6.9522
-6.9467  -6.9088  -6.3798  -6.3782  -5.0396  -5.0385  -4.8055  -4.8016
-2.9700  -2.3738  -2.3735  -2.1789  -2.1764  -1.8244  -1.8197  -0.1813
0.3902   0.3909   0.4404   0.5333   0.6119   0.6178   0.6886   0.7548
0.7578   0.7763   1.1057   1.1764   1.2288   1.2302   1.3717   1.4616
while, bands data from bands.x is
0.000000  0.000000  0.880282
-23.263 -22.817 -22.815 -21.554 -21.552 -19.638 -19.633 -19.257 -18.850 -
18.848
-17.334 -17.332 -17.710 -15.833 -17.708 -15.514 -15.513 -15.720 -15.715 -
15.040
-15.040 -13.540 -13.545 -12.687 -12.684 -13.521 -13.521 -11.623 -11.075 -
11.076
-11.392 -11.391 -11.074 -11.074  -9.763  -9.761  -8.504  -8.504 -10.048  -
8.362
-8.361  -7.618  -7.619  -7.384  -6.955  -6.947  -6.909  -6.952  -6.380  -
2.970
-2.374  -6.378  -4.805  -4.802  -5.040  -5.038  -2.374  -2.179  -2.176  -
1.824
-1.820  -0.181   0.390   0.391   0.440   0.533   0.612   0.618   0.689
0.755
0.758   0.776   1.176   1.106   1.229   1.230  * *1.372* -10.979 -10.981*
1.462

How to explain this  difference ?   My input files are attached.

--
Hai-Ping Lan
Department of Electronics ,
Peking University , Bejing, 100871
lanhaiping at gmail.com, hplan at pku.edu.cn

--
Hai-Ping Lan
Department of Electronics ,
Peking University , Bejing, 100871
lanhaiping at gmail.com, hplan at pku.edu.cn
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