[Pw_forum] Band energy plots

[Mitul Mundra]

Hello,

I am a beginner in using Quantum Espresso. I have a 64 atom Si supercell
for which I am trying to plot band diagrams. I have gone through the
tutorial "PWSCF: First Steps" available at
http://www.fisica.uniud.it/~giannozz/QE-Tutorial/tutorial_pwscf_ex.pdf .
The problem I am facing is that when I run a scf calculation using 4*4*4
k-points, my output file has energies of 128 bands for every k-point. For
example,
*k = 0.0000 0.0000 0.0000 ( 12797 PWs)   bands (ev):*

*    -5.6509  -4.5410  -4.5410  -4.5410  -4.5410  -4.5410  -4.5410  -3.5502*
*    -3.5502  -3.5502  -3.5502  -3.5502  -3.5502  -3.5502  -3.5502  -3.5502*
*    -3.5502  -3.5502  -3.5502  -3.2434  -3.2434  -3.2434  -3.2434  -1.3979*
*    -1.3979  -1.3979  -1.3978  -1.3978  -1.3978  -1.2206  -1.2206  -1.2206*
*    -1.2206  -1.2206  -1.2206  -1.2205  -1.2205  -1.2205  -1.2205  -1.2205*
*    -1.2205  -0.5951  -0.5951  -0.5951  -0.5951   0.9797   0.9797   0.9797*
*     0.9797   0.9797   0.9797   0.9797   0.9797   0.9797   0.9797   0.9797*
*     0.9797   2.5385   2.5385   2.5385   2.5385   2.5385   2.5385   2.5385*
*     2.5385   2.5385   2.5385   2.5385   2.5385   2.6504   2.6504   2.6504*
*     2.6504   2.6504   2.6504   2.6504   2.6504   2.6504   2.6504   2.6504*
*     2.6504   3.0031   3.0031   3.0031   3.0031   3.0031   3.0031   3.5849*
*     3.5849   3.5849   3.5849   3.5849   3.5849   4.5713   4.5713   4.5713*
*     4.5713   4.5713   4.5713   4.5713   4.5713   4.5713   4.5713   4.5713*
*     4.5713   5.1567   5.1567   5.1567   5.1567   5.1568   5.1568   5.1568*
*     5.1568   5.1568   5.1568   5.1568   5.1568   5.2932   5.2932   5.2932*
*     5.2932   5.2932   5.2932   5.2932   5.2932   6.5240   6.5240   6.5240*

On doing calculation = 'bands' and nbnd = 8, the output file contains
energies of only 8 bands for every k-point which are the lowermost bands.
*k = 0.0000 0.0000 0.0000     band energies (ev):*

*    -5.6509  -4.5410  -4.5410  -4.5410  -4.5410  -4.5410  -4.5410  -3.5502*
Then I run a bands.x executable to genrate bands.dat. On using plotband.x,
I get the following.

*/opt/apps/espresso-5.0.1/bin/plotband.x*
*Input file > bands.dat*
*Reading    8 bands at     10 k-points*
*Range:   -5.6510   -3.5500eV  Emin, Emax > -6, -3*

*high-symmetry point:  0.0000 0.0000 0.0000   x coordinate   0.0000*
*...*

*high-symmetry point:  -0.5000-0.5000-0.5000   x coordinate   0.0000*
*output file (xmgr) > si.bands.xmgr*
*bands in xmgr format written to file si.bands.xmgr


                                                                  *
*output file (ps) > si.bands.ps <http://si.bands.ps>*
*Efermi > -3.987           *
*deltaE, reference E (for tics) 1.0, -3.987*
*n=           2           3*
*  0.0000000E+00  0.0000000E+00*
*  -5.651000      -5.581000    *
* NaN            NaN    *
....
....
....
and more NaNs and my *si.bands.ps <http://si.bands.ps>* file contains no
plot.

I would be extremely thankful if someone could tell me where am I wrong and
what different can I do to obtain the band plot (4 valence bands and 4
conduction bands).

Thanks,
Mitul Mundra
Final Year Dual Degree Student
Department of Chemical Engineering
IIT Kanpur, India.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.quantum-espresso.org/pipermail/users/attachments/20140123/d85b0ccd/attachment.html>